Photodynamic release of fullerenes from within carbon nanohorn

We have found that oxidized single-wall carbon nanohorns (SWNHox) can exhibit a near-infrared (NIR) laser-triggered accelerated release of encapsulated fullerenes (C₆₀) from within their inner nanospaces. After the NIR laser irradiation of an aqueous SWNHox encapsulating C₆₀ solution/toluene biphasic system, C₆₀ molecules are enriched in the toluene phase. NIR laser-driven SWNHs encapsulating substrates could initiate the development of a new range of drug-delivery systems.     

Determination of trace elements in carbonate reference samples by instrumental neutron activation analysis

Twenty elements (Sm, U, As, Sb, La, Ce, Yb, Th, Cr, Eu, Hf, Ba, Cs, Tb, Sc, Rb, Fe, Zn, Ta, Co) have been determined by instrumental neutron activation analysis in GSJ/AIST carbonate reference samples, JCp-1 (Coral) and JCt-1 (Giant Clam), together with JLk-1 (Lake Sediment), JDo-1 (Dolomite) and JLs-1 (Limestone) reference samples.     

Slow Magnetic Relaxation of Ni(III) Complexes toward Molecular Spin Qubits

Molecule-based magnetic materials are promising candidates for molecular spin qubits, which utilize spin relaxation behavior. Various kinds of transition metal complexes with S=1/2 have been reported to act as spin qubits with long spin-spin relaxation times (T₂). However, the spin qubit properties of low-spin Ni(III) complexes are not as well known since Ni(III) compounds are often unstable. We report here the slow magnetic relaxation behavior and T₂ values for three kinds of low-spin Ni(III) based complexes with S=1/2 under magnetically diluted conditions. [Ni(cyclam)X₂]Y (cyclam=1,4,8,11-tetraazacyclotetradecane) with octahedral structures and [Ni(mnt)₂]⁻ (mnt=maleonitriledithiolate) with a square-planar structure underwent slow magnetic relaxations in the presence of a dc magnetic bias field. From electron spin resonance (ESR) spectroscopy, the Ni(III) complexes exhibited observable T₂, indicating that Ni(III) complexes are promising candidates for use as molecule-based spin qubits.     

Direct chiral separation of abscisic acid by high-performance liquid chromatography with a phenyl column and a mobile phase containing γ-cyclodextrin

Abscisic acid (2-cis,4-trans-abscisic acid) is a plant hormone that has an asymmetric carbon atom. We tried to separate the enantiomers of native abscisic acid by HPLC using a phenyl column and a chiral mobile phase containing γ-cyclodextrin. The optimum mobile phase conditions were found to be 0.8% (w/v) γ-cyclodextrin, 4% (v/v) acetonitrile, and 20 mM phosphate buffer (pH 6.0). It was found that (R)-abscisic acid was earlier detected than (S)-abscisic acid. Since γ-cyclodextrin is hardly retained on a phenyl column, it was suggested that (R)-abscisic acid formed a more stable complex with γ-cyclodextrin than the (S)-abscisic acid. Abscisic acid in an acacia honey sample was successfully enantioseparated with the proposed method and only (S)-abscisic acid was detected. A biologically inactive 2-trans,4-trans-abscisic acid, which was prepared by irradiation of abscisic acid with a light-emitting diode lamp at 365 nm, was partially enantioseparated by the proposed method. Since the irradiation of (S)-abscisic acid-induced cis-to-trans isomerization to produce one 2-trans,4-trans-abscisic acid enantiomer, it is reasonable that racemization did not proceed during the cis-to-trans isomerization. (S)-Abscisic acid and probably (S)-2-trans,4-trans-abscisic acid were detected in a honey sample, where the peak area of (S)-abscisic acid was 7 times larger than that of (S)-2-trans,4-trans-abscisic acid.     

Properties of hollow bent output tips in CO2 laser light delivery system

In order to change the output direction of laser light in a small operation space, two types of hollow bent output tips are proposed for medical laser light delivery system. One is the hollow fiber insert-type, which is of the minimum bending radius of 3 cm. The other type, based on a fixed-bent pyrex glass tube, is of the minimum bending radius of 2 mm. Both types of tips are inner-coated with a silver layer and a cyclic olefin polymer (COP) layer. Loss properties for CO₂ laser light are clarified for the insert-type tips with various bending angles and radii. For the fixed-bent tips, the losses are around 0.7 dB, which are almost not dependent on the bending angles and radii. Transmissions of the tips remain undamaged after 1-h-delivery of 5 W output CO₂ laser light. A nickel layer is coated on the outside wall of fixed-bent tips so as to increase the mechanical strength and lower the surface temperature. Characteristics of surface temperature distribution and time response were experimentally discussed. Transmission properties of pilot beams are also evaluated.     

Twist of Lie algebras by a rank-3 subalgebra

A new nonstandard deformation of all types of classical Lie algebras is constructed by means of twisting based on a six-dimensional subalgebra. This is an extension of extended twists introduced by Kulish et al. It is also shown that the new nonstandard so(3, 2) has a close connection with the symmetry of a discrete analog of the Klein-Gordon equation in (1+2) spacetime.     

In-plane mechanical behaviors of 2D repetitive frameworks with four-coordinate flexible joints and elbowed beam members

The mechanical properties of an open-framework structure constructed of joints and beam members are strongly influenced by both its geometrical configuration and joint flexibility. This paper clarifies the relationship between joint flexibility and Poisson's ratio, which is a mechanical criterion for solid deformation, and discusses two types of in-plane anisotropic structures made up of four-coordinate flexible joints and elbowed beam members. Uniaxial tensile analyses estimate the linear and nonlinear elastic properties of these frameworks by applying straightforward joint modeling with multi-rotational degrees of freedom. The numerical results show that these proposed frameworks produce a variety of deformability dependent on the joint flexibility in auxetic deformation with a negative Poisson's ratio, the folding mechanics under kinematic indeterminacy, and the transition of Poisson's ratio between the positive and negative values. The geometrical and topological aspects of the obtained mechanical behaviors are discussed.     

Fluorescent supramolecular polymers of barbiturate dyes with thiophene-cored twisted π-systems

Because supramolecular polymerization of emissive π-conjugated molecules depends strongly on π–π stacking interaction, the formation of well-defined one-dimensional nanostructures often results in a decrease or only a small increase of emission efficiency. This is also true for our barbiturate-based supramolecular polymers wherein hydrogen-bonded rosettes of barbiturates stack quasi-one-dimensionally through π–π stacking interaction. Herein we report supramolecular polymerization-induced emission of two regioisomeric 2,3-diphenylthiophene derivatives functionalized with barbituric acid and tri(dodecyloxy)benzyl wedge units. In CHCl₃, both compounds are molecularly dissolved and accordingly poorly emissive due to a torsion-induced non-radiative decay. In methylcyclohexane-rich conditions, these barbiturates self-assemble to form crystalline nanofibers and exhibit strongly enhanced emission through supramolecular polymerization driven by hydrogen-bonding. Our structural analysis suggests that the barbiturates form a tape-like hydrogen-bonding motif, which is rationalized by considering that the twisted geometries of 2,3-diphenylthiophene cores prevend the competing rosettes from stacking into columnar supramolecular polymers. We also found that a small difference in the molecular polarity originating from the substitutional position of the thiophene core influences interchain association of the supramolecular polymers, affording different luminescent soft materials, gel and nanosheet.

Two barbiturate dyes with regioisomeric thiophene-cored twisted π-systems show strongly enhanced emission through supramolecular polymerization. The supramolecular polymers thus formed exhibit distinct emission colors and degree of agglomeration.     

Leaky pseudo surface wave on the water–Si(110) interface

The present letter demonstrates that a leaky pseudo surface wave (LPSW) should exist on the interface of water and a cubic crystal silicon (110) plane. The phase velocity distribution of the LPSW on the above interface has been theoretically predicted by the reflection coefficient analysis and experimentally measured by using acoustic spectro-microscopy (ASM). The measured phase velocity distribution of the LPSW is in good agreement with the predicted one.