Gaussian channels and the optimal coding

For the Gaussian channel Y(t) = Φ(ξ(s), Y(s); s ≦ t) + X(t), the mutual information I(ξ, Y) between the message ξ(·) and the output Y(·) is evaluated, where X(·) is a Gaussian noise. Furthermore, the optimal coding under average power constraints is constructed.     

Determination of the equilibrium structure of the charge-transfer state of (p-Cyanophenyl)pentamethyldisilane by means of transient infrared spectroscopy

An equilibrium structure of the charge-transfer (CT) state of (p-cyanophenyl)pentamethyldisilane was determined by transient infrared absorption spectroscopy of its CH stretching vibration region, and by the spectral simulation with quantum chemical calculations. It was found that a pattern of the CH stretching vibration bands of the CT state is substantially different from that of the S0 state. This band feature of the CT state was well reproduced assuming the planar sigma(Si-Si)pi* state, where the disilanyl group and the phenyl ring lie in the same plane. Considering that the disilanyl group in the S0 and the locally excited pipi* states lie in the plane perpendicular to the phenyl ring, an occurrence of a twisting-type structural change during the ICT process was experimentally identified in the present study.     

Mass‐selective axial ejection from a linear ion trap with a direct current extraction field

We have developed a new mass‐selective axial ejection method from a linear ion trap (LIT). In this method, a set consisting of a trap wire lens and an extraction wire lens positioned orthogonally to each other was placed between quadrupole rods. The trap wire lens confines the ions inside the trap, and the extraction wire axially extracts ions from the trap. Ions introduced into the LIT are trapped between the inlet lens and the trap wire lens. In addition to the wire lenses, a set of excitation lenses, which are aligned orthogonally to the trap wire lens, are inserted between rods. The ions are resonantly excited in the direction perpendicular to the trap wire lens by applying a supplemental alternating current (AC) to the excitation lenses. Excited ions with a large motion pass over the trap wire lens, while unexcited ions remain trapped inside. Ions that have passed over the trap wire lens are then extracted by the extraction wire lens. The characteristics of the mass‐selective ejection with a direct current (DC) extraction field were investigated by both simulation and experiment. A mass resolving power of m/Δm = 1300 was achieved at a scan rate of 500 Th/s. The dependence of the ejection efficiency on trap wire lens bias was measured, and an ejection efficiency of 20% at a scan rate of 500 Th/s was achieved by optimizing the DC bias on the trap wire lens. Copyright © 2009 John Wiley & Sons, Ltd.     

Solvent reorientation process in the "twisted" intramolecular charge-transfer process of cyanophenyldisilane-(H2O)2 cluster investigated by transient infrared spectroscopy

The solvent reorientation process of the intramolecular charge-transfer (ICT) process of the (p-cyanophenyl)pentamethyldisilane-(H2O)2 (CPDS-(H2O)2) cluster in the excited-state was investigated by transient infrared (IR) absorption spectroscopy. It was found that there are at least two isomers in the charge-transfer (CT) state: one of the isomers exhibits a band of a pi-hydrogen-bonded OH stretch of the water moiety. Analyses of the IR spectra in the dominant isomers revealed that water molecules are hydrogen-bonded with each other in the CT state. This indicates that the reorientation process of the water molecules takes place to form such a dimer structure during the ICT process.     

Iridium-catalyzed coupling of simple primary or secondary amines, aldehydes and trimethylsilylacetylene: preparation of propargylic amines

The coupling of amines, aldehydes and trimethylsilylacetylene was found to be promoted in the presence of a catalytic amount of [IrCl(cod)]2; 1 : 1 : 1 or 1 : 2 : 2 coupling products were obtained by allowing primary amine to react with aldehyde and trimethylsilylacetylene.     

Direct observation of the solvent reorientation dynamics in the "twisted" intramolecular charge-transfer process of cyanophenyldisilane-water cluster by transient infrared spectroscopy

The solvent reorientation dynamics of the intramolecular charge-transfer (ICT) process of the (p-cyanophenyl)pentamethyldisilane-H(2)O (CPDS-H(2)O) cluster was investigated by transient infrared (IR) absorption spectroscopy. Transient IR bands of two distinct charge-transfer (CT) states appeared in both the OH and the CN-stretching vibration regions. Analyses of the IR spectra and the time profiles of the transient bands revealed that the ICT process of the CPDS-H(2)O cluster proceeds in two steps. The first step is a transition from a photo-prepared locally excited (LE) state to the CT state, which is accompanied by a minor reorientation of the H(2)O moiety. In contrast, the second step is an extensive reorientation process of the H(2)O molecule in the CT state. These two reorientation processes exhibit very distinct pico- and nano-second time scales. In the latter case, a relatively slow time constant of 2 ns was related to a large geometric change in the orientation.     

Tightness problem and stochastic evolution equation arising from fluctuation phenomena for interacting diffusions

The central limit (or fluctuation) phenomena are discussed in the interacting diffusion system. The tightness in the Kolmogorov-Prokhorov sense is proved for a sequence of distribution valued processes arising from finite particle systems. Further, the stochastic differential equation for the limit process is derived by constructing an infinite dimensional Brownian motion.     

Mutual information in Gaussian channels

In the Gaussian channel Y(t) = Φ(t) + X(t) = message + noise, where Φ(t) and X(t) are mutually independent, the information I(Y, Φ) is evaluated. One of the results is that I(Y, Φ) < ∞ if and only if Φ ? $\text{H}$(X) = the reproducing kernel Hilbert space for X(·). And the causal formula of I(Y, Φ) is given.     

Intramolecular charge-transfer process of jet-cooled (p-cyanophenyl)pentamethyldisilane: roles of the torsional motion and the Si-Si bond change

To investigate the intramolecular charge-transfer (ICT) process of (p-cyanophenyl)pentamethyldisilane (CPDS), laser-induced fluorescence, dispersed fluorescence, and two-color resonance enhanced two-photon ionization spectra were measured in a jet-cooled isolated condition. Dual fluorescence of CPDS was observed from a ground vibrational level in the locally excited pipi state. Similar to an emission from the charge-transfer (CT) state in solution, one of the dual emissions of the isolated molecule in the jet was assigned as the CT emission. A significant vibrational dependence on the ICT process was found as exciting vibronic levels of the molecule. It was identified that the promoting mode of the ICT process is a torsional motion of the disilanyl group with respect to the phenyl ring. It was also revealed that an effective appearance energy of the CPDS cation via the CT state is much lower than that via the locally excited pipi state suggesting that the electronic configuration of the CT state is similar to that of the cation. On the basis of an electronic configuration of the cationic state, that of the CT state was suggested to be of the (sigma(Si)(-)(Si), 2ppi) type.