排序方式: 共有90条查询结果,搜索用时 15 毫秒
51.
52.
Terence Davis Matthew C Dix Michal J Rokicki Amy JC Brook Caroline S Widdowson David Kipling Mark C Bagley 《Chemistry Central journal》2011,5(1):1-5
To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H2O2 was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation. 相似文献
53.
C. Adloff et al. 《The European Physical Journal C - Particles and Fields》1998,5(4):575-584
A search for events with an imbalance in transverse momentum and with isolated high energy leptons has been carried out at
the positron-proton collider HERA. One event with an and five events with a are found together with evidence for undetected particles carrying transverse momentum. Within the Standard Model the dominant
origin of events with this kind of topology is the production of W bosons with subsequent leptonic decay. Three of the six events are within measurement errors found in a region of phase space
likely to be populated by this process, while the remaining events show kinematic properties which are atypical of all Standard
Model processes considered.
Received: 9 June 1998 / Published online: 26 August 1998 相似文献
54.
The relative rates of H-transfer between partners in ion-neutral complexes were compared with those in intramolecular rearrangements using results of first differential photoionization mass spectrometry measurements. Complex-mediated H-transfers are inferred to have rates of the same order as those for intramolecular hydrogen rearrangements, suggesting a similar range of motion of the reactive sites in both types of reactions. It is also concluded that at their fastest H-transfers take place between the partners in ion-neutral complexes within at most the time of several rotations of the partners in the complexes. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
55.
56.
57.
I. G. Abdullaev J. C. Adloff I. G. Bersina B. Bisplinghoff V. Bradnova R. Brandt V. S. Butsev H. H. Cui M. Debeauvais K. K. Dwivedi E. M. Friedlander S. Gosh S. L. Guo S. Heise M. I. Krivopustov B. A. Kulakov E. J. Langrock C. Laue L. Lerman V. P. Perelygin Th. Schmidt A. N. Sosnin P. Vater S. Vonderau X. L. Wang M. Zamani 《Radiation measurements》1995,25(1-4):219-230
An extended Cu-target was irradiated with 22 and 44 GeV carbon ions. The target was in contact with a (CH2)n-block for the moderation of secondary neutrons. Small holes in the moderator were filled with either lanthanium salts or uranium oxide. The reaction 139La (n,γ) 140La
was studied via the decay of 140La (40 h), and the reaction 238U (n, γ) 239U
239Np
was studied via the decay of 239Np (2.3 d). In addition, a variety of solid state nuclear track detectors (SSNTD) were used. Results will be presented. The yields for the formation of (n, γ) products agree essentially with other experiments on extended targets carried out at the Synchrophasotron LHE, JINR (Dubna). To a first approximation, the breeding rate of (n, γ) products, as well as the specific track density, seen with several SSNTDs, doubles when the carbon energy is increased from 22 to 44 GeV. If, however, results at 44 GeV are compared in detail to those at 22 GeV, we observe an excess of (37 ± 9) % in the experimentally observed 239Np-breeding rate over theoretical estimations. Experiments using solid state nuclear track detectors are giving similar results. We also observed in the past such excess in the yield of other secondary particles in relativistic heavy ion interactions above a total energy of approximately 35–40 GeV. 相似文献
58.
A. A. Stefanini G. Casini P. R. Maurenzig A. Olmi R. J. Charity R. Freifelder A. Gobbi N. Herrmann K. D. Hildenbrand M. Petrovici F. Rami H. Stelzer J. P. Wessels M. Gnirs D. Pelte J. Galin D. Guerreau U. Jahnke A. Péghaire J. C. Adloff B. Bilwes R. Bilwes G. Rudolf 《Zeitschrift für Physik A Hadrons and Nuclei》1995,351(2):167-186
Events with 2, 3 and 4 heavy fragments (A≥20) detected in the reactions100Mo +100Mo at 18.7, 23.7 A·MeV and120Sn +120Sn at 18.4 A·MeV were analyzed by means of an improved version of the kinematic coincidence method. The phase-space distributions prove that 3- (and possibly 4-) body events predominantly originate from a two-step mechanism and are compatible with the hypothesis of a binary deep-inelastic interaction followed by the further fissionlike decay of one (or both) of the primary fragments. The characteristics of the fission step — mass asymmetry, relative velocity, in-plane and out-of-plane angles — have been reconstructed for the 3-body events and indications are found that nonequilibrium effects at the end of the deep-inelastic phase may influence the fissionlike decay. 相似文献
59.
Hannu?TiitinenEmail author Anna?Mari?M?kel? Ville?M?kinen Patrick?JC?May Paavo?Alku 《BMC neuroscience》2005,6(1):62
Background
The cortical activity underlying the perception of vowel identity has typically been addressed by manipulating the first and second formant frequency (F1 & F2) of the speech stimuli. These two values, originating from articulation, are already sufficient for the phonetic characterization of vowel category. In the present study, we investigated how the spectral cues caused by articulation are reflected in cortical speech processing when combined with phonation, the other major part of speech production manifested as the fundamental frequency (F0) and its harmonic integer multiples. To study the combined effects of articulation and phonation we presented vowels with either high (/a/) or low (/u/) formant frequencies which were driven by three different types of excitation: a natural periodic pulseform reflecting the vibration of the vocal folds, an aperiodic noise excitation, or a tonal waveform. The auditory N1m response was recorded with whole-head magnetoencephalography (MEG) from ten human subjects in order to resolve whether brain events reflecting articulation and phonation are specific to the left or right hemisphere of the human brain. 相似文献60.
Blewitt G LoSecco JM Bionta RM Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,55(20):2114-2117