Determination of the hydrogen concentration in silicon nitride films with the resonant nuclear reaction H(N, αγ)C

The resonant nuclear reaction ¹H(¹⁵N, αγ)¹²C at resonance energy E(¹⁵N²⁺) = 6.40 MeV has been used to investigate the hydrogen concentration in silicon nitride films.This method is very suitable to determine hydrogen concentration profiles with a good depth resolution (~5 nm) over a large depth (~2 μm) and has a sensitivity of a few tenth of an atomic percent.     

Pyrazoles XI. The synthesis of 1,1′-dimethylbipyrazolyls

The synthesis of al six isomers of 1,1′-dimethylbipyrazolyl is reported. Their structure assignments were based on mnr data. Nmr spectra were determined in widely different solvents and structure assignments were based on these data, particularly on the found solvent effect. Uv spectral data are also reported.     

Simultaneous coherent imaging and strain measurement using coupled photorefractive holography and shearography

By coupling photorefractive holography with speckle shearography, it is possible to simultaneously perform both coherent imaging and strain measurement. Use of the photorefractive effect, which is insensitive to incoherently scattered light, is a significant advantage in coherent imaging as described. Experimental results obtained from a centrally loaded steel plate are presented.     

Validation of a 3D multi-physics model for unidirectional silicon solidification

A model for transient movements of solidification fronts has been added to X-stream, an existing multi-physics simulation program for high temperature processes with flow and chemical reactions. The implementation uses an enthalpy formulation and works on fixed grids. First we show the results of a 2D tin solidification benchmark case, which allows a comparison of X-stream to two other codes and to measurements. Second, a complete 3D solar silicon Heat Exchange Method (HEM) furnace, as built by PVA TePla is modeled. Here, it was necessary to model the complete geometry including the quartz crucible, radiative heaters, bottom cooling, inert flushing gas, etc. For one specific recipe of the transient heater power steering, PVA TePla conducted dip-rod measurements of the silicon solidification front position as function of time. This yields a validation of the model when applied to a real life industrial crystallization process. The results indicate that melt convection does influence the energy distribution up to the start of crystallization at the crucible bottom. But from that point on, the release of latent heat seems to dominate the solidification process, and convection in the melt does not significantly influence the transient front shape.     

Pyrazoles. XVIII. Synthesis of a novel tripyrazolyl by two consecutive cine substitution reactions

Preparation of the C-N coupled tripyrazolyl VII, by two consecutive cine substitution reactions starting from 1,4-dinitropyrazole and using pyrazole as a nucleophile, is described. Solvent dependent nitrations of 4-nitro-3(5)-(1′-pyrazolyl)pyrazole I are reported.     

Peptide block copolymers by N‐carboxyanhydride ring‐opening polymerization and atom transfer radical polymerization: The effect of amide macroinitiators

The synthesis of polypeptide‐containing block copolymers combining N‐carboxyanhydride (NCA) ring‐opening polymerization and atom transfer radical polymerization (ATRP) was investigated. An amide initiator comprising an amine function for the NCA polymerization and an activated bromide for ATRP was used. Well‐defined polypeptide macroinitiators were obtained from γ‐benzyl‐L ‐glutamate NCA, O‐benzyl‐serine NCA, and N‐benzyloxy‐L ‐lysine. Subsequent ATRP macroinitiation from the polypeptides resulted in higher than expected molecular weights. Analysis of the reaction products and model reactions confirmed that this is due to the high frequency of termination reactions by disproportionation in the initial phase of the ATRP, which is inherent in the amide initiator structure. In some cases selective precipitation could be applied to remove unreacted macroinitiator to yield well‐defined block copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009