The chemical complexity of atmospheric organic aerosol (OA) has caused substantial uncertainties in understanding its origins and environmental impacts. Here, we provide constraints on OA origins through compositional characterization with molecular-level details. Our results suggest that secondary OA (SOA) from monoterpene oxidation accounts for approximately half of summertime fine OA in Centreville, AL, a forested area in the southeastern United States influenced by anthropogenic pollution. We find that different chemical processes involving nitrogen oxides, during days and nights, play a central role in determining the mass of monoterpene SOA produced. These findings elucidate the strong anthropogenic-biogenic interaction affecting ambient aerosol in the southeastern United States and point out the importance of reducing anthropogenic emissions, especially under a changing climate, where biogenic emissions will likely keep increasing.

Presented is a new approach for laminar-flow water condensation that produces saturations above 1.5 while maintaining temperatures of less than 30°C in the majority of the flow and providing an exiting dew point below 15°C. With the original laminar flow water condensation method, the particle activation and growth occurs in a region with warm, wetted walls throughout, which has the side-effect of heating the flow. The “moderated” approach presented here replaces this warm region with a two sections – a short, warm, wet-walled “initiator”, followed by a cool-walled “moderator”. The initiator provides the water vapor that creates the supersaturation, while the moderator provides the time for particle growth. The combined length of the initiator and moderator sections is the same as that of the original, warm-walled growth section. Model results show that this new approach reduces the added heat and water vapor while achieving the same peak supersaturation and similar droplet growth. Experimental measurements confirm the trends predicted by the modeling.

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We have measured the amount of nonreciprocal circular birefringence of 50 to 800 A YBa2Cu3C>7 films in transmission with a 15-j/m beam diameter. A novel instrument with a sensitivity of 2 //rad for nonreciprocal phase shifts was developed by modifying a fiber-optic gyroscope. It is insensitive to reciprocal phase shifts. We observed no nonreciprocal phase shifts in any samples.PACS numbers: 74.65.+nOne of the most exciting proposals for the theory of the cuprate high-temperature superconductors (HTSC) is the so-called "anyon superconductivity." 1 " 3 This theory is based on the concept that in two spatial dimensions, one can obtain not only quantum ideal Bose and Fermi gases, but also quantum ideal gases of new types of particles that interpolate between those two extremes, and hence obey fractional statistics. Those particles are known generically as anyons. It was first pointed out by Laughlin and co-workers 4~6 that these gases form superfluids, and become superconductors if the anyons are electrically charged. A striking property of such a superconductor is that its ground state exhibits violation of parity (P) and time-reversal (T) symmetries. 3 Similar to a magnetic material, an anyon superconductor will exhibit a spontaneous Hall effect and magneto-optical effects. If the cuprates are indeed anyon superconductors then in a transmission experiment through a thin HTSC film, one expects to observe a nonreciprocal rotation of polarization equivalent to the Faraday effect. In reflection, one expects to see an effect resembling the polar Kerr effect. Both effects are nonreciprocal as a consequence of the breakdown of time-reversal symmetry. 1 ' 3In a recent experiment, Lyons et al. 1 reported such nonreciprocal optical effects in reflection from various HTSC. They constructed an optical system to measure the circular dichroism which is related to the reflectivity for right and left circularly polarized light by R± ^Re-*.Since one expects the anyon material to break into domains, the averaged nonreciprocal optical effect will be zero. The distribution width a of the values of is related to the circular dichroism of a single domain 0o by o~-od/s, where d is the domain size and s is the beam size. Lyon et al. reported a nonzero value for a that increased from the noise level ( -25 /irad) at 300 K to -250 //rad as the temperature was lowered.In this paper we present data taken on high-quality YBa2Cu3<>7 (YBCO) films which indicate no measurable nonreciprocal effect. Using a modified fiber gyroscope we have been able to measure nonreciprocal phase shifts with high sensitivity while simultaneously rejecting all reciprocal effects. The phase shift we measure is AQ> sss 27rl(n + -n-)/X, where n+ and n-are the indices of refraction for circularly polarized light of the same handedness propagating in opposite directions through the sample. Equivalently /*+ and n-could refer to the two circular components of a single beam of linearly polarized light, in which case AO is related to the Faraday rotation angle 0 by...