Criterion for craze nucleation in polycarbonate

Plastic deformation and crazes were initiated in polycarbonate bars containing a round notch by three-point bending. Morphological observations revealed that internal crazes are nucleated by a hydrostatic stress component caused by plastic constraint ahead of the fully developed plastic deformation zone. The characteristics of the deformation bands for quenched and slowly cooled materials are in good agreement with the logarithmic spiral curves predicted from a slip-line theory. The distribution of the stress components in the plastic deformation zone was analyzed using this theory. The critical hydrostatic stress is 87 MN/m² for slowly cooled polycarbonate and 89 MN/m² for quenched material. These results are compared with those of the craze nucleation models of Gent and Argon.     

Frequency-locking of a CW dye laser to some absorption lines of a neon discharge by a Faraday filter

Single-mode oscillations of a CW dye laser at the center of five absorption lines from the 1s states to the 2p states of neon were obtained by means of a neon discharge Faraday filter, without any other frequency-selective elements. The most striking thing observed is that saturated absorption takes place at the center of several absorption lines in a Faraday filter, in addition to optical rotation.     

Human proinsulin. C-peptide radioimmunoassay method. 125I labeling of human proinsulin. C-petide

125I-labelled human-C-peptide was prepared by chloramin T method, enzymic method and active ester method, respectively. Using respective 125I-labelled human-C-peptides in human proinsulin-C-peptide RIA, we compared the binding (Bo/T%) to antibody, displacement by standard human-C-peptide, the recovery test and stability. The usable 125I-labelled antigen for human proinsulin-C-peptide RIA could be prepared by chloramin T method and enzymic method wich labelled 125I to tyrosyl human proinsulin connecting peptide, and active ester method which conjugates 125I-labelled active ester to human proinsulin connecting peptide. The differences among those 125I-labelled antigens was not observed in displacement (B/Bo%) by standard human-C-peptide and the recovery test. In the case of constant preparation of 125I-labelled antigen for RIA, the enzymic method was the best from the viewpoint the reaction ratio is stable and stability of Bo/T% is good.     

2,5-Dialkyl cyclohexenones by Fe(CO)5-mediated carbonylation of alkenyl cyclopropanes: functional group compatibility

The preparation of alkenyl cyclopropanes 1 with a variety of common organic functionalities is reported. These substrates were subjected to the Fe(CO)(5)-mediated carbonylation process under a CO atmosphere, leading to the formation of 2,5-disubstituted cyclohexenones 2, important intermediates for target-directed synthesis.     

Diastereoselective total synthesis of isocarbacyclin from L-ascorbic acid

Diastereoselective total synthesis of isocarbacyclin, which features a fused bicyclic key intermediate available from l-ascorbic acid, is described. The key intermediate was prepared in multigram quantities by the Pauson-Khand reaction of l-ascorbic acid-based (R)-4,4-diallyl-2,2-dimethyl-5-(trimethylsilyl)ethynyl-1,3-dioxolane (3), discriminating diastereotopic groups and faces of the geminal allyl substituents.     

Single-walled carbon nanotubes acquire a specific lectin-affinity through supramolecular wrapping with lactose-appended schizophyllan

Single-walled carbon nanotubes can be entrapped within a helical superstructure composed of schizophyllan bearing lactoside-appendages to show an excellent water-solubility as well as a specific lectin-affinity.