F A Mahmoud | PubMed Health

PubMed2001

Tilted bilayer membranes as simple transmission quarter-wave retardation plates.

A tilted bilayer membrane, which consists of two thin films of transparent optically isotropic materials of different refractive indices, can function as a transmission quarter-wave retarder (QWR) at a high angle of incidence. A specific design using a cryolite-Si membrane in the infrared is presented, and its tolerances to small shifts of wavelength, incidence angle, and film thickness errors are discussed. Some designs provide a dual QWR in transmission and reflection. Such devices provide simple linear-to-circular (and circular-to-linear) polarization transformers. Bilayer eighth-wave retarders without diattenuation are also introduced.

Journal Article↗

PubMedDate not supplied

Prenatal nicotine and CNS development.

The teratological effect of nicotine has been studied during different trimesters of pregnancy. Three groups of pregnant albino Swiss mice were used for each trimester. The daily doses of nicotine base used were equivalent to 10 (900 micrograms/kg), 20 (1,800 micrograms/kg), or 30 (2,700 micrograms/kg) cigarettes. The control groups were given normal saline. The drug and the saline solution were administered subcutaneously. The results showed that prenatal nicotine prolonged the latency and delayed the onset and extinction of audiogenic seizures in the offspring. These effects were more pronounced during the third trimester and particularly with the largest dose. These findings indicate that prenatal nicotine might delay the postnatal development of the CNS if it is given during the late stage of pregnancy.

Acoustic Stimulation↗