Pt Schottky diode gas sensors formed on GaN and AlGaN/GaN heterostructure

Exposure of Pt/GaN and Pt/AlGaN/GaN Schottky diodes to H2 gas at moderately high temperatures around 100 °C resulted in marked increase of forward and reverse currents. Increase was much larger in the Pt/AlGaN/GaN diode than in the Pt/GaN diode. Rapid turn-on responses and somewhat slower turn-off responses were observed with reproducible response magnitudes. A rigorous computer simulation of I–V curves indicated that current changes are due to changes in the Schottky barrier height caused either by H-induced formation of interfacial dipole or by hydrogen passivation of interface states

Al2O3 Insulated-Gate Structure for AlGaN/GaN Heterostructure Field Effect Transistors Having Thin AlGaN Barrier Layers

An Al2O3 insulated-gate (IG) structure was utilized for controlling the surface potential and suppressing the gate leakage in Al0.2Ga0.8N/GaN heterostructure field effect transistors (HFETs) having thin AlGaN barrier layers (less than 10 nm). In comparison with Schottky-gate devices, the Al2O3 IG device showed successful gate control of drain current up to VGS= +4 V without leakage problems. The threshold voltage in the Al2O3 IG HFET was about -0.3 V, resulting in the quasi-normally-off mode operation

Increase in participation of vasoactive intestinal peptide in relaxation of the distal colon of Wistar rats with age

1. Changes in participation of vasoactive intestinal peptide (VIP) in nonadrenergic noncholinergic (NANC) relaxation of longitudinal muscle of the distal colon with age were studied in 2- to 50-week-old Wistar rats in vitro. 2. The extent of the VIP-mediated component of the relaxation induced by electrical field stimulation (EFS) was determined by the effect of VIP(10–28), a VIP receptor antagonist. In 2-week-old rats, the extent of the VIP-mediated component of the relaxation was scarce, about 10%, whereas the component gradually increase with age and reached the maximum extent 66% at 50-week-old. 3. Since our previous results suggest that VIP induces NANC relaxation via activation of charybdotoxin (ChTx, a blocker of large conductance Ca(2+)-activated K(+) channel)-sensitive K(+) channels with concomitant slow hyperpolarization in the muscle cells, we next studied whether ChTx-sensitive component and slow hyperpolarization changes with age. Extent of ChTx-sensitive component of the relaxation increased with age, showing a very similar pattern to VIP-mediated one. 4. EFS induced monophasic inhibitory junction potentials (i.j.ps) in longitudinal muscle cells of the distal colon of 2- and 4-week-old. EFS also induced biphasic i.j.ps in many longitudinal muscle cells of 8- and 50-week-old: rapid and subsequent slow hyperpolarization. A VIP receptor antagonist selectively inhibited the slow hyperpolarization. 5. Exogenously added VIP induced no appreciable change in the membrane potential of longitudinal muscle cells of 2-week-old, whereas it induced slight slow hyperpolarization of the cell membrane in 4-week-old and magnitude of the hyperpolarization increased with age. On the other hand, relaxant response of the longitudinal muscle to exogenously added VIP was high in younger rats. 6. The present results suggest that the role of VIP in mediating NANC relaxation of longitudinal muscle of the Wistar rat distal colon is very little at neonatal stage, but it increases with age

Concise SAR Exploration Based on the “Head-to-Tail” Approach: Discovery of PI4KIIIα Inhibitors Bearing Diverse Scaffolds

In typical kinase inhibitor programs, a hinge binder showing best potency with preferential specificity is initially selected, followed by fine-tuning of the accompanying substituents on its core module. A shortcoming of this approach is that the exclusive focus on a single chemotype can endanger all the analogues in the series if a critical shortcoming is revealed. Thus, an early evaluation of structure–activity relationships (SARs) can mitigate unforeseen outcomes within a series of multiple compounds, although there have been very few examples to follow such a policy. PI4KIIIα is one of four mammalian phosphatidylinositol-4 kinases and has recently drawn significant attention as an emerging target for hepatitis C virus (HCV) treatment. In this letter, a novel “head-to-tail” approach to discover a diverse set of PI4KIIIα inhibitors is reported. We believe this method will generate distinct core scaffolds, a rational strategy to circumvent potential risks in general kinase programs