A study of the reaction of pentacyclic triterpenoids with concentrated sulfuric acid
SummaryThe conditions for the reaction of triterpenoids with concentrated sulfuric acid have been studied by the method of mathematical planning, and the optimum conditions for performing this reaction have been found.
Zur spektralphotometrischen Bestimmung von steroiden und triterpenoiden Verbindungen
Sterole, Steroide, Steroidsaponine, Triterpensaponine und deren Aglykone weisen bei der spektralphotometrischen Messung in konzentrierter Schwefelsäure im UV‐Bereich eine Absorptionsbande auf, die zur quantitativen Bestimmung der genannten Verbindungen verwendet werden kann. Die Messung kann mit den freien oder an ein DC‐Sorptionsmittel adsorbierten Verbindungen durchgeführt werden. Die Schwefelsäureumsetzungsprodukte wurden isoliert und analysiert, jedoch konnte der Reaktionsmechanismus noch nicht endgültig aufgeklärt werden.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.