A Numerical Study of Calm Air Sampling with a Blunt Sampler

The performance of an idealized spherical sampler facing both vertically upwards and downwards in calm air is studied numerically. To describe the air flow around the sampler, both potential and viscous flow models have been adopted. The equations of particle motion are then solved to calculate the aspiration efficiency. The dependence of the aspiration efficiency upon the various parameters of importance in calm air sampling are investigated and compared where possible with the experimental work of Su and Vincent (2003 Su, W. C. and Vincent, J. H. 2003. Experimental Measurements of Aspiration Efficiency for Idealized Spherical Aerosol Samplers in Calm Air. J. Aerosol Sci., 34: 1151–1165. [CSA][CROSSREF][Crossref], [Web of Science ®] , [Google Scholar], 2004a Su, W. C. and Vincent, J. H. 2004a. Experimental Measurements and Numerical Calculations of Aspiration Efficiency for Cylindrical Thin-Walled Aerosol Samplers in Perfectly Calm Air. Aerosol Sci. Tech., 38: 766–781. [CSA][CROSSREF][Taylor & Francis Online], [Web of Science ®] , [Google Scholar], b Su, W. C. and Vincent, J. H. 2004b. Towards a General Semi-Empirical Model for the Aspiration Efficiencies of Aerosol Samplers in Perfectly Calm Air. J. Aerosol Sci., 35: 1119–1134. [CSA][CROSSREF][Crossref] , [Google Scholar]).

It is found that in the case of upwards sampling the bluntness of the sampler only has a significant effect upon aspiration for large sampling velocities, values that would not generally be physically realistic. In the case of downwards sampling an important non-dimensional quantity, B ² R _C , is identified, where B represents the sampler bluntness and R _C represents the gravitational effects. This quantity determines the physical conditions for which aspiration will not occur and also the limiting values of the aspiration efficiency when aspiration does occur. In the case of low sampling velocities a difference is noted between experimental and numerical results for aspiration efficiency raising the need for more experimental data in this area. For both upwards and downwards sampling the semi-empirical models of Su and Vincent (2004b) Su, W. C. and Vincent, J. H. 2004b. Towards a General Semi-Empirical Model for the Aspiration Efficiencies of Aerosol Samplers in Perfectly Calm Air. J. Aerosol Sci., 35: 1119–1134. [CSA][CROSSREF][Crossref] , [Google Scholar] have been modified to account for the information gained from the study. This is particularly important in the downwards sampling case where the modified model is found to agree particularly well with the results obtained.     

Bias in Filter-Based Aerosol Light Absorption Measurements Due to Organic Aerosol Loading: Evidence from Laboratory Measurements

Light absorption by soot or nigrosin dye aerosol particles were measured in the laboratory using a particle soot absorption photometer (PSAP) and a photo-acoustic spectrometer (PAS) to assess the influence of non-absorbing organic aerosol (OA) on the PSAP measurements. For the PSAP, particle light absorption is measured after collection on a filter, whereas for the PAS light absorption is measured while the particles remain suspended in the gas phase. OA was generated from the reaction of α -pinene with ozone. It was observed that the presence of this OA in an external mixture of absorbing aerosol and OA can cause an increase in the light absorption measured by the PSAP, relative to that measured by the PAS, by more than a factor of two. This enhancement in the PSAP absorption was found to increase as the amount of OA increased relative to the absorbing compound. Additionally, experiments where absorbing aerosol was deposited on a PSAP filter prior to addition of OA demonstrated that the non-absorbing OA can actually appear as if it were absorbing, with measured single scattering albedo values as low as 0.92. These results indicate that filter-based measurement techniques may significantly overestimate light absorption by aerosols in the atmosphere under conditions where the organic loading is large, with consequent implications for understanding and calculating the Earth's radiation budget. These laboratory experiments aid in the interpretation of results from a recent field study, discussed in a companion article (Lack et al. 2008 Lack, D. A., Cappa, C. D., Baynard, T., Massoli, P., Covert, D. S., Sierau, B., Bates, T. S., Quinn, P. K., Lovejoy, E. R. and Ravishankara, A. R. 2008. Bias in Filter-Based Aerosol Absorption Measurements Due to Organic Aerosol Loading: Evidence from Ambient Measurements. Aerosol Sci. and Technol., 42: 1033–1041. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]).     

Theory of Multi-Nozzle Impactor Stages and the Interpretation of Stage Mensuration Data

We describe a general theory of multi-nozzle cascade impactor stages and show how testers of inhaled drug products, such as metered-dose or dry-powder inhalers, can decide, solely from the stage nozzle dimensions, whether any used impactor is satisfactorily operating within its expected aerodynamic performance range. We first account for the realistic shape of particle collection efficiency curves and show that the effective diameter, described by Roberts and Romay (2005) Roberts D. L.Romay F. J.Relationship of Stage Mensuration Data to the Performance of New and Used Cascade ImpactorsJ. Aerosol Med2005184396–413[Crossref], [PubMed] , [Google Scholar], is sufficiently accurate as the primary indication of the aerodynamic performance.

To ensure that a used impactor is performing in the same aerodynamic range allowed for new impactors, one must also satisfy the other, more secondary factors of cascade impaction aerodynamics, most notably the distance to the collection surface relative to the nozzle diameter. We show what this constraint means in practice for used Next Generation Impactors (NGIs; Marple et al. 2003a Marple V. A.Roberts D. L.Romay F. J.Miller N. C.Truman K. G.Van Oort M.Olsson B.Holroyd M. J.Mitchell J. P.Hochrainer D.Next Generation Pharmaceutical Impactor, Part I: DesignJ. Aerosol Med2003a16283–299[Crossref], [PubMed] , [Google Scholar], b Marple V. A.Olson B. A.Santhanakrishnan K.Mitchell J. P.Murray S. C.Hudson-Curtis B. L.Next Generation Pharmaceutical Impactor—Part II: Archival CalibrationJ. Aerosol Med2003b16[Crossref], [PubMed] , [Google Scholar]; 2004 Marple V. A.Olson B. A.Santhanakrishnan K.Roberts D. L.Mitchell J. P.Hudson-Curtis B. L.Next Generation Pharmaceutical Impactor: A New Impactor for Pharmaceutical Inhaler Testing. Part III. Extension of Archival Calibration to 15 L/minJ. Aerosol Med200417335–343[Crossref], [PubMed] , [Google Scholar]), and show that partially occluded nozzles are the most likely nozzles to fail this test.

Applying this principle that used impactors should perform in the same aerodynamic range as new impactors, we derive constraints on the nozzle diameters of any used NGI (Table 6, main text). We can partially apply this principle to other common impactors used for inhaler testing, such as the Andersen and the Marple-Miller, but are hindered by the absence of a published acceptable range for the distance to the impaction collection surface and by the limited published information on the shape of their stage collection efficiency curves.     

Quantification of Carboxylic and Carbonyl Functional Groups in Organic Aerosol Infrared Absorbance Spectra

Atmospheric aerosols are one of the least understood components of the climate system and incur adverse health effects on susceptible populations. Organic aerosols can make up as much as 80% of atmospheric aerosols (Lim and Turpin 2002 Lim, H. J. and Turpin, B. J. 2002. Origins of Primary and Secondary Organic Aerosol in Atlanta: Results’ of Time-Resolved Measurements During the Atlanta supersite experiment. Environ. Sci. Technol., 36: 4489–4496. 10.1021/es0206487[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), and so its quantification and characterization plays an important role in reducing our uncertainty with regards to aerosol impacts on health and climate. As the number of organic molecules in the atmosphere are diverse in number (Hamilton et al. 2004 Hamilton, J. F., Webb, P. J., Lewis, A. C., Hopkins, J. R., Smith, S. and Davy, P. 2004. Partially Oxidised Organic Components in Urban Aerosol using GCXGC-TOF/MS. Atmos. Chem. Phys., 4: 1279–1290. [Crossref], [Web of Science ®] , [Google Scholar]), we advance a functional group representation of organic molecules as measured by Fourier transform infrared spectroscopy (FTIR) to characterize the chemical composition of particle samples. This study describes and evaluates the algorithm introduced by Russell et al. (2009 Russell, L. M., Takahama, S., Liu, S., Hawkins, L. N., Covert, D. S.Quinn, P. K. 2009. Oxygenated Fraction and Mass of Organic Aerosol from Direct Emission and Atmospheric Processing Measured on the R/V Ronald Brown During TEXAQS/GoMACCS 2006. J. Geophys. Res.-Atmos., 114: D00F05 10.1029/2008JD011275[Crossref], [Web of Science ®] , [Google Scholar]) for apportionment and quantification of oxygenated (carbonyl and hydroxyl) functional groups from infrared absorption spectra. Molar absorptivities for carbonyl and hydroxyl bonds in carboxylic groups are obtained for several dicarboxylic compounds, and applied to a multifunctional compound and mixture to demonstrate the applicability of this method for more complex samples. Furthermore, functional group abundances of two aldehydic compounds, 2-deoxy-d-ribose and glyceraldehyde, atomized from aqueous solution are in quantitative agreement with number of bonds predicted after transformation of these compounds into diols. The procedure for spectra interpretation and quantitative analysis is described through the context of an algorithm in which contributions of background and analyte absorption to the infrared spectrum are apportioned by the superposition of lineshapes constrained by laboratory measurements.

Copyright 2013 American Association for Aerosol Research     

Numerical Evaluation of the Transfer Function of a Low Pressure DMA by Using the Langevin Dynamic Equation

The effect of Brownian diffusive particle trajectory of nanoparticles on the transfer function of the low pressure Differential Mobility Analyzer (LPDMA) was evaluated by a numerical simulation of the Langevin dynamic equation. The results of the simulation were compared with previously reported experimental results (Seto et al. 1997 Seto, T., Nakamoto, T., Okuyama, K., Adachi, M., Kuga, Y. and Takeuchi, K. 1997. Size Distribution Measurement of Nanometer-Sized Aerosol Particles using DMA under Low-Pressure Conditions. J. Aerosol Sci., 28: 193–206. [CROSSREF][Crossref] , [Google Scholar]; Seol et al. 2000 Seol, K. S., Tsutatani, Y., Camata, R. P., Yabumoto, J., Isomura, S., Okada, Y., Okuyama, K. and Takeuchi, K. 2000. A Differential Mobility Analyzer and A Faraday Cup Electrometer for Operation at 200-930 Pa Pressure. J. Aerosol Sci., 31: 1389–1395. [CSA][CROSSREF][Crossref] , [Google Scholar]) and Stolzenburg's transfer function (1988). As the operational pressure decreased, the peak and FWHM (full width of the transfer function at half of its maximum) values of transfer function, as calculated by numerical simulation, were increased, which was not evident from Stolzenburg's transfer function. In comparison with the experiments of Seto et al., discrepancies in the higher electrical mobility regime than from central mobility were found, which could be caused by the incomplete flow control of their LPDMA. However, the transfer function, as calculated by numerical simulation was in good agreement with experimental results reported by Seol et al., performed with the improved LPDMA at well-controlled operation conditions.     

Experimental Measurement and Numerical Study of Particle Deposition in Highly Idealized Mouth-Throat Models

Particle deposition in the human mouth-throat is an important factor in evaluating efficiency of drug delivered by inhalation devices, such as pMDIs or DPIs. Current USP standard impactor induction ports (which serve as an in vitro representative of the adult mouth-throat) underpredict in vivo mouth-throat deposition. However, preliminary experimental data in the prototype geometry of a highly idealized mouth-throat has indicated that it is a promising replacement for the USP mouth-throat (Zhang et al. 2004 Zhang, Y., Finlay, W. H. and Matida, E. A. 2004. Particle Deposition Measurements and Numerical Simulation in a Highly Idealized Mouth-Throat. J. Aerosol Sci., 35: 789–803. [CROSSREF][CSA][Crossref] , [Google Scholar]).

In this study, partial optimization design of the highly idealized mouth-throat was performed using computational fluid dynamics (CFD) simulations. The performance of six candidate highly idealized mouth-throat geometries, each with a straight tube inlet of inner diameter 17.3 mm, was evaluated experimentally by measuring monodisperse particle deposition efficiency. Gravimetry was used to determine particle deposition in these geometries. Monodisperse particles of di-2-ethylhexyl-sebecate (DEHS) oil with mass median diameters of 2.1–7.5 μm (GSD < 1.1) were used at two steady inhalation flow rates of 30 and 90 l/min. The results showed that, at the higher flow rate of 90 l/min, a mouth-throat with a bend region 8.5 mm in diameter and a curvature radius of 50 mm follows the in vivo average summarized by Stahlhofen et al. (1989) Stahlhofen, W., Rudolf, G. and James, A. C. 1989. Intercomparison of Experimental Regional Aerosol Deposition Data. J. Aerosol Med., 2(3): 285–308. [CSA][Crossref] , [Google Scholar] most closely. In contrast, at the lower flow rate of 30 l/min, the mouth-throat with a bend region 7.5 mm in diameter mimics the above in vivo curve but the in vivo-in vitro match is worse than for 90 l/min case. Enhanced particle deposition caused by a Reynolds number effect was observed in all geometries studied. Overall, an adequately designed highly idealized mouth-throat can largely reproduce in vivo mouth-throat deposition. For different flow rates, different key dimensions are required with the present highly idealized mouth-throats in order to adequately reproduce the in vivo average curve.     

Skylight Color Shifts due to Variations of Urban-Industrial Aerosol Properties: Observer Color Difference Sensitivity Compared to a Digital Camera

Simulations of the sky dome color shifts of a cloudless sky have been performed, assuming three urban-industrial tropospheric aerosol cases. Each of these aerosols is represented by the bimodal lognormal volume distribution (Dubovik et al. 2002 Dubovik, O., Holben, B., Eck, T. F., Smirnov, A., Kaufman, Y. J., King, M. D., Tanré, D. and Slutsker, I. 2002. Variability of Absorption and Optical Properties of Key Aerosol Types Observed in Worldwide Locations. J. Atm. Sci., 59: 590–608. [Crossref], [Web of Science ®] , [Google Scholar]). A total of ten parameters are used to control the aerosol characteristics. These ten parameters are perturbed and the resulting sky color shifts are estimated. All simulations have been performed relative to the reference cases that represent the time-averaged state of each aerosol case. We have simulated the sensitivity of the theoretical CIE (Commission Internationale de l′ Eclairage) standard human observer to discriminate sky color changes, due to changes of the aerosol control parameters. A Digital color Camera Model (DCM) has also been incorporated in the simulation scheme. The DCM simulates the performance of a camera-colorimeter created specifically to measure sky color. The DCM has been used to investigate whether a color digital camera can replicate the behavior of the CIE standard observer, with respect to sky color shifts. The standard observer is most sensitive to perturbations of the parameters of the aerosol fine mode, which are particles with diameters less than 0.6 μ m. However his sensitivity is highly variable, depending on the parameter varied, on the aerosol case and on the direction of the observation. The DCM was in excellent agreement with the behavior of the CIE standard observer. The camera simulated sky color measurement accuracy was high. The results show that the camera sensitivity in discriminating color differences is much better than that of the observer.     

Numerical Modeling of Nanoparticle Collection Efficiency of Single-Stage Wire-in-Plate Electrostatic Precipitators

The numerical models for predicting the collection efficiency of particles in the size range of 0.3 ～ 10.0 μm in electrostatic precipitators (ESPs) have been well developed. However, for nanoparticles, or particles with the diameter below 100 nm, the existing models can't predict the collection efficiency very well because the electric field and ion concentration distribution were not simulated, or charging models were not adopted appropriately to calculate particle charges. In this study, a 2-D numerical model was developed to predict the nanoparticle collection efficiency in single-stage wire-in-plate ESPs. Laminar flow field was solved by using the Semi-Implicit Method for Pressure-Linked Equation (SIMPLER Method), while electric field strength and ion concentration distribution were solved based on Poisson and diffusion-convection equations, respectively. The charged particle concentration distribution and the particle collection efficiency were then calculated based on the convection-diffusion equation with particle charging calculated by Fuchs diffusion charging theory. The simulated collection efficiencies of 6–100 nm nanoparticles were compared with the experimental data of Huang and Chen (2002 Huang, S. H. and Chen, C. C. 2002. Ultrafine Aerosol Penetration through Electrostatic Precipitators.. Environ. Sci. Technol., 36: 4625–4632. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) for a wire-in-plate dry ESP (aerosol flow rate: 100 L/min, applied voltage: ?15.5 ～ –21.5 kV). Good agreement was obtained. The simulated particle collection efficiencies were further shown to agree with the experimental data obtained in the study for a wire-in-plate wet ESP (Lin et al. 2010 Lin, G. Y., Tsai, C. J., Chen, S. C., Tzu, M. C. and Li, S. N. 2010. An Efficient Single-Stage Wet Electrostatic Precipitator for Fine and Nanosized Particle Control.. Aerosol Sci. Technol, 44: 38–45. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) (aerosol flow rate: 5 L/min, applied voltage: +3.6 ～+4.3 kV) using monodisperse NaCl particles of 10 and 50 nm in diameter. It is expected that the present model can be used to facilitate the design of ESPs for nanoparticle control and electrostatic nanoparticle samplers.     

Design,synthesis, and preliminary evaluation as antimicrobial activity of novel spiro-1, 3-thiazolidine C-acyclic nucleoside analogs

Synthesis of a new class of 1, 3-thiazolidine nucleoside analogs is described. Reaction of 2-amino-2-deoxy-D-glucopyranose hydrochloride 2 with carbon disulfide yielded 5-hydroxy-4-(D-arabino-1, 2, 3, 4-tetrahydroxybutyl)-thiazolidin-2-thione 3, which on acetylation yielded 5-acetoxy-4-(D-arabino-1, 2, 3, 4-tetraacetoxy-butyl)-thiazolidin-2-thione 4. The acetylated sugar 4 reacted with hydrazonoyl chlorides 1a–f, affording the 5-acetoxy-4-(D-arabino-1, 2, 3, 4-tetraacetoxybutyl)-spiro-1 Chen, H., Fan, Y-H., Natarajan, A., Guo, Y., Iyasere, J., Harbinski, F., Luus, L., Christ, W., Aktas, H. and Halperin, J. A. 2004. Bioorg. Med. Chem. Lett., 14: 5401–5405. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar] 3 Nasr, M. N., Gineinah, M. M. and El-Bendary, E. R. 2003. Arch. Pharm., 336: 560–566. [Crossref] , [Google Scholar]thiazolidine-2,2′ -1 Chen, H., Fan, Y-H., Natarajan, A., Guo, Y., Iyasere, J., Harbinski, F., Luus, L., Christ, W., Aktas, H. and Halperin, J. A. 2004. Bioorg. Med. Chem. Lett., 14: 5401–5405. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar] 3 Nasr, M. N., Gineinah, M. M. and El-Bendary, E. R. 2003. Arch. Pharm., 336: 560–566. [Crossref] , [Google Scholar] 4 Belleau, B., Brasilli, L., Chan, L. and Zacheri, B. 1993. Cameron J. Bioorg. Med. Chem. Lett., 3: 1723–1928. [Crossref], [Web of Science ®] , [Google Scholar]thiadiazole derivatives 8a–f. The antibacterial activity of the novel 1, 3-thiazolidine-2,2′ -spiro- 1 Chen, H., Fan, Y-H., Natarajan, A., Guo, Y., Iyasere, J., Harbinski, F., Luus, L., Christ, W., Aktas, H. and Halperin, J. A. 2004. Bioorg. Med. Chem. Lett., 14: 5401–5405. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar] 3 Nasr, M. N., Gineinah, M. M. and El-Bendary, E. R. 2003. Arch. Pharm., 336: 560–566. [Crossref] , [Google Scholar] 4 Belleau, B., Brasilli, L., Chan, L. and Zacheri, B. 1993. Cameron J. Bioorg. Med. Chem. Lett., 3: 1723–1928. [Crossref], [Web of Science ®] , [Google Scholar]thiadiazole nucleoside analogs is highlighted. All compounds with free NH group in the thiazolidine series 8a–f showed significant biological activity against all the standard strains.     

Development of an Aerosol Dynamics Model for Dry Deposition Process Using the Moment Method

An aerosol dynamics model for dry deposition process is developed based on the moment method. Since it is hard to fully apply the moment method to the widely used dry deposition velocity expressions based on the resistance theory, the dry deposition velocity expression by Raupach et al. (2001) Raupach, M. R., Briggs, P. R., Ahmad, N. and Edge, V. E. 2001. Endosulfan Tansport: II. Modeling airborne Dispersal and Deposition by Spray and Vapor. J. Environ. Qual., 30: 729–740. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar] is used. Detailed deposition mechanisms such as Brownian diffusion, gravitational settling, and impaction are considered in the expression. To verify the validity of the derived dynamic equation, aerosol dynamics for the dry deposition process is estimated with the expressions of Raupach et al. (2001) Raupach, M. R., Briggs, P. R., Ahmad, N. and Edge, V. E. 2001. Endosulfan Tansport: II. Modeling airborne Dispersal and Deposition by Spray and Vapor. J. Environ. Qual., 30: 729–740. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar], of Wesely (1989) Wesely, M. L. 1989. Parameterizations of Surface Resistance to Gaseous Dry Deposition in Regional-Scale, Numerical Models. Atmos. Environ., 23: 1293–1304. [Crossref], [Web of Science ®] , [Google Scholar] modified for particles (Seinfeld and Pandis 1998 Seinfeld, J. H. and Pandis, S. N. 1998. Atmospheric Chemistry and Physics, 958–996. New York, , USA: Wiley.  [Google Scholar]), in CMAQ, and with constant value used in RAINS-ASIA. Those expressions give different dynamics. Generally, the result for this study is between the result of modified Wesely's expression and CMAQ. When using the modified Wesely's expression with the number of sections being equal or smaller than 10, the resultant size distribution does not give the peak shape accurately.     

Fibrous Filter Efficiency and Pressure Drop in the Viscous-Inertial Transition Flow Regime

Fibrous filter pressure drop and aerosol collection efficiency were measured at low air pressures (0.2–0.8 atm) and high face velocities (5–19 m/s) to give fiber Reynolds numbers lying in the viscous-inertial transition flow regime (1–15). In this regime, contemporary filtration theory based on Kuwabara's viscous flow through an ensemble of fibers underpredicts single fiber impaction by several orders of magnitude. Streamline curvature increases substantially as air stream inertial forces become significant. Dimensionless pressure drop measurements followed the viscous-inertial theory of Robinson and Franklin (1972 Robinson, M. and Franklin, H. 1972. The Pressure Drop of a Fibrous Filter at Reduced Ambient Pressures. J. Aerosol Sci., 3: 413–427. [Crossref] , [Google Scholar]) rather than Darcy's linear pressure–velocity relationship. Sodium chloride and iron nano-agglomerate aerosols were tested to provide a comparison between particles of dissimilar densities and shape factors. Total filter efficiency collapsed when plotted against the particle Stokes number and fiber Reynolds number. Efficiencies were then modeled with an impactor type equation where the cutpoint Stokes number and a steepness parameter described data well in the sharply increasing portion of the curve (20%–80% efficiency). A minimum in collection efficiency was observed at small Stokes numbers and attributed to interception and diffusive effects. The cutpoint Stokes number was a linearly decreasing function of fiber Reynolds number. Single fiber efficiencies were calculated from total filter efficiencies and compared to contemporary viscous flow impaction theory (Stechkina et al. 1969 Stechkina, I. B., Kirsch, A. A. and Fuchs, N. A. 1969. Studies on Fibrous Aerosol Filters—IV. Calculation of Aerosol Deposition in Model Filters in the Range of Maximum Penetration. Ann. Occup. Hyg., 12: 1–8. [Crossref], [PubMed] , [Google Scholar]), and numerical simulations of single fiber efficiencies from the literature. Existing theories underpredicted measured single fiber efficiencies, although comparison is problematic. The assumption of uniform flow conditions for each successive layer of fibers is questionable; thus, the common exponential relationship between single fiber efficiency and total filter efficiency may not be appropriate in this regime.

Copyright 2012 American Association for Aerosol Research     

Selective Deflection and Localization of Flowing Aerosols onto a Substrate

Pulsed airflow cued by the fluorescence spectrum of a particular aerosol can be used to distinguish and deflect particles of biological origin out of an aerosol stream, permitting concentration of these particles for subsequent analysis (Pan et al. 2004 Pan, Y. L., Boutou, V., Bottiger, J. R., Zhang, S. S., Wolf, J. P. and Chang, R. K. 2004. A Puff of Air Sorts Bioaerosols for Pathogen Identification. Aerosol Sci. Technol., 38: 598–602. [CROSSREF][CSA][Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). However, these high velocity pulses of air have an inherent tendency to scatter particles, confounding efforts to concentrate these deflected particles for analysis. The ability to concentrate large numbers of biological particles into a small area on a collection substrate is particularly important for more species-specific techniques such as Raman and FTIR (Fourier Transform Infra-Red) spectroscopy, which require long integration times due to their weak signal strength. In the present work, a simple method is developed for deflecting and localizing particles after classification by a pulsed airflow. The concept is both modeled and experimentally tested. A specially designed funnel is used to localize the scattered particles onto an area of substrate as small as 1 mm in diameter. Computational fluid dynamics simulations were performed to investigate the interaction of the pulsed airflow with the deflected particles and the localizing funnel, in order to gain insight into design parameters and operating conditions that affect the efficiency of this technique. The results show that the combination of pulsed airflow with a localizing funnel effectively deflects and localizes the concentrated bioaerosol onto a small area of substrate or an opening of a microfluidic cell.     

DYNAMICS OF IMINE AND ACETOPHENONE DERIVATIVES IN SOLUTION STUDIED BY ONE-DIMENSIONAL DIFFUSION-ORDERED NMR SPECTROSCOPY (DOSY)

This paper describes the usefulness of one-dimensional diffusion-ordered NMR spectroscopy (1D-DOSY) in investigating dynamics and interactions of molecules in solution as well as in analyzing the structure of molecules. We synthesized the three imines, N-benzylidene-4-methylbenzene-Sulfonamide (1 Kondo, K., Kazuta, K., Saitoh, A. and Murakami, Y. 2003. Heterocycles, 59: 97–100.  [Google Scholar]), N-(4-chloro-benzylidene)4-methyl-benzene-sulfonamide (2 Horibe, H., Kazuta, K., Kotoku, M., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2003. Synlett, : 2047–2051. [Web of Science ®] , [Google Scholar]), and N- (4-methoxybenzylidene)-4-methyl-benzene sulfonamide (3 Horibe, H., Fukuda, Y., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2004. Tetrahedron, 60: 10701–10709. [Crossref], [Web of Science ®] , [Google Scholar]), and acetophenone (4 Sakamoto, Y., Kondo, K., Tokunaga, M., Kazuta, K., Fujita, H., Murakami, Y. and Aoyama, T. 2004. Heterocycles, 63: 1345–1357. [Crossref], [Web of Science ®] , [Google Scholar]) and its three derivatives, 4-chloroacetophenone (5 Sakamoto, Y., Kondo, K., Onozato, M. and Aoyama, T. 2006. Polycycl. Aromat. Comp., 26: 59–68. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]), 4-nitro-acetophenone (6 Kondo, K., Kazuta, K., Fujita, H., Sakamoto, Y. and Murakami, Y. 2002. Tetrahedron, 58: 5209–5214. [Crossref], [Web of Science ®] , [Google Scholar]), and 4-methoxyaceto -phenone (7 Gostam, T., Morean, C., Jutean, A., Guichard, E. and Delsuc, M. A. 2004. Magn. Reson. Chem., 42: 496–499.  [Google Scholar]). 1D-DOSY was applied to a mixture of compounds (1 Kondo, K., Kazuta, K., Saitoh, A. and Murakami, Y. 2003. Heterocycles, 59: 97–100.  [Google Scholar]), (2 Horibe, H., Kazuta, K., Kotoku, M., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2003. Synlett, : 2047–2051. [Web of Science ®] , [Google Scholar]), and (3 Horibe, H., Fukuda, Y., Kondo, K., Okuno, H., Murakami, Y. and Aoyama, T. 2004. Tetrahedron, 60: 10701–10709. [Crossref], [Web of Science ®] , [Google Scholar]) and to a mixture of compounds (4 Sakamoto, Y., Kondo, K., Tokunaga, M., Kazuta, K., Fujita, H., Murakami, Y. and Aoyama, T. 2004. Heterocycles, 63: 1345–1357. [Crossref], [Web of Science ®] , [Google Scholar]), (5 Sakamoto, Y., Kondo, K., Onozato, M. and Aoyama, T. 2006. Polycycl. Aromat. Comp., 26: 59–68. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]), (6 Kondo, K., Kazuta, K., Fujita, H., Sakamoto, Y. and Murakami, Y. 2002. Tetrahedron, 58: 5209–5214. [Crossref], [Web of Science ®] , [Google Scholar]), and (7 Gostam, T., Morean, C., Jutean, A., Guichard, E. and Delsuc, M. A. 2004. Magn. Reson. Chem., 42: 496–499.  [Google Scholar]). Although ¹ H NMR chemical shifts of the molecules in the mixtures resembled one another in the surrounding, we could distinguish signals of the individual molecules in each mixture on the basis of the NMR data and the values of the diffusion coefficient. Also, we could found the correlation of the measured diffusion coefficients and the calculated molecular volumes.     

SYNTHESES OF ADDUCTS OF ACTIVE METABOLITES OF CARCINOGENIC POLYCYCLIC AROMATIC HYDROCARBONS WITH 2′-DEOXYRIBONUCLEOSIDES

Syntheses are reported for: (1 Harvey, R. G. 1991. Polycyclic Aromatic Hydrocarbons: Chemistry and Carcinogenicity, Cambridge, , U.K.: Cambridge University Press.  [Google Scholar]) adducts of the quinone metabolites of benzo[a]pyrene (BPQ) and benz[a]anthracene (BAQ) with 2′-deoxyadenosine and 2′-deoxyguanosine; (2 Conney, A. H. 1982. Induction of Microsomal Enzymes by Foreign Chemicals and Carcinogenesis by Polycyclic Aromatic Hydrocarbons. Cancer Res., 42: 4875–4917. [PUBMED][INFOTRIEVE][CSA][PubMed], [Web of Science ®] , [Google Scholar]) ¹⁵ N-labelled analogs of these adducts (four or five nitrogen atoms ¹⁵ N-labelled); (3 Dipple, A. 1994. “Reactions of Polycyclic Aromatic Hydrocarbons with DNA”. In DNA Adducts: Identification and Biological Significance, Edited by: Hemminki, K., Dipple, A., Segerbäck, D., Kadulbar, F. F., Shuker, D. and Bartsch, H. pp. 107–129. IARC Scientific Publication No. 125.  [Google Scholar]) depurinated adducts of BPQ and BAQ with adenine or guanine covalently linked to the N7 or N9 positions of the purine bases; (4 Jeffrey, A. M., Weinstein, I. B., Jennette, K., Grzeskowiak, K., Nakanishi, K., Harvey, R. G., Autrup, H. and Harris, C. 1977. Structures of Benzo[a]pyrene-Nucleic Acid Adducts Formed in Human and Bovine Bronchial Explants. Nature (London)., 269: 348–350. [CSA][CROSSREF][Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) ¹³ C-labelled derivatives of benzo[a]pyrene, BPQ, benzo[a]pyrene trans-7,8-dihydrodiol, and the benzo[a]pyrene anti-diol epoxide (with ¹³ C-atoms at the 5- and 11-positions); and (5 Jennette, K., Jeffrey, A. M., Blobstein, S. H., Beland, F. A., Harvey, R. G. and Weinstein, I. B. 1977. Characterization of Nucleoside Adducts from the in Vitro Reaction of Benzo[a]pyrene-7,8-dihydrodiol-9,10-oxide or Benzo[a]pyrene-4,5-oxide with Nucleic Acids. Biochemistry, 16: 932–938. [PUBMED][INFOTRIEVE][CSA][CROSSREF][Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) depurinated adducts formed by reactions of the benzo[a]pyrene radical-cation at the C ⁸ -, N ⁷ -, and N ⁹ -positions of adenine and guanine.     

Vienna-Type DMA of High Resolution and High Flow Rate

A variant of the Vienna DMA (Winklmayr et al. 1991 Winklmayr, W., Reischl, G. P., Lindner, A. O. and Berner, A. 1991. A New Electromobility Spectrometer for the Measurement of Aerosol Size Distributions in the Size Range From 1 to 1000 nm. J. Aerosol Sci., 22: 289–296. [CROSSREF][CSA][Crossref], [Web of Science ®] , [Google Scholar]; Reischl et al. 1997 Reischl, G. P., Makela, J. M. and Necid, J. 1997. Performance of Vienna Type Differential Mobility Analyzer at 1.2–20 Nanometer. Aerosol Sci. Technol., 27: 651–672. [CSA][Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) with inner and outer electrode radii of 25 and 33 mm, and a conventional trumpet inlet diameter of 97 mm has been tested. It incorporates a reduced pressure drop sheath gas exhaust system that enables reaching flow rates approaching 4000 L/min. Several new additional flow features are included to delay the transition to turbulent conditions. A cylindrical geometry with a DMA length L of 97 mm (distance between the aerosol inlet and outlet slits) is seen to keep the flow laminar up to the highest Reynolds number achieved, though showing slight signs of flow quality deterioration at about Re = 20,000. An equally long DMA with an inner electrode shaped as a 5° cone caped by a spherical dome remains stable up to the highest Reynolds number achieved. It is expected to continue this trend to considerably higher flow rates. Both these long configurations exhibit line widths close to the ideal Brownian diffusion limit, reaching FWHH of 4% for a particle mass diameter of 1 nm. A short DMA with an axial length L of 18 mm and an inner electrode shaped as a 5° cone caped by an ellipse of 3/2 aspect ratio remains also laminar at the highest speeds attained, and exhibits FWHH as small as 2.4%. It departs moderately from ideal behaviour at small flow rates, presumably due to its non-cylindrical geometry. More serious departures observed at high Reynolds numbers may perhaps be due to flow unsteadiness radiated into the working section by sound waves from the turbulent exhaust region. This is the first report of a DMA capable of excellent resolution at 1 nm, yet with a sufficiently wide and long working section to enable (in principle) covering the size range up to 100 nm.     

Bipolar Diffusion Charging of Soot Aggregates

Experimental measurements of bipolar diffusion charging efficiency over the range of 15–400 nm are compared for oil droplets, flame generated soot aggregates, and diesel engine exhaust particulate matter to explore possible effects of particle morphology. Charging efficiency is recorded using a tandem differential mobility analyzer (DMA) approach; the first DMA selects a monodisperse aerosol and the second compares the flux of these particles through a neutralizer versus an identical blank housing. Electrostatic precipitation of mobility selected soot particles onto TEM grids provides comparative data on changes in soot particle morphology with mobility diameter. The measurements yield soot charging efficiencies that slightly, but systematically, differ from those of equal mobility diameter oil droplets. Single positive charging of soot climbs to ～ 10% higher than oil droplets at 50 nm and then decreases to 15% lower by 400 nm as the soot develops a progressively more fractal-like structure. Negative charging exhibits the same pattern, except the variations are +15% and –10%, respectively. These trends, as well as those for double and triple charging, fall intermediate between Fuchs predictions and the model of Wen et al. (1984a) Wen, H. Y., Reischl, G. P. and Kasper, G. 1984a. Bipolar Diffusion Charging of Fibrous Aerosol Particles—I. Charging Theory. J. Aerosol Sci., 15: 89–101. [Crossref], [Web of Science ®] , [Google Scholar] for charging of fibrous particles.     

Ion Beam Charging of Aerosol Nanoparticles

In our ongoing efforts to achieve the high-efficiency charging of aerosol nanoparticles under low-pressure conditions, our group has recently developed an ion beam aerosol charger (IBAC) that ionizes aerosol nanoparticles using an He⁺ ion beam (Seto et al. 2003 Seto, T., Orii, T., Hirasawa, M., Aya, N. and Shimura, H. 2003. Ion Beam Charging of Silicon Nanoparticles in Helium Background Gas—Design of the Ion Beam Aerosol Charger (IBAC). Rev. Sci. Inst., 74: 3027–3030. [CROSSREF][Crossref] , [Google Scholar]). In earlier studies we have observed both increases and decreases in the currents from the charged particles, depending on the pressure when the polydisperse particles were irradiated by the ion beam. None of our previous studies elucidated the mechanisms of the charging itself, however. In the present paper we evaluate the charging probability of monodisperse aerosol nanoparticles using a low-pressure differential mobility analyzer (LP-DMA) and aerosol electrical condenser (AEC). The particles were negatively charged by the attachment of free electrons generated via the ionization of carrier gas by ion beam irradiation under a pressure of more than 350 Pa. A charging probability of more than 60% was obtained experimentally for the particles of 10–40 nm in mobility diameter under the pressure of 350–650 Pa. The mobility of the particles was almost the same before and after charging in a tandem LP-DMA analysis, with no multiply charged particles observed. The charging probability of nanoparticles was estimated based on the diffusion charging theory. Lastly, experiments were performed to demonstrate the performance of the IBAC in the charging of neutral particles in comparison with that of an α-ray source.     

2-Aminothiophenol as building blocks for novel heterocycles

Herein, the chemistry of 2-aminothiophenol has been utilized in the synthesis of several interesting products such as oxidation and reaction with π-deficient compounds. On oxidizing 2-aminothiophenol by sodium hypochlorite furnishes 2-[(2-aminophenyl)-dithio]aniline. Treatment of the obtained product with acetyl chloride affords N-(2-[2-(acetylamino)-phenyl-disulphanyl)-phenyl]acetamide. Reaction of the former acetamide with POCl₃ yields 2-methyl-1,3-benzothiazole. Moreover, (3,4,8,9)-dibenzo-2,7-dithia-5,10-diaza4 Field, L. and Lawson, J. E. 1958. J. Am. Chem. Soc., 80: 838[Crossref], [Web of Science ®] , [Google Scholar] 4 Field, L. and Lawson, J. E. 1958. J. Am. Chem. Soc., 80: 838[Crossref], [Web of Science ®] , [Google Scholar] 4 Field, L. and Lawson, J. E. 1958. J. Am. Chem. Soc., 80: 838[Crossref], [Web of Science ®] , [Google Scholar]propellane is formed on reacting the target 2-aminothiophenol with cyclohexane-1,2-dione, whereas its reactions with electron π-acceptors such as 2,3-dichloro-1,4-naphthoquinone (DCHNQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetra-cyanoethylene (TCNE), and 1-(dicyanomethylen)acenaphthen-2-one yield various heterocycles.     

Characteristics of Aerosol Charge Distribution by Surface-Discharge Microplasma Aerosol Charger (SMAC)

The surface discharge on a dielectric barrier induced by dc pulses was successfully utilized as a stable bipolar ion source for neutralizing submicron aerosol particles where the concentration of positive and negative ions could be adjusted independently (a surface-discharge microplasma aerosol charger: SMAC; Kwon et al., 2005 Kwon, S. B., Sakurai, H., Seto, T. and Kim, Y. J. 2005. Charge Neutralization of Submicron Aerosols Using Surface-Discharge Microplasma. J. Aerosol Sci., in press[CSA] [Google Scholar]). The aim of this study was to determine the charge distribution obtained by the SMAC, which has been qualitatively presented in our previous study, and to investigate the effect of unequal bipolar ion concentration on the charge distribution. For this purpose, we performed quantitative analysis of the charge distribution of monodisperse particles in the size range of 30–200 nm acquired by the SMAC and compared the charge distributions with calculated charge fractions obtained from the diffusion charging theory. The ion parameters were calculated by measuring the ion mobility of positive and negative ions and they were used to obtain the analytic solutions of charge distribution. The charge distributions obtained by the equal or unequal concentration of bipolar ions adjusted by the SMAC showed general agreement with the diffusion charging theory.     

Influence of Humidity on Clogging of Flat and Pleated HEPA Filters

The influence of humidity on changes to the pressure drop of flat and pleated HEPA filters clogged by polydisperse hygroscopic and non-hygroscopic aerosols has been studied. For flat filters, the results confirm the observations reported by Gupta et al. (1993) Gupta, A., Novick, V. J., Biswas, P. and Monson, P. R. 1993. Effect of Humidity and Particle Hygroscopicity on the Mass Loading Capacity of High Efficiency Particulate Air (HEPA) Filter.. Aerosol Sci. Tech., 19: 94–107. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar] that with a hygroscopic aerosol at humidity below the deliquescent point, or with a non-hygroscopic aerosol, the particulate specific cake resistance decreases as relative humidity increases. For pleated filters as for flat filters, the results reveal that during the formation of the particulate cake, the increase in relative humidity leads to a decrease in the specific cake resistance. When the reduction in filtration area, specific to pleated filters, becomes large, the presence of humidity accelerates the filling of pleats causing a greater pressure drop for a same aerosol mass loading. With a hygroscopic aerosol at a humidity above its deliquescent point, the change in pressure drop through flat or pleated filters is not linear but characteristic of liquid aerosol filtration. The influence of humidity on the efficiency of pleated filters, measured by a soda fluorescein aerosol, has also been studied. For clean filters, the efficiency decreases with increasing relative humidity above 90%. For filters clogged with solid aerosol, change in efficiency versus collected surface mass reaches a maximum whose value depends on the relative humidity; when the aerosol is liquid, the efficiency decreases throughout the clogging.