Particle Mass Spectra Research Articles

Analysis of rainwater samples: Comparison of single particle residues with ambient particle chemistry from the northeast Pacific and Indian oceans

Individual particles produced from atomized rainwater samples collected in California and the Indian Ocean were analyzed with an aerosol time‐of‐flight mass spectrometer (ATOFMS) to investigate the chemical composition of the individual rain residue particles. Insoluble residue particle types were determined on the basis of a comparison of the rainwater particle mass spectra with ambient particle spectra. Major particle types found in rainwater include dust, organic carbon with sodium, aromatic organic carbon, vegetative detritus, and an internally mixed sea salt and elemental carbon class. A unique internally mixed sea salt–elemental carbon particle type was detected in both the ambient and rainwater samples, suggesting this particle type was most likely formed by cloud processing occurring during long‐range transport. The presence of this particle type in remote marine locations has important climate ramifications as it is anticipated it will be strongly absorbing on the basis of the combination of an absorbing particle (elemental carbon) mixed with a high refractive index material (sea salt). Most of the particle types detected in rainwater were detected in the ambient particles with the exception of a unique aromatic particle type detected in rainwater samples from both locations. The presence of the aromatic type coupled with the absence of biomass particles in the rainwater samples leads to the hypothesis the aromatic components were originally associated with atmospheric biomass burning particles. The ubiquitous presence of this aromatic type in rainwater samples highlights the potential importance of biomass burning and/or humic‐like substances (HULIS) compounds in cloud formation and rain processes.

Comparison of two cluster analysis methods using single particle mass spectra

Cluster analysis of aerosol time-of-flight mass spectrometry (ATOFMS) data has been an effective tool for the identification of possible sources of ambient aerosols. In this study, the clustering results of two typical methods, adaptive resonance theory-based neural networks-2a (ART-2a) and density-based clustering of application with noise (DBSCAN), on ATOFMS data were investigated by employing a set of benchmark ATOFMS data. The advantages and disadvantages of these two methods are discussed and some feasible remedies proposed for problems encountered in the clustering process. The results of this study will provide promising directions for future work on ambient aerosol cluster analysis, suggesting a more effective and feasible clustering strategy based on the integration of ART-2a and DBSCAN.

10.1007/s11447-008-2005-0

We consider (d_0+2)-dimensional configurations with global strings in the two extra dimensions and a flat metric in d_0 dimensions, endowed with a warp factor e^{2\gamma} depending on the distance l from the string center. All possible regular solutions to the field equations are classified by the behavior of the warp factor and the extra-dimensional circular radius r(l). Solutions with r\to \infty and r\to \const >0 as l\to \infty are interpreted in terms of thick brane world models. Solutions with r \to 0 as l \to l_c > 0, i.e., those with a second center, are interpreted as either multi-brane systems (which is appropriate for large enough distances l_c between the centers) or as Kaluza-Klein type configurations with extra dimensions invisible due to their smallness. For the case of the Mexican-hat symmetry breaking potential, we build a full map of regular solutions on the (\epsilon,\Gamma) parameter plane, where \epsilon acts as an effective cosmological constant while \Gamma characterizes the strength of gravity. The trapping properties of candidate brane worlds for test scalar fields are discussed. Good trapping properties for massive fields are found for models with growing warp factors. Kaluza-Klein type models are shown to possess nontrivial warp factor behaviors, leading to matter particle mass spectra which seem promising from the standpoint of hierarchy problems.

The E-ring in the vicinity of Enceladus: II. Probing the moon's interior—The composition of E-ring particles

The population of Saturn's outermost tenuous E-ring is dominated by tiny water ice particles. Active volcanism on the moon Enceladus, embedded in the E-ring, has since late 2005 been known to be a major source of particles replenishing the ring. Therefore particles in the vicinity of Enceladus may provide crucial information about the dynamical and chemical processes occurring below the moon's icy surface. Here we present a statistical evaluation of more than 2000 impact ionisation mass spectra of Saturn's E-ring particles, with sizes predominantly below 1 μm, detected by the Cosmic Dust Analyser onboard the Cassini spacecraft. We focus on the identification of non-water features in spectra otherwise dominated by water ice signatures. Here we specify the categorisation of two different spectrum types, which probably represent two particle populations. Type I spectra imply pure water ice particles, whereas in Type II spectra organic compounds and/or silicate minerals are identified as impurities within the icy particles. This finding supports the hypothesis of a dynamic interaction of Enceladus' rocky core with liquid water.

Critical behavior of the particle mass spectra in a family of gelling systems

The critical and post-critical behavior of coagulating systems, where the coagulation efficiency grows with the masses of colliding particles g and l as K(g,l)=0.5(g(alpha)(l)(beta)+g(beta)(l)(alpha), lambda=alpha+beta>1, mu=/alpha - beta/ <1 is studied. The instantaneous sink that removes the particles with masses exceeding G is introduced which allows one to describe the coagulation kinetics by a finite set of equations and define the gel as the deposit of particles with masses between G+1 and 2G . This system displays the critical behavior (the sol-gel transition) in the limit G-->infinity if lambda=alpha+beta>1. The exact post-critical particle mass spectrum is shown to be an algebraic function of g times a growing exponent. All critical parameters of the systems are determined as the functions of alpha and beta .

Measurements of Ammonium and Sodium salt Aerosol Particles Using a Laser-ionization Single-particle Aerosol Mass Spectrometer

Abstract Using a laser-ionization single-particle aerosol mass spectrometer (LISPA-MS), mass spectra of ammonium and sodium salt particles were obtained. In the negative-ion mass spectra, HSO4−, and NO2− and NO3− were dominant ions for (NH4)2SO4 and NH4NO3 particles, respectively, while ions with sodium were also dominant for Na2SO4 and NaNO3 particles. The chemical compositions of such salt aerosol particles can be inferred from the distribution of ions in those negative-ion mass spectra obtained using the LISPA-MS.

Mass Spectral Evidence That Small Changes in Composition Caused by Oxidative Aging Processes Alter Aerosol CCN Properties

Oxidative processing (i.e., "aging") of organic aerosol particles in the troposphere affects their cloud condensation nuclei (CCN) activity, yet the chemical mechanisms remain poorly understood. In this study, oleic acid aerosol particles were reacted with ozone while particle chemical composition and CCN activity were simultaneously monitored. The CCN activated fraction at 0.66 +/- 0.06% supersaturation was zero for 200 nm mobility diameter particles exposed to 565 to 8320 ppmv O3 for less than 30 s. For greater exposure times, however, the particles became CCN active. The corresponding chemical change shown in the particle mass spectra was the oxidation of aldehyde groups to form carboxylic acid groups. Specifically, 9-oxononanoic acid was oxidized to azelaic acid, although the azelaic acid remained a minor component, comprising 3-5% of the mass in the CCN-inactive particles compared to 4-6% in the CCN-active particles. Similarly, the aldehyde groups of alpha-acyloxyalkylhydroperoxide (AAHP) products were also oxidized to carboxylic acid groups. On a mass basis, this conversion was at least as important as the increased azelaic acid yield. Analysis of our results with Köhler theory suggests that an increase in the water-soluble material brought about by the aldehyde-to-carboxylic acid conversion is an insufficient explanation for the increased CCN activity. An increased concentration of surface-active species, which decreases the surface tension of the aqueous droplet during activation, is an interpretation consistent with the chemical composition observations and Köhler theory. These results suggest that small changes in particle chemical composition caused by oxidation could increase the CCN activity of tropospheric aerosol particles during their atmospheric residence time.

Sticking coefficient and SIMS of hydrocarbons on fusion relevant plasma-sprayed tungsten surfaces

In this work we concentrate on the quantification of the sticking coefficient of CD3+ on fusion relevant plasma-sprayed tungsten (PSW) surfaces in the collision energy range from about 0 up to 100eV. PSW samples were cut from ASDEX Upgrade tiles and both untreated and electropolished surfaces are investigated. A collision energy, Ecoll, selected CD3+ ion beam deposits hydrocarbon layers onto the target surfaces which are ex-situ analyzed by nuclear reaction analysis (NRA) via D(3He,p)4He at 800kV and 2.5MeV, respectively. The sticking coefficient, S, for deuterium has been found to be collision energy dependent, decreasing with increasing energy. It is in the order of S∼0.4 for PSW and S∼0.1 for electro polished PSW at Ecoll=10eV. Secondary ion mass spectra of charged particles are recorded after ion–surface collisions with the polished PSW surface for collision energies up to 100eV. While at very low collision energies below about 10eV only simple reflection of CD3+ is observed, at higher collision energies both fragmentation of the projectile and fragmentation of ion–surface reaction products are observed. Concerning the stability of the layers we prove that hydrogen exchange plays a role on the time scale of weeks.

A High Resolution Study of the Effect of Morphology On the Mass Spectra of Single PSL Particles with Na-containing Layers and Nodules

The interpretation and quantification of measurements of particle composition by laser ablation based single particle mass spectrometry is complex. Among the most difficult systems to quantify are internally mixed particles containing alkali metals and organics. The alkali atoms in such particles tend to suppress the formation of other ions sometimes to below the detection limit. Here we present a study of the behavior of single particle mass spectral peak intensities as a function of the amount of the sodium containing compounds deposited on the surface of 240 nm polystyrene latex (PSL) spheres. We generate three morphologically distinct and well defined coating types: uniform layers, cubic nodules and rounded nodules, and measure the individual particle mass spectra as a function of the vacuum aerodynamic diameter with nanometer resolution. The data show that the probability of detecting the PSL spheres depends on the amount of the alkali metal on the PSL sphere surface, its morphological distribution and the ablation laser power. The data suggest that PSL spheres with localized Na-containing nodules are easier to detect than those which are completely encapsulated. We show, for example, that at low laser power, PSL particles that are completely encapsulated with Na-containing compounds, whose weight fraction is close to 50%, cannot be detected, while 35% of PSL spheres with same amount of coating can be detected if coating is localized in nodules on a fraction of the particle surface.

Detecting singly charged ions during field evaporation of tantalum at high temperatures

The field evaporation of tantalum from point emitters in a broad range of temperatures from T = 300 to 2500 K was studied using a static magnetic mass spectrometer equipped with a special field ion source. The room-temperature mass spectrum of field-evaporated particles displayed only the peaks of triply charged ions (Ta3+). As the temperature was increased, the charge of field-evaporated ions exhibited a decrease: at T ∼ 1000 K, the peaks of doubly charged ions (Ta2+) prevailed. The peaks of singly charged ions (Ta+) were detected for the first time at temperatures in the interval 1900 K < T < 2500 K. The rate of evaporation of singly charged tantalum ions was several orders of magnitude lower than that of doubly charged ions.

Evaporation of Water from Particles in the Aerodynamic Lens Inlet: An Experimental Study

The extremely high particle transmission efficiency of aerodynamic lens inlets resulted in their wide use in aerosol mass spectrometers. One of the consequences of transporting particles from high ambient pressure into the vacuum is that it is accompanied by a rapid drop in relative humidity (RH). Since many atmospheric particles exist in the form of hygroscopic water droplets, a drop in RH may result in a significant loss of water and even a change in phase. How much water is lost in these inlets is presently unknown. Since water loss can affect particle size, transmission efficiency, ionization probability, and mass spectrum, it is imperative to provide definitive experimental data that can serve to guide the field to a reasonable and uniform sampling approach. In this study, we present the results of a number of highly resolved measurements, conducted under well-defined conditions, of water evaporation from a range of particles, during their transport through an aerodynamic lens inlet. We conclude that the only sure way to avoid ambiguities during measurements of aerodynamic diameter in instruments that utilize low-pressure aerodynamic lens inlets is to dry the particles prior to sampling.

SpectraMiner, an interactive data mining and visualization software for single particle mass spectroscopy: A laboratory test case

Single particle mass spectrometers are sophisticated instruments designed to measure the sizes and compositions of a wide range of individual particles in situ, in real-time. They characterize hundreds of thousands or millions of particles, generating vast amounts of rich and complex data, the proper mining of which requires dedicated state of the art tools. The analysis of individual particle mass spectra is particularly difficult because of their high dimensionality—each data point, representing a single particle, includes the 450 mass spectral peak intensities, particle size, and time of detection. The first step is to organize the data; a process typically accomplished by grouping particles of similar attributes. Since the common assumption is that the data should be reduced to become manageable, they are typically classified into a small number of clusters (∼10), each of which is represented by an average/representative spectrum. Our approach is quite different. We have developed a data mining and visualization software package we call SpectraMiner that makes it possible to handle hundreds of clusters, limiting loss of information and thus overcoming the boundaries set by traditional statistical data analysis approaches. Data, which often include over 1 million particle spectra, are organized using K-mean clustering algorithm. The clusters are merged into nodes by sequentially combining similar clusters. The final structure is displayed in a hierarchical dynamical tree or circular dendogram. This interactive dendogram is the visual interface that allows for real-time data exploration and mining. Clicking on any of the clusters/nodes in the dendogram reveals the detailed information about the particles that reside at that position. At each step the scientist is in control of the level of detail and the visualization format, rapidly switching between them while running the program on a PC. Here we present a study that puts the classification aspect of SpectraMiner to the test. Twelve types of laboratory generated particles are carefully chosen to test some of the difficult aspects of single particle mass spectroscopy. We quantify the degree of particle identification and separation at a number of levels and demonstrate how the visualization tools that SpectraMiner provides can be used to refine, steer and control the data mining process.

Sol-gel transition in a source-enhanced coagulating system

This paper considers the time evolution of disperse systems in which binary coagulation and a source of fresh particles govern the temporal changes to the particle mass spectra. The source is assumed to produce fresh particles at a constant rate. The Smoluchowski equation describing the time evolution of the particle mass spectrum is solved exactly for the coagulation kernel proportional to the product of masses of two coalescing particles. It is shown that after a critical time tc a gel forms in the system and the sol spectrum becomes an algebraic function of the particle mass at t=tc. It begins to shrink after the critical time due to the mass loss supporting the growth of the gel mass. The pre- and post-critical behavior of the mass spectrum and its integral characteristics (total particle number and mass concentrations) are investigated for the source productivity I(g) dropping down algebraically with the particle mass g as I(g) proportional variant g -gamma. The critical particle mass spectrum is proved to be a universal function of (it drops down as g -5/2) if the third moment of I(g) is finite (gamma>4). Otherwise (3<gamma< or =4)this and other critical exponents begin to depend on . Still the mass spectrum remains self-similar, i.e., it depends on a combination of g and t. At smaller gamma the gelation process is shown to begin at t=0. All critical characteristics of the particle mass spectrum are determined for this case.

Reactions and mass spectra of complex particles using Aerosol CIMS

Aerosol chemical ionization mass spectrometry (CIMS) is used both on- and off-line for the analysis of complex laboratory-generated and ambient particles. One of the primary advantages of Aerosol CIMS is the low degree of ion fragmentation, making this technique well suited for investigating the reactivity of complex particles. To demonstrate the usefulness of this “soft” ionization, particles generated from meat cooking were reacted with ozone and the composition was monitored as a function of reaction time. Two distinct kinetic regimes were observed with most of the oleic acid in these particles reacting quickly but with 30% appearing to be trapped in the complex mixture. Additionally, detection limits are measured to be sufficiently low (100–200 ng/m 3) to detect some of the more abundant constituents in ambient particles, including sulfate, which is measured in real-time at 1.2 μg/m 3. To better characterize complex aerosols from a variety of sources, a novel off-line collection method was also developed in which non-volatile and semi-volatile organics are desorbed from particles and concentrated in a cold U-tube. Desorption from the U-tube followed by analysis with Aerosol CIMS revealed significant amounts of nicotine in cigarette smoke and levoglucosan in oak and pine smoke, suggesting that this may be a useful technique for monitoring particle tracer species. Additionally, secondary organic aerosol formed from the reaction of ozone with R-limonene and volatile organics from orange peel were analyzed off-line showing large molecular weight products ( m/ z > 300 amu) that may indicate the formation of oligomers. Finally, mass spectra of ambient aerosol collected offline reveal a complex mixture of what appears to be highly processed organics, some of which may contain nitrogen.

Nonlinear behavior of the renormalization group flow and standard model parameters

The standard model for high-energy physics (SM) describes fundamental interactions between subatomic particles down to a distance scale on the order of 10−18m. Despite its widespread acceptance, a consistent and comprehensive understanding of SM parameters is missing. Starting from a less conventional standpoint, our work suggests that the spectrum of particle masses, gauge couplings and fermion mixing angles may be derived from the chaotic regime of the renormalization group flow. In particular, we argue that the observed hierarchies of standard model parameters amount to a series of scaling ratios depending on the Feigenbaum constant. Leading order predictions are shown to agree well with experimental data.

Feigenbaum scaling, Cantorian space–time and the hierarchical structure of standard model parameters

Abstract The standard model for high-energy physics (SM) describes fundamental interactions between subatomic particles down to a distance scale on the order of 10 −18 m. Despite its widespread acceptance, a consistent and comprehensive understanding of SM parameters is missing. Starting from a less conventional standpoint, our work suggests that the spectrum of particle masses, gauge couplings and fermion mixing angles may be derived from the chaotic regime of the renormalization group flow. In particular, we argue that the observed hierarchies of standard model parameters amount to a series of scaling ratios depending on the Feigenbaum constant. Leading order predictions are shown to agree well with experimental data. A brief discussion on the unexpected connection between our work and El Naschie’s e ∞ theory is included.

Composition of jovian dust stream particles

The Cassini spacecraft encountered Jupiter in late 2000. Within more than 1 AU of the gas giant the Cosmic Dust Analyser onboard the spacecraft recorded the first ever mass spectra of jovian stream particles. To determine the chemical composition of particles, a comprehensive statistical analysis of the dataset was performed. Our results imply that the vast majority (>95%) of the observed stream particles originate from the volcanic active jovian satellite Io from where they are sprinkled out far into the Solar System. Sodium chloride (NaCl) was identified as the major particle constituent, accompanied by sulphurous as well as potassium bearing components. This is in contrast to observations of gas in the ionian atmosphere, its co-rotating plasma torus, and the neutral cloud, where sulphur species are dominant while alkali and chlorine species are only minor components. Io has the largest active volcanoes of the Solar System with plumes reaching heights of more than 400 km above the moons surface. Our in situ measurements indicate that alkaline salt condensation of volcanic gases inside those plumes could be the dominant formation process for particles reaching the ionian exosphere.

Pentaquarks and the mass spectrum of the elementary particles of the standard model

Abstract In the present work some new expressions for the expectation value of the mass of the pentaquark 〈mpenta〉 are presented. The possible connection between the Higgs mass and the 〈mpenta〉 is explored following [El Naschie MS. Pentaquark mass sum rule and the Higgs. Chaos, Solitons & Fractals (in press)]. The Higgs and the pentaquark mass may be expressed in terms of couplings α ¯ g and α ¯ gs as well as of the predicted number of elementary particles of the standard model N(MS) ≈ 69. Theoretical predictions of the mass spectrum of elementary particles of the standard model is presented in Table 1 together with the scaling factors.

Conformally sequestered supersymmetry breaking in vectorlike gauge theories

We provide, in a framework of vector-like gauge theories, concrete models for conformal sequestering of dynamical supersymmetry (SUSY) breaking in the hidden sector. If the sequestering is sufficiently strong, anomaly mediation of the SUSY breaking may give dominant contributions to the mass spectrum of SUSY standard-model particles, leading to negative slepton masses squared. Thus, we also consider a model with gravitational gauge mediation to circumvent the tachyonic slepton problem in pure anomaly mediation models.

Baltimore Supersite: Highly time- and size-resolved concentrations of urban PM 2.5 and its constituents for resolution of sources and immune responses

Protection of public health from the effects of air particulate matter (PM) requires measurements and methods that assess the PM chemical constituents, physical properties, and their sources. Sampling was conducted at three sites in the Baltimore area: a source-oriented (industrial) area in south Baltimore (FMC site), and two receptor area sites (Clifton Park and Ponca Street). FMC measurements were made for the initial 1-month of the project; Clifton measurements lasted for about 2 months, while measurements at Ponca Street lasted for about 9.5 months. Pollutant samples were collected at intervals ranging from 5 min to 1 h using semi-continuous monitors for PM 2.5 mass, sulfate, nitrate, elemental and organic carbon, particle number size distributions (10–20,000 nm), CO, NO x , O 3, 11 metals, and mass spectra of individual particles, throughout the project. In addition to standard meteorological measurements, a 3D-sonic anemometer and a LIDAR system were operated during selected periods as were a rotating drum impactor with 3- to 6-h resolution and a filter/PUF sampler for 3-h measurements of organic compounds. Standard speciation and FRM mass measurements were also made. This report describes the types of measurements that were made at the various sites of the Baltimore Supersite program as well as presents the summary statistics for some of the PM measurements that have been made. The measurements of aerosol mass, major components, and size distribution data for the three sites are compared. Results show comparable PM concentrations at Ponca Street and Clifton Park. Increased variability was observed at Ponca Street.