Water-soluble polydepsipeptides with functionalized side-chain groups, i. e., alternating copolymers, consisting of glycolic acid (Glc) and L-lysine (L-LYS), L-aspartic acid (LAsp) or L-glutamic acid (L-Gh) residues as a-hydroxy acid and a-amino acid residues, respectively, were synthesized, and their biodegradation behavior was investigated. Three kinds of polydepsipeptides, poly(G1c-alt-Lys), poly(G1c-alt-Asp) and poly(Glc-altGlu), were synthesized by means of ring-opening polymerization of the corresponding cyclodepsipeptides and subsequent deprotection of benzyl and benzyloxycarbonyl groups. In order to estimate the main-chain cleavage behavior of polydepsipeptides with functionalized side-chain groups, the hydrolysis behavior of the obtained water-soluble polydepsipeptides was first investigated in phosphate buffer solution with or without an enzyme in vitro.
100-mm-diameter <100> undoped InP single crystals were grown
by the vertical gradient freezing (VGF) method using a high-pressure
furnace. In order to reduce the temperature fluctuation in the furnace
for preventing twinning during crystal growth, we investigated the gas
flow in the furnace by a computer simulation. The simulation results
showed that the gas flow was quite unstable because of the collision
between the gas and the hot-zone or other gas flows. After we
developed a hot-zone to control the gas flow, the temperature
fluctuation near the seed crystal reduced from ±0.3°C to
±0.03°C. The axial temperature gradient was lower than
10°C/cm and the growth rate was higher than
0.4 mm/h. Twin-free 100-mm-diameter single crystals could be obtained
for the first time under these conditions. The average EPD(Etch Pit
Density) of the grown crystals was about 2000 cm-2, less than
that of the conventional 75-mm-diameter InP LEC (liquid encapsulated
Czochralski) crystals.
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