FOCUS: fast Monte Carlo approach to coherence of undulator sources.

FOCUS (Fast Monte CarlO approach to Coherence of Undulator Sources) is a new GPU-based simulation code to compute the transverse coherence of undulator radiation from ultra-relativistic electrons. The core structure of the code, which is written in the language C++ accelerated with CUDA, combines an analytical description of the emitted electric fields and massively parallel computations on GPUs. The combination is rigorously justified by a statistical description of synchrotron radiation based on a Fourier optics approach. FOCUS is validated by direct comparison with multi-electron Synchrotron Radiation Workshop (SRW) simulations, evidencing a reduction in computation times by up to five orders of magnitude on a consumer laptop. FOCUS is then applied to systematically study the transverse coherence in typical third- and fourth-generation facilities, highlighting peculiar features of undulator sources close to the diffraction limit. FOCUS is aimed at fast evaluation of the transverse coherence of undulator radiation as a function of the electron beam parameters, to support and help prepare more advanced and detailed numerical simulations with traditional codes like SRW.

Azithromycin is more allergenic than clarithromycin in children with suspected hypersensitivity reaction to macrolides.

BACKGROUND: Macrolides are considered safe antibiotics with reduced allergenic activity. However, studies on the safety of macrolides are scarce, particularly in children. OBJECTIVE: The aim of this study was to assess the frequency of hypersensitivity reactions to clarithromycin and azithromycin in a group of children referred to our allergy unit for suspected macrolide allergy. METHODS: We retrospectively reviewed the charts of 90 children aged 1-17 years with symptoms suggestive of hypersensitivity reaction to clarithromycin or azithromycin between December 31, 2008 and December 31, 2013. The allergy workup included skin tests (ie, skin prick tests and/or intradermal tests), determination of serum specific IgE (sIgE) to clarithromycin and azithromycin, and, if necessary to reach a diagnosis, oral provocation tests. RESULTS: Seventy-seven children completed the allergy workup. A reaction to clarithromycin was recorded in 58 children (75.3%): 21 (36.2%) had a history of immediate reactions, and 37 (63.8%) had a history of nonimmediate reactions. A reaction to azithromycin was recorded in 19 children (24.6%): 6 (31.5%) had a history of immediate reaction, and 13 (68.42%) had a history of nonimmediate reaction. Positive results in skin tests and oral provocation tests with the suspect drug confirmed the diagnosis in 15.5% of reactions to clarithromycin (9 of 58) and in 47.3% of reactions to azithromycin (9 of 19) (P = .004). CONCLUSION: A complete allergy workup enabled us to confirm a diagnosis of clarithromycin and azithromycin allergy in 15.5% and 47.3% of cases, respectively. Azithromycin was more allergenic than clarithromycin in children.