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61.
Govindarao Sathyamoorthi Mou-Ling Soong Timothy W. Ross Joseph H. Boyer 《Heteroatom Chemistry》1993,4(6):603-608
Boron trifluoride reacted with dipyrid-2-ylamine 6 , its N-methyl and 6,6′-dimethyl derivatives 8 and 10 , and 3,3′,5,5′-tetraphenyl-6-azapyrromethene 13 to give fluorescent β-azavinamidine (1,3,5-triazapenta-1,3-diene) dyes: 10-azapyridomethene–BF2 complex 5 (λf 422 nm, λlas 426 nm), its quaternary 10-methyl tetrafluoroborate and 4,6-dimethyl derivatives 9 (λf 362 nm) and 11 (λf 416 nm), and 1,3,5,7-tetraphenyl-8-azapyrromethene–BF2 complex 17 (λf 696 nm). Treating 3,3′,4,4′-tetraphenyl-5,5′,6-trimethylpyrromethene (prepared in situ from ethyl 3,4-diphenyl-5-methylpyrrole-2-carboxylate in a reaction with acetyl chloride) with boron trifluoride gave 1,2,6,7-tetraphenyl-3,5,8-trimethylpyrromethene–BF2 complex 21 . Absorption for the vinamidine chromophore differed from that for the β-azavinamidine chromophore by a hypsochromic shift of 86 nm in a comparison of pyridomethene–BF2 complex 3 with its 10-aza derivative 5 and by a bathochromic shift of 105 nm in a comparison of the pyrromethene–BF2 complex 20 with the 8-azapyrromethene–BF2 complex 17 . 相似文献
62.
A parallel-plate rheometer (PPR) has been constructed for use with the Materials Test System (MTS) for the measurement of fast transient and steady-state responses of polymeric liquids. This particular combination exploits the versatility and capability of the MTS programmable drive system, while the design of the PPR ensures the ideal simple shearing configuration. Instrument compliance, material inertia and mechanical lag in both the input and output components of the system are minimal, thus avoiding defects of most existing rheometers. Reproducible data on a 20% polyisobutylene-in-decalin solution have been obtained for various complicated flow programs. This test system is thus suitable for extensive rheological characterization of complex viscous liquids. 相似文献
63.
64.
Studies on the Formosan Soft Corals I-Cytotoxic Cembrane Diterpenes from Sarcophyton Trocheliophorum
Yang-Chang Wu Pei-Wen Hsieh Chang-Yih Duh Shang-Kwei Wang Keryea Soong Lee-Shing Fang 《中国化学会会志》1992,39(4):355-357
Two cytotoxic cembranoid diterpenes, (+)-isosarcophytoxide (1) and ( + )-isosarcophine (2), were isolated from the soft coral Sarcophyton trocheliophorum by cytotoxicity-guided fractionation. These two compounds demonstrated potent cytotoxicity against P-388 and HL-60 cells. 相似文献
65.
In this study, we developed a fabrication method of conductive and transparent Ag mesh electrodes on flexible polymer film at temperatures lower than 100?°C. Random patterned Ag mesh film was fabricated on a flexible PET substrate over 15?×?15?cm2 by a self-assembly process. It became conductive by a coupling process at low temperatures. The coupled Ag mesh film showed more than 88% transmittance in visible wavelength and less than 8.2?Ω?sq?1 in sheet resistance with figure of merit (FoM) value of 350. This transparent flexible EMI shield film fabricated with a coupled Ag mesh pattern showed high EM shielding effectiveness of ?23?dB?at 1.5–10?GHz frequency with a high transparency of 88%. 相似文献
66.
Mertz C Vellidis CE Alarcon R Barkhuff DH Bernstein AM Bertozzi W Burkert V Chen J Comfort JR Dodson G Dolfini S Dow K Farkhondeh M Finn JM Gilad S Gothe RW Jiang X Joo K Kaloskamis NI Karabarbounis A Kelly JJ Kowalski S Kunz C Lourie RW McIntyre JI Milbrath BD Miskimen R Mitchell JH Papanicolas CN Perdrisat CF Sarty AJ Shaw J Soong SB Tieger D Tschalaer C Turchinetz W Ulmer PE Van Verst S Warren GA Weinstein LB Williamson S Woo RJ Young A 《Physical review letters》2001,86(14):2963-2966
High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account. 相似文献
67.
68.
Che Soong Kim Vilena V. Mushko Alexander N. Dudin 《Annals of Operations Research》2012,201(1):307-323
We consider a multi-server retrial queueing system with the Batch Markovian Arrival Process and phase type service time distribution. Such a general queueing system suits for modeling and decision making in many real life objects including modern wireless communication networks. Behavior of such a system is described by the level dependent multi-dimensional Markov chain. Blocks of the generator of this chain, which is the block structured matrix of infinite size, can have large size if the number of servers is large and distribution of service time is not exponential. Due to this fact, the existing in literature algorithms allow to compute key performance measures of such a system only for a small number of servers. Here we describe the algorithm that allows to compute the stationary distribution of the system for larger number of servers and numerically illustrate its advantage. Importance of taking into account correlation in the arrival process is numerically demonstrated. 相似文献
69.
Xiang D Colby E Dunning M Gilevich S Hast C Jobe K McCormick D Nelson J Raubenheimer TO Soong K Stupakov G Szalata Z Walz D Weathersby S Woodley M 《Physical review letters》2012,108(2):024802
Echo-enabled harmonic generation free electron lasers hold great promise for the generation of fully coherent radiation in x-ray wavelengths. Here we report the first evidence of high harmonics from the echo-enabled harmonic generation technique in the realistic scenario where the laser energy modulation is comparable to the beam slice energy spread. In this experiment, coherent radiation at the seventh harmonic of the second seed laser is generated when the energy modulation amplitude is about 2-3 times the slice energy spread. The experiment confirms the underlying physics of echo-enabled harmonic generation and may have a strong impact on emerging seeded x-ray free electron lasers that are capable of generating laserlike x rays which will advance many areas of science. 相似文献
70.
Mayur Shah Kannappan Thangaraj Mou-Ling Soong Lionel T. Wolford Joseph H. Boyer Ieva R. Politzer Theodore G. Pavlopoulos 《Heteroatom Chemistry》1990,1(5):389-399
Condensations between 3-X-2,4-dimethylpyrroles (X = H, CH3, C2H5, and CO2C2H5) and acyl chlorides gave derivatives of 3,5,3′,5′-tetramethylpyrromethene (isolated as their hydrochloride salts): 6-methyl, 6-ethyl, 4,4′,6-trimethyl, 4,4′-diethyl-6-methyl, and 4,4′-dicarboethoxy-6-ethyl derivatives for conversion on treatment with boron trifluoride to 1,3,5,7-tetramethylpyrromethene–BF2 complex (TMP–BF2) and its 8-methyl (PMP–BF2), 8-ethyl, 2,6,8-trimethyl (HMP–BF2),2,6,-diethyl-8-methyl (PMDEP–BF2), and 2,6-dicarboethoxy-8-ethyl derivatives. Chlorosulfonation converted, 1,3,5,7,8-pentamethylpyrromethene–BF2 complex to its 2,6-disulfonic acid isolated as the lithium, sodium (PMPDS–BF2), potassium, rubidium, cesium, ammonium, and tetramethylammonium disulfonate salts and the methyl disulfonate ester. Sodium 1,3,5,7-tetramethyl-8-ethylpyrromethene-2,6-disulfonate–BF2 complex was obtained from the 8-ethyl derivative of TMP–BF2. Nitration and bromination converted PMP–BF2 to its 2,6-dinitro-(PMDNP–BF2) and 2,6-dibromo- derivatives. The time required for loss of fluorescence by irradiation from a sunlamp showed the following order for P–BF2 compounds (10−3 to 10−4 M) in ethanol: PMPDS–BF2, 7 weeks; PMP–BF2, 5 days; PMDNP–BF2, 72 h; HMP–BF2, 70 h; and PMDEP–BF2, 65 h. Under similar irradiation PMPDS–BF2 in water lost fluorescence after 55 h. The dibromo derivative was inactive, but each of the other pyrromethene–BF2 complexes under flashlamp excitation showed broadband laser activity in the region λ 530–580 nm. In methanol PMPDS–BF2 was six times more resistant to degradation by flashlamp pulses than was observed for Rhodamine-6G (R-6G). An improvement (up to 66%) in the laser power efficiency of PMPDS–BF2 (10−4 M in methanol) in the presence of caffeine (a filter for light <300 nm) was dependent on flashlamp pulse width (2.0 to 7.0 μsec). 相似文献