Artigos de revistas: "Atmospheric microlidar"

1

Arumov, G. P., e A. V. Bukharin. "Miniaturization of elastic scattering lidars: determination of the microstructure of the surface layer of the atmosphere". Izmeritel`naya Tekhnika, n.º 4 (26 de junho de 2024): 32–38. http://dx.doi.org/10.32446/0368-1025it.2024-4-32-38.

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Miniature elastic scattering lidars with similar schemes for determining the microstructure of the surface layer of the atmosphere are considered. In the considered microlidar model, it is assumed that in the limiting case there may be no particles in a small probed volume. In this case, the minimum value of the return signal corresponds to molecular scattering. The excess of the signal above this level is associated with the presence of a particle. The molecular component of the backscatter signal is constant and can be compared to a tabulated value of the backscatter coefficient using an optical atmospheric model. This makes it possible to compare the average value of the total backscattering signal from molecules and particles with the overall backscattering coefficient. A scheme similar to a microlidar, but on an enlarged scale – a minilidar – is considered. For both such schemes, the average values of atmospheric backscatter signals are the same. For a minilidar, the return signal is formed by scattering from a layer ranging in size from several meters to several tens of meters. In this case, the probed volume can be determined using perforated screens and reflective spheres. It is shown that the ratio of the probed volumes for the minilidar and microlidar is equal to the similarity coefficient to the fourth power. The considered lidars can be used to determine the concentration of equivalent particles.

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2

Krichbaumer, W. "Airborne Cloud Measurements with the DLR Microlidar during the CLEOPATRA Campaign". Journal of Atmospheric and Oceanic Technology 13, n.º 1 (fevereiro de 1996): 54–57. http://dx.doi.org/10.1175/1520-0426(1996)013<0054:acmwtd>2.0.co;2.

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3

Mariage, Vincent, Jacques Pelon, Frédéric Blouzon, Stéphane Victori, Nicolas Geyskens, Nadir Amarouche, Christine Drezen et al. "IAOOS microlidar-on-buoy development and first atmospheric observations obtained during 2014 and 2015 arctic drifts". Optics Express 25, n.º 4 (13 de janeiro de 2017): A73. http://dx.doi.org/10.1364/oe.25.000a73.

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Fierli, F., G. Di Donfrancesco, F. Cairo, V. Marécal, M. Zampieri, E. Orlandi e G. Durry. "Variability of cirrus clouds in a convective outflow during the Hibiscus campaign". Atmospheric Chemistry and Physics 8, n.º 16 (6 de agosto de 2008): 4547–58. http://dx.doi.org/10.5194/acp-8-4547-2008.

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Abstract. Light-weight microlidar and water vapour measurements were taken on-board a stratospheric balloon during the HIBISCUS 2004 campaign, held in Bauru, Brazil (49° W, 22° S). Cirrus clouds were observed throughout the flight between 12 and 15 km height with a high mesoscale variability in optical and microphysical properties. It was found that the cirrus clouds were composed of different layers characterized by marked differences in height, thickness and optical properties. Simultaneous water vapour observations show that the different layers are characterized by different values of the saturation with respect to ice. A mesoscale simulation and a trajectory analysis clearly revealed that the clouds had formed in the outflow of a large and persistent convective region and that the observed variability of the optical properties and of the cloud structure is likely linked to the different residence times of the convectively-processed air in the upper troposphere.

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5

Chen, Lee Chuin, Tsubasa Naito, Satoshi Ninomiya e Kenzo Hiraoka. "Hyphenation of high-temperature liquid chromatography with high-pressure electrospray ionization for subcritical water LC-ESI-MS". Analyst 143, n.º 22 (2018): 5552–58. http://dx.doi.org/10.1039/c8an01113c.

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6

Budke, C., e T. Koop. "BINARY: an optical freezing array for assessing temperature and time dependence of heterogeneous ice nucleation". Atmospheric Measurement Techniques 8, n.º 2 (10 de fevereiro de 2015): 689–703. http://dx.doi.org/10.5194/amt-8-689-2015.

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Abstract. A new optical freezing array for the study of heterogeneous ice nucleation in microliter-sized droplets is introduced, tested and applied to the study of immersion freezing in aqueous Snomax® suspensions. In the Bielefeld Ice Nucleation ARraY (BINARY) ice nucleation can be studied simultaneously in 36 droplets at temperatures down to −40 °C (233 K) and at cooling rates between 0.1 and 10 K min−1. The droplets are separated from each other in individual compartments, thus preventing a Wegener–Bergeron–Findeisen type water vapor transfer between droplets as well as avoiding the seeding of neighboring droplets by formation and surface growth of frost halos. Analysis of freezing and melting occurs via an automated real-time image analysis of the optical brightness of each individual droplet. As an application ice nucleation in water droplets containing Snomax® at concentrations from 1 ng mL−1 to 1 mg mL−1 was investigated. Using different cooling rates, a small time dependence of ice nucleation induced by two different classes of ice nucleators (INs) contained in Snomax® was detected and the corresponding heterogeneous ice nucleation rate coefficient was quantified. The observed time dependence is smaller than those of other types of INs reported in the literature, suggesting that the BINARY setup is suitable for quantifying time dependence for most other INs of atmospheric interest, making it a useful tool for future investigations.

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Ma, Chang-Jin, Cheol-Soo Lim e Takuro Sakai. "Preliminary Study on the Elemental Quantification of in Ambient Liquid Samples of Microliter Volume Using the In-air Micro-PIXE Technique". Asian Journal of Atmospheric Environment 11, n.º 1 (31 de março de 2017): 54–60. http://dx.doi.org/10.5572/ajae.2017.11.1.054.

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8

Budke, C., e T. Koop. "BINARY: an optical freezing array for assessing temperature and time dependence of heterogeneous ice nucleation". Atmospheric Measurement Techniques Discussions 7, n.º 9 (10 de setembro de 2014): 9137–72. http://dx.doi.org/10.5194/amtd-7-9137-2014.

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Abstract. A new optical freezing array for the study of heterogeneous ice nucleation in microliter-sized droplets is introduced, tested and applied to the study of immersion freezing in aqueous Snomax® suspensions. In the Bielefeld Ice Nucleation ARraY (BINARY) ice nucleation can be studied simultaneously in 36 droplets at temperatures down to −40 °C (233 K) and at cooling rates between 0.1 K min−1 and 10 K min−1. The droplets are separated from each other in individual compartments, thus preventing a Wegener–Bergeron–Findeisen type water vapor transfer between droplets as well as avoiding the seeding of neighboring droplets by formation and surface growth of frost halos. Analysis of freezing and melting occurs via an automated real time image analysis of the optical brightness of each individual droplet. As an application ice nucleation in water droplets containing Snomax® at concentrations from 1 ng mL−1 to 1 mg mL−1 was investigated. Using different cooling rates a minute time dependence of ice nucleation induced by Class A and Class C ice nucleators contained in Snomax® was detected. For the Class A IN a very strong increase of the heterogeneous ice nucleation rate coefficient with decreasing temperature of λ ≡ −dln(jhet)/dT = 8.7 K−1 was observed emphasizing the capability of the BINARY device. This value is larger than those of other types of IN reported in the literature, suggesting that the BINARY setup is suitable for quantifying time dependence for most other IN of atmospheric interest, making it a useful tool for future investigations.

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9

Kunert, Anna T., Mark Lamneck, Frank Helleis, Ulrich Pöschl, Mira L. Pöhlker e Janine Fröhlich-Nowoisky. "Twin-plate Ice Nucleation Assay (TINA) with infrared detection for high-throughput droplet freezing experiments with biological ice nuclei in laboratory and field samples". Atmospheric Measurement Techniques 11, n.º 11 (23 de novembro de 2018): 6327–37. http://dx.doi.org/10.5194/amt-11-6327-2018.

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Abstract. For efficient analysis and characterization of biological ice nuclei under immersion freezing conditions, we developed the Twin-plate Ice Nucleation Assay (TINA) for high-throughput droplet freezing experiments, in which the temperature profile and freezing of each droplet is tracked by an infrared detector. In the fully automated setup, a couple of independently cooled aluminum blocks carrying two 96-well plates and two 384-well plates, respectively, are available to study ice nucleation and freezing events simultaneously in hundreds of microliter-range droplets (0.1–40 µL). A cooling system with two refrigerant circulation loops is used for high-precision temperature control (uncertainty <0.2 K), enabling measurements over a wide range of temperatures (∼ 272–233 K) at variable cooling rates (up to 10 K min−1). The TINA instrument was tested and characterized in experiments with bacterial and fungal ice nuclei (IN) from Pseudomonas syringae (Snomax®) and Mortierella alpina, exhibiting freezing curves in good agreement with literature data. Moreover, TINA was applied to investigate the influence of chemical processing on the activity of biological IN, in particular the effects of oxidation and nitration reactions. Upon exposure of Snomax® to O3 and NO2, the cumulative number of IN active at 270–266 K decreased by more than 1 order of magnitude. Furthermore, TINA was used to study aqueous extracts of atmospheric aerosols, simultaneously investigating a multitude of samples that were pre-treated in different ways to distinguish different kinds of IN. For example, heat treatment and filtration indicated that most biological IN were larger than 5 µm. The results confirm that TINA is suitable for high-throughput experiments and efficient analysis of biological IN in laboratory and field samples.

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Hawkins, Lelia Nahid, Hannah G. Welsh e Matthew V. Alexander. "Evidence for pyrazine-based chromophores in cloud water mimics containing methylglyoxal and ammonium sulfate". Atmospheric Chemistry and Physics 18, n.º 16 (28 de agosto de 2018): 12413–31. http://dx.doi.org/10.5194/acp-18-12413-2018.

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Abstract. Simulating aqueous brown carbon (aqBrC) formation from small molecule amines and aldehydes in cloud water mimics provides insight into potential humic-like substance (HULIS) contributors and their effect on local and global aerosol radiative forcing. Previous work has shown that these (Maillard type) reactions generate products that are chemically, physically, and optically similar to atmospheric HULIS in many significant ways, including in their complexity. Despite numerous characterization studies, attribution of the intense brown color of many aqBrC systems to specific compounds remains incomplete. In this work, we present evidence of novel pyrazine-based chromophores (PBCs) in the product mixture of aqueous solutions containing methylglyoxal and ammonium sulfate. PBCs observed here include 2,5-dimethyl pyrazine (DMP) and products of methylglyoxal addition to the pyrazine ring. This finding is significant as the literature of Maillard reactions in food chemistry tightly links the formation of pyrazine (and related compounds) to browning in foods. We investigated the roles of both cloud processing (by bulk evaporation) and pH in absorptivity and product distribution in microliter samples to understand the contribution of these PBCs to aqBrC properties. In agreement with previous work, we observed elevated absorptivity across the entire UV–visible spectrum following simulated cloud processing as well as higher absorptivity in more basic samples. Absorptivity of the pH 2 sample, following evaporation over a period of days, exceeded that of the unevaporated pH 9 sample. In addition, mixtures of ammonium sulfate and methylglyoxal at pH 5 that were dried in under 1 h and analyzed 24 h later were as absorptive as pH 9 samples allowed to react for 7 days, indicating that evaporation occurring during cloud processing may provide a reaction pathway favorable for carbonyl–ammonia chemistry even under acidic conditions of aerosol and cloud water. The fraction of pyrazine compounds in the product mixture increased by up to a factor of 4 in response to drying with a maximum observed contribution of 16 % at pH 5. Therefore, cloud processing under acidic conditions may produce PBCs at the expense of imine- and imidazole-derived compounds. This finding has implications for further BrC reactivity and degradation pathways.

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11

Grawe, Sarah, Stefanie Augustin-Bauditz, Hans-Christian Clemen, Martin Ebert, Stine Eriksen Hammer, Jasmin Lubitz, Naama Reicher et al. "Coal fly ash: linking immersion freezing behavior and physicochemical particle properties". Atmospheric Chemistry and Physics 18, n.º 19 (2 de outubro de 2018): 13903–23. http://dx.doi.org/10.5194/acp-18-13903-2018.

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Abstract. To date, only a few studies have investigated the potential of coal fly ash particles to trigger heterogeneous ice nucleation in cloud droplets. The presented measurements aim at expanding the sparse dataset and improving process understanding of how physicochemical particle properties can influence the freezing behavior of coal fly ash particles immersed in water. Firstly, immersion freezing measurements were performed with two single particle techniques, i.e., the Leipzig Aerosol Cloud Interaction Simulator (LACIS) and the SPectrometer for Ice Nuclei (SPIN). The effect of suspension time on the efficiency of the coal fly ash particles when immersed in a cloud droplet is analyzed based on the different residence times of the two instruments and employing both dry and wet particle generation. Secondly, two cold-stage setups, one using microliter sized droplets (Leipzig Ice Nucleation Array) and one using nanoliter sized droplets (WeIzmann Supercooled Droplets Observation on Microarray setup) were applied. We found that coal fly ash particles are comparable to mineral dust in their immersion freezing behavior when being dry generated. However, a significant decrease in immersion freezing efficiency was observed during experiments with wet-generated particles in LACIS and SPIN. The efficiency of wet-generated particles is in agreement with the cold-stage measurements. In order to understand the reason behind the deactivation, a series of chemical composition, morphology, and crystallography analyses (single particle mass spectrometry, scanning electron microscopy coupled with energy dispersive X-ray microanalysis, X-ray diffraction analysis) were performed with dry- and wet-generated particles. From these investigations, we conclude that anhydrous CaSO4 and CaO – which, if investigated in pure form, show the same qualitative immersion freezing behavior as observed for dry-generated coal fly ash particles – contribute to triggering heterogeneous ice nucleation at the particle–water interface. The observed deactivation in contact with water is related to changes in the particle surface properties which are potentially caused by hydration of CaSO4 and CaO. The contribution of coal fly ash to the ambient population of ice-nucleating particles therefore depends on whether and for how long particles are immersed in cloud droplets.

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12

Gabel, J. C., K. D. Fallon, G. A. Laine e R. E. Drake. "Lung lymph flow during volume infusions". Journal of Applied Physiology 60, n.º 2 (1 de fevereiro de 1986): 623–29. http://dx.doi.org/10.1152/jappl.1986.60.2.623.

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We investigated the effect of intravenous isotonic crystalloid solution infusion on lung lymph flow. Tracheobronchial lung lymph vessels were cannulated in 13 anesthetized dogs. The lymph flow rate was measured 1) with the lymph flowing against atmospheric pressure (QL), and 2) with the pressure at the outflow end of the lymph cannula equal to systemic venous pressure (QLV). QL and QLV were measured alternately in each lymph vessel. In one group of nine dogs, the base-line QL and QLV were 18 +/- 9 and 13 +/- 6 (SD) microliter/min, respectively (P less than 0.05). QL increased by 4.8 +/- 1.4-fold, and QLV increased by 3.5 +/- 2.1-fold during a 4-h infusion of 25 ml X kg-1 X h-1 of Ringer solution. QLV was significantly less than QL at all times. The increases in lymph flow were caused primarily by a reduction in the effective resistance of the lymph vessels with little rise in the pressure driving lymph from the lungs. Because QLV flowed against systemic venous pressure, the increase in QLV was blunted by a 3.1 +/- 2.3 cmH2O rise in venous pressure during the infusions. In the remaining four dogs, we infused Ringer solution rapidly in order to raise venous pressure to greater than 15 cmH2O. This caused QL to increase by 25 +/- 7-fold; however, QLV decreased to zero. We conclude that elevations in venous pressure which occur during volume infusions oppose lung lymph flow and lead to accumulation of excess fluid in the lungs.

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13

Huang, Shuquan, Jessica Connolly, Andrei Khlystov e Richard B. Fair. "Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols". Sensors 20, n.º 5 (27 de fevereiro de 2020): 1281. http://dx.doi.org/10.3390/s20051281.

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A prototype aerosol detection system is presented that is designed to accurately and quickly measure the concentration of selected inorganic ions in the atmosphere. The aerosol detection system combines digital microfluidics technology, aerosol impaction and chemical detection integrated on the same chip. Target compounds are the major inorganic aerosol constituents: sulfate, nitrate and ammonium. The digital microfluidic system consists of top and bottom plates that sandwich a fluid layer. Nozzles for an inertial impactor are built into the top plate according to known, scaling principles. The deposited air particles are densely concentrated in well-defined deposits on the bottom plate containing droplet actuation electrodes of the chip in fixed areas. The aerosol collection efficiency for particles larger than 100 nm in diameter was higher than 95%. After a collection phase, deposits are dissolved into a scanning droplet. Due to a sub-microliter droplet size, the obtained extract is highly concentrated. Droplets then pass through an air/oil interface on chip for colorimetric analysis by spectrophotometry using optical fibers placed between the two plates of the chip. To create a standard curve for each analyte, six different concentrations of liquid standards were chosen for each assay and dispensed from on-chip reservoirs. The droplet mixing was completed in a few seconds and the final droplet was transported to the detection position as soon as the mixing was finished. Limits of detection (LOD) in the final droplet were determined to be 11 ppm for sulfate and 0.26 ppm for ammonium. For nitrate, it was impossible to get stable measurements. The LOD of the on-chip measurements for sulfate was close to that obtained by an off-chip method using a Tecan spectrometer. LOD of the on-chip method for ammonium was about five times larger than what was obtained with the off-chip method. For the current impactor collection air flow (1 L/min) and 1 h collection time, the converted LODs in air were: 0.275 μg/m3 for sulfate, 6.5 ng/m3 for ammonium, sufficient for most ambient air monitoring applications.

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14

Pelon, J., M. Mallet, A. Mariscal, P. Goloub, D. Tanré, D. Bou Karam, C. Flamant, J. Haywood, B. Pospichal e S. Victori. "Microlidar observations of biomass burning aerosol over Djougou (Benin) during African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and Biomass-Burning Experiment". Journal of Geophysical Research 113 (13 de dezembro de 2008). http://dx.doi.org/10.1029/2008jd009976.

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15

Shao, Fangchi, Kuangwen Hsieh, Pengfei Zhang, Aniruddha M. Kaushik e Tza-Huei Wang. "Facile and scalable tubing-free sample loading for droplet microfluidics". Scientific Reports 12, n.º 1 (3 de agosto de 2022). http://dx.doi.org/10.1038/s41598-022-17352-3.

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AbstractDroplet microfluidics has in recent years found a wide range of analytical and bioanalytical applications. In droplet microfluidics, the samples that are discretized into droplets within the devices are predominantly loaded through tubings, but such tubing-based sample loading has drawbacks such as limited scalability for processing many samples, difficulty for automation, and sample wastage. While advances in autosamplers have alleviated some of these drawbacks, sample loading that can instead obviate tubings offers a potentially promising alternative but has been underexplored. To fill the gap, we introduce herein a droplet device that features a new Tubing Eliminated Sample Loading Interface (TESLI). TESLI integrates a network of programmable pneumatic microvalves that regulate vacuum and pressure sources so that successive sub-microliter samples can be directly spotted onto the open-to-atmosphere TESLI inlet, vacuumed into the device, and pressurized into nanoliter droplets within the device with minimal wastage. The same vacuum and pressure regulation also endows TESLI with cleaning and sample switching capabilities, thus enabling scalable processing of many samples in succession. Moreover, we implement a pair of TESLIs in our device to parallelize and alternate their operation as means to minimizing idle time. For demonstration, we use our device to successively process 44 samples into droplets—a number that can further scale. Our results demonstrate the feasibility of tubing-free sample loading and a promising approach for advancing droplet microfluidics.

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Artigos de revistas sobre o tema "Atmospheric microlidar"

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