Electrical current distribution across a metal-insulator-metal structure during bistable switching

Combining scanning electron microscopy (SEM) and electron-beam-induced current (EBIC) imaging with transport measurements, it is shown that the current flowing across a two-terminal oxide-based capacitor-like structure is preferentially confined in areas localized at defects. As the thin-film device switches between two different resistance states, the distribution and intensity of the current paths, appearing as bright spots, change. This implies that switching and memory effects are mainly determined by the conducting properties along such paths. A model based on the storage and release of charge carriers within the insulator seems adequate to explain the observed memory effect.Comment: 8 pages, 7 figures, submitted to J. Appl. Phy

Hafnium carbide formation in oxygen deficient hafnium oxide thin films

On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO$_{2-x}$) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfC$_x$) at the surface during vacuum annealing at temperatures as low as 600 {\deg}C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfC$_x$ surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO$_2$ thin films prepared and measured under identical conditions, the formation of HfC$_x$ was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating

Characterization of the Active Site of Acetylcholinesterases by Application of Sterically Modified Acetylcholine Homologues

Our aim was to find steric limitations for the model of the active site of acetylcholinesterase and cho1inesterase. For thi<s purpose we used homologues of acetylcholine with hydrocarbon chains of increasing size at the cationic head. Catalysis of hydrolysis ceased for both enzymes, when the methyl groups of the cationic head of acetylcholine were substituted by three n-propyl groups. With data already documented in the literature and our additional experiments, under the same conditions, we were able to present models of the active sites for both enzymes

Characterization of the Active Site of Acetylcholinesterases by Application of Sterically Modified Acetylcholine Homologues

Our aim was to find steric limitations for the model of the active site of acetylcholinesterase and cho1inesterase. For thi<s purpose we used homologues of acetylcholine with hydrocarbon chains of increasing size at the cationic head. Catalysis of hydrolysis ceased for both enzymes, when the methyl groups of the cationic head of acetylcholine were substituted by three n-propyl groups. With data already documented in the literature and our additional experiments, under the same conditions, we were able to present models of the active sites for both enzymes

DISTRIBUTION AND KINETICS OF 14C-VECURONIUM IN RATS AND MICE

The distribution and kinetics of 14C-vecuronium were studied in rats and mice. 14C-Vecuronium accumulated rapidly in the liver. Both unchanged and metabolized vecuronium were excreted with the bile into the intestines and stomach. Reabsorption in the gut was probably responsible for an enterohepatic increase in radioactivity in the liver after one hour. Excretion through the kidneys increased continuously from low values after the initial peak. Binding in compartments with acid mucopolysaccharides such as cartilage, connective tissue etc., was less important. Bloodbrain barrier and placenta were permeable only to a small degre

Численное исследование влияния условий распыления воды на температуру в следе "водяного снаряда"

С использованием нескольких моделей "водяных снарядов" малых размеров выполнено численное исследование макроскопических закономерностей испарения монодисперсной совокупности капель тонкораспыленной воды при прохождении через высокотемпературные продукты сгорания. Установлены зависимости интегральных характеристик тепломассопереноса от отношения площадей испарения и площадей, занимаемых "водяным снарядом". Определены условия распыления воды для эффективного снижения температуры в зоне горения

Synthesis of 1-[(Triisopropylsilyl)ethynyl]-1 lambda(3),2-benziodoxol-3(1H)-one and Alkynylation of Indoles, Thiophenes, and Anilines

An efficient procedure was developed for the synthesis of 1-[(triisopropylsilyl)ethynyl]-1 lambda(3),2-benziodoxol-3(1H)-one on a 100-mmol (36-g) scale. The benziodoxolone can be used for the gold-catalyzed direct alkynylation of indole, 2-hexylthiophene, or N,N-dibenzylaniline on a 5- to 10-mmol scale

Para-Selective Gold-Catalyzed Direct Alkynylation of Anilines

A method for the para-selective alkynylation of anilines is reported using AuCl as catalyst and triisopropylsilylethynyl-1,2-benziodoxol-3(1H)-one (TIPS-EBX) as an electrophilic acetylene equivalent. Para-alkynyl anilines substituted at positions 2 or 3 were obtained in one step from simple anilines under mild conditions (room temperature to 60 degrees C) under air. The methodology could also be extended to the alkynylation of trimethoxybenzenes