Determination of ppt levels of atmospheric volatile organic compounds in Yakushima, a remote south-west island of Japan

An analytical method was utilized to detect ppt levels of VOCs in air. The method was based on the US-EPA method TO-14, consisting of canister sampling, three module enrichment and GC/MS analysis. Target compounds included chlorofluorocarbons (four kinds), benzene and its derivatives (14), halogenated hydrocarbons (20), and others (three). The minimum detection limits of the method for the target compounds ranged from 0.016 to 0.040 ppb (0.06–0.23 μg/m³). The recoveries of the target compounds ranged from 77 to 113% and relative coefficients of variation (n=4) were 3.0–9.0%. The sampled air was stable for at least 14 days after pressurizing with humidified nitrogen gas at 200 kPa (absolute pressure). The method was applied to analyze the VOCs in the air of Yakushima, a remote island of south-west Japan where no distinct local pollution source is considered.     

CFD by first order PDEs

This research originally was aimed at modeling all flows (except free-molecular) by systems of hyperbolic-relaxation equations (moments of the Boltzmann equation), and developing efficient numerical methods for these. Such systems have many potential numerical advantages, mainly because there are no second or higher derivatives to be approximated. This avoids accuracy problems on adaptive unstructured grids, and the source terms, though often stiff, are only local; the compact stencils facilitate code parallelization. A single code could simulate flows up to intermediate Knudsen numbers, and be hybridized with DSMC where needed. In this project, one major problem arose that we have not yet solved: the accurate representation of shock structures. This makes the methodology currently unsuited for, e.g., re-entry flows. We have validated it for subsonic and transonic flows and are concentrating on applications to MEMS-related flows. We discuss the challenges of our approach, present numerical algorithms and results based on the 10-moment model, and report progress in our latest research topic: formulating accurate solid-boundary conditions.     

Origin of low melting point of ionic liquids: dominant role of entropy

Ionic liquids (ILs) are salts with an extremely low melting point. Substantial efforts have been made to address their low melting point from the enthalpic standpoint (i.e. interionic interactions). However, this question is still open. In this study, we report our findings that entropic (large fusion entropy), rather than enthalpic, contributions are primarily responsible for lowering the melting point in many cases, based on a large thermodynamic dataset. We have established a computational protocol using molecular dynamics simulations to decompose fusion entropy into kinetic (translational, rotational, and intramolecular vibrational) and structural (conformational and configurational) terms and successfully applied this approach for two representatives of ILs and NaCl. It is revealed that large structural contribution, particularly configurational entropy in the liquid state, plays a deterministic role in the large fusion entropy and consequently the low melting point of the ILs.

Large structural entropy makes salts liquid at room temperature.     

The Microwave Spectrum of Methyl Formate (HCOOCH3) in the Frequency Range from 7 to 200 GHz

The rotational spectrum of methyl formate (HCOOCH₃) has been observed in the frequency range from 7 to 200 GHz. We newly assigned 1612 lines in the ground torsional state and simultaneously analyzed both A- and E-species data including previously reported lines on the basis of the internal axis method. A total of 3077 lines were fitted to a 1σ standard deviation of 139 kHz, and molecular parameters were determined.     

Reactions of C60 with Pyridazine and Phthalazine

Cage-opened bisfulleroids are one of suitable building blocks for making a large hole on fullerenes. This work focuses on the Diels-Alder reaction of C₆₀ with azines, among synthetic methods developed thus far, to provide bisfulleroids. Surprisingly, the computational study predicted that the reaction proceeds with normal electron demand in contrast to hitherto considered inverse-electron-demand pathway. The benzoannulation to the pyridazine ring, i. e., phthalazine, resulted in the remarkably shortened reaction time due to the better interaction between the HOMO of phthalazine and the LUMO of C₆₀ as well as stronger 2,3-diaza-1,3-butadiene character in the phthalazine as confirmed crystallographically. Contrary to expectations, the benzobisfulleroid was converted into corresponding orifice-enlarged derivative via the photooxygenation slightly faster than the fulleroid derived from pyridazine.     

Emission-Color Control in Polymer Films by Memorized Fluorescence Solvatochromism in a New Class of Totally Organic Fluorescent Nanogel Particles

In this work, a new class of totally organic fluorescent nanogel particles and their exceptionally specific behaviors based on their unique structures are introduced, which draws a sharp line from conventional fluorophore-doped and fluorophore-branched-type particles. The nanogel particles, the diameter of which could be controlled by adjusting reaction conditions, such as the solvent system, were spontaneously fabricated with a spherical shape by direct polymerization of non-heterocyclic aromatic compounds, such as 2,6-dihydroxyanthracene, 2,6-dihydroxynaphthalene, and 9,9-bis(4-hydroxyphenyl)fluorene with triazinane as the cross-linker. A fluorophoric moiety formed from a polymer main chain was realized in the particle, and consequently, the resultant content of the fluorophoric moiety was around 70–80 wt % per particle. The uniqueness and versatility of the particles can be emphasized by their good compatibility with various solvents due to their amphiphilic and ampholytic swelling properties, but also by their remarkable fluorescent solvatochromism in the dispersion state. Furthermore, these behaviors were preserved even in their polymer composite system. This study also demonstrates that various fluorescent polymer films can be fabricated with emission color control due to memorization of the solvatochromism phenomenon of the dispersed fluorescent nanoparticles.     

Resonance effect in solvolysis of 1-methylbenzyl chlorides

Substituent effects of p-MeO and p-MeS groups deactivated by additional m-substituents in cumyl and α-phenylethyl solvolyses were studied to provide evidence for the higher resonance demand in the α-phenylethyl system.     

Equivalent electric circuit analyses of ionic thermocurrent in sodium-doped CaF2 crystals

The characteristics of high-temperature ionic thermocurrent (HT ITC) in CaF₂ doped with different sodium concentrations were studied by the Teflon-insulated electrode ITC method. It was shown that, with increasing sodium concentration, the HT ITC band moved toward a Na⁺-F_V dipole band with a peak at 162 K. The results of analyses of the HT ITC spectra using an equivalent electric circuit proved that the activation energy of space charge migration related to HT ITC was also strongly dependent on the doped sodium concentrations if varied from 0.94 to 0.46 eV with increasing sodium concentration in our ITC study. In addition, the broadening of the Na⁺-F_V dipole band was observed in 3 nominal mole% NaF-doped CaF₂, which was accompanied by a considerable decrease of the activation energy from 0.46 to 0.29 eV without showing marked temperature shifts of the peak ITC bands.     

Synthesis of bicyclic 1,3,5-triazine-2,4(3H)-diones: Reaction of amidines with diphenyl iminodicarboxylate

The preparation of bicyclic 1,3,5-triazine-2,4(3H)-diones 3 has been investigated. Diphenyl iminodicarboxylate ( 2 ) reacted smoothly with cyclic amidines to give bicyclic triazinediones in good yields.