Connie Henson, Boe Rambaldini, Ben Freedman, Bronwyn Carlson, Carmen Parter, Vita Christie, John Skinner, David Meharg, Morwenna Kirwan, Katrina Ward, Sophia Nala 'Ḵixsisa 'las Speier, Kylie Gwynne
Wearables for early detection of atrial fibrillation and timely referral for Indigenous people ≥55 years: mixed-methods protocol
BMJ open
conspectusthe atmosphere key part earth system comprising myriad chemical species basic forms matter ubiquitous nano microscopic aerosol particles cloud droplets suspended air play crucial roles earths climate formation air pollution surfaces prominent part aerosols droplets due high surface area bulk volume ratios little known specific properties many atmospheric compounds surfaceactive leading enhanced surface concentrations aqueous solutions distribution surface bulk may determine heterogeneous chemistry many properties aerosol cloud droplets directly observedwe used xray photoelectron spectroscopy xps obtain direct molecularlevel information surface composition structure aqueous solutions surfaceactive organics model systems atmospheric aerosol cloud droplets xps vacuumbased technique enabled volatile aqueous organic samples application highspeed liquid microjet combination brilliant synchrotron xrays chemical specificity xps allows distinction elements different chemical states positions within molecular structures used corelevel c 1s n 1s signals identify alkyl hydrophilic groups atmospheric carboxylic acids alkylamines conjugate acids bases infer changes orientation surfaceadsorbed species quantify relative abundances surface xpsderived surface enrichments organics follow trends expected surface activities observed preferential orientation surface hydrophobic alkyl chains pointing increasingly outward solution higher concentrations provides first direct experimental observation wellestablished concepts surface adsorption confirms soundness methodwe mapped relative abundances conjugate acidbase pairs aqueous solution surfaces respective intensities distinctive xps signals pair protonation equilibrium significantly shifted toward neutral form surface compared bulk solution across full ph range represents apparent shift pka surface may toward either higher lower ph depending whether acid base form pair neutral species surface shifts broadly consistent relative differences surface enrichment individual acid base conjugates binary aqueous solutions additional contributions nonideal interactions surface aqueous mixtures surfaceactive carboxylate anions ammonium salts nearneutral ph found conjugate carboxylic acids strongly enhanced occurs coadsorption weakly basic carboxylate anions weakly acidic ammonium cations forms ionpair surface layers strongly enhanced local abundances increasing probability net proton transfer according le chateliers principle effect stronger evaporation ammonia surface contributes irreversibly perturb protonation equilibrium leaving surplus carboxylic acid surfacespecific effects may profoundly influence atmospheric chemistry mediated aqueous aerosols cloud droplets currently taken account atmospheric models