Spatial carrier distribution in InP/GaAs type II quantum dots and quantum posts.

We performed a detailed investigation of the structural and optical properties of multi-layers of InP/GaAs quantum dots, which present a type II interface arrangement. Transmission electronic microscopy analysis has revealed relatively large dots that coalesce forming so-called quantum posts when the GaAs layer between the InP layers is thin. We observed that the structural properties and morphology affect the resulting radiative lifetime of the carriers in our systems. The carrier lifetimes are relatively long, as expected for type II systems, as compared to those observed for single layer InP/GaAs quantum dots. The interface intermixing effect has been pointed out as a limiting factor for obtaining an effective spatial separation of electrons and holes in the case of single layer InP/GaAs quantum-dot samples. In the present case this effect seems to be less critical due to the particular carrier wavefunction distribution along the structures.

Modular method for calculation of transmission and reflection in multilayered structures.

We describe a new modular method for the calculation of wave propagation in stratified media based on the direct use of reflection and transmission coefficients. Within this reflection from the left, transmission, and reflection from the right (LTR) method we define addition and multiplication operators that enable the theoretical construction of any multilayered structures from substructures. This modular concept allows for the design and analysis of complex multilayer structures for optical devices.

[Ultrastructural research on the sensorimotor cortex in adult rats. I. Intranuclear inclusions in the neurons and astrocytes]. / Ultrastrukturno izsledvane na senzorimotoronata kora vuv vuzrastni plukhove. I. Vutreiadreni vkliuchvaniia v nevronite i astrotsitite.

The morphological peculiarities of neurones and astrocytes in the sensorimotor cortex of mature (over 3 months) and elderly (over 24 months) rats were studied at electron microscopic level. Intranuclear inclusions are found in the nuclei of pyramidal neurones from the third and fifth layer. On the basis of their fine structure they could be grouped into the following types: 1. Filamentous bundles. 2. Filamentous crystalloids. 3. Granulofilamentous bodies. 4. Membrane-enclosed inclusions. 5. Combined intranuclear inclusions. Filamentous crystalloids are found in two varieties, composed of filaments with various diameter and way of arrangement. Membrane-enclosed bodies are formed as small vesicles or large vacuoles. Combinations from various types of inclusions in the nucleus of a neurone are discovered frequently. Only intranuclear inclusions of the type of membrane-enclosed bodies are observed in the nuclei of astrocytes. These bodies are found only in the nuclei of astrocytes of elderly animals. On the basis of the comparative analysis between ultrastructural characteristics and frequency of intranuclear inclusions in pyramidal neurones and astrocytes in sensorimotor cortex of mature and elderly rats their probable connection with age changes in the central nervous system is discussed.

[Immunohistochemical demonstration of changes in the distribution of glial fibrillary acidic proteins of the auditory cortex in aging rats]. / Imunokhistokhimichno demonstrirane na promenite v razpredelenieto na glialniia fibrilaren kisel protein v slukhovata kora na stari plukhove.

Changes in the distribution of glial fibrillary acid protein-positive astrocytes in the auditory cortex of aged rats were investigated by an immunocytochemical method. It was established that there was an increase of these glial cells in all layers of the cortex. Possible causes for these changes are discussed.