TY - JOUR AB - No catalyst required! A highly efficient, catalyst-free process to generate diimide in situ from hydrazine monohydrate and molecular oxygen for the selective reduction of alkenes has been developed. The use of a gas–liquid segmented flow system allowed safe operating conditions and dramatically enhanced this atom-economical reaction, resulting in short processing times. AU - Pieber, Bartholomäus AU - Martinez, Sabrina Teixeira AU - Cantillo, David AU - Kappe, C. Oliver ID - 11959 IS - 39 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - In situ generation of diimide from hydrazine and oxygen: Continuous-flow transfer hydrogenation of olefins VL - 52 ER - TY - JOUR AB - It's not magic! The effects observed in microwave-irradiated chemical transformations can in most cases be rationalized by purely bulk thermal phenomena associated with rapid heating to elevated temperatures. As discussed in this Essay, the existence of so-called nonthermal or specific microwave effects is highly doubtful. AU - Kappe, C. Oliver AU - Pieber, Bartholomäus AU - Dallinger, Doris ID - 11960 IS - 4 JF - Angewandte Chemie International Edition SN - 1433-7851 TI - Microwave effects in organic synthesis: Myth or reality? VL - 52 ER - TY - JOUR AB - The use of high-temperature/pressure gas–liquid continuous flow conditions dramatically enhances the iron-catalyzed aerobic oxidation of 2-benzylpyridines to their corresponding ketones. Pressurized air serves as a readily available oxygen source and propylene carbonate as a green solvent in this radically intensified preparation of synthetically valuable 2-aroylpyridines. AU - Pieber, Bartholomäus AU - Kappe, C. Oliver ID - 11973 IS - 2 JF - Green Chemistry SN - 1463-9262 TI - Direct aerobic oxidation of 2-benzylpyridines in a gas-liquid continuous-flow regime using propylene carbonate as a solvent VL - 15 ER - TY - JOUR AB - Near-surface air temperature, typically measured at a height of 2 m, is the most important control on the energy exchange and the melt rate at a snow or ice surface. It is distributed in a simplistic manner in most glacier melt models by using constant linear lapse rates, which poorly represent the actual spatial and temporal variability of air temperature. In this paper, we test a simple thermodynamic model proposed by Greuell and Böhm in 1998 as an alternative, using a new dataset of air temperature measurements from along the flowline of Haut Glacier d’Arolla, Switzerland. The unmodified model performs little better than assuming a constant linear lapse rate. When modified to allow the ratio of the boundary layer height to the bulk heat transfer coefficient to vary along the flowline, the model matches measured air temperatures better, and a further reduction of the root-mean-square error is obtained, although there is still considerable scope for improvement. The modified model is shown to perform best under conditions favourable to the development of katabatic winds – few clouds, positive ambient air temperature, limited influence of synoptic or valley winds and a long fetch – but its performance is poor under cloudy conditions. AU - Petersen, Lene AU - Pellicciotti, Francesca AU - Juszak, Inge AU - Carenzo, Marco AU - Brock, Ben ID - 12642 IS - 63 JF - Annals of Glaciology KW - Earth-Surface Processes SN - 0260-3055 TI - Suitability of a constant air temperature lapse rate over an Alpine glacier: Testing the Greuell and Böhm model as an alternative VL - 54 ER - TY - JOUR AB - Parameterizations of incoming longwave radiation are increasingly receiving attention for both low and high elevation glacierized sites. In this paper, we test 13 clear-sky parameterizations combined with seven cloud corrections for all-sky atmospheric emissivity at one location on Haut Glacier d'Arolla. We also analyze the four seasons separately and conduct a cross-validation to test the parameters’ robustness. The best parameterization is the one by Dilley and O'Brien, B for clear-sky conditions combined with Unsworth and Monteith cloud correction. This model is also the most robust when tested in cross-validation. When validated at different sites in the southern Alps of Switzerland and north-western Italian Alps, all parameterizations show a substantial decrease in performance, except for one site, thus suggesting that it is important to recalibrate parameterizations of incoming longwave radiation for different locations. We argue that this is due to differences in the structure of the atmosphere at the sites. We also quantify the effect that the incoming longwave radiation parameterizations have on energy-balance melt modeling, and show that recalibration of model parameters is needed. Using parameters from other sites leads to a significant underestimation of melt and to an error that is larger than that associated with using different parameterizations. Once recalibrated, however, the parameters of most models seem to be stable over seasons and years at the location on Haut Glacier d'Arolla. AU - Juszak, I. AU - Pellicciotti, Francesca ID - 12643 IS - 8 JF - Journal of Geophysical Research: Atmospheres KW - Space and Planetary Science KW - Earth and Planetary Sciences (miscellaneous) KW - Atmospheric Science KW - Geophysics SN - 2169-897X TI - A comparison of parameterizations of incoming longwave radiation over melting glaciers: Model robustness and seasonal variability VL - 118 ER -