A multilevel soliton communication system

A multilevel soliton communication system is proposed and assessed. In this system, at the transmitter end each channel transmits its data via fundamental solitons with a pre-specified amplitude (i.e., soliton width). At the receiver end we take advantage of the sensitive relationship between the amount or fundamental soliton self-wavelength shift and the width of the soliton in the subpicosecond region. We first compress the incoming soliton noises to the subpicosecond level and pass them through a short length of fiber at the end of which the pulses have become separated in the wavelength domain since each soliton, corresponding to a data channel, has experienced a different Raman self-wavelength shift. The channels are then easily separated by optical filters. We have derived the design constraint relations for such a system. We have then heuristically designed a 40 Gbs (four channels) system for a 1000 km propagation distance (total data-rate distance product of 40 Tb/km). Numerical simulations and noise analyses have verified the feasibility and practicality of the proposed system with very good design margins. The wavelength jitter is found to be much smaller than the desired filter spacing, and thus its contribution to the bit error rate is negligible. We also argue that the system is more tolerant to Gordon-Haus timing jitter than conventional TDM soliton systems. The system is all fiber and is, therefore very cost effective as it does not require sophisticated electro-optic and microwave circuits for demultiplexing. The system can potentially operate at much higher speeds than those achievable in conventional soliton systems and it can be used in parallel with WDM soliton system     

A menu-driven environment for automated urban and regional analysis: a GIS application for educational purposes

Geographical information systems (GIS) constitute an important development offering wide application potential in geography, urban and regional planning and associated disciplines. Current debates entail two kinds of criticism; the first involves GIS themselves and the fact that they are often cumbersome and difficult to use; the second involves the ‘poverty‘ of some GIS applications. The result is a worldwide endeavour to produce answers to both questions. The main objective of the system proposed here, known as URAP (urban and regional analysis for planning), is to make a contribution to these goals, by upgrading conventional GIS capabilities, while simplifying the means by which results from advanced statistical analysis are obtained and subsequently plotted. It entails a menu-driven environment and involves the dynamic formation of customised databases to meet the geographical, methodological and other choices made by the user. While the arguments in the paper involve an emphasis on education, the system is also suitable for supporting public policy making.     

Charge comparison protection of transmission lines-relayingconcepts

The authors describe the relaying concepts of charge comparison. Charge comparison is a new transmission line protection system. It is a form of current differential relaying. Charge comparison largely resolves the traditional problems of current differential relaying of transmission lines, which are that protection is lost if a channel fails, a large channel capacity is required, and precise channel delay compensation is required. This technique is suitable for the protection of two- or three-terminal AC transmission lines, of all lengths and voltage levels, with or without series of shunt compensation, with three-hole or single-pole tripping     

Synthesis and release of ATP by soluble mitochondrial F1 in complex with its inhibitor protein during dimethylsulfoxide-water transitions

Soluble mitochondrial F1 and F1 in complex with the natural ATPase inhibitor protein (F1-IP) catalyze the spontaneous synthesis of [gamma-32P]ATP from medium [32P]phosphate and enzyme-bound ADP when incubated in media with dimethylsulfoxide (Me2SO); under these conditions, the synthesized [gamma-32P]ATP is not released into the media, it remains tightly bound to the enzymes [Gómez-Puyou, A., Tuena de Gómez-Puyou, M. & de Meis, L. (1986) Eur. J. Biochem. 159, 133-140]. Some of the characteristics of the synthesized [gamma-32P]ATP were studied in F1 and F1-IP (ATPase activities of 70 and 1-3 micromol x min(-1) x mg(-1), respectively). In Me2SO media, gamma-phosphate of synthesized ATP in F1 or F1-IP exchanges with medium phosphate. From the rates of the exchange reaction, the half-times for hydrolysis of the synthesized ATP in F1 and F1-IP were calculated: 45 min and 58 min for F1 and F1-IP, respectively. The course that synthesized [gamma-32P]ATP follows after dilution of the Me2SO synthetic mixture with aqueous buffer was determined. After dilution, the half-life of synthesized ATP in F1 was less than 1 min. In F1-IP, ATP was also hydrolyzed, but at significantly lower rates. In F1-IP, dilution also produced release of the synthesized [gamma-32P]ATP. This was assayed by the accessibility of [gamma-32P]ATP to hexokinase. About 25% of [gamma-32P]ATP synthesized in F1-IP, but not in F1, was released into the media after dilution with aqueous buffer that contained 20 mM phosphate. Release of tightly bound ATP required the binding energy of phosphate and solvation of F1-IP, however, the particular kinetics of F1-IP were also central for medium ATP synthesis in the absence of electrochemical H+ gradients.     

Identification and disruption of a plant shaker-like outward channel involved in K+ release into the xylem sap

SKOR, a K+ channel identified in Arabidopsis, displays the typical hydrophobic core of the Shaker channel superfamily, a cyclic nucleotide-binding domain, and an ankyrin domain. Expression in Xenopus oocytes identified SKOR as the first member of the Shaker family in plants to be endowed with outwardly rectifying properties. SKOR expression is localized in root stelar tissues. A knockout mutant shows both lower shoot K+ content and lower xylem sap K+ concentration, indicating that SKOR is involved in K+ release into the xylem sap toward the shoots. SKOR expression is strongly inhibited by the stress phytohormone abscisic acid, supporting the hypothesis that control of K+ translocation toward the shoots is part of the plant response to water stress.     

Response spectrum analysis of piping systems with elastic-plastic gap supports

A new seismic support device and its application in piping systems is described. The device, E-BAR (patented), can be cost effectively used for snubber replacement programs, mitigation of hydraulic transients, pipe whip and as a thermal stop. The device has pre-set gaps to allow free thermal movement. During a seismic or other dynamic load event, if the pipe movement exceeds the gap dimension, the device acts as an elastic or elastic-plastic restraint. The device also has a unique design feature for not exceeding the restraint force beyond a specified limit design value. To analyze piping systems with gap supports having elastic-plastic characteristics, modal analysis procedures for both response spectrum and time history methods are developed. The comparison of responses obtained from the procedures with nonlinear time history analysis and test results available in the literature shows excellent correlation. A pilot program conducted for snubber replacement with E-BARs demonstrates that the limit force feature of E-BAR makes them very attractive for snubber replacement. This is because a particular E-BAR with a specified limit design force can be selected, such that, the E-BAR replacing the snubber does not require any modifications be made to the existing support steel and hardware.     

A comparative cerebral blood flow study in a baboon model with acetazolamide provocation: 99mTc-HMPAO vs 123I(IMP)

Pharmacological interactions are important when nuclear medical procedures are applied to patients under drug therapy, or drug provocation. This study compares in baboon models (regional) cerebral blood flow [(r)CBF] results from 99mTc-HMPAO and 123I-iodoamphetamine [123I(IMP)] each with and without acetazolamide, the latter a suggested drug for testing cerebrovascular reserve. Expected differences in cerebral uptake were observed between the two radio-tracers without acetazolamide. The increase in tracer uptake resulting from acetazolamide is significantly enhanced for 123I(IMP), which could have diagnostic implications.     

Threshold voltage-minimum gate length trade-off in buried channelPMOS devices for scaled supply voltage CMOS technologies

The trade-off between threshold voltage (V_th) and the minimum gate length (L_min) is discussed for optimizing the performance of buried channel PMOS transistors for low voltage/low power high-speed digital CMOS circuits. In a low supply voltage CMOS technology it is desirable to scale V_th and L_min for improved circuit performance. However, these two parameters cannot be scaled independently due to the channel punch-through effect. Statistical process/device modeling, split lot experiments, circuit simulations, and measurements are performed to optimize the PMOS transistor current drive and CMOS circuit speed. We show that trading PMOS transistor V_th for a smaller L_min results in faster circuits for low supply voltage (3.3 to 1.8 V) n⁺-polysilicon gate CMOS technology, Circuit simulation and measurements are performed in this study. Approximate empirical expressions are given for the optimum buried channel PMOS transistor V _th for minimizing CMOS circuit speed for cases involving: (1) constant capacitive load and (2) load capacitance proportional to MOS gate capacitance. The results of the numerical exercise are applied to the centering of device parameters of a 0.5 μm 3.3 V CMOS technology that (a) matches the speed of our 0.5 μm 5 V CMOS technology, and (b) achieves good performance down to 1.8 V power supply. For this process the optimum PMOS transistor V_th (absolute value) is approximately 0.85-0.90 V