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排序方式: 共有485条查询结果,搜索用时 31 毫秒
41.
42.
Navasardyan T Adams GS Ahmidouch A Angelescu T Arrington J Asaturyan R Baker OK Benmouna N Bertoncini C Blok HP Boeglin WU Bosted PE Breuer H Christy ME Connell SH Cui Y Dalton MM Danagoulian S Day D Dodario T Dunne JA Dutta D El Khayari N Ent R Fenker HC Frolov VV Gan L Gaskell D Hafidi K Hinton W Holt RJ Horn T Huber GM Hungerford E Jiang X Jones M Joo K Kalantarians N Kelly JJ Keppel CE Kubarovski V Li Y Liang Y Malace S Markowitz P McGrath E McKee P Meekins DG Mkrtchyan H Moziak B 《Physical review letters》2007,98(2):022001
A large data set of charged-pion (pi+/-) electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark-->pion production mechanisms. 相似文献
43.
44.
R. F. Payne S. M. Schulte M. Douglas J. I. Friese O. T. FarmerIII E. C. Finn 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(3):863-867
Lanthanides are common fission products and the ability to separate and quantify these elements is critical to rapid radiochemistry
applications. Published lanthanide separations using Eichrom Ln Spec resin utilize an HCl gradient. Here it is shown that
the efficacy and resolution of the separation is improved when a nitric acid gradient is used instead. The described method
allows parallel processing of many samples in 1.5 h followed by 60 min counting for quantification of 9 radioisotopes of 7
lanthanide elements. 相似文献
45.
Conrady FM Fröhlich R Schulte to Brinke C Pape T Hahn FE 《Journal of the American Chemical Society》2011,133(30):11496-11499
The β,β'-bis(triisopropylsiloxy)phenyl-1,4-diisocyanide 3 and [Ir(Cp*)Cl(2)](2) were used for the stepwise assembly of the [Ir(Cp*)Cl] cornered molecular square [6](Cl)(4). Synthesis of the tetrakis(diisocyanide) bridged molecular square [Ir(Cp*)Cl(3)](4)(BF(4))(4) [5](BF(4))(4) followed by cleavage of the O-Si(i-Pr)(3) bonds of the diisocyanide bridges with HCl/i-PrOH led to an intramolecular attack of the liberated hydroxyl groups at the isocyanide carbon atoms with formation of molecular square [6](Cl)(4) featuring four dicarbene linkers. 相似文献
46.
47.
Abstract The elemental metals Zn, Cd, Ga, In and TI are studied by energy dispersive X-ray diffraction under pressures up to 30 GPa and above. Room temperature equation of state (EOS) data are derived and compared with results of earlier static and dynamic measurements at lower and higher pressures, respectively. 相似文献
48.
G. Giovannetti F. Frijia V. Hartwig L. Menichetti V. Positano J. H. Ardenkjaer-Larsen V. Lionetti G. D. Aquaro D. De Marchi R. F. Schulte F. Wiesinger L. Landini M. Lombardi M. F. Santarelli 《Applied magnetic resonance》2013,44(10):1125-1138
Hyperpolarized 13C magnetic resonance spectroscopy in pig models enables metabolic activity mapping, providing a powerful tool for the study of the heart physiology, but requires the development of dedicated radiofrequency coils, capable of providing large field of view with high signal-to-noise ratio (SNR) data. This work describes the simulations and the tests of a transmit-only (TX) volume coil/receive-only (RX) surface coil both designed for hyperpolarized studies of pig heart with a clinical 3T scanner. The coil characterization is performed by developing an SNR model for coil performance in terms of coil resistance, sample-induced resistance and magnetic field pattern. In particular, coil resistances were calculated from Ohm’s law, while magnetic field patterns and sample-induced resistances were calculated using a numerical finite-difference time-domain algorithm. Experimental phantom chemical shift image, showed good agreement with the theoretical SNR-vs-depth profiles and highlighted the advantage of the novel configuration over the single transmit–receive coils throughout the volume of interest for cardiac imaging in pig. Finally, the TX-birdcage/RX-circular configuration was tested by acquiring metabolic maps with hyperpolarized [1-13C] pyruvate injected i.v. in a pig. The results of the phantom and pig experiments show the ability of the coil configuration to image well the metabolites distribution. 相似文献
49.
W. Hoheisel U. Schulte M. Vollmer F. Träger 《Applied Physics A: Materials Science & Processing》1990,51(4):271-280
Desorption induced by electronic excitation with laser light is discussed. Emphasis is placed on nonthermal desorption where surface plasma excitation in small particles precedes the rupture of the surface chemical bond. A scenario for the mechanism underlying such a process is proposed. In this context, calculations of the electronic spectra of small sodium particles are presented and the influence of different multipole orders of the collective electron oscillation, of different shapes of the clusters and of the substrate are outlined. Furthermore, manipulation of the size distribution of metal particles on supports is described as an application of the effect. This allows the preparation of very special surfaces with novel physical and chemical properties. Methods to characterize such adsorbate-substrate combinations, especially by use of the optical spectra of the particles, are also discussed. Finally, prospects for future experiments in this field are outlined. 相似文献
50.
We report on growth results achieved in AIXTRON multiwafer planetary reactors for the growth of phosphide-arsenide and nitride based novel semiconductor structures and devices. In case of the phosphide-arsenide based structures we focused on growth on 6-in GaAs wafers. Ga/sub 0.47/InP layers were grown with standard deviations for the Ga-concentration of 0.75% and 0.3% on wafer and wafer-to-wafer, respectively. We attribute this result to the excellent temperature homogeneity of 1/spl deg/C throughout the reactor. This factor also plays a role in the deposition of nitride-based semiconductors that was investigated for the growth of InGaN multiquantum wells for the blue (472 nm) and green (522 nm) wavelengths. Wafer-to-wafer wavelength distributions of max-min of /spl plusmn/2.1 nm (blue) and /spl plusmn/4.2 nm (green) were achieved. On wafer standard deviations of the wavelength fell in the range of 1.6-1.7 nm, respectively. 相似文献