Tunneling mechanism of light transmission through metallic films.

A mechanism of light transmission through metallic films is proposed, assisted by tunneling between resonating buried dielectric inclusions. This is illustrated by arrays of Si spheres embedded in Ag. Strong transmission peaks are observed near the Mie resonances of the spheres. The interaction among various planes of spheres and interference effects between these resonances and the surface plasmons of Ag lead to mixing and splitting of the resonances. Transmission is proved to be limited only by absorption. For small spheres, the effective dielectric constant of the resulting material can be tuned to values close to unity, and a method is proposed to turn the resulting materials invisible.

Control of spontaneous emission by complex nanostructures.

Spontaneous emission in the presence of complex nanostructures is discussed by use of a calculational scheme that permits us to deal with interfaces of arbitrary shape. Control over the field associated with the emission is shown to be attainable. In particular, decay rates are offered for geometries that lead to focusing and collimation of near- and far-field distributions. Emission from axially symmetric gratings is shown to lead to narrow angular distributions of emission, and focusing at the foci of dielectric ellipsoids is achieved for dimensions comparable with the wavelength. In the latter case the total emission rate for two atoms in an ellipsoidal cavity is shown to be enhanced in a way that deviates from the predictions of the Dicke effect by means of intermediate- and far-field contributions.

Empty follicle syndrome due to human errors: its occurrence in an in-vitro fertilization programme.

We report five cases in which no oocytes were retrieved after standard ovarian stimulation for in-vitro fertilization (IVF), and in which it was found that mistakes had been made at the time of human chorionic gonadotrophin (HCG) administration. In all five cases, oocyte retrieval was achieved after injecting HCG, when necessary, and reprogramming aspiration 24-36 h later. A mean of 7+/-3.2 MII oocytes were recovered per patient and 3.2+/-0.8 embryos were transferred. Three clinical pregnancies were obtained, and four healthy infants were born. In our programme, these were the only cases of empty follicle syndrome (EFS) that appeared over a total of 1118 cycles, and were all explained by human error in the administration of HCG. Our experience shows that human error could be considered a significant factor in the aetiology of empty follicle syndrome, and that EFS may be in part avoided by taking simple preventive measures.

[Pregnancy obtained by intracytoplasmic oocyte injection of spermatozoa retrieved from a cryopreserved testicular biopsy]. / Embarazo logrado por inyección intracitoplasmática de ovocitos con espermatozoides provenientes de una biopsia de testículo criopreservada.

We have obtained a clinical pregnancy in a 26 year old patient by means of in vitro oocyte fertilization by intracytoplasmic injection of spermatozoa obtained from a cryopreserved testicular biopsy. In a first attempt performed with fresh biopsy material, the woman became pregnant, but the pregnancy ended in a spontaneous abortion. In a second cycle, the spermatozoa were retrieved from a cryopreserved sample saved from the first attempt. Twelve metaphase II oocytes were collected and injected; from these, nine became fertilized, three preembryos were transferred at the eighth-cell stage and the other six were cryopreserved. An ongoing clinical pregnancy was obtained with two gestational sacs.