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Experimental measurements and correlation of the solubility of N,N-dialkylamides in supercritical carbon dioxide
No full textN,N-Dialkylamides are the potential ligands for the extraction of actinides in nuclear-fuel cycle operations. Supercritical carbon dioxide (SCCO2) containing N,N-dialkylamides is a green solvent for the extraction of actinides with minimum liquid waste generation. In this connection, the solubilities of six N,N-dialkylamides in SCCO2 (313-333 K and 10-20 MPa) were measured to evaluate their utility as extractants for actinide separations. The solubilities are ranging from 0.005 x 10(-3) to 102 x 10(-3) mol mol(-1). The solubility of amides can be improved by increasing pressure and reducing temperature in the investigated region. The internal-consistency of solubility data was tested with Mendez-Teja equation. The solubility data was correlated with Chrastil, Mendez-Teja, solution theory with Wilson activity coefficient model and association theory with van Laar activity coefficient model. The correlation results demonstrated that, association theory with van Laar activity coefficient model predicts the solubilities with an average deviation of < 8% and is best among the models studied
Macroporous epoxy-carbon fiber structures with a sacrificial 3D printed polymeric mesh suppresses electromagnetic radiation
No full textMetals are known to be highly conducing and can shield electromagnetic waves quite well. In a quest to explore materials that are lightweight, corrosion free, easy to fabricate and integrate/embed, epoxy-carbon fiber composite structures have attracted a great deal of attention for myriad applications. Herein, we have fabricated macroporous structures involving epoxy and bi-directional carbon fiber (CF) for suppressing electromagnetic (EM) radiation, using 3D printed polymer mesh as a sacrificial layer in the laminate. This strategy reduces the weight of the composites by 15% besides retaining the EM blocking capability. In order to further enhance the shield-ability of the composite structures, ferromagnetic nanoparticles were electrodeposited directly on the bidirectional CF and infused with epoxy, using vacuum assisted resin transfer, and the 3D printed mesh. The latter was used as a sacrificial layer and was etched out from the final laminate structure to fabricate macroporous epoxy-CF laminates. The laminates with CF deposited with nickel on one side and cobalt on the other side showed better shielding manifesting in -40 dB (for 1.4 mm) as compared to other laminate structures. Upon etching the 3D printed mesh from the laminates, the resultant macroporous epoxy-modified CF laminates exhibited a shielding of - 45 dB (for 1.4 mm thick) along with a thermal stability up to 200 degrees C, enhanced flame-retardant properties and excellent heat dissipation ability. Taken together, this macroporous epoxy-CF laminates exhibited multifunctional properties and can further be explored for advanced EM suppressing material
Structural and magnetic properties of Al-doped yttrium iron garnet ceramics: Fe-57 internal field NMR and Mossbauer spectroscopy study
No full textThe structural and magnetic properties of Al substituted yttrium-iron garnet (Y3AlxFe5-xO12, x = 0, 0.1, 0.2, 0.3, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6 and 1.8) ceramic powders synthesized using solution combustion method were investigated. Post combustion, the samples were calcination at 1045 degrees C for 6 h and subsequently at 1200 degrees C for 6 h to obtain phase-pure garnets. X-ray diffraction (XRD) results confirm the formation of garnets with la (3) over bard structure. The occupancy of Y3+ ions in the dodecahedral site and the distribution of Al3+ and Fe3+ ions in the tetrahedral and octahedral sites in the bcc structure of the garnet were confirmed by Rietveld refinement of XRD patterns, Mossbauer spectroscopy and( 57)Fe internal field NMR spectroscopy. For low Al content, Al3+ ions have preference to occupy tetrahedral (T-d) sites than the octahedral (O-h) sites. At higher Al content the distribution of Al tends towards a ratio of 3:2 at the tetrahedral:octahedral site. Increase in Al doping results in the decrease in the lattice parameter due to smaller size of Al-3 + as compared to Fe3+ ion. All the studied samples show coral-network-like surface morphology. The saturation magnetization (M-s) values decrease from -26.94 emu/g to 0.17 emu/g with increase in Al content from 0.0 to 1.8. Further addition of Al makes the sample paramagnetic at RT. Substitution of non-magnetic Al3+ reduces the saturation magnetization rapidly due to the decrease in the superexchange interaction in the crystal. (C) 2018 Elsevier B.V. All rights reserved
Observation of oscillation like magnetocaloric effect in multiferroic Ni0.95Zn0.05Cr2O4
No full textIn this study, the magnetic and magnetocaloric effects of Ni0.95Zn0.05Cr2O4 have been investigated systematically. The distinct magnetic phases in different temperature zones were identified using a combined analysis of Arrott plots and virgin magnetization curves. The magnetocaloric phenomenon is sensitive to the spin correlation of the nickel and chromium magnetic sublattices within each distinct temperature zone, as is reflected by the modulation of the magnetocaloric sign. This unique oscillatory like magnetocaloric effect within the multiferroic phase may indicate the possibility of a multicaloric effect in Ni0.95Zn0.05Cr2O4. (C) 2018 Elsevier B.V. All rights reserved
Development of tin (II) sulfide nanostructured films with uniform surface morphology by two-step growth process
No full textTin (II) sulfide (SnS), one of the most abundant materials, is being considered as an absorber material for the development of low-cost and nontoxic solar cell devices. In this direction, we have developed nanocrystalline films of SnS with uniform morphology on different substrates by adopting two-step thermal evaporation process. The surface studies show that irrespective of substrate nature, the as-grown SnS films possess uniform surface-morphology with well-defined facets. Structural studies reveal that SnS films grown on various substrates possess an orthorhombic crystal structure. However, as compared to other substrates, the structures developed on sapphire and copper exhibit (010) as preferential growth direction. From the electrical measurements, it is noticed that the films deposited on highly-conductive substrates consist of low electrical resistance, whereas the films are slightly resistive on insulating substrates. Based on these investigations it is emphasized that high-quality SnS films can be developed with uniform morphology on any substrates by adopting our two-step process. (C) 2018 Elsevier B.V. All rights reserved
Rim-to-Disc Ratio Outperforms Cup-to-Disc Ratio for Glaucoma Prescreening
No full textWe present a novel and fully automated fundus image processing technique for glaucoma prescreening based on the rim-to-disc ratio (RDR). The technique accurately segments the optic disc and optic cup and then computes the RDR based on which it is possible to differentiate a normal fundus from a glaucomatous one. The technique performs a further categorization into normal, moderate, or severely glaucomatous classes following the disc-damage-likelihood scale (DDLS). To the best of our knowledge, this is the first engineering attempt at using RDR and DDLS to perform glaucoma severity assessment. The segmentation of the optic disc and cup is based on the active disc, whose parameters are optimized to maximize the local contrast. The optimization is performed efficiently by means of a multiscale representation, accelerated gradient-descent, and Green's theorem. Validations are performed on several publicly available databases as well as data provided by manufacturers of some commercially available fundus imaging devices. The segmentation and classification performance is assessed against expert clinician annotations in terms of sensitivity, specificity, accuracy, Jaccard, and Dice similarity indices. The results show that RDR based automated glaucoma assessment is about 8% to 10% more accurate than a cup-to-disc ratio (CDR) based system. An ablation study carried out considering the ground-truth expert outlines alone for classification showed that RDR is superior to CDR by 5.28% in a two-stage classification and about 3.21% in a three-stage severity grading
RT-Polar: An HARQ Scheme with Universally Competitive Rates
No full textWe present a construction for a universal channel code with feedback using Polar Codes. Our construction includes an error detection mechanism that is used to compute the ACK/NACK feedback directly from the received vector, without a higher layer CRC. Our scheme, termed the Repeat-Top Polar Code (RT-Polar), builds on a rate-compatible Polar Code and retransmits the t message bits sent over the most reliable polarized good channels over the least reliable good channels. At the decoder, these two t-bit strings are decoded and compared to detect an error. Through simulations, we illustrate the universal performance of our scheme for a binary symmetric channel with an unknown flipover probability. Our scheme performs comparably with a genie-aided scheme, where the detection mechanism is assumed to be error-free, for practically relevant message lengths of roughly 512 bits; this is the first instance of such a universal performance reported in literature. The proposed scheme is suitable for use as a HARQ in low-latency communication where including a higher-layer CRC will induce computational delays
Homogeneous 2-Shifts
No full textThe classification of homogeneous scalar weighted shifts is known. Recently, Koranyi obtained a large class of inequivalent irreducible homogeneous bi-lateral 2-by-2 block shifts. In this paper, we construct two distinct classes of examples not in the list of Koranyi. It is then shown that these new examples of irreducible homogeneous bi-lateral 2-by-2 block shifts, together with the ones found earlier by Koranyi, account for every unitarily inequivalent irreducible homogeneous bi-lateral 2-by-2 block shift
Facile measurement of protein stability and folding kinetics using a nano differential scanning fluorimeter
No full textWith advancements in high-throughput generation of phenotypic data on mutant proteins, it has become important to individually characterize different proteins or their variants rapidly and with minimal sample consumption. We have made use of a nano differential scanning fluorimetric device, from NanoTemper technologies, to rapidly carry out isothermal chemical denaturation and measure folding/unfolding kinetics of proteins and compared these to corresponding data obtained from conventional spectrofluorimetry. We show that using sample volumes 10-50-fold lower than with conventional fluorimetric techniques, one can rapidly and accurately measure thermodynamic and kinetic stability, as well as folding/unfolding kinetics. This method also facilitates characterization of proteins that are difficult to express and purify
Probing the superconducting ground state of ZrIrSi: A muon spin rotation and relaxation study
No full textThe superconducting ground state of recently discovered ZrIrSi is probed by means of muon spin rotation and relaxation (mu SR) and resistivity measurements. The occurrence of superconductivity at T-C = 1.7 K is confirmed by resistivity measurements. Zero field mu SR study revealed that below T-C there is no spontaneous magnetic field in the superconducting state, which indicates time-reversal symmetry is preserved in the case of ZrIrSi. From transverse field mu SR measurement, we have estimated the superfluid density as a function of temperature, which is described by an isotropic s-wave model with a superconducting gap 2 Delta(0)/k(B)T(C) = 5.10(2) and indicates the presence of strong coupling superconductivity. Ab initio electronic structure calculation indicates that there are four bands passing through the Fermi level, forming four Fermi surface pockets. We find that the low-energy bands are dominated by the 4d orbitals of the transition metal Zr, with substantially less weight from the 5d orbitals of the Ir atoms