Cascade Schemes Research Articles

Transmission Electron Microscopy Applied to Water Fractionation Studies - A New Look at DOC

Abstract Research on the particle-mediated transport of “bound pollutants” tends to be conducted in the absence of a proper definition of particle and with a minimal consideration of colloidal phenomena. Recent developments in the use of transmission electron microscopy to monitor water fractionation schemes are providing a technology to correct this situation. This review summarizes the current status of the routine application of TEM in monitoring such schemes and in extending them into new areas of water research. It summarizes new findings on DOC relating to the extensive interpenetration of aggregated DOC “particles” with their aquatic milieu. Also, it relates colloidal phenomena to artifact generation in filter cascade schemes and in "particle-pollutant" interaction experiments. The usefulness of TEM in defining the ultrastructure of carbon-rich particulate materials and in elucidating colloid-particle interactions is demonstrated, as is the relevance of such measures to understanding pollutant dispersion.

Evaluation of inferential and parallel cascade schemes for distillation control

Evaluation of inferential and parallel cascade schemes for distillation control

New cascade analysis techniques for determining spontaneous atomic transition probabilities

Several new analysis techniques which account for the effects of cascades in the measurement of atomic transition probabilities have been developed at the University of Toledo, and will be described here. These techniques involve the incorporation of information from the direct measurement of the decay curves of cascading transitions into the analysis of the decay curve of the main level of interest. The traditional curve fitting techniques, as well as the new analysis techniques, are investigated by the use of computer simulated data containing various numbers of known exponentials. A diagrammatic mnemonic which trivially generates the theoretical decay curves for cascade schemes of arbitrary complexity will be described. The traditional curve fitting techniques are extended to include constraints imposed by the coefficients in the theoretical decay curve, which can be measured in terms of relative intensities of the cascading transitions. The population differential equation is converted to an integral equation involving only experimentally measurable quantities and the desired transition probability. Integrals over some arbitrary time interval of the decay curves can be photometrically measured, and given a common normalization through a wavelength relative efficiency calibration of the detection system. Integrated decay curves of all transitions, either directly into or out of the level of interest, can be summed in a manner which determines its transition probability. By varying the choice of time interval it can be verified that all contributing transitions have been correctly included. A variation of this technique allows the construction of the decay curve of an unmeasured cascade, provided the transition probability of the level into which it cascades is known. This variation can be used to investigate radiationless transitions and transitions outside the range of available detectors. Further, if there is additional a priori information concerning the shape of the unseen cascade decay curve, both its litetime and that level into which it cascades can be determined.

Optimum Conditions for the Dual Temperature Exchange Process of Producing Heavy Water

The equations which represent the head-separation factors of the dual-temperature-exchange columns are derived and the optimum operating conditions for them as well as the design of the columns to bring about the following four possible cascade schemes are discussed.Cascade Schemes:Non-Mixing cascade (Cf. Fig. 3)The stripped output from the second stage enters the top of the enriching column together with the enriched output from the first stage.Scheme 1: Gas is circulated.Scheme 2: Liquid is circulated.Mixing cascade (Cf. Fig. 4)The stripped output from the second stage enters the top of the stripping column.Scheme 3 Gas is circulated.Scheme 4: Liquid is circulated.Assumptions:(1) Only the low-deuterium-content region is made the subject of study.(2) Liquid-phase catalysts may be employed in these cascades, although no catalyst will be necessary in water-H2 S system.(3) The cross sectional area of each column is proportional to its gas throughput.(4) The stage variables (γ, N, n, δ, Tl, Th, etc.) are constant throughout each of the entire cascades.Summaries of the results obtained are as follows:(1) The head separation factors β are given by the following equations, Scheme 1:Scheme 2:Scheme 3:Scheme 4:(2) The total volumes of the enriching and stripping columns, V, are given by:Scheme 1:Scheme 2:Scheme 3:Scheme 4:(3) Some numerical calculations are carried out for each of the cascade schemes and the following results are obtained.a) There is an optimum condition for the minimum total volume of the cascade, and it depends upon the variables of each stage.b) The liquid circulating cascade is preferable to the gas circulating cascade.c) If the cost of feed may be left out of consideration, the cascade of Scheme 4 will be the most preferable, as shown in Table 1.

The Radiative Capture of Alpha Particles in15N

The 15N(α, γ)19F reaction has been examined with bombarding energy from 1.2 to 2.35 MeV. Three resonances have been found, two narrow and one of measurable width. The cascade schemes at each of the resonances have been partly elucidated, and the partial radiative widths of the resonances have been determined, except for a statistical factor. Some of the angular distributions have been measured, and conclusions have been drawn about the possible values of the spins and parities of the levels concerned. The relation of these results to the predictions of Elliott and Flowers is briefly discussed.