On the analysis of two-dimensional discrete singular systems

In contrast to 1-D systems, the 2-D systems have no natural notion of causality. An artificial restriction traditionally imposed to allow recursive solution of these systems is that of recursibility. In this paper we study 2-Dsingular systems, taking advantage of the nonoriented or noncausal nature of these systems to provide a solution even if the requirement of recursibility does not hold. It is shown thatnonrecursible masks may be described using singular 2-D systems. The analysis approach relies on thefundamental matrix.Research supported by the US Fulbright Foundation in Greece and NSF Grant ECS-8805932.     

Electrical polarization control of vertical-cavity surface-emittinglasers using polarized feedback and a liquid crystal

We report electrical control of the polarization state of a vertical-cavity surface-emitting laser (VCSEL), The VCSEL is subject to strong external optical feedback (up to 6% of emission), with polarization controlled by a liquid-crystal (LC) element, It is found that the contrast ratio of the complete system can be enhanced compared to the contrast ratio of the LC element alone     

Preliminary investigations on some potential sources of protected methionine derivatives for ruminant rations

A series of N-substituted methionine derivatives were investigated for their potential to resist rumen degradation but still to release methionine in the duodenum. The method adopted was (a) to measure rumen methyl mercaptan concentrations in sheep following intraruminal doses of the materials and (b) to measure the ability of the materials to promote the growth of chicks receiving a methionine deficient diet.     

通过可重配置手机对付移动电话盗窃

在英国现在每3分钟就有一部移动电话被盗。这一现象并不仅局限于英国,而是一个全球问题,并且数量在不断上升。例如,在澳大利亚的新南威尔士,1999年10月至2000年9月间约有4万部移动电话被偷或被抢,比前一年增长了100%。     

用于辅助驾驶系统的可编程平台

安全性是汽车消费者最关心的问题了。图1给出了Visteon进行的一项研究结果,图中显示出客户对汽车的要求,而车辆安全性位于核心。对于汽车安全性的关注不仅仅是为了司机和乘客,还有道路上的其他人。安全设备已经从物理领域转向电子领域,从轮胎和刹车技术的进步,到侧撞保护和安全     

In-situ cleaning and passivation of oxidized Cu surfaces by alkanethiols and its application to wire bonding

The treatment of oxidized Cu surfaces using an alkanethiol as a reducing agent has been investigated. Exposure to a dilute solution of 1-decanethiol resulted in the complete removal and/or conversion of CuO and subsequent formation of a passivating thiolate film, a so-called self-assembled monolayer (SAM), on the underlying Cu/Cu₂O surface as evidenced by x-ray photoelectron spectroscopy (XPS) analysis. Morphological changes, monitored by scanning electron microscopy (SEM) and atomic force microscopy (AFM), revealed transformation of the rough, porous CuO layer into a comparatively smooth Cu/Cu₂O surface. Experiments performed on integrated circuit back-end-of-line (BEOL) die structures, comprising Cu/SiO₂ bond pads used as substrates for Cu wire bonding, demonstrate the potential application of a thiol-based in-situ cleaning-passivation procedure in microelectronics.     

Extracellular recordings from patterned neuronal networks using planar microelectrode arrays

Neuronal cell networks have been reconstructed on planar microelectrode arrays (MEAs) from dissociated hippocampal pyramidal neurons. Microcontact printing (microCP) and a photoresist-liftoff method were used to selectively localize poly-L-lysine (PLL) on the surface of MEAs. Haptotaxis led to the organization of the neurons into networks localized adjacent to microelectrodes. Various grids of PLL with 2-25-microm-wide lines spaced by 50-200 microm with 15-25-microm nodes at intersection points were used to guide cell body attachment and neurite outgrowth. Bursting activity with spike amplitude attenuation was observed, and multichannel recordings detected instances of coincident firing activity. Finally, we present here an extracellular recording from a approximately 2 microm bundle of guided neurites.     

740 nm InP/GaInP quantum-dot laser with 190 A cm/sup -2/ room temperature threshold current density

InP quantum-dot lasers grown on GaAs substrates and emitting in the 730-740 nm band with threshold current density as low as 190 A cm/sup -2/ for a 2000 /spl mu/m-long device with uncoated facets are reported.     

Nitrite tolerance and nitrite reduction in lactic acid bacteria associated with cured meat products

The effect of 0, 50, 100 and 200 μg/ml of nitrite on the growth of isolated and reference strains of lactic acid bacteria associated with cured meat products was studied in broth cultures and the presence of an active nitrite reductase enzyme system in these strains was determined. Half of the 10 reference strains and 16 of 25 isolated strains were resistant to all levels of nitrite tested Strains which did not show a significant decrease in growth rate or cell yield in the presence of 200 μg/ml of nitrite under anaerobic conditions were homofermentative. All heterofermentative strains showed a decrease in growth rate or cell yield or both. Inhibition due to nitrite increased as the concentration increased and was greatest under anaerobic conditions. Enzymatic ability to reduce nitrite was detected in 5 homofermentative and 1 heterofermentative strains. The presence of an active nitrite reductase enzyme system in lactic acid bacteria was not related to their resistance to nitrite.     

The volatile flavour components of commercial port wines

Gas chromatographic-mass spectrometric examination of aroma extracts from both Ruby and Tawny port has led to the identification of 141 components, notably 2-methoxyphenol, dihydro-2-(3H)-furanone, β-methyl-γ-octalactone, cis-4-hydroxy-methyl-2-methyl-l,3-dioxolane, ethyl pyroglutamate and vitispirane. Odour evaluation of the components separated by gas chromatography indicates five regions as being of potential importance in port. 2-Methoxyphenol and dihydro-2-(3H)-furanone were found in two of these regions, three others being associated with esters of succinic acid. None of these components can, however, wholly explain the port-like odour.