6,206 research outputs found
Characterization of defect structures in nanocrystalline materials by X-ray line profile analysis
X-ray line profile analysis is a powerful alternative tool for determining dislocation densities, dislocation type, crystallite and subgrain size and size-distributions, and planar defects, especially the frequency of twin boundaries and stacking faults. The method is especially useful in the case of submicron grain size or nanocrystalline materials, where X-ray line broadening is a well pronounced effect, and the observation of defects with very large density is often not easy by transmission electron microscopy. The fundamentals of X-ray line broadening are summarized in terms of the different qualitative breadth methods, and the more sophisticated and more quantitative whole pattern fitting procedures. The efficiency and practical use of X-ray line profile analysis is shown by discussing its applications to metallic, ceramic, diamond-like and polymer nanomaterials
On Soliton-type Solutions of Equations Associated with N-component Systems
The algebraic geometric approach to -component systems of nonlinear
integrable PDE's is used to obtain and analyze explicit solutions of the
coupled KdV and Dym equations. Detailed analysis of soliton fission, kink to
anti-kink transitions and multi-peaked soliton solutions is carried out.
Transformations are used to connect these solutions to several other equations
that model physical phenomena in fluid dynamics and nonlinear optics.Comment: 43 pages, 16 figure
Imidazolyl Alanes - Synthesis, Structures, and Reactivity Studies â Imidazolyl Alanes - Synthesis, Structures, and Reactivity Studies
Targeting the synthesis of Al/C based ambiphilic molecules, we investigated the dehydrohalogenation of a series of (benz)imidazole alane adducts. Depending on the steric bulk of the heterocycle, different dimeric products with various ring sizes were obtained. Dehydrohalogenation of the adduct of 1âmesityl imidazole (Im) and 0.5 [tBuAlBr] furnished the dimer 2, featuring a âclassicalâ Nâheterocyclic carbene (NHC) and a mesoionic or âabnormalâ NHC (aNHC) subunit within a single molecule. The dimer is bound loosely enough to allow thermally induced isomerization of 2 into the isomers 2 (all NHC) and 2 (all aNHC). Dehydrohalogenation of the adduct of 1âmesitylâ2âmethyl imidazole (Im) and 0.5 [tBuAlBr] (4) yielded the dimeric compound 5 consisting of two Nâheterocyclic olefin (NHO) subunits. Although these sixâ and eightâmembered heterocycles show no FLPâtype reactivity towards small molecules like H, CO or CO, we observed an ambiphilic behavior of the imidazolyl alanes during our studies. Salt metathesis reactions using Im resulted in the formation of 3, which can be viewed as tBuAlBr adduct of an Al/N ambiphile. Utilizing heterocycles such as benzimidazole or spiroindole provided the entry point to CâH (7, 9) and NâH (10) activation products, most likely resulting from a reactivity of intermediate species as Al/C ambiphiles
Isospin Purity of T=1 States in the A=38 Nuclei Studied Via Lifetime Measurements in K38
The Doppler Shift Attenuation Method was used to measure lifetimes for levels in 38K at excitation energies of 1698, 2404, 2830, 2996, and 3671 keV, populated using the 40Ca(d, Îą) 38K reaction at a beam energy of 4.5 MeV. Values of 109(29), 95(22), 457(63), 130(40), and 160(50) fs, respectively, were measured and are compared with previous values obtained using different stopping powers. The matrix element for the transition between the JĎ = 2+ T=1 and 0+ T=1 states in this Tz = 0 nucleus is compared with the analogous transition in the other nuclei in the T = 1 triplet, 38Ca (Tz = â1) and 38Ar (Tz = +1), and with the results of shell-model calculations
- âŚ