Abstract. Size-resolved particle number fluxes in the size range of 10 nm < diameter (Dp) 200 were measured over a 3-year period (April 2017–March 2020) using eddy-covariance technique at an urban site Berlin, Germany. The observations indicated as net source particles with median total flux FTNC=0.86 × 108 m−2 s−1. turbulent surface–atmosphere exchange was clearly dominated by ultrafine (Dp...

In the external shock model, gamma-ray burst (GRB) emissions are produced by the energization and deceleration of a thin relativistic blast wave due to its interactions with the circumburst medium (CBM). We study the physical properties of an analytic function which describes temporally-evolving GRB spectra in the limit of a smooth CBM with density n(x) ∝ x−η, where x is the radial coordinate. ...