8-ns CMOS 64 K×4 and 256 K×1 SRAMs

SRAMs (static random-access memory) with a 64 K×4 and 256 K×1 structure and with 8-ns access time have been developed on a 1.0-μm CMOS process. Circuits are designed with source-coupling techniques to achieve high speed with small signal swings, using only CMOS devices. A metal option permits selection of the 64 K×4 or 256 K×1 configuration. The same core architecture has also been used to generate ×8 and ×9 designs. An output-enable (OE) version achieves 3-ns response time. As system speeds have recently increased toward 100-MHz operation, the need for address transition detection (ATD) has diminished as a means for improving the SRAM speed/power ratio. This trend in SRAM design stems mainly from the fact that AC current becomes the most significant fraction of the total current. Accordingly, the design described here employs a purely static path through the entire SRAM, with no requirement of ATD at any point. The resulting DC current is countered with a combined strategy of array subdivision, small-signal techniques, and active preamplification at key points in the data path     

Effect of fatigue loading on the modal properties of composite structures and its utilization for prediction of residual life

The design of composite structures for fatigue loading utilizes S-N curves to predict the fatigue life based on coupon testing. Due to the complex manufacturing process, the initial fabrication inconsistencies may cause the predicted number of cycles to failure to be off by one or two orders of magnitude. An experimental method is developed to predict the residual fatigue life of composite structures and continuously refine the prediction during the service life of these structures. Global effects on modal parameters, natural frequencies and damping ratios are investigated during the fatigue process. The Random Decrement signal processing technique is used. Changes of modal parameters are correlated with the prediction of fatigue failure life for selected graphite/epoxy composite specimens. The nature of the proposed method lends itself to real-time applications, especially, in service structures, as a nondestructive indicator.     

A kilohertz repetition rate 1.9 μm H2 Ramanoscillator

Raman conversion of a high-repetition-rate Q-switched Nd:YAG laser using a gaseous H₂ Raman medium is reported. With a H₂ cell placed in a focusing intracavity Raman oscillator, 3 W of average power at 1.9 μm was obtained from a 15-W 1.06-μm laser operating at 2 kHz. Although the pump beam was multimode, the Stokes output was diffraction limited. At kilohertz repetition rates, conversion efficiencies were improved with a flowing gas cell which substantially reduced the thermal lensing effect in the Raman medium. A rate equation approach was used to model the intracavity conversion process     

The coordinating model of the ganga basin

A scheme of model studies required to analyse a complex large scale system through decomposition approach is outlined. First, the total system is proposed to be modelled to identify interlinkages of the subsystems. Then the subsystems are analysed in detail to develop response functions. Finally the optimal system functioning is obtained by modelling the entire system in terms of response functions of the components. A linear programming model is developed for modelling the total system to identify the interlinkages. Its application is demonstrated in the Greater Ganga Basin using published data. Trade-off is developed between power generation and irrigated area in various seasons. A list of symbols is given at the end of the paper.     

微波反馈放大器的匹配和增益带宽的探讨

本文介绍了小信号微波反馈放大器的分析与综合。放大器采用通常的增益级框图表示和并联反馈。文中提供了全部网络元件的估算值和闭环宽频带增益、带宽和双端口的匹配值。用图解法对匹配值与增益进行了权衡。最后用实例描述了综合方法。     

Stimulation of large-conductance Ca2+-activated K+ channels by Evans blue in cultured endothelial cells of human umbilical veins

The effect of Evans blue (EB) on large-conductance Ca2+-activated K+ (BKCa) channels was investigated in cultured endothelial cells of human umbilical veins. In whole-cell configuration, EB (50 microM) reversibly increased the amplitude of K+ outward currents (IK). When the patch pipettes were filled with 10 mM EGTA, its stimulatory effect on IK was unaltered. Further application of EB in the presence of suramin, a blocker of P2-purinergic receptor, or AOPCP, an inhibitor of 5'-nucleotidase, still increased IK. However, charybdotoxin (100 nM) suppressed EB-induced increase in IK. In inside-out configuration, bath application of EB (50 microM) did not change single channel conductance but significantly increased the activity of BKCa channels. The EB-induced increase in the activity of BKCa channels was independent on internal Ca2+. EB (50 microM) shifted the activation curve of BKCa channels to less positive membrane potentials by approximately 20 mV. The change in the kinetic behavior of BKCa channels caused by EB in these cells is due to an increase in mean open time and a decrease in mean closed time. These results indicate that EB can stimulate the activity of BKCa channel in endothelial cells. This effect is unrelated to its blockade of P2-purinergic receptors or inhibition of 5'-nucleotidase. The direct stimulation of these ionic channels by EB may contribute to its effect on capillary permeability.     

Response map properties of units in the dorsal cochlear nucleus of barbiturate-anesthetized gerbil (Meriones unguiculatus)

The response map scheme introduced by Evans and Nelson (1973) and modified by others, including Davis et al. (1996) for use with gerbils, has been used primarily for classifying units recorded in the cochlear nucleus of unanesthetized decerebrate preparations. Units lacking spontaneous activity (SpAc) have been classified as either type I/III or type II units based on the relative strength of their responses to broad-band noise compared to their responses to best-frequency (BF) tones. The relative noise index (rho), a ratio of these responses after SpAc is subtracted out, provides a convenient measure of this relative strength. In this paper, responses of 320 units recorded in the dorsal cochlear nucleus (DCN) of barbiturate-anesthetized gerbils to short-duration BF tones and broad-band noise were recorded. Since 87.5% of these units lacked SpAc, their response maps resembled those of type II and type I/III units. Units were characterized by rho and the normalized slope (m) of a best line fit to the BF rate versus level plot starting from the sound level corresponding to the first inflection point of the rate curve (typically its maximum value or the start of its sloping saturation). The distributions of rho and m values do not form distinct clusters as they do for units in the decerebrate preparation. Thus, the criteria developed for classifying DCN units in the decerebrate preparation do not appear appropriate for units in the barbiturate-anesthetized preparation. Deposits of horseradish peroxidase were used to locate 52 units. Most of the low SpAc units, 56% with poor noise responses (5/9) and nearly 70% with strong noise responses (25/36), and nearly all of the high SpAc units (6/7), were located either within or below the fusiform cell layer.     

Multiplexed DNA sequencing and diagnostics by hybridization with enriched stable isotope labels

A new DNA diagnostic and sequencing system has been developed that uses time-of-flight resonance ionization mass spectrometry (TOF-RIMS) to provide a rapid method of analyzing stable isotope-labeled oligonucleotides in form 1 sequencing by hybridization (SBH). With form 1, the DNA is immobilized on a nylon membrane and enriched isotope-labeled individual oligonucleotide probes are free to seek out complementary DNAs during hybridization. The major advantage of this new approach is that multiple oligonucleotides can be labeled with different enriched isotopes and can all be simultaneously hybridized to the genosensor matrix. The probes can then be simultaneously detected with TOF-RIMS with high selectivity, sensitivity, and efficiency. By using isotopically enriched tin labels, up to 10 labeled oligonucleotides could be examined in a single hybridization to the DNA matrix. Greater numbers of labels are available if rare earth isotopes are employed. In the present study, matrices containing three different DNAs were prepared and simultaneously hybridized with two different probes under a variety of conditions. The results show that DNAs, immobilized on nylon surfaces, can be specifically hybridized to probes labeled with different enriched in isotopes. Discrimination between complementary and noncomplementary sites of better than 100 was obtained in multiplexed samples. This new SBH method, which employs stable isotopic labels to locate target DNAs and TOF-RIMS to detect the labels, will be a very versatile and extensive multiplexing method.