“Polylactides exist in different stereochemical compositions, as pure L-(PLLA), pure D-(PDLA), or mixtures containing the two enantiomeric forms in varying amounts. Polylactides of different stereochemical compositions differ
in their solubility in THF. Based on the difference in solubility a gradient chromatographic method was developed allowing separation of polylactides differing in their stereochemical compositions (excess of enantiomers, e.e.). Moreover, blends composed of polylactides having different stereochemical purity could be separated into their individual components. However, for mixtures of PDLA with PLLA an additional peak was observed at higher elution volume. Since this peak cannot be attributed to any of the individual components, this peak might result from the formation of the stereocomplex described in literature. (C) 2010 Elsevier Ltd. ZVADFMK All rights reserved.”
“The effect of Zn content on microstructure, existing phases, and mechanical properties of rapidly solidified MgZn (x) Y1LaMM1Mn0.5 alloys Cyclosporin A mouse (X = 2, 3, 4 at. pct) has been investigated. To assess the microstructural characterization of nanocrystalline alloys, the study also includes microstructural characterization of the master alloys. The microstructure of the
alloys in as-rapidly solidified condition consisted of supersaturated magnesium dendrites and fine (Mg,Zn)(17)La-2 and W phase (Mg3Y2Zn3) segregated at grain and cell boundaries. During continuous heating, the metastable solid solution in Mg dendrites breaks down, increasing the volume fraction of second-phase particles. After annealing for 1 hour at 673 K (400 A degrees C), very small spherical Mn-rich precipitates appeared in the three alloys and a long-period stacking ordered (LPS) phase of rectangular morphology precipitated inside the Mg grains in the alloy with the lowest Zn content. The nanocrystalline nature of the ribbons accounts for the high hardness and yield stress values in as-rapidly solidified state, although both decrease with increasing zinc content. This fact has been related to a coarser microstructure and higher volume fraction of the IPI-145 W phase as the
Zn content increases. The highest yield stress value of 350 MPa is attained by the MgZn2Y1LaMM1 ribbon in as-rapidly solidified condition. A decrease in yield stress values (about 50 MPa) is observed for all ribbons when they are heated at 673 K (400 A degrees C) for 1 hour.”
“A new asymmetric three-component domino process, based on a diastereoselective hetero-Diels-Alder reaction, involving an aldehyde, an alkene, and a chiral thiocarbamate was developed. The chiral auxiliary is directly removed during this process, leading to enantioenriched 2H-1,3-thiazin-2-ones with up to 96% ee.”
“BACKGROUND: The development of direct peroral cholangioscopy (DPOC) using an ultraslim endoscope simplifies biliary cannulation. The conventional techniques are cumbersome to perform and require advanced skills.