Effect of inorganic metal ion impurities on lyoluminescence

It is observed that the intensity of lyoluminescence (LL) (the emission during the dissolution of irradiated crystals) is considerably enhanced in the presence of certain transition metal ions in low concentration, while the LL is quenched due to the presence of certain other transition metal ions. A detailed investigation is carried out to understand the effect of these metal ions and probable mechanisms are proposed.     

Quantum Painlevé equations: from continuous to discrete and back

We present a cascade of quantum Painlevé equations consisting in successive contiguity relations, whereupon starting form a continuous equations we obtain a discrete one, and continuous limits of the latter. We start from the quantum Painlevé V and in the process derive the quantum form of continuous PIII which was missing in previous studies.      

Singularity Confinement Property for the (Non-Autonomous) Adler–Bobenko–Suris Integrable Lattice Equations

We examine the integrable lattice systems proposed by Adler, Bobenko and Suris from the point of view of the existence of integrable non-autonomous forms. We show, using the singularity confinement criterion, that both the H and Q families can be deautonomised, leading to a lattice with variable step in each dimension, as already assumed in the original paper. A new linearisable equation is identified as a special case of the Q₄ lattice. We present its linearisation and obtain its non-autonomous extension.     

Comment on “painleve property of anharmonic systems with an external periodic field”

We show that the result of Steeb and Kunick concerning the singularity structure of the Van der Pol equation is false.     

A hierarchical algorithm for fast debye summation with applications to small angle scattering

Debye summation, which involves the summation of sinc functions of distances between all pair of atoms in three‐dimensional space, arises in computations performed in crystallography, small/wide angle X‐ray scattering (SAXS/WAXS), and small angle neutron scattering (SANS). Direct evaluation of Debye summation has quadratic complexity, which results in computational bottleneck when determining crystal properties, or running structure refinement protocols that involve SAXS or SANS, even for moderately sized molecules. We present a fast approximation algorithm that efficiently computes the summation to any prescribed accuracy ? in linear time. The algorithm is similar to the fast multipole method (FMM), and is based on a hierarchical spatial decomposition of the molecule coupled with local harmonic expansions and translation of these expansions. An even more efficient implementation is possible when the scattering profile is all that is required, as in small angle scattering reconstruction (SAS) of macromolecules. We examine the relationship of the proposed algorithm to existing approximate methods for profile computations, and show that these methods may result in inaccurate profile computations, unless an error‐bound derived in this article is used. Our theoretical and computational results show orders of magnitude improvement in computation complexity over existing methods, while maintaining prescribed accuracy. © 2012 Wiley Periodicals, Inc.     

Highly enantioselective synthesis of chiral allenes by sequential creation of stereogenic center and chirality transfer in a single pot operation

Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent chirality transfer via an intramolecular hydride shift to produce chiral allenes with high enantiomeric purities.     

Thermoluminescence studies of γ-irradiated nanocrystalline Y3Al5O12

Nanocrystalline yttrium aluminum garnet (Y₃Al₅O₁₂) is synthesized by combustion technique. The X-ray diffraction (XRD) pattern of 900 °C annealed sample revealed a cubic structure. The average crystallite size is found to be 20.5 nm. γ-irradiated Y₃Al₅O₁₂ exhibits two thermoluminescence (TL) glows: a prominent one with a peak at ～410 K and another one with a peak at ～575 K. It is found that the TL glow peak intensity at 410 K increases, while its glow peak temperature is almost steady with an increase in the γ-dose. The effect of the heating rate on the TL glow curve is studied. It is found that T_m1 shifts towards higher temperature region while the I_m1 decreases with an increase in the heating rate. The TL glow curves are analyzed by Chen's peak shape method and the TL parameters are estimated.     

Measurement of circulation rates of coal particles in standpipe of a circulating fluidized bed system (CFBS) using radiotracer technique

Radiotracer technique was applied to measure the circulation rates of fine coal particles in standpipe of a pilot-scale bubbling circulating fluidized bed system (CFBS). ¹⁹⁸Au adsorbed on coal particles was used as a radiotracer. The radiotracer was injected into the standpipe and monitored at four different downstream locations. The circulation times and circulation rates were determined from the measured tracer concentration curves at different operating conditions. The measured parameters were intended to be used for optimizing the performance of existing CFBSs operating in industry and design of a new CFBS to be used as coal gasifier.     

13C NMR studies of methylnucleosides

The ¹³C chemical shifts of 22 methylated ribonucleosides and deoxyribonucleosides have been measured and assigned. The chemical shift differences between methylated and unmodified nucleosides are correlated with their characteristic modifications of structure. The significance of the chemical shift and tautomeric variations is discussed.