The molecular structure and orientation of antiferroelectric liquid crystal using the density-functional theory and two-dimensional correlation-polarized infrared spectroscopy

The structure and vibrational frequencies of the chiral antiferroelectric liquid-crystal molecule, 4-(1-methyheptyloxycarbonyl) phenyl-4-(4'-octyloxy) benzoate (MHOCPOOB), have been calculated using the density-functional theory (DFT) with the Becke-3 Lee-Yang-Parr/6-31G(d,p) level. The observed vibrational spectra have been resolved and assigned in detail by comparison to the computed values. The results indicate that the computed and observed spectra are in good agreement with each other. The stable molecular structure obtained with the DFT theory shows that the two hydrocarbon chains are all-trans zigzag conformer and nearly perpendicular to each other. The orientation of the mesogen part and the hydrocarbon chains for MHOCPOOB in the Sm-C*A phase are investigated by employing the polarization-angle-dependent infrared spectra in the electric-field induced and the two-dimensional correlation spectroscopy. After combining the experimental and theoretical results, it can be concluded that the azimuth of the achiral and chiral chains is opposite to each other, the orientation of the achiral chain is almost the same direction as the mesogen core, and the orientation of the chiral chain is nearly perpendicular to the mesogen part. The achiral and chiral CH2 chains are both a probable all-trans zigzag conformer.     

An efficient and tunable route to AG7088, a rhinovirus protease inhibitor

Aldol reaction of N,N-dibenzyl valinal with propiolic acid ethyl ester derived lithium reagent provides anti-aminoalcohol 8 and syn-aminoalcohol 9, which are converted into the lactone 6 via two different routes. Alkylation of 6 followed by lactone ring opening afford the acid 2a, which is coupled with the amine 3 and 5-methylisoxazole-3-carboxylate acid 1, respectively, to deliver AG7088.     

Capillary electrophoretic determination of the constituents of Artemisiae Capillaris Herba

Two capillary electrophoretic methods, a micellar electrokinetic electrophoretic (MEKC) one and a capillary zone electrophoretic (CZE) one, were developed for the separation of 12 constituents in Artemisiae Capillaris Herba. Detection at 254 nm with 20 mM sodium dodecyl sulfate and 20 mM sodium borate buffer (pH 9.82) in MEKC or with 25 mM sodium borate and 6.75 mg/ml 2,3,6-tri-O-methyl-beta-cyclodextrin buffer in CZE was found to be the most suitable approach for this analysis. Within 42 min, the MEKC method could successfully separate 12 authentic constituents, whereof chlorogenic acid, however, appeared as a broad and split peak, and capillarisin and chlorogenic acid overlapped partially with other coexisting substances in crude extract of the herb. The CZE method could completely overcome these problems and was used to determine the amounts of capillarisin, chlorogenic acid, scopoletin and caffeic acid in the extract. The effect of buffers on the constituent separation and the validation of the two methods were discussed.     

Sol-gel Preparation of Fluoridated Hydroxyapatite in Ca(NO3)2-PO(OH)3− x (OEt) x -HPF6 System

Fluoridated hydroxyapatite (FHA) has been successfully synthesized via sol-gel method with HPF₆ as the fluorine containing reagent. The chemical reactions induced by HPF₆ addition and the formation process of fluoridated hydroxyapatite (FHA) are investigated. The hydrolysis and alcoholysis of HPF₆ release F ion into the solution which, in turn, reacts with Ca ion to form nanocrystalline CaF₂ (nc-CaF₂). These nc-CaF₂ improves the gelation ability of the system through formation of F‒H hydrogen bonding between F in nc-CaF₂ and H in P precursors. Increasing HPF₆ leads to more nc-CaF₂ thus less Ca(NO₃)₂ in the dried gel, or the presence of nc-CaF₂ in the gel suppresses the formation of Ca(NO₃)₂. At elevated firing temperatures, the P containing groups react with each other to form condensed phosphate. These condensed calcium phosphate, nc-CaF₂/Ca(NO₃)₂, reacts with the rest of the amorphous phase to form FHA phase at above 400°C.     

高温煤气脱硫 Ⅰ.铁基脱硫剂的相态特征和活性

用穆斯堡尔谱考察了氧化铁脱硫剂在高温煤气中还原及硫化时的铁形态变化规律。在反应开始阶段，原脱硫剂中的α-Fe2O3即被迅速还原成Fe3O,Fe3O4可进一步还原转化成α-Fe。反应初期Fe3O4和α-Fe都参与脱硫反应，其中α-Fe具有较高的脱硫活性，对整个脱硫过程而言α-Fe是主要的脱硫活性相。铁化合物与硅铝氧化物载体间存在相互作用，形成磁微 晶颗粒及少量γ-Fe。在高温煤气条件下，FeS是唯一的铁硫化物，θ－Fe3C则是α－Fe转化中的主要产物。适量的θ－F e3C对脱硫有促进作用。     

Surface-enhanced Raman spectroscopy study on the structure changes of 4-mercaptopyridine adsorbed on silver substrates and silver colloids

Surface-enhanced Raman scattering (SERS) of 4-mercaptopyridine (4-mpy) adsorbed on HNO3 etched silver foil, chemically deposited silver films (silver mirror) and silver colloids were measured. The SERS study has revealed that 4-mpy was adsorbed onto the three kinds of silver surfaces by a sulfur-silver bond with the plane of pyridine ring being normal to the silver substrates. The structure of 4-mpy adsorbed on the silver surfaces depends largely on the pH values of environment. When the pH values of the environment are changed, the structure of 4-mpy adsorbed on silver surfaces can easily be altered through a protonation or deprotonation reaction occurring on the N atom of the pyridine ring, and the modified structure shows unique characters on the SERS spectrum. Owing to the remarkable enhancement ability of SERS technique and characteristic spectrum of different species, a monolayer of 4-mpy assembled on a silver mirror holds potential as a H+ sensor for highly sensitive detection of the proton concentration in an aqueous solution.     

Two polymorphs of cobalt(II) imidazolate polymers synthesized solvothermally by using one organic template N,N-dimethylacetamide

Two structurally different polymorphs of cobalt(II) imidazolate frameworks are solvothermally synthesized by using N,N-dimethylacetamide as a template: The polymorph 6 (a = 9.797 (4) angstroms, b = 15.301(6) angstroms, c =14.902(6) angstroms, beta = 98.904(6) degrees, monoclinic, P21/n) shows structures of silicate CaAl2Si2O8 with CrB4 topology, while polymorph 7 (a = 15.173(4) angstroms, b = 15.173(4) angstroms, c = 19.089(5) angstroms, Pbca) shows CaGa2O4-related topological structures. In addition, the 7' (a = 15.9712(18) angstroms, b = 15.9253(19) angstroms, c = 18.475(2) angstroms, Pbca), a compound isostructural with 7, is synthesized by using cyclohexanol as a template. Thus, these cobalt(II) imidazolate polymers are reminiscent of the zeolite syntheses in that not only the same topological structure can be synthesized by using the different organic templates, but also different topological structures can be synthesized by using the same organic template.     

Solventless polymerization: spatial migration of a catalyst to form polymeric thin films in microchannels

This paper reports a simple, additive process to generate patterned polymer films without using any solvent. This process involves a highly efficient catalyst, a Grubbs's catalyst, and a volatile monomer, norbornene. The catalyst and monomers have higher local concentrations inside the microchannels, formed by contacting poly(dimethylsiloxane) stamps to a solid surface, and allow the polymeric thin films to be defined by the microchannels. The patterned thin film serves as an excellent resistant to reactive ion etching, which promises that this process is a complementary, useful alternative to spin-coating and plasma polymerization in microfabrication.     

INVESTIGATION OF MICROSTRUCTURE AND CONDUCTIVE MECHANISM OF HIGH DENSITY POLYETHYLENE/CARBON BLACK PARTICLE COMPOSITE BY POSITRON ANNIHILATION LIFETIME SPECTROSCOPY

The microstructure and conductive mechanism of high density polyethylene/carbon black (HDPE/CB) compositewere investigated by positron annihilation lifetime spectroscopy (PALS). The PALS were measured in two series of samples,one with various CB contents in the composites and the other with various γ-irradiation doses in HDPE/CB compositecontaining 20 wt% CB. It was found that CB particles distribute in the amorphous regions, the CB critical content value inHDPE/CB composite is about 16.7 wtO/ and the suitable γ-irradiation dose for improving the conductive behavior ofHDPE/CB composite is about 20 Mrad. T'he result observed for the second set of samples suggests that γ-irradiation causesnot only cross-linking in amorphous regions but also destruction of the partial crystalline structure. Therefore, a suitableirradiation dose, about 20 Mrad, can induce sufficient cross-linking in the amorphous regions without enhancing thedecomposition of crystalline structure, so that the positive temperature coefficient (PTC) effect remains while the negativetemperature coefficient (NTC) effect is suppressed. A new interpretation of the conductive mechanism, which might providea more detailed explanation of the PTC effect and the NTC effect has been proposed.