Polarized photoreflectance and photoluminescence spectroscopy of InGaAs/GaAs quantum rods grown with As2 and As4 sources

We report photoreflectance (PR) and photoluminescence (PL) investigations of the electronic and polarization properties of different aspect ratio (height/diameter) InGaAs quantum rods (QRs) embedded in InGaAs quantum wells (QWs). These nanostructures were grown by molecular beam epitaxy using As2 or As4 sources. The impact of the As source on the spectral and polarization features of the QR- and QW-related interband transitions was investigated and explained in terms of the carrier confinement effects caused by variation of composition contrast between the QR material and the surrounding well. Polarized PR and PL measurements reveal that the polarization has a preferential direction along the [ 110] crystal axis with a large optical anisotropy of about 60% in the (001) plane for high aspect ratio (4.1:1) InGaAs QRs. As a result, in PL spectra, the transverse magnetic mode dominated (110)-cleaved surfaces (TM[001] > TE[110]), whereas the transverse electric mode prevailed for (110)-cleaved surfaces (TM[001] < TE[110] ¯ ). This strong optical anisotropy in the (001) plane is interpreted in terms of the hole wavefunction orientation along the [ 110] direction for high aspect ratio QRs

Investigation of post-thaw bull semen capacitacion in vitro

The aim of this study was to investigate the ability of acrosomal reaction, motility during capacitation at different time of bovine spermatozoa in relationship to in vitro fertility. . Frozen sperm from a Holsteins bulls were capacitated first group – 60 min., (n-17 samples) and second group – 120 min. (n-17 samles) by a swim-up methods. After incubation Trypan blue (Sigma, JAV) stained was used to evaluate viability and acrosome status of spermatozoa. Stained spermatozoides was counting and divided in three groups: non-viable, hyperactivated and with acrosomal changes. Amount of nonviable spermatozoa after 120 min. capacitation were 20 % less compared with 60 min. capacitation (p0,05)