Electromagnetic field effect on weak-coupling piezoelectric polaron in an asymmetrical Gaussian confinement potential quantum well.

The properties of an electron weakly coupled to piezo-acoustic phonon in asymmetrical Gaussian confinement potential quantum well (AGCPQW) subject to external electric field (EF) and magnetic field (MF) has been investigated using the Lee-Low-Pines unitary transformation and linear combination operation methods. We have obtained the ground state energy (GSE) and the ground state binding energy (GSBE) of piezoelectric polaron. The effects of the EF, the MF, the range of the asymmetrical Gaussian confinement potential (RAGCP), Debye cut-off wavenumber (DCOW) and the electron-phonon coupling strength on the GSE and the GSBE are also analyzed. It is found that the GSE is an increasing function of the EF and the cyclotron frequency (CF), whereas it is a decreasing one of the RAGCP, the DCOW and electron-phonon coupling strength. The GSBE is an increasing function of the DCOW and the electron-phonon coupling strength. It is also an aggrandizing function with decreasing of the RAGCP, whereas it is a decayed one of the EF and CF. It is shown that the EF, the RAGCP, the MF, the DCOW and electron-phonon coupling strength are important factors that have great influence on the properties of the piezoelectric polaron in AGCPQW.

Vaginal delivery after caesarean section: a propective study of 146 cases.

We report on a series of 146 cases of vaginal delivery after previous Caesarean section conducted between 1993 and 2002 at the University Teaching Hospital, Yaounde (Cameroon). During the period under review 945 cases of Caesarean section were done out of a total of 9 439 deliveries (10 %). Delivery was spontaneous in 141 cases whereas in 5 cases it was assisted by vacuum extraction. In 13 cases Caesarean section was carried out after failure of trial of labour. Maternal mortality, resulting from pulmonary embolism, was observed in 1 case. We conclude that strict selection of patients who had previous Caesarean section for trial of labour renders vaginal delivery a safe alternative to Caesarean section.

Prevention of mother-to-child transmission of HIV in Cameroon: experiences from the University Teaching Hospital in Yaounde (Cameroon).

OBJECTIVE: The aim of this study was to assess the effectiveness of nevirapine (NVP) in the prevention of mother-to-child transmission (MTVT) of HIV-1 in children in the Yaounde University Teaching Hospital, Cameroon. METHODS: This was a prospective and descriptive hospital-based study in which pre-counselled HIV-infected pregnant women who gave their consent were included. At the onset of labour a single dose of 200 mg oral NVP was administered to each woman. Their newborns were also given 2 mg/kg of oral NVP syrup within 72 hours of their birth. These NVP-treated babies were assessed at 6 weeks, 6 months and between 15 and 18 months for viral load levels, using a branched DNA technology. Viral load levels were classified as undetectable (< 50 copies/ml); intermediate (50-3 500 cp/ml) or high (> 3 500 cp/ml). RESULTS: Of the 350 women screened for HIV 22 (6.3 %) were positive for HIV-1, but only 18 children were duly tested until 18 months. Viral load levels were undetectable at 6 weeks in 61.1 % of the children; intermediate in 38.9 % and no child had a high VL (> 3 500 cp/ml). At 6 months 5 of 7 children with intermediate levels had dropped to undetectable levels. By 15-18 months, a total of 16 children (88.9 %) had undetectable levels while 2 children (11.1 %) with detectable levels were confirmed to be HIV positive using ELISA test and immunoblot analysis. CONCLUSIONS: We conclude that the rate of HIV-1 MTCT with NVP is about 11 % in CHU Yaounde.