Tetrazolverbindungen. 1. 1-Aryl-5-(2-dialkylamino-vinyl)-1H-tetrazole aus 3-Chlor-propen-iminiumsalzen

Tetrazole Compounds. 1. 1-Aryl-5-(2-dialkylamino-vinyl)-1H-tetrazoles from 3-Chloropropeniminium Salts 3-Chloropropeniminium salts 1 react with excess sodium azide in refluxing alcohols to give mainly 1-aryl-5-(2-dialkylamino-vinyl)-1H-tetrazoles 3 ; in minor quantities isomeric 5-aryl-1-(2-dialkylamino-vinyl)-1H-tetrazoles 4 are formed. The reaction involves splitting off N₂ and C → N migration of the aryl and dialkylaminovinyl group, respectively. A cross-over experiment indicated that the rearrangement step proceeds intramolecularly. — The i.r., u.v., and n.m.r. spectroscopic data of the novel 1H-tetrazoles 3 as well as the u.v. spectra of some new starting products 1k—v are reported.     

The dune size distribution and scaling relations of barchan dune fields

Barchan dunes emerge as a collective phenomena involving the generation of thousands of them in so called barchan dune fields. By measuring the size and position of dunes in Moroccan barchan dune fields, we find that these dunes tend to distribute uniformly in space and follow an unique size distribution function. We introduce an analytical mean-field approach to show that this empirical size distribution emerges from the interplay of dune collisions and sand flux balance, the two simplest mechanisms for size selection. The analytical model also predicts a scaling relation between the fundamental macroscopic properties characterizing a dune field, namely the inter-dune spacing and the first and second moments of the dune size distribution.     

Development of a micro-miniature nanoindentation instrument with a force resolution of 1 nN

Accurate material testing based on the nanoindentation method always demands more and more accurate and sensible indentation instruments. A microelectromechanical system-based microminiature nanoindentation instrument is proposed, which features high force resolution (about 1 nN) and relatively large measurement range (up to 1 mN). The design of the microelectromechanical system is detailed, including the simulation of the mechanical system and the system performance. Preliminary experiments have been carried out with the aim to demonstrate the feasibility of this microminiature indentation system.     

Photoelectric properties of MISM phthalocyanine structure

Langmuir-Blodgett films have been prepared from copper tetra-4-t-butylphthalocyanine. A voltage dependence of capacitance can be attributed to the presence of a Schottky depletion layer. The barrier potential was determined as l·4eV, and the carrier concentration about 10²⁴m^?3     

High-efficiency thermoluminescent detectors for measuring the absorbed ionizing radiation dose in the environment

A study has been conducted with the goal of comparing the characteristics of TLD-K detectors based on sodium silicate ceramics to the characteristics of monocrystalline lithium fluoride detectors that contain traces of titanium and magnesium (TLD-100), as well as anion-defected aluminum oxide (TLD-500), which are widely used in thermoluminescent dosimetry. Because they are soil-equivalent, SiO₂ detectors are well suited for measuring the absorbed radiation dose in soils. The results of the comparison indicate that TLD-K detectors are preferable to LiF detectors in environmental applications due to the better uniformity of the detector sensitivity in a batch, the wider range of measurable doses, and the lower threshold in determining small doses.     

Wear behaviour of α- and α/β-SiAlON ceramics stabilized with Nd2O3 and Y2O3

α- and α/β-SiAlON compositions, doped with Y₂O₃ or Nd₂O₃, were densified by gas pressure sintering (GPS). The wear and mechanical properties of the materials were investigated and compared to β-Si₃N₄ materials. Microstructure evolution and its change with composition as well as the influence of the microstructural changes on the mechanical and tribological properties were reported. Wear tests were performed using a tribometer with ball-on-plate geometry in reciprocating sliding contact under dry condition. It was observed that α/β-SiAlON compositions, doped with Y₂O₃, have better wear properties in comparison to α-SiAlON and β-Si₃N₄ samples. Field emission scanning electron microscopy (FESEM) was used to analyse the worn surfaces after wear tests. The results showed that α/β-SiAlON and β-Si₃N₄ materials have different wear behaviour.     

Pattern storage and processing in attractor networks with short-time synaptic dynamics

Neurophysiological experiments show that the strength of synaptic connections can undergo substantial changes on a short time scale. These changes depend on the history of the presynaptic input. Using mean-field techniques, we study how short-time dynamics of synaptic connections influence the performance of attractor neural networks in terms of their memory capacity and capability to process external signals. For binary discrete-time as well as for firing rate continuous-time neural networks, the fixed points of the network dynamics are shown to be unaffected by synaptic dynamics. However, the stability of patterns changes considerably. Synaptic depression turns out to reduce the storage capacity. On the other hand, synaptic depression is shown to be advantageous for processing of pattern sequences. The analytical results on stability, size of the basins of attraction and on the switching between patterns are complemented by numerical simulations.     

用于AMLCD微显示的新型驱动

新型交流耦合结构使低功耗近眼微显示器使用3.3V供电的CMOS电路成为可能。