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排序方式: 共有173条查询结果,搜索用时 31 毫秒
101.
通过固定化酶Novozyme435(NV435)催化聚乙二醇(PEG)开环聚合己内酯(CL)得到端基带有羟基的ABA型三嵌段聚合物,用2,2-二氯代乙酰氯将聚合物的端羟基功能化形成H型大分子引发剂,在CuCl/HMTETA体系中引发4-乙烯基吡啶(4VP)进行原子转移自由基聚合反应(ATRP),得到了具有两亲性的H型五嵌段聚合物(PVP)2-b—PCL-b.PEG-PCL-(PVP)2,用红外光谱(FT IR),核磁共振(^1H NMR),凝胶渗透色谱(GPC)对其结构与分子量及其分子量分布进行了表征,结果表明:H型五嵌段聚合物分子量46121g/mol,分子量分布1.30.并利用动态光散射(DLS)和原子力显微镜(AFM)对聚合物在水溶液中的自组装行为进行了研究,H型嵌段聚合物的胶束呈球形结构,平均直径为70nm左右. 相似文献
102.
Mixed-metal carbonyl clusters of W2Ir2(CO)10(η^5-C5H4Me)2 1 and W2Ir2(μ-L)(CO)8(η^5-C5H4Me)2 (L = dppe 2, dppf 3) have been studied by TDDFT method focusing on their electronic and nonlinear optical properties. These three clusters exhibit the first static hyperpolarizabilities of medium magnitude (βtot-10×10^-30 esu). The origin of β is discussed by the new proposed orbital-pair decomposition scheme by Barandes et al. The result suggests that the β values of the two clusters are mainly originated from d-d electron transition within the metal skeleton, and d-p (π*) electron transition from metals to carbonyls and phenyl. The additional coordination by the electron donor group, ferrocene, makes cluster 3 own much larger β values, and the relatively longer range charge transfer from d orbitals of ferrocene to d orbirals of Ir and W is responsible for the enhanced β values. 相似文献
103.
Besson D Pedlar TK Cronin-Hennessy D Gao KY Gong DT Hietala J Kubota Y Klein T Lang BW Poling R Scott AW Smith A Dobbs S Metreveli Z Seth KK Tomaradze A Zweber P Ernst J Arms K Severini H Dytman SA Love W Mehrabyan S Mueller JA Savinov V Li Z Lopez A Mendez H Ramirez J Huang GS Miller DH Pavlunin V Sanghi B Shipsey IP Adams GS Anderson M Cummings JP Danko I Napolitano J He Q Muramatsu H Park CS Thorndike EH Coan TE Gao YS Liu F Artuso M Boulahouache C Blusk S Butt J Li J Menaa N Mountain R 《Physical review letters》2006,96(9):092002
We measure the cross section for e+e- -->psi(3770) -->hadrons at Ec.m.=3773 MeV to be (6.38+/-0.08(+0.41)(-0.30) nb using the CLEO detector at the CESR e+e- collider. The difference between this and the e+e- -->psi(3770) -->DD cross section at the same energy is found to be (-0.01+/-0.08(+0.41)(-0.30) nb. With the observed total cross section, we extract Gamma(ee)(psi(3770))=(0.204+/-0.003(+0.041)(-0.027) keV. Uncertainties shown are statistical and systematic, respectively. 相似文献
104.
以Fe(NO3)3.9H2O和Cd(NO3)2.4H2O为原料,以柠檬酸为还原剂,采用燃烧法制备了CdFe2O4纳米粉体,用X射线粉末衍射仪(XRD)、透射电子显微镜(TEM)、红外光谱(IR)和振动样品磁强计(VSM)等手段对样品进行了表征,结果表明,样品为尖晶石型铁酸镉纳米粉体,其粒径大约为20—50nm,且具有超顺磁性。 相似文献
105.
Pedlar TK Cronin-Hennessy D Gao KY Gong DT Hietala J Kubota Y Klein T Lang BW Li SZ Poling R Scott AW Smith A Dobbs S Metreveli Z Seth KK Tomaradze A Zweber P Ernst J Arms K Severini H Dytman SA Love W Mehrabyan S Mueller JA Savinov V Li Z Lopez A Mendez H Ramirez J Huang GS Miller DH Pavlunin V Sanghi B Shipsey IP Adams GS Anderson M Cummings JP Danko I Napolitano J He Q Muramatsu H Park CS Thorndike EH Coan TE Gao YS Liu F Artuso M Boulahouache C Blusk S Butt J Dorjkhaidav O Li J Menaa N 《Physical review letters》2005,95(26):261803
Using 20.7 pb(-1) of e(+)e(-) annihilation data taken at sq.rt(r) = 3.671 GeV with the CLEO-c detector, precision measurements of the electromagnetic form factors of the charged pion, charged kaon, and proton have been made for timelike momentum transfer of |Q(2)| = 13.48 GeV(2) by the reaction e(+)e(-) --> h(+)h(-). The measurements are the first ever with identified pions and kaons of |Q(2)| > 4 GeV(2), with the results F(13.48 GeV(2)) = 0.075 +/- 0.008(stat) +/- 0.005(syst) and F(K)(13.48 GeV(2)) = 0.063 +/- 0.004(stat) +/- 0.001(syst). The result for the proton, assuming G(p)(E) = G(p)(M), is G(p)(M)(13.48 GeV(2)) = 0.014 +/- 0.002(stat) +/- 0.001(syst), which is in agreement with earlier results. 相似文献
106.
Brandenburg G Ershov A Kim DY Wilson R Bergfeld T Eisenstein BI Ernst J Gladding GE Gollin GD Hans RM Johnson E Karliner I Marsh MA Plager C Sedlack C Selen M Thaler JJ Williams J Edwards KW Sadoff AJ Ammar R Bean A Besson D Zhao X Anderson S Frolov VV Kubota Y Lee SJ Poling R Smith A Stepaniak CJ Urheim J Ahmed S Alam MS Athar SB Jian L Ling L Saleem M Timm S Wappler F Anastassov A Eckhart E Gan KK Gwon C Hart T Honscheid K Hufnagel D Kagan H Kass R Pedlar TK Thayer JB von Toerne E Zoeller MM 《Physical review letters》2001,87(7):071802
We present an observation and time-integrated rate measurement of the decay D(0)-->K(+)pi(-)pi(0) produced in 9 fb(-1) of e(+)e(-) collisions near the Upsilon(4S) resonance. The signal is inconsistent with an upward fluctuation of the background by 4.9 standard deviations. We measured the time-integrated rate of D(0)-->K(+)pi(-)pi(0) normalized to the rate of D(0)-->K(+)pi(-)pi(0) to be 0.0043(+0.0011)(-0.0010) (stat)+/-0.0007 (syst). This decay can be produced by doubly Cabibbo-suppressed decays or by the D(0) evolving into a D(0) through mixing, followed by a Cabibbo-favored decay to K(+)pi(-)pi(0). We also found the CP asymmetry A = (9(+25)(-22))% be consistent with zero. 相似文献
107.
Ammar R Besson D Zhao X Anderson S Frolov VV Kubota Y Lee SJ Li SZ Poling R Smith A Stepaniak CJ Urheim J Ahmed S Alam MS Jian L Saleem M Wappler F Eckhart E Gan KK Gwon C Hart T Honscheid K Hufnagel D Kagan H Kass R Pedlar TK Thayer JB von Toerne E Wilksen T Zoeller MM Muramatsu H Richichi SJ Severini H Skubic P Dytman SA Nam S Savinov V Chen S Hinson JW Lee J Miller DH Pavlunin V Shibata EI Shipsey IP Cronin-Hennessy D Lyon AL Park CS Park W Thorndike EH Coan TE Gao YS Liu F Maravin Y 《Physical review letters》2002,89(17):171803
Using the CLEO detector at the Cornell Electron Storage Ring we have observed the Omega(0)(c) (css ground state) in the decay Omega(0)(c)-->Omega(-)e(+)nu(e). We find a signal of 11.4+/-3.8(stat) events. The probability that we have observed a background fluctuation is 7.6x10(-5). We measure B(Omega(0)(c)-->Omega(-)e(+)nu(e)).sigma(e(+)e(-)-->Omega(0)(c)X)=(42.2+/-14.1(stat)+/-5.7(syst)) fb and R=[Gamma(Omega(0)(c)-->Omega(-)pi(+))]/[Gamma(Omega(0)(c)-->Omega(-)enu(e))]=00.41+/-0.19(stat)+/-0.04(syst). This is the first statistically significant observation of an individual decay mode of the Omega(0)(c) in e(+)e(-) annihilation and the first example of a baryon decaying via beta emission, where no quarks from the first generation participate in the reaction. 相似文献
108.
109.
A hadron and string cascade model, JPCIAE, together with the corresponding Monte Carlo event generator, has been employed in this paper to investigate further the charge fluctuations in Au+Au collisions at Snn = 130 GeV. The default JPCIAE calculations are in good agreement with PHENIX and STAR data. We found that the thermal predictions for the π gas, the resonance π gas and quark matter deviate, respectively, from the corresponding dynamical simulations from the JPCIAE model. The discrepancies were also found between the π charge fluctuations and the charge fluctuations of all species of hadrons. However the charge fluctuations for "π from ρ and ω decay" and for all the hadrons from resonance decay are close to each other, indicating the correlation between positively and negatively charged hadrons is not sensitive to the species of hadrons. This work shows further that it is questionable to use the charge fluctuations as a signature of QGP. 相似文献
110.
Bowcock T Giles RT Hassard J Kinoshita K Pipkin FM Wilson R Wolinski J Xiao D Gentile T Haas P Hempstead M Jensen T Kagan H Kass R Behrends S Guida JM Guida JA Morrow F Poling R Thorndike EH Tipton P Alam MS Katayama N Kim IJ Sun CR Tanikella V Bortoletto D Chen A Garren L Goldberg M Holmes R Horwitz N Jawahery A Lubrano P Moneti GC Sharma V Csorna SE Mestayer MD Panvini RS Word GB Bean A Bobbink GJ Brock IC Engler A Ferguson T Kraemer RW Rippich C Vogel H Bebek C Berkelman K Blucher E 《Physical review letters》1987,58(4):307-310