Real-time monitoring of antibody secretion from B-cells on a microchip stimulated with a minute amount of mitogen

This paper describes the cultivation of primary cells in a microchamber and the real-time monitoring of small amounts of antibody secretion after the introduction of a minute amount of stimulus by a microinjector using time-resolved fluorescence anisotropy analysis.     

Microscopic basis for the mechanism of carrier dynamics in an operating p-n junction examined by using light-modulated scanning tunneling spectroscopy

The doping characteristics and carrier transport in a GaAs p-n junction were visualized with a approximately 10 nm spatial resolution, using light-modulated scanning tunneling spectroscopy. The dynamics of minority carriers under operating conditions, such as recombination, diffusion, and electric field induced drift, which had previously been analyzed on the basis of empirical electric properties, were successfully examined on the nanoscale. These results provide a solid basis for elucidating the mechanism of the carrier transport properties predicted by using the macroscopic analysis.     

Rapid and efficient synthesis of dysiherbaine and analogues to explore structure-activity relationships

A rapid and efficient total synthesis of dysiherbaine (1), a potent and subtype-selective agonist for ionotropic glutamate receptors, has been accomplished. A key intermediate 15 was synthesized by two approaches. The first synthetic route utilized compound 9, an advanced intermediate in our previous total synthesis of neodysiherbaine A, as the starting point, and the cis-oriented amino alcohol functionality on the tetrahydropyran ring was installed by using an intramolecular S(N)2 cyclization of N-Boc-protected amino alcohol 20. An alternative and even more efficient synthetic approach to 15 featured stereoselective introduction of an amino group at C8 by iodoaminocyclization prior to constructing the bicyclic ether skeleton. The amino acid appendage was efficiently constructed by a catalytic asymmetric hydrogenation of enamide ester 36. The synthetic route developed here provided access to several dysiherbaine analogues, including 9-epi-dysiherbaine (38), 9-deoxydysiherbaine (39), 9-methoxydysiherbaine (40), and N-ethyldysiherbaine (41). The preliminary structure-activity relationship studies revealed that the presence and stereochemistry of the C9 hydroxy group in dysiherbaine is important for high-affinity and selective binding to glutamate subtype receptors.     

Selective fluorination of adamantanes by an electrochemical method

Selective fluorination of adamantanes was achieved by the electrochemical fluorination method, using Et 3N-5HF as electrolyte and a fluorine source. Mono-, di-, tri-, and tetrafluoroadamantanes were selectively prepared from adamantanes by controlling the oxidation potential, and the fluorine atoms were introduced selectively at the tertiary carbons. Adamantanes that have functional groups such as ester, cyano, and acetoxymethyl were also fluorinated selectively.     

Reversible emergence of a self-assembled layered structure from three-dimensional isotropic ionic crystal of a cluster compound (4-HNC5H4OH)2Mo6Cl14 driven by absorption of water and alcohols

The compound comprising nanometer scale cluster molecules showed unusual reversible structural transformation between an isotropic ionic crystal and a layered structure of which the interlayer spaces are filled with the absorbed molecules.     

Topochemical 3D polymerization of C60 under high pressure at elevated temperatures

Fullerene C60 monomer crystals were compressed to a face-centered cubic (fcc) phase with a lattice parameter of a = 11.93(5) A and a micro-Vickers hardness of 4500 kg/mm2 using high-pressure and high-temperature conditions of 15 GPa at 500-600 degrees C. The hardness is compatible with that of cubic boron nitride (c-BN), suggesting the formation of a 3D C60 polymer. The single-crystal X-ray structural analysis revealed that each C60 molecule in the polymer was linked to the 12 nearest neighbors by [2+2] cycloaddition between the common pentagon-hexagon (56) edges. However, ab initio geometry optimization and molecular dynamics calculations suggested that the 3D polymer should have a rhombohedral structure with the space group of R containing [3+3] cycloaddition between the pentagons of C60 molecules within the plane perpendicular to the 3-fold axis. The higher apparent symmetry of fcc was observed as an averaged structure of different orientations of the rhombohedral structure. The R structure can be derived by only a slight rotation of each C60 unit in the (111) plane of the fcc structure. The band-structure calculation suggested that the 3D polymer (R) was a semiconductor; the activation energy for the electrical conductivity was experimentally determined to be 0.25 eV at 550 K.     

Synthesis of cross-linked chitosan functionalized with threonine moiety and its application to on-line collection/concentration and determination of Mo, V and Cu

A novel chitosan-based resin functionalized with threonine moiety was synthesized, and applied to the collection/concentration of Mo, V and Cu in environmental water samples, followed by their determination using inductively coupled plasma-atomic emission spectrometer (ICP-AES). The synthesized resin, cross-linked chitosan-threonine (CCTS-Thr), showed good adsorption behavior toward trace amounts of Mo, V and Cu in a wide pH range. The adsorbed elements can be easily eluted using 2molL(-1) of nitric acid, and their recoveries were found to be 90-100%. The CCTS-Thr was packed in a mini-column, which was then installed in a computer-controlled auto-pretreatment system (Auto-Pret System) for on-line trace elements collection and determination by ICP-AES. Experimental parameters related to the improvement of sensitivity and reproducibility were optimized. The limits of detection (LODs) for target metals were found to be in sub-ppb level. The proposed method with CCTS-Thr resin was successfully applied to the determination of Mo, V and Cu in environmental water samples. The recovery test showed that common matrices which exist in environmental water samples did not interfere with the determination.     

An Oxysulfide Photocatalyst Evolving Hydrogen with an Apparent Quantum Efficiency of 30 % under Visible Light

Photocatalytic water splitting is a simple means of converting solar energy into storable hydrogen energy. Narrow-band gap oxysulfide photocatalysts have attracted much attention in this regard owing to the significant visible-light absorption and relatively high stability of these compounds. However, existing materials suffer from low efficiencies due to difficulties in synthesizing these oxysulfides with suitable degrees of crystallinity and particle sizes, and in constructing effective reaction sites. The present work demonstrates the production of a Gd₂Ti₂O₅S₂ (λ<650 nm) photocatalyst capable of efficiently driving photocatalytic reactions. Single-crystalline, plate-like Gd₂Ti₂O₅S₂ particles with atomically ordered surfaces were synthesized by flux and chemical etching methods. Ultrafine Pt-IrO₂ cocatalyst particles that promoted hydrogen (H₂) and oxygen (O₂) evolution reactions were subsequently loaded on the Gd₂Ti₂O₅S₂ while ensuring an intimate contact by employing a microwave-heating technique. The optimized Gd₂Ti₂O₅S₂ was found to evolve H₂ from an aqueous methanol solution with a remarkable apparent quantum efficiency of 30 % at 420 nm. This material was also stable during O₂ evolution in the presence of a sacrificial reagent. The results presented herein demonstrates a highly efficient narrow-band gap oxysulfide photocatalyst with potential applications in practical solar hydrogen production.     

Probably certifiably correct <Emphasis Type="Italic">k</Emphasis>-means clustering

Recently, Bandeira (C R Math, 2015) introduced a new type of algorithm (the so-called probably certifiably correct algorithm) that combines fast solvers with the optimality certificates provided by convex relaxations. In this paper, we devise such an algorithm for the problem of k-means clustering. First, we prove that Peng and Wei’s semidefinite relaxation of k-means Peng and Wei (SIAM J Optim 18(1):186–205, 2007) is tight with high probability under a distribution of planted clusters called the stochastic ball model. Our proof follows from a new dual certificate for integral solutions of this semidefinite program. Next, we show how to test the optimality of a proposed k-means solution using this dual certificate in quasilinear time. Finally, we analyze a version of spectral clustering from Peng and Wei (SIAM J Optim 18(1):186–205, 2007) that is designed to solve k-means in the case of two clusters. In particular, we show that this quasilinear-time method typically recovers planted clusters under the stochastic ball model.     

Fluctuation characteristics of two-phase flow splitting at a vertical impacting T-junction

In order to investigate the fluctuation characteristics of two-phase flow splitting at a T-junction, particular attention was paid on Churn flow which had the strongest fluctuation comparing with bubble flow and annular flow. The main tube of the T-junction was vertical and the two branches were horizontal. All three pipes connecting to the junction were of 15 mm inner diameter. A statistical analysis based on Root Mean Square (RMS) was applied to temporal differential pressure signals and gas flow rate signals. The Power Spectral Density (PSD) was also employed to reveal their peculiar features in frequency domain as well. The effects of the extraction flow ratio and the gas and liquid superficial velocity upstream on fluctuation characteristics of gas-liquid two-phase flow splitting at the T-junction were investigated in detail. It is found that there is a wide fluctuation in both differential pressure and gas flow rate downstream at every extraction ratio (W₃/W₁) and the fluctuation intensity increases as W₃/W₁ increasing. It is also made clear that increasing either water superficial velocity or gas superficial velocity in inlet causes fluctuation to become more intensive.