Rates for intramolecular excimer formation of poly(α-methylstyrene) measured by using picosecond pulse radiolysis

Summary The rate constants for intramolecular excimer formation, k_DM, of poly(α-methylstyrene) with different molecular weight were determined by using picosecond pulse radiolysis. Values of k_DM for poly(α-methylstyrene) are a little smaller than those for polystyrene with nearly same molecular weight. It appears to be mainly due to steric hindrance by methyl substituent of main chain.     

Reworkable adhesives composed of photoresponsive azobenzene polymer for glass substrates

ABSTRACT

A reversible isothermal phase transition between the liquid and solid states in response to light irradiation was achieved in side chain-type azobenzene polymers. These materials can be used as adhesives that are detachable without applying any mechanical and thermal stress but also repeatedly reworkable because of their photoinduced liquefaction and solidification properties. The adhesive strength to glass plates was more than 3 MPa in single lap shear tests. This value is three times higher than previously reported and is sufficiently strong for glass substrates.     

Dependence of Lanthanide-Ion Binding Performance on HDEHP Concentration in HDEHP Impregnation to Porous Sheet

An octadecylamino-group-introduced polymer chain grafted onto a porous sheet was impregnated with bis(2-ethylhexyl)hydrogen phosphate (HDEHP). A mixture of HDEHP and ethanol of various HDEHP concentrations was used for the impregnation. The porous sheet into which a C₁₈H₃₇NH group was introduced was immersed in HDEHP/ethanol solution before ethanol evaporation. The liquid permeability of a cartridge charged with the HDEHP-impregnated porous sheet in disk form prepared in 50 (v/v)% HDEHP/ethanol solution was 96% that of the starting-porous-disk-packed cartridge. The equilibrium binding capacity of the HDEHP-impregnated porous disk for yttrium ions was 0.32 mol per kg of the disk. In addition, the HDEHP-impregnated-porous-disc-packed cartridge was found to be applicable to the preconcentration of trace amounts of lanthanides in a multielement solution prior to their measurement by inductively coupled plasma mass spectrometry.     

Osteoinduction by Functionally Graded Apatites of Bovine Origin Loaded with Bone Morphogenetic Protein-2

Bioresorbable and functionally graded apatites (fg-HAp) ceramics, which are characterized by gradations in crystallinity and the grain size of hydroxyapatite (HAp:Ca₁₀(PO₄)₆(OH)₂), were designed using bovine bone by the calcination and partial dissolution–precipitation method. The fg-HAp ceramics had macropores of 100–600 μm originated from spongy bone, and micropores of 10–160 nm. Fg-HAp ceramics loaded with recombinant human bone morphogenetic protein-2 (rhBMP-2/fg-HAp) were implanted into the subcutaneous tissue of rats. Eight weeks after the implantation, the surface and bulk degradations of the fg-HAp-containing body fluid occured, and small pieces of fg-HAp were incorporated into the induced bone and fatty marrow, suggesting that osteoinduction occurred in conjunction with bone remodeling. The rhBMP-2/fg-HAp ceramics developed could become a resorbable biomimetic material with fast bioresorption and osteoinduction characteristics.     

Effects of Light‐Induced Regularity on the Physical Properties of Multiphase Polymers

A method that combines UV irradiation and pausing was developed to manipulate the regularity and the length scales of the morphology generated by phase separation in full‐interpenetrating polymer networks of polystyrene and poly(methyl methacrylate). Upon increasing the pause time of photopolymerization and photo‐crosslink processes, the morphology gradually changes from hexagonal‐like packing to random structures. The width of the loss tan δ obtained for these phase‐separated materials changes with the morphological regularity, suggesting a potential technique for fabrication of mechanical bandgap materials.

     

Ingestion of gelatinized potato starch containing a high level of phosphorus decreases serum and liver lipids in rats

Potato starch is known to have a higher concentration of phosphate than other starches. The presence of phosphate groups in amylopectin results in resistance to digestion by amylase. Therefore, there is a possibility that potato starch is slowly digested, inducing a physiological effect similar to that of resistant starch and indigestible oligosaccharides. The amount of phosphate group in starch differs with potato cultivar. In the present study, we investigated the effects of gelatinized potato starch containing a high level of phosphorus on lipid metabolism in rats. For this purpose, we determined lipid levels in the serum and liver in rats fed two kinds of gelatinized potato starches with different phosphorus contents. Four groups of male Sprague-Dawley rats were fed a 60% sucrose diet (control) or one of three diets containing cornstarch (CS), Benimaru (BM) potato starch or Hokkaikogane (HK) potato starch. Fat pad weight was slightly decreased in the HK diet group compared with that in the other groups. Free fatty acids in serum were significantly lowered by dietary HK starch compared with control, and serum triglyceride in rats fed the HK diet was also decreased. In the BM and HK diet groups, triglyceride levels in the liver were decreased compared with that in the control and CS groups. As for hepatic total cholesterol level, there were no significant differences among three starch diet groups. Fecal bile acid excretion was greater in the two potato starch groups than in the control group. On the other hand, there were no significant differences in cecal short-chain fatty acid content or pH. Thus, we conclude that dietary gelatinized potato starch reduces free fatty acid and triglyceride in serum and hepatic triglyceride, but does not affect cecal fermentation.     

Synthesis and photoinduced surface relief grating formation of novel photo-responsive amorphous molecular materials, 4-[bis(9,9-dimethylfluoren-2-yl)amino]-4′-cyanoazobenzene and 4-[bis(9,9-dimethylfluoren-2-yl)-amino]-4′-nitroazobenzene

Novel azobenzene-based photo-responsive amorphous molecular materials, 4-[bis(9,9-dimethylfluoren-2-yl)amino]-4′-cyanoazobenzene and 4-[bis(9,9-dimethylfluoren-2-yl)amino]-4′-nitroazobenzene, have been synthesized and the formation of surface relief grating on their amorphous films has been investigated. It was found that a relatively large surface relief grating could be inscribed on both amorphous films upon interference exposure to the writing laser beams. The modulation depth of the surface relief grating inscribed on the amorphous film of the cyano-substituted material was found to be larger than that inscribed on the film of the nitro-substituted one and seemed to be comparable to that inscribed on the amorphous film of the parent material, 4-[bis(9,9-dimethylfluoren-2-yl)amino]azobenzene. These results were discussed from the viewpoint of their trans–cis photoisomerizations as amorphous films and glass-transition temperatures.     

Application of tritium radioluminography to the detection of hydrogen diffusion in Ti-Cr alloy

Tritium radioluminography has been applied to determine the hydrogen (H) diffusion coefficients in Ti₅₀Cr₅₀ and Ti₄₀Cr₆₀ alloys, both with two-phase structures of a body-centered cubic (bcc) phase and a Laves phase. Using radioluminography, H distributions in those phases have been observed, and H penetration profiles have been measured. The tritium diffusion coefficients in the Ti₅₀Cr₅₀ and Ti₄₀Cr₆₀ alloys have been successfully determined by analyzing the tritium penetration profiles to be 3.3±0.3 × 10^?12 and 1.4±0.1×10^?12 m²/s, respectively. These values suggest that the H diffusion in the Laves phase is slower than that in the bcc phase. It is also suggested that H diffuses by short-circuiting diffusion through the interface between the bcc phase and the Laves phase.     

Two Triterpene Synthases from Imperata cylindrica Catalyzing the Formation of a Pair of Diastereoisomers through Boat or Chair Cyclization

Imperata cylindrica is known to produce a pair of triterpenes, isoarborinol and fernenol, that exhibit identical planar structures but possess opposite stereochemistry at six of the nine chiral centers. These differences arise from a boat or a chair cyclization of the B-ring of the substrate. Herein, we report the characterization of three OSC genes from I. cylindrica. IcOSC1 and IcOSC5 were identified as isoarborinol and fernenol synthases, respectively, while IcOSC3 was characterized as a multifunctional enzyme that produces glutinol and friedelin as its major products. Mutational studies of isoarborinol and fernenol synthases revealed that the residues surrounding the DCTAE motif partially affected the conformation of the B-ring during cyclization. Additionally, the IcOSC1-W255H mutant produced the rare triterpene boehmerol. The introduced histidine residue presumably abstracted a proton from the intermediary carbocation at C18 during the 1,2-rearrangement. Expression analysis indicated that all OSC genes were highly expressed in stems.