Study on chemical speciation in aluminum chloride solution by ESI-Q-MS

AlCl(3) solution was analyzed at concentrations from 0.02 to 100 mM using an electrospray ionization quadrupole mass spectrometer (ESI-Q-MS), and the dissolution state of aluminum ions is discussed. Results obtained using ESI-Q-MS were consistent with those obtained using (27)Al nuclear magnetic resonance ((27)Al NMR). Aluminum species existed mainly as positively charged monomeric aluminum hydroxide coordinated with several water molecules in solution. The complexation of chloride ions by aluminum ions differed between the positive and negative ion modes. Chemical reactions that partially modified chemical forms of species through ESI-Q-MS measurement were also observed. In the same aluminum chloride solution, using ESI-TOF-MS and ESI-Q-MS/MS studies, the disagreement of the reports is discussed. It is concluded that ESI-TOF-MS might show also the gas-phase reaction in the mass spectrometer but the dissolution state of aluminum species can be shown by ESI-Q-MS.     

Thermoresponsive characteristics of fluoroalkyl end-capped co-oligomers in aqueous solutions and on the poly(methyl methacrylate) film surface

Fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide--acryloylmorpholine co-oligomers were prepared by the co-oligomerizations of fluoroalkanoyl peroxides with the corresponding monomers. These fluorinated co-oligomers exhibited a lower critical solution temperature (LCST) characteristic in aqueous solutions. Of particular interest, a steep time dependence of contact angle values for dodecane was observed from 40 to 60 degrees C to decrease their values, effectively, on the modified PMMA [poly(methyl methacrylate)] film surface treated with fluorinated co-oligomer possessing the LCST: 36 degrees C (in water), although such a steep time dependence was not observed from 20 to 30 degrees C.     

A theoretical study for mechanical contact between carbon nanotubes

We have theoretically investigated motions of single-walled carbon nanotubes (SWNTs) which are mounted on a flat substrate layer of SWNTs by tight-binding molecular dynamics simulations. One of the most interesting motions is the conversion of force and torque, where the force and torque acting initially on the mounted tube finally results in the lateral motion and rolling of the supporting tubes in the substrate. This motion is well understood in terms of the total energy surface of the SWNT/SWNT system. It is suggested that an undulation of the total energy surface plays a role as an atomic-scale gear tooth in the field of nanomechanics, in spite of the atomically smooth surface of SWNT.     

Tail molecule dependence of thiolate adsorption on Au(111) surface: Theoretical study

The adsorption of thiolates with various tail molecules on the Au(111) surface has been investigated by first-principles calculations. We have considered six typical thiolate molecules, that is, methylthiolate, ethylthiolate, ethylenethiolate, acetylenethiolate, benzenethiolate, and thiophenethiolate. It is found that these thiolates exhibit little difference in their stable adsorption geometries. They are adsorbed at the bridge site with being significantly tilted from the surface normal. The adsorption energy of thiolate on Au, on the other hand, largely varies depending on the type of tail molecule, and is linearly proportional to the binding energy of thiolate with H. We discuss the tail molecule dependence in terms of the bonding environment around the C atom connected to the head S atom.     

Electronic transport properties of the Ising quantum Hall ferromagnet in a Si quantum well

Magnetotransport properties are investigated for a high mobility Si two-dimensional electron system in the vicinity of a Landau level crossing point. At low temperatures, the resistance peak having a strong anisotropy shows large hysteresis which is attributed to Ising quantum Hall ferromagnetism. The peak is split into two peaks in the paramagnetic regime. A mean field calculation for the peak positions indicates that electron scattering is strong when the pseudospin is partially polarized. We also study the current-voltage characteristics which exhibit a wide voltage plateau.     

Universal Single-Mode Lasing in Fully Chaotic Billiard Lasers

By numerical simulations and experiments of fully chaotic billiard lasers, we show that single-mode lasing states are stable, whereas multi-mode lasing states are unstable when the size of the billiard is much larger than the wavelength and the external pumping power is sufficiently large. On the other hand, for integrable billiard lasers, it is shown that multi-mode lasing states are stable, whereas single-mode lasing states are unstable. These phenomena arise from the combination of two different nonlinear effects of mode-interaction due to the active lasing medium and deformation of the billiard shape. Investigations of billiard lasers with various shapes revealed that single-mode lasing is a universal phenomenon for fully chaotic billiard lasers.     

Molecular Dynamics Simulation of the Excited-State Dynamics of Bacteriorhodopsin

Abstract— The excited-state dynamics of bacteriorhodopsin was studied by molecular dynamics simulation. For the purpose of suppressing large displacement of amino acid residues on the surface of bacteriorhodopsin, positional restraints were imposed on these residues. A new method was developed to investigate the movement of amino acid residues upon photoexcitation and their role on the ultrafast photoisomerization of the chromophore. The structural change of bacteriorhodopsin was then traced up to 200 fs, i.e. until the formation of the intermediate I. We found that when all the conjugated bonds of the chromophore were allowed to twist freely in the excited state, many bonds including the C13=C14 bond twist in large scale within 100 fs. When only the C13=C14 bond and the single bonds were allowed to twist freely, the twisting took place at most 20° within 200 fs. From these results, it is claimed that a special potential surface is provided for the C13=C14 bond twisting by the protein environment in the course of the isomerization reaction, giving rise to the specific, ultrafast photoisomerization of bacteriorhodopsin. As a trace of such a mechanism, we observed that several functionally important residues incuding Asp85, Asp212 and Tyr185 responded quickly to the photoexcitation of the chromophore.     

Improvement of Laser-Beam Irradiation-Intensity Distribution Using Multi Lens Array and Edge-Shaped Plates

A new concept for improving the laser intensity distribution on an inertial confinement fusion target using a phase-controlled multi lens array has been proposed. Circular and hexagonal element lens apertures have been examined, and the circular aperture which eliminated azimuthally asymmetric intensity distribution was chosen. The diffraction fringe of the elementary lens was mitigated in a one-dimensional lens array using edge-shaped plates of a super-Gaussian phase profile. Uniform beam profiles were obtained using a one-dimensional array with 7 spherical lenses and a two-dimensional array with 37 lenses. An approximately flat-top intensity distribution was realized with the lens array with 37 lenses.     

Anticorrelated bidirectional output of quasistadium-shaped semiconductor microlasers

Time-domain properties of the output from quasistadium-shaped microcavity semiconductor lasers are studied. Ring modes generating a bidirectional output are selectively excited by partial pumping. We observe a high anticorrelation between the two beams output from the ring modes. This can be considered as the generalization of alternate oscillations reported previously. We find that the outputs exhibit a robust slow modulation of 4–10 MHz, and explain it by the quasi-degeneracy of the resonator modes.     

Formation of Essential Kaonic Nuclei, “K − pp”

We have reviewed our theoretical calculations of the formation of a deeply bound K ^? pp state with I = 1/2, J ^π  = 0^? by the ³He(in-flight K ^?, n) reaction at ${p_{K^-} = 1.0}$ rm GeV/c and θ _lab = 0° for the forthcoming J-PARC E15 experiment. The expected inclusive and semiexclusive spectra have been calculated within the framework of a distorted-wave impulse approximation using the Green’s function method. The advantage of the use of the ³He target for the ³He(K ^?, N) reactions are emphasized.