Crystalline nanofibers of linear polyethylene with an ultrahigh molecular weight (6,200,000) and a diameter of 30 to 50 nanometers were formed by the polymerization of ethylene with mesoporous silica fiber-supported titanocene, with methylalumoxane as a cocatalyst. Small-angle x-ray scattering analysis indicated that the polyethylene fibers consist predominantly of extended-chain crystals. This observation indicates a potential utility of the honeycomb-like porous framework as an extruder for nanofabrication of polymeric materials.
;The Purple leaf (Pl) locus of rice (Oryza sativa L.) affects regulation of anthocyanin biosynthesis in various plant tissues. The tissue-specific patterns of anthocyanin pigmentation, together with the syntenic relationship, indicate that the rice Pl locus may play a role in the anthocyanin pathway similar to the maize R/B loci. We isolated two cDNAs showing significant identity to the basic helix-loophelix (bHLH) proteins found in the maize R gene family. OSB1 appeared to be allelic to the previously isolated R homologue, Ra1, but showed a striking difference at the Cterminus because of a 2-bp deletion. Characterization of the corresponding genomic region revealed that the sequence identical to a 5¢ ¢ ¢ ¢-portion of OSB2 existed~10-kb downstream of the OSB1 coding region. OSB2 lacks a conserved C-terminal domain. Restriction fragment length polymorphism analyses using an F 2 population indicate that both genes co-segregate with the purple leaf phenotype. A transient complementation assay showed that the anthocyanin pathway is inducible by OSB1 or OSB2. These results suggest that the Pl w allele may be complex and composed of at least two genes encoding bHLH proteins.
Novel monolithic thermoelectric (TE) devices were fabricated using multilayer co-fired ceramics technology and p-type, n-type, and insulator layers of oxide materials. (La1.97,Sr0.03)CuO4 and (Nd1.97,Ce0.03)CuO4 served as p- and n-type thermoelectric materials, respectively. A mixture of Mg2SiO4 and silicate glass was utilized as an insulator sandwiched between p- and n-type layers. The materials constituting a TE device must have mutually matching thermal shrinkage characteristics. The dimensions of a TE device comprising 25 pairs of p–i–n junctions were 9.6 ×6.9 ×5.0 mm3. The observed maximum open-circuit voltage and electric output power of the TE devices were 2.3 V and 40 mW/cm2 at ΔT = 360 K (between 653 and 293 K), respectively.
Polymerization of lactones such as δ-valerolactone (VL) and
ε-caprolactone (CL) with protic
compounds proceeded in the presence of an aluminosilicate mesoporous
zeolite Al−MCM-41 (pore diameter
of 27 Å, surface area = 1010 m2
g-1, and Si/Al = 17), to give polyesters
with a narrow molecular weight
distribution. A sequential two-stage polymerization of VL and CL
with Al−MCM-41/butanol gave a block
copolymer. NMR and GPC studies showed that the produced polymer
carries a terminal group originating
from the protic compound. In contrast with Al−MCM-41, pure
silicate MCM-41, an MCM-41 with masked
SiOH functionalities, and a “microporous” aluminosilicate with much
narrower pores (zeolite-Y; pore
diameter = 8 Å) were not effective for the polymerization under
similar conditions. Infrared spectroscopy
of an inclusion adduct of Al−MCM-41 with VL suggested a possible
interaction of the monomer onto the
aluminosilicate surface. Al−MCM-41, isolated from the
polymerization mixture, could be used again for
the polymerization.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.