We present a new compilation of Type Ia supernovae (SNe Ia), a new data set of low-redshift nearby-Hubble-flow SNe, and new analysis procedures to work with these heterogeneous compilations. This ''Union'' compilation of 414 SNe Ia, which reduces to 307 SNe after selection cuts, includes the recent large samples of SNe Ia from the Supernova Legacy Survey and ESSENCE Survey, the older data sets, as well as the recently extended data set of distant supernovae observed with the Hubble Space Telescope (HST ). A single, consistent, and blind analysis procedure is used for all the various SN Ia subsamples, and a new procedure is implemented that consistently weights the heterogeneous data sets and rejects outliers. We present the latest results from this Union compilation and discuss the cosmological constraints from this new compilation and its combination with other cosmological measurements (CMB and BAO). The constraint we obtain from supernovae on the dark energy density is à ¼ 0:713 þ0:027 À0:029 (stat) þ0:036 À0:039 (sys), for a flat, ÃCDM universe. Assuming a constant equation of state parameter, w, the combined constraints from SNe, BAO, and A CMB give w ¼ À0:969 þ0:059 À0:063 (stat) þ0:063 À0:066 (sys). While our results are consistent with a cosmological constant, we obtain only relatively weak constraints on a w that varies with redshift. In particular, the current SN data do not yet significantly constrain w at z > 1. With the addition of our new nearby Hubble-flow SNe Ia, these resulting cosmological constraints are currently the tightest available.

Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei 1 . Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes 2 . Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases 2 . However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere 3 . It is thought that amines may enhance nucleation 4-16 , but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.The primary vapour responsible for atmospheric nucleation is thought to be sulphuric acid (H 2 SO 4 ), derived from the oxidation of sulphur dioxide. However, peak daytime H 2 SO 4 concentrations in the atmospheric boundary layer are about 10 6 to 3 3 10 7 cm 23 (0.04-1.2 parts per trillion by volume (p.p.t.v.)), which results in negligible binary homogeneous nucleation of H 2 SO 4 -H 2 O (ref. 3). Additional species such as ammonia or amines 4,5 are therefore necessary to stabilize the embryonic clusters and decrease evaporation. However, ammonia cannot account for particle formation rates observed in the boundary layer 3 and, despite numerous field and laboratory studies [6][7][8][9][10][11][12][13][14][15][16] , amine ternary nucleation has not yet been observed under atmospheric conditions. Amine emissions are dominated by anthropogenic activities (mainly animal husbandry), but about 30% of emissions are thought to arise from the breakdown of organic matter in the oceans, and 20% from biomass burning and soil 8,17 . Atmospheric measurements of gasphase amines ...

In the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber the sulfuric acid concentration is precisely controlled via OH oxidation of SO 2 , while BioOxOrg is produced via OH oxidation of pinanediol (PD, C 10 H 18 O 2 ). PD is a model compound for monoterpene oxidation products, which have recently been proposed as key mediators of new-particle formation (41) via terpene secondary organic aerosol (42). Pinanediol is added to the chamber by flushing clean air through an evaporator containing PD (Sigma Aldrich, 99%) at 69°C, just above its melting point. OH is generated by ozone photolysis driven by uniform UV illumination from a fiber-optic system. All experiments were performed at 278 (±0.01) K and 38% (±2%) relative humidity.Extreme care was applied to minimize possible contamination to the highest possible extent. After a full cleaning cycle the chamber (including flushing the chamber with water and baking it at 100°C), the contamination by NH 3 and dimethylamine was <2 and <0.1 pptv, respectively. Organic contamination was present, however on a very low level: reported that the total volatile organic compound (VOC) contamination was usually below 1 ppbv (43). On average more than 80% of the total VOCs was coming from only 5 exact masses (tentatively assigned as formaldehyde, acetaldehyde, acetone, formic acid, and acetic acid), which have a rather high vapor pressure and are therefore not important for nucleation and growth of particles. Some additional contamination by dimethylamine was present in these experiments, due to intentional injection of this compound in experiments immediately preceding those described here. This contamination is described in detail below, and it is shown that it is negligible for the determination of the nucleation rates described here. The gas and the particle phases were monitored by an SO 2 monitor (Enhanced Trace Level SO 2 Analyzer, Model 43i-TLE, Thermo Scientific, USA), an O 3 monitor (TEI 49C, Thermo Environmental Instruments, USA), a dew point mirror hygrometer (DewMaster Chilled Mirror Hygrometer, EdgeTech, USA), a chemical ionization mass spectrometer (CIMS) to measure H 2 SO 4 concentration (44), a proton transfer reaction time of flight (PTR-TOF) mass spectrometer to measure organic vapor concentrations such as [PD] (45), an ion chromatograph (IC) to measure ammonia (NH 3 ) and dimethylamine (DMA, C 2 H 7 N) (46), two atmospheric pressure interface time of flight (APi-TOF) mass spectrometers to measure the composition of positively and negatively charged clusters (47), and a wide array of condensation particle counters (CPC), including a particle size magnifier (PSM; Airmodus 09) (48) which was operated in a scanning mode to measure the growth rate of particles smaller than 2.5 nm, two diethylene glycol (DEG) CPCs (49), and a butanol CPC (TSI 3776). J 1.7 data were calculated on the one hand directly from the PSM data and on the other hand from the formation rate (dN 2 /dt) measured by the DEG CPC with a 50% efficiency (D 50 ) at 2 nm (50). In the latter case, the ...

Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. The experiments involved sulfuric acid vapor and different stabilizing species, including ammonia and dimethylamine, as well as oxidation products of pinanediol, a surrogate for organic vapors formed from monoterpenes. A striking resemblance is revealed between the mass spectra from the chamber experiments with oxidized organics and ambient data obtained during new particle formation events at the Hyytiälä boreal forest research station. We observe that large oxidized organic compounds, arising from the oxidation of monoterpenes, cluster directly with single sulfuric acid molecules and then form growing clusters of one to three sulfuric acid molecules plus one to four oxidized organics. Most of these organic compounds retain 10 carbon atoms, and some of them are remarkably highly oxidized (oxygen-to-carbon ratios up to 1.2). The average degree of oxygenation of the organic compounds decreases while the clusters are growing. Our measurements therefore connect oxidized organics directly, and in detail, with the very first steps of new particle formation and their growth between 1 and 2 nm in a controlled environment. Thus, they confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions. Changes to CCN number concentrations from preindustrial times constitute a major uncertainty in estimates of anthropogenic climate forcing (1). New particle formation dominates the total number concentrations of atmospheric aerosol particles; however, newly formed particles must grow from D p ∼ 1.5 to D p ∼ 50-100 nm to be able to act as CCN, and the vast majority are SignificanceThe formation of nanoparticles by condensable vapors in the atmosphere influences radiative forcing and therefore climate. We explored the detailed mechanism of particle formation, in particular the role of oxidized organic molecules that arise from the oxidation of monoterpenes, a class of volatile organic compounds emitted from plants. We mimicked atmospheric conditions in a well-controlled laboratory setup and found that these oxidized organics form initial clusters directly with single sulfuric acid molecules. The clusters then grow by the further addition of both sulfuric acid and organic molecules. Some of the organics are remarkably highly oxidized, a critical feature that enables them to participate in forming initial stable molecular clusters and to facilitate the first steps of atmospheric nanoparticle formation.

Young massive clusters (YMCs) with stellar masses of 10 4 -10 5 M and core stellar densities of 10 4 -10 5 stars per cubic pc are thought to be the "missing link" between open clusters and extreme extragalactic super star clusters and globular clusters. As such, studying the initial conditions of YMCs offers an opportunity to test cluster formation models across the full cluster mass range. G0.253 + 0.016 is an excellent candidate YMC progenitor. We make use of existing multi-wavelength data including recently available far-IR continuum (Herschel/Herschel Infrared Galactic Plane Survey) and mm spectral line (H 2 O Southern Galactic Plane Survey and Millimetre Astronomy Legacy Team 90 GHz Survey) data and present new, deep, multiple-filter, near-IR (Very Large Telescope/NACO) observations to study G0.253 + 0.016. These data show that G0.253 + 0.016 is a high-mass (1.3 × 10 5 M ), low-temperature (T dust ∼ 20 K), high-volume, and column density (n ∼ 8 × 10 4 cm −3 ; N H 2 ∼ 4 × 10 23 cm −2 ) molecular clump which is close to virial equilibrium (M dust ∼ M virial ) so is likely to be gravitationally bound. It is almost devoid of star formation and, thus, has exactly the properties expected for the initial conditions of a clump that may form an Arches-like massive cluster. We compare the properties of G0.253 + 0.016 to typical Galactic cluster-forming molecular clumps and find it is extreme, and possibly unique in the Galaxy. This uniqueness makes detailed studies of G0.253 + 0.016 extremely important for testing massive cluster formation models.

The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

The genomes of four Lactobacillus reuteri strains isolated from human breast milk and the gastrointestinal tract have been recently sequenced as part of the Human Microbiome Project. Preliminary genome comparisons suggested that these strains belong to two different clades, previously shown to differ with respect to antimicrobial production, biofilm formation, and immunomodulation. To explain possible mechanisms of survival in the host and probiosis, we completed a detailed genomic comparison of two breast milk–derived isolates representative of each group: an established probiotic strain (L. reuteri ATCC 55730) and a strain with promising probiotic features (L. reuteri ATCC PTA 6475). Transcriptomes of L. reuteri strains in different growth phases were monitored using strain-specific microarrays, and compared using a pan-metabolic model representing all known metabolic reactions present in these strains. Both strains contained candidate genes involved in the survival and persistence in the gut such as mucus-binding proteins and enzymes scavenging reactive oxygen species. A large operon predicted to encode the synthesis of an exopolysaccharide was identified in strain 55730. Both strains were predicted to produce health-promoting factors, including antimicrobial agents and vitamins (folate, vitamin B12). Additionally, a complete pathway for thiamine biosynthesis was predicted in strain 55730 for the first time in this species. Candidate genes responsible for immunomodulatory properties of each strain were identified by transcriptomic comparisons. The production of bioactive metabolites by human-derived probiotics may be predicted using metabolic modeling and transcriptomics. Such strategies may facilitate selection and optimization of probiotics for health promotion, disease prevention and amelioration.

Abstract. The formation of particles from precursor vapors is an important source of atmospheric aerosol. Research at the Cosmics Leaving OUtdoor Droplets (CLOUD) facility at CERN tries to elucidate which vapors are responsible for this new-particle formation, and how in detail it proceeds. Initial measurement campaigns at the CLOUD stainless-steel aerosol chamber focused on investigating particle formation from ammonia (NH 3 ) and sulfuric acid (H 2 SO 4 ). Experiments were conducted in the presence of water, ozone and sulfur dioxide. Contaminant trace gases were suppressed at the technological limit. For this study, we mapped out the compositions of small NH 3 -H 2 SO 4 clusters over a wide range of atmospherically relevant environmental conditions. We covered [NH 3 ] in the range from < 2 to 1400 pptv, [H 2 SO 4 ] from 3.3 × 10 6 to 1.4 × 10 9 cm −3 (0.1 to 56 pptv), and a temperature range from −25 to +20 • C. Negatively and positively charged clusters were directly measured by an atmospheric pressure interface time-of-flight (APi-TOF)Published by Copernicus Publications on behalf of the European Geosciences Union. S. Schobesberger et al.: On the composition of ammonia-sulfuric-acid clustersmass spectrometer, as they initially formed from gas-phase NH 3 and H 2 SO 4 , and then grew to larger clusters containing more than 50 molecules of NH 3 and H 2 SO 4 , corresponding to mobility-equivalent diameters greater than 2 nm. Water molecules evaporate from these clusters during sampling and are not observed. We found that the composition of the NH 3 -H 2 SO 4 clusters is primarily determined by the ratio of gas-phase concentrations [NH 3 ] is mostly larger than 10. We compared our results from CLOUD with APi-TOF measurements of NH 3 -H 2 SO 4 anion clusters during new-particle formation in the Finnish boreal forest. However, the exact role of NH 3 -H 2 SO 4 clusters in boundary layer particle formation remains to be resolved.