Future contributions toJournal of Crystallographic and Spectroscopic Research

Future contributions toJournal of Crystallographic and Spectroscopic Research     

On the geometries of the rational unfoldings of X k

With a view to applications to self-regulating dynamical processes in biology, we determine the geometric structure of what we call isotangent curves, i.e. curves parametrized by the slopes of their points. They come up naturally as bifurcation curves of rational unfoldings of X ^k, and we classify them according to degree and number of cusps. They, as well as their isotangent involute curves, turn up in simulations of these processes.     

Synthesis and X-ray analysis of 1-((1S)-phenylethyl)-azetidine-(2R)-piperidinamide

The crystal and molecular structure of a new azetidine-2-carboxylic amide derivative is described. The structure was solved by direct methods and refined by least squares methods toR1=0.0393 for 4264 reflections (withI>2(I)) The structure consists of two independent molecules which are chemically the same with slight differences in geometry. Crystal data: C₁₇H₂₄N₂O, monoclinic, space groupP2₁,a=8.3782(4),b=20.0342(13),c=9.7769(8) Å, =109.687(6)°,V=1545.1(2)ų,Z=4.     

The expected time to end the tug-of-war in a wedge

Using a solution of a nonhomogeneous partial differential equation involving the p-Laplacian, we study the finiteness of the expected time to end the tug-of-war in a wedge.     

Chelating 2,2′-Diaminodiethylamine Cellulose Filters and X-ray Fluorescence for Preconcentration and Trace Analysis of Natural Waters

Abstract

The 2,2′-diaminodiethylamine (DEN) functional group can be expected to have ideal properties for the chelation of transition metals and their collection from aqueous solutions, independent of the alkali and alkaline earth ions concentration. Introducing DEN into cellulose filters allows straightforward preconcentration of trace cations by a simple filtration step, and the DEN-filter constitutes a suitable target for X-ray fluorescence (XRF) analysis. The linearity between the XRF-response on the loaded DEN-filter and the trace cation concentration in the solution appears excellent, up to a total filter capacity of ca. 3 μeq.cm^?2. The detection limits are around 0.5 μg. l^?1 in most practical cases. Accuracy and precision are around 10%. The applicability of the proposed procedure is illustrated on a comparative basis by XRF-analysis of drinking water and surface water, after preconcentration by DEN-filtration and by alternative procedures.     

Experimental determination of k 0 , Q 0 , \bar{E}_{r} factors and neutron cross-sections for 41 isotopes of interest in Neutron Activation Analysis

The k ₀ -literature has been reviewed every decade but some of its nuclear data is still more than 30 years old. Sometimes Q ₀ values were adopted from the nuclear data at that time or were experimentally determined by only 1 laboratory. Other isotopes were listed with accurate pairs of (k ₀ , Q ₀ ) values but were also quoted as candidates for redetermination for different reasons (i.e. imprecise cadmium transmission factors, half-lives). In this work we aim at the experimental re-determination of k ₀ and Q ₀ values for 41 isotopes of analytical interest while introducing a methodology for simultaneous $ \bar{E}_{r} $ and Q ₀ determination employing N irradiation channels. In order to satisfy the metrological level required, up to 12 repeats per standard were irradiated in up to 4 irradiation channels of the Belgian Reactor 1 (BR1, SCK?CEN) having a wide spread in neutron characteristics. Our relative percentile differences to the literature values were usually ≤10 % for Q ₀ factors, ≥25 % for $ \bar{E}_{r} $ values and ≤4 % for k ₀ values. Our precision and accuracy are discussed thoroughly.     

Experimental k 0 and k 0-fission factors for the determination of the n(235U)/n(238U) enrichment levels and correction for 235U fission interferences in samples containing uranium

In 2010 we investigated the applicability of the current k ₀ and k ₀-fission factors for the determination of the n(²³⁵U)/n(²³⁸U) isotopic ratio in multi-elemental samples containing uranium. An overestimation 3–4 % was observed in our determinations when employing the recommended 2003 k ₀-literature. After a recalibration of all our laboratory instruments, a 3 % overestimation was still observed in this work when employing this nuclear data. Therefore we aimed at the experimental re-determination of these composite nuclear constants in order to enhance the reliability of the isotopic ratio determination method and the accuracy of our data-filtering algorithms. New k ₀-fission factors are given for 7 nuclides that are not currently present in the 2012 k ₀-database. Several additional k ₀ factors are introduced for some nuclides in this library. Our k ₀ results are also compared with those recently reported by Blaauw et al.