Spontaneous vesicle formation of single chain and double chain cationic surfactant mixtures

The concentration vs composition diagram of aggregate formation of the dodecyltrimethylammonium bromide (DTAB) and didodecyldimethylammonium bromide (DDAB) mixture in aqueous solution at rather dilute region was constructed by analyzing the surface tension, turbidity, and electrical conductivity data and inspected by cryo-TEM images and dynamic light scattering data. Although the aqueous solution of DTAB forms only micelles, the transition from monomer to small aggregates and then to vesicle was found at 0.1 < X2 相似文献   

Flow-injection determination of total organic fluorine with off-line defluorination reaction on a solid sorbent bed

Considering recent reports on widespread occurrence and concerns about perfluoroalkyl substances (PFAS) in environmental and biological systems, analysis of these compounds have gained much attention in recent years. Majority of analyte-specific methods are based on a LC/MS/MS or a GC/MS detection, however many environmental or biological studies would benefit from a total organic fluorine (TOF) determination. Presented work was aimed at developing a method for TOF determination. TOF is determined as an amount of inorganic fluoride obtained after defluorination reaction conducted off-line using sodium biphenyl reagent directly on the sorbent without elution of retained analytes. Recovered fluoride was analyzed using flow-injection system with either fluorimetric or potentiometric detection. The TOF method was tested using perfluorocarboxylic acids (PFCA), including perfluorooctanoic acid (PFOA), as model compounds. Considering low concentrations of PFAS in natural samples, solid-phase extraction as a preconcentration procedure was evaluated. Several carbon-based sorbents were tested, namely multi-wall carbon nanotubes, carbon nanofibres and activated carbon. Good sorption of all analytes was achieved and defluorination reaction was possible to carry out directly on a sorbent bed. Recoveries obtained for PFCAs, adsorbed on an activated carbon sorbent, and measured as TOF, were 99.5 ± 1.7, 110 ± 9.4, 95 ± 26, 120 ± 32, 110 ± 12 for C4, C6, C8, C10 and C12-PFCA, respectively. Two flow systems that would enable the defluorination reaction and fluoride determination in a single system were designed and tested.     

A recyclable catalyst for asymmetric transfer hydrogenation with a formic acid-triethylamine mixture in ionic liquid

A novel task-specific ionic ligand with an imidazolium salt moiety was synthesized, and its catalytic ability and recyclability for asymmetric transfer hydrogenation of acetophenone derivatives with a formic acid-triethylamine azeotropic mixture in an ionic liquid [bmim][PF6] was examined.     

Synthesis of polyanionic glycopolymers for the facile assembly of glycosyl arrays

Polyanionic glycopolymers were synthesized aiming at establishing a simple process for assembling glycosyl arrays. The synthetic glycopolymers carry the key carbohydrate epitopes of α-d-galactobioside (Gb₂), β-lactoside, and α-d-mannopyranoside, each of which serves as a ligand of bacterial toxins and adhesion proteins. The Gb₂ epitope, prepared from penta-O-acetyl-d-galactopyranose, was coupled with poly(ethylene-alt-maleic anhydride) in a polymer reaction to afford a Gb₂-embedded glycopolymer having also carboxylate (COO⁻) polyanions at the side chain. The polyanionic glycopolymer was then applied to a preparation of sugar-coated gold electrodes, which involves an alternating layer-by-layer adsorption based on electrostatic interactions. The presence of the Gb₂-coat on the surface was evidenced by Fourier transform infrared reflection absorption spectroscopy. The Gb₂-coated glyco-chip was stable in 10 mM HEPES buffer containing 150 mM NaCl aq. Other glycopolymers carrying the β-lactoside and α-d-mannopyranoside epitopes were applied to the same assembling process. The derived glycosyl arrays will be useful for detecting Shiga toxins, other pathogenic toxins and viruses when applied as glyco-chips for surface plasmon resonance or quartz crystal microbalance technique.     

Chemical and electrochemical oxidation of thiophene-pyridine and thiophene-pyrimidine co-oligomers in solutions

Chemical and electrochemical oxidation (or p-doping) of three types of pi-conjugated co-oligomers, Py-Th-(Th)n-Th-Py (Py = pyridine unit; Th = thiophene unit; 5a, n = 1; 6a, n = 2), Th-Py-(Th)n-Py-Th (5b: n = 1; 6b: n = 2), and Pym-Th-(Th)n-Th-Pym (Pym = pyrimidine unit; 5c: n = 1; 6c: n = 2), in solution systems has been studied. The chemical oxidation with NOBF(4) proceeded with isosbestic points in the UV-vis spectrum. The UV-vis absorption peak of 5a at 418 nm in CH(2)Cl(2) shifted to 456 nm after oxidation of 5a with NOBF(4). The oxidized 5a was easily reduced by N(2)H(4) to give the original UV-vis spectrum of 5a, and 5b, 6b, and 5c behaved similarly in the oxidation and reduction. In the oxidation by NOBF4, an (oxidized co-oligomer)/(original neutral co-oligomer) ratio of 1 was attained at [NOBF4] = 1.3 x 10(-6), 4 x 10(-6), 7 x 10(-6), and 9 x 10(-6) M for 5a, 6b, 5b, and 5c, respectively. The obtained data are considered to reflect the ease of oxidation of the co-oligomer, which is affected by the electron-accepting nature of the N-containing aromatic unit in the co-oligomer and effective pi-conjugated length of the co-oligomer. The cyclic voltammogram of 5a showed three redox couples with anodic peak current potentials of Epa = 0.75, 1.10, and 1.34 V versus Ag+/Ag, respectively. The first oxidation peak was assigned to one-electron oxidation of 5a, and electronic current of the first anodic peak (i) of 5a and 5c was proportional to (scanning rate)1/2. From the i- (scanning rate)1/2 relationship, diffusion constants, D's, of 5a and 5c were estimated to be 9.6 x 10(-6) and 1.7 x 10(-5) cm2 s(-1), respectively. CV data of 5b with the terminal thiophene units indicated occurrence of electrochemical oxidative polymerization of 5b.     

Highly selective photoinduced perfluoroalkylation of vinylsilanes and its application to synthesis of water-shedding polysilanes

The functionalization of polysilanes is an important subject in materials science because functionalized polysilanes are expected to exhibit potentially innovative properties. This research aims at the addition of a water-shedding property to polysilanes by introducing perfluoroalkyl groups into their skeleton. The photoinduced iodoperfluoroalkylation of various vinylsilanes takes place successfully upon irradiation with a xenon lamp: vinylmonosilanes undergo iodoperfluoroalkylation with perfluoroalkyl iodides (R_fI) regioselectively, and the corresponding perfluoroalkylated silanes are obtained in moderate to high yields. Detailed optimization of the photoinduced iodoperfluoroalkylation has been investigated to apply this method to the functionalization of polysilanes. Polysilanes having vinyl groups can be synthesized by the reductive coupling of dichlorovinylsilanes with samarium diiodide (SmI₂) and samarium metal (Sm) upon irradiation with visible light. The synthesized vinylpolysilanes and R_fI (about 1.0 mM CHCl₃ solution) are coated on a glass plate sequentially, and then the following photoirradiation with light of a wavelength over 300 nm successfully adds an excellent water-shedding property to the glass plate.     

Transversality family of expanding rational semigroups

We study finitely generated expanding semigroups of rational maps with overlaps on the Riemann sphere. We show that if a d$d$-parameter family of such semigroups satisfies the transversality condition, then for almost every parameter value the Hausdorff dimension of the Julia set is the minimum of 2 and the zero of the pressure function. Moreover, the Hausdorff dimension of the exceptional set of parameters is estimated. We also show that if the zero of the pressure function is greater than 2$2$, then typically the 2-dimensional Lebesgue measure of the Julia set is positive. Some sufficient conditions for a family to satisfy the transversality conditions are given. We give non-trivial examples of families of semigroups of non-linear polynomials with the transversality condition for which the Hausdorff dimension of the Julia set is typically equal to the zero of the pressure function and is less than 2$2$. We also show that a family of small perturbations of the Sierpinski gasket system satisfies that for a typical parameter value, the Hausdorff dimension of the Julia set (limit set) is equal to the zero of the pressure function, which is equal to the similarity dimension. Combining the arguments on the transversality condition, thermodynamical formalisms and potential theory, we show that for each a∈C$a\in \mathbb{C}$ with |a|≠0,1$\left|a\right|\ne 0,1$, the family of small perturbations of the semigroup generated by {z²,az²}$\{z^2,a{z}^2\}$ satisfies that for a typical parameter value, the 2-dimensional Lebesgue measure of the Julia set is positive.     

Interaction cohomology of forward or backward self-similar systems

We investigate the dynamics of forward or backward self-similar systems (iterated function systems) and the topological structure of their invariant sets. We define a new cohomology theory (interaction cohomology) for forward or backward self-similar systems. We show that under certain conditions, the space of connected components of the invariant set is isomorphic to the inverse limit of the spaces of connected components of the realizations of the nerves of finite coverings U of the invariant set, where each U consists of (backward) images of the invariant set under elements of finite word length. We give a criterion for the invariant set to be connected. Moreover, we give a sufficient condition for the first cohomology group to have infinite rank. As an application, we obtain many results on the dynamics of semigroups of polynomials. Moreover, we define postunbranched systems and we investigate the interaction cohomology groups of such systems. Many examples are given.     

Asymptotics for functionals of self-normalized residuals of discretely observed stochastic processes

The purpose of this paper is to derive the stochastic expansion of self-normalized-residual functionals stemming from a class of diffusion type processes observed at high frequency, where total observing period may or may not tend to infinity. The result enables us to construct some explicit statistics for goodness of fit tests, consistent against “presence of a jump component” and “diffusion-coefficient misspecification”; then, the acceptance of the null hypothesis may serve as a collateral evidence for using the correctly specified diffusion type model. Especially, our asymptotic result clarifies how to remove the bias caused by plugging in a diffusion-coefficient estimator.