Quadpack computation of Feynman loop integrals

The paper addresses a numerical computation of Feynman loop integrals, which are computed by an extrapolation to the limit as a parameter in the integrand tends to zero. An important objective is to achieve an automatic computation which is effective for a wide range of instances. Singular or near singular integrand behavior is handled via an adaptive partitioning of the domain, implemented in an iterated/repeated multivariate integration method. Integrand singularities possibly introduced via infrared (IR) divergence at the boundaries of the integration domain are addressed using a version of the Dqags algorithm from the integration package Quadpack, which uses an adaptive strategy combined with extrapolation. The latter is justified for a large class of problems by the underlying asymptotic expansions of the integration error. For IR divergent problems, an extrapolation scheme is presented based on dimensional regularization.     

Selective guest inclusion in a non-porous H-bonded host

A hydrogen-bonded host solid demonstrates reversible and selective guest inclusion, despite not having a porous interlayer.     

Mechanistic study on adsorptive removal of tert-butanethiol on Ag-Y zeolite under ambient conditions

The dynamics and surface chemistry of tert-butanethiol (TBT) adsorptive removal over silver-exchanged Y zeolite (Ag-Y) were studied under ambient conditions. Saturation uptake on Ag-Y was higher than that on H-Y and Na-Y. The structural analyses by a combination of X-ray diffraction, Ag K-edge X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structures (EXAFS), Ag L(III)-edge XANES, S K-edge XANES, and in situ UV-vis show that the AgSH molecule, Ag(2)S monomer, and Ag(4)S(2) cluster are the dominant silver species in TBT-saturated Ag-Y. Dynamic changes in adsorbed intermediates, gas-phase products, and the silver sulfides were followed by in situ FTIR, mass spectroscopy and in situ UV-vis, respectively. The results show the following reaction mechanism: (1) formation of iso-butene and adsorbed H(2)S on the Ag(+) site via C-S cleavage of hydrogen-bonded TBT initially adsorbed on the Ag(+) site; (2) conversion of the adsorbed H(2)S to AgSH and H(+) on zeolite; (3) the reaction of two Ag-SH species to yield Ag(2)S and H(+) on zeolite.     

High-performance liquid chromatography of aromatic compounds with photochemical decomposition and tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection

A novel high-performance liquid chromatographic method for the determination of aromatic compounds based on the on-line photochemical degradation and subsequent tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection has been developed. Chemiluminescence intensity depended upon the number of aromatic rings, UV irradiation time, and variety of substituted functional groups. One of the decomposition products of aromatic compounds by UV irradiation was identified as oxalic acid. As one application of this methodology, determination of catechins in tea has been shown. Calibration graphs, based on standard (-)-epicatechin and (-)-epigallocatechin gallate solutions, were linear over the range of 0.1-50 microM. The detection limits (signal-to-noise ratio=3) were 0.8 pmol for (-)-epigallocatechin gallate and 1.2 pmol for (-)-epicatechin. The high-performance liquid chromatography-chemiluminescence (HPLC-CL) detection method with a post-column photochemical reactor can be applied to the sensitive and selective determination of catechins in tea.     

Construction of highly glycosylated mucin-type glycopeptides based on microwave-assisted solid-phase syntheses and enzymatic modifications

A MUC1-related glycopeptide having five core-2 hexasaccharide branches (C330H527N46O207, MW = 8450.9) was synthesized by a new strategy using a combination of microwave-assisted solid-phase synthesis (MA-SPGS) and enzymatic sugar elongation. Synthesis of a key glycopeptide intermediate was best achieved in a combination of PEGA [poly(ethylene glycol)-poly-(N,N-dimethylacrylamide) copolymer] resin and MA-SPGS using glycosylated amino acid building blocks with high speed and high purity. Deprotection of the glycopeptide intermediate and subsequent glycosyltransferase-catalyzed sugar elongations were performed for generation of the additional diversities with the sugar moieties of glycopeptides using beta1,4-galactosyltransferase (beta1,4-GalT) and two kinds of alpha2,3-sialyltransferases [ST3Gal III; alpha2,3-(N)-SiaT and ST3Gal II; alpha2,3-(O)-SiaT]. These reactions proceeded successfully in the presence of 0.2% Triton X-100 to convert the chemically synthesized trisaccharide glycans to disialylated hexasaccharide.     

Solid-phase synthesis of oligodeoxyribonucleoside boranophosphates by the boranophosphotriester method

Oligodeoxyribonucleoside boranophosphates (BH3-ODNs), containing four kinds of nucleobases, were synthesized by the solid-phase boranophosphotriester method. The 2'-deoxyribonucleoside 3'-boranophosphate monomers having 2-cyanoethyl (CE) groups as the phosphorus protecting groups were synthesized in good yields. A new condensing reagent, 1,3-dimethyl-2-(3-nitro-1,2,4-triazol-1-yl)-2-pyrrolidin-1-yl-1,3,2-diazaphospholidinium hexafluorophosphate, was found to be highly effective for the condensation reaction on the solid support. We also found that 1,8-bis(N,N-dimethylamino)naphthalene could accelerate the condensation reaction without causing beta-elimination of the CE groups from the boranophosphate triesters. The internucleotidic CE groups were selectively removed by treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) under anhydrous conditions. The acetylation of the terminal 5'-hydroxy group was found to be effective to suppress the decomposition of the BH3-ODNs during the DBU treatment on the solid support. Under optimized conditions for the solid-phase synthesis and the deprotection reactions, BH3-ODNs (4mers and 12mers) containing four kinds of nucleobases were synthesized in good yields. The hybridization properties of the BH3-ODN 12mers with the complementary native DNAs and RNAs were determined by the thermal denaturing studies. In contrast to the low thermal melting (Tm) value of the duplex composed of T((PB)T)11 and native dA12 (12.8 degrees C), the duplex consisting of d(C(PB)A(PB)G(PB)T)3 and d(ACTG)3 showed a higher Tm value (44.7 degrees C) under high-salt conditions. Furthermore, d(C(PB)A(PB)G(PB)T)3 formed a more stable duplex with the complementary RNA, r(ACUG)3 with a Tm value of 50.5 degrees C. Thus, we first demonstrated that the binding affinity of BH3-ODN to a complementary DNA or RNA is dramatically increased, owing to the inclusion of the four kinds of nucleobases.     

Zeolite LTA Nanoparticles Prepared by Laser-Induced Fracture of Zeolite Microcrystals

Zeolite LTA nanoparticles are prepared by laser-induced fragmentation of zeolite LTA microparticles using a pulsed laser. Zeolite nanoparticle formation is attributed to absorption of the laser at impurities or defects within the zeolite microcrystal generating thermoelastic stress that mechanically fractures the microparticle into smaller nanoparticle fragments. Experimentally, it is found that nanoparticles have a wide size and morphology distribution. Large nanoparticles (>200 nm) are typically irregularly shaped crystals of zeolite LTA, whereas small nanoparticles (<50 nm) tend to be spherical, dense, and amorphous, indicative of destruction of the original LTA crystal structure. Results of the fragmentation versus laser parameters show that shorter laser wavelengths are more efficient at producing zeolite nanoparticles, which is explained based on a larger cross section for optical absorption in the zeolite crystal. Increasing the laser energy density irradiating the sample was found to be a trade-off between increasing the amount of fragmentation and increasing the amount of structural damage to the zeolite crystal. It is suggested that in the presence of strongly absorbing defects, plasma formation is induced resulting in dramatically higher temperatures. On the basis of these results it is suggested the optimal laser processing conditions are 355 nm and 10 mJ/pulse laser energy for our LTA samples.     

Dynamic Contact Behavior of a Golf Ball during an Oblique Impact

The oblique impact between a golf ball and a rigid steel target was studied using a high-speed video camera. Video images recorded before and after the impact were used to determine the inbound velocity v _i, rebound velocity v _r, inbound angle θ_i, rebound angle θ_r, and the coefficient of restitution e. The results showed that θ_r and e decreased as v _i increased. The maximum compression ratio η_c, contact time t _c, average angular velocity , and tangential velocity , along the target were determined from images obtained during the impact. The images demonstrated that η_c increased with v _i while t _c decreased. In addition, and increased almost linearly as v _i increased. A rigid body model was used to estimate the final angular velocity ω* and tangential velocity ν_t* at the end of the impact; these results were then compared with experimental data.     

Enhancement of the Curie temperature by isomerization of diarylethene (DAE) for an organic-inorganic hybrid system: Co4(OH)7(DAE)0.5.3H2O

Intercalation of an organic photochromic molecule into layered magnetic systems may provide multifunctional properties such as photomagnetism. To build up a photosensitive multifunctional magnet, an organic-inorganic hybrid system coupled with a photochromic diarylethene anion, 2,2'-dimethyl-3,3'-(perfluorocyclopentene-1,2-diyl)bis(benzo[b]thiophene-6-sulfonate) (DAE), and cobalt LDHs (layered double hydroxides), Co4(OH)7(DAE)0.5.3H2O, was synthesized by the anion exchange reaction between Co2(OH)3(CH3COO).H2O and DAE. In the dark and under UV-irradiated (313 nm) conditions, Co4(OH)7(DAE)0.5.3H2O with open and closed forms of DAE were obtained, respectively. The magnetic susceptibility measurements elucidated ferromagnetic intra- and interlayer interactions and Curie temperatures of TC = 9 and 20 K for cobalt LDHs with the open and closed forms of DAE, respectively. The enhancement of the Curie temperature from 9 to 20 K by substitution of the open form of DAE with the closed form of DAE as an intercalated molecule is attributed to the delocalization of the pi-electrons in the closed form of DAE, which enhances the interlayer magnetic interaction. The enhancement of the interlayer magnetic interaction induced by the delocalization of pi-electrons in intercalated molecules is strongly supported by the fact that the Curie temperature (26.0 K) of cobalt LDHs with (E,E)-2,4-hexadienedioate having a conjugated pi-electron system is enormously higher than that (7.0 K) of the cobalt LDHs with hexanedioate. By UV irradiation at 313 nm, Co4(OH)7(DAE)0.5.3H2O shows the photoisomerization of DAE from the open form to the closed one in the solid state, which leads to the enhancement of Curie temperature.