On the applicability of a semi-analytical approach to determining the transient electron transport response of gallium arsenide, gallium nitride, and zinc oxide

We critically examine the applicability of the semi-analytical approach of Shur (M. Shur, Electron Lett 12, 615 (1976)) in evaluating the transient electron transport response of gallium arsenide, gallium nitride, and zinc oxide. In particular, we contrast results obtained using this semi-analytical approach of Shur with those obtained using Monte Carlo simulations of the electron transport. Our approach will be to examine the response of an ensemble of electrons to the application of a constant and uniform applied electric field. For the purposes of this analysis, three aspects of the transient electron transport response will be considered: (1) the dependence of the electron drift velocity on the time elapsed since the onset of the applied electric field, (2) the dependence of the average electron energy on the time elapsed since the onset of the applied electric field, and (3) the dependence of the average electron displacement on the time elapsed since the onset of the applied electric field. The results obtained show that this semi-analytical approach of Shur produces results that are very similar to those produced using Monte Carlo simulations. Thus, this semi-analytical approach of Shur should be applicable for the treatment of non-uniform and time-varying electric fields, making it a useful tool for the treatment of the transient electron transport response within electron device configurations.     

Receptor-ligand-based specific cell adhesion on solid surfaces: hippocampal neuronal cells on bilinker functionalized glass

Cell adhesion through binding between specific cell membrane receptors and corresponding cell-adhesion-molecule (CAM)-coated solid surfaces is examined. The morphology of surfaces at various modification steps leading to functionalization with cell-binding CAMs is characterized. In one week neuron cultures, enhanced growth on surfaces modified with neuron-binding versus astrocyte-binding CAMs is observed. However, nonspecific adhesion on a poly-D-lysine-coated positive control surface is found to be even higher. Potential reasons and further studies needed are discussed.     

Public news announcements and quoting activity in the Euro/Dollar foreign exchange market

The effect of public news announcements on dealers’ quoting activity is analyzed with the multivariate double autoregressive conditional Poisson model. Quoting activity is measured by the frequency of price revisions in the Euro/Dollar foreign exchange market. The multivariate double autoregressive conditional Poisson model is designed for time series of count data. It is based on the double Poisson distribution, which can be both over- and underdispersed. The main findings are first a significant interaction between dealers’ quoting activity, which confirms hot potato trading. Second, news announcements have a different impact on the quoting activity of different banks. Third, impulse-response functions to news announcements show the dynamic nature of the reaction to these news releases.     

Under flow impedimetric measurements using magnetic particles for label-free detection affinity target

The necessity to adapt sensors based on electrochemical techniques for high throughput analysis control increases the interest to develop new analytical systems able to perform measurements under buffer flow.

In this report we explored the possibility of employing a new system to make impedimetric measurements to detect the interaction between proteins and small molecules. The well-known biotin–streptavidin interaction was adopted to evaluate the proposed assembly. This system allows us to perform experiments under flow. Magnetic beads functionalized with streptavidin were used and first characterized using AFM and FTIR.

Non-faradic impedance spectroscopy allowed the detection of the biotin–streptavidin interaction. Using our new system and under a flow of PBS buffer, 5 10^− 5 M of biotin was detected with a stable signal.