Synchrotron μ‐XRF study on compositional uniformity of uranium–thorium oxide pellets prepared by different processes

A μ‐XRF study to assess the distribution of uranium and thorium in (U,Th)O₂ pellets covering the composition of advanced heavy water reactor (AHWR) fuel pellets prepared by powder metallurgical compaction (PMC) and coated agglomerate pelletization (CAP) routes was made using micro‐focus beam line (BL‐16) of Indus‐2 synchrotron radiation facility. The methodology thus developed was successfully applied to these pellets. The study reveals that the uranium distribution in pellets prepared by PMC route is uniform, whereas the pellets prepared through CAP route have a wide range of compositional variation. In addition, the uniformity in CAP route‐prepared pellets improves with increase in the relative amount of uranium in the pellets. The sample preparation in present methodology is very simple compared with scanning electron microscopy. The study reveals the utility of synchrotron‐based μ‐XRF for fuel pellet characterization of AHWR reactors. Alhough CAP route of fuel pellet preparation requires less exposure of personnel to high radiation dose, the non‐uniformity in the fuel pellet must be considered when using these pellets in reactors. Copyright © 2014 John Wiley & Sons, Ltd.     

A quaternionic map for the steady states of the Heisenberg spin-chain

We show that the steady states of the classical Heisenberg XXX spin-chain in an external magnetic field can be found by iterations of a quaternionic map. A restricted model, e.g., the xy spin-chain is known to have spatially chaotic steady states and the phase space occupied by these chaotic states is known to go through discrete changes as the field strength is varied. The same phenomenon is studied for the xxx spin-chain. It is seen that in this model the phase space volume varies smoothly with the external field.     

Ion transport properties of NaPF6- and NaCl-doped poly(N-phenylene N′imino pentyl)imminium propane sulfonate

New polymer-salt systems have been prepared by doping synthesized poly(N-phenylene N′imino pentyl) imminium propane sulfonate with NaPF₆ and NaCl. The higher conductivity of the NaPF₆-doped system in comparison to the NaCl-containing sample indicated that a larger-sized anion is facilitating ion conduction. FTIR spectra confirmed the complexation of salt with polymer. The conductivity power law exponent, studied in the frequency range from 42 Hz to 5 MHz, varies with frequency and has values >1, demonstrating dominance of caged ion movement. The dominance of caged motion is more pronounced in the NaCl-doped sample, signifying that a smaller anion has greater chances of being caged. Anion size signature is also visible in temperature and humidity dependence of exponent n.     

On minimal realization of fuzzy behaviour and associated categories

This paper is towards the study of minimal deterministic automata with fuzzy output which realizes the given fuzzy behaviour. The construction of such automaton is based on Myhill-Nerode’s theory, and it is shown that this automaton is a canonical realization of given fuzzy behaviour. Meanwhile, we introduce the categories of deterministic automata with fuzzy output and fuzzy behaviour. The relationship between both the categories through functors is also studied.     

Localized electric field induced transition and miniaturization of two‐phase flow patterns inside microchannels

Strategic application of external electrostatic field on a pressure‐driven two‐phase flow inside a microchannel can transform the stratified or slug flow patterns into droplets. The localized electrohydrodynamic stress at the interface of the immiscible liquids can engender a liquid‐dielectrophoretic deformation, which disrupts the balance of the viscous, capillary, and inertial forces of a pressure‐driven flow to engender such flow morphologies. Interestingly, the size, shape, and frequency of the droplets can be tuned by varying the field intensity, location of the electric field, surface properties of the channel or fluids, viscosity ratio of the fluids, and the flow ratio of the phases. Higher field intensity with lower interfacial tension is found to facilitate the oil droplet formation with a higher throughput inside the hydrophilic microchannels. The method is successful in breaking down the regular pressure‐driven flow patterns even when the fluid inlets are exchanged in the microchannel. The simulations identify the conditions to develop interesting flow morphologies, such as (i) an array of miniaturized spherical or hemispherical or elongated oil drops in continuous water phase, (ii) “oil‐in‐water” microemulsion with varying size and shape of oil droplets. The results reported can be of significance in improving the efficiency of multiphase microreactors where the flow patterns composed of droplets are preferred because of the availability of higher interfacial area for reactions or heat and mass exchange.     

Fluorogenic dual click derived bis-glycoconjugated triazolocoumarins for selective recognition of Cu(II) ion

Carbohydrate based fluorescent sensors S1 and S2 have been developed by fluorogenic dual click chemistry and are characterized by various spectroscopic techniques. Both the fluorescent probes displayed highly selective detection of Cu²⁺ ions by means of fluorescence quenching. The job plot experiment suggested 1:1 complexation of probes S1 and S2 with Cu²⁺ ions having detection limit of 6.99 μM and 7.30 μM, respectively. The binding constants for S1-Cu²⁺ and S2-Cu²⁺ complexation were evaluated to be 3.34 × 10³ M⁻¹ and 5.93 × 10³ M⁻¹, respectively.     

New benzotriazole-based reagents for the phosphonylation of various N-, O-, and S-nucleophiles

Benzotriazole surrogates showing higher stabilities than the corresponding chlorophosphates, allow phosphonylation of a variety of N-, O-, and S-nucleophiles in good yields.     

Multi-Component Diffusion Coefficients in Nitrogen Plasma Under Thermal Equilibrium and Non-equilibrium Conditions

Multi-component diffusion coefficients are calculated for a seven species model of nitrogen plasma under thermal non-equilibrium following the first order perturbation technique of Chapman and Enskog. Binary, thermal, thermal ambipolar, general and general ambipolar diffusion coefficients are presented over electron temperatures ranging from 300 to 50,000 K and thermal non-equilibrium parameter (Te/Th) ranging from 1 to 5. Considering large volume of data, binary, general and general ambipolar diffusion coefficients are presented only for atmospheric pressure. Thermal and thermal ambipolar diffusion coefficients are presented for pressures ranging from 0.1 to 2 atm. The results are compared with published experimental and theoretical data. Necessary electronic levels, associated transition data and collision integrals are collected from recent literature. Details of behaviour of each of the coefficients are presented.     

Significant Structural Differences between Transient Amyloid‐β Oligomers and Less‐Toxic Fibrils in Regions Known To Harbor Familial Alzheimer′s Mutations

Small oligomers of the amyloid β (Aβ) peptide, rather than the monomers or the fibrils, are suspected to initiate Alzheimer′s disease (AD). However, their low concentration and transient nature under physiological conditions have made structural investigations difficult. A method for addressing such problems has been developed by combining rapid fluorescence techniques with slower two‐dimensional solid‐state NMR methods. The smallest Aβ₄₀ oligomers that demonstrate a potential sign of toxicity, namely, an enhanced affinity for cell membranes, were thus probed. The two hydrophobic regions (residues 10–21 and 30–40) have already attained the conformation that is observed in the fibrils. However, the turn region (residues 22–29) and the N‐terminal tail (residues 1–9) are strikingly different. Notably, ten of eleven known Aβ mutants that are linked to familial AD map to these two regions. Our results provide potential structural cues for AD therapeutics and also suggest a general method for determining transient protein structures.     

The Role of Functional Moieties on Carbon Nanotube Surfaces in Solar Energy Conversion

An easily dispersible multiwalled carbon nanotube (MWCNT) derivative is prepared, and provides a platform for the synthesis of the phenyl butyric acid methyl ester (PCBM) analog. The carbene addition reaction of MWCNTs makes derivatives that are less soluble in organic solvents; by exploiting this differential solubility, PCBM analogs can be separated from the unreacted functionalized MWCNTs. Our experimental evidences indicate that it is the unique properties of the butyric acid methyl ester moiety that makes the acceptor material perform better in organic photovoltaics (OPVs). Studying the combination of the butyric acid methyl ester moiety and the deagglomerated functionalized MWCNT structures provides us an insight into nanoscale charge transfer and transportation inside the donor–acceptor domain. It is demonstrated that a strong structure–property relationship exists for the functionalized MWCNTs, which enables us to correlate the functionality on the carbon nanostructures with performance in OPVs.