Inclusion Complex Formation of Thiacalix[4]arene and Xe in Aqueous Solution Studied by Hyperpolarized 129Xe NMR

The inclusion complex formation of 4-sulfothiacalix[4]arene sodium salt (STCAS) and Xe has been investigated by using hyperpolarized ¹²⁹Xe NMR spectroscopy. Our new continuous-flow type hyperpolarizing system has advantageous capabilities that can supply hyperpolarized gases continuously and directly to a sample solution in a NMR tube. Consequently saturated Xe concentration in the aqueous solution of STCAS is maintained during the NMR experiment, and ¹²⁹Xe NMR spectra can be obtained in remarkably short time. STCAS concentration dependence of ¹²⁹Xe chemical shift has been analyzed in an elaborated way by a computer method as well as a simple graphic method that we have proposed. The association constant K:13.6±0.8 M⁻¹ at 25 °C was obtained, and further analysis of the temperature dependence has successfully given thermodynamic parameters of enthalpy (ΔH) and entropy (ΔS) for the inclusion complex formation: ΔH = −11.9±1.9 kJ mol⁻¹ and ΔS = −17.4±5.8 JK⁻¹ mol⁻¹. The energetic aspects of complex formation are discussed from the size effect and from the molecular theory of standard entropy, and a release of definite number of water molecules from STCAS cavity is suggested in the inclusion complex formation with Xe.     

Quantum mechanical Monte Carlo approach to electron transport at heterointerface

With the progress of LSI technology, the electronic device size is scaled down to the sub 0.1μ m region. In such an ultrasmall device, it is indispensable to take quantum mechanical effects into account in device modeling. In this paper, we present a newly developed quantum Monte Carlo device simulation applicable to ultrasmall semiconductor devices. In this model, the quantum effects are represented in terms of quantum mechanically corrected potential in the classical Boltzmann equation. It is demonstrated that the quantum transport effects such as tunneling and energy quantization in ultrasmall semiconductor devices are obtained for the first time by using the standard Monte Carlo techniques.     

Superconvergence of the iterated collocation methods for Hammerstein equations

In this paper, we analyse the iterated collocation method for Hammerstein equations with smooth and weakly singular kernels. The paper expands the study which began in [16] concerning the superconvergence of the iterated Galerkin method for Hammerstein equations. We obtain in this paper a similar superconvergence result for the iterated collocation method for Hammerstein equations. We also discuss the discrete collocation method for weakly singular Hammerstein equations. Some discrete collocation methods for Hammerstein equations with smooth kernels were given previously in [3, 18].     

Influence of wall heat loss on the emission characteristics of premixed ammonia-air swirling flames interacting with the combustor wall

The influence of wall heat loss on the emission characteristics of ammonia-air swirling flames has been investigated employing Planar Laser-Induced Fluorescence imaging of OH radicals and Fourier Transform Infrared spectrometry of the exhaust gases in combustors with insulated and uninsulated walls over a range of equivalence ratios, ?, and pressures up to 0.5 MPa. Strong influence of wall heat loss on the flames led to quenching of the flame front near the combustor wall at 0.1 MPa, resulting in large unburned NH₃ emissions, and inhibited the stabilization of flames in the outer recirculating zone (ORZ). A decrease in heat loss effects with an increase in pressure promoted extension of the fuel-rich stabilization limit owing to increased recirculation of H₂ from NH₃ decomposition in the ORZ. The influence of wall heat loss resulted in emission trends that contradict already reported trends in literature. NO emissions were found to be substantially low while unburned NH₃ and N₂O emissions were high at fuel-lean conditions during single-stage combustion, with values such as 55 ppmv of NO, 580 ppmv of N₂O and 4457 ppmv of NH₃ at ? = 0.8. In addition, the response of the flame to wall heat loss as pressure increased was more important than the effects of pressure on fuel-NO emission, thereby leading to an increase in NO emission with pressure. It was found that a reduction in wall heat loss or a sufficiently long fluid residence time in the primary combustion zone is necessary for efficient control of NH₃ and N₂O emissions in two-stage rich-lean ammonia combustors, the latter being more effective for N₂O in addition to NO control. This study demonstrates that the influence of wall heat loss should not be ignored in emissions measurements in NH₃-air combustion, and also advances the understanding of previous studies on ammonia micro gas turbines.     

Experimental Study on Time-Spread/Wavelength-Hop Optical Code Division Multiplexing with Dispersion-Compensating En/Decoder

10Gbit/s time-spread/wavelength-hop optical code generation and decoding are performed by dispersion-compensating fiber Bragg grating (FBG) en/decoder pair. Error-free 10km single mode fiber (SMF) transmission of 10Gbit/s optical code division multiplexing (OCDM) has been experimentally demonstrated.     

Results of 0.5% cold-leg small-break LOCA experiments at ROSA-IV/LSTF: Effect of break orientation

Three 0.5% cold-leg small-break loss-of-coolant accident (SBLOCA) experiment were conducted at the ROSA-IV Large Scale Test Facility (LSTF) to investigate the effects of break orientation on system thermal-hydraulic responses. In these three experiments, the break hole was located at the side, bottom, and top of the horizontal cold leg, respectively. Although the key phenomena observed in the three experiments were basically the same, the break flow rate was affected by the break orientation when phase stratification occured in the cold leg; the break flow rate was largest for the side break and smallest for the top break. The RELAP5/MOD2 code failed to predict the difference in the break flow rate observed in the experiments. Modification to the break flow calculation models, for both subcooled and two-phase flow discharge conditions, resulted in good agreement between data and predictions.     

Direct numerical simulation of wall turbulent flows with microbubbles

The marker‐density‐function (MDF) method has been developed to conduct direct numerical simulation (DNS) for bubbly flows. The method is applied to turbulent bubbly channel flows to elucidate the interaction between bubbles and wall turbulence. The simulation is designed to clarify the structure of the turbulent boundary layer containing microbubbles and the mechanism of frictional drag reduction. It is deduced from the numerical tests that the interaction between bubbles and wall turbulence depends on the Weber and Froude numbers. The reduction of the frictional resistance on the wall is attained and its mechanism is explained from the modulation of the three‐dimensional structure of the turbulent flow. Copyright © 2001 John Wiley & Sons, Ltd.     

Ishigadine A,a new canthin-6-one alkaloid from an Okinawan marine sponge Hyrtios sp.

A new indole alkaloid with the canthin-6-one skeleton, ishigadine A, has been isolated from an Okinawan marine sponge Hyrtios sp. The structure of ishigadine A was elucidated on the basis of spectroscopic analyses. Ishigadine A is a new canthin-6-one alkaloid possessing a hydroxy group, a 1,3-dimethyl-4-methylthioimidazolium, and a 1-propylguanidine. Ishigadine A is the third canthin-6-one alkaloid from sponges. Ishigadine A might be generated from l-arginine, l-histidine, and l-tryptophan. Ishigadine A exhibited moderate cytotoxicity against L1210 murine leukemia cells.     

Organic–Inorganic Hybrid Gold Halide Perovskites: Structural Diversity through Cation Size

Crystal structures of a series of organic–inorganic hybrid gold iodide perovskites, formulated as A₂[Au^II₂][Au^IIII₄] [A=methylammonium (MA) ( 1 ) and formamidinium (FA) ( 2 )], A′₂[I₃]_1−x[Au^II₂]_x[Au^IIII₄] [A′=imidazolium (IMD) ( 3 ), guanidinium (GUA) ( 4 ), dimethylammonium (DMA) ( 5 ), pyridinium (PY) ( 6 ), and piperizinium (PIP) ( 7 )], systematically changed depending on the cation size. In addition, triiodide (I₃⁻) ions were partly incorporated into the AuI₂⁻ sites of 3 – 7 , whereas they were not incorporated into those of 1 and 2 . Such a difference comes from the size of the organic cation. Optical absorption spectra showed characteristic intervalence charge-transfer bands from Au^I to Au^III species, and the optical band gap increased as the size of the cation became larger.