Construction of a pulsed perforated-plate extraction unit

Liquid-liquid extraction is an important operation in the production and reprocessing of nuclear fuels. In the purification of uranium by liquid-liquid extraction, uranyl nitrate is separated from impurities by extraction into an organic solvent, followed by re-extraction into an aqueous phase. Further processing of the aqueous uranyl nitrate solution is tailored to yield uranium metal or any desired uranium compound. In order that students in nuclear and chemical engineering may have an understanding of the practical as well as theoretical aspects of liquid-liquid extraction, a model of a uranium purification plant was designed and built in the Unit Operations Laboratory of the Missouri School of Mines and Metallurgy. For reasons of safety, the system used in the model could not include radioactive materials or heavy metals; therefore, the chemical processing of nuclear fuels was illustrated using methanol, trichloroethylene, and water. The model includes a rotating disc extraction column and a pulsed perforated-plate column for carrying out separations based on solubility relationships, and a bubble cap distillation column in which separations are based on vapor pressure differences. Methanol (representing uranyl nitrate) was extracted from a methanol-trichloroethylene solution (representing the impure uranyl nitrate solution) into a water phase (which represented the organic solvent). The resulting methanol-water solution was separated in a distillation column which represented the re-extraction of uranyl nitrate into an aqueous phase. The model unit was highly instrumented to illustrate the use and operation of control instruments and to provide a permanent record of important variables. Analytical instruments were included to provide additional information necessary to the study of material and energy relationships. The extraction and distillation columns were glass to allow visual observation of their operation. The objectives of this investigation were: to construct a pulsed perforated-plate extraction column and associated equipment which, together with the rotating disc column, comprise the extraction unit; to prepare operating instructions; and to perform preliminary experiments in the equipment --Introduction, pages 1-2

Questions to Americans from Latin Americans

The following are some of the more stereotyped questions about the United States that are often in the minds of the people and are reflected in publica­tions in Latin America. They all have a thread of logic; some are Communist-inspired, some are not

Radium ion: A possible candidate for measuring atomic parity violation

Single trapped and laser cooled Radium ion as a possible candidate for measuring the parity violation induced frequency shift has been discussed here. Even though the technique to be used is similar to that proposed by Fortson [1], Radium has its own advantages and disadvantages. The most attractive part of Radium ion as compared to that of Barium ion is its mass which comes along with added complexity of instability as well as other issues which are discussed hereComment: Conference proceedin

Summer distribution and abundance of the giant devil ray (<em>Mobula mobular</em>) in the Adriatic Sea: Baseline data for an iterative management framework

The giant devil ray (Mobula mobular) is a poorly understood protected endemic species of the eastern Atlantic-Mediterranean region. However, to date there are no range-wide management actions in place. This paper provides the first overview of the summer distribution and abundance of this species and other Myliobatiformes within the Adriatic Sea based on an aerial survey. Although the survey´s primary targets were cetaceans and sea turtles, the study showed that it was possible to use the survey to monitor other species. Abundance estimates are derived using conventional distance sampling analysis. Giant devil rays were observed mainly in the central-southern Adriatic (88% of total sightings). A total of 1595 giant devil rays were estimated in the central-southern Adriatic Sea [coefficient of variation(CV)=25%, uncorrected estimate for perception and availability bias]. When corrected for availability bias the number of specimens was estimated at 3255 (CV=56%). Population growth rate was estimated using life history traits and a sensitivity analysis was conducted to evaluate the benefit of improving biological knowledge on this data-poor species. A power analysis showed that a long-term commitment to an aerial survey would be necessary to monitor population trends. Conservation implications and future work, including how the study could be used to conduct an ecological risk assessment are discussed

Finality revived: powers and intentionality

Proponents of physical intentionality argue that the classic hallmarks of intentionality highlighted by Brentano are also found in purely physical powers. Critics worry that this idea is metaphysically obscure at best, and at worst leads to panpsychism or animism. I examine the debate in detail, finding both confusion and illumination in the physical intentionalist thesis. Analysing a number of the canonical features of intentionality, I show that they all point to one overarching phenomenon of which both the mental and the physical are kinds, namely finality. This is the finality of ‘final causes’, the long-discarded idea of universal action for an end to which recent proponents of physical intentionality are in fact pointing whether or not they realise it. I explain finality in terms of the concept of specific indifference, arguing that in the case of the mental, specific indifference is realised by the process of abstraction, which has no correlate in the case of physical powers. This analysis, I conclude, reveals both the strength and weakness of rational creatures such as us, as well as demystifying (albeit only partly) the way in which powers work

Nuclear Anapole Moments

Nuclear anapole moments are parity-odd, time-reversal-even E1 moments of the electromagnetic current operator. Although the existence of this moment was recognized theoretically soon after the discovery of parity nonconservation (PNC), its experimental isolation was achieved only recently, when a new level of precision was reached in a measurement of the hyperfine dependence of atomic PNC in 133Cs. An important anapole moment bound in 205Tl also exists. In this paper, we present the details of the first calculation of these anapole moments in the framework commonly used in other studies of hadronic PNC, a meson exchange potential that includes long-range pion exchange and enough degrees of freedom to describe the five independent $S-P$ amplitudes induced by short-range interactions. The resulting contributions of pi-, rho-, and omega-exchange to the single-nucleon anapole moment, to parity admixtures in the nuclear ground state, and to PNC exchange currents are evaluated, using configuration-mixed shell-model wave functions. The experimental anapole moment constraints on the PNC meson-nucleon coupling constants are derived and compared with those from other tests of the hadronic weak interaction. While the bounds obtained from the anapole moment results are consistent with the broad ``reasonable ranges'' defined by theory, they are not in good agreement with the constraints from the other experiments. We explore possible explanations for the discrepancy and comment on the potential importance of new experiments.Comment: 53 pages; 10 figures; revtex; submitted to Phys Rev

Ebola virus disease: an update on post-exposure prophylaxis

The massive outbreak of Ebola virus disease in west Africa between 2013 and 2016 resulted in intense efforts to evaluate the efficacy of several specific countermeasures developed through years of preclinical work, including the first clinical trials for therapeutics and vaccines. In this Review, we discuss how the experience and data generated from that outbreak have helped to advance the understanding of the use of these countermeasures for post-exposure prophylaxis against Ebola virus infection. In future outbreaks, post-exposure prophylaxis could play an important part in reducing community transmission of Ebola virus by providing more immediate protection than does immunisation as well as providing additional protection for health-care workers who are inadvertently exposed over the course of their work. We propose provisional guidance for use of post-exposure prophylaxis in Ebola virus disease and identify the priorities for future preparedness and further research