Biomedical subjects
Publications and source records attributed to W Amir.
We demonstrate the use of a simple tool to simultaneously visualize and characterize chromatic and spherical aberrations that are present in multiphoton microscopy. Using two-dimensional Fourier transform spectral interferometry, we measured these aberrations, deducing in a single shot spatiotemporal effects in high-numerical-aperture objectives.
By using the third-harmonic signal generated at an air-dielectric interface, we demonstrate a novel way of correcting wavefront aberrations induced by high-numerical-aperture optics. The third harmonic is used as the input physical parameter of a genetic algorithm working in closed loop with a 37-actuator deformable mirror. This method is simple and reliable and can be used to correct aberrations of tightly focused beams, a regime where other methods have limitations. Improvement of the third-harmonic signal generated with an f/1.2 parabolic mirror by 1 order of magnitude is demonstrated.
The incidence of the main indications for cesarean sections in the last 20 years was analysed. Starting in 1981, we changed our attitude to cesarean sections and gradually initiated various means of decreasing our overall cesarean section rate. As a result, our increasing section rate was reversed in two phases: first by halting the upward trend, plateauing around 12%, followed by a 20% decrease to 9.7% in 1985. The change was in both the primary section rate and the repeat rate. The major decrease was in breech indication (1.2% vs. 2.8%), as a result of more external cephalic versions and fewer elective sections for this indication. By allowing more trials of labor after a prior cesarean section, combined with the reduction in the primary cesarean sections, a decrease in the repeat cesarean sections was noted (2.6% vs. 3.7%). By preventing the self-perpetuation of repeat sections, a reduction in multiple repeat sections is expected in the future. The intrapartum fetal mortality rate was not affected by the decreasing cesarean section rate. A further decrease in our cesarean section rate is expected in the future.
In a 30-month period, 261 of 557 (46.8%) patients underwent a trial of labor. Of these, 215 patients (82.4%) achieved vaginal delivery. The major controversial issues regarding vaginal delivery in patients with a prior cesarean section are oxytocin administration, the inclusion of patients with recurring indications, and the use of epidural analgesia. Oxytocin was not used in this study. When our results were compared to those of others who used oxytocin liberally we found that oxytocin augmentation was not a major factor in increasing significantly the success and vaginal delivery rate. We believe that oxytocin usage should be reserved for selected patients with well-defined indications. When the primary cesarean section was for cephalopelvic disproportion, 66.6% delivered vaginally. This success rate justifies the inclusion of these patients in a trial of labor. Epidural analgesia proved to be a safe and efficient procedure. There was no maternal or perinatal mortality related to trial of labor.