Thermodynamic properties of methane/water interface predicted by molecular dynamics simulations

Molecular dynamics simulations have been performed to examine the thermodynamic properties of methane/water interface using two different water models, the TIP4P/2005 and SPC/E, and two sets of combining rules. The density profiles, interfacial tensions, surface excesses, surface pressures, and coexisting densities are calculated over a wide range of pressure conditions. The TIP4P/2005 water model was used, with an optimized combining rule between water and methane fit to the solubility, to provide good predictions of interfacial properties. The use of the infinite dilution approximation to calculate the surface excesses from the interfacial tensions is examined comparing the surface pressures obtained by different approaches. It is shown that both the change of methane solubilities in pressure and position of maximum methane density profile at the interface are independent of pressure up to about 2 MPa. We have also calculated the adsorption enthalpies and entropies to describe the temperature dependency of the adsorption.     

Atom transfer cyclization catalyzed by InCl3 via halogen activation

[reaction: see text] Indium trichloride was found to be an efficient catalyst for the cyclization of allylic halides and alkynes with atom transfer in methylene chloride. Mechanistic evidence supports a cationic reaction pathway with Lewis acid activation of the allylic halogen. Concomitant nucleophilic attack by the alkyne and trapping with halide led to atom transfer cyclization products. Depending on alkyne substitution, a bromine atom was transferred from the substrate or a chlorine atom was transferred from the solvent.     

Multiple existence of non-radial solutions with group invariance for sublinear elliptic equations

We deal with sublinear elliptic equations in a ball and prove the existence of infinitely many solutions which are not radially symmetric but G invariant. Here G is any closed subgroup of the orthogonal group and is not transitive on the unit sphere.     

Observations on the reactivity of tris(tetramethylethylenedioxyboryl)methide ion

Treatment of tetrakis(tetramethylethylenedioxyboryl)methane, (Me₄C₂ - O₂B)₄C, in THF with butyllithium at ?78° generates the tris(tetramethylethylenedioxyboryl)methide ion, (Me₄C₂O₂B)₃C^?, which reacts with chlorotrimethylsilane at ?78° to form trichlorosilyltris(tetramethylethylenedioxyboryl)-methane, (Me₄C₂O₂B)₃CSiMe₃. The yield was low, but other attempts to form silyltriborylmethanes have failed altogether. The ion (Me₄C₂O₂B)₃C^? reacts with tetraphenylcyclopentadienone at ?78° to form the expected fulvene, 1,1-bis-(tetramethylethylenedioxyboryl)-2,3,4,5-tetraphenylfulvene. The red color of the tetraphenylcyclopentadienone is converted immediately to the brown of the fulvene product, indicating that the β-elimination of boron and oxygen occurs rapidly under basic conditions at ?78°.     

PSDF of log-amplitude scintillation for 7 μm band laser beam with absorption by water vapour

The power spectral density function (PSDF) of the log-amplitude scintillation for an infrared laser beam was measured experimentally. To investigate the contribution of the absorption and the dispersion that cause the scintillation, we chose 16 wavelengths of infrared light and one wavelength of visible light. It is found that the spectral density of scintillation for the infrared beam does not agree with that for the visible beam, as predicted by Tatarskii's theory in the low-frequency region below 1 Hz. This disagreement between the experiment and the theory in the low-frequency region should be attributed to water vapour absorption.     

Field Analysis of Pillbox Resonator with Radiation Loss Utilizing Finite-Element Beam Propagation Method Formulation

To deal with the radiation from an axially symmetric pillbox resonator embedded in LiNbO₃ substrate, an eigenvalue equation is derived from the expression of the finite-element beam propagation method in a cylindrical coordinate system. By solving the eigenvalue equation iteratively, the field distributions and the angular phase constants of the pillbox resonator are evaluated. The iterative scheme of solving the eigenvalue equation is an extension of our previous direct solution method which was described for a lossless case. The results obtained by this method are compared with those obtained analytically, and excellent agreement is found.     

Inductive effect-assisted chain-growth polycondensation. synthetic development from para- to meta-substituted aromatic polyamides with low polydispersities

The polycondensation of m-(octylamino)benzoic acid esters (1) with base was investigated in order to extend the synthesis of well-defined condensation polymers from para-substituted polymers to meta-substituted ones. We expected that the aminyl anion of 2 would deactivate the ester moiety at the meta position of 2 owing to the strong inductive effect of the anion, resulting in, not self-polycondensation, but chain-growth polycondensation. The methyl ester monomer 1a polymerized with lithium hexamethyldisilazide (LiHMDS) in the presence of phenyl benzoate (3a) as an initiator at 0 degrees C to afford a polymer with a low polydispersity, but the product contained a small amount of self-condensation polymer. On the other hand, the polymerization of the ethyl ester monomer (1b) with phenyl 4-methylbenzoate (3b) proceeded through chain polymerization without self-polycondensation. The Mn values of the polymers increased linearly in proportion to the [1b]0/[3b]0 ratio, and the Mw/Mn ratios remained narrow over the entire [1b]0/[3b]0 range. Furthermore, a block copolymer of N-alkylated poly(m-benzamide) and poly(p-benzamide) with a low polydispersity was synthesized by the monomer addition method under this polymerization condition.     

Synthesis and properties of a new fluorescent bicyclic 4-N-carbamoyldeoxycytidine derivative

[reaction: see text] A bicyclic 4-N-carbamoyldeoxycytidine derivative (1, dC(hpp)) geometrically locked was synthesized as a new fluorescent nucleobase. The hybridization properties of oligodeoxynucleotides containing dC(hpp) were investigated by use of T(m) analysis. It was found that dC(hpp) forms stable base pairs not only with the complementary guanine base, but also with the adenine base. Interestingly, the fluorescence of dC(hpp) was suppressed only when a dC(hpp)-dG base pair was formed.     

Long wavelength InAs self-assembled quantum dots embedded in GaNAs strain-compensating layers

We investigated the effect of GaNAs strain-compensating layers (SCLs) on the properties of InAs self-assembled quantum dots (QDs) grown on GaAs (0 0 1) substrates. The GaNAs material can be used as SCL thereby minimizing the net strain, and thus is advantageous for multi-stacking of InAs QDs structures and achieving long wavelength emission. The emission wavelength of InAs QDs can be tuned by changing the nitrogen (N) composition in GaNAs SCLs due to both effects of strain compensation and lowering of potential barrier height. A photoluminescence emission at 77 K was clearly observed for sample with GaN_0.024As_0.976 SCL. Further, we observed an improvement of optical properties of InAs QDs by replacing the more popular GaAs embedding layers with GaNAs SCLs, which is a result of decreasing non-radiative defects owing to minimizing the total net strain.