A systematic study on the uptake of 57Co ions on amidoxime functionalized PAN-PVDF beads: preliminary studies towards fabrication of 57Co point sources

Journal of Radioanalytical and Nuclear Chemistry - This study describes the fabrication of 57Co point sources utilizing the metal sorption properties of amidoxime functionalized PAN-PVDF beads....     

Palladium based heterogeneous catalyst by evaporation-induced self-assembly: use of biopolymer as a surface functionalizing and reducing agent

Palladium-based composites are widely used as a heterogeneous catalyst in carbon–carbon coupling reactions and in catalytic converters used in the car industry. In this work, we demonstrate a simple, green and scalable synthesis procedure to obtain palladium (Pd) based heterogeneous catalyst. Surface functionalized silica microparticles were obtained in one-step by spray-drying a colloidal suspension of silica nanoparticles and gum arabic, an environmental-friendly biopolymer. Subsequently, palladium nanoparticles were reduced and attached to the substrate by gum arabic. The as-synthesized composite was characterized by field-emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), small angle x-ray scattering (SAXS), and high-resolution transmission electron microscopy (HR-TEM). The Pd@SiO₂ composite was used as a catalyst in the reduction reaction of 4-nitrophenol by sodium borohydride. The catalyst showed good recycling properties. The present environmental-friendly approach for fabrication of Pd-based heterogeneous catalyst circumvents various complex chemical steps involved in conventional chemical methods and could be generalized for the production of ceramic or magnetite-based Pd composites.     

Thermosolutal Convection in a Rectangular Concentric Annulus: A Comprehensive Study

This investigation presents numerical treatment of governing equations pertaining to thermosolutal flow within an annulus and an application of a model describing the important physical phenomenon as found in muffle furnace. The inner side of the annulus is exposed to high temperature and high solute concentration while the outer side of the annulus is maintained at low temperature and low solute concentration. Darcy-Brinkman-Forchheimer model is used to study the flow, heat and solute transfer in a non-Darcian saturated porous media. The solution is obtained upon application of control volume integration. Modified MAC method is used for the numerical solution of governing equations. Gradient dependent consistent hybrid upwind scheme of second order (GDCHUSSO) is used for discretization of the convective terms. The parameters such as Rayleigh-Darcy number, Darcy number, buoyancy ratio and width ratio, that govern the flow phenomenon have been identified and their effects are critically examined. The fluid flow pattern in the annular space and the associated heat and mass transfer are conceptualized from the obtained isoconcentration, isotherm and flowline contour maps.     

Length-scale dependent superconductor-insulator quantum phase transitions in one dimension

We study the dissipation physics of a one dimensional mesoscopic superconducting quantum interference device array using the field-theoretical renormalization group method. We observe length scale dependent, superconductor-insulator quantum phase transition at very low temperature and also observe the dual behavior of the system for higher and lower values of magnetic field. At a critical magnetic field, we also observe a critical behavior where the resistance is independent of length.     

A new and general route to 2-pyrrolylglycine, 2-pyrrolylalanine and homo-2-pyrrolylalanine derivatives

A general route to α-, β- and γ-pyrrole-branched α-amino acid derivatives has been developed, which featured a one-pot ring-closing metathesis and aromatization reaction as the key step.     

Laser-induced breakdown spectroscopy for determination of uranium in thorium-uranium mixed oxide fuel materials

Laser-induced breakdown spectroscopy (LIBS) has been developed for determining the percentage of uranium in thorium-uranium mixed oxide fuel samples required as a part of the chemical quality assurance of fuel materials. The experimental parameters were optimized using mixed oxide pellets prepared from 1:1 (w/w) mixture of thorium-uranium mixed oxide standards and using boric acid as a binder. Calibration curves were established using U(II) 263.553 nm, U(II) 367.007 nm, U(II) 447.233 nm and U(II) 454.363 nm emission lines. The uranium amount determined in two synthetic mixed oxide samples using calibration curves agreed well with that of the expected values. Except for U(II) 263.553 nm, all the other emission lines exhibited a saturation effect due to self-absorption when U amount exceeded 20 wt.% in the Th-U mixture. The present method will be useful for fast and routine determination of uranium in mixed oxide samples of Th and U, without the need for dissolution, which is difficult and time consuming due to the refractory nature of ThO₂. The methodology developed is encouraging since a very good analytical agreement was obtained considering the limited resolution of the spectrometer employed in the work.     

Solving a class of modular polynomial equations and its relation to modular inversion hidden number problem and inversive congruential generator

In this paper we revisit the modular inversion hidden number problem (MIHNP) and the inversive congruential generator (ICG) and consider how to attack them more efficiently. We consider systems of modular polynomial equations of the form \(a_{ij}+b_{ij}x_i+c_{ij}x_j+x_ix_j=0~(\mathrm {mod}~p)\) and show the relation between solving such equations and attacking MIHNP and ICG. We present three heuristic strategies using Coppersmith’s lattice-based root-finding technique for solving the above modular equations. In the first strategy, we use the polynomial number of samples and get the same asymptotic bound on attacking ICG proposed in PKC 2012, which is the best result so far. However, exponential number of samples is required in the work of PKC 2012. In the second strategy, a part of polynomials chosen for the involved lattice are linear combinations of some polynomials and this enables us to achieve a larger upper bound for the desired root. Corresponding to the analysis of MIHNP we give an explicit lattice construction of the second attack method proposed by Boneh, Halevi and Howgrave-Graham in Asiacrypt 2001. We provide better bound than that in the work of PKC 2012 for attacking ICG. Moreover, we propose the third strategy in order to give a further improvement in the involved lattice construction in the sense of requiring fewer samples.     

Properties of singular integral operators $$\varvec{S}_{\varvec{\alpha ,\beta }}$$

For \(\alpha , \beta \in L^{\infty } (S^1),\) the singular integral operator \(S_{\alpha ,\beta }\) on \(L^2 (S^1)\) is defined by \(S_{\alpha ,\beta }f:= \alpha Pf+\beta Qf\), where P denotes the orthogonal projection of \(L^2(S^1)\) onto the Hardy space \(H^2(S^1),\) and Q denotes the orthogonal projection onto \(H^2(S^1)^{\perp }\). In a recent paper, Nakazi and Yamamoto have studied the normality and self-adjointness of \(S_{\alpha ,\beta }\). This work has shown that \(S_{\alpha ,\beta }\) may have analogous properties to that of the Toeplitz operator. In this paper, we study several other properties of \(S_{\alpha ,\beta }\).