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Facile microwave-assisted synthesis of Cr2O3 nanoparticles with high near-infrared reflection for roof-top cooling applications
No full textMicrowave-assisted solution synthesis was employed for the preparation of Cr2O3 nanoparticles using Cr(acac)(3) and ethylene glycol. The optimum conditions for the completion of the reaction forming a green precipitate (yield-95%) were: irradiation for 40-60 min at 220 degrees C solution temperature. The as-prepared sample was barely crystalline; annealing in air at above 300 degrees C formed nanocrystalline Cr2O3, as shown by X-ray diffraction (XRD). High-resolution transmission electron microscopy (HRTEM) of the ``700 degrees C sample'' confirmed the well-crystallised Cr2O3 formation with similar to 37 nm average size. The asprepared powder (bluish-green) showed high near-infrared (NIR) reflectance, whereas the annealed samples showed bright-green reflectance, whose International Commission on Illumination L*a*b* (CIE L*a*b*) values shifted towards the green region. The higher D-q/B value (3.76), suggested that Cr3+ lies in a strong crystal field. Stainless steel blocks covered with the as-prepared (intermediate) material reduced heating under sunlight by 5 degrees C, indicating its suitability as an easily prepared tile coating for roof-top applications. The annealed samples are found suitable as an anti-dazzling coating for automobile windscreens and rear-view mirrors. (C) 2019 Elsevier B.V. All rights reserved
Measurement of prompt psi(2S) production cross sections in proton-lead and proton-proton collisions at root s(NN)=5.02 TeV
No full textMeasurements of prompt psi(2S) meson production cross sections in proton-lead (pPb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of root s(NN) = 5.02 TeV are reported. The results are based on pPb and pp data collected by the CMS experiment at the LHC, corresponding to integrated luminosities of 34.6 nb(-1) and 28.0 pb(-1), respectively. The nuclear modification factor R-pPb is measured for prompt psi(2S) in the transverse momentum range 4 < p(T) < 30 GeV/c and the center-of-mass rapidity range -2.4 < y(CM) < 1.93. The results on psi(2S) R-pPb are compared to the corresponding modification factor for prompt J/psi mesons. The results point to different nuclear effects at play in the production of the excited charmonium state compared to the ground state, in the region of backward rapidity and for PT < 10 GeV/c. (C) 2019 The Author. Published by Elsevier B.V
Halogen-Mediated Membrane Transport: An Efficient Strategy for the Enhancement of Cellular Uptake of Synthetic Molecules
No full textThe poor uptake of fluorescent probes and therapeutics by mammalian cells is a major concern in biological applications ranging from fluorescence imaging to drug delivery in living cells. Although gaseous molecules such as oxygen and carbon dioxide, hydrophobic substances such as benzene, and small polar but uncharged molecules such as water and ethanol can cross the cell plasma membrane by simple passive diffusion, many synthetic as well as biological molecules require specific membrane transporters and channel proteins that control the traffic of these molecules into and out of the cell. This work reports that the introduction of halogen atoms into a series of fluorescent molecules remarkably enhances their cellular uptake, and that their transport can be increased to more than 95% by introducing two iodine atoms at appropriate positions. The nature of the fluorophore does not play a major role in the cellular uptake when iodine atoms are present in the molecules, as compounds bearing naphthalimide, coumarin, BODIPY, and pyrene moieties show similar uptakes. Interestingly, the introduction of a maleimide-based fluorophore bearing two hydroxyethylthio moieties allows the molecules to cross the plasma and nuclear membranes, and the presence of iodine atoms further enhances the transport across both membranes. Overall, this study provides a general strategy for enhancing the uptake of organic molecules by mammalian cells
Al-27 MAS NMR investigations on Al23Te77 glass: Observation of 5-coordinated Al and its influence on electrical switching
No full textAl-27 Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopic studies show that Al resides in 4-, 5- and 6- fold coordination in bulk Al23Te77 glass. Also Al23Te77, glass is found to exhibit threshold type switching. Earlier studies report memory type switching in Al-Te glasses wherein Al has been found only in Al-4] and Al-6] environments. X-Ray Photo Electron Spectroscopic (XPS) measurements show the presence of Al2O3 in Al23Te77 glass network. The structural network of Al-Te glass has been cross linked by the presence of higher coordinated Al atoms. The structural reorganization becomes difficult due to the increased network connectivity. Thus, the memory switching (which requires an easy structural reorganization) is retarded, resulting in the observation of threshold switching
Estimation of structural composition of the inverse spinel ferrites using Fe-57-Zero Field Nuclear Magnetic Resonance
No full textWe have demonstrated Fe-57 Zero Field Nuclear Magnetic Resonance (ZFNMR) as a powerful tool in determining the structural composition of nickel-cadmium spinel ferrites of various compositions of Ni1-xCdxFe2O4 from x = 0 to1, which are synthesized via one-step auto combustion technique. The XRD measurements confirm the phase purity of all the samples. Vibrating Sample Magnetometry (VSM) measurements show that saturation magnetization (M-s) increases initially (up to x = 0.3) and then decreases for higher concentrations of cadmium. The Fe3+ ions in the inverted spinel ferrite distribute equally among two possible sites (tetrahedral A and octahedral B) with different hyperfine fields. Therefore for x = 0 under the assumption that Ni enters B sites, Fe-57 NMR of Fe3+ ions yield two signals of equal integral intensities in spectral lines corresponding to these sites. Thus, for the sample series Ni1-xCdxFe2O4, the contribution of Fe3+ nuclei varies for A and B sub-spectra with the substitution of a non-magnetic Cd2+ ion. By measuring the Fe3+ distribution on A and B sites which is determined from relative spectral areas of A and B NMR sub-spectra the cation distribution is estimated and has been verified by the binomial distribution. Further, XRD Rietveld refinement results are also in good agreement with the composition estimated by NMR technique and the ideal composition. We have demonstrated the usefulness of NMR technique to quantify the accurate composition of the mixed spinel ferrite systems using Ni-Cd ferrite as a test case. Further, the estimated inversion parameter (at around x = 0.4), for the studied system, obtained from ZFNMR, XRD, and VSM techniques are in excellent agreement with each other
Jet Shapes of Isolated Photon-Tagged Jets in Pb-Pb and pp Collisions at root S-NN=5.02 TeV
No full textThe modification of jet shapes in Pb-Pb collisions, relative to those in pp collisions, is studied for jets associated with an isolated photon. The data were collected with the CMS detector at the LHC at a nucleon- nucleon center-of-mass energy of 5.02 TeV. Jet shapes are constructed from charged particles with track transverse momenta (p(T)) above 1 GeV/c in annuli around the axes of jets with p(T)(jet) > 30 GeV/c associated with an isolated photon with p(T)(gamma) > 60 GeV/c. The jet shape distributions are consistent between peripheral Pb-Pb and pp collisions, but are modified for more central Pb-Pb collisions. In these central Pb-Pb events, a larger fraction of the jet momentum is observed at larger distances from the jet axis compared to pp, reflecting the interaction between the partonic medium created in heavy ion collisions and the traversing partons
Search for resonant production of second-generation sleptons with same-sign dimuon events in proton-proton collisions at root s=13 TeV
No full textA search is presented for resonant production of second-generation sleptons ((mu) over tilde (L),(nu) over tilde (mu)) via the R-parityviolating coupling. gimel'(211) to quarks, in events with two samesign muons and at least two jets in the final state. The smuon ( muon sneutrino) is expected to decay into amuon and a neutralino (chargino), which will then decay into a second muon and at least two jets. The analysis is based on the 2016 data set of proton- proton collisions at root s = 13 TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb(-1). No significant deviation is observed with respect to standard model expectations. Upper limits on cross sections, ranging from 0.24 to 730 fb, are derived in the context of two simplified models representing the dominant signal contributions leading to a same- sign muon pair. The cross section limits are translated into coupling limits for a modified constrained minimal supersymmetric model with. gimel'(211) as the only nonzero R-parity violating coupling. The results significantly extend restrictions of the parameter space compared with previous searches for similar models
Blue emitting Ce3+ -doped CaYAl3O7 phosphors prepared by combustion route
No full textThe solution-combustion route was used to synthesize series of Ce3+-ion-activated CaYAl3O7 (CYO) blue-light-emitting phosphors. Formation of the tetragonal CYO structure was confirmed by the powder X-ray diffraction (XRD) studies. On substitution of Ce3+ ion to Ca site in CaYAl3O7 system, the photoluminescence spectra recorded at ultraviolet-light (360 nm) excitation. Photoluminescence excitation spectra at 360 nm showed the characteristic emission at 434 nm of the Ce3+ ion caused by 5d -> 4f transitions. Increase in intensity can be seen up to 1 mol % of Ce3+ followed by quenching due to dipole-dipole interaction. The Commission Internationale de l'Eclairage (CIE - 1931) coordinates x = 0.1484 and y = 0.0987 of this phosphor are in the violet blue region. The blue-color purity was found to be maximum 90% for 1 mol% Ce3+-doped phosphor. The obtained CIE, CCT, and color-purity results illustrate the potentiality of Ce3+ activated CYO phosphor for household-lighting and display-device applications
Search for vector-like quarks in events with two oppositely charged leptons and jets in proton-proton collisions at root s=13TeV
No full textA search for the pair production of heavy vector-like partners T and B of the top and bottom quarks has been performed by the CMS experiment at the CERN LHC using proton-proton collisions at . The data sample was collected in 2016 and corresponds to an integrated luminosity of 35.9 production include those where one of the T quarks decays via TtZ and the other via TbW, tZ, or tH, where H is a Higgs boson. For the BB case, final states include those where one of the B quarks decays via BbZ and the other BtW, bZ, or bH. Events with two oppositely charged electrons or muons, consistent with coming from the decay of a Z boson, and jets are investigated. The number of observed events is consistent with standard model background estimations. Lower limits at 95% confidence level are placed on the masses of the T and B quarks for a range of branching fractions. Assuming 100% branching fractions for TtZ, and BbZ, T and B quark mass values below 1280 and 1130 respectively, are excluded
Electronic structure of Fe and magnetism in the 3d/5d double perovskites Ca2FeReO6 and Ba2FeReO6
No full textThe Fe electronic structure and magnetism in (i) monoclinic Ca2FeReO6 with a metal-insulator transition at T-MI similar to 140 K and (ii) quasicubic half-metallic Ba2FeReO6 ceramic double perovskites are probed by soft x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). These materials show distinct Fe L-2,L-3 XAS and XMCD spectra, which are primarily associated with their different average Fe oxidation states (close to Fe3+ for Ca2FeReO6 and intermediate between Fe2+ and Fe3+ for Ba2FeReO6) despite being related by an isoelectronic (Ca2+/Ba2+) substitution. For Ca2FeReO6, the powder-averaged Fe spin moment along the field direction (B = 5 T), as probed by the XMCD experiment, is strongly reduced in comparison with the spontaneous Fe moment previously obtained by neutron diffraction, consistent with a scenario where the magnetic moments are constrained to remain within an easy plane. For B = 1 T, the unsaturated XMCD signal is reduced below T-MI consistent with a magnetic transition to an easy-axis state that further reduces the powder-averaged magnetization in the field direction. For Ba2FeReO6, the field-aligned Fe spins are larger than for Ca2FeReO6 (B = 5 T) and the temperature dependence of the Fe magnetic moment is consistent with the magnetic ordering transition at T-C(Ba) = 305 K. Our results illustrate the dramatic influence of the specific spin-orbital configuration of Re 5d electrons on the Fe 3d local magnetism of these Fe/Re double perovskites