Los Angeles Summer Midday Particulate Carbon: Primary and Secondary Aerosol

Aerosol sampling during photochemically active times across the Los Angeles Basin has provided evidence of secondary formation of organic aerosol from gas-phase precursors at midday. Ambient organic carbon/elemental carbon ratios exceeded the estimated ratio of organic carbon/elemental carbon in primary source emissions on most sampling days at all sites. The concentration of secondary organic aerosol was calculated by using ambient data and estimates of the organic carbon/elemental carbon ratio in primary source emissions. Nonparametric sign correlations comparing calculated secondary organic carbon concentrations with tracers of both primary and secondary aerosols supported the method used to quantify secondary organic carbon. Secondary organic aerosol appears to have contributed roughly half of the organic aerosol in Pasadena during midday summer conditions

The magnetic transition, heat capacity, and thermodynamic properties of uranium dioxide from 5 to 350 K

The heat capacity of high purity uranium dioxide has been re-examined over the low-temperature range especially in the vicinity of the λ-type anomaly reported to occur at 28·7 K as a consequence of magnetic ordering. The present study indicates a very sharp transition at 30·44 K with a maximum Cp of 391 cal mol-1 K-1. The heat capacity at constant pressure Cp, the entropy S°, the enthalpy (H° - H°0), and Gibbs energy function (G° - H°)/T are tabulated and at 298.15 K have the following values: 15.20 cal mol-1 K-1, 18.41 cal mol-1 K-1, 2696 cal mol-1 K-1, and -9.37 cal mol-1 K-1. The heat capacity results are compared with those derived from the neutron scattering work and also with the theory of Allen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33729/1/0000242.pd

Elemental carbon concentrations: Estimation of an historical data base

While recent advances in instrumentation permit routine determination of elemental carbon concentrations in atmospheric aerosol samples, historical data on elemental C concentrations are absent. Two methods are available for the estimation of an historical data base for elemental C concentrations: calibration of reflectance-based tape samplers and analysis of archived high volume sampler filters. These methods are described and applied to the problem of reconstructing an historical data base for elemental C concentrations in Los Angeles. Twenty-four year average elemental C concentrations at seven monitoring sites in the Los Angeles area are estimated to range from 6.4 μg m^(−3) at Downtown Los Angeles to 4.5 μg m^(−3) at West Los Angeles. At most monitoring sites studied, elemental C concentrations were lower in recent years than during the late 1950s and early 1960s

Characteristics of atmospheric organic and elemental carbon particle concentrations in Los Angeles

A fine particle air monitoring network was operated in the Los Angeles area during 1982. It was found that carbonaceous aerosols accounted for typically 40% of total fine particle mass loadings at most monitoring sites. The ratio of total carbon (TC) to elemental carbon (EC) in ambient samples and in primary source emissions was examined as an indicator of the extent of secondary organic aerosol formation. It was found that TC to EC ratios at all sites on average are no higher than recent estimates of the TC to EC ratio in primary source emissions. There is little evidence of the sustained summer peak in the ratio of TC to EC that one might expect if greatly enhanced secondary organics production occurs during the photochemical smog season. The TC to EC ratio does rise by the time that air masses reach the prevailing downwind edge of the air basin as would be expected if secondary organics are being formed during air parcel transport, but the extent of that increase is modest. These results suggest that primary particulate carbon emissions were the principal contributor to long-term average fine aerosol carbon concentrations in the Los Angeles area during 1982

Los Angeles Summer Midday Particulate Carbon: Primary and Secondary Aerosol

Aerosol sampling during photochemically active times across the Los Angeles Basin has provided evidence of secondary formation of organic aerosol from gas-phase precursors at midday. Ambient organic carbon/elemental carbon ratios exceeded the estimated ratio of organic carbon/elemental carbon in primary source emissions on most sampling days at all sites. The concentration of secondary organic aerosol was calculated by using ambient data and estimates of the organic carbon/elemental carbon ratio in primary source emissions. Nonparametric sign correlations comparing calculated secondary organic carbon concentrations with tracers of both primary and secondary aerosols supported the method used to quantify secondary organic carbon. Secondary organic aerosol appears to have contributed roughly half of the organic aerosol in Pasadena during midday summer conditions

Computational Prediction and Experimental Verification of New MAP Kinase Docking Sites and Substrates Including Gli Transcription Factors

In order to fully understand protein kinase networks, new methods are needed to identify regulators and substrates of kinases, especially for weakly expressed proteins. Here we have developed a hybrid computational search algorithm that combines machine learning and expert knowledge to identify kinase docking sites, and used this algorithm to search the human genome for novel MAP kinase substrates and regulators focused on the JNK family of MAP kinases. Predictions were tested by peptide array followed by rigorous biochemical verification with in vitro binding and kinase assays on wild-type and mutant proteins. Using this procedure, we found new ‘D-site’ class docking sites in previously known JNK substrates (hnRNP-K, PPM1J/PP2Czeta), as well as new JNK-interacting proteins (MLL4, NEIL1). Finally, we identified new D-site-dependent MAPK substrates, including the hedgehog-regulated transcription factors Gli1 and Gli3, suggesting that a direct connection between MAP kinase and hedgehog signaling may occur at the level of these key regulators. These results demonstrate that a genome-wide search for MAP kinase docking sites can be used to find new docking sites and substrates

Analysis of Germline GLI1 Variation Implicates Hedgehog Signalling in the Regulation of Intestinal Inflammatory Pathways

Charlie Lees and colleagues identify a reduced-function variant of the hedgehog signaling pathway protein GLI1 that associates with inflammatory bowel disease, and investigate its role in a mouse model of colitis