  We present an analysis of time-resolved, medium resolution optical
spectroscopic observations of UX UMa in the blue (3920-5250 A) and red
(6100-7200 A) wavelength ranges, that were obtained in April 1999 and March
2008 respectively. The observed characteristics of our spectra indicate that UX
UMa has been in different states during those observations. The blue spectra
are very complex. They are dominated by strong and broad single-peaked emission
lines of hydrogen. The high-excitation lines of HeII 4686 and the Bowen blend
are quite strong as well. All the lines consist of a mixture of absorption and
emission components. Using Doppler tomography we have identified four distinct
components of the system: the accretion disc, the secondary star, the bright
spot from the gas stream/disc impact region, and the unique compact area of
absorption in the accretion disc seen as a dark spot in the lower-left quadrant
of the tomograms. In the red wavelength range, both the hydrogen (H_alpha) and
neutral helium (HeI 6678 and HeI 7065) lines were observed in emission and both
exhibited double-peaked profiles. Doppler tomography of these lines reveals
spiral structure in the accretion disc, but in contrast to the blue wavelength
range, there is no evidence for either the dark spot or the gas stream/disc
impact region emission, while the emission from the secondary star is weak.
During the observations in 1999, UX UMa showed many of the defining properties
of the SW Sex stars. However, all these features almost completely disappeared
in 2008. We have also estimated the radial velocity semi-amplitudes K_1 and K_2
and evaluated the system parameters of UX UMa. These estimates are inconsistent
with previous values derived by means of analysis of WD eclipse features in the
light curve in the different wavelength ranges.
