Cloud chemistry at the Puy de Dôme: variability and relationships with environmental factors

The chemical composition of cloud water was investigated during the winter-spring months of 2001 and 2002 at the Puy de D&#244;me station (1465 m above sea level, 45&deg;46&prime;22&prime;&prime; N, 2&deg;57&prime;43&prime;&prime; E) in an effort to characterize clouds in the continental free troposphere. Cloud droplets were sampled with single-stage cloud collectors (cut-off diameter approximately 7 &micro;m) and analyzed for inorganic and organic ions, as well as total dissolved organic carbon. Results show a very large variability in chemical composition and total solute concentration of cloud droplets, ranging from a few mg l^-1 to more than 150 mg l^-1. Samplings can be classified in three different categories with respect to their total ionic content and relative chemical composition: background continental (BG, total solute content lower than 18 mg l^-1), anthropogenic continental (ANT, total solute content from 18 to 50 mg l^-1), and special events (SpE, total solute content higher than 50 mg l^-1). The relative chemical composition shows an increase in anthropogenic-derived species (NO₃^-, SO₄^2- and NH₄⁺) from BG to SpE, and a decrease in dissolved organic compounds (ionic and non-ionic) that are associated with the anthropogenic character of air masses. <P style='line-height: 20px;'> We observed a high contribution of solute in cloud water derived from the dissolution of gas phase species in all cloud events. This was evident from large solute fractions of nitrate, ammonium and mono-carboxylic acids in cloud water, relative to their abundance in the aerosol phase. The comparison between droplet and aerosol composition clearly shows the limited ability of organic aerosols to act as cloud condensation nuclei. The strong contribution of gas-phase species limits the establishment of direct relationships between cloud water solute concentration and LWC that are expected from nucleation scavenging

Nearby Optical Galaxies: Selection of the Sample and Identification of Groups

In this paper we describe the Nearby Optical Galaxy (NOG) sample, which is a complete, distance-limited ($cz\leq$6000 km/s) and magnitude-limited (B$\leq$14) sample of $\sim$7000 optical galaxies. The sample covers 2/3 (8.27 sr) of the sky ($|b|>20^{\circ}$) and appears to have a good completeness in redshift (98%). We select the sample on the basis of homogenized corrected total blue magnitudes in order to minimize systematic effects in galaxy sampling. We identify the groups in this sample by means of both the hierarchical and the percolation {\it friends of friends} methods. The resulting catalogs of loose groups appear to be similar and are among the largest catalogs of groups presently available. Most of the NOG galaxies ($\sim$60%) are found to be members of galaxy pairs ($\sim$580 pairs for a total of $\sim$15% of objects) or groups with at least three members ($\sim$500 groups for a total of $\sim$45% of objects). About 40% of galaxies are left ungrouped (field galaxies). We illustrate the main features of the NOG galaxy distribution. Compared to previous optical and IRAS galaxy samples, the NOG provides a denser sampling of the galaxy distribution in the nearby universe. Given its large sky coverage, the identification of groups, and its high-density sampling, the NOG is suited for the analysis of the galaxy density field of the nearby universe, especially on small scales

Geometrical tests of cosmological models. II. Calibration of rotational widths and disc scaling relations

This series of papers is dedicated to a new technique to select galaxies that can act as standard rods and standard candles in order to perform geometrical tests on large samples of high redshift galaxies to constrain different cosmological parameters. The goals of this paper are (1) to compare different rotation indicators in order to understand the relation between rotation velocities extracted from observations of the Halpha line and the [OII]3727 line, and (2) determine the scaling relations between physical size, surface brightness and magnitude of galaxies and their rotation velocity using the SFI++, a large catalog of nearby galaxies observed at I-band. A good correlation is observed between the rotation curve-derived velocities of the Halpha and [OII] observations, as well as between those calculated from velocity histograms, justifying the direct comparison of velocities measured from Halpha rotation curves in nearby galaxies and from [OII] line widths at higher redshifts. To provide calibration for the geometrical tests, we give expressions for the different scaling relations between properties of galaxies (size, surface brightness, magnitude) and their rotation speeds. Apart from the Tully-Fisher relation, we derive the size-rotation velocity and surface brightness-rotation velocity relations with unprecedentedly small scatters. We show how the best size-rotation velocity relation is derived when size is estimated not from disc scale lengths but from the isophotal diameter r23.5, once these have been corrected for inclination and extinction effects.Comment: 14 pages and 10 figures. A&A submitte

The double RGB in M 2: C, N, Sr and Ba abundances

The globular cluster M 2 has a photometrically detected double red giant branch (RGB) sequence. We investigate here the chemical differences between the two RGBs in order to gain insight in the star formation history of this cluster. The low-resolution spectra, covering the blue spectral range, were collected with the MODS spectrograph on the LBT, and analyzed via spectrum synthesis technique. The high quality of the spectra allows us to measure C, N, Ba, and Sr abundances relative to iron for 15 RGB stars distributed along the two sequences. We add to the MODS sample C and N measurements for 35 additional stars belonging to the blue RGB sequence, presented in Lardo et al. (2012). We find a clear separation between the two groups of stars in s-process elements as well as C and N content. Both groups display a C-N anti-correlation and the red RGB stars are on average richer in C and N with respect to the blue RGB. Our results reinforce the suggestion that M2 belongs to the family of globular clusters with complex star formation history, together with Omega Cen, NGC 1851, and M 22.Comment: 11 pages, 8 figures. Accepted for publication in MNRA

Numerical assessment of integrated thermal management systems in electrified powertrains

Temperatures in internal combustion engines (ICE) impact fuel consumption and pollutant emissions, especially under transient operating conditions. In hybrid powertrains, where the reciprocating internal combustion engine has intermittent operating conditions, a optimum control of these temperatures is critical. In this work, a detailed methodology for studying integrated thermal management systems for hybrid propulsion system was presented. Both experimental measurements and 0D/1D models were implemented and validated for the different components of the hybrid vehicle powertrain. The novelty of this work consists in the extensive experimental measurements involved for the development of the different models, specially the ICE, in order to study the integration of the different thermal flows of a hybrid powertrain. Furthermore, the simulation methodology used in this work integrates different modelling tools and takes advantage of their strengths when compared to using a single modelling tool. Two different thermal management systems have been evaluated under different Real Driving Emission (RDE) cycles at two different temperatures (at 20 °C and -20 °C). Results have shown that during the ICE warming up, the integrated thermal management system improved energy consumption by 1.74% and 3% for warm and cold conditions, respectively. This was because, the integrated TMS allows to avoid the temperature drop of the ICE when the propulsive system is in pure electric mode. © 2022 Elsevier Lt