Asphaltene precipitation causes several problems during crude oil production, transportation, and refinery processes. Therefore, finding an inhibitor to prevent or delay asphaltene precipitation is of paramount importance. In this work, effects of TiO2, ZrO2, and SiO2 fine nanoparticles in organic-based nanofluids have been investigated to study their potential for stabilizing asphaltene particles in oil. To this end, polarized light microscopy has been applied to determine the onset of asphaltene precipitation by titration of dead oil samples from Iranian crude oil reservoirs with n-heptane in the presence of nanofluids. Results show that rutile (TiO2) fine nanoparticles can effectively enhance the asphaltene stability in acidic conditions and act inversely in basic conditions. It was found that the required amount of n-heptane for destabilizing the colloidal asphaltene is considerably higher in presence of TiO2 nanofluids at pH below 4. The FTIR spectroscopy indicates changes in n-heptane insoluble asphaltene when acidic TiO2 nanofluid is used as inhibitor. According to the results obtained by FTIR spectroscopy, TiO2 nanoparticles can enhance the stability of asphaltene nanoaggregates through formation of hydrogen bond at acidic conditions. This is while other materials used in this experiment, as well as the TiO2 nanoparticles in basic conditions, are unable to form any hydrogen bond – hence their incapability to prevent asphaltene precipitation. Dynamic light scattering (DLS) measurements also have been performed to explain the mechanism of asphaltene precipitation in the presence of nanoparticles.

SIGNIFICANCE The overall objective of this study was to evaluate facial asymmetry in patients with unilateral Duane retraction syndrome (DRS). The results showed a high frequency of facial asymmetry parameters of the opposite side of head turn in unilateral DRS patients. PURPOSE The purposes of this study were to evaluate the characteristics of facial asymmetry in unilateral exotropic and esotropic DRS and to compare the findings with orthotropic subjects. METHODS This cross-sectional comparative case series study was performed in 44 consecutive patients with head turn caused by DRS and 44 orthotropic subjects from 2016 to 2019. Four pictures were taken from the patients' faces. The first and second pictures were taken when patients had head turn and when the head was completely straight for calculating the facial angle and relative facial size, respectively. The third and fourth pictures were taken when the head was positioned downward (to compare the size of the cheek) and upward (to evaluate nose asymmetry). RESULTS The mean ± SD age of DRS patients and orthotropic subjects was 16.23 ± 9.92 and 20.68 ± 11.82 years, respectively. The frequency of facial asymmetry and all facial parameters (cheek compression, nasal tip and columella deviation, and compression of one of the nostrils) was significantly higher in DRS patients compared with orthotropic subjects (P < .001). In DRS patients with facial asymmetry, columella and nasal tip deviation (P = .006) and cheek and face compression (P = .03) were significantly more prevalent in the opposite direction of head turn. In the DRS group, the mean ± SD age of the patients with and without facial asymmetry was 17.37 ± 9.76 and 7.40 ± 6.54 years, respectively (P = .02). CONCLUSIONS The frequency of facial asymmetry and all facial parameters was significantly higher in DRS patients compared with orthotropic subjects. In unilateral DRS patients, the face was more commonly affected on the opposite side of head turn.

Thinning of the GCIPL is first detectable at 1 month after NAION and persists for 3 months. GCIPL thinning occurs before RFNL thinning in NAION.