Open Access

We synthesised observations of total particle number (CN) concentration from 36 sites around the world. We found that annual mean CN concentrations are typically 300–2000 cm -3 in the marine boundary layer and free troposphere (FT) and 1000–10 000 cm -3 in the continental boundary layer (BL). Many sites exhibit pronounced seasonality with summer time concentrations a factor of 2–10 greater than wintertime concentrations. We used these CN observations to evaluate primary and secondary sources of particle number in a global aerosol microphysics model. We found that emissions of primary particles can reasonably reproduce the spatial pattern of observed CN concentration (R2=0.46) but fail to explain the observed seasonal cycle (R2=0.1). The modeled CN concentration in the FT was biased low (normalised mean bias, NMB=& -88%) unless a secondary source of particles was included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB= -25%). Simulated CN concentrations in the continental BL were also biased low (NMB= -74%) unless the number emission of anthropogenic primary particles was increased or a mechanism that results in particle formation in the BL was included. We ran a number of simulations where we included an empirical BL nucleation mechanism either using the activation-type mechanism (nucleation rate, J, proportional to gas-phase sulfuric acid concentration to the power one) or kinetic-type mechanism (J proportional to sulfuric acid to the power two) with a range of nucleation coefficients. We found that the seasonal CN cycle observed at continental BL sites was better simulated by BL particle formation (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). The nucleation constants that resulted in best overall match between model and observed CN concentrations were consistent with values derived in previous studies from detailed case studies at individual sites. In our model, kinetic and activation-type nucleation parameterizations gave similar agreement with observed monthly mean CN concentrations.

The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host–symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human–bed bug and symbiont–bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as a human ectoparasite.

BLACK KIRBY is a collaborative "entity" that is the creative doppelganger of artists / designers John Jennings and Stacey "Blackstar" Robinson. The manifestation of this avatar is an exhibition and catalog1 of primarily visual artworks-on-paper that celebrate the groundbreaking work of legendary comics creator Jack Kirby regarding his contributions to the pop culture landscape and his development of some of the conventions of the comics medium. BLACK KIRBY also functions as a highly syncretic mythopoetic framework by appropriating Jack Kirby’s bold forms and revolutionary ideas combined with themes centered around AfroFuturism social justice, Black history, media criticism, science fiction, magical realism, and the utilization of Hip Hop culture as a methodology for creating visual expression. This collection of work also focuses on the digital medium and how its inherent affordances offer much more flexibility in the expression of visual communication and what that means in its production and consumption in the public sphere. In a sense, BLACK KIRBY appropriates the gallery as a conceptual "crossroads" to examine identity as a socialized concept and to show the commonalities between Black comics creators and Jewish comics creators and how they both utilize the medium of comics as space of resistance. The duo attempts to re-mediate "Blackness" and other identity contexts as "sublime technologies" that produce experiences that sometime limit human progress and possibility. This paper / presentation will examine some of the themes of this inaugural exhibition of this new artistic team and share the processes involved with the ideation, execution, and installation of the exhibition.