.[1] The impacts of meteorology and air quality on the concentrations and relative distributions of free and combined amino acids (FAA; CAA) are evaluated during a monthlong sampling campaign at a semiurban site in the southeastern U.S. The average FAA concentration in fine aerosols (PM 2.5 ) was 11 AE 6 ng m -3 , while CAA was found to be several times higher at 46 AE 21 ng m -3 . Glycine and alanine were the most abundant amino acids, accounting for 48% of FAA and 58% of the CAA, while distinct differences were observed in compound distributions; glutamic acid, aspartic acid, serine, and threonine accounted for a further 29% of FAA and 30% of the total CAA. An intense rainfall event during the campaign demonstrated the significant impact of meteorological and air quality conditions on FAA-CAA concentrations and distributions. Correlative trends with atmospheric oxidant (ozone) and inorganic nitrogen levels suggest an important role for atmospheric processing. The liquid chromatography-mass spectrometry (quadrupole timeof-flight) technique used in this study allowed for detection of coextracted water-soluble organic compounds and characterization of a larger fraction of the organic nitrogen mass. N-heterocyclic compounds were detected in samples from this campaign, indicating a likely biomass burning source contribution for organic nitrogen.

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Methodology for detection of native (underivatized) amino acids (AA) in atmospheric aerosols has been developed. This article describes the use of LC-MS (Q-TOF) and microwave-assisted gas phase hydrolysis for detection of free and combined amino acids in aerosols collected in a Southeastern U.S. forest environment. Accurate mass detection and the addition of isotopically labeled surrogates prior to sample preparation allows for sensitive quantitation of target AA in a complex aerosol matrix. A total of 16 native AA were detected above the reporting threshold as water-soluble free AA, with an average concentration of 22 ± 9 ng m(-3) (N = 13). Following microwave-assisted gas phase hydrolysis, the total AA concentration in the forest environment increased significantly (70 ± 35 ng m(-3)) and additional compounds (methionine, isoleucine) were detected above the reporting threshold. The ability to quantify AA in aerosol samples without derivatization reduces time-consuming preparation procedures while providing the advancement of selective mass determination for important organic nitrogen (ON) species. Details on sample preparation that eliminates the freeze-drying approach typically practiced for water removal with biological samples, and vapor phase microwave hydrolysis parameters are provided. Method application for determination of atmospheric ON is discussed.

Surgical closure of the anteriorly located tympanic membrane perforation can present a problem. The lack of anterior support for the graft frequently leads to graft failure if an underlay method is used whereas anterior blunting is a complication of onlay techniques in this situation. The experience with the Kerr flap, an underlay graft fashioned to include a tab of fascia which is placed laterally under the annulus and the anterior meatal skin, is presented. This method gave a 97.5 per cent closure rate with no cases of anterior marginal blunting and a mean auditory threshold gain of 8.5 dB (95 per cent confidence limits 5 to 11.9 dB, P<O.O1) was achieved at the frequencies tested. The use of the Kerr flap is recommended when repairing the anteriorly placed tympanic membrane perforation