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Du YD, Tse CW, Xu ZJ, Liu Y, Che CM. [FeIII(TF4DMAP)OTf] catalysed anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant. Chem Commun (Camb) 2014; 50:12669-72. [DOI: 10.1039/c4cc05972g] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
[FeIII(TF4DMAP)OTf] catalysed anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and the transformation of N-methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant with moderate to good product yields.
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Kondo T, Palczewski AD, Hamaya Y, Takeuchi T, Wen JS, Xu ZJ, Gu G, Kaminski A. Formation of gapless Fermi arcs and fingerprints of order in the pseudogap state of cuprate superconductors. PHYSICAL REVIEW LETTERS 2013; 111:157003. [PMID: 24160620 DOI: 10.1103/physrevlett.111.157003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Indexed: 06/02/2023]
Abstract
We use angle-resolved photoemission spectroscopy and a new quantitative approach based on the partial density of states to study properties of seemingly disconnected portions of the Fermi surface (FS) that are present in the pseudogap state of cuprates called Fermi arcs. We find that the normal state FS collapses very abruptly into Fermi arcs at the pseudogap temperature (T*). Surprisingly, the length of the Fermi arcs remains constant over an extended temperature range between T* and T(pair), consistent with the presence of an ordered state below T*. These arcs collapse again at the temperature below which pair formation occurs (T(pair)) either to a point or a very short arc, whose length is limited by our experimental resolution. The tips of the arcs span between points defining a set of wave vectors in momentum space, which are the fingerprints of the ordered state that causes the pseudogap.
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He J, Zhang W, Bok JM, Mou D, Zhao L, Peng Y, He S, Liu G, Dong X, Zhang J, Wen JS, Xu ZJ, Gu GD, Wang X, Peng Q, Wang Z, Zhang S, Yang F, Chen C, Xu Z, Choi HY, Varma CM, Zhou XJ. Coexistence of two sharp-mode couplings and their unusual momentum dependence in the superconducting state of Bi2Sr2CaCu2O(8+δ) revealed by laser-based angle-resolved photoemission. PHYSICAL REVIEW LETTERS 2013; 111:107005. [PMID: 25166699 DOI: 10.1103/physrevlett.111.107005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 02/12/2013] [Indexed: 06/03/2023]
Abstract
High-resolution laser-based angle-resolved photoemission measurements have been carried out on Bi2Sr2CaCu2O(8+δ) (Bi2212) superconductors to investigate momentum dependence of electron coupling with collective excitations (modes). Two coexisting energy scales are clearly revealed over a large momentum space for the first time in the superconducting state of the overdoped Bi2212 superconductor. These two energy scales exhibit distinct momentum dependence: one keeps its energy near 78 meV over a large momentum space while the other changes its energy from ∼40 meV near the antinodal region to ∼70 meV near the nodal region. These observations provide a new picture on momentum evolution of electron-boson coupling in Bi2212 that electrons are coupled with two sharp modes simultaneously over a large momentum space in the superconducting states. Their unusual momentum dependence poses a challenge to our current understanding of electron-mode-coupling and its role for high-temperature superconductivity in cuprate superconductors.
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Sakai S, Blanc S, Civelli M, Gallais Y, Cazayous M, Méasson MA, Wen JS, Xu ZJ, Gu GD, Sangiovanni G, Motome Y, Held K, Sacuto A, Georges A, Imada M. Raman-scattering measurements and theory of the energy-momentum spectrum for underdoped Bi2Sr2CaCuO(8+δ) superconductors: evidence of an s-wave structure for the pseudogap. PHYSICAL REVIEW LETTERS 2013; 111:107001. [PMID: 25166695 DOI: 10.1103/physrevlett.111.107001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Indexed: 06/03/2023]
Abstract
We reveal the full energy-momentum structure of the pseudogap of underdoped high-Tc cuprate superconductors. Our combined theoretical and experimental analysis explains the spectral-weight suppression observed in the B2g Raman response at finite energies in terms of a pseudogap appearing in the single-electron excitation spectra above the Fermi level in the nodal direction of momentum space. This result suggests an s-wave pseudogap (which never closes in the energy-momentum space), distinct from the d-wave superconducting gap. Recent tunneling and photoemission experiments on underdoped cuprates also find a natural explanation within the s-wave pseudogap scenario.
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Wang JC, Zhang Y, Xu ZJ, Lo VKY, Che CM. Enantioselective Intramolecular Carbene C–H Insertion Catalyzed by a Chiral Iridium(III) Complex of D4-Symmetric Porphyrin Ligand. ACS Catal 2013. [DOI: 10.1021/cs4001656] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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56
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Dean MPM, James AJA, Springell RS, Liu X, Monney C, Zhou KJ, Konik RM, Wen JS, Xu ZJ, Gu GD, Strocov VN, Schmitt T, Hill JP. High-energy magnetic excitations in the cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+δ): towards a unified description of its electronic and magnetic degrees of freedom. PHYSICAL REVIEW LETTERS 2013; 110:147001. [PMID: 25167025 DOI: 10.1103/physrevlett.110.147001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Indexed: 06/03/2023]
Abstract
We investigate the high-energy magnetic excitation spectrum of the high-T(c) cuprate superconductor Bi(2)Sr(2)CaCu(2)O(8+δ) (Bi-2212) using Cu L(3) edge resonant inelastic x-ray scattering. Broad, dispersive magnetic excitations are observed, with a zone boundary energy of ∼ 300 meV and a weak dependence on doping. These excitations are strikingly similar to the bosons proposed to explain the high-energy "kink" observed in photoemission. A phenomenological calculation of the spin response, based on a parametrization of the the angle-resolved photoemission spectroscopy derived electronic structure and Yang-Rice-Zhang quasiparticles, provides a reasonable prediction of the energy dispersion of the observed magnetic excitations. These results indicate a possible unified framework to reconcile the magnetic and electronic properties of the cuprates and we discuss the advantages and disadvantages of such an approach.
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Arham HZ, Hunt CR, Park WK, Gillett J, Das SD, Sebastian SE, Xu ZJ, Wen JS, Lin ZW, Li Q, Gu G, Thaler A, Budko SL, Canfield PC, Greene LH. Gap-like feature in the normal state of X(Fe1−xCox)2As2, X = Ba, Sr and Fe1+yTe revealed by Point Contact Spectroscopy. ACTA ACUST UNITED AC 2012. [DOI: 10.1088/1742-6596/400/2/022001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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58
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Zhou CY, Wang JC, Wei J, Xu ZJ, Guo Z, Low KH, Che CM. Dirhodium Carboxylates Catalyzed Enantioselective Coupling Reactions of α-Diazophosphonates, Anilines, and Electron-Deficient Aldehydes. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201206551] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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59
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Zhou CY, Wang JC, Wei J, Xu ZJ, Guo Z, Low KH, Che CM. Dirhodium carboxylates catalyzed enantioselective coupling reactions of α-diazophosphonates, anilines, and electron-deficient aldehydes. Angew Chem Int Ed Engl 2012; 51:11376-80. [PMID: 23074015 DOI: 10.1002/anie.201206551] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Indexed: 11/07/2022]
Abstract
Chiral dirhodium carboxylate complexes ([Rh(2)(S-PTAD)(4)] or [Rh(2)(S-PTTL)(4)]) efficiently catalyze asymmetric three-component coupling reactions of α-diazophosphonates, anilines, and electron-deficient aldehydes to give α-amino-β-hydroxyphosphonates. The high level of enantiocontrol provides evidence for the intermediacy of metal-bound ammonium ylide in the product-forming step.
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60
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Xu ZJ, Che CM, Gu X, Lo V. Asymmetric [3+2] Cycloaddition of Azomethine Ylides Catalyzed by Silver(I) Triflate with a Chiral Bipyrrolidine-Derived Phosphine Ligand. SYNTHESIS-STUTTGART 2012. [DOI: 10.1055/s-0032-1316779] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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61
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Wang H, Fang H, Dai J, Liu G, Xu ZJ. Induced pluripotent stem cells for spinal cord injury therapy: current status and perspective. Neurol Sci 2012; 34:11-7. [PMID: 22797773 DOI: 10.1007/s10072-012-1145-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2012] [Accepted: 06/13/2012] [Indexed: 12/29/2022]
Abstract
Spinal cord injury (SCI) is induced by a variety of damages such as trauma, ischemia, and iatrogenic injury, resulting in sense and motion dysfunction. Despite the improvements in medical and surgical care, current treatment methods for SCI demonstrate poor and delayed efficiency, leading to different degree of permanent loss of neural function and disability in the patients. Rapid advances in stem-cells research suggest that stem cells may be applied in SCI therapy. Indeed, SCI is a major field in which stem-cell therapy has been proposed and practised, and most recently the clinical trials of stem-cell therapy were initiated, which aroused a number of clinical concerns. In this review, we summarize current status of SCI repair, then introduce the sources and biological characteristics of induced pluripotent stem cells (iPSCs), and discuss the differentiation potential of iPSCs and the perspective of the application of iPSCs in SCI therapy.
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62
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Wang JC, Xu ZJ, Guo Z, Deng QH, Zhou CY, Wan XL, Che CM. Highly enantioselective intermolecular carbene insertion to C-H and Si-H bonds catalyzed by a chiral iridium(III) complex of a D4-symmetric Halterman porphyrin ligand. Chem Commun (Camb) 2012; 48:4299-301. [PMID: 22447038 DOI: 10.1039/c2cc30441d] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The chiral iridium porphyrin [Ir((-)-D(4)-Por*)(Me)(EtOH)] displays excellent reactivity and stereoselectivity towards carbene insertion to C-H and Si-H bonds, affording corresponding products in high yields (up to 96%) and high enantioselectivities (up to 98% ee).
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63
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Che CM, Chen GQ, Xu ZJ, Chan S, Zhou CY. Homogeneous Silver(I) Salts and Heterogeneous Ag3PW12O40-Catalyzed Intermolecular Allylation of Arenes with Allylic Alcohols. Synlett 2011. [DOI: 10.1055/s-0031-1289548] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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64
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Xu ZJ, Che CM, Deng QH, Wang JC, Zhou CY. Metal-Free Intramolecular Aziridination of Allylic Carbamates Mediated by Hypervalent Iodine Compounds. SYNTHESIS-STUTTGART 2011. [DOI: 10.1055/s-0030-1260150] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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65
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Moon SJ, Homes CC, Akrap A, Xu ZJ, Wen JS, Lin ZW, Li Q, Gu GD, Basov DN. Incoherent c-axis interplane response of the iron chalcogenide FeTe(0.55)Se(0.45) superconductor from infrared spectroscopy. PHYSICAL REVIEW LETTERS 2011; 106:217001. [PMID: 21699329 DOI: 10.1103/physrevlett.106.217001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2010] [Indexed: 05/31/2023]
Abstract
We report on the interplane c-axis electronic response of FeTe(0.55)Se(0.45) investigated by infrared spectroscopy. We find that the normal-state c-axis electronic response of FeTe(0.55)Se(0.45) is incoherent and bears significant similarities to those of mildly underdoped cuprates. The c-axis optical conductivity σ(c)(ω) of FeTe(0.55)Se(0.45) does not display well-defined Drude response at all temperatures. As temperature decreases, σ(c)(ω) is continuously suppressed. The incoherent c-axis response is found to be related to the strong dissipation in the ab-plane transport: a pattern that holds true for various correlated materials as well as FeTe(0.55)Se(0.45).
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66
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Che CM, Chen GQ, Xu ZJ, Liu Y, Zhou CY. Iron-Catalyzed Nitrene Insertion Reaction for Facile Construction of Amide Compounds. Synlett 2011. [DOI: 10.1055/s-0030-1260531] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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67
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Chen GQ, Xu ZJ, Zhou CY, Che CM. Selective oxidation of terminal aryl and aliphatic alkenes to aldehydes catalyzed by iron(iii) porphyrins with triflate as a counter anion. Chem Commun (Camb) 2011; 47:10963-5. [DOI: 10.1039/c1cc13574k] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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68
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Qin H, Shi J, Cao Y, Wu K, Zhang J, Plummer EW, Wen J, Xu ZJ, Gu GD, Guo J. Direct determination of the electron-phonon coupling matrix element in a correlated system. PHYSICAL REVIEW LETTERS 2010; 105:256402. [PMID: 21231605 DOI: 10.1103/physrevlett.105.256402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Indexed: 05/30/2023]
Abstract
High-resolution electron energy loss spectroscopy measurements have been carried out on an optimally doped cuprate Bi(2)Sr(2)CaCu(2)O(8+δ). The momentum-dependent energy and linewidth of an A1 optical phonon were obtained. Based on these data as well as detailed knowledge of the electronic structure, we developed a scheme to determine the electron-phonon coupling (EPC) matrix element related to a specific phonon mode. Such an approach is general and applicable to elucidating the full structure of EPC in a system with anisotropic electronic structure.
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69
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Zhang XZ, Xu ZJ, Tai RZ, Zhen XJ, Wang Y, Guo Z, Yan R, Chang R, Wang B, Li M, Zhao J, Gao F. Ratio-contrast imaging of dual-energy absorption for element mapping with a scanning transmission X-ray microscope. JOURNAL OF SYNCHROTRON RADIATION 2010; 17:804-809. [PMID: 20975228 DOI: 10.1107/s0909049510031250] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 08/04/2010] [Indexed: 05/30/2023]
Abstract
The detection of chemical mapping with a spatial resolution of 30 nm has been achieved with a scanning transmission X-ray microscope at the Shanghai Synchrotron Radiation Facility. For each specimen, two absorption images were scanned separately with energies E(1) and E(2): E(1) was focused on the absorption edge of the chosen element and E(2) was focused below the edge. A K-edge division method is proposed and applied to obtain the element mapping. Compared with the frequently used K-edge subtraction method, this ratio-contrast method is shown to be more accurate and sensitive in identifying the elements of interest, where the definition of the contrast threshold is simple and clear in physics. Several examples are presented to illustrate the effectiveness of the method.
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70
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Xu ZJ, Zhu D, Zeng X, Wang F, Tan B, Hou Y, Lv Y, Zhong G. Diastereoselective HOTf-catalyzed three-component one-pot 1,3-dipolar cycloaddition of α-diazo ester, nitrosobenzene and electron-deficient alkene. Chem Commun (Camb) 2010; 46:2504-6. [DOI: 10.1039/b924575h] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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71
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Xu ZJ, Fang R, Zhao C, Huang JS, Li GY, Zhu N, Che CM. cis-β-Bis(carbonyl) Ruthenium−Salen Complexes: X-ray Crystal Structures and Remarkable Catalytic Properties toward Asymmetric Intramolecular Alkene Cyclopropanation. J Am Chem Soc 2009; 131:4405-17. [DOI: 10.1021/ja8086399] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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72
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Zhang W, Liu G, Meng J, Zhao L, Liu H, Dong X, Lu W, Wen JS, Xu ZJ, Gu GD, Sasagawa T, Wang G, Zhu Y, Zhang H, Zhou Y, Wang X, Zhao Z, Chen C, Xu Z, Zhou XJ. High energy dispersion relations for the high temperature Bi2Sr2CaCu2O8 superconductor from laser-based angle-resolved photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2008; 101:017002. [PMID: 18764144 DOI: 10.1103/physrevlett.101.017002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Indexed: 05/26/2023]
Abstract
Laser-based angle-resolved photoemission spectroscopy measurements have been carried out on the high energy electron dynamics in Bi2Sr2CaCu2O8 high temperature superconductor. Our superhigh resolution data, momentum-dependent measurements, and complete analysis provide important information to judge the nature of the high energy dispersion and kink. Our results rule out the possibility that the high energy dispersion from the momentum distribution curve (MDC) may represent the true bare band as believed in previous studies. We also rule out the possibility that the high energy kink represents electron coupling with some high energy modes as proposed before. Through detailed MDC and energy distribution curve analyses, we propose that the high energy MDC dispersion may not represent intrinsic band structure.
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73
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Deng QH, Xu HW, Yuen AWH, Xu ZJ, Che CM. Ruthenium-catalyzed one-pot carbenoid N-H insertion reactions and diastereoselective synthesis of prolines. Org Lett 2008; 10:1529-32. [PMID: 18351765 DOI: 10.1021/ol800087p] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aryl- and aliphatic-substituted 3-hydroxyprolines and various other amino esters are conveniently prepared by [RuCl2(p-cymene)]2-catalyzed one-pot intramolecular and intermolecular carbenoid N-H insertion reactions, respectively, and the prolines are formed with high diastereoselectivities. The catalytic reactions are tolerant toward air/moisture, and the product yields are insensitive to the organic solvents used.
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74
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Xu ZJ, Liu W, Zhang N, Wang MW, Zhu XN. Effect of intensity clamping on laser ablation by intense femtosecond laser pulses. OPTICS EXPRESS 2008; 16:3604-3609. [PMID: 18542453 DOI: 10.1364/oe.16.003604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have experimentally demonstrated that because of intensity clamping, when the laser peak power is higher than the critical power for self-focusing, further increase of the laser power cannot result in corresponding increase of the laser ablation rate of a metallic sample placed in gases. The ablation rate will finally approach a stabilized value. Also, the experimental technique implemented in our work could be potentially used to measure the self-focusing critical power and the nonlinear refractive index.
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75
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Zhang W, Liu G, Zhao L, Liu H, Meng J, Dong X, Lu W, Wen JS, Xu ZJ, Gu GD, Sasagawa T, Wang G, Zhu Y, Zhang H, Zhou Y, Wang X, Zhao Z, Chen C, Xu Z, Zhou XJ. Identification of a new form of electron coupling in the Bi2Sr2CaCu2O8 superconductor by laser-based angle-resolved photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2008; 100:107002. [PMID: 18352224 DOI: 10.1103/physrevlett.100.107002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Indexed: 05/26/2023]
Abstract
Laser-based angle-resolved photoemission measurements with superhigh resolution have been carried out on an optimally doped Bi(2)Sr(2)CaCu(2)O(8) high temperature superconductor. New high energy features at approximately 115 meV and approximately 150 meV, in addition to the prominent approximately 70 meV one, are found to develop in the nodal electron self-energy in the superconducting state. These high energy features, which cannot be attributed to electron coupling with single phonon or magnetic resonance mode, point to the existence of a new form of electron coupling in high temperature superconductors.
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