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Aircraft observations have revealed ubiquitous new particle formation in the tropical upper troposphere over the Amazon 1 , 2 and the Atlantic and Pacific oceans 3 , 4 . Although the vapours involved remain unknown, recent satellite observations have revealed surprisingly high night-time isoprene mixing ratios of up to 1 part per billion by volume (ppbv) in the tropical upper troposphere 5 . Here, in experiments performed with the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we report new particle formation initiated by the reaction of hydroxyl radicals with isoprene at upper-tropospheric temperatures of −30 °C and −50 °C. We find that isoprene-oxygenated organic molecules (IP-OOM) nucleate at concentrations found in the upper troposphere, without requiring any more vapours. Moreover, the nucleation rates are enhanced 100-fold by extremely low concentrations of sulfuric acid or iodine oxoacids above 10 5  cm −3 , reaching rates around 30 cm −3  s −1 at acid concentrations of 10 6  cm −3 . Our measurements show that nucleation involves sequential addition of IP-OOM, together with zero or one acid molecule in the embryonic molecular clusters. IP-OOM also drive rapid particle growth at 3–60 nm h −1 . We find that rapid nucleation and growth rates persist in the presence of NO x at upper-tropospheric concentrations from lightning. Our laboratory measurements show that isoprene emitted by rainforests may drive rapid new particle formation in extensive regions of the tropical upper troposphere 1 , 2 , resulting in tens of thousands of particles per cubic centimetre. Experiments performed in the CERN CLOUD chamber show that, under upper-tropospheric conditions, new atmospheric particle formation may be initiated by the reaction of hydroxyl radicals with isoprene emitted by rainforests.

Isoprene (C 5 H 8 ) is the non-methane hydrocarbon with the highest emissions to the atmosphere. It is mainly produced by vegetation, especially broad-leaved trees, and efficiently transported to the upper troposphere in deep convective clouds, where it is mixed with lightning NO x . Isoprene oxidation products drive rapid formation and growth of new particles in the tropical upper troposphere. However, isoprene oxidation pathways at low temperatures are not well understood. Here, in experiments at the CERN CLOUD chamber at 223 K and 243 K, we find that isoprene oxygenated organic molecules (IP-OOM) all involve two successive OH ∙ oxidations. However, depending on the ambient concentrations of the termination radicals ( HO 2 ∙ , NO ∙ , and NO 2 ∙ ), vastly-different IP-OOM emerge, comprising compounds with zero, one or two nitrogen atoms. Our findings indicate high IP-OOM production rates for the tropical upper troposphere, mainly resulting in nitrate IP-OOM but with an increasing non-nitrate fraction around midday, in close agreement with aircraft observations. Experiments under upper-tropospheric conditions map the chemical formation of isoprene oxygenated organic molecules (important molecules for new particle formation) and reveal that relative radical ratios control their composition

During summer, ammonia emissions in Southeast Asia influence air pollution and cloud formation. Convective transport by the South Asian monsoon carries these pollutant air masses into the upper troposphere and lower stratosphere (UTLS), where they accumulate under anticyclonic flow conditions. This air mass accumulation is thought to contribute to particle formation and the development of the Asian Tropopause Aerosol Layer (ATAL). Despite the known influence of ammonia and particulate ammonium on air pollution, a comprehensive understanding of the ATAL is lacking. In this modelling study, the influence of ammonia on particle formation is assessed with emphasis on the ATAL. We use the EMAC chemistry-climate model, incorporating new particle formation parameterisations derived from experiments at the CERN CLOUD chamber. Our diurnal cycle analysis confirms that new particle formation mainly occurs during daylight, with a 10-fold enhancement in rate. This increase is prominent in the South Asian monsoon UTLS, where deep convection introduces high ammonia levels from the boundary layer, compared to a baseline scenario without ammonia. Our model simulations reveal that this ammonia-driven particle formation and growth contributes to an increase of up to 80% in cloud condensation nuclei (CCN) concentrations at cloud-forming heights in the South Asian monsoon region. We find that ammonia profoundly influences the aerosol mass and composition in the ATAL through particle growth, as indicated by an order of magnitude increase in nitrate levels linked to ammonia emissions. However, the effect of ammonia-driven new particle formation on aerosol mass in the ATAL is relatively small. Ammonia emissions enhance the regional aerosol optical depth (AOD) for shortwave solar radiation by up to 70%. We conclude that ammonia has a pronounced effect on the ATAL development, composition, the regional AOD, and CCN concentrations.

Of these 212 patients, only 86% received intra operative radio therapy alone, meaning that about 14% received external-beam radiotherapy as well. 65% of patients also received endocrine treatment, which is known to be associated with a significant decrease or at least delay in the rate of local recurrences,5 which become apparent after more than 5 years' follow-up.4 Another area of concern is the postpathology stratum: 672 patients had a postpathology entry to the trial, meaning that about 336 patients allocated to TARGIT (most of the Danish and the Australian patients) were referred for a second surgical procedure. Given their intriguing findings, we think it is important to highlight that the radiation doses used in TARGIT-A are substantially lower than historical standards.2-4 Standard doses of tumour-bed radiation in the postoperative setting are 50-66 Gy (in 2 Gy per fraction) when whole breast irradiation is used and 38.5 Gy in 10 fractions (equivalent to 49 Gy in 2 Gy per fraction) when accelerated partial breast irradiation is used.4 Further, in nearly all of the published experience with breast brachytherapy,5 the radiation dose has been reported as the minimum dose delivered to at least a 1 cm rim of tissue immediately adjacent to the lumpectomy cavity. Twentyyear follow-up of a randomized trial comparing total mastectomy, lumpectomy, and lumpectomy plus irradiation for the treatment of invasive breast cancer.