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Analysis of microbial communities by high-throughput pyrosequencing of SSU rRNA gene PCR amplicons has transformed microbial ecology research and led to the observation that many communities contain a diverse assortment of rare taxa-a phenomenon termed the Rare Biosphere. Multiple studies have investigated the effect of pyrosequencing read quality on operational taxonomic unit (OTU) richness for contrived communities, yet there is limited information on the fidelity of community structure estimates obtained through this approach. Given that PCR biases are widely recognized, and further unknown biases may arise from the sequencing process itself, a priori assumptions about the neutrality of the data generation process are at best unvalidated. Furthermore, post-sequencing quality control algorithms have not been explicitly evaluated for the accuracy of recovered representative sequences and its impact on downstream analyses, reducing useful discussion on pyrosequencing reads to their diversity and abundances. Here we report on community structures and sequences recovered for in vitro-simulated communities consisting of twenty 16S rRNA gene clones tiered at known proportions. PCR amplicon libraries of the V3-V4 and V6 hypervariable regions from the in vitro-simulated communities were sequenced using the Roche 454 GS FLX Titanium platform. Commonly used quality control protocols resulted in the formation of OTUs with >1% abundance composed entirely of erroneous sequences, while over-aggressive clustering approaches obfuscated real, expected OTUs. The pyrosequencing process itself did not appear to impose significant biases on overall community structure estimates, although the detection limit for rare taxa may be affected by PCR amplicon size and quality control approach employed. Meanwhile, PCR biases associated with the initial amplicon generation may impose greater distortions in the observed community structure.

We examine the changing relationship between unionization and wage inequality in Canada and the United States. Our study is motivated by profound recent changes in the composition of the unionized workforce. Historically, union jobs were concentrated among low-skilled men in private sector industries. With the steady decline in private sector unionization and rising influence in the public sector, half of unionized workers are now in the public sector. Accompanying these changes was a remarkable rise in the share of women among unionized workers. Currently, approximately half of unionized employees in North America are women. While early studies of unions and inequality focused on males, recent studies find that unions reduce wage inequality among men but not among women. In both countries, we find striking differences between the private and public sectors in the effects of unionization on wage inequality. At present, unions reduce economy-wide wage inequality by less than 10%. However, union impacts on wage inequality are much larger in the public sector. Once we disaggregate by sector, the effects of unions on male and female wage inequality no longer differ. The key differences in union impacts are between the public and private sectors—not between males and females. Dans cet article, nous examinons l’évolution de la relation entre syndicalisation et inégalités salariales au Canada et aux États-Unis. Notre étude se fonde sur les changements récents et profonds de la composition de la main d’œuvre syndiquée. Historiquement, les emplois syndiqués étaient occupés par des hommes peu qualifiés travaillant dans les industries du secteur privé. Avec le déclin régulier de la syndicalisation au sein du secteur privé et son influence croissante au sein du secteur public, la moitié des travailleurs syndiqués fait désormais partie du secteur public. Ces changements ont été accompagnés d’une hausse spectaculaire du pourcentage de femmes parmi les travailleurs syndiqués. Actuellement, près de la moitié des employés syndiqués en Amérique du Nord sont des femmes. Tandis que les premières études sur les syndicats et les inégalités portaient sur les hommes, certaines plus récentes ont montré que les syndicats permettaient de réduire les inégalités salariales entre les hommes, mais pas entre les femmes. Dans les deux pays, nous avons découvert des différences frappantes entre secteur privé et secteur public relativement aux effets de la syndicalisation sur les inégalités salariales. Aujourd’hui, les syndicats permettent de réduire les inégalités salariales de moins de 10 % dans l’ensemble de l’économie. Néanmoins, l’influence des syndicats sur les inégalités salariale est bien plus forte dans le secteur public. En décomposant les données par secteur, les effets des syndicats sur les inégalités salariales entre hommes et femmes sont les mêmes. En matière d’influence des syndicats, les différences fondamentales se situent entre le secteur privé et le secteur public, et non entre les hommes et les femmes.

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. However, it has been recognized in the 21st century that equally significant changes in ionospheric conditions are apparently associated with energy and momentum propagating upward from our own atmosphere. ICON’s goal is to weigh the competing impacts of these two drivers as they influence our space environment. Here we describe the specific science objectives that address this goal, as well as the means by which they will be achieved. The instruments selected, the overall performance requirements of the science payload and the operational requirements are also described. ICON’s development began in 2013 and the mission is on track for launch in 2018. ICON is developed and managed by the Space Sciences Laboratory at the University of California, Berkeley, with key contributions from several partner institutions.

Do fast, competitive markets yield liquidity measurement problems when using the popular Monthly Trade and Quote (MTAQ) database? Yes. MTAQ yields distorted measures of spreads, trade location, and price impact compared with the expensive Daily Trade and Quote (DTAQ) database. These problems are driven by (1) withdrawn quotes, (2) second (versus millisecond) time stamps, and (3) other causes, including canceled quotes. The expensive solution, using DTAQ, is first-best. For financially constrained researchers, the cheap solution—using MTAQ with our new Interpolated Time technique, adjusting for withdrawn quotes, and deleting economically nonsensical states—is second-best. These solutions change research inferences.

Climate change is altering the frequency and severity of drought events. Recent evidence indicates that drought may produce legacy effects on soil microbial communities. However, it is unclear whether precedent drought events lead to ecological memory formation, i.e., the capacity of past events to influence current ecosystem response trajectories. Here, we utilize a long-term field experiment in a mountain grassland in central Austria with an experimental layout comparing 10 years of recurrent drought events to a single drought event and ambient conditions. We show that recurrent droughts increase the dissimilarity of microbial communities compared to control and single drought events, and enhance soil multifunctionality during drought (calculated via measurements of potential enzymatic activities, soil nutrients, microbial biomass stoichiometry and belowground net primary productivity). Our results indicate that soil microbial community composition changes in concert with its functioning, with consequences for soil processes. The formation of ecological memory in soil under recurrent drought may enhance the resilience of ecosystem functioning against future drought events. Legacies of past ecological disturbances are expected but challenging to demonstrate. Here the authors report a 10-year field experiment in a mountain grassland that shows ecological memory of soil microbial community and functioning in response to recurrent drought.