Electrochemical assembly and potential-dependent plasmon absorption of au nanoclusters covered with a 4-aminothiophenol self-assembled monolayer

Gold nanoclusters covered with 4-aminothiophenol (4-ATP) self-assembled monolayers (SAMs) were electrochemically assembled on an Au or ITO electrode. The assembly mechanism is discussed on the basis of results of electrochemical, FT-IR, and XPS measurements. The intensity of plasmon absorption of the gold nanocluster assembly was shown to be dependent on applied potential as a result of electrochemical doping/undoping of a counteranion in the polyaniline film.     

Simulation of winter air pollution dispersion mechanism of Kathmandu valley by water-tank experiment

The air pollution concentration in Kathmandu valley in the winter season was found to be higher than in the summer season due to the formation of the inversion layer. This mechanism was simulated in the water-tank experiment by measuring the temperature and flow field using liquid crystal thermometry and particle image velocimetry. Thermal stratification was made at the beginning of the experiment and the surface temperature of the valley model was changed with 12 minutes period matching the diurnal field temperature pattern of the Kathmandu valley. The updraft wind and Bernard convection occurred during daytime and downdraft wind and inversion layer were realized during nighttime. The temperature, flow field and mass dispersion characteristics obtained in the water-tank experiment explained clearly the mechanism of air pollution in Kathmandu valley.     

Ionization and solvation of HCl adsorbed on the D2O-ice surface

The interaction of HCl with the D(2)O-ice surface has been investigated in the temperature range 15-200 K by utilizing time-of-flight secondary ion mass spectroscopy, temperature-programmed desorption, and x-ray photoelectron spectroscopy. The intensities of sputtered H(+)(D(2)O) and Cl(-) ions (the H(+) ions) are increased (decreased) markedly above 40 K due to the hydrogen bond formation between the HCl and D(2)O molecules. The HCl molecules which form ionic hydrates undergo H/D exchange at 110-140 K and a considerable fraction of them dissolves into the bulk above 140 K. The neutral hydrates of HCl should coexist as evidenced by the desorption of HCl above 170 K. They are incorporated completely in the D(2)O layer up to 140 K. The HCl molecules embedded in the thick D(2)O layer dissolve into the bulk, and the ionic hydrate tends to segregate to the surface above 150 K.     

Hypnotic action of N3-substituted arabinofuranosyluracils on mice

Methyl (2), ethyl (3), propyl (4), butyl (5), allyl (6), benzyl (7), o-, m-, p-xylyl (8-10), and alpha-phenylethyl (11) derivatives of arabinofuranosyluracil (1) were synthesized and their pharmacological effects in mice were examined by using hypnotic activity and synergism with pentobarbital as indices for the CNS depressant effects. At a dose of 2.0 micromol/mouse by intracerebroventricular injection, the values of mean sleeping time induced by 7-11 were 144, 154, 117, 33, and 34 min, respectively, whereas the alkyl (2-6) derivatives did not cause any hypnotic activity. N3-o-Xylylarabinofuranosyluracil (8) displayed the most potent hypnotic activity among the derivatives tested. Certain derivatives (6-11) significantly prolonged the pentobarbital-induced sleeping time compared to control. The present study indicated that substitution with benzyl and/or related groups on the N3-position of arabinofuranosyluracil produced CNS depressant effects.     

Author Index

Authors Index

Author Index     

STM images apparently corresponding to a stable structure: considerable fluctuation of a phase boundary of the Si(111)-(square root of (3) x square root of (3))-Ag surface

We study scanning tunneling microscopy (STM) images near a phase boundary of the Si(111)- (square root of (3) x square root of (3))-Ag surface by using Monte Carlo simulations based on results of first-principles calculations. The boundary is found to fluctuate from snapshot to snapshot, and the feature of the simulated STM images differs distinctly from the observed one with a straightly extending honeycomb pattern of bright spots. Remarkably, statistical averages of the simulated images reproduce the observed feature. This study gives a warning of our tendency to relate STM images revealing clear arrangement of bright spots with some stable structure.     

Optical guidance of terrawatt laser pulses by the implosion phase of a fast Z-pinch discharge in a gas-filled capillary

A new method of optical guidance by the implosion phase of a fast Z-pinch discharge in a gas-filled capillary is proposed. An imploding plasma column has a concave electron-density profile in the radial direction, just before a stagnation phase driven by a converging current sheet and a shock wave. The feasibility of optical guidance of a high-intensity (>1 x 10(17) W/cm(2)) Ti:sapphire laser pulse by use of this method over a distance of 2 cm, corresponding to 12.5 times the Rayleigh length, has been experimentally demonstrated. The guiding-channel formation process was directly probed with a He-Ne laser beam. The electron density in the fully ionized channel was estimated to be 2.0 x 10(17) cm(-3) on the axis and 7.0 x 10(17) cm(-3) on the peaks of the channel edge, with a diameter of 70 mum, as indicated by the experimental results, which were corroborated by a magnetohydrodynamics simulation.     

A Method for Measuring the Three-Dimensional Refractive-Index Distribution of Single Cells Using Proximal Two-Beam Optical Tweezers and a Phase-Shifting Mach—Zehnder Interferometer

This paper describes a method for measuring the three-dimensional (3D) refractive-index distribution in a single cell. The method can be used to observe the distribution of cell components without fluorescence staining. The two-dimensional optical path length distributions from multiple directions are obtained by non-contact rotation of the cell. These optical path lengths are converted into the line integrals of the refractive index, and the 3D refractive-index distribution is reconstructed by means of computed tomography. The refractive-index distribution in a breast cancer cell can be measured using a phase-shifting Mach—Zehnder interferometer in conjunction with proximal two-beam optical tweezers.