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Radionuclides released during the Fukushima Daiichi nuclear accident caused altitude-dependent surface contamination in the mountainous areas of Japan. To explore the possible cloudwater deposition that formed a distinctive contamination profile, data from pollen sensors deployed nationwide were analyzed. Utilizing the polarization of scattered light, Cedar pollen and water droplets were distinguished. On March 15, when surface contamination was simulated in previous studies, dense clouds with high droplet number concentrations were observed outside the

This study assessed the significance of measuring liver stiffness using virtual touch quantification before hepatectomy to predict posthepatectomy refractory ascites. A total of 267 patients with hepatocellular carcinoma who underwent hepatectomy were prospectively analyzed. Liver stiffness was defined as the median value of the virtual touch quantification (Vs; m/s) by acoustic radio-force-impulse-based virtual touch. A multivariate analysis showed that Vs and the aspartate aminotransferase-to-platelet ratio index were independent risk factors for postoperative refractory ascites (odds ratio = 3.27 and 3.08, respectively). The cutoff value for Vs was 1.52 m/s (sensitivity: 59.5%, specificity: 88.6%) as determined by the analysis of the receiver-operating characteristic curve, and the area under the receiver-operating characteristic curve was 0.79. The cutoff value for the aspartate aminotransferase-to-platelet ratio was 0.952 (sensitivity: 65.5%, specificity: 82.9%), and the area under the receiver-operating characteristic curve was 0.75. Vs is an independent risk factor for refractory ascites after hepatectomy. The measurement of liver stiffness by virtual touch quantification before hepatectomy can help estimate the risk of postoperative refractory ascites. Nonsurgical treatments should be considered for the management of patients who are at high risk for refractory ascites.

Background/aims Although adhesion formation is a frequent adverse event following intraperitoneal surgery, efficient prophylactic interventions have not yet been established. We recently reported that blockade of interleukin (IL)-6 prevented postoperative adhesion after cecum cauterization. Intriguingly, this intervention dampened tumor necrosis factor (TNF) induction in the injured serosa. Herein, we addressed whether TNF might be a key target and, if so, how TNF blockade rescued adhesion formation. Methods Mice were administered an anti-TNF biologic (etanercept) on days -2 and -1 before and upon cecal cauterization. The adhesion scores were evaluated at day 7 postoperatively. Histological alterations were examined by immunochemistry/immunofluorescence studies. We incubated human neutrophils and mesothelial cell line cells with recombinant TNF in the presence of etanercept and measured transcript levels of cytokines and chemokines by quantitative reverse transcription-polymerase chain reaction (RT-qPCR). Results Etanercept rescued mice from adhesion formation, accompanied by a robust reduction of neutrophilia in the injured serosa. Immunofluorescence revealed a substantial formation of neutrophil extracellular traps (NETs) with the potential to induce tissue damage and profibrotic responses. In contrast, the etanercept-treated mice lacked NET formation. In addition, etanercept inhibited TNF-induced IL-6, TNF, and neutrophil-recruiting chemokines in neutrophils and mesothelial cells, a major cellular source of myofibroblasts in the adhesion band. Conclusion Prophylactic administration of etanercept might be a potential strategy for preventing postoperative adhesion formation.

This study aimed to clarify what hepatocellular carcinoma (HCC) phenotype, as categorized by intraoperative contrast-enhanced ultrasonography (CEUS), showed a high risk of recurrence after hepatic resection. Patients who underwent initial curative hepatectomy with intraoperative CEUS for a single HCC nodule were retrospectively assigned to three patterns of fine (FI), vascular (VA), and irregular (IR) according to the maximum intensity projection pattern based on intraoperative CEUS. Staining was performed for Ki-67, pyruvate kinase type M2 (PKM2), and vascular endothelial growth factor (VEGF) to assess the tumor proliferative activity, tumor glucose metabolism, and angiogenesis, respectively. Of 116 patients, 18, 50, and 48 were assigned to the FI, VA and IR patterns, respectively. IR patients demonstrated a significantly worse prognosis for both the recurrence-free survival (RFS) and overall survival (OS) (P = 0.0002, 0.0262, respectively) than did patients with other patterns. A multivariate analysis revealed an IR pattern in intraoperative CEUS to be an independent predictive factor for a poor RFS, and major hepatectomy and an IR pattern were independent predictive factors for a poor OS. An IR pattern was closely related to the tumor size (≥ 3.3 cm) and poor histological differentiation and showed a high Ki-67 index, low VEGF expression, and high PKM2 expression. IR-pattern HCCs as classified by intraoperative CEUS may be associated with a higher risk of recurrence and worse outcomes in HCC patients after hepatic resection than other patterns.

A method to determine the cutoff diameter and counting efficiency of single-particle optical particle counters (OPC) is presented. An aerodynamic aerosol classifier (AAC) coupled with an atomizer was used to generate monodisperse dioctyl phthalate particles with a condensation particle counter (CPC) as the reference instrument. This method is accurate for capturing the counting efficiency of OPCs at lower size ranges and determining the cutoff diameter. The CPC was found to be a poor reference instrument for particles larger than 1 µm in which case an inkjet aerosol generator (IAG) was used as the monodisperse particle source and reference instrument. Two different particle materials were used with the IAG: lactose monohydrate and an ionic liquid (1-ethyl-3-methylimidazolium trifluoromethanesulfonate). A combination of the AAC to size smaller particles ( µm) and IAG to generate larger particles (>1 µm) was found to provide a comprehensive method capable of covering the counting efficiency over the entire operating range of OPCs. Copyright © 2020 American Association for Aerosol Research

This study introduces a method to deposit polystyrene latex (PSL) particles on a silicon wafer in a manner that allows their number to be predicted with a high degree of accuracy. A laminar...

Background The aim of this study was to determine the predictive factors for pancreatic fistula (PF) after distal pancreatectomy (DP) among preoperative and intraoperative parameters, and to clarify the patients who did not require drain placement. Methods Between July 2009 and April 2017, a total of 102 consecutive patients underwent DP at Hyogo College of Medicine. Preoperative and intraoperative data were collected, and the predictors of PF after DP were identified. PF was identified in 35 patients (34%). In the multivariate analysis, 3 factors [body mass index (BMI) ≥22.4, contiguous organ resection, and pancreatic thickness ≥11 mm] were found to be independent predictors of PF (odds ratio, 5.7; 95% confidence interval, 1.9–17; P = 0.002 odds ratio, 6.7; 95% confidence interval, 1.6–28; P = 0.009; odds ratio, 11.6; 95% confidence interval, 3.7–36; P Results A scoring scale for the prediction of PF was developed. BMI ≥22.4 (score: 1), contiguous organ resection (score: 1), and pancreatic thickness ≥11 mm (score: 2) were included in the scoring scale. Patients with a score of 0 never developed PF, whereas PF occurred in all patients with a score of 4. Conclusions BMI ≥22.4, contiguous organ resection, and pancreatic thickness ≥11 mm were predictive factors for PF after DP. No patients with BMI

The first bilateral comparison of particle number concentration (PNC) standards via calibrating the counting efficiency (CE) of an optical particle counter (OPC) at high concentration of 1000 cm-3 is reported. An OPC (GRIMM 11-D) has been used as the transfer standard between NMC and NMIJ, with its CE being calibrated using monodisperse polystyrene latex (PSL) particles around 0.3 µm by the Faraday Cup Aerosol Electrometers (FCAE) of both metrology institutes. The CE of the OPC has been evaluated for a series of increasing concentrations to determine the highest concentration level which is free from coincidence loss. The OPC was also calibrated at 0.5 µm using an inkjet aerosol generator (IAG) and FCAE to compare its CE at different concentration levels. We have analysed the CE’s stability at decreasing concentration levels from 1228 to 0.5 cm-3 to derive the evidence for the equivalence of CE at different concentration levels. The CE values of the OPC around 0.3 and 0.5 µm measured by two institutes have agreement within 1.5% (normalized error En

Background Only few studies in literature have analyzed the clinical effects of peritoneal lavage status in biliary tract cancers. Aim We aimed to assess the effect of cytology-positive peritoneal lavage on survival for patients with biliary tract cancer who underwent curative resection. Methods The KHBO1701 study was a multi-institutional retrospective study that assessed the clinical effects of peritoneal lavage cytology in biliary tract cancers. Using clinicopathological data from 11 Japanese institutions, we compared long-term outcomes between patients with cytology-positive and cytology-negative peritoneal lavage. Results Of 169 patients who underwent curative resection, 164 were cytology-negative, and five were cytology-positive. The incidence of portal invasion and preoperative carbohydrate antigen 19-9 levels were higher in the cytology-positive group than in the cytology-negative group. The incidence of peritoneal metastatic recurrence was also higher, and overall survival tended to be worse in the cytology-positive group. In contrast, recurrence-free survival was similar between the cytology-negative and cytology-positive groups. Conclusions The positive status of peritoneal lavage cytology could moderately affect the survival of patients with biliary tract cancers. Given that surgical resection is the only curative treatment option, it may be acceptable to resect biliary tract cancers without other non-curative factors, regardless of peritoneal lavage cytology status.

This study introduces the method to evaluate the counting efficiencies of optical particle counters (OPCs), , at particle diameter greater than 1 μm by using an inkjet aerosol generator (IAG). This study demonstrates the evaluations at 5 and 10 μm in volume equivalent diameter. The chemical composition of the particles is either sodium chloride or lactose monohydrate. The aerosol flowrate of the IAG is set at 0.3 L/min, and the aerosol is delivered to an OPC with sampling flowrate 6 L/min (Omron, ZN-PD50S). The mismatch of the flowrates is compensated for by adding particle-free air in a laminar flow chamber. In order to simulate the sampling of uniformly mixed aerosol from a real environment, the particles are delivered to different points over the inlet plane of the isokinetic probe attached to the OPC. Particle flux into the isokinetic probe is proportional to the gas-velocity into the probe; however, the true velocity distribution is usually unknown. It is assumed that the true velocity distri...

A 75-year-old male was admitted to our hospital because of bile duct stenosis. He had no medical history of autoimmune disease. The level of tumor markers, serum IgG, and IgG4 were within normal ranges. Computed tomography showed perihilar and distal bile duct stenosis and wall thickening without swelling or abnormal enhancement of the pancreas. Endoscopic retrograde cholangiopancreatography showed perihilar and distal bile duct stenosis. A biopsy and cytology from the distal bile duct stenosis suggested adenocarcinoma, and cytology from the perihilar bile duct also suggested adenocarcinoma. A preoperative diagnosis of perihilar and distal bile duct cancer was made, and the patient underwent left hepatectomy and pancreaticoduodenectomy. Resected specimens showed wall thickening in the perihilar and distal bile duct; however, tumors were unclear. A histopathological examination revealed lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis in the perihilar and distal bile ducts. Immunohistochemistry revealed diffuse infiltration of IgG4-positive plasma cells in the perihilar and distal bile ducts. Lymphoplasmacytic infiltration, inflammatory change, storiform fibrosis, and obliterative phlebitis were shown in the pancreas. A final diagnosis of IgG4-related sclerosing cholangitis (IgG4-SC) with autoimmune pancreatitis was made. We herein report a case in which a preoperative diagnosis of IgG4-SC was difficult due to normal serum IgG4 levels and no obvious pancreatic lesion.

In this study, we present a traceable method for determining the counting efficiency of optical particle size spectrometers (OPSS), also known as aerosol spectrometers. The primary standard consists of an aerosol generation setup, a vertical flow tube for particle homogenization and a reference optical particle counter. The OPSS under testing and the reference optical particle counter sample aerosol simultaneously through specially designed isokinetic sampling probes at number concentrations ranging from 0.5 cm−3 up to several hundred particles per cm3 (depending on the particle size). Calibration in terms of particle size relies by convention on the use of certified PS (polystyrene) spheres in the size range 100 nm - 10 μm. Here, the counting efficiency profiles of two commonly used OPSS, namely the Model 3330 OPS (TSI Inc., USA) and the 11-D monitor (Grimm GmbH, Germany) are presented for the first time and discussed within the context of the ISO 21501–1:2009 and 21501–4:2018 standards on the calibration of OPSS for indoor/outdoor measurements and optical particle counters (OPC) for clean rooms applications, respectively. We believe that this study can help manufacturers improve the design of their instruments, contribute to the further development of relevant national and international standards and pave the way for a standardised and traceable calibration of OPSS units installed at air quality monitoring stations and industrial/workplace environments.

A butanol-type ultrafine condensation particle counter (UCPC, Model 3776, TSI, Inc., Shoreview, MN, USA), which can achieve a 50% detection efficiency diameter (d50) of 2.5 nm using a capillary-sheath structure, was modified and tested in the laboratory for airborne measurements. The aerosol flow rate through the capillary is a key factor affecting the quantification of aerosol particle number concentrations. A pressure-dependent correction factor for the aerosol flow rate was determined using a newly added mass flow meter for the sheath flow and the external calibration system. The effect of particle coincidence in the optical sensing volume was evaluated using an aerosol electrometer (AE, Model 3068B, TSI, Inc.) as a reference. An additional correction factor for the coincidence effect was derived to improve the quantification accuracy at higher concentrations. The particle detection efficiency relative to the AE was measured for mobility diameters of 3.1–50 nm and inlet absolute pressures of 101–40 kPa. The pressure dependence of the d50 value, asymptotic detection efficiency, and shape of the particle detection efficiency curve is discussed, along with simple theoretical calculations for the diffusion loss of particles and the butanol saturation ratio in the condenser. © 2017 American Association for Aerosol Science

We report on an inter-laboratory comparison for the calibration of light-scattering optical particle counters measuring the number concentration of airborne particles in the size range 300 nm–5 µm. This comparison, registered as EURAMET pilot study Nr. 1453, is an important first step towards internationally recognized SI traceability in the measurement of low particle number concentrations encountered in clean-room facilities. The participating particle metrology laboratories of NMIJ (Japan), DFM (Denmark) and METAS (Switzerland) each provided a portable optical particle counter as a transfer standard to be circulated amongst the partners. The comparison covered particle number concentrations up to about 2 cm−3. The individual measurements for the transfer standards at each laboratory are in good agreement with the reference value, typically within 7%, which supports the applied national primary methods of measurement.

The classical nucleation theory predicts that a decrease in nucleation temperature under a constant saturation ratio increases the energy barrier for homogeneous nucleation to occur; therefore lower nucleation temperature would allow higher saturation ratio inside a condensation particle counter (CPC) while suppressing homogenous nucleation of working fluid vapor below a threshold value. On the other hand, the classical theory also predicts that a decrease in nucleation temperature increases the energy barrier for heterogeneous nucleation to occur, which potentially increases the minimum detectable size of CPC. Accordingly, it is important to investigate experimentally whether higher super-saturation under lower nucleation temperature decreases the minimum detectable size or not. Minimum detectable sizes of a diethylene glycol (DEG)-based nanoparticle size magnifier (nano-PSM) developed by Ito et al. (Ito, E., Seto, T., Otani, Y., and Sakurai, H. [2011]. Aerosol Sci. Technol. 45:1250–1259) were investigat...

This article introduces an aerosol-based technique to make aqueous suspension of hydrophobic nanomaterial without adding dispersant. The method is intended for making a test-sample for evaluating the toxicities of nanomaterial by intra-tracheal administration. The method can wet the surface of hydrophobic nanomaterial within a few seconds. After the wetting process five to ten minutes of sonication assisted with manual stirring can fully disperse the hydrophobic nanomaterials in water. Two types of TiO2 nanomaterial were used in this study; Tayca JMT-150IB whose surfaces are coated with negatively charged hydrophobic functional group, and P25 whose surfaces are naturally hydrophilic. Nanomaterials are aerosolized by a dry-method and become micrometer-sized agglomerates. Then supersaturated water vapor is condensed onto these airborne agglomerates by using a growth tube collector. The collected suspension (CS) of hydrophobic nanomaterial (JMT-150IB) is prepared in two steps; airborne agglomerates are collected onto a flat surface then transferred to liquid-water and subsequently sonicated for complete dispersion. This method works equally well for making the CS of hydrophilic nanomaterial. Size distribution measurements of the CS show that airborne agglomerates of TiO2 dissociate into smaller units of agglomerates once they are captured into water, and the sizes of the agglomerates are in the nanometer to sub-micrometer range. Light scattering technique is used to show that a short sonication process can reproduce the particle number concentration of the CS after long storage. Copyright © 2017 American Association for Aerosol Research

We carried out a set of experiments to compare three particle number concentration standards (NCSs) by calibrating the same condensation particle counter (CPC) unit (Model 3772, TSI Inc., Shoreview, MN, USA). The standards were, in the order of operation size range, the primary NCS of the National Institute of Advanced Industrial Science and Technology (AIST, Japan), the Single Charged Aerosol Reference (SCAR) (Finland), and the Inkjet Aerosol Generator (IAG) of AIST. The results obtained with the 3 standards were found to agree at all overlapping particle sizes within the uncertainty limits. The relative expanded uncertainties varied between 0.6% and 2.6%, depending on the size and standard, while the overall agreement between the standards was within 0.5%. The observed consistency of the results is an important step toward establishing internationally coherent particle NCSs. As a result, the CPC 3772 was successfully calibrated in a particularly wide size range, approximately from 10 nm to 10 μm. The re...

The effect of working fluid on size-dependent activation efficiencies with the laminar flow ultrafine condensation particle counter described by Stolzenburg and McMurry (1991) was studied theoretically and experimentally. Criteria considered include tendency to avoid homogeneous nucleation within the condenser and toxicity. The working fluids that were identified have vapor pressures below that of butanol, so particles grow to smaller sizes and are more difficult to detect optically. Therefore we use a second, conventional CPC as a “booster” to grow particles to a detectable size. Experiments were performed to obtain the size- and material-dependent activation efficiencies for ethylene glycol, diethylene glycol, propylene glycol, oleic acid, and DOS. Using diethylene glycol and oleic acid, values of the 50% activation efficiency diameter, Dp50 , for negatively charged particles generated by evaporating sodium chloride, ammonium sulfate, and silver were < 1.2 (< 0.8) nm, 1.4–1.5 (1.0–1.2) nm, and 1.9–2.0 (...

An ultrafine, water-based condensation particle counter (U-WCPC, TSI Model 3786) has been compared to a butanol-based ultrafine counter (U-BCPC, TSI Model 3025) for measurement of atmospheric and freeway-tunnel aerosols. The U-WCPC utilizes a warm, wet-walled growth tube to activate and grow particles through water condensation in a laminar-flow. It has an aerosol sampling rate of 0.3 L/min, and a nominal detection limit near 3 nm. Several field comparisons were made to the butanol-based instrument with the same nominal detection limit. For measurements of size-selected aerosols with diameters of 5 nm and larger the two instruments generally agreed, with a mean response within 5%. At 3 nm particle size differences were observed, and these differences varied with the data set. Measurements of ambient aerosol in Boulder, Colorado showed higher counting efficiency at 3 nm with the U-BCPC, while in a California freeway tunnel the opposite trend was observed, with higher counting efficiencies at 3 nm observed ...

Chromated copper arsenate (CCA) has been the predominant wood preservative used in North America in recent years. The emission of volatile metals and leaching from the combustion ash of CCA-treated wood pose serious concerns. In this work, mineral sorbents were evaluated for their capabilities to control both problems. Results of thermodynamic analyses suggested that alkali and alkaline earth metal-based sorbents can potentially react with the metals during combustion. Experiments were conducted by mixing and burning mineral sorbents including lime and soda ash with CCA-treated wood in a fixed bed. Calcium-based sorbents showed great increase in the retention of arsenic (from 60 to 85%) and chromium (from 55 to 80%) and reduction in the leaching of arsenic (from 200 down to 0.1 mg/L) and copper (from 100 down to 1 mg/L). Sodium-based sorbents successfully retained metals in the ash below 750°C, but the products were highly leachable (over 1000 mg/L). The speciation of the products plays a critical role in...

Inkjet technology can be applied to generate highly monodisperse aerosol particles in micrometer range at a precisely controlled rate. AIST has been developing an inkjet aerosol generator (AIST-IAG), and the device will soon become the secondary measurement standard for aerosol particle number concentration in 0.35 μm to 10 μm range. The AIST-IAG can generate both solid and liquid particles consisting of water-soluble ionic compounds. We first report the characteristics of the particle sizes of the generated particles. The full width half maximum of the particle size distribution is about 2 percent, and the particle diameter of the IAG particles was calibrated as a function of the particle mass within 0.6-10 μm range using polystyrene latex sphere as reference material. Then we report the capability of the AIST-IAG as the particle number standard. The particle generation efficiency ηIAG was defined as the number of aerosol particles exiting from the AIST-IAG divided by the rate of the droplet generation, and the values of ηIAG within 0.35-10 μm is essentially 100%, and the 95% confidence interval of the values is less than 1%. The result strongly supports that the AISTIAG can be used to calibrate the counting efficiency of the optical particle counters in submicrometer to micrometer range.

[1] A method to estimate nanoparticle diameter growth rates (GR) during new particle formation (NPF) events from the measured dependence of charged fraction, f, on size, Dp, is introduced. The method is especially useful for observations during intense particle production rates, when the mode in the distribution of newly formed particles does not grow monotonically with time. This method assumes that the observed profile of f versus Dp during the nucleation and growth period is controlled by condensational growth, ion-particle combination/recombination, scavenging by preexisting particles, and coagulation among growing nanoparticles. Values of growth rates obtained by this method (GRf) agree well with independently obtained particle growth rates due to gas-to-particle conversion processes (GRPSD) during regional NPF events. The method was then applied to characterize the NPF events observed at Tecamac, Mexico. These growth rates were found to range from 15–40 nm/h, which is significantly higher than values reported for other urban areas. The production rates for 1 nm particles calculated from the estimated growth rates and measured Fuchs surface area (J1nm = 1900–3000 particles/cm3 s) are comparable to those recently observed in New Delhi. Because critical nuclei are likely close to 1 nm in size, J1nm should provide a reasonable estimate for nucleation rates.

[1] We report Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) measurements of the composition of ambient 10–33 nm diameter particles formed from nucleation on 16 March 2006 in Tecamac, Mexico during the Megacity Initiative: Local and Global Research Observations (MILAGRO) field study. On this day, nucleated particles contained far more organics than sulfates: average ion molar ratios with measurement uncertainties for nitrate, organics and sulfur species were 6 ± 2%, 84 ± 5%, and 10 ± 1%, respectively. The measured organic species include nitrogen-containing organic compounds, organic acids, and hydroxy organic acids. Independent calculations show that sulfuric acid condensation could have accounted for only 10 ± 2% of the growth that was observed on this day, which is consistent with the TDCIMS measurements of composition. It follows that organic compounds play a dominant role the high growth rates that were observed.

An ethylene glycol based ultrafine condensation particle counter (EG- UCPC) was developed by modifying the laminar flow ultrafine condensation particle counter which was originally developed by Stolzenburg and McMurry (1991) (1). Prior to experiments, theoretical analyses were performed using different working fluids to predict activation efficiency and condensational growth after activation. Ethylene glycol was chosen as the working fluid since it is less toxic than other compounds investigated and it has a predicted 50% cutoff diameter is below 2 nm. Experiments were performed using sodium chloride, ammonium sulfate, and silver as test aerosols. To obtain the activation efficiency from the experimental data we have accounted the size dependence of input particle size distribution and particle penetration within the diffusion-broadened mobility window of transfer function of the DMA. The 50% cutoff sizes of negatively charged particles are 1.3, 1.3, and 1.5 nm mobility diameter for sodium chloride, ammonium sulfate, and silver, respectively. The lower cutoff size for the first two compounds suggests that ethyl- ene glycol vapor heterogeneously nucleates more easily on hygroscopic material.

[1] This paper investigates the role of ion-induced nucleation (IIN) in new particle formation events observed near ground level at a sampling site located near Boulder, Colorado (14 March 2004 to 27 October 2005). Measurements of mobility distributions of small and intermediate ions (0.4–6.3 nm), size distributions of total particles (3 nm to 5 μm), and charged fractions (2.5–25 nm) were carried out. The relative contributions of neutral nucleation and IIN were inferred using both qualitative and quantitative analyses. First, a simple theoretical analysis is performed to show what can be learned about the initial charge state of the nucleated particles from charged fractions measured after they had grown to 3.0–5.5 nm. We found that for much of our data the charge fractions of freshly nucleated particles below 5 nm were significantly below stationary-state values, and that this tendency increased with decreasing size, indicating that neutral nucleation was dominant. However, the data also show that there were occasionally asymmetries between negative and positive charge fractions that we could not explain unless positive or negative IIN occurred to some extent. A quantitative analysis is then performed to estimate the fractional contribution of positive and negative IIN to new particle formation rates for each nucleation event observed during this period. The results show the average contribution of IIN is about 0.5% for both polarities indicating that IIN was a relatively insignificant contributor to new particle formation in this study. This result is consistent with the direct mass spectrometric measurements of sulfuric acid ion cluster compositions and concentrations performed at the same measurement site.

[1] Mass identified ion cluster distributions were measured under ambient atmospheric conditions and compared with model predictions based on laboratory ion cluster thermodynamics data. The results are shown from several days where atmospheric sulfur concentrations were high and thus ion-induced cluster growth was anticipated. Atmospheric gas phase sulfuric acid, temperature, relative humidity, SO2, mobility distributions of ions and small charged particles, and aerosol size distributions were also measured in support of the model calculations. The relative agreement of measurement and model for the first and second sulfuric acid clusters (HSO4−(H2SO4)m) for m = 1 and 2 is quite good but suggests that sulfuric acid clustering may not occur at the collision rate. Clusters for higher m values were not observed, which is also consistent with model predictions for the conditions under which measurements were performed. The lack of both observed and predicted large ion clusters is also consistent with the independent measurements of ion mobility distributions and particle size distributions, which showed similar numbers of positively and negatively charged ultrafine particles, suggesting that neither positive nor negative ion-induced nucleation processes were likely to have contributed significantly to observed new particle formation rates during this study. The relatively low observed concentrations of the bisulfate ion also suggest that the processes leading to the first sulfuric acid/bisulfate cluster (HSO4−H2SO4) may be more complicated than simple sulfuric acid clustering or exchange reactions. While nucleation was observed on some days, measurements suggest that ion-induced nucleation did not contribute significantly to new particle production or growth during these events. This does not rule out the possibility that ion-induced nucleation could contribute significantly to atmospheric new particle formation under very different atmosphere conditions such as in areas with much lower temperatures and higher ion concentrations.

Schemes of conditional data processing are evaluated based on either the peak-to-base ratio or the signal-to-noise ratio as a metric for analyte detection in single-shot laser-induced breakdown spectra. The analyte signal investigated is the 288.1-nm Si I emission line provided by an aerosol stream of monodisperse 2.5-microm-sized silica microspheres. Both the Si emission line and a spectral region corresponding to continuum emission are used to evaluate the statistical distribution of spectral noise. The probability of false hits is determined by evaluating various conditional processing thresholds. As the detection threshold increases, the rate of detected silica particle hits decreases along with the expected fraction of false-particle hits (i.e., spectral noise). For all threshold values the signal-to-noise ratio is found to provide a more robust metric for single-shot analyte detection compared with the peak-to-base ratio.