We report on a boy and a girl with bilateral anophthalmia and proximal esophageal atresia. In addition to vestigial optic nerves and chiasma, MRI studies showed other central nervous system abnormalities; one had ectopic tissue in the hypothalamic region, and the other hand generalized ventriculomegaly associated with atrophy. Two other cases, both males, have been reported with anophthalmia and esophageal atresia as their only malformations. These 4 cases are reviewed in light of recent advances in the understanding of ocular embryogenesis and of the midbrain as a development field. Concurrence of these defects appears to be non-random.
A biphasic one-pot polymerization method enables the preparation of block copolymers from monomers with similar and competitive reactivities without the addition of external materials. AB diblock copolymers were prepared by encapsulating a frozen solution of monomer B on the bottom of a reaction vessel, while the solution polymerization of monomer A was conducted in a liquid layer above. Physical separation between the solid and liquid phases permitted only homopolymerization of monomer A until heating above the melting point of the lower phase, which released monomer B, allowing the addition of the second block to occur. The triggered release of monomer B allowed for chain extension without additional deoxygenation steps or exogenous monomer addition. A method for the closed (i.e., without addition of external reagents) one-pot synthesis of block copolymers with conventional glassware using straightforward experimental techniques has thus been developed.
Ab iphasic one-pot polymerization method enables the preparation of blockc opolymers from monomers with similar and competitive reactivities without the addition of external materials.A Bd iblock copolymers were prepared by encapsulating af rozen solution of monomer Bo nt he bottom of ar eaction vessel, while the solution polymerization of monomer Aw as conducted in al iquid layer above. Physical separation between the solid and liquid phases permitted only homopolymerization of monomer Au ntil heating above the melting point of the lower phase,w hich released monomer B, allowing the addition of the second blockt oo ccur.T he triggered release of monomer Ba llowed for chain extension without additional deoxygenation steps or exogenous monomer addition. Amethod for the closed (i.e., without addition of external reagents) one-pot synthesis of blockc opolymers with conventional glassware using straightforwarde xperimental techniques has thus been developed.Reversible deactivation radical polymerization (RDRP) techniques have provided access to ah ost of previously inaccessible,well-defined macromolecular architectures.Precision block copolymer synthesis is ac ommon and attractive goal of RDRP that has enabled the preparation of stimuliresponsive polymers (i.e., sugar-, [1,2] temperature-, [3,4] and redox-responsive [5,6] systems), the in situ preparation of nanoparticles, [7,8] and the synthesis of functional nanomaterials. [9,10] Reversible addition fragmentation chain transfer (RAFT) is ac ommonly employed RDRP technique owing to its amenable experimental conditions,m onomer versatility,a nd functional-group tolerance. [11] This controlled chain-growth procedure has led to innovative strategies to ease the synthesis of complex architectures. [12,13] Recently,Perrier and co-workers outlined the synthesis of multiblock copolymers through iterative additions of monomers with high propagation rate constants (k p ). [14][15][16] This innovative method allows reactive monomers to reach quantitative conversion (> 99%) while high chain-end retention is maintained. As the number of terminated chains is directly related to the initiator concentration and the rate of termination, chain-end retention at high monomer conversion can be achieved by reducing the radical concentration (i.e., lowering the amount of initiator). Thesequential addition of fresh monomer and initiator following near-quantitative monomer conversion for each step allowed for block copolymer chain extensions without purification between blocking steps.We reasoned that an ideal scenario might involve aclosed, one-pot method in which all reaction components (RAFT agent, initiator, and co-monomers) are present prior to as ingle deoxygenation step,t op rovide af acile strategy towards well-defined block copolymers.H owever,s uch am ethod would require some form of physical separation between the monomers present in the reaction vessel to prevent cross-propagation and the formation of statistical copolymers.I nm ost other reports of block copolymer synthesis by...
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