Movement and amplification of exciton condensed phase pulses and interaction between pulses in semiconductor quantum wells

Formation and movement of an exciton pulse in an inhomogeneous potential are studied. It is shown that the pulse does not blur and the maximum of the exciton density in the pulse remains constant during the exciton lifetime if the pulse is formed from the condensed phase. The path, traversed by the excitons, can be increased by imposing an additional laser pulse on the system. Thereby, such a system can be used for information transmission over the exciton condensed phase.     

Bioelectrochemical detection of L-lactate respiration using genetically modified Hansenula polymorpha yeast cells overexpressing flavocytochrome b2

In general, L-lactate respiration is difficult to detect in living yeast cells due to the small activity of L-lactate oxidizing enzymes within the mitochondria. Genetically modified cells of methylotrophic yeast Hansenula polymorpha overproducing L-lactate:cytochrome c-oxidoreductase (EC 1.1.2.3, also known as flavocytochrome b₂, FC b₂) were physically immobilized by means of a dialysis membrane onto various types of electrode materials in order to investigate the possibility of electrochemically detecting L-lactate respiration. It could be shown that in the case of genetically modified Hansenula polymorpha cells in contrast to cells from the parental strain, enhanced L-lactate-dependent respiration could be detected. Due to overproduction of FC b₂ the O₂ reduction current is decreased upon addition of L-lactate to the electrolyte solution. The electron transfer pathway in the L-lactate-dependent respiration process involves a cascade over three redox proteins, FC b₂, cytochrome c and Complex-IV, starting with L-lactate oxidation and ending with oxygen reduction. By means of selective inhibition of Complex IV with CN⁻, lactate respiration could be proven for causing the decrease in the O₂ reduction.     

Advective–diffusive mass transfer in binary regular structures in the steady-state regime

Having analyzed the stationary processes of admixture transfer in two-phase regular structures with taking into account periodical character of advective phenomena, we propose a method of constructing exact analytic solutions for such class of boundary value problems. This technique is based on the application of integral transformations individually for each contacting domain. The relation between these corresponding integral transformations is obtained from the nonideal boundary conditions. We have obtained the analytic solution of a diffusion problem for a two-phase layer of a regular structure with advective mass transfer mechanism in one of its phases. The expressions describing admixture flow through a certain body surface are derived, mass flows through the interface is investigated. Having analyzed the concentration of migrating particles in the structural elements of the body and the admixture flow through the given body surface, we present results graphically. The conditions of the existence of a limit passage from the contact boundary value problem of advective diffusion in regular structures to the continual model of advective two-way heterodiffusion are determined. A natural dimensionless form is introduced.