Zur Chlorierung von N-Aryl-2,4-dimethyl-buta-1,3-dien-1,4-sultamen

About Chlorination of N-Aryl-2,4-dimethyl-buta-1,3-dien-1,4-sultames The sultames of structure 1 are easily chlorinated by sulfurylchloride, chlorine or tertbutylhypochlorite. The structure of the mono-( 2a-c,3a, d ), di-( 4a-d ), tri- ( 5c, d ) and pentachlorosultames ( 6a, b ) is determined by ¹³C-n.m.r. spectroscopy. Contrary to the bromination the chlorination (by SO₂Cl₂) starts with the substitution of the sultamring (formation of mono- and di-chlorosultames) followed of the substitution of the (C-4)-CH₃- group (formation of trichlorosultames). By 1,4-addition of an other molecule of chlorine to 5 the pentachlorosultames 6a, b are obtained. Already by recrystalisation of 6a, b in an alcohol the chlorine in 4-position is exchanged by the corresponding alkoxy group (CH₃O, C₂H₅O, n-C₃H₇O) and the compounds 7-9 are formed.     

PIXE analysis and fission track dating of obsidian from South American prehispanic cultures (Colombia, Ecuador)

In the present work we have coupled PIXE with fission track dating to characterise obsidian artefacts from about 40 archaeological sites of Colombia and Ecuador. PIXE analysis, carried out with the external beam line of the AGLAE tandem accelerator, yields the content in about 15 elements with Z > 8, whereas fission track dating is applied to ages in excess of about 10 000 years. About 120 artefacts were investigated by PIXE, of which 50 were dated by fission tracks. Ages and compositions were compared to those of obsidians from all known geological sources of the region. We show that this double characterisation allows us to determine the number of obsidian sources exploited in an ancient past and to give some insight into obsidian circulation.     

Finite difference transmission line model for the design of safe multi-section cables in MRI

Magnetic Resonance Materials in Physics, Biology and Medicine - To show the relevance of a simple finite difference transmission line model to help design safe implanted cables in 1.5T MRI’s...     

Bibliometric and text mining approaches to evaluate landfill design standards

Scientometrics - In 2014, Canadians generated 961 kg of waste per capita. Landfilling is a logical choice for many Canadian communities because of land availability. This paper examines...     

Si Doping of GaN in Hydride Vapor-Phase Epitaxy

Growth of GaN boules by hydride vapor-phase epitaxy (HVPE) is very attractive for fabrication of GaN substrates. Use of dichlorosilane as a source for Si doping of bulk GaN is investigated. It is shown that no tensile strain is incorporated into mm-thick, Si-doped GaN layers on sapphire substrates if the threading dislocation density is previously reduced to 2.5 × 10⁷ cm^?2 or below. High-quality GaN layers with electron densities up to 1.5 × 10¹⁹ cm^?3 have been achieved, and an upper limit of about 4 × 10¹⁹ cm^?3 for Si doping of GaN boules was deduced considering the evolution of dislocations with thickness. A 2-inch, Si-doped GaN crystal with length exceeding 6 mm and targeted Si doping of about 1 × 10¹⁸ cm^?3 is demonstrated.