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981.
Lee JS Kao CC Nelson CS Jang H Ko KT Kim SB Choi YJ Cheong SW Smadici S Abbamonte P Park JH 《Physical review letters》2011,107(3):037206
We investigated the orbital and antiferromagnetic ordering behaviors of the half-doped bilayer manganite La(2-2x)Sr(1+2x)Mn2O7 (x ? 0.5) by using Mn L(2,3)-edge resonant soft x-ray scattering. Resonant soft x-ray scattering reveals the CE-type orbital order below T(oo) ? 220 K, which shows partial melting behavior below T(m) ? 165 K. We also found coexistence CE- and A-type antiferromagnetic orders. Both orders involve the CE-type orbital order with nearly the same orbital character and are coupled with each other. These results manifest that the ground state with the CE-type antiferromagnetic order is easily susceptible to destabilization into the A-type one even with a small fluctuation of the doping level, as suggested by the extremely narrow magnetic phase boundaries at x ? 0.5±0.005. 相似文献
982.
Cho S Furumoto T Hyodo T Jido D Ko CM Lee SH Nielsen M Ohnishi A Sekihara T Yasui S Yazaki K;ExHIC Collaboration 《Physical review letters》2011,106(21):212001
Identifying hadronic molecular states and/or hadrons with multiquark components either with or without exotic quantum numbers is a long-standing challenge in hadronic physics. We suggest that studying the production of these hadrons in relativistic heavy ion collisions offers a promising resolution to this problem as yields of exotic hadrons are expected to be strongly affected by their structures. Using the coalescence model for hadron production, we find that, compared to the case of a nonexotic hadron with normal quark numbers, the yield of an exotic hadron is typically an order of magnitude smaller when it is a compact multiquark state and a factor of 2 or more larger when it is a loosely bound hadronic molecule. We further find that some of the newly proposed heavy exotic states could be produced and realistically measured in these experiments. 相似文献
983.
Won E Ko BR Adachi I Aihara H Arinstein K Asner DM Aushev T Bakich AM Barberio E Bay A Bhardwaj V Bhuyan B Bischofberger M Bondar A Bozek A Bračko M Brodzicka J Browder TE Chang P Chen A Chen P Cheon BG Chilikin K Cho IS Cho K Choi SK Choi Y Dalseno J Danilov M Doležal Z Drásal Z Drutskoy A Eidelman S Fast JE Gaur V Gabyshev N Garmash A Goh YM Golob B Haba J Hara T Hayasaka K Hayashii H Horii Y Hoshi Y Hou WS Hsiung YB Hyun HJ Iijima T Inami K Ishikawa A Itoh R Iwabuchi M Iwasaki Y Iwashita T 《Physical review letters》2011,107(22):221801
We report the first observation of the doubly Cabibbo-suppressed decays D(+)→K(+)η((')) using a 791 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The ratio of the branching fractions of doubly Cabibbo-suppressed relative to singly Cabibbo-suppressed D(+)→π(+)η((')) decays are B(D(+)→K(+)η)/B(D(+)→π(+)η)=(3.06±0.43±0.14)% and B(D(+)→K(+)η')/B(D(+)→π(+)η')=(3.77±0.39±0.10)%. From these, we find that the relative final-state phase difference between the tree and annihilation amplitudes in D(+) decays, δ(TA), is (72±9)° or (288±9)°. We also report the most precise measurements of CP asymmetries to date: A(CP)(D(+)→π(+)η)=(+1.74±1.13±0.19)% and A(CP)(D(+)→π(+)η')=(-0.12±1.12±0.17)%. 相似文献
984.
Fu W Zhang J Fuhrer T Champion H Furukawa K Kato T Mahaney JE Burke BG Williams KA Walker K Dixon C Ge J Shu C Harich K Dorn HC 《Journal of the American Chemical Society》2011,133(25):9741-9750
The dimetallic endohedral heterofullerene (EHF), Gd(2)@C(79)N, was prepared and isolated in a relatively high yield when compared with the earlier reported heterofullerene, Y(2)@C(79)N. Computational (DFT), chemical reactivity, Raman, and electrochemical studies all suggest that the purified Gd(2)@C(79)N, with the heterofullerene cage, (C(79)N)(5-) has comparable stability with other better known isoelectronic metallofullerene (C(80))(6-) cage species (e.g., Gd(3)N@C(80)). These results describe an exceptionally stable paramagnetic molecule with low chemical reactivity with the unpaired electron spin density localized on the internal diatomic gadolinium cluster and not on the heterofullerene cage. EPR studies confirm that the spin state of Gd(2)@C(79)N is characterized by a half-integer spin quantum number of S = 15/2. The spin (S = ?) on the N atom of the fullerene cage and two octet spins (S = 7/2) of two encapsulated gadoliniums are coupled with each other in a ferromagnetic manner with a small zero-field splitting parameter D. Because the central line of Gd(2)@C(79)N is due to the Kramer's doublet with a half-integer spin quantum number of S = 15/2, this relatively sharp line is prominent and the anisotropic nature of the line is weak. Interestingly, in contrast with most Gd(3+) ion environments, the central EPR line (g = 1.978) is observable even at room temperature in a toluene solution. Finally, we report the first EHF derivative, a diethyl bromomalonate monoadduct of Gd(2)@C(79)N, which was prepared and isolated via a modified Bingel-Hirsch reaction. 相似文献
985.
Ko S Verploegen E Hong S Mondal R Hoke ET Toney MF McGehee MD Bao Z 《Journal of the American Chemical Society》2011,133(42):16722-16725
We demonstrate that poly(3,4-dialkylterthiophenes) (P34ATs) have comparable transistor mobilities (0.17 cm(2) V(-1) s(-1)) and greater environmental stability (less degradation of on/off ratio) than regioregular poly(3-alkylthiophenes) (P3ATs). Unlike poly(3-hexylthiophene) (P3HT), P34ATs do not show a strong and distinct π-π stacking in X-ray diffraction. This suggests that a strong π-π stacking is not always necessary for high charge-carrier mobility and that other potential polymer packing motifs in addition to the edge-on structure (π-π stacking direction parallel to the substrate) can lead to a high carrier mobility. The high charge-carrier mobilities of the hexyl and octyl-substituted P34AT produce power conversion efficiencies of 4.2% in polymer:fullerene bulk heterojunction photovoltaic devices. An enhanced open-circuit voltage (0.716-0.771 eV) in P34AT solar cells relative to P3HT due to increased ionization potentials was observed. 相似文献
986.
Maha M. Abdelrahman Amal B. Ahmed Mahmoud A. Omar Sayed M. Derayea Nada S. Abdelwahab 《Journal of separation science》2020,43(15):2981-2988
Citicoline and piracetam were subjected separately to different stress conditions as recommended by the international conference on harmonization. In addition, new stability indicating thin layer chromatographic and ultra high performance liquid chromatographic methods have been developed and validated for simultaneous determination of citicoline and piracetam in presence of their degradation products. Separation on the proposed thin layer chromatographic method was carried out using a developing system containing methanol:chloroform:ammonium chloride buffer (9:1:2, v/v/v) on silica gel plates at 230 nm. On the other hand, the mobile phase in the ultra high performance liquid chromatographic method was composed of water (containing 0.1% triethylamine):ethanol (92:8, v/v). The flow rate was 1 mL/min and ultraviolet detection was at 230 nm. Moreover, results of the developed methods were statistically compared to those obtained by the reported high‐performance liquid chromatography method and no significant difference between them was found. The greenness profile of ultra high performance liquid chromatographic method was assessed and compared with those of the previously published high‐performance liquid chromatography methods, it was noticed that the proposed ultra high performance liquid chromatographic method more environmentally friendly and greener than other methods. 相似文献
987.
Hong Hee Lee Tae Su Choi Shin Jung C. Lee Jong Wha Lee Junghong Park Dr. Young Ho Ko Prof. Dr. Won Jong Kim Prof. Dr. Kimoon Kim Prof. Dr. Hugh I. Kim 《Angewandte Chemie (International ed. in English)》2014,53(29):7461-7465
Amyloid fibrils are insoluble protein aggregates comprised of highly ordered β‐sheet structures and they are involved in the pathology of amyloidoses, such as Alzheimer’s disease. A supramolecular strategy is presented for inhibiting amyloid fibrillation by using cucurbit[7]uril (CB[7]). CB[7] prevents the fibrillation of insulin and β‐amyloid by capturing phenylalanine (Phe) residues, which are crucial to the hydrophobic interactions formed during amyloid fibrillation. These results suggest that the Phe‐specific binding of CB[7] can modulate the intermolecular interaction of amyloid proteins and prevent the transition from monomeric to multimeric states. CB[7] thus has potential for the development of a therapeutic strategy for amyloidosis. 相似文献
988.
Dr. Shintaro Ishida Fumiya Hirakawa Prof. Dr. Ko Furukawa Dr. Kenji Yoza Prof. Dr. Takeaki Iwamoto 《Angewandte Chemie (International ed. in English)》2014,53(42):11172-11176
Stibinyl and bismuthinyl radicals are recognized as representative intermediates of antimony and bismuth compounds, but still elusive in the condensed phase. We successfully synthesized persistent stibinyl and bismuthinyl radicals in solution by facile dissociation of the corresponding dimers with bulky substituents. We characterized the radicals by NMR and UV/Vis spectroscopy and estimated the thermodynamic parameters for the dissociation equilibria. The radicals show n→p (HOMO→SOMO) transition bands at 497 nm (stibinyl) and 543 nm (bismuthinyl) in 3‐methylpentane and react with a stable nitroxyl radical to give the cross‐radical coupling products in good yields. 相似文献
989.
Guest Modulation of Spin‐Crossover Transition Temperature in a Porous Iron(II) Metal–Organic Framework: Experimental and Periodic DFT Studies
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Dr. Daniel Aravena Zulema Arcís Castillo Prof. Dr. M. Carmen Muñoz Dr. Ana B. Gaspar Dr. Ko Yoneda Dr. Ryo Ohtani Dr. Akio Mishima Prof. Dr. Susumu Kitagawa Prof. Dr. Masaaki Ohba Prof. Dr. José Antonio Real Prof. Dr. Eliseo Ruiz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12864-12873
The synthesis, structure, and magnetic properties of three clathrate derivatives of the spin‐crossover porous coordination polymer {Fe(pyrazine)[Pt(CN)4]} ( 1 ) with five‐membered aromatic molecules furan, pyrrole, and thiophene is reported. The three derivatives have a cooperative spin‐crossover transition with hysteresis loops 14–29 K wide and average critical temperatures Tc=201 K ( 1?fur ), 167 K ( 1?pyr ), and 114.6 K ( 1?thio ) well below that of the parent compound 1 (Tc=295 K), confirming stabilization of the HS state. The transition is complete and takes place in two steps for 1?fur , while 1?pyr and 1?thio show 50 % spin transition. For 1?fur the transformation between the HS and IS (middle of the plateau) phases occurs concomitantly with a crystallographic phase transition between the tetragonal space groups P4/mmm and I4/mmm, respectively. The latter space group is retained in the subsequent transformation involving the IS and the LS phases. 1?pyr and 1?thio display the tetragonal P4/mmm and orthorhombic Fmmm space groups, respectively, in both HS and IM phases. Periodic calculations using density functional methods for 1?fur , 1?pyr , 1?thio , and previously reported derivatives 1?CS2 , 1?I, 1?bz (benzene), and 1?pz (pyrazine) have been carried out to investigate the electronic structure and nature of the host–guest interactions as well as their relationship with the changes in the LS–HS transition temperatures of 1?Guest . Geometry‐optimized lattice parameters and bond distances in the empty host 1 and 1?Guest clathrates are in general agreement with the X‐ray diffraction data. The concordance between the theoretical results and the experimental data also comprises the guest molecule orientation inside the host and intermolecular distances. Furthermore, a general correlation between experimental Tc and calculated LS–HS electronic energy gap was observed. Finally, specific host–guest interactions were studied through interaction energy calculations and crystal orbital displacement (COD) curve analysis. 相似文献
990.
The First Heteropentanuclear Extended Metal‐Atom Chain: [Ni+Ru25+Ni2+Ni2+(tripyridyldiamido)4(NCS)2]
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Dr. Min‐Jie Huang Dr. Shao‐An Hua Dr. Ming‐Dung Fu Dr. Gin‐Chen Huang Prof. Caixia Yin Chih‐Hung Ko Dr. Ching‐Kuo Kuo Chia‐Hung Hsu Dr. Gene‐Hsiang Lee Kuan‐Yi Ho Dr. Chia‐Hsin Wang Prof. Yaw‐Wen Yang Prof. I‐Chia Chen Prof. Shie‐Ming Peng Prof. Chun‐hsien Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(16):4526-4531
This study develops the first heteropentametal extended metal atom chain (EMAC) in which a string of nickel cores is incorporated with a diruthenium unit to tune the molecular properties. Spectroscopic, crystallographic, and magnetic characterizations show the formation of a fully delocalized Ru25+ unit. This [Ru2]‐containing EMAC exhibits single‐molecule conductance four‐fold superior to that of the pentanickel complex and results in features of negative differential resistance (NDR), which are unobserved in analogues of pentanickel and pentaruthenium EMACs. A plausible mechanism for the NDR behavior is proposed for this diruthenium‐modulated EMAC. 相似文献