Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime

Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed.     

Electro-optic sampling system for the testing of high-speedintegrated circuits using a free running solid-state laser

This paper deals with the indirect electro-optic sampling technique for the low-invasive detection of periodical voltage waveforms on lines in high-speed integrated circuits. The system introduced here is based on a passive mode-coupled Ti:Sapphire-Laser as light source for generating optical pulses in the subpicosecond regime. Therefore, we have to synchronize the resulting electric measurement signal and its external trigger onto the pulse repetition rate of this free running solid-state laser. The multi user function of the laser system forces us to transmit the pulses via a single-mode fiber into the measurement setup. For that purpose we developed a special optical arrangement to minimize the widening of the pulses in the time domain. The system's high-temporal resolution of nearly 10 ps in combination with its high-voltage sensitivity of about 800 μV/√(Hz) is demonstrated by measurements of an integrated microwave frequency divider     

Clinical applications of cytokines in pediatrics

The use of adjuvants for immunopotentiation has been investigated since the 1920s and a number of comprehensive reviews and monographs have been published on this subject. A recent trend in immunopotentiation has been the use of delivery systems which allow for sustained or controlled release of antigens and which induce prolonged immunity following a single dose. This concept has been termed either single-step or single-shot immunization. The delivery system has been modulated to potentiate the immune response either by delivering the antigen (and perhaps an adjuvant or adjuvants) either over a prolonged period of time or in a predetermined sequence or by incorporating substances with immunoadjuvant properties (e.g., lecithin and certain biodegradable polymers) as carriers within the delivery system. This Review focuses on the progress made in the design of delivery systems for immunopotentiation. Particular emphasis is given to delivery systems designed to achieve single-step immunization.     

High fibre bread containing brewer's spent grains and its effect on lipid metabolism in rats

Bread samples containing milled brewer's spent grain (BSG) at levels of 10–25% were prepared. The protein content of the bread ws found to be 15.4, 16.3 and 18.8%, when BSG was added at levels of 10, 20 and 25%, respectively. Fibre content however was 4.9, 6.4 and 7.5%, repectively. Amino acid pattern of the bread samples revealed that most of the essential amino acids were found in considerable amounts compared to the FAO provisional pattern with exception to lysine, threonine and tryptophan which showed deficiencies. The bread samples were fed to rats for 28 days, after which total lipids and cholesterol were measured. The results indicated impaired growth weight (7.1–10.0%) compared with the control. Total lipids as well as total cholesterol were also reduced by 5.7–8.0% and 6.0–8.3%, respectively. Sensory evaluations of prepared bread showed high score acceptance for fino bread, rolls and baton salie amounted to 70.0, 63.0 and 62.7%, respectively.     

Reliability and performance analysis of time – space – time switching networks with multiple separated space switches

Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches.     

Depth of intergranular oxygen diffusion during environment-dependent fatigue crack growth in alloy 718

The elevated-temperture fatigue crack growth behavior in alloy 718, when subjected to a loading frequency lower than the transitional frequency of this alloy, is viewed as fully environment dependent. In this process, the crack growth increment per loading cycle is assumed to be equal to the intergranular oxygen diffusion depth at the crack tip during the cycle effective oxidation time. In order to identify the trend of this diffusion depth an experimental program was carried out on compact tension specimens made of alloy 718 at 650 °C in which fatigue crack growth measurements were made for cyclic load conditions with and without hold time periods at minimum load level. This work resulted in establishing a relationship correlating the intergranular oxygen diffusion depth and the value of the stress intensity factor range ΔK. This relationship, when integrated over the cycle effective oxidation time, results in a closed-form solution describing the environment-dependent fatigue crack growth rate. A comparison is made between the results of this solution when applied to different loading frequencies and the corresponding experimental results. This comparison shows good agreement between the two sets of results. Furthermore, by combining the parabolic rate law of diffusion and the equation for the intergranular oxygen diffusion depth, an explicit expression for the oxygen diffusivity of grain boundaries is derived. It is found that this diffusivity is both a ΔK- and a frequency-dependent parameter.     

Parallel simulated annealing for power system decomposition

This paper proposes a parallel optimization approach to power system decomposition for voltage control. In this paper, a parallel simulated annealing (PSA) technique is developed to decompose power systems so that subsystems are equally separated in terms of the number of nodes and control variables. System decomposition is one of difficult discrete number combinatorial problems. The PSA technique provides better solutions than the conventional SA because of searching a solution near a global minimum over a wide range. The proposed method is tested in IEEE 30, 57, and 118 node systems