  We present results from a comprehensive study of ultrafast outflows (UFOs)
detected in a sample of fourteen quasars, twelve of which are gravitationally
lensed, in a redshift range of 1.41-3.91, near the peak of the AGN and star
formation activity. New XMM-Newton observations are presented for six of them
which were selected to be lensed and contain a narrow absorption line (NAL) in
their UV spectra. Another lensed quasar was added to the sample, albeit already
studied, because it was not searched for UFOs. The remaining seven quasars of
our sample are known to contain UFOs. The main goals of our study are to infer
the outflow properties of high-z quasars, constrain their outflow induced
feedback, study the relationship between the outflow properties and the
properties of the ionizing source, and compare these results to those of nearby
AGN. Our study adds six new detections ( > 99% confidence) of UFOs at z > 1.4,
almost doubling the current number of cases. Based on our survey of six quasars
selected to contain a NAL and observed with XMM-Newton, the coexistence of
intrinsic UV NALs and UFOs is found to be significant in > 83% of these quasars
suggesting a link between multiphase AGN feedback properties of the meso- and
micro-scale. The kinematic luminosities of the UFOs of our high-z sample are
large compared to their bolometric luminosities (median of L_K/L_Bol ~ 50%).
This suggests they provide efficient feedback to influence the evolution of
their host galaxies and that magnetic driving may be a significant contributor
to their acceleration.
