Transient operation of a catalytic liquid-liquid plug flow reactor for kinetics measurements

A centrifugal partition chromatograph (CPC) was used as a liquid-liquid catalytic reactor for the isomerisation of hexen-3-ol into ethylpropylketone with a water soluble rhodium catalyst. Global mass transfer coefficients were measured and shown to depend on both the nature of the solute and the flow rate. Liquid-liquid partition isotherms were also determined with the CPC using elution chromatography. Finally, a reactor model was derived to account for the experimental results obtained both under stationary and transient (pulse) conditions. A parameter sensitivity evaluation is also presented.     

Simultaneous design of power stage and controller for switchingpower supplies

This paper develops a method for simultaneously designing the power stage and controller for a switching power supply. The method utilizes a numerical optimization procedure, which facilitates computer-aided design. It is found that better performance can be achieved than with a traditional two-step design process, where the power stage and controller are designed sequentially. Optimization and simulation results for a buck power converter are presented to illustrate the design process and benefits     

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     

Molecular analysis of chromosomal polymorphism in the South American cricetid, Graomys griseoflavus

Graomys griseoflavus is a South American phyllotine rodent widespread in Argentina that shows a high frequency of Robertsonian fusions (RFs). DNA restriction with EcoRI produced a 250-bp repeated family (EG250) specific for the genus. Southern hybridization and sequencing analysis indicate that the EG250 family is heterogeneous, comprising at least two subfamilies. In situ hybridized EG250 probe showed a centromere location in almost all chromosomes. In all karyomorphs C-banding was negative, but restriction enzyme banding (Re-banding) with Alul and Mbol showed centromeric blocks in the autosomes that will generate Robertsonian fusions. Thus, we found three groups of chromosomes: (a) EG250 and Re-banding negative; (b) EG250 positive and Re-banding negative; and (c) EG250 and Re-banding positive. We consider that group (b) is more the result of chromatin condensation state than that of the frequency of recognition sites for the enzymes used. Restriction enzyme blocks would appear in regions with heterochromatic EG250 subfamilies, while lack of banding would be due to decondensed EG250 subfamilies becoming an easier target for chromosomal restriction. It is suggested that heterochromatic EG250 DNA provides a favourable molecular environment for Robertsonian fusion occurrence.     

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