Integrated polarization beam splitter with relaxed fabrication tolerances.

Polarization handling is a key requirement for the next generation of photonic integrated circuits (PICs). Integrated polarization beam splitters (PBS) are central elements for polarization management, but their use in PICs is hindered by poor fabrication tolerances. In this work we present a fully passive, highly fabrication tolerant polarization beam splitter, based on an asymmetrical Mach-Zehnder interferometer (MZI) with a Si/SiO(2) Periodic Layer Structure (PLS) on top of one of its arms. By engineering the birefringence of the PLS we are able to design the MZI arms so that sensitivities to the most critical fabrication errors are greatly reduced. Our PBS design tolerates waveguide width variations of 400nm maintaining a polarization extinction ratio better than 13dB in the complete C-Band.

Fetal echocardiography in ectopia cordis.

Ectopia cordis is an extremely rare congenital abnormality occurring in 5.5 to 7.9 per 1 million live births with high lethality. Between January 1995 and October 1997 eight cases of ectopia cordis were diagnosed at our institute before birth. On the basis of echocardiography the fetal heart anatomy was categorized as either normal heart anatomy (NHA; n = 3) or congenital heart defect (CHD; n = 5). In the majority of cases (seven of eight) other abnormalities were present. Some reports have described ectopia cordis being diagnosed in the first trimester of pregnancy. In our study group the average gestational age at diagnosis was 26 weeks. The prenatal diagnosis of isolated ectopia cordis is easy; counseling the patient, the perinatal management including term, place, and method of delivery, and optimal care of the newborn are more difficult. Ectopia cordis is a malformation that pediatricians rarely encounter, even at pediatric cardiology centers. Much more frequently it is a problem for sonographers and obstetricians; however, pediatric cardiologists should be aware of diagnostic algorithm for such cases, especially when additional abnormalities are present.

[Analysis of perinatal death at the Institute of the Health Center of the Polish mother in 1995, 1996 and 1997. The reason for making changes in the accountability for perinatal death]. / Analiza zgonów w okresie perinatalnym w Instytucie Centrum Zdrowia Matki Polki w latach 1995, 1996 I 1997. Przyczynek do koniecznosci wprowadzenia zmian w sprawozdawczosci na temat umieralnosci okoloporodowej.

Perinatal death's causes of fetuses and newborns from single and twin pregnancies delivered at the PMMHI from 1995-1997 were discussed. Data from the Pathology Department were analysed and compared to information regarding prenatal US + ECHO diagnoses coming from the Department for Diagnoses of Congenital Malformations at the PMMHI. The most frequent cause of death of fetuses and newborns from single pregnancies were congenital malformations (42%). In twins there prevailed such typical for multiple pregnancies' death causes as TTTS (27%), intrauterine demise of one of the twins (17%). Premature labor occupies the second most frequent cause of death both in single and multiple pregnancies. Most of perinatal deaths may be predicted prenatally by means of ultrasound and fetal echocardiography.

[The significance of cardiography in the diagnosis of cardiac ectopia of the fetus]. / Znaczenie echokardiograficznej diagnostyki ektopii serca plodu.

Retrospective analysis of echocardiographic examinations of 7 fetuses with ectopia cordis was presented. The majority of abnormalities were found in low risk pregnancies. There was only one case of isolated ectopia cordis with normal heart anatomy and no extracardiac malformations. There was no survival. Theoretically the prenatal diagnosis of isolated ectopia cordis may help to choose the proper term, place and method of delivery and also to plan the optimal care of newborn. Parents should be counseled about the prognosis in such cases, at the tertiary center, after detailed fetal echocardiography.