Phosphinimines as potential technetium environmental sensors

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on September 4, 2007)Vita.Includes bibliographical references.Thesis (Ph. D.) University of Missouri-Columbia 2007.Dissertations, Academic -- University of Missouri--Columbia -- Chemistry.Phosphinimines, R₃P=NSiMe₃, undergo hydrolysis to form the phosphiniminiumcation, R₃P=NH₂+, which forms the ion pair [R₃P=NH₂+][X-] in the presence of an anion.Preliminary studies show that in the presence of TcO₄-, Ph₃P=NSiMe₃ forms [Ph₃P=NH₂+][TcO₄-] and [Ph₃P=NH₂+] is selective for TcO₄- over other anions.Technetium-99 is present as environmental contamination in the form of ⁹⁹TcO₄-, which is extremely mobile. Currently available methods to measure this contamination are time consuming and tedious. A method to preconcentrate and measure ⁹⁹Tc environmental contamination in a quick and efficient manner is needed. The selectivity of the phosphiniminium cation for TcO₄- may make phosphinimines suitable for such preconcentration and possibly for measurement. Several phosphinimines were synthesized and characterized for their stability and selectivity with ⁹⁹TcO₄-, including Ph₃P=NSiMe₃, (9-anthracenyl)Ph₂P=NSiMe₃, (1-napthyl)Ph₂P=NSiMe₃, and (p-COOMe)C₆H₄Ph₂P=NSiMe₃. (9-anthracenyl)Ph₂P=NSiMe₃ and (1-napthyl)Ph₂P=NSiMe₃ include possible reporter groups and (p-COOMe)C₆H₄Ph₂P=NSiMe₃ contains a linking moiety for incorporating reporter groups or attaching the phosphinimine to a polymer support. The use of internal and external reporter groups to generate a signal in the presence of TcO₄- is also investigated

Fourier transform based procedure for investigations on the grid frequency signal

The continuous growth of PV and wind sources makes the inertia of power systems decrease and creates larger frequency deviations. Frequency oscillation is a stochastic signal and, consequently, it could be complex to compare the effectiveness of different control approaches devoted to manage this problem. In this paper a Fourier transform procedure is proposed in order to define a standard frequency oscillation and to set up the dynamic model of the electric grid. The final goal is to numerically simulate a realistic transient behavior; using this grid, such a model results to be the ideal starting point for evaluating the effectiveness of different possible approaches to manage the energy balance problem

Dynamic phasors to enable distributed real-time simulation

© 2017 IEEE. Distributed real-time simulation allows the sharing of simulator equipment and components connected in Hardware-In-the-Loop experiments. In this paper, we analyze the challenges of geographically distributed real-time power system simulation and how dynamic phasors could be applied to improve the accuracy of the simulation results for large time steps. The time step is of particular interest since the communication delay between simulators interconnected through wide area network is much larger than the simulation time step typically used in electromagnetic transient real-time simulations. However, commercially available real-time simulators use either the electromagnetic transient or classic complex phasor representation. Results in the dynamic phasor and electromagnetic transient domain are compared to quantify the advantage of dynamic phasor simulations in practice. The test platform for this evaluation is a power system simulator which is currently under development

Uranium: The problem, or the solution?

Abstract only availableUranium is of great importance as a nuclear fuel and is used to generate electrical power, produce isotopes, and to make weapons. The possibility of developing a realistic flow scheme for nuclear fuel reprocessing or separation for segregation is one that the Chemistry Department at MU consistently looks into. One way to better optimize waste extraction is to possibly bind two separate functional groups to uranyl(VI) [UO22+] so that the reactions will occur selectively. The product of interest is a mixed uranyl iodide/amide and is a novel uranium compound generated for further study. This is accomplished with the following reactions. UO3 --TfOTf--- UO2(OTf)2 UO2I2(THF)3 + 2KOTfUO2(OTf)2 + 2KI ---THF---- UO2I[N(SiMe3)] + KIUO2I2(THF)3 + K[N(SiMe3)3] ----THF- After completing the reactions under an inert atmosphere, an orange product formed. The next step in this research requires NMR analysis and X-Ray crystallography to determine if this product is the target molecule desired.NSF-REU Radiochemistr

Properties of graphene-related materials controlling the thermal conductivity of their polymer nanocomposites

Different types of graphene-related materials (GRM) are industrially available and have been exploited for thermal conductivity enhancement in polymers. These include materials with very different features, in terms of thickness, lateral size and composition, especially concerning the oxygen to carbon ratio and the possible presence of surface functionalization. Due to the variability of GRM properties, the differences in polymer nanocomposites preparation methods and the microstructures obtained, a large scatter of thermal conductivity performance is found in literature. However, detailed correlations between GRM-based nanocomposites features, including nanoplatelets thickness and size, defectiveness, composition and dispersion, with their thermal conductivity remain mostly undefined. In the present paper, the thermal conductivity of GRM-based polymer nanocomposites, prepared by melt polymerization of cyclic polybutylene terephtalate oligomers and exploiting 13 different GRM grades, was investigated. The selected GRM, covering a wide range of specific surface area, size and defectiveness, secure a sound basis for the understanding of the effect of GRM properties on the thermal conductivity of their relevant polymer nanocomposites. Indeed, the obtained thermal conductivity appeares to depend on the interplay between the above GRM feature. In particular, the combination of low GRM defectiveness and high filler percolation density was found to maximize the thermal conductivity of nanocomposites

Influence of Different Dry-Mixing Techniques on the Mechanical, Thermal and Electrical Behavior of Ultra High Molecular Weight Polyethylene/Exhausted Tire Carbon Composites

The mechanical, thermal and electrical behavior of ultra high molecular weight (UHMWPE) composites containing different amount of pyrolyzed exhausted tire carbon (ETC) is investigated. Composites were obtained by dry-mixing the powders with a homogenizer and an impact mill. The results clearly indicate that, by changing the mixing method, it is possible to tune the rheological and morphological characteristics of the composites and in turn their mechanical, thermal and electrical properties. Better performances were observed for the composites obtained with the impact mill, which showed improved Young modulus, reduced electrical and thermal resistance with respect to those of homogenized counterparts. All the composites exhibited a relevant decrease of electrical resistivity

Efficacy of adalimumab as second-line therapy in a pediatric cohort of crohn’s disease patients who failed infliximab therapy: The Italian society of pediatric gastroenterology, hepatology, and nutrition experience

Background: Adalimumab (Ada) treatment is an available option for pediatric Crohn’s disease (CD) and the published experience as rescue therapy is limited. Objectives: We investigated Ada efficacy in a retrospective, pediatric CD cohort who had failed previous infliximab treatment, with a minimum follow-up of 6 months. Methods: In this multicenter study, data on demographics, clinical activity, growth, laboratory values (CRP) and adverse events were collected from CD patients during follow-up. Clinical remission (CR) and response were defined with Pediatric CD Activity Index (PCDAI) score ≤10 and a decrease in PCDAI score of ≥12.5 from baseline, respectively. Results: A total of 44 patients were consecutively recruited (mean age 14.8 years): 34 of 44 (77%) had active disease (mean PCDAI score 24.5) at the time of Ada administration, with a mean disease duration of 3.4 (range 0.3–11.2) years. At 6, 12, and 18 months, out of the total of the enrolled population, CR rates were 55%, 78%, and 52%, respectively, with a significant decrease in PCDAI scores (P<0.01) and mean CRP values (mean CRP 5.7 and 2.4 mL/dL, respectively; P<0.01) at the end of follow-up. Steroid-free remission rates, considered as the total number of patients in CR who were not using steroids at the end of this study, were 93%, 95%, and 96% in 44 patients at 6, 12, and 18 months, respectively. No significant differences in growth parameters were detected. In univariate analysis of variables related to Ada efficacy, we found that only a disease duration >2 years was negatively correlated with final PCDAI score (P<0.01). Two serious adverse events were recorded: 1 meningitis and 1 medulloblastoma. Conclusion: Our data confirm Ada efficacy in pediatric patients as second-line biological therapy after infliximab failure. Longer-term prospective data are warranted to define general effectiveness and safety in pediatric CD patients

A multi-layer extension of the stochastic heat equation

Motivated by recent developments on solvable directed polymer models, we define a 'multi-layer' extension of the stochastic heat equation involving non-intersecting Brownian motions.Comment: v4: substantially extended and revised versio