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81.
82.
Abbondanno U Aerts G Alvarez-Velarde F Alvarez-Pol H Andriamonje S Andrzejewski J Badurek G Baumann P Becvár F Benlliure J Berthoumieux E Calviño F Cano-Ott D Capote R Cennini P Chepel V Chiaveri E Colonna N Cortes G Cortina D Couture A Cox J Dababneh S Dahlfors M David S Dolfini R Domingo-Pardo C Duran I Embid-Segura M Ferrant L Ferrari A Ferreira-Marques R Frais-Koelbl H Furman W Goncalves I Gallino R Gonzalez-Romero E Goverdovski A Gramegna F Griesmayer E Gunsing F Haas B Haight R Heil M 《Physical review letters》2004,93(16):161103
The151Sm(n,gamma)152Sm cross section has been measured at the spallation neutron facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The new facility combines excellent resolution in neutron time-of-flight, low repetition rates, and an unsurpassed instantaneous luminosity, resulting in rather favorable signal/background ratios. The 151Sm cross section is of importance for characterizing neutron capture nucleosynthesis in asymptotic giant branch stars. At a thermal energy of kT=30 keV the Maxwellian averaged cross section of this unstable isotope (t(1/2)=93 yr) was determined to be 3100+/-160 mb, significantly larger than theoretical predictions. 相似文献
83.
From Mesomorphic Phosphine Oxide to Clustomesogens Containing Molybdenum and Tungsten Octahedral Cluster Cores
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Dr. Viorel Cîrcu Dr. Yann Molard Dr. Maria Amela‐Cortes Ahmed Bentaleb Dr. Philippe Barois Dr. Vincent Dorcet Dr. Stéphane Cordier 《Angewandte Chemie (International ed. in English)》2015,54(37):10921-10925
New clustomesogens (i.e., metal atom clusters containing liquid crystalline (LC) materials) have been obtained by grafting neutral cyanobiphenyl (CB)‐ or cholesteryl‐containing tailor‐made dendritic mesomorphic triphenylphosphine oxide ligands on luminescent (M6Cli8)4+ octahedral cluster cores (M=Mo, W). The LC properties were studied by a combination of polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X‐ray powder diffraction analyses. While the organic ligands showed various mesophase types ranging from nematic, SmA columnar (SmACol), SmA, and SmC phases, it turned out that the corresponding clustomesogens formed layered phases (SmA) over a wide range of temperatures that depend on the nature and density of mesogenic groups employed. Intrinsic luminescence properties of the cluster precursors are preserved over the entire range of LC phase existence. 相似文献
84.
This work describes the performance of a compact “in-house built” radio–frequency (RF)-excited CO2 slab waveguide laser which has the innovation of having a plugged-in RF generator–amplifier module directly connected into the positive electrode of the laser head. The design circuit parameters include a matching circuit and a feed-through element as a whole. The overall laser performance takes into account the waveguide dimension (y-axis) as approximately one-tenth of the free space transverse dimension (x-axis). The optical resonator is calculated to be in the regime of the negative branch for unstable confocal resonators, having focal lengths of and with geometrical amplification of 1.108. Optical output coupling mirror was set to 9.7%. The calculated waveguide length is 37.73 cm whilst the total resonator length was adjusted to 42 cm to allow coupling losses less than 1%. The laser operational efficiency was about 12% and the output beam quality of 1.13 which is close to the ideal Gaussian beam. The optical output power was accomplished by playing with different gas compositions to have a final optimized gas proportion of 1:1:2.7:0.3 correspondingly to CO2, N2, He and Xe as admixture. 相似文献
85.
Barry D. Howes Luca Guerrini Santiago Sanchez‐Cortes Mario P. Marzocchi Jos V. Garcia‐Ramos Giulietta Smulevich 《Journal of Raman spectroscopy : JRS》2007,38(7):859-864
The influence of pH and anions on the adsorption mechanism of rifampicin on colloidal silver nanoparticles has been analysed by electronic absorption, resonance Raman (RR) and surface‐enhanced resonance Raman spectroscopy (SERRS). Rifampicin is a widely used antibiotic with a zwitterionic nature. SERRS spectra of rifampicin adsorbed on silver sols, prepared using hydroxylamine hydrochloride as reducing agent, undergo dramatic changes upon lowering the pH. The spectral form changes progressively from that characteristic of chemisorbed rifampicin (at pH > 7) to one very similar to the rifampicin RR spectrum (at lower pH), indicative of a modification of the adsorption mechanism on the surface of the Ag nanoparticles. The RR‐type SERRS spectrum is proposed to result from formation of an ion pair between rifampicin and Cl− anions, which, deriving from the colloid preparation, are adsorbed on the Ag surface. The addition of anions to the hydroxylamine hydrochloride sol facilitates conversion from the chemisorbed to ion pair form and leads to an order of magnitude increase in the SERRS signal. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
86.
Jacqkis Davis Mojgan Gharaee Dr. Chamini V. Karunaratne Jose Cortes Vazquez Mikayla Haynes Prof. Weiwei Luo Dr. Vladimir N. Nesterov Prof. Thomas Cundari Prof. Hong Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(27):e202200224
Cooperative enamine-metal Lewis acid catalysis has emerged as a powerful tool to construct carbon-carbon and carbon-heteroatom bond forming reactions. A concise synthetic method for asymmetric synthesis of chromans from cyclohexanones and salicylaldehydes has been developed to afford tricyclic chromans containing three consecutive stereogenic centers in good yields (up to 87 %) and stereoselectivity (up to 99 % ee and 11 : 1 : 1 dr). This difficult organic transformation was achieved through bifunctional enamine-metal Lewis acid catalysis. It is believed that the strong activation of the salicylaldehydes through chelating to the metal Lewis acid and the bifunctional nature of the catalyst accounts for the high yields and enantioselectivity of the reaction. The absolute configurations of the chroman products were established through X-ray crystallography. DFT calculations were conducted to understand the mechanism and stereoselectivity of this reaction. 相似文献
87.
88.
In this paper, we introduce the ring of Colombeau full generalized quaternion, and we study its algebraic and topological properties. We prove that the ring of Colombeau full generalized quaternion is Gelfand, normal, duo and some related properties. Moreover, we study the essential ideals of this ring. 相似文献
89.
Dr. Vijaya B. Kenche Dr. Lin W. Hung Keyla Perez Irene Volitakes Dr. Guiseppe Ciccotosto Jeffrey Kwok Nicole Critch Nikki Sherratt Mikhalina Cortes Varsha Lal Prof. Colin L. Masters Kazuma Murakami Prof. Roberto Cappai Dr. Paul A. Adlard Prof. Kevin J. Barnham 《Angewandte Chemie (International ed. in English)》2013,52(12):3374-3378
90.
Quantification of the effect of antiretroviral drugs on the insulin aggregation process is an important area of research due to the serious metabolic diseases observed in AIDS patients after prolonged treatment with these drugs. In this work, multivariate curve resolution alternating least squares (MCR-ALS) was applied to infrared monitoring of the insulin aggregation process in the presence of three antiretroviral drugs to quantify their effect. To evidence concentration dependence in this process, mixtures at two different insulin:drug molar ratios were used. The interaction between insulin and each drug was analysed by 1H NMR spectroscopy. In all cases, the aggregation process was monitored during 45 min by infrared spectroscopy. The aggregates were further characterised by scanning electron microscopy (SEM). MCR-ALS provided the spectral and concentration profiles of the different insulin–drug conformations that are involved in the process. Their feasible band boundaries were calculated using the MCR-BANDS methodology. The kinetic profiles describe the aggregation pathway and the spectral profiles characterise the conformations involved. The retrieved results show that each of the three drugs modifies insulin conformation in a different way, promoting the formation of aggregates. Ritonavir shows the strongest promotion of aggregation, followed by efavirenz and zidovudine. In the studied concentration range, concentration dependence was only observed for zidovudine, with shorter aggregation time obtained as the amount of zidovudine increased. This factor also affected the aggregation pathway. 相似文献