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Gabriela Ionita Petre Ionita Victor EM. Sahini Constantin Luca 《Journal of inclusion phenomena and macrocyclic chemistry》2001,39(3-4):269-271
The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin. 相似文献
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Methods of employing scanning moiré at high magnification are developed and demonstrated. Modern lithographic techniques for
producing custom moiré gratings with a frequency up to 250l/mm are described. On a probing station equipped with a video system, pseudo-color moiré fringes are produced using the scannning
lines of the color charge-coupled-device (CCD) camera. Fringe multiplication from 1 to 5 is possible with correct combinations
of magnification and grating pitch. An analysis is given to show that strain sensitivity depends only on the number of scanning
lines used to record the image. The grating pitch and the magnification are important because they reduce the gage length
of the strain measurement. The high-magnification scanning moiré was used to study plastic- strain fields in an aluminum tensile
specimen. Local disturbances in the strain field were observed at 2 to 2.5 percent applied strain. These discontinuities became
more significant at higher levels of applied strain. 相似文献
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We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux
lines in low T
c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line
lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends
to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the
destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has
employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo
technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing
μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation
of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors. 相似文献
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A method is presented for the interpretation of receptor docking score values (rough measures of binding affinities) of ligands in terms of 3D molecular field interaction contributions. The FlexX and FlexX-Pharm methods were used to dock the structures of designed sets of ligands into the ligand-binding pocket of a selected receptor. In the next step the relationship was investigated between the FlexX and CScore scores and 3D molecular fields obtained for the docked conformations of the ligands, using the CoMFA (Comparative Molecular Field Analysis) and CoMSIA (Comparative Molecular Similarity Indices Analysis) methods. The approach yielded highly significant CoMFA and CoMSIA models demonstrating that a high portion of the variance in the docking score values of the ligands can be explained by steric, electrostatic, hydrophobic, and hydrogen bond donor and acceptor molecular field interaction contributions. The approach was exemplified by using the crystal structure of the ligand-binding domain of the ecdysone receptor (EcR) of the moth Heliotis virescens as well as virtual molecule libraries of analogues of known diacyl-hydrazine (DAH) type ecdysteroid agonists. By docking appropriately designed virtual compound libraries into the DAH binding pocket of EcR followed by CoMFA and CoMSIA of the docked conformations, hitherto unexplored regions of the receptor cavity could be mapped. By mapping the significant molecular field interaction contributions onto the model of the receptor-ligand complex, important receptor-ligand interactions could be highlighted that may help the design of novel highly scored receptor ligands. An advantage of the method is that no experimental biological activity data are required to exhaustively map the receptor-binding site. 相似文献
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A Szanto de Toledo N Carlin N Added E M Szanto M G Munhoz J Takahashi A Suaide M M de Moura 《Pramana》1999,53(3):483-483
Considerable interest has been devoted to fusion reactions between light heavy ions specially between weakly bound ones, due
to the anomalous decrease of the fusion cross sections when compared to the total reaction cross section in the energy region
around the barrier [1–4].
While the exact nature of the process responsible for the fusion cross section limitation at barrier energies is still unclear,
this study shows an inhibition of the yield as the system mass decreases, resulting from the progressive increase of the barrier
height and decrease of the effective barrier radius [3]. Furthermore, extensive efforts have been made recently in the study
of energy-damped binary yields from light heavy-ion collisions [2,4]. Based on the substantial amount of data accumulated
so far, it is now generally accepted and supported by the transition state model [4], that the observed yields arise mostly
from a fusion-fission process. Data on complete fusion, fusion-fission and ‘elastic fission’ for the 9Be, 10,11B+10,11B; 16,17,18O + 10,11B; 19F+12C; 6,7Li+9Be, 12C reactions among others, are presented. For the loosely bound nuclei it was found that the severe fusion cross section limitation
is due to a low survival probability of the weakly bound nuclei until the instant of the collision [1]. 相似文献