The surging interest in manipulating the polarization of piezo/ferroelectric materials by means of light has driven an increasing number of studies toward their light-polarization interaction. One way to investigate such interaction is by performing piezoresponse force microscopy (PFM) while/after the sample is exposed to light illumination. However, caution must be exercised when analyzing and interpreting the data, as demonstrated in this paper, because sizeable photo-response observed in the PFM amplitude image of the sample is shown to be caused by the electrostatic interaction between the photo-induced surface charge and tip. Through photo-assisted Kelvin probe force microscopy (KPFM), positive surface potential is found to be developed near the sample's surface under 405 nm light illumination, whose effects on the measured PFM signal is revealed by the comparative studies on its amplitude curves that are obtained using PFM spectroscopy mode with/without illumination. This work exemplifies the need for complementary use of KPFM, PFM imaging mode, and PFM spectroscopy mode in order to distinguish real behavior from artifacts.
We have studied the antiemetic efficacy of droperidol alone, and in combination with metoclopramide in first trimester termination of pregnancy in day surgery. The aim was to determine whether the addition of metoclopramide could further reduce the incidence of postoperative nausea and vomiting (PONV) but avoid excessive sedation. Group I (control, n = 40) received i.v. droperidol 0.625 mg at induction. Group II (study, n = 40) received i.v. droperidol 0.625 mg and i.v. metoclopramide 10 mg at induction. The incidence of nausea at 1 and 2 hours postoperatively was 23% and 10% in group I, and 5% and nil in group II respectively. The difference in the incidence of nausea was significant at p < 0.05 at one hour but not at two hours postoperatively. No patients vomited. There was no difference in the sedation and pain score between them. We did not observe any significant side effects attributable to either drug. All patients were discharged home within 3 hours. We conclude that in the prevention of PONV, the combination of metoclopramide and droperidol is superior to the use of droperidol alone at one hour but not at two hours postoperatively.