@article{NishikawaFrederiksenNordlundetal.2016, author = {Nishikawa, Ken-Ichi and Frederiksen, J. T. and Nordlund, A. and Mizuno, Y. and Hardee, P. E. and Niemiec, J. and Gomez, J. L. and Dutan, I. and Meli, A. and Sol, H. and Pohl, Martin and Hartmann, D. H.}, title = {EVOLUTION OF GLOBAL RELATIVISTIC JETS: COLLIMATIONS AND EXPANSION WITH kKHI AND THE WEIBEL INSTABILITY}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {820}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/0004-637X/820/2/94}, pages = {14}, year = {2016}, abstract = {In the study of relativistic jets one of the key open questions is their interaction with the environment. Here. we study the initial evolution of both electron-proton (e(-) - p(+)) and electron-positron (e(+/-)) relativistic jets, focusing on their lateral interaction with ambient plasma. We follow the evolution of toroidal magnetic fields generated by both the kinetic Kelvin-Helmholtz and Mushroom instabilities. For an e(-) - p(+) jet, the induced magnetic field collimates the jet and electrons are perpendicularly accelerated. As the instabilities saturate and subsequently weaken, the magnetic polarity switches from clockwise to counterclockwise in the middle of the jet. For an e(+/-) jet, we find strong mixing of electrons and positrons with the ambient plasma, resulting in the creation of a bow shock. The merging of current filaments generates density inhomogeneities that. initiate a forward shock. Strong jet-ambient plasma mixing prevents a full development of the jet (on the scale studied), revealing evidence for both jet collimation and particle acceleration in the forming bow shock. Differences in the magnetic field structure generated by e(-) - p(+) and e(+/-) jets may contribute to the polarization properties of the observed emission in AGN jets and gamma-ray bursts.}, language = {en} } @article{ThomasCarvalhoHaileetal.2019, author = {Thomas, Jessica E. and Carvalho, Gary R. and Haile, James and Rawlence, Nicolas J. and Martin, Michael D. and Ho, Simon Y. W. and Sigfusson, Arnor P. and Josefsson, Vigfus A. and Frederiksen, Morten and Linnebjerg, Jannie F. and Castruita, Jose A. Samaniego and Niemann, Jonas and Sinding, Mikkel-Holger S. and Sandoval-Velasco, Marcela and Soares, Andre E. R. and Lacy, Robert and Barilaro, Christina and Best, Juila and Brandis, Dirk and Cavallo, Chiara and Elorza, Mikelo and Garrett, Kimball L. and Groot, Maaike and Johansson, Friederike and Lifjeld, Jan T. and Nilson, Goran and Serjeanston, Dale and Sweet, Paul and Fuller, Errol and Hufthammer, Anne Karin and Meldgaard, Morten and Fjeldsa, Jon and Shapiro, Beth and Hofreiter, Michael and Stewart, John R. and Gilbert, M. Thomas P. and Knapp, Michael}, title = {Demographic reconstruction from ancient DNA supports rapid extinction of the great auk}, series = {eLife}, volume = {8}, journal = {eLife}, publisher = {eLife Sciences Publications}, address = {Cambridge}, issn = {2050-084X}, doi = {10.7554/eLife.47509}, pages = {35}, year = {2019}, abstract = {The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species' geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16th century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.}, language = {en} }