Molecularly defined graphitic interface toward proton manipulation

Proton plays a critical role in electrochemical systems to control electrochemical reactivity or isotopic enrichment. Graphene is intensively investigated owing to its unique electronic structure and device fabrication. Through the structural tunability of graphitic materials by chemical or physical modification of the surface, graphene is revealed to be an ideal material for proton manipulation. Here, we review the use of graphene or graphitic materials toward the manipulation of proton with regard to the following three points. (1) Electronic properties of graphene: The electronic band structure of graphene can be modified by metal contacts owing to the interaction with a metal surface. (2) Molecular control of graphitic interface: The chemical structure of graphene can be modified, as is done in molecular chemistry, and can be used as a catalytic platform. (3) Proton conduction by graphene: Proton transport through a graphene layer occurs with a unique mechanism such as tunneling. We provide a perspective on the use of graphitic materials toward controlling the behavior of protons on the basis of the aforementioned points. From the above, graphene can be used as a platform for proton manipulation.     

Synthesis of Well‐Defined Polybenzamide‐block‐Polystyrene by Combination of Chain‐Growth Condensation Polymerization and RAFT Polymerization

Well‐defined diblock copolymers composed of poly(N‐octylbenzamide) and polystyrene were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization of styrene with a polyamide chain transfer agent (CTA) prepared via chain‐growth condensation polymerization. Synthesis of a dithioester‐type macro‐CTA possessing the polyamide segment as an activating group was unsatisfactory due to side reactions and incomplete introduction of the benzyl dithiocarbonyl unit. On the other hand, a dithiobenzoate‐CTA containing poly(N‐octylbenzamide) as a radical leaving group was easily synthesized, and the RAFT polymerization of styrene with this CTA afforded poly(N‐octylbenzamide)‐block‐polystyrene with controlled molecular weight and narrow polydispersity.

     

Hypocenter interval statistics between successive earthquakes in the two-dimensional Burridge-Knopoff model

We study statistical properties of spatial distances between successive earthquakes, the so-called hypocenter intervals, produced by a two-dimensional (2D) Burridge-Knopoff model involving stick-slip behavior. It is found that cumulative distributions of hypocenter intervals can be described by the q-exponential distributions with q<1, which is also observed in nature. The statistics depend on a friction and stiffness parameters characterizing the model and a threshold of magnitude. The conjecture which states that q_t+q_r∼2, where q_t and q_r are an entropy index of time intervals and spatial intervals, respectively, can be reproduced semi-quantitatively. It is concluded that we provide a new perspective on the Burridge-Knopoff model which addresses that the model can be recognized as a realistic one in view of the reproduction of the spatio-temporal interval statistics of earthquakes on the basis of nonextensive statistical mechanics.     

ASACUSA MUSASHI: New progress with intense ultra slow antiproton beam

Our group “ASACUSA MUSASHI” has established an efficient way for accumulating antiprotons and extracting them as intense ultra-slow mono-energetic beams at the CERN-AD facility. This novel beam opens new frontiers for investigating a variety of physics. For realizing H? spectroscopy and the test for charge-parity-time symmetry, we have also developed the cusp trap, a combination of an anti-Helmholz superconducting coil and a multi-ring electrode trap, for trapping both antiprotons and positrons and then synthesizing antihydrogens. Recently, the cusp trap was practically used to accumulate antiprotons. The last piece for synthesizing antihydrogens in the cusp trap is the positron accumulator. We have developed a compact system to effectively accumulate positrons based on N₂ gas-buffer scheme with a specially designed high precision cylindrical multi-ring electrode trap. The recent progress of the developing work is an important milestone for upcoming antihydrogen science of ASACUSA MUSASHI.     

UV absorption and fluorescence properties of fused aromatic hydrocarbons having trimethylsilyl, trimethylgermyl, and trimethylstannyl groups

Effects of trimethylsilyl, trimethylgermyl, and trimethylstannyl substituents attached to fused aromatic hydrocarbons such as pyrene, anthracene, phenanthrene, and naphthalene were studied in terms of UV absorption and fluorescence properties in aerated cyclohexane solutions. Absorption maxima of trimethylsilyl-, trimethylgermyl-, and trimethylstannyl-substituted aromatic hydrocarbons shifted to longer wavelengths than those of unsubstituted ones. Absorption maxima of mono-, bis-, tris-, and tetrakis(trimethylsilyl)pyrenes shifted to longer wavelength consecutively at intervals of 10 nm. Fluorescence intensities and fluorescence lifetimes of trimethylsilyl-substituted aromatic hydrocarbons were larger and longer than those of unsubstituted ones, and they decreased in the order of Me₃SiAr > Me₃GeAr > Me₃SnAr. Fluorescence intensity of 1,3,6,8-tetrakis(trimethylsilyl)pyrene was largest among those of a series of mono-, bis-, tris-, and tetrakis(trimethylsilyl)pyrenes under aerated conditions.     

Surface modification of polymer latex particles by AGET ATRP of a styrene derivative bearing a lactose residue

Grafting of a styrene derivative bearing a lactose residue, i.e., N-2-4-(vinylbenzenesulfonamido)ethyl lactobionamide (VBSAELA), onto polymer latex particles was carried out in aqueous media by activator generated electron transfer atom transfer radical polymerization (AGET ATRP). The core polymer latex particles having α-chloroester groups as ATRP-initiating groups were prepared by miniemulsion polymerization of styrene and 2-chloropropionyloxyethyl methacrylate (CPEM) in the presence of a polymerizable surfactant, i.e., N,N-dimethyl-N-dodecyl-N-2-methacryloyloxyethylammonium bromide (C₁₂Br). AGET ATRP was initiated with tris[(2-pyridylmethyl)amine] copper (II) dichloride and l-ascorbic acid. Dynamic light scattering (DLS) revealed that the P(St-CPEM)-g-P(VBSAELA) particles possess graft layers of 10 nm in thickness on the core particles of 91 nm in diameter. Critical coagulation concentration measurement revealed that the dispersion stability of the particles in water increased due to hydrated P(VBSAELA) shell layers. Adsorption of bovine serum albumin (BSA) onto the particles was considerably suppressed by the hydrated shell layers.     

First application of the depth profile of silica species as a tracer by fast‐atom bombardment mass spectrometry: investigation of the circulation of seawater and silica uptake by diatoms

Silica, represented by SiO₂, is the general name for the compounds composed of Si, O and H with their derivative complexes. Silica forms various chemical species in aquatic solutions, such as a monomer (Si(OH)₃O⁻), dimer (Si₂(OH)₅O), and others. These species are known to vary in their relative abundances in solution depending on the chemical and physical conditions. Silica species dissolved in seawater have been examined by fast-atom bombardment mass spectrometry (FAB-MS) to elucidate the behavior of silica and its circulation as a novel tracer reflecting the chemical and physical conditions of seawater and the bioactivity of diatoms, which take up silica. In the seawater of Tokyo Bay, silica species such as [Si(OH)₂O₂Na]⁻ ([monomer–Na]⁻), [Si₂(OH)₅O₂]⁻ ([dimer]⁻), [Si₂(OH)₄O₃Na]⁻ ([dimer–Na]⁻), [Si₄(OH)₇O₅]⁻ ([cyclic tetramer]⁻), [Si₄(OH)₆O₆Na]⁻ ([cyclic tetramer–Na]⁻), [Si₄(OH)₉O₄]⁻ ([linear tetramer]⁻) and [Si₄(OH)₈O₅Na]⁻ ([linear tetramer–Na]⁻) were observed and assigned by FAB-MS. To investigate the suitability of silica species as a tracer, the relative peak intensity ratios of silica species observed in the mass spectra, i.e. the profiles of the ratio of the linear tetramer to the cyclic tetramer (m/z 329/311) and the ratio of the dimer to the cyclic tetramer (m/z 173/311) against depth, were examined to determine the annual changes and reproducibility of the depth profiles. In particular, the depth profile of the relative ratio of the linear tetramer to the cyclic tetramer, 329/311, exhibits critical changes depending on the seawater budget. These changes in the relative ratios were identified by an experiment involving a simple sodium chloride solution system. Our measurement is expected to elucidate the dynamics of silica and its role as ‘food’ for diatoms, and we showed that speciation using mass spectrometry is a powerful tool for examining elemental behavior in nature and environmental changes. Our results suggest that a silica tracer is useful for investigating the behavior of seawater in small coastal regions and the uptake of silica by diatoms. Copyright © 2009 John Wiley & Sons, Ltd.     

Gas chromatography/time‐of‐flight mass spectrometry of triacetone triperoxide based on femtosecond laser ionization

Triacetone triperoxide (TATP), which is used as an explosive in acts of terrorism, was measured by means of gas chromatography/multiphoton ionization/time‐of‐flight mass spectrometry using a deep‐ultraviolet (deep‐UV) femtosecond laser as an ionization source. The fragmentation process was investigated by changing the intensity of the laser at the center axis of a molecular beam. A molecular ion was observed using a femtosecond laser, and the ratio of the intensities of the molecular and fragment ions decreased as the intensity of the laser increased. These results suggest that TATP can be efficiently ionized using a deep‐UV, ultrashort optical pulse. Furthermore, fragmentation was accelerated by excess energy supplied through higher‐order multiphoton processes under a strong radiation field. The detection limits obtained using the molecular ion and two dominant fragment ions, C₂H₃O⁺ and CH, were determined to be 670, 83 and 150 pg, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Enantioselective visualization of <Emphasis Type="SmallCaps">D</Emphasis>-alanine in rat anterior pituitary gland: localization to ACTH-secreting cells

The cellular localization of D-alanine (D-Ala) in the rat pituitary gland, the tissue containing the highest amount of D-Ala, has been clarified for the first time by enantioselective visualization of D-Ala using our own established mouse monoclonal antibody against D-Ala. D-Ala immunopositive cells were present predominantly in the anterior lobe, while no intense staining was observed in the intermediate and posterior lobes. The anterior pituitary gland contains five types of cells secreting specific hormones (growth hormone, adrenocorticotropic hormone (ACTH), gonadotropic hormone, prolactin, and thyroid-stimulating hormone), and the double staining results indicated that D-Ala is localized to the ACTH-secreting cells. The localization of D-Ala is clearly different from that of D-aspartic acid (D-Asp), which is observed in the prolactin cells. Considered together with our previous findings that D-Ala is localized to the insulin-secreting beta-cells in the pancreas, and both ACTH and insulin are typical regulatory hormones of blood glucose, D-Ala is suggested to have some functional relationships to blood glucose level regulation in mammals.     

Physical Gels of a Syndiotactic Polystyrene Derivative with a Large Side-Chain Group

Summary: Gelation of syndiotactic poly(p-tert-butylstyrene) (sPTBS), a syndiotactic polystyrene (sPS) derivative having a larger side-chain group, was first examined with several solvents. The temperature-concentration phase diagram of sPTBS/trans-decalin gel clearly exhibited that sPTBS formed a polymer-solvent molecular compound with a ratio of 2.7 trans-decalin per one monomer unit. Our polarized fluorescence technique demonstrated that there appeared to exist more spacious free volume among sPTBS chains than sPS in a gel state. A cause determining the morphology of sPTBS with organic solvents was discussed in the present paper.