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21.
Insight is gained into about the processes governing cavitational activity and acoustic streaming induced by high frequency (500 kHz) ultrasound by the use of microelectrodes with short time resolution electrochemical equipment to allow monitoring of the activity of single cavitating bubbles. Current transients are interpreted as showing the flux of solution towards the electrode surface due to microstreaming. In order to explain the current amplitude, a simplified model is produced. Important parameters such as bubble size and shape on the surface as well as the boundary layer thickness for microstreaming are taken into account. This model leads to the amplitude of the oscillations of the cavitating bubble. Introducing realistic bubble sizes, this amplitude is found to be in the order of 1 micron. The conclusions arising from this work allow a further interpretation of previous observations at millimeter scale electrodes. 相似文献
22.
Quinolines substituted in the 3-position by an iodo or phenylseleno group are readily prepared in good to excellent yields by the reaction of propargylic anilines with appropriate electrophiles under mild reaction conditions. [reaction: see text] 相似文献
23.
Novel palladium migration/arylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement with the idea that these palladium-catalyzed C-H activation reactions parallel electrophilic aromatic substitution. 相似文献
24.
Liang JF Shapira D Gross CJ Beene JR Bierman JD Galindo-Uribarri A Gomez del Campo J Hausladen PA Larochelle Y Loveland W Mueller PE Peterson D Radford DC Stracener DW Varner RL 《Physical review letters》2003,91(15):152701
Evaporation residue cross sections have been measured with neutron-rich radioactive 132Sn beams on 64Ni in the vicinity of the Coulomb barrier. The average beam intensity was 2 x 10(4) particles per second and the smallest cross section measured was less than 5 mb. Large sub-barrier fusion enhancement was observed. Coupled-channel calculations taking into account inelastic excitation significantly underpredict the measured cross sections below the barrier. The presence of several neutron transfer channels with large positive Q values suggests that multinucleon transfer may play an important role in enhancing the fusion of 132Sn and 64Ni. 相似文献
25.
Gareth AD Hardy Nesrina Imami Mark R Nelson Ann K Sullivan Ron Moss Marlén MI Aasa-Chapman Brian Gazzard Frances M Gotch 《Journal of immune based therapies and vaccines》2007,5(1):6-12
Background
Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection. 相似文献26.
27.
Vanessa L. Campo 《Tetrahedron》2009,65(27):5343-7358
This work describes the synthesis in solution of a series of related diketopiperazines with potential biological activities: cyclo(l-Pro-l-Ser), cyclo(l-Phe-l-Ser), cyclo(d-Phe-l-Ser) and the corresponding glycosylated analogs of the latter, cyclo[d-Phe-l-Ser(αGlcNAc)] and cyclo[d-Phe-l-Ser(βGlcNAc)]. The synthetic approach involved coupling reactions of -OH or O-glycosylated serine benzyl esters with NFmoc-protected amino acids (Pro or Phe), followed by one-pot deprotection-cyclization reaction in the presence of 20% piperidine in DMF. 相似文献
28.
This paper presents a comparative study between a carbon molecular sieve (CMS) membrane and a commercial CMS adsorbent; these materials are suited for selective gas permeation and adsorption-based gas separations, respectively. The purpose of this analysis is to better understand the mass transport mechanism in CMS membranes and how it is related to the material's structure. The structural characterization based on the adsorption of CO2 at 0 °C revealed that the adsorbent has a greater micropore volume, a smaller mean pore width and a micropore size distribution shifted to the left, when compared to the membrane. This translates into a lower adsorption capacity of the membrane towards N2, Ar, CO2 and O2 at 29.5 °C and 0–7 bar. The adsorption kinetics were also studied and the pressure-dependence of the apparent time constants established; different models were used to predict the experimental results, emphasizing the very important role of the ultramicroporosity on the properties of the materials. The CMS membrane exhibited a pore blockage effect when permeating O2 and CO2. Further morphologic characterization was performed by SEM, X-ray diffraction and mercury porosimetry. 相似文献
29.
Päivi Mäki-Arvela Elena V. Murzina Betiana Campo Teemu Heikkilä Anne-Riikka Leino Krisztian Kordas Dorit Wolf Anton V. Tokarev Dmitry Yu. Murzin 《Research on Chemical Intermediates》2010,36(4):423-442
Lactose oxidation was investigated at 70 °C and at pH 8 using oxygen as an oxidant over a comprehensive set of commercially
available mono- and multi-metallic as well as promoted Pd catalysts with active carbon, alumina and calcium carbonate as catalyst
supports. An optimum cluster size of 6–10 nm resulted in the highest initial turnover frequencies. High conversion levels
above 90% were achieved on Pd/C catalyst, as well as over Pd/Al2O3 and (Pd–Pb)/CaCO3, whereas (Pd–V)/C catalyst gave only 30% conversion after 200 min. The latter catalyst was relatively inactive due to its
high support acidity and profound deactivation during oxidation. Besides the main oxidation product, lactobionic acid, also,
lactulose was generated as a result of lactose isomerisation under alkaline conditions. The electrochemical potentials of
the catalysts were measured during lactose oxidation. The main result of these measurements was that, when the electrochemical
potential of the catalyst increased very quickly, its oxidation activity was low due to metal over-oxidation. The selectivities
to the desired product, lactobionic acid, were relatively high, above 80% for most of the catalysts, except for (Pd–V)/C.
Furthermore, the selectivity to the lactobionic acid decreased with increasing metal dispersion, thus, indicating that the
optimum metal particle sizes for producing high amounts of lactobionic acid is above 3 nm. 相似文献
30.