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991.
Generation of onions and nanotubes of GaS and GaSe through laser and thermally induced exfoliation 总被引:1,自引:0,他引:1
Gautam UK Vivekchand SR Govindaraj A Kulkarni GU Selvi NR Rao CN 《Journal of the American Chemical Society》2005,127(11):3658-3659
Although theoretical calculations have predicted that layered GaS and GaSe should form nanotube and related structures, they have not been prepared experimentally to date. We have carried out laser irradiation as well as thermal treatment of GaS and GaSe to cause exfoliation, which yielded onionlike structures and nanotubes by the rolling of the exfoliated sheets. 相似文献
992.
Mechanical shearing of crystals of a polymorph with a layered structure may be used to separate them from harder crystals of a visually indistinguishable polymorph that resist such shearing. 相似文献
993.
Kramer K Armstrong DS Averett TD Bertozzi W Binet S Butuceanu C Camsonne A Cates GD Chen JP Choi S Chudakov E Cusanno F Deur A Djawotho P Dutta D Finn JM Gao H Garibaldi F Gayou O Gilman R Glamazdin A Gorbenko V Griffioen KA Hansen JO Higinbotham DW Hinton W Horn T de Jager CW Jiang X Korsch W LeRose J Lhuillier D Liyanage N Margaziotis DJ McCormick K Meziani ZE Michaels R Milbrath B Moffit B Nanda S Perdrisat CF Pomatsalyuk R Punjabi V Reitz B Roche J Roché R Roedelbronn M Savvinov N Secrest J 《Physical review letters》2005,95(14):142002
We present the first measurement of the Q2 dependence of the neutron spin structure function g2(n) at five kinematic points covering 0.57 (GeV/c)2 < or = Q2 < or = 1.34 (GeV/c)2 at x approximately = 0.2. Though the naive quark-parton model predicts g2 = 0, nonzero values occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses, or orbital angular momentum. When scattering from a noninteracting quark, g2(n) can be predicted using next-to-leading order fits to world data for g1(n). Deviations from this prediction provide an opportunity to examine QCD dynamics in nucleon structure. Our results show a positive deviation from this prediction at lower Q2, indicating that contributions such as quark-gluon interactions may be important. Precision data obtained for g1(n) are consistent with next-to-leading order fits to world data. 相似文献
994.
Qattan IA Arrington J Segel RE Zheng X Aniol K Baker OK Beams R Brash EJ Calarco J Camsonne A Chen JP Christy ME Dutta D Ent R Frullani S Gaskell D Gayou O Gilman R Glashausser C Hafidi K Hansen JO Higinbotham DW Hinton W Holt RJ Huber GM Ibrahim H Jisonna L Jones MK Keppel CE Kinney E Kumbartzki GJ Lung A Margaziotis DJ McCormick K Meekins D Michaels R Monaghan P Moussiegt P Pentchev L Perdrisat C Punjabi V Ransome R Reinhold J Reitz B Saha A Sarty A Schulte EC Slifer K Solvignon P Sulkosky V 《Physical review letters》2005,94(14):142301
We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at Q2 values of 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was determined to 4%-8% and showed mu(p)G(E)/G(M) approximately 1. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques. 相似文献
995.
The polymeric precursor [RuCl2(CO)2]n reacts with the ligands, P∩P (a, b) and P∩O (c, d), in 1:1 M ratio to generate six-coordinate complexes [RuCl2(CO)2(?2-P∩P)] (1a, 1b) and [RuCl2(CO)2(?2-P∩O)] (1c, 1d), where P∩P: Ph2P(CH2)nPPh2, n = 2(a), 3(b); P∩O: Ph2P(CH2)nP(O)Ph2, n = 2(c), 3(d). The complexes are characterized by elemental analyses, mass spectrometry, thermal studies, IR, and NMR spectroscopy. 1a–1d are active in catalyzed transfer hydrogenation of acetophenone and its derivatives to corresponding alcohols with turnover frequency (TOF) of 75–290 h?1. The complexes exhibit higher yield of hydrogenation products than catalyzed by RuCl3 itself. Among 1a–1d, the Ru(II) complexes of bidentate phosphine (1a, 1b) show higher efficiency than their monoxide analogs (1c, 1d). However, the recycling experiments with the catalysts for hydrogenation of 4-nitroacetophenone exhibit a different trend in which the catalytic activities of 1a, 1b, and 1d decrease considerably, while 1c shows similar activity during the second run. 相似文献
996.
A pH-induced differential derivative spectrophotometric procedure has been developed for the simultaneous determination of Phenobarbitone (PBT) and Phenytoin sodium (DPH Na) in tablet preparations. The method comprized of measurement of difference absorptivities derivatized in second order (DeltaD(2)) of a tablet extract in 0.01 N NaOH relative to that of an equimolar solution in 0.01 N HCl at wavelengths of 244.8 and 252.8 nm respectively. The presence of identical zero-crossing points for pure drug and tablet extract solutions established the non-interference of the excipients in the absorption at these wavelengths. The compliance of Beer's law was adhered over a concentration range of 7.5-25 mug ml(-1) for both PBT and DPH. 相似文献
997.
N. C. Dutta 《Journal of Radioanalytical and Nuclear Chemistry》1997,224(1-2):173-175
A study of fixation of cobalt on the crystalline matrix of titania by co-precipitation was carried out. The tracer level solid-liquid distribution of60Co over preformed hydrous titania showed an appreciable uptake of 71%. Macro amounts of Co2+ ions were precipitated along with Ti(IV) hydroxide (pH 8–9) and a maximum loading of 29 wt% was observed. The Soxhlet leachabilities of the calcined mixed mass, heated at 1000 °C, were found to be in the order of 10–1 g·m–2·d–1 and the observation of structural changes of the original host matrix of titania revealed the fixation of cobalt in the mineral assemblage of CoTiO3 (rhombohedral) and the rutile form of titania. 相似文献
998.
999.
Shital K. Chattopadhyay Shankar P. Roy Debalina Ghosh Gautam Biswas 《Tetrahedron letters》2006,47(38):6895-6898
A new route to various medium ring heterocycle-annulated tetra-, penta- and hexacyclic carbazole derivatives has been developed using successive applications of three atom economic processes, viz. Claisen rearrangement, olefin metathesis and Diels-Alder reactions. 相似文献
1000.
Kaushik Dutta A. S. Brar 《Journal of polymer science. Part A, Polymer chemistry》1999,37(21):3922-3928
The configurational assignment of poly(vinylpyrrolidone) (PVP) prepared by peroxide-initiated solution polymerization was studied by the combination of one- and two-dimensional NMR spectroscopy. The broad and overlapping 1H-NMR and 13C{1H}-NMR spectra of PVP were assigned to the configurational triad, pentad (CH, 2CH2, 3CH2, and 4CH2 regions), and tetrad (β-CH2 region) sequences. The configurational assignments of the various carbon resonances were confirmed with the help of two-dimensional experiments such as heteronuclear single quantum correlation (HSQC), heteronuclear single quantum correlation–total correlation spectroscopy (2-D HSQC–TOCSY). The various geminal and vicinal couplings within the configurational sequences were assigned with the help of total correlation spectroscopy (TOCSY low mixing time). The propagation pathway was studied using the 13C{1H}-NMR (carbonyl carbon) and 15N{1H}-NMR spectra. The 15N{1H} resonance signals were assigned to pentad-level configurational sequences. The results obtained by the analysis of the area under the resonance signals confirmed that poly(vinylpyrrolidone) obeys Bernoullian statistics. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3922–3928, 1999 相似文献