Immunobiological properties of selected natural and chemically modified phenylpropanoids

Effects of natural and structurally transformed lignans compared with stilbenes or stilbenoids on production of nitric oxide (NO) triggered by lipopolysaccharide (LPS) and interferon-γ (IFN-γ), tested under in vitro conditions using murine resident peritoneal macrophages, are reviewed. Relation between the molecular structure and immunobiological activity was investigated, and implication of substituents, double bond stereochemistry, or cyclic attachments (double bond geometry fixation) was assessed. The focus was on lignans and stilbenoids because they were originally selected for a joint project of common interest to phytochemical and pharmacological investigation and because they represent well interesting and universally attractive groups of polyphenols with a feasible potential for therapeutic or nutraceutic utilization

Trap-Assisted Tunneling in the Schottky Barrier

The paper presents a new way how to calculate the currents in a Schottky barrier. The novel phenomeno-logical model extends the Shockley-Read-Hall recombi-nation-generation theory of trap-assisted tunneling. The proposed approach explains the occurrence of large leakage currents in Schottky structures on wide band semi-conductors with a high Schottky barrier (above 1 eV) and with a high density of traps. Under certain conditions, trap-assisted tunneling (TAT) plays a more important role than direct tunneling

Properties of the Si-SiO2 interfaces in MOS structures with nitrogen doped silicon

The article presents the results of capacitance measurements on MOS structures with a silicon substrate that was doped by nitrogen during the growth of the single crystal by Czochralski’s method. Attention is paid to the energy distribution of the trap density at the Si-SiO2 interface. The effect of the bond of nitrogen and oxygen brought about a slight increase in the trap density with a typical distribution of energy maxima of the deep levels in the forbidden band of Si

Simulation of electrical parameters for Ru/Ta2O5/SiO2/Si(p) high-k MOS structure

The contribution presents the results of simulation of direct tunnelling of free charge carriers through a thin gate insulator in MOS structures consisting of a Ta2O5/SiO2 bilayer taking into account also indirect tunnelling of free charge carriers through the SiO2/Si interface traps. The calculated I–V and C–V curves reveal the processes of electron and hole tunnelling through the insulator-to-semiconductor potential barrier that can be divided into four classes

Long-term effects on food choice of land snail Arianta arbustorum mediated by petasin and furanopetasin, two sesquiterpenes from Petasites hybridus

Sesquiterpenes (STs) from the Senecioneae have been found to be potent snail repellents. We investigated the range of activity of the STs petasin, isopetasin, furanopetasin, kablicin, and cacalol, which were isolated from Petasites hybridus, P. kablikianus, and Adenostyles alpina. We found the petasin content of leaves of P. hybridus to lie within the range of deterrence of the isolated compound. Furthermore, leaf extracts containing petasin proved to be deterrent, and leaf discs with low petasin content were preferred over discs with higher petasin content. The cacalol-containing fraction of a leaf extract of A. alpina was not deterrent to the snails. When the snails had experience with the relevant ST one week before a choice test, their sensitivity towards petasine and furanopetasine increased whereas for the other ST it remained at the same level. We speculate that this sensitivity increase could be the result of a rapid long-term associative learning process, but there is also the possibility that these STs are directly interfering with the feeding motor program of the snails, thereby eliciting a direct neurophysiological sensitization reaction which prevents them from further feeding

Defect Analysis of Pentacene Diode

This paper demonstrates the analysis of defect states in pentacene film sandwiched between Au and Al electrodes by the deep-level transient spectroscopy method. Three hole-like deep energy levels were observed. The effective mass obtained from the simulation is applied and defect parameters, namely the capture cross-sections and the activation energy 3.7 × $10^{-18} cm^2$ at 0.34 eV, 3.1 × $10^{-17} cm^2$ at 0.41 eV, and 2.9 × $10^{-15} cm^2$ at 0.63 eV is determined from the Arrhenius plot. Reliability of obtained defect parameters is confirmed by simulation of deep level transient spectra and comparison with experiment

A New Model of Multiphonon Excitation Trap-Assisted Band-to-Band Tunneling

The paper describes a new approach to calculating the currents in a pn-diode based on the extension of the Shockley-Read-Hall recombination-generation model. The presented theory is an alternative to Schenk’s model of trap-assisted tunneling. The new approach takes into account generation and recombination as well as tunneling processes in pn-junctions. Using this model, the real “soft” I-V curve usually observed in the case of switching diodes and transistors was modeled as a result of the high concentration of traps that assist in the process of tunneling