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981.
Sk.F. Ahmed P.K. Ghosh S. Khan M.K. Mitra K.K. Chattopadhyay 《Applied Physics A: Materials Science & Processing》2007,86(1):139-143
We have observed low-macroscopic field electron emission from wide bandgap nanocrystalline Al doped SnO2 thin films deposited on glass substrates. The emission properties have been studied for different anode-sample spacings and for different Al concentrations in the films. The turn-on field and approximate work function were calculated and we have tried to explain the emission mechanism from this. The turn-on field was found to vary in the range 5.6–7.5 V/μm for a variation of anode sample spacing from 80–120 μm. The turn-on field was also found to vary from 4.6–5.68 V/μm for a fixed anode-sample separation of 80 μm with a variation of Al concentration in the films 8.16–2.31%. The Al concentrations in the films have been measured by energy dispersive X-ray analysis. Optical transmittance measurement of the films showed a high transparency with a direct bandgap ∼3.98 eV. Due to the wide bandgap, the electron affinity of the film decreased. This, along with the nanocrystalline nature of the films, enhanced the field emission properties. PACS 81.20.Fw; 61.10.-i; 79.70.+q 相似文献
982.
F
A1:Ag+ color center at the low coordination (100) and (110) surface sites of KCl and KBr thin films play an important role in providing
tunable laser oscillation and adsorbatesubstrate interactions. Double-well potentials at this site are investigated using
ab initio molecular electronic structure calculations. The calculated Stokes shifted (optical transition bands), opticaloptical
conversion efficiencies, the probability of orientational destruction, exciton (energy) transfer and Glasner-Tompkins empirical
rule suggest that laser light generation is sensitive to (i) the lattice anion, (ii) the coordination number of surface ions,
and (iii) the choice of the basis set centered on the anion vacancy. The adsorbate-substrate interactions were found to be
dependent on the electronegativity of the adatom and on the lattice anion. Optimised geometries and the coadsorption of CO
and (F, Cl, Br, I) on KCl and KBr (100) crystals are presented. Calculated chemisorption energies for CO on the (halogen atom/defect
free sites of KCl and KBr (100) crystals) showed that the coadsorption of halogen atom tends to block other adsorbate-substrate
interactions at the nearest neighbour sites. Thus if halogen atom coverage increases, the CO prefers to be adsorbed on the
K+ site of the KCl and KBr (100) surfaces and on KBr relative to KCl.
相似文献
983.
M. Ali Paracha Ishtiaq Ahmed M. Jamil Aslam 《The European Physical Journal C - Particles and Fields》2007,52(4):967-973
We study long-distance effects in the rare exclusive semileptonic decays B→K1ℓ+ℓ-, where K1 is the axial vector meson. The form factors describing the meson transition amplitudes of the effective Hamiltonian are calculated
using the Ward identities, which are then used to calculate the branching ratio and the forward–backward asymmetry in these
decay modes. The zero of the forward–backward asymmetry is of special interest and provides us with a precision test of the
standard model. 相似文献
984.
985.
The water-silicas interfacial interaction energies were calculated for samples of quartz, silicas and silicas outgassed at high temperatures using own and published data of the spreading pressure of water, its surface tension, its contact angle and using formulas obtained by the combination of the Young equation with a general equation of pair interaction. The values obtained for 18 different samples were in the range 7.80-6.92 kJ mol−1. Lower values of energies are for samples that contain relatively less amounts of water at P/P0 = 0.25 and are characterized also by relatively low values of surface pressures. 相似文献
986.
M.M. EL-Nicklawy A.F. Hassan A.T. Matar A.A. Hemeda A.I. Ali 《Optics & Laser Technology》2007,39(6):1243-1253
Through the differential equation describing the behavior of the nonlinear polarization of a medium with respect to an incident field, the Maxwell field equations and the boundary conditions of the field inside a resonator, the relationship between the output and the incident fields is obtained, describing a bistability phenomena. The effect of the spectral profile of the incident field and its spectral halfwidth on the bistability phenomena is studied. 相似文献
987.
Ahmed M. Eissa Michael J.P. Smith Artur Kubilis Jackie A. Mosely Neil R. Cameron 《Journal of polymer science. Part A, Polymer chemistry》2013,51(24):5184-5193
Copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)–poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne‐terminated PE‐b‐PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne‐terminated PE‐b‐PEG was prepared by etherification reaction between hydroxyl‐terminated PE‐b‐PEG (Mn ~ 875 g mol?1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2‐azidoethanol. Atmospheric pressure solids analysis probe‐mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end‐capping of PE‐b‐PEG by the azidoethyl glycoside group. The aqueous solution self‐assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate‐bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self‐assemble via electro‐formation into giant carbohydrate‐bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate‐bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5184–5193 相似文献
988.
Afaq Shagufta Khan Sadia Kazmi Mehdi Hassan Fatima Itrat Malik Abdul Inamullah Farah Farhad Zahid Abbas Tanveer Tareen Rasool Bakhsh 《Chemistry of Natural Compounds》2021,57(2):269-273
Chemistry of Natural Compounds - Armatans A (1) and B (2), new isoflavans, have been isolated from the EtOAc-soluble fraction of the MeOH extract of Colutea armata Hemsl. & Lace, along with... 相似文献
989.
Najwa Sbei Belen Batanero Fructuoso Barba Beya Haouas Mohamed Lamine Benkhoud Isidoro Barba 《Tetrahedron》2018,74(16):2068-2072
A new series of 3,4-disubstituted quinazolin-2-ones, with potential T-type calcium channel antagonist activity, and new 4-methylene-quinazolin-2-ones, promising catalysts as N-heterocyclic olefins, have been prepared in good yield by a simple reaction between 2-aminobenzophenone, or 2-aminoacetophenone, and cyanomethyl anion electrogenerated by acetonitrile reduction at a graphite electrode, followed by the addition of different organic isocyanates and subsequent heterocyclization. 相似文献
990.
Gholam‐Reza Nejabat Mehdi Nekoomanesh Hassan Arabi Hamid Salehi‐Mobarakeh Gholam‐Hossein Zohuri Mojtaba Omidvar Stephen A. Miller 《Journal of polymer science. Part A, Polymer chemistry》2013,51(3):724-731
Various elastomeric polypropylenes (PPs) are synthesized through homogeneous propylene polymerization with metallocene catalyst (2‐PhInd)2ZrCl2 in the presence of different cocatalyst mixtures: triethylaluminum (TEA)/methylaluminoxane (MAO) or triisobutylaluminum (TIBA)/MAO in the range of AlAlR3/AlMAO = 0.0–0.9. The cocatalyst formulation impacts the resultant polymer microstructure and the thermal and dynamic mechanical properties of the produced PPs. 13C NMR analysis of the polymers reveals essentially atactic PP, with mmmm = 7.9%, when AlAlR3/AlMAO = 0.0. The mmmm pentad content is maximized when AlAlR3/AlMAO = 0.8; for TIBA, mmmm = 23.5%; and for TEA, mmmm = 17.6%. Differential scanning calorimetry analysis and dynamic mechanical thermal analysis corroborate these findings. Specifically, Tm, ΔHm, and Tg are essentially maximized under these conditions, and the minimum damping is observed for AlAlR3/AlMAO = 0.6–0.8. 1H NMR analysis of the mixtures of catalyst and cocatalysts (without monomer) shows very minor differences for [Zr]:AlAlR3 in the range of 1:1–1:5. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献