A biomimetic complex which mimics the arginine-phosphonate diester interaction of the arginine fork is investigated with respect to structure and energetics of stable configurations. Within this work, we provide knowledge on local minima of the isolated system obtained from first-principles calculations. Non-negligible solvation effects are studied in a microsolvation approach. The interactions which govern the structural patterns of molecular recognition in this tweezer-guest complex can be significantly modulated by the action of hydrogen bond accepting and donating solvent molecules, such as dimethyl sulfoxide or water, which were present in experimental investigations on this system. Different tweezer-guest structures are evaluated with respect to their temperature-dependent thermodynamical properties as products of the first association reaction step of the bisphosphonate tweezer template and the guanidinium moiety. 相似文献
Using on-line mass separation of evaporation residues from heavy-ion-induced fusion reactions, three new isotopes were identified by their alpha decay, Eα given in keV: 183Pb, 6715(20), 184Pb, 6632(10) and 188Bi, 6820(20). Half-lives were determined for 184Pb, 0.55(6)s, 185Pb, 4.1(3)s and 183Tl, 0.060(15) s. The alpha branching ratios were re-measured for 182–184Hg and 178, 179Pt, the results are discussed within the framework of alpha width systematics. 相似文献
The properties of isolated AlCl3 clusters and the bulk system are investigated by means of static and dynamic electronic structure methods. We find important structural motifs with the edge connectivity dominant in a dimer and the corner connectivity dominant in a trimer. Furthermore, the trimer cluster exhibits an interesting ring structure with large cooperative effects relative to the dimer. Comparing the found structural motifs in isolated molecule calculations with the structure of the liquid allows us to determine the dominance of edge connectivity in the liquid. The size of the clusters present in the liquid indicates indeed that the dimer is the most abundant species, but there are also trimers, tetramers, and pentamers present. From the local dipole analysis both for the isolated clusters as well as for the liquid, further proof for the edge connectivity is given. However, all results point to the fact that there is also some small percentage of corner connectivity present that might be attributed to the most stable corner-connected cluster, namely the trimer. Importantly, we find that energetic considerations of isolated (static) clusters only do not represent the findings in liquid phase. Instead, a quantum cluster equilibrium approach or simulations are needed. 相似文献
Antiplane shear cracks moving in square lattices have been studied in a molecular dynamics simulation. They become unstable when a critical stress intensity at the tip is reached. Within picoseconds they accelerate to steady state velocity, which can be supersonic or not, depending on the interatomic potential. If the surface energy is low, they become supersonic; if the surface energy is high, they reach only subsonic speeds before the crystal reaches the theoretical shear strength. A simple modification of the interatomic potential switches the crystal behaviour from brittle to ductile, substituting dislocations to daughter cracks. The steady state velocities are the same, whether the model crystal is brittle or ductile. The steady state velocity is a function of the applied stress, not the stress intensity. 相似文献
A calorimetric gas sensor for the detection of vapourised H2O2 in aseptic filling processes was built up on a polyimide foil instead of silicon as substrate material in order to optimise the sensor response behaviour. The sensor was catalytically activated with a dispersion of manganese(IV) oxide. The reaction mechanism of the exothermic H2O2 decomposition on the catalyst involves two pathways: an initial reaction with electron exchange between the catalyst surface and H2O2 creating free radicals, and a chain reaction of these radicals with H2O2, in which the final products, namely water and oxygen, are formed. The calorimetric gas sensor possesses a linear response behaviour with a sensitivity of 7.15 °C/(% v/v) in a H2O2 concentration range from 0 to 8% v/v.
Partial dislocations in thin foils split trapezoidally. In numerical calculations the presence of the surface and the elastic anisotropy of the medium is taken into account. In Cu–10 at% Al this tendency for nonparallel orientation of the partials is stronger than in silver. The computation is done on the force level by adjusting the geometry of the arrangement till forces and moments are zero. Deviations from isotropic fitting are considerable. The tendency of screw dislocations to cross slip at surfaces is confirmed. 相似文献
