New force field for molecular simulation of guanidinium-based ionic liquids

An all-atom force field was proposed for a new class of room temperature ionic liquids (RTILs), N,N,N',N'-tetramethylguanidinium (TMG) RTILs. The model is based on the AMBER force field with modifications on several parameters. The refinements include (1) fitting the vibration frequencies for obtaining force coefficients of bonds and angles against the data obtained by ab initio calculations and/or by experiments and (2) fitting the torsion energy profiles of dihedral angles for obtaining torsion parameters against the data obtained by ab initio calculations. To validate the force field, molecular dynamics (MD) simulations at different temperatures were performed for five kinds of RTILs, where TMG acts as a cation and formate, lactate, perchlorate, trifluoroacetate, and trifluoromethylsulfonate act as anions. The predicted densities were in good agreement with the experimental data. Radial distribution functions (RDFs) and spatial distribution functions (SDFs) were investigated to depict the microscopic structures of the RTILs.     

Critical exponents and self-similarity for sol-gel transition in aqueous alginate systems induced by in situ release of calcium cations

The sol-gel transition in aqueous alginate systems induced by in situ released calcium cations was monitored with rheology methods. Four alginate samples with different molecular weights and M/G ratios were used over the concentration C(Alg) of 2 approximately 6 wt % with different mole ratios f of Ca2+ to the alginate repeat unit. The scaling for the zero shear viscosity eta(0) before the gel point and the equilibrium modulus Ge after the gel point was described as eta(0) approximately epsilon(-k) and Ge approximately epsilon(z), respectively, where the relative distance to the gel point f(gel) was epsilon = (/f-f(gel)/)/f(gel). The relaxation critical exponent n was determined with Winter's criterion, and the critical exponents k and z estimated respectively from independent measurements of eta(0) and Ge gave n from z/(k + z). Before the gel point, the storage and loss moduli G' and G' obtained at various epsilon can be superposed fairly well to form the master curve. The critical exponents n, k, and z were also evaluated from the shift factors and the structure self-similarity was found in the critical gel. The critical exponents evaluated with different methods agreed well with each other, suggesting two categories of the gelation as growth and cross-link. For the alginate with lower molecular weight, the critical exponents were almost independent of alginate concentration and close to the percolation prediction. For the alginate with higher molecular weight, the critical exponents, however, changed with alginate sample and concentration. The relative alginate concentration C(Alg)/C(Alg)* was found to serve as a criterion to divide these two transitions.     

Comparative study of hydrogen adsorption on carbon and BN nanotubes

The physisorption and chemisorption of hydrogen in BN nanotubes, investigated by density functional theory (DFT), were compared with carbon nanotubes. The physisorption of H2 on BN nanotubes is less favorable energetically than on carbon nanotubes; BN nanotubes cannot adsorb hydrogen molecules effectively in this manner. Chemisorption of H2 molecules on pristine BN nanotubes is endothermic. Consequently, perfect BN nanotubes are not good candidates for hydrogen storage by either mechanism. Other strategies must be utilized if BN nanotubes are to be employed as hydrogen storage media such as utilizing them as supporting media for hydrogen-absorbing metal nanoclusters.     

Synthesis of functionalized quinolines via Ugi and Pd-catalyzed intramolecular arylation reactions

Two types of quinoline scaffolds were constructed in a combinatorial format via the Ugi four-component reaction (U-4CR) and Pd-catalyzed intramolecular arylation reaction. The scope of this two-step synthetic sequence was examined from commercially available and synthetically accessible starting materials.     

Separation and identification of compounds in Adinandra nitida by comprehensive two-dimensional liquid chromatography coupled to atmospheric pressure chemical ionization source ion trap tandem mass spectrometry

A comprehensive two-dimensional liquid chromatographic (2D-LC) separation system based on the combination of a CN column and a Merck Chromolith Flash reversed-phase column was developed for the separation of components in Adinandra nitida, one type of traditional Chinese medicine (TCM). The two dimensions were connected by a ten-port, dual-position valve controlled automatically by software written in-house. The effluents were detected by both ultraviolet and atmospheric pressure chemical ionization source ion trap tandem mass spectrometry (MS). The calculated peak capacity of the 2D-LC–MS/MS system was above 1240. More than 57 components were resolved in the methanol extract from Adinandra nitida leaves, and five of these were identified based on their relative retention times, molecular weights and MS/MS spectra.     

A fast luminosity monitor for BEPCⅡ

The fast luminosity monitor counting the γ photons above a given energy threshold emitted from radiative Bhabha scattering has been operated in the BEPC Ⅱ to measure the relative luminosity bunch by bunch for the first time and used successfully in beam tuning of BEPC Ⅱ. In the relative mode the monitor is able to deliver the relative luminosities with an accuracy of 0.8 %. By steering the electron beam while observing the counting rate changes of the monitor the horizontal and vertical sizes of the bunch spots can be estimated as： Sxe＋ =Sxe =0.356 mm, Sye＋ =Sye- =0.011 mm.     

Antennal morphology and sensilla ultrastructure of Dendroctonus valens LeConte (Coleoptera: Curculionidae,Seolytinae), an invasive forest pest in China

Dendroctonus valens LeConte, an invasive forest pest, is highly dependent on its olfactory system for activities such as host seeking, mating, oviposition and population aggregation. The antennae are the primary olfactory organs in bark beetles. We describe four morphological types of sensilla on the antenna of D. valens: (1) 3 subtypes of sensilla trichodea located at the apex and lateral surface of the club. Sensilla trichodea types 1 and 3 were innervated by 5 and 13 dendrites, respectively. Sensilla trichode type 2 was not found dendrites in a lumen, (2) sensilla chaetica found on the scape and funicle and innervated by 7 dendrites, (3) a pair of sensilla basiconica distributed primarily on the three sensory bands, each innervated by 2 dendrites at the base, and (4) one fluted cone type of grooved peg dispersed throughout the sensory bands. The possible functions of these sensilla are discussed in relation to their morphology and ultrastructure.     

Modeling abnormal strain states in ferroelastic systems: the role of point defects

Recent experiments have revealed a rich variety of strain states in doped ferroelastic systems. We study the origin of two abnormal strain states; precursory tweed and strain glass, and their relationship with the well-known austenite and martensite (the para- and ferroelastic states). A Landau free energy model is proposed, which assumes that point defects alter the global thermodynamic stability of martensite and create local lattice distortions that interact with the strain order parameters and break the symmetry of the Landau potential. Phase field simulations based on the model have predicted all the important signatures of a strain glass found in experiment. Moreover, the generic "phase diagram" constructed from the simulation results shows clearly the relationships among all the strain states, which agrees well with experimental measurements.     

Schwarz Lemma at the Boundary on the Classical Domain of Type III

LetRIII(n) be the classical domain of typeIII with n≥2. This article is devoted to a deep study of the Schwarz lemma onRIII(n) via not only exploring the smooth boundary points ofRIII(n) but also proving the Schwarz lemma at the smooth boundary point for holomorphic self-mappings ofRIII(n).