Crystal structure of friction-transferred poly(2,5-dioctyloxy-1,4-phenylenevinylene)

Poly(2,5-dioctyloxy-1,4-phenylenevinylene) (DOPPV) was found to form a highly oriented film by a friction-transfer technique. Structural investigation of friction-transferred DOPPV was studied by means of polarized ultraviolet-visible (UV-vis) absorption spectroscopy, polarized photoluminescence (PL) spectroscopy, and synchrotron-sourced grazing incident X-ray diffraction (GIXD) analysis. The polarized UV-vis absorption and PL spectra indicate clear axial alignment. DOPPV backbones in friction-transferred film are highly aligned along the drawing direction of the friction-transfer. Further information of the molecular arrangement in friction-transferred DOPPV film was investigated by both the out-of-plane and the in-plane GIXD analyses with synchrotron source. The DOPPV molecules in friction-transferred films were perfectly arranged three-dimensionally: the backbones aligned along the drawing direction of friction-transfer, the alkyl side chains lay in the film plane, and the planar backbones were arranged parallel to the film surface. Additionally, two neighboring DOPPV molecules along the direction of inter-backbones separation by alkyl side chains were found to be shifted with respect to one another by the mean distance of half of a monomeric repeat.     

Growth Curve Model with Hierarchical Within-Individuals Design Matrices

This paper deals with some inferential problems under an extended growth curve model with several hierarchical within-individuals design matrices. The model includes the one whose mean structure consists of polynomial growth curves with different degrees. First we consider the case when the covariance matrix is unknown positive definite. We derive a LR test for examining the hierarchical structure for within individuals design matrices and a model selection criterion. Next we consider the case when a random coefficients covariance structure is assumed, under certain assumption of between-individual design matrices. Similar inferential problems are also considered. The dental measurement data (see, e.g., Potthoff and Roy (1964, Biometrika, 51, 313-326)) is reexamined, based on extended growth curve models.     

Phase separation of gas–liquid and liquid–liquid microflows in microchips

Phase separation of gas–liquid and liquid–liquid microflows in microchannels were examined and characterized by interfacial pressure balance. We considered the conditions of the phase separation, where the phase separation requires a single phase flow in each output of the microchannel. As the interfacial pressure, we considered the pressure difference between the two phases due to pressure loss in each phase and the Laplace pressure generated by the interfacial tension at the interface between the separated phases. When the pressure difference between the two phases is balanced by the Laplace pressure, the contact line between the two phases is static. Since the contact angle characterizing the Laplace pressure is restricted to values between the advancing and receding contact angles, the Laplace pressure has a limit. When the pressure difference between the two phases exceeds the limiting Laplace pressure, one of the phases leaks into the output channel of the other phase, and the phase separation fails. In order to experimentally verify this physical picture, microchips were used having a width of 215 μm and a depth of 34 μm for the liquid–liquid microflows, a width of 100 μm and a depth of 45 μm for the gas–liquid microflows. The experimental results of the liquid–liquid microflows agreed well with the model whilst that of the gas–liquid microflows did not agree with the model because of the compressive properties of the gas phase and evaporation of the liquid phase. The model is useful for general liquid–liquid microflows in continuous flow chemical processing.     

Tuning of Electronic Properties of Single‐Walled Carbon Nanotubes under Homogenous Conditions

Reversible and non‐bonding interaction between SWNTs and ODCB is observed from the analyses of visible near‐infrared absorption data and Raman spectroscopies (see spectra). The solvent effect on SWNTs effectively controls the electronic structure of SWNTs under homogeneous conditions.

     

Fast screening of pesticide multiresidues in aqueous samples by dual stir bar sorptive extraction-thermal desorption-low thermal mass gas chromatography-mass spectrometry

A method for fast screening of pesticide multiresidues in aqueous samples using dual stir bar sorptive extraction-thermal desorption-low thermal mass gas chromatography-mass spectrometry (dual SBSE-TD-LTM-GC-MS) has been developed. Recovery of 82 pesticides - organochlorine, carbamate, organophosphorous, pyrethroid and others - for the SBSE was evaluated as a function of octanol-water distribution coefficients (logK(o/w): 1.7-8.35), sample volume (2-20mL), salt addition (0-30% NaCl), and methanol addition (0-20%). The optimized method consists of a dual SBSE performed simultaneously on respectively a 20-mL sample containing 30% NaCl and a 20-mL sample without modifier (100% sample solution). One extraction with 30% NaCl is mainly targeting solutes with low K(o/w) (logK(o/w)<3.5) and another extraction with unmodified sample solution is targeting solutes with medium and high K(o/w) (logK(o/w)>3.5). After extraction, the two stir bars are placed in a single glass desorption liner and are simultaneously desorbed. The desorbed compounds are analyzed by use of LTM-GC-MS with fast temperature programming (75 degrees Cmin(-1)) using a 0.18mm i.d. narrow-bore capillary column and fast scanning (10.83 scan s(-1)) using quadrupole MS. The method showed good linearity (r(2)>0.9900) and high sensitivity (limit of detection: <10ngL(-1)) for most of the target pesticides. The method was applied to the determination of pesticides at nanograms per liter levels in river water and brewed green tea.     

Imaging of a soft, weakly adsorbing, living cell with a colloid probe tapping atomic force microscope technique

Here, we propose a new method to improve the atomic force microscopy (AFM) image resolution of soft samples, such as cells, in liquid. Attaching a colloid probe to a cantilever was seen improve the image resolution of a living cell in a physiological buffer solution, obtained by the normal tapping mode, when compared to an image obtained using a regular cantilever tip. This may be due to the averaging out of the cantilever tip swinging caused by the visco-elasticity of the cell. The resolution was best, when silica spheres with a 3.3 microm diameter were attached. Although larger spheres gave a resolution better than a bare cantilever tip, their resolution was less than that obtained for the 3.3 microm diameter silica colloid. This dependency of the image resolution on the colloid probe size may be a result of the increased macroscopic van der Waals attraction between the cell and probe, the decreased repulsive force dependence on the cantilever probe radius, and the decrease in resolution due to the increased probe size. The size of the colloid probe, which should be attached to the cantilever to give the best image resolution, would be the one that optimises the combined result of these facts.     

Microarray techniques for more rapid protein quantification: use of single spot multiplex analysis and a vibration reaction unit

Protein microarray technology is a powerful, popular tool for the high-throughput analysis of protein interactions. One important use for protein microarray technology is protein quantification by immunoassay, which was originally based on enzyme linked immunosorbent assay (ELISA) methods. Recently, new research and diagnostic applications have created a need for a rapid and easily applied high-throughput protein quantification method. Here, we introduce several novel techniques that address these needs. Our improved protein microarray-based sandwich immunoassay techniques allow researchers to: (1) control the size and shape of protein spots on the microarray using a perforated seal; (2) analyze two proteins within a single spot, thus increasing the number of tests run on a single microarray without increasing the number of protein spots; (3) improve the efficiency and speed of the Ag-Ab interaction through vibratory reagent convection, which increased the signal intensity by more than two-fold and decreased the reaction time from 30 to 10 min. These new techniques will facilitate rapid immunoassays for diagnostic purposes and other research areas utilizing protein microarray analysis, such as investigations of ligand-receptor or protein-small molecule interactions.     

Efficient method for the deprotection of tert-butyldimethylsilyl ethers with TiCl4-Lewis base complexes: application to the synthesis of 1beta-methylcarbapenems

TiCl4-Lewis base (AcOEt, CH3NO2) complexes smoothly deprotected tert-butyldimethylsilyl (TBDMS) ethers. The reaction velocity with these complexes, which seemed less reactive due to the influence of Lewis bases, was considerably greater than that with TiCl4 alone. Selective desilylations between aliphatic and aromatic TBDMS ethers (1 and 5), between 1 and benzyl, allyl, tosyl, methoxyphenyl, and chloroacetyl ethers (13, 14, 15, 16, and 17), and between TBDMS and TBDPS ethers (18 and 19) were successfully performed. Desilylation of TBDMS-aldol, acyloin, and beta-lactam analogues 9-12 proceeded smoothly due to anchimeric assistance by the neighboring carbonyl groups. The present method was successfully applied to the practical synthesis of 1beta-methylcarbapenems 20a'-f'.     

Structural Transitions from Triangular to Square Molecular Arrangements in the Quasi-One-Dimensional Molecular Conductors (DMEDO-TTF)(2)XF(6) (X = P, As, and Sb)

A series of quasi-one-dimensional molecular conductors (DMEDO-TTF)(2)XF(6) (X = P, As, and Sb), where DMEDO-TTF is dimethyl(ethylenedioxy)tetrathiafulvalene, undergo characteristic structural transitions in the range of 130-195 K for the PF(6) salt and 222-242 K for the AsF(6) salt. The dramatic structural transition is induced by the order of the ethylenedioxy moiety, and the resulting anion rotation leads to the reconstruction of the H···F interaction between the methyl groups and the anions. The unique hydrogen bonds play a crucial role in the transition. As a result, the molecular packing is rearranged entirely; the high-temperature molecular stacks with an ordinary quasi-triangular molecular network transforms to a quasi-square-like network, which has never been observed among organic conductors. Nonetheless, the low-temperature phase exhibits a good metallic conductivity as well, so the transition is a metal-metal (MM) transition. The resistivity measured along the perpendicular direction to the conducting ac-plane (ρ(⊥)) and the calculation of the Fermi surface demonstrate that the high-temperature metal phase is a one-dimensional metal, whereas the low-temperature metal phase has considerable interchain interaction. In the SbF(6) salt, a similar structural transition takes place around 370 K, so that the quasi-square-like lattice is realized even at room temperature. Despite the largely different MM transition temperatures, all these salts undergo metal-insulator (MI) transitions approximately at the same temperature of 50 K. The low-temperature insulator phase is nonmagnetic, and the reflectance spectra suggest the presence of charge disproportionation with small charge difference (0.14).