Atmospheric pressure waves in the field of volcanology

Atmospheric pressure waves are a notable phenomenon associated with explosive volcanic eruptions. They can provide us with information about eruption processes that are useful both scientifically and practically. In this paper, we give a brief review of studies that have been carried out on this phenomenon in the field of volcanology. Then, we introduce a prototype tool called ‘MOVE’ (Mobile Observatory for Volcanic Explosions). It is a remote-controlled vehicle carrying various instruments to observe pressure waves and the eruption processes. PACS 91.40.Dr · 91.40.Ft · 93.65.+e · 93.85.+qThis paper was based on work presented at the 2nd International Symposium on Interdisciplinary Shock Wave Research, Sendai, Japan on March 1–3, 2005.     

Controlled-release system mediated by a retro Diels-Alder reaction induced by the photothermal effect of gold nanorods

Controlled-release systems that respond to external stimuli have received great interest for use in medical treatments such as for drug delivery to specific sites. Gold nanorods have an absorption band at the near-infrared region and convert the absorbed light energy into heat, which is known as a "photothermal effect". Therefore, gold nanorods are expected to act not only as an on-demand thermal converter for photothermal therapy but also as a controller of a drug-release system capable of responding to the near-infrared light irradiation. In this study, to construct a controlled-release system that responds to near-infrared light irradiation, we modified gold nanorods with polyethylene glycol (PEG) through Diels-Alder cycloadducts. When the modified gold nanorods were irradiated by near-infrared light, the PEG chains were released from the gold nanorods because of the retro Diels-Alder reaction induced by the photothermal effect. As a result of the PEG release, the gold nanorods formed aggregates. This type of controlled-release system coupled with the aggregate formation of the gold nanorods triggered by near-infrared light could be expanded to applications of gold nanorods in medical fields such as drug and photothermal therapy.     

Spectral properties of the Cu-hyperaccumulating moss Scopelophilacataractae

To determine the characteristics of a Cu-hyperaccumulating moss Scopelophilacataractae and the influence of Cu on its structure and on chlorophyll (Chl), we measured reflectance and fluorescence (FL) spectra of S.cataractae samples with different Cu concentrations before and after wetting and the absorption spectra of Chl extracted from these samples. We found relationships between the spectral properties and Cu concentration. These relationships can be explained as follows. The higher the Cu concentration is, the lower is the plasticity of the cell wall, and the smaller is the increase in illuminated area due to the opening of the leaves after wetting. This results in a smaller increase in absorption and smaller decrease in reabsorption of the FL by Chl itself, and accordingly, a smaller increase in the FL band of Chl after wetting. Moreover, we found that the Chl concentration in S.cataractae is much higher than that in other common mosses and is correlated with an increase in the FL band of Chl after wetting. The remarkable increase in FL seen in S.cataractae and the slight increase in FL observed in other common mosses after wetting can be explained based on these findings.     

Simple and effective application of the Wang-Landau method for multicanonical molecular dynamics simulation

We propose a novel application of the Wang-Landau method (WLM) for multicanonical molecular dynamics (McMD) simulations. Originally, WLM was developed for Monte Carlo (MC) simulations. Fundamentally, WLM remarkably reduces simulation efforts because it estimates the optimal multicanonical energy function automatically. When WLM is applied to McMD, not only the multicanonical energy but also energy gradient must be estimated adequately. However, because of the rugged multicanonical energy function at the early simulation stage, applications of WLM for MD simulations are difficult and require a smoothing procedure: simulation efforts such as cubic-spline extrapolation and gathering multiple preruns are utilized for smoothing. We propose a simple and effective smoothing method that requires only one additional equation and two time-dependent parameters. As a result, our method produced the correct multicanonical energy function and succeeded in the flat sampling of a small biomolecule with reduced simulation effort.     

Water-dispersible ultrathin Au nanowires prepared using a lamellar template of a long-chain amidoamine derivative

Straight ultrathin Au nanowires (NWs) with diameters less than 2 nm were synthesized using the lamellar structure of C18AA in an organogel and its selective adsorption for specific gold surfaces. In addition, the potential to form a bilayer structure with interdigitated hydrocarbon chains enabled the production of water-dispersible Au NWs without morphological change.     

Seven New Monoterpenoid Indole Alkaloids from Gelsemium elegans

Seven new indole alkaloids were isolated from the roots of Gelsemium elegans Benth. and their structures were determined by spectroscopic analysis and chemical transformation from known alkaloids. Kounaminal ( 1 ) is a new koumine‐type alkaloid that contains an unusual aminal moiety. Humantenoxenine ( 2 ) and 15‐hydroxyhumantenoxenine ( 3 ) are humantenine‐type alkaloids that contain a novel β‐amino‐α,β‐unsaturated ketone residue. The other four novel alkaloids are two gelsedilam‐related and two gelsenicine‐related alkaloids.     

Evaluation of boundary-layer effects in shock-tube studies of chemical kinetics

Particle times of flight in incident shock flow were determined experimentally by marking several positions of the test gas (mainly Ar) in the shock tube with an infrared emitting gas (NO or CO₂). From the local particle velocity, derived from the particle flight times, temperature and pressure changes behind the shock front were evaluated. Several experimental data were found to be correctly described by Mirels's formulations when used properly. The limitations of the formulations are discussed. It is found to be advisable to evaluate boundary-layer effects on shock-tube flow by experiments, rather than theory, in carrying out chemical kinetics studies.     

Nickel-catalyzed indium(I)-mediated double addition of aldehydes to 1,3-dienes

In the presence of InI, Ni(acac)2 and PPh3, several 1,3-dienes were reacted with two molecules of aldehyde to give the corresponding 1,4- and 1,6-diols. The regioselectivity of the 1,4-/1,6-diol was efficiently regulated by the addition of water; the 1,6-diol was obtained selectively in dry THF, whereas the 1,4-diol was obtained predominantly in DMI containing a small amount of water.     

127I NQR and 1H NMR studies of 4-aminopyridinium tetraiodoantimonate(III); molecular motion and phase transition

The crystals of 4-NH₂PyHSbI₄ (Py = C₅H₄N) have been investigated by means of ¹²⁷I NQR, ¹H NMR T ₁ and DTA. The crystals can exist in two modifications of β and α(I) at room temperatures. The α(I)-phase is a metastable state which is obtained when the stable β form is heated. The α(I)-phase undergoes a first-order type phase transition of α(I) $\leftrightarrow \alpha $ (II) at 272 K (on heating), while the β-phase is stable down to 77 K. Four and two ¹²⁷I (m = ±1/2 $\leftrightarrow \pm $ 3/2) NQR lines have been found for the β- and α(II)-phases, respectively. One half of them is assignable to the terminal I atom(s) and the other to the bridging I atom(s) in each phase. All the resonance lines of the α(II)-phase underwent a disappearance above ca. 240 K and no resonance line was observed in the α(I)-phase. The second moment M ₂ value of ¹H NMR spectra with 8 G² at 290 K shows that the 4-NH₂PyH^?+? cations reside in the rigid lattice in the β-phase. In contrast, in the α(I)-phase the cation rotates about an axis more symmetric than pseudo threefold axis. The activation energy of 21 kJ mol^???1 was estimated for the reorientational motion in the α(I)-phase from the ¹H NMR T ₁ measurements. The nature of phase transitions in the 4-NH₂PyHSbI₄ is discussed in comparison with that in 4-NH₂PyHSbBr₄.