.[1] Nitric acid (HNO 3 ) is the dominant end product of NO x (= NO + NO 2 ) oxidation in the troposphere, and its dry deposition is considered to be a major removal pathway for the atmospheric reactive nitrogen. Here we present both field and laboratory results to demonstrate that HNO 3 deposited on ground and vegetation surfaces may undergo effective photolysis to form HONO and NO x , 1 -2 orders of magnitude faster than in the gas phase and aqueous phase. With this enhanced rate, HNO 3 photolysis on surfaces may significantly impact the chemistry of the overlying atmospheric boundary layer in remote low-NO x regions via the emission of HONO as a radical precursor and the recycling of HNO 3 deposited on ground surfaces back to NO x .

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[1] Significant production of HONO was observed on glass sample manifold wall surface when exposed to sunlight during the PROPHET 2000 summer measurement intensive. It is hypothesized that the artifact HONO was produced by photolysis of adsorbed nitric acid/nitrate on the manifold wall surfaces followed by the subsequent reaction of produced NO 2 and adsorbed H 2 O on surface. This observation suggests against the use of an unshielded glass manifold as a sampling inlet for the measurement of atmospheric HONO. It may also have some implications in interpreting field NO x data measured using similar glass inlet manifolds, especially from the clean remote environments where NO x is low and HNO 3 is a major fraction of NO y .

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[1] Hydroxyl (OH), hydroperoxy (HO 2 ) radicals, collectively known as HO x , and OH reactivity, were measured during the PMTACS-NY (PM2.5 Technology Assessment and Characteristics Study-New York) summer 2002 intensive at Whiteface Mountain, Wilmington, New York. The measurement results of OH and HO 2 for 4 weeks are presented. Diurnal cycles show that the average noontime maximum mixing ratios were about 0.11 pptv (2.6 Â 10 6 cm À3 ) for OH and 20 pptv for HO 2 . Measured HO 2 to OH ratios were typically between 40 and 400, which are greater than those obtained in polluted and semipolluted rural environments. Low but significant mixing ratios of OH and HO 2 persisted into early evening and were frequently observed during nighttime, consistent with previous studies in different environments. Steady state OH and HO 2 were calculated with a zero-dimensional chemical model using a complete Regional Atmospheric Chemical Mechanism (RACM) and a parameterized RACM which was constrained to the measured OH reactivity. Good agreement was obtained between the complete RACM and the parameterized RACM models. On average, the complete RACM model reproduced the observed OH with a median measured-to-modeled OH ratio of 0.82 and daytime HO 2 with a median measured-to-modeled HO 2 ratio of 1.21. The reasonably good agreement in this study is inconsistent with the significant underestimation of OH in the Program for Research on Oxidants: Photochemistry, Emissions, and Transport in 1998 (PROPHET98) study at a similar forested site. HO x budget analysis indicates that OH was primarily from the photolysis of HONO and O 3 during the day and from O 3 + alkenes reactions at night. The main HO x loss was the self reaction of HO 2 . The good agreement between the measured and calculated OH reactivity in this environment contrasts with findings in the PROPHET2000 study, in which significant OH reactivity was missing and the missing OH reactivity was temperature-dependent.

This study describes a novel phage display method based on an iterative subtraction strategy to identify candidate vaccine antigens of Brugia malayi. A cDNA library of the infective larval stage of B. malayi expressed on the surface of T7 phage was sequentially screened with sera samples from human subjects showing different manifestations of the disease. Antigens that selectively and specifically bind to immune sera were then enriched using a multi-step panning procedure. This strategy identified five antigens, four of which were previously reported (ALT-2, TPX-2, VAH and COX-2) and the other one was a novel cuticular collagen (Col-4). Sera from immune individuals specifically recognized all the five antigens. However, ALT-2 appeared to be the most predominantly recognized antigen by the immune sera. Therefore, it was decided to evaluate the vaccine potential of recombinant ALT-2 (rALT-2) in a mouse and jird model. The results presented show that immunization with rALT-2 conferred over 73% protection against a challenge infection in the jird model and over 64% protection in the mouse model. The present study suggests that phage display-based cDNA screening may be a powerful tool to identify candidate vaccine antigens of infectious agents.

[1] Mechanisms regarding formation and loss of nitrous acid (HONO) in the rural atmosphere are not well understood. Results of field observations and laboratory experiments implicate the importance of dew in controlling the surface-atmosphere exchange of HONO. Dew water, abundantly available on ground surfaces, especially on canopy surfaces in forested regions, during summer and autumn nights, serves as a sink and a temporary reservoir of atmospheric HONO and as a source in the morning when the dew droplets evaporate.