Acceleration of particles by black hole with gravitomagnetic charge   immersed in magnetic field
  The collision of test charged particles in the vicinity of an event horizon of a weakly magnetized non-rotating black hole with gravitomagnetic charge has been studied. The presence of the external magnetic field decreases the innermost stable circular orbits (ISCO) radii of charged particles. The opposite mechanism occurs when there is nonvanishing gravitomagnetic charge. For a collision of charged particle moving at ISCO and the neutral particle falling from infinity the maximal collision energy can be decreased by gravitomagnetic charge in the presence of external asymptotically uniform magnetic field. 
Ahmadjon Abdujabbarov, Arman Tursunov, Bobomurat Ahmedov, and Abdulla   Kuvatov
gr-qc astro-ph.HE