Surfaces in 4-manifolds and their mapping class groups

A surface in a smooth 4-manifold is called flexible if, for any diffeomorphism ? on the surface, there is a diffeomorphism on the 4-manifold whose restriction on the surface is ? and which is isotopic to the identity. We investigate a sufficient condition for a smooth 4-manifold M to include flexible knotted surfaces, and introduce a local operation in simply connected 4-manifolds for obtaining a flexible knotted surface from any knotted surface.     

Charge transport in carbon nanotubes based materials: a Kubo–Greenwood computational approach

In this contribution, we present a numerical study of quantum transport in carbon nanotubes based materials. After a brief presentation of the computational approach used to investigate the transport coefficient (Kubo method), the scaling properties of quantum conductance in ballistic regime as well as in the diffusive regimes are illustrated. The impact of elastic (impurities) and dynamical disorders (phonon vibrations) are analyzed separately, with the extraction of main transport length scales (mean free path and localization length), as well as the temperature dependence of the nanotube resistance. The results are found in very good agreement with both analytical results and experimental data, demonstrating the predictability efficiency of our computational strategy. To cite this article: H. Ishii et al., C. R. Physique 10 (2009).     

137Cs activity in surface water in the western North Pacific

Temporal and spatial variations of ¹³⁷Cs activity in surface waters in the western North Pacific are examined along the 165°E transect. ¹³⁷Cs in seawater of the western North Pacific has been introduced by global fallout originating from atmospheric nuclear weapons tests, which caused major fallout in the early 1960's. At this time ¹³⁷Cs activities in the surface waters in mid latitudes of the North Pacific were 10–20 Bq·m^-3. South of 30°N, ¹³⁷Cs activity decreased gradually towards the south. The surface ¹³⁷Cs activity was about 5 Bq·m^-3 in the Equatorial region. In the 1970's, the difference in ¹³⁷Cs activities in surface water between mid latitudes and the Equatorial region became smaller. The ¹³⁷Cs activity in surface water at 40°N – Equatorial region was almost constant at the level of 1.7–3.7 Bq·m^-3 in the late 1990's. In the Equatorial region, the ¹³⁷Cs activity in surface water showed no temporal change except for radioactive decay over these four decades. The surface ¹³⁷Cs level was 1.4–1.8 Bq·m^-3 in the north subarctic region around 50°N in the late 1990's. The lower ¹³⁷Cs activity may have been caused by deeper convection in this sea area and dilution by fresh water flux.     

A Practical Guide for the Determination of Binding Constants

When working in the field ofhost–guest chemistry, the binding constants have to bedetermined on many occasions. Here is a detaileddocument of how to determine the binding constantswhich covers both the basic principle and thepractical issue: a practical experimental guideline,a representative method for the determination ofstoichiometry and for the evaluation of a complexconcentration, precautions to be taken on setting upconcentration conditions of the titration experiment,practical data-treatment methods and estimation ofstatistical errors. This document is described indetail using the basic level of mathematics,statistics, and programs of spreadsheet software.Especially, the titration experiments by means ofUV-visible and NMR spectroscopy are carried out anddescribed.     

Time-resolved EPR, fluorescence, and transient absorption studies on phthalocyaninatosilicon covalently linked to one or two TEMPO radicals.

The photophysical properties of tetra-tert-butylphthalocyaninatosilicon (SiPc) covalently linked to one or two 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radicals (R1, R2) have been studied by fluorescence, transient absorption, and time-resolved electron paramagnetic resonance (TREPR) spectroscopies. It is found that the fluorescence quantum yields and lifetimes of R1 and R2 decrease compared with those of (dihydroxy)SiPc ((dihydroxy)SiPc = 6.8 ns, R1 = 4.7 ns and 42 ps, and R2 = 4.7 ns and <30 ps). Transient absorption measurements indicate that the lifetime of the excited triplet SiPc is markedly dependent on the number of linking TEMPO radicals ((dihydroxy)SiPc = 500 micros, R1 = 7.6 micros, and R2 = 3.7 micros). These short lifetimes of R1 and R2 in the excited states are explained as a result of the interaction with TEMPO changing the ISC between the singlet and triplet states to spin-allowed transitions. Quantitative TREPR investigations have been carried out for the radical-quartet pair mechanism of R1 and the photoinduced population transfer of R2. It is determined that the rise and decay times of these electron spin polarizations denote the spin-lattice relaxation time of the ground state and the lifetime of the excited multiplet state, respectively. This study contributes not only to an elucidation of radical-chromophore interactions but also to a novel approach for controlling magnetic properties by photoexcitation.     

Bleustein–Gulyaev waves in 6 mm piezoelectric materials loaded with a viscous liquid layer of finite thickness

In this paper, we analyze the propagation of Bleustein–Gulyaev waves in an unbounded piezoelectric half-space loaded with a viscous liquid layer of finite thickness within the linear elastic theories. Exact solutions of the phase velocity equations are obtained in the cases of both electrically open circuit and short circuit by solving the equilibrium equations of piezoelectric materials and the diffusion equation of viscous liquid. A PZT-5H/Glycerin system is selected to perform the numerical calculation. The results show that the mass density and the viscous coefficient have different effects on the propagation attenuation and phase velocity under different electrical boundary conditions. In particular, the penetration depth of the waves is of the same order as the wavelength in the case of electrically short circuit. These effects can be used to manipulate the behavior of the waves and have implications in the application of acoustic wave devices.     

A novel type of transverse surface wave propagating in a layered structure consisting of a piezoelectric layer attached to an elastic half-space

The existence and propagation of transverse surface waves in piezoelectric coupled solids is investigated, in which perfect bonding between a metal/dielectric substrate and a piezoelectric layer of finite-thickness is assumed. Dis- persion equations relating phase velocity to material con- stants for the existence of various modes are obtained in a simple mathematical form for a piezoelectric material of class 6mm. It is discovered and proved by numerical examples in this paper that a novel Bleustein-Gulyaev （B-G） type of transverse surface wave can exist in such piezoelectric cou- pled solid media when the bulk-shear-wave velocity in the substrate is less than that in the piezoelectric layer but greater than the corresponding B-G wave velocity in the same pie- zoelectric material with an electroded surface. Such a wave does not exist in such layered structures in the absence of pie- zoelectricity. The mode shapes for displacement and electric potential in the piezoelectric layer are obtained and discussed theoretically. The study extends the regime of transverse sur- face waves and may lead to potential applications to surface acoustic wave devices.     

A new taxoid from a callus culture of Taxus cuspidata as an MDR reversal agent

A new taxoid, 5alpha,13alpha-diacetoxy-10beta-cinnamoyloxy-4(20),11-taxadien-9alpha-ol (1) along with its 9,10-isomer, taxinine NN-11 (2) were isolated from the callus cultures of Taxus cuspidata. The structures were identified by the analyses of the spectral data and chemical method. Their in vitro cytotoxicity against 3 cell lines (HepG2, WI-38 and VA-13) and multidrug resistance (MDR) reversal activity toward 2780AD tumor cells were preliminarily evaluated, the low cytotoxicities and potent MDR reversal activities suggested that they might be good lead compounds of tumor MDR reversal agent.     

Adsorption of colloidal particles to curved interfaces

As a simple model for a Pickering emulsion droplet, we consider the adsorption of spherical particles to a spherical liquid-liquid interface in order to investigate the curvature effect on the particle adsorption. By taking into account both the surface and the volume energies due to the presence of a particle, we show that the equilibrium contact angle is determined by the classical Young's equation although the adsorption energy depends on the curvature. We also calculate the partitioning of the colloidal particles among the two liquids and the interface. The distribution of colloidal particles is expressed in terms of the interfacial curvature as well as the relative wettability of the particle.