Experimental study for adsorption and photocatalytic reaction of ethyl methylphosphonate molecule as organophosphorus compound adsorbed at surface of titanium dioxide under UV irradiation in ambient condition

The adsorption and photocatalytic degradation of Ethyl methylphosphonate (EMPA) on powdery TiO₂ film has experimentally investigated using attenuated total reflection-infrared Fourier transform spectroscopy (ATR-FTIR) in ambient condition. Characteristic IR frequency as P-O-C vibration mode as EtO was observed by EMPA adsorbed at the surface of TiO₂. By TiO₂ photocatalysis, the adsorbed EMPA was decomposed to methyl phosphonic acid and phosphoric acid. The increment of IR intensity of which is assigned to Ti–O-P-O-Ti of EMPA was accompanied with increasing the IR peak intensity assigned to MPA. About that, we suggest that the appearance of the Ti–O-P-O-Ti of EMPA by the TiO₂ photocatalysis is regarded as acceleration of the hydrolysis of EMPA by the surface OH groups of TiO₂. The plausible adsorption structure and the photocatalytic reaction mechanism of EMPA at the surface of TiO₂ photocatalyst were elucidated.

     

Mode of complement activation by acidic heteroglycans from the leaves of Artemisia princeps PAMP.

The mode of action of the anti-complementary acidic heteroglycans, AAF-IIb-2 and IIb-3 which consisted of rhamnogalacturonan core and arabinogalactan moieties, purified from the leaves of Artemisia princeps PAMP (Japanese name = Gaiyo) were investigated. The anti-complementary activities of AAF-IIb-2 and IIb-3 were reduced partially in the absence of Ca2+ ions. A marked consumption of C4 was observed to have occurred when serum was incubated with both polysaccharides in the presence of Ca2+ ions. AAF-IIb-2 showed more potent C4 consumption than IIb-3. After the incubation of the serum with AAF-IIb-2 in the absence of Ca2+ ions, a cleavage of C3 in the serum was detected by immunoelectrophoresis. AAF-IIb-2 showed more significant consumption of the complement than IIb-3 when rabbit erythrocytes were used in the assay system in the absence of Ca2+ ions. These results indicate that AAF-IIb-2 activates the complement via both the alternative and classical pathways, whereas IIb-3 mainly activates the complement via the classical pathway. The absorption of serum with Protein A-Sepharose results in a decrease of the activity of AAF-IIb-2 and IIb-3. However, the decrease of the activity was restored by the replacement of the immunoglobulin G (IgG) fraction after its recovery from the Protein A-Sepharose. These results suggest that IgG dependent mechanisms are both involved in the anti-complementary activity of AAF-IIb-2 and IIb-3.     

Syntheses and characterization of 16‐arm star and star diblock copolymer and AB8 9‐miktoarm star copolymer via NMRP and ROP from dendritic multifunctional macroinitiators

A dendritic macroinitiator having 16 TEMPO‐based alkoxyamines, Star‐16 , was prepared by the reaction of a dendritic macroinitiator having eight TEMPO‐based alkoxyamines, [G‐3]‐OH , with 4,4′‐bis(chlorocarbonyl)biphenyl. The nitroxide‐mediated radical polymerization (NMRP) of styrene (St) from Star‐16 gave 16‐arm star polymers with PDI of 1.19–1.47, and NMPR of 4‐vinylpyridine from the 16‐arm star polymer gave 16‐arm star diblock copolymers with PDI of 1.30–1.43. The ring‐opening polymerization of ε‐caprolactone from [G‐3]‐OH and the subsequent NMRP of St gave AB₈ 9‐miktoarm star copolymers with PDI of 1.30–1.38. The benzyl ether linkages of the 16‐arm star polymers and the AB₈ 9‐miktoarm star copolymers were cleaved by treating with Me₃SiI, and the resultant poly(St) arms were investigated by size exclusion chromatography (SEC). The SEC results showed PDIs of 1.23–1.28 and 1.18–1.22 for the star polymers and miktoarm stars copolymers, respectively, showing that they have well‐controlled poly(St) arms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1159–1169, 2007.     

Fast and Accurate Floating Point Summation with Application to Computational Geometry

We present several simple algorithms for accurately computing the sum of n floating point numbers using a wider accumulator. Let f and F be the number of significant bits in the summands and the accumulator, respectively. Then assuming gradual underflow, no overflow, and round-to-nearest arithmetic, up to ?2 ^F?f /(1?2^?f )?+1 numbers can be accurately added by just summing the terms in decreasing order of exponents, yielding a sum correct to within about 1.5 units in the last place. In particular, if the sum is zero, it is computed exactly. We apply this result to the floating point formats in the IEEE floating point standard, and investigate its performance. Our results show that in the absence of massive cancellation (the most common case) the cost of guaranteed accuracy is about 30–40% more than the straightforward summation. If massive cancellation does occur, the cost of computing the accurate sum is about a factor of ten. Finally, we apply our algorithm in computing a robust geometric predicate (used in computational geometry), where our accurate summation algorithm improves the existing algorithm by a factor of two on a nearly coplanar set of points.     

Synthesis and characterization of 6‐ and 12‐arm star polymers by nitroxide‐mediated radical polymerization of St and MA from dendritic TIPNO‐based hexafunctional and dodecafunctional macroinitiators

Dendritic multifunctional macroinitiators having six and 12 TIPNO‐based alkoxyamines, TIPNO‐6 and TIPNO‐12 , were synthesized and used in the living radical polymerization of styrene (St), methyl acrylate (MA), N,N‐dimethylacrylamide (DMAAm), and isoprene (IP). The polymerizations of St initiated with TIPNO‐6 gave 6‐arm star polymers with narrow polydispersities of 1.14–1.18. In the polymerizations of MA initiated with TIPNO‐6 and TIPNO‐12 , the influences of added TIPNO on the polydispersity indexes (PDIs) of the resulting star polymers were first investigated, and this led to the successful formation of poly(MA) star polymers with narrow polydispersities (1.10–1.18). Moreover, the polymerizations of DMAAm and IP from TIPNO‐6 in the presence or absence of TIPNO were briefly investigated. The benzyl ether bonds of the poly(St) and poly(MA) star polymers were cleaved by treating with Me₃SiI or Pd/C, and the resulting arm's parts were analyzed with SEC. The PDIs of the resulting arm parts were low (1.19–1.23), and the M_ns agreed with the M_n,theor, indicating that the poly(St) and poly(MA) star polymers had well‐controlled arms. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4364–4376, 2007     

Chiral discrimination of a helically organized crown ether array parallel to the helix axis of polyisocyanate

The asymmetric polymerization of 4′‐isocyanatobenzo‐18‐crown‐6 with the lithium amide of (S)‐(2‐methoxymethyl)pyrrolidine successfully proceeded to afford end‐functionalized poly(4′‐isocyanatobenzo‐18‐crown‐6) with (S)‐(2‐methoxymethyl)pyrrolidine (polymer 2 ). In the circular dichroism (CD) spectrum of 2 , a clear positive Cotton effect was observed in the range of 240–350 nm corresponding to the absorption of the polymer backbone, indicating that 2 partially formed a one‐handed helical structure, which was preserved by the chirality of (S)‐(2‐methoxymethyl)pyrrolidine bonding to the terminal end in 2 . In the titration experiments for the CD intensity of 2 in the presence of D ‐ and L ‐Phe·HClO₄ (where Phe is phenylalanine), a small but remarkable difference was observed in the amount of the chiral guest needed for saturation of the CD intensity and in the saturated CD intensity, indicating that the extremely stable, one‐handed helical part should exist in the main chain of 2 , which was not inverted even when the unfavorable chiral guest for the predominant helical sense, L ‐Phe·HClO₄, was added. In addition, helical polymer 2 exhibited a chiral discrimination ability toward racemic guests; that is, the guests were extracted from the aqueous phase into the organic phase with enantiomeric excess. The driving force of the chiral discrimination ability of 2 should certainly be attributed to the one‐handed helical structure in 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 325–334, 2006