Hilbert Transform Design Based on Fractional Derivatives and Swarm Optimization.

This paper presents a new efficient method for implementing the Hilbert transform using an all-pass filter, based on fractional derivatives (FDs) and swarm optimization. In the proposed method, the squared error difference between the desired and designed responses of a filter is minimized. FDs are introduced to achieve higher accuracy at the reference frequency ( ω0 ), which helps to reduce the overall phase error. In this paper, two approaches are used for finding the appropriate values of the FDs and reference frequencies. In the first approach, these values are estimated from a series of experiments, which require more computation time but produce less accurate results. These experiments, however, justify the behavior of the error function, with respect to the FD and ω0 , as a multimodal and nonconvex problem. In the second approach, a variant of the swarm-intelligence-based multimodal search space technique, known as the constraint-factor particle swarm optimization, is exploited for finding the suitable values for the FD and ω0 . The performance of the proposed FD-based method is measured in terms of fidelity aspects, such as the maximum phase error, total squared phase error, maximum group delay error, and total squared group delay error. The FD-based approach is found to reduce the total phase error by 57% by exploiting only two FDs.

The Case of Sacrococcygeal Teratoma in an IVF Pregnancy: Is There any Association between Congenital Tumors and Assisted Reproduction Techniques?

BACKGROUND: Sacrococcygeal teratoma (SCT) is a rare congenital tumor and its association with IVF pregnancy is not clear. There are limited reports of congenital tumors in IVF pregnancy. The exact embryogenesis of SCT is not known but a genetic etiology has been reported. Whether these congenital tumors have any association with assisted reproductive techniques remains obscure. CASE PRESENTATION: In this study, a case of SCT in an IVF pregnancy with donor oocytes was reported. IVF was performed for bilateral tubal blockade and poor ovarian reserve. It was diagnosed antenatally by ultrasonography. Successful surgical treatment was performed in postnatal period and six months follow-up remained uneventful. CONCLUSION: The purpose of reporting this case is to emphasize on the possibility of association of congenital tumors with assisted reproductive techniques and hence, the need for screening in these pregnancies. An association could not be detected based on few case reports and therefore, large population based studies are required to elucidate the effect of these reproductive techniques on occurrence of congenital tumors.