Comparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material,during a comparative nuclear forensics exercise

Journal of Radioanalytical and Nuclear Chemistry - This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear...     

The Site‐Assembly Determines Catalytic Activity of Nanoparticles

Heterogeneous catalysts are often designed as metal nanoparticles supported on oxide surfaces. Here, the relation between particle morphology and reaction kinetics is investigated by scaling relation kinetic Monte Carlo simulations using CO oxidation over Pt nanoparticles as a model reaction. We find that different particle morphologies result in vastly different catalytic activities. The activity is strongly affected by kinetic couplings between sites, and a wide site distribution generally enhances the activity. The present study highlights the role of site‐assemblies as a concept that, in addition to isolated active sites, can be used to understand catalytic reactions over nanoparticles.     

Wilson's functional equation on C

Summary We find the complete set of continuous solutionsf, g of Wilson's functional equation _{n = 0} ^{N – 1} f(x + wⁿy) = Nf(x)g(y), x, y C, given a primitiveN ^th rootw of unity.Disregarding the trivial solutionf = 0 andg any complex function, it is known thatg satisfies a version of d'Alembert's functional equation and so has the formg(z) = g (z) = N^–1 _{n = 0} ^{N – 1} E(wⁿz) for some C². HereE ₍₁, ₂)(x + iy) = exp( ₁x + ₂).For fixedg = g the space of solutionsf of Wilson's functional equation can be decomposed into theN isotypic subspaces for the action of Z _N on the continuous functions on C. We prove that ther ^th component, wherer {0, 1, ,N – 1}, of any solution satisfies the signed functional equation _{n = 0} ^{N – 1} f(x + wⁿy)w^nr = Ng(x)f(y), x, y C. We compute the solution spaces of each of these signed equations: They are 1-dimensional and spanned byz _{n = 0} ^{N – 1} w^nr E(wⁿz), except forg = 1 andr 0 where they are spanned by andz ^{N – r}. Adding the components we get the solution of Wilson's equation. Analogous results are obtained with the action ofZ _N on C replaced by that ofSO(2).The case ofg = 0 in the signed equations is special and solved separately both for Z _N andSO(2).     

Schauder decompositions and functional calculus

We establish a functional calculus, with nice properties, for one and several continuous operators on some non-normable locally convex spaces, more specifically, for operators on the space of entire functions and on other power series spaces. In particular we obtain spectral mapping theorems. The calculus rests on Schauder decompositions for the spaces under consideration, which are of independent interest.     

Principles for different modes of multiple-injection CZE

This paper introduces four different modes of multiple-injection CZE (MICZE). The validity of these MICZE models was evaluated by the experimental data. Prior to the application of MICZE, the electrophoretic conditions are developed in the single-injection mode by adjusting different experimental parameters such as pH, type and concentration of buffer additives and temperature. Based on the migration time difference (Deltatmig) between the analyte and the internal standard or injection marker, one or more MICZE modes can be employed. The injection marker is added to the sample to compensate for injection-volume fluctuations. The inter-plug distance is regulated by applying an electrical field over the capillary for a short period of time between each injection. After the final injection, the separation is completed by electrophoresis for a time period corresponding to that in the single-injection mode.     

Evaluation of a glucose sensing antibody using weak affinity chromatography

Continuous monitoring of drug levels and endogenous molecules in biological fluids is a developing research area with many applications. One example is the need to improve life for millions of diabetes mellitus patients by continuously monitoring the glucose level. In order to have a dynamic response, the recognition molecule in a continuous sensor should preferentially have a fast dissociation rate and a dissociation constant in the millimolar range. We have evaluated the monoclonal antibody (mAb) 3F1E8-A2 for its potential to be used in a future glucose sensor application. The mAb was generated from hybridomas by immunizing mice with 10 kDa dextran (an alpha1,6-glucose polymer) with the aim of obtaining mAbs that can recognize the glucose monomer. The mAb was immobilized to macroporous silica and the interaction with dextran-derived oligosaccharides was evaluated with weak affinity chromatography (WAC). To measure the low affinities between the mAb 3F1E8-A2 and different monosaccharides, a competitive weak affinity chromatography approach was employed. It was found that the mAb had a higher specificity for glucose compared with other monosaccharides and the dissociation constant (K(d)) towards glucose was determined as 18.8 +/- 2.6 mm.     

Calculated electronic transitions in sulfuric acid and implications for its photodissociation in the atmosphere

We have calculated electronic transitions for sulfuric acid in the ultraviolet region using a hierarchy of coupled cluster response functions and correlation consistent basis sets. Our calculations indicate that the lowest energy singlet transition occurs at 8.42 eV with an oscillator strength of 0.01. The lowest energy triplet state occurs at 8.24 eV. Thus, the cross section of sulfuric acid in the actinic region is likely to be very small and smaller than the upper limit put on this cross section by previous experimental investigations. We estimate the cross section of sulfuric acid in the atmospherically relevant Lyman-alpha region ( approximately 10.2 eV) to be approximately 6 x 10 (-17) cm (2) molecule (-1), a value approximately 30 times larger than the speculative value used in previous atmospheric simulations. We have calculated the J values for photodissociation of sulfuric acid with absorption of visible, UV, and Lyman-alpha radiation, at altitudes between 30 and 100 km. We find that the dominant photodissociation mechanism of sulfuric acid below 70 km is absorption in the visible region by OH stretching overtone transitions, whereas above 70 km, absorption of Lyman-alpha radiation by high energy Rydberg excited states is the favored mechanism. The low lying electronic transitions of sulfuric acid in the UV region do not contribute significantly to its dissociation at any altitude.     

Decontamination of chemical warfare agents using perchloroethylene–Marlowet IHF–H2O-based microemulsions: wetting and extraction properties on realistic surfaces

At the present time, considerable efforts are being made to develop new media for the decontamination of a variety of toxic compounds. In the present contribution, new microemulsions with promising properties are presented. Moreover, the decontamination of surfaces, with an emphasis on varnished metal surfaces of exterior and interior equipment, is investigated using these microemulsions. Studies of the phase behavior of the system water–perchloroethylene–IHF–2-propanol are reported and the microemulsion phases are recognized. The wetting behavior on contaminated surfaces and the extraction capabilities with respect to contaminants are essential for an efficient decontamination. Hence, suitable microemulsions are identified on the basis of these properties. The decontamination efficiency of these microemulsions is first estimated on the basis of the ability to wet typical chemical nonresistant varnished steel sheets, which are authentic model systems for real surfaces. Afterwards, promising microemulsions and, as reference, different solvents are tested with respect to their capability to solubilize sulfur-mustard agent, again using realistic surfaces contaminated with this chemical warfare agent. Several microemulsions are found, which have the desired properties.     

One-pot organocatalytic domino Michael/alpha-alkylation reactions: direct catalytic enantioselective cyclopropanation and cyclopentanation reactions

The development of one-pot organocatalytic domino Michael/alpha-alkylation reactions between bromomalonates or bromoacetoacetate esters and alpha,beta-unsaturated aldehydes is presented. The chiral-amine-catalyzed reactions with bromomalonates as substrates give access to the corresponding 2-formylcyclopropane derivatives in high yields with excellent diastereoselectivity and up to 99 % ee. The catalytic domino Michael/alpha-alkylation reactions between 4-bromo-acetoacetate and enals provide a route for the synthesis of functionalized cyclopentanones in good to high yields with 93-99 % ee. The products from the organocatalytic reactions were also reduced with high diastereoselectivity to the corresponding cyclopropanols and cyclopentanols, respectively. Moreover, one-pot combinations of amine and heterocyclic carbene catalysis (AHCC) enabled the highly enantioselective synthesis of beta-malonate esters (91-97 % ee) from the reaction between bromomalonates and enals. The tandem catalysis included the catalytic domino reaction followed by catalytic in situ chemoselective ring-opening of the 2-formylcyclopropane intermediates.