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Sample records for supersaturated mgso4 aerosols

  1. 腔增强拉曼技术下的过饱和硫酸镁液滴蒸发动力学初探%Preliminary Assessment of Evaporating Supersaturated MgSO4 Droplet at Low Relative Humidity with Cavity Enhanced Raman Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    陈斯华; 蔡宸; 冷春波; 张韫宏

    2013-01-01

    This paper is aimed to study the response of a single MgSO4 droplet to the variation of relative humidity through the combination of single beam gradient force optical tweezers and Raman spectroscopy.The evaporation dynamic of a single MgSO4 droplet which is trapped by a single beam gradient force optical tweezers is investigated by varying the relative humidity in a stepwise manner.The measurements of the variation in equilibrium wet droplet size with relative humidity (RH) are made using cavity enhanced Raman scattering(CERS),where the stimulated Raman signals appear at wavelength commensurate to the Whispering Gallery Modes (WGMs) are applied to determine the size of droplet with high precision.This study demonstrates the real time monitoring of MgSO4 droplet size over a RH range that had not previously been explored with aerosol optical tweezers.The results show that the MgSO4 droplet radius variation gradually becomes smaller as the RH=~44% and is greatly depressed when RH lower than 40%,indicating that water evaporation rate of captured MgSO4 droplet is limited at high concentration.On the other hand,the deliquescence of shrinked MgSO4 droplet is not equivalent with the dehumidification process.The re-growth of MgSO4 droplet size is observed to be significantly slower in response to the increase of RH.It is suggested that mass transfer effect caused by the gel formation has contributed to the retardation of water mass transfer.%本文通过单光束梯度力光学镊子-拉曼光谱系统,对硫酸镁单液滴随着相对湿度变化的反应进行了探究.当硫酸镁单液滴被光镊捕获之后,通过相对湿度的梯度变化探究了捕获液滴的蒸发动力学变化.发生在与耳语回音模相称波长的受激拉曼散射可以用来准确地确定液滴半径,因此,可以通过腔增强拉曼散射得到在不同湿度下处于平衡的液滴半径信息.本研究通过光镊对硫酸镁单液滴的实时监测,阐述了在某个相对

  2. Measurement of electric properties of the single supersaturated aerosol droplet

    Institute of Scientific and Technical Information of China (English)

    HE KeJuan; CHENG Hua; ZHU YanYing; WANG LiangYu; ZHANG YunHong

    2008-01-01

    A system for measuring the electric properties of single aerosol droplet is designed and applied to the NaCIO4 aerosol droplet in different relative humidity (RH). The conductance and capacitance are obtained within the whole RH range, especially in the supersaturated state which cannot be acquired from the bulk solution. These results reflect the situation of ions in the droplet macroscopically and supply useful information for other relative study fields, such as crystallogeny and aerography.

  3. State of water and its implications for supersaturated structures in Mg(NoO3)2 aerosols

    Institute of Scientific and Technical Information of China (English)

    ZHAO LiJun; ZENG QingXuan; ZHANG YunHong

    2009-01-01

    One technique based on the difference spectra was developed to study the state of water in super-saturated Mg(NO3)2 aerosols. The technique could be derived from the observation that the Raman scattering and infrared absorbance cross sections of molecular vibrations of interest remain practically constant from diluted solutions to supersaturated aerosols. The spectra of solvated water were ob-tained and primarily related to the first hydration layers of solute molecules in supersaturated Mg(NO3)2aerosols. Based on this investigation, a chain structure was proposed to occur in the supersaturated Mg(NO3)2 aerosols at low relative humidities (RHs).

  4. Laboratory and field studies of stratospheric aerosols: Phase changes under high supersaturation

    Science.gov (United States)

    Hallet, John

    1991-02-01

    It is well known that water in the form of isolated small droplets supercool as much as 40 C below their equilibrium melting point. Solutions similarly supercool (with respect to water) and supersaturate (with respect of the solute). Experiments are described in which bulk solutions typical of atmospheric aerosols (nitric acid, sulfuric acid, and hydrates; ammonium sulfate; ammonium bisulfate; sodium chloride) are supercooled and/or supersaturated and nucleated to initiate crystal growth. Supersaturation of 300 percent is readily attainable, with linear growth of crystals increasing roughly as (supercooling/supersaturation)sup 2. The implication of the experiments is that the situation of metastability in polar stratosphere clouds is very likely, with nucleation only occuring under a high degree of supercooling or supersaturation.

  5. Laboratory and field studies of stratospheric aerosols: Phase changes under high supersaturation

    Science.gov (United States)

    Hallet, John

    1991-01-01

    It is well known that water in the form of isolated small droplets supercool as much as 40 C below their equilibrium melting point. Solutions similarly supercool (with respect to water) and supersaturate (with respect of the solute). Experiments are described in which bulk solutions typical of atmospheric aerosols (nitric acid, sulfuric acid, and hydrates; ammonium sulfate; ammonium bisulfate; sodium chloride) are supercooled and/or supersaturated and nucleated to initiate crystal growth. Supersaturation of 300 percent is readily attainable, with linear growth of crystals increasing roughly as (supercooling/supersaturation)sup 2. The implication of the experiments is that the situation of metastability in polar stratosphere clouds is very likely, with nucleation only occuring under a high degree of supercooling or supersaturation.

  6. Aerosol removal and cloud collapse accelerated by supersaturation fluctuations in turbulence

    Science.gov (United States)

    Chandrakar, K. K.; Cantrell, W.; Ciochetto, D.; Karki, S.; Kinney, G.; Shaw, R. A.

    2017-05-01

    Prior observations have documented the process of cloud cleansing, through which cloudy, polluted air from a continent is slowly transformed into cloudy, clean air typical of a maritime environment. During that process, cloud albedo changes gradually, followed by a sudden reduction in cloud fraction and albedo as drizzle forms and convection changes from closed to open cellular. Experiments in a cloud chamber that generates a turbulent environment show a similar cloud cleansing process followed by rapid cloud collapse. Observations of (1) cloud droplet size distribution, (2) interstitial aerosol size distribution, (3) cloud droplet residual size distribution, and (4) water vapor supersaturation are all consistent with the hypothesis that turbulent fluctuations of supersaturation accelerate the cloud cleansing process and eventual cloud collapse. Decay of the interstitial aerosol concentration occurs slowly at first then more rapidly. The accelerated cleansing occurs when the cloud phase relaxation time exceeds the turbulence correlation time.

  7. The ternary system K2SO4MgSO4CaSO4

    Science.gov (United States)

    Rowe, J.J.; Morey, G.W.; Silber, C.C.

    1967-01-01

    Melting and subsolidus relations in the system K2SO4MgSO4CaSO4 were studied using heating-cooling curves, differential thermal analysis, optics, X-ray diffraction at room and high temperatures and by quenching techniques. Previous investigators were unable to study the binary MgSO4CaSO4 system and the adjacent area in the ternary system because of the decomposition of MgSO4 and CaSO4 at high temperatures. This problem was partly overcome by a novel sealed-tube quenching method, by hydrothermal synthesis, and by long-time heating in the solidus. As a result of this study, we found: (1) a new compound, CaSO4??3MgSO4 (m.p. 1201??C) with a field extending into the ternary system; (2) a high temperature form of MgSO4 with a sluggishly reversible inversion. An X-ray diffraction pattern for this polymorphic form is given; (3) the inversion of ??-CaSO4 (anhydrite) to ??-CaSO4 at 1195??C, in agreement with grahmann; (1) (4) the melting point of MgSO4 is 1136??C and that of CaSO4 is 1462??C (using sealed tube methods to prevent decomposition of the sulphates); (5) calcium langbeinite (K2SO4??2CaSO4) is the only compound in the K2SO4CaSO4 binary system. This resolved discrepancies in the results of previous investigators; (6) a continuous solid solution series between congruently melting K2SOP4??2MgSO4 (langbeinite) and incongruently melting K2SO4??2CaSO4 (calcium langbeinite); (7) the liquidus in the ternary system consists of primary phase fields of K2SO4, MgSO4, CaSO4, langbeinite-calcium langbeinite solid solution, and CaSO4??3MgSO4. The CaSO4 field extends over a large portion of the system. Previously reported fields for the compounds (K2SO4??MgSO4??nCaSO4), K2SO4??3CaSO4 and K2SO4??CaSO4 were not found; (8) a minimum in the ternary system at: 740??C, 25% MgSO4, 6% CaSO4, 69% K2SO4; and ternary eutectics at 882??C, 49% MgSO4, 19% CaSO4, 32% K2SO4; and 880??, 67??5% MgSO4, 5% CaSO4, 27??5% K2SO4. ?? 1967.

  8. Water Transport in MgSO4·7H2O during Dehydration in View of Thermal Storage

    NARCIS (Netherlands)

    Donkers, P.A.J.; Beckert, S.; Pel, L.; Stallmach, F.; Steiger, M.; Adan, O.C.G.

    2015-01-01

    The water phases in a MgSO4·7H2O crystal during heating were studied with the help of NMR. The thermogravimetric analysis (TGA) data showed that the heating rate has a strong effect on the dehydration process. NMR experiments showed that pore water, i.e., an aqueous solution of MgSO4, was produced d

  9. Supersaturation of Calcipotriene and Betamethasone Dipropionate in a Novel Aerosol Foam Formulation for Topical Treatment of Psoriasis Provides Enhanced Bioavailability of the Active Ingredients.

    Science.gov (United States)

    Lind, Marianne; Nielsen, Kim Troensegaard; Schefe, Line Hollesen; Nørremark, Kasper; Eriksson, André Huss; Norsgaard, Hanne; Pedersen, Brian Thoning; Petersson, Karsten

    2016-09-01

    Previous studies have demonstrated the superior efficacy of a novel aerosol foam formulation of fixed combination calcipotriene 0.005% (Cal) and betamethasone dipropionate 0.064% (BD), compared with the ointment formulation. The aim of this study is to ascertain whether enhanced bioavailability of the active ingredients due to supersaturation and/or occlusive properties can explain the observed greater clinical efficacy. Solubility and evaporation experiments were conducted to examine the abilities of Cal/BD aerosol foam ingredients to create a supersaturated environment. Optical microscopy, Raman imaging and X-ray powder diffraction were used to examine the physical state of Cal and BD in the formulations after application, and determine whether a supersaturated state remained stable for clinically relevant time periods. In vitro skin penetration and ex vivo biomarker assays were conducted to compare the skin penetration and bioavailability of Cal and BD from the aerosol foam and ointment formulations, respectively. Occlusive properties were examined via transepidermal water loss. Solubility studies showed that Cal and BD solubility increased with increasing dimethyl ether (DME) content. Both active ingredients are completely dissolved in the final aerosol foam formulation. DME rapidly evaporates after spraying, and the amount was reduced to 0.5% of the initial amount after 2 min. This led to the formation of a supersaturated environment, where Cal and BD crystals were absent for at least 26 h after application. Cal/BD aerosol foam had significantly greater in vitro skin penetration and had increased bioavailability compared with Cal/BD ointment. Both formulations effectively occluded the skin. A stable supersaturated solution of Cal/BD in the aerosol foam leads to increased bioavailability and explains the improved clinical effect when compared to the Cal/BD ointment. The studies included in the paper are all conducted by LEO Pharma A/S or CROs on behalf of LEO

  10. DEVELOPMENT OF THIN FILM NANOCOMPOSITE EMBEDDED WITH GRAPHENE OXIDE FOR MgSO4 REMOVAL

    Directory of Open Access Journals (Sweden)

    I. WAN AZELEE

    2016-07-01

    Full Text Available Thin film nanocomposite (TFN membrane with graphene oxide (GO embedded into the polyamide (PA selective top layer has been developed for salt removal. 0.1 wt% of GO were dispersed in the trimesoyl chloride (TMC organic solution and incorporated into the PA layer during interfacial polymerization with piperazine. The fabricated TFN membrane was characterized in terms of the membrane morphological structure and surface hydrophilicity. The divalent magnesium sulfate (MgSO4 salt removal performance of the TFN was evaluated and compared with the thin film composite (TFC counterpart. The surface morphology of the TFN membranes was altered and the surface hydrophilicity was increased with the presence of GO. The incorporation of GO has improved the permeate water flux, in which maximum improvement of 140% compared to that of TFC has been obtained, without sacrificing much on the salt rejection properties. Although further investigation is required, this study has experimentally verified the potential application of GO to heighten the salt separation performance of TFN membranes.

  11. Structure of MgSO4 in Concentrated Aqueous Solutions by X-Ray Diffraction

    Institute of Scientific and Technical Information of China (English)

    CAO Ling-di; FANG Yan; FANG Chun-hui

    2011-01-01

    Detailed time-and-space-averaged structure of MgSO4 in the concentrated aqueous solutions was investigated via X-ray diffraction with an X'pert Pro θ-θ diffractometer at 298 K, yielding structural function and radial distribution function(RDF). The developed KURVLR program was employed for the theoretical investigation in consideration of the ionic hydration and ion association. Multi-peaks Gaussian fitting method was applied to deconvolving the overlapping bands of Differential radial distribution function(DRDF). The calculation of the geometric model shows that octahedrally six-coordinated Mg(H2O)62+, with an Mg2+…Ow bond length of 0.201 nm dominates in the solutions. There exists contact ion-pair(CIP) in the more concentrated solution(1:18, H2O/salt molar ratio) with a coordination number of 0.8 and a characteristic Mg…S distance of 0.340 nm. The result indicates the hydrated SO42ion happens in the solution. The S…Ow bond distance was determined to be 0.382 nm with a coordination number of 13. The fraction of CIP increases significantly with the increasing concentration. The symmetry of the hydration structure of sulfate ion is lowered by forming complex with magnesium ion.

  12. Simulation experiments on the reaction system of CH4-MgSO4-H2O

    Institute of Scientific and Technical Information of China (English)

    DING KangLe; LI ShuYuan; YUE ChangTao; ZHONG NingNing

    2008-01-01

    H2S-rich gas in carbonate reservoirs is usually attributed to thermochemical sulfate reduction (TSR). In this paper, thermal simulation experiments on the reaction system of CH4-MgSO4-H2O were carried out using autoclave at 425℃-525℃. The threshold temperature for initiating TSR is much lower than our previous studies (550℃). Properties of the reaction products were analyzed by microcoulometry, gas-chromatography (GC), Fourier transform-infrared spectrometry (FT-IR) and X-ray diffraction (XRD) methods. Thermodynamics and reaction kinetics of TSR processes were investigated on the basis of the experimental data. The results show that thermochemical reduction of magnesium sulfate with methane can proceed spontaneously to produce magnesium oxide, hydrogen sulfur, and carbon diox-ide as the main products, and high temperature is thermodynamically favorable to the reaction. Ac-cording to the reaction model, the calculated activation energy of TSR is 101.894 kJ/mol, which is lower than that by most previous studies. Mg2+ may have played a role of catalytic action in the process of TSR. The elementary steps of TSR and reaction mechanism were discussed tentatively. The study can provide important information on the explanation of geochemical depth limit for natural gas and on the generation of high H2S gas in deep carbonates reservoirs.

  13. Meridianiite (MgSO4-11H2O): A New Mineral Species Observed on Earth and Predicted to Exist on Mars

    Science.gov (United States)

    Peterson, R. C.; Nelson, W.; Madu, B.; Shurvell, H. F.

    2007-07-01

    Meridianiite, MgSO4-11H2O, was recently discovered on the surface of a frozen pond in central British Columbia, Canada. Meridianiite is stable below 2°C. Above 2°C it melts incongruently to a slurry of epsomite (MgSO4-7H2O) and water.

  14. Water uptake of biomass burning aerosol at sub- and supersaturated conditions: closure studies and implications for the role of organics

    Directory of Open Access Journals (Sweden)

    U. Dusek

    2010-12-01

    Full Text Available We investigate the CCN activity of freshly emitted biomass burning particles and their hygroscopic growth at a relative humidity (RH of 85%. The particles were produced in the Mainz combustion laboratory by controlled burning of various wood types, peat and grass. The water uptake at sub- and supersaturations is parameterized by deriving a soluble volume fraction (ε. It is defined as the volume fraction of ammonium sulfate in the total aerosol material, which would be sufficient to explain the observed water uptake. For the wood burns, soluble volume fractions are low, generally around 0.11. This translates to a hygroscopicity parameter κ (another widely used parameterization; cf. Petters and Kreidenweis, 2007 of around 0.07. The main emphasis of this study is a comparison of ε derived from measurements at sub- and supersaturated conditions εG and εCCN, in order to see whether the water uptake at 85% RH can predict the CCN properties of the biomass burning particles. Differences in εG and εCCN can arise through solution non-idealities, the presence of slightly soluble or surface active compounds, or non-spherical particle shape. We find that εG and εCCN agree within experimental uncertainties (of around 30% for particle sizes of 100 and 150 nm; only for 50 nm particles is εCCN larger than εG by a factor of 2. The magnitude of this difference and its dependence on particle size is consistent with the presence of surface active organic compounds. These compounds mainly facilitate the CCN activation of small particles, which form the most concentrated solution droplets at the point of activation. The 50 nm particles, however, are only activated at supersaturations higher than 1% and are therefore of minor importance as CCN in ambient clouds. By comparison with the actual chemical composition of the biomass burning particles, we estimate that the

  15. Water uptake of biomass burning aerosol at sub- and supersaturated conditions: closure studies and implications for the role of organics

    Science.gov (United States)

    Dusek, U.; Frank, G. P.; Massling, A.; Zeromskiene, K.; Iinuma, Y.; Schmid, O.; Helas, G.; Hennig, T.; Wiedensohler, A.; Andreae, M. O.

    2010-12-01

    We investigate the CCN activity of freshly emitted biomass burning particles and their hygroscopic growth at a relative humidity (RH) of 85%. The particles were produced in the Mainz combustion laboratory by controlled burning of various wood types, peat and grass. The water uptake at sub- and supersaturations is parameterized by deriving a soluble volume fraction (ɛ). It is defined as the volume fraction of ammonium sulfate in the total aerosol material, which would be sufficient to explain the observed water uptake. For the wood burns, soluble volume fractions are low, generally around 0.11. This translates to a hygroscopicity parameter κ (another widely used parameterization; cf. Petters and Kreidenweis, 2007) of around 0.07. The main emphasis of this study is a comparison of ɛ derived from measurements at sub- and supersaturated conditions ɛG and ɛCCN), in order to see whether the water uptake at 85% RH can predict the CCN properties of the biomass burning particles. Differences in ɛG and ɛCCN can arise through solution non-idealities, the presence of slightly soluble or surface active compounds, or non-spherical particle shape. We find that ɛG and ɛCCN agree within experimental uncertainties (of around 30%) for particle sizes of 100 and 150 nm; only for 50 nm particles is ɛCCN larger than ɛG by a factor of 2. The magnitude of this difference and its dependence on particle size is consistent with the presence of surface active organic compounds. These compounds mainly facilitate the CCN activation of small particles, which form the most concentrated solution droplets at the point of activation. The 50 nm particles, however, are only activated at supersaturations higher than 1% and are therefore of minor importance as CCN in ambient clouds. By comparison with the actual chemical composition of the biomass burning particles, we estimate that the hygroscopicity of the organic fraction is roughly 1/3 that of ammonium sulfate and can be represented by κ

  16. Sensitivity of the mayfly Adenophlebia auriculata (Ephemeroptera: Leptophlebiidae) to MgSO4 and Na2SO4

    Science.gov (United States)

    Vellemu, E. C.; Mensah, P. K.; Griffin, N. J.; Odume, O. N.

    2017-08-01

    Acid mine drainage (AMD) continues to deteriorate water quality in freshwater ecosystems. Sulphates, a major salt component in AMD, can exacerbate AMD effects in freshwater because salts are toxic to aquatic life in high concentrations. Sulphates are predominant in South African AMD impacted freshwater ecosystems. In this study, the sensitivity of nymphs of the mayfly Adenophlebia auriculata (Ephemeroptera: Leptophlebiidae) was investigated by exposing the organisms to magnesium sulphate (MgSO4) and sodium sulphate (Na2SO4) as models of mining salinisation in short-term (96 h) and long-term (240 h) in static system tests. Short-term and long-term lethal concentrations of each salt were estimated using regression analyses. The results indicated that A. auriculata was more sensitive to MgSO4 (LC50 = 3.81 g/L) than Na2SO4 (LC50 = 8.78 g/L) after short-term exposures. However, this species became sensitive to Na2SO4 (LC10 = 0.19 g/L) but tolerant to MgSO4 (LC10 = 0.35 g/L) after long-term exposures. These results suggest that the 0.25 g/L sulphate compliance limit for South Africa is inadequate to protect A. auriculata from Na2SO4 toxicity in the long-term, yet it overprotects this species from MgSO4 exposures in the short-term. The findings of this study are an important major step in understanding the ecological effects of AMD to aquatic life.

  17. Photosynthetic capacity, nutrient status and growth of maize (Zea mays L. upon MgSO4 leaf-application

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    Mareike eJezek

    2015-01-01

    Full Text Available The major plant nutrient magnesium is involved in numerous physiological processes and its deficiency can severely reduce the yield and quality of crops. Since Mg availability in soil and uptake into the plant is often limited by unfavorable soil or climatic conditions, application of Mg onto leaves, the site with highest physiological Mg demand, might be a reasonable alternative fertilization strategy. This study aimed to investigate, if MgSO4 leaf-application in practically relevant amounts can efficiently alleviate the effects of Mg starvation in maize, namely reduced photosynthesis capacity, disturbed ion homeostasis and growth depression. Results clearly demonstrated that Mg deficiency could be mitigated by MgSO4 leaf-application as efficiently as by resupply of MgSO4 via the roots in vegetative maize plants. Significant increases in SPAD values and net rate of CO2-assimilation as well as enhanced shoot biomass have been achieved. Ion analysis furthermore revealed an improvement of the nutrient status of Mg-deficient plants with regard to [Mg], [K] and [Mn] in distinct organs, thereby reducing the risk of Mn-toxicity at the rootside, which often occurs together with Mg deficiency on acid soils. In conclusion, foliar fertilization with Mg proved to be an efficient strategy to adequately supply maize plants with magnesium and might hence be of practical relevance to correct nutrient deficiencies during the growing season.

  18. Photosynthetic capacity, nutrient status, and growth of maize (Zea mays L.) upon MgSO4 leaf-application.

    Science.gov (United States)

    Jezek, Mareike; Geilfus, Christoph-Martin; Bayer, Anne; Mühling, Karl-Hermann

    2014-01-01

    The major plant nutrient magnesium (Mg) is involved in numerous physiological processes and its deficiency can severely reduce the yield and quality of crops. Since Mg availability in soil and uptake into the plant is often limited by unfavorable soil or climatic conditions, application of Mg onto leaves, the site with highest physiological Mg demand, might be a reasonable alternative fertilization strategy. This study aimed to investigate, if MgSO4 leaf-application in practically relevant amounts can efficiently alleviate the effects of Mg starvation in maize, namely reduced photosynthesis capacity, disturbed ion homeostasis and growth depression. Results clearly demonstrated that Mg deficiency could be mitigated by MgSO4 leaf-application as efficiently as by resupply of MgSO4 via the roots in vegetative maize plants. Significant increases in SPAD values and net rate of CO2-assimilation as well as enhanced shoot biomass have been achieved. Ion analysis furthermore revealed an improvement of the nutrient status of Mg-deficient plants with regard to [Mg], [K], and [Mn] in distinct organs, thereby reducing the risk of Mn-toxicity at the rootside, which often occurs together with Mg deficiency on acid soils. In conclusion, foliar fertilization with Mg proved to be an efficient strategy to adequately supply maize plants with Mg and might hence be of practical relevance to correct nutrient deficiencies during the growing season.

  19. Supersaturation of Calcipotriene and Betamethasone Dipropionate in a Novel Aerosol Foam Formulation for Topical Treatment of Psoriasis Provides Enhanced Bioavailability of the Active Ingredients

    OpenAIRE

    2016-01-01

    Introduction Previous studies have demonstrated the superior efficacy of a novel aerosol foam formulation of fixed combination calcipotriene 0.005% (Cal) and betamethasone dipropionate 0.064% (BD), compared with the ointment formulation. The aim of this study is to ascertain whether enhanced bioavailability of the active ingredients due to supersaturation and/or occlusive properties can explain the observed greater clinical efficacy. Methods Solubility and evaporation experiments were conduct...

  20. Solubility measurement and solid-liquid equilibrium model for the ternary system MgBr2 + MgSO4 + H2O at 288.15 K

    Directory of Open Access Journals (Sweden)

    Li Dan

    2014-06-01

    Full Text Available The solubility of magnesium minerals and the refractive index of the ternary system MgBr2 + MgSO4 + H2O at 288.15 K were investigated using an isothermal dissolution method. It was found that there are two invariant points in the phase diagram and the solubility isotherm of this ternary system consists of three branches, corresponding to equilibrium crystallization of Epsomite (MgSO4·7H2O, Eps, hexahydrite (MgSO4·6H2O, Hex and magnesium bromide hexahydrate (MgBr2·6H2O, Mb. Neither solid solutions nor double salts were found. The refractive indices calculated from empirical equation are in good agreement with the experimental data. Combining the results from solubility measurements with the single-salt parameters for MgBr2 and MgSO4, and the mixed ion-interaction parameter θBr,S0(4, the parameter ψMg,Br,S0(4 at 288.15 K was fitted using the Pitzer theory and Harvie-Weare (HW approach. In addition, the average equilibrium constants of the stable equilibrium solids at 288.15 K were obtained by a method using the activity product constant. A chemical model, which combined the Pitzer parameters and the average equilibrium constants, was constructed to calculate the solid + liquid equilibria in the ternary system MgBr2 + MgSO4 + H2O at 288.15 K. The model agreed well with the equilibrium solubility data for the magnesium salts.

  1. Water uptake by biomass burning aerosol at sub- and supersaturated conditions: closure studies and implications for the role of organics

    Science.gov (United States)

    Dusek, U.; Frank, G. P.; Massling, A.; Zeromskiene, K.; Iinuma, Y.; Schmid, O.; Helas, G.; Hennig, T.; Wiedensohler, A.; Andreae, M. O.

    2011-09-01

    We investigate the CCN activity of freshly emitted biomass burning particles and their hygroscopic growth at a relative humidity (RH) of 85%. The particles were produced in the Mainz combustion laboratory by controlled burning of various wood types. The water uptake at sub- and supersaturations is parameterized by the hygroscopicity parameter, κ (c.f. Petters and Kreidenweis, 2007). For the wood burns, κ is low, generally around 0.06. The main emphasis of this study is a comparison of κ derived from measurements at sub- and supersaturated conditions (κG and κCCN), in order to see whether the water uptake at 85% RH can predict the CCN properties of the biomass burning particles. Differences in κGand κCCN can arise through solution non-idealities, the presence of slightly soluble or surface active compounds, or non-spherical particle shape. We find that κG and κCCN agree within experimental uncertainties (of around 30%) for particle sizes of 100 and 150 nm; only for 50 nm particles is κCCN larger than κG by a factor of 2. The magnitude of this difference and its dependence on particle size is consistent with the presence of surface active organic compounds. These compounds mainly facilitate the CCN activation of small particles, which form the most concentrated solution droplets at the point of activation. The 50 nm particles, however, are only activated at supersaturations higher than 1% and are therefore of minor importance as CCN in ambient clouds. By comparison with the actual chemical composition of the biomass burning particles, we estimate that the hygroscopicity of the water-soluble organic carbon (WSOC) fraction can be represented by a κWSOC value of approximately 0.2. The effective hygroscopicity of a typical wood burning particle can therefore be represented by a linear mixture of an inorganic component with κ ≅ 0.6, a WSOC component with κ ≅ 0.2, and an insoluble component with κ = 0.

  2. Water uptake by biomass burning aerosol at sub- and supersaturated conditions: closure studies and implications for the role of organics

    Directory of Open Access Journals (Sweden)

    U. Dusek

    2011-09-01

    Full Text Available We investigate the CCN activity of freshly emitted biomass burning particles and their hygroscopic growth at a relative humidity (RH of 85%. The particles were produced in the Mainz combustion laboratory by controlled burning of various wood types. The water uptake at sub- and supersaturations is parameterized by the hygroscopicity parameter, κ (c.f. Petters and Kreidenweis, 2007. For the wood burns, κ is low, generally around 0.06. The main emphasis of this study is a comparison of κ derived from measurements at sub- and supersaturated conditions (κG and κCCN, in order to see whether the water uptake at 85% RH can predict the CCN properties of the biomass burning particles. Differences in κGand κCCN can arise through solution non-idealities, the presence of slightly soluble or surface active compounds, or non-spherical particle shape. We find that κG and κCCN agree within experimental uncertainties (of around 30% for particle sizes of 100 and 150 nm; only for 50 nm particles is κCCN larger than κG by a factor of 2. The magnitude of this difference and its dependence on particle size is consistent with the presence of surface active organic compounds. These compounds mainly facilitate the CCN activation of small particles, which form the most concentrated solution droplets at the point of activation. The 50 nm particles, however, are only activated at supersaturations higher than 1% and are therefore of minor importance as CCN in ambient clouds. By comparison with the actual chemical composition of the biomass burning particles, we estimate that the hygroscopicity of the water-soluble organic carbon (WSOC fraction can be represented by a κWSOC value of approximately 0.2. The effective hygroscopicity of a typical wood burning particle can therefore be represented by a linear mixture of an inorganic component with κ ≅ 0.6, a WSOC

  3. A comparison of amorphous calcium carbonate crystallization in aqueous solutions of MgCl2 and MgSO4: implications for paleo-ocean chemistry

    Science.gov (United States)

    Han, Mei; Zhao, Yanyang; Zhao, Hui; Han, Zuozhen; Yan, Huaxiao; Sun, Bin; Meng, Ruirui; Zhuang, Dingxiang; Li, Dan; Liu, Binwei

    2017-07-01

    Based on the terminology of "aragonite seas" and "calcite seas", whether different Mg sources could affect the mineralogy of carbonate sediments at the same Mg/Ca ratio was explored, which was expected to provide a qualitative assessment of the chemistry of the paleo-ocean. In this work, amorphous calcium carbonate (ACC) was prepared by direct precipitation in anhydrous ethanol and used as a precursor to study crystallization processes in MgSO4 and MgCl2 solutions having different concentrations at 60 °C (reaction times 240 and 2880 min). Based on the morphology of the aragonite crystals, as well as mineral saturation indices and kinetic analysis of geochemical processes, it was found that these crystals formed with a spherulitic texture in 4 steps. First, ACC crystallized into columnar Mg calcite by nearly oriented attachment. Second, the Mg calcite changed from columnar shapes into smooth dumbbell forms. Third, the Mg calcite transformed into rough dumbbell or cauliflower-shaped aragonite forms by local dissolution and precipitation. Finally, the aragonite transformed further into spherulitic radial and irregular aggregate forms. The increase in Ca2+ in the MgSO4 solutions compared with the MgCl2 solutions indicates the fast dissolution and slow precipitation of ACC in the former solutions. The phase transition was more complete in the 0.005 M MgCl2 solution, whereas Mg calcite crystallized from the 0.005 M MgSO4 solution, indicating that Mg calcite could be formed more easily in an MgSO4 solution. Based on these findings, aragonite and Mg calcite relative to ACC could be used to provide a qualitative assessment of the chemistry of the paleo-ocean. Therefore, calcite seas relative to high-Mg calcite could reflect a low concentration MgSO4 paleo-ocean, while aragonite seas could be related to an MgCl2 or high concentration of MgSO4 paleo-ocean.

  4. Earliest use of initial prophylactic dose of magnesium sulphate (MgSO4 in severe pre-eclampsia to improve maternal and perinatal outcome, in a rural medical college, WB, India

    Directory of Open Access Journals (Sweden)

    Suresh Chandra Mondal

    2014-06-01

    Conclusions: Initial dose prophylactic magnesium sulphate (MgSO4 the earliest, can prevent both maternal perinatal maternal mortality. So, prophylactic magnesium sulphate (MgSO4 must be started at the first point of contact by trained health providers. [Int J Reprod Contracept Obstet Gynecol 2014; 3(3.000: 653-655

  5. Properties of CO2 clathrate hydrates formed in the presence of MgSO4 solutions with implications for icy moons

    Science.gov (United States)

    Safi, E.; Thompson, S. P.; Evans, A.; Day, S. J.; Murray, C. A.; Parker, J. E.; Baker, A. R.; Oliveira, J. M.; van Loon, J. Th.

    2017-04-01

    Context. There is evidence to suggest that clathrate hydrates have a significant effect on the surface geology of icy bodies in the solar system. However the aqueous environments believed to be present on these bodies are likely to be saline rather than pure water. Laboratory work to underpin the properties of clathrate hydrates in such environments is generally lacking. Aims: We aim to fill this gap by carrying out a laboratory investigation of the physical properties of CO2 clathrate hydrates produced in weak aqueous solutions of MgSO4. Methods: We use in situ synchrotron X-ray powder diffraction to investigate clathrate hydrates formed at high CO2 pressure in ice that has formed from aqueous solutions of MgSO4 with varying concentrations. We measure the thermal expansion, density and dissociation properties of the clathrates under temperature conditions similar to those on icy solar system bodies. Results: We find that the sulphate solution inhibits the formation of clathrates by lowering their dissociation temperatures. Hysteresis is found in the thermal expansion coefficients as the clathrates are cooled and heated; we attribute this to the presence of the salt in solution. We find the density derived from X-ray powder diffraction measurements is temperature and pressure dependent. When comparing the density of the CO2 clathrates to that of the solution in which they were formed, we conclude that they should sink in the oceans in which they form. We also find that the polymorph of ice present at low temperatures is Ih rather than the expected Ic, which we tentatively attribute to the presence of the MgSO4. Conclusions: We (1) conclude that the density of the clathrates has implications for their behaviour in satellite oceans as their sinking and floating capabilities are temperature and pressure dependent; (2) conclude that the presence of MgSO4 inhibits the formation of clathrates and in some cases may even affect their structure and (3) report the dominance of Ih throughout the experimental procedure despite Ic being the stable phase at low temperature.

  6. Effect of NaHCO3, MgSO4, Sodium Ascorbate, Sodium Glutamate, Phosphate Buffer on Survival of Lactobacillus bulgaricus During Freeze-drying

    Directory of Open Access Journals (Sweden)

    He Chen

    2013-06-01

    Full Text Available In the present study, the experiments were investigated the effects of different concentrations of cryoprotective agents, such as NaHCO3, MgSO4, sodium ascorbate, sodium glutamate, phosphate buffer, respectively, which used on survival of Lactobacillus bulgaricus during freeze drying. The number of viable cells and survival ratio were measured by the plate count method. The results were as follows: cryoprotective agents played important roles in survival of Lactobacillus bulgaricus during freeze drying. When the relative volume of phosphate buffer was 1.5 (v/v, the number of viable cells was highest, while the survival ratio reached highest, the concentration of sodium ascorbate was 4.5%.

  7. Conjugation of silica nanoparticles with cellulose acetate/polyethylene glycol 300 membrane for reverse osmosis using MgSO4 solution.

    Science.gov (United States)

    Sabir, Aneela; Shafiq, Muhammad; Islam, Atif; Jabeen, Faiza; Shafeeq, Amir; Ahmad, Adnan; Zahid Butt, Muhammad Taqi; Jacob, Karl I; Jamil, Tahir

    2016-01-20

    Thermally-induced phase separation (TIPS) method was used to synthesize polymer matrix (PM) membranes for reverse osmosis from cellulose acetate/polyethylene glycol (CA/PEG300) conjugated with silica nanoparticles (SNPs). Experimental data showed that the conjugation of SNPs changed the surface properties as dense and asymmetric composite structure. The results were explicitly determined by the permeability flux and salt rejection efficiency of the PM-SNPs membranes. The effect of SNPs conjugation on MgSO4 salt rejection was more significant in magnitude than on permeation flux i.e. 2.38 L/m(2)h. FTIR verified that SNPs were successfully conjugated on the surface of PM membrane. DSC of PM-SNPs shows an improved Tg from 76.2 to 101.8 °C for PM and PM-S4 respectively. Thermal stability of the PM-SNPs membranes was observed by TGA which was significantly enhanced with the conjugation of SNPs. The micrographs of SEM and AFM showed the morphological changes and increase in the valley and ridges on membrane surface. Experimental data showed that the PM-S4 (0.4 wt% SNPs) membrane has maximum salt rejection capacity and was selected as an optimal membrane.

  8. Isothermal equation of state and high-pressure phase transitions of synthetic meridianiite (MgSO4·11D2O) determined by neutron powder diffraction and quasielastic neutron spectroscopy

    Science.gov (United States)

    Fortes, A. Dominic; Fernandez-Alonso, Felix; Tucker, Matthew; Wood, Ian G.

    2017-01-01

    We have collected neutron powder diffraction data from MgSO4·11D2O (the deuterated analogue of meridianiite), a highly hydrated sulfate salt that is thought to be a candidate rock-forming mineral in some icy satellites of the outer solar system. Our measurements, made using the PEARL/HiPr and OSIRIS instruments at the ISIS neutron spallation source, covered the range 0.1 < P < 800 MPa and 150 < T < 280 K. The refined unit-cell volumes as a function of P and T are parameterized in the form of a Murnaghan integrated linear equation of state having a zero-pressure volume V 0 = 706.23 (8) Å3, zero-pressure bulk modulus K 0 = 19.9 (4) GPa and its first pressure derivative, K′ = 9 (1). The structure’s compressibility is highly anisotropic, as expected, with the three principal directions of the unit-strain tensor having compressibilities of 9.6 × 10−3, 3.4 × 10−2 and 3.4 × 10−3 GPa−1, the most compressible direction being perpendicular to the long axis of a discrete hexadecameric water cluster, (D2O)16. At high pressure we observed two different phase transitions. First, warming of MgSO4·11D2O at 545 MPa resulted in a change in the diffraction pattern at 275 K consistent with partial (peritectic) melting; quasielastic neutron spectra collected simultaneously evince the onset of the reorientational motion of D2O molecules with characteristic time-scales of 20–30 ps, longer than those found in bulk liquid water at the same temperature and commensurate with the lifetime of solvent-separated ion pairs in aqueous MgSO4. Second, at ∼ 0.9 GPa, 240 K, MgSO4·11D2O decomposed into high-pressure water ice phase VI and MgSO4·9D2O, a recently discovered phase that has hitherto only been formed at ambient pressure by quenching small droplets of MgSO4(aq) in liquid nitrogen. The fate of the high-pressure enneahydrate on further compression and warming is not clear from the neutron diffraction data, but its occurrence indicates that it may also be a rock-forming mineral in the deep mantles of large icy satellites.

  9. Anti-inflammation of MgSO4 on acute pulmonary hypertension%硫酸镁抗急性肺动脉高压的炎症机制

    Institute of Scientific and Technical Information of China (English)

    卢宏志; 高国芹; 李昨飞; 单冰竹

    2013-01-01

    Objective To investigate the effect and the anti-inflammatory mechanism of magnesium sulfate (MgSO4) on acute pulmonary hypertension.Methods 30 mongrel dogs were randomly divided into five groups:control group,surgical group,MgSO4 7.0 group,MgSO4 8.0 group,and MgSO4 9.0 group.The control group was not given any treatment,and the surgical group was operated to induce acute pulmonary hypertension,and the three MgSO4 groups were given MgSO4 to maintain intravenous concentration with 7.0 mmol/L,8.0 mmol/L,and 9.0 mmol/L respectively after acute pulmonary hypertension.The mean pulmonary artery pressure (MPAP) and circulation mean arterial pressure (MAP) were detected.Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in serum were measured by enzyme-linked immunosorbent assay and radioimmunoassay,monocyte chemoattractant protein-1 (MCP-1) expression in the lung tissue was determined by western blot.Results ①MPAP,TNF-α,IL-6,and MCP 1 protein expression were significantly higher in surgical group than those in control group,and were decreased significantly in MgSO4 7.0 group,MgSO4 8.0 group,and MgSO4 9.0 group with dose dependence.②MAP was significantly lower in surgical group than that in control group.MAP in MgSO4 7.0 group,MgSO4 8.0 group,and MgSO4 9.0 group was significantly increased compared with surgical group and MAP in MgSO4 9.0 group was the highest.Conclusions MgSO4 significantly reduces pulmonary hypertension,which is probably associated with reduction of the inflammatory response by inhibition of MCP-1 expression in lung tissue and decrease of TNF-α and IL-6 in serum.%目的 探讨硫酸镁(MgSO4)对急性肺栓塞肺动脉高压的影响及其抗炎机制.方法 30只雄性杂种犬,体质量(15±2.1) kg,随机分为5组:空白组、对照组以及MgSO47.0组、MgSO48.0组、MgSO4 9.0组,每组6只,其中空白组不给予任何处理;对照组造成急性肺动脉高压;其余三组造成急性肺动脉高压后给予MgSO4静滴,稳定30 min后,MgSO4 200 mg/kg静脉滴注0.5h,然后维持血MgSO4浓度分别为7.0 mmol/L、8.0 mmol/L以及9.0 mmol/L.肺动脉、股动脉插管检测平均肺动脉压(MPAP)、体循环平均动脉压(MAP),应用酶联免疫吸附以及放免法分别测定血清中白介素6(IL-6)和肿瘤坏死因子α(TNF-α),Western blot测定肺组织中单核细胞趋化蛋白-1(MCP-1)蛋白表达.结果 ①对照组MPAP较空白组显著升高(P<0.01),MgSO4 7.0组、MgSO48.0组以及MgSO49.0组MPAP较对照组显著下降(P<0.05或P<0.01),其中MgSO49.0组下降最明显;对照组MAP较空白组显著降低(P <0.05或P<0.01),MgSO4 7.0组、MgSO48.0组以及MgSO49.0组MAP较对照组显著升高(P <0.05或P<0.01),其中MgSO49.0组升高最明显.②对照组血清中TNF-α以及IL-6较空白组升高(P<0.05),MgSO4 7.0组、MgSO4 8.0组以及MgSO4 9.0组TNF-α以及IL-6较对照组显著下降(P<0.05或P<0.01),MgSO4 9.0组下降最明显;③对照组MCP-1蛋白表达较空白组显著升高(P<0.01),MgSO4 7.0组、MgSO4 8.0组以及MgSO49.0组MCP-1蛋白表达较对照组显著下降(P<0.01),MgSO49.0组蛋白表达最低.结论 MgSO4可显著降低肺动脉高压,这可能与其抑制肺组织MCP-1表达,降低TNF-α以及IL-6,从而抑制炎症反应增强有关.

  10. Method for the preparation of cellulose acetate flat sheet composite membranes for forward osmosis—Desalination using MgSO4 draw solution

    KAUST Repository

    Sairam, M.

    2011-06-01

    A lab scale method for the preparation of defect free flat sheet composite membranes for forward osmosis (FO) has been developed. Membranes containing a thin layer of cellulose acetate (CA) cast on a nylon fabric of 50μm thick were prepared by phase inversion in water. Cellulose acetate (CA) membranes with an overall thickness of 70-80μm have been prepared with lactic acid, maleic acid and zinc chloride as pore forming agents, at different annealing temperatures, for forward osmosis. These membranes have been tested in the desalination of saline feeds (35g·L-1 of NaCl) using magnesium sulphate solution (150g·L-1) as the draw solution. The water flux, and rejection of NaCl, were compared with those of commercially available membranes tested under the same FO conditions. The commercially available FO membrane from Hydration Technologies Inc, OR (M1) has a permeability of 0.13L·h-1·m-2·bar-1 with a NaCl rejection of 97% when tested with 150g·L-1 of MgSO4 in the draw solution. Another commercially available membrane for FO from Hydration Technologies Inc, OR, M2 has a water permeability of 0.014L·h-1·m-2·bar-1 with NaCl rejection of 100%. The flux and rejection of the CA membranes prepared in this work are found to be dependent on the nature of the pore forming agent, and annealing temperature. Impregnation of an inorganic filler, sodium montmorrillonite in CA membranes and coating of CA membranes with hydrophilic PVA did not enhance the flux of base CA membranes. Cellulose acetate membranes cast from dope solutions containing acetone/isopropanol and lactic acid, maleic acid and zinc chloride as pore forming agents have water permeabilities of 0.13, 0.09 and 0.68L·h-1·m-2·bar-1 respectively, with NaCl rejections of 97.7, 99.3 and 88% when annealed at 50°C. CA membranes prepared with zinc chloride as a pore forming agent have good permeability of 0.27L·h-1·m-2·bar-1 with a NaCl rejection of 95% when annealed at 70°C. © 2011.

  11. Study of the reversible water vapour sorption process of MgSO4.7H2O and MgCl2.6H2O under the conditions of seasonal solar heat storage

    Science.gov (United States)

    Ferchaud, C. J.; Zondag, H. A.; Veldhuis, J. B. J.; de Boer, R.

    2012-11-01

    The characterization of the structural, compositional and thermodynamic properties of MgSO4.7H2O and MgCl2.6H2O has been done using in-situ X-ray Diffraction and thermal analyses (TG/DSC) under practical conditions for seasonal heat storage (Tmax=150°C, p(H2O)=13 mbar). This study showed that these two materials release heat after a dehydration/hydration cycle with energy densities of 0.38 GJ/m3 for MgSO4.7H2O and 0.71 GJ/m3 MgCl2.6H2O. The low heat release found for MgSO4.7H2O is mainly attributed to the amorphization of the material during the dehydration performed at 13 mbar which reduces its sorption capacity during the rehydration. MgCl2.6H2O presents a high energy density which makes this material interesting for seasonal heat storage in domestic applications. This material would be able to fulfil the winter heat demand of a passive house estimated at 6 GJ with a packed bed reactor of 8.5 m3. However, a seasonal heat storage system built with this material should be carefully set with a restricted temperature at 40°C for the hydration reaction to avoid the liquefaction of the material at lower temperature which limits its performances for long term storage.

  12. Hydrothermal Synthesis and the Effect of Reaction Time on Morphology of MgSO4 · 5Mg(OH)2 · 3H2O%MgSO4·5Mg(OH)2·3H2O的水热合成及反应时间对其形貌的影响

    Institute of Scientific and Technical Information of China (English)

    朱黎霞; 岳涛; 高世扬; 夏树屏

    2003-01-01

    Both whisker and nanometer MgSO4 @ 5Mg(OH)2 @ 3H2O(MOS) were prepared by hydrothermal method at140℃ for different times, using NaOH and MgSO4 @ 7H2O as raw materials. The MgSO4 @ 5Mg(OH)2 @ 3H2O part-icles were characterized by powder X-ray diffraction(XRD), thermal analysis(TGA-DSC), infrared spectroscopy(FT-IR), transmission electron microscopy (SEM) and scanning electron microscopy (TEM). The size distribution inwhisker-like and nanocrystalline materials are in the range of 10~50μm and 10~20nm respectively. The whiskerMOS is metastable phase in MgSO4-NaOH-H2O system at 140℃, whereas nanometer MOS is stable phase.

  13. Experimental research of MgSO4 water soluble sand core hardened by twice microwave heating%二次微波加热制备硫酸镁水溶性砂芯试验研究

    Institute of Scientific and Technical Information of China (English)

    何家庆; 樊自田; 刘鑫旺; 刘富初

    2014-01-01

    Twice microwave heating technology was applied to harden MgSO4 water soluble sand core , and the effect of kaolin reinforcement on properties of the core was tested .The performance character-istics of the MgSO4 water soluble sand core were also analyzed and compared with sodium silicate sand hardened by twice microwave heating technology .Scanning electron microscope (SEM ) was used to investigate the micro-morphology of the MgSO4 water soluble sand core ,and the optimized water sol-uble sand core was applied to cast AZ91D alloy .The results indicate that the MgSO4 water soluble sand core hardened by twice microwave heating technology has advantages of high tensile strength , excellent surface stability ,good humidity resistance ,and high removability by collapsing in the wa-ter ,which has good application prospects .The SEM analysis demonstrates that with the addition of kaolin ,there are less cracks and holes in the binder bridge of the water soluble sand core ,and the mixed-mode fracture mechanism is instead of the cohesive fracture mechanism .%采用二次微波加热工艺制备硫酸镁水溶性砂芯,测试研究了增强剂高岭土对硫酸镁水溶性砂芯性能的影响,对比分析了二次微波加热制备的硫酸镁水溶性砂芯和二次微波硬化水玻璃砂的性能特征,通过扫描电子显微镜(SEM )分析了硫酸镁水溶性砂芯的微观形貌,采用优化配方的硫酸镁水溶性砂芯进行了AZ91D的浇铸试验.试验结果表明:二次微波加热制备的硫酸镁水溶性砂芯具有较高的抗拉强度、表面安定性和抗吸湿性,砂芯铸后的水溶溃散性良好,具有良好的应用前景.SEM分析结果表明:加入高岭土后水溶性砂芯粘结桥中的裂纹和孔隙减少,断裂方式由内聚断裂变成复合断裂.

  14. 气液两相流强化卷式纳滤膜分离硫酸镁水溶液%Enhancement of spiral nanofiltration membranes using gas sparging: application to MgSO4 solution

    Institute of Scientific and Technical Information of China (English)

    柳琦杰; 王枢; 郭竹洁; 谢成胜

    2012-01-01

    气液两相流强化卷式纳滤膜分离实验是针对DK2540卷式纳滤膜,采用气液两相流强化分离技术,对硫酸镁溶液进行研究,较系统地研究了温度、料液浓度、过膜压力、料液流速、气体流速等因素在分离硫酸镁溶液时,对膜通量、截留率和膜通量增加率的影响,并总结了气液两相流强化效果.结果表明,气液两相流强化卷式纳滤膜分离有明显的效果.温度宜在30~40℃.料液浓度越大、过膜压力越小、气液比越大,气液两相流强化效果越明显.%This study aims at the enhancement in nanofiltration process of aqueous solutions of inorganic salts and provides reference values for industrial application. Gas-sparged nanofiltration experiments with aqueous solution of MgSO4 were performed using a DK2540F element spiral nanofilitration membrane module. The permeate flux and the enhancement from gas sparging were measured in the following operation ranges; temperature 28-36℃,feed concentration 20-50 g o L-1 ,transmembrane pressure 0.4-0.7 MPa,air/liquid ratio 1.0-3.5,and air velocity 1.0-3.5 m o s-1 . The effects of different conditions on the permeate flux,rejection and increment rate of permeate flux of nanofiltration membrane were investigated. The experimental results show that gas sparging can significantly increase the permeate flux and rejection of MgSO4 aqueous solution,appropriate temperature is between 30℃ and 40℃ and feed concentration,transmembrane pressure,and air/liquid have profound effects on the permeate flux and rejection rate of MgSO4 aqueous solution,and the flux enhancement is more significant at higher feed concentration,lower transmembrane pressure,and higher air/liquid.

  15. Supersaturation in human gastric fluids.

    Science.gov (United States)

    Bevernage, Jan; Hens, Bart; Brouwers, Joachim; Tack, Jan; Annaert, Pieter; Augustijns, Patrick

    2012-05-01

    The current study reports on supersaturation, precipitation and excipient mediated precipitation inhibition of five poorly soluble drugs (loviride, glibenclamide, itraconazole, danazol, and etravirine) in human and simulated gastric fluids. Upon induction of supersaturation in human gastric fluids (HGFs), simulated gastric fluid (SGF), and fasted state simulated gastric fluid (FaSSGF) using a solvent shift method, supersaturation and precipitation were assessed as a function of time. In addition, the precipitation inhibitory capacity of three polymers (Eudragit® E PO, HPMC-E5, and PVP K25) was investigated. Supersaturation in human gastric fluids was observed for all model compounds, but proved to be relatively unstable (fast precipitation), except for itraconazole. Only modest excipient-mediated stabilizing effects on supersaturation were observed using HPMC-E5 and Eudragit® E PO whereas PVP K25 exerted no effect. In contrast to SGF, the observed precipitation behavior in FaSSGF was similar to the behavior in human gastric fluids. The present study demonstrates that supersaturation stability of drugs in human gastric fluids is in general inferior to supersaturation stability in intestinal fluids. As the potential for excipient mediated precipitation inhibition in gastric fluids was only limited, our data suggest that supersaturation should preferably be targeted to the intestine. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Ion Transport and All-Solid Battery Characterization Studies on Mg2+-ION Conducting Nano-Composite Polymer Electrolyte (NCPEs):. (75PEO: 25MgSO4) + x MgO

    Science.gov (United States)

    Agrawal, R. C.; Mahipal, Y. K.; Sahu, Dinesh; Keshrawani, Priyanka

    2013-07-01

    Characterization of ion transport property on Mg2+-ion conducting Nano Composite Polymer Electrolytes (NCPEs): (75PEO: 25MgSO4) + x MgO, where x = 0, 1, 2, 3, 4, 5, 6, 8, 10, 12 wt. (%) has been reported. Solid Polymer Electrolyte (SPE) composition: [75PEO: 25MgSO4)], identified as the highest conducting film in an earlier study with room temperature conductivity σ ˜ 3.38 × 10-7 S /cm, has been used as Ist-phase host matrix and active filler MgO particles (micro / nano-dimension) as IInd - phase dispersoid. NCPE films have been prepared by a novel hot-press technique in place of the traditional solution cast method. Hot-press technique is recently receiving wider acceptability to cast polymeric electrolyte films due to the fact that it is a completely dry/solvent free/rapid/inexpensive procedure as compared to solution cast method. The Optimum Conducting Composition (OCC) of NCPE film has been identified from the filler-dependent conductivity measurements. As a consequence of dispersal of nano-size particles, the room temperature conductivity (σ) in NCPE OCC film increased by an order of magnitude i.e. σ ˜ 2.29 × 10-6 Scm-1. The quality of the film also improved substantially. The total ionic transference number (tion) and the cationic (Mg2+) transport number (t+) have been determined using dc polarization and a combined ac/dc technique respectively. A considerable increase in t+ could be achieved with the dispersal of nanoparticles. The confirmation of the salt-complexation in PEO polymer was done by FTIR spectroscopic studies. The temperature dependent conductivity measurements were carried out in NCPE OCC film and the activation energy (Ea) has been computed from `log σ - 1/T' Arrhenius plot. All-solid-state battery has been fabricated in the cell configuration: Mg (anode) // NCPE OCC film// MnO2 + C + Electrolyte (cathode), in which both the cathode and anode were in the form of thin pellet. The Open Circuit Voltage (OCV) ˜ 1.82 V was obtained. The cell performance has been studied by recording the cell potential discharge profiles at room temperature under different load conditions.

  17. Observation of pH Value in Electrokinetic Remediation using various electrolyte (MgSO4, KH2PO4 and Na(NO3)) for Barren Acidic Soil at Ayer Hitam, Johor, Malaysia

    Science.gov (United States)

    Norashira, J.; Zaidi, E.; Aziman, M.; Saiful Azhar, A. T.

    2016-07-01

    Barren acidic soil collected at Ayer Hitam, Johor Malaysia was recorded at pH value of 2.36 with relative humidity of 86%. This pH value is not suitable for the growth of any plants especially for the soil stabilization purposes. Gradation weathering within the range of 4 to 6 indicates an incomplete/partial weathering process. The soil grade in this range is known as a black shale mudstone. Beside, this also influences to a factor of the high surface water runoff at this particular soil species. As the acidic pH become a major problem for soil fertilizing hence an appropriate technique was implemented known as using ‘Electrokinetic Remediation’, EKR. This technique has a great potential in changing the soil pH value from acidic to less acidic and also kept maintain the pH at the saturated rate of electrochemical process. This research study presents the monitoring data of pH value due to the effect of various electrolyte consist of 0.5M of MgSO4, KH2PO4, and Na(NO3). Here, the distilled water (DW) was used as reference solution. The electric field was provided by dipping two pieces of identical rectangular aluminum foil as anode and cathode. The EKR was conducted under a constant voltage gradient of 50 V/m across the sample bulk at 0.14 m length measured between both electrodes. The data collection was conducted during the total period of 7 days surveillance. The variation of pH values at the remediation area between anode and cathode for various type of electrolyte indicates that there are a significant saturated value as it reaches 7 days of treatment. During the analysis, it is found that the highest pH value at the remediation area after 7 days treatment using Na(NO3), KH2PO4 and MgSO4 was 3.93, 3.33 and 3.39 respectively. Hence from the last stage of pH value observation, it can be conclude that the best electrolyte for barren soil treatment is Na(NO3) whereby it contribute to highest pH value and turn the soil to be less acidic.

  18. CCN-supersaturation spectra slopes (k)

    Science.gov (United States)

    Jiusto, J. E.; Lala, G. G.

    1981-01-01

    Theoretically the slope k of a CCN-supesaturation spectrum should equal two thirds of the slope of the total (soluble) aerosol size distribution. Workshop results tended to verify this relation. The k values are markedly different depending on whether one is measuring ambient CCN concentrations at supersaturations S above or below approximately 0.1-0.2%. The larger k values for S approximately 0.1% is consistent with the greater decrease in large particle concentration with increasing size. It is concluded that over the S range of 0.02% to 2%, two power fits (and k values) may sometimes suffice for a reasonable approximation of the CCN distribution. At other times, and with laboratory generated aeosols, such an approach is inadequate and requires refinement.

  19. Studying the Propensity of Compounds to Supersaturate

    DEFF Research Database (Denmark)

    Palmelund, Henrik; Madsen, Cecilie Maria; Plum, Jakob;

    2016-01-01

    Supersaturating drug delivery systems can enhance the oral bioavailability of poorly soluble drug compounds. Supersaturation of such compounds has been studied in many different ways; however, a more standardized method is required. The rationale of choosing suitable concentrations of supersatura......Supersaturating drug delivery systems can enhance the oral bioavailability of poorly soluble drug compounds. Supersaturation of such compounds has been studied in many different ways; however, a more standardized method is required. The rationale of choosing suitable concentrations...... of supersaturation to study has previously been very inconsistent. This makes comparisons between studies and compounds difficult, as the propensity of compounds to supersaturate varies greatly. This study presents a standardized method to study the supersaturation of drug compounds. The method allows, both......, for a ranking of compounds according to their supersaturation propensity and the effectiveness of precipitation inhibitors. The time-concentration profile of supersaturation and precipitation was studied in situ for 4 different concentrations for 6 model compounds (albendazole, aprepitant, danazol, felodipine...

  20. SUPERSATURATED DESIGN WITH MORE THAN TWO LEVELS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Supersaturated designs are useful in screening experiments. This paper discusses the topic of multi-level supersaturated design. Two quantities, E(d2) and Df, are proposed to evaluate the optimality of supersaturated designs. A lower bound of E(d2) is obtained with a necessary condition for achieving it. Some E(d2)-optimal supersaturated designs of 3, 4, and 5 levels are given.

  1. Transient drug supersaturation kinetics of beclomethasone dipropionate in rapidly drying films.

    Science.gov (United States)

    Reid, Monica L; Jones, Stuart A; Brown, Marc B

    2009-04-17

    Supersaturation is an effective method to enhance the delivery of active compounds into the skin, however the long-term instability of the drug in these formulations that exceed thermodynamic unity prevents clinical use. The creation of supersaturation in situ by volatile solvent evaporation after application may overcome this. The aim of this study was to determine how altering the kinetics of transient supersaturation and recrystallisation would effect the rate of beclomethasone dipropionate (BDP) release from metered dose aerosols (MDA) that also consisted of hydrofluoroalkane 134a, ethanol (EtOH), and poly(vinyl pyrrolidone) (PVP) K90. An MDA containing 10% EtOH generated a sub-saturated concentration of BDP immediately after dose actuation and did not become supersaturated until 30 min post-actuation. Increasing the EtOH to 20% (w/w) and thus the BDP to 1.76% created supersaturation upon dose actuation but the drug recyrstallised within minutes of application. It was shown that the formulations with higher DS had accelerated rates of release despite rapid recrystallisation (444.9+/-79.3 microg/(cm2 h) for the fastest compared to 206.5+/-23.0 microg/(cm2 h) for the slowest). In highly volatile sprays maintaining BDP supersaturation for extended periods of time was less important than generating instantaneous, high levels of supersaturation to enhance drug release.

  2. Supersaturation in the Boolean lattice

    NARCIS (Netherlands)

    Dove, A.P.; Griggs, J.R.; Kang, Ross; Sereni, Jean-Sébastien

    2014-01-01

    We seek families of subsets of an n-set of given size that contain the fewest k-chains. We prove a “supersaturation-type” extension of both Sperner’s Theorem (1928) and its generalization by Erd˝os (1945). Erd˝os showed that a largest k-chain free family in the Boolean lattice is formed by taking

  3. Ice supersaturations exceeding 100% at the cold tropical tropopause: implications for cirrus formation and dehydration

    Directory of Open Access Journals (Sweden)

    E. J. Jensen

    2005-01-01

    Full Text Available Recent in situ measurements at tropical tropopause temperatures as low as 187 K indicate supersaturations with respect to ice exceeding 100% with little or no ice present. In contrast, models used to simulate cloud formation near the tropopause assume a supersaturation threshold for ice nucleation of about 65% based on laboratory measurements of aqueous aerosol freezing. The high supersaturations reported here, along with cloud simulations assuming a plausible range of temperature histories in the sampled air mass, indicate that the vast majority of aerosols in the air sampled on this flight must have had supersaturation thresholds for ice nucleation exceeding 100% (i.e. near liquid water saturation at these temperatures. Possible explanations for this high threshold are that (1 the expressions used for calculating vapor pressure over supercooled water at low temperatures give values are at least 20% too low, (2 organic films on the aerosol surfaces reduce their accommodation coefficient for uptake of water, resulting in aerosols with more concentrated solutions when moderate-rapid cooling occurs and correspondingly inhibited homogeneous freezing, and (3 if surface freezing dominates, organic coatings may increase the surface energy of the ice embryo/vapor interface resulting in suppressed ice nucleation. Simulations of in situ cloud formation in the tropical tropopause layer (TTL throughout the tropics indicate that if decreased accommodation coefficients and resulting high thresholds for ice nucleation prevailed throughout the tropics, then the calculated occurrence frequency and areal coverage of TTL cirrus would be significantly suppressed. However, the simulations also show that even if in situ TTL cirrus form only over a very small fraction of the tropics in the western Pacific, enough air passes through them due to rapid horizontal transport such that they can still effectively freeze-dry air entering the stratosphere. The TTL cirrus

  4. The global impact of supersaturation in a coupled chemistry-climate model

    Directory of Open Access Journals (Sweden)

    A. Gettelman

    2007-01-01

    Full Text Available Ice supersaturation is important for understanding condensation in the upper troposphere. Many general circulation models however do not permit supersaturation. In this study, a coupled chemistry climate model, the Whole Atmosphere Community Climate Model (WACCM, is modified to include supersaturation for the ice phase. Rather than a study of a detailed parameterization of supersaturation, the study is intended as a sensitivity experiment, to understand the potential impact of supersaturation, and of expected changes to stratospheric water vapor, on climate and chemistry. High clouds decrease and water vapor in the stratosphere increases at a similar rate to the prescribed supersaturation (20% supersaturation increases water vapor by nearly 20%. The stratospheric Brewer-Dobson circulation slows at high southern latitudes, consistent with slight changes in temperature likely induced by changes to cloud radiative forcing. The cloud changes also cause an increase in the seasonal cycle of near tropopause temperatures, increasing them in boreal summer over boreal winter. There are also impacts on chemistry, with small increases in ozone in the tropical lower stratosphere driven by enhanced production. The radiative impact of changing water vapor is dominated by the reduction in cloud forcing associated with fewer clouds (~+0.6 Wm−2 with a small component likely from the radiative effect (greenhouse trapping of the extra water vapor (~+0.2 Wm−2, consistent with previous work. Representing supersaturation is thus important, and changes to supersaturation resulting from changes in aerosol loading for example, might have a modest impact on global radiative forcing, mostly through changes to clouds. There is no evidence of a strong impact of water vapor on tropical tropopause temperatures.

  5. Ice supersaturations exceeding 100% at the cold tropical tropopause: implications for cirrus formation and dehydration

    Directory of Open Access Journals (Sweden)

    E. Jensen

    2004-11-01

    Full Text Available Recent in situ measurements at tropical tropopause temperatures as low as 187 K indicate supersaturations with respect to ice exceeding 100% with little or no ice present. In contrast, models used to simulate cloud formation near the tropopause assume a supersaturation threshold for ice nucleation of about 65% based on laboratory measurements of sulfate aerosol freezing. The high supersaturations reported here, along with cloud simulations assuming a plausible range of temperature histories in the sampled air mass, indicate that the vast majority of aerosols in the air sampled on this flight must have had supersaturation thresholds for ice nucleation exceeding 100% (i.e. near liquid water saturation at these temperatures. Possible explanations for this high threshold are that (1 the expressions used for calculating vapor pressure over supercooled water at low temperatures give values at least 20% too low, (2 most of the available aerosols had a composition that makes them much more resistant to ice nucleation than aerosols used in laboratory experiments, and (3 organic films on the aerosol surfaces reduce their accommodation coefficient for uptake of water, resulting in aerosols with more concentrated solutions when moderate-rapid cooling occurs and correspondingly inhibited homogeneous freezing. Simulations of in situ cloud formation in the tropical tropopause layer (TTL throughout the tropics indicate that if these decreased accommodation coefficients and resulting high thresholds for ice nucleation prevailed throughout the tropics, then the calculated occurrence frequency and areal coverage of TTL cirrus would be significantly suppressed. However, the simulations also show that even if in situ TTL cirrus form only over a very small fraction of the tropics in the western Pacific, enough air passes through them due to rapid horizontal transport such that they can still effectively freeze-dry air entering the stratosphere.

  6. On supersaturation evaluation for solution growth

    Science.gov (United States)

    Söhnel, O.; Garside, J.

    1981-08-01

    The relation between the thermodynamic driving force for crystallization and the relative supersaturation is considered. A method devised by Van Leeuwen and Blomen, J. Crystal Growth 46 (1979) 96, for converting growth rat constant derived using relative supersaturation into those based on the thermodynamic driving force is discussed, its range of utility assessed and illustrated for several substances.

  7. Evolution of supersaturation of amorphous pharmaceuticals: nonlinear rate of supersaturation generation regulated by matrix diffusion.

    Science.gov (United States)

    Sun, Dajun D; Lee, Ping I

    2015-04-06

    The importance of rate of supersaturation generation on the kinetic solubility profiles of amorphous systems has recently been shown by us; however, the previous focus was limited to constant rates of supersaturation generation. The objective of the current study is to further examine the effect of nonlinear rate profiles of supersaturation generation in amorphous systems, including (1) instantaneous or infinite rate (i.e., initial degree of supersaturation), (2) first-order rate (e.g., from dissolution of amorphous drug particles), and (3) matrix diffusion regulated rate (e.g., drug release from amorphous solid dispersions (ASDs) based on cross-linked poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels), on the kinetic solubility profiles of a model poorly soluble drug indomethacin (IND) under nonsink dissolution conditions. The previously established mechanistic model taking into consideration both the crystal growth and ripening processes was extended to predict the evolution of supersaturation resulting from nonlinear rates of supersaturation generation. Our results confirm that excessively high initial supersaturation or a rapid supersaturation generation leads to a surge in maximum supersaturation followed by a rapid decrease in drug concentration owing to supersaturation-induced precipitation; however, an exceedingly low degree of supersaturation or a slow rate of supersaturation generation does not sufficiently raise the supersaturation level, which results in a lower but broader maximum kinetic solubility profile. Our experimental data suggest that an optimal area-under-the-curve of the kinetic solubility profiles exists at an intermediate initial supersaturation level for the amorphous systems studied here, which agrees well with the predicted trend. Our model predictions also support our experimental findings that IND ASD in cross-linked PHEMA exhibits a unique kinetic solubility profile because the resulting supersaturation level is governed by a matrix

  8. Solid-liquid stable phase equilibria of the ternary systems MgCl2 + MgB6O10+ H2O AND MgSO4 + MgB6O10 + H2O at 308.15 K

    Directory of Open Access Journals (Sweden)

    Lingzong Meng

    2014-03-01

    Full Text Available The solubilities and the relevant physicochemical properties of the ternary systems MgCl2 + MgB6O10 + H2O and MgSO4 + MgB6O10 + H2O at 308.15 K were investigated using an isothermal dissolution method. It was found that there is one invariant point, two univariant curves, and two crystallization regions of the systems. The systems belong to a simple co-saturated type, and neither double salts nor solid solutions were found. Based on the extended HW model and its temperature-dependent equations, the single-salt Pitzer parameters β(0, β(1, β(2 and CØ for MgCl2, MgSO4, and Mg(B6O7(OH6, the mixed ion-interaction parameters θCl,B6O10, θSO4,B6O10, ΨMg,Cl,B6O10, ΨMg,SO4,B6O10 of the systems at 308.15 K were fitted, In addition, the average equilibrium constants of the stable equilibrium solids at 308.15 K were obtained by a method using the activity product constant. Then the solubilities of the ternary systems are calculated. The calculated solubilities agree well with the experimental values.

  9. Micro-Raman studies on the kinetics of the exchange between H2O and D2O of MgSO4 droplets%硫酸镁微液滴水和重水交换动力学的微区拉曼研究

    Institute of Scientific and Technical Information of China (English)

    李开开; 曾光; 郭郁葱; 张韫宏

    2011-01-01

    本文利用微区拉曼技术,研究硫酸镁液滴水和重水交换的动力学.在低湿度时,由接触离子对连接形成的链状结构使硫酸镁液滴表面形成胶态结构,阻碍其与环境之间的水交换,造成表面和内部的结构差异.拉曼光谱的高空间分辨能力为观测这一特殊的表面结构提供了便利.沉积在聚四氟乙烯疏水基底上的硫酸镁重水液滴呈球形,可以实现对液滴表面和中心的两次聚焦,为研究水从液滴表面逐步扩散到中心的动力学过程提供了可能.同时,利用拉曼光谱的时间分辨能力,可以观测硫酸镁微液滴中水和重水的交换过程,从而揭示传质受阻硫酸镁液滴中水的扩散机制.%In this paper, we will reveal the kinetics of evaporation of MgSO4/D2O droplets and the exchange between H2O and D2O in the mass transfer-limited MgSO4 droplets by micro-Raman spectroscopy. The gel layer causes a delay of the droplet in response to the change of ambient relative humidity, and results in the structural difference between the surface and the centre of MgSO4 droplets. Micro-Raman technique provides a good approach for detecting the surface structure in virtue of its high spatial resolution. In particular, as droplets are likely to maintain a spherical shape on a hydrophobic Teflon substrate, the laser beam can be tightly focused twice on the surface and in the center of the typically spherical droplets, thus the Raman spectra of the surface and the centre of the droplet can be obtained respectively and the diffusion of water in the droplet can be monitored. On the other hand, with an accumulation time of less than one second in a static mode, micro-Raman spectra of droplets can be obtained with high signal-to-noise ratio. The temporal scale allows the observation on the exchange of H2O and D2O in MgSO4 droplets with a slow exchanging rate, which is critical to understand the kinetics of the e-vaporation and condensation of water in mass transfer-limited MgSO4 droplet.

  10. Uniform supersaturated design and its construction

    Institute of Scientific and Technical Information of China (English)

    方开泰; 葛根年; 刘民千

    2002-01-01

    Supersaturated designs are factorial designs in which the number of main effects is greater than the number of experimental runs. In this paper, a discrete discrepancy is proposed as a measure of uniformity for supersaturated designs, and a lower bound of this discrepancy is obtained asa benchmark of design uniformity. A construction method for uniform supersaturated designs via resolvable balanced incomplete block designs is also presented along with the investigation of properties of the resulting designs. The construction method shows a strong link between these two different kinds of designs.

  11. Can Supersaturation Affect Protein Crystal Quality?

    Science.gov (United States)

    Gorti, Sridhar

    2013-01-01

    In quiescent environments (microgravity, capillary tubes, gels) formation of a depletion zone is to be expected, due either to limited sedimentation, density driven convection or a combination of both. The formation of a depletion zone can: Modify solution supersaturation near crystal; Give rise to impurity partitioning. It is conjectured that both supersaturation and impurity partitioning affect protein crystal quality and size. Further detailed investigations on various proteins are needed to assess above hypothesis.

  12. Effect of Different Concentration of MgSO4 and KH2PO4 on Biomass of Shiitake Liquid Culture%不同浓度MgSO4和KH2PO4对香菇液体培养生长量的影响

    Institute of Scientific and Technical Information of China (English)

    康健; 王海华; 左斌; 吴辉群

    2001-01-01

    本文研究了MgSO4、KH2PO4二种无机物与香菇Cr-02液体发酵生长量的关系。结果证明:在27℃摇床转速为134r/min的培养条件下,MgSO4浓度0 .05%,KH2PO4浓度为0.10%,发酵96h香菇生长量最大,发酵液透光率T在630nm波长时达135.8%,其湿菌体产量32.6g/100mL,发酵液由深褐色变成黄色、粘度大、透明,菌丝体个体较大且数目较多%In this paper we study the relationship between MgSO4,KH2P O4 and biomass of shiitake.The results reveal that the biomass of shiitake is the largest after fermented for 96h on condition that the temperature is at 27℃ ,the shaker rotation speed is at 134 r/mim,the concentration of MgSO4 is 0.05 %,that of KH2PO4 is 0.01%.The transmittance of the fermentation solution is 135.8%.When the wavelengh is 630nm and the yield of wet somatic is 32.6g/100m L,the fermentation solution turns light yellow,which is transparent,the body of myc elium pellet is a bit large and the number of mycelium pellet is a bit large too .

  13. Persistent Ice Supersaturation in Tropical Anvil Cirrus

    Science.gov (United States)

    Jensen, E.; Fridlind, A.; Ackerman, A.; Pfister, L.; Herman, R.; Bui, T.; Baumgardner, D.; Lawson, P.

    2003-12-01

    During the 2002 Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE), the NASA WB-57 spent many hours sampling cloud microphysical properties, temperature, turbulence, and water vapor concentration within subtropical anvil cirrus. These measurements indicate that air within the cirrus is often substantially supersaturated with respect to ice, with average ice supersaturations increasing from about 5 to 30% as cloud temperature decreases from 220 to 195 K. The persistence of large supersaturations in cirrus with high ice crystal surface areas is unexpected. In this study, we examine the dependence of the measured anvil supersaturations on parameters such as ice water content, turbulence, anvil age, and temperature. We also use a three-dimensional cloud model that resolves the size distributions of cloud particles to investigate the physical processes responsible for the maintenance of ice supersaturation in anvils. The effects of radiatively driven turbulence, wave-driven temperature oscillations, and entrainment of ambient air will be discussed.

  14. Dynamical characteristics of ice supersaturated regions

    Directory of Open Access Journals (Sweden)

    K. Gierens

    2012-12-01

    Full Text Available The typical distributions of dynamical fields within ice supersaturated regions are investigated. The dynamical fields divergence, relative vorticity, and vertical velocity are analysed statistically in two ways, namely using the unconditioned data and data conditioned on the presence of ice supersaturation. Two geographical regions are considered, namely Europe (250 hPa level and the tropical belt from 30° S to 30° N on two pressure levels (200 and 150 hPa. The study is based on forecast data from the European Centre for Medium-Range Weather Forecasts for four months covering the four seasons, June, September, December 2011 and March 2012. We find that histograms (frequency distributions and low order moments of the dynamical fields differ substantially and statistically significantly inside and outside of ice supersaturated regions. As expected, upward and divergent flow favours ice supersaturation. But we find also that ice supersaturation is mostly located in anti-cyclonic flow. The latter result is probably due to the structure of warm/moist and cold/dry air streams in synoptic disturbances in mid-latitudes, but probably merely coincidental in the tropical belt.

  15. Dynamical characteristics of ice supersaturated regions

    Directory of Open Access Journals (Sweden)

    K. Gierens

    2012-08-01

    Full Text Available The typical distributions of dynamical fields within ice supersaturated regions are investigated. The dynamical fields divergence, relative vorticity, and vertical velocity are analysed statistically in two ways, namely using the unconditioned data and data conditioned on the presence of ice supersaturation. Two geographical regions are considered, namely Europe (250 hPa level and the tropical belt from 30° S to 30° N on two pressure levels (200 and 150 hPa. The study is based on forecast data from the European Centre for Medium-Range Weather Forecasts for March 2012 solely. We find that histograms (frequency distributions and low order moments of the dynamical fields differ substantially and statistically significantly inside and outside of ice supersaturated regions. As expected, upward and divergent flow favours ice supersaturation. But we find also that ice supersaturation is mostly located in anti-cyclonic flow. The latter result is probably due to the structure of warm/moist and cold/dry air streams in synoptic disturbances in mid-latitudes, but probably merely coincidental in the tropical belt.

  16. Evolution of supersaturation of amorphous pharmaceuticals: the effect of rate of supersaturation generation.

    Science.gov (United States)

    Sun, Dajun D; Lee, Ping I

    2013-11-04

    The combination of a rapidly dissolving and supersaturating "spring" with a precipitation retarding "parachute" has often been pursued as an effective formulation strategy for amorphous solid dispersions (ASDs) to enhance the rate and extent of oral absorption. However, the interplay between these two rate processes in achieving and maintaining supersaturation remains inadequately understood, and the effect of rate of supersaturation buildup on the overall time evolution of supersaturation during the dissolution of amorphous solids has not been explored. The objective of this study is to investigate the effect of supersaturation generation rate on the resulting kinetic solubility profiles of amorphous pharmaceuticals and to delineate the evolution of supersaturation from a mechanistic viewpoint. Experimental concentration-time curves under varying rates of supersaturation generation and recrystallization for model drugs, indomethacin (IND), naproxen (NAP) and piroxicam (PIR), were generated from infusing dissolved drug (e.g., in ethanol) into the dissolution medium and compared with that predicted from a comprehensive mechanistic model based on the classical nucleation theory taking into account both the particle growth and ripening processes. In the absence of any dissolved polymer to inhibit drug precipitation, both our experimental and predicted results show that the maximum achievable supersaturation (i.e., kinetic solubility) of the amorphous solids increases, the time to reach maximum decreases, and the rate of concentration decline in the de-supersaturation phase increases, with increasing rate of supersaturation generation (i.e., dissolution rate). Our mechanistic model also predicts the existence of an optimal supersaturation rate which maximizes the area under the curve (AUC) of the kinetic solubility concentration-time profile, which agrees well with experimental data. In the presence of a dissolved polymer from ASD dissolution, these observed trends

  17. Supersaturation of vertically propagating internal gravity waves

    Science.gov (United States)

    Lindzen, Richard S.

    1988-01-01

    The usual assumption that vertically propagating internal gravity waves will cease growing with height once their amplitudes are such as to permit convective instability anywhere within the wave is reexamined. Two factors lead to amplitude limitation: (1) wave clipping associated with convective mixing, and (2) energetic constraints associated with the rate at which the wave can supply energy to the convection. It is found that these two factors limit supersaturation to about 50 percent for waves with short horizontal wavelengths and high relative phase speeds. Usually the degree of supersaturation will be much less. These factors also lead to a gradual, rather than sudden, cessation of wave growth with height.

  18. Implications of Observed High Supersaturation for TTL Cloud Formation and Dehydration

    Science.gov (United States)

    Jensen, Eric

    2004-01-01

    In situ measurements of water vapor concentration made during the CRYSTAL-FACE and Pre-AVE missions indicate higher than expected supersaturations in both clear and cloudy air near the cold tropical tropopause: (1) steady-state ice supersaturations of 20-30% were measured within cirrus at T supersaturations exceeding 100% (near water saturation) were observed under cloud-free conditions near 187 K. The in-cloud measurements challenge the conventional belief that any water vapor in excess of ice saturation should be depleted by crystal growth given sufficient time. The high clear-sky supersaturations imply that thresholds for ice nucleation due to homogeneous freezing of aerosols (or any other mechanism) are much higher than those inferred from laboratory measurements. We will use simulations of Tropical Tropopause Layer (TTL) transport and cloud formation throughout the tropics to show that these effects have important implications for TTL cloud frequency and freeze-drying of air crossing the tropical tropopause cold trap.

  19. Maintenance of supersaturation II: indomethacin crystal growth kinetics versus degree of supersaturation.

    Science.gov (United States)

    Patel, Dhaval D; Anderson, Bradley D

    2013-05-01

    This study compares the kinetics of crystal growth of indomethacin from supersaturated suspensions at varying degrees of supersaturation (2 ≤ S ≥ 9) in the presence of seed crystals of the γ-form of indomethacin, the lowest energy polymorph. At high S (6 ≤ S ≥ 9), the crystal growth was first order with rate coefficients (kG ) that were nearly constant and consistent with the value predicted for bulk-diffusion control. At lower S (supersaturation suggesting that a higher energy surface layer was deposited on the γ-form seed crystals during crystal growth. When growth experiments were repeated at low S in the presence of indomethacin seed crystals isolated from a previous crystal growth experiment (i.e., seed crystals having higher energy surface), kG matched the higher values observed for bulk diffusion-controlled crystal growth. Crystal growth experiments were also conducted at S supersaturation during oral absorption. Copyright © 2013 Wiley Periodicals, Inc.

  20. Aerosol Observing System (AOS) Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Jefferson, A

    2011-01-17

    The Aerosol Observing System (AOS) is a suite of in situ surface measurements of aerosol optical and cloud-forming properties. The instruments measure aerosol properties that influence the earth’s radiative balance. The primary optical measurements are those of the aerosol scattering and absorption coefficients as a function of particle size and radiation wavelength and cloud condensation nuclei (CCN) measurements as a function of percent supersaturation. Additional measurements include those of the particle number concentration and scattering hygroscopic growth. Aerosol optical measurements are useful for calculating parameters used in radiative forcing calculations such as the aerosol single-scattering albedo, asymmetry parameter, mass scattering efficiency, and hygroscopic growth. CCN measurements are important in cloud microphysical models to predict droplet formation.

  1. Experimental study on total dissolved gas supersaturation in water

    Directory of Open Access Journals (Sweden)

    Lu QU

    2011-12-01

    Full Text Available More and more high dams have been constructed and operated in China. The total dissolved gas (TDG supersaturation caused by dam discharge leads to gas bubble disease or even death of fish. Through a series of experiments, the conditions and requirements of supersaturated TDG generation were examined in this study. The results show that pressure (water depth, aeration, and bubble dissolution time are required for supersaturated TDG generation, and the air-water contact area and turbulence intensity are the main factors that affect the generation rate of supersaturated TDG. The TDG supersaturation levels can be reduced by discharging water to shallow shoals downstream of the dam or using negative pressure pipelines. Furthermore, the TDG supersaturation levels in stilling basins have no direct relationship with those in reservoirs. These results are of great importance for further research on the prediction of supersaturated TDG generation caused by dam discharge and aquatic protection.

  2. Study on conductance of supersaturated chloride microdroplets

    Institute of Scientific and Technical Information of China (English)

    HE KeJuan; CHENG Hua; ZHU YanYing; WANG LiangYu; ZHANG YunHong

    2009-01-01

    By using the measuring system previously designed by the authors,the conductance of KCI,NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range,especially in the supersaturation region,which cannot be acquired from the bulk solutions and fills the gap of lack of experimental data of conductance under the supersaturated state.The ERH and DRH of these three kinds of microdroplets observed from a microscope are 80.5% and 95.4% (KCI),75.7% and 93.3% (NaCl),and 69.9% and 96.6% (NH4Cl),respectively.In addition,it can be found from the dependence of conductance on RH that conductance is very sensitive to the existence of water molecules inside the microdroplet and the threshold of the deliquescence process can be predicted by the variation of conductance.

  3. Study on conductance of supersaturated chloride microdroplets

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    By using the measuring system previously designed by the authors, the conductance of KCl, NaCl and NH4Cl microdroplets is obtained in the whole measuring RH range, especially in the supersaturation region, which cannot be acquired from the bulk solutions and fills the gap of lack of experimental data of conductance under the supersaturated state. The ERH and DRH of these three kinds of microdroplets observed from a microscope are 80.5% and 95.4% (KCl), 75.7% and 93.3% (NaCl), and 69.9% and 96.6% (NH4Cl), respectively. In addition, it can be found from the dependence of conductance on RH that conductance is very sensitive to the existence of water molecules inside the microdroplet and the threshold of the deliquescence process can be predicted by the variation of conductance.

  4. Decomposition of supersaturated sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    陈启元; 李洁; 尹周澜; 张平民

    2003-01-01

    The decomposition of supersaturated sodium aluminate solution in the process of alumina production was reviewed. Some fundamental problems, such as the structure of supersaturated sodium aluminate solution and the growth unit of gibbsite precipitation as well as the decomposition mechanism of sodium aluminate solution, were investigated by model analytic technique and theoretical calculation. It is found that the main Al-contained species is S4 symmetric [Al(OH)4(H2O)4]-. [Na+(H2O)4*Al(OH)-4] is found to form in intermediate concentrated solution while [Na+(H2O)2*Al(OH)-4] in highly concentrated solution. Meanwhile, it is proved that [(H2O)2Al(OH)4]- is the basic growth unit of gibbsite and [Al6(OH)18(H2O)6] is a favorable growth unit. Based on above results and ab initio quantum mechanical calculation and transition state theory, a reaction pathway of the decomposition of supersaturated sodium aluminate solution was put forward, in which the transformation of pentacoordinate aluminates ion to hexacoordinate basic growth unit as well as the formation of circled growth unit [Al6(OH)22(H2O)2]4- are the controlling steps.

  5. Impact of Micellar Surfactant on Supersaturation and Insight into Solubilization Mechanisms in Supersaturated Solutions of Atazanavir.

    Science.gov (United States)

    Indulkar, Anura S; Mo, Huaping; Gao, Yi; Raina, Shweta A; Zhang, Geoff G Z; Taylor, Lynne S

    2017-06-01

    The goals of this study were to determine: 1) the impact of surfactants on the "amorphous solubility"; 2) the thermodynamic supersaturation in the presence of surfactant micelles; 3) the mechanism of solute solubilization by surfactant micelles in supersaturated solutions. The crystalline and amorphous solubility of atazanavir was determined in the presence of varying concentrations of micellar sodium dodecyl sulfate (SDS). Flux measurements, using a side-by-side diffusion cell, were employed to determine the free and micellar-bound drug concentrations. The solubilization mechanism as a function of atazanavir concentration was probed using fluorescence spectroscopy. Pulsed gradient spin-echo proton nuclear magnetic resonance (PGSE-NMR) spectroscopy was used to determine the change in micelle size with a change in drug concentration. Changes in the micelle/water partition coefficient, K m/w , as a function of atazanavir concentration led to erroneous estimates of the supersaturation when using concentration ratios. In contrast, determining the free drug concentration using flux measurements enabled improved determination of the thermodynamic supersaturation in the presence of micelles. Fluorescence spectroscopic studies suggested that K m/w changed based on the location of atazanavir solubilization which in turn changed with concentration. Thus, at a concentration equivalent to the crystalline solubility, atazanavir is solubilized by adsorption at the micelle corona, whereas in highly supersaturated solutions it is also solubilized in the micellar core. This difference in solubilization mechanism can lead to a breakdown in the prediction of amorphous solubility in the presence of SDS as well as challenges with determining supersaturation. PGSE-NMR suggested that the size of the SDS micelle is not impacted at the crystalline solubility of the drug but increases when the drug concentration reaches the amorphous solubility, in agreement with the proposed changes in

  6. Shallow cirrus convection – a source for ice supersaturation

    Directory of Open Access Journals (Sweden)

    Peter Spichtinger

    2014-09-01

    Full Text Available The origin and persistence of high ice supersaturation is still not well understood. In this study, the impact of local dynamics as source for ice supersaturation inside cirrus clouds is investigated. Nucleation and growth of ice crystals inside potentially unstable layers in the tropopause region might lead to shallow convection inside (layered cirrus clouds due to latent heat release. The intrinsic updraught inside convective cells constitutes a dominant but transient source for ice supersaturation. A realistic case of shallow cirrus convection is investigated using radiosonde data, meteorological analyses and large-eddy simulations of cirrus clouds. The simulations corroborate the existence of ice supersaturation inside cirrus clouds as a transient phenomenon. Ice supersaturation is frequent, but determined by the life cycle of convective cells in shallow cirrus convection. Cirrus clouds driven by shallow cirrus convection are mostly not in thermodynamic equilibrium; they are usually in a subsaturated or supersaturated state.

  7. Response of cloud supersaturation to radiative forcing

    Science.gov (United States)

    Davies, R.

    1985-01-01

    Time-dependent solutions are obtained for droplet temperatures and supersaturation, in a study of the diffusional growth or evaporation of cloud droplets due to net emission or absorption of radiation, taking into account the partitioning of the net radiation budget between the droplets and the ambient air. Radiative perturbations are noted to result in very high rates of change in droplet temperatures. As the droplets evaporate or grow due to radiative effects, the saturation ratio of the ambient air adjusts in keeping with changes in the water vapor density and temperature of the air.

  8. Construction, Analysis, and Data-Driven Augmentation of Supersaturated Designs

    Science.gov (United States)

    2013-09-01

    CONSTRUCTION, ANALYSIS, AND DATA-DRIVEN AUGMENTATION OF SUPERSATURATED DESIGNS DISSERTATION Alex J. Gutman, AFIT-ENC-DS-13-S-02 DEPARTMENT OF THE AIR...DRIVEN AUGMENTATION OF SUPERSATURATED DESIGNS DISSERTATION Presented to the Faculty Graduate School of Engineering and Management Air Force Institute...13-S-02 CONSTRUCTION, ANALYSIS, AND DATA-DRIVEN AUGMENTATION OF SUPERSATURATED DESIGNS Alex J. Gutman, BS, MS Approved: //signed// September 2013

  9. Can Solution Supersaturation Affect Protein Crystal Quality?

    Science.gov (United States)

    Gorti, Sridhar

    2013-01-01

    The formation of large protein crystals of "high quality" is considered a characteristic manifestation of microgravity. The physical processes that predict the formation of large, high quality protein crystals in the microgravity environment of space are considered rooted in the existence of a "depletion zone" in the vicinity of crystal. Namely, it is considered reasonable that crystal quality suffers in earth-grown crystals as a result of the incorporation of large aggregates, micro-crystals and/or large molecular weight "impurities", processes which are aided by density driven convective flow or mixing at the crystal-liquid interface. Sedimentation and density driven convection produce unfavorable solution conditions in the vicinity of the crystal surface, which promotes rapid crystal growth to the detriment of crystal size and quality. In this effort, we shall further present the hypothesis that the solution supersaturatoin at the crystal surface determines the growth mechanism, or mode, by which protein crystals grow. It is further hypothesized that protein crystal quality is affected by the mechanism or mode of crystal growth. Hence the formation of a depletion zone in microgravity environment is beneficial due to inhibition of impurity incorporatoin as well as preventing a kinetic roughening transition. It should be noted that for many proteins the magnitude of neither protein crystal growth rates nor solution supersaturation are predictors of a kinetic roughening transition. That is, the kinetic roughening transition supersaturation must be dtermined for each individual protein.

  10. RACORO aerosol data processing

    Energy Technology Data Exchange (ETDEWEB)

    Elisabeth Andrews

    2011-10-31

    The RACORO aerosol data (cloud condensation nuclei (CCN), condensation nuclei (CN) and aerosol size distributions) need further processing to be useful for model evaluation (e.g., GCM droplet nucleation parameterizations) and other investigations. These tasks include: (1) Identification and flagging of 'splash' contaminated Twin Otter aerosol data. (2) Calculation of actual supersaturation (SS) values in the two CCN columns flown on the Twin Otter. (3) Interpolation of CCN spectra from SGP and Twin Otter to 0.2% SS. (4) Process data for spatial variability studies. (5) Provide calculated light scattering from measured aerosol size distributions. Below we first briefly describe the measurements and then describe the results of several data processing tasks that which have been completed, paving the way for the scientific analyses for which the campaign was designed. The end result of this research will be several aerosol data sets which can be used to achieve some of the goals of the RACORO mission including the enhanced understanding of cloud-aerosol interactions and improved cloud simulations in climate models.

  11. A 6-year global climatology of occurrence of upper-tropospheric ice supersaturation inferred from the Atmospheric Infrared Sounder after synergetic calibration with MOZAIC

    Directory of Open Access Journals (Sweden)

    N. Lamquin

    2011-04-01

    Full Text Available Ice supersaturation in the upper troposphere is a complex and important issue for the understanding of cirrus cloud formation. Infrared sounders have the ability to provide cloud properties and atmospheric profiles of temperature and humidity. On the other hand, they suffer from coarse vertical resolution, especially in the upper troposphere and therefore are unable to detect shallow ice supersaturated layers. We have used data from the Measurements of OZone and water vapour by AIrbus in-service airCraft experiment (MOZAIC in combination with Atmospheric InfraRed Sounder (AIRS relative humidity measurements and cloud properties to develop a calibration method for an estimation of occurrence frequencies of ice supersaturation. This method first determines the occurrence probability of ice supersaturation, detected by MOZAIC, as a function of the relative humidity determined by AIRS. The occurrence probability function is then applied to AIRS data, independently of the MOZAIC data, to provide a global climatology of upper-tropospheric ice supersaturation occurrence. Our climatology is then related to high cloud occurrence from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP and compared to ice supersaturation occurrence statistics from MOZAIC alone. Finally it is compared to model climatologies of ice supersaturation from the Integrated Forecast System (IFS of the European Centre for Medium-Range Weather Forecasts (ECMWF and from the European Centre HAmburg Model (ECHAM. All the comparisons show good agreements when considering the limitations of each instrument and model. This study highlights the benefits of multi-instrumental synergies for the investigation of upper tropospheric ice supersaturation.

  12. An automatic system for crystal growth studies at constant supersaturation

    Science.gov (United States)

    March, J. G.; Costa-Bauzá, A.; Grases, F.; Söhnel, O.

    1992-01-01

    An automatic system for growing crystals from seeded supersaturated solutions at constant supersaturation is described. Control of burettes and data acquisition are controlled by computer. The system was tested with a study of the calcium oxalate kinetics of crystal growth. PMID:18924950

  13. Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions.

    Science.gov (United States)

    Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A; Yang, Fan

    2016-12-13

    The influence of aerosol concentration on the cloud-droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud-droplet growth and fallout. As aerosol concentration is increased, the cloud-droplet mean diameter decreases, as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics ([Formula: see text]) for high aerosol concentration, and slow microphysics ([Formula: see text]) for low aerosol concentration; here, [Formula: see text] is the phase-relaxation time and [Formula: see text] is the turbulence-correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as [Formula: see text], and the measurements are in excellent agreement with this finding. The result underscores the importance of droplet size dispersion for aerosol indirect effects: increasing aerosol concentration changes the albedo and suppresses precipitation formation not only through reduction of the mean droplet diameter but also by narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol/slow microphysics limit are likely of leading importance for precipitation formation.

  14. Thermodynamics of supersaturated steam: Molecular simulation results

    Science.gov (United States)

    Moučka, Filip; Nezbeda, Ivo

    2016-12-01

    Supersaturated steam modeled by the Gaussian charge polarizable model [P. Paricaud, M. Předota, and A. A. Chialvo, J. Chem. Phys. 122, 244511 (2005)] and BK3 model [P. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)] has been simulated at conditions occurring in steam turbines using the multiple-particle-move Monte Carlo for both the homogeneous phase and also implemented for the Gibbs ensemble Monte Carlo molecular simulation methods. Because of these thermodynamic conditions, a specific simulation algorithm has been developed to bypass common simulation problems resulting from very low densities of steam and cluster formation therein. In addition to pressure-temperature-density and orthobaric data, the distribution of clusters has also been evaluated. The obtained extensive data of high precision should serve as a basis for development of reliable molecular-based equations for properties of metastable steam.

  15. Evaluation of gastrointestinal drug supersaturation and precipitation: strategies and issues.

    Science.gov (United States)

    Bevernage, Jan; Brouwers, Joachim; Brewster, Marcus E; Augustijns, Patrick

    2013-08-30

    Supersaturating drug delivery systems (SDDS) hold the promise of enabling intestinal absorption for difficult-to-formulate, poorly soluble drug candidates based on a design approach that includes (1) converting the drug into a high energy or rapidly dissolving system which presents a supersaturated solution to the gastrointestinal environment and (2) dosage form components that act to stabilize the formed metastable drug solution through nucleation and/or crystal growth inhibition. The appropriate development and study of SDDS require that useful and biorelevant supersaturation and precipitation assays are available. This review summarizes different methodological aspects of currently available in vitro assays, including the generation of supersaturation (solvent shift, pH shift or formulation-induced), the quantification of supersaturation and the detection of precipitation. Also down-scaled approaches, including 96-well plate setups, are described and situated in the pharmaceutical development cycle based on their consumption of API as well as time requirements. Subsequently, the ability to extrapolate in vitro supersaturation assessment to the in vivo situation is discussed as are direct and indirect clinical tools that can shed light on SDDS. By emphasizing multiple variables that affect the predictive power of in vitro assays (e.g. the nature of the test media, hydrodynamics, temperature and sink versus non-sink conditions), this review finally highlights the need for further harmonization and biorelevance improvement of currently available in vitro procedures for supersaturation and precipitation evaluation. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Cloud condensation nucleus activation properties of biogenic secondary organic aerosol

    Science.gov (United States)

    Vanreken, Timothy M.; Ng, Nga L.; Flagan, Richard C.; Seinfeld, John H.

    2005-04-01

    Organic aerosols in general and secondary organic aerosol (SOA) in particular are known to contribute significantly to the atmospheric population of cloud condensation nuclei (CCN). However, current knowledge is limited with respect to the nature of this contribution. This study presents a series of experiments wherein the potential for biogenically derived SOA to act as CCN is explored. Five compounds were studied: four monoterpenes (α-pinene, β-pinene, limonene, and Δ3-carene) and one terpenoid alcohol (terpinene-4-ol). In each case the aerosol formation was driven by the reaction of ozone with the biogenic precursor. The SOA produced in each experiment was allowed to age for several hours, during which CCN concentrations were periodically measured at four supersaturations: S = 0.27%, 0.32%, 0.54%, and 0.80%. The calculated relationships between particle dry diameter and critical supersaturation were found to fall in the range of previously reported data for single-component organic aerosols; of the systems studied, α-pinene SOA was the least CCN active, while limonene SOA exhibited the strongest CCN activity. Interestingly, the inferred critical supersaturation of the SOA products was considerably more sensitive to particle diameter than was found in previous studies. Furthermore, the relationships between particle size and critical supersaturation for the monoterpene SOA shifted considerably over the course of the experiments, with the aerosol becoming less hygroscopic over time. These results are consistent with the progressive oligomerization of the SOA.

  17. Supersaturation-limited amyloid fibrillation of insulin revealed by ultrasonication.

    Science.gov (United States)

    Muta, Hiroya; Lee, Young-Ho; Kardos, József; Lin, Yuxi; Yagi, Hisashi; Goto, Yuji

    2014-06-27

    Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. We proposed that ultrasonication may be an effective agitation to trigger nucleation that would otherwise not occur under the persistent metastability of supersaturation. However, the roles of supersaturation and effects of ultrasonication have not been elucidated in detail except for limited cases. Insulin is an amyloidogenic protein that is useful for investigating the mechanisms underlying amyloid fibrillation with biological relevance. We studied the alcohol-induced amyloid fibrillation of insulin using various concentrations of 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol at pH 2.0 and 4.8. Ultrasonic irradiation effectively triggered fibrillation under conditions in which insulin retained persistent supersaturation. Structural analyses by circular dichroism, Fourier transform infrared spectroscopy, transmission electron microscopy, and atomic force microscopy revealed that the dominant structures of fibrils varied between parallel and antiparallel β-sheets depending on the solvent conditions. pH and alcohol concentration-dependent phase diagrams showed a marked difference before and after the ultrasonic treatment, which indicated that the persistent metastability of supersaturation determined the conformations of insulin. These results indicate the importance of an alternative view of amyloid fibrils as supersaturation-limited crystal-like aggregates formed above the solubility limit. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Supersaturation-limited Amyloid Fibrillation of Insulin Revealed by Ultrasonication*

    Science.gov (United States)

    Muta, Hiroya; Lee, Young-Ho; Kardos, József; Lin, Yuxi; Yagi, Hisashi; Goto, Yuji

    2014-01-01

    Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. We proposed that ultrasonication may be an effective agitation to trigger nucleation that would otherwise not occur under the persistent metastability of supersaturation. However, the roles of supersaturation and effects of ultrasonication have not been elucidated in detail except for limited cases. Insulin is an amyloidogenic protein that is useful for investigating the mechanisms underlying amyloid fibrillation with biological relevance. We studied the alcohol-induced amyloid fibrillation of insulin using various concentrations of 2,2,2-trifluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol at pH 2.0 and 4.8. Ultrasonic irradiation effectively triggered fibrillation under conditions in which insulin retained persistent supersaturation. Structural analyses by circular dichroism, Fourier transform infrared spectroscopy, transmission electron microscopy, and atomic force microscopy revealed that the dominant structures of fibrils varied between parallel and antiparallel β-sheets depending on the solvent conditions. pH and alcohol concentration-dependent phase diagrams showed a marked difference before and after the ultrasonic treatment, which indicated that the persistent metastability of supersaturation determined the conformations of insulin. These results indicate the importance of an alternative view of amyloid fibrils as supersaturation-limited crystal-like aggregates formed above the solubility limit. PMID:24847058

  19. Structure of supersaturated solution and crystal nucleation induced by diffusion

    Science.gov (United States)

    Ooshima, Hiroshi; Igarashi, Koichi; Iwasa, Hideo; Yamamoto, Ren

    2013-06-01

    The effect of a seed crystal on nucleation of L-alanine from a quiescent supersaturated solution was investigated. When a seed crystal was not used, nucleation did not occur at least for 5 h. When a seed crystal was introduced into the supersaturated solution with careful attention to avoid convection of the solution, fine crystals appeared at the place far from the seed crystal. At that time, there was no convection at the place that fine crystals appeared. Namely, there was no possibility that those fine crystals came from the surface of seed crystal. We supposed that nucleation was induced by directional diffusion of solute molecules caused by growth of the seed crystal. In order to prove this hypothesis, we designed an experiment using an apparatus composed of two compartments divided by a dialysis membrane that L-alanine molecules could freely permeate. Two supersaturated solutions having a supersaturation ratio of 1.2 and a smaller ratio were placed in the two compartments in the absence of seed crystals. This apparatus allowed the directional diffusion of solute molecules between two solutions. Nucleation occurred within 30 min. The frequency of nucleation among 7-times repeated experiments was in proportion to the difference of supersaturation ratio between the two solutions. This result poses a new mechanism of the secondary nucleation that the directional diffusion caused by growth of existing crystals induces nucleation.

  20. Physical chemistry of supersaturated solutions and implications for oral absorption.

    Science.gov (United States)

    Taylor, Lynne S; Zhang, Geoff G Z

    2016-06-01

    Amorphous solid dispersion (ASD) formulations are widely used for delivery of poorly soluble drugs for dissolution enhancement and bioavailability improvement. When administered, ASDs often exhibit fast dissolution to yield supersaturated solutions. The physical chemistry of these supersaturated solutions is not well understood. This review will discuss the concepts of solubility, supersaturation, and the connection to membrane transport rate. Liquid-liquid phase separation (LLPS), which occurs when the amorphous solubility is exceeded, leading to solutions with interesting properties is extensively discussed as a phenomenon that is relevant to all enabling formulations. The multiple physical processes occurring during dissolution of the ASD and during oral absorption are analyzed. The beneficial reservoir effect of a system that has undergone LLPS is demonstrated, both experimentally and conceptually. It is believed that formulations that rapidly supersaturate and subsequently undergo LLPS, with maintenance of the supersaturation at this maximum value throughout the absorption process, i.e. those that exhibit "spring and plateau" behavior, will give superior performance in terms of absorption. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Analysis of sulfur in deposited aerosols by thermal decomposition and sulfur dioxide analyzer.

    Science.gov (United States)

    Yamamoto, Masatoshi

    2005-07-15

    A thermal decomposition method that measures aerosol sulfur at the nanogram level directly from the collection substrate is described. A thermal decomposition apparatus was designed. A stainless steel strip was used as the aerosol collection substrate. A 0.1 mol/L MnCl2 solution was added as the thermal decomposition catalyst. Currents were passed through the strip where aerosol particles had been deposited. In this way, the strip was heated at 780 +/- 10 degrees C, and particulate sulfur was evaporated. A sulfur dioxide analyzer (SDA) with flame photometric detector (FPD) was used to detect gaseous sulfur. High sulfur recoveries from (NH4)2SO4 and other inorganic sulfates, such as NH4HSO4, K2SO4, MgSO4, and CaSO4, were obtained. From the sulfur blank and the calibration, a lower limited detection of 0.2 ng of sulfur and the determination range of 3.3-167 ng of sulfur were estimated. The method is effective for measuring the sulfate size distributions of urban aerosols in a small sample air volume of 50-60 L. The method is applicable to measuring the sulfur in aqueous extracts of size-segregated urban aerosols collected by impactor and comparing the results with the sulfate data measured by ion chromatography.

  2. Construction of optimal supersaturated designs by the packing method

    Institute of Scientific and Technical Information of China (English)

    FANG; Kaitai; GE; Gennian; LIU; Minqian

    2004-01-01

    A supersaturated design is essentially a factorial design with the equal occurrence of levels property and no fully aliased factors in which the number of main efits potential in factor screening experiments. A packing design is an important object in combinatorial design theory. In this paper, a strong link between the two apparently unrelated kinds of designs is shown. Several criteria for comparing supersaturated designs are proposed, their properties and connections with other existing criteria are discussed.A combinatorial approach, called the packing method, for constructing optimal supersaturated designs is presented, and properties of the resulting designs are also investigated.Comparisons between the new designs and other existing designs are given, which show that our construction method and the newly constructed designs have good properties.

  3. The dependence of homogeneous nucleation rate on supersaturation.

    Science.gov (United States)

    Girshick, Steven L

    2014-07-14

    The claim that classical nucleation theory (CNT) correctly predicts the dependence on supersaturation of the steady-state rate of homogeneous nucleation is reexamined in light of recent experimental studies of nucleation of a range of substances, including water, argon, nitrogen, and several 1-alcohols. Based on these studies (which include, for water, a compilation of nine different studies), it is concluded that the dependence of nucleation rate on supersaturation is not correctly predicted by CNT. It is shown that CNT's incorrect prediction of the supersaturation dependence of nucleation rate is due to its incorrect prediction of the Gibbs free energy change associated with formation of small clusters from the monomer vapor, evaluated at the substance's equilibrium vapor pressure, even though that free energy change is itself a function only of temperature.

  4. Aerosol effects on deep convective clouds: impact of changes in aerosol size distribution and aerosol activation parameterization

    Science.gov (United States)

    Ekman, A. M. L.; Engström, A.; Söderberg, A.

    2010-03-01

    defined by 23 nm≤d≤100.0 nm) may result in a larger impact on the convective strength compared to an increased number of aerosols in the accumulation mode (here defined by 100 nm≤d≤900.0 nm). When accumulation mode aerosols are activated and grow at the beginning of the cloud cycle, the supersaturation near the cloud base is lowered which to some extent limits further aerosol activation.

  5. Aerosol effects on deep convective clouds: impact of changes in aerosol size distribution and aerosol activation parameterization

    Directory of Open Access Journals (Sweden)

    A. M. L. Ekman

    2010-03-01

    Aitken mode (here defined by 23 nm≤d≤100.0 nm may result in a larger impact on the convective strength compared to an increased number of aerosols in the accumulation mode (here defined by 100 nm≤d≤900.0 nm. When accumulation mode aerosols are activated and grow at the beginning of the cloud cycle, the supersaturation near the cloud base is lowered which to some extent limits further aerosol activation.

  6. Improving estimates of aerosol radiative forcing through a particle-based aerosol microphysical scheme

    Science.gov (United States)

    Fierce, L.; McGraw, R. L.

    2016-12-01

    Forcing by atmospheric aerosols remains a large source of uncertainty in assessing human influences on the climate. Although global models have moved toward including more detailed representations of aerosol populations, aerosol microphysical schemes have been evaluated against benchmark models in only limited cases. Here we introduce a new framework for simulating atmospheric aerosols based on the Quadrature Method of Moments. This new aerosol model has been designed to reproduce key features of benchmark populations simulated by the particle-resolved model PartMC-MOSAIC, while tracking as little information about aerosol distributions as is necessary. The quadrature-based model simulates the aerosol evolution using a small number of weighted particles and is, therefore, decided as a reduced particle-based model. By applying principles of maximum entropy, the quadrature-based model efficiently reproduces distributions with respect to key aerosol properties, such as critical supersaturation for cloud condensation nuclei activation and optical cross sections, with high accuracy. In addition to providing an optimized aerosol model, the present study also describes how multi-scale modeling can be used as a tool for development of advanced aerosol microphysical schemes.

  7. Precipitation from supersaturated aluminate solutions. II. Role of temperature

    NARCIS (Netherlands)

    Straten, H.A. van; Bruyn, P.L. de

    1984-01-01

    The effect of temperature on the precipitation of aluminum hydroxide from dilute potassium aluminate solutions (CAl(OH)4 = 4 × 10−3 M) was studied in acid titration and pH-stat experiments. The precipitation sequence is largely dictated by the supersaturation (II) and follows the Ostwald rule of

  8. A kinetic study of precipitation from supersaturated calcium phosphate solutions

    NARCIS (Netherlands)

    Kemenade, M.J.J.M. van; Bruyn, P.L. de

    The formation of three different crystalline calcium phosphates (DCPD, OCP, HAP) and an amorphous calcium phosphate was studied as a function of pH and supersaturation. Under the experimental conditions the formation of HAP is always found to be preceded by one or more precursors in a sequence that

  9. Zn-Ni sulfide selective precipitation: The role of supersaturation

    NARCIS (Netherlands)

    Sampaio, R.M.M.; Timmers, R.A.; Kocks, N.; Andre, V.; Duarte, M.T.; Hullebusch, van E.D.; Farges, F.; Lens, P.N.L.

    2010-01-01

    The selective removal of Zn with Na2S from a mixture of Zn and Ni was studied in a continuously stirred tank reactor. At pH 5 and pS 18 the selectivity was improved from 61% to 99% by reducing the supersaturation at the dosing points by means of the reduction of the influent concentrations. The

  10. The use of supersaturation for the vaginal application of microbicides

    DEFF Research Database (Denmark)

    Grammen, Carolien; Plum, Jakob; Van Den Brande, Jeroen;

    2014-01-01

    In this study, we investigated the potential of supersaturation for the formulation of the poorly water-soluble microbicide dapivirine (DPV) in an aqueous vaginal gel in order to enhance its vaginal tissue uptake. Different excipients such as hydroxypropylmethylcellulose, polyethylene glycol 1000...

  11. Thermodynamic and statistical studies of supersaturated ternary solutions.

    Science.gov (United States)

    Izmailov, A F; Myerson, A S

    1999-09-01

    The influence of chromium ions Cr3+ on properties of supersaturated aqueous solution of ammonium sulfate (NH4)2SO4 has been studied employing containerless electrodynamic levitation of single microdroplets of this solution with known concentration of Cr3+ ions. The water activity versus solute concentration was measured in three different sets of experiments corresponding to different initial concentrations of Cr3+ ions. Theoretical treatment of the experimental results obtained is developed employing the theory of supersaturated electrolyte solutions [Phys. Rev. E 52, 1325 (1995)]. This treatment has allowed the following two conclusions. First, spinodal concentration is a decreasing function of Cr3+ concentration. Second, solute clusters formed in the presence of Cr3+ ions demonstrate complex behavior with respect to binding water molecules: (a) at low and moderate supersaturations, they bind more water molecules than clusters formed in the absence of an impurity; and (b) at high supersaturations, they bind less water molecules than clusters formed in the absence of an impurity.

  12. Excipient-mediated supersaturation stabilization in human intestinal fluids.

    Science.gov (United States)

    Bevernage, Jan; Forier, Thomas; Brouwers, Joachim; Tack, Jan; Annaert, Pieter; Augustijns, Patrick

    2011-04-04

    It was the purpose of this study to investigate excipient-mediated precipitation inhibition upon induction of supersaturation of poorly water-soluble drugs in aspirated human intestinal fluids (HIF) representing both the fasted and fed state. Etravirine, ritonavir, loviride, danazol and fenofibrate were selected as model compounds. For comparative purposes, precipitation inhibition was also evaluated in simple aqueous buffer, and in intestinal simulation media representative for the fasted and fed state (FaSSIF and FeSSIF, respectively). Supersaturation was induced in the test media containing predissolved excipient (HPMC-AS, HPMC-E5, HPMC-E50, HPMC-E4M, HPMC-P and PVP) at a defined degree of supersaturation (DS = 20) using the solvent shift method. The results illustrate that cellulosic polymers can reduce the precipitation rate and stabilize supersaturation in HIF. The extent of stabilization was compound and excipient dependent but independent of the nutritional state. Whenever excipient effects were observed, the predictive value of simple buffer or FaSSIF/FeSSIF was rather limited. In general, excipient-mediated precipitation inhibition was less pronounced in HIF compared to simple aqueous buffer or FaSSIF/FeSSIF. However, excipients showing no effect in simple aqueous buffer or FaSSIF/FeSSIF also proved to be ineffective in HIF, indicating the value of these simulation media in the elimination of excipients during formulation development.

  13. Drug precipitation-permeation interplay: supersaturation in an absorptive environment.

    Science.gov (United States)

    Bevernage, Jan; Brouwers, Joachim; Annaert, Pieter; Augustijns, Patrick

    2012-10-01

    The present study investigated the interplay between supersaturation, absorption, precipitation, and excipient-mediated precipitation inhibition by comparing classic precipitation assessment in a non-absorption environment with precipitation/permeation assessment in an absorption environment. Loviride and HPMC-E5 were selected as poorly soluble model drug and precipitation inhibitor, respectively. To investigate supersaturation in an absorptive environment, supersaturation was induced at different degrees (DS), using a solvent shift method, in shaken Caco-2 Transwell® inserts containing fasted state simulated intestinal fluid (FaSSIF); to simulate a non-absorption environment, the inserts were parafilm-sealed and did not contain a cell monolayer. Donor and acceptor compartments were sampled as a function of time to determine precipitation kinetics and transport, respectively. In absence of precipitation, loviride transport increased proportionally with the initial DS; however, precipitation limited the supersaturation-induced transport enhancement. Loviride precipitation was found to be less extensive in an absorption environment compared to a non-absorption environment. As a result, the optimal DS obtained in a non-absorption environment (highest amount maintained in solution) did not correlate with the highest transport in an absorption environment. In addition, the impact of HPMC-E5 on loviride transport was inferior to its precipitation inhibitory capacity observed in a non-absorption environment. For the first time, the present study explicitly demonstrated that implementation of permeation in precipitation assays is critical to predict the impact of supersaturation, precipitation, and precipitation inhibition on the absorption of poorly soluble drugs. Copyright © 2012 Elsevier B.V. All rights reserved.

  14. Properties of jet engine combustion particles during the PartEmis experiment. Hygroscopic growth at supersaturated conditions

    Science.gov (United States)

    Hitzenberger, R.; Giebl, H.; Petzold, A.; Gysel, M.; Nyeki, S.; Weingartner, E.; Baltensperger, U.; Wilson, C. W.

    2003-07-01

    During the EU Project PartEmis, the microphysical properties of aircraft combustion aerosol were investigated. This study is focused on the ability of exhaust aerosols to act as cloud condensation nuclei (CCN). The combustor was operated at two different conditions representing old and modern aircraft engine technology. CCN concentrations were measured with the University of Vienna CCN counter [ Giebl et al., 2002] at supersaturations around 0.7%. The activation ratio (fraction of CCN in total aerosol) depended on the fuel sulphur content (FSC) and also on the operation conditions. CCN/CN ratios increased from 0.93 through 1.43 to 5.15 . 10-3 (old cruise conditions) and 0.67 through 3.04 to 7.94 . 10-3 (modern cruise conditions) when FSC increased from 50 through 410 to1270 μg/g. The activation behaviour was modelled using classical theories and with a semi-empirical model [ Gysel et al., 2003] based on measured hygroscopicity of the aerosol under subsaturated conditions, which gave the best agreement.

  15. Drug supersaturation in simulated and human intestinal fluids representing different nutritional states.

    Science.gov (United States)

    Bevernage, Jan; Brouwers, Joachim; Clarysse, Sarah; Vertzoni, Maria; Tack, Jan; Annaert, Pieter; Augustijns, Patrick

    2010-11-01

    It was the purpose of this study to explore supersaturation of poorly soluble drugs in human intestinal fluids (HIF), and to assess potential food effects on the creation and maintenance of supersaturation. Duodenal fluids were collected from healthy volunteers and pooled according to three nutritional states (fasted-, fed-, and fat-enriched fed state). Supersaturation was created at a fixed degree of supersaturation (DS=20) using the solvent-shift method. Fasted- and fed-state simulated intestinal fluids (FaSSIF and FeSSIF) were used as intestinal simulation media. Supersaturation in HIF showed to be stable up to a certain degree for different poorly soluble drugs. In HIF as well as in FaSSIF and FeSSIF, supersaturation appeared to be compound and medium specific. Supersaturation stability was found to be inversely proportional to the solubility in the corresponding media. Food intake affected itraconazole supersaturation positively. On the contrary, etravirine and loviride supersaturation decreased upon food intake. Supersaturation experiments in FaSSIF and FeSSIF showed similar results as in HIF for etravirine and loviride, whereas itraconazole supersaturation behaved differently in HIF versus simulation media. The present study illustrates, for the first time, that supersaturation can be created and maintained in HIF, even in the absence of excipients. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association

  16. Effects of gas supersaturation on lethality and avoidance responses in juvenile rock carp (Procypris rabaudi Tchang)*

    Science.gov (United States)

    Huang, Xiang; Li, Ke-feng; Du, Jun; Li, Ran

    2010-01-01

    Laboratory experiments were conducted to determine the effects of total dissolved gas (TDG) supersaturation on acute lethality and avoidance responses in juvenile rock carp (Procypris rabaudi Tchang). The juvenile rock carp were exposed to water with different levels of supersaturation (105%, 115%, 120%, 125%, 130%, 135%, 140%, and 145%) and depth of 0.20 m at 25 °C for 60 h. Median lethal time (LT50) was used to assess the lethal responses corresponding to different levels of gas supersaturation. The results show that half of the juvenile rock carp died at the 120%, 125%, 130%, 135%, 140%, and 145% levels of supersaturation, and the LT50 corresponding to different levels of supersaturation was 18.7, 15.4, 8.2, 6.6, 3.5, and 1.7 h. When the level of supersaturated water is below 115%, the mortality is negligible. Avoidance responses were observed 5 min after the fish were put into equilibrated water (99%, 0.08 m deep) and water with different supersaturated levels (105%, 115%, 125%, 135%, and 145%, 0.08 m deep) at 25 °C. The fish exhibited strong avoidance responses in supersaturated water when the gas supersaturation was above 135%. However, they exhibited an obvious preference to supersaturated water when the gas supersaturation was below 115%. Thus, the juvenile rock carp can likely survive in water with a supersaturated level of 115%. PMID:20872989

  17. Effects of gas supersaturation on lethality and avoidance responses in juvenile rock carp (Procypris rabaudi Tchang).

    Science.gov (United States)

    Huang, Xiang; Li, Ke-feng; Du, Jun; Li, Ran

    2010-10-01

    Laboratory experiments were conducted to determine the effects of total dissolved gas (TDG) supersaturation on acute lethality and avoidance responses in juvenile rock carp (Procypris rabaudi Tchang). The juvenile rock carp were exposed to water with different levels of supersaturation (105%, 115%, 120%, 125%, 130%, 135%, 140%, and 145%) and depth of 0.20 m at 25 °C for 60 h. Median lethal time (LT(50)) was used to assess the lethal responses corresponding to different levels of gas supersaturation. The results show that half of the juvenile rock carp died at the 120%, 125%, 130%, 135%, 140%, and 145% levels of supersaturation, and the LT(50) corresponding to different levels of supersaturation was 18.7, 15.4, 8.2, 6.6, 3.5, and 1.7 h. When the level of supersaturated water is below 115%, the mortality is negligible. Avoidance responses were observed 5 min after the fish were put into equilibrated water (99%, 0.08 m deep) and water with different supersaturated levels (105%, 115%, 125%, 135%, and 145%, 0.08 m deep) at 25 °C. The fish exhibited strong avoidance responses in supersaturated water when the gas supersaturation was above 135%. However, they exhibited an obvious preference to supersaturated water when the gas supersaturation was below 115%. Thus, the juvenile rock carp can likely survive in water with a supersaturated level of 115%.

  18. Aerosol indirect effect from turbulence-induced broadening of cloud-droplet size distributions

    Energy Technology Data Exchange (ETDEWEB)

    Chandrakar, Kamal Kant; Cantrell, Will; Chang, Kelken; Ciochetto, David; Niedermeier, Dennis; Ovchinnikov, Mikhail; Shaw, Raymond A.; Yang, Fan

    2016-11-28

    The influence of aerosol concentration on cloud droplet size distribution is investigated in a laboratory chamber that enables turbulent cloud formation through moist convection. The experiments allow steady-state microphysics to be achieved, with aerosol input balanced by cloud droplet growth and fallout. As aerosol concentration is increased the cloud droplet mean diameter decreases as expected, but the width of the size distribution also decreases sharply. The aerosol input allows for cloud generation in the limiting regimes of fast microphysics (τc < τt) for high aerosol concentration, and slow microphysics (τc > τt) for low aerosol concentration; here, τc is the phase relaxation time and τt is the turbulence correlation time. The increase in the width of the droplet size distribution for the low aerosol limit is consistent with larger variability of supersaturation due to the slow microphysical response. A stochastic differential equation for supersaturation predicts that the standard deviation of the squared droplet radius should increase linearly with a system time scale defined as τs-1c-1 + τt-1, and the measurements are in excellent agreement with this finding. This finding underscores the importance of droplet size dispersion for the aerosol indirect effect: increasing aerosol concentration not only suppresses precipitation formation through reduction of the mean droplet diameter, but perhaps more importantly, through narrowing of the droplet size distribution due to reduced supersaturation fluctuations. Supersaturation fluctuations in the low aerosol / slow microphysics limit are likely of leading importance for precipitation formation.

  19. A unified mechanism for the stability of surface nanobubbles: contact line pinning and supersaturation.

    Science.gov (United States)

    Liu, Yawei; Zhang, Xianren

    2014-10-07

    In this paper, we apply the molecular dynamics simulation method to study the stability of surface nanobubbles in both pure fluids and gas-liquid mixtures. First, we demonstrate with molecular simulations, for the first time, that surface nanobubbles can be stabilized in superheated or gas supersaturated liquid by the contact line pinning caused by the surface heterogeneity. Then, a unified mechanism for nanobubble stability is put forward here that stabilizing nanobubbles require both the contact line pinning and supersaturation. In the mechanism, the supersaturation refers to superheating for pure fluids and gas supersaturation or superheating for the gas-liquid mixtures, both of which exert the same effect on nanobubble stability. As the level of supersaturation increases, we found a Wenzel or Cassie wetting state for undersaturated and saturated fluids, stable nanobubbles at moderate supersaturation with decreasing curvature radius and contact angle, and finally the liquid-to-vapor phase transition at high supersaturation.

  20. Bioavailability Improvement Strategies for Poorly Water-Soluble Drugs Based on the Supersaturation Mechanism: An Update.

    Science.gov (United States)

    Yang, Meiyan; Gong, Wei; Wang, Yuli; Shan, Li; Li, Ying; Gao, Chunsheng

    2016-01-01

    The formulation development for poorly soluble drugs still remains a challenge. Supersaturating drug delivery systems (SDDS) or drug delivery systems based on supersaturating provide a promising way to improve the oral bioavailability of poorly water-soluble drugs. In supersaturable formulations, drug concentration exceeds the equilibrium solubility when exposed to gastrointestinal fluids, and the supersaturation state is maintained long enough to be absorbed, resulting in compromised bioavailability. In this article, the mechanism of generating and maintaining supersaturation and the evaluation methods of supersaturation assays are discussed. Recent advances in different drug delivery systems based on supersaturating are the focus and are discussed in detail.This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

  1. Improved supersaturation and oral absorption of dutasteride by amorphous solid dispersions.

    Science.gov (United States)

    Beak, In-Hwan; Kim, Min-Soo

    2012-01-01

    In this study, amorphous solid dispersions containing dutasteride and various excipients, manufactured by spray-drying processes, were characterized to determine the effects on their ability to form supersaturated solutions and to identify the effects of supersaturation on increasing the bioavailability of dutasteride. The excipients included Eudragit E, hydroxypropyl-β-cyclodextrin (HP-β-CD), hydroxypropyl cellulose (HPC), hydroxypropylmethyl cellulose (HPMC), and polyvinylpyrrolidone (PVP K30). A solid dispersion with Eudragit E displayed a high maximum supersaturation with extended supersaturation, compared with a water-soluble polymer. The maximum concentration and the degree of supersaturation increased in the following order: PVP K30supersaturation concentration. These results suggest that amorphous solid dispersions containing Eudragit E, formed by a spray-drying process, offer enhanced supersaturation characteristics, leading to increased oral absorption of dutasteride.

  2. Neurodegenerative diseases and widespread aggregation are associated with supersaturated proteins

    Science.gov (United States)

    Ciryam, Prajwal; Tartaglia, Gian Gaetano; Morimoto, Richard I.; Dobson, Christopher M.; Vendruscolo, Michele

    2013-01-01

    Summary The maintenance of protein solubility is a fundamental aspect of protein homeostasis, as aggregation is associated with cytotoxicity and a variety of human diseases. Numerous proteins unrelated in sequence and structure, however, can misfold and aggregate, and widespread aggregation can occur in living systems under stress or ageing. A crucial question in this context is why only certain proteins aggregate in vivo while others do not. We identify here the proteins most vulnerable to aggregation as those whose cellular concentrations are high relative to their solubilities. These supersaturated proteins represent a metastable sub-proteome involved in pathological aggregation during stress and ageing, and are overrepresented in biochemical processes associated with neurodegenerative disorders. Consequently, such cellular processes become dysfunctional when the ability to keep intrinsically supersaturated proteins soluble is compromised. Thus, the simultaneous analysis of abundance and solubility can rationalize the diverse cellular pathologies linked to neurodegenerative diseases and aging. PMID:24183671

  3. Revisiting supersaturation as a factor determining amyloid fibrillation.

    Science.gov (United States)

    So, Masatomo; Hall, Damien; Goto, Yuji

    2016-02-01

    Amyloid fibrils involved in various diseases are formed by a nucleation-growth mechanism, similar to the crystallization of solutes from solution. Solubility and supersaturation are two of the most important factors determining crystallization of solutes. Moreover, crystallization competes with glass formation in which solutes collapse into amorphous aggregates. Recent studies on the formation of amyloid fibrils and amorphous aggregates indicate that the partition between distinct types of aggregates can be rationally explained by a kinetic and thermodynamic competition between them. Understanding the role of supersaturation in determining aggregation-based phase transitions of denatured proteins provides an important complementary point of view to structural studies of protein aggregates. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Supersaturation in the spontaneous formation of nuclei in water vapor

    Science.gov (United States)

    Sander, Adolf; Damkohler, Gerhard

    1953-01-01

    According to experience, a certain supersaturation is required for condensation of water vapor in the homogeneous phase; that is, for inception of the condensation, at a prescribed temperature, the water vapor partial pressure must lie above the saturation pressure. The condensation starts on so-called condensation nuclei. Solid or liquid suspended particles may serve as nuclei; these particles may either a priori be present in the gas phase (dust, soot), or may spontaneously be formed from the vapor molecules to be condensed themselves. Only the second case will be considered. Gas ions which facilitate the spontaneous formation of nuclei may be present or absent. The supersaturations necessary for spontaneous nucleus formation are in general considerable higher than those in the presence of suspended particles.

  5. Formation of ice supersaturation by mesoscale gravity waves

    Directory of Open Access Journals (Sweden)

    P. Spichtinger

    2005-01-01

    Full Text Available We investigate the formation and evolution of an ice-supersaturated region (ISSR that was detected by means of an operational radiosonde sounding launched from the meteorological station of Lindenberg on 21 March 2000, 00:00 UTC. The supersaturated layer was 5 situated below the local tropopause, between 320 and 408 hPa altitude. Our investigation uses satellite imagery (METEOSAT, AVHRR and analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF. Mesoscale simulations reveal that the ISSR was formed by a temporary vertical uplift of upper tropospheric air parcels by 20 to 40 hPa in 1 to 2 h. This resulted in a significant local increase of the 10 specific humidity by the moisture transport from below. The ascent was triggered by the superposition of two internal gravity waves, a mountain wave induced by flow past the Erzgebirge and Riesengebirge south of Lindenberg, and an inertial gravity wave excited by the anticyclonically curved jet stream over the Baltic Sea. The wave-induced ISSR was rather thick with a depth of about 2 km. The wave-induced upward motion 15 causing the supersaturation also triggered the formation of a cirrus cloud. METEOSAT imagery shows that the cirrus cloud got optically thick within two hours. During this period another longer lasting thin but extended cirrus existed just beneath the tropopause. The wave-induced ISSR disappeared after about half a day in accordance with the decaying wave activity.

  6. CCN activity of aliphatic amine secondary aerosol

    Directory of Open Access Journals (Sweden)

    X. Tang

    2014-01-01

    Full Text Available Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g. hydroxyl radical and nitrate radical. The particle composition can contain both secondary organic aerosol (SOA and inorganic salts. The fraction of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN activity. SOA formed from trimethylamine (TMA and butylamine (BA reactions with hydroxyl radical (OH is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ ≤ 0.25. Secondary aerosol formed from the tertiary aliphatic amine (TMA with N2O5 (source of nitrate radical, NO3, contains less volatile compounds than the primary aliphatic amine (BA aerosol. TMA + N2O5 form semi-volatile organics in low RH conditions that have κ ~ 0.20, indicative of slightly soluble organic material. As RH increases, several inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR ideal mixing rules. Higher CCN activity (κ > 0.3 was also observed for humid BA+N2O5 aerosols compared with dry aerosol (κ ~ 0.2, as a result of the formation of inorganic salts such as NH4NO3 and butylamine nitrate (C4H11N · HNO3. Compared with TMA, BA+N2O5 reactions produce more volatile aerosols. The BA+N2O5 aerosol products under humid experiments were found to be very sensitive to the temperature within the stream-wise continuous flow thermal gradient CCN counter. The CCN counter, when set above a 21 °C temperature difference, evaporates BA+N2O5 aerosol formed at RH ≥ 30%; κ ranges from 0.4 to 0.7 and is dependent on the instrument supersaturation (ss settings. The aerosol behaves non-ideally, hence simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems κ ranges from 0.2 < κ < 0.7. This work indicates that

  7. Effects of supersaturation on pore shape in solid

    Science.gov (United States)

    Wei, P. S.; Hsiao, S. Y.

    2017-02-01

    The shape of a pore resulting from a bubble entrapped by a solidification front with different supersaturation ratios is predicted in this work. Supersaturation ratio, representing the ratio between solute concentration and saturation solute concentration, determines nucleation of a bubble and development of the pore shape in the early stage. Pore formation and its shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work extends and combines previous models accounting for realistic mass and momentum transport, and physico-chemical equilibrium of solute gas across the bubble cap to self-consistently determine shape of the bubble cap beyond the solidification front and the pore shape in solid. The study also deal with that pore formation can be resulted from three different mechanisms, depending on the directions and magnitude of solute gas transport across the bubble cap. Case 1 is subject to solute transport from the pore across the cap into the surrounding liquid in the early stage. Cases 2a and 2b indicate opposite direction of solute transport. In contrast to Case 2b, the effect of solute transport on solute gas pressure in the pore in Case 2a is stronger than that of pore volume expansionin the last stage. The results find that an increase in supersaturation ratio decreases pore radius and time for bubble entrapment in Case 1. The bubble cannot be entrapped in Case 2. The predicted pore shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the pore shape have therefore been obtained.

  8. The Background Level of the Summer Tropospheric Aerosol over Greenland and the North Atlantic Ocean

    DEFF Research Database (Denmark)

    Flyger, H.; Hansen, K. A.; Megaw, W.J.;

    1973-01-01

    An experiment to measure the concentration and size of Aitken nuclei, the concentration of cloud nuclei active at a supersaturation of 1%, the concentration of freezing nuclei activated at -20C, and the chemical nature of the tropospheric aerosol over Greenland and the seas surrounding it is desc...

  9. Nucleation of insulin crystals in a wide continuous supersaturation gradient.

    Science.gov (United States)

    Penkova, Anita; Dimitrov, Ivaylo; Nanev, Christo

    2004-11-01

    Modifying the classical double pulse technique, by using a supersaturation gradient along an insulin solution contained in a glass capillary tube, we found conditions appropriate for the direct measurement of nucleation parameters. The nucleation time lag has been measured. Data for the number of crystal nuclei versus the nucleation time were obtained for this hormone. Insulin was chosen as a model protein because of the availability of solubility data in the literature. A comparison with the results for hen-egg-white lysozyme, HEWL was performed.

  10. A CASE STUDY IN THE APPLICATION OF SUPERSATURATED DESIGNS TO COMPUTER EXPERIMENTS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Supersaturated design is essentially a fractional factorial design in which the number of potential effects is greater than the number of runs. In this article, the supersaturated design is applied to a computer experiment through an example of steady current circuit model problem. A uniform mixed-level supersaturated design and the centered quadratic regression model are used. This example shows that supersaturated design and quadratic regression modeling method are very effective for screening effects and building the predictor. They are not only useful in computer experiments but also in industrial and other scientific experiments.

  11. The effects of dissolved gas supersaturation on white sturgeon larvae

    Science.gov (United States)

    Counihan, T.D.; Miller, Allen I.; Mesa, M.G.; Parsley, M.J.

    2000-01-01

    Spill at dams has caused supersaturation of atmospheric gas in waters of the Columbia and Snake rivers and raised concerns about the effects of dissolved gas supersaturation (DGS) on white sturgeons Acipenser transmontanus. The timing and location of white sturgeon spawning and the dispersal of white sturgeon larvae from incubation areas makes the larval stage potentially vulnerable to the effects of DGS. To assess the effects of DGS on white sturgeon larvae, we exposed larvae to mean total dissolved gas (TDG) levels of 118% and 131% saturation in laboratory bioassay tests. Gas bubble trauma (GBT) was manifested as a gas bubble in the buccal cavity, nares, or both and it first occurred at developmental stages characterized by the formation of the mouth and gills. Exposure times of 15 min were sufficient to elicit these signs in larvae in various stages of development. No mortality was observed in larvae exposed to 118% TDG for 10 d, but 50% mortality occurred after a 13-d exposure to 131% TDG. The signs of GBT we observed resulted in positive buoyancy and alterations in behavior that may affect the dispersal and predation vulnerability of white sturgeon larvae. The exact depth distribution of dispersing white sturgeon larvae in the Columbia River currently is unknown. Thus, our results may represent a worst-case scenario if white sturgeon larvae are dispersed at depths with insufficient hydrostatic pressure to compensate for high TDG levels.

  12. Gaseous abundances and methane supersaturation in Titan's troposphere

    Science.gov (United States)

    Samuelson, Robert E.; Nath, Nitya R.; Borysow, Aleksandra

    1997-01-01

    Various properties of Titan's troposphere are inferred from an analysis of Voyager I infrared spectrometer (IRIS) data between 200 and 600/ cm. Two homogeneous spectral averages acquired at widely separated emission angles are chosen for the analysis. Both data sets are associated with northern low latitudes very close to that of the radio science ingress occultation point. Solutions require simultaneous nonlinear least-squares fits to the two IRIS data sets, coupled with iteration of the radio occultation refractivity data. Values and associated 1-sigma uncertainties of several parameters are inferred from our analysis. These include mole fractions for molecular hydrogen (approx. 0.0011), argon (small), and methane near the surface ( approx. 0.057). Solutions are also obtained for the hydrogen parafraction (close to equilibrium, with considerable uncertainty), air temperature near the surface ( approx. 93 K), surface surface temperature discontinuity (approx. 1 K), and maximum degree of methane supersaturation in the upper troposphere (approx. 1.5). Actual values for the above-mentioned parameters depend on the amount of ethane cloud near the tropopause. There is no evidence for methane clouds in the upper troposphere, nor is their presence compatible with large degrees of supersaturation. A wave number dependence for the stratospheric haze opacity is inferred similar to that found for a polymeric residue created in laboratory discharge experiments. This haze appears to be uniformly distributed with latitude between altitudes of 40 and 160 km, provided those nighttime data at southern high latitudes that are discounted.

  13. The effect of phase partitioning of semivolatile compounds on the measured CCN activity of aerosol particles

    Directory of Open Access Journals (Sweden)

    S. Romakkaniemi

    2013-09-01

    Full Text Available The effect of inorganic semivolatile aerosol compounds on the CCN activity of aerosol particles was studied by using a computational model for a DMT-CCN counter, a cloud parcel model for condensation kinetics and experiments to quantify the modelled results. Concentrations of water vapour and semivolatiles as well as aerosol trajectories in the CCN column were calculated by a computational fluid dynamics model. These trajectories and vapour concentrations were then used as an input for the cloud parcel model to simulate mass transfer kinetics of water and semivolatiles between aerosol particles and the gas phase. Two different questions were studied: (1 how big fraction of semivolatiles is evaporated from particles before activation in the CCN counter? (2 How much the CCN activity can be increased due to condensation of semivolatiles prior to the maximum water supersaturation in the case of high semivolatile concentration in the gas phase? The results show that, to increase the CCN activity of aerosol particles, a very high gas phase concentration (as compared to typical ambient conditions is needed. We used nitric acid as a test compound. A concentration of several ppb or higher is needed for measurable effect. In the case of particle evaporation, we used ammonium nitrate as a test compound and found that it partially evaporates before maximum supersaturation is reached in the CCN counter, thus causing an underestimation of CCN activity. The effect of evaporation is clearly visible in all supersaturations, leading to an underestimation of the critical dry diameter by 10 to 15 nanometres in the case of ammonium nitrate particles in different supersaturations. This result was also confirmed by measurements in supersaturations between 0.1 and 0.7%.

  14. Cloud condensation nuclei (CCN) activity of aliphatic amine secondary aerosol

    Science.gov (United States)

    Tang, X.; Price, D.; Praske, E.; Vu, D. N.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

    2014-06-01

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g., hydroxyl radical and nitrate radical). The particle can contain both secondary organic aerosol (SOA) and inorganic salts. The ratio of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ, ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3) contains less volatile compounds than the primary aliphatic amine (BA) aerosol. As relative humidity (RH) increases, inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. The humid BA + N2O5 aerosol products were found to be very sensitive to the temperature at which the measurements were made within the streamwise continuous-flow thermal gradient CCN counter; κ ranges from 0.4 to 0.7 dependent on the instrument supersaturation (ss) settings. The variance of the measured aerosol κ values indicates that simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems' κ ranges within 0.2 systems.

  15. Interaction of Microphysical Aerosol Processes with Hydrodynamics Mixing

    KAUST Repository

    Alshaarawi, Amjad

    2015-12-15

    This work is concerned with the interaction between condensing aerosol dynamics and hydrodynamic mixing within ow configurations in which aerosol particles form (nucleate) from a supersaturated vapor and supersaturation is induced by the mixing of two streams (a saturated stream and a cold one). Two canonical hydrodynamic configurations are proposed for the investigation. The First is the steady one-dimensional opposed-ow configuration. The setup consists of the two (saturated and cold) streams owing from opposite nozzles. A mixing layer is established across a stagnation plane in the center where nucleation and other aerosol dynamics are triggered. The second is homogeneous isotropic turbulence in a three-dimensional periodic domain. Patches of a hot saturated gas mix with patches of a cold one. A mixing layer forms across the growing interface where the aerosol dynamics of interest occur. In both configurations, a unique analogy is observed. The results reveal a complex response to variations in the mixing rates. Depending on the mixing rate, the response of the number density falls into one of two regimes. For fast mixing rates, the maximum reached number density of the condensing droplets increases with the hydrodynamic time. We refer to this as the nucleation regime. On the contrary, for low mixing rates, the maximum reached number density decreases with the hydrodynamic time. We refer to this as the consumption regime. It is shown that vapor scavenging by the aerosol phase is key to explaining the transition between these two regimes.

  16. Size-resolved and bulk activation properties of aerosols in the North China plain: the importance of aerosol size distribution in the prediction of CCN number concentration

    Directory of Open Access Journals (Sweden)

    Z. Z. Deng

    2011-01-01

    Full Text Available Size-resolved and bulk activation properties of aerosols were measured at a regional/suburban site in the North China Plain (NCP, which is occasionally heavily polluted by anthropogenic aerosol particles and gases. A CCN (Cloud Condensation Nuclei closure study is conducted with bulk CCN number concentration (NCCN and calculated NCCN based on the aerosol number size distribution and size-resolved activation properties.

    The observed NCCN are higher than those observed in other locations than China, with average NCCN of roughly 2000, 3000, 6000, 10 000 and 13 000 cm−3 at supersaturations of 0.056, 0.083, 0.17, 0.35 and 0.70%, respectively. An inferred critical dry diameter (Dm is calculated based on the measured NCCN and aerosol number size distribution assuming homogeneous chemical composition. This inferred cut off diameter varies in a wide range, indicating that it is impossible to predict NCCN with a fixed critical diameter.

    Size-resolved activation measurements show that most of the 300 nm particles are activated at the investigated supersaturations, while almost no particles of 30 nm are activated even at the highest supersaturation of 0.72%. The activation ratio increases with increasing supersaturation and particle size. The slopes of the activation curves for ambient aerosols are not as steep as those observed in calibrations with ammonium sulfate suggesting that the observed aerosols is an external mixture of more hygroscopic and hydrophobic particles. This conclusion is confirmed by hygroscopicity measurements performed during two intensive field studies in 2009.

    The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlate well with the measured NCCN, and show an average overestimation

  17. Automated Supersaturation Stability Assay to Differentiate Poorly Soluble Compounds in Drug Discovery.

    Science.gov (United States)

    Skolnik, Suzanne M; Geraci, Gina M; Dodd, Stephanie

    2017-05-25

    Increasingly, in vitro assays evaluate a compound's tendency to maintain supersaturation toward improving oral absorption. Throughput remains a challenge and only small sets of compounds are evaluated in reported studies. The present work describes an automated workflow and data analysis approach to determine supersaturation stability after 16 min. Eight increasing concentrations were targeted and supernatant concentration was measured following solvent shift in fasted-state simulated intestinal fluid. The effect of dimethyl sulfoxide both on equilibrium solubility and on induced supersaturation was addressed, whereas the change in concentration was evaluated over time. Our sample set included 24 commercial compounds, along with comparison to literature results. To demonstrate in vivo relevance of in vitro supersaturation, classification of supersaturation stability was proposed based on the target concentration achieved and the percentage of area under the curve dose proportionality in 42 preclinical and clinical studies. Eighty-one percent of low supersaturation stability compounds (target concentrations ≤50 μM) had proportionality supersaturation stability compounds (target concentrations ≥200 μM) demonstrated proportionality ≥0.8. The robust, automated assay and its impact on dose proportionality downstream make this approach applicable in drug discovery where low-soluble compounds with otherwise attractive properties may be differentiated on the basis of supersaturation stability. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  18. CCN activity of aliphatic amine secondary aerosol

    Science.gov (United States)

    Tang, X.; Price, D.; Praske, E.; Vu, D.; Purvis-Roberts, K.; Silva, P. J.; Cocker, D. R., III; Asa-Awuku, A.

    2014-01-01

    Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g. hydroxyl radical and nitrate radical). The particle composition can contain both secondary organic aerosol (SOA) and inorganic salts. The fraction of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N2O5 (source of nitrate radical, NO3), contains less volatile compounds than the primary aliphatic amine (BA) aerosol. TMA + N2O5 form semi-volatile organics in low RH conditions that have κ ~ 0.20, indicative of slightly soluble organic material. As RH increases, several inorganic amine salts are formed as a result of acid-base reactions. The CCN activity of the humid TMA-N2O5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. Higher CCN activity (κ > 0.3) was also observed for humid BA+N2O5 aerosols compared with dry aerosol (κ ~ 0.2), as a result of the formation of inorganic salts such as NH4NO3 and butylamine nitrate (C4H11N · HNO3). Compared with TMA, BA+N2O5 reactions produce more volatile aerosols. The BA+N2O5 aerosol products under humid experiments were found to be very sensitive to the temperature within the stream-wise continuous flow thermal gradient CCN counter. The CCN counter, when set above a 21 °C temperature difference, evaporates BA+N2O5 aerosol formed at RH ≥ 30%; κ ranges from 0.4 to 0.7 and is dependent on the instrument supersaturation (ss) settings. The aerosol behaves non-ideally, hence simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems κ ranges from 0.2 systems.

  19. Evidence of High Ice Supersaturation in Cirrus Clouds Using ARM Raman Lidar Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Comstock, Jennifer M.; Ackerman, Thomas P.; Turner, David D.

    2004-06-05

    Water vapor amounts in the upper troposphere are crucial to understanding the radiative feedback of cirrus clouds on the Earth’s climate. We use a unique, year-long dataset of water vapor mixing ratio inferred from ground-based Raman lidar measurements to study the role of ice supersaturation in ice nucleation processes. We find that ice supersaturation occurs 31% of the time in over 300,000 data points. We also examine the distribution of ice supersaturation with height and find that in the uppermost portion of a cloud layer, the air is ice supersaturated 43% of the time. These measurements show that large ice supersaturation is common in cirrus clouds, which supports the theory of ice forming homogeneously. Given the continuous nature of these Raman lidar measurements, our results have important implications for studying ice nucleation processes using cloud microphysical models.

  20. ARM Raman Lidar Measurements of High Ice Supersaturation in Cirrus Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Comstock, Jennifer M.; Ackerman, Thomas P.; Turner, David D.

    2004-09-01

    Water vapor amounts in the upper troposphere are crucial to understanding the radiative feedback of cirrus clouds on the Earth's climate. We use a unique, year-long dataset of water vapor mixing ratio inferred from ground-based Raman lidar measurements to study the role of ice supersaturation in ice nucleation processes. We find that ice supersaturation occurs 31% of the time in over 300,000 data points. We also examine the distribution of ice supersaturation with height and find that in the uppermost portion of a cloud layer, the air is ice supersaturated 43% of the time. These measurements show that large ice supersaturation is common in cirrus clouds, which supports the theory of ice forming homogeneously. Given the continuous nature of these Raman lidar measurements, our results have important implications for studying ice nucleation processes using cloud microphysical models.

  1. Haste Makes Waste: The Interplay Between Dissolution and Precipitation of Supersaturating Formulations.

    Science.gov (United States)

    Sun, Dajun D; Lee, Ping I

    2015-11-01

    Contrary to the early philosophy of supersaturating formulation design for oral solid dosage forms, current evidence shows that an exceedingly high rate of supersaturation generation could result in a suboptimal in vitro dissolution profile and subsequently could reduce the in vivo oral bioavailability of amorphous solid dispersions. In this commentary, we outline recent research efforts on the specific effects of the rate and extent of supersaturation generation on the overall kinetic solubility profiles of supersaturating formulations. Additional insights into an appropriate definition of sink versus nonsink dissolution conditions and the solubility advantage of amorphous pharmaceuticals are also highlighted. The interplay between dissolution and precipitation kinetics should be carefully considered in designing a suitable supersaturating formulation to best improve the dissolution behavior and oral bioavailability of poorly water-soluble drugs.

  2. Revision of the classical nucleation theory for supersaturated solutions

    CERN Document Server

    Borisenko, Alexander

    2015-01-01

    During the processes of nucleation and growth of a precipitate cluster from a supersaturated solution, the diffusion flux between the cluster and the solution changes the solute concentration near the cluster-solution interface from its average bulk value. This feature affects the rates of attachment and detachment of solute atoms at the interface and, therefore, alters the entire nucleation kinetics. Unless quite obvious, this effect has been ignored in the classical nucleation theory. To illustrate the results of this new approach, for the case of homogeneous nucleation, we calculate the total solubility (including the contribution from heterophase fluctuations) and the nucleation rate as functions of two parameters of the model and compare these results to the classical ones. One can conclude that discrepancies with the classical nucleation theory are great in the diffusion-limited regime, when the bulk diffusion mobility of solute atoms is small compared to the interfacial one, while in the opposite inter...

  3. Detonation wave driven by condensation of supersaturated carbon vapor.

    Science.gov (United States)

    Emelianov, A; Eremin, A; Fortov, V; Jander, H; Makeich, A; Wagner, H Gg

    2009-03-01

    An experimental observation of a detonation wave driven by the energy of condensation of supersaturated carbon vapor is reported. The carbon vapor was formed by the thermal decay of unstable carbon suboxide C3O2 behind shock waves in mixtures containing 10-30% C3O2 in Ar. In the mixture 10% C3O2+Ar the insufficient heat release resulted in a regime of overdriven detonation. In the mixture 20% C3O2+Ar measured values of the pressure and wave velocity coincident with calculated Chapman-Jouguet parameters were attained. In the richest mixture 30% C3O2+Ar an excess heat release caused the slowing down of the condensation rate and the regime of underdriven detonation was observed.

  4. Nucleation of protein crystals in a wide continuous supersaturation gradient.

    Science.gov (United States)

    Penkova, A; Chayen, N; Saridakis, E; Nanev, Chr N

    2002-10-01

    By using a supersaturation gradient along a protein solution contained in a glass capillary tube, we modified the classical double pulse technique, thus substantially accelerating the procedure of measurement of nucleation parameters. Data for the number of crystal nuclei, n vs nucleation time, t, were obtained for hen-egg-white lysozyme, chosen as a model because of the availability of reliable solubility data in the literature. The stationary nucleation rate and the nucleation time lag have been measured. Quantitative data for the work required for nucleus formation (A(k) = 4.3 x 10 (-1)3 erg) and the size of the critical cluster (three molecules) were also obtained. Besides, it was observed that Ostwald ripening seems to play an important role for nucleation times longer than 150 min. Using the same technique, semi-quantitative investigations were performed with porcine pancreatic trypsin.

  5. Closure between measured and modeled cloud condensation nuclei (CCN using size-resolved aerosol compositions in downtown Toronto

    Directory of Open Access Journals (Sweden)

    K. Broekhuizen

    2006-01-01

    Full Text Available Measurements of cloud condensation nuclei (CCN were made in downtown Toronto during August and September, 2003. CCN measurements were performed at 0.58% supersaturation using a thermal-gradient diffusion chamber, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and APS system and an Aerodyne Aerosol Mass Spectrometer (AMS, respectively. Aerosol composition data shows that the particles were predominately organic in nature, in particular for those with a vacuum aerodynamic diameter of predicted/CCNobserved=1.12±0.05. However, several sample days showed distinct bimodal distributions, and a closure analysis was performed after decoupling the two particle modes. This analysis yielded an average value of CCNpredicted/CCNobserved=1.03±0.05. A sensitivity analysis was also performed to determine the aerosol/CCN closure if the organic solubility, droplet surface tension, or chamber supersaturation were varied.

  6. Oxygen supersaturated fluid using fine micro/nanobubbles

    Directory of Open Access Journals (Sweden)

    Matsuki N

    2014-09-01

    Full Text Available Noriaki Matsuki,1 Takuji Ishikawa,2 Shingo Ichiba,3 Naoki Shiba,3 Yoshihito Ujike,3 Takami Yamaguchi4 1Department of Biomedical Engineering, Graduate School of Engineering, Okayama University of Science, Okayama, 2Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai, 3Department of Emergency and Critical Care Medicine, Okayama University Hospital, Okayama, 4Graduate School of Biomedical Engineering, Tohoku University, Sendai, JapanAbstract: Microbubbles show peculiar properties, such as shrinking collapse, long lifetime, high gas solubility, negative electric charge, and free radical production. Fluids supersaturated with various gases can be easily generated using microbubbles. Oxygen microbubble fluid can be very useful for oxygen delivery to hypoxic tissues. However, there have been no reports of comparative investigations into adding fluids containing oxygen fine micro/nanobubbles (OFMNBs to common infusion solutions in daily medical care. In this study, it was demonstrated that OFMNBs can generate oxygen-supersaturated fluids, and they may be sufficiently small to infuse safely into blood vessels. It was found that normal saline solution is preferable for generating an oxygen-rich infusion fluid, which is best administered as a 30-minute intravenous infusion. It was also concluded that dextran solution is suitable for drug delivery substances packing oxygen gas over a 1-hour intravenous infusion. In addition, normal saline solution containing OFMNBs was effective for improving blood oxygenation. Thus, the use of OFMNB-containing fluids is a potentially effective novel method for improving blood oxygenation in cases involving hypoxia, ischemic diseases, infection control, and anticancer chemoradiation therapies.Keywords: microbubble, fine micro/nanobubble, nanobubble, oxygenation, fluid oxygenation

  7. Comprehensive airborne characterization of aerosol from a major bovine source

    Directory of Open Access Journals (Sweden)

    A. Sorooshian

    2008-06-01

    Full Text Available We report an extensive airborne characterization of aerosol downwind of a massive bovine source in the San Joaquin Valley (California on two flights during July 2007. The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS Twin Otter probed chemical composition, particle size distribution, mixing state, sub- and supersaturated water uptake behavior, light scattering properties, and the interrelationship between these parameters and meteorology. Total PM1.0 levels and concentrations of organics, nitrate, and ammonium were enhanced in the plume from the source as compared to the background aerosol. Organics dominated the plume aerosol mass (~56–64%, followed either by sulfate or nitrate, and then ammonium. Particulate amines were detected in the plume aerosol by a particle-into-liquid sampler (PILS and via mass spectral markers in the Aerodyne cToF-AMS. Amines were found to be a significant atmospheric base even in the presence of ammonia; particulate amine concentrations are estimated as at least 14–23% of that of ammonium in the plume. Enhanced sub- and supersaturated water uptake and reduced refractive indices were coincident with lower organic mass fractions, higher nitrate mass fractions, and the detection of amines. Kinetic limitations due to hydrophobic organic material are shown to have likely suppressed droplet growth. After removing effects associated with size distribution and mixing state, the normalized activated fraction of cloud condensation nuclei (CCN increased as a function of the subsaturated hygroscopic growth factor, with the highest activated fractions being consistent with relatively lower organic mass fractions and higher nitrate mass fractions. Subsaturated hygroscopic growth factors for the organic fraction of the aerosol are estimated based on employing the Zdanovskii-Stokes Robinson (ZSR mixing rule. Representative values for a parameterization treating particle water uptake in both the

  8. Comprehensive airborne characterization of aerosol from a major bovine source

    Directory of Open Access Journals (Sweden)

    H. Jonsson

    2008-09-01

    Full Text Available We report an extensive airborne characterization of aerosol downwind of a massive bovine source in the San Joaquin Valley (California on two flights during July 2007. The Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS Twin Otter probed chemical composition, particle size distribution, mixing state, sub- and supersaturated water uptake behavior, light scattering properties, and the interrelationship between these parameters and meteorology. Total PM1.0 levels and concentrations of organics, nitrate, and ammonium were enhanced in the plume from the source as compared to the background aerosol. Organics dominated the plume aerosol mass (~56–64%, followed either by sulfate or nitrate, and then ammonium. Particulate amines were detected in the plume aerosol by a particle-into-liquid sampler (PILS and via mass spectral markers in the Aerodyne C-ToF-AMS. Amines were found to be a significant atmospheric base even in the presence of ammonia; particulate amine concentrations are estimated as at least 14–23% of that of ammonium in the plume. Enhanced sub- and supersaturated water uptake and reduced refractive indices were coincident with lower organic mass fractions, higher nitrate mass fractions, and the detection of amines. The likelihood of suppressed droplet growth owing to kinetic limitations from hydrophobic organic material is explored. After removing effects associated with size distribution and mixing state, the normalized activated fraction of cloud condensation nuclei (CCN increased as a function of the subsaturated hygroscopic growth factor, with the highest activated fractions being consistent with relatively lower organic mass fractions and higher nitrate mass fractions. Subsaturated hygroscopic growth factors for the organic fraction of the aerosol are estimated based on employing the Zdanovskii-Stokes Robinson (ZSR mixing rule. Representative values for a parameterization treating particle water

  9. Development of an aerosol microphysical module: Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS

    Directory of Open Access Journals (Sweden)

    H. Matsui

    2014-04-01

    Full Text Available Number concentrations, size distributions, and mixing states of aerosols are essential parameters for accurate estimation of aerosol direct and indirect effects. In this study, we develop an aerosol module, designated Aerosol Two-dimensional bin module for foRmation and Aging Simulation (ATRAS, that can represent these parameters explicitly by considering new particle formation (NPF, black carbon (BC aging, and secondary organic aerosol (SOA processes. A two-dimensional bin representation is used for particles with dry diameters from 40 nm to 10 μm to resolve both aerosol size (12 bins and BC mixing state (10 bins for a total of 120 bins. The particles with diameters from 1 to 40 nm are resolved using an additional 8 size bins to calculate NPF. The ATRAS module is implemented in the WRF-chem model and applied to examine the sensitivity of simulated mass, number, size distributions, and optical and radiative parameters of aerosols to NPF, BC aging and SOA processes over East Asia during the spring of 2009. BC absorption enhancement by coating materials is about 50% over East Asia during the spring, and the contribution of SOA processes to the absorption enhancement is estimated to be 10–20% over northern East Asia and 20–35% over southern East Asia. A clear north-south contrast is also found between the impacts of NPF and SOA processes on cloud condensation nuclei (CCN concentrations: NPF increases CCN concentrations at higher supersaturations (smaller particles over northern East Asia, whereas SOA increases CCN concentrations at lower supersaturations (larger particles over southern East Asia. Application of ATRAS to East Asia also shows that the impact of each process on each optical and radiative parameter depends strongly on the process and the parameter in question. The module can be used in the future as a benchmark model to evaluate the accuracy of simpler aerosol models and examine interactions between NPF, BC aging, and SOA

  10. Deliquescence and Efflorescence Processes of Aerosol Particles Studied by in situ FTIR and Raman Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Li-jun Zhao; Feng Wang; Kun Zhang; Qing-xuan Zeng; Yun-hong Zhang

    2008-01-01

    Deliquescence and efflorescence are the two most important physicochemical processes of aerosol particles.In deliquescence and efflorescence cycles of aerosol particles,many fundamental problems need to be investigated in detail on the molecular level,including ion and molecule interactions in supersaturated aerosols,metastable solid phases that may be formed,and microscopic structures and deliquescence mechanisms of aerosol particles.This paper presents a summary of the progress made in recent investigations of deliquescence and efflorescence processes of aerosol particles by four common spectral techniques,which are known as Raman/electrodynamic balance,Fourier transform infrared/aerosol flow tube,Fourier transform infrared/attenuated total reflection,and confocal Raman on a quartz substrate.

  11. Asymptotic solution of nonlinear moment equations for constant-rate aerosol reactors

    Directory of Open Access Journals (Sweden)

    B. D. Shaw

    1998-01-01

    Full Text Available Nonlinear evolution equations based upon moments of the aerosol size distribution function are solved asymptotically for constant-rate aerosol reactors (i.e., where condensible monomer is added at a constant rate operating in the free-molecular limit. The governing equations are nondimensionalized and a large parameter that controls nucleation behavior is identified. Asymptotic analyses are developed in terms of this parameter. Comparison of the asymptotic results with direct numerical integration of the governing equations is favorable. The asymptotic results provide a simplified analytical approach to estimating average particle sizes, particle number densities, and peak supersaturation values for constant-rate aerosol reactors.

  12. Combining ibuprofen sodium with cellulosic polymers: a deep dive into mechanisms of prolonged supersaturation.

    Science.gov (United States)

    Terebetski, Jenna L; Michniak-Kohn, Bozena

    2014-11-20

    The combination of a highly soluble salt form of a drug with a polymeric precipitation inhibitor has the potential to prolong drug supersaturation even following salt disproportionation. In this study, dissolution profiles of ibuprofen sodium in the presence of various cellulosic polymers, including hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and hydroxypropyl cellulose (HPC), were examined in order to assess degree and duration of supersaturation. In addition, the roles that the polymers played in altering drug solubility, media viscosity, physical form, and particle morphology were also assessed. A deep dive into the mechanisms of supersaturation revealed that intermolecular hydrogen bonding between ibuprofen and HPMC was driving supersaturation through nucleation inhibition and crystal growth modification. Polymer viscosity was proposed as the primary factor prolonging supersaturation of ibuprofen in the presence of MC, while mechanisms other than hydrogen bonding were likely to be attributed to supersaturation with the most hydrophobic polymer evaluated, HPC. Overall, the study suggested that induction of intermolecular interactions between ibuprofen and HPMC were more effective at inhibiting nucleation and maintaining prolonged supersaturation than physical modulation of solution properties, such as viscosity. Copyright © 2014. Published by Elsevier B.V.

  13. Small fraction of marine cloud condensation nuclei made up of sea spray aerosol

    Science.gov (United States)

    Quinn, P. K.; Coffman, D. J.; Johnson, J. E.; Upchurch, L. M.; Bates, T. S.

    2017-09-01

    Sea spray aerosols impact Earth's radiation balance by directly scattering solar radiation. They also act as cloud condensation nuclei, thereby altering cloud properties including reflectivity, lifetime and extent. The influence of sea spray aerosol on cloud properties is thought to be particularly strong over remote ocean regions devoid of continental particles. Yet the contribution of sea spray aerosol to the population of cloud condensation nuclei in the marine boundary layer remains poorly understood. Here, using a lognormal-mode-fitting procedure, we isolate sea spray aerosols from measurements of particle size and abundance over the Pacific, Southern, Arctic and Atlantic oceans to determine the contribution of sea spray aerosol to the population of cloud condensation nuclei in the marine boundary layer. On a global basis, with the exception of the high southern latitudes, sea spray aerosol makes a contribution of less than 30% to the cloud condensation nuclei population for air that is supersaturated at 0.1 to 1.0%--the supersaturation range typical of marine boundary layer clouds. Instead, the cloud condensation nuclei population between 70° S and 80° N is composed primarily of non-sea-salt sulfate aerosols, due to large-scale meteorological features that result in entrainment of particles from the free troposphere.

  14. Misfit dislocation generation in SiGe epitaxial layers supersaturated with intrinsic point defects

    Energy Technology Data Exchange (ETDEWEB)

    Vdovin, V.I. [Institute for Chemical Problems of Microelectronics, B. Tolmachevsky per. 5, 119017 Moscow (Russian Federation)], E-mail: vivdov@gmail.com; Zakharov, N.D. [Max-Planck-Institut fuer Mikrostrukturphysik, 06120 Halle (Saale) (Germany)], E-mail: zakharov@mpi-halle.mpg.de

    2008-11-03

    Misfit dislocation generation in SiGe/Si(001) heterostructures supersaturated with the vacancies (LT epitaxial growth) or self-interstitials (ion implantation) was studied by transmission electron microscopy. A model of 'optimal' intrinsic point defects (IPDs) for effective strain relaxation is suggested and verified. Supersaturation of compressed SiGe layers with the vacancies ('optimal' IPDs) promotes high strain relaxation, whereas supersaturation with the self-interstitials ('inverse' IPDs) promotes a generation of V-shaped TDs which cannot extend to form MDs.

  15. Urinary supersaturation with respect to brushite in patients suffering calcium oxalate lithiasis.

    Science.gov (United States)

    Berland, Y; Boistelle, R; Olmer, M

    1990-01-01

    The urines of 23 stone-formers presenting repeated calcium oxalate lithiasis and 12 control subjects were collected at six different time periods daily. Supersaturations for calcium oxalate and brushite (DCPD) were calculated using ionic and solubility products. Urines of both groups were supersaturated for calcium oxalate but only urines of the stone-formers were supersaturated for brushite, the most simple calcium phosphate which nucleates very easily at the urinary pH. This fact suggests that the core of the calcium oxalate stone could be made of either a calcium oxalate crystallite or a brushite seed onto which hetergeneous nucleation of calcium oxalate can take place.

  16. Supersaturation-dependent surface structure evolution: from ionic, molecular to metallic micro/nanocrystals.

    Science.gov (United States)

    Lin, Hai-xin; Lei, Zhi-chao; Jiang, Zhi-yuan; Hou, Chang-ping; Liu, De-yu; Xu, Min-min; Tian, Zhong-qun; Xie, Zhao-xiong

    2013-06-26

    Deduced from thermodynamics and the Thomson-Gibbs equation that the surface energy of crystal face is in proportion to the supersaturation of crystal growth units during the crystal growth, we propose that the exposed crystal faces can be simply tuned by controlling the supersaturation, and higher supersaturation will result in the formation of crystallites with higher surface-energy faces. We have successfully applied it for the growth of ionic (NaCl), molecular (TBPe), and metallic (Au, Pd) micro/nanocrystals with high-surface-energy faces. The above proposed strategy can be rationally designed to synthesize micro/nanocrystals with specific crystal faces and functionality toward specific applications.

  17. The use of magnesium sulphate (MgSO4) for seizure prophylaxis ...

    African Journals Online (AJOL)

    MJP

    respiratory rate and urine output are currently well recognised. .... liver function, thrombocytopenia and fetal growth restriction.[28] ... Variable. Eclampsia. N=28. Severe Pre-eclampsia. N=47 p-value (95% CI) ..... Wolf H, Boer K,Sanders GT.

  18. Aerosolized Antibiotics.

    Science.gov (United States)

    Restrepo, Marcos I; Keyt, Holly; Reyes, Luis F

    2015-06-01

    Administration of medications via aerosolization is potentially an ideal strategy to treat airway diseases. This delivery method ensures high concentrations of the medication in the targeted tissues, the airways, with generally lower systemic absorption and systemic adverse effects. Aerosolized antibiotics have been tested as treatment for bacterial infections in patients with cystic fibrosis (CF), non-CF bronchiectasis (NCFB), and ventilator-associated pneumonia (VAP). The most successful application of this to date is treatment of infections in patients with CF. It has been hypothesized that similar success would be seen in NCFB and in difficult-to-treat hospital-acquired infections such as VAP. This review summarizes the available evidence supporting the use of aerosolized antibiotics and addresses the specific considerations that clinicians should recognize when prescribing an aerosolized antibiotic for patients with CF, NCFB, and VAP.

  19. Supersaturation, droplet spectra, and turbulent mixing in clouds

    Science.gov (United States)

    Gerber, H.

    1990-01-01

    Much effort has recently gone into explaining the observed broad precoalescence size distribution of droplets in cloud and fogs, because this differs from the results of condensational growth calculations which lead to much narrower distributions. A good example of droplet size-distribution broadening was observed on flight 17 (25 July) of the NRL tethered balloon during the 1987 FIRE San Nicolas Island IFO. These observations caused the interactions between cloud microphysics and turbulent mixing to be re-examined. The findings of Broadwell and Breidenthal (1982) who conducted laboratory and theoretical studies of mixing in shear flow, and those of Baker et al. (1984) who applied the earlier work to mixing in clouds, were used. Rather than looking at the 25 July case at SNI, earlier fog observations made at SUNY (6 Oct. 1982) which also indicated that shear-induced mixing was taking place, and which had a better collection of microphysical measurements including more precise supersaturation measurements and detailed vertical profiles of meteorological parameters were chosen instead.

  20. Supersaturation of poorly soluble drugs induced by mesoporous magnesium carbonate.

    Science.gov (United States)

    Zhang, Peng; Zardán Gómez de la Torre, Teresa; Welch, Ken; Bergström, Christel; Strømme, Maria

    2016-10-10

    This work investigates whether the solubility of poorly soluble compounds can be improved by using mesoporous magnesium carbonate (MMC) as the drug delivery system. A solvent evaporation method was used to load structurally diverse model drugs (celecoxib, cinnarizine and griseofulvin) into the pores of MMC. The drug-loaded carrier system was then characterized in terms of porosity, crystallinity, and release profiles by a variety of experimental techniques, including X-ray diffraction, nitrogen adsorption analysis, differential scanning calorimetry, infrared spectroscopy, UV absorption spectroscopy, and thermogravimetric analysis. All three drugs were in a non-crystalline state after loading into the pores of MMC. The concentrations of the drugs in solution over time (a measure of the release rates from loaded MMC) were higher than the corresponding concentrations (dissolution rates) of equal amounts of the crystalline drugs. The release rates were five (celecoxib), three (cinnarizine) and two times (griseofulvin) higher than the dissolution rates of their crystalline counterparts. Supersaturation release profiles were also observed; the areas under the concentration-time curves (0-240min) were 25- (celecoxib), 5- (cinnarizine) and 2-fold (griseofulvin) greater than those of the crystalline drugs. Hence, MMC shows promise as a general drug delivery vehicle for increasing the bioavailability of compounds with dissolution rate- or solubility-limited absorption. Copyright © 2016. Published by Elsevier B.V.

  1. Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.

    Directory of Open Access Journals (Sweden)

    E. Hammer

    2014-01-01

    Full Text Available Aerosols influence the Earth's radiation budget directly through absorption and scattering of solar radiation in the atmosphere but also indirectly by modifying the properties of clouds. However, climate models still suffer from large uncertainties as a result of insufficient understanding of aerosol-cloud interactions. At the high altitude research station Jungfraujoch (JFJ; 3580 m a.s.l., Switzerland cloud condensation nuclei (CCN number concentrations at eight different supersaturations (SS from 0.24% to 1.18% were measured using a CCN counter during Summer 2011. Simultaneously, in-situ aerosol activation properties of the prevailing ambient clouds were investigated by measuring the total and interstitial (non-activated dry particle number size distributions behind two different inlet systems. Combining all experimental data, a new method was developed to retrieve the so-called effective peak supersaturation SSpeak, as a measure of the SS at which ambient clouds are formed. A 17-month CCN climatology was then used to retrieve the SSpeak values also for four earlier summer campaigns (2000, 2002, 2004 and 2010 where no direct CCN data were available. The SSpeak values varied between 0.01% and 2.0% during all campaigns. An overall median SSpeak of 0.35% and dry activation diameter of 87 nm was observed. It was found that the difference in topography between northwest and southeast plays an important role for the effective peak supersaturation in clouds formed in the vicinity of the JFJ, while differences in the number concentration of potential CCN only play a minor role. Results show that air masses coming from the southeast (with the slowly rising terrain of the Aletsch Glacier generally experience lower SSpeak values than air masses coming from the northwest (steep slope. The observed overall median values were 0.41% and 0.22% for northwest and southeast wind conditions, respectively, corresponding to literature values for cumulus clouds and

  2. Supersaturation dependence of glycine polymorphism using laser-induced nucleation, sonocrystallization and nucleation by mechanical shock.

    Science.gov (United States)

    Liu, Yao; van den Berg, Mees H; Alexander, Andrew J

    2017-07-26

    The nucleation of glycine from aqueous supersaturated solution has been studied using non-photochemical laser-induced nucleation (NPLIN), ultrasound (sonocrystallization), and mechanical shock of sample vials. It was found that at higher supersaturation, samples were more susceptible to nucleation and produced more of the γ-glycine polymorph. The results are described in terms of a mechanism common to all three nucleation methods, involving the induction of cavitation events and pressure shockwaves. The switch in preference from α- to γ-glycine was observed to occur over a narrower range of supersaturation values for NPLIN. We attribute this to induction of cavitation events with higher energies, which result in higher localized pressures and supersaturations. Experiments on NPLIN using circularly versus linearly polarized light showed no evidence for binary polarization switching control of glycine polymorphism.

  3. Effect of supersaturation on hillock of directional Growth of KDP crystals.

    Science.gov (United States)

    Liu, Fa-Fu; Yu, Guang-Wei; Zhang, Li-Song; Li, Liang; Wang, Bo; Gan, Xiao-Yu; Ren, Hong-Kai; Zhou, Hai-Liang; Zhu, Li-Li; Ji, Shao-Hua; Xu, Ming-Xia; Liu, Bao-An; Xu, Xin-Guang; Gu, Qing-Tian; Sun, Xun

    2014-11-03

    KDP single crystals were grown in aqueous solution by using "point seeds" with a defined crystallographic direction of 59° to the Z axis. When hillock slopes on the (100) face of KDP crystals were measured within the supersaturation (σ) range of 0 supersaturation. Below σ = 0.02, the hillock slope depended on supersaturation, but when σ was ≥ 0.02, the hillock slope increased more gradually and was less dependent on supersaturation. Hollow funnel-shaped growth dislocation on the (100) face of KDP crystals was observed at σ = 0.04, characterized by large holes with micro-steps and step bunching inside, the formation of which were analyzed. The result verified that the reversed growth appears to occur within hollow channels found on growth hillocks.

  4. Calculated Grain Size-Dependent Vacancy Supersaturation and its Effect on Void Formation

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Foreman, A. J. E.

    1974-01-01

    In order to study the effect of grain size on void formation during high-energy electron irradiations, the steady-state point defect concentration and vacancy supersaturation profiles have been calculated for three-dimensional spherical grains up to three microns in size. In the calculations...... of vacancy supersaturation as a function of grain size, the effects of internal sink density and the dislocation preference for interstitial attraction have been included. The computations show that the level of vacancy supersaturation achieved in a grain decreases with decreasing grain size. The grain size...... dependence of the maximum vacancy supersaturation in the centre of the grains is found to be very similar to the grain size dependence of the maximum void number density and void volume swelling measured in the central regions of austenitic stainless steel grains. This agreement reinforces the interpretation...

  5. Supersaturation calculation in large eddy simulation models for prediction of the droplet number concentration

    Directory of Open Access Journals (Sweden)

    O. Thouron

    2011-12-01

    Full Text Available A new parameterization scheme is described for calculation of supersaturation in LES models that specifically aims at the simulation of cloud condensation nuclei (CCN activation and prediction of the droplet number concentration. The scheme is tested against current parameterizations in the framework of the Meso-NH LES model. It is shown that the saturation adjustment scheme based on parameterizations of CCN activation in a convective updraft over estimates the droplet concentration in the cloud core while it cannot simulate cloud top supersaturation production due to mixing between cloudy and clear air. A supersaturation diagnostic scheme mitigates these artefacts by accounting for the presence of already condensed water in the cloud core but it is too sensitive to supersaturation fluctuations at cloud top and produces spurious CCN activation during cloud top mixing. The proposed pseudo-prognostic scheme shows performance similar to the diagnostic one in the cloud core but significantly mitigates CCN activation at cloud top.

  6. About supersaturation and growth rates of hydrargillite Al(OH) 3 in alumina caustic solutions

    Science.gov (United States)

    Veesler, Stéphane; Boistelle, Roland

    1993-06-01

    Growth rates of hydrargillite crystals, Al(OH) 3, growing from concentrated caustic solutions, are traditionally plotted and discussed as a function of the difference between actual concentration and solubility of alumina. This way to express supersaturation is probably due to practical or technical reasons, as hydrargillite is mainly grown in industrial plants. However, as the solubility of hydrargillite is greatly affected by the presence of caustic soda there are as many growth rate curves as there are solutions at different soda concentrations, if supersaturation is expressed as a concentration difference. In the present paper we show that all growth rates, measured in different caustic solutions, lie on a single curve if supersaturation is normalized with respect to solubility, i.e. expressed as a ratio of actual concentration over solubility. Accordingly, growth rates become independent of the caustic concentrations when growth takes place at the same supersaturation.

  7. Laboratory-generated primary marine aerosol via bubble-bursting and atomization

    Directory of Open Access Journals (Sweden)

    E. Fuentes

    2009-09-01

    Full Text Available A range of bubble and sea spray aerosol generators has been tested in the laboratory and compared with ocean measurements. We have shown that the method of generation has a significant influence on the properties of the aerosol particles produced. Hence, the validity of a generation system to mimic atmospheric aerosol is dependent on its capacity of generating bubbles and particulate in a realistic manner. A bubble-bursting aerosol generator consisting in the production of bubbles by the impingement of water jets on seawater was shown to best reproduce the real oceanic bubble and aerosol distributions signatures.

    Two aeration methods and a plunging-water jet system were tested as bubble-bursting aerosol generators for comparison with a standard nebulizer. The methods for aerosol production were evaluated by analysing the bubble spectrum generated by the bubble-bursting systems and the submicron size distribution, hygroscopicity and cloud condensation nucleus activity of the aerosols generated by the different techniques. Significant differences in the bubble spectrum and aerosol properties were observed when using different aerosol generators.

    The hygroscopicity and cloud condensation nucleus activity of aerosols generated by the different methods were similar when a sample of purely inorganic salts was used as a parent seawater solution; however, significant differences in the aerosol properties were found when biogenic organics were incorporated in the seawater samples. The presence of organics in the aerosol caused suppression of the growth factor at humidities above 75% RH and an increase in the critical supersaturation when compared with the case without organics. Unequal extent of these effects was observed for aerosols generated by the different methods of particle production. While the highest reductions of the growth factor were observed for the plunging-water jet aerosol, the largest effect on the critical

  8. Tropospheric Aerosols

    Science.gov (United States)

    Buseck, P. R.; Schwartz, S. E.

    2003-12-01

    It is widely believed that "On a clear day you can see forever," as proclaimed in the 1965 Broadway musical of the same name. While an admittedly beautiful thought, we all know that this concept is only figurative. Aside from Earth's curvature and Rayleigh scattering by air molecules, aerosols - colloidal suspensions of solid or liquid particles in a gas - limit our vision. Even on the clearest day, there are billions of aerosol particles per cubic meter of air.Atmospheric aerosols are commonly referred to as smoke, dust, haze, and smog, terms that are loosely reflective of their origin and composition. Aerosol particles have arisen naturally for eons from sea spray, volcanic emissions, wind entrainment of mineral dust, wildfires, and gas-to-particle conversion of hydrocarbons from plants and dimethylsulfide from the oceans. However, over the industrial period, the natural background aerosol has been greatly augmented by anthropogenic contributions, i.e., those produced by human activities. One manifestation of this impact is reduced visibility (Figure 1). Thus, perhaps more than in other realms of geochemistry, when considering the composition of the troposphere one must consider the effects of these activities. The atmosphere has become a reservoir for vast quantities of anthropogenic emissions that exert important perturbations on it and on the planetary ecosystem in general. Consequently, much recent research focuses on the effects of human activities on the atmosphere and, through them, on the environment and Earth's climate. For these reasons consideration of the geochemistry of the atmosphere, and of atmospheric aerosols in particular, must include the effects of human activities. (201K)Figure 1. Impairment of visibility by aerosols. Photographs at Yosemite National Park, California, USA. (a) Low aerosol concentration (particulate matter of aerodynamic diameter less than 2.5 μm, PM2.5=0.3 μg m-3; particulate matter of aerodynamic diameter less than 10

  9. Effect of Extent of Supersaturation on the Evolution of Kinetic Solubility Profiles.

    Science.gov (United States)

    Han, Yi Rang; Lee, Ping I

    2017-01-03

    Solubility limited compounds require enabling formulations such as amorphous solid dispersions (ASDs) to increase the apparent solubility by dissolving to a concentration higher than the equilibrium solubility of the drug. This may lead to subsequent precipitation and thus the loss of the solubility advantage. Although higher supersaturation is known to result in faster precipitation, the overall effect of this faster precipitation on the bioavailability is not well understood. The objective of this study is to gain a better understanding of the impact of extent of supersaturation (i.e., dose) on the resulting kinetic solubility profiles of supersaturating dosage forms. Experimental concentration-time curves of two model compounds with different recrystallization tendencies, indomethacin (IND) and naproxen (NAP), were explored under varying sink indices (SIs) by infusing varying volumes of dissolved drug (e.g., in ethanol) into the dissolution medium. The experimental results were simulated with a mechanistic model considering classical nucleation theory and interface controlled growth on the nucleus surface. In the absence of dissolved polymer to inhibit precipitation, experimental and predicted results show that there exists a critical supersaturation below which no precipitation is observed, and due to this supersaturation maintenance, there exists an optimal dose which maximizes the area under the curve (AUC) of the kinetic solubility concentration-time profile. In the presence of dissolved polymer from ASD dissolution, similar trends were observed except the critical supersaturation was increased due to crystallization inhibition by the dissolved polymer. The importance of measuring the experimental "kinetic solubility" is emphasized. However, we show that the true solubility advantage of amorphous solids depends not on the "kinetic solubility" of amorphous dosage forms, typically arising from the balance between the rate of supersaturation generation and the

  10. Atmospheric moisture supersaturation in the near-surface atmosphere at Dome C, Antarctic Plateau

    Science.gov (United States)

    Genthon, Christophe; Piard, Luc; Vignon, Etienne; Madeleine, Jean-Baptiste; Casado, Mathieu; Gallée, Hubert

    2017-01-01

    Supersaturation often occurs at the top of the troposphere where cirrus clouds form, but is comparatively unusual near the surface where the air is generally warmer and laden with liquid and/or ice condensation nuclei. One exception is the surface of the high Antarctic Plateau. One year of atmospheric moisture measurement at the surface of Dome C on the East Antarctic Plateau is presented. The measurements are obtained using commercial hygrometry sensors modified to allow air sampling without affecting the moisture content, even in the case of supersaturation. Supersaturation is found to be very frequent. Common unadapted hygrometry sensors generally fail to report supersaturation, and most reports of atmospheric moisture on the Antarctic Plateau are thus likely biased low. The measurements are compared with results from two models implementing cold microphysics parameterizations: the European Center for Medium-range Weather Forecasts through its operational analyses, and the Model Atmosphérique Régional. As in the observations, supersaturation is frequent in the models but the statistical distribution differs both between models and observations and between the two models, leaving much room for model improvement. This is unlikely to strongly affect estimations of surface sublimation because supersaturation is more frequent as temperature is lower, and moisture quantities and thus water fluxes are small anyway. Ignoring supersaturation may be a more serious issue when considering water isotopes, a tracer of phase change and temperature, largely used to reconstruct past climates and environments from ice cores. Because observations are easier in the surface atmosphere, longer and more continuous in situ observation series of atmospheric supersaturation can be obtained than higher in the atmosphere to test parameterizations of cold microphysics, such as those used in the formation of high-altitude cirrus clouds in meteorological and climate models.

  11. Direct NMR Monitoring of Phase Separation Behavior of Highly Supersaturated Nifedipine Solution Stabilized with Hypromellose Derivatives.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu

    2017-07-03

    We investigated the phase separation behavior and maintenance mechanism of the supersaturated state of poorly water-soluble nifedipine (NIF) in hypromellose (HPMC) derivative solutions. Highly supersaturated NIF formed NIF-rich nanodroplets through phase separation from aqueous solution containing HPMC derivative. Dissolvable NIF concentration in the bulk water phase was limited by the phase separation of NIF from the aqueous solution. HPMC derivatives stabilized the NIF-rich nanodroplets and maintained the NIF supersaturation with phase-separated NIF for several hours. The size of the NIF-rich phase was different depending on the HPMC derivatives dissolved in aqueous solution, although the droplet size had no correlation with the time for which NIF supersaturation was maintained without NIF crystallization. HPMC acetate and HPMC acetate succinate (HPMC-AS) effectively maintained the NIF supersaturation containing phase-separated NIF compared with HPMC. Furthermore, HPMC-AS stabilized NIF supersaturation more effectively in acidic conditions. Solution (1)H NMR measurements of NIF-supersaturated solution revealed that HPMC derivatives distributed into the NIF-rich phase during the phase separation of NIF from the aqueous solution. The hydrophobicity of HPMC derivative strongly affected its distribution into the NIF-rich phase. Moreover, the distribution of HPMC-AS into the NIF-rich phase was promoted at lower pH due to the lower aqueous solubility of HPMC-AS. The distribution of a large amount of HPMC derivatives into NIF-rich phase induced the strong inhibition of NIF crystallization from the NIF-rich phase. Polymer distribution into the drug-rich phase directly monitored by solution NMR technique can be a useful index for the stabilization efficiency of drug-supersaturated solution containing a drug-rich phase.

  12. An Insight into Different Stabilization Mechanisms of Phenytoin Derivatives Supersaturation by HPMC and PVP.

    Science.gov (United States)

    Otsuka, Naoya; Ueda, Keisuke; Ohyagi, Naoko; Shimizu, Kozue; Katakawa, Kazuaki; Kumamoto, Takuya; Higashi, Kenjirou; Yamamoto, Keiji; Moribe, Kunikazu

    2015-08-01

    In this study, we examined the stabilization mechanism of drug supersaturation by hypromellose (HPMC) and polyvinylpirrolidone (PVP). The poorly water-soluble drugs, phenytoin (diphenylhydantoin, DPH), and its synthesized derivatives monomethylphenytoin (MDPH) and dimethylphenytoin (DMDPH) were used. DPH supersaturation was efficiently maintained by both HPMC and PVP. HPMC maintained the supersaturation of MDPH and DMDPH in a similar manner to that of DPH, whereas the ability of PVP to maintain drug supersaturation increased as follows: DPH > MDPH > DMDPH. Caco-2 permeation studies and nuclear magnetic resonance measurements revealed that the permeability and molecular state of the drug in a HPMC solution barely changed. In fact, the solubilization of the drug into PVP changed its apparent permeability and molecular state. The drug solubilization efficiency by PVP was higher and followed the order: DPH > MDPH > DMDPH. The different drug solubilization efficiencies most likely result from the different strengths in the intermolecular interaction between the DPH derivatives and PVP. The difference in the stabilization mechanism of drug supersaturation by HPMC and PVP could determine whether the efficient maintenance of the drug supersaturation was dependent on the drug species. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  13. Preserving the supersaturation generation capability of amorphous drug-polysaccharide nanoparticle complex after freeze drying.

    Science.gov (United States)

    Kiew, Tie Yi; Cheow, Wean Sin; Hadinoto, Kunn

    2015-04-30

    While the supersaturation generation capability of amorphous nanopharmaceuticals (NPs) in their aqueous suspension form has been well established, their supersaturation generation is adversely affected after drying. Herein we investigated the effects of freeze drying on the supersaturation generation capability of a new class of amorphous NPs referred to as drug nanoplex prepared and stabilized by electrostatic complexation of drug molecules with polysaccharides (dextran sulfate). Using ciprofloxacin as the model drug, two types of freeze-drying adjuvants were investigated, i.e., (1) highly water-soluble excipient (trehalose, mannitol), whose role was to prevent irreversible NPs aggregations upon drying, and (2) crystallization inhibitor (hydroxypropylmethylcellulose (HPMC)), whose role was to suppress crystallization of the dissolved drug and the remaining solid phase. The results showed that dual-adjuvant formulations (i.e. trehalose-HPMC and mannitol-HPMC) were required to preserve the supersaturation generation capability of the drug nanoplex suspension after drying. Freeze drying with only one adjuvant type, or incorporating HPMC as physical mixtures with the freeze-dried nanoplex, were ineffective in preserving the supersaturation. The dual-adjuvant formulations produced prolonged supersaturation levels over 240min at ≈6-8× of the saturation solubility with comparable area under the curve (AUC) in the concentration versus time plot as that exhibited by the suspension form. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. The use of supersaturation for the vaginal application of microbicides: a case study with dapivirine.

    Science.gov (United States)

    Grammen, Carolien; Plum, Jakob; Van Den Brande, Jeroen; Darville, Nicolas; Augustyns, Koen; Augustijns, Patrick; Brouwers, Joachim

    2014-11-01

    In this study, we investigated the potential of supersaturation for the formulation of the poorly water-soluble microbicide dapivirine (DPV) in an aqueous vaginal gel in order to enhance its vaginal tissue uptake. Different excipients such as hydroxypropylmethylcellulose, polyethylene glycol 1000, and cyclodextrins were evaluated for their ability to inhibit precipitation of supersaturated DPV in the formulation vehicle as such as well as in biorelevant media. In vitro permeation assessment across HEC-1A cell layers demonstrated an enhanced DPV flux from supersaturated gels compared with suspension gels. The best performing supersaturated gel containing 500 μM DPV (supersaturation degree of 4) in the presence of sulfobutyl ether-beta-cyclodextrin (2.5%) appeared to be stable for at least 3 months. In addition, the gel generated a significant increase in vaginal drug uptake in rabbits as compared with suspension gels. We conclude that supersaturation is a possible strategy to enhance the vaginal concentration of hydrophobic microbicides, thereby increasing permeation into the vaginal submucosa. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  15. Cloud condensation nuclei closure study on summer arctic aerosol

    Directory of Open Access Journals (Sweden)

    M. Martin

    2011-11-01

    Full Text Available We present an aerosol – cloud condensation nuclei (CCN closure study on summer high Arctic aerosol based on measurements that were carried out in 2008 during the Arctic Summer Cloud Ocean Study (ASCOS on board the Swedish ice breaker Oden. The data presented here were collected during a three-week time period in the pack ice (>85° N when the icebreaker Oden was moored to an ice floe and drifted passively during the most biological active period into autumn freeze up conditions.

    CCN number concentrations were obtained using two CCN counters measuring at different supersaturations. The directly measured CCN number concentration was then compared with a CCN number concentration calculated using both bulk aerosol mass composition data from an aerosol mass spectrometer (AMS and aerosol number size distributions obtained from a differential mobility particle sizer, assuming κ-Köhler theory, surface tension of water and an internally mixed aerosol. The last assumption was supported by measurements made with a hygroscopic tandem differential mobility analyzer (HTDMA for particles >70 nm.

    For the two highest measured supersaturations, 0.73 and 0.41%, closure could not be achieved with the investigated settings concerning hygroscopicity and density. The calculated CCN number concentration was always higher than the measured one for those two supersaturations. This might be caused by a relative larger insoluble organic mass fraction of the smaller particles that activate at these supersaturations, which are thus less good CCN than the larger particles. On average, 36% of the mass measured with the AMS was organic mass. At 0.20, 0.15 and 0.10% supersaturation, closure could be achieved with different combinations of hygroscopic parameters and densities within the uncertainty range of the fit. The best agreement of the calculated CCN number concentration with the observed one was achieved when the organic fraction of the

  16. [Urinary calcium oxalate supersaturation beyond nephrolithiasis. Relationship with tubulointerstitial damage].

    Science.gov (United States)

    Toblli, Jorge E; Angerosa, Margarita; Stella, Inés; Ferder, León; Inserra, Felipe

    2003-01-01

    A number of studies have demonstrated that the urinary ion activity product (IAP) of calcium oxalate (CaOx), as an index of urinary CaOx supersaturation (SS), is higher in renal stone formers than in normal subjects. Besides, the relation between CaOx SS and lithogenesis, crystal CaOx exposition can produce tubular cell as well as renal interstitial lesions. The aim of our study was to evaluate the possible relationship between CaOx SS and tubulointerstitial (TI) damage in an animal model of hyperoxaluria. During four weeks, male Sprague-Dawley rats received: G1 (n = 8) control regular water, and G2 (n = 8) 1% ethylene glycol (ETG) (precursor for oxalates) in drinking water. In order to evaluate urinary CaOx SS, IAP assessed by Tisselius formula was performed. At the end of the study, renal lesions were evaluated by light microscopy and immunohistochemistry. Animals from G2 (ETG) presented higher (p intersticial fibrosis; e) interstitial alpha-smooth muscle actin; f) collagen type III; g) TI TGF beta 1 compared with G1 (control). Rats from G2 (ETG) presented a high correlation between urinary CaOx SS and most of the TI damage parameters evaluated, in especial with interstitial fibrosis. Both, inflammatory infiltrates and urinary CaOx SS were the most significant variables related to interstitial fibrosis. Finally, since hyperoxaluric animals showed higher urinary CaOx SS associated with higher renal TI damage, the results from this study suggest the presence of a tight link between urinary CaOx SS and renal TI damage. Considering these findings we think that urinary CaOx SS control rises in importance beyond nephrolithiasis.

  17. Simulation of aerosol nucleation and growth in a turbulent mixing layer

    KAUST Repository

    Zhou, Kun

    2014-06-25

    A large-scale simulation of aerosol nucleation and growth in a turbulent mixing layer is performed and analyzed with the aim of elucidating the key processes involved. A cold gaseous stream is mixed with a hot stream of vapor, nanometer sized droplets nucleate as the vapor becomes supersaturated, and subsequently grow as more vapor condenses on their surface. All length and time scales of fluid motion and mixing are resolved and the quadrature method of moments is used to describe the dynamics of the condensing, non-inertial droplets. The results show that a region of high nucleation rate is located near the cold, dry stream, while particles undergo intense growth via condensation on the hot, humid vapor side. Supersaturation and residence times are such that number densities are low and neither coagulation nor vapor scavenging due to condensation are significant. The difference in Schmidt numbers of aerosol particles (approximated as infinity) and temperature and vapor (near unity) causes a drift of the aerosol particles in scalar space and contributes to a large scatter in the conditional statistics of aerosol quantities. The spatial distribution of the aerosol reveals high volume fraction on the hot side of the mixing layer. This distribution is due to drift against the mean and is related to turbulent mixing, which displaces particles from the nucleation region (cold side) into the growth region (hot side). Such a mechanism is absent in laminar flows and is a distinct feature of turbulent condensing aerosols.

  18. Review of Current Literature and Research on Gas Supersaturation and Gas Bubble Trauma: Special Publication Number 1, 1986.

    Energy Technology Data Exchange (ETDEWEB)

    Colt, John; Bouck, Gerald R.; Fidler, Larry

    1986-12-01

    This report presents recently published information and on-going research on the various areas of gas supersaturation. Growing interest in the effects of chronic gas supersaturation on aquatic animals has been due primarily to heavy mortality of salmonid species under hatchery conditions. Extensive examination of affected animals has failed to consistently identify pathogenic organisms. Water quality sampling has shown that chronic levels of gas supersaturation are commonly present during a significant period of the year. Small marine fish larvae are significantly more sensitive to gas supersaturation than salmonids. Present water quality criteria for gas supersaturation are not adequate for the protection of either salmonids under chronic exposure or marine fish larvae, especially in aquaria or hatcheries. To increase communication between interested parties in the field of gas supersaturation research and control, addresses and telephone numbers of all people responding to the questionnaire are included. 102 refs.

  19. Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    G. J. Roelofs

    2006-01-01

    Full Text Available A parameterization for cloud processing is presented that calculates activation of aerosol particles to cloud drops, cloud drop size, and pH-dependent aqueous phase sulfur chemistry. The parameterization is implemented in the global aerosol-climate model ECHAM5-HAM. The cloud processing parameterization uses updraft speed, temperature, and aerosol size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum supersaturation at the cloud base, and subsequently the cloud drop number concentration (CDNC due to activation. In-cloud sulfate production occurs through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The model simulates realistic distributions for annually averaged CDNC although it is underestimated especially in remote marine regions. On average, CDNC is dominated by cloud droplets growing on particles from the accumulation mode, with smaller contributions from the Aitken and coarse modes. The simulations indicate that in-cloud sulfate production is a potentially important source of accumulation mode sized cloud condensation nuclei, due to chemical growth of activated Aitken particles and to enhanced coalescence of processed particles. The strength of this source depends on the distribution of produced sulfate over the activated modes. This distribution is affected by uncertainties in many parameters that play a direct role in particle activation, such as the updraft velocity, the aerosol chemical composition and the organic solubility, and the simulated CDNC is found to be relatively sensitive to these uncertainties.

  20. Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    G. J. Roelofs

    2006-01-01

    Full Text Available A parameterization for cloud processing is presented that calculates activation of aerosol particles to cloud drops, cloud drop size, and pH-dependent aqueous phase sulfur chemistry. The parameterization is implemented in the global aerosol-climate model ECHAM5-HAM. The cloud processing parameterization uses updraft speed, temperature, and aerosol size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum supersaturation at the cloud base, and subsequently the cloud drop number concentration (CDNC due to activation. In-cloud sulfate production occurs through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The model simulates realistic distributions for annually averaged CDNC although it is underestimated especially in remote marine regions. On average, CDNC is dominated by particles from the accumulation mode, with smaller contributions from the Aitken and coarse modes. The simulations indicate that in-cloud sulfate production is a potentially important source of accumulation mode sized cloud condensation nuclei, due to chemical growth of activated Aitken particles and to enhanced coalescence of processed particles. The strength of this source depends on the distribution of produced sulfate over the activated modes. This distribution is affected by uncertainties in many parameters that play a direct role in particle activation, such as the updraft velocity, the aerosol chemical composition and the organic solubility, and the simulated CDNC is found to be relatively sensitive to these uncertainties.

  1. Supersaturation of zafirlukast in fasted and fed state intestinal media with and without precipitation inhibitors.

    Science.gov (United States)

    Madsen, Cecilie Maria; Boyd, Ben; Rades, Thomas; Müllertz, Anette

    2016-08-25

    Poor water solubility is a bottle neck in the development of many new drug candidates, and understanding and circumventing this is essential for a more effective drug development. Zafirlukast (ZA) is a leukotriene antagonist marketed for the treatment of asthma (Accolate®). ZA is poorly water soluble, and is formulated in an amorphous form (aZA) to improve its solubility and oral bioavailability. It has been shown that upon dissolution of aZa, the concentration of ZA in solution is supersaturated with respect to its stable crystalline form (ZA monohydrate), and thus, in theory, the bioavailability increases upon amorphization of ZA. The polymers hydroxypropylmethylcellulose (HPMC) and polyvinylpyrrolidone (PVP), often used as stabilizers of the supersaturated state, are in the excipient list of Accolate®. It is not recommended to take Accolate® with food, as this reduces the bioavailability by 40%. The aim of this study was to investigate the effect of simulated fasted and fed state intestinal media as well as the effect of HPMC and PVP on the supersaturation and precipitation of ZA in vitro. Supersaturation of aZA was studied in vitro in a small scale setup using the μDiss Profiler™. Several media were used for this study: One medium simulating the fasted state intestinal fluids and three media simulating different fed state intestinal fluids. Solid state changes of the drug were investigated by small angle x-ray scattering. The duration wherein aZA was maintained at a supersaturated state was prolonged in the presence of HPMC and lasted more than 20h in the presence of PVP in a fasted state intestinal medium. The presence of PVP increased the concentration of drug dissolved in the supersaturated state. The duration of supersaturation was shorter in fed than in a fasted state simulated intestinal media, but the concentration during supersaturation was higher. It was thus not possible to predict any positive or negative food effects from the dissolution

  2. Evaluation of drug supersaturation by thermodynamic and kinetic approaches for the prediction of oral absorbability in amorphous pharmaceuticals.

    Science.gov (United States)

    Ozaki, Shunsuke; Kushida, Ikuo; Yamashita, Taro; Hasebe, Takashi; Shirai, Osamu; Kano, Kenji

    2012-11-01

    Supersaturation behavior of model drugs, danazol, griseofulvin, itraconazole, vemurafenib, and ER-34122, was analyzed by both thermodynamic and kinetic approaches to better understand the absorption characteristics of amorphous pharmaceuticals. For each amorphous drug, the extent of supersaturation during in vitro dissolution was proved to be similar to that in vivo, which was estimated from relative bioavailability data. The theoretical limit of supersaturation was thermodynamically calculated from several thermal properties and water sorption isotherms of amorphous solids. in vitro and in vivo supersaturation of amorphous vemurafenib was thermodynamically controlled and was in good agreement with the theoretical limit. On the contrary, the supersaturation ratio of the other four drugs was highly overestimated by the thermodynamic calculation. However, it was satisfactorily explained by considering supersaturation stability, which indicated how long supersaturation can be maintained without crystal nucleation. Supersaturation stability was evaluated by measuring the induction time for crystal nucleation kinetically. Concomitant use of thermodynamic and kinetic approaches is, therefore, invaluable in evaluating supersaturation behavior of amorphous materials and assessing development potential of poorly water-soluble drugs. Copyright © 2012 Wiley Periodicals, Inc.

  3. Cloud Condensation Nuclei Activity of Aerosols during GoAmazon 2014/15 Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Martin, S. T. [Harvard Univ., Cambridge, MA (United States); Kleinman, L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Thalman, R. M. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-03-01

    Aerosol indirect effects, which represent the impact of aerosols on climate through influencing the properties of clouds, remain one of the main uncertainties in climate predictions (Stocker et al. 2013). Reducing this large uncertainty requires both improved understanding and representation of aerosol properties and processes in climate models, including the cloud activation properties of aerosols. The Atmospheric System Research (ASR) science program plan of January 2010 states that: “A key requirement for simulating aerosol-cloud interactions is the ability to calculate cloud condensation nuclei and ice nuclei (CCN and IN, respectively) concentrations as a function of supersaturation from the chemical and microphysical properties of the aerosol.” The Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/15) study seeks to understand how aerosol and cloud life cycles are influenced by pollutant outflow from a tropical megacity (Manaus)—in particular, the differences in cloud-aerosol-precipitation interactions between polluted and pristine conditions. One key question of GoAmazon2014/5 is: “What is the influence of the Manaus pollution plume on the cloud condensation nuclei (CCN) activities of the aerosol particles and the secondary organic material in the particles?” To address this question, we measured size-resolved CCN spectra, a critical measurement for GoAmazon2014/5.

  4. Structure and Supersaturation of Highly Concentrated Solutions of Buckyball in 1-Butyl-3-Methylimidazolium Tetrafluoroborate

    DEFF Research Database (Denmark)

    Fileti, E. E.; Chaban, V. V.

    2014-01-01

    Solubilization of fullerenes is of high interest because of their wide usage in both fundamental research and numerous applications. This paper reports molecular dynamics (MD) simulations of saturated and supersaturated solutions of C-60 in 1-butyl-3-methylimidazolium tetrafluoroborate, [C4C1IM......][BF4], room-temperature ionic liquid (RTIL). The simulations cover a wide range of temperatures between 280 and 500 K at ambient pressure. Unlike in simpler solvents, C-60 in [C4C1IM][BF4] forms highly supersaturated solutions, whose internal arrangement remains unaltered during nearly a microsecond......-long real-time dynamics. The ion-molecular structure patterns in saturated and supersaturated solutions are distinguished in terms of radial distribution functions and cluster analysis of the solute particles. The cation separated solute pair is found to be a common structure in both saturated...

  5. Effect of supersaturation on L-glutamic acid polymorphs under droplet-based microchannels

    Science.gov (United States)

    Jiang, Nan; Wang, Zhanzhong; Dang, Leping; Wei, Hongyuan

    2016-07-01

    Supersaturation is an important controlling factor for crystallization process and polymorphism. Droplet-based microchannels and conventional crystallization were used to investigate polymorphs of L-gluatamic acid in this work. The results illustrate that it is easy to realize the accurate and rapid control of the crystallization temperature in the droplets, which is especially beneficial to heat and mass transfer during crystallization. It is also noted that higher degree of supersaturation favors the nucleation of α crystal form, while lower degree of supersaturation favors the nucleation of β crystal form under droplet-based microchannels for L-gluatamic acid. In addition, there is a different nucleation behavior to be found under droplet-based microchannels both for the β form and α form of L-glutamic acid. This new finding can provide important insight into the development and design of investigation meanings for drug polymorph.

  6. Molecular dynamics simulations of the surface tension of oxygen-supersaturated water

    Directory of Open Access Journals (Sweden)

    S. Jain

    2017-04-01

    Full Text Available In this work, non-reactive molecular dynamic simulations were conducted to determine the surface tension of water as a function of the concentration of the dissolved gaseous molecules (O2, which would in turn help to predict the pressure inside the nanobubbles under supersaturation conditions. Knowing the bubble pressure is a prerequisite for understanding the mechanisms behind the spontaneous combustion of the H2/O2 gases inside the nanobubbles. First, the surface tension of pure water was determined using the planar interface method and the Irving and Kirkwood formula. Next, the surface tension of water containing four different supersaturation concentrations (S of O2 gas molecules was computed considering the curved interface of a nanobubble. The surface tension of water was found to decrease with an increase in the supersaturation ratio or the concentration of the dissolved O2 gas molecules.

  7. Prediction for supersaturated total dissolved gas in high-dam hydropower projects

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The supersaturated total dissolved gas(TDG)generated during high dam spills may cause gas bubble disease for fish and ultimately endanger their existence.As more and more high-dam hydropower projects have been constructed in China,the environmental assessment of the supersaturated TDG is becoming more and more important.It is of great importance for quantitative impact assessment of the supersaturated TDG of high dams and for the construction of ecological friendly high-dam hydropower projects.Based on the conceptual summarization of the TDG production process,the TDG prediction model for high-dam projects,in which the ski-jump energy dissipation is adopted,is developed in the paper.The model is validated by field data and employed in the TDG prediction of a high-dam hydropower project to be built in southwest China.

  8. TOMS Absorbing Aerosol Index

    Data.gov (United States)

    Washington University St Louis — TOMS_AI_G is an aerosol related dataset derived from the Total Ozone Monitoring Satellite (TOMS) Sensor. The TOMS aerosol index arises from absorbing aerosols such...

  9. Intestinal bile secretion promotes drug absorption from lipid colloidal phases via induction of supersaturation.

    Science.gov (United States)

    Yeap, Yan Yan; Trevaskis, Natalie L; Quach, Tim; Tso, Patrick; Charman, William N; Porter, Christopher J H

    2013-05-06

    The oral bioavailability of poorly water-soluble drugs (PWSD) is often significantly enhanced by coadministration with lipids in food or lipid-based oral formulations. Coadministration with lipids promotes drug solubilization in intestinal mixed micelles and vesicles, however, the mechanism(s) by which PWSD are absorbed from these dispersed phases remain poorly understood. Classically, drug absorption is believed to be a product of the drug concentration in free solution and the apparent permeability across the absorptive membrane. Solubilization in colloidal phases such as mixed micelles increases dissolution rate and total solubilized drug concentrations, but does not directly enhance (and may reduce) the free drug concentration. In the absence of changes to cellular permeability (which is often high for lipophilic, PWSD), significant changes to membrane flux are therefore unexpected. Realizing that increases in effective dissolution rate may be a significant driver of increases in drug absorption for PWSD, we explore here two alternate mechanisms by which membrane flux might also be enhanced: (1) collisional drug absorption where drug is directly transferred from lipid colloidal phases to the absorptive membrane, and (2) supersaturation-enhanced drug absorption where bile mediated dilution of lipid colloidal phases leads to a transient increase in supersaturation, thermodynamic activity and absorption. In the current study, collisional uptake mechanisms did not play a significant role in the absorption of a model PWSD, cinnarizine, from lipid colloidal phases. In contrast, bile-mediated dilution of model intestinal mixed micelles and vesicles led to drug supersaturation. For colloids that were principally micellar, supersaturation was maintained for a period sufficient to promote absorption. In contrast, for primarily vesicular systems, supersaturation resulted in rapid drug precipitation and no increase in drug absorption. This work suggests that ongoing

  10. Laboratory Studies of the Effects of Pressure and Dissolved Gas Supersaturation on Turbine-Passed Fish

    Energy Technology Data Exchange (ETDEWEB)

    Neitzel, Duane A.

    2009-09-14

    Migratory and resident fish in the Columbia River Basin are exposed to stresses associated with hydroelectric power production, including changes in pressure as they pass through turbines and dissolved gas supersaturation (resulting from the release of water from the spillway). To examine pressure changes as a source of turbine-passage injury and mortality, Pacific Northwest National Laboratory scientists conducted specific tests using a hyperbaric chamber. Tests were designed to simulate Kaplan turbine passage conditions and to quantify the response of fish to rapid pressure changes, with and without the complication of fish being acclimated to gas-supersaturated water.

  11. Empirical estimates of CCN from aerosol optical properties at four remote sites

    Directory of Open Access Journals (Sweden)

    A. Jefferson

    2010-07-01

    Full Text Available This study presents an empirical method to estimate the CCN concentration as a function of percent supersaturation. The aerosol optical properties, backscatter fraction and single scatter albedo, function as proxies for the aerosol size and composition in a power law relationship to CCN. This method is tested at four sites with aged aerosol: SGP (Oklahoma, USA, FKB (Black Forest, Germany, HFE (Hefei, China and GRW (Graciosa, Azores. Each site represents a different aerosol type and thus demonstrates the method robustness and limitations. Good agreement was found between the calculated and measured CCN with slopes between 0.81 and 1.03 and correlation coefficients (r2 values between 0.59 and 0.67. The fit quality declined at low CCN concentrations.

  12. Aerosol Observation System

    Data.gov (United States)

    Oak Ridge National Laboratory — The aerosol observation system (AOS) is the primary Atmospheric Radiation Measurement (ARM) platform for in situ aerosol measurements at the surface. The principal...

  13. Influence of supersaturation on structure of sodium aluminate solutions with medium concentration: a solution X-ray diffraction study

    Institute of Scientific and Technical Information of China (English)

    李洁; 陈启元; 尹周澜; 张平民; 李元高

    2002-01-01

    Influence of supersaturation on the structure of a series of freshly prepared supersaturated sodium aluminate solutions with medium concentration was investigated by solution X-ray diffraction. Experimental results show that the basic Al-containing species in all kinds of supersaturated solution is four-coordinated ions. Opposite to Al-O distance contracted in highly concentrated solution, a little expand of the Al-O distance from 1.75 to 1.85 occurs with increasing supersaturation, which is consistent with the occurrence of oligomeric aluminate species. Meanwhile, O-O distance in the first shell of H2O-H2O(OH) in supersaturated sodium aluminate solution is obviously longer than in hydroxide sodium solution and becomes longer and longer with increasing supersaturation. Na-O bond length is about 2.4 and changes little with supersaturation. The reason for Al-O bond expanding with supersaturation and its influence on the stability of solution was discussed.

  14. Study of Decomposition of a Highly Supersaturated Solid Solution of a Granulated Alloy, Al-1, 5Cr-1, 5Zr,

    Science.gov (United States)

    The mechanism and kinetics of decomposition of a highly supersaturated solid solution in an alloy is of importance in stating the proper technology...that during annealing up to 250 C, there is a great density of dislocations. A hypothesis is presented concerning the structural changes occurring at heating the highly supersaturated solid solution of this alloy.

  15. Aircraft measurements of aerosol properties during GoAmazon - G1 and HALO inter-comparison

    Science.gov (United States)

    Mei, F.; Cecchini, M. A.; Wang, J.; Tomlinson, J. M.; Comstock, J. M.; Hubbe, J. M.; Pekour, M. S.; Machado, L.; Wendisch, M.; Longo, K.; Martin, S. T.; Schmid, B.; Weinzierl, B.; Krüger, M. L.; Zöger, M.

    2015-12-01

    Currently, the indirect effects of atmospheric aerosols remain the most uncertain components in forcing of climate change over the industrial period (IPCC, 2013). This large uncertainty is partially a result of our incomplete understanding of the ability of particles to form cloud droplets under atmospherically relevant supersaturations. One objective of the US Department of Energy (DOE) Green Ocean Amazon Project (GoAmazon2014/5) is to understand the influence of the emission from Manaus, a tropical megacity, on aerosol size, concentration, and chemical composition, and their impact on cloud condensation nuclei (CCN) spectrum. The GoAmazon2014/5 study was an international campaign with the collaboration efforts from US, Brazil and Germany. During the intensive operation period, in the dry season (Sep. 1st - Oct. 10th, 2014), aerosol concentration, size distributions, and CCN spectra, both under pristine conditions and inside the Manaus plume, were characterized in-situ from the DOE Gulfstream-1 (G-1) research aircraft and German HALO aircraft during 4 coordinated flights on Sep. 9th, Sep. 16th, Sep 21st and Oct. 1st, 2014. During those four flights, aerosol number concentrations and CCN concentrations at two supersaturations (0.25% and 0.5%) were measured by condensation particle counters (CPCs) and a DMT dual column CCN counter onboard both G-1 and HALO. Aerosol size distribution was also measured by a Fast Integrated Mobility Spectrometer (FIMS) aboard the G-1 and is compared with the size distribution from Ultra High Sensitivity Aerosol Spectrometer - Airborne (UHSAS-A, DMT), which were deployed both on the G-1 and the HALO. Good agreement between the aerosol properties measured from the two aircraft has been achieved. The vertical profiles of aerosol size distribution and CCN spectrum will be discussed.

  16. Molecular Dynamics Simulation of Surface Tension of NaCl Aqueous Solution at 298.15K: from Diluted to Highly Supersaturated Concentrations

    Science.gov (United States)

    Wang, Xiaoxiang; Chen, Chuchu; Poeschl, Ulirch; Su, Hang; Cheng, Yafang

    2017-04-01

    Sodium chloride (NaCl) is one of the key components of atmospheric aerosol particles. Concentration-depend surface tension of aqueous NaCl solution is essential to determine the equilibrium between droplet NaCl solution and water vapor, which is important in regards to aerosol-cloud interaction and aerosol climate effects. Although supersaturated NaCl droplets can be widely found under atmospheric conditions, the experimental determined concentration dependency of surface tension is limited up to the saturated concentration range due to technical difficulties, i.e., heterogeneous nucleation since nearly all surface tension measurement techniques requires contact of the sensor and solution surface. In this study, the surface tension of NaCl aqueous solution with solute mass fraction from 0 to 1 was calculated using molecular dynamics (MD) simulation. The surface tension increases monotonically and near linearly when mass fraction of NaCl (xNaCl) is lower than 0.265 (saturation point), which follows theoretical predictions (e.g., E-AIM, SP parameterization, and PK parameterization). Once entering into the supersaturated concentration range, the calculated surface tension starts to deviate from the near-linear extrapolation and adopts a slightly higher increasing rate until xNaCl of 0.35. We found that these two increasing phases (xNaCl 0.35) is mainly driven by the increase of excessive surface enthalpy when the solution becomes concentrated. After that, the surface tension remains almost unchanged until xNaCl of 0.52. This phenomenon is supported by the results from experiment based Differential Koehler Analyses. The stable surface tension in this concentration range is attributed to a simultaneous change of surface excess enthalpy and entropy at similar degree. When the NaCl solution is getting more concentrated than xNaCl of 0.52, the simulated surface tension regains an even faster growing momentum and shows the tendency of ultimately approaching the surface

  17. Primary marine aerosol-cloud interactions off the coast of California

    Science.gov (United States)

    Modini, R. L.; Frossard, A. A.; Ahlm, L.; Russell, L. M.; Corrigan, C. E.; Roberts, G. C.; Hawkins, L. N.; Schroder, J. C.; Bertram, A. K.; Zhao, R.; Lee, A. K. Y.; Abbatt, J. P. D.; Lin, J.; Nenes, A.; Wang, Z.; Wonaschütz, A.; Sorooshian, A.; Noone, K. J.; Jonsson, H.; Seinfeld, J. H.; Toom-Sauntry, D.; MacDonald, A. M.; Leaitch, W. R.

    2015-05-01

    Primary marine aerosol (PMA)-cloud interactions off the coast of California were investigated using observations of marine aerosol, cloud condensation nuclei (CCN), and stratocumulus clouds during the Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies. Based on recently reported measurements of PMA size distributions, a constrained lognormal-mode-fitting procedure was devised to isolate PMA number size distributions from total aerosol size distributions and applied to E-PEACE measurements. During the 12 day E-PEACE cruise on the R/V Point Sur, PMA typically contributed less than 15% of total particle concentrations. PMA number concentrations averaged 12 cm-3 during a relatively calmer period (average wind speed 12 m/s1) lasting 8 days, and 71 cm-3 during a period of higher wind speeds (average 16 m/s1) lasting 5 days. On average, PMA contributed less than 10% of total CCN at supersaturations up to 0.9% during the calmer period; however, during the higher wind speed period, PMA comprised 5-63% of CCN (average 16-28%) at supersaturations less than 0.3%. Sea salt was measured directly in the dried residuals of cloud droplets during the SOLEDAD study. The mass fractions of sea salt in the residuals averaged 12 to 24% during three cloud events. Comparing the marine stratocumulus clouds sampled in the two campaigns, measured peak supersaturations were 0.2 ± 0.04% during E-PEACE and 0.05-0.1% during SOLEDAD. The available measurements show that cloud droplet number concentrations increased with >100 nm particles in E-PEACE but decreased in the three SOLEDAD cloud events.

  18. Second organic aerosol formation from the ozonolysis of α-pinene in the presence of dry submicron ammonium sulfate aerosol

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zhe; HAO Jiming; LI Junhua; WU Shan

    2008-01-01

    An indoor chamber facility is described for investigation of atmospheric aerosol chemistry. Two sets of α-pinene ozonolysisexperiments were conducted in the presence of dry ammonium sulfate seed particle: ozone limited experiments and α-pinene limitedexperiments. The concentration of gas phase and particle phase species was monitored continuously by on-line instruments andrecorded automatically by data sampling system. The evolution of size distribution was measured by a scanning mobility particlesizer (SMPS), and α-pinene consumed was measured using GC-FID. Secondary organic aerosol (SOA) produced for seed-free systemis 100% organic in content, resulting from a sufficient supersaturation of low volatility organics to produce homogeneous nucleationfollowed by condensation to the aerosol. Secondary organic aerosol produced in seeded system is a mixture of organic and inorganicconstituents, initially forms via condensation onto the inorganic particles, and subsequent growth occurs via absorption into the organicsurface coating the inorganic core. Although the formation process and the size distribution for seed-free system and seeded system isdifferent, the ultimate mass of SOA formed is equal, and SOA yield for the two system located in the same regression line when usingone-product model, suggesting that the presence of dry ammonium sulfate seed has no measurable effect on the total aerosol yield, and the dry seed particle acts solely as a site upon which organic deposition occurs.

  19. Enhancements and limits in drug membrane transport using supersaturated solutions of poorly water soluble drugs.

    Science.gov (United States)

    Raina, Shweta A; Zhang, Geoff G Z; Alonzo, David E; Wu, Jianwei; Zhu, Donghua; Catron, Nathaniel D; Gao, Yi; Taylor, Lynne S

    2014-09-01

    Amorphous solid dispersions (ASDs) give rise to supersaturated solutions (solution concentration greater than equilibrium crystalline solubility). We have recently found that supersaturating dosage forms can exhibit the phenomenon of liquid-liquid phase separation (LLPS). Thus, the high supersaturation generated by dissolving ASDs can lead to a two-phase system wherein one phase is an initially nanodimensioned and drug-rich phase and the other is a drug-lean continuous aqueous phase. Herein, the membrane transport of supersaturated solutions, at concentrations above and below the LLPS concentration has been evaluated using a side-by-side diffusion cell. Measurements of solution concentration with time in the receiver cell yield the flux, which reflects the solute thermodynamic activity in the donor cell. As the nominal concentration of solute in the donor cell increases, a linear increase in flux was observed up to the concentration where LLPS occurred. Thereafter, the flux remained essentially constant. Both nifedipine and felodipine solutions exhibit such behavior as long as crystallization is absent. This suggests that there is an upper limit in passive membrane transport that is dictated by the LLPS concentration. These results have several important implications for drug delivery, especially for poorly soluble compounds requiring enabling formulation technologies.

  20. Biopharmaceutical modeling of drug supersaturation during lipid-based formulation digestion considering an absorption sink.

    Science.gov (United States)

    Stillhart, Cordula; Imanidis, Georgios; Griffin, Brendan T; Kuentz, Martin

    2014-12-01

    In vitro lipolysis is widely utilized for predicting in vivo performance of oral lipid-based formulations (LBFs). However, evaluation of LBFs in the absence of an absorption sink may have limited in vivo relevance. This study aimed at employing biopharmaceutical modeling to simulate LBF digestion and drug supersaturation in a continuous absorptive environment. Three fenofibrate-loaded LBFs were characterized in vitro (dispersion and lipolysis) and drug precipitation was monitored using in-line Raman spectroscopy. In vitro data were combined with pharmacokinetic data derived from an in vivo study in pigs to simulate intestinal LBF transit. This biopharmaceutical model allowed calculation of lipolysis-triggered drug supersaturation while drug and lipolysis products are absorbed from the intestine. The biopharmaceutical model predicted that, in a continuous absorption environment, fenofibrate supersaturation was considerably lower compared to in vitro lipolysis (non-sink). Hence, the extensive drug precipitation observed in vitro was predicted to be unlikely in vivo. The absorption of lipolysis products increased drug supersaturation, but drug precipitation was unlikely for highly permeable drugs. Biopharmaceutical modeling is a valuable approach for predicting LBFs performance in vivo. In the absence of in vitro tools simulating absorptive conditions, modeling strategies should be further considered.

  1. Spinal motor neuron protein supersaturation patterns are associated with inclusion body formation in ALS.

    Science.gov (United States)

    Ciryam, Prajwal; Lambert-Smith, Isabella A; Bean, Daniel M; Freer, Rosie; Cid, Fernando; Tartaglia, Gian Gaetano; Saunders, Darren N; Wilson, Mark R; Oliver, Stephen G; Morimoto, Richard I; Dobson, Christopher M; Vendruscolo, Michele; Favrin, Giorgio; Yerbury, Justin J

    2017-05-16

    Amyotrophic lateral sclerosis (ALS) is a heterogeneous degenerative motor neuron disease linked to numerous genetic mutations in apparently unrelated proteins. These proteins, including SOD1, TDP-43, and FUS, are highly aggregation-prone and form a variety of intracellular inclusion bodies that are characteristic of different neuropathological subtypes of the disease. Contained within these inclusions are a variety of proteins that do not share obvious characteristics other than coaggregation. However, recent evidence from other neurodegenerative disorders suggests that disease-affected biochemical pathways can be characterized by the presence of proteins that are supersaturated, with cellular concentrations significantly greater than their solubilities. Here, we show that the proteins that form inclusions of mutant SOD1, TDP-43, and FUS are not merely a subset of the native interaction partners of these three proteins, which are themselves supersaturated. To explain the presence of coaggregating proteins in inclusions in the brain and spinal cord, we observe that they have an average supersaturation even greater than the average supersaturation of the native interaction partners in motor neurons, but not when scores are generated from an average of other human tissues. These results suggest that inclusion bodies in various forms of ALS result from a set of proteins that are metastable in motor neurons, and thus prone to aggregation upon a disease-related progressive collapse of protein homeostasis in this specific setting.

  2. A CONTROLLED METABOLIC DIET REDUCES CALCIUM OXALATE SUPERSATURATION BUT NOT OXALATE EXCRETION AFTER BARIATRIC SURGERY

    Science.gov (United States)

    Pang, Ran; Linnes, Michael; O’Connor, Helen M.; Li, Xujian; Bergstralh, Eric; Lieske, John C.

    2012-01-01

    Objective To identify the effect of controlled metabolic diet on reducing urinary calcium oxalate supersaturation in subjects with hyperoxaluric nephrolithiasis after potentially malabsorptive forms of bariatric surgery. Materials and Methods Subjects with a history of CaOx kidney stones and mild hyperoxaluria after bariatric surgery (n=9) collected baseline 24-hour urine samples while on a free choice diet. They were then placed on a controlled diet low in oxalate (70 – 80 mg/day), normal in calcium (1000 mg/day), and moderate in protein prior to 2 final 24-hour urine collections. Results Overall urinary CaOx supersaturation fell from 1.97 ± 0.49 delta Gibbs (DG) on the free choice diet to 1.13 ± 0.75 DG on the controlled diet (P0.05), contributing to the significant CaOx supersaturation change. Conclusions A controlled metabolic diet normal in calcium, moderate in protein and reduced in oxalate can positively impact urinary CaOx supersaturation after bariatric surgery. However, this diet did not appear to decrease urinary oxalate excretion. Therefore, restriction of dietary oxalate alone may not be enough to reduce urinary oxalate excretion to normal levels in this group of known enteric hyperoxaluric patients. Additional strategies may be necessary, such as use of oral calcium supplements as oxalate binders and a lower fat diet. PMID:22554593

  3. Triggered in situ drug supersaturation and hydrophilic matrix self-assembly.

    Science.gov (United States)

    Benaouda, F; Brown, M B; Martin, G P; Jones, S A

    2012-12-01

    To understand in situ drug thermodynamic activity when embedded in a supramolecular structured hydrophilic matrix that simultaneously self-assembled during drug supersaturation. A propylene glycol (PG)/water, hydroxypropyl methyl cellulose matrix containing ethanol was used to support diclofenac supersaturation. Phase behaviour, thermodynamics and drug transport were assessed through the determination of evaporation kinetics, supersaturation kinetics and transmembrane penetration. Initial ethanol evaporation from the drug loaded matrix (2.9 ± 0.4 mg.min(-1).cm(-2)) was comparable to that of the pure solvent (ca. 3 mg.min(-1).cm(-2)). When 25% w/w of the total ethanol from the applied phase was lost (ethanol/water/PG molar ratio of 7:5:1.2), an inflection point in the evaporation profile and a sudden decrease in drug solubility demonstrated that a defined supramolecular structure was formed. The 55-fold decrease in drug solubility observed over the subsequent 8 h drove in situ supersaturation, the rate of which was a function of the drug load in the matrix (y = 0.0078x, R(2) 24 h, but did not hinder mobility and this allowed the thermodynamic activity of the drug to be directly translated into highly efficient transmembrane penetration.

  4. Controlled metabolic diet reduces calcium oxalate supersaturation but not oxalate excretion after bariatric surgery.

    Science.gov (United States)

    Pang, Ran; Linnes, Michael P; O'Connor, Helen M; Li, Xujian; Bergstralh, Eric; Lieske, John C

    2012-08-01

    To identify the effect of a controlled metabolic diet on reducing urinary calcium oxalate (CaOx) supersaturation in subjects with hyperoxaluric nephrolithiasis after potentially malabsorptive forms of bariatric surgery. Subjects with a history of CaOx kidney stones and mild hyperoxaluria after bariatric surgery (n = 9) collected baseline 24-hour urine samples while consuming a free choice diet. They were then instructed to consume a controlled diet low in oxalate (70-80 mg/d), normal in calcium (1000 mg/d), and moderate in protein before 2 final 24-hour urine collections. Overall, the urinary CaOx supersaturation decreased from 1.97 ± 0.49 delta Gibbs (DG) with the free choice diet to 1.13 ± 0.75 DG with the controlled diet (P .05), contributing to the significant CaOx supersaturation change. A controlled metabolic diet normal in calcium, moderate in protein, and reduced in oxalate can positively affect urinary CaOx supersaturation after bariatric surgery. However, this diet did not appear to decrease urinary oxalate excretion. Therefore, restriction of dietary oxalate alone might not be enough to reduce urinary oxalate excretion to normal levels in this group of patients with known enteric hyperoxaluria. Additional strategies could be necessary, such as the use of oral calcium supplements as oxalate binders and a lower fat diet. Copyright © 2012 Elsevier Inc. All rights reserved.

  5. Some Aspects of PVT Low Supersaturation Nucleation and Contactless Crystal Growth

    Science.gov (United States)

    Grasza, K.; Palosz, W.

    1996-01-01

    The basic principles of the contactless growth of crystals from the vapor in combination with the process of low-supersaturation nucleation are discussed. The mathematical formulation of the morphological stability criterion in vapor growth systems is given and its implications for contactless growth technique are analyzed. A diagram for selection of proper temperature conditions for growth of CdTe crystals is presented.

  6. Nucleation and droplet growth from supersaturated vapor at temperatures below the triple point temperature

    DEFF Research Database (Denmark)

    Toxværd, Søren

    2016-01-01

    nucleation without the use of a thermostat. The simulations of homogeneous nucleation in a Lennard-Jones system from supersaturated vapor at temperatures below Ttr.p. reveals that the nucleation to a liquid-like critical nucleus is initiated by a small cold cluster [S. Toxvaerd, J. Chem. Phys. \\textbf{143...

  7. Activation of "synthetic ambient" aerosols - Relation to chemical composition of particles <100 nm

    Science.gov (United States)

    Burkart, J.; Hitzenberger, R.; Reischl, G.; Bauer, H.; Leder, K.; Puxbaum, H.

    2012-07-01

    Cloud condensation nuclei (CCN) are an important fraction of atmospheric aerosols because of their role in cloud formation. Experimental studies focus either on direct field measurements of complex ambient aerosols or laboratory investigations on well defined aerosols produced from single substances or substance mixtures. In this study, we focussed on the ultrafine aerosol because in terms of number concentration, the majority of the CCN are expected to have sizes in this range. A field study was performed from July 2007 to October 2008 to investigate the activation behaviour of the atmospheric aerosol in Vienna (Burkart et al., 2011). Filter samples of the aerosol aerosol in a nebulizer. Chemical analyses of the ultrafine water soluble material were also performed. The CCN properties of the "synthetic ambient" aerosol were obtained using the University of Vienna CCN counter (Giebl et al., 2002; Dusek et al., 2006b) at a nominal supersaturation (SS) of 0.5%. Activation diameters dact ranged from 54.5 nm to 66 nm, were larger than dact of typical single inorganic salts and showed no seasonal pattern in contrast to the fraction of water soluble organic carbon (WSOC), which ranged from 44% in spring to 15% in winter. The average hygroscopicity parameter κ (Petters and Kreidenweis, 2007) obtained from the activation curves ranged from 0.20 to 0.30 (average 0.24), which was significantly lower than κchem calculated from the chemical composition (0.43 ± 0.07).

  8. Meteorological and Aerosol effects on Marine Cloud Microphysical Properties

    Science.gov (United States)

    Sanchez, K. J.; Russell, L. M.; Modini, R. L.; Frossard, A. A.; Ahlm, L.; Roberts, G.; Hawkins, L. N.; Schroder, J. C.; Wang, Z.; Lee, A.; Abbatt, J.; Lin, J.; Nenes, A.; Wonaschuetz, A.; Sorooshian, A.; Noone, K.; Jonsson, H.; Albrecht, B. A.; Desiree, T. S.; Macdonald, A. M.; Seinfeld, J.; Zhao, R.

    2015-12-01

    Both meteorology and microphysics affect cloud formation and consequently their droplet distributions and shortwave reflectance. The Eastern Pacific Emitted Aerosol Cloud Experiment (EPEACE) and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) studies provide detailed measurements in 6 case studies of both cloud thermodynamic properties and initial particle number distribution and composition, as well as the resulting cloud drop distribution and composition. This study uses simulations of a detailed chemical and microphysical aerosol-cloud parcel (ACP) model with explicit kinetic drop activation to reproduce the observed cloud droplet distribution and composition. Four of the cases examined had a sub-adiabatic lapse rate, which was shown to have fewer droplets due to decreased maximum supersaturation, lower LWC and higher cloud base height, consistent with previous findings. These detailed case studies provided measured thermodynamics and microphysics that constrained the simulated droplet size distribution sufficiently to match the droplet number within 6% and the size within 19% for 4 of the 6 cases, demonstrating "closure" or consistency of the measured composition with the measured CCN spectra and the inferred and modeled supersaturation. The contribution of organic components to droplet formation shows small effects on the droplet number and size in the 4 marine cases that had background aerosol conditions with varying amounts of coastal, ship or other non-biogenic sources. In contrast, the organic fraction and hygroscopicity increased the droplet number and size in the cases with generated smoke and cargo ship plumes that were freshly emitted and not yet internally mixed with the background particles. The simulation results show organic hygroscopicity causes small effects on cloud reflectivity (smoke plume which increased absolute cloud reflectivity fraction by 0.02 and 0.20 respectively. In addition, the ACP model

  9. Supersaturating silicon with transition metals by ion implantation and pulsed laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Recht, Daniel; Aziz, Michael J. [Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts 02138 (United States); Smith, Matthew J.; Gradečak, Silvija [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Charnvanichborikarn, Supakit; Williams, James S. [Research School of Physics and Engineering, The Australian National University, Canberra, ACT (Australia); Sullivan, Joseph T.; Winkler, Mark T.; Buonassisi, Tonio [Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge Massachusetts 02139 (United States); Mathews, Jay; Warrender, Jeffrey M. [Benet Laboratories, U.S. Army ARDEC, Watervliet, New York 12189 (United States)

    2013-09-28

    We investigate the possibility of creating an intermediate band semiconductor by supersaturating Si with a range of transition metals (Au, Co, Cr, Cu, Fe, Pd, Pt, W, and Zn) using ion implantation followed by pulsed laser melting (PLM). Structural characterization shows evidence of either surface segregation or cellular breakdown in all transition metals investigated, preventing the formation of high supersaturations. However, concentration-depth profiling reveals that regions of Si supersaturated with Au and Zn are formed below the regions of cellular breakdown. Fits to the concentration-depth profile are used to estimate the diffusive speeds, v{sub D,} of Au and Zn, and put lower bounds on v{sub D} of the other metals ranging from 10{sup 2} to 10{sup 4} m/s. Knowledge of v{sub D} is used to tailor the irradiation conditions and synthesize single-crystal Si supersaturated with 10{sup 19} Au/cm{sup 3} without cellular breakdown. Values of v{sub D} are compared to those for other elements in Si. Two independent thermophysical properties, the solute diffusivity at the melting temperature, D{sub s}(T{sub m}), and the equilibrium partition coefficient, k{sub e}, are shown to simultaneously affect v{sub D}. We demonstrate a correlation between v{sub D} and the ratio D{sub s}(T{sub m})/k{sub e}{sup 0.67}, which is exhibited for Group III, IV, and V solutes but not for the transition metals investigated. Nevertheless, comparison with experimental results suggests that D{sub s}(T{sub m})/k{sub e}{sup 0.67} might serve as a metric for evaluating the potential to supersaturate Si with transition metals by PLM.

  10. Impact of Solubilizing Additives on Supersaturation and Membrane Transport of Drugs.

    Science.gov (United States)

    Raina, Shweta A; Zhang, Geoff G Z; Alonzo, David E; Wu, Jianwei; Zhu, Donghua; Catron, Nathaniel D; Gao, Yi; Taylor, Lynne S

    2015-10-01

    Many enabling formulations give rise to supersaturated solutions wherein the solute possesses higher thermodynamic activity gradients than the solute in a saturated solution. Since flux across a membrane is driven by solute activity rather than concentration, understanding how solute thermodynamic activity varies with solution composition, particularly in the presence of solubilizing additives, is important in the context of passive absorption. In this study, a side-by-side diffusion cell was used to evaluate solute flux for solutions of nifedipine and felodipine in the absence and presence of different solubilizing additives at various solute concentrations. At a given solute concentration above the equilibrium solubility, it was observed that the solubilizing additives could reduce the membrane flux, indicating that the extent of supersaturation can be reduced. However, the flux could be increased back to the same maximum value (which was determined by the concentration where liquid-liquid phase separation (LLPS) occurred) by increasing the total solute concentration. Qualitatively, the shape of the curves of solute flux through membrane as a function of total solute concentration is the same in the absence and presence of solubilizing additives. Quantitatively, however, LLPS occurs at higher solute concentrations in the presence of solubilizing additives. Moreover, the ratios of the LLPS onset concentration and equilibrium solubility vary significantly in the absence and presence of additives. These findings clearly point out the flaws in using solute concentration in estimating solute activity or supersaturation, and reaffirm the use of flux measurements to understand supersaturated systems. Clear differentiation between solubilization and supersaturation, as well as thorough understanding of their respective impacts on membrane transport kinetics is important for the rational design of enabling formulations for poorly soluble compounds.

  11. Effects of supersaturation control strategies on hydroxyapatite (HAP) crystallization for phosphorus recovery from wastewater.

    Science.gov (United States)

    Dai, Hongliang; Lu, Xiwu; Peng, Yonghong; Yang, Zixuan; Zhsssu, Huaqing

    2017-02-01

    The HAP crystallization for phosphorus removal from wastewater contributes to an environmental friendly production due to the fact that it helps reduce or eliminate the water eutrophication as well as increases the recovery of mineral resources. However, the generated microcrystalline with poor settleability in high levels of supersaturation solution has a negative effect on the phosphorus recovery efficiency. To overcome the drawback, multiple reagent feed ports (four feed ports) and different recirculation ratio (1.0, 1.5, 2.0, 2.5, 3.0) were investigated to control the levels of supersaturation in an air-agitated reactor with calcite as seeds. Results showed that the approach of multiple reagent feed ports could improve the conversion ratio of orthophosphate, but it had a limited effect (∼3% improvement) on phosphorus recovery efficiency (deposition on the seeds). With the increase of the recirculation ratio, the recovery efficiency was increased gradually and reached an optimal value of 85.63% under the recirculation ratio of 2.5 and four feed ports. This is because the adopted strategies could reduce the level of supersaturation by diluting the concentration of the reagents and inhibit large numbers of microcrystalline coinstantaneous occurrence. Meanwhile, the crystallized products were detected and analyzed by scanning electron micrograph (SEM) with energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD), which were proved to be HAP with a high purity. Collectively, these results demonstrated that supersaturation control using conventional approaches had a limited improvement on the phosphorus recovery efficiency in the form of HAP, and the new control strategies for supersaturation dispersion should be developed in the further study.

  12. Indoor aerosols

    DEFF Research Database (Denmark)

    Morawska, L.; Afshari, Alireza; N. Bae, G.

    2013-01-01

    Motivated by growing considerations of the scale, severity, and risks associated with human exposure to indoor particulate matter, this work reviewed existing literature to: (i) identify state-of-the-art experimental techniques used for personal exposure assessment; (ii) compare exposure levels...... reported for domestic/school settings in different countries (excluding exposure to environmental tobacco smoke and particulate matter from biomass cooking in developing countries); (iii) assess the contribution of outdoor background vs indoor sources to personal exposure; and (iv) examine scientific...... understanding of the risks posed by personal exposure to indoor aerosols. Limited studies assessing integrated daily residential exposure to just one particle size fraction, ultrafine particles, show that the contribution of indoor sources ranged from 19% to 76%. This indicates a strong dependence on resident...

  13. Lipid-based formulations and drug supersaturation: harnessing the unique benefits of the lipid digestion/absorption pathway.

    Science.gov (United States)

    Williams, Hywel D; Trevaskis, Natalie L; Yeap, Yan Yan; Anby, Mette U; Pouton, Colin W; Porter, Christopher J H

    2013-12-01

    Drugs with low aqueous solubility commonly show low and erratic absorption after oral administration. Myriad approaches have therefore been developed to promote drug solubilization in the gastrointestinal (GI) fluids. Here, we offer insight into the unique manner by which lipid-based formulations (LBFs) may enhance the absorption of poorly water-soluble drugs via co-stimulation of solubilization and supersaturation. Supersaturation provides an opportunity to generate drug concentrations in the GI tract that are in excess of the equilibrium crystalline solubility and therefore higher than that achievable with traditional formulations. Incorporation of LBF into lipid digestion and absorption pathways provides multiple drivers of supersaturation generation and the potential to enhance thermodynamic activity and absorption. These drivers include 1) formulation dispersion, 2) lipid digestion, 3) interaction with bile and 4) lipid absorption. However, high supersaturation ratios may also stimulate drug precipitation and reduce exposure where re-dissolution limits absorption. The most effective formulations are likely to be those that generate moderate supersaturation and do so close to the site of absorption. LBFs are particularly well suited to these criteria since solubilization protects against high supersaturation ratios, and supersaturation initiation typically occurs in the small intestine, at the absorptive membrane.

  14. Utility of hydroxypropylmethylcellulose acetate succinate (HPMCAS) for initiation and maintenance of drug supersaturation in the GI milieu.

    Science.gov (United States)

    Curatolo, William; Nightingale, James A; Herbig, Scott M

    2009-06-01

    To identify materials and processes which effect supersaturation of the GI milieu for low solubility drugs in order to increase oral bioavailability. A variety of small and polymeric molecules were screened for their ability to inhibit drug precipitation in supersaturated solutions. The best polymeric materials were utilized to create spray-dried dispersions (SDDs) of drug and polymer, and these were tested for drug form and homogeneity. Dispersions were tested in vitro for their ability to achieve and maintain drug supersaturation, for a variety of drug structures. Of the 41 materials tested, HPMCAS was the most effective at maintaining drug supersaturation. Drug/HPMCAS SDDs were consistently more effective at achieving and maintaining drug supersaturation in vitro than were SDDs prepared with other polymers. Drug/HPMCAS SDDs were effective in vitro for eight low solubility drugs of widely varying structure. Drug/HPMCAS SDDs were more effective at achieving and maintaining supersaturation than were rotoevaporated Drug/HPMCAS dispersions or physical mixtures of Drug and HPMCAS. The degree of achievable drug supersaturation increased with increasing polymer content in the SDD. The drug in Drug /HPMCAS SDDs was amorphous, and the dispersions were demonstrated to have a single glass transition and were thus homogeneous. HPMCAS has been identified as a uniquely effective polymer for use in SDDs of low solubility drugs, with broad applicability across a variety of drug structures and properties.

  15. Vertically Resolved Aerosol Optical Properties over the ARM SGP Site

    Science.gov (United States)

    Schmid, B.; Jonsson, H.; Strawa, A.; Provencal, B.; Covert, D.; Arnott, P.; Bucholtz, A.; Pilewskie, P.; Pommier, J.; Rissman, T.

    2003-01-01

    In order to meet one of its goals - to relate observations of radiative fluxes and radiances to the atmospheric composition - the Department of Energy's Atmospheric Radiation Measurement (ARM) program has pursued measurements and modeling activities that attempt to determine how aerosols impact atmospheric radiative transfer, both directly and indirectly. However, significant discrepancies between aerosol properties measured in situ or remotely remain. To this end, the ARM program will conduct an Aerosol Intensive Operational Period (IOP) in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma. The IOP involves airborne measurements from two airplanes over the heavily instrumented SGP site. We will give an overview of early airborne results obtained aboard Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The aircraft will carry instrumentation to perform in-situ measurements of aerosol absorption, scattering, extinction and particle size including such novel techniques as the photoacoustic and cavity ring-down methods. Aerosol optical depth and extinction will be measured with the NASA Ames Airborne Tracking 14-channel sunphotometer. Furthermore up- and downwelling solar (broadband and spectral) and infrared radiation will be measured using three different instruments. The up-looking radiation instruments will be mounted on a newly developed stabilized platform, which will keep the instruments level up to aircraft pitch and roll angles of 10 degrees. Additional effort will be directed toward measurement of cloud condensation nucleus concentration as a function of supersaturation and relating CCN concentration to aerosol composition and size distribution. This relation is central to description of the aerosol indirect effect.

  16. Aerosol Size, CCN, and Black Carbon Properties at a Coastal Site in the Eastern U.S.

    Science.gov (United States)

    Royalty, T. M.; Petters, M. D.; Grieshop, A. P.; Meskhidze, N.; Reed, R. E.; Phillips, B.; Dawson, K. W.

    2015-12-01

    Atmospheric aerosols play an important role in regulating the global radiative budget through direct and indirect effects. To date, the role of sea spray aerosols in modulating climate remains poorly understood. Here we present results from measurements performed at the United States Army Corps of Engineers' Field Research Facility in Duck, North Carolina, USA. Aerosol mobility size distributions (10-600 nm), refractory black carbon (rBC) and scattering particle size distributions (200-620 nm), and size resolved cloud condensation nuclei distributions (.07% - .6% supersaturation) were collected at the end of a 560m pier. Aerosol characteristics associated with northerly, high wind speed (15+ m s-1) flow originating from an oceanic trajectory are contrasted with aerosol properties observed during a weak to moderate westerly flow originating from a continental trajectory. Both marine and continental air masses had aerosol with bi-modal number size distributions with modes centered at 30nm and 140nm. In the marine air-mass, the CCN concentration at supersaturation of 0.4%, total aerosol number, surface, and volume concentration were low. rBC number concentration (D > 200 nm) associated with the marine air-mass was an order of magnitude less than continental number concentration and indicative of relatively unpolluted air. These measurements are consistent with measurements from other coastal sites under marine influence. The relative proportion of Aitken mode size particles increased from 1:2 to 2:1 while aerosol surface area was < 25 μm2 cm-3, suggesting that conditions upwind were potentially conducive to new particle formation. Overall, these results will contribute a better understanding to composition and size variation of marine aerosols.

  17. Size-resolved and bulk activation properties of aerosols in the North China Plain

    Directory of Open Access Journals (Sweden)

    Z. Z. Deng

    2011-04-01

    Full Text Available Size-resolved and bulk activation properties of aerosols were measured at a regional/suburban site in the North China Plain (NCP, which is occasionally heavily polluted by anthropogenic aerosol particles and gases. A Cloud Condensation Nuclei (CCN closure study is conducted with bulk CCN number concentration (NCCN and calculated CCN number concentration based on the aerosol number size distribution and size-resolved activation properties.

    The observed CCN number concentration (NCCN-obs are higher than those observed in other locations than China, with average NCCN-obs of roughly 2000, 3000, 6000, 10 000 and 13 000 cm−3 at supersaturations of 0.056, 0.083, 0.17, 0.35 and 0.70%, respectively. An inferred critical dry diameter (Dm is calculated based on the NCCN-obs and aerosol number size distribution assuming homogeneous chemical composition. The inferred cut-off diameters are in the ranges of 190–280, 160–260, 95–180, 65–120 and 50–100 nm at supersaturations of 0.056, 0.083, 0.17, 0.35 and 0.7%, with their mean values 230.1, 198.4, 128.4, 86.4 and 69.2 nm, respectively.

    Size-resolved activation measurements show that most of the 300 nm particles are activated at the investigated supersaturations, while almost no particles of 30 nm are activated even at the highest supersaturation of 0.72%. The activation ratio increases with increasing supersaturation and particle size. The slopes of the activation curves for ambient aerosols are not as steep as those observed in calibrations with ammonium sulfate suggesting that the observed aerosols is an external mixture of more hygroscopic and hydrophobic particles.

    The calculated CCN number concentrations (NCCN-calc based on the size-resolved activation ratio and aerosol number size distribution correlate well with the NCCN-obs, and

  18. Study of real time detection and size distribution measurement of ultrafine aerosol with a particle growth system (PGS)

    Energy Technology Data Exchange (ETDEWEB)

    Rebours, A.

    1994-06-29

    First, the theoretical knowledge on condensation phenomena of a supersaturated vapor in a cylindrical duct where an ultrafine aerosol of nanometers size is flowing, is recalled. Then, a Particle Growth-System (PGS) of original design is developed: the aerosol is confined in a region with a uniform vapor supersaturation profile. When imperfectly filtered atmospheric air is used as source of condensation nuclei, the produced droplets are found to be monodisperse. Therefore, our PGS offers a simple method of calibrating Optical Particle Counters because the size distribution of theses droplets is controlled. After an experimental study validated by a theoretical model, we establish that, under certain supersaturation conditions, the droplet size in our PGS is a function of ultrafine particle size on which the vapor condenses. Furthermore, when the sampled aerosol is constituted of an ultrafine fraction and a fine fraction, we show that the size distribution of the droplets that come out from the PGS is bimodal too. Finally, a simple redesign of our fluids inlet system should reduce particles losses in the PGS due to brownian diffusion and, in that manner improve their detection. (author). 72 refs., 46 figs., 8 tabs., 4 appends.

  19. Aerosol typing - key information from aerosol studies

    Science.gov (United States)

    Mona, Lucia; Kahn, Ralph; Papagiannopoulos, Nikolaos; Holzer-Popp, Thomas; Pappalardo, Gelsomina

    2016-04-01

    Aerosol typing is a key source of aerosol information from ground-based and satellite-borne instruments. Depending on the specific measurement technique, aerosol typing can be used as input for retrievals or represents an output for other applications. Typically aerosol retrievals require some a priori or external aerosol type information. The accuracy of the derived aerosol products strongly depends on the reliability of these assumptions. Different sensors can make use of different aerosol type inputs. A critical review and harmonization of these procedures could significantly reduce related uncertainties. On the other hand, satellite measurements in recent years are providing valuable information about the global distribution of aerosol types, showing for example the main source regions and typical transport paths. Climatological studies of aerosol load at global and regional scales often rely on inferred aerosol type. There is still a high degree of inhomogeneity among satellite aerosol typing schemes, which makes the use different sensor datasets in a consistent way difficult. Knowledge of the 4d aerosol type distribution at these scales is essential for understanding the impact of different aerosol sources on climate, precipitation and air quality. All this information is needed for planning upcoming aerosol emissions policies. The exchange of expertise and the communication among satellite and ground-based measurement communities is fundamental for improving long-term dataset consistency, and for reducing aerosol type distribution uncertainties. Aerosol typing has been recognized as one of its high-priority activities of the AEROSAT (International Satellite Aerosol Science Network, http://aero-sat.org/) initiative. In the AEROSAT framework, a first critical review of aerosol typing procedures has been carried out. The review underlines the high heterogeneity in many aspects: approach, nomenclature, assumed number of components and parameters used for the

  20. Evidence That Most Florida Anvil Crystals Derive From Midtropospheric Aerosols

    Science.gov (United States)

    Fridlind, A. M.; Ackerman, A. S.; Jensen, E. J.; Stevens, D. E.; Wang, D.; Heymsfield, A. J.; Poellot, M. R.; Milosevich, L. M.; Baumgardner, D.; Lawson, P.; Wilson, J.; Flagan, R. C.; Seinfeld, J. H.; Jonsson, H.; Vanreken, T.; Varutbangkul, V.; Rissman, T.

    2003-12-01

    NASA's 2002 CRYSTAL-FACE field experiment focused on the formation and properties of cirrus cloud systems in southern Florida, including extensive measurements of aerosol number and size distribution throughout the atmospheric column. Coupling these field measurements with large-eddy simulations that resolve the size distributions of aerosols and cloud particles, we find several lines of evidence pointing to the predominance of midtropospheric aerosols as the seminal cloud nuclei for anvil crystals, in contrast to the general assumption that boundary layer aerosols are more important. Turning first to measurements made during the only penetration of a powerful updraft during the campaign, at an altitude of approximately 10 km on July 18, we find that the inclusion of tropospheric aerosols above 6 km is required to properly simulate the large number of cloud particles measured in the updraft. Furthermore, in both model simulations and observations, peak particle numbers are found not in the heart of the updraft core at 10 km, where peak supersaturations are located, but instead are found in the upwind entraining boundary of the updraft. Observed and modeled particle size distributions also demonstrate that the additional particles in the entraining region are much smaller than those in the heart of the core, consistent with cloud particle activation on recently-entrained tropospheric aerosols. Turning next to upper anvil ice crystal size distributions, observations consistently indicate peak crystal numbers in the 20 to 30 um diameter range. Model simulations reproduce this peak accurately when aerosols are included throughout the atmospheric column,but the peak shifts to 40 to 50 um when excluding aerosols above 6 km,and further shifts to 90 um when excluding aerosols above 2 km, which well exceeds the boundary layer depth. While no anvil data are available on July 18, coincident with the strong updraft measurements, we find that upper tropospheric aerosols are

  1. CCN Activation Properties of Multiple-Component, Smog Chamber Generated, and Ambient Aerosols

    Science.gov (United States)

    Raymond, T. M.; Pandis, S. N.

    2002-12-01

    Ambient aerosols are a complex mixture of inorganic and hundreds of organic compounds varying in structure and physical properties. Despite the considerable fraction of organic matter in atmospheric aerosol, relatively little is known about the ability of complex, mixed particles to act as cloud condensation nuclei (CCN). Previous work has focused on pure-component and dual-component aerosols and theoretical modeling of their activation. This work expands the investigation by studying the CCN-forming ability of multiple-component organic-inorganic mixed aerosol compounds produced in a smog chamber, and ambient aerosols. The CCN properties of aerosols produced in an indoor five cubic meter Teflon smog chamber and ambient aerosol are investigated experimentally combining a Tandem Differential Mobility Analyzer (TDMA) with a static diffusion CCN counter (M1 Model, DH Associates). Data was obtained for ozone oxidation products of alpha-pinene, beta-pinene, limonene, gasoline, and diesel fuel. Multiple-component aerosols were produced from atomizing a mixed solution of chemical components and studying the particles with the TDMA-CCNC system. Mixtures included ammonium sulfate, sodium chloride, pinonic acid, pinic acid, norpinic acid, glutamic acid, and leucine. Studies were performed at supersaturations of 0.3% and 1.0% with dry particle diameters ranging from 0.02 to 0.2 micrometers. The results were analyzed to gain insights into CCN properties of atmospheric aerosols composed of known mixtures of inorganic and organic species, mixed oxidation products of primary organic species, and actual ambient aerosols. The results are compared to the behavior of pure organic aerosols and theory.

  2. The influence of chemical composition and mixing state of Los Angeles urban aerosol on CCN number and cloud properties

    Directory of Open Access Journals (Sweden)

    M. J. Cubison

    2008-03-01

    Full Text Available The relationship between cloud condensation nuclei (CCN number and the physical and chemical properties of the atmospheric aerosol distribution is explored for a polluted urban data set from the Study of Organic Aerosols at Riverside I (SOAR-1 campaign conducted at Riverside, California, USA during summer 2005. The mixing state and, to a lesser degree, the average chemical composition are shown to be important parameters in determining the activation properties of those particles around the critical activation diameters for atmospherically-realistic supersaturation values. Closure between predictions and measurements of CCN number at several supersaturations is attempted by modeling a number of aerosol chemical composition and mixing state schemes of increasing complexity. It is shown that a realistic treatment of the state of mixing of the urban aerosol distribution is critical in order to eliminate model bias. Fresh emissions such as elemental carbon and small organic particles must be treated as non-activating and explicitly accounted for in the model scheme. The relative number concentration of these particles compared to inorganics and oxygenated organic compounds of limited hygroscopicity plays an important role in determining the CCN number. Furthermore, expanding the different composition/mixing state schemes to predictions of cloud droplet number concentration in a cloud parcel model highlights the dependence of cloud optical properties on the state of mixing and hygroscopic properties of the different aerosol modes, but shows that the relative differences between the different schemes are reduced compared to those from the CCN model.

  3. An Assessment of the Radiative Effects of Ice Supersaturation Based on in Situ Observations

    Science.gov (United States)

    Tan, Xiaoxiao; Huang, i; Diao, Minghui; Bansemer, Aaron; Zondlo, Mark A.; DiGangi, Joshua P.; Volkamer, Rainer; Hu, Yongyun

    2016-01-01

    We use aircraft observations combined with the reanalysis data to investigate the radiative effects of ice supersaturation (ISS). Our results show that although the excess water vapor over ice saturation itself has relatively small radiative effects, mistaking it as ice crystals in climate models would lead to considerable impacts: on average, +2.49 W/m(exp 2) change in the top of the atmosphere (TOA) radiation, -2.7 W/m(exp 2) change in surface radiation, and 1.47 K/d change in heating rates. The radiative effects of ISS generally increase with the magnitudes of supersaturation. However, there is a strong dependence on the preexisting ice water path, which can even change the sign of the TOA radiative effect. It is therefore important to consider coexistence between ISS and ice clouds and to validate their relationship in the parameterizations of ISS in climate models.

  4. Room-temperature operation of a titanium supersaturated silicon-based infrared photodetector

    Science.gov (United States)

    García-Hemme, E.; García-Hernansanz, R.; Olea, J.; Pastor, D.; del Prado, A.; Mártil, I.; González-Díaz, G.

    2014-05-01

    We report room-temperature operation of 1 × 1 cm2 infrared photoconductive photodetectors based on silicon supersaturated with titanium. We have fabricated these Si-based infrared photodetectors devices by means of ion implantation followed by a pulsed laser melting process. A high sub-band gap responsivity of 34 mV W-1 has been obtained operating at the useful telecommunication applications wavelength of 1.55 μm (0.8 eV). The sub-band gap responsivity shows a cut-off frequency as high as 1.9 kHz. These Si-based devices exhibit a non-previous reported specific detectivity of 1.7 × 104 cm Hz1/2 W-1 at 660 Hz, under a 1.55 μm wavelength light. This work shows the potential of Ti supersaturated Si as a fully CMOS-compatible material for the infrared photodetection technology.

  5. Laboratory studies of the effects of pressure and dissolved gas supersaturation on turbine-passed fish

    Energy Technology Data Exchange (ETDEWEB)

    Abernethy, C. S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Amidan, B. G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Cada, G. F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2001-03-01

    Designing advanced turbine systems requires knowledge of environmental conditions that injure or kill fish such as the stresses associated with hydroelectric power production, including pressure changes fish experience during turbine passage and dissolved gas supersaturation (resulting from the release of water from the spillway). The objective of this study was to examine the relative importance of pressure changes as a source of turbine-passage injury and mortality. Specific tests were designed to quantify the response of fish to rapid pressure changes typical of turbine passage, with and without the complication of the fish being acclimated to gas supersaturated water. The study investigated the responses of rainbow trout (Oncorhynchus mykiss), chinook salmon (O. tshawytscha), and bluegill sunfish (Lepomis macrochirus) to these two stresses, both singly and in combination.

  6. Growth kinetics of calcium fluoride at high supersaturation in a fluidized bed reactor.

    Science.gov (United States)

    Jiang, K; Zhou, K G; Yang, Y C; Du, H

    2014-01-01

    Crystallization process in a fluidized bed reactor (FBR) has been regarded as an environmentally friendly technology for the removal and recovery of fluoride from industrial wastewater. The growth kinetics of calcium fluoride at high supersaturation was studied for design, control, and operation of an FBR. The main variables, including supersaturation, superficial velocity, pH value, and particle size of seed that influenced the crystal growth were investigated. Then, a growth model was used to predict the linear growth rate of calcium fluoride at a high influent concentration of fluoride. The pressure difference in the FBR was used as a feature to characterize the growth rate of calcium fluoride. The aggregation and adsorption between seeds and fine particles were proven to be a possible mechanism for growth of calcium fluoride.

  7. Clinopyroxene in postshield Haleakala ankaramite: 2. Texture, compositional zoning and supersaturation in the magma

    Science.gov (United States)

    Welsch, Benoit; Hammer, Julia; Baronnet, Alain; Jacob, Samantha; Hellebrand, Eric; Sinton, John

    2016-01-01

    We investigated the external morphologies and internal compositional zoning patterns of clinopyroxene phenocrysts in an ankaramite of Haleakala volcano (Hawaii) to constrain magma crystallization conditions in the volcano's postshield stage. The phenocrysts are characterized by euhedral faceted morphologies and crystallographically coherent subcrystals. Quantitative EPMA and X-ray element mapping reveal two domains within the crystals: porous, Si-Mg-Ca-Cr-rich zones associated with the forms {100}, {010} and {110}, and nonporous, Al-Ti-Na-rich zones associated with the forms {-111}. The chemical variations, internal porosity and parallel subcrystals are consistent with nonconcentric crystal growth at varying degrees of supersaturation. We infer that initial growth occurred in a diffusion-limited regime to produce dendritic crystals; subsequent growth was markedly slower, with lesser supersaturation allowing dendrites to infill and produce polyhedral external morphologies. This sequence promoted the evolution of crystals from an hourglass shape with dominant {-111} forms, to sector-zoned euhedral crystals in which elements were partitioned according to: (Al + Ti + Na){-111} = (Si + Mg + Cr + Ca){110},{100},{010}. Infilling of dendritic crystals occurred to a greater extent on faster-growing sectors and was interrupted by the eruption, resulting in porosity of the slower-growing {hk0} sectors. Outermost Na-poor rims formed on all sectors due to slower growth rate under interface-limited conditions. Paradoxically, high levels of supersaturation producing large crystals of clinopyroxene (and olivine) are indicated in the volcano's deep-seated reservoir and lower degrees of supersaturation characterize syn-eruptive crystal growth. The presence of vapor bubbles within the melt-filled crystal embayments and inclusions suggests rapid clinopyroxene growth caused volatile saturation and reservoir pressurization, leading to eruption of the ankaramite.

  8. Influence of Isovalent Impurity Ge on Nucleation and Morphology of Supersaturated Oxygen Precipitate in CZSi

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The effects of Ge in CZSi on the density and the rate of nucleation of supersaturated oxygen precipitation at lower annealing temperatures were examined.It is discovered that rod-like precipitation was suppressed when annealing at 700℃,but Ge has no effect on the morphology and the growth of oxygen precipitation at annealing temperatures more than 900℃.The results indicated that Ge neither acted as center of nucleation nor was involved in oxygen precipitation and its defect.

  9. In Silico Modeling Approach for the Evaluation of Gastrointestinal Dissolution, Supersaturation, and Precipitation of Posaconazole.

    Science.gov (United States)

    Hens, Bart; Pathak, Shriram M; Mitra, Amitava; Patel, Nikunjkumar; Liu, Bo; Patel, Sanjaykumar; Jamei, Masoud; Brouwers, Joachim; Augustijns, Patrick; Turner, David B

    2017-09-05

    The aim of this study was to evaluate gastrointestinal (GI) dissolution, supersaturation, and precipitation of posaconazole, formulated as an acidified (pH 1.6) and neutral (pH 7.1) suspension. A physiologically based pharmacokinetic (PBPK) modeling and simulation tool was applied to simulate GI and systemic concentration-time profiles of posaconazole, which were directly compared with intraluminal and systemic data measured in humans. The Advanced Dissolution Absorption and Metabolism (ADAM) model of the Simcyp Simulator correctly simulated incomplete gastric dissolution and saturated duodenal concentrations of posaconazole in the duodenal fluids following administration of the neutral suspension. In contrast, gastric dissolution was approximately 2-fold higher after administration of the acidified suspension, which resulted in supersaturated concentrations of posaconazole upon transfer to the upper small intestine. The precipitation kinetics of posaconazole were described by two precipitation rate constants, extracted by semimechanistic modeling of a two-stage medium change in vitro dissolution test. The 2-fold difference in exposure in the duodenal compartment for the two formulations corresponded with a 2-fold difference in systemic exposure. This study demonstrated for the first time predictive in silico simulations of GI dissolution, supersaturation, and precipitation for a weakly basic compound in part informed by modeling of in vitro dissolution experiments and validated via clinical measurements in both GI fluids and plasma. Sensitivity analysis with the PBPK model indicated that the critical supersaturation ratio (CSR) and second precipitation rate constant (sPRC) are important parameters of the model. Due to the limitations of the two-stage medium change experiment the CSR was extracted directly from the clinical data. However, in vitro experiments with the BioGIT transfer system performed after completion of the in silico modeling provided an almost

  10. Effectiveness of supersaturation promoting excipients on albendazole concentrations in upper gastrointestinal lumen of fasted healthy adults.

    Science.gov (United States)

    Kourentas, Alexandros; Vertzoni, Maria; Symillides, Mira; Goumas, Konstantinos; Gibbon, Robert; Butler, James; Reppas, Christos

    2016-08-25

    To evaluate the impact of dosage form relevant levels of a polymeric precipitation inhibitor and of lipid excipients on supersaturation of upper gastrointestinal contents with albendazole, a lipophilic weak base. Albendazole concentrations in stomach and in duodenum were evaluated after administration of 1) a suspension in water (Susp-Control), 2) a suspension in water in which hydroxyprolylmethylcellulose E5 (HPMC E5) had been pre-dissolved (Susp-HPMC), and 3) and 4) two contrasting designs of lipid based suspensions dispersed in water (Susp-IIIA and Susp-IV), on a cross-over basis to fasted healthy adults. Limited, but statistically significant supersaturation of duodenal contents was observed after Susp-HPMC, Susp-IIIA, and Susp-IV; supersaturation was more consistent after Susp-HPMC administration. Based on total albendazole amount per volume, gastric secretions did not significantly alter volumes of bulk gastric contents during the first 40min post administration of a glass of non-caloric water-based fluid. Αlbendazole gastric concentrations were higher than in the administered suspensions, but similar for all four formulations. Gastric emptying of albendazole after administration of Susp-Control or Susp-HPMC was slower than after administration of Susp-IIIA or Susp-IV. Small amounts of HPMC E5 were as effective as lipid excipients in achieving supersaturation of duodenal contents with albendazole, a fast precipitating weak base, in fasted adults. However, compared with the effect of HPMC E5 the effect of lipid excipients was delayed and variable. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Metal sulphides from wastewater: assessing the impact of supersaturation control strategies.

    Science.gov (United States)

    Mokone, T P; van Hille, R P; Lewis, A E

    2012-05-01

    Metal sulphide precipitation forms an important component of acid mine drainage remediation systems based on bacterial sulphate reduction. However, the precipitation reaction is inherently driven by very high levels of supersaturation with the generation of small particles with poor solid-liquid separation characteristics. In this study, the effect of strategies used to manage supersaturation was investigated during copper and zinc sulphide precipitation reactions. Initial batch studies showed the origin of sulphide (biological or chemical) had no significant effect on the efficiency of zinc sulphide precipitation. For copper, low metal removal efficiency was obtained at metal to sulphide molar ratios below 1.6 in the synthetic sulphide system. This was improved in the biogenic sulphide system, due to the presence of residual volatile fatty acids, but the presence or absence of particulate organic matter had no effect on recovery. Subsequent studies, conducted using synthetic sulphide solutions in a seeded fluidised bed reactor with multiple reagent feed points (2FP and 6FP) and different recirculation flow rates (300 and 120 mL min(-1)) showed efficient zinc sulphide precipitation, but limited (supersaturation to the extent of altering particle characteristics. The copper sulphide fines could not be recovered by settling, remaining in a stable colloidal suspension due to their highly charged surfaces (zeta potential -50 mV). The change in recirculation flow rate had a limited effect (ca 5% improvement) on process efficiency. The results show that the extremely high supersaturation prevalent during metal sulphide precipitation is difficult to control using conventional approaches and suggest that the seeded fluidised bed reactor is not suitable for this application. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Experimental Study of the Low Supersaturation Nucleation in Crystal Growth by Contactless Physical Vapor Transport

    Science.gov (United States)

    Grasza, K.; Palosz, W.; Trivedi, S. B.

    1998-01-01

    The process of the development of the nuclei and of subsequent seeding in 'contactless' physical vapor transport is investigated experimentally. Consecutive stages of the Low Supersaturation Nucleation in 'contactless' geometry for growth of CdTe crystals from the vapor are shown. The effects of the temperature field, geometry of the system, and experimental procedures on the process are presented and discussed. The experimental results are found to be consistent with our earlier numerical modeling results.

  13. Aerosol mobility size spectrometer

    Science.gov (United States)

    Wang, Jian; Kulkarni, Pramod

    2007-11-20

    A device for measuring aerosol size distribution within a sample containing aerosol particles. The device generally includes a spectrometer housing defining an interior chamber and a camera for recording aerosol size streams exiting the chamber. The housing includes an inlet for introducing a flow medium into the chamber in a flow direction, an aerosol injection port adjacent the inlet for introducing a charged aerosol sample into the chamber, a separation section for applying an electric field to the aerosol sample across the flow direction and an outlet opposite the inlet. In the separation section, the aerosol sample becomes entrained in the flow medium and the aerosol particles within the aerosol sample are separated by size into a plurality of aerosol flow streams under the influence of the electric field. The camera is disposed adjacent the housing outlet for optically detecting a relative position of at least one aerosol flow stream exiting the outlet and for optically detecting the number of aerosol particles within the at least one aerosol flow stream.

  14. Codissolution of calcium hydrogenphosphate and sodium hydrogencitrate in water. Spontaneous supersaturation of calcium citrate increasing calcium bioavailability

    DEFF Research Database (Denmark)

    Hedegaard, Martina Vavrusova; Danielsen, Bente Pia; Garcia, André Castilho

    2017-01-01

    The sparingly soluble calcium hydrogenphosphate dihydrate, co-dissolving in water during dissolution of freely soluble sodium hydrogencitrate sesquihydrate as caused by proton transfer from hydrogencitrate to hydrogenphosphate, was found to form homogenous solutions supersaturated by a factor up......, as identified from FT-IR spectra, from these spontaneously formed supersaturated solutions was several hours, and the time to reach solubility equilibrium was several days. Initial calcium ion activity was found to be almost independent of the degree of supersaturation as determined electrochemically....... The supersaturated solutions had a pH around 4.7, and calcium binding to hydrogencitrate as the dominant citrate species during precipitation was found to be exothermic with a determined association constant of 357 L mol-1 at 25 °C for unit ionic strength, and δH° = -22 ± 2 kJ mol-1, δS° = -26 ± 8 J K-1 mol-1...

  15. Amelogenin–chitosan matrix for human enamel regrowth: effects of viscosity and supersaturation degree

    Science.gov (United States)

    Ruan, Qichao; Siddiqah, Nadia; Li, Xiaochen; Nutt, Steven; Moradian-Oldak, Janet

    2015-01-01

    We recently reported an amelogenin-chitosan (CS-AMEL) hydrogel as a promising biomimetic material for future in situ human enamel regrowth. To further optimize the necessary conditions for clinical applicability of CS-AMEL hydrogel, herein we studied the effects of viscosity and supersaturation degree on the size and orientation of synthetic crystals by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Raising the hydrogel viscosity by increasing chitosan concentration from 1% to 2% (w/v) improved the orientation of the crystals, while a higher supersaturation (σ(HAp) >10.06, [Ca2+] >5 mM) resulted in the formation of random crystals with larger sizes and irregular structures. We conclude that optimal conditions to produce organized enamel-like crystals in a CS-AMEL hydrogel are: 2% (w/v) chitosan, 2.5 mM calcium, and 1.5 mM phosphate (degree of supersaturation = 8.23) and 200 μg/ml of amelogenin. PMID:25158201

  16. Quartz Crystal Microbalance Technique for in Situ Analysis of Supersaturation in Cooling Crystallization.

    Science.gov (United States)

    Liu, Li-Shang; Kim, Jong-Min; Kim, Woo-Sik

    2016-06-07

    A quartz crystal microbalance (QCM) is used as a novel in situ strategy for analyzing the supersaturation profile during cooling crystallization. The main concept is based on preventing any solid mass loading on the QCM sensor by modifying the sensor surface. As a result, the QCM responses only depend on the solution concentration changes during the crystallization. The proposed strategy is confirmed on the basis of an analysis of sulfamerazine (SMZ) crystallization. When the QCM sensor is modified using 11-amino-1-undecanethiol (AUT), crystal formation on the sensor is completely prevented due to a repulsive interaction between the -NH2 functional groups of the AUT and SMZ crystals. Thus, the QCM responses reflect only the property changes in the solution phase during the crystallization. The supersaturation in the solution is then estimated on the basis of the difference in the frequency shifts between the SMZ solution and a blank solution. The accuracy of the in situ QCM analysis of supersaturation is confirmed using an off-line gravimetric method.

  17. Amorphization strategy affects the stability and supersaturation profile of amorphous drug nanoparticles.

    Science.gov (United States)

    Cheow, Wean Sin; Kiew, Tie Yi; Yang, Yue; Hadinoto, Kunn

    2014-05-05

    Amorphous drug nanoparticles have recently emerged as a promising bioavailability enhancement strategy of poorly soluble drugs attributed to the high supersaturation solubility generated by the amorphous state and fast dissolution afforded by the nanoparticles. Herein we examine the effects of two amorphization strategies in the nanoscale, i.e., (1) molecular mobility restrictions and (2) high energy surface occupation, both by polymer excipient stabilizers, on the (i) morphology, (ii) colloidal stability, (iii) drug loading, (iv) amorphous state stability after three-month storage, and (v) in vitro supersaturation profiles, using itraconazole (ITZ) as the model drug. Drug-polyelectrolyte complexation is employed in the first strategy to prepare amorphous ITZ nanoparticles using dextran sulfate as the polyelectrolyte (ITZ nanoplex), while the second strategy employs pH-shift precipitation using hydroxypropylmethylcellulose as the surface stabilizer (nano-ITZ), with both strategies resulting in >90% ITZ utilization. Both amorphous ITZ nanoparticles share similar morphology (∼300 nm spheres) with the ITZ nanoplex exhibiting better colloidal stability, albeit at lower ITZ loading (65% versus 94%), due to the larger stabilizer amount used. The ITZ nanoplex also exhibits superior amorphous state stability, attributed to the ITZ molecular mobility restriction by electrostatic complexation with dextran sulfate. The higher stability, however, is obtained at the expense of slower supersaturation generation, which is maintained over a prolonged period, compared to the nano-ITZ. The present results signify the importance of selecting the optimal amorphization strategy, in addition to formulating the excipient stabilizers, to produce amorphous drug nanoparticles having the desired characteristics.

  18. Eudragit® RL as a stabilizer for supersaturation and a substrate for nanocrystal formation.

    Science.gov (United States)

    Dereymaker, Aswin; Cinghia, Giulia; Van den Mooter, Guy

    2017-05-01

    In order to optimize supersaturation levels and avoid early drug precipitation, Eudragit® RL was tested as a carrier in solid dispersions, either alone or in combination with a hydrophilic polymer (PVP K25). In vitro dissolution performance of the spray dried solid dispersions was tested. The phase behavior of the produced solid dispersions was analyzed as well as dissolution precipitates. In case of weak acid model compounds (indomethacin and naproxen), the incorporation of Eudragit® RL resulted in a prolongation of supersaturation. A combination of PVP and Eudragit® RL led to high and stable drug concentrations. Eudragit® RL was only suited as a carrier in combination with higher drug loadings. Phase behavior analysis of the produced solid dispersions showed that Eudragit® RL could form glass solutions, and precipitate analysis showed that these drug-polymer combinations remained amorphous after in vitro dissolution for 24h. Surprisingly, indomethacin and naproxen also formed nanocrystals in presence of Eudragit® RL. These nanocrystals were formed by a dynamic interplay of dissolution, sorption and desorption. A charge interaction between anionic drugs and a cationic polymer provided a high driving force for sorption, which was necessary for nanocrystal formation and supersaturation stabilization. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. An improved model of homogeneous nucleation for high supersaturation conditions: aluminum vapor.

    Science.gov (United States)

    Savel'ev, A M; Starik, A M

    2016-12-21

    A novel model of stationary nucleation, treating the thermodynamic functions of small clusters, has been built. The model is validated against the experimental data on the nucleation rate of water vapor obtained in a broad range of supersaturation values (S = 10-120), and, at high supersaturation values, it reproduces the experimental data much better than the traditional classical nucleation model. A comprehensive analysis of the nucleation of aluminum vapor with the usage of developed stationary and non-stationary nucleation models has been performed. It has been shown that, at some value of supersaturation, there exists a double potential nucleation barrier. It has been revealed that the existence of this barrier notably delayed the establishment of a stationary distribution of subcritical clusters. It has also been demonstrated that the non-stationary model of the present work and the model of liquid-droplet approximation predict different values of nucleation delay time, τs. In doing so, the liquid-droplet model can underestimate notably (by more than an order of magnitude) the value of τs.

  20. Supersaturation-limited and Unlimited Phase Transitions Compete to Produce the Pathway Complexity in Amyloid Fibrillation*

    Science.gov (United States)

    Adachi, Masayuki; So, Masatomo; Sakurai, Kazumasa; Kardos, József; Goto, Yuji

    2015-01-01

    Although amyloid fibrils and amorphous aggregates are two types of aggregates formed by denatured proteins, their relationship currently remains unclear. We used β2-microglobulin (β2m), a protein responsible for dialysis-related amyloidosis, to clarify the mechanism by which proteins form either amyloid fibrils or amorphous aggregates. When ultrasonication was used to accelerate the spontaneous fibrillation of β2m at pH 2.0, the effects observed depended on ultrasonic power; although stronger ultrasonic power effectively accelerated fibrillation, excessively strong ultrasonic power decreased the amount of fibrils formed, as monitored by thioflavin T fluorescence. An analysis of the products formed indicated that excessively strong ultrasonic power generated fibrillar aggregates that retained β-structures but without high efficiency as seeds. On the other hand, when the spontaneous fibrillation of β2m was induced at higher concentrations of NaCl at pH 2.0 with stirring, amorphous aggregates became more dominant than amyloid fibrils. These apparent complexities in fibrillation were explained comprehensively by a competitive mechanism in which supersaturation-limited reactions competed with supersaturation-unlimited reactions. We link the kinetics of protein aggregation and a conformational phase diagram, in which supersaturation played important roles. PMID:26063798

  1. Diet, but not oral probiotics, effectively reduces urinary oxalate excretion and calciumoxalate supersaturation

    Science.gov (United States)

    Lieske, John C.; Tremaine, William J.; De Simone, Claudio; O’Connor, Helen M.; Li, Xujian; Bergstralh, Eric J.; Goldfarb, David S.

    2014-01-01

    We examined the effect of a controlled diet and two probiotic preparations on urinary oxalate excretion, a risk factor for calcium oxalate kidney stone formation, in patients with mild hyperoxaluria. Patients were randomized to a placebo, a probiotic, or a synbiotic preparation. This tested whether these probiotic preparations can increase oxalate metabolism in the intestine and/or decrease oxalate absorption from the gut. Patients were maintained on a controlled diet to remove the confounding variable of differing oxalate intake from food. Urinary oxalate excretion and calcium oxalate supersaturation on the controlled diet were significantly lower compared with baseline on a free-choice diet. Neither study preparation reduced urinary oxalate excretion nor calcium oxalate supersaturation. Fecal lactobacilli colony counts increased on both preparations, whereas enterococcal and yeast colony counts were increased on the synbiotic. Total urine volume and the excretion of oxalate and calcium were all strong independent determinants of urinary calcium oxalate supersaturation. Hence, dietary oxalate restriction reduced urinary oxalate excretion, but the tested probiotics did not influence urinary oxalate levels in patients on a restricted oxalate diet. However, this study suggests that dietary oxalate restriction is useful for kidney stone prevention. PMID:20736987

  2. Supersaturation-limited and Unlimited Phase Transitions Compete to Produce the Pathway Complexity in Amyloid Fibrillation.

    Science.gov (United States)

    Adachi, Masayuki; So, Masatomo; Sakurai, Kazumasa; Kardos, József; Goto, Yuji

    2015-07-17

    Although amyloid fibrils and amorphous aggregates are two types of aggregates formed by denatured proteins, their relationship currently remains unclear. We used β2-microglobulin (β2m), a protein responsible for dialysis-related amyloidosis, to clarify the mechanism by which proteins form either amyloid fibrils or amorphous aggregates. When ultrasonication was used to accelerate the spontaneous fibrillation of β2m at pH 2.0, the effects observed depended on ultrasonic power; although stronger ultrasonic power effectively accelerated fibrillation, excessively strong ultrasonic power decreased the amount of fibrils formed, as monitored by thioflavin T fluorescence. An analysis of the products formed indicated that excessively strong ultrasonic power generated fibrillar aggregates that retained β-structures but without high efficiency as seeds. On the other hand, when the spontaneous fibrillation of β2m was induced at higher concentrations of NaCl at pH 2.0 with stirring, amorphous aggregates became more dominant than amyloid fibrils. These apparent complexities in fibrillation were explained comprehensively by a competitive mechanism in which supersaturation-limited reactions competed with supersaturation-unlimited reactions. We link the kinetics of protein aggregation and a conformational phase diagram, in which supersaturation played important roles. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  3. Nitrous oxide supersaturation at the liquid/air interface of animal waste

    Energy Technology Data Exchange (ETDEWEB)

    Makris, Konstantinos C., E-mail: kcmakris@gmail.co [Cyprus International Institute for the Environment and Public Health in association with the Harvard School of Public Health, 5 Iroon Street, Nicosia 1105 (Cyprus); Andra, Syam S. [Environmental Geochemistry Laboratory, University of Texas at San Antonio, San Antonio, TX (United States); Hardy, Michael; Sarkar, Dibyendu [Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ (United States); Datta, Rupali [Department of Biological Sciences, Michigan Technological University, Houghton, MI (United States); Bach, Stephan B.H.; Mullens, Conor P. [Department of Chemistry, University of Texas at San Antonio, San Antonio, TX (United States)

    2009-12-15

    Concentrated animal feeding operations around the globe generate large amounts of nitrous oxide (N{sub 2}O) in the surrounding atmosphere. Liquid animal waste systems have received little attention with respect to N{sub 2}O emissions. We hypothesized that the solution chemistry of animal waste aqueous suspensions would promote conditions that lead to N{sub 2}O supersaturation at the liquid/air interface. The concentration of dissolved N{sub 2}O in poultry litter (PL) aqueous suspensions at 25 deg. C was 0.36 mug N{sub 2}O mL{sup -1}, at least an order of magnitude greater than that measured in water in equilibrium with ambient air, suggesting N{sub 2}O supersaturation. There was a nonlinear increase in the N{sub 2}O Henry constants of PL from 2810 atm/mole fraction at 35 deg. C to 17 300 atm/mole fraction at 41 deg. C. The extremely high N{sub 2}O Henry constants were partially ascribed to N{sub 2}O complexation with aromatic moieties. Complexed N{sub 2}O structures were unstable at temperatures > 35 deg. C, supplying the headspace with additional free N{sub 2}O concentrations. - Temperature-dependent N{sub 2}O supersaturation at the liquid/air interface of animal waste.

  4. Understanding the Effect of Aerosol Properties on Cloud Droplet Formation during TCAP Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Cziczo, Daniel [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2016-05-01

    The formation of clouds is an essential element in understanding the Earth’s radiative budget. Liquid water clouds form when the relative humidity exceeds saturation and condensedphase water nucleates on atmospheric particulate matter. The effect of aerosol properties such as size, morphology, and composition on cloud droplet formation has been studied theoretically as well as in the laboratory and field. Almost without exception these studies have been limited to parallel measurements of aerosol properties and cloud formation or collection of material after the cloud has formed, at which point nucleation information has been lost. Studies of this sort are adequate when a large fraction of the aerosol activates, but correlations and resulting model parameterizations are much more uncertain at lower supersaturations and activated fractions.

  5. Aerosol water parameterization: a single parameter framework

    Science.gov (United States)

    Metzger, S.; Steil, B.; Abdelkader, M.; Klingmüller, K.; Xu, L.; Penner, J. E.; Fountoukis, C.; Nenes, A.; Lelieveld, J.

    2015-11-01

    We introduce a framework to efficiently parameterize the aerosol water uptake for mixtures of semi-volatile and non-volatile compounds, based on the coefficient, νi. This solute specific coefficient was introduced in Metzger et al. (2012) to accurately parameterize the single solution hygroscopic growth, considering the Kelvin effect - accounting for the water uptake of concentrated nanometer sized particles up to dilute solutions, i.e., from the compounds relative humidity of deliquescence (RHD) up to supersaturation (Köhler-theory). Here we extend the νi-parameterization from single to mixed solutions. We evaluate our framework at various levels of complexity, by considering the full gas-liquid-solid partitioning for a comprehensive comparison with reference calculations using the E-AIM, EQUISOLV II, ISORROPIA II models as well as textbook examples. We apply our parameterization in EQSAM4clim, the EQuilibrium Simplified Aerosol Model V4 for climate simulations, implemented in a box model and in the global chemistry-climate model EMAC. Our results show: (i) that the νi-approach enables to analytically solve the entire gas-liquid-solid partitioning and the mixed solution water uptake with sufficient accuracy, (ii) that, e.g., pure ammonium nitrate and mixed ammonium nitrate - ammonium sulfate mixtures can be solved with a simple method, and (iii) that the aerosol optical depth (AOD) simulations are in close agreement with remote sensing observations for the year 2005. Long-term evaluation of the EMAC results based on EQSAM4clim and ISORROPIA II will be presented separately.

  6. Aerosol water parameterisation: a single parameter framework

    Science.gov (United States)

    Metzger, Swen; Steil, Benedikt; Abdelkader, Mohamed; Klingmüller, Klaus; Xu, Li; Penner, Joyce E.; Fountoukis, Christos; Nenes, Athanasios; Lelieveld, Jos

    2016-06-01

    We introduce a framework to efficiently parameterise the aerosol water uptake for mixtures of semi-volatile and non-volatile compounds, based on the coefficient, νi. This solute-specific coefficient was introduced in Metzger et al. (2012) to accurately parameterise the single solution hygroscopic growth, considering the Kelvin effect - accounting for the water uptake of concentrated nanometer-sized particles up to dilute solutions, i.e. from the compounds relative humidity of deliquescence (RHD) up to supersaturation (Köhler theory). Here we extend the νi parameterisation from single to mixed solutions. We evaluate our framework at various levels of complexity, by considering the full gas-liquid-solid partitioning for a comprehensive comparison with reference calculations using the E-AIM, EQUISOLV II and ISORROPIA II models as well as textbook examples. We apply our parameterisation in the EQuilibrium Simplified Aerosol Model V4 (EQSAM4clim) for climate simulations, implemented in a box model and in the global chemistry-climate model EMAC. Our results show (i) that the νi approach enables one to analytically solve the entire gas-liquid-solid partitioning and the mixed solution water uptake with sufficient accuracy, (ii) that ammonium sulfate mixtures can be solved with a simple method, e.g. pure ammonium nitrate and mixed ammonium nitrate and (iii) that the aerosol optical depth (AOD) simulations are in close agreement with remote sensing observations for the year 2005. Long-term evaluation of the EMAC results based on EQSAM4clim and ISORROPIA II will be presented separately.

  7. Degree of supersaturation: An effective tool to control the luminescence efficiency and size distribution in CdTe quantum dots

    Science.gov (United States)

    Kumar, Indrajit; Priyam, Amiya; Choubey, Ravi Kant

    2013-06-01

    Supersaturation controlled synthesis of thioglycollic acid (TGA) capped CdTe quantum dots in aqueous medium has been carried out. With a four-fold increase in the degree of supersaturation, the photoluminescence quantum efficiency of the nanoparticles was enhanced more than five times to a remarkably high value of 46%. This was accompanied by concomitant narrowing of the size distribution of the QDs. The simplified approach obviates the need for post-preparative treatments to improve the particle characteristics.

  8. Impact of mixing state and hygroscopicity on CCN activity of biomass burning aerosol in Amazonia

    Science.gov (United States)

    Sánchez Gácita, Madeleine; Longo, Karla M.; Freire, Julliana L. M.; Freitas, Saulo R.; Martin, Scot T.

    2017-02-01

    Smoke aerosols prevail throughout Amazonia because of widespread biomass burning during the dry season, and external mixing, low variability in the particle size distribution and low particle hygroscopicity are typical. There can be profound effects on cloud properties. This study uses an adiabatic cloud model to simulate the activation of smoke particles as cloud condensation nuclei (CCN) for three hypothetical case studies, chosen as to resemble biomass burning aerosol observations in Amazonia. The relative importance of variability in hygroscopicity, mixing state, and activation kinetics for the activated fraction and maximum supersaturation is assessed. For a population with κp = 0.04, an overestimation of the cloud droplet number concentration Nd for the three selected case studies between 22.4 ± 1.4 and 54.3 ± 3.7 % was obtained when assuming a hygroscopicity parameter κp = 0.20. Assuming internal mixing of the aerosol population led to overestimations of up to 20 % of Nd when a group of particles with medium hygroscopicity was present in the externally mixed population cases. However, the overestimations were below 10 % for external mixtures between very low and low-hygroscopicity particles, as seems to be the case for Amazon smoke particles. Kinetic limitations were significant for medium- and high-hygroscopicity particles, and much lower for very low and low-hygroscopicity particles. When particles were assumed to be at equilibrium and to respond instantly to changes in the air parcel supersaturation, the overestimation of the droplet concentration was up to ˜ 100 % in internally mixed populations, and up to ˜ 250 % in externally mixed ones, being larger for the higher values of hygroscopicity. In addition, a perceptible delay between the times when maximum supersaturation and maximum aerosol activated fraction are reached was noticed and, for aerosol populations with effective hygroscopicity κpeff higher than a certain threshold value, the delay in

  9. Supersaturation induced by Itraconazole/Soluplus® micelles provided high GI absorption in vivo

    Directory of Open Access Journals (Sweden)

    Yue Zhong

    2016-04-01

    Full Text Available To investigate the effect of supersaturation induced by micelle formation during dissolution on the bioavailability of itraconazole (ITZ/Soluplus® solid dispersion. Solid dispersions prepared by hot melt extrusion (HME were compressed into tablets directly with other excipients. Dissolution behavior of ITZ tablets was studied by dissolution testing and the morphology of micelles in dissolution media was studied using transmission electron microscopy (TEM. Drug transferring from stomach into intestine was simulated to obtain a supersaturated drug solution. Bioavailability studies were performed on the ITZ tablets and Sporanox® in beagle dogs. The morphology of micelles in the dissolution media was observed to be spherical in shape, with an average size smaller than 100 nm. The supersaturated solutions formed by Soluplus® micelles were stable and no precipitation took place over a period of 180 min. Compared with Sporanox®, ITZ tablets exhibited a 2.50-fold increase in the AUC(0–96 of ITZ and a 1.95-fold increase in its active metabolite hydroxyitraconazole (OH-ITZ in the plasma of beagle dogs. The results obtained provided clear evidence that not only the increase in the dissolution rate in the stomach, but also the supersaturation produced by micelles in the small intestine may be of great assistance in the successful development of poorly water-soluble drugs. The micelles formed by Soluplus® enwrapped the molecular ITZ inside the core which promoted the amount of free drug in the intestinal cavity and carried ITZ through the aqueous boundary layer (ABL, resulting in high absorption by passive transportation across biological membranes. The uptake of intact micelles through pinocytosis together with the inhibition of P-glycoprotein-mediated drug efflux in intestinal epithelia contributed to the absorption of ITZ in the gastrointestinal tract. These results indicate that HME with Soluplus®, which can induce supersaturation by micelle

  10. Aerosol distribution apparatus

    Science.gov (United States)

    Hanson, W.D.

    An apparatus for uniformly distributing an aerosol to a plurality of filters mounted in a plenum, wherein the aerosol and air are forced through a manifold system by means of a jet pump and released into the plenum through orifices in the manifold. The apparatus allows for the simultaneous aerosol-testing of all the filters in the plenum.

  11. The effects of mineral dust particles, aerosol regeneration and ice nucleation parameterizations on clouds and precipitation

    Directory of Open Access Journals (Sweden)

    A. Teller

    2012-03-01

    Full Text Available This study focuses on the effects of aerosol particles on the formation of convective clouds and precipitation in the Eastern Mediterranean sea with a special emphasis on the role of mineral dust particles in these processes. We used a new detailed numerical cloud microphysics scheme that has been implemented in the Weather Research and Forecast (WRF model in order to study aerosol-cloud interaction in 3-D configuration based on realistic meteorological data. Using a number of case studies we tested the contribution of mineral dust particles and different ice nucleation parameterizations to precipitation development. In this study we also investigated the importance of recycled (regenerated aerosols that had been released to the atmosphere following the evaporation of cloud droplets.

    The results showed that increased aerosol concentration due to the presence of mineral dust enhanced the formation of ice crystals. The dynamic evolution of the cloud system sets the time periods and regions in which heavy or light precipitation occurred in the domain. The precipitation rate, the time and duration of precipitation were affected by the aerosol properties only at small area scales (with areas of about 20 km2. Changes of the ice nucleation scheme from ice supersaturation dependent parameterization to a recent approach of aerosol concentration and temperature dependent parameterization modified the ice crystals concentrations but did not affect the total precipitation in the domain. Aerosol regeneration modified the concentration of cloud droplets at cloud base by dynamic recirculation of the aerosols but also had only a minor effect on precipitation.

    The major conclusion from this study is that the effect of mineral dust particles on clouds and total precipitation is limited by the properties of the atmospheric dynamics and the only effect of aerosol on precipitation may come from significant increase in the concentration

  12. Aerosol-droplet relations in Arctic clouds: insight from the Indirect and Semi-Direct Aerosol Campaign (ISDAC)

    Science.gov (United States)

    Earle, M. E.; Liu, P.; Strapp, J. W.; Zelenyuk, A.; Ovchinnikov, M.; MacDonald, A.; Shantz, N. C.; Leaitch, W. R.; Ghan, S. J.

    2010-12-01

    The relationships between atmospheric aerosol particles and Arctic cloud microphysics are investigated through a droplet number closure study using aircraft observational data from the US Department of Energy ISDAC study conducted in Alaska in April, 2008. In-situ measurements of aerosol physicochemical properties and atmospheric state are used to simulate droplet activation and growth in an adiabatic cloud parcel model. Size distributed aerosol particle concentration and composition measurements were obtained below-cloud using a Passive Cavity Aerosol Spectrometer Probe (PCASP; size range ~ 0.12 - 3 µm) and SPLAT II, a single particle mass spectrometer. The updraft velocity defines the development of supersaturation, and so dictates the onset of droplet nucleation. For model simulations in the present work, the updraft velocity was determined from a combination of gust probe observations and updraft trajectories computed using a large eddy simulation cloud-resolving model (LES-CRM). The simulated droplet concentrations are compared against in situ measurements from a DMT Cloud Droplet Probe (CDP; size range 2 - 50 µm) and/or Forward-Scattering Spectrometer Probe (FSSP-100X; size range 3 - 45 µm). The sensitivity of the comparison of simulated and observed cloud droplet number concentrations is examined for reasonable variations of the aerosol physicochemical properties (e.g. mass accommodation coefficient) and updraft velocity. Droplet closure analysis is presented for selected cases during ISDAC, comprising both clean and polluted air masses with respect to aerosol particle number concentration and composition. The applicability of the results to model parameterizations is considered, with emphasis on the description of the updraft velocity. The findings increase our knowledge of factors affecting the lifetime and radiative properties of Arctic clouds, which are critical to our understanding of the role of climate change in the Arctic.

  13. Lipid digestion as a trigger for supersaturation: evaluation of the impact of supersaturation stabilization on the in vitro and in vivo performance of self-emulsifying drug delivery systems.

    Science.gov (United States)

    Anby, Mette U; Williams, Hywel D; McIntosh, Michelle; Benameur, Hassan; Edwards, Glenn A; Pouton, Colin W; Porter, Christopher J H

    2012-07-02

    The generation of supersaturation in the gastrointestinal (GI) tract is an increasingly popular means of promoting oral absorption for poorly water-soluble drugs. The current study examined the impact of changes to the quantities of medium-chain (MC) lipid (Captex 300:Capmul MCM), surfactant (Cremophor EL) and cosolvent (EtOH), and the addition of polymeric precipitation inhibitors (PPI), on supersaturation during the dispersion and digestion of MC self-emulsifying drug delivery systems (SEDDS) containing danazol. The data suggest that digestion acts as a "trigger" for enhanced supersaturation and that solubilization/precipitation behavior is correlated with the degree of supersaturation on dispersion (S(M)DISP) or digestion (S(M)DIGEST). The ability of the formulation to maintain solubilization in vitro decreased as the S(M) of the formulation increased. PPI significantly increased supersaturation stabilization and precipitation was inhibited where S(M)DISP DIGEST DIGEST ∼ 8. Differentiation in the ability of SEDDS to maintain drug solubilization stems from the ability to stabilize supersaturation and for MC SEDDS, utilization of lower drug loads, higher surfactant levels (balanced against increases in S(M)DISP), lower cosolvent and the addition of PPI enhanced formulation performance. In vivo studies confirmed the ability of PPI to promote drug exposure at moderate drug loads (40% of saturated solubility in the formulation). At higher drug loads (80% saturation) and in lipid-free SEDDS, this effect was lost, suggesting that the ability of PPIs to stabilize supersaturation in vitro may, under some circumstances, overestimate utility in vivo.

  14. Aerosol hygroscopicity and cloud droplet activation of extracts of filters from biomass burning experiments

    Science.gov (United States)

    Carrico, Christian M.; Petters, Markus D.; Kreidenweis, Sonia M.; Collett, Jeffrey L.; Engling, Guenter; Malm, William C.

    2008-04-01

    In this laboratory closure study, we compare sub- and supersaturated water uptake properties for aerosol particles possessing a range of hygroscopicity. Measurements for water sub-saturated conditions used a hygroscopic tandem differential mobility analyzer (HTDMA). Simultaneously, measurements of particle critical supersaturation were conducted on the same sample stream with a continuous flow cloud condensation nuclei (CCN) counter. For these experiments, we used filter-collected samples of biomass smoke generated in the combustion of two common wildland fire fuels, western sagebrush and Alaskan duff core. Extractions of separate sections of the filter were performed using two solvents, ultrapure water and methanol. The extracts were subsequently atomized, producing aerosols having a range of hygroscopic responses. HTDMA and CCN measurements were fit to a single-parameter model of water uptake, in which the fit parameter is denoted κ, the hygroscopicity parameter. Here, for the four extracts we observed mean values of the hygroscopicity parameter of 0.06 CCN-derived values of κ for each experiment agreed within approximately 20%. Applicability of the κ-parameterization to other multicomponent aerosols relevant to the atmosphere remains to be tested.

  15. Prediction of oral absorption of cinnarizine--a highly supersaturating poorly soluble weak base with borderline permeability.

    Science.gov (United States)

    Berlin, Mark; Przyklenk, Karl-Heinz; Richtberg, Annette; Baumann, Wolfgang; Dressman, Jennifer B

    2014-11-01

    Two important driving forces for oral absorption of active pharmaceutical ingredients are drug dissolution and permeability in the gastrointestinal tract. Poorly soluble weak bases typically exhibit high solubility under fasted gastric conditions. However, the solubility of such drugs usually decreases drastically in the fasted small intestine, constraining drug absorption. Since there is a discrepancy in solubility between the fasted state stomach and intestine, it is crucial to examine the influence of dissolution, supersaturation and precipitation on the oral absorption of poorly soluble weak bases during and after fasted state gastric emptying. Cinnarizine is a poorly soluble weak base with borderline permeability, exhibiting supersaturation and precipitation under simulated fasted state gastric emptying conditions. Interestingly, supersaturation and precipitation of cinnarizine under fed state conditions is not expected to occur, since the drug shows good solubility in fed state biorelevant media and exhibits a positive food effect in pharmacokinetic studies. The present work is aimed at investigating the dissolution, supersaturation and precipitation behavior of marketed cinnarizine tablets under fasted and fed state conditions using biorelevant dissolution and transfer methods. In order to predict the in vivo performance of these cinnarizine formulations, the in vitro results were then coupled with different physiologically based pharmacokinetic (PBPK) models, which considered either only dissolution or a combination of dissolution, supersaturation and precipitation kinetics. The results of the in silico predictions were then compared with in vivo observations. The study revealed that under fasting conditions, plasma profiles could be accurately predicted only when supersaturation and precipitation as well as dissolution were taken into account. It was concluded that for poorly soluble weak bases with moderate permeability, supersaturation and precipitation

  16. Effect of precipitation inhibitors on indomethacin supersaturation maintenance: mechanisms and modeling.

    Science.gov (United States)

    Patel, Dhaval D; Anderson, Bradley D

    2014-05-05

    This study quantitatively explores the mechanisms underpinning the effects of model pharmaceutical polymeric precipitation inhibitors (PPIs) on the crystal growth and, in turn, maintenance of supersaturation of indomethacin, a model poorly water-soluble drug. A recently developed second-derivative UV spectroscopy method and a first-order empirical crystal growth model were used to determine indomethacin crystal growth rates in the presence of model PPIs. All three model PPIs including HP-β-CD, PVP, and HPMC inhibited indomethacin crystal growth at both high and low degrees of supersaturation (S). The bulk viscosity changes in the presence of model PPIs could not explain their crystal growth inhibitory effects. At 0.05% w/w, PVP (133-fold) and HPMC (28-fold) were better crystal growth inhibitors than HP-β-CD at high S. The inhibitory effect of HP-β-CD on the bulk diffusion-controlled indomethacin crystal growth at high S was successfully modeled using reactive diffusion layer theory, which assumes reversible complexation in the diffusion layer. Although HP-β-CD only modestly inhibited indomethacin crystal growth at either high S (∼15%) or low S (∼2-fold), the crystal growth inhibitory effects of PVP and HPMC were more dramatic, particularly at high S (0.05% w/w). The superior crystal growth inhibitory effects of PVP and HPMC as compared with HP-β-CD at high S were attributed to a change in the indomethacin crystal growth rate-limiting step from bulk diffusion to surface integration. Indomethacin crystal growth inhibitory effects of all three model PPIs at low S were attributed to retardation of the rate of surface integration of indomethacin, a phenomenon that may reflect the adsorption of PPIs onto the growing crystal surface. The quantitative approaches outlined in this study should be useful in future studies to develop tools to predict supersaturation maintenance effects of PPIs.

  17. Characterization of supersaturated lidocaine/polyacrylate pressure sensitive adhesive systems: thermal analysis and FT-IR.

    Science.gov (United States)

    Cui, Yong; Frank, Sylvan G

    2006-03-01

    Supersaturated and crystallized lidocaine (LC)/pressure sensitive adhesive (PSA) systems have been studied by differential scanning calorimetry (DSC) and FT-IR with the objective of characterizing the thermodynamic states and compatibility of the two-component systems. Analysis of the phase behavior of LC/DT2287 systems indicates that LC and DT2287 are thermodynamically miscible within the composition range containing less than approximately 20% w/w LC, beyond which LC may crystallize from the blends forming a separated crystalline phase. The composition dependence of the glass transition temperature (T(g)) was used to characterize the physical and thermodynamic states of the supersaturated systems. The Fox, Gordon-Taylor, Kwei, Kovacs, and Brekner, Schneider and Cantow (BSC) equations were employed to conduct the analysis. It was found that the PSA in the supersaturated LC/PSA systems underwent significant entropic relaxation upon mixing. LC in the miscible systems is absorbed into and swells the polymer network of the PSA, thereby exhibiting reduced molecular mobility, while the PSA attains significant molecular conformation relaxation and entropy increase. It was also found that LC molecules extensively participate in molecular relaxation of the PSA throughout the composition range studied. The molecular mobility of LC is inhibited as the volume fraction of DT2287 increases, suggesting that the PSA molecular network reduces the molecular mobility of LC by closely involving LC molecules in its relaxation, and thereby may enhancing the physical stability of the systems. No strong intermolecular interactions between the two components were found based upon the results of T(g)-composition analysis, and was confirmed by FT-IR studies. This indicates that the analysis based on the BSC equation provides more precise characterization of polymer systems than the T(g) -composition analysis based on other equations cited. Copyright 2006 Wiley-Liss, Inc. and the American

  18. Isothermal crystallization kinetics of lidocaine in supersaturated lidocaine/polyacrylate pressure sensitive adhesive systems.

    Science.gov (United States)

    Cui, Yong; Frank, Sylvan G

    2005-09-01

    Isothermal crystallization of lidocaine (LC) in supersaturated LC/Duro-Tak 87-2287 (DT2287) polyacrylate pressure sensitive adhesive (PSA) systems has been studied by differential scanning calorimetry (DSC). It was found that crystallization of LC in supersaturated LC/DT2287 systems was governed by the nucleation process, which in turn was dependent on temperature and composition of the systems. A critical temperature T(crit) was found at approximately 26 degrees C, above which the crystallization of LC in LC/DT2287 systems becomes slow. The lack of dependence of T(crit) on the composition of the mixtures indicates that the presence of the PSA affected the kinetics (diffusion) rather than the thermodynamics of the nucleation process. A critical degree of saturation S(crit) of approximately 4 was also found, above which the nucleation rate sharply increases. Kinetic analysis based on the classical theory of nucleation indicates that nucleation of LC in the PSA medium is a diffusion-controlled process. The activation energy of crystallization had a two-phase dependence on temperature suggesting that the mechanism of crystallization may change at the transition temperatures. As the weight fraction of LC increased in the systems, the activation energy of crystallization, DeltaG(c), was minimal at approximately 15 degrees C, indicating that the nucleation of LC in the LC/DT2287 systems is at its fastest rate around this temperature. These fundamental analyses of nucleation and crystallization mechanisms are of practical significance in the design of supersaturated drug delivery systems.

  19. Non-Catalytic and MgSO4 - Catalyst based Degradation of Glycerol in Subcritical and Supercritical Water Media

    Directory of Open Access Journals (Sweden)

    Mahfud Mahfud

    2011-02-01

    Full Text Available This research aims to study the glycerol degradation reaction in subcritical and supercritical water media. The degradation of glycerol into other products was performed both with sulphate salt catalysts and without catalyst. The reactant was made from glycerol and water with the mass ratio of 1:10. The experiments were carried out using a batch reactor at a constant pressure of 250 kgf/cm2, with the temperature range of 200-400oC, reaction time of 30 minutes, and catalyst mol ratio in glycerol of 1:10 and 1:8. The products of the non-catalytic glycerol degradation were acetaldehyde, methanol, and ethanol. The use of sulphate salt as catalyst has high selectivity to acetaldehyde and still allows the formation alcohol product in small quantities. The mechanism of ionic reaction and free radical reaction can occur at lower temperature in hydrothermal area or subcritical water. Conversion of glycerol on catalytic reaction showed a higher yield when compared with the reaction performed without catalyst

  20. Mesos components (CaC12, MgSO4, KH2P04) are critical for improving pear micropropagation

    Science.gov (United States)

    The USDA-ARS National Clonal Germplasm Repository in vitro collection contains over 200 pear accessions in 18 species. Due to the wide genetic diversity of this collection there is also a diverse response to growth on standard tissue culture media. An initial study of mineral nutrition using a syste...

  1. Characterization of halophiles in natural MgSO 4 salts and laboratory enrichment samples: Astrobiological implications for Mars

    Science.gov (United States)

    Foster, Ian S.; King, Penelope L.; Hyde, Brendt C.; Southam, Gordon

    2010-03-01

    The presence of sulfate salts and limited subsurface water (ice) on Mars suggests that any liquid water on Mars today will occur as (magnesium) sulfate-rich brines in regions containing sources of magnesium and sulfur. The Basque Lakes of British Columbia, Canada, represent a hypersaline terrestrial analogue site, which possesses chemical and physical properties similar to those observed on Mars. The Basque Lakes also contain diverse halophilic organisms representing all three Kingdoms of life, growing in surface and near-subsurface environments. Of interest from an astrobiological perspective, crushed magnesium sulfate samples that were analyzed using a modified Lowry protein assay contained biomass in every crystal inspected, with biomass values from 0.078 to 4.21 mg biomass/g salt; average=0.74±0.7 mg biomass/g salt. Bacteria and Archaea cells were easily observed even in low-biomass samples using light microscopy, and bacteria trapped within magnesium sulfate crystals were observed using confocal microscopy. Regions within the salt also contained bacterial pigments, e.g., carotenoids, which were separate from the cells, indicating that cell lysis might have occurred during entrapment within the salt matrix. These biosignatures, cells, and any 'soluble' organic constituents were primarily found trapped within fluid inclusions or fluid-filled void spaces between intergrown crystals. Diffuse reflectance infrared Fourier transform spectroscopy (reflectance IR) analysis of enrichment cultures, containing cyanobacteria, Archaea, or dissimilatory sulfate-reducing bacteria, highlighted molecular biosignature features between 550-1650 and 2400-3000 cm -1. Spectra from natural salts demonstrated that we can detect biomass within salt crystals using the most sensitive biosignatures, which are the 1530-1570 cm -1, C-N, N-H, -COOH absorptions and the 1030-1050 cm -1 C-OH, C-N, PO 43- bond features. The lowest detection limit for a biosignature absorption feature using reflectance IR was with a natural sample that possessed 0.78 mg biomass/g salt. In a model cell, i.e., a 0.5 by 1 μm bacillus, this biomass value corresponds to approximately 7.8×10 8 cells/g salt. Based on its ability to detect biomass entrapped within natural sulfate salts, reflectance IR may make an effective remote-sensing tool for finding enrichments of organic carbon within outcrops and surficial sedimentary deposits on Mars.

  2. Supersaturation is a major driving force for protein aggregation in neurodegenerative diseases

    Science.gov (United States)

    Ciryam, Prajwal; Kundra, Rishika; Morimoto, Richard I.; Dobson, Christopher M.; Vendruscolo, Michele

    2015-01-01

    The solubility of proteins is an essential requirement for their function. Yet these ubiquitous molecules can undergo aggregation when the protein homeostasis system becomes impaired. Here we ask which is the driving force for protein aggregation in the cellular environment. Emerging evidence suggests that this phenomenon arises because the native states of many proteins are inherently metastable as their cellular concentrations exceed their critical values. Such `supersaturated' proteins are strongly driven towards aggregation, and are over-represented in specific biochemical pathways associated with neurodegenerative conditions. These observations suggest that effective therapeutic approaches to combat neurodegenerative diseases could be aimed at enhancing the ability of the cell to maintain protein solubility. PMID:25636813

  3. Gastrointestinal dissolution, supersaturation and precipitation of the weak base indinavir in healthy volunteers.

    Science.gov (United States)

    Rubbens, Jari; Brouwers, Joachim; Tack, Jan; Augustijns, Patrick

    2016-12-01

    This study investigated the impact of relevant gastrointestinal conditions on the intraluminal dissolution, supersaturation and precipitation behavior of the weakly basic drug indinavir. The influence of (i) concomitant PPI intake and (ii) the nutritional state on the gastrointestinal behavior of indinavir was assessed in order to identify the underlying mechanisms responsible for previously reported interactions. Five healthy volunteers were recruited into a crossover study containing the following arms: fasted state, fed state and fasted state with concomitant proton pump inhibitor (PPI) use. In each condition, one Crixivan® capsule (400mg indinavir) was orally administered with 240mL of water. Gastric and duodenal fluids, aspirated as a function of time, were monitored for total and dissolved indinavir concentrations on a UPLC-MS/MS system. Indinavir's thermodynamic solubility was determined in individual aspirates to evaluate supersaturation. The bioaccessible fraction of indinavir in aspirated duodenal fluids was determined in an ex vivo permeation experiment through an artificial membrane. A nearly complete dissolution of indinavir in the fasted stomach was observed (90±3%). Regardless of dosing conditions, less indinavir was in solution in the duodenum compared to the stomach. Duodenal supersaturation was observed in all three testing conditions. The highest degrees of duodenal supersaturation (6.5±5.9) were observed in the fasted state. Concomitant PPI use resulted in an increased gastric pH and a smaller fraction of indinavir being dissolved (58±24%), eventually resulting in lower intestinal concentrations. In fed state conditions, drug release from the capsule was delayed and more gradually, although a similar fraction of the intragastric indinavir dissolved compared to the fasted state (83±12%). Indinavir was still present in the lumen of the duodenum three hours after oral administration, although it already reached 70% (on average) of the fasted

  4. Quantifying Main Trends in Lysozyme Nucleation: The Effects of Precipitant Concentration, Supersaturation and Impurities

    Science.gov (United States)

    Burke, Michael W.; Leardi, Riccardo; Judge, Russell A.; Pusey, Marc L.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Full factorial experimental design incorporating multi-linear regression analysis of the experimental data allows quick identification of main trends and effects using a limited number of experiments. In this study these techniques were employed to identify the effect of precipitant concentration, supersaturation, and the presence of an impurity, the physiological lysozyme dimer, on the nucleation rate and crystal dimensions of the tetragonal forin of chicken egg white lysozyme. Decreasing precipitant concentration, increasing supers aturation, and increasing impurity, were found to increase crystal numbers. The crystal axial ratio decreased with increasing precipitant concentration, independent of impurity.

  5. Growth of a gas bubble in a supersaturated and slightly compressible liquid at low Mach number

    Science.gov (United States)

    Mohammadein, S. A.; Mohamed, K. G.

    2011-12-01

    In this paper, the growth of a gas bubble in a supersaturated and slightly compressible liquid is discussed. The mathematical model is solved analytically by using the modified Plesset and Zwick method. The growth process is affected by: sonic speed in the liquid, polytropic exponent, diffusion coefficient, initial concentration difference, surface tension, viscosity, adjustment factor and void fraction. The famous formula of Plesset and Zwick is produced as a special case of the result at some values of the adjustment factor. Moreover, the resultant formula is implemented to the case of the growth of underwater gas bubble.

  6. In vitro-in vivo correlation of the effect of supersaturation on the intestinal absorption of BCS Class 2 drugs.

    Science.gov (United States)

    Higashino, Haruki; Hasegawa, Tsubasa; Yamamoto, Mari; Matsui, Rie; Masaoka, Yoshie; Kataoka, Makoto; Sakuma, Shinji; Yamashita, Shinji

    2014-03-03

    The aim of this study was to establish an in vitro method for evaluating the effect of supersaturation on oral absorption of poorly water-soluble drugs in vivo. Albendazole, dipyridamole, gefitinib, and ketoconazole were used as model drugs. Supersaturation of each drug was induced by diluting its stock solution by fasted state simulated intestinal fluid (FaSSIF) (solvent-shift method), then dissolution and precipitation profile of the drug was observed in vitro. The crystalline form of the precipitate was checked by differential scanning calorimetry (DSC). For comparison, control suspension was prepared by suspending a drug powder directly into FaSSIF (powder-suspending method). In vivo intestinal absorption of the drug was observed in rats by determined the plasma concentration after intraduodenal administration of drug suspensions. For all drugs, suspensions prepared by solvent-shift method showed significantly higher dissolved concentration in vitro than that prepared by powder-suspending method, clearly indicated the induction of supersaturation. DSC analysis revealed that crystalline form of the precipitate profoundly affects the extent and the duration of supersaturation. A rat in vivo study confirmed that the supersaturation of these drugs increased the fraction absorbed from the intestine, which corresponded well to the in vitro dissolution and precipitation profile of drugs except for ketoconazole. For ketoconazole, an in vivo absorption study was performed in rats pretreated with 1-aminobenzotriazole, a potent inhibitor of CYP mediated metabolism. CYP inhibition study suggested that the high luminal concentration of ketoconazole caused by supersaturation saturated the metabolic enzymes and further increased the systemic exposure of the absorbed drug. The additional effects of supersaturation on the absorption of ketoconazole are consistent with previous studies in humans under differing gastric pH conditions. In conclusion, effects of supersaturation on

  7. Modeling the evolution of aerosol particles in a ship plume using PartMC-MOSAIC

    Science.gov (United States)

    Tian, J.; Riemer, N.; West, M.; Pfaffenberger, L.; Schlager, H.; Petzold, A.

    2014-06-01

    This study investigates the evolution of ship-emitted aerosol particles using the stochastic particle-resolved model PartMC-MOSAIC (Particle Monte Carlo model-Model for Simulating Aerosol Interactions and Chemistry). Comparisons of our results with observations from the QUANTIFY (Quantifying the Climate Impact of Global and European Transport Systems) study in 2007 in the English Channel and the Gulf of Biscay showed that the model was able to reproduce the observed evolution of total number concentration and the vanishing of the nucleation mode consisting of sulfate particles. Further process analysis revealed that during the first hour after emission, dilution reduced the total number concentration by four orders of magnitude, while coagulation reduced it by an additional order of magnitude. Neglecting coagulation resulted in an overprediction of more than one order of magnitude in the number concentration of particles smaller than 40 nm at a plume age of 100 s. Coagulation also significantly altered the mixing state of the particles, leading to a continuum of internal mixtures of sulfate and black carbon. The impact on cloud condensation nuclei (CCN) concentrations depended on the supersaturation threshold S at which CCN activity was evaluated. For the base case conditions, characterized by a low formation rate of secondary aerosol species, neglecting coagulation, but simulating condensation, led to an underestimation of CCN concentrations of about 37% for S = 0.3% at the end of the 14-h simulation. In contrast, for supersaturations higher than 0.7%, neglecting coagulation resulted in an overestimation of CCN concentration, about 75% for S = 1%. For S lower than 0.2% the differences between simulations including coagulation and neglecting coagulation were negligible. Neglecting condensation, but simulating coagulation did not impact the CCN concentrations below 0.2% and resulted in an underestimation of CCN concentrations for larger supersaturations, e.g., 18

  8. Dissolution of Danazol Amorphous Solid Dispersions: Supersaturation and Phase Behavior as a Function of Drug Loading and Polymer Type.

    Science.gov (United States)

    Jackson, Matthew J; Kestur, Umesh S; Hussain, Munir A; Taylor, Lynne S

    2016-01-04

    Amorphous solid dispersions (ASDs) are of great interest as enabling formulations because of their ability to increase the bioavailability of poorly soluble drugs. However, the dissolution of these formulations under nonsink dissolution conditions results in highly supersaturated drug solutions that can undergo different types of phase transitions. The purpose of this study was to characterize the phase behavior of solutions resulting from the dissolution of model ASDs as well as the degree of supersaturation attained. Danazol was chosen as a poorly water-soluble model drug, and three polymers were used to form the dispersions: polyvinylpyrrolidone (PVP), hydroxypropylmethyl cellulose (HPMC), and hydroxypropylmethyl cellulose acetate succinate (HPMCAS). Dissolution studies were carried out under nonsink conditions, and solution phase behavior was characterized using several orthogonal techniques. It was found that liquid-liquid phase separation (LLPS) occurred following dissolution and prior to crystallization for most of the dispersions. Using flux measurements, it was further observed that the maximum attainable supersaturation following dissolution was equivalent to the amorphous solubility. The dissolution of the ASDs led to sustained supersaturation, the duration of which varied depending on the drug loading and the type of polymer used in the formulation. The overall supersaturation profile observed thus depended on a complex interplay between dissolution rate, polymer type, drug loading, and the kinetics of crystallization.

  9. Preparation and characterization of dipyridamole solid dispersions for stabilization of supersaturation: effect of precipitation inhibitors type and molecular weight.

    Science.gov (United States)

    Vora, Chintan; Patadia, Riddhish; Mittal, Karan; Mashru, Rajashree

    2016-11-01

    Dipyridamole (DPL) is a weakly basic BCS class II drug which precipitates upon entering into intestine leading to pH dependant and variable absorption. Thus, research envisaged focuses on developing formulations that maintain supersaturation following upon acid to neutral pH transition. In an endeavor to accomplish the objective, solid dispersion (SD) with hydroxypropylmethyl cellulose (HPMC) and polyvinylpyrrolidone (PVP) was prepared by a quench cooling method. The three molecular weight grades of HPMC (HPMC E5, HPMC E15 and HPMC E50) and two molecular weight grades of PVP (PVP K30 and PVP K90) were investigated to observe effect of increasing molecular weight on stabilizing DPL supersaturated solutions. Equilibrium solubility studies revealed increase in solubility with both HPMC and PVP with greater benefit from HPMC. In vitro supersaturated dissolution results demonstrated that HPMC formulations provided greater degree and extent of supersaturation as compared to PVP formulations. The formulation with HPMC E50 provided maximum stabilization to supersaturation upon acid to neutral pH transition. Moreover, the effect of increase in molecular weight was more pronounced in HPMC rather than PVP. Stronger interactions were observed for DPL with HPMC, while no interaction was observed with PVP which was evident from Fourier transform infra-red studies. Differential scanning calorimetry and powder X-ray diffraction studies revealed the amorphous state of DPL in SD.

  10. Role of Self-Association and Supersaturation in Oral Absorption of a Poorly Soluble Weakly Basic Drug.

    Science.gov (United States)

    Narang, Ajit S; Badawy, Sherif; Ye, Qingmei; Patel, Dhaval; Vincent, Maria; Raghavan, Krishnaswamy; Huang, Yande; Yamniuk, Aaron; Vig, Balvinder; Crison, John; Derbin, George; Xu, Yan; Ramirez, Antonio; Galella, Michael; Rinaldi, Frank A

    2015-08-01

    Precipitation of weakly basic drugs in intestinal fluids can affect oral drug absorption. In this study, the implications of self-association of brivanib alaninate in acidic aqueous solution, leading to supersaturation at basic pH condition, on its solubility and oral absorption were investigated. Self-association of brivanib alaninate was investigated by proton NMR spectroscopy, surface tension measurement, dynamic light scattering, isothermal titration calorimetry, and molecular modeling. Drug solubility was determined in various pH media, and its tendency to supersaturate upon pH shift was investigated in buffered and biorelevant aqueous solutions. Pharmacokinetic modeling of human oral drug absorption was utilized for parameter sensitivity analyses of input variables. Brivanib alaninate exhibited continuous, and pH- and concentration-dependent self-association. This phenomenon resulted in positive deviation of drug solubility at acidic pH and the formation of a stable supersaturated drug solution in pH-shift assays. Consistent with the supersaturation phenomenon observed in vitro, oral absorption simulations necessitated invoking long precipitation time in the intestine to successfully predict in vivo data. Self-association of a weakly basic drug in acidic aqueous solution can increase its oral absorption by supersaturation and precipitation resistance at the intestinal pH. This consideration is important to the selection of parameters for oral absorption simulation.

  11. A combination turbidity and supernatant microplate assay to rank-order the supersaturation limits of early drug candidates.

    Science.gov (United States)

    Morrison, John S; Nophsker, Michelle J; Haskell, Roy J

    2014-10-01

    A unique opportunity exists at the drug discovery stage to overcome inherently poor solubility by selecting drug candidates with superior supersaturation propensity. Existing supersaturation assays compare either precipitation-resistant or precipitation-inhibiting excipients, or higher-energy polymorphic forms, but not multiple compounds or multiple concentrations. Furthermore, these assays lack sufficient throughput and compound conservation necessary for implementation in the discovery environment. A microplate-based combination turbidity and supernatant concentration assay was therefore developed to determine the extent to which different compounds remain in solution as a function of applied concentration in biorelevant media over a specific period of time. Dimethyl sulfoxide stock solutions at multiple concentrations of four poorly soluble, weak base compounds (Dipyridamole, Ketoconazole, Albendazole, and Cinnarizine) were diluted with pH 6.5 buffer as well as FaSSIF. All samples were monitored for precipitation by turbidity at 600 nm over 1 h and the final supernatant concentrations were measured. The maximum supersaturation ratio was calculated from the supersaturation limit and the equilibrium solubility in each media. Compounds were rank-ordered by supersaturation ratio: Ketoconazole > Dipyridamole > Cinnarizine ∼ Albendazole. These in vitro results correlated well with oral AUC ratios from published in vivo pH effect studies, thereby confirming the validity of this approach. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  12. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    Science.gov (United States)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-09-01

    The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosol particles that have re-vitrified in contact

  13. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    Directory of Open Access Journals (Sweden)

    B. J. Murray

    2012-04-01

    Full Text Available The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA, levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosols that have re-vitrified in

  14. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    Directory of Open Access Journals (Sweden)

    R. Wagner

    2012-09-01

    Full Text Available The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA, levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosol particles that have re

  15. Aerosol MTF revisited

    Science.gov (United States)

    Kopeika, Norman S.; Zilberman, Arkadi; Yitzhaky, Yitzhak

    2014-05-01

    Different views of the significance of aerosol MTF have been reported. For example, one recent paper [OE, 52(4)/2013, pp. 046201] claims that the aerosol MTF "contrast reduction is approximately independent of spatial frequency, and image blur is practically negligible". On the other hand, another recent paper [JOSA A, 11/2013, pp. 2244-2252] claims that aerosols "can have a non-negligible effect on the atmospheric point spread function". We present clear experimental evidence of common significant aerosol blur and evidence that aerosol contrast reduction can be extremely significant. In the IR, it is more appropriate to refer to such phenomena as aerosol-absorption MTF. The role of imaging system instrumentation on such MTF is addressed too.

  16. Supersaturation and Precipitation of Posaconazole Upon Entry in the Upper Small Intestine in Humans.

    Science.gov (United States)

    Hens, Bart; Brouwers, Joachim; Corsetti, Maura; Augustijns, Patrick

    2016-09-01

    The purpose of this study was to explore gastrointestinal dissolution, supersaturation and precipitation of the weakly basic drug posaconazole in humans, and to assess the impact of formulation pH and type on these processes. In a cross-over study, two posaconazole suspensions (40 mg dispersed in 240 mL water at pH 1.6 and pH 7.1, respectively) were intragastrically administered; subsequently, gastric and duodenal fluids were aspirated. In parallel, blood samples were collected. Additionally, posaconazole was intragastrically administered as a solution (20 mg in 240 mL water, pH 1.6). When posaconazole was administered as an acidified suspension, supersaturated duodenal concentrations of posaconazole were observed for approximately 45 min. However, extensive intestinal precipitation was observed. Administration of the neutral suspension resulted in subsaturated concentrations with a mean duodenal AUC0-120 min and Cmax being approximately twofold lower than for the acidified suspension. The mean plasma AUC0-8 h of posaconazole was also twofold higher following administration of the acidified suspension. Similar to the acidified suspension, significant intestinal precipitation (up to 92%) was observed following intragastric administration of the posaconazole solution. This study demonstrated for the first time the gastrointestinal behavior of a weakly basic drug administered in different conditions, and its impact on systemic exposure.

  17. Cirrus, contrails, and ice supersaturated regions in high pressure systems at northern mid latitudes

    Science.gov (United States)

    Immler, F.; Treffeisen, R.; Engelbart, D.; Krüger, K.; Schrems, O.

    2008-03-01

    During the European heat wave summer 2003 with predominant high pressure conditions we performed a detailed study of upper tropospheric humidity and ice particles which yielded striking results concerning the occurrence of ice supersaturated regions (ISSR), cirrus, and contrails. Our study is based on lidar observations and meteorological data obtained at Lindenberg/Germany (52.2° N, 14.1° E) as well as the analysis of the European centre for medium range weather forecast (ECMWF). Cirrus clouds were detected in 55% of the lidar profiles and a large fraction of them were subvisible (optical depth <0.03). Thin ice clouds were particularly ubiquitous in high pressure systems. The radiosonde data showed that the upper troposphere was very often supersaturated with respect to ice. Relating the radiosonde profiles to concurrent lidar observations reveals that the ISSRs almost always contained ice particles. Persistent contrails observed with a camera were frequently embedded in these thin or subvisible cirrus clouds. The ECMWF cloud parametrisation reproduces the observed cirrus clouds consistently and a close correlation between the ice water path in the model and the measured optical depth of cirrus is demonstrated.

  18. Homogeneous nucleation and growth in supersaturated zinc vapor investigated by molecular dynamics simulation

    Science.gov (United States)

    Römer, F.; Kraska, T.

    2007-12-01

    Homogeneous nucleation and growth of zinc from supersaturated vapor are investigated by nonequilibrium molecular dynamics simulations in the temperature range from 400to800K and for a supersaturation ranging from logS =2 to 11. Argon is added to the vapor phase as carrier gas to remove the latent heat from the forming zinc clusters. A new parametrization of the embedded atom method for zinc is employed for the interaction potential model. The simulation data are analyzed with respect to the nucleation rates and the critical cluster sizes by two different methods, namely, the threshold method of Yasuoka and Matsumoto [J. Chem. Phys. 109, 8451 (1998)] and the mean first passage time method for nucleation by Wedekind et al. [J. Chem. Phys. 126, 134103 (2007)]. The nucleation rates obtained by these methods differ approximately by one order of magnitude. Classical nucleation theory fails to describe the simulation data as well as the experimental data. The size of the critical cluster obtained by the mean first passage time method is significantly larger than that obtained from the nucleation theorem.

  19. Stabilization of supersaturated solutions of a lipophilic drug for dermal delivery.

    Science.gov (United States)

    Moser, K; Kriwet, K; Kalia, Y N; Guy, R H

    2001-08-14

    The stability of supersaturated solutions of a model lipophilic drug (LAP, a lavendustin derivative) in propylene glycol-water mixtures prepared using the method of mixed cosolvents was investigated. The solutions had a fixed degree of saturation (DS=4), but contained different ratios of propylene glycol-water. The absolute concentrations of LAP in these solutions varied by approximately a factor of 40, but the solutions at lower concentrations were no more stable than the more concentrated solutions. This shows that stability is primarily a question of the degree of saturation and not of the absolute drug concentration. Solutions of up to 5 degrees of saturation in 7:3 propylene glycol-water mixture were stable when stored for several hours; those at higher degrees of saturation recrystallized immediately. When the solutions were stirred, recrystallization occurred more rapidly. The influence of various polymeric additives on the stability of the supersaturated solutions showed that only sodium carboxymethyl cellulose had a stabilizing effect; however, the solution was very viscous and it is not clear whether the stabilizing effect was due to this high viscosity or to a specific interaction between drug and polymer.

  20. Oral bioavailability enhancement through supersaturation: an update and meta-analysis.

    Science.gov (United States)

    Fong, Sophia Yui Kau; Bauer-Brandl, Annette; Brandl, Martin

    2017-03-01

    With the increasing number of poorly water-soluble compounds in drug discovery pipelines, supersaturating drug delivery systems (SDDS) have attracted increased attention as an effective bioavailability enhancing approach. However, a systematic and quantitative synopsis of the knowledge about performance of SDDS is currently lacking. Such analysis of the recent achievements is to provide insights for formulation scientists dealing with poorly soluble compounds. Areas covered: A systematic search of two evidence-based International databases, Medline and Embase, from 2010 to Dec 2015, has been performed. By conducting meta-analysis, box-plots, and correlation plots of the relevant data retrieved from literature, the current review addresses three quantitative questions: (1) how promising are SDDS for bioavailability enhancement? (2) which types of SDDS perform best? and (3) what are the most promising drug candidates? Four widely reported types of SDDS were compared: amorphous solid dispersions, nano-drug systems, supersaturable lipid-based formulations, and silica-based systems. Expert opinion: While SDDS formulations appear to be a promising candidate-enabling technique for drug development, the prediction of their in vivo performance by in vitro testing remains challenging. A transition from a trial-and-error development approach towards an approach guided by mechanistic insight, as well as the development of more efficient predictive tools for performance ranking is urgently needed.

  1. Amelogenin-chitosan matrix for human enamel regrowth: effects of viscosity and supersaturation degree.

    Science.gov (United States)

    Ruan, Qichao; Siddiqah, Nadia; Li, Xiaochen; Nutt, Steven; Moradian-Oldak, Janet

    2014-08-01

    We recently reported an amelogenin-chitosan (CS-AMEL) hydrogel as a promising biomimetic material for future in situ human enamel regrowth. To further optimize the necessary conditions for clinical applicability of CS-AMEL hydrogel, herein we studied the effects of viscosity and supersaturation degree on the size and orientation of synthetic crystals by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Raising the hydrogel viscosity by increasing chitosan concentration from 1% to 2% (w/v) improved the orientation of the crystals, while a higher supersaturation (σ(HAp) >10.06, [Ca(2+)] >5 mM) resulted in the formation of random crystals with larger sizes and irregular structures. We conclude that optimal conditions to produce organized enamel-like crystals in a CS-AMEL hydrogel are: 2% (w/v) chitosan, 2.5 mM calcium, and 1.5 mM phosphate (degree of supersaturation = 8.23) and 200 µg/ml of amelogenin.

  2. Amelogenin-assisted ex vivo remineralization of human enamel: effects of supersaturation degree and fluoride concentration

    Science.gov (United States)

    Fan, Yuwei; Nelson, James R.; Alvarez, Jason R.; Hagan, Joseph; Berrier, Allison; Xu, Xiaoming

    2011-01-01

    The formation of organized nanocrystals that resemble enamel is crucial for successful enamel remineralization. Calcium, phosphate and fluoride ions and amelogenin are important ingredients for the formation of organized hydroxyapatite (HAP) crystals in vitro. However, the effects of these remineralization agents on the enamel crystal morphology have not been thoroughly studied. The objective of this study was to investigate the effects of fluoride ions, supersaturation degree and amelogenin on the crystal morphology and organization of ex vivo remineralized human enamel. Extracted third molars were sliced thin and acid-etched to provide the enamel surface for immersion in different remineralization solutions. The crystal morphology and mineral phase of the remineralized enamel surface were analyzed by FE-SEM, ATR-FTIR and XRD. The concentration of fluoride and supersaturation degree of hydroxyapatite had significant effects on the crystal morphology and crystal organization, which varied from plate-like loose crystals to rod-like densely packed nanocrystal arrays. Densely packed arrays of fluoridated hydroxyapatite nanorods were observed under the following conditions: σ(HAP) = 10.2±2.0 with fluoride 1.5±0.5 mg/L and amelogenin 40±10 µg/mL, pH 6.8±0.4. A phase diagram summarized the conditions that form dense or loose hydroxyapatite nanocrystal structures. This study provides the basis for the development of novel dental materials for caries management. PMID:21256987

  3. Nucleation stage in supersaturated vapor with inhomogeneities due to nonstationary diffusion onto growing droplets

    CERN Document Server

    Kuchma, Anatoly; Shchekin, Alexander

    2013-01-01

    An analytical description of nucleation stage in a supersaturated vapor with instantly created supersaturation is given with taking into account the vapor concentration inhomogeneities arising as a result of depletion due to non-stationary diffusion onto growing droplets. This description suggests that the intensity of the nucleation of new droplets is suppressed in spherical diffusion regions of a certain size surrounding previously nucleated droplets, and remains at the initial level in the remaining volume of the vapor-gas medium. The value of volume excluded from nucleation depends on the explicit form of the vapor concentration profile in the space around the growing droplet, and we use for that the unsteady self-similar solution of time-dependent diffusion equation with a convective term describing the flow of the gas-vapor mixture caused by moving surface of single growing droplet. The main characteristics of the phase transition at the end of the nucleation stage are found and compared with those in t...

  4. Nucleation and droplet growth from supersaturated vapor at temperatures below the triple point temperature

    CERN Document Server

    Toxvaerd, Søren

    2016-01-01

    In 1897 Ostwald formulated his step rule for formation of the most stable crystal state for a system with crystal polymorphism. The rule describes the irreversible way a system converts to the crystal with lowest free energy. But in fact the irreversible way a supercooled gas below the triple point temperature $T_{tr.p.}$ crystallizes via a liquid droplet is an example of Ostwald's step rule. The homogeneous nucleation in the supersaturated gas is not to a crystal, but to a liquid-like critical nucleus. We have for the first time performed constant energy (NVE) Molecular Dynamics (MD) of homogeneous nucleation without the use of a thermostat. The simulations of homogeneous nucleation in a Lennard-Jones system from supersaturated vapor at temperatures below $T_{tr.p.}$ reveals that the nucleation to a liquid-like critical nucleus is initiated by a small cold cluster [S. Toxvaerd, J. Chem. Phys. \\textbf{143} 154705 (2015)]. The release of latent heat at the subsequent droplet growth increases the temperature in...

  5. A laterally averaged two-dimensional simulation of unsteady supersaturated total dissolved gas in deep reservoir

    Institute of Scientific and Technical Information of China (English)

    FENG Jing-jie; LI Ran; YANG Hui-xia; LI Jia

    2013-01-01

    Elevated levels of the Total Dissolved Gas (TDG) may be reached downstream of dams,leading to increased incidences of gas bubble diseases in fish.The supersaturated TDG dissipates and transports more slowly in reservoirs than in natural rivers because of the greater depth and the lower turbulence,which endangers the fish more seriously.With consideration of the topographical characteristics of a deep reservoir,a laterally averaged two-dimensional unsteady TDG model for deep reservoir is proposed.The dissipation process of the TDG inside the waterbody and the mass transfer through the free surface are separately modeled with different functions in the model.Hydrodynamics equations are solved coupling with those of water temperature and density.The TDG concentration is calculated based on the density current field.A good agreement is found in the simulation of the Dachaoshan Reservoir between the simulation results and the field data of the hydrodynamics parameters and the TDG distribution in the vertical direction and their unsteady evolution with time.The hydrodynamics parameters,the temperature and the TDG concentration are analyzed based on the simulation results.This study demonstrates that the model can be used to predict the evolutions of hydrodynamics parameters,the temperature and the TDG distribution in a deep reservoir with unsteady inflow and outflow.The results can be used in the study of the mitigation measures of the supersaturated TDG.

  6. Improved arterial blood oxygenation following intravenous infusion of cold supersaturated dissolved oxygen solution.

    Science.gov (United States)

    Grady, Daniel J; Gentile, Michael A; Riggs, John H; Cheifetz, Ira M

    2014-01-01

    One of the primary goals of critical care medicine is to support adequate gas exchange without iatrogenic sequelae. An emerging method of delivering supplemental oxygen is intravenously rather than via the traditional inhalation route. The objective of this study was to evaluate the gas-exchange effects of infusing cold intravenous (IV) fluids containing very high partial pressures of dissolved oxygen (>760 mm Hg) in a porcine model. Juvenile swines were anesthetized and mechanically ventilated. Each animal received an infusion of cold (13 °C) Ringer's lactate solution (30 mL/kg/hour), which had been supersaturated with dissolved oxygen gas (39.7 mg/L dissolved oxygen, 992 mm Hg, 30.5 mL/L). Arterial blood gases and physiologic measurements were repeated at 15-minute intervals during a 60-minute IV infusion of the supersaturated dissolved oxygen solution. Each animal served as its own control. Five swines (12.9 ± 0.9 kg) were studied. Following the 60-minute infusion, there were significant increases in PaO2 and SaO2 (P dissolved oxygen solution may be intravenously administered to improve arterial blood oxygenation and ventilation parameters and induce a mild therapeutic hypothermia in a porcine model.

  7. Role of nearest-neighbor drops in the kinetics of homogeneous nucleation in a supersaturated vapor

    Science.gov (United States)

    Grinin, A. P.; Zhuvikina, I. A.; Kuni, F. M.; Reiss, H.

    2004-12-01

    A theory of simultaneous nucleation and drop growth in a supersaturated vapor is developed. The theory makes use of the concept of "nearest-neighbor" drops. The effect of vapor heterogeneity caused by vapor diffusion to a growing drop, formed previously, is accounted for by considering the nucleation of the nearest-neighbor drop. The diffusional boundary value problem is solved through the application of a recent theory that maintains material balance between the vapor and the drop, even though the drop boundary is a moving one. This is fundamental to the use of the proper time and space dependent vapor supersaturation in the application of nucleation theory. The conditions are formulated under which the mean distance to the nearest-neighbor drop and the mean time to its appearance can be determined reliably. Under these conditions, the mean time provides an estimate of the duration of the nucleation stage, while the mean distance provides an estimate of the number of drops formed per unit volume during the nucleation stage. It turns out, surprisingly, that these estimates agree fairly well with the predictions of the simpler and more standard approach based on the approximation that the density of the vapor phase remains uniform during the nucleation stage. Thus, as a practical matter, in many situations, the use of the simpler and less rigorous method is justified by the predictions of the more rigorous, but more complicated theory.

  8. Phase transitions and hygroscopic growth of aerosol particles containing humic acid and mixtures of humic acid and ammonium sulphate

    Directory of Open Access Journals (Sweden)

    C. L. Badger

    2006-01-01

    Full Text Available The phase transitions and hygroscopic growth of two humic acid aerosols (Aldrich sodium salt and Leonardite Standard (IHSS and their mixtures with ammonium sulphate have been investigated using a combination of two techniques, Fourier transform infra-red (FTIR spectroscopy and tandem differential mobility analysis (TDMA. A growth factor of 1.16 at 85% relative humidity (RH was found for the Aldrich humic acid which can be regarded as an upper limit for growth factors of humic-like substances (HULIS found in atmospheric aerosol and is significantly smaller than that of typical atmospheric inorganics. We find that the humic acid aerosols exhibit water uptake over all relative humidities with no apparent phase changes, suggesting that these aerosols readily form supersaturated droplets. In the mixed particles, the humic acid component decreases the deliquescence relative humidity (DRH and increases the efflorescence relative humidity (ERH of the ammonium sulphate component, and there is some degree of water uptake prior to ammonium sulphate deliquescence. In addition, at low RH, the FTIR spectra show that the ammonium is present in a different chemical environment in the mixed aerosols than in crystalline ammonium sulphate, perhaps existing as a complex with the humic materials. The growth factors of the mixed aerosols are intermediate between those of the single-component aerosols and can be predicted assuming that the inorganic and organic fractions take up water independently.

  9. Aerosols Science and Technology

    CERN Document Server

    Agranovski, Igor

    2011-01-01

    This self-contained handbook and ready reference examines aerosol science and technology in depth, providing a detailed insight into this progressive field. As such, it covers fundamental concepts, experimental methods, and a wide variety of applications, ranging from aerosol filtration to biological aerosols, and from the synthesis of carbon nanotubes to aerosol reactors.Written by a host of internationally renowned experts in the field, this is an essential resource for chemists and engineers in the chemical and materials disciplines across multiple industries, as well as ideal supplementary

  10. Arctic Aerosols and Sources

    DEFF Research Database (Denmark)

    Nielsen, Ingeborg Elbæk

    2017-01-01

    winter and spring explained by expansion of the polar dome enabling long-range transport of aerosols from source regions outside the Arctic. This phenomenon is better known as the Arctic haze. Contrary, the summer and fall concentrations were lower due to the retreat of the polar dome. These seasonal...... species. The aerosol concentration decreased during spring as the Arctic haze leveled off. A source apportionment analysis showed that three factors were contributing to organic aerosols. A hydrocarbon-like organic aerosol factor was assigned to fossil fuel combustion and a second factor, less oxygenated...

  11. Effect of pepsin on maintaining the supersaturation of the HCl salt of a weakly basic drug: a case study.

    Science.gov (United States)

    Pinnamaneni, Swathi; Rinaldi, Frank A; Jayawickrama, Dimuthu A; Li, Jinjiang; Dali, Mandar V

    2016-01-01

    The impact of pepsin on the maintenance of supersaturated solution of the HCl salt of a weakly basic drug was evaluated in simulated gastric fluid by monitoring the drug solubility in the absence and presence of pepsin. In the presence of pepsin, the HCl salt maintained its apparent solubility through 24 h, whereas, no such solubility advantage was seen in the absence of pepsin. Consequently, a minimum inhibitory concentration of pepsin is required for maintenance of supersaturation. In addition, NMR study seems to indicate a molecular level interaction between pepsin and HCl salt leading to a weak binding between the two. Therefore, for the HCl salts of weak bases having disproportionation potential, it is preferred that preformulation solubility studies are conducted in the presence of pepsin to reflect their in vivo behavior in maintaining supersaturation solubility.

  12. Constraining the supersaturation density equation of state from core-collapse supernova simulations - Excluded volume extension of the baryons

    CERN Document Server

    Fischer, Tobias

    2016-01-01

    In this article the role of the supersaturation density equation of state (EOS) is explored in simulations of failed core-collapse supernova explosions. Therefore the nuclear EOS is extended via a one-parameter excluded volume description for baryons, taking into account their finite and increasing volume with increasing density in excess of saturation density. Parameters are selected such that the resulting supernova EOS represent extreme cases, with high pressure variations at supersaturation density which feature extreme stiff and soft EOS variants of the reference case, i.e. without excluded volume corrections. Unlike in the interior of neutron stars with central densities in excess of several times saturation density, central densities of core-collapse supernovae reach only slightly above saturation density. Hence, the impact of the supersaturation density EOS on the supernova dynamics as well as the neutrino signal is found to be negligible. It is mainly determined from the low- and intermediate-density...

  13. Sensitivity and specificity of 24-hour urine chemistry levels for detecting elevated calcium oxalate and calcium phosphate supersaturation

    Science.gov (United States)

    Rossi, M. Adrian; Singer, Eric A; Golijanin, Dragan J; Monk, Rebeca D; Erturk, Erdal; Bushinsky, David A

    2008-01-01

    Objectives The gold standard for determining likelihood of calcium oxalate (CaOx) and calcium phosphate (CaPhos) stone formation in urine is supersaturation of CaOx and CaPhos. Our objective was to investigate whether traditional measurement of total calcium, oxalate and phosphate in a 24-hour urine collection is sufficiently sensitive and specific for detecting elevated supersaturation to preclude the more expensive supersaturation test. Methods We performed a retrospective review of 150 consecutive patients with nephrolithiasis who underwent measurement of CaOx supersaturation (CaOxSS) and CaPhos supersaturation (CaPhosSS), as well as total calcium, oxalate and phosphate in a 24-hour urine collection. We used various cut-off values to determine sensitivity and specificity of 24-hour urine measurements for detecting elevated CaOxSS and CaPhosSS. Results In men and women, the sensitivity of 24-hour calcium for detecting elevated CaOxSS was 71% and 79%, respectively; for oxalate, sensitivity was 59% and 36%, respectively. In men and women, the sensitivity of 24-hour calcium for detecting elevated CaPhosSS was 74% and 88%, respectively; for phosphate, sensitivity was 57% and 8%, respectively. In men and women, the specificity of 24-hour calcium for detecting elevated CaOxSS was 55% and 48%, respectively; it was 60% for detecting elevated CaPhosSS in both men and women. Conclusion Traditional 24-hour urine analysis is sensitive, but not specific, for detecting elevated CaOxSS and CaPhosSS. Most patients with abnormal 24-hour urine analysis have normal supersaturation, and treatment decisions based on traditional urine analysis would lead to overtreatment in these patients. PMID:18542745

  14. Measurements of CCN-concentrations in the European alpine aerosol using a newly developed static thermal diffusion counter

    Science.gov (United States)

    Hitzenberger, R.; Giebl, H.; Berner, A.; Kromp, R.; Reischl, G.; Kasper-Giebl, A.; Puxbaum, H.

    2000-08-01

    The CCN counter developed at the University of Vienna operates on the principle of a static thermal diffusion chamber. Since 1997, it was used to obtain CCN concentrations in the European alpine background aerosol during intensive measurement campaigns. The 1997 campaign was performed on Mt. Sonnblick (3104 m a.s.l.), while in 1999 and 2000, intensive campaigns were performed on Mt. Rax (1644 m a.s.l.). CCN concentrations at 0.5% supersaturation were found to be comparable ar both sites and also comparable to earlier measurements performed with a commercial CCN counter (DH Associates) on Mt. Sonnblick. Simultaneous measurements of CCN concentration, aerosol number size distribution (measured with a differential mobility particle spectrometer) and cloud liquid water content provided insights into the aerosol/cloud dynamics on Mt. Rax

  15. Effects of Dissolved Gas Supersaturation on Fish Residing in the Snake and Columbia Rivers, 1996 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Schrank, Boyd P.

    1998-03-01

    Increased spill at dams has commonly brought dissolved gas supersaturation higher than levels established by state and federal water quality criteria in the Columbia and Snake Rivers. These increased spill volumes are intended to provide safe passage for migrating juvenile salmon. However, dissolved gas supersaturation resulting from spill in past decades has led to gas bubble disease (GBD) in fish. Therefore, during the period of high spill in 1996, the authors monitored the prevalence and severity of gas bubble disease by sampling resident fish in Priest Rapids Reservoir and downstream from Bonneville, Priest Rapids, and Ice Harbor Dams.

  16. Supersaturated solid solution obtained by mechanical alloying of 75% Fe, 20% Ge and 5% Nb mixture at different milling intensities

    Energy Technology Data Exchange (ETDEWEB)

    Blazquez, J.S.; Ipus, J.J.; Millan, M.; Franco, V. [Departamento de Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, Apartado 1065, 41080 Sevilla (Spain); Conde, A. [Departamento de Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, Apartado 1065, 41080 Sevilla (Spain)], E-mail: conde@us.es; Oleszak, D.; Kulik, T. [Faculty of Materials Science and Engineering, Warsaw University of Technology, ul. Woloska 141, 02-507 Warsaw (Poland)

    2009-02-05

    Mechanical alloying process of Fe{sub 75}Ge{sub 20}Nb{sub 5} composition has been studied at different milling frequencies from initial pure powder mixture to the development of a single bcc phase (supersaturated solid solution). As an intermediate state, an intermetallic phase is formed, which disappears after further milling or after thermal treatment (ascribed to an endothermic process at 700-800 K). A preferential partition of Nb and Ge to the boundaries between nanocrystals of bcc Fe-Ge-Nb supersaturated solid solution is observed from X-ray diffraction (XRD) and Moessbauer results.

  17. COMPUTATION OF THE E(s2) VALUES OF SOME E(s2) OPTIMAL SUPERSATURATED DESIGNS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A supersaturated design is a design whose run size is not enough for estimating all the main effects represented by the columns of the design matrix.It is widely used in the preliminary stages of industrial statistics and other scientific experiments.In this paper,formulas for computing the E(s2) values of E(s2) optimal supersaturated designs with m=t(n-1) ± e(e = 1 and 2) are given,and the accuracy and convenience of using these formulas are demonstrated by an example.

  18. The role of the particle size distribution in assessing aerosol composition effects on simulated droplet activation

    Directory of Open Access Journals (Sweden)

    D. S. Ward

    2010-02-01

    Full Text Available Variations in the chemical composition of atmospheric aerosols alter their hygroscopicity and can lead to changes in the cloud-active fraction of the aerosols, or cloud condensation nuclei (CCN number concentration. To investigate the importance of this effect under different atmospheric conditions, cloud droplet formation was simulated with a Lagrangian parcel model. Initial values of updraft speed and temperature were systematically varied along with aerosol number concentration, size and hygroscopicity (represented by the hygroscopicity parameter, κ. A previous study classifies the sensitivity of CCN activity to compositional changes based on the supersaturation reached in the parcel model. We found that these classifications could not be generalized to a range of aerosol size distribution median radii. Instead, variations in sensitivity with size depend on the location of the dry critical radius for droplet activation relative to the size distribution median radius. The parcel model output was used to construct droplet activation lookup tables based on κ that were implemented in the Regional Atmospheric Modeling System (RAMS microphysical scheme. As a first application of this system, aerosol hygroscopicity and size were varied in a series of RAMS mesoscale simulations designed to investigate the sensitivity of a mixed-phase orographic cloud case to the parameter variations. Observations from a recent field campaign in northwestern Colorado provided the basis for the aerosol field initializations. Model results show moderate sensitivity in the distribution of total case precipitation to extreme changes in κ, and minimal sensitivity to observed changes in estimated κ. The impact of varying aerosol hygroscopicity diminished with increasing median radius, as expected from the parcel model results. The conclusions drawn from these simulations could simplify similar research in other cloud regimes by defining the need, or lack of need, for

  19. Size-resolved CCN distributions and activation kinetics of aged continental and marine aerosol

    Directory of Open Access Journals (Sweden)

    A. Bougiatioti

    2011-04-01

    Full Text Available We present size-segregated measurements of cloud condensation nucleus (CCN activity of aged aerosol sampled at Finokalia, Crete, during the Finokalia Aerosol Measurement Experiment of summer 2007 (FAME07. From analysis of the data, hygroscopicity and activation kinetics distributions are derived. The CCN are found to be highly hygroscopic, (expressed by a size- and time-averaged hygroscopicity parameter κ ~ 0.22, with the majority of particles activating at ~0.5–0.6% supersaturation. Air masses originating from Central-Eastern Europe tend to be associated with higher CCN concentrations and slightly lower hygroscopicity (κ ~ 0.18 than for other airmass types. The particles were always well mixed, as reflected by the high activation ratios and narrow hygroscopicity distribution widths. Smaller particles (~30 nm were found to be more hygroscopic (~0.1 κ units higher than the larger ones (~100 nm. The particles with diameters less than 80 nm exhibited a diurnal hygroscopicity cycle (with κ peaking at ~14:00 h local time, consistent with photochemical aging and volatilization of less hygroscopic material from the aerosol. Use of bulk chemical composition and the aerosol number distribution results in excellent CCN closure when applying Köhler theory in its simplest form. Using asymptotic and threshold droplet growth analysis, the "aged" organics present in the aerosol were found not to suppress or delay the water uptake kinetics of particles in this environment.

  20. CCN activity and hygroscopic growth of organic aerosols following reactive uptake of ammonia.

    Science.gov (United States)

    Dinar, E; Anttila, T; Rudich, Y

    2008-02-01

    Recent field observations suggest that ammonium salts of organic acids may be very important in accounting for aerosols' properties in many environments. In this study we present laboratory experiments and calculations on the influence of ammonia reaction with organic aerosol components and its effect upon their (1) subsaturation hygroscopic growth (HG) and (2) supersaturation cloud condensation nuclei (CCN) activity. By using adipic acid (slightly soluble), citric acid (soluble), and di(ethylene glycol) monovinyl ether (DEGMVE, nonacidic compound) aerosols we show the feasibility and importance of atmospherically relevant acid-base neutralization by ammonia for different organic species. It is suggested that the formation of ammonium salts due to reaction of ammonia with slightly soluble organic acids (such as adipic acid) can affect the CCN activity and hygroscopic growth of aerosols with a significant organic component. It is further confined that the reaction involves carboxylic groups, it requires presence of water in the aerosol, and that the effects are stronger for less soluble organic acids.

  1. Supersaturation driven tailoring of photoluminescence efficiency and size distribution: a simplified aqueous approach for producing high-quality, biocompatible quantum dots.

    Science.gov (United States)

    Priyam, A; Ghosh, S; Bhattacharya, S C; Saha, A

    2009-05-01

    Supersaturation was found to play a pivotal role during nanoparticle-synthesis and its subtle variation helped achieve two prime objectives: (a) high photoluminescence quantum efficiency (PLQE) and (b) narrow size distribution, thereby obviating the need for post-preparative treatments. Degree of supersaturation of initial synthetic mixture was varied by changing the concentration of reagents while keeping their molar ratio constant at 1:2.5:0.5 for [Cd(2+)]:[cysteine]:[chalcogenide]. An eight-fold increase in supersaturation caused a sharp focusing of size distribution by 64% for CdS quantum dots (QDs). The as-prepared CdS and CdTe QDs were found to have size distribution as low as 4% at higher supersaturation. For a four-fold increase in supersaturation, PLQE of as-prepared CdTe QDs (4.3 nm) rose by 5 times to a remarkably high value of 54%. The focusing of size distribution with increasing supersaturation was found to work well even in the absence of any stabilizer. A substantial overlap of nucleation and growth was found at low supersaturation (0.5S(CdTe)), whereas a good separation of the two events is achieved at a higher supersaturation (4S(CdTe)). This study provides a simplified aqueous route for producing highly monodisperse, photoluminescent and biocompatible nanoparticles.

  2. Transient Supersaturation Supports Drug Absorption from Lipid-Based Formulations for Short Periods of Time, but Ongoing Solubilization Is Required for Longer Absorption Periods.

    Science.gov (United States)

    Crum, Matthew F; Trevaskis, Natalie L; Pouton, Colin W; Porter, Christopher J H

    2017-02-06

    The current studies sought to explore the impact of drug supersaturation and precipitation during the dispersion and digestion of lipid-based formulations (LBFs), on in vivo absorption using a coupled in vitro digestion-in vivo perfusion absorption model. Fenofibrate absorption was evaluated from a number of LBFs with different solubilization and supersaturation capacities, and conditions at the absorptive membrane manipulated by changing perfusion conditions, intestine segment lengths, and by the conduct of experiments in the presence or absence of suspended/precipitated drug. LBF dispersion and digestion resulted in varying periods of supersaturation across the different formulations. Even fleeting (5-10 min) periods of supersaturation were able to drive flux across a perfused 10 cm intestinal segment for up to 60 min, although over longer infusion periods (60-80 min) flux dropped in the absence of ongoing drug solubilization and supersaturation. In contrast, the presence or absence of precipitated/suspended drug, had little impact on drug flux. When perfused intestinal segment lengths were extended, the role of initial supersaturation was attenuated and ongoing solubilization conditions became the primary driver of absorptive flux. The data suggest that for highly permeable drugs such as fenofibrate, a short period of supersaturation at the absorptive membrane may be sufficient to drive absorptive drug flux in spite of significant drug precipitation on formulation dispersion or digestion in vitro. In contrast, where longer periods of absorption are required, for example, at higher doses, the requirement for ongoing solubilization and supersaturation becomes more apparent.

  3. Supersaturation-nucleation behavior of poorly soluble drugs and its impact on the oral absorption of drugs in thermodynamically high-energy forms.

    Science.gov (United States)

    Ozaki, Shunsuke; Minamisono, Takuma; Yamashita, Taro; Kato, Takashi; Kushida, Ikuo

    2012-01-01

    In order to better understand the oral absorption behavior of poorly water-soluble drugs, their supersaturation-nucleation behavior was characterized in fasted state simulated intestinal fluid. The induction time (t(ind)) for nucleation was measured for four model drugs: itraconazole, erlotinib, troglitazone, and PLX4032. Supersaturated solutions were prepared by solvent shift method, and nucleation initiation was monitored by ultraviolet detection. The relationship between t(ind) and degree of supersaturation was analyzed in terms of classical nucleation theory. The defined supersaturation stability proved to be compound specific. Clinical data on oral absorption were investigated for drugs in thermodynamically high-energy forms such as amorphous forms and salts and was compared with in vitro supersaturation-nucleation characteristics. Solubility-limited maximum absorbable dose was proportionate to intestinal effective drug concentrations, which are related to supersaturation stability and thermodynamic solubility. Supersaturation stability was shown to be an important factor in determining the effect of high-energy forms. The characterization of supersaturation-nucleation behavior by the presented method is, therefore, valuable for assessing the potential absorbability of poorly water-soluble drugs. Copyright © 2011 Wiley-Liss, Inc.

  4. Phytoplankton blooms weakly influence the cloud forming ability of sea spray aerosol

    Science.gov (United States)

    Collins, Douglas B.; Bertram, Timothy H.; Sultana, Camille M.; Lee, Christopher; Axson, Jessica L.; Prather, Kimberly A.

    2016-09-01

    After many field studies, the establishment of connections between marine microbiological processes, sea spray aerosol (SSA) composition, and cloud condensation nuclei (CCN) has remained an elusive challenge. In this study, we induced algae blooms to probe how complex changes in seawater composition impact the ability of nascent SSA to act as CCN, quantified by using the apparent hygroscopicity parameter (κapp). Throughout all blooms, κapp ranged between 0.7 and 1.4 (average 0.95 ± 0.15), consistent with laboratory investigations using algae-produced organic matter, but differing from climate model parameterizations and in situ SSA generation studies. The size distribution of nascent SSA dictates that changes in κapp associated with biological processing induce less than 3% change in expected CCN concentrations for typical marine cloud supersaturations. The insignificant effect of hygroscopicity on CCN concentrations suggests that the SSA production flux and/or secondary aerosol chemistry may be more important factors linking ocean biogeochemistry and marine clouds.

  5. Sea salt aerosols as a reactive surface for inorganic and organic acidic gases in the arctic troposphere

    Directory of Open Access Journals (Sweden)

    J. W. Chi

    2015-06-01

    Full Text Available Sea salt aerosols (SSA are dominant particles in the arctic atmosphere and determine the polar radiative balance. SSA react with acidic pollutants that lead to changes of physical and chemical properties of their surface, which in turn alter their hygroscopic and optical properties. Transmission electron microscopy with energy-dispersive X-ray spectrometry was used to analyze morphology, composition, size, and mixing state of individual SSA at Ny-Ålesund, Svalbard in summertime. Individual fresh SSA contained cubic NaCl coated by certain amounts of MgCl2 and CaSO4. Individual partially aged SSA contained irregular NaCl coated by a mixture of NaNO3, Na2SO4, Mg(NO32, and MgSO4. The comparison suggests the hydrophilic MgCl2 coating in fresh SSA likely intrigued the heterogeneous reactions at the beginning of SSA and acidic gases. Individual fully aged SSA normally had Na2SO4 cores and an amorphous coating of NaNO3. Elemental mappings of individual SSA particles revealed that as the particles ageing Cl gradually decreased but the C, N, O, and S content increased. 12C14N− mapping from nanoscale secondary ion mass spectrometry indicates that organic matter increased in the aged SSA compared with the fresh SSA. 12C14N− line scans further show that organic matter was mainly concentrated on the aged SSA surface. These new findings indicate that this mixture of organic matter and NaNO3 on particle surfaces determines their hygroscopic and optical properties. These abundant SSA, whose reactive surfaces absorb inorganic and organic acidic gases in the arctic troposphere, need to be incorporated into atmospheric chemical models.

  6. Gas Bubble Growth Dynamics in a Supersaturated Solution: Henry's and Sievert's Solubility Laws

    CERN Document Server

    Gor, Gennady Yu; Kuni, Fedor M

    2012-01-01

    Theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution is presented. We study the influence of Laplace pressure on the bubble growth. We consider two different solubility laws: Henry's law, which is fulfilled for the systems where no gas molecules dissociation takes place and Sievert's law, which is fulfilled for the systems where gas molecules completely dissociate in the solvent into two parts. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux of dissolved gas molecules to the bubble is steady we obtain differential equations on bubble radius for both solubility laws. For the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop bubble dynamics equations for Henry's and Sievert's laws are solved analytically. For both solubility laws three characteristic stages of bubble growth are mar...

  7. Construction of Supersaturated Design with Large Number of Factors by the Complementary Design Method

    Institute of Scientific and Technical Information of China (English)

    Yan LIU; Min-Qian LIU

    2013-01-01

    Supersaturated designs (SSDs) have been widely used in factor screening experiments.The present paper aims to prove that the maximal balanced designs are a kind of special optimal SSDs under the E(fNOD)criterion.We also propose a new method,called the complementary design method,for constructing E(fNoD)optimal SSDs.The basic principle of this method is that for any existing E(fNOD) optimal SSD whose E(fNoD)value reaches its lower bound,its complementary design in the corresponding maximal balanced design is also E(fNOD) optimal.This method applies to both symmetrical and asymmetrical (mixed-level) cases.It provides a convenient and efficient way to construct many new designs with relatively large numbers of factors.Some newly constructed designs are given as examples.

  8. Perennial N2 supersaturation in an Antarctic lake. [biological processes in thin martian atmosphere

    Science.gov (United States)

    Wharton, Robert A., Jr.; Mckay, Christopher P.; Mancinelli, Rocco L.; Simmons, George M., Jr.

    1987-01-01

    The results of a study are reported which, for the first time, documents the supersaturation of N2 in a lake. Dissolved N2 levels of 145 percent and 163 percent were determined for Antarctica's Lake Hoare from samples taken just below the ice cover and at a depth of 12 m, respectively. The relative importance of biological and abiological sources is reflected in the ratio of N2 concentration to O2 concentration. In Lake Hoare this ratio was 1.20 at the ice/water interface and 1.05 at 12 m, considerably different from the ratio in equilibrium with air (about 1.8). Based on these results, it is determined that about half of the net O2 production in the lake is the result of biological processes. The significance of these results for the putative ice-covered paleolakes in the canyon regions of Mars is discussed.

  9. Surface supersaturation in flow-rate modulation epitaxy of GaN

    Science.gov (United States)

    Akasaka, Tetsuya; Lin, Chia-Hung; Yamamoto, Hideki; Kumakura, Kazuhide

    2017-06-01

    Hillocks on N-face GaN (000 1 bar) films are effectively eliminated by group-III-source flow-rate modulation epitaxy (FME), wherein the flow-rate of group-III sources are sequentially modulated under a constant supply of NH3. A hillock-free smooth surface obtained by group-III-source FME is attributed to the enhancement of step-flow growth. We found that a hillock originates from a micropipe and grows by spiral growth around the micropipe. The spiral growth rate rapidly decreases with decreasing the degree of surface supersaturation σ, while the step-flow growth rate decreases linearly. For group-III-source FME, wherein σ is lower than conventional continuous growth, the spiral growth rate could be lower than the step-flow growth one so that the formation of hillocks is suppressed.

  10. Oxygen supersaturation in ice-covered Antarctic lakes - Biological versus physical contributions

    Science.gov (United States)

    Craig, H.; Wharton, R. A., Jr.; Mckay, C. P.

    1992-01-01

    Lake Hoare is one of a number of ice-covered polar lakes in the Dry Valley Region of southern Victoria Land, Antarctica. Analysis of N2, O2, and Ar in bubbles from this lake's ice indicates that while O2 is about 2.4 times supersaturated in the water below the ice, only 11 percent of the O2 input to this lake is due to biological activity and the balance is derived from meltwater inflow. In Lake Hoare, as much as 70 percent of total gas loss may occur by advection through the ice cover; the remaining gas fractions are removed by respiration at the lower boundary in the case of O2, and by molecular exchange with the atmosphere in the peripheral summer moat around the ice.

  11. Gasometer: An inexpensive device for continuous monitoring of dissolved gases and supersaturation

    Science.gov (United States)

    Bouck, G.R.

    1982-01-01

    The “gasometer” is a device that measures differential dissolved-gas pressures (δP) in water relative to barometric pressure (as does the “Weiss saturometer”), but operates continuously without human attention. The gasometer can be plumbed into a water-supply system and requires 8 liters/minute of water or more at 60 kilopascals. The gasometer's surfaces are nontoxic, and flow-through water can be used for fish culture. The gasometer may be connected to a small submersible pump and operated as a portable unit. The gasometer can activate an alarm system and thus protect fish from hyperbaric (supersaturation) or hypobaric gas pressures (usually due to low dissolved oxygen). Instructions are included for calculating and reporting data including the pressure and saturation of individual gases. Construction and performance standards are given for the gasometer. Occasional cleaning is required to remove biofouling from the gas-permeable tubing.PDF

  12. Tolerance to gas supersaturation in freshwater and seawater by steelhead trout (Salmo gairdneri)

    Science.gov (United States)

    Bouck, G.R.; King, R.E.

    1983-01-01

    The euryhaline status of steelhead trout, Salmo gairdneri, smolts was challenged in sea water for 2 weeks after which half of the total fish population was returned to fresh water. Acclimation continued and created two test populations in 29%osea water and fresh water. Subsequently these fish were exposed in fresh water or sea water to approximately equal hyperbaric dissolved total gas pressures (ΔP) of 190 mm Hg or about 125% of barometric pressure. Sea water was easier to supersaturate with air and required only about 10% of the entrained air which was required in fresh water at the same temperature and pressure. Mean time to first mortality was sooner in sea water. Mean times to mortality (10–50%) were not significantly different between fresh water and sea water, but there was a noticeable trend for longer survival in fresh water.

  13. Influence of supersaturation and structurally related additives on the crystal growth of α-lactose monohydrate

    Science.gov (United States)

    Garnier, Stéphanie; Petit, Samuel; Coquerel, Gérard

    2002-01-01

    It is shown that increasing the supersaturation during crystal growth of the title compound in water at room temperature induces an important increase in the mean crystal size, which can be explained by taking into account the role of the solvent and that of the β-lactose anomer acting as large scale impurities in the crystallizing medium. Among the six structurally related additives tested, four of them lead to significant morphological changes, due to their anisotropic adsorption abilities. Depending on the nature of the additive, crystal habit varies from "elongated" along the b direction or "flattened" along the a axis. These data could be rationalized by a careful analysis of the 3D hydrogen bond network and by using molecular modelling for the simulation of the adsorption mechanisms, assuming that adsorption ability and desorption difficulty were directly dependent on the proportion of preserved intermolecular hydrogen bonds.

  14. Dynamics of gas bubble growth in a supersaturated solution with Sievert's solubility law.

    Science.gov (United States)

    Gor, G Yu; Kuchma, A E

    2009-07-21

    This paper presents a theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution. We study systems where gas molecules completely dissociate in the solvent into two parts, thus making Sievert's solubility law valid. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux is steady we obtain a differential equation on bubble radius. Bubble dynamics equation is solved analytically for the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop. We also obtain conditions of diffusion flux steadiness. The fulfillment of these conditions is studied for the case of nucleation of water vapor bubbles in magmatic melts.

  15. Thermal stability of a supersaturated Fe-Ge-Nb solid solution produced by ball milling

    Energy Technology Data Exchange (ETDEWEB)

    Ipus, J J; Blazquez, J S; Conde, A, E-mail: conde@us.e [Dpto. Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, PO Box 1065, 41080, Sevilla (Spain)

    2010-03-01

    Thermal evolution of Fe neighbourhood in a supersaturated bcc Fe(Ge,Nb) solid solution, obtained as the final product of mechanical alloying of Fe{sub 75}Ge{sub 20}Nb{sub 5}, was studied. No changes in Fe neighbourhood were detected after heating up to 473 K, although differential scanning calorimetry shows a clear deviation of the baseline at 400 K. After heating up to 723 K, a similar nanocrystalline microstructure is derived from X-ray diffraction. However, Moessbauer spectra evidence changes in the Fe neighbourhood. A proposed deconvolution of the hyperfine field distribution yields a Ge content of {approx}10 at. %, in agreement with the maximum solubility of Ge in bcc Fe in thermodynamical equilibrium.

  16. Supercritical supersaturations and ultrafast cooling of the growth solution in liquid-phase epitaxy of semiconductors

    Science.gov (United States)

    Abramov, A. V.; Deryagin, N. G.; Tret'yakov, D. N.

    1996-04-01

    A method for accomplishing ultrafast cooling is proposed which makes possible supercritical supersaturations of the growth solution in liquid-phase epitaxy. Growth boat designs providing cooling rates as high as 0268-1242/11/4/025/img1 are considered. The temperatures of contact, 0268-1242/11/4/025/img2, of a GaAs substrate with a Ga-based solution and of a Si substrate with a Sn-based growth solution, calculated for various substrate 0268-1242/11/4/025/img3 and solution temperatures 0268-1242/11/4/025/img4, are in good agreement with experimental values. The maximum attainable supercooling is markedly increased to as high as 0268-1242/11/4/025/img5 for the Ga - As system, when the growth solution is subjected to ultrafast cooling. The prospects of using the method for fabricating heterostructures with a large lattice mismatch are discussed.

  17. A look at aerosol formation using data mining techniques

    Directory of Open Access Journals (Sweden)

    S. Hyvönen

    2005-01-01

    Full Text Available Atmospheric aerosol particle formation is frequently observed throughout the atmosphere, but despite various attempts of explanation, the processes behind it remain unclear. In this study data mining techniques were used to find the key parameters needed for atmospheric aerosol particle formation to occur. A dataset of 8 years of 80 variables collected at the boreal forest station (SMEAR II in Southern Finland was used, incorporating variables such as radiation, humidity, SO2, ozone and present aerosol surface area. This data was analyzed using clustering and classification methods. The aim of this approach was to gain new parameters independent of any subjective interpretation. This resulted in two key parameters, relative humidity and preexisting aerosol particle surface (condensation sink, capable in explaining 88% of the nucleation events. The inclusion of any further parameters did not improve the results notably. Using these two variables it was possible to derive a nucleation probability function. Interestingly, the two most important variables are related to mechanisms that prevent the nucleation from starting and particles from growing, while parameters related to initiation of particle formation seemed to be less important. Nucleation occurs only with low relative humidity and condensation sink values. One possible explanation for the effect of high water content is that it prevents biogenic hydrocarbon ozonolysis reactions from producing sufficient amounts of low volatility compounds, which might be able to nucleate. Unfortunately the most important biogenic hydrocarbon compound emissions were not available for this study. Another effect of water vapour may be due to its linkage to cloudiness which may prevent the formation of nucleating and/or condensing vapours. A high number of preexisting particles will act as a sink for condensable vapours that otherwise would have been able to form sufficient supersaturation and initiate the

  18. Aerosol hygroscopic growth parameterization based on a solute specific coefficient

    Science.gov (United States)

    Metzger, S.; Steil, B.; Xu, L.; Penner, J. E.; Lelieveld, J.

    2011-09-01

    Water is a main component of atmospheric aerosols and its amount depends on the particle chemical composition. We introduce a new parameterization for the aerosol hygroscopic growth factor (HGF), based on an empirical relation between water activity (aw) and solute molality (μs) through a single solute specific coefficient νi. Three main advantages are: (1) wide applicability, (2) simplicity and (3) analytical nature. (1) Our approach considers the Kelvin effect and covers ideal solutions at large relative humidity (RH), including CCN activation, as well as concentrated solutions with high ionic strength at low RH such as the relative humidity of deliquescence (RHD). (2) A single νi coefficient suffices to parameterize the HGF for a wide range of particle sizes, from nanometer nucleation mode to micrometer coarse mode particles. (3) In contrast to previous methods, our analytical aw parameterization depends not only on a linear correction factor for the solute molality, instead νi also appears in the exponent in form x · ax. According to our findings, νi can be assumed constant for the entire aw range (0-1). Thus, the νi based method is computationally efficient. In this work we focus on single solute solutions, where νi is pre-determined with the bisection method from our analytical equations using RHD measurements and the saturation molality μssat. The computed aerosol HGF and supersaturation (Köhler-theory) compare well with the results of the thermodynamic reference model E-AIM for the key compounds NaCl and (NH4)2SO4 relevant for CCN modeling and calibration studies. The equations introduced here provide the basis of our revised gas-liquid-solid partitioning model, i.e. version 4 of the EQuilibrium Simplified Aerosol Model (EQSAM4), described in a companion paper.

  19. Formulation of a danazol cocrystal with controlled supersaturation plays an essential role in improving bioavailability.

    Science.gov (United States)

    Childs, Scott L; Kandi, Praveen; Lingireddy, Sreenivas Reddy

    2013-08-05

    Cocrystals have become an established and adopted approach for creating crystalline solids with improved physical properties, but incorporating cocrystals into enabling pre-clinical formulations suitable for animal dosing has received limited attention. The dominant approach to in vivo evaluation of cocrystals has focused on deliberately excluding additional formulation in favor of "neat" aqueous suspensions of cocrystals or loading neat cocrystal material into capsules. However, this study demonstrates that, in order to take advantage of the improved solubility of a 1:1 danazol:vanillin cocrystal, a suitable formulation was required. The neat aqueous suspension of the danazol:vanillin cocrystal had a modest in vivo improvement of 1.7 times higher area under the curve compared to the poorly soluble crystal form of danazol dosed under identical conditions, but the formulated aqueous suspension containing 1% vitamin E-TPGS (TPGS) and 2% Klucel LF Pharm hydroxypropylcellulose improved the bioavailability of the cocrystal by over 10 times compared to the poorly soluble danazol polymorph. In vitro powder dissolution data obtained under non-sink biorelevant conditions correlate with in vivo data in rats following 20 mg/kg doses of danazol. In the case of the danazol:vanillin cocrystal, using a combination of cocrystal, solubilizer, and precipitation inhibitor in a designed supersaturating drug delivery system resulted in a dramatic improvement in the bioavailability. When suspensions of neat cocrystal material fail to return the anticipated bioavailability increase, a supersaturating formulation may be able to create the conditions required for the increased cocrystal solubility to be translated into improved in vivo absorption at levels competitive with existing formulation approaches used to overcome solubility limited bioavailability.

  20. Evaluation of the difficulty of crystallization of organic compounds using the critical supersaturation ratio (Sc)

    Science.gov (United States)

    Nagamatsu, Daiki; Ida, Yasuo; Takiyama, Hiroshi

    2014-11-01

    In the case of solvent selection, supersolubility is an index for improving crystallization behavior. However, supersolubility is affected by kinetic factors such as the cooling rate. An index for suitable solvent selection is needed. The supersaturation ratio (S) is one of the operation design indices of controlling crystallization behavior such as supersolubility. The S at 298 K (S298) of the pharmaceutical compounds theophylline, noscapine, clotrimazole, indomethacin, carbamazepine, naproxene and tolbutamide were measured in ethanol using a polythermal method. If the compound had a large lnS298, the cooling rate strongly affected the temperature of the cloud point in the cooling crystallization method. In order to estimate the crystallization behavior without the cooling rate effect, the critical supersaturation ratio (Sc) was proposed. Sc at 298 K (Sc298) was calculated from dissolution/cloud points at 0 K/min extrapolated from that of several heating/cooling rates to remove the kinetic effects on S. The lnSc298 values of theophylline, noscapine and clotrimazole were estimated in acetonitrile, methyl ethyl ketone, tetrahydrofuran, ethyl acetate, methanol, ethanol and isopropanol. The lnSc298 value of clotrimazole was the largest in all solvents. The results showed that lnSc298 was a simple index which could be used to evaluate the crystallization behavior resulting from the interaction between the solvent and the compound. In conclusion, the proposed lnSc298 should be useful for comparing the difficulty of crystallization which indicates how we should obtain desired crystals within a certain finite time period for development API in the manufacturing field without considering the effect of the heating/cooling rate.

  1. Atmosphere aerosol satellite project Aerosol-UA

    Science.gov (United States)

    Milinevsky, Gennadi; Yatskiv, Yaroslav; Syniavskyi, Ivan; Bovchaliuk, Andrii; Degtyaryov, Oleksandr; Sosonkin, Mikhail; Mishchenko, Michael; Danylevsky, Vassyl; Ivanov, Yury; Oberemok, Yevgeny; Masley, Volodymyr; Rosenbush, Vera; Moskalev, Sergii

    2017-04-01

    The experiment Aerosol-UA is Ukrainian space mission aimed to the terrestrial atmospheric aerosol spatial distribution and microphysics investigations. The experiment concept is based on idea of Glory/APS mission of precise orbital measurements of polarization and intensity of the sunlight scattered by the atmosphere, aerosol and the surface the multichannel Scanning Polarimeter (ScanPol) with narrow field-of-view. ScanPol measurements will be accompanied by the wide-angle MultiSpectral Imager-Polarimeter (MSIP). The ScanPol is designed to measure Stokes parameters I, Q, U within the spectral range from the UV to the SWIR in a wide range of phase angles along satellite ground path. Expected ScanPol polarimetric accuracy is 0.15%. A high accuracy measurement of the degree of linear polarization is provided by on-board calibration of the ScanPol polarimeter. On-board calibration is performed for each scan of the mirror scanning system. A set of calibrators is viewed during the part of the scan range when the ScanPol polarimeter looks in the direction opposite to the Earth's surface. These reference assemblies provide calibration of the zero of the polarimetric scale (unpolarized reference assembly) and the scale factor for the polarimetric scale (polarized reference assembly). The zero of the radiometric scale is provided by the dark reference assembly.The spectral channels of the ScanPol are used to estimate the tropospheric aerosol absorption, the aerosol over the ocean and the land surface, the signals from cirrus clouds, stratospheric aerosols caused by major volcanic eruptions, and the contribution of the Earth's surface. The imager-polarimeter MSIP will collect 60°x60° field-of-view images on the state of the atmosphere and surface in the area, where the ScanPol polarimeter will measure, to retrieve aerosol optical depth and polarization properties of aerosol by registration of three Stokes parameters simultaneously in three spectral channels. The two more

  2. DARE : Dedicated Aerosols Retrieval Experiment

    NARCIS (Netherlands)

    Smorenburg, K.; Courrèges-Lacoste, G.B.; Decae, R.; Court, A.J.; Leeuw, G. de; Visser, H.

    2004-01-01

    At present there is an increasing interest in remote sensing of aerosols from space because of the large impact of aerosols on climate, earth observation and health. TNO has performed a study aimed at improving aerosol characterisation using a space based instrument and state-of-the-art aerosol retr

  3. Fractions of Rechtschaffner matrices as supersaturated designs in screening experiments aimed at evaluating main and two-factor interaction effects.

    Science.gov (United States)

    Cela, R; Phan-Tan-Luu, R; Claeys-Bruno, M; Sergent, M

    2012-04-06

    Optimal fractions of resolution V design matrices proposed by Rechtschaffner in 1967 are developed and applied as supersaturated designs in screening experiments. Rechtschaffner matrices allow evaluation of all main factors and two-factor interactions, which in many real-world studies are of practical significance. However, the number of experimental runs increases rapidly with the number of factors in the matrices, which are therefore impractical for more than 5-6 factors. On the contrary, saturated fractions based on Hadamard matrices, which are commonly applied in screening studies, cannot evaluate the interaction effects. Here, a procedure for selecting the optimum fractions of Rechtschaffner matrices is presented and provides supersaturated matrices that are well adapted to a variety of problems, thus allowing the development of screening studies with a relatively small number of experiments. The procedures developed to derive the size-reduced matrices and to evaluate the active factors are discussed and compared in terms of efficiency and reliability, by means of simulation studies and application to a real problem. These fractions are the first supersaturated design matrices capable of estimating interaction effects. Additionally, one important advantage of these supersaturated matrices is that they enable development of follow-up procedures in cases of inconclusive results, by enlarging the matrix and eventually resolving the full Rechtschaffner matrix of departure when it is necessary to evaluate the active factors and their interactions.

  4. Influence of hydrophilic additives on the supersaturation and bioavailability of dutasteride-loaded hydroxypropyl-β-cyclodextrin nanostructures.

    Science.gov (United States)

    Kim, Min-Soo

    2013-01-01

    The objectives of this study were to develop a novel solid dutasteride formulation with improved physicochemical properties and oral bioavailability, and to examine the correlation between its in vitro dissolution and in vivo pharmacokinetic parameters. Hydroxypropyl-β-cyclodextrin (HP-β-CD) nanostructures with or without hydrophilic additives were manufactured using the supercritical antisolvent process. The dutasteride-loaded HP-β-CD nanoparticles formed aggregates with a mean particle size of less than 160 nm and a specific surface area greater than 100 m(2)/g. Increases in the supersaturation and dissolution rate for dutasteride were dependent on the type of additive; increases in maximum solubility and extended supersaturation were observed in dutasteride-loaded HP-β-CD nanostructures with hydroxypropylmethyl cellulose, whereas the dissolution rate was the highest for nanostructures containing d-α-tocopheryl polyethylene glycol 1000 succinate. In rats, the oral bioavailability of dutasteride increased with the supersaturation induced by the HP-β-CD nanostructures. In addition, compared with the in vitro drug release rate, the in vivo pharmacokinetic parameters were more closely correlated with in vitro parameters related to supersaturation (solubility). Further, the bioavailability of the dutasteride-loaded HP-β-CD nanostructures with hydroxypropylmethyl cellulose was similar to that of the commercially available soft gelatin capsule (Avodart®). In conclusion, preparation of dutasteride-loaded HP-β-CD nanostructures using the supercritical antisolvent process affords a viable alternative solid dosage form for dutasteride.

  5. Effects of total dissolved gas supersaturated water on lethality and catalase activity of Chinese sucker (Myxocyprinus asiaticus Bleeker)*

    Science.gov (United States)

    Chen, Shi-chao; Liu, Xiao-qing; Jiang, Wen; Li, Ke-feng; Du, Jun; Shen, Dan-zhou; Gong, Quan

    2012-01-01

    Total dissolved gas (TDG) supersaturation caused by dam sluicing can result in gas bubble trauma (GBT) in fish and threaten their survival. In the present study, Chinese suckers (Myxocyprinus asiaticus Bleeker) were exposed to TDG supersaturated water at levels ranging from 120% to 145% for 48 h. The median lethal concentration (LC50) and the median lethal time (LT50) were determined to evaluate acute lethal effects on Chinese suckers. The results showed that the LC50 values of 4, 6, 8, and 10 h were 142%, 137%, 135%, and 130%, respectively. The LT50 values were 3.2, 4.7, 7.8, 9.2, and 43.4 h, respectively, when TDG supersaturated levels were 145%, 140%, 135%, 130%, and 125%. Furthermore, the biological responses in Chinese suckers were studied by assaying the catalase (CAT) activities in gills and muscles at the supersaturation level of 140% within LT50. The CAT activities in the gills and muscle tissues exhibited a regularity of a decrease after an increase. CAT activities in the muscles were increased significantly at 3/5LT50 (P0.05), but the activities were significantly lower than the normal level at 4/5LT50 and LT50 (P<0.05). PMID:23024046

  6. Chirally Pure Prodrugs and Their Converting Enzymes Lead to High Supersaturation and Rapid Transcellular Permeation of Benzodiazepines.

    Science.gov (United States)

    Kapoor, Mamta; Cheryala, Narsihmulu; Rautiola, Davin; Georg, Gunda I; Cloyd, James C; Siegel, Ronald A

    2016-08-01

    Water-soluble prodrugs can be rapidly converted by enzymes to hydrophobic drugs, whose aqueous thermodynamic solubilities are low, but are maintained in aqueous solution at supersaturated concentrations due to slow precipitation kinetics. Recently, we investigated avizafone (AVF) in combination with Aspergillus oryzae protease as a prodrug/enzyme system intended to produce supersaturated diazepam (DZP). Several fold enhancement of permeation of supersaturated DZP across Madin-Darby canine kidney II-wild type (MDCKII-wt) monolayers was observed, compared to saturated DZP solutions. However, prodrug conversion was incomplete, putatively due to partial racemization of AVF and stereoselectivity of A oryzae protease. Here we report synthesis of chirally pure AVF, and demonstrate complete conversion to supersaturated DZP followed by complete DZP permeation at enhanced rates across MDCKII-wt cell monolayers. We also synthesized, for the first time, a chirally pure prodrug of midazolam (MDZ-pro) and carried out the same sequence of studies. A oryzae protease was identified as a benign and efficient activating enzyme for MDZ-pro. The MDZ-pro/A oryzae protease system showed greater than 25-fold increase in absorption rate of MDZ across MDCKII-wt monolayers, compared to saturated MDZ. Such chirally pure prodrug/enzyme systems are promising candidates for efficient intranasal delivery of benzodiazepine drugs used in the treatment of seizure emergencies. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  7. Study of drug supersaturation for rational early formulation screening of surfactant/co-solvent drug delivery systems.

    Science.gov (United States)

    Stillhart, Cordula; Cavegn, Martin; Kuentz, Martin

    2013-02-01

    To advance in vitro screening of surfactant/co-solvent formulations in early development by considering drug supersaturation and the mechanism of solubilization upon aqueous dilution. Two surfactant/co-solvent model systems were studied at practically relevant aqueous dilution ratios. Precipitation of the model drug fenofibrate was characterized by focused beam reflectance measurement, X-ray diffraction, and Raman spectroscopy. We calculated drug supersaturation in diluted systems and introduced a theoretical model to study the role of excipient interaction in the process of drug solubilization. Finally, vehicle phase changes upon dilution were examined using dynamic light scattering and ultrasound analysis. Phase changes occurred at low dilution levels, while more extensive dilution barely led to further structural changes. In undiluted formulations, ethanol-surfactant domains were responsible for fenofibrate solubilization. In dispersed formulations, however, the co-solvent partitioned out of the surfactant microstructure, leading to drug solubilization by independent micellization and co-solvency. This loss of excipient interaction caused formulation-specific supersaturation, which was indicative for the risk of drug precipitation. Experimental protocols of in vitro formulation screening should include both low and high dilution levels of physiological relevance. The study of excipient interaction and estimation of supersaturation allows the identification of formulations that are prone to drug precipitation. © 2012 The Authors. JPP © 2012. Royal Pharmaceutical Society.

  8. Combined use of crystalline sodium salt and polymeric precipitation inhibitors to improve pharmacokinetic profile of ibuprofen through supersaturation.

    Science.gov (United States)

    Terebetski, Jenna L; Cummings, John J; Fauty, Scott E; Michniak-Kohn, Bozena

    2014-10-01

    To maximize the pharmacological effect of a pain reliever such as ibuprofen, early onset of action is critical. Unfortunately, the acidic nature of ibuprofen minimizes the amount of drug that can be solubilized under gastric conditions and would be available for immediate absorption upon entry into the intestine. Although the sodium salt of ibuprofen has higher solubility, rapid conversion from the salt to the poorly soluble free acid phase occurs under gastric conditions. Therefore, the combination of the highly soluble sodium salt form of ibuprofen with polymers was evaluated as an approach to prolong supersaturation of ibuprofen during the disproportionation of the salt. Binary combinations of ibuprofen sodium with polymers resulted in the identification of several formulations that demonstrated high degrees and extended durations of supersaturation during in vitro dissolution experiments. These formulations included HPMC, polyvinyl pyrrolidone-vinyl acetate copolymer (PVP-VA64), methylcellulose (MC), and hydroxypropyl cellulose (HPC). The in vitro supersaturation observed with these ibuprofen-polymer formulations translated to an increase in Cmax and an earlier Tmax for the PVP-VA64, MC, and HPC formulations relative to ibuprofen only controls when administered orally to rats under fasted conditions. Based on these observations, combining ibuprofen sodium with polymers such as PVP-VA64, MC, or HPC is a viable formulation approach to prolong supersaturation in the stomach and enable an optimized pharmacokinetic profile in vivo where rapid onset of action is desired.

  9. Effect of total dissolved gas supersaturated water on early life of David’s schizothoracin (Schizothorax davidi)*

    Science.gov (United States)

    Liang, Rui-feng; Li, Bo; Li, Ke-feng; Tuo, You-cai

    2013-01-01

    The effect of total dissolved gas (TDG) supersaturation on fish living downstream of dams is one of the main ecological risks of high dam construction. A strategy for mitigating the negative effects is needed urgently since many high dams are under construction in the upper reaches of the Yangtze River in China. Experiments on the hatching process of David’s schizothoracin were carried out and the results show that the hatching rate decreased with increasing TDG levels, and that most eggs hatched within a very short time in the higher TDG saturation groups. By using a stereomicroscope, damages to the head, yolk sac, body, anus, etc. were found in larvae which hatched in TDG supersaturated water. Results show that the lesion rate increased with increasing TDG levels. Furthermore, 7-d-old David’s schizothoracin were exposed to TDG supersaturated water levels of 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, and 140% for testing their tolerance to TDG supersaturation. We found that the median lethal concentrations (LC50) for 13, 14, 20, 35, 52, 73, and 96 h exposure were 138%, 138%, 134%, 130%, 129%, 128%, and 126%, respectively. The median lethal times (LT50) were 7.49, 11.04, 19.25, and 35.38 h for exposure to water with TDG levels of 145%, 140%, 135%, and 130%, respectively. PMID:23825149

  10. An improved method for the characterization of supersaturation and precipitation of poorly soluble drugs using pulsatile microdialysis (PMD).

    Science.gov (United States)

    Shah, Kosha B; Patel, Piyush G; Khairuzzaman, Akm; Bellantone, Robert A

    2014-07-01

    In current pharmaceutical drug discovery, most candidates are poorly soluble in water, which can result in poor bioavailability. To overcome this problem, formulations that create supersaturation of the drug are a well-studied alternative. Characterizing the dissolution from these systems is challenging because conventional methods, such as sampling with a syringe then filtering with a 0.2-0.45 μm filter before an HPLC assay, can overestimate the concentration of dissolved drug by allowing nuclei or small precipitated particles to pass, which then dissolve in the HPLC mobile phase. Nuclei and small particles can also cause overestimation of the dissolved concentration when using optical methods. Such overestimations can lead to failure of in vivo prediction of drug bioavailability from supersaturated systems. This paper reports a novel method to determine the free dissolved drug concentration in a dissolution medium using pulsatile microdialysis (PMD). Ibuprofen was used as a model drug for determining precipitation and supersaturation. Supersaturation was induced chemically by changing pH, and also by dissolution/release from an in-house formulation. The adaptation of a previously developed PMD model is summarized, and experimental results comparing dissolved concentrations determined using PMD and direct sampling by syringe and filtering are presented. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Preparation and performance of hydroxypropyl methylcellulose esters of substituted succinates for in vitro supersaturation of a crystalline hydrophobic drug.

    Science.gov (United States)

    Yin, Ligeng; Hillmyer, Marc A

    2014-01-06

    We prepared hydroxypropyl methylcellulose (HPMC) esters of substituted succinates and examined their performance for improving the aqueous solubility of crystalline hydrophobic drugs in spray-dried dispersions (SDDs). From one HPMC, we synthesized five HPMC esters using various monosubstituted succinic anhydrides. These HPMC esters along with a commercial HPMC acetate succinate (HPMCAS) were spray-dried from solutions with phenytoin. The SDDs with different matrices at 10 wt % loading had very similar bulk properties with a minimal amount of detectable crystalline phenytoin as revealed by scanning electron microscopy (SEM), powder X-ray diffraction (powder XRD), and differential scanning calorimetry (DSC). In solution, while the SDD with HPMCAS was very effective at achieving high levels of phenytoin supersaturation initially, it was not competent at maintaining such supersaturation due to the rapid crystallization of the dissolved phenytoin. Alternatively, SDDs with several synthesized HPMC esters of substituted succinates not only achieved rather high initial supersaturation but also maintained high concentrations for extended time (i.e., 1.5 h and longer). Such maintenance was largely ascribed to the inhibition of phenytoin nucleation. Structure-property relationships were established, and the most successful systems contained a high degree of substitution and a combination of a thioether with neighboring weak electron-withdrawing groups in the substituted succinic anhydrides. The effective maintenance of supersaturated solutions was only found in SDDs with rather low drug loadings, which indicates the significance of sufficiently high concentrations of polymer additives in the dissolution media.

  12. Strain effects in Nb3Al multifilamentary conductors prepared by phase transformation from bcc supersaturated-solid solution

    NARCIS (Netherlands)

    Takeuchi, T.; Iijima, Y.; Inoue, K.; Wada, H.; Haken, ten B.; Kate, ten H.H.J.; Fukuda, K.; Iwaki, G.; Sakai, S.; Moriai, H.

    1997-01-01

    Strain effects on critical current densities have been examined for conductors containing nearly stoichiometric Nb3Al filaments with fine grains. The Nb3Al phase in these multifilamentary conductors are prepared by phase transformation from supersaturated Nb(Al) bcc solid solution and show high-fiel

  13. A global off-line model of size-resolved aerosol microphysics: I. Model development and prediction of aerosol properties

    Directory of Open Access Journals (Sweden)

    D. V. Spracklen

    2005-01-01

    Full Text Available A GLObal Model of Aerosol Processes (GLOMAP has been developed as an extension to the TOMCAT 3-D Eulerian off-line chemical transport model. GLOMAP simulates the evolution of the global aerosol size distribution using a sectional two-moment scheme and includes the processes of aerosol nucleation, condensation, growth, coagulation, wet and dry deposition and cloud processing. We describe the results of a global simulation of sulfuric acid and sea spray aerosol. The model captures features of the aerosol size distribution that are well established from observations in the marine boundary layer and free troposphere. Modelled condensation nuclei (CN>3nm vary between about 250–500 cm-3 in remote marine boundary layer regions and are generally in good agreement with observations. Modelled continental CN concentrations are lower than observed, which may be due to lack of some primary aerosol sources or the neglect of nucleation mechanisms other than binary homogeneous nucleation of sulfuric acid-water particles. Remote marine CN concentrations increase to around 2000–10 000 cm (at standard temperature and pressure in the upper troposphere, which agrees with typical observed vertical profiles. Cloud condensation nuclei (CCN at 0.2% supersaturation vary between about 1000 cm-3 in polluted regions and between 10 and 500 cm-3 in the remote marine boundary layer. New particle formation through sulfuric acid-water binary nucleation occurs predominantly in the upper troposphere, but the model results show that these particles contribute greatly to aerosol concentrations in the marine boundary layer. For this sulfur-sea salt system it is estimated that sea spray emissions account for only ~10% of CCN in the tropical marine boundary layer, but between 20 and 75% in the mid-latitude Southern Ocean. In a run with only natural sulfate and sea salt emissions the global mean surface CN concentration is more than 60% of that from a run with 1985 anthropogenic

  14. Hygroscopic growth of atmospheric aerosol particles and its relation to nucleation scavenging in clouds

    Energy Technology Data Exchange (ETDEWEB)

    Svenningsson, B.

    1997-11-01

    Aerosol particles in the atmosphere are important in several aspects. Some major aerosol constituents that are deposited in ecosystems are acidic or fertilizers and some minor or trace constituents are toxic. Aerosol particles are also involved in the earth`s radiation balance, both directly by scattering the sunlight and indirectly by influencing the clouds. All these effects are influenced by the interaction between the aerosol particles and water vapour. A tandem differential mobility analyser (TDMA) has been designed to measure hygroscopic growth, i.e. the particle diameter change due to uptake of water at well defined relative humidities below 100%. Tests of the instrument performance have been made using aerosol particles of pure inorganic salts. Three field experiments have been performed as parts of large fog and cloud experiments. Bimodal hygroscopic growth spectra were found: less-hygroscopic particles containing a few percent and more-hygroscopic particles around 50% by volume of hygroscopically active material. In general the fraction of less-hygroscopic particles decreases with particle size and it is larger in polluted continental aerosols than in remote background aerosols. This external mixing cannot be fully understood using present views on the formation of aerosols. Evidence or the importance of the external mixing on the cloud nucleating properties of the particles are found in comparisons between hygroscopic growth spectra for the total aerosol, the interstitial aerosol in clouds, and cloud drop residuals. Cloud condensation nuclei spectra, calculated using aerosol particle size distributions and hygroscopic growth spectra, in combination with information on the major inorganic ions are presented. These CCN spectra reveal for instance that the influence of less-hygroscopic particles on the cloud droplets increases with increasing peak supersaturation. The fraction of the particles that were scavenged to cloud drops, as a function of particle

  15. Evaluation and intercomparison of the aerosol number concentrations and CCNs in global models

    Science.gov (United States)

    Fanourgakis, Georgios; Myriokefalitakis, Stelios; Kanakidou, Maria; Makkonen, Risto; Grini, Alf; Stier, Philip; Watson-Parris, Duncan; Schutgens, Nick; Neubauer, David; Lohmann, Ulrike; Nenes, Athanasis

    2017-04-01

    In this work preliminary results of the current status of BACCHUS global modeling of aerosol number concentrations and cloud condensation nuclei (CCN) are presented and compared to observations. So far, simulation results from the TM4-ECPL, ECHAM-HAM, ECHAM6-HAM2 and NorESM models have become available. Hourly model results for the aerosol number concentrations and CCN concentrations at various supersaturation ratios, as well as their corresponding daily and monthly averaged values are compared to the measurements from nine ACTRIS sites for the years 2010-2015. CCN concentration persistence obtained from the auto-correlation function of observational and model data is compared. Seasonal variations are also considered in the present analysis. In order to identify any common biases against observations, the model results are further analyzed in terms of the particles chemical composition and the set of hygroscopicity parameters used for the calculation of CCNs. Annual mean surface-level number concentrations of various particle sizes and CCNs at 0.2% supersaturation predicted by the models along with their corresponding chemical composition are presented and discussed.

  16. MSA in Beijing aerosol

    Institute of Scientific and Technical Information of China (English)

    YUAN Hui; WANG Ying; ZHUANG Guoshun

    2004-01-01

    Methane sulphonate (MSA) and sulfate (SO42-), the main oxidation products of dimethyl sulfide (DMS), are the target of atmospheric chemistry study, as sulfate aerosol would have important impact on the global climate change. It is widely believed that DMS is mainly emitted from phytoplankton production in marine boundary layer (MBL), and MSA is usually used as the tracer of non-sea-salt sulfate (nss- SO42-) in marine and coastal areas (MSA/SO42- = 1/18). Many observations of MSA were in marine and coastal aerosols. To our surprise, MSA was frequently (>60%) detected in Beijing TSP, PM10, and PM2.5 aerosols, even in the samples collected during the dust storm period. The concentrations of MSA were higher than those measured in marine aerosols. Factor analysis, correlation analysis and meteorology analysis indicated that there was no obvious marine influence on Beijing aerosols. DMS from terrestrial emissions and dimethyl sulphoxide (DMSO) from industrial wastes could be the two possible precursors of MSA. Warm and low-pressure air masses and long time radiation were beneficial to the formation of MSA. Anthropogenic pollution from regional and local sources might be the dominant contributor to MSA in Beijing aerosol. This was the first report of MSA in aerosols collected in an inland site in China. This new finding would lead to the further study on the balance of sulfur in inland cities and its global biogeochemical cycle.

  17. Dynamical Conditions of Ice Supersaturation and Ice Nucleation in Convective Systems: A Comparative Analysis Between in Situ Aircraft Observations and WRF Simulations

    Science.gov (United States)

    D’Alessandro, John J.; Diao, Minghui; Wu, Chenglai; Liu, Xiaohong; Chen, Ming; Morrison, Hugh; Eidhammer, Trude; Jensen, Jorgen B.; Bansemer, Aaron; Zondlo, Mark A.; hide

    2017-01-01

    Occurrence frequency and dynamical conditions of ice supersaturation (ISS, where relative humidity with respect to ice (RHi) greater than 100%) are examined in the upper troposphere around convective activity. Comparisons are conducted between in situ airborne observations and the Weather Research and Forecasting model simulations using four double-moment microphysical schemes at temperatures less than or or equal to -40degdegC. All four schemes capture both clear-sky and in-cloud ISS conditions. However, the clear-sky (in-cloud) ISS conditions are completely (significantly) limited to the RHi thresholds of the Cooper parameterization. In all of the simulations, ISS occurrence frequencies are higher by approximately 3-4 orders of magnitude at higher updraft speeds (greater than 1 m s(exp -1) than those at the lower updraft speeds when ice water content (IWC) greater than 0.01 gm(exp -3), while observations show smaller differences up to approximately 1-2 orders of magnitude. The simulated ISS also occurs less frequently at weaker updrafts and downdrafts than observed. These results indicate that the simulations have a greater dependence on stronger updrafts to maintain/generate ISS at higher IWC. At lower IWC (less than or equal or 0.01 gm(exp -3), simulations unexpectedly show lower ISS frequencies at stronger updrafts. Overall, the Thompson aerosol-aware scheme has the closest magnitudes and frequencies of ISS greater than 20% to the observations, and the modified Morrison has the closest correlations between ISS frequencies and vertical velocity at higher IWC and number density. The Cooper parameterization often generates excessive ice crystals and therefore suppresses the frequency and magnitude of ISS, indicating that it should be initiated at higher ISS (e.g.,lees than or equal to 25%).

  18. Modal aerosol dynamics modeling

    Energy Technology Data Exchange (ETDEWEB)

    Whitby, E.R.; McMurry, P.H.; Shankar, U.; Binkowski, F.S.

    1991-02-01

    The report presents the governing equations for representing aerosol dynamics, based on several different representations of the aerosol size distribution. Analytical and numerical solution techniques for these governing equations are also reviewed. Described in detail is a computationally efficient numerical technique for simulating aerosol behavior in systems undergoing simultaneous heat transfer, fluid flow, and mass transfer in and between the gas and condensed phases. The technique belongs to a general class of models known as modal aerosol dynamics (MAD) models. These models solve for the temporal and spatial evolution of the particle size distribution function. Computational efficiency is achieved by representing the complete aerosol population as a sum of additive overlapping populations (modes), and solving for the time rate of change of integral moments of each mode. Applications of MAD models for simulating aerosol dynamics in continuous stirred tank aerosol reactors and flow aerosol reactors are provided. For the application to flow aerosol reactors, the discussion is developed in terms of considerations for merging a MAD model with the SIMPLER routine described by Patankar (1980). Considerations for incorporating a MAD model into the U.S. Environmental Protection Agency's Regional Particulate Model are also described. Numerical and analytical techniques for evaluating the size-space integrals of the modal dynamics equations (MDEs) are described. For multimodal logonormal distributions, an analytical expression for the coagulation integrals of the MDEs, applicable for all size regimes, is derived, and is within 20% of accurate numerical evaluation of the same moment coagulation integrals. A computationally efficient integration technique, based on Gauss-Hermite numerical integration, is also derived.

  19. Aerosols from biomass combustion

    Energy Technology Data Exchange (ETDEWEB)

    Nussbaumer, T.

    2001-07-01

    This report is the proceedings of a seminar on biomass combustion and aerosol production organised jointly by the International Energy Agency's (IEA) Task 32 on bio energy and the Swiss Federal Office of Energy (SFOE). This collection of 16 papers discusses the production of aerosols and fine particles by the burning of biomass and their effects. Expert knowledge on the environmental impact of aerosols, formation mechanisms, measurement technologies, methods of analysis and measures to be taken to reduce such emissions is presented. The seminar, visited by 50 participants from 11 countries, shows, according to the authors, that the reduction of aerosol emissions resulting from biomass combustion will remain a challenge for the future.

  20. Supersaturation, nucleation, and crystal growth during single- and biphasic dissolution of amorphous solid dispersions: polymer effects and implications for oral bioavailability enhancement of poorly water soluble drugs.

    Science.gov (United States)

    Sarode, Ashish L; Wang, Peng; Obara, Sakae; Worthen, David R

    2014-04-01

    The influence of polymers on the dissolution, supersaturation, crystallization, and partitioning of poorly water soluble compounds in biphasic media was evaluated. Amorphous solid dispersions (ASDs) containing felodipine (FLD) and itraconazole (ITZ) were prepared by hot melt mixing (HMM) using various polymers. The ASDs were analyzed using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and HPLC. Amorphous drug conversion was confirmed using DSC and PXRD, and drug stability by HPLC. Single- and biphasic dissolution studies of the ASDs with concurrent dynamic light scattering (DLS) and polarized light microscopic (PLM) analysis of precipitated drugs were performed. HPLC revealed no HMM-induced drug degradation. Maximum partitioning into the organic phase was dependent upon the degree of supersaturation. Although the highest supersaturation of FLD was attained using Eudragit® EPO and AQOAT® AS-LF with better nucleation and crystal growth inhibition using the latter, higher partitioning of the drug into the organic phase was achieved using Pharmacoat® 603 and Kollidon® VA-64 by maintaining supersaturation below critical nucleation. Critical supersaturation for ITZ was surpassed using all of the polymers, and partitioning was dependent upon nucleation and crystal growth inhibition in the order of Pharmacoat® 603>Eudragit® L-100-55>AQOAT® AS-LF. HMM drug-polymer systems that prevent drug nucleation by staying below critical supersaturation are more effective for partitioning than those that achieve the highest supersaturation.

  1. pH-Induced precipitation behavior of weakly basic compounds: determination of extent and duration of supersaturation using potentiometric titration and correlation to solid state properties.

    Science.gov (United States)

    Hsieh, Yi-Ling; Ilevbare, Grace A; Van Eerdenbrugh, Bernard; Box, Karl J; Sanchez-Felix, Manuel Vincente; Taylor, Lynne S

    2012-10-01

    To examine the precipitation and supersaturation behavior of ten weak bases in terms of the relationship between pH-concentration-time profiles and the solid state properties of the precipitated material. Initially the compound was dissolved at low pH, followed by titration with base to induce precipitation. Upon precipitation, small aliquots of acid or base were added to induce slight subsaturation and supersaturation respectively and the resultant pH gradient was determined. The concentration of the unionized species was calculated as a function of time and pH using mass and charge balance equations. Two patterns of behavior were observed in terms of the extent and duration of supersaturation arising following an increase in pH and this behavior could be rationalized based on the crystallization tendency of the compound. For compounds that did not readily crystallize, an amorphous precipitate was formed and a prolonged duration of supersaturation was observed. For compounds that precipitated to crystalline forms, the observed supersaturation was short-lived. This study showed that supersaturation behavior has significant correlation with the solid-state properties of the precipitate and that pH-metric titration methods can be utilized to evaluate the supersaturation behavior.

  2. Inhibition of crystal nucleation and growth by water-soluble polymers and its impact on the supersaturation profiles of amorphous drugs.

    Science.gov (United States)

    Ozaki, Shunsuke; Kushida, Ikuo; Yamashita, Taro; Hasebe, Takashi; Shirai, Osamu; Kano, Kenji

    2013-07-01

    The impact of water-soluble polymers on drug supersaturation behavior was investigated to elucidate the role of water-soluble polymers in enhancing the supersaturation levels of amorphous pharmaceuticals. Hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP), and Eudragit L-100 (Eudragit) were used as representative polymers, and griseofulvin and danazol were used as model drugs. Supersaturation profiles of amorphous drugs were measured in biorelevant dissolution tests. Crystal growth rate was measured from the decrease in dissolved drug concentration in the presence of seed crystals. Nucleation kinetics was evaluated by measuring the induction time for nucleation. All experiments were performed in the presence and absence of polymers. The degree of supersaturation of the amorphous model drugs increased with an increase in the inhibitory efficiency of polymers against crystal nucleation and growth (HPMC > PVP > Eudragit). In the presence of HPMC, the addition of seed crystals diminished the supersaturation ratio dramatically for griseofulvin and moderately for danazol. The results demonstrated that the polymers contributed to drug supersaturation by inhibiting both nucleation and growth. The effect of the polymers was drug dependent. The detailed characterization of polymers would allow selection of appropriate crystallization inhibitors and a planned quality control strategy for the development of supersaturable formulations. Copyright © 2013 Wiley Periodicals, Inc.

  3. Use of a molecular form technique for the penetration of supersaturated solutions of salicylic acid across silicone membranes and human skin in vitro.

    Science.gov (United States)

    Leveque, N; Raghavan, S L; Lane, M E; Hadgraft, J

    2006-08-01

    Permeation enhancement of salicylic acid (SA) from supersaturated solutions formed using a 'molecular form' technique was investigated. In a conventional cosolvent technique, two solvents are used, one in which the drug is considerably more soluble than the other. Propylene glycol and water have been predominantly used as cosolvents to create supersaturation in skin permeation enhancement. In this paper, we report the use of buffer solutions with different pHs as media for producing different molecular forms. Supersaturated solutions were prepared using pH 8:pH 2 (80:20 v/v), which gave a nominal pH when mixed of around 5. Model silicone membranes and human skin were used. Hydroxypropyl methyl cellulose (HPMC) was employed to stabilise the supersaturated states. Stability data showed that while the SA supersaturated solutions without HPMC crystallised between 15 min and 46 h depending on the degree of supersaturation, the solutions with HPMC were stable for more than 2 months. The flux of SA increased with the degree of saturation for solutions prepared in a 80:20 buffer pH 8/buffer pH 2 mixture. Although the fluxes of SA with and without HPMC were similar both through silicone membrane and human skin, HPMC was found to be effective in increasing the stability of supersaturated solutions of SA.

  4. MISR Aerosol Typing

    Science.gov (United States)

    Kahn, Ralph A.

    2014-01-01

    AeroCom is an open international initiative of scientists interested in the advancement of the understanding of global aerosol properties and aerosol impacts on climate. A central goal is to more strongly tie and constrain modeling efforts to observational data. A major element for exchanges between data and modeling groups are annual meetings. The meeting was held September 20 through October 2, 1014 and the organizers would like to post the presentations.

  5. Emergency Protection from Aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Cristy, G.A.

    2001-11-13

    Expedient methods were developed that could be used by an average person, using only materials readily available, to protect himself and his family from injury by toxic (e.g., radioactive) aerosols. The most effective means of protection was the use of a household vacuum cleaner to maintain a small positive pressure on a closed house during passage of the aerosol cloud. Protection factors of 800 and above were achieved.

  6. Effect of surfactants, gastric emptying, and dosage form on supersaturation of dipyridamole in an in vitro model simulating the stomach and duodenum.

    Science.gov (United States)

    Mitra, A; Fadda, H M

    2014-08-04

    The purpose of this study was to investigate the influence of gastric emptying patterns, surfactants, and dosage form on the supersaturation of a poorly soluble weakly basic drug, dipyridamole, using an in vitro model mimicking the dynamic environment of the upper gastrointestinal tract, and, furthermore, to evaluate the usefulness of this model in establishing correlations to in vivo bioavailability for drugs with solubility/dissolution limited absorption. A simulated stomach duodenum model comprising four compartments was used to assess supersaturation and precipitation kinetics as a function of time. It integrates physiologically relevant fluid volumes, fluid transfer rates, and pH changes of the upper GI tract. Monoexponential gastric emptying patterns simulating the fasted state were compared to linear gastric emptying patterns simulating the fed state. The effect of different surfactants commonly used in oral preparations, specifically, sodium lauryl sulfate (SLS), poloxamer-188, and polysorbate-80, on dipyridamole supersaturation was investigated while maintaining surface tension of the simulated gastric fluids at physiological levels and without obtaining artificial micellar solubilization of the drug. The supersaturation behavior of different dose strengths of dipyridamole was explored. Significant levels of dipyridamole supersaturation were observed in the duodenal compartment under all the different in vivo relevant conditions explored. Dipyridamole supersaturation ratios of up to 11-fold have been observed, and supersaturation has been maintained for up to 120 min. Lower duodenal concentrations of dipyridamole were observed under linear gastric emptying patterns compared to mononexponential gastric emptying. The mean duodenal area under concentration-time curves (AUC60min) for the dipyridamole concentration profile in the duodenal compartment is significantly different for all the surfactants explored (P supersaturation/precipitation kinetics of weakly

  7. Global distribution and climate forcing of marine organic aerosol – Part 1: Model improvements and evaluation

    Directory of Open Access Journals (Sweden)

    N. Meskhidze

    2011-07-01

    Full Text Available Marine organic aerosol emissions have been implemented and evaluated within the National Center of Atmospheric Research (NCAR's Community Atmosphere Model (CAM5 with the Pacific Northwest National Laboratory's 7-mode Modal Aerosol Module (MAM-7. Emissions of marine primary organic aerosols (POA, phytoplankton-produced isoprene- and monoterpenes-derived secondary organic aerosols (SOA and methane sulfonate (MS are shown to affect surface concentrations of organic aerosols in remote marine regions. Global emissions of submicron marine POA is estimated to be 7.9 and 9.4 Tg yr−1, for the Gantt et al. (2011 and Vignati et al. (2010 emission parameterizations, respectively. Marine sources of SOA and particulate MS (containing both sulfur and carbon atoms contribute an additional 0.2 and 5.1 Tg yr−1, respectively. Widespread areas over productive waters of the Northern Atlantic, Northern Pacific, and the Southern Ocean show marine-source submicron organic aerosol surface concentrations of 100 ng m−3, with values up to 400 ng m−3 over biologically productive areas. Comparison of long-term surface observations of water insoluble organic matter (WIOM with POA concentrations from the two emission parameterizations shows that both Gantt et al. (2011 and Vignati et al. (2010 formulations are able to capture the magnitude of marine organic aerosol concentrations, with the Gantt et al. (2011 parameterization attaining better seasonality. Model simulations show that the mixing state of the marine POA can impact the surface number concentration of cloud condensation nuclei (CCN. The largest increases (up to 20 % in CCN (at a supersaturation (S of 0.2 % number concentration are obtained over biologically productive ocean waters when marine organic aerosol is assumed to be externally mixed with sea-salt. Assuming marine organics are internally-mixed with sea-salt provides

  8. Global distribution and climate forcing of marine organic aerosol - Part 1: Model improvements and evaluation

    Science.gov (United States)

    Meskhidze, N.; Xu, J.; Gantt, B.; Zhang, Y.; Nenes, A.; Ghan, S. J.; Liu, X.; Easter, R.; Zaveri, R.

    2011-07-01

    Marine organic aerosol emissions have been implemented and evaluated within the National Center of Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM5) with the Pacific Northwest National Laboratory's 7-mode Modal Aerosol Module (MAM-7). Emissions of marine primary organic aerosols (POA), phytoplankton-produced isoprene- and monoterpenes-derived secondary organic aerosols (SOA) and methane sulfonate (MS-) are shown to affect surface concentrations of organic aerosols in remote marine regions. Global emissions of submicron marine POA is estimated to be 7.9 and 9.4 Tg yr-1, for the Gantt et al. (2011) and Vignati et al. (2010) emission parameterizations, respectively. Marine sources of SOA and particulate MS- (containing both sulfur and carbon atoms) contribute an additional 0.2 and 5.1 Tg yr-1, respectively. Widespread areas over productive waters of the Northern Atlantic, Northern Pacific, and the Southern Ocean show marine-source submicron organic aerosol surface concentrations of 100 ng m-3, with values up to 400 ng m-3 over biologically productive areas. Comparison of long-term surface observations of water insoluble organic matter (WIOM) with POA concentrations from the two emission parameterizations shows that both Gantt et al. (2011) and Vignati et al. (2010) formulations are able to capture the magnitude of marine organic aerosol concentrations, with the Gantt et al. (2011) parameterization attaining better seasonality. Model simulations show that the mixing state of the marine POA can impact the surface number concentration of cloud condensation nuclei (CCN). The largest increases (up to 20 %) in CCN (at a supersaturation (S) of 0.2 %) number concentration are obtained over biologically productive ocean waters when marine organic aerosol is assumed to be externally mixed with sea-salt. Assuming marine organics are internally-mixed with sea-salt provides diverse results with increase and decrease in the concentration of CCN over different parts of

  9. Global distribution and climate forcing of marine organic aerosol: 1. Model improvements and evaluation

    Science.gov (United States)

    Meskhidze, N.; Xu, J.; Gantt, B.; Zhang, Y.; Nenes, A.; Ghan, S. J.; Liu, X.; Easter, R.; Zaveri, R.

    2011-11-01

    Marine organic aerosol emissions have been implemented and evaluated within the National Center of Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM5) with the Pacific Northwest National Laboratory's 7-mode Modal Aerosol Module (MAM-7). Emissions of marine primary organic aerosols (POA), phytoplankton-produced isoprene- and monoterpenes-derived secondary organic aerosols (SOA) and methane sulfonate (MS-) are shown to affect surface concentrations of organic aerosols in remote marine regions. Global emissions of submicron marine POA is estimated to be 7.9 and 9.4 Tg yr-1, for the Gantt et al. (2011) and Vignati et al. (2010) emission parameterizations, respectively. Marine sources of SOA and particulate MS- (containing both sulfur and carbon atoms) contribute an additional 0.2 and 5.1 Tg yr-1, respectively. Widespread areas over productive waters of the Northern Atlantic, Northern Pacific, and the Southern Ocean show marine-source submicron organic aerosol surface concentrations of 100 ng m-3, with values up to 400 ng m-3 over biologically productive areas. Comparison of long-term surface observations of water insoluble organic matter (WIOM) with POA concentrations from the two emission parameterizations shows that despite revealed discrepancies (often more than a factor of 2), both Gantt et al. (2011) and Vignati et al. (2010) formulations are able to capture the magnitude of marine organic aerosol concentrations, with the Gantt et al. (2011) parameterization attaining better seasonality. Model simulations show that the mixing state of the marine POA can impact the surface number concentration of cloud condensation nuclei (CCN). The largest increases (up to 20%) in CCN (at a supersaturation (S) of 0.2%) number concentration are obtained over biologically productive ocean waters when marine organic aerosol is assumed to be externally mixed with sea-salt. Assuming marine organics are internally-mixed with sea-salt provides diverse results with increases

  10. Impact of aerosol composition on cloud condensation nuclei activity

    Directory of Open Access Journals (Sweden)

    Q. Zhang

    2012-04-01

    Full Text Available The impact of aerosol composition on cloud condensation nuclei (CCN activity were analyzed in this study based on field experiments carried out at downtown Tianjin, China in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS, respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%, and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5±2.6% to 12.8±6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reached up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7±19.0% to 46.5±12.3% correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlated well with observed NCCN at high SS (0.4%, but this consistence decreased with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4% respectively. Moreover, the stand deviation (SD of calculated NCCN increased with the decreasing of SS. A case study of CCN closure analyses indicated that the calculated error of NCCN could reach up to 34% at SS of 0.1% if aerosol composition were not included, and the calculated error decreased with the raising of SS. It is decreased to 9% at SS of 0.2%, and further decreased to 4% at SS of 0.4%.

  11. Impact of aerosol composition on cloud condensation nuclei activity

    Directory of Open Access Journals (Sweden)

    Q. Zhang

    2012-01-01

    Full Text Available The impact of aerosol composition on cloud condensation nuclei (CCN activity was analyzed in this study based on field experiments carried out at downtown Tianjin, China, in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC, whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS, respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%, and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5 ± 2.6% to 12.8 ± 6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reaches up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7 ± 19.0% to 46.5 ± 12.3%, correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlates well with observed NCCN at high SS (0.4%, but this correlation decreases with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4%, respectively. Moreover, the standard deviation (SD of calculated NCCN increases with the decreasing of SS. A case study of CCN closure analyses indicates that the calculated error of NCCN can reach up to 34% at SS of 0.1% if aerosol composition is not included, and the calculated error decreases with the raising of SS. It decreases to 9% at SS of 0.2%, and further decreases to 4% at SS of 0.4%.

  12. Patient's Guide to Aerosol Drug Delivery

    Science.gov (United States)

    ... Table of Contents Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 ................................................................ 1. Aerosol Drug Delivery: The Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Aerosol Drugs: The Major Categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 3. Aerosol Drug Delivery Devices: Small-Volume Nebulizers . . . . . . . . . . . . .17 4. Aerosol Drug ...

  13. Supersaturation of Dissolved Hydrogen and Methane in Rumen of Tibetan Sheep

    Science.gov (United States)

    Wang, Min; Ungerfeld, Emilio M.; Wang, Rong; Zhou, Chuan She; Basang, Zhu Zha; Ao, Si Man; Tan, Zhi Liang

    2016-01-01

    Hydrogen (H2) is an essential substrate for methanogens to produce methane (CH4), and also influences pathways of volatile fatty acids (VFA) production in the rumen. Dissolved H2 (H2 (aq)) is the form of H2 available to microbes, and dissolved CH4 (CH4 (aq)) is important for indicating methanogens activity. Rumen H2 (aq) concentration has been estimated by assuming equilibrium with headspace gaseous H2 (H2 (g)) concentration using Henry's law, and has also been directly measured in the liquid phase in some in vitro and in vivo experiments. In this in vivo study, H2 (aq) and CH4 (aq) concentration measured directly in rumen fluid and their corresponding concentrations estimated from their gaseous phase concentrations, were compared to investigate the existence of equilibrium between the gas and liquid phases. Twenty-four Tibetan sheep were randomly assigned to two mixed diets containing the same concentrate mixed with oat grass (OG diet) or barley straw (BS diet). Rumen gaseous phase and contents were sampled using rumenocentesis and oral stomach tubing, respectively. Rumen H2 (aq) and CH4 (aq) concentration and VFA profile differed between sheep fed OG and BS diets. Measured H2 (aq) and CH4 (aq) concentration were greater than H2 (aq) and CH4 (aq) concentrations estimated using gas concentrations, indicating lack of equilibrium between gas and liquid phase and supersaturation of H2 and CH4 in rumen fluid. As a consequence, Gibbs energy changes (ΔG) estimated for various metabolic pathways were different when calculated using dissolved gases concentrations directly measured and when using dissolved gases concentrations assuming equilibrium with the gaseous phase. Dissolved CH4, but not CH4 (g), was positively correlated with H2 (aq). Both H2 (aq) and H2 (g) concentrations were positively correlated with the molar percentage of butyrate and negatively correlated with the molar percentage of acetate. In summary, rumen fluid was supersaturated with both H2 and CH4

  14. Marine boundary layer sea spray aerosol number concentrations during VOCALS-REx

    Science.gov (United States)

    BLOT, R. P.; Clarke, A. D.; Howell, S. G.; Kapustin, V. N.

    2012-12-01

    Marine boundary layer (MBL) sea spray aerosols include all the inorganic material (sea-salt), organic matter from biogenic activity (plankton, bacteria, microalgae) and other surface active material (exopolymer) found at the surface ocean. SSA are released into the MBL by bursting air bubbles originating from wind-induced breaking waves at the ocean surface. SSA play a major role in the Earth's radiative budget due to their ability to significantly scatter the solar radiation and because of their high hygroscopicity SSA are effective as cloud condensation nuclei (CCN), thereby influencing cloud droplet numbers. Early studies generally focused on sizes larger than about 0.2μm due to their influence on atmospheric light propagation and also because of the instrumental difficulty to distinguish SSA from the more numerous natural sulfate and fine anthropogenic aerosol. During the last two decades, evidence from laboratory and field experiments showed the existence of SSA aerosol down to 0.01μm . Even though ultrafine SSA (fraction of the size distribution that dominate CCN at low supersaturations characteristic of stratus clouds near 0.3%. We analyze thermally resolved airborne aerosol measurements made in the MBL during the VAMOS Ocean-Cloud-Atmosphere-Land-Study Regional Experiment (VOCALS-REx) over the the Southeast Pacific. We confirm that open-ocean SSA effective as CCN are produced from bubble bursting processes are present at dry sizes as small as 0.040μm.

  15. Aerosol physicochemical effects on CCN activation simulated with the chemistry-climate model EMAC

    Science.gov (United States)

    Chang, D. Y.; Lelieveld, J.; Tost, H.; Steil, B.; Pozzer, A.; Yoon, J.

    2017-08-01

    This study uses the EMAC atmospheric chemistry-climate model to simulate cloud properties with a prognostic cloud droplet nucleation scheme. We present modeled global distributions of cloud condensation nuclei (CCN) number concentrations and CCN activation rates, together with the effective hygroscopicity parameter κ, to describe the aerosol chemical composition effect on CCN activation. Large particles can easily activate into cloud droplets, even at low κ values due to the dominant size effect in cloud droplet formation. Small particles are less efficiently activated as CCN, and are more sensitive to aerosol composition and supersaturation. Since the dominant fraction of small particles generally originates from anthropogenic precursor emissions over land, this study focuses on the influence of the continental atmosphere, using a prognostic cloud droplet nucleation scheme that considers aerosol-cloud interactions during cloud formation, together with a double-moment cloud microphysics scheme. The agreement of simulated clouds and climate with observations generally improves over the Northern Hemisphere continents, particularly high air pollution regions such as Eastern US, Europe, East Asia by accounting for aerosol-cloud interactions that include impacts of chemical composition on CCN activation.

  16. A key process controlling the wet removal of aerosols: new observational evidence

    Science.gov (United States)

    Ohata, Sho; Moteki, Nobuhiro; Mori, Tatsuhiro; Koike, Makoto; Kondo, Yutaka

    2016-01-01

    The lifetime and spatial distributions of accumulation-mode aerosols in a size range of approximately 0.05–1 μm, and thus their global and regional climate impacts, are primarily constrained by their removal via cloud and precipitation (wet removal). However, the microphysical process that predominantly controls the removal efficiency remains unidentified because of observational difficulties. Here, we demonstrate that the activation of aerosols to cloud droplets (nucleation scavenging) predominantly controls the wet removal efficiency of accumulation-mode aerosols, using water-insoluble black carbon as an observable particle tracer during the removal process. From simultaneous ground-based observations of black carbon in air (prior to removal) and in rainwater (after removal) in Tokyo, Japan, we found that the wet removal efficiency depends strongly on particle size, and the size dependence can be explained quantitatively by the observed size-dependent cloud-nucleating ability. Furthermore, our observational method provides an estimate of the effective supersaturation of water vapour in precipitating cloud clusters, a key parameter controlling nucleation scavenging. These novel data firmly indicate the importance of quantitative numerical simulations of the nucleation scavenging process to improve the model’s ability to predict the atmospheric aerosol burden and the resultant climate forcings, and enable a new validation of such simulations. PMID:27703169

  17. Physical metrology of aerosols; Metrologie physique des aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Boulaud, D.; Vendel, J. [CEA Saclay, 91 - Gif-sur-Yvette (France). Inst. de Protection et de Surete Nucleaire

    1996-12-31

    The various detection and measuring methods for aerosols are presented, and their selection is related to aerosol characteristics (size range, concentration or mass range), thermo-hydraulic conditions (carrier fluid temperature, pressure and flow rate) and to the measuring system conditions (measuring frequency, data collection speed, cost...). Methods based on aerosol dynamic properties (inertial, diffusional and electrical methods) and aerosol optical properties (localized and integral methods) are described and their performances and applications are compared

  18. A parameter analysis of a two-phase flow model for supersaturated total dissolved gas downstream spillways

    Institute of Scientific and Technical Information of China (English)

    杨慧霞; 李然; 梁瑞峰; 魏娟; 张沁

    2016-01-01

    A high concentration of the total dissolved gas (TDG) in a flow downstream high dams may cause the gas bubble disease in fishes. To better understand the spatial distribution of a supersaturated TDG, a numerical simulation approach for determining the TDG concentration is shown to be effective and convenient; however, the determination of the model parameters relies to a great extent on the observed field data, which are scarce but are very sensitive to the accuracy of the simulation. In this regard, determining the source parameter in the TDG transport equation is the primary concern of this paper. Observed field data from six different spillways in China are used to calibrate the source parameter. A relationship between the source parameter and the hydrodynamic characteristics is established. The inclusion of this relationship in the predictive relationship will enable an accurate and rapid estimation of the source parameter and may help in developing mitigation measures for the TDG supersaturation downstream the spillways.

  19. Effects of Dissolved Gas Supersaturation on Fish Residing in the Snake and Columbia Rivers, 1997 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, Brad A.

    1998-04-01

    Large amounts of spill at dams has commonly generated levels of dissolved gas supersaturation that are higher than levels established by state and federal agencies setting criteria for acceptable water quality in the Columbia and Snake Rivers. Large spill volumes are sometimes provided voluntarily to increase the proportion of migrating juvenile salmon that pass dams through nonturbine routes. However, total dissolved gas supersaturation (TDGS) resulting from spill in past decades has led to gas bubble disease (GBD) in fish. Therefore, during the period of high spill in 1997, the authors monitored the prevalence and severity of gas bubble disease by sampling resident fish in Ice Harbor reservoir and downstream from Ice Harbor and Bonneville Dams.

  20. One year of operation of Mammoth Pacific`s MP1-100 turbine with metastable, supersaturated expansions

    Energy Technology Data Exchange (ETDEWEB)

    Mines, G.L. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1997-12-31

    The Idaho National Engineering and Environmental Laboratory`s Heat Cycle Research project is developing a technology base that will increase the use of moderate-temperature hydrothermal resources to generate electrical power. One of the concepts under investigation is the use of a metastable, supersaturated turbine expansion. This expansion process supports a supersaturated vapor. If brought to equilibrium conditions, liquid condensate would be present in the expanding vapor. Analytical studies show that a plant designed to operate with this expansion will have an improvement in the brine effectiveness of up to 8% provided there is no adverse impact on turbine performance. Determining the impact of this expansion on turbine performance is focus of the project investigations being reported.

  1. Formation of Cosmic Crystals in Highly-Supersaturated Silicate Vapor Produced by Planetesimal Bow Shocks

    CERN Document Server

    Miura, H; Yamamoto, T; Nakamoto, T; Yamada, J; Tsukamoto, K; Nozawa, J

    2010-01-01

    Several lines of evidence suggest that fine silicate crystals observed in primitive meteorite and interplanetary dust particles (IDPs) nucleated in a supersaturated silicate vapor followed by crystalline growth. We investigated evaporation of $\\mu$m-sized silicate particles heated by a bow shock produced by a planetesimal orbiting in the gas in the early solar nebula and condensation of crystalline silicate from the vapor thus produced. Our numerical simulation of shock-wave heating showed that these {\\mu}m-sized particles evaporated almost completely when the bow shock is strong enough to cause melting of chondrule precursor dust particles. We found that the silicate vapor cools very rapidly with expansion into the ambient unshocked nebular region; the cooling rate is estimated, for instance, to be as high as 2000 K s$^{-1}$ for a vapor heated by a bow shock associated with a planetesimal of radius 1 km. The rapid cooling of the vapor leads to nonequilibrium gas-phase condensation of dust at temperatures muc...

  2. Mechanosynthesis of supersaturated solid solutions of Sn in near-equiatomic bcc FeCo

    Energy Technology Data Exchange (ETDEWEB)

    Loureiro, J.M. [CEMDRX, Physics Department, University of Coimbra, P-3004-516 Coimbra (Portugal); Costa, B.F.O., E-mail: benilde@ci.uc.pt [CEMDRX, Physics Department, University of Coimbra, P-3004-516 Coimbra (Portugal); Le Caeer, G. [IPR, UMR URI-CNRS 6251, Universite de Rennes I, Campus de Beaulieu, Bat 11A, F-35042 Rennes Cedex (France)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer (Fe{sub 50-x/2}Co{sub 50-x/2})Sn{sub x} mixtures are mechanically alloyed for x {<=} 33 at.%. Black-Right-Pointing-Pointer As-ground powders are studied by X-ray diffraction and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy. Black-Right-Pointing-Pointer Supersaturated solutions of Sn in disordered bcc FeCo alloys are formed in our dynamical conditions up to x {<=} 20 at.%. Black-Right-Pointing-Pointer This maximum Sn solubility found is much larger than the equilibrium solubility which is about 0.5 at.%. Black-Right-Pointing-Pointer The mean {sup 119}Sn hyperfine field in the bcc alloys is essentially constant with x and equal to 9.6 T at room temperature. - Abstract: The mechanosynthesis of Fe-Co-Sn ternary alloys from initial powder mixtures of composition (Fe{sub 50-x/2}Co{sub 50-x/2})Sn{sub x} is studied for x {<=} 33 at.%. Disordered nanocrystalline bcc solid solutions are formed in that way up to Sn contents as large as {approx}20 at.%. The dissolution of Sn in near-equiatomic bcc Fe-Co is unambiguously proven by X-ray diffraction and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy.

  3. Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

    Energy Technology Data Exchange (ETDEWEB)

    Herz, A., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.; Theska, F.; Wang, D., E-mail: andreas.herz@tu-ilmenau.de, E-mail: dong.wang@tu-ilmenau.de; Schaaf, P. [Department of Materials for Electronics and Electrical Engineering, Institute of Materials Science and Engineering and Institute of Micro- and Nanotechnologies MacroNano, TU Ilmenau, D-98693 Ilmenau (Germany); Friák, M. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v.v.i., Žižkova 22, CZ-616 62 Brno (Czech Republic); Central European Institute of Technology, CEITEC MU, Masaryk University, Kamenice 5, CZ-625 00 Brno (Czech Republic); Holec, D. [Department of Physical Metallurgy and Materials Testing, Montanuniversität Leoben, A-8700 Leoben (Austria); Šob, M. [Central European Institute of Technology, CEITEC MU, Masaryk University, Kamenice 5, CZ-625 00 Brno (Czech Republic); Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v.v.i., Žižkova 22, CZ-616 62 Brno (Czech Republic); Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 2, CZ-611 37 Brno (Czech Republic); Schneeweiss, O. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v.v.i., Žižkova 22, CZ-616 62 Brno (Czech Republic)

    2015-08-17

    Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observed phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.

  4. Heat of supersaturation-limited amyloid burst directly monitored by isothermal titration calorimetry

    Science.gov (United States)

    Ikenoue, Tatsuya; Lee, Young-Ho; Kardos, József; Yagi, Hisashi; Ikegami, Takahisa; Naiki, Hironobu; Goto, Yuji

    2014-01-01

    Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. Although the structural features of amyloid fibrils have become increasingly clearer, knowledge on the thermodynamics of fibrillation is limited. Furthermore, protein aggregation is not a target of calorimetry, one of the most powerful approaches used to study proteins. Here, with β2-microglobulin, a protein responsible for dialysis-related amyloidosis, we show direct heat measurements of the formation of amyloid fibrils using isothermal titration calorimetry (ITC). The spontaneous fibrillation after a lag phase was accompanied by exothermic heat. The thermodynamic parameters of fibrillation obtained under various protein concentrations and temperatures were consistent with the main-chain dominated structural model of fibrils, in which overall packing was less than that of the native structures. We also characterized the thermodynamics of amorphous aggregation, enabling the comparison of protein folding, amyloid fibrillation, and amorphous aggregation. These results indicate that ITC will become a promising approach for clarifying comprehensively the thermodynamics of protein folding and misfolding. PMID:24753579

  5. Deuterium supersaturation in low-energy plasma-loaded tungsten surfaces

    Science.gov (United States)

    Gao, L.; Jacob, W.; von Toussaint, U.; Manhard, A.; Balden, M.; Schmid, K.; Schwarz-Selinger, T.

    2017-01-01

    Fundamental understanding of hydrogen-metal interactions is challenging due to a lack of knowledge on defect production and/or evolution upon hydrogen ingression, especially for metals undergoing hydrogen irradiation with ion energy below the displacement thresholds reported in literature. Here, applying a novel low-energy argon-sputter depth profiling method with significantly improved depth resolution for tungsten (W) surfaces exposed to deuterium (D) plasma at 300 K, we show the existence of a 10 nm thick D-supersaturated surface layer (DSSL) with an unexpectedly high D concentration of ~10 at.% after irradiation with ion energy of 215 eV. Electron back-scatter diffraction reveals that the W lattice within this DSSL is highly distorted, thus strongly blurring the Kikuchi pattern. We explain this strong damage by the synergistic interaction of energetic D ions and solute D atoms with the W lattice. Solute D atoms prevent the recombination of vacancies with interstitial W atoms, which are produced by collisions of energetic D ions with W lattice atoms (Frenkel pairs). This proposed damaging mechanism could also be active on other hydrogen-irradiated metal surfaces. The present work provides deep insight into hydrogen-induced lattice distortion at plasma-metal interfaces and sheds light on its modelling work.

  6. Simulation and experimental analyses of dynamic strain aging of a supersaturated age hardenable aluminum alloy

    Energy Technology Data Exchange (ETDEWEB)

    Anjabin, N. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-9466 (Iran, Islamic Republic of); Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Karimi Taheri, A. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-9466 (Iran, Islamic Republic of); Kim, H.S., E-mail: hskim@postech.ac.kr [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2013-11-15

    In this paper, dynamic strain aging (DSA) behavior in a temperature range of (25–235 °C) and strain rate range of (10{sup −4}–5×10{sup −2} s{sup −1}) was investigated using a supersaturated age hardenable aluminum alloy. It was found that two mechanisms consisted of pinning of solute atoms to mobile dislocations and dynamic precipitation, were responsible for DSA in the testing conditions. The effects of both mechanisms on the macroscopic flow curve were studied using experimental and improved physically based material modeling approaches. It was shown that both phenomena lead to a negative strain rate hardening in the alloy. Dynamic precipitation acting at high temperature results in considerable work hardening and material strengthening. Taking into account these microstructural phenomena, the effects of deformation temperature and strain rate on the macroscopic flow behavior were discussed. The proposed modeling approach could successfully predict the experimental flow curve, possible jerky flow, and the corresponding serration types. Also, the spatial nucleation and propagation of the localized deformation bands along the specimen gauge length were recorded by a digital image correlation method and compared with the proposed model predictions.

  7. Ambulation During Periods of Supersaturation Increase Decompression Stress in Spacewalk Simulations

    Science.gov (United States)

    Pollock, N. W.; Natoli, M. J.; Martina, S. D.; Conkin, J.; Wessel, J. H., III; Gernhardt, M. L.

    2016-01-01

    Musculoskeletal activity accelerates inert gas elimination during oxygen breathing prior to decompression (prebreathe), but may also promote bubble formation (nucleation) and increase the risk of decompression sickness (DCS). The timing, pattern and intensity of musculoskeletal activity and the level of tissue supersaturation are likely critical to the net effect. Understanding the relationships is important to evaluate exercise prebreathe protocols and quantify decompression risk in gravity and microgravity environments. The NASA Prebreathe Reduction Program (PRP) combined oxygen prebreathe and exercise preceding a low pressure (4.3 psia; altitude equivalent of 30,300 ft [9,235 m]) simulation exposure of non-ambulatory subjects (a microgravity analog) to produce two protocols now used by astronauts preparing for extravehicular activity. One protocol included both upright cycling and non-cycling exercise (CEVIS: 'cycle ergometer vibration isolation system') and one protocol relied on non-cycling exercise only (ISLE: 'in-suit light exercise'). CEVIS trial data serve as control data for the current study to investigate the influence of ambulation exercise in 1G environments on bubble formation and the subsequent risk of DCS.

  8. Supersaturation and crystallization: non-equilibrium dynamics of amorphous solid dispersions for oral drug delivery.

    Science.gov (United States)

    Kawakami, Kohsaku

    2017-06-01

    Amorphous solid dispersions (ASDs) are one of the key formulation technologies that aid the development of poorly soluble candidates. However, their dynamic behaviors, including dissolution and crystallization processes, are still full of mystery. Further understanding of these processes should enhance their wider use. Areas covered: The first part of this review describes the current understanding of the dissolution of ASDs, where phase separation behavior is frequently involved and attempts to develop appropriate dissolution tests to achieve an in vitro-in vivo correlation are examined. The second part of this review discusses crystallization of the drug molecule with the eventual aim of establishing an accelerated testing protocol for predicting its physical stability. Expert opinion: The phase separation behavior from the supersaturated state during the dissolution test must be understood, and its relevance to the oral absorption behavior needs to be clarified. Research efforts should focus on the differences between the phase behavior in in vitro and in vivo situations. Initiation time of the crystallization was shown to be predicted only from storage and glass transition temperatures. This finding should encourage the establishment of testing protocol of the physical stability of ASDs.

  9. Understanding Ice Supersaturation, Particle Growth, and Number Concentration in Cirrus Clouds

    Science.gov (United States)

    Comstock, Jennifer M.; Lin, Ruei-Fong; Starr, David O'C.; Yang, Ping

    2008-01-01

    Many factors control the ice supersaturation and microphysical properties in cirrus clouds. We explore the effects of dynamic forcing, ice nucleation mechanisms, and ice crystal growth rate on the evolution and distribution of water vapor and cloud properties in nighttime cirrus clouds using a one-dimensional cloud model with bin microphysics and remote sensing measurements obtained at the Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility located near Lamont, OK. We forced the model using both large-scale vertical ascent and, for the first time, mean mesoscale velocity derived from radar Doppler velocity measurements. Both heterogeneous and homogeneous nucleation processes are explored, where a classical theory heterogeneous scheme is compared with empirical representations. We evaluated model simulations by examining both bulk cloud properties and distributions of measured radar reflectivity, lidar extinction, and water vapor profiles, as well as retrieved cloud microphysical properties. Our results suggest that mesoscale variability is the primary mechanism needed to reproduce observed quantities. Model sensitivity to the ice growth rate is also investigated. The most realistic simulations as compared with observations are forced using mesoscale waves, include fast ice crystal growth, and initiate ice by either homogeneous or heterogeneous nucleation. Simulated ice crystal number concentrations (tens to hundreds particles per liter) are typically two orders of magnitude smaller than previously published results based on aircraft measurements in cirrus clouds, although higher concentrations are possible in isolated pockets within the nucleation zone.

  10. Manufacture of nanosized apatite coatings on titanium with different surface treatments using a supersaturated calcification solution

    Directory of Open Access Journals (Sweden)

    Adrian Paz Ramos

    Full Text Available The biomimetic method is used for the deposition of calcium phosphate coatings (Ca - P on the surface of different biomaterials. However, the application of this method requires long exposure times in order to obtain a suitable layer thickness for its use in medical devices. In this paper, we present a fast approach to obtain apatite coatings on titanium, using a combination of supersaturated calcification solution (SCS with chemical modification of the titanium surface. Also, it was evaluated the effect of four different surface treatments on the apatite deposition rate. Commercially pure titanium plates were activated by chemical or thermochemical treatments. Then, the activated samples were immersed in a solution with high content of calcium and phosphate ions at 37 ºC for 24 h, mimicking the physiological conditions. The coatings were studied by Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD, scanning electron microscopy (SEM and energy dispersive X-ray spectroscopy (EDX. The use of SCS solutions allowed the formation of crystalline hydroxyapatite coatings within a period of 24 h with a thickness between 1 and 5.3 µm. Besides, precipitates of hydroxyapatite nanoparticles with a globular configuration, forming aggregates with submicrometer size, were found in SCS solutions.

  11. Influence of the bath gas on the condensation of supersaturated iron atom vapour at room temperature

    Science.gov (United States)

    Eremin, A.; Gurentsov, E.; Schulz, C.

    2008-03-01

    The influence of the kind of bath gas and its pressure on the iron nanoparticle formation and growth was investigated experimentally. Iron nanoparticles were synthesized from supersaturated iron vapour generated by ArF excimer laser pulse photolysis of gaseous Fe(CO)5 at room temperature. The particle size was determined by time-resolved laser-induced incandescence (TiRe-LII) as a function of time after photolysis at different experimental conditions. Additionally, final particles were sampled and analysed by transmission electron microscopy and by energy-dispersive x-ray analysis. The particle growth rate and the final particle size depended on the bath-gas composition and pressure. Increasing the argon bath-gas pressure accelerated the iron nanoparticle growth rate. In contrast to argon, no influence of helium on the particle growth rate was observed. The experimental results are compared with numerical simulations of particle surface growth, based on the model developed in previous investigations. The simulations indicate that the observed differences in the influence of the bath gas on the particle formation are caused by the species-dependent quenching probability of the active atom-particle complexes by the bath gas.

  12. Energy levels distribution in supersaturated silicon with titanium for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Pérez, E., E-mail: eduper@ele.uva.es; Castán, H.; García, H.; Dueñas, S.; Bailón, L. [Dept. de Electricidad y Electrónica, Universidad de Valladolid, ETSI Telecomunicación, Paseo de Belén 15, 47011 Valladolid (Spain); Montero, D.; García-Hernansanz, R.; García-Hemme, E.; González-Díaz, G. [Dept. de Física Aplicada III (Electricidad y Electrónica), Univ. Complutense de Madrid, 28040 Madrid (Spain); CEI Campus Moncloa, UCM-UPM, 28040 Madrid (Spain); Olea, J. [CEI Campus Moncloa, UCM-UPM, 28040 Madrid (Spain); Instituto de Energía Solar, E.T.S.I. de Telecomunicación, Univ. Politécnica de Madrid, 28040 Madrid (Spain)

    2015-01-12

    In the attempt to form an intermediate band in the bandgap of silicon substrates to give it the capability to absorb infrared radiation, we studied the deep levels in supersaturated silicon with titanium. The technique used to characterize the energy levels was the thermal admittance spectroscopy. Our experimental results showed that in samples with titanium concentration just under Mott limit there was a relationship among the activation energy value and the capture cross section value. This relationship obeys to the well known Meyer-Neldel rule, which typically appears in processes involving multiple excitations, like carrier capture/emission in deep levels, and it is generally observed in disordered systems. The obtained characteristic Meyer-Neldel parameters were Tmn = 176 K and kTmn = 15 meV. The energy value could be associated to the typical energy of the phonons in the substrate. The almost perfect adjust of all experimental data to the same straight line provides further evidence of the validity of the Meyer Neldel rule, and may contribute to obtain a deeper insight on the ultimate meaning of this phenomenon.

  13. Quantifying compositional impacts of ambient aerosol on cloud droplet formation

    Science.gov (United States)

    Lance, Sara

    It has been historically assumed that most of the uncertainty associated with the aerosol indirect effect on climate can be attributed to the unpredictability of updrafts. In Chapter 1, we analyze the sensitivity of cloud droplet number density, to realistic variations in aerosol chemical properties and to variable updraft velocities using a 1-dimensional cloud parcel model in three important environmental cases (continental, polluted and remote marine). The results suggest that aerosol chemical variability may be as important to the aerosol indirect effect as the effect of unresolved cloud dynamics, especially in polluted environments. We next used a continuous flow streamwise thermal gradient Cloud Condensation Nuclei counter (CCNc) to study the water-uptake properties of the ambient aerosol, by exposing an aerosol sample to a controlled water vapor supersaturation and counting the resulting number of droplets. In Chapter 2, we modeled and experimentally characterized the heat transfer properties and droplet growth within the CCNc. Chapter 3 describes results from the MIRAGE field campaign, in which the CCNc and a Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) were deployed at a ground-based site during March, 2006. Size-resolved CCN activation spectra and growth factor distributions of the ambient aerosol in Mexico City were obtained, and an analytical technique was developed to quantify a probability distribution of solute volume fractions for the CCN in addition to the aerosol mixing-state. The CCN were shown to be much less CCN active than ammonium sulfate, with water uptake properties more consistent with low molecular weight organic compounds. The pollution outflow from Mexico City was shown to have CCN with an even lower fraction of soluble material. "Chemical Closure" was attained for the CCN, by comparing the inferred solute volume fraction with that from direct chemical measurements. A clear diurnal pattern was observed for the CCN solute

  14. The potential for drug supersaturation during intestinal processing of lipid-based formulations may be enhanced for basic drugs.

    Science.gov (United States)

    Yeap, Yan Yan; Trevaskis, Natalie L; Porter, Christopher J H

    2013-07-01

    Co-administration of poorly water-soluble drugs (PWSD) with dietary or formulation lipids stimulates the formation of lipid colloidal phases such as vesicular and micellar species, and significantly expands the drug solubilization capacity of the small intestine. The mechanism of drug absorption from the solubilizing phases, however, has not been fully elucidated. Recently, we observed that drug supersaturation may be triggered during endogenous processing of lipid colloidal phases containing medium-chain lipid digestion products and that this may represent a mechanism to reverse the reduction in thermodynamic activity inherent in drug solubilization and thereby enhance absorption. The current studies expand these preliminary findings and explore the supersaturation tendency of five model PWSD during endogenous processing of intestinal colloidal phases containing long-chain lipid digestion products. Bile-lipid concentration ratios progressively increase during colloid transit through the gastrointestinal tract due to biliary dispersion of lipid digestion products and lipid absorption. The supersaturation potential was therefore evaluated under conditions of increasing bile and decreasing lipid concentrations and was found to be greater for the basic drugs cinnarizine (CIN) and halofantrine (HF), than the neutral drugs fenofibrate (FF) and danazol (DAN), and acidic drug meclofenamic acid (MFA). Assessment of intestinal absorptive flux using rat jejunal perfusion experiments subsequently showed that the absorption enhancement afforded by bile dilution of lipid colloidal phases was greater for CIN than DAN. The results confirm that bile plays a significantly greater role in the absorption of CIN (a weak base) from long-chain intestinal colloids when compared to DAN (an uncharged molecule) and that the difference reflects a greater propensity for supersaturation as intestinal colloids are dispersed and diluted by bile. The data suggest that coadministered digestible

  15. Effects of total dissolved gas supersaturated water on lethality and catalase activity of Chinese sucker (Myxocyprinus asiaticus Bleeker)

    Institute of Scientific and Technical Information of China (English)

    Shi-chao CHEN; Xiao-qing LIU; Wen JIANG; Ke-feng LI; Jun DU; Dan-zhou SHEN; Quan GONG

    2012-01-01

    Total dissolved gas (TDG) supersaturation caused by dam sluicing can result in gas bubble trauma (GBT) in fish and threaten their survival.In the present study,Chinese suckers (Myxocyprinus asiaticus Bleeker) were exposed to TDG supersaturated water at levels ranging from 120% to 145% for 48 h.The median lethal concentration (LC50) and the median lethal time (LT50) were determined to evaluate acute lethal effects on Chinese suckers.The results showed that the LC50 values of 4,6,8,and 10 h were 142%,137%,135%,and 130%,respectively.The LT50 values were 3.2,4.7,7.8,9.2,and 43.4 h,respectively,when TDG supersaturated levels were 145%,140%,135%,130%,and 125%.Furthermore,the biological responses in Chinese suckers were studied by assaying the catalase (CAT) activities in gills and muscles at the supersaturation level of 140% within LT50.The CAT activities in the gills and muscle tissues exhibited a regularity of a decrease after an increase.CAT activities in the muscles were increased significantly at 3/5LT50 (P<0.05) and then came back to the normal level.However,there were no significant differences between the treatment group (TDG level of 140%) and the control group (TDG level of 100%) on CAT activities in the gills before 3/5LT50 (P>0.05),but the activities were significantly lower than the normal level at 4/5LT50 and LT50 (P<0.05).

  16. Enhancing and Sustaining AMG 009 Dissolution from a Matrix Tablet Via Microenvironmental pH Modulation and Supersaturation

    OpenAIRE

    Bi, Mingda; Kyad, Ali; Kiang, Yuan-Hon; Alvarez-Nunez, Fernando; Alvarez, Francisco

    2011-01-01

    The objective of this study was to investigate the combined effect of pH modifiers and nucleation inhibitors on enhancing and sustaining the dissolution of AMG 009 tablet via supersaturation. Several bases and polymers were added as pH modifiers and nucleation inhibitors, respectively, to evaluate their impact on the dissolution of AMG 009 tablets. The results indicate that sodium carbonate, among the bases investigated, enhanced AMG 009 dissolution the most. HPMC E5 LV, among the nucleation ...

  17. Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions

    Science.gov (United States)

    Riipinen, I.; Rastak, N.; Pandis, S. N.

    2015-06-01

    We present a theoretical study investigating the cloud activation of multicomponent organic particles. We modeled these complex mixtures using solubility distributions (analogous to volatility distributions in the VBS, i.e., volatility basis set, approach), describing the mixture as a set of surrogate compounds with varying water solubilities in a given range. We conducted Köhler theory calculations for 144 different mixtures with varying solubility range, number of components, assumption about the organic mixture thermodynamics and the shape of the solubility distribution, yielding approximately 6000 unique cloud condensation nucleus (CCN)-activation points. The results from these comprehensive calculations were compared to three simplifying assumptions about organic aerosol solubility: (1) complete dissolution at the point of activation; (2) combining the aerosol solubility with the molar mass and density into a single effective hygroscopicity parameter κ; and (3) assuming a fixed water-soluble fraction ϵeff. The complete dissolution was able to reproduce the activation points with a reasonable accuracy only when the majority (70-80%) of the material was dissolved at the point of activation. The single-parameter representations of complex mixture solubility were confirmed to be powerful semi-empirical tools for representing the CCN activation of organic aerosol, predicting the activation diameter within 10% in most of the studied supersaturations. Depending mostly on the condensed-phase interactions between the organic molecules, material with solubilities larger than about 0.1-100 g L-1 could be treated as soluble in the CCN activation process over atmospherically relevant particle dry diameters and supersaturations. Our results indicate that understanding the details of the solubility distribution in the range of 0.1-100 g L-1 is thus critical for capturing the CCN activation, while resolution outside this solubility range will probably not add

  18. Aerosol chemistry in GLOBE

    Science.gov (United States)

    Clarke, Antony D.; Rothermel, Jeffry; Jarzembski, Maurice A.

    1993-01-01

    This task addresses the measurement and understanding of the physical and chemical properties of aerosol in remote regions that are responsible for aerosol backscatter at infrared wavelengths. Because it is representative of other clean areas, the remote Pacific is of extreme interest. Emphasis is on the determination size dependent aerosol properties that are required for modeling backscatter at various wavelengths and upon those features that may be used to help understand the nature, origin, cycling and climatology of these aerosols in the remote troposphere. Empirical relationships will be established between lidar measurements and backscatter derived from the aerosol microphysics as required by the NASA Doppler Lidar Program. This will include the analysis of results from the NASA GLOBE Survey Mission Flight Program. Additional instrument development and deployment will be carried out in order to extend and refine this data base. Identified activities include participation in groundbased and airborne experiments. Progress to date includes participation in, analysis of, and publication of results from Mauna Loa Backscatter Intercomparison Experiment (MABIE) and Global Backscatter Experiment (GLOBE).

  19. Generation of aerosolized drugs.

    Science.gov (United States)

    Wolff, R K; Niven, R W

    1994-01-01

    The expanding use of inhalation therapy has placed demands on current aerosol generation systems that are difficult to meet with current inhalers. The desire to deliver novel drug entities such as proteins and peptides, as well as complex formulations including liposomes and microspheres, requires delivery systems of improved efficiency that will target the lung in a reproducible manner. These efforts have also been spurred by the phase out of chlorofluorocarbons (CFCs) and this has included a directed search for alternative propellants. Consequently, a variety of new aerosol devices and methods of generating aerosols are being studied. This includes the use of freon replacement propellants, dry powder generation systems, aqueous unit spray systems and microprocessor controlled technologies. Each approach has advantages and disadvantages depending upon each principle of action and set of design variables. In addition, specific drugs may be better suited for one type of inhaler device vs. another. The extent to which aerosol generation systems achieve their goals is discussed together with a summary of selected papers presented at the recent International Congress of Aerosols in Medicine.

  20. Constraining the supersaturation density equation of state from core-collapse supernova simulations? Excluded volume extension of the baryons

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Tobias [University of Wroclaw, Wroclaw (Poland)

    2016-03-15

    In this article the role of the supersaturation density equation of state (EOS) is explored in simulations of failed core-collapse supernova explosions. Therefore the nuclear EOS is extended via a one-parameter excluded-volume description for baryons, taking into account their finite and increasing volume with increasing density in excess of saturation density. Parameters are selected such that the resulting supernova EOS represent extreme cases, with high pressure variations at supersaturation density which feature extreme stiff and soft EOS variants of the reference case, i.e. without excluded-volume corrections. Unlike in the interior of neutron stars with central densities in excess of several times saturation density, central densities of core-collapse supernovae reach only slightly above saturation density. Hence, the impact of the supersaturation density EOS on the supernova dynamics as well as the neutrino signal is found to be negligible. It is mainly determined from the low- and intermediate-density domain, which is left unmodified within this generalized excluded volume approach. (orig.)

  1. Gastrointestinal behavior of itraconazole in humans - Part 1: Supersaturation from a solid dispersion and a cyclodextrin-based solution.

    Science.gov (United States)

    Brouwers, Joachim; Geboers, Sophie; Mols, Raf; Tack, Jan; Augustijns, Patrick

    2017-06-15

    This study evaluated the fasted state gastrointestinal behavior of the lipophilic drug itraconazole, orally administered to healthy volunteers as either a solid dispersion (Sporanox(®) capsules) or a cyclodextrin-based solution (Sporanox(®) solution). Following intake of the drug products, gastric and duodenal fluids were aspirated and analyzed for itraconazole concentration, total content and solubilizing capacity. Release of itraconazole from the solid dispersion generated high and metastable supersaturated levels in the stomach, but the dissolved fraction in the duodenum remained extremely low (median 2.5%). After intake of the itraconazole solution, precipitation was limited in the stomach but pronounced in the small intestine. Still, the dissolved fraction of itraconazole in the duodenum (median 38%) appeared much higher than after intake of the solid dispersion, possibly explaining the improved absorption of itraconazole from the solution. As for the solid dispersion, the absorption-enabling ability of the solution appeared mainly related to increased intraluminal concentrations by means of supersaturation. Cyclodextrin-based solubilization of itraconazole occurred only in the case of limited intraluminal dilution, but did not further enhance itraconazole absorption. The obtained data will help to understand critical aspects of supersaturating drug delivery systems and act as direct reference for the optimization of in vitro simulation tools for gastrointestinal drug behavior. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Trends in the Assessment of Drug Supersaturation and Precipitation In Vitro Using Lipid-Based Delivery Systems.

    Science.gov (United States)

    Stillhart, Cordula; Kuentz, Martin

    2016-09-01

    The generation of drug supersaturation close to the absorptive site is an important mechanism of how several formulation technologies enhance oral absorption and bioavailability. Lipid-based formulations belong to the supersaturating drug delivery systems although this is not the only mechanism of how drug absorption is promoted in vivo. Different methods to determine drug supersaturation and precipitation from lipid-based formulations are described in the literature. Experimental in vitro setups vary according to their complexity and proximity to the in vivo conditions and, therefore, some tests are used for early formulation screening, while others better qualify for a later stage of development. The present commentary discusses this rapidly evolving field of in vitro testing with a special focus on the advancements in analytical techniques and new approaches of mechanistic modeling. The importance of considering a drug absorption sink is particularly emphasized. This commentary should help formulators in the pharmaceutical industry as well as in academia to make informed decisions on how to conduct in vitro tests for lipid-based delivery systems and to decide on the implications of experimental results. Copyright © 2016. Published by Elsevier Inc.

  3. Calcite Supersaturation and Precipitation Kinetics in the Lower Colorado River, Ail-American Canal and East Highline Canal

    Science.gov (United States)

    Suarez, D. L.

    1983-06-01

    In situ pH determinations and analysis of major ions in solution indicated that the lower Colorado River is supersaturated with respect to calcite throughout the entire daily cycle, in both winter and summer. Although the ion activity product was 4 to 6 times greater than the calcite solubility product, there was no detectable precipitation. Chemical analyses of water samples taken along 350 km of the river and canals from Parker Dam to the Salton Sea also revealed no evidence of calcium carbonate precipitation despite the inflow of saline and highly supersaturated irrigation return flows. Laboratory kinetic studies indicated that calcite crystal growth rates with Colorado River water are about 30% of the rate for pure Ca-HCO3 waters and about 70% of that for synthetic Colorado River water. Calcite precipitation by crystal growth in the river is limited by the combination of short residence times and unavailability of reactive calcite. Critical supersaturation levels necessary for heterogeneous nucleation do not occur; a high suspended load limits algal photosynthesis and thus prevents large decreases in daytime H2CO3 levels.

  4. CCN frequency distributions and aerosol chemical composition from long-term observations at European ACTRIS supersites

    Science.gov (United States)

    Decesari, Stefano; Rinaldi, Matteo; Schmale, Julia Yvonne; Gysel, Martin; Fröhlich, Roman; Poulain, Laurent; Henning, Silvia; Stratmann, Frank; Facchini, Maria Cristina

    2016-04-01

    Cloud droplet number concentration is regulated by the availability of aerosol acting as cloud condensation nuclei (CCN). Predicting the air concentrations of CCN involves knowledge of all physical and chemical processes that contribute to shape the particle size distribution and determine aerosol hygroscopicity. The relevance of specific atmospheric processes (e.g., nucleation, coagulation, condensation of secondary organic and inorganic aerosol, etc.) is time- and site-dependent, therefore the availability of long-term, time-resolved aerosol observations at locations representative of diverse environments is strategic for the validation of state-of-the-art chemical transport models suited to predict CCN concentrations. We focused on long-term (year-long) datasets of CCN and of aerosol composition data including black carbon, and inorganic as well as organic compounds from the Aerosol Chemical Speciation Monitor (ACSM) at selected ACTRIS supersites (http://www.actris.eu/). We discuss here the joint frequency distribution of CCN levels and of aerosol chemical components concentrations for two stations: an alpine site (Jungfraujoch, CH) and a central European rural site (Melpitz, DE). The CCN frequency distributions at Jungfraujoch are broad and generally correlated with the distributions of the concentrations of aerosol chemical components (e.g., high CCN concentrations are most frequently found for high organic matter or black carbon concentrations, and vice versa), which can be explained as an effect of the strong seasonality in the aerosol characteristics at the mountain site. The CCN frequency distributions in Melpitz show a much weaker overlap with the distributions of BC concentrations or other chemical compounds. However, especially at high CCN concentration levels, a statistical correlation with organic matter (OM) concentration can be observed. For instance, the number of CCN (with particle diameter between 20 and 250 nm) at a supersaturation of 0.7% is

  5. Chemical aerosol Raman detector

    Science.gov (United States)

    Aggarwal, R. L.; Farrar, L. W.; Di Cecca, S.; Amin, M.; Perkins, B. G.; Clark, M. L.; Jeys, T. H.; Sickenberger, D. W.; D'Amico, F. M.; Emmons, E. D.; Christesen, S. D.; Kreis, R. J.; Kilper, G. K.

    2017-03-01

    A sensitive chemical aerosol Raman detector (CARD) has been developed for the trace detection and identification of chemical particles in the ambient atmosphere. CARD includes an improved aerosol concentrator with a concentration factor of about 40 and a CCD camera for improved detection sensitivity. Aerosolized isovanillin, which is relatively safe, has been used to characterize the performance of the CARD. The limit of detection (SNR = 10) for isovanillin in 15 s has been determined to be 1.6 pg/cm3, which corresponds to 6.3 × 109 molecules/cm3 or 0.26 ppb. While less sensitive, CARD can also detect gases. This paper provides a more detailed description of the CARD hardware and detection algorithm than has previously been published.

  6. The Atmospheric Radiation Measurement Program May 2003 Intensive Operations Period Examining Aerosol Properties and Radiative Influences: Preface to Special Section

    Science.gov (United States)

    Ferrare, Richard; Feingold, Graham; Ghan, Steven; Ogren, John; Schmid, Beat; Schwartz, Stephen E.; Sheridan, Pat

    2006-01-01

    Atmospheric aerosols influence climate by scattering and absorbing radiation in clear air (direct effects) and by serving as cloud condensation nuclei, modifying the microphysical properties of clouds, influencing radiation and precipitation development (indirect effects). Much of present uncertainty in forcing of climate change is due to uncertainty in the relations between aerosol microphysical and optical properties and their radiative influences (direct effects) and between microphysical properties and their ability to serve as cloud condensation nuclei at given supersaturations (indirect effects). This paper introduces a special section that reports on a field campaign conducted at the Department of Energy Atmospheric Radiation Measurement site in North Central Oklahoma in May, 2003, examining these relations using in situ airborne measurements and surface-, airborne-, and space-based remote sensing.

  7. Stratospheric Aerosol Measurements

    Science.gov (United States)

    Pueschel, Rudolf, F.; Gore, Warren J. (Technical Monitor)

    1998-01-01

    Stratospheric aerosols affect the atmospheric energy balance by scattering and absorbing solar and terrestrial radiation. They also can alter stratospheric chemical cycles by catalyzing heterogeneous reactions which markedly perturb odd nitrogen, chlorine and ozone levels. Aerosol measurements by satellites began in NASA in 1975 with the Stratospheric Aerosol Measurement (SAM) program, to be followed by the Stratospheric Aerosol and Gas Experiment (SAGE) starting in 1979. Both programs employ the solar occultation, or Earth limb extinction, techniques. Major results of these activities include the discovery of polar stratospheric clouds (PSCs) in both hemispheres in winter, illustrations of the impacts of major (El Chichon 1982 and Pinatubo 1991) eruptions, and detection of a negative global trend in lower stratospheric/upper tropospheric aerosol extinction. This latter result can be considered a triumph of successful worldwide sulfur emission controls. The SAGE record will be continued and improved by SAGE III, currently scheduled for multiple launches beginning in 2000 as part of the Earth Observing System (EOS). The satellite program has been supplemented by in situ measurements aboard the ER-2 (20 km ceiling) since 1974, and from the DC-8 (13 km ceiling) aircraft beginning in 1989. Collection by wire impactors and subsequent electron microscopic and X-ray energy-dispersive analyses, and optical particle spectrometry have been the principle techniques. Major findings are: (1) The stratospheric background aerosol consists of dilute sulfuric acid droplets of around 0.1 micrometer modal diameter at concentration of tens to hundreds of monograms per cubic meter; (2) Soot from aircraft amounts to a fraction of one percent of the background total aerosol; (3) Volcanic eruptions perturb the sulfuric acid, but not the soot, aerosol abundance by several orders of magnitude; (4) PSCs contain nitric acid at temperatures below 195K, supporting chemical hypotheses

  8. Probabilistic description of ice-supersaturated layers in low resolution profiles of relative humidity

    Directory of Open Access Journals (Sweden)

    N. C. Dickson

    2010-02-01

    Full Text Available The global observation, assimilation and prediction in numerical models of ice super-saturated (ISS regions (ISSR are crucial if the climate impact of aircraft condensations trails (contrails is to be fully understood, and if, for example, contrail formation is to be avoided through aircraft operational measures. A robust assessment of the global distribution of ISSR will further this debate, and ISS event occurrence, frequency and spatial scales have recently attracted significant attention. The mean horizontal path length through ISSR as observed by MOZAIC aircraft is 150 km (±250 km. The average vertical thickness of ISS layers is 600–800 m (±575 m but layers ranging from 25 m to 3000 m have been observed, with up to one third of ISS layers thought to be less than 100 m deep. Given their small scales compared to typical atmospheric model grid sizes, statistical representations of the spatial scales of ISSR are required, in both horizontal and vertical dimensions, if global occurrence of ISSR is to be adequately represented in climate models.

    This paper uses radiosonde launches made by the UK Meteorological Office, from the British Isles, Gibraltar, St. Helena and the Falkland Islands between January 2002 and December 2006, to investigate the probabilistic occurrence of ISSR. Specifically each radiosonde profile is divided into 50- and 100-hPa pressure layers, to emulate the coarse vertical resolution of some atmospheric models. Then the high resolution observations contained within each thick pressure layer are used to calculate an average relative humidity and an ISS fraction for each individual thick pressure layer. These relative humidity pressure layer descriptions are then linked through a probability function to produce an s-shaped curve describing the ISS fraction in any average relative humidity pressure layer. An empirical investigation has shown that this one curve is statistically valid for mid-latitude locations

  9. Effect of layer thickness on device response of silicon heavily supersaturated with sulfur

    Directory of Open Access Journals (Sweden)

    David Hutchinson

    2016-05-01

    Full Text Available We report on a simple experiment in which the thickness of a hyperdoped silicon layer, supersaturated with sulfur by ion implantation followed by pulsed laser melting and rapid solidification, is systematically varied at constant average sulfur concentration, by varying the implantation energy, dose, and laser fluence. Contacts are deposited and the external quantum efficiency (EQE is measured for visible wavelengths. We posit that the sulfur layer primarily absorbs light but contributes negligible photocurrent, and we seek to support this by analyzing the EQE data for the different layer thicknesses in two interlocking ways. In the first, we use the measured concentration depth profiles to obtain the approximate layer thicknesses, and, for each wavelength, fit the EQE vs. layer thickness curve to obtain the absorption coefficient of hyperdoped silicon for that wavelength. Comparison to literature values for the hyperdoped silicon absorption coefficients [S.H. Pan et al. Applied Physics Letters 98, 121913 (2011] shows good agreement. Next, we essentially run this process in reverse; we fit with Beer’s law the curves of EQE vs. hyperdoped silicon absorption coefficient for those wavelengths that are primarily absorbed in the hyperdoped silicon layer, and find that the layer thicknesses obtained from the fit are in good agreement with the original values obtained from the depth profiles. We conclude that the data support our interpretation of the hyperdoped silicon layer as providing negligible photocurrent at high S concentrations. This work validates the absorption data of Pan et al. [Applied Physics Letters 98, 121913 (2011], and is consistent with reports of short mobility-lifetime products in hyperdoped layers. It suggests that for optoelectronic devices containing hyperdoped layers, the most important contribution to the above band gap photoresponse may be due to photons absorbed below the hyperdoped layer.

  10. Effect of layer thickness on device response of silicon heavily supersaturated with sulfur

    Science.gov (United States)

    Hutchinson, David; Mathews, Jay; Sullivan, Joseph T.; Akey, Austin; Aziz, Michael J.; Buonassisi, Tonio; Persans, Peter; Warrender, Jeffrey M.

    2016-05-01

    We report on a simple experiment in which the thickness of a hyperdoped silicon layer, supersaturated with sulfur by ion implantation followed by pulsed laser melting and rapid solidification, is systematically varied at constant average sulfur concentration, by varying the implantation energy, dose, and laser fluence. Contacts are deposited and the external quantum efficiency (EQE) is measured for visible wavelengths. We posit that the sulfur layer primarily absorbs light but contributes negligible photocurrent, and we seek to support this by analyzing the EQE data for the different layer thicknesses in two interlocking ways. In the first, we use the measured concentration depth profiles to obtain the approximate layer thicknesses, and, for each wavelength, fit the EQE vs. layer thickness curve to obtain the absorption coefficient of hyperdoped silicon for that wavelength. Comparison to literature values for the hyperdoped silicon absorption coefficients [S.H. Pan et al. Applied Physics Letters 98, 121913 (2011)] shows good agreement. Next, we essentially run this process in reverse; we fit with Beer's law the curves of EQE vs. hyperdoped silicon absorption coefficient for those wavelengths that are primarily absorbed in the hyperdoped silicon layer, and find that the layer thicknesses obtained from the fit are in good agreement with the original values obtained from the depth profiles. We conclude that the data support our interpretation of the hyperdoped silicon layer as providing negligible photocurrent at high S concentrations. This work validates the absorption data of Pan et al. [Applied Physics Letters 98, 121913 (2011)], and is consistent with reports of short mobility-lifetime products in hyperdoped layers. It suggests that for optoelectronic devices containing hyperdoped layers, the most important contribution to the above band gap photoresponse may be due to photons absorbed below the hyperdoped layer.

  11. Theoretical Analysis of Bubble Nucleation in Molten Steel Supersaturated with Nitrogen or Hydrogen

    Science.gov (United States)

    Li, Kangwei; Liu, Jianhua; Zhang, Jie; Shen, Shaobo

    2017-08-01

    The nucleation of bubbles in molten steel supersaturated with nitrogen or hydrogen was studied based on the theory of classical solidification nucleation. The mathematical models of critical radii for homogeneous and heterogeneous nucleation processes were derived. The results show that these critical radii are identical, but the volume of the bubble formed via the heterogeneous nucleation is only part of the spherical volume of the bubble formed via the homogeneous nucleation. Thus, the bubbles easily undergo heterogeneous nucleation on the surface of inclusions with poor wettability in molten steel. The effects of melt depth, nitrogen- or hydrogen-pretreatment pressure, and vacuum-treatment pressure on the critical-nucleation radius were studied based on the models derived. The results show that when the molten liquid is pretreated using nitrogen or hydrogen at 1 bar and, subsequently, treated at a vacuum pressure of 10-3 bar and a temperature of 1873 K (1600 °C), the bubbles nucleate spontaneously if the melt depth is below 0.39 m. Moreover, when the melt depths are 0.39 and 1.09 m, the critical-nucleation radii are 0 and 100 μm, respectively. When the melt depth is above 1.09 m, the critical-nucleation radius is greater than 100 μm. The critical melt depth for spontaneous nucleation and formation of different sizes of bubble nuclei increases when the molten steel is treated with nitrogen or hydrogen at a higher pretreatment pressure. However, the effects of the vacuum-treatment pressure on the critical melt depth for spontaneous nucleation and formation of different sizes of bubble nuclei are negligible. The experiments performed in this study helped in confirming part of the results of the theoretical analysis.

  12. Continuous, Pulsed Export of Methane-Supersaturated Meltwaters from the Bed of the Greenland Ice Sheet

    Science.gov (United States)

    Lamarche-Gagnon, G.; Wadham, J.; Beaton, A.; Fietzek, P.; Stanley, K. M.; Tedstone, A.; Sherwood Lollar, B.; Lacrampe Couloume, G.; Telling, J.; Liz, B.; Hawkings, J.; Kohler, T. J.; Zarsky, J. D.; Stibal, M.; Mowlem, M. C.

    2016-12-01

    Both past and present ice sheets have been proposed to cap large quantities of methane (CH4), on orders of magnitude significant enough to impact global greenhouse gas concentrations during periods of rapid ice retreat. However, to date most evidence for sub-ice sheet methane has been indirect, derived from calculations of the methanogenic potential of basal-ice microbial communities and biogeochemical models; field-based empirical measurements are lacking from large ice sheet catchments. Here, we present the first continuous, in situ record of dissolved methane export from a large catchment of the Greenland Ice Sheet (GrIS) in South West Greenland from May-July 2015. Our results indicate that glacial runoff was continuously supersaturated with methane over the observation period (dissolved CH4 concentrations of 30-700 nM), with total methane flux rising as subglacial discharge increased. Periodic subglacial drainage events, characterised by rapid changes (i.e. pulses) in meltwater hydrochemistry, also coincided with a rise in methane concentrations. We argue that these are likely indicative of the flushing of subglacial reservoirs of CH4 beneath the ice sheet. Total methane export was relatively modest when compared to global methane budgets, but too high to be explained by previously determined methanogenic rates from Greenland basal ice. Discrepancies between estimated Greenland methane reserves and observed fluxes stress the need to further investigate GrIS methane fluxes and sources, and suggest a more biogeochemically active subglacial environment than previously considered. Results indicate that future warming, and a coincident increase in ice melt rates, would likely make the GrIS, and by extension the Antarctic Ice Sheet, more significant sources of atmospheric methane, consequently acting as a positive feedback to a warming climate.

  13. Incorporation of Advanced Activation Treatments into CESM/CAM5: Model Evaluation and Impacts on Aerosol Indirect Forcing

    Science.gov (United States)

    Gantt, B.; He, J.; Zhang, X.; Zhang, Y.; Nenes, A.

    2013-12-01

    One of the greatest sources of uncertainty in climate science is the influence of aerosols on clouds through indirect effects, especially processes affecting the activation of aerosols into cloud droplets. Aerosol activation parameterizations incorporate much of the complexity of these processes, but the small differences between parameterizations can have a large impact on the spatiotemporal distribution of activated aerosols and the resulting cloud properties. Currently, most models simulate aerosol activation using the Abdul-Razzak and Ghan [2000] (AR-G00) scheme which derives an empiric calculation of the maximum parcel supersaturation based on the regression of numerical parcel calculations. The Community Atmosphere Model version 5.1.1 within the Community Earth Systems Model version 1.0.5 (CESM/CAM5) is an online-coupled Earth Systems model that simulates the interactions among aerosols, clouds, and radiation. CESM/CAM5 uses the AR-G00 scheme to simulate aerosol activation. In this work, we update CESM/CAM5 by incorporating a series of explicit aerosol activation schemes (Fountoukis and Nenes [2005]; Barahona and Nenes [2007]; Kumar et al. [2009]; and Barahona et al. [2010]) which account for the impacts of insoluble aerosol adsorption, giant cloud condensation nuclei activation kinetics, and entrainment on cloud droplet number concentrations (CDNC). CESM/CAM5 results with the empiric and explicit aerosol activation schemes are evaluated against several global datasets including observed low-level CDNC and satellite-derived cloud optical thickness (COT), liquid water path (LWP), and shortwave cloud forcing (SWCF). Globally, the incorporation of all explicit schemes leads to an average increase in column CDNC of 155%, increase (more negative) in SWCF of 13%, and decrease in surface shortwave radiation of -4%. In terms of climate impacts, these schemes result in an annual mean decrease in surface temperature and precipitation of -0.9 K (~0.2%) and -0.04 mm day

  14. Size Resolved measurements of aerosol hygroscopicity and mixing state during Green Ocean Amazon (GoAmazon) 2014

    Science.gov (United States)

    Thalman, R. M.; Artaxo, P.; Campuzano Jost, P.; Barbosa, H. M.; Day, D. A.; de Sá, S. S.; Hu, W.; Jimenez, J. L.; Kuang, C.; Palm, B. B.; Krüger, M. L.; Manzi, A. O.; Martin, S. T.; Poeschl, U.; Sedlacek, A. J., III; Senum, G.; Souza, R. A. F. D.; Springston, S. R.; Alexander, M. L.; Watson, T. B.; Wang, J.

    2014-12-01

    Measurements of size-resolved cloud condensation nucleai (CCN) spectra were performed at the T3 site of the Green Ocean Amazon (GoAmazon) field project located near Manacapuru, Brazil during 2014. The T3 site is a receptor site for both polluted urban down-wind (Manaus, BR a city of several million 70 km up wind) and background (Amazon rainforest) air-masses and can provide a contrast between clean and polluted conditions. Particle hygroscopicity (kappa) and mixing state were calculated from the particle activation spectrum measured by size selecting aerosols and exposing them to a wide range of supersaturation in the CCN counter (Droplet Measurement Technologies Continuous-Flow Streamwise Thermal Gradient CCN Chamber). The supersaturation was varied between 0.07 and 1.1% by changing a combination of both total flow rate and temperature gradient in the CCN counter. Measured spectra were examined for air masses with different level of influence from Manaus plume. Particle hygroscopicity generally peaked near noon local time which was broadly consistent with the trend in aerosol sulfate. The average kappa values during the first intensive operation period were 0.14±0.05, 0.14±0.04 and 0.16±0.06 for 75, 112 and 171 nm particles respectively. Evaluation of particle hygroscopicity and dispersion (mixing state) will be presented with respect to size and level of pollution.

  15. Use of In Situ Cloud Condensation Nuclei, Extinction, and Aerosol Size Distribution Measurements to Test a Method for Retrieving Cloud Condensation Nuclei Profiles From Surface Measurements

    Science.gov (United States)

    Ghan, Stephen J.; Rissman, Tracey A.; Ellman, Robert; Ferrare, Richard A.; Turner, David; Flynn, Connor; Wang, Jian; Ogren, John; Hudson, James; Jonsson, Haflidi H.; VanReken, Timothy; Flagan, Richard C.; Seinfeld, John H.

    2006-01-01

    If the aerosol composition and size distribution below cloud are uniform, the vertical profile of cloud condensation nuclei (CCN) concentration can be retrieved entirely from surface measurements of CCN concentration and particle humidification function and surface-based retrievals of relative humidity and aerosol extinction or backscatter. This provides the potential for long-term measurements of CCN concentrations near cloud base. We have used a combination of aircraft, surface in situ, and surface remote sensing measurements to test various aspects of the retrieval scheme. Our analysis leads us to the following conclusions. The retrieval works better for supersaturations of 0.1% than for 1% because CCN concentrations at 0.1% are controlled by the same particles that control extinction and backscatter. If in situ measurements of extinction are used, the retrieval explains a majority of the CCN variance at high supersaturation for at least two and perhaps five of the eight flights examined. The retrieval of the vertical profile of the humidification factor is not the major limitation of the CCN retrieval scheme. Vertical structure in the aerosol size distribution and composition is the dominant source of error in the CCN retrieval, but this vertical structure is difficult to measure from remote sensing at visible wavelengths.

  16. Aerosol mixing state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

    Directory of Open Access Journals (Sweden)

    S. Lance

    2013-05-01

    Full Text Available Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. κ-Köhler theory is used to evaluate the characteristic hygroscopicity parameter, κ*, for the CCN active aerosol population using both size-resolved HTMDA and size-resolved CCNc measurements. Organic mass fractions (forg are evaluated from size-resolved aerosol mass spectrometer (AMS measurements, from which predictions of the hygroscopicity parameter are compared against κ*. Strong diurnal changes in aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF events are correlated with an increased κ* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN at 0.51% ± 0.06% supersaturation can surpass by more than a factor of two the corresponding concentrations of 100 nm particles. We also find that at 06:00–08:00 LT throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally mixed fraction for 40 nm particles and 30% externally mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as "internally mixed". Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events, the early morning "rush hour" and the entire campaign. We show that κ* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for κ* versus particle size, which can be attributed to unresolved mixing state and the presence of refractory

  17. In vivo evaluation of supersaturation/precipitation/re-dissolution behavior of cinnarizine, a lipophilic weak base, in the gastrointestinal tract: the key process of oral absorption.

    Science.gov (United States)

    Tanaka, Yusuke; Kawakami, Ayaka; Nanimatsu, Ami; Horio, Misaki; Matsuoka, Jumpei; Wada, Takami; Kasaoka, Satoshi; Yoshikawa, Hiroshi

    2017-01-01

    The aim of this study is to evaluate how supersaturation, precipitation, and re-dissolution processes influence the intestinal absorption of cinnarizine (CNZ), a lipophilic weak base, by monitoring its plasma and luminal concentration-time profile, after oral administration as a HCl solution containing fluorescein isothiocyanate dextran (FD-4), a non-absorbable marker. In the in vitro pH shift experiment, the supersaturation stability was significantly lower when the higher-concentration solution of CNZ (pH1.5) was added to the simulated intestinal fluid. However, although the in vivo bioavailability after oral administration of high and low dose as HCl solutions was greatly improved compared to those as neutral suspensions, the difference in the supersaturation stability was not reflected in the improvement of the in vivo bioavailability. Analysis of CNZ and FD-4 concentrations in each segment of the gastrointestinal tract revealed that most of the CNZ precipitated in the duodenum after gastric emptying, and supersaturation was observed only in the duodenum. Thereafter, the precipitate was rapidly re-dissolved and absorbed in the upper and middle small intestine. The rapid re-dissolution may be caused by smaller particles of the precipitate. In this case, it is considered that the key process for the absorption of CNZ was re-dissolution, not supersaturation. Therefore, different supersaturation stabilities in different doses observed in in vitro precipitation experiment was not reflected to in vivo absorption. These findings may be useful to design efficient supersaturable formulations and to validate and improve current prediction methods. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Size-resolved aerosol and cloud condensation nuclei (CCN) properties in the remote marine South China Sea - Part 1: Observations and source classification

    Science.gov (United States)

    Atwood, Samuel A.; Reid, Jeffrey S.; Kreidenweis, Sonia M.; Blake, Donald R.; Jonsson, Haflidi H.; Lagrosas, Nofel D.; Xian, Peng; Reid, Elizabeth A.; Sessions, Walter R.; Simpas, James B.

    2017-01-01

    Ship-based measurements of aerosol and cloud condensation nuclei (CCN) properties are presented for 2 weeks of observations in remote marine regions of the South China Sea/East Sea during the southwestern monsoon (SWM) season. Smoke from extensive biomass burning throughout the Maritime Continent advected into this region during the SWM, where it was mixed with anthropogenic continental pollution and emissions from heavy shipping activities. Eight aerosol types were identified using a k-means cluster analysis with data from a size-resolved CCN characterization system. Interpretation of the clusters was supplemented by additional onboard aerosol and meteorological measurements, satellite, and model products for the region. A typical bimodal marine boundary layer background aerosol population was identified and observed mixing with accumulation mode aerosol from other sources, primarily smoke from fires in Borneo and Sumatra. Hygroscopicity was assessed using the κ parameter and was found to average 0.40 for samples dominated by aged accumulation mode smoke; 0.65 for accumulation mode marine aerosol; 0.60 in an anthropogenic aerosol plume; and 0.22 during a short period that was characterized by elevated levels of volatile organic compounds not associated with biomass burning impacts. As a special subset of the background marine aerosol, clean air masses substantially scrubbed of particles were observed following heavy precipitation or the passage of squall lines, with changes in observed aerosol properties occurring on the order of minutes. Average CN number concentrations, size distributions, and κ values are reported for each population type, along with CCN number concentrations for particles that activated at supersaturations between 0.14 and 0.85 %.

  19. The importance of aerosol mixing state and size-resolved composition on CCN concentration and the variation of the importance with atmospheric aging of aerosols

    Directory of Open Access Journals (Sweden)

    J. Wang

    2010-08-01

    Full Text Available Aerosol microphysics, chemical composition, and CCN concentrations were measured at the T0 urban supersite in Mexico City during Megacity Initiative: Local and Global Research Observations (MILAGRO in March 2006. The aerosol size distribution and composition often showed strong diurnal variation associated with traffic emissions and aging of aerosols through coagulation and local photochemical production of secondary aerosol species. CCN concentrations (NCCN are derived using Köhler theory from the measured aerosol size distribution and various simplified aerosol mixing state and chemical composition, and are compared to concurrent measurements at five supersaturations ranging from 0.11% to 0.35%. The influence of assumed mixing state on calculated NCCN is examined using both aerosols observed during MILAGRO and representative aerosol types. The results indicate that while ambient aerosols often consist of particles with a wide range of compositions at a given size, NCCN may be derived within ~20% assuming an internal mixture (i.e., particles at a given size are mixtures of all participating species, and have the identical composition if great majority of particles has an overall κ (hygroscopicity parameter value greater than 0.1. For a non-hygroscopic particle with a diameter of 100 nm, a 3 nm coating of sulfate or nitrate is sufficient to increase its κ from 0 to 0.1. The measurements during MILAGRO suggest that the mixing of non-hygroscopic primary organic aerosol (POA and black carbon (BC particles with photochemically produced hygroscopic species and thereby the increase of their κ to 0.1 take place in a few hours during daytime. This rapid process suggests that during daytime, a few tens of kilometers away for POA and BC sources, NCCN may be derived with sufficient accuracy by assuming an internal mixture, and using bulk chemical composition. The rapid mixing also

  20. Coexistence effect of UVA absorbers to increase their solubility and stability of supersaturation.

    Science.gov (United States)

    Endo, M; Mukawa, T; Sato, N; Maezawa, D; Ohtsu, Y; Kuroda, A; Wakabayashi, M; Asakura, K

    2014-12-01

    Sunscreens containing UVA absorbers in high concentrations are expected to be developed, since recent studies have suggested the possibility of involvement of UVA ray in skin cancer and early skin aging. Solubility and stability of supersaturation of UVA absorbers in UVB absorber were determined in the absence and the presence of cosmetic oil. Coexistence effect of UVA absorbers was analyzed to dissolve them in high concentrations. Two UVA absorbers, diethylamino hydroxybenzoyl hexyl benzoate (DHHB) and butyl methoxydibenzoylmethane (BMDM), a UVB absorber, 2-ethylhexyl methoxycinnamate (EHMC), and a cosmetic oil, 2-ethylhexyl ester of oligomer of hydroxystearic acid (EH-O-HSA), were used. Their solutions were prepared at 80°C and cooled to 5°C. The solid DHHB and/or BMDM were added to it, and the time evolution of concentrations of the UVA absorbers in the solution phase was monitored. At the saturation in the absence of EH-O-HSA at 5°C, weight ratio of DHHB and BMDM to EHMC was 0.39/1.00 and 0.22/1.00, respectively. Addition of EH-O-HSA slightly changed the solubility of DHHB and BMDM. When the weight ratio of EH-O-HSA to EHMC was 0.20/1.00, weight ratio of DHHB and BMDM to EHMC was 0.35/1.00 and 0.25/1.00, respectively at the saturation at 5°C. In the presence of EH-O-HSA, a strong coexistence effect of DHHB and BMDM was found on their solubility. A thermodynamically stable saturated solution at 5°C having the composition that DHHB: BMDM: EHMC: EH-O-HSA = 0.47: 0.46: 1.00: 0.20 was obtained by the simultaneous addition of solid DHHB and BMDM into the initial solution. The solution type composite having the highest concentrations of DHHB and BMDM prepared in this study exhibited critical wavelength at 368 nm that was just below the border for sunscreens being qualified as 'Broad Spectrum' protection under the new rule launched by US FDA. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  1. Inhibitory effect of hydroxypropyl methylcellulose acetate succinate on drug recrystallization from a supersaturated solution assessed using nuclear magnetic resonance measurements.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Yamamoto, Keiji; Moribe, Kunikazu

    2013-10-07

    We examined the inhibitory effect of hydroxypropyl methylcellulose acetate succinate (HPMC-AS) on drug recrystallization from a supersaturated solution using carbamazepine (CBZ) and phenytoin (PHT) as model drugs. HPMC-AS HF grade (HF) inhibited the recrystallization of CBZ more strongly than that by HPMC-AS LF grade (LF). 1D-1H NMR measurements showed that the molecular mobility of CBZ was clearly suppressed in the HF solution compared to that in the LF solution. Interaction between CBZ and HF in a supersaturated solution was directly detected using nuclear Overhauser effect spectroscopy (NOESY). The cross-peak intensity obtained using NOESY of HF protons with CBZ aromatic protons was greater than that with the amide proton, which indicated that CBZ had hydrophobic interactions with HF in a supersaturated solution. In contrast, no interaction was observed between CBZ and LF in the LF solution. Saturation transfer difference NMR measurement was used to determine the interaction sites between CBZ and HF. Strong interaction with CBZ was observed with the acetyl substituent of HPMC-AS although the interaction with the succinoyl substituent was quite small. The acetyl groups played an important role in the hydrophobic interaction between HF and CBZ. In addition, HF appeared to be more hydrophobic than LF because of the smaller ratio of the succinoyl substituent. This might be responsible for the strong hydrophobic interaction between HF and CBZ. The intermolecular interactions between CBZ and HPMC-AS shown by using NMR spectroscopy clearly explained the strength of inhibition of HPMC-AS on drug recrystallization.

  2. Lipid absorption triggers drug supersaturation at the intestinal unstirred water layer and promotes drug absorption from mixed micelles.

    Science.gov (United States)

    Yeap, Yan Yan; Trevaskis, Natalie L; Porter, Christopher J H

    2013-12-01

    To evaluate the potential for the acidic intestinal unstirred water layer (UWL) to induce drug supersaturation and enhance drug absorption from intestinal mixed micelles, via the promotion of fatty acid absorption. Using a single-pass rat jejunal perfusion model, the absorptive-flux of cinnarizine and (3)H-oleic acid from oleic acid-containing intestinal mixed micelles was assessed under normal acidic microclimate conditions and conditions where the acidic microclimate was attenuated via the co-administration of amiloride. As a control, the absorptive-flux of cinnarizine from micelles of Brij® 97 (a non-ionizable, non-absorbable surfactant) was assessed in the absence and presence of amiloride. Cinnarizine solubility was evaluated under conditions of decreasing pH and decreasing micellar lipid content to assess likely changes in solubilization and thermodynamic activity during micellar passage across the UWL. In the presence of amiloride, the absorptive-flux of cinnarizine and (3)H-oleic acid from mixed micelles decreased 6.5-fold and 3.0-fold, respectively. In contrast, the absorptive-flux of cinnarizine from Brij® 97 micelles remained unchanged by amiloride, and was significantly lower than from the long-chain micelles. Cinnarizine solubility in long-chain micelles decreased under conditions where pH and micellar lipid content decreased simultaneously. The acidic microclimate of the intestinal UWL promotes drug absorption from intestinal mixed micelles via the promotion of fatty acid absorption which subsequently stimulates drug supersaturation. The observations suggest that formulations (or food) containing absorbable lipids (or their digestive precursors) may outperform formulations that lack absorbable components since the latter do not benefit from lipid absorption-induced drug supersaturation.

  3. In situ molecular elucidation of drug supersaturation achieved by nano-sizing and amorphization of poorly water-soluble drug.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Yamamoto, Keiji; Moribe, Kunikazu

    2015-09-18

    Quantitative evaluation of drug supersaturation and nanoparticle formation was conducted using in situ evaluation techniques, including nuclear magnetic resonance (NMR) spectroscopy. We prepared a ternary complex of carbamazepine (CBZ) with hydroxypropyl methylcellulose (HPMC) and sodium dodecyl sulfate (SDS) to improve the drug concentration. Different preparation methods, including grinding and spray drying, were performed to prepare the ternary component products, ground mixture (GM) and spray-dried sample (SD), respectively. Although CBZ was completely amorphized in the ternary SD, CBZ was partially amorphized with the remaining CBZ crystals in the ternary GM. Aqueous dispersion of the ternary GM formed nanoparticles of around 150 nm, originating from the CBZ crystals in the ternary GM. In contrast, the ternary SD formed transparent solutions without a precipitate. The molecular-level evaluation using NMR measurements revealed that approximately half a dose of CBZ in the ternary GM dispersion was present as nanoparticles; however, CBZ in the ternary SD was completely dissolved in the aqueous solution. The characteristic difference between the solid states, followed by different preparation methods, induced different solution characteristics in the ternary GM and SD. The permeation study, using a dialysis membrane, showed that the CBZ concentration dissolved in the bulk water phase rapidly reduced in the ternary SD dispersion compared to the ternary GM dispersion; this demonstrated the advantage of ternary GM dispersion in the maintenance of CBZ supersaturation. Long-term maintenance of a supersaturated state of CBZ observed in the ternary GM dispersion rather than in the ternary SD dispersion was achieved by the inhibition of CBZ crystallization owing to the existence of CBZ nanoparticles in the ternary GM dispersion. Nanoparticle formation, combined with drug amorphization, could be a promising approach to improve drug concentrations. The detailed elucidation

  4. Sea Spray Aerosols

    DEFF Research Database (Denmark)

    Butcher, Andrew Charles

    emissions produced directly from bubble bursting as the result of air entrainment from breaking waves and particles generated from secondary emissions of volatile organic compounds. In the first paper, we study the chemical properties of particles produced from several sea water proxies with the use...... of a cloud condensation nuclei ounter. Proxy solutions with high inorganic salt concentrations and some organics produce sea spray aerosol particles with little change in cloud condensation activity relative to pure salts. Comparison is made between a frit based method for bubble production and a plunging...... a relationship between plunging jet particle ux, oceanic particle ux, and energy dissipation rate in both systems. Previous sea spray aerosol studies dissipate an order of magnitude more energy for the same particle ux production as the open ocean. A scaling factor related to the energy expended in air...

  5. Sea Spray Aerosols

    DEFF Research Database (Denmark)

    Butcher, Andrew Charles

    emissions produced directly from bubble bursting as the result of air entrainment from breaking waves and particles generated from secondary emissions of volatile organic compounds. In the first paper, we study the chemical properties of particles produced from several sea water proxies with the use...... of a cloud condensation nuclei ounter. Proxy solutions with high inorganic salt concentrations and some organics produce sea spray aerosol particles with little change in cloud condensation activity relative to pure salts. Comparison is made between a frit based method for bubble production and a plunging...... a relationship between plunging jet particle ux, oceanic particle ux, and energy dissipation rate in both systems. Previous sea spray aerosol studies dissipate an order of magnitude more energy for the same particle ux production as the open ocean. A scaling factor related to the energy expended in air...

  6. Acidic aerosol in urban air

    Energy Technology Data Exchange (ETDEWEB)

    Fukuda, M.; Yamaoka, S.; Miyazaki, T.; Oka, M.

    1982-01-01

    The distribution and chemical composition of acidic aerosol in Osaka City were investigated. Samples were collected at five sites in the city from June to September, 1979. Acidic aerosol was determined by the acid-base titration method, sulfate ion by barium chloride turbidimetry, nitrate ion by the xylenol method, and chloride ion by the mercury thiocyanate method. The concentration of acidic aerosol at five sites ranged from 7.7 micrograms per cubic meter to 10.0 micrograms per cubic meter, but mean concentrations in the residential area were slightly higher than those in the industrial area. When acidic aerosol concentrations were compared with concentrations of sulfate, nitrate, and chloride ions, a significant correlation was found between acidic aerosol and sulfate ion. The sum of the ion equivalents of the three types showed good correlation with the acidic aerosol equivalent during the whole period.

  7. Aerosol characterization during project POLINAT

    Energy Technology Data Exchange (ETDEWEB)

    Hagen, D.E.; Hopkins, A.R.; Paladino, J.D.; Whitefield, P.D. [Missouri Univ., Rolla, MO (United States). Cloud and Aerosol Sciences Lab.; Lilenfeld, H.V. [McDonnell Douglas Aerospace-East, St. Louis, MO (United States)

    1997-12-31

    The objectives of the aerosol/particulate characterization measurements of project POLINAT (POLlution from aircraft emissions In the North ATlantic flight corridor) are: to search for aerosol/particulate signatures of air traffic emissions in the region of the North Atlantic Flight Corridor; to search for the aerosol/particulate component of large scale enhancement (`corridor effects`) of air traffic related species in the North Atlantic region; to determine the effective emission indices for the aerosol/particulate component of engine exhaust in both the near and far field of aircraft exhaust plumes; to measure the dispersion and transformation of the aerosol/particulate component of aircraft emissions as a function of ambient condition; to characterize background levels of aerosol/particulate concentrations in the North Atlantic Region; and to determine effective emission indices for engine exhaust particulates for regimes beyond the jet phase of plume expansion. (author) 10 refs.

  8. Nanosuspensions of 10-hydroxycamptothecin that can maintain high and extended supersaturation to enhance oral absorption: preparation, characterization and in vitro/in vivo evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Pu, Xiaohui; Sun, Jin, E-mail: sunjin66@21cn.com [Shenyang Pharmaceutical University, Department of Biopharmaceutics, School of Pharmacy (China); Han, Jihong [Keele University, School of Pharmacy and Institute for Science and Technology in Medicine (United Kingdom); Lian, He; Zhang, Peng [Shenyang Pharmaceutical University, Department of Biopharmaceutics, School of Pharmacy (China); Yan, Zhongtian [Nantion Institutes for Food and Drug Control (China); He, Zhonggui, E-mail: hezhgui_student@yahoo.com.cn [Shenyang Pharmaceutical University, Department of Biopharmaceutics, School of Pharmacy (China)

    2013-11-15

    The purpose of the study was to prepare and characterize nanosuspensions that can maintain high and extended supersaturation to improve the dissolution and absorption of poorly soluble 10-hydroxycamptothecin (10-HCPT). 10-HCPT oral nanosuspensions (HCPT-Nanosuspensions) were produced on a laboratory-scale by microprecipitation- high pressure homogenization method. The particle morphology and the physical state were studied using transmission electron microscopy, X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC). Supersaturated dissolution tests were carried out with the paddle method. Caco-2 cell experiments were performed to imitate the oral absorption. The in vivo pharmacokinetics studies were undertaken in rats following oral administration. The 10-HCPT nanoparticles were 135 nm in dimension before lyophilization and were claviform or lump in shape. XRPD and DSC both confirmed that a portion of 10-HCPT was present in a crystalline state in nanosuspension. Supersaturated dissolution tests showed HCPT-Nanosuspensions could maintain high supersaturated level for an extended period time. The cell experiment on HCPT-Nanosuspensions showed a significantly higher uptake and greater membrane permeability compared with the other formulations. The pharmacokinetic test exhibited HCPT-Nanosuspensions had a similar pharmacokinetic performance with 10-HCPT solution. In conclusion, highly and extendedly supersaturated HCPT-Nanosuspensions have been prepared which could result in high peak concentration (C{sub max}) and great exposure (AUC) after oral administration.

  9. Nanosuspensions of 10-hydroxycamptothecin that can maintain high and extended supersaturation to enhance oral absorption: preparation, characterization and in vitro/in vivo evaluation

    Science.gov (United States)

    Pu, Xiaohui; Sun, Jin; Han, Jihong; Lian, He; Zhang, Peng; Yan, Zhongtian; He, Zhonggui

    2013-11-01

    The purpose of the study was to prepare and characterize nanosuspensions that can maintain high and extended supersaturation to improve the dissolution and absorption of poorly soluble 10-hydroxycamptothecin (10-HCPT). 10-HCPT oral nanosuspensions (HCPT-Nanosuspensions) were produced on a laboratory-scale by microprecipitation- high pressure homogenization method. The particle morphology and the physical state were studied using transmission electron microscopy, X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC). Supersaturated dissolution tests were carried out with the paddle method. Caco-2 cell experiments were performed to imitate the oral absorption. The in vivo pharmacokinetics studies were undertaken in rats following oral administration. The 10-HCPT nanoparticles were 135 nm in dimension before lyophilization and were claviform or lump in shape. XRPD and DSC both confirmed that a portion of 10-HCPT was present in a crystalline state in nanosuspension. Supersaturated dissolution tests showed HCPT-Nanosuspensions could maintain high supersaturated level for an extended period time. The cell experiment on HCPT-Nanosuspensions showed a significantly higher uptake and greater membrane permeability compared with the other formulations. The pharmacokinetic test exhibited HCPT-Nanosuspensions had a similar pharmacokinetic performance with 10-HCPT solution. In conclusion, highly and extendedly supersaturated HCPT-Nanosuspensions have been prepared which could result in high peak concentration ( C max) and great exposure (AUC) after oral administration.

  10. Molecular mechanism of polymer-assisting supersaturation of poorly water-soluble loratadine based on experimental observations and molecular dynamic simulations.

    Science.gov (United States)

    Zhang, Shenwu; Sun, Mengchi; Zhao, Yongshan; Song, Xuyang; He, Zhonggui; Wang, Jian; Sun, Jin

    2017-07-05

    Polymers have been usually used to retard nucleation and crystal growth in order to maintain supersaturation, yet their roles in inhibition of nucleation and crystal growth are poorly understood. In our work, the polymer-based supersaturation performances and molecular mechanisms of poorly aqueous soluble loratadine were investigated. Two common hydrophilic polymers (hydroxylpropylmethyl cellulose acetate succinate (HPMC-AS) and poly(vinylpyrrolidone-co-vinyl-acetate) (PVP-VA)) were used. It was found that HPMC-AS was a better polymer to prevent drug molecules from aggregation and to maintain the supersaturated state in solution than PVP-VA. The in vitro dissolution experiments showed that HPMC-AS solid dispersions had more rapid release at pH 4.5 and 6.8 media than PVP-VA solid dispersions under the un-sink condition. Moreover, molecular dynamic simulation results showed that HPMC-AS was more firmly absorbed onto a surface of the drug nanoparticles than PVP-VA due to bigger hydrophobic areas of HPMC-AS. Thereby, crystallization process of loratadine was inhibited in the presence of water to provide prolonged stability of the supersaturated state. In conclusion, polymers played a key role in maintaining supersaturation state of loratadine solid dispersions by strong drug-polymer interactions and the hydrophobic characteristic of polymers.

  11. Source attribution of climatically important aerosol properties measured at Paposo (Chile during VOCALS

    Directory of Open Access Journals (Sweden)

    D. Chand

    2010-11-01

    Full Text Available Measurements of submicron aerosol composition, light scattering, and size distribution were made from 17 October to 15 November 2008 at the elevated Paposo site (25° 0.4' S, 70° 27.01' W, 690 m a.s.l. on the Chilean coast as part of the VOCALS* Regional Experiment (REx. Based on the chemical composition measurements, a receptor modeling analysis using Positive Matrix Factorization (PMF was carried out, yielding four broad source categories of the aerosol mass, light scattering coefficient, and a proxy for cloud condensation nucleus (CCN concentration at 0.4% supersaturation derived from the size distribution measurements assuming an observed soluble mass fraction of 0.53. The sources resolved were biomass burning, marine, an urban-biofuels mix and a somewhat ambiguous mix of smelter emissions and mineral dust. The urban-biofuels mix is the most dominant aerosol mass component (52% followed by biomass burning (25%, smelter/soil dust (12% and marine (9% sources. The average (mean±std submicron aerosol mass concentration, aerosol light scattering coefficient and proxy CCN concentration were, 8.77±5.40 μg m−3, 21.9±11.0 Mm−1 and 548±210 cm−3, respectively. Sulfate is the dominant identified submicron species constituting roughly 40% of the dry mass (3.64±2.30 μg m−3, although the indentified soluble species constitute only 53% of the mass. Much of the unidentified mass is likely organic in nature. The relative importance of each aerosol source category is different depending upon whether mass, light scattering, or CCN concentration is being considered, indicating that the mean size of aerosols associated with each source are different. Marine aerosols do not appear to contribute to more than 10% to either mass, light scattering, or CCN concentration at this site. Back trajectory cluster analysis proved consistent with the PMF source attribution.

    *VOCALS: VAMOS** Ocean

  12. Source attribution of climatically important aerosol properties measured at Paposo (Chile during VOCALS

    Directory of Open Access Journals (Sweden)

    D. Chand

    2010-07-01

    Full Text Available Measurements of submicron aerosol composition, light scattering, and size distribution were made from 17 October to 15 November 2008 at the elevated Paposo site (25° 0.4' S, 70°27.01' W, 690 m a.s.l. on the Chilean coast as part of the VOCALS1 Regional Experiment (REx. Based on the chemical composition measurements, a receptor modeling analysis using Positive Matrix Factorization (PMF was carried out, yielding four broad source categories of the aerosol mass, light scattering coefficient, and a proxy for cloud condensation nucleus (CCN concentration at 0.4% supersaturation derived from the size distribution measurements assuming an observed soluble mass fraction of 0.53. The sources resolved were biomass burning, marine, an urban-biofuels mix and a somewhat ambiguous mix of smelter emissions and mineral dust. The urban-biofuels mix is the most dominant aerosol mass component (52% followed by biomass burning (25%, smelter/soil dust (12% and marine (9% sources. The average (mean±std submicron aerosol mass concentration, aerosol light scattering coefficient and proxy CCN concentration were, 8.77±5.40 μg m−3, 21.9±11.0 Mm−1 and 548±210 cm−3, respectively. Sulfate is the dominant identified submicron species constituting roughly 40% of the dry mass (3.64±2.30 μg m−3, although the indentified soluble species constitute only 53% of the mass. Much of the unidentified mass is likely organic in nature. The relative importance of each aerosol source category is different depending upon whether mass, light scattering, or CCN concentration is being considered, indicating that the mean size of aerosols associated with each source are different. Marine aerosols do not appear to contribute to more than 10% to either mass, light scattering, or CCN concentration at this site. Back trajectory cluster analysis proved consistent with the PMF source attribution.


    1 VOCALS

  13. Hygroscopic properties of urban aerosols and their cloud condensation nuclei activities measured in Seoul during the MAPS-Seoul campaign

    Science.gov (United States)

    Kim, Najin; Park, Minsu; Yum, Seong Soo; Park, Jong Sung; Song, In Ho; Shin, Hye Jung; Ahn, Joon Young; Kwak, Kyung-Hwan; Kim, Hwajin; Bae, Gwi-Nam; Lee, Gangwoong

    2017-03-01

    Aerosol physical properties, chemical compositions, hygroscopicity and cloud condensation nuclei (CCN) activities were measured in Seoul, the highly populated capital city of Korea, during the Megacity Air Pollution Studies (MAPS-Seoul) campaign, in May-June 2015. The average aerosol concentration for particle diameters >10 nm was 11787 ± 7421 cm-3 with dominant peaks at morning rush hours and in the afternoon due to frequent new particle formation (NPF) events. The average CCN concentration was 4075 ± 1812 cm-3 at 0.6% supersaturation, with little diurnal variation. The average hygroscopicity parameter (κ) value determined using a humidified tandem differential mobility analyzer (HTDMA) ranged 0.17-0.27 for a range of particle diameters (30-150 nm). The κ values derived using the aerosol mass spectrometer (AMS) data with three different methods were 0.32-0.34, significantly higher than those from HTDMA due to the uncertainties in the hygroscopicity values of different chemical compositions, especially organics and black carbon. Factors affecting the aerosol hygroscopicity seemed to be traffic and chemical processes during the NPF events. The CCN concentration predicted based on HTDMA κ data showed very good agreement with the measured one. Because of the overestimation of κ, CCN closure with the predicted CCN concentration based on AMS κ data over-predicted CCN concentration although the linear correlation between measured and predicted CCN concentration was still very good.

  14. The effect of mixing rates on the formation and growth of condensation aerosols in a model stagnation flow

    KAUST Repository

    Alshaarawi, Amjad

    2015-03-01

    A steady, laminar stagnation flow configuration is adopted to investigate numerically the interaction between condensing aerosol particles and gas-phase transport across a canonical mixing layer. The mixing rates are varied by adjusting the velocity and length scales of the stagnation flow parametrically. The effect of mixing rates on particle concentration, polydispersity, and mean droplet diameter is explored and discussed. This numerical study reveals a complex response of the aerosol to varying flow times. Depending on the flow time, the variation of the particle concentration in response to varying mixing rates falls into one of the two regimes. For fast mixing rates, the number density and volume fraction of the condensing particles increase with residence time (nucleation regime). On the contrary, for low mixing rates, number density decreases with residence time and volume fraction reaches a plateau (condensation regime). It is shown that vapor scavenging by the aerosol phase is key to explaining the transition between these two regimes. The results reported here are general and illustrate genuine features of the evolution of aerosols forming by condensation of supersaturated vapor from heat and mass transport across mixing layers.

  15. Integrated approach towards understanding interactions of mineral dust aerosol with warm clouds

    Science.gov (United States)

    Kumar, Prashant

    2011-12-01

    Mineral dust is ubiquitous in the atmosphere and represents a dominant type of particulate matter by mass. Dust particles can serve as cloud condensation nuclei (CCN), giant CCN (GCCN), or ice nuclei (IN), thereby, affecting cloud microphysics, albedo, and lifetime. Despite its well-recognized importance, assessments of dust impacts on clouds and climate remain highly uncertain. This thesis addresses the role of dust as CCN and GCCN with the goal of improving our understanding of dust-warm cloud interactions and their representation in climate models. Most studies to date focus on the soluble fraction of aerosol particles when describing cloud droplet nucleation, and overlook the interactions of the hydrophilic insoluble fraction with water vapor. A new approach to include such interactions (expressed by the process of water vapor adsorption) is explored, by combining multilayer Frenkel-Halsey-Hill (FHH) physical adsorption isotherm and curvature (Kelvin) effects. The importance of adsorption activation theory (FHH-AT) is corroborated by measurements of CCN activity of mineral aerosols generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. A new aerosol generation setup for CCN measurements was developed based on a dry generation technique capable of reproducing natural dust aerosol emission. Based on the dependence of critical supersaturation with particle dry diameter, it is found that the FHH-AT is a better framework for describing fresh (and unprocessed) dust CCN activity than the classical Kohler theory (KT). Ion Chromatography (IC) measurements performed on fresh regional dust samples indicate negligible soluble fraction, and support that water vapor adsorption is the prime source of CCN activity in the dust. CCN measurements with the commonly used wet generated mineral aerosol (from atomization of a dust aqueous suspension) are also carried out. Results indicate that the method is subject

  16. Topics in current aerosol research

    CERN Document Server

    Hidy, G M

    1971-01-01

    Topics in Current Aerosol Research deals with the fundamental aspects of aerosol science, with emphasis on experiment and theory describing highly dispersed aerosols (HDAs) as well as the dynamics of charged suspensions. Topics covered range from the basic properties of HDAs to their formation and methods of generation; sources of electric charges; interactions between fluid and aerosol particles; and one-dimensional motion of charged cloud of particles. This volume is comprised of 13 chapters and begins with an introduction to the basic properties of HDAs, followed by a discussion on the form

  17. Aerosol Data Assimilation at GMAO

    Science.gov (United States)

    da Silva, Arlindo M.; Buchard, Virginie

    2017-01-01

    This presentation presents an overview of the aerosol data assimilation work performed at GMAO. The GMAO Forward Processing system and the biomass burning emissions from QFED are first presented. Then, the current assimilation of Aerosol Optical Depth (AOD), performed by means of the analysis splitting method is briefly described, followed by some results on the quality control of observations using a Neural Network trained using AERONET AOD. Some applications are shown such as the Mount Pinatubo eruption in 1991 using the MERRA-2 aerosol dataset. Finally preliminary results on the EnKF implementation for aerosol assimilation are presented.

  18. Variations of atmospheric aerosols inside and outside cloud air

    Science.gov (United States)

    Kandalgaonkar, Suvarna; Tinmaker, M. I. R.

    2000-08-01

    Aitken Nuclei are present in the size range of 0.001 to 0.1 μm in appreciable concentrations in the continental and maritime environments. The main sources of these nuclei are mainly trace gases and they form out of gas to particle conversion which can occur through the nucleation of aerosol from the supersaturated gases and by the photochemical reactions associated with the absorption of solar radiation by molecules. Gas to particle conversions may be enhanced by high relative humidity and the presence of liquid water. During the summer monsoon months of 1980-1982 warm cloud modification experiment was conducted by IITM at Pune. During this experiment Aitken nuclei observations were made inside and outside the stratocumulus and cumulus clouds at the same altitude during three monsoon seasons. The results of the study suggested that observed higher concentration of Aitken nuclei inside the cloud may be due to more active gas-to-particle conversion process than in the cloud free air.

  19. Insulator-to-metal transition in vanadium supersaturated silicon: variable-range hopping and Kondo effect signatures

    Science.gov (United States)

    García-Hemme, E.; Montero, D.; García-Hernansanz, R.; Olea, J.; Mártil, I.; González-Díaz, G.

    2016-07-01

    We report the observation of the insulator-to-metal transition in crystalline silicon samples supersaturated with vanadium. Ion implantation followed by pulsed laser melting and rapid resolidification produce high quality single-crystalline silicon samples with vanadium concentrations that exceed equilibrium values in more than 5 orders of magnitude. Temperature-dependent analysis of the conductivity and Hall mobility values for temperatures from 10 K to 300 K indicate that a transition from an insulating to a metallic phase is obtained at a vanadium concentration between 1.1  ×  1020 and 1.3  ×  1021 cm-3. Samples in the insulating phase present a variable-range hopping transport mechanism with a Coulomb gap at the Fermi energy level. Electron wavefunction localization length increases from 61 to 82 nm as the vanadium concentration increases in the films, supporting the theory of impurity band merging from delocalization of levels states. On the metallic phase, electronic transport present a dispersion mechanism related with the Kondo effect, suggesting the presence of local magnetic moments in the vanadium supersaturated silicon material.

  20. Amorphous Aggregation of Cytochrome c with Inherently Low Amyloidogenicity Is Characterized by the Metastability of Supersaturation and the Phase Diagram.

    Science.gov (United States)

    Lin, Yuxi; Kardos, József; Imai, Mizue; Ikenoue, Tatsuya; Kinoshita, Misaki; Sugiki, Toshihiko; Ishimori, Koichiro; Goto, Yuji; Lee, Young-Ho

    2016-03-01

    Despite extensive studies on the folding and function of cytochrome c, the mechanisms underlying its aggregation remain largely unknown. We herein examined the aggregation behavior of the physiologically relevant two types of cytochrome c, metal-bound cytochrome c, and its fragment with high amyloidogenicity as predicted in alcohol/water mixtures. Although the aggregation propensity of holo cytochrome c was low due to high solubility, markedly unfolded apo cytochrome c, lacking the heme prosthetic group, strongly promoted the propensity for amorphous aggregation with increases in hydrophobicity. Silver-bound apo cytochrome c increased the capacity of fibrillar aggregation (i.e., protofibrils or immature fibrils) due to subtle structural changes of apo cytochrome c by strong binding of silver. However, mature amyloid fibrils were not detected for any of the cytochrome c variants or its fragment, even with extensive ultrasonication, which is a powerful amyloid inducer. These results revealed the intrinsically low amyloidogenicity of cytochrome c, which is beneficial for its homeostasis and function by facilitating the folding and minimizing irreversible amyloid formation. We propose that intrinsically low amyloidogenicity of cytochrome c is attributed to the low metastability of supersaturation. The phase diagram constructed based on solubility and aggregate type is useful for a comprehensive understanding of protein aggregation. Furthermore, amorphous aggregation, which is also viewed as a generic property of proteins, and amyloid fibrillation can be distinguished from each other by the metastability of supersaturation.

  1. Displacement of itraconazole from cyclodextrin complexes in biorelevant media: In vitro evaluation of supersaturation and precipitation behavior.

    Science.gov (United States)

    Stappaerts, Jef; Augustijns, Patrick

    2016-09-10

    Intestinal fluids contain several constituents with affinity for cyclodextrins that have the potential of displacing drugs from the cyclodextrin cavity by competition. In this study, the solubilizing capacity of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) for itraconazole was studied in presence of selected bile salts and phosphatidylcholine. Despite the fact that these competing agents significantly lowered the solubility of itraconazole in presence of cyclodextrins, the addition of concentrated solutions of these bile constituents to a solution containing itraconazole solubilized by HP-β-CD did not result in precipitation, even at bile salt and phospholipid concentrations where itraconazole precipitation would be anticipated based on solubility studies. This phenomenon was further investigated in more dynamic conditions via in vitro transfer studies, mimicking the gastrointestinal transfer of HP-β-CD solutions saturated with itraconazole. Intestinal supersaturation upon transfer was observed for all conditions tested and a concentration dependent impact of bile salts and phospholipids on the precipitation behavior of itraconazole was demonstrated: high concentrations of bile salts and phospholipids generated the highest degrees of supersaturation shortly after the transfer step but also resulted in stronger itraconazole precipitation at later time points. These findings demonstrate the possible impact of the variable intestinal fluid composition on the behavior of cyclodextrin containing formulations. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Treatment test of supernatant from sewage sludge by irradiation of high energy electron beams under supersaturation with oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Hosono, Masakazu; Arai, Hidehiko (Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment); Aizawa, Masaki; Shimooka, Toshio; Yamamoto, Ichiro; Shimizu, Ken; Sugiyama, Masashi.

    1993-02-01

    Supernatant comes from dewaterization of sewage sludge, and contains biologically nondegradable organics. Therefore, it is hard to be treated by conventional activated sludge method. The development of a new technology is required to decrease the chemical oxygen demand (COD) effectively below 30 mg/l. Irradiation of high energy electron beams can convert nondegradable organics in water into substances which are biodegradable. However, sufficient dissolved oxygen in water is needed to induce oxidation effectively. In the present study, the treatment of supernatant was studied using an apparatus which can be irradiated by high intensity electron beams in flow system under supersaturation with oxygen by pressurization up to 3 atms. The dependence of oxygen concentration on the reduction in absorbance at 230 nm of azo dye (Acid Red 265) aqueous solution was examined, and it was clarified that sufficient oxygen was supplied in the solution up to about 14 kGy under 3 atms of oxygen. Radiation treatment of supernatant which came from the leather works was carried out using the above apparatus. However, as this supernatant contained high concentration of nitrite, the nitrite was removed by limited aeration activated sludge method. By this pretreatment, COD was reduced from 200 mg/l to 53 mg/l. Then, the biodegradability of supernatant irradiated under supersaturation with oxygen was examined. The final COD of the supernatant was reduced below 30 mg/l by the combined method of irradiation of 7 kGy and biological treatment. (author).

  3. Enhancing and sustaining AMG 009 dissolution from a matrix tablet via microenvironmental pH modulation and supersaturation.

    Science.gov (United States)

    Bi, Mingda; Kyad, Ali; Kiang, Y-H; Kiang, Yuan-Hon; Alvarez-Nunez, Fernando; Alvarez, Francisco

    2011-12-01

    The objective of this study was to investigate the combined effect of pH modifiers and nucleation inhibitors on enhancing and sustaining the dissolution of AMG 009 tablet via supersaturation. Several bases and polymers were added as pH modifiers and nucleation inhibitors, respectively, to evaluate their impact on the dissolution of AMG 009 tablets. The results indicate that sodium carbonate, among the bases investigated, enhanced AMG 009 dissolution the most. HPMC E5 LV, among the nucleation inhibitors tested, was the most effective in sustaining AMG 009 supersaturation. The release of AMG 009 went from 4% for tablets which did not contain both sodium carbonate and HPMC E5 LV to 70% for the ones that did, resulting in a 17.5-fold increase in the extent of dissolution. The effect of compression force and disintegrant on the dissolution of tablets were also evaluated. The results indicate that compression force had no effect on AMG 009 release. The addition of disintegrating agents, on the other hand, decreased the dissolution of AMG 009.

  4. Optical and Hygroscopic Studies of Aerosols In Simulated Planetary Atmospheres

    Science.gov (United States)

    Hasenkopf, Christa A.

    2011-08-01

    in the UV-Vis than Khare et al. (1984) values. These results may imply that (a) photolysis is not the dominant source of aerosol on Titan, and/or (b) the optical retrievals are dominated by the more absorbing and scattering electric discharge generated aerosol. For the hygroscopicity studies, the optical growth of the early Earth analog at various relative humidities (RH) was measured, as well as a Titan analog for comparison. The retrieved hygroscopic parameter for the early Earth analog indicates that a humidified early Earth aerosol could have contributed to a larger antigreenhouse effect on the early Earth atmosphere than previously modeled with dry aerosol. Such effects would be important in regions where RH is greater than 50% because such high humidities are needed for significant amounts of water to be on the aerosol. The retrieved hygroscopicity parameter also indicates that the particles could activate into cloud droplets at reasonable supersaturations. In regions where the haze was dominant, it is expected that low particle concentrations, once activated into cloud droplets, would create short-lived, optically thin clouds. Such clouds, if predominant on the early Earth, would have a lower albedo than clouds today, thereby warming the planet relative to current day clouds.

  5. Determination of the supersaturation in the LiIO 3-HIO 3-H 2O system using a refractive index value at near saturation concentration

    Science.gov (United States)

    Lyutov, Lyudmil G.

    2009-09-01

    The exact determination of supersaturation is essential for the studies of crystal growth processes in solutions. Due to peculiarities in the solubility of LiIO 3, the refractive index of the solution is chosen as a measure of the supersaturation instead of undercooling. The experimental setup is based on a refractometer and a special setup to create supersaturation in the cuvette by means of successive evaporation of small amounts of solvent. The refractive index is measured at different solution concentrations and pH and the data are correlated as dependences of concentration and pH on the refractive index. The accuracy of the method and the adequacy of the model are discussed.

  6. Highly CO2-supersaturated melts in the Pannonian lithospheric mantle - A transient carbon reservoir?

    Science.gov (United States)

    Créon, Laura; Rouchon, Virgile; Youssef, Souhail; Rosenberg, Elisabeth; Delpech, Guillaume; Szabó, Csaba; Remusat, Laurent; Mostefaoui, Smail; Asimow, Paul D.; Antoshechkina, Paula M.; Ghiorso, Mark S.; Boller, Elodie; Guyot, François

    2017-08-01

    determined by Raman spectroscopy and microthermometry (0.1-1.1 GPa). The CO2/silicate melt mass ratios in the metasomatic agent that percolated through the lithospheric mantle below the Pannonian Basin are estimated to be between 9.0 and 25.4 wt.%, values consistent with metasomatism either by (1) silicate melts already supersaturated in CO2 before reaching lithospheric depths or (2) carbonatite melts that interacted with mantle peridotite to generate carbonated silicic melts. Taking the geodynamical context of the Pannonian Basin and our calculations of the CO2/silicate melt mass ratios in the metasomatic agent into account, we suggest that slab-derived melts initially containing up to 25 wt.% of CO2 migrated into the lithospheric mantle and exsolved CO2-rich fluid that became trapped in secondary fluid inclusions upon fracturing of the peridotite mineral matrix. We propose a first-order estimate of 2000 ppm as the minimal bulk CO2 concentration in the lithospheric mantle below the Pannonian Basin. This transient carbon reservoir is believed to be degassed through the Pannonian Basin due to volcanism and tectonic events, mostly focused along the lithospheric-scale regional Mid-Hungarian shear Zone.

  7. Aerosol absorption and radiative forcing

    Directory of Open Access Journals (Sweden)

    P. Stier

    2007-05-01

    Full Text Available We present a comprehensive examination of aerosol absorption with a focus on evaluating the sensitivity of the global distribution of aerosol absorption to key uncertainties in the process representation. For this purpose we extended the comprehensive aerosol-climate model ECHAM5-HAM by effective medium approximations for the calculation of aerosol effective refractive indices, updated black carbon refractive indices, new cloud radiative properties considering the effect of aerosol inclusions, as well as by modules for the calculation of long-wave aerosol radiative properties and instantaneous aerosol forcing. The evaluation of the simulated aerosol absorption optical depth with the AERONET sun-photometer network shows a good agreement in the large scale global patterns. On a regional basis it becomes evident that the update of the BC refractive indices to Bond and Bergstrom (2006 significantly improves the previous underestimation of the aerosol absorption optical depth. In the global annual-mean, absorption acts to reduce the short-wave anthropogenic aerosol top-of-atmosphere (TOA radiative forcing clear-sky from –0.79 to –0.53 W m−2 (33% and all-sky from –0.47 to –0.13 W m−2 (72%. Our results confirm that basic assumptions about the BC refractive index play a key role for aerosol absorption and radiative forcing. The effect of the usage of more accurate effective medium approximations is comparably small. We demonstrate that the diversity in the AeroCom land-surface albedo fields contributes to the uncertainty in the simulated anthropogenic aerosol radiative forcings: the usage of an upper versus lower bound of the AeroCom land albedos introduces a global annual-mean TOA forcing range of 0.19 W m−2 (36% clear-sky and of 0.12 W m−2 (92% all-sky. The consideration of black carbon inclusions on cloud radiative properties results in a small global annual-mean all-sky absorption of 0.05 W

  8. A case study on the formation and evolution of ice supersaturation in the vicinity of a warm conveyor belt's outflow region

    Directory of Open Access Journals (Sweden)

    P. Spichtinger

    2005-01-01

    Full Text Available A case study is presented on the formation and evolution of an ice-supersaturated region (ISSR that was detected by a radiosonde in NE Germany at 06:00 UTC 29 November 2000. The ISSR was situated in the vicinity of the outflow region of a warm conveyor belt associated with an intense event of cyclogenesis in the eastern North Atlantic. Using ECMWF analyses and trajectory calculations it is determined when the air parcels became supersaturated and later subsaturated again. In the case considered, the state of air parcel supersaturation can last for longer than 24h. The ISSR was unusually thick: while the mean vertical extension of ISSRs in NE Germany is about 500m, the one investigated here reached 3km. The ice-supersaturated region investigated was bordered both vertically and horizontally by strongly subsaturated air. Near the path of the radiosonde the ISSR was probably cloud free, as inferred from METEOSAT infrared images. However, at other locations within the ISSR it is probable that there were cirrus clouds. Relative humidity measurements obtained by the Lindenberg radiosonde are used to correct the negative bias of the ECMWF humidity and to construct two-dimensional maps of ice supersaturation over Europe during the considered period. A systematic backward trajectory analysis for the ISSRs on these maps shows that the ISSR air masses themselves experienced only a moderate upward motion during the previous days, whereas parts of the ISSRs were located just above strongly ascending air masses from the boundary layer. This indicates qualitatively that warm conveyor belts associated with mid-latitude cyclogenesis are disturbances that can induce the formation of ISSRs in the upper troposphere. The ISSR maps also lead us to a new perception of ISSRs as large dynamic regions of supersaturated air where cirrus clouds can be embedded at some locations while there is clear air at others.

  9. A case study on the formation and evolution of ice supersaturation in the vicinity of a warm conveyor belt’s outflow region

    Directory of Open Access Journals (Sweden)

    P. Spichtinger

    2004-12-01

    Full Text Available A case study is presented on the formation and evolution of an ice-supersaturated region (ISSR that was detected by a radiosonde in NE Germany at 06:00 UTC 29 November 2000. The ISSR was situated in the vicinity of the outflow region of a warm conveyor belt associated with an intense event of cyclogenesis in the eastern North Atlantic. Using ECMWF analyses and trajectory calculations it is determined when the air parcels became supersaturated and later subsaturated again. In the case considered, the state of air parcel supersaturation can last for longer than 24 h. The ISSR was unusually thick: while the mean vertical extension of ISSRs in NE Germany is about 500 m, the one investigated here reached 3 km. The investigated ice-supersaturated region was bordered both vertically and horizontally by strongly subsaturated air. Near the path of the radiosonde the ISSR was probably cloud free, as inferred from METEOSAT infrared images. However, at other locations within the ISSR it is probable that there were cirrus clouds. Relative humidity measurements are used to correct the negative bias of the ECMWF humidity and to construct two-dimensional maps of ice supersaturation over Europe during the considered period. A systematic backward trajectory analysis for the ISSRs on these maps shows that the ISSR air masses themselves experienced only a moderate upward motion during the previous days, whereas parts of the ISSRs were located just above strongly ascending air masses from the boundary layer. This indicates qualitatively that warm conveyor belts associated with mid-latitude cyclogenesis are disturbances that can induce the formation of ISSRs in the upper troposphere. The ISSR maps also lead us to a new perception of ISSRs as large dynamic regions of supersaturated air where cirrus clouds can be embedded at some locations while there is clear air at others.

  10. A win-win solution in oral delivery of lipophilic drugs: supersaturation via amorphous solid dispersions increases apparent solubility without sacrifice of intestinal membrane permeability.

    Science.gov (United States)

    Miller, Jonathan M; Beig, Avital; Carr, Robert A; Spence, Julie K; Dahan, Arik

    2012-07-02

    Recently, we have revealed a trade-off between solubility increase and permeability decrease when solubility-enabling oral formulations are employed. We have shown this trade-off phenomenon to be ubiquitous, and to exist whenever the aqueous solubility is increased via solubilizing excipients, regardless if the mechanism involves decreased free fraction (cyclodextrins complexation, surfactant micellization) or simple cosolvent solubilization. Discovering a way to increase drug solubility without concomitant decreased permeability represents a major advancement in oral delivery of lipophilic drugs and is the goal of this work. For this purpose, we sought to elucidate the solubility-permeability interplay when increased apparent solubility is obtained via supersaturation from an amorphous solid dispersion (ASD) formulation. A spray-dried ASD of the lipophilic drug progesterone was prepared in the hydrophilic polymer hydroxypropyl methylcellulose acetate succinate (HPMC-AS), which enabled supersaturation up to 4× the crystalline drug's aqueous solubility (8 μg/mL). The apparent permeability of progesterone from the ASD in HPMC-AS was then measured as a function of increasing apparent solubility (supersaturation) in the PAMPA and rat intestinal perfusion models. In contrast to previous cases in which apparent solubility increases via cyclodextrins, surfactants, and cosolvents resulted in decreased apparent permeability, supersaturation via ASD resulted in no decrease in apparent permeability with increasing apparent solubility. As a result, overall flux increased markedly with increasing apparent solubility via ASD as compared to the other formulation approaches. This work demonstrates that supersaturation via ASDs has a subtle yet powerful advantage over other solubility-enabling formulation approaches. That is, increased apparent solubility may be achieved without the expense of apparent intestinal membrane permeability. Thus, supersaturation via ASDs presents a

  11. Ultrafine sea spray aerosol over the southeastern Pacific: open-ocean contributions to marine boundary layer CCN

    Directory of Open Access Journals (Sweden)

    R. Blot

    2013-07-01

    Full Text Available Accurate measurements of natural aerosol emissions over the ocean are needed to estimate the anthropogenic impact on the environment. In this study, we measured sea spray aerosol (SSA concentrations with diameters larger than 0.040 μm produced by open-ocean breaking waves over the SEP (southeastern Pacific. Robust statistics were established through repeated airborne flights over 1000 km along 20° S from the coastline of Chile to 85° W during VOCALS-REx (VAMOS Ocean-Cloud-Atmosphere-Land-Study Regional Experiment. Non-volatile SSA number concentrations were inferred using a thermally resolved technique constrained for clean conditions with an Ångström exponent below 0.5, black carbon mass concentration at values lower than 15 ng m−3 and organic aerosol concentration less than 0.02 μg m−3. We found that number concentrations of SSAs active as cloud condensation nuclei (CCN for a supersaturation of 0.25% varied between 17 and 36 cm−3, but these did not increase with the increasing mean wind speed typically observed further offshore along 20° S. Concurrent increases in mean offshore precipitation rate in excess of about 1 mm d−1 indicate that scavenging of SSAs by precipitation exceeds increases in production at wind speeds above about 8 m s−1. This demonstrates the critical role of precipitation as a major sink of SSA over the remote ocean. Finally, we found that under clean conditions and for estimated stratus supersaturations between 0.20 and 0.43%, SSA represented about 20% of the total potential CCN along 20° S.

  12. Ultrafine sea spray aerosol over the south eastern Pacific: open-ocean contributions to marine boundary layer CCN

    Directory of Open Access Journals (Sweden)

    R. Blot

    2013-02-01

    Full Text Available Accurate measurements of natural aerosol emissions over the ocean are needed to estimate the anthropogenic impact on the environment. In this study, we measured Sea Spray Aerosol (SSA concentrations with diameters larger than 0.040 μm produced by open-ocean breaking waves over the SEP (South Eastern Pacific. Robust statistics were established through repeated airborne flights over 1000 km along 20° S from the coastline of Chile to 85° W during VOCALS-Rex (VAMOS Ocean-Cloud-Atmosphere-Land-Study Regional Experiment. Non-volatile SSA number concentrations were inferred using a thermally resolved technique constrained for clean conditions with Ångström exponent below 0.5, Black Carbon (BC mass concentration at values lower than 15 ng m−3 and Organic aerosols (Org concentration less than 0.02 μg m−3. We found that number concentrations of SSA active as CCN for a supersaturation of 0.25% varied between 17 cm−3 and 36 cm−3 but these did not increase with the increasing mean wind speed typically observed further offshore along 20° S. Concurrent increases in mean offshore precipitation rate in excess of about 1 mm d−1 indicate scavenging of SSA by precipitation exceeds increases in production at wind speeds above about 8 m s−1. This demonstrates the critical role of precipitation as a major sink of SSA over the remote ocean. Finally, we found that under clean conditions and for estimated stratus supersaturations between 0.20% and 0.43%, SSA represented about 20% of the total ambient CCN along 20° S.

  13. Importance of aerosol composition and mixing state for cloud droplet activation in the high Arctic

    Directory of Open Access Journals (Sweden)

    C. Leck

    2014-08-01

    Full Text Available Concentrations of cloud condensation nuclei (CCN were measured throughout an expedition by icebreaker around the central Arctic Ocean, including a 3 week ice drift operation at 87° N, from 3 August to 9 September 2008. In agreement with previous observations in the area and season median daily CCN concentrations at 0.2% water vapor supersaturation were typically in the range of 15 to 30 cm−3, but concentrations varied by two to three orders of magnitude over the expedition and were occasionally below 1 cm−3. The CCN concentrations were highest near the ice edge and fell by a factor of three in the first 48 h of transport from the open sea into the pack ice region. For longer transport times they increased again indicating a local source over the pack ice, suggested to be polymer gels, via drops injected into the air by bubbles bursting on open leads. By assuming Köhler theory and simulating the cloud nucleation process using a Lagrangian adiabatic air parcel model that solves the kinetic formulation for condensation of water on size resolved aerosol particles we inferred the properties of the unexplained non-water soluble aerosol fraction that is necessary for reproducing the observed concentrations of CCN. We propose that the portion of the internally/externally mixed water insoluble particles was larger in the corresponding smaller aerosol sizes ranges. These particles were physically and chemically behaving as polymer gels: the interaction of the hydrophilic and hydrophobic entities on the structures of polymer gels during cloud droplet activation would at first only show a partial wetting character and only weak hygroscopic growth. Given time, a high CCN activation efficiency is achieved, which is promoted by the hydrophilicity or surface-active properties of the gels. Thus the result in this study argues for that the behavior of the high Arctic aerosol in CCN-counters operating at water vapor supersaturations > 0.4% (high relative

  14. Competing effects of viscosity and surface-tension depression on the hygroscopicity and CCN activity of laboratory surrogates for oligomers in atmospheric aerosol

    Science.gov (United States)

    Hodas, N.; Zuend, A.; Shiraiwa, M.; Flagan, R. C.; Seinfeld, J.; Schilling, K.; Berkemeier, T.

    2015-12-01

    The presence of oligomers in biomass burning aerosol, as well as secondary organic aerosol derived from other sources, influences particle viscosity and can introduce kinetic limitations to water uptake. This, in turn, impacts aerosol optical properties and the efficiency with which these particles serve as cloud condensation nuclei (CCN). To explore the influence of organic-component viscosity on aerosol hygroscopicity, the water-uptake behavior of aerosol systems comprised of polyethylene glycol (PEG) and mixtures of PEG and ammonium sulfate (AS) was measured under sub- and supersaturated relative humidity (RH) conditions. Experiments were conducted with systems containing PEG with average molecular weights ranging from 200 to 10,000 g/mol, corresponding to a range in viscosity of 0.004 - 4.5 Pa s under dry conditions. While evidence suggests that viscous aerosol components can suppress water uptake at RH activity with increasing PEG molecular weight was observed. We attribute this to an increase in the efficiency with which PEG serves as a surfactant with increasing molecular weight. This effect is most pronounced for PEG-AS mixtures and, in fact, a modest increase in CCN activity is observed for the PEG 10,000-AS mixture as compared to pure AS, as evidenced by a 4% reduction in critical activation diameter. Experimental results are compared with calculations of hygroscopic growth at thermodynamic equilibrium using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients model and the potential influence of kinetic limitations to observed water uptake is further explored with the Kinetic Multi-Layer Model of Gas-Particle Interactions. Results suggest the competing effects of organic-component viscosity and surface-tension depression may lead to RH-dependent differences in hygroscopicity for oligomers and other surface-active compounds present in atmospheric aerosols, for which PEG serves as a surrogate in these experiments.

  15. Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state

    Science.gov (United States)

    Partanen, A.-I.; Dunne, E. M.; Bergman, T.; Laakso, A.; Kokkola, H.; Ovadnevaite, J.; Sogacheva, L.; Baisnée, D.; Sciare, J.; Manders, A.; O'Dowd, C.; de Leeuw, G.; Korhonen, H.

    2014-11-01

    Recently developed parameterizations for the sea spray aerosol source flux, encapsulating wave state, and its organic fraction were incorporated into the aerosol-climate model ECHAM-HAMMOZ to investigate the direct and indirect radiative effects of sea spray aerosol particles. Our simulated global sea salt emission of 805 Tg yr-1 (uncertainty range 378-1233 Tg yr-1) was much lower than typically found in previous studies. Modelled sea salt and sodium ion concentrations agreed relatively well with measurements in the smaller size ranges at Mace Head (annual normalized mean model bias -13% for particles with vacuum aerodynamic diameter Dva particles with aerodynamic diameter Da particles with Da particles with 2.5 μm biologically active months, suggesting a need to improve the parameterization of the organic sea spray fraction. Globally, the satellite-retrieved AOD over the oceans, using PARASOL data, was underestimated by the model (means over ocean 0.16 and 0.10, respectively); however, in the pristine region around Amsterdam Island the measured AOD fell well within the simulated uncertainty range. The simulated sea spray aerosol contribution to the indirect radiative effect was positive (0.3 W m-2), in contrast to previous studies. This positive effect was ascribed to the tendency of sea salt aerosol to suppress both the in-cloud supersaturation and the formation of cloud condensation nuclei from sulfate. These effects can be accounted for only in models with sufficiently detailed aerosol microphysics and physics-based parameterizations of cloud activation. However, due to a strong negative direct effect, the simulated effective radiative forcing (total radiative) effect was -0.2 W m-2. The simulated radiative effects of the primary marine organic emissions were small, with a direct effect of 0.03 W m-2 and an indirect effect of -0.07 W m-2.

  16. Effect of dysprosium on the kinetics and structural transformations during the decomposition of the supersaturated solid solution in magnesium-samarium alloys

    Science.gov (United States)

    Rokhlin, L. L.; Luk'yanova, E. A.; Tabachkova, N. Yu.; Dobatkina, T. V.; Tarytina, I. E.; Korol'kova, I. G.

    2017-03-01

    The effect of dysprosium added in the amounts such that it does not form an individual phase in equilibrium with solid magnesium on the decomposition of the supersaturated magnesium solid solution in Mg-Sm alloys is studied. The presence of dysprosium in Mg-Sm alloys is found to retard the decomposition of the supersaturated magnesium solid solution and to increase the hardening effect upon aging. When these alloys are aged, dysprosium is partly retained in the magnesium solid solution and partly enters into the compositions of the phases that form during the decomposition of the solid solution and are characteristic of Mg-Sm alloys.

  17. Why the free floating macrophyte Stratiotes aloides mainly grows in highly CO2-supersaturated waters

    DEFF Research Database (Denmark)

    Nielsen, Lasse Tor; Borum, Jens

    2008-01-01

    terrestrial traits with stomata, low specific leaf area and high chlorophyll a content, while offsets formed vegetatively and basal, submerged parts of mature plants showed traits in between. All submerged leaf types exhibited some ability to use HCO3- but only rosettes formed from turions had efficient HCO3....... We conclude that S. aloides requires consistently high CO2-supersaturation to support high growth and to complete its life cycle, and we infer that this requirement explains why S. aloides mainly grows in ponds, ditches and reed zones that are characterized by strong CO2-supersaturation....

  18. The relationship between cloud condensation nuclei (CCN concentration and light extinction of dried particles: indications of underlying aerosol processes and implications for satellite-based CCN estimates

    Directory of Open Access Journals (Sweden)

    Y. Shinozuka

    2015-01-01

    Full Text Available We examine the relationship between the number concentration of boundary-layer cloud condensation nuclei (CCN and light extinction to investigate underlying aerosol processes and satellite-based CCN estimates. Regression applied to a variety of airborne and ground-based measurements identifies the CCN (cm−3 at 0.4 ± 0.1% supersaturation with 100.3α +1.3 σ0.75 where σ (M m−1 is the 500 nm extinction coefficient by dried particles and α is the Angstrom exponent. The deviation of one kilometer horizontal average data from this approximation is typically within a factor of 2.0. ∂ log CCN/∂ log σ is less than unity because, among other explanations, aerosol growth processes generally make particles scatter more light without increasing their number. This, barring extensive data aggregation and special meteorology-aerosol connections, associates doubling of aerosol optical depth with less than doubling of CCN, contrary to common assumptions in satellite-based analysis of aerosol-cloud interactions.

  19. Aerosol dynamics in porous media

    NARCIS (Netherlands)

    Ghazaryan, Lilya

    2014-01-01

    In this thesis, a computational model was developed for the simulation of aerosol formation through nucleation, followed by condensation and evaporation and filtration by porous material. Understanding aerosol dynamics in porous media can help improving engineering models that are used in various in

  20. The Climatology of Australian Aerosol

    Science.gov (United States)

    Mitchell, Ross M.; Forgan, Bruce W.; Campbell, Susan K.

    2017-04-01

    Airborne particles or aerosols have long been recognised for their major contribution to uncertainty in climate change. In addition, aerosol amounts must be known for accurate atmospheric correction of remotely sensed images, and are required to accurately gauge the available solar resource. However, despite great advances in surface networks and satellite retrievals over recent years, long-term continental-scale aerosol data sets are lacking. Here we present an aerosol assessment over Australia based on combined sun photometer measurements from the Bureau of Meteorology Radiation Network and CSIRO/AeroSpan. The measurements are continental in coverage, comprising 22 stations, and generally decadal in timescale, totalling 207 station-years. Monthly climatologies are given at all stations. Spectral decomposition shows that the time series can be represented as a weighted sum of sinusoids with periods of 12, 6 and 4 months, corresponding to the annual cycle and its second and third harmonics. Their relative amplitudes and phase relationships lead to sawtooth-like waveforms sharply rising to an austral spring peak, with a slower decline often including a secondary peak during the summer. The amplitude and phase of these periodic components show significant regional change across the continent. Fits based on this harmonic analysis are used to separate the periodic and episodic components of the aerosol time series. An exploratory classification of the aerosol types is undertaken based on (a) the relative periodic amplitudes of the Ångström exponent and aerosol optical depth, (b) the relative amplitudes of the 6- and 4-month harmonic components of the aerosol optical depth, and (c) the ratio of episodic to periodic variation in aerosol optical depth. It is shown that Australian aerosol can be broadly grouped into three classes: tropical, arid and temperate. Statistically significant decadal trends are found at 4 of the 22 stations. Despite the apparently small

  1. An Indigenously Developed Insecticidal Aerosol

    Directory of Open Access Journals (Sweden)

    R. N. Varma

    1969-10-01

    Full Text Available A total of 6 "Test" insecticidal aerosols (TA-I to VI indigenously produced were tested during the years 1966-67 as suitable replacements for imported aerosols.TA-I produced deep yellow staining and a yellowish spray mist. Its capacity was only 120 ml fluid. TA-III types II and III containing modified aerosol formulation with "Esso solvent 3245" and mineral turpentine oil (Burmah Shelland Freon 12 11 (all indigenouswere comparable to he "SRA" in insecticidial efficacy. The container was also manufactured in the country and it compared well with the "SRA" in construction, resistance against rough usage and mechanical function. They were both finally approved for introduction in the services as replacement for imported aerosols. TA-IV performed well in inscticidial assessment, but the aerosols formulation. TA-V and VI were similar to TA-III types II and III respectively.

  2. Aerosols indirectly warm the Arctic

    Directory of Open Access Journals (Sweden)

    T. Mauritsen

    2010-07-01

    Full Text Available On average, airborne aerosol particles cool the Earth's surface directly by absorbing and scattering sunlight and indirectly by influencing cloud reflectivity, life time, thickness or extent. Here we show that over the central Arctic Ocean, where there is frequently a lack of aerosol particles upon which clouds may form, a small increase in aerosol loading may enhance cloudiness thereby likely causing a climatologically significant warming at the ice-covered Arctic surface. Under these low concentration conditions cloud droplets grow to drizzle sizes and fall, even in the absence of collisions and coalescence, thereby diminishing cloud water. Evidence from a case study suggests that interactions between aerosol, clouds and precipitation could be responsible for attaining the observed low aerosol concentrations.

  3. Mass-based hygroscopicity parameter interaction model and measurement of atmospheric aerosol water uptake

    Directory of Open Access Journals (Sweden)

    E. Mikhailov

    2013-01-01

    collected from boreal rural air and from pristine tropical rainforest air (secondary organic aerosol we present first mass-based measurements of water uptake over a wide range of relative humidity (1–99.4% obtained with a new filter-based differential hygroscopicity analyzer (FDHA technique. For these samples the concentration dependence of κm can be described by a simple KIM model equation based on observable mass growth factors and a total of only six fit parameters summarizing the combined effects of the dilute hygroscopicity parameters, self- and cross-interaction parameters, and solubilities of all involved chemical components. One of the fit parameters represents κm0 and can be used to predict critical dry diameters for the activation of cloud condensation nuclei (CCN as a function of water vapor supersaturation according to Köhler theory. For sodium chloride and ammonium sulfate reference particles as well as for pristine rainforest aerosols consisting mostly of secondary organic matter, we obtained good agreement between the KIM predictions and measurement data of CCN activation.

    The application of KIM and mass-based measurement techniques shall help to bridge gaps in the current understanding of water uptake by atmospheric aerosols: (1 the gap between hygroscopicity parameters determined by hygroscopic growth measurements under sub-saturated conditions and by CCN activation measurements at water vapor supersaturation, and (2 the gap between the results of simplified single parameter models widely used in atmospheric or climate science and the results of complex multi-parameter ion- and molecule-interaction models frequently used in physical chemistry and solution thermodynamics (e.g., AIM, E-AIM, ADDEM, UNIFAC, AIOMFAC.

  4. Aerosol and cloud microphysics covariability in the northeast Pacific boundary layer estimated with ship-based and satellite remote sensing observations: NE Pacific Aerosol-Cloud Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Painemal, David [Science Systems and Applications, Inc., Hampton Virginia USA; NASA Langley Research Center, Hampton Virginia USA; Chiu, J. -Y. Christine [Department of Meteorology, University of Reading, Reading UK; Minnis, Patrick [NASA Langley Research Center, Hampton Virginia USA; Yost, Christopher [Science Systems and Applications, Inc., Hampton Virginia USA; Zhou, Xiaoli [Department of Atmospheric and Oceanic Sciences, McGill University, Montreal Quebec Canada; Cadeddu, Maria [Environmental Science Division, Argonne National Laboratory, Lemont Illinois USA; Eloranta, Edwin [Space Science and Engineering Center, University of Wisconsin-Madison, Madison Wisconsin USA; Lewis, Ernie R. [Brookhaven National Laboratory, Upton New York USA; Ferrare, Richard [NASA Langley Research Center, Hampton Virginia USA; Kollias, Pavlos [School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook New York USA

    2017-02-27

    Ship measurements collected over the northeast Pacific along transects between the port of Los Angeles (33.7°N, 118.2°W) and Honolulu (21.3°N, 157.8°W) during May to August 2013 were utilized to investigate the covariability between marine low cloud microphysical and aerosol properties. Ship-based retrievals of cloud optical depth (τ) from a Sun photometer and liquid water path (LWP) from a microwave radiometer were combined to derive cloud droplet number concentration Nd and compute a cloud-aerosol interaction (ACI) metric defined as ACICCN = ∂ ln(Nd)/∂ ln(CCN), with CCN denoting the cloud condensation nuclei concentration measured at 0.4% (CCN0.4) and 0.3% (CCN0.3) supersaturation. Analysis of CCN0.4, accumulation mode aerosol concentration (Na), and extinction coefficient (σext) indicates that Na and σext can be used as CCN0.4 proxies for estimating ACI. ACICCN derived from 10 min averaged Nd and CCN0.4 and CCN0.3, and CCN0.4 regressions using Na and σext, produce high ACICCN: near 1.0, that is, a fractional change in aerosols is associated with an equivalent fractional change in Nd. ACICCN computed in deep boundary layers was small (ACICCN = 0.60), indicating that surface aerosol measurements inadequately represent the aerosol variability below clouds. Satellite cloud retrievals from MODerate-resolution Imaging Spectroradiometer and GOES-15 data were compared against ship-based retrievals and further analyzed to compute a satellite-based ACICCN. Satellite data correlated well with their ship-based counterparts with linear correlation coefficients equal to or greater than 0.78. Combined satellite Nd and ship-based CCN0.4 and Na yielded a maximum ACICCN = 0.88–0.92, a value slightly less than the ship-based ACICCN, but still consistent with aircraft-based studies in the eastern Pacific.

  5. Impacts of new particle formation on aerosol cloud condensation nuclei (CCN activity in Shanghai: case study

    Directory of Open Access Journals (Sweden)

    C. Leng

    2014-07-01

    Full Text Available New particle formation (NPF events and their impacts on cloud condensation nuclei (CCN were investigated using continuous measurements collected in urban Shanghai from 1 to 30 April 2012. During the campaign, NPF occurred in 8 out of the 30 days and enhanced CCN number concentration (NCCN by a actor of 1.2–1.8, depending on supersaturation (SS. The NPF event on 3 April 2012 was chosen as an example to investigate the NPF influence on CCN activity. In this NPF event, secondary aerosols were produced continuously and increased PM2.5 mass concentration at a~rate of 4.33 μg cm−3 h−1, and the growth rate (GR and formation rate (FR were on average 5 nm h−1 and 0.36 cm−3 s−1, respectively. The newly formed particles grew quickly from nucleation mode (10–20 nm into CCN size range. NCCN increased rapidly at SS of 0.4–1.0% but weakly at SS of 0.2%. Correspondingly, aerosol CCN activities (fractions of activated aerosol particles in total aerosols, NCCN / NCN were significantly enhanced from 0.24–0.60 to 0.30–0.91 at SS of 0.2–1.0% due to the NPF. On the basis of the κ-Köhler theory, aerosol size distributions and chemical composition measured simultaneously were used to predict NCCN. There was a good agreement between the predicted and measured NCCN (R2 = 0.96, Npredicted / Nmeasured = 1.04. This study reveals that NPF exerts large impacts on aerosol particle abundance and size spectra, thus significantly promotes NCCN and aerosol CCN activity in this urban environment. The GR of NPF is the key factor controlling the newly formed particles to become CCN at all SS levels, whereas the FR is an effective factor only under high SS (e.g. 1.0% conditions.

  6. Plume-exit modeling to determine cloud condensation nuclei activity of aerosols from residential biofuel combustion

    Science.gov (United States)

    Mena, Francisco; Bond, Tami C.; Riemer, Nicole

    2017-08-01

    Residential biofuel combustion is an important source of aerosols and gases in the atmosphere. The change in cloud characteristics due to biofuel burning aerosols is uncertain, in part, due to the uncertainty in the added number of cloud condensation nuclei (CCN) from biofuel burning. We provide estimates of the CCN activity of biofuel burning aerosols by explicitly modeling plume dynamics (coagulation, condensation, chemical reactions, and dilution) in a young biofuel burning plume from emission until plume exit, defined here as the condition when the plume reaches ambient temperature and specific humidity through entrainment. We found that aerosol-scale dynamics affect CCN activity only during the first few seconds of evolution, after which the CCN efficiency reaches a constant value. Homogenizing factors in a plume are co-emission of semi-volatile organic compounds (SVOCs) or emission at small particle sizes; SVOC co-emission can be the main factor determining plume-exit CCN for hydrophobic or small particles. Coagulation limits emission of CCN to about 1016 per kilogram of fuel. Depending on emission factor, particle size, and composition, some of these particles may not activate at low supersaturation (ssat). Hygroscopic Aitken-mode particles can contribute to CCN through self-coagulation but have a small effect on the CCN activity of accumulation-mode particles, regardless of composition differences. Simple models (monodisperse coagulation and average hygroscopicity) can be used to estimate plume-exit CCN within about 20 % if particles are unimodal and have homogeneous composition, or when particles are emitted in the Aitken mode even if they are not homogeneous. On the other hand, if externally mixed particles are emitted in the accumulation mode without SVOCs, an average hygroscopicity overestimates emitted CCN by up to a factor of 2. This work has identified conditions under which particle populations become more homogeneous during plume processes. This

  7. Atmospheric and aerosol chemistry

    Energy Technology Data Exchange (ETDEWEB)

    McNeill, V. Faye [Columbia Univ., New York, NY (United States). Dept. of Chemical Engineering; Ariya, Parisa A. (ed.) [McGill Univ. Montreal, QC (Canada). Dept. of Chemistry; McGill Univ. Montreal, QC (Canada). Dept. of Atmospheric and Oceanic Sciences

    2014-09-01

    This series presents critical reviews of the present position and future trends in modern chemical research. Short and concise reports on chemistry, each written by the world renowned experts. Still valid and useful after 5 or 10 years. More information as well as the electronic version of the whole content available at: springerlink.com. Christian George, Barbara D'Anna, Hartmut Herrmann, Christian Weller, Veronica Vaida, D. J. Donaldson, Thorsten Bartels-Rausch, Markus Ammann Emerging Areas in Atmospheric Photochemistry. Lisa Whalley, Daniel Stone, Dwayne Heard New Insights into the Tropospheric Oxidation of Isoprene: Combining Field Measurements, Laboratory Studies, Chemical Modelling and Quantum Theory. Neil M. Donahue, Allen L. Robinson, Erica R. Trump, Ilona Riipinen, Jesse H. Kroll Volatility and Aging of Atmospheric Organic Aerosol. P. A. Ariya, G. Kos, R. Mortazavi, E. D. Hudson, V. Kanthasamy, N. Eltouny, J. Sun, C. Wilde Bio-Organic Materials in the Atmosphere and Snow: Measurement and Characterization V. Faye McNeill, Neha Sareen, Allison N. Schwier Surface-Active Organics in Atmospheric Aerosols.

  8. Size-resolved aerosol water uptake and cloud condensation nuclei measurements as measured above a Southeast Asian rainforest during OP3

    Directory of Open Access Journals (Sweden)

    M. Irwin

    2011-11-01

    Full Text Available The influence of the properties of fine particles on the formation of clouds and precipitation in the tropical atmosphere is of primary importance to their impacts on radiative forcing and the hydrological cycle. Measurements of aerosol number size distribution, hygroscopicity in both sub- and supersaturated regimes and composition were taken between March and July 2008 in the tropical rainforest in Borneo, Malaysia, marking the first study of this type in an Asian tropical rainforest. Hygroscopic growth factors (GF at 90 % relative humidity (RH for the dry diameter range D0 = 32–258 nm, supersaturated water uptake behaviour for the dry diameter range D0 = 45–300 nm and aerosol chemical composition were simultaneously measured using a Hygroscopicity Tandem Differential Mobility Analyser (HTDMA, a Droplet Measurement Technologies Cloud Condensation Nuclei counter (CCNc and an Aerodyne Aerosol Mass Spectrometer (AMS respectively.

    The hygroscopicity parameter κ was derived from both CCNc and HTDMA measurements, with the resulting values of κ ranging from 0.05–0.37, and 0.17–0.37, respectively. Although the total range of κ values is in good agreement, there are inconsistencies between CCNc and HTDMA derived κ values at different dry diameters. Results from a study with similar methodology performed in the Amazon rainforest report values for κ within a similar range to those reported in this work, indicating that the aerosol as measured from both sites shows similar hygroscopic properties. However, the derived number of cloud condensation nuclei (NCCN were much higher in the present experiment than the Amazon, resulting in part from the increased total particle number concentrations observed in the Bornean rainforest. This contrast between the two environments may be of substantial importance in describing the impacts of particles in the tropical atmosphere.

  9. International Cooperative for Aerosol Prediction Workshop on Aerosol Forecast Verification

    Science.gov (United States)

    Benedetti, Angela; Reid, Jeffrey S.; Colarco, Peter R.

    2011-01-01

    The purpose of this workshop was to reinforce the working partnership between centers who are actively involved in global aerosol forecasting, and to discuss issues related to forecast verification. Participants included representatives from operational centers with global aerosol forecasting requirements, a panel of experts on Numerical Weather Prediction and Air Quality forecast verification, data providers, and several observers from the research community. The presentations centered on a review of current NWP and AQ practices with subsequent discussion focused on the challenges in defining appropriate verification measures for the next generation of aerosol forecast systems.

  10. Indirect radiative forcing by ion-mediated nucleation of aerosol

    Directory of Open Access Journals (Sweden)

    F. Yu

    2012-12-01

    Full Text Available A clear understanding of particle formation mechanisms is critical for assessing aerosol indirect radiative forcing and associated climate feedback processes. Recent studies reveal the importance of ion-mediated nucleation (IMN in generating new particles and cloud condensation nuclei (CCN in the atmosphere. Here we implement the IMN scheme into the Community Atmosphere Model version 5 (CAM5. Our simulations show that, compared to globally averaged results based on H2SO4-H2O binary homogeneous nucleation (BHN, the presence of ionization (i.e., IMN halves H2SO4 column burden, but increases the column integrated nucleation rate by around one order of magnitude, total particle number burden by a factor of ~3, CCN burden by ~10% (at 0.2% supersaturation to 65% (at 1.0% supersaturation, and cloud droplet number burden by ~18%. Compared to BHN, IMN increases cloud liquid water path by 7.5%, decreases precipitation by 1.1%, and increases total cloud cover by 1.9%. This leads to an increase of total shortwave cloud radiative forcing (SWCF by 3.67 W m−2 (more negative and longwave cloud forcing by 1.78 W m−2 (more positive, with large spatial variations. The effect of ionization on SWCF derived from this study (3.67 W m−2 is a factor of ~3 higher that of a previous study (1.15 W m−2 based on a different ion nucleation scheme and climate model. Based on the present CAM5 simulation, the 5-yr mean impacts of solar cycle induced changes in ionization rates on CCN and cloud forcing are small (~−0.02 W m−2 but have larger inter-annual (from −0.18 to 0.17 W m−2 and spatial variations.

  11. Growth kinetics and morphology of snowflakes in supersaturated atmosphere using a three-dimensional phase-field model

    Science.gov (United States)

    Demange, G.; Zapolsky, H.; Patte, R.; Brunel, M.

    2017-08-01

    Simulating ice crystal growth is a major issue for meteorology and aircraft safety. Yet, very few models currently succeed in reproducing correctly the diversity of snow crystal forms, and link the model parameters to thermodynamic quantities. Here, we demonstrate that the new three-dimensional phase-field model developed in Demange et al. [npj Comput. Mater. 3, 1 (2017), 10.1038/s41524-017-0015-1] is capable of reproducing properly the morphology and growth kinetics of snowflakes in supersaturated atmosphere. Aside from that, we show that the growth dynamics of snow crystals satisfies the selection theory, consistently with previous experimental observations. Finally, we link the parameters of the phase-field model to atmospheric parameters.

  12. Separation in liquid and the formation of supersaturated solid solutions in Fe-Cu alloys upon rapid laser melting

    Science.gov (United States)

    Kharanzhevskiy, E. V.

    2016-09-01

    The structure of compacted specimens produced using the rapid laser melting of ultradispersed Fe-50 wt % Cu powders has been studied. The original powder was produced via the mechanical milling of iron and copper powders in a planetary-type ball mill. It has been found that the structure of the compacted specimens produced using rapid laser melting exhibits signs of the initial stages of separation in supercooled liquid. It has been shown using X-ray diffraction analysis as well as scanning and transmission electron microscopy that the final structure contains a supersaturated (Fe; Cu) solid solution formed from the high-speed movement of the solidification front and the nonequilibrium capture of copper by the moving front.

  13. Homogeneous nucleation in supersaturated vapors of methane, ethane, and carbon dioxide predicted by brute force molecular dynamics

    CERN Document Server

    Horsch, Martin; Bernreuther, Martin; Grottel, Sebastian; Reina, Guido; Wix, Andrea; Schaber, Karlheinz; Hasse, Hans

    2009-01-01

    Molecular dynamics (MD) simulation is applied to the condensation process of supersaturated vapors of methane, ethane, and carbon dioxide. Simulations of systems with up to a million particles were conducted with a massively parallel MD program. This leads to reliable statistics and makes nucleation rates down to the order of 10^30/(m^3 s) accessible to the direct simulation approach. Simulation results are compared to the classical nucleation theory (CNT) as well as the theory of Laaksonen, Ford, and Kulmala (LFK) which introduces a size dependence of the specific surface energy. CNT describes the nucleation of ethane and carbon dioxide excellently over the entire studied temperature range, whereas LFK provides a better approach to methane at low temperatures.

  14. Effects of temperature and pressure on the nucleation and growth of silver clusters from supersaturated vapor: A molecular dynamics analysis

    Science.gov (United States)

    Wang, Qin; Xie, Hui; Chen, Yongshi; Liu, Chao

    2017-04-01

    The nucleation and growth of silver nanoparticles in the supersaturated system are investigated by molecular dynamics simulation at different temperatures and pressures. The variety of the atoms in the biggest cluster and the size of average clusters in the system versus the time are estimated to reveal the relationship between the nucleation as well as cluster growth. The nucleation rates in different situations are calculated with the threshold method. The effect of temperature and pressure on the nucleation rate is identified as obeying a linear function. Finally, the development of basal elements, such as monomers, dimers and trimmers, is revealed how the temperature and pressure affect the nucleation and growth of the silver cluster.

  15. Growth of a Gas Bubble in a Supersaturated Liquid Under the Effect of Variant Cases of Surface Tension

    Science.gov (United States)

    Mohammadein, S. A.; Mohamed, K. G.

    In this paper, the growth of a gas bubble in a supersaturated liquid is discussed for a constant and variable cases of surface tension effect. The mathematical model is solved analytically by using the method of Plesset and Zwick18 after modified it. The growth process is affected by: diffusion coefficient D, Jacob number Ja, surface tension σ, adjustment factor b and void fraction ϕ0. The famous formula of Plesset and Zwick is produced as a special case of the results at some values of the adjustment factors. Moreover, for some values of the adjustment factors, good approximation is obtained when a comparison between our results and the result that produced by Hashemi et al., 9 who solved the problem with the method of combining variables.

  16. The GRAPE aerosol retrieval algorithm

    Directory of Open Access Journals (Sweden)

    G. E. Thomas

    2009-11-01

    Full Text Available The aerosol component of the Oxford-Rutherford Aerosol and Cloud (ORAC combined cloud and aerosol retrieval scheme is described and the theoretical performance of the algorithm is analysed. ORAC is an optimal estimation retrieval scheme for deriving cloud and aerosol properties from measurements made by imaging satellite radiometers and, when applied to cloud free radiances, provides estimates of aerosol optical depth at a wavelength of 550 nm, aerosol effective radius and surface reflectance at 550 nm. The aerosol retrieval component of ORAC has several incarnations – this paper addresses the version which operates in conjunction with the cloud retrieval component of ORAC (described by Watts et al., 1998, as applied in producing the Global Retrieval of ATSR Cloud Parameters and Evaluation (GRAPE data-set.

    The algorithm is described in detail and its performance examined. This includes a discussion of errors resulting from the formulation of the forward model, sensitivity of the retrieval to the measurements and a priori constraints, and errors resulting from assumptions made about the atmospheric/surface state.

  17. Cost-effective alternative to nano-encapsulation: Amorphous curcumin-chitosan nanoparticle complex exhibiting high payload and supersaturation generation.

    Science.gov (United States)

    Nguyen, Minh Hiep; Yu, Hong; Kiew, Tie Yi; Hadinoto, Kunn

    2015-10-01

    While the wide-ranging therapeutic activities of curcumin have been well established, its successful delivery to realize its true therapeutic potentials faces a major challenge due to its low oral bioavailability. Even though nano-encapsulation has been widely demonstrated to be effective in enhancing the bioavailability of curcumin, it is not without drawbacks (i.e. low payload and costly preparation). Herein we present a cost-effective bioavailability enhancement strategy of curcumin in the form of amorphous curcumin-chitosan nanoparticle complex (or curcumin nanoplex in short) exhibiting a high payload (>80%). The curcumin nanoplex was prepared by a simple yet highly efficient drug-polysaccharide complexation method that required only mixing of the curcumin and chitosan solutions under ambient condition. The effects of (1) pH and (2) charge ratio of chitosan to curcumin on the (i) physical characteristics of the nanoplex (i.e. size, colloidal stability and payload), (ii) complexation efficiency, and (iii) production yield were investigated from which the optimal preparation condition was determined. The nanoplex formation was found to favor low acidic pH and charge ratio below unity. At the optimal condition (i.e. pH 4.4. and charge ratio=0.8), stable curcumin nanoplex (≈260nm) was prepared at >90% complexation efficiency and ≈50% production yield. The amorphous state stability, colloidal stability, and in vitro non-cytotoxicity of the nanoplex were successfully established. The curcumin nanoplex produced prolonged supersaturation (3h) in the presence of hydroxypropyl methylcellulose (HPMC) at five times of the saturation solubility of curcumin. In addition, curcumin released from the nanoplex exhibited improved chemical stability owed to the presence of chitosan. Both results (i.e. high supersaturation and improved chemical stability) bode well for the ability of the curcumin nanoplex to enhance the bioavailability of curcumin clinically. Copyright © 2015

  18. Mechanistic differences in permeation behavior of supersaturated and solubilized solutions of carbamazepine revealed by nuclear magnetic resonance measurements.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Limwikrant, Waree; Sekine, Shuichi; Horie, Toshiharu; Yamamoto, Keiji; Moribe, Kunikazu

    2012-11-05

    A solid dispersion (SPD) of carbamazepine (CBZ) with hydroxypropyl methylcellulose acetate succinate (HPMC-AS) was prepared by the spray drying method. The apparent solubility (37 °C, pH 7.4) of CBZ observed with the SPD was over 3 times higher than the solubility of unprocessed CBZ. The supersaturated solution was stable for 7 days. A higher concentration of CBZ in aqueous medium was also achieved by mixing with Poloxamer 407 (P407), a solubilizing agent. From permeation studies of CBZ using Caco-2 monolayers and dialysis membranes, we observed improved CBZ permeation across the membrane in the supersaturated solution of CBZ/HPMC-AS SPD. On the contrary, the CBZ-solubilized P407 solution exhibited poor permeation by CBZ. The chemical shifts of CBZ on the (1)H NMR spectrum from CBZ/HPMC-AS SPD solution were not altered significantly by coexistence with HPMC-AS. In contrast, an upfield shift of CBZ was observed in the CBZ/P407 solution. The spin-lattice relaxation time (T(1)) over spin-spin relaxation time (T(2)) indicated that the mobility of CBZ in the HPMC-AS solution was much lower than that in water. Meanwhile, the mobility of CBZ in P407 solution was significantly higher than that in water. NMR data indicate that CBZ does not strongly interact with HPMC-AS. CBZ mobility was suppressed due to self-association and microviscosity around CBZ, which do not affect permeation behavior. Most of the CBZ molecules in the CBZ/P407 solution were solubilized in the hydrophobic core of P407, and a few were free to permeate the membrane. The molecular state of CBZ, as evaluated by NMR measurements, directly correlated with permeation behavior.

  19. Supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) enhance the bioavailability of the poorly water-soluble drug Simvastatin in dogs

    DEFF Research Database (Denmark)

    Thomas, Nicky; Holm, René; Garmer, Mats

    2013-01-01

    This study investigates the potential of supersaturated self-nanoemulsifying drug delivery systems (super-SNEDDS) to improve the bioavailability of poorly water-soluble drugs compared to conventional SNEDDS. Conventional SNEDDS contained simvastatin (SIM) at 75% of the equilibrium solubility (S (eq...

  20. The impact of supersaturation level for oral absorption of BCS class IIb drugs, dipyridamole and ketoconazole, using in vivo predictive dissolution system: Gastrointestinal Simulator (GIS).

    Science.gov (United States)

    Tsume, Yasuhiro; Matsui, Kazuki; Searls, Amanda L; Takeuchi, Susumu; Amidon, Gregory E; Sun, Duxin; Amidon, Gordon L

    2017-05-01

    The development of formulations and the assessment of oral drug absorption for Biopharmaceutical Classification System (BCS) class IIb drugs is often a difficult issue due to the potential for supersaturation and precipitation in the gastrointestinal (GI) tract. The physiological environment in the GI tract largely influences in vivo drug dissolution rates of those drugs. Thus, those physiological factors should be incorporated into the in vitro system to better assess in vivo performance of BCS class IIb drugs. In order to predict oral bioperformance, an in vitro dissolution system with multiple compartments incorporating physiologically relevant factors would be expected to more accurately predict in vivo phenomena than a one-compartment dissolution system like USP Apparatus 2 because, for example, the pH change occurring in the human GI tract can be better replicated in a multi-compartmental platform. The Gastrointestinal Simulator (GIS) consists of three compartments, the gastric, duodenal and jejunal chambers, and is a practical in vitro dissolution apparatus to predict in vivo dissolution for oral dosage forms. This system can demonstrate supersaturation and precipitation and, therefore, has the potential to predict in vivo bioperformance of oral dosage forms where this phenomenon may occur. In this report, in vitro studies were performed with dipyridamole and ketoconazole to evaluate the precipitation rates and the relationship between the supersaturation levels and oral absorption of BCS class II weak base drugs. To evaluate the impact of observed supersaturation levels on oral absorption, a study utilizing the GIS in combination with mouse intestinal infusion was conducted. Supersaturation levels observed in the GIS enhanced dipyridamole and ketoconazole absorption in mouse, and a good correlation between their supersaturation levels and their concentration in plasma was observed. The GIS, therefore, appears to represent in vivo dissolution phenomena and

  1. Cloud condensation nuclei in pristine tropical rainforest air of Amazonia: size-resolved measurements and modeling of atmospheric aerosol composition and CCN activity

    Science.gov (United States)

    Gunthe, S. S.; King, S. M.; Rose, D.; Chen, Q.; Roldin, P.; Farmer, D. K.; Jimenez, J. L.; Artaxo, P.; Andreae, M. O.; Martin, S. T.; Pöschl, U.

    2009-10-01

    Atmospheric aerosol particles serving as cloud condensation nuclei (CCN) are key elements of the hydrological cycle and climate. We have measured and characterized CCN at water vapor supersaturations in the range of S=0.10-0.82% in pristine tropical rainforest air during the AMAZE-08 campaign in central Amazonia. The effective hygroscopicity parameters describing the influence of chemical composition on the CCN activity of aerosol particles varied in the range of κ≍0.1-0.4 (0.16±0.06 arithmetic mean and standard deviation). The overall median value of κ≍0.15 was by a factor of two lower than the values typically observed for continental aerosols in other regions of the world. Aitken mode particles were less hygroscopic than accumulation mode particles (κ≍0.1 at D≍50 nm; κ≍0.2 at D≍200 nm), which is in agreement with earlier hygroscopicity tandem differential mobility analyzer (H-TDMA) studies. The CCN measurement results are consistent with aerosol mass spectrometry (AMS) data, showing that the organic mass fraction (forg) was on average as high as ~90% in the Aitken mode (D≤100 nm) and decreased with increasing particle diameter in the accumulation mode (~80% at D≍200 nm). The κ values exhibited a negative linear correlation with forg (R2=0.81), and extrapolation yielded the following effective hygroscopicity parameters for organic and inorganic particle components: κorg≍0.1 which can be regarded as the effective hygroscopicity of biogenic secondary organic aerosol (SOA) and κinorg≍0.6 which is characteristic for ammonium sulfate and related salts. Both the size dependence and the temporal variability of effective particle hygroscopicity could be parameterized as a function of AMS-based organic and inorganic mass fractions (κp=κorg×forg +κinorg×finorg). The CCN number concentrations predicted with κp were in fair agreement with the measurement results (~20% average deviation). The median CCN number concentrations at S=0

  2. eDPS Aerosol Collection

    Energy Technology Data Exchange (ETDEWEB)

    Venzie, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-10-13

    The eDPS Aerosol Collection project studies the fundamental physics of electrostatic aerosol collection for national security applications. The interpretation of aerosol data requires understanding and correcting for biases introduced from particle genesis through collection and analysis. The research and development undertaken in this project provides the basis for both the statistical correction of existing equipment and techniques; as well as, the development of new collectors and analytical techniques designed to minimize unwanted biases while improving the efficiency of locating and measuring individual particles of interest.

  3. Instrumentation for tropospheric aerosol characterization

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Z.; Young, S.E.; Becker, C.H.; Coggiola, M.J. [SRI International, Menlo Park, CA (United States); Wollnik, H. [Giessen Univ. (Germany)

    1997-12-31

    A new instrument has been developed that determines the abundance, size distribution, and chemical composition of tropospheric and lower stratospheric aerosols with diameters down to 0.2 {mu}m. In addition to aerosol characterization, the instrument also monitors the chemical composition of the ambient gas. More than 25.000 aerosol particle mass spectra were recorded during the NASA-sponsored Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) field program using NASA`s DC-8 research aircraft. (author) 7 refs.

  4. Aerosol measurement program strategy for global aerosol backscatter model development

    Science.gov (United States)

    Bowdle, David A.

    1985-01-01

    The purpose was to propose a balanced program of aerosol backscatter research leading to the development of a global model of aerosol backscatter. Such a model is needed for feasibility studies and systems simulation studies for NASA's prospective satellite-based Doppler lidar wind measurement system. Systems of this kind measure the Doppler shift in the backscatter return from small atmospheric aerosol wind tracers (of order 1 micrometer diameter). The accuracy of the derived local wind estimates and the degree of global wind coverage for such a system are limited by the local availability and by the global scale distribution of natural aerosol particles. The discussions here refer primarily to backscatter model requirements at CO2 wavelengths, which have been selected for most of the Doppler lidar systems studies to date. Model requirements for other potential wavelengths would be similar.

  5. Aerosol measurement program strategy for global aerosol backscatter model development

    Science.gov (United States)

    Bowdle, David A.

    1985-01-01

    The purpose was to propose a balanced program of aerosol backscatter research leading to the development of a global model of aerosol backscatter. Such a model is needed for feasibility studies and systems simulation studies for NASA's prospective satellite-based Doppler lidar wind measurement system. Systems of this kind measure the Doppler shift in the backscatter return from small atmospheric aerosol wind tracers (of order 1 micrometer diameter). The accuracy of the derived local wind estimates and the degree of global wind coverage for such a system are limited by the local availability and by the global scale distribution of natural aerosol particles. The discussions here refer primarily to backscatter model requirements at CO2 wavelengths, which have been selected for most of the Doppler lidar systems studies to date. Model requirements for other potential wavelengths would be similar.

  6. Insights into atomic-level interaction between mefenamic acid and eudragit EPO in a supersaturated solution by high-resolution magic-angle spinning NMR spectroscopy.

    Science.gov (United States)

    Higashi, Kenjirou; Yamamoto, Kazutoshi; Pandey, Manoj Kumar; Mroue, Kamal H; Moribe, Kunikazu; Yamamoto, Keiji; Ramamoorthy, Ayyalusamy

    2014-01-06

    The intermolecular interaction between mefenamic acid (MFA), a poorly water-soluble nonsteroidal anti-inflammatory drug, and Eudragit EPO (EPO), a water-soluble polymer, is investigated in their supersaturated solution using high-resolution magic-angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy. The stable supersaturated solution with a high MFA concentration of 3.0 mg/mL is prepared by dispersing the amorphous solid dispersion into a d-acetate buffer at pH 5.5 and 37 °C. By virtue of MAS at 2.7 kHz, the extremely broad and unresolved (1)H resonances of MFA in one-dimensional (1)H NMR spectrum of the supersaturated solution are well-resolved, thus enabling the complete assignment of MFA (1)H resonances in the aqueous solution. Two-dimensional (2D) (1)H/(1)H nuclear Overhauser effect spectroscopy (NOESY) and radio frequency-driven recoupling (RFDR) under MAS conditions reveal the interaction of MFA with EPO in the supersaturated solution at an atomic level. The strong cross-correlations observed in the 2D (1)H/(1)H NMR spectra indicate a hydrophobic interaction between the aromatic group of MFA and the backbone of EPO. Furthermore, the aminoalkyl group in the side chain of EPO forms a hydrophilic interaction, which can be either electrostatic or hydrogen bonding, with the carboxyl group of MFA. We believe these hydrophobic and hydrophilic interactions between MFA and EPO molecules play a key role in the formation of this extremely stable supersaturated solution. In addition, 2D (1)H/(1)H RFDR demonstrates that the molecular MFA-EPO interaction is quite flexible and dynamic.

  7. Stratospheric aerosol geoengineering

    Energy Technology Data Exchange (ETDEWEB)

    Robock, Alan [Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, NJ 08901 (United States)

    2015-03-30

    The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, has found that insolation reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. Temperature changes would also not be uniform; the tropics would cool, but high latitudes would warm, with continuing, but reduced sea ice and ice sheet melting. Temperature extremes would still increase, but not as much as without geoengineering. If geoengineering were halted all at once, there would be rapid temperature and precipitation increases at 5–10 times the rates from gradual global warming. The prospect of geoengineering working may reduce the current drive toward reducing greenhouse gas emissions, and there are concerns about commercial or military control. Because geoengineering cannot safely address climate change, global efforts to reduce greenhouse gas emissions and to adapt are crucial to address anthropogenic global warming.

  8. Stratospheric aerosol geoengineering

    Science.gov (United States)

    Robock, Alan

    2015-03-01

    The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, has found that insolation reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. Temperature changes would also not be uniform; the tropics would cool, but high latitudes would warm, with continuing, but reduced sea ice and ice sheet melting. Temperature extremes would still increase, but not as much as without geoengineering. If geoengineering were halted all at once, there would be rapid temperature and precipitation increases at 5-10 times the rates from gradual global warming. The prospect of geoengineering working may reduce the current drive toward reducing greenhouse gas emissions, and there are concerns about commercial or military control. Because geoengineering cannot safely address climate change, global efforts to reduce greenhouse gas emissions and to adapt are crucial to address anthropogenic global warming.

  9. Aerosol Transmission of Filoviruses

    Directory of Open Access Journals (Sweden)

    Berhanu Mekibib

    2016-05-01

    Full Text Available Filoviruses have become a worldwide public health concern because of their potential for introductions into non-endemic countries through international travel and the international transport of infected animals or animal products. Since it was first identified in 1976, in the Democratic Republic of Congo (formerly Zaire and Sudan, the 2013–2015 western African Ebola virus disease (EVD outbreak is the largest, both by number of cases and geographical extension, and deadliest, recorded so far in medical history. The source of ebolaviruses for human index case(s in most outbreaks is presumptively associated with handling of bush meat or contact with fruit bats. Transmission among humans occurs easily when a person comes in contact with contaminated body fluids of patients, but our understanding of other transmission routes is still fragmentary. This review deals with the controversial issue of aerosol transmission of filoviruses.

  10. Aerosol Transmission of Filoviruses.

    Science.gov (United States)

    Mekibib, Berhanu; Ariën, Kevin K

    2016-05-23

    Filoviruses have become a worldwide public health concern because of their potential for introductions into non-endemic countries through international travel and the international transport of infected animals or animal products. Since it was first identified in 1976, in the Democratic Republic of Congo (formerly Zaire) and Sudan, the 2013-2015 western African Ebola virus disease (EVD) outbreak is the largest, both by number of cases and geographical extension, and deadliest, recorded so far in medical history. The source of ebolaviruses for human index case(s) in most outbreaks is presumptively associated with handling of bush meat or contact with fruit bats. Transmission among humans occurs easily when a person comes in contact with contaminated body fluids of patients, but our understanding of other transmission routes is still fragmentary. This review deals with the controversial issue of aerosol transmission of filoviruses.

  11. On the competition among aerosol number, size and composition in predicting CCN variability: a multi-annual field study in an urbanized desert

    Directory of Open Access Journals (Sweden)

    E. Crosbie

    2015-02-01

    Full Text Available A two-year dataset of measured CCN concentrations at 0.2% supersaturation is combined with aerosol size distribution and aerosol chemistry data to probe the effects of aerosol number concentrations, size distribution and composition on CCN patterns. Data have been collected over a period of two years (2012–2014 in central Tucson, Arizona: a significant urban area surrounded by a sparsely populated desert. Average CCN concentrations are typically lowest in spring (233 cm−3, highest in winter (430 cm−3 and have a secondary peak during the North American Monsoon season (July to September; 372 cm−3. There is significant variability outside of seasonal patterns with extreme concentrations (1 and 99% levels ranging from 56 to 1945 cm−3 as measured during the winter, the season with highest variability. Modeled CCN concentrations based on fixed chemical composition achieve better closure in winter, with size and number alone able to predict 82% of the variance in CCN concentration. Changes in aerosol chemistry are typically aligned with changes in size and aerosol number, such that composition can be parameterized even though it is still variable. In summer, models based on fixed chemical composition explain at best only 41% (pre-monsoon and 36% (monsoon of the variance. This is attributed to the effects of secondary organic aerosol (SOA production, the competition between new particle formation and condensational growth, and the complex interaction of meteorology, regional and local emissions, and multi-phase chemistry during the North American Monsoon. Chemical composition is found to be an important factor for improving predictability in spring and on longer timescales in winter. Regimes where parameterized models exhibit improved predictive skill are typically explained by strong relationships between CCN concentrations and the prevailing meteorology and dominant aerosol chemistry mechanisms suggesting that similar findings could be

  12. Charge inversion and ion-ion correlation effects at the mercury/aqueous MgSO4 interface: Toward the solution of a long-standing issue

    NARCIS (Netherlands)

    Wennersson, E.; Kjellander, R.; Lyklema, J.

    2010-01-01

    Charge inversion is the phenomenon in which an electric double layer contains more counterions than needed to compensate the surface charge. For colloidal particles this has the consequence that the apparent surface charge, as inferred from electrophoresis or interaction studies, has a sign opposite

  13. Screening genetically diverse pear species for in vitro CaCl2, MgSO4 and KH2PO4 requirements

    Science.gov (United States)

    Conservation of important plant germplasm is often difficult due to the specific growth requirements of genetically diverse species. This also applies to in vitro culture collections where a wide range of plants may have suboptimal growth or remain recalcitrant to growth on standard media. A series ...

  14. Aerosol Inlet Characterization Experiment Report

    Energy Technology Data Exchange (ETDEWEB)

    Bullard, Robert L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Kuang, Chongai [Brookhaven National Lab. (BNL), Upton, NY (United States); Uin, Janek [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, Scott [Brookhaven National Lab. (BNL), Upton, NY (United States); Springston, Stephen R. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-05-01

    The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Aerosol Observation System inlet stack was characterized for particle penetration efficiency from 10 nm to 20 μm in diameter using duplicate scanning mobility particle sizers (10 nm-450 nm), ultra-high-sensitivity aerosol spectrometers (60 nm-μm), and aerodynamic particle sizers (0.5 μm-20 μm). Results show good model-measurement agreement and unit transmission efficiency of aerosols from 10 nm to 4 μm in diameter. Large uncertainties in the measured transmission efficiency exist above 4 μm due to low ambient aerosol signal in that size range.

  15. Hygroscopic growth and activation of HULIS particles: experimental data and a new iterative parameterization scheme for complex aerosol particles

    Directory of Open Access Journals (Sweden)

    A. Massling

    2008-03-01

    Full Text Available The hygroscopic growth and activation of two HULIS (HUmic LIke Substance and one Aerosol-Water-Extract sample, prepared from urban-type aerosol, were investigated. All samples were extracted from filters, redissolved in water and atomized for the investigations presented here. The hygroscopic growth measurements were done using LACIS (Leipzig Aerosol Cloud Interaction Simulator together with a HH-TDMA (High Humidity Tandem Differential Mobility Analyzer. Hygroscopic growth was determined for relative humidities (RHs up to 99.75%. The critical diameters for activation were measured for supersaturations between 0.2 and 1%. All three samples showed a similar hygroscopic growth behavior, and the two HULIS samples also were similar in their activation behavior, while the Aerosol-Water-Extract turned out to be more CCN active than the HULIS samples. The experimental data was used to derive parameterizations for the hygroscopic growth and activation of HULIS particles. The concept of ρion (Wex et al., 2007a and the Szyszkowski-equation (Szyszkowski, 1908; Facchini, 1999 were used for parameterizing the Raoult and the Kelvin (surface tension terms of the Köhler equation, respectively. This concept proved to be very successful for the HULIS samples in the saturation range from RHs larger than 98% up to activation. It was also shown to work well with data on HULIS taken from literature. Here, different atmospheric life-times and/or different sources for the different samples showed up in different coefficients for the parameterization. However, the parameterization did not work out well for the Aerosol-Water-Extract.

  16. Measurement and Modeling of Vertically Resolved Aerosol Optical Properties and Radiative Fluxes Over the ARM SGP Site

    Science.gov (United States)

    Schmid, B.; Arnott, P.; Bucholtz, A.; Colarco, P.; Covert, D.; Eilers, J.; Elleman, R.; Ferrare, R.; Flagan, R.; Jonsson, H.

    2003-01-01

    In order to meet one of its goals - to relate observations of radiative fluxes and radiances to the atmospheric composition - the Department of Energy's Atmospheric Radiation Measurement (ARM) program has pursued measurements and modeling activities that attempt to determine how aerosols impact atmospheric radiative transfer, both directly and indirectly. However, significant discrepancies between aerosol properties measured in situ or remotely remain. One of the objectives of the Aerosol Intensive Operational Period (TOP) conducted by ARM in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma was to examine and hopefully reduce these differences. The IOP involved airborne measurements from two airplanes over the heavily instrumented SGP site. We give an overview of airborne results obtained aboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The Twin Otter performed 16 research flights over the SGP site. The aircraft carried instrumentation to perform in-situ measurements of aerosol absorption, scattering, extinction and particle size. This included such novel techniques as the photoacoustic and cavity ring-down methods for in-situ absorption (675 nm) and extinction (675 and 1550 nm) and a new multiwavelength, filter-based absorption photometer (467, 530, 660 nm). A newly developed instrument measured cloud condensation nucleus concentration (CCN) concentrations at two supersaturation levels. Aerosol optical depth and extinction (354-2139 nm) were measured with the NASA Ames Airborne Tracking 14-channel sunphotometer. Furthermore, up-and downwelling solar (broadband and spectral) and infrared radiation were measured using seven individual radiometers. Three up-looking radiometers werer mounted on a newly developed stabilized platform, keeping the instruments level up to aircraft pitch and roll angles of approximately 10(exp 0). This resulted in unprecedented continuous vertical profiles

  17. Do atmospheric aerosols form glasses?

    OpenAIRE

    Zobrist, B.; Marcolli, C.; Pedernera, D. A.; Koop, T.

    2008-01-01

    A new process is presented by which water soluble organics might influence ice nucleation, ice growth, chemical reactions and water uptake of aerosols in the upper troposphere: the formation of glassy aerosol particles. Glasses are disordered amorphous (non-crystalline) solids that form when a liquid is cooled without crystallization until the viscosity increases exponentially and molecular diffusion practically ceases. The glass transition temperatures, Tg

  18. From hygroscopic aerosols to cloud droplets: The HygrA-CD campaign in the Athens basin - An overview.

    Science.gov (United States)

    Papayannis, A; Argyrouli, A; Bougiatioti, A; Remoundaki, E; Vratolis, S; Nenes, A; Solomos, S; Komppula, M; Giannakaki, E; Kalogiros, J; Banks, R; Eleftheriadis, K; Mantas, E; Diapouli, E; Tzanis, C G; Kazadzis, S; Binietoglou, I; Labzovskii, L; Vande Hey, J; Zerefos, C S

    2017-01-01

    The international experimental campaign Hygroscopic Aerosols to Cloud Droplets (HygrA-CD), organized in the Greater Athens Area (GAA), Greece from 15 May to 22 June 2014, aimed to study the physico-chemical properties of aerosols and their impact on the formation of clouds in the convective Planetary Boundary Layer (PBL). We found that under continental (W-NW-N) and Etesian (NE) synoptic wind flow and with a deep moist PBL (~2-2.5km height), mixed hygroscopic (anthropogenic, biomass burning and marine) particles arrive over the GAA, and contribute to the formation of convective non-precipitating PBL clouds (of ~16-20μm mean diameter) with vertical extent up to 500m. Under these conditions, high updraft velocities (1-2ms(-1)) and cloud condensation nuclei (CCN) concentrations (~2000cm(-3) at 1% supersaturation), generated clouds with an estimated cloud droplet number of ~600cm(-3). Under Saharan wind flow conditions (S-SW) a shallow PBL (cloud droplet number of ~200cm(-3) and without observed significant PBL cloud formation. The largest contribution to cloud droplet number variance is attributed to the updraft velocity variability, followed by variances in aerosol number concentration. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Vertical microphysical profiles of convective clouds as a tool for obtaining aerosol cloud-mediated climate forcings

    Energy Technology Data Exchange (ETDEWEB)

    Rosenfeld, Daniel [Hebrew Univ. of Jerusalem (Israel)

    2015-12-23

    Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Developing and validating this methodology was possible thanks to the ASR/ARM measurements of CCN and vertical updraft profiles. Validation against ground-based CCN instruments at the ARM sites in Oklahoma, Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25º restricts the satellite coverage to ~25% of the world area in a single day. This methodology will likely allow overcoming the challenge of quantifying the aerosol indirect effect and facilitate a substantial reduction of the uncertainty in anthropogenic climate forcing.

  20. Global distribution and climate forcing of marine organic aerosol: 1. Model improvements and evaluation

    Directory of Open Access Journals (Sweden)

    N. Meskhidze

    2011-11-01

    Full Text Available Marine organic aerosol emissions have been implemented and evaluated within the National Center of Atmospheric Research (NCAR's Community Atmosphere Model (CAM5 with the Pacific Northwest National Laboratory's 7-mode Modal Aerosol Module (MAM-7. Emissions of marine primary organic aerosols (POA, phytoplankton-produced isoprene- and monoterpenes-derived secondary organic aerosols (SOA and methane sulfonate (MS are shown to affect surface concentrations of organic aerosols in remote marine regions. Global emissions of submicron marine POA is estimated to be 7.9 and 9.4 Tg yr−1, for the Gantt et al. (2011 and Vignati et al. (2010 emission parameterizations, respectively. Marine sources of SOA and particulate MS (containing both sulfur and carbon atoms contribute an additional 0.2 and 5.1 Tg yr−1, respectively. Widespread areas over productive waters of the Northern Atlantic, Northern Pacific, and the Southern Ocean show marine-source submicron organic aerosol surface concentrations of 100 ng m−3, with values up to 400 ng m−3 over biologically productive areas. Comparison of long-term surface observations of water insoluble organic matter (WIOM with POA concentrations from the two emission parameterizations shows that despite revealed discrepancies (often more than a factor of 2, both Gantt et al. (2011 and Vignati et al. (2010 formulations are able to capture the magnitude of marine organic aerosol concentrations, with the Gantt et al. (2011 parameterization attaining better seasonality. Model simulations show that the mixing state of the marine POA can impact the surface number concentration of cloud condensation nuclei (CCN. The largest increases (up to 20% in CCN (at a supersaturation (S of 0.2% number concentration are obtained over biologically productive ocean waters when marine organic aerosol is assumed to be externally mixed with sea-salt. Assuming

  1. Devices and methods for generating an aerosol

    KAUST Repository

    Bisetti, Fabrizio

    2016-03-03

    Aerosol generators and methods of generating aerosols are provided. The aerosol can be generated at a stagnation interface between a hot, wet stream and a cold, dry stream. The aerosol has the benefit that the properties of the aerosol can be precisely controlled. The stagnation interface can be generated, for example, by the opposed flow of the hot stream and the cold stream. The aerosol generator and the aerosol generation methods are capable of producing aerosols with precise particle sizes and a narrow size distribution. The properties of the aerosol can be controlled by controlling one or more of the stream temperatures, the saturation level of the hot stream, and the flow times of the streams.

  2. CALIPSO Observations of Aerosol Properties Near Clouds

    Science.gov (United States)

    Marshak, Alexander; Varnai, Tamas; Yang, Weidong

    2010-01-01

    Clouds are surrounded by a transition zone of rapidly changing aerosol properties. Characterizing this zone is important for better understanding aerosol-cloud interactions and aerosol radiative effects as well as for improving satellite measurements of aerosol properties. We present a statistical analysis of a global dataset of CALIPSO (Cloud-Aerosol Lidar and infrared Pathfinder Satellite Observation) Lidar observations over oceans. The results show that the transition zone extends as far as 15 km away from clouds and it is ubiquitous over all oceans. The use of only high confidence level cloud-aerosol discrimination (CAD) data confirms the findings. However, the results underline the need for caution to avoid biases in studies of satellite aerosol products, aerosol-cloud interactions, and aerosol direct radiative effects.

  3. Composition, size and cloud condensation nuclei activity of biomass burning aerosol from northern Australian savannah fires

    Science.gov (United States)

    Mallet, Marc D.; Cravigan, Luke T.; Milic, Andelija; Alroe, Joel; Ristovski, Zoran D.; Ward, Jason; Keywood, Melita; Williams, Leah R.; Selleck, Paul; Miljevic, Branka

    2017-03-01

    The vast majority of Australia's fires occur in the tropical north of the continent during the dry season. These fires are a significant source of aerosol and cloud condensation nuclei (CCN) in the region, providing a unique opportunity to investigate the biomass burning aerosol (BBA) in the absence of other sources. CCN concentrations at 0.5 % supersaturation and aerosol size and chemical properties were measured at the Australian Tropical Atmospheric Research Station (ATARS) during June 2014. CCN concentrations reached over 104 cm-3 when frequent and close fires were burning - up to 45 times higher than periods with no fires. Both the size distribution and composition of BBA appeared to significantly influence CCN concentrations. A distinct diurnal trend in the proportion of BBA activating to cloud droplets was observed, with an activation ratio of 40 ± 20 % during the night and 60 ± 20 % during the day. BBA was, on average, less hygroscopic during the night (κ = 0. 04 ± 0.03) than during the day (κ = 0.07 ± 0.05), with a maximum typically observed just before midday. Size-resolved composition of BBA showed that organics comprised a constant 90 % of the aerosol volume for aerodynamic diameters between 100 and 200 nm. While this suggests that the photochemical oxidation of organics led to an increase in the hygroscopic growth and an increase in daytime activation ratios, it does not explain the decrease in hygroscopicity after midday. Modelled CCN concentrations assuming typical continental hygroscopicities produced very large overestimations of up to 200 %. Smaller, but still significant, overpredictions up to ˜ 100 % were observed using aerosol mass spectrometer (AMS)- and hygroscopicity tandem differential mobility analyser (H-TDMA)-derived hygroscopicities as well as campaign night and day averages. The largest estimations in every case occurred during the night, when the small variations in very weakly hygroscopic species corresponded to large

  4. Aerosol modeling in CNRM-CM: evaluation of recent developments on natural aerosols and implications for aerosol radiative forcing

    Science.gov (United States)

    Nabat, Pierre; Michou, Martine; Watson, Laura; Saint-Martin, David

    2017-04-01

    Aerosols interact with shortwave and longwave radiation with ensuing consequences on the radiative budget and climate. Their representation in climate models is consequently essential to estimate their radiative forcing and their role in the climate system. However, up to now, the evaluation of these aerosol schemes is often limited to the integrated atmospheric aerosol content given by the aerosol optical depth (AOD). In the climate model CNRM-CM, the TACTIC (Tropospheric Aerosols for ClimaTe in CNRM-CM, Michou et al., 2015) aerosol scheme includes the five main aerosol species (desert dust, sea-salt, sulfate, black carbon and organic matter). Recent developments have been carried out to improve the representation of natural aerosols, namely the inclusion of the parameterization of Grythe et al. (2014) for sea-salt emissions, the revision of the size distribution of sea-salt aerosols, and the increase of the number of bins to represent dust aerosols. The objective of this work is to evaluate the contribution of these developments to the representation of aerosols in CNRM-CM, using not only AOD from satellite data, but also aerosol vertical distribution and concentrations from in-situ measurements. Simulations have thus been carried out using different configurations of the aerosol scheme over the period 2000-2015, to allow for an evaluation against available measurements. The results show a relatively good performance of the model, but also reveal some discrepancies in the aerosol vertical distribution. The impact on the radiative budget of these changes in aerosol loads has been estimated, and shows the importance of the representation of natural aerosols for the estimation of aerosol radiative forcing.

  5. A high-resolution study of surfactant partitioning and kinetic limitations for two-component internally mixed aerosols

    Science.gov (United States)

    Suda, S. R.; Petters, M. D.

    2013-12-01

    Atmospheric aerosols serve as cloud condensation nuclei (CCN), altering cloud properties and ultimately affecting climate through their effect on the radiative balance. Aerosol CCN activity depends in part on aerosol composition and surfactant compounds are of particular interest because surfactants are enriched at the water/air interface, resulting in a radial concentration gradient within the aqueous droplet. Accurate treatment of the surfactant concentration gradient complicates the otherwise straightforward predictions of CCN activity for aerosols of known composition. To accurately evaluate predictions made by theory, laboratory studies investigating the relationship between critical supersaturation and dry diameter of particles that include surfactants require significant reduction in measurement uncertainty for both water-uptake and CCN measurements. Furthermore, uncertainties remain regarding kinetic limitations to surfactant partitioning that could result in deviation from predictions based on equilibrium thermodynamics. This study attempts to address some of these issues through high-resolution analysis of CCN activity of two-component mixed surfactant/non-surfactant aerosols at different internal mixing ratios performed with and without a water-uptake time delay to ascertain whether or not the observed effects are kinetically limited. We present new data for the aerosols consisting of 1) the ionic surfactant sodium dodecyl sulfate (SDS) with ammonium sulfate, 2) SDS with sodium chloride and 3) the strong non-ionic fluorosurfactant Zonyl with an organic proxy glucose. As a point of reference we also evaluated the mixture of ammonium sulfate with glucose. Aerosol activation diameters were determined using CCN analysis in conjunction with scanning mobility size classification and high sheath-to-aerosol flow ratios. This resulted in CCN-derived kappa values that could be determined within +/-5% relative error. To test whether dynamic surfactant partitioning

  6. Study of Aerosol Chemical Composition Based on Aerosol Optical Properties

    Science.gov (United States)

    Berry, Austin; Aryal, Rudra

    2015-03-01

    We investigated the variation of aerosol absorption optical properties obtained from the CIMEL Sun-Photometer measurements over three years (2012-2014) at three AERONET sites GSFC; MD Science_Center and Tudor Hill, Bermuda. These sites were chosen based on the availability of data and locations that can receive different types of aerosols from land and ocean. These absorption properties, mainly the aerosol absorption angstrom exponent, were analyzed to examine the corresponding aerosol chemical composition. We observed that the retrieved absorption angstrom exponents over the two sites, GSFC and MD Science Center, are near 1 (the theoretical value for black carbon) and with low single scattering albedo values during summer seasons indicating presence of black carbon. Strong variability of aerosol absorption properties were observed over Tudor Hill and will be analyzed based on the air mass embedded from ocean side and land side. We will also present the seasonal variability of these properties based on long-range air mass sources at these three sites. Brent Holben, NASA GSFC, AERONET, Jon Rodriguez.

  7. Unprecedented Al supersaturation in single-phase rock salt structure VAlN films by Al+ subplantation

    Science.gov (United States)

    Greczynski, G.; Mráz, S.; Hans, M.; Primetzhofer, D.; Lu, J.; Hultman, L.; Schneider, J. M.

    2017-05-01

    Modern applications of refractory ceramic thin films, predominantly as wear-protective coatings on cutting tools and on components utilized in automotive engines, require a combination of excellent mechanical properties, thermal stability, and oxidation resistance. Conventional design approaches for transition metal nitride coatings with improved thermal and chemical stability are based on alloying with Al. It is well known that the solubility of Al in NaCl-structure transition metal nitrides is limited. Hence, the great challenge is to increase the Al concentration substantially while avoiding precipitation of the thermodynamically favored wurtzite-AlN phase, which is detrimental to mechanical properties. Here, we use VAlN as a model system to illustrate a new concept for the synthesis of metastable single-phase NaCl-structure thin films with the Al content far beyond solubility limits obtained with conventional plasma processes. This supersaturation is achieved by separating the film-forming species in time and energy domains through synchronization of the 70-μs-long pulsed substrate bias with intense periodic fluxes of energetic Al+ metal ions during reactive hybrid high power impulse magnetron sputtering of the Al target and direct current magnetron sputtering of the V target in the Ar/N2 gas mixture. Hereby, Al is subplanted into the cubic VN grains formed by the continuous flux of low-energy V neutrals. We show that Al subplantation enables an unprecedented 42% increase in metastable Al solubility limit in V1-xAlxN, from x = 0.52 obtained with the conventional method to 0.75. The elastic modulus is 325 ± 5 GPa, in excellent agreement with density functional theory calculations, and approximately 50% higher than for corresponding films grown by dc magnetron sputtering. The extension of the presented strategy to other Al-ion-assisted vapor deposition methods or materials systems is straightforward, which opens up the way for producing supersaturated single

  8. Theoretical and experimental investigation of drug-polymer interaction and miscibility and its impact on drug