Data-aquisition system for cyclic voltammetry at a microelectrode and application to fast electrode kinetics

A data-aquisition system for fast micro-electrode voltammetry is described. The computer-controlled system can be used at scan rates up to 10 000 V s^?1. The response of the system was examined by monitoring fast electrochemical reactions. A heterogeneous rate constant of 1.1 cm s^?1 was obtained for oxidation of ferrocene in acetonitrile. Oxidation of anthracene in acetonitrile was also studied; the enthalpy of activation was evaluated as 13 kJ mol^?1 for the reaction of the anthracene radical cation with acetonitrile.     

Realization of transient memory-loss with NiO-based resistive switching device

A resistive switching device based on a nickel-rich nickel oxide thin film, which exhibits inherent learning and memory-loss abilities, is reported in this work. The conductance of the device gradually increases and finally saturates with the number of voltage pulses (or voltage sweepings), which is analogous to the behavior of the short-term and long-term memory in the human brain. Furthermore, the number of the voltage pulses (or sweeping cycles) required to achieve a given conductance state increases with the interval between two consecutive voltage pulses (or sweeping cycles), which is attributed to the heat diffusion in the material of the conductive filaments formed in the nickel oxide thin film. The phenomenon resembles the behavior of the human brain, i.e., forgetting starts immediately after an impression, a larger interval of the impressions leads to more memory loss, thus the memorization needs more impressions to enhance.     

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as factor Xa inhibitors V. A series of new derivatives containing a spiro[imidazo[1,2-a]pyrazine-2(3H),4'-piperidin]-5(1H)-one scaffold

We have already reported unique compounds containing a N,O-spiro acetal structure as an orally active factor Xa (FXa) inhibitor. This time, we described a N,N-spiro acetal structure as an analogue of the N,O-spiro acetal structure for an orally active FXa inhibitor. The synthesis of these analogues could be achieved in a similar fashion to the N,O-spiro acetal synthesis. Consequently, FXa inhibitory activity was increased and more active compounds could be found (M58163: IC50 = 0.61 nM, M58169: IC50 = 0.58 nM). Additionally, the absolute configuration could be determined by X-ray crystallography analysis (M58169: (R)-config.).     

Kinetic analysis of the mechanolysis of polymethylmethacrylate in the course of vibratory ball milling at various mechanical energy

We carried out the mechanolysis of polymethylmethacrylate (PMMA) at various mechanical energies and analyzed kinetically the mechanoradical concentration and molecular weight at various mechanical energies. The radical concentration gradually increased to a maximum and then gradually decreased after reaching the maximum value. It is suggested that the radical quenching reaction (disproportionation and/or recombination) progressed together with radical formation. Kinetic analysis of the mechanoradical concentration indicated that the actual amounts of mechanoradicals produced were larger than observed. It is also suggested that vast numbers of reactions take place in mechanolysis. The molecular weight decreased exponentially toward the limiting value, and the limiting molecular weight was larger with decreases in mechanical energy. It is also suggested that mechanoradical formation is inversely proportional to the change in molecular weight at any given mechanical energy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4161–4167, 2004     

Synthesis of (Z)-3-Butylidene-4-hydroxyphthalide

(Z)-3-Butylidene-4-hydroxyphthalide (5) was first synthesized regio- and stereoselectively from 3-methoxybenzyl alcohol (1)     

Nano-optical image and probe in a scanning near-field optical microscope

We study a nanometer-sized optical probe and image in a scanning near-field optical microscope (SNOM). We demonstrated the potential to observe 5-nm wide optical patterns using the SNOM. The probe profile was measured by using a knife-edge method and a modulated transfer function evaluation method. An aluminum covered and pipet-pulled fiber probe used here has two optical probes, one which has a large diameter of 350 nm and one which has a small diameter of around 10 nm.     

Electrochemically monitoring the binding of concanavalin A and ovalbumin

To evaluate protein-protein interactions, a new voltammetric method was developed using a protein labeled with an electroactive compound. Concanavalin A (ConA), which is a lectin, recognizes α-mannose residues. Because the ConA was to be bound to ovalbumin (OVA), which has a high-mannose sugar chain, ConA labeled with daunomycin was prepared as the probe to monitor the binding. The binding to OVA was caused by the label modification of the ConA. As a result, the electrode response of the labeled ConA decreased as the OVA concentration increased. The electrode response of the labeled ConA was linearly over the range of 1.5 × 10⁻¹⁰ and 1.5 × 10⁻⁹ M OVA. The relative standard deviation of 1.5 × 10⁻⁸ M labeled ConA and 1.5 × 10⁻¹⁰ M OVA was 6.9% (n = 5). The labeled ConA-OVA binding could then be conveniently monitored based on the change in response. In contrast, interactions between the labeled ConA and a protein with no specific sugar chain also were investigated. Incubation scarcely influenced the peak current of the labeled ConA. When several concentrations of OVA were added to a serum, good recovery determined it. Consequently, this method could be applied to the measurement of protein-protein interactions.     

Doubly Charmed Exotic Mesons

We discuss the mass spectrum of doubly charmed mesons as hadronic molecules composed by D and D^* meson. Considering the heavy quark symmetry and chiral symmetry, we introduce the one-boson ( ${\pi , \rho , \omega}$ ) exchange potential between D and D^* meson. For all possible quantum numbers I(J ^P ) with isospin I, total angular momentum J( ≤ 2) and parity P, we solve the fully coupled channel Schrödinger equation. We find that in many quantum numbers the bound and resonant states composed by D or D^* meson can exist near the DD, DD^* and D^*D^* thresholds.     

Exotic hadrons in s-wave chiral dynamics

We study s-wave scattering of a hadron and a Nambu-Goldstone boson induced by the model-independent low energy interaction in the flavor SU(3) symmetric limit. Establishing the general structure of the interaction based on group theoretical arguments, we find that the interaction in the exotic channels are in most cases repulsive, and that for possible attractive channels the coupling strengths are weak and uniquely given independent of channel. Solving the scattering problem, we show that the attraction in the exotic channels is not strong enough to generate a bound state.