Synthesis of dodecaborate-conjugated cholesterols for efficient boron delivery in neutron capture therapy

Dodecaborate-conjugated cholesterols 3a-c were synthesized for liposomal boron delivery systems in neutron capture therapy. The current synthesis is based on the S-alkylation protocol of the cyanoethyl-protected BSH with alkyl halides. The dodecaborate-conjugated cholesterol 3a liposome, which was prepared from dimyristoylphosphatidylcholine (DMPC), cholesterol, dodecaborate-conjugated cholesterol 3a, and polyethyleneglycol-conjugated distearoylphosphatidylethanolamine (PEG-DSPE) (1:0.5:0.5:0.1), exhibited higher cytotoxicity than BSH at the same boron concentration and IC₅₀ values of the 3a liposome and BSH toward colon 26 cells were estimated as 25 and 78 ppm of boron concentration, respectively.     

On the Rate of Decay of the Oseen Semigroup in Exterior Domains and its Application to Navier–Stokes Equation

We prove L_p-L_q estimates of the Oseen semigroup in n-dimensional exterior domains which refine and improve those obtained by Kobayashi and Shibata [15]. As an application, we give a globally in time stability theory for the stationary Navier–Stokes flow whose velocity at infinity is a non-zero constant vector. We thus extend the result of Shibata [21]. In particular, we find an optimal rate of convergence of solutions of the non-stationary problem to those of the corresponding stationary problem.     

Bifurcation of an elliptic vortex ring

Time-dependent vorticity fields of elliptic vortex rings of aspect ratios 2, 3 and 4 were measured by means of hot-wire anemometry. The time evolution of their vorticity fields was analyzed and the processes of vortex ring formation, advection, interaction and decay, and the mechanism of vortex bifurcation are studied. The following crosslinking model is proposed: A thick vortical region composed of many equivalent vortex filaments with distributed cores is initially formed at the orifice and they behave as inviscid filaments. The elliptic ring deforms and the end parts of its major axis get closer. Then, the vortex filaments interact at the touching point and the ring partially bifurcates. Almost simultaneously, turbulent spot appears at this point, and propagates around the ring cross section, thus preventing further bifurcation. And it becomes a turbulent blob. This model is also supported by numerical simulation by a high-order vortex method and the Navier-Stokes solution.     

Plasmon‐Induced Ammonia Synthesis through Nitrogen Photofixation with Visible Light Irradiation

We have successfully developed a plasmon‐induced technique for ammonia synthesis that responds to visible light through a strontium titanate (SrTiO₃) photoelectrode loaded with gold (Au) nanoparticles. The photoelectrochemical reaction cell was divided into two chambers to separate the oxidized (anodic side) and reduced (cathodic side) products. To promote NH₃ formation, a chemical bias was applied by regulating the pH value of these compartments, and ethanol was added to the anodic chamber as a sacrificial donor. The quantity of NH₃ formed at the ruthenium surface, which was used as a co‐catalyst for SrTiO₃, increases linearly as a function of time under irradiation with visible light at wavelengths longer than 550 nm. The NH₃ formation action spectrum approximately corresponds to the plasmon resonance spectrum. We deduced that plasmon‐induced charge separation at the Au/SrTiO₃ interface promotes oxidation at the anodic chamber and subsequent nitrogen reduction on the cathodic side.     

Acid‐Promoted Chemoselective Introduction of Amide Functionality onto Aromatic Compounds Mediated by an Isocyanate Cation Generated from Carbamate

Carbamates have been used as precursors of isocyanates, but heating in the presence of strong acids is required because cleavage of the C? O bond in carbamates is energy‐demanding even in acid media. Direct amidation of aromatic compounds by isocyanate cations generated at room temperature from carbamoyl salicylates in trifluoromethanesulfonic acid (TfOH) was examined. Carbamates with ortho‐salicylate as an ether group (carbamoyl salicylates) showed dramatically accelerated O? C bond dissociation in TfOH, which resulted in facile generation of the isocyanate cation. These chemoselective intermolecular aromatic amidation reactions proceeded even at room temperature and showed good compatibility with other electrophilic functionalities and high discrimination between N‐monosubstituted carbamate and N,N‐disubstituted carbamate. The reaction rates of secondary and tertiary amide formation were markedly different, and this difference was utilized to achieve successive (tandem) amidation reactions of molecules with an N‐monosubstituted carbamate and an N,N‐disubstituted carbamate with two kinds of aromatic compounds.     

Development of a Sensitive Bioluminogenic Probe for Imaging Highly Reactive Oxygen Species in Living Rats

A sensitive bioluminogenic probe for highly reactive oxygen species (hROS), SO₃H‐APL, was developed based on the concept of dual control of bioluminescence emission by means of bioluminescent enzyme‐induced electron transfer (BioLeT) and modulation of cell‐membrane permeability. This probe enables non‐invasive visualization of physiologically relevant amounts of hROS generated deep inside the body of living rats for the first time. It is expected to serve as a practical analytical tool for investigating a wide range of biological functions of hROS in vivo. The design concept should be applicable to other in vivo bioluminogenic probes.     

The complete classification of fibres in pencils of curves of genus two

This article contains geometrical classification of all fibres in pencils of curves of genus two, which is essentially different from the numerical one given by Ogg ([11]) and Iitaka ([7]). Given a family π:X→D of curves of genus two which is smooth overD′=D?{0}, we define a multivalued holomorphic mapT _π fromD′ into the Siegel upper half plane of degree two, and three invariants called “monodromy”, “modulus point” and “degree”. We assert that the family π is completely determined byT _π, and its singular fibre by these three invariants. Hence all types of fibres are classified by these invariants and we list them up in a table, which is the main part of this article.     

Spin glasses with long-range interactions

A spin-glass model with a general form of long-range interactions is introduced. The replica method and the renormalization group theory are used and the results are explained from the viewpoint of frustration effects compared with the non- random case. The so-called mean field approximation is shown to be invalid for 3-d RKKY interaction systems.     

Phosphorescence of biacetyl sensitized by benzene in gas phase pulse radiolysis

The phophorescence of biacetyl induced by an energy transfer to biacetyl from triplet benzene produced in the pulse radiolysis of benzene-biacetyl mixtures has been studied. The time required to reach the maximum intensity of phosphorescence, t_max, after the electron pulse, varies as a function of biacetyl pressure at constant benzene pressure (40 torr), which gives the lifetime of triplet benzene τ = (6.7 ± 3.2) × 10⁻⁶ s and the rate constant of the energy transfer k_{C6H6^*(T1) + biacetyl} = (1.6 ± 0.7) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹.     

Intercalated formation of two-dimensional and multi-layered perovskites in organic thin films

Two-dimensional and multi-layered perovskites, [NH3(CH2)12NH3]PbBr4 and [NH3(CH2)12NH3](CH3NH3)(n-1)Pb(n)Br(3n+1), with a quantum confinement effect have been naturally formed by intercalating lead bromide into organic alkyldiammonium bromide frameworks.