Experimental investigation of ion–ion recombination under atmospheric conditions

We present the results of laboratory measurements of the ion–ion recombination coefficient at different temperatures, relative humidities and concentrations of ozone and sulfur dioxide. The experiments were carried out using the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber at CERN, the walls of which are made of conductive material, making it possible to measure small ions. We produced ions in the chamber using a 3.5 GeV c^(−1) beam of positively charged pions (π^+) generated by the CERN Proton Synchrotron (PS). When the PS was switched off, galactic cosmic rays were the only ionization source in the chamber. The range of the ion production rate varied from 2 to 100 cm^(−3) s^(−1), covering the typical range of ionization throughout the troposphere. The temperature ranged from −55 to 20 °C, the relative humidity (RH) from 0 to 70 %, the SO_2 concentration from 0 to 40 ppb, and the ozone concentration from 200 to 700 ppb. The best agreement of the retrieved ion–ion recombination coefficient with the commonly used literature value of 1.6 × 10^(−6) cm^3 s^(−1) was found at a temperature of 5 °C and a RH of 40 % (1.5 ± 0.6) × 10^(−6) cm^3 s^(−1). At 20 °C and 40 % RH, the retrieved ion–ion recombination coefficient was instead (2.3 ± 0.7) × 10^(−6) cm^3 s^(−1). We observed no dependency of the ion–ion recombination coefficient on ozone concentration and a weak variation with sulfur dioxide concentration. However, we observed a more than fourfold increase in the ion–ion recombination coefficient with decreasing temperature. We compared our results with three different models and found an overall agreement for temperatures above 0 °C, but a disagreement at lower temperatures. We observed a strong increase in the recombination coefficient for decreasing relative humidities, which has not been reported previously

Evolution of particle composition in CLOUD nucleation experiments

Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed from these compounds in the CLOUD (Cosmics Leaving Outdoor Droplets) chamber experiments at CERN (Centre européen pour la recherche nucléaire). The investigation was carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during their growth from sizes of a few nanometers to tens of nanometers was derived from measured hygroscopicity assuming the Zdanovskii–Stokes–Robinson relationship, and compared to values gained from the spectrometers. The ZSR-relationship was also applied to obtain the measured ethanol affinities during the particle growth, which were used to derive the volume fractions of sulphuric acid and the other inorganics (e.g. ammonium salts). In the presence of sulphuric acid and ammonia, particles with a mobility diameter of 150 nm were chemically neutralised to ammonium sulphate. In the presence of oxidation products of pinanediol, the organic volume fraction of freshly nucleated particles increased from 0.4 to ~0.9, with an increase in diameter from 2 to 63 nm. Conversely, the sulphuric acid volume fraction decreased from 0.6 to 0.1 when the particle diameter increased from 2 to 50 nm. The results provide information on the composition of nucleated aerosol particles during their growth in the presence of various combinations of sulphuric acid, ammonia, dimethylamine and organic oxidation products

Ion Mobility-Mass Spectrometry with a Radial Opposed Migration Ion and Aerosol Classifier (ROMIAC)

The first application of a novel differential mobility analyzer, the radial opposed migration ion and aerosol classifier (ROMIAC), is demonstrated. The ROMIAC uses antiparallel forces from an electric field and a cross-flow gas to both scan ion mobilities and continuously transmit target mobility ions with 100% duty cycle. In the ROMIAC, diffusive losses are minimized, and resolution of ions, with collisional cross-sections of 200–2000 Å^2, is achieved near the nondispersive resolution of ~20. Higher resolution is theoretically possible with greater cross-flow rates. The ROMIAC was coupled to a linear trap quadrupole mass spectrometer and used to classify electrosprayed C2–C12 tetra-alkyl ammonium ions, bradykinin, angiotensin I, angiotensin II, bovine ubiquitin, and two pairs of model peptide isomers. Instrument and mobility calibrations of the ROMIAC show that it exhibits linear responses to changes in electrode potential, making the ROMIAC suitable for mobility and cross-section measurements. The high resolution of the ROMIAC facilitates separation of isobaric isomeric peptides. Monitoring distinct dissociation pathways associated with peptide isomers fully resolves overlapping peaks in the ion mobility data. The ability of the ROMIAC to operate at atmospheric pressure and serve as a front-end analyzer to continuously transmit ions with a particular mobility facilitates extensive studies of target molecules using a variety of mass spectrometric methods

The Defence of Responsible Communication

Defamatory statements of fact published in mass media give rise to a legal problem of particular difficulty. When a defamatory statement of fact is published by mass media, the breadth of the statement’s dissemination is likely to maximize the harm to the person defamed. Yet in recent decades there has been an increasing consciousness among legislators and the judiciary of the importance of freedom of expression in democratic societies. Defamation cases are free speech cases in microcosm. Judicial appreciation of the important values at stake on both sides of cases involving defamatory statements of fact in mass media has led to recognition that the publication of such statements, when they relate to subjects of legitimate public interest, should in some circumstances be legally protected. As a result, Canadian law as to the availability of a defence of privilege for mass media has been in a state of evolution for many years. This article surveys the history of that evolution, which has led to a restatement of libel law in terms of free expression the ory. A cornerstone of that restatement is the recent recognition by the Supreme Court, in Grant v. Torstar, of a new defence of responsible communication on matters of public interest

Actinobacillosis in a Bull

On March 20. 1950, a two year old Guernsey bull was admitted to Stange Memorial Clinic with a large pendulous growth on the left side of the throat near the midline and approximately four in. posterior to the angle of the mandible. This growth had first been noted 30 days before being brought to the clinic and had increased rapidly in size during this 30 day period. The growth appeared to involve the skin only; however, it was very vascular and hemorrhaged easily when traumatized

The Defence of Responsible Communication

Defamatory statements of fact published in mass media give rise to a legal problem of particular difficulty. When a defamatory statement of fact is published by mass media, the breadth of the statement’s dissemination is likely to maximize the harm to the person defamed. Yet in recent decades there has been an increasing consciousness among legislators and the judiciary of the importance of freedom of expression in democratic societies. Defamation cases are free speech cases in microcosm. Judicial appreciation of the important values at stake on both sides of cases involving defamatory statements of fact in mass media has led to recognition that the publication of such statements, when they relate to subjects of legitimate public interest, should in some circumstances be legally protected. As a result, Canadian law as to the availability of a defence of privilege for mass media has been in a state of evolution for many years. This article surveys the history of that evolution, which has led to a restatement of libel law in terms of free expression the ory. A cornerstone of that restatement is the recent recognition by the Supreme Court, in Grant v. Torstar, of a new defence of responsible communication on matters of public interest

Chiral Heterocyclic Ligands. XI. Self-assembly and X-Ray Crystal Structures of Chiral Silver Coordination Polymers of (S)-(-)-Nicotine

Three chiral coordination polymers have been prepared by reaction of (S)-(-)-nicotine with silver(I) salts. X-Ray crystal structure determinations revealed that these all contain polymer chains in which the nicotine molecule acts as a bridging ligand between four-coordinate silver atoms. In one case additional bridging by nitrate anions leads to a three-dimensional network structure

Oxidation products of biogenic emissions contribute to nucleation of atmospheric particles

Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations