Particle Mass Distribution Research Articles

Characterisation of particle mass and number concentration on the east coast of the Malaysian Peninsula during the northeast monsoon

Particle mass concentrations (PM10, PM2.5 and PM1) and particle number concentration ((PNC); 0.27 μm ≤ Dp ≤ 34.00 μm) were measured in the tropical coastal environment of Bachok, Kelantan on the Malaysian Peninsula bordering the southern edge of the South China Sea. Statistical methods were applied on a three-month hourly data set (9th January to 24th March 2014) to study the influence of north-easterly winds on the patterns of particle mass and PNC size distributions. The 24-h concentrations of particle mass obtained in this study were below the standard values detailed by the Recommended Malaysian Air Quality Guideline (RMAQG), United States Environmental Protection Agency (US EPA) and European Union (EU) except for PM2.5, which recorded a 24-h average of 30 ± 18 μg m−3 and exceeded the World Health Organisation (WHO) threshold value (25 μg m−3). Principal component analysis (PCA) revealed that PNC with smaller diameter sizes (0.27–4.50 μm) showed a stronger influence, accounting for 57.6% of the variability in PNC data set. Concentrations of both particle mass and PNC increased steadily in the morning with a distinct peak observed at around 8.00 h, related to a combination of dispersion of accumulated particles overnight and local traffic. In addition to local anthropogenic, agricultural burning and forest fire activities, long-range transport also affects the study area. Hotspot and backward wind trajectory observations illustrated that the biomass burning episode (around February–March) significantly influenced PNC. Meteorological parameters influenced smaller size particles (i.e. PM1 and Dp (0.27–0.43 μm)) the most.

Effect of the jet production on pseudorapidity, transverse momentum and transverse mass distributions of charged particles produced in pp-collisions at Tevatron energy**Supported by Higher Education Commission (HEC) Government of Pakistan under Indigenous5000 PhD Scholarship Program Batch-IV

We investigate the effects of jet production on the following parameters: pseudorapidity, transverse momentum and transverse mass distributions of secondary charged particles produced in pp-collisions at 1.8 TeV, using the HIJING code. These distributions are analyzed for the whole range and for six selected regions of the polar angle as a function of the different number of jets. The obtained simulation results for these parameters are interpreted and discussed in connection to the increase observed in the multiplicity of secondary charged particles as a result of its multi-jet dependence, and are also discussed in comparison with the experimental results from the CDF Collaboration.

Effect of drying method on rheological, thermal, and structural properties of chestnut flour doughs

The objective of this work was to characterize the functional, thermal and rheological properties of chestnut flour doughs produced through freeze-drying (FD) and tray-drying (TD) process. Drying method did not influence the physicochemical properties (e.g. bulk density, water holding capacity and sediment volume fraction) of chestnut flour however affected both particle mass distribution and color values (a and b) significantly. Thermal analysis of chestnut doughs showed two distinct peaks attributed by starch gelatinization and melting of starch–lipid complex, respectively. Although there were only minor differences in the total starch contents between two chestnut flour, they displayed significant variability in pasting properties and oscillatory rheology during heating. The amylograms of the chestnut dispersions showed higher maximum viscosity and heat stability for the FD sample, as well as a higher tendency to the molecular re-association during cooling than for the TD flour. Pasting properties of chestnut doughs were well described by rheometric measurement and data obtained through both measurements are comparable. The chestnut doughs exhibited predominating solid-like property (G′ > G″). The mechanical rigidity (G′) of doughs significantly influenced by the concentration and the increase in G′ with concentration was well described by a power-type relationship. The chestnut granules exhibited a range of shapes, varying from round, oval, rectangular to irregular. Average particle diameter of the tray-dried sample was larger than the freeze-dried sample. This study provides in-depth knowledge on structural/rheological properties of chestnut flour by two drying processes, which would be helpful for selection of ingredients and their application in food industries.

Developing and Evaluating Ice Cloud Parameterizations for Forward Modeling of Radar Moments Using in situ Aircraft Observations

AbstractObserving ice clouds using zenith pointing millimeter cloud radars is challenging because the transfer functions relating the observables to meteorological quantities are not uniquely defined. Here, the authors use a spectral radar simulator to develop a consistent dataset containing particle mass, area, and size distribution as functions of size. This is an essential prerequisite for radar sensitivity studies and retrieval development. The data are obtained from aircraft in situ and ground-based radar observations during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) campaign in Alaska. The two main results of this study are as follows: 1) An improved method to estimate the particle mass–size relation as a function of temperature is developed and successfully evaluated by combining aircraft in situ and radar observations. The method relies on a functional relation between reflectivity and Doppler velocity. 2) The impact on the Doppler spectrum by replacing measurements of particle area and size distribution by recent analytical expressions is investigated. For this, higher-order moments such as skewness and kurtosis as well as the slopes of the Doppler spectrum are also used as a proxy for the Doppler spectrum. For the area–size relation, it is found that a power law is not sufficient to describe particle area and small deviations from a power law are essential for obtaining consistent higher moments. For particle size distributions, the normalization approach for the gamma distribution of Testud et al., adapted to maximum diameter as size descriptor, is preferred.

SPH Modeling Improvements for Hypervelocity Impacts

Smoothed Particle Hydrodynamics (SPH) are often used to model solid bodies undergoing large deformation during hypervelocity impacts due to the ability of the method to handle distortion without the mesh entanglement issues posed by other Lagrangian discretizations such as the finite element method. Rather than using mesh connectivity, SPH uses a kernel function and performs smoothed integration over nearest neighbors to enforce the conservation laws of continuum dynamics. A number of improvements to the formulation have been proposed to increase stability and accuracy of the results.Despite such improvements, the performance of the SPH method is limited by the way in which boundary conditions are applied. Deficiency in the SPH field near solid boundaries is a shortcoming inherent to the formulation resulting in an inaccurate representation of contact mechanics during an impact event. To address this, the first part of this work focuses on improving SPH contact by treating the particles as if they were nodes in a finite element mesh. We investigate the effect of distributing contact loads across free surfaces using a Lagrange multiplier scheme. In addition, we propose a method for improving the initial distribution of Lagrangian particle mass and evaluate its effective on pressure waves traveling through a body.There is also potential to improve SPH modeling during non-uniform deformation resulting from impact. As deformation occurs, compressive forces cause SPH particle density to increase in the impact direction and decrease perpendicular to the impact. This can reduce accuracy in the perpendicular plane as the spatial resolution is coarsened. In the most extreme cases, numerical fracture can occur when the particles disperse to the degree that immediate neighbors are no longer recognized. We demonstrate the use of an ellipsoid kernel method, allowing the kernel to deform anisotropically with the particle field to maintain resolution and prevent numerical fracture. We discuss the implications of the method with respect to hypervelocity impacts, and compare results with baseline output obtained using a typical spherical kernel to evaluate its effectiveness.

Novel Inhaled Combination Powder Containing Amorphous Colistin and Crystalline Rifapentine with Enhanced Antimicrobial Activities against Planktonic Cells and Biofilm of Pseudomonas aeruginosa for Respiratory Infections.

Colistin has been increasingly used for the treatment of respiratory infections caused by Gram-negative bacteria. Unfortunately parenteral administration of colistin can cause severe adverse effects. This study aimed to develop an inhaled combination dry powder formulation of colistin and rifapentine for the treatment of respiratory infections. The combination formulation was produced by spray-drying rifapentine particles suspended in an aqueous colistin solution. The combination dry powder had enhanced antimicrobial activities against planktonic cells and biofilm cultures of Pseudomonas aeruginosa, with both minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC) values (2 and 4 mg/L, respectively) being half that of pure colistin (MIC 4 mg/L and MBIC 8 mg/L) and 1/16th that of pure rifapentine (MIC 32 mg/L and MBIC 64 mg/L). High aerosol performance, as measured via an Aerolizer device, was observed with emitted doses>89% and fine particle fraction (FPF) total>76%. The proportion of submicron particles of rifapentine particles was minimized by the attachment of colistin, which increased the overall particle mass and aerodynamic size distribution. Using the spray-drying method described here, stable particles of amorphous colistin and crystalline rifapentine were distributed homogeneously in each stage of the impinger. Unlike the colistin alone formulation, no deterioration in aerosol performance was found for the combination powder when exposed to a high relative humidity of 75%. In our previous study, surface coating by rifampicin contributed to the moisture protection of colistin. Here, a novel approach with a new mechanism was proposed whereby moisture protection was attributed to the carrier effect of elongated crystalline rifapentine particles, which minimized contact between hygroscopic colistin particles. This inhaled combination antibiotic formulation with enhanced aerosol dispersion efficiency and in vitro efficacy could become a superior treatment for respiratory infections.

Analogue experimental study on centrifugal-air blast granulation for molten slag

Blast furnace slag is a by-product in iron and steel production process which has a high yield with extremely high discharge temperature. Aiming at energy and water saving as well as emission reduction, dry granulation technique appears to be a good application for the treatment of blast furnace slag. In this study, a granulation technique combining a high-speed rotating cup with air blast is proposed. The performance of this design was investigated by adopting a mixture of rosin and paraffin wax as the analogue of blast furnace slag. The effects of rotating speed of the atomizer, liquid flow rate and blast air flow rate on particle size, particle mass distribution and fiber mass fraction were studied. The effect of the function of air blast on the granulation performance was particularly discussed. The results showed that at a higher rotating speed and a smaller liquid flow rate, smaller particles can be easily obtained, yet the fiber mass fraction also increases. However, the increasing blast air leads to the increase of particle size and fiber mass fraction. For the operating conditions tested in this study, over 60% of total mass of particles fall within the size range of 0.5–1 mm, which means that the present system has a good performance in centrifugal granulation.

Model-independent probe of anomalous heavy neutral Higgs bosons at the LHC

We first formulate, in the framework of effective Lagrangian, the general form of the effective interactions of the lightest Higgs boson h and a heavier neutral Higgs boson H in a multi-Higgs system taking account of Higgs mixing effect. We regard h as the discovered Higgs boson which has been shown to be consistent with the standard model (SM) Higgs boson. The obtained effective interactions contain extra parameters reflecting the Higgs mixing effect. Next, We study the constraints on the anomalous coupling constants of H from both the requirement of the unitarity of the S matrix and the exclusion bounds on the SM Higgs boson obtained from the experimental data at the 7--8 TeV LHC. From this we obtain the available range of the anomalous coupling constants of H, with which H is not excluded by the yet known theoretical and experimental constraints. We then study the signatures of H at the 14 TeV LHC. In this paper, we suggest taking weak-boson scattering and pp to VH* to VVV as sensitive processes for probing H model independently at the 14 TeV LHC. We take several examples with the anomalous HVV coupling constants in the available ranges to do the numerical study. a full tree-level calculation at the hadron level is given with signals and backgrounds carefully calculated. We impose a series of proper kinematic cuts to effectively suppress the backgrounds. It is shown that, in both the VV scattering and the pp to VH* to VVV processes, H boson can be discovered from the invariant mass distributions of the final state particles with reasonable integrated luminosity. Especially, in the pp to VH* to VVV process, the invariant mass distribution of the final state jets can show a clear resonance peak of H. Finally, we propose several physical observables from which the values of the anomalous coupling constants f_W and f_{WW} can be measured experimentally.

Size-resolved effective density of urban aerosols in Shanghai

Size-resolved effective density of 50–400 nm urban particles was determined by a TDMA–APM system in Shanghai during wintertime. The average effective density ranged from 1.36 to 1.55 g cm−3, increasing with the particle diameter. The size dependent increase of density was consistent with previous hygroscopic measurements. We attributed the increase in density to the condensation of hygroscopic secondary aerosols and large massive organics. The diurnal variation of effective density was pronounced for smaller particles. A similar diurnal pattern was observed between particle density and the contribution of secondary NH4NO3 and (NH4)2SO4 to PM1.0, suggesting that density change in response to particle compositions. The effective density of Aitken mode particles had a considerable increase during the NPF event, in agreement with the contribution of sulfate. Particle mass distribution was derived from particle number distribution in combination with effective density. PM0.6 was highly correlated with PM1.0, revealing that secondary aerosols tend to condense on smaller particles.

Synaptic effects of cannabinoids: complexity, behavioral effects, and potential clinical implications.

<h3>OBJECTIVES</h3> To characterise the distribution of particle size and mass of glove powder aerosol released from powdered and powder free non-sterile latex gloves under controlled conditions. <h3>METHODS</h3> Gravimetric sampling and aerodynamic particle size analysis were performed during simulated use of gloves on a prosthetic hand in a chamber designed to minimise background particle concentrations. <h3>RESULTS</h3> Aerosol was detectable for both powdered and powder free gloves under both aggressive and non-aggressive handling conditions. Most of the particles detected had aerodynamic diameter less than 10 μm. <h3>CONCLUSION</h3> Powder free gloves were not entirely free of powder aerosol. Particles from both powdered and powder free gloves are sufficiently fine to penetrate into the thoracic region of the respiratory tract.

Ejecta production from shocked Pb surface via molecular dynamics

Molecular dynamics simulations are employed to examine the relation between ejecta production and shock-breakout pressure for single crystal Pb subjected to a decaying shockwave loading. To better understand the physical mechanism of ejecta formation, a surface with multiple triangular grooves representing the imperfections left from machining finish is taken into consideration. It is found that the ejecta volume density distribution displays a smooth nature and the amount of ejecta increases significantly after melting on release or shock. Additionally, the ejecta particle mass distribution is captured by a power law scaling, revealing the self-similarity. These results are in reasonable agreement with the characteristics of experimentally diagnosed findings.

Experimental Investigation on Influence of Important Parameters in Centrifugal Granulation for MBFS

The difficulties of molten metallurgical slag heat recovery caused by low thermal conductivity and high enthalpy are analyzed.Centrifugal granulation is an environment-friendly process in treating the slag. The existing researches on centrifugal granulation are concentrated in the shape, size and mass distribution of slag particles. The relations between flight distance of slag, divorced speed of slag and outside speed of cup and rotary speed and rotary cup diameter were studied. The experimental results indicate that flight distance is farther from the cup and the speeds increase with increasing rotary speed. While rotary speed reaches 1000 rpm, divorced speed and flight distance of slag are almost invariant. When rotary cup diameter increases, the flight distance and the speeds increase simultaneously. Flight is reasonably simplified as:uniform motion in horizontal direction and motion of free falling body in the vertical direction,The experimental results have certain guiding significance to design of heat recovery equipment.

Mass and elemental distributions of atmospheric particles nearby blast furnace and electric arc furnace operated industrial areas in Australia

The improved understanding of mass and elemental distributions of industrial air particles is important due to their heterogeneous atmospheric behaviour and impact on human health and the environment. In this study, particles of different size ranges were collected from three sites in Australia located in the vicinity of iron and steelmaking industries and one urban background site with very little industrial influence. In order to determine the importance of the type of industrial activity on the urban atmospheric quality, the industrial sites selected in this study were in the close proximity to two blast furnace operated and one electric arc furnace based steelmaking sites. The chemical compositions of the collected air particles were analysed using the proton induced X-ray emission (PIXE) technique. This study revealed significantly higher metal concentrations in the atmospheric particles collected in the industrial sites, comparing to the background urban site, demonstrating local influence of the industrial activities to the air quality. The modality types of the particles were found to be variable between the mass and elements, and among elements in the urban and industrial areas indicating that the elemental modal distribution is as important as particle mass for particle pollution modelling. The highest elemental number distribution at all studied sites occurred with particle size of 0.1μm. Iron was found as the main dominant metal at the industrial atmosphere in each particle size range. The industrial Fe fraction in the submicron and ultrafine size particles was estimated at up to 95% which may be released from high temperature industrial activities with the iron and steelmaking industries being one of the major contributors. Hence, these industrial elemental loadings can highly influence the atmospheric pollution at local urban and regional levels and are required to consider in the atmospheric modelling settings.

Sequential fragmentation/transport theory, pyroclast size–density relationships, and the emplacement dynamics of pyroclastic density currents — A case study on the Mt. St. Helens (USA) 1980 eruption

Pyroclastic density currents (PDCs) are the most dangerous hazard associated with explosive volcanic eruptions. Despite recent advancements in the general understanding of PDC dynamics, limited direct observation and/or outcrop scarcity often hinder the interpretation of specific transport and depositional processes at many volcanoes. This study explores the potential of sequential fragmentation/transport theory (SFT; cf. Wohletz et al., 1989), a modeling method capable of predicting particle mass distributions based on the physical principles of fragmentation and transport, to retrieve the transport and depositional dynamics of well-characterized PDCs from the size and density distributions of individual components within the deposits. The extensive vertical and lateral exposures through the May 18th, 1980 PDC deposits at Mt. St. Helens (MSH) provide constraints on PDC regimes and flow boundary conditions at specific locations across the depositional area. Application to MSH deposits suggests that SFT parameter distributions can be effectively used to characterize flow boundary conditions and emplacement processes for a variety of PDC lithofacies and deposit locations. Results demonstrate that (1) the SFT approach reflects particle fragmentation and transport mechanisms regardless of variations in initial component distributions, consistent with results from previous studies; (2) SFT analysis reveals changes in particle characteristics that are not directly observable in grain size and fabric data; and (3) SFT parameters are more sensitive to regional transport conditions than local (outcrop-scale) depositional processes. The particle processing trends produced using SFT analysis are consistent with the degree of particle processing inferred from lithofacies architectures: for all lithofacies examined in this study, suspension sedimentation products exhibit much better processing than concentrated current deposits. Integrated field observations and SFT results provide evidence for increasing density segregation within the depositional region of the currents away from source, as well as for comparable density-segregation processes acting on lithic concentrations and pumice lenses within the current. These findings further define and reinforce the capability of SFT analysis to complement more conventional PDC study methods, significantly expanding the information gained regarding flow dynamics. Finally, this case study demonstrates that the SFT methodology has the potential to constrain regional flow conditions at volcanoes where outcrop exposures are limited.

Convecting particle diffusion in a binary particle system under vertical vibration

We studied the separation behaviour of binary granular particles in a vertically vibrated container. The final separation of the binary particle system exhibited the Brazil-Nut (BN) effect, though it was not complete. Particle convection occurred, and four different typical convection modes were observed when the frequency f changed from 20 Hz to 80 Hz at constant dimensionless acceleration Γ = 4πAf(2)/g. However, when Γ changed from 2 to 4 at constant f, the system's convection mode stayed almost the same. In our experiments, one type of particle generally moved much faster than the other, so the former was termed the 'convecting' particle, and the latter was termed the 'non-convecting' particle. To study the separation results qualitatively, we divided the system into vertical layers and calculated the mass distribution of the binary particles along the z axis. The results showed that when f increased at constant Γ or Γ decreased at constant f, the convecting particles, usually the smaller and lighter ones, distributed less to the top side and more to the bottom side of the container. Finally, to explain the experimental results, we derived a mass conservation equation for the convecting particles considering simultaneous convection and diffusion. The equation described the experimental results well. We also analysed the effects of f, Γ, diameter ratio, density ratio, etc., on the final separation results.

Quantification of Low Pressure Impactor Wall Deposits during Zinc Nanoparticle Sampling

A Dekati low pressure impactor (DLPI) is used to determine the mass distribution of airbome particles from 7 nm to 10 urn as a function of aerodynamic diameter. Quantification of wall deposits inside this sampling device was performed for the first time using poly disperse zinc aerosol produced by a thermal spraying process. This aerosol is more representative of the size distribution found in occupational atmospheres than aerosols usually produced in laboratories. Each experiment (3 replicates) was carried out for two durations. The results showed that wall deposits were quite considerable and in relation with aerosol modes. 13% and 14% of the total mass was found on the wall after sampling periods of 5 and 20 minutes, respectively. Relative losses could reach 50% for certain impaction stages and these losses were also quite different between replicates.

Quantification of Low Pressure Impactor Wall Deposits during Zinc Nanoparticle Sampling

A Dekati® low pressure impactor (DLPI) is used to determine the mass distribution of airborne particles from 7 nm to 10 µm as a function of aerodynamic diameter. Quantification of wall deposits inside this sampling device was performed for the first time using polydisperse zinc aerosol produced by a thermal spraying process. This aerosol is more representative of the size distribution found in occupational atmospheres than aerosols usually produced in laboratories. Each experiment (3 replicates) was carried out for two durations. The results showed that wall deposits were quite considerable and in relation with aerosol modes. 13% and 14% of the total mass was found on the wall after sampling periods of 5 and 20 minutes, respectively. Relative losses could reach 50% for certain impaction stages and these losses were also quite different between replicates.

Considerations of particle vaporization and analyte diffusion in single-particle inductively coupled plasma-mass spectrometry

The intensity of individual gold nanoparticles with nominal diameters of 80, 100, 150, and 200nm was measured using single-particle inductively coupled plasma-mass spectrometry (ICP-MS). Since the particles are not perfectly monodisperse, a distribution of ICP-MS intensity was obtained for each nominal diameter. The distribution of particle mass was determined from the transmission electron microscopy (TEM) image of the particles. The distribution of ICP-MS intensity and the distribution of particle mass for each nominal diameter were correlated to give a calibration curve. The calibration curves are linear, but the slope decreases as the nominal diameter increases. The reduced slope is probably due to a smaller degree of vaporization of the large particles.In addition to the degree of particle vaporization, the rate of analyte diffusion in the ICP is an important factor that determines the measured ICP-MS intensity. Simulated ICP-MS intensity versus particle size was calculated using a simple computer program that accounts for the vaporization rate of the gold nanoparticles and the diffusion rate and degree of ionization of the gold atoms. The curvature of the simulated calibration curves changes with sampling depth because the effects of particle vaporization and analyte diffusion on the ICP-MS intensity are dependent on the residence time of the particle in the ICP. Calibration curves of four hypothetical particles representing the four combinations of high and low boiling points (2000 and 4000K) and high and low analyte diffusion rates (atomic masses of 10 and 200Da) were calculated to further illustrate the relative effects of particle vaporization and analyte diffusion. The simulated calibration curves show that the sensitivity of single-particle ICP-MS is smaller than that of the ICP-MS measurement of continuous flow of standard solutions by a factor of 2 or more. Calibration using continuous flow of standard solution is semi-quantitative at best.An empirical equation is formulated for the estimation of the position of complete vaporization of a particle in the ICP. The equation takes into account the particle properties (diameter, density, boiling point, and molecular weight of the constituents of the particle) and the ICP operating parameters (ICP forward power and central channel gas flow rate). The proportional constant and exponents of the variables in the equation were solved using literature values of ICP operating conditions for single-particle inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) measurements of 6 kinds of particles in 12 studies. The calculated position is a useful guide for the selection of sampling depth or observation height for ICP-MS and ICP-AES measurements of single particles as well as discrete particles in a flow, such as laser-ablated materials and airborne particulates.

Laboratory characterization of PM emissions from combustion of wildland biomass fuels

Particle emissions from open burning of southwestern (SW) and southeastern (SE) U.S. fuel types during 77 controlled laboratory burns are presented. The fuels include SW vegetation types: ceanothus, chamise/scrub oak, coastal sage scrub, California sagebrush, manzanita, maritime chaparral, masticated mesquite, oak savanna, and oak woodland, as well as SE vegetation types: 1 year, 2 year rough, pocosin, chipped understory, understory hardwood, and pine litter. The SW fuels burned at higher modified combustion efficiency (MCE) than the SE fuels resulting in lower particulate matter mass emission factor. Particle mass distributions for six fuels and particle number emission for all fuels are reported. Excellent mass closure (slope = 1.00,r2 = 0.94) between ions, metals, and carbon with total weight was obtained. Organic carbon emission factors inversely correlated (R2 = 0.72) with average MCE, while elemental carbon (EC) had little correlation with average MCE (R2 = 0.10). The EC/total carbon ratio sharply increased with MCE for MCEs exceeding 0.94. The average levoglucosan and total polycyclic aromatic hydrocarbon (PAH) emissions factors ranged from 25 to 1272 mg/kg fuel and 1.8 to 11.3 mg/kg fuel, respectively. No correlation between average MCE and emissions of PAHs/levoglucosan was found. Additionally, PAH diagnostic ratios were observed to be poor indicators of biomass burning. Large fuel type and regional dependency were observed in the emission rates of ammonium, nitrate, chloride, sodium, and potassium.

Particle Production in Reflection and Transmission Mode Laser Ablation: Implications for Laserspray Ionization

Particles were ablated from laser desorption and inlet ionization matrix thin films with a UV laser in reflection and transmission geometries. Particle size distributions were measured with a combined scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS) system that measured particles in the size range from 10nm to 20μm. The matrixes investigated were 2,5-dihydroxybenzoic acid (DHB), α-cyano-4-hydroxycinnamic acid (CHCA), sinapic acid (SA), 2,5-dihydroxy-acetophenone (DHAP), and 2-nitrophloroglucinol (NPG). Nanoparticles with average diameters between 20 and 120nm were observed in both transmission and reflection geometry. The particle mass distribution was significantly different in reflection and transmission geometry. In reflection geometry, approximately equal mass was distributed between particles in the 20 to 450nm range of diameters and particles in the 450nm to 1.5μm diameter range. In transmission mode, the particle mass distribution was dominated by large particles in the 2 to 20μm diameter range. Ablation of inlet ionization matrices DHAP and NPG produced particles that were 3 to 4 times smaller compared with the other matrices. The results are consistent with ion formation by nanoparticle melting and breakup or melting and breakup of the large particles through contact with heated inlet surfaces. ᅟ