Synthetic aperture magnetometry and excess kurtosis mapping of Magnetoencephalography (MEG) is predictive of epilepsy surgical outcome in a large pediatric cohort.

OBJECTIVE: Resective surgery is the most effective treatment option for patients with refractory epilepsy; however identification of patients who will benefit from epilepsy surgery remains challenging. Synthetic aperture magnetometry and excess kurtosis mapping (SAM(g2)) of magnetoencephalography (MEG) is a non-invasive tool that warrants further examination in the pediatric epilepsy population. Here, we examined the utility of MEG with SAM(g2) to determine if MEG epileptiform foci correlates with surgical outcome and to develop a predictive model incorporating MEG information to best assess likelihood of seizure improvement/freedom from resective surgery. METHODS: 564 subjects who had MEG at the Children's Hospital of Philadelphia between 2010-2015 were screened. Clinical epilepsy history and prior electrographic records were extracted and reviewed and correlated with MEG findings. MEG assessments were made by both a neurologist and neuroradiologist. Predictive models were developed to assess the utility of MEG in determining Engel class at one year and five years after resective epilepsy surgery. RESULTS: The number of MEG spike foci was highly associated with Engel class outcome at both one year and five years; however, using MEG data in isolation was not significantly predictive of 5 year surgical outcome. When combined with clinical factors; scalp EEG (single ictal onset zone), MRI (lesional or not), age and sex in a logistic regression model MEG foci was significant for Engel class outcome at both 1 year (p = 0.03) and 5 years (0.02). The percent correctly classified for Engel class at one year was 78.43% and the positive predictive value was 71.43. SIGNIFICANCE: MEG using SAM(g2) analysis in an important non-invasive tool in the identification of those patients who will benefit most from surgery. Integrating MEG data analysis into pre-surgical evaluation can help to predict epilepsy outcome after resective surgery in the pediatric population if utilized with skilled interpretation.

Modeling aerosol formation from alpha-pinene + NOx in the presence of natural sunlight using gas-phase kinetics and gas-particle partitioning theory.

A kinetic mechanism was used to link and model the gas-phase reactions and aerosol accumulation resulting from alpha-pinene reactions in the presence of sunlight, ozone (O3), and oxides of nitrogen (NOx). Reaction products and aerosol formation from the kinetic model were compared to outdoor smog chamber experiments conducted under natural sunlight in the presence of NOx and in the dark in the presence of O3. The gas-particle partitioning of semivolatile organics generated in the gas phase was treated as an equilibrium process between particle absorption and desorption. Models vs experimental aerosol yields illustrate that reasonable predictions of secondary aerosol formation are possible from both dark ozone and light NOx/alpha-pinene systems over a variety of different outdoor conditions. On average, measured gas- and particle-phase products accounted for approximately 54-72% of the reacted alpha-pinene carbon. Model predictions suggest that organic nitrates account for another approximately 25% of the reacted carbon, and most of this is in the gas phase. Measured particle-phase products accounted for 60-100% of the particle filter mass, with pinic acid and pinonic acid being the primary aerosol-phase products. In the gas phase, pinonaldehyde and pinonic acid are major products. Model simulations of these and other products show generally reasonable fits to the experimental data from the perspective of timing and concentrations. These results are very encouraging for a compound such as pinonaldehyde, since it is being formed from OH attack on alpha-pinene and is also simultaneously photolyzed and reacted with OH.

Characterization of secondary aerosol from the photooxidation of toluene in the presence of NOx and 1-propene.

Secondary organic aerosol (SOA) from the photooxidation of toluene in a hydrocarbon-NOx mixture was generated in a 190 m3 outdoor Teflon chamber. The photooxidation reaction of toluene in the gas phase leads to substituted aromatics (TOL-AR), nonaromatic ring retaining (TOL-R), and ring opening products (TOL-RO). In this work, the following ring opening oxycarboxylic acids were newly identified: glyoxylic acid, methylglyoxylic acid, 4-oxo-2-butenoic acid, oxo-C5-alkenoic acids, dioxopentenoic acids, oxo-C7-alkadienoic acids, dioxo-C6-alkenoic acids, hydroxydioxo-C7-alkenoic acids, and hydroxytrioxo-C6-alkanoic acids. The newly characterized TOL-R and TOL-RO products included methylcyclohexenetriones, hydroxymethylcyclohexentriones, 2-hydroxy-3-penten-1,5-dial, hydroxyoxo-C6-alkenals, hydroxy-C5-triones, hydroxydioxo-C7-alkenals, and hydroxy-C6-tetranones. Products in both the gas and aerosol phases were derivatized with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) for carbonyls and pentafluorobenzyl bromide (PFBBr) for carboxylic acid and phenol groups and analyzed using a gas chromatograph/mass spectrometry (GC/MS) in an electron impact mode (EI) and a gas chromatograph/ion trap mass spectrometry (GC/ITMS) in both chemical impact and EI modes. To confirm different isomers, the PFBHA-derivatives of products were rederivatized by silylation using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). The Fourier transform infrared spectroscope (FTIR) was used to obtain additional functional group information for SOA products impacted on a zinc selenide FTIR disk. The major SOA products under the high NOx conditions of the above experiment included methylnitrophenols, methyldinitrophenols, methylbenzoquinones, methylcyclohexenetriones, 4-oxo-2-butenoic acid, oxo-C5-alkenoic acids, hydroxy-C3-diones, hydroxyoxo-C5-alkenals, hydroxyoxo-C6-alkenals, and hydroxydioxo-C7-alkenals. Of the major SOA products, the experimental partitioning coefficients (iKp) of aldehyde products were much higher and deviated more from predicted iKp values. This is an extremely important result, because it shows that aldehyde products can further react through heterogeneous processes, which may be a very significant SOA generation mechanism from the oxidation of aromatics in the atmosphere.

Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst.

Particle growth by the heterogeneous reaction of aldehydes was evaluated in 0.5 m3 Teflon film bags under darkness in the presence of background seed aerosols. The aldehydes used were as follows: glyoxal, butanal, hexanal, octanal, and decanal. To study acid catalyst effects on aldehyde heterogeneous reactions, one of the Teflon bags was initially filled with seed aerosols composed of ammonium sulfate-aerosol acidified with sulfuric acid. These results were compared to particle growth reactions that contained only ammonium sulfate as a background seed aerosol. The gas-phase aldehydes were then added to the Teflon bags. In selected experiments, 1-decanol was also added to the Teflon bags with aldehydes to clarify particle growth via a heterogeneous hemiacetal/acetal formation in the presence/absence of an acid catalyst. The particle size distribution and growth were measured using a scanning mobility particle sizer (TSI-SMPS), and the results were applied to predicting aerosol growth and size distribution changes by condensation and heterogeneous reactions. Aerosols created from the heterogeneous reactions of aldehydes were collected directly on an ungreased zinc selenide (ZnSe) FTIR disk (25 mm in diameter) by impaction. The ZnSe disks were directly analyzed for product functional groups inthe aerosol phase using a Fourier transform infrared (FTIR) spectrometer with a deuterated triglycine sulfate (DTGS) detector. Aerosol growth by heterogeneous aldehyde reactions proceeds via a hydration, polymerization process, and hemiacetal/acetal formation from the reaction of aldehydes with alcohols. These aldehyde heterogeneous reactions were accelerated in the presence of an acid catalyst, H2SO4, and led to higher aerosol yields than when H2SO4 was not present in the seed aerosol. The FTIR spectra obtained from the growing aerosol, also illustrated aldehyde group transformation in the particle phase as a function of the heterogeneous reaction. It was concluded that aldehydes, which can be produced by atmospheric photochemical reactions, can significantly contribute on secondary aerosol formation through heterogeneous reactions in the presence of an acid catalyst.

Experimental considerations for the study of contaminant dispersion near the body.

Experimental considerations are discussed for conducting controlled studies of the dispersion of contaminants released near a mannequin. A 183 cm x 183 cm cross section wind tunnel was modified to study the low velocity range of 10 to 100 cm/sec (20 to 200 ft/min). Installation of a removable biplanar slat grid produced turbulent intensities up to 15%. The results of validation testing for selected experimental components are reported, including (1) a minimum, unambiguous velocity measurement capability of 2.0 cm/sec (4.0 ft/min); (2) a minimum required integration interval for velocity and contaminant measurements of at least 3 min; (3) a determination that smoke streamline plume settling may be a problem at velocities < or = approximately 15 cm/sec (approximately 30 ft/min); (4) a determination that a 14% tunnel blockage by the mannequin was not of consequence for frontal measurements; and (5) a finding that the biplanar grid produced turbulence spectra representative of low velocity indoor settings. A deceleration zone was noted that extended 50 cm upstream from the mannequin, with freestream velocities reduced 50 to 60%, 2.5 cm from the chest. A contaminant tracer released as a point source 60 cm upstream typically dispersed laterally only 10 to 15 cm and diluted by a factor of 10(4) before reaching the chest.

Evaluation of the mutagenicity of combustion particles from several common biomass fuels in the Ames/Salmonella microsome test.

We have evaluated the mutagenicity of dichloromethane extracts of combustion particles from several biomass fuels that are commonly used in developing countries in Salmonella strains TA98 +/- S9 and TA100 +/- S9. Combustion-particle extracts from dried cow dung and crop residue exhibited mutagenic potencies similar to wood-smoke extracts (0.0-1.0 rev./microgram extract). However, extracts from coconut-shell-smoke particles showed relatively potent direct-acting mutagenicity (1.6 rev./micrograms, TA98-S9). Results from testing this sample in nitroreductase- and acetylase- deficient strains TA98NR and TA98 (1,8-DNP-6) revealed no contribution from nitroarenes.

Analysis of cyclopentafused isomers of benz(a)anthracene in wood smoke.

A previously-unidentified peak occurring in chromatograms of the polycyclic aromatic hydrocarbon fraction from wood smoke particulate extracts analysed by capillary gas chromatography on a DB-5 column was found to correspond in retention index and molecular mass either to benzo(a)fluoranthene or to benzo(1)aceanthrylene, one of a series of four novel and highly mutagenic cyclopentafused isomers of benz(a)anthracene. Detailed subfractionation, and re-analysis on a liquid crystal capillary column, indicated that the identity of this peak was most likely to be benzo(a)fluoranthene, a compound not previously reported in woodsmoke.

Photochemical smog systems: effect of dilution on ozone formation.

Dilution of a photochemical system containing hydrocarbons and oxides of nitrogen can lead to higher ozone concentrations than are observed in a static system. This effect was observed in an outdoor smog chamber with a hydrocarbon mix simulating urban systems.