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81.
The olefin metathesis reaction has underpinned spectacular achievements in organic synthesis in recent years. Arguably, metathesis has now become the foremost choice for a carbon-carbon double bond disconnection. Despite this general utility, de novo routes to heteroaromatic compounds using the cross-metathesis (CM) reaction have only recently emerged as an efficient strategy. This approach allows a convergent union of simple, functionalised, three- to four-carbon olefinic core building blocks, to generate furans, pyrroles and pyridines with a high degree of control of substitution pattern in the product. 相似文献
82.
83.
Synthesis and structure of pristine and alkali-metal-intercalated single-walled carbon nanotubes 总被引:1,自引:0,他引:1
C. Bower S. Suzuki K. Tanigaki O. Zhou 《Applied Physics A: Materials Science & Processing》1998,67(1):47-52
8 (M=K or Cs). No crystalline structure was observed in the reacted materials by X-ray diffraction. In situ metal deposition,
TEM, and electron energy loss spectroscopy (EELS) measurements were performed on individual SWNT bundles at 300 K. The results
showed that alkali metals can be reversibly intercalated into the SWNT bundles. Although intercalation induced structural
disorder, individual nanotubes and to a large extent the bundles maintained their structural integrity after intercalation
and de-intercalation.
Received: 10 February 1998 相似文献
84.
J. A. Webb D. I. Bower I. M. Ward P. T. Cardew 《Journal of Polymer Science.Polymer Physics》1993,31(7):743-757
A study has been made of the gas transport properties of polyethylene films of two different grades, Hizex 7000F and Rigidex 002-55, one-way drawn at 115°C to draw ratios in the range 1–20. Measurements of the permeability and diffusion coefficients of helium, oxygen, carbon dioxide and nitrogen have been made with a dynamic flow rate technique, utilizing a mass spectrometer detection system, and of oxygen using a commercial OXTRAN system. The samples were characterized by the measurement of density, birefringence and modulus and by wide-angle x-ray diffraction and differential scanning calorimetry. There is a large decrease in both the permeability and diffusion coefficients for all gases with increasing polymer draw ratio, with up to an 80-fold decrease in permeability for the larger permeants compared with the 10-fold decrease observed for helium. The solubilities of all the gases decrease only by a factor of ~ 2. The diffusion results are discussed in terms of geometric impedance and chain immobilization factors. The solubilities, on the other hand, appear to relate primarily to the amorphous volume fraction of the polymer. © 1993 John Wiley & Sons, Inc. 相似文献
85.
Glenzer SH MacGowan BJ Meezan NB Adams PA Alfonso JB Alger ET Alherz Z Alvarez LF Alvarez SS Amick PV Andersson KS Andrews SD Antonini GJ Arnold PA Atkinson DP Auyang L Azevedo SG Balaoing BN Baltz JA Barbosa F Bardsley GW Barker DA Barnes AI Baron A Beeler RG Beeman BV Belk LR Bell JC Bell PM Berger RL Bergonia MA Bernardez LJ Berzins LV Bettenhausen RC Bezerides L Bhandarkar SD Bishop CL Bond EJ Bopp DR Borgman JA Bower JR Bowers GA Bowers MW Boyle DT Bradley DK Bragg JL Braucht J 《Physical review letters》2011,106(8):085004
We demonstrate the hohlraum radiation temperature and symmetry required for ignition-scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2.2 mm-diameter capsules are heated with unprecedented laser energies of 1.2 MJ delivered by 192 ultraviolet laser beams on the National Ignition Facility. Laser backscatter measurements show that these hohlraums absorb 87% to 91% of the incident laser power resulting in peak radiation temperatures of T(RAD)=300 eV and a symmetric implosion to a 100 μm diameter hot core. 相似文献
86.
VGKM Pisipati D Madhavi Latha P Pardhasaradhi PV Datta Prasad 《Liquid Crystals Today》2013,22(4):70-76
Refractive index studies are carried out on two highly polar liquid crystals: 1. N-(p-n-methoxy benzylidene)-p-amino benzonitrile, PmBAB, 2. N-(p-n-ethoxy benzylidene)-p-amino benzonitrile, PeBAB. The experimental investigations are carried out in the visible region at four different wavelengths, namely, 633, 589, 546 and 436 nm. The two compounds exhibit only the nematic liquid crystalline phase in between the isotropic and crystalline solid. The dispersive power ω is estimated for two consecutive wavelengths for the case of <n>, ne and no for different wavelengths and found to be constant with temperature. Further the temperature gradients of ne and no are estimated, and the crossover temperature is obtained using dno/dT for all the wavelengths. 相似文献
87.
88.
Andrew G. Dalling Takayuki Yamauchi Niall G. McCreanor Lydia Cox John F. Bower 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):227-231
Rh‐catalyzed carbonylative C?C bond activation of cyclopropylamides generates configurationally stable rhodacyclopentanones that engage tethered alkenes in (3+1+2) cycloadditions. These studies provide the first examples of multicomponent cycloadditions that proceed through C?C bond activation of “simple” electron poor cyclopropanes. 相似文献
89.
Alexander G Barley J Batygin Y Berridge S Bharadwaj V Bower G Bugg W Decker FJ Dollan R Efremenko Y Gharibyan V Hast C Iverson R Kolanoski H Kovermann J Laihem K Lohse T McDonald KT Mikhailichenko AA Moortgat-Pick GA Pahl P Pitthan R Pöschl R Reinherz-Aronis E Riemann S Schälicke A Schüler KP Schweizer T Scott D Sheppard JC Stahl A Szalata ZM Walz D Weidemann AW 《Physical review letters》2008,100(21):210801
An experiment (E166) at the Stanford Linear Accelerator Center has demonstrated a scheme in which a multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with GEANT4 simulations that include the dominant polarization-dependent interactions of electrons, positrons, and photons in matter. 相似文献
90.
The National Coal Board has developed a process for converting coal into distillable liquids based on the extraction by supercritical fluids of fragments of coal molecules produced by thermolysis. The resultant coal extract has desirable properties for subsequent hydroprocessing. This paper outlines process requirements and describes how these were realised in a 10 kg h−1 pilot plant. Results illustrating the effects of main process variables are given, using examples taken from experimental work employing a simulated process-derived solvent as extractant. Yields and analyses are presented for products obtained under varied processing conditions. 相似文献