Parallel computation of turbulent flows using moment base lattice Boltzmann method

This paper describes parallel computing approach for simulating turbulent flows using a moment base lattice Boltzmann method. The distribution functions of the lattice Boltzmann method are expressed by corresponding moments. Choosing proper relaxation times for higher order moments, a minimum numerical dissipation is implicitly added to stabilise the method at high Reynolds numbers. Validation of the method is made by computing free decaying periodic turbulent flows and fully developed turbulent channel flows on a GPU platform. Though the present method requires additional work to calculate the higher order moments, it is shown that additional computational cost is negligible in the GPU computing. The numerical results stably obtained for the turbulent flows are in good agreement with those of a pseudo-spectral method and corresponding DNS database.     

Mechanism underlying bioinertness of self-assembled monolayers of oligo(ethyleneglycol)-terminated alkanethiols on gold: protein adsorption, platelet adhesion, and surface forces

The mechanism underlying the bioinertness of the self-assembled monolayers of oligo(ethylene glycol)-terminated alkanethiol (OEG-SAM) was investigated with protein adsorption experiments, platelet adhesion tests, and surface force measurements with an atomic force microscope (AFM). In this work, we performed systematic analysis with SAMs having various terminal groups (-OEG, -OH, -COOH, -NH(2), and -CH(3)). The results of the protein adsorption experiment by the quartz crystal microbalance (QCM) method suggested that having one EG unit and the neutrality of total charges of the terminal groups are essential for protein-resistance. In particular, QCM with energy dissipation analyses indicated that proteins absorb onto the OEG-SAM via a very weak interaction compared with other SAMs. Contrary to the protein resistance, at least three EG units as well as the charge neutrality of the SAM are found to be required for anti-platelet adhesion. When the identical SAMs were formed on both AFM probe and substrate, our force measurements revealed that only the OEG-SAMs possessing more than two EG units showed strong repulsion in the range of 4 to 6 nm. In addition, we found that the SAMs with other terminal groups did not exhibit such repulsion. The repulsion between OEG-SAMs was always observed independent of solution conditions [NaCl concentration (between 0 and 1 M) and pH (between 3 and 11)] and was not observed in solution mixed with ethanol, which disrupts the three-dimensional network of the water molecules. We therefore concluded that the repulsion originated from structured interfacial water molecules. Considering the correlation between the above results, we propose that the layer of the structured interfacial water with a thickness of 2 to 3 nm (half of the range of the repulsion observed in the surface force measurements) plays an important role in deterring proteins and platelets from adsorption or adhesion.     

Stereochemistry-dependent, mechanoresponsive supramolecular host assemblies for fullerenes: a guest-induced enhancement of thixotropy

Self-assembly behaviors of a series of systems (G1, G2, and G3) possessing same organic building blocks based on a substituted anthracene have been investigated in decalin. G2 and G3 are dominated by head-to-tail (ht) and head-to-head (hh) type dimers of G1, respectively. G1 gives a thermoresponsive gel that behaves ideally, showing frequency-independent elastic and viscous moduli. Interestingly, G2 produces a thixotropic gel that shows the signature of structural relaxation, signifying the dynamic nature of the system. In contrast, G3 remains fluidlike. As investigated by scanning electron microscopy (SEM), in the assembly process of G2, first disklike nanoaggregates are formed, and in the second step these aggregates interact to construct the densely packed secondary assembly. A transition from secondary assembly to primary assembly under shear initiates the mechanoresponsive destruction of the gel. In the self-assembly process, G1 propagates in a one-dimensional fashion, whereas G2 and G3 can propagate in a two-dimensionional fashion. The same side orientation of the substituents in G3 facilitates the formation of a compact closed-shell-type structure, which results in the generation of isolated nanocrystals. The long-range weak interaction together with the capability of propagating in two dimensions is found to be essential for the construction of such a mechanoresponsive assembly. C(60) and C(70) could be incorporated successfully in G2 assembly to develop mechanoresponsive fullerene assemblies. The presence of fullerenes not only enhances the elastic properties of G2 but also intensifies the thixotropy. C(70) appears to be a superior guest in terms of property enhancement due to its better size fitting with the concave-shaped host.     

Iridium-catalyzed addition of aroyl chlorides and aliphatic acid chlorides to terminal alkynes

Iridium complexes show high catalytic activity in intermolecular additions of acid chlorides to terminal alkynes to afford valuable (Z)-β-chloro-α,β-unsaturated ketones. Ligands in the catalytic system play a crucial role in this reaction. An N-heterocyclic carbene (NHC) is an efficient ligand for the addition of aroyl chlorides, while dicyclohexyl(2-methylphenyl)phosphine (PCy(2)(o-Tol)) is indispensable for the reaction of aliphatic acid chlorides. The addition reactions proceed regio- and stereoselectively with suppression of decarbonylation and β-hydrogen elimination, which have been two major intrinsic problems in transition-metal-catalyzed reactions. Stoichiometric reactions of active iridium catalysts with aroyl chlorides and aliphatic acid chlorides are carried out to gain insights into the reaction mechanisms.     

Hubble induced mass in radiation-dominated universe

We reconsider the effective mass of a scalar field which interact with visible sector via Planck-suppressed coupling in supergravity framework. We focus on the radiation-dominated (RD) era after inflation. In this era, the effective mass is given by thermal average of interaction terms. To make our analysis clear, we rely on Kadanoff–Baym equations to evaluate the thermal average. We find that, in RD era, a scalar field acquires the effective mass of the order of H.     

Vector WIMP miracle

Weakly interacting massive particle (WIMP) is well known to be a good candidate for dark matter, and it is also predicted by many new physics models beyond the standard model at the TeV scale. We found that, if the WIMP is a vector particle (spin-one particle) which is associated with some gauge symmetry broken at the TeV scale, the Higgs mass is often predicted to be 120–125 GeV, which is very consistent with the result of Higgs searches recently reported by ATLAS and CMS Collaborations at the Large Hadron Collider experiment. In this Letter, we consider the vector WIMP using a non-linear sigma model in order to confirm this result as general as possible in a bottom-up approach. Near-future prospects to detect the vector WIMP at both direct and indirect detection experiments of dark matter are also discussed.     

Chromatic aberration free liquid crystal adaptive optics for flood illuminated retinal camera

A high-resolution, flood-illumination retinal camera using liquid crystal (LC) adaptive optics (AO) is presented. The retinal camera uses light at 780 nm for ocular aberration measurement while light at 655 nm and 593 nm for retinal imaging. In order to avoid chromatic aberrations due to wavelength dependence of LC, we adopt an open-loop technique, in which dynamic correction of aberrations is applied only to the imaging light. A compensation pattern projected on the LC wavefront corrector is adjusted to provide phase wrapping of 2 π for illumination light. We confirmed feasibility of this technique by performing in vivo retinal imaging experiments. Photoreceptors were clearly revealed at both imaging light at 655 nm and 593 nm. Feasibility of the technique was also supported by comparison of the retinal images taken by the present open-loop technique with those taken by the conventional closed-loop one and by analysis of the spatial distribution of the photoreceptors.     

Effect of an inter-electrode distance in VHF-PECVD and gas flow ratios on a-SiGeC:H films and solar cells by using monomethyl germane as a germanium source

Hydrogenated amorphous silicon–germanium–carbide (a-SiGeC:H) has been fabricated by monomethyl germane (MMG, GeH₃CH₃) under various deposition conditions, inter-electrode distance (d_ele) in VHF-PECVD and gas flow ratios. With decreasing d_ele, it is observed from optical emission spectroscopy (OES) that the generation of atomic hydrogen in plasma gradually increases. It is also found that the enhanced atomic hydrogen tends to take both Ge and C away from growing surfaces, leading to the decrease in Ge and C contents. The total content of hydrogen bonds increases as a result of the increase in both SiH and GeH bonds as the d_ele decreases. Consequently, the a-SiGeC:H solar cells fabricated at narrower d_ele exhibit the improved performance. Even though the optical band gap (E_opt) of the a-SiGeC:H increases with decreasing d_ele, the quantum efficiency (QE) spectra reveal even an increasing trend of long wavelength regions because of the significant improvement in i-layers. It is also confirmed that a lot lower MMG/SiH₄ was needed for the films having certain E_opt, when fabricated near amorphous-to-crystalline transition, and the solar cell fabricated near the transition region shows the better performance.     

Nonlinear fluorescence response driven by ATP-induced self-assembly of guanidinium-tethered tetraphenylethene

Nonlinear fluorescence response, which is particularly important to attain the high signal-to-background ratio, was realized by the aggregation-induced fluorescence increase of guanidinium-tethered tetraphenylethene with ATP.     

Coherent interactions of dyes assembled on DNA

The optical behavior of an organized dye assembly is different from that of the isolated dye; this difference is explained using molecular exciton theory. The theory predicts that mutual orientation, the number of dyes in the cluster, and combinations of different dyes should display given characteristic spectroscopic behaviors due to coherent interactions. Comparison of theoretical predictions with experimental results has been limited so far. One of the reasons is the absence of a rigid and well-organized system that can control the orientation and size of the dye assembly. Recently, the DNA duplex has been used to assemble chromophores in a programmed manner. Use of DNA allows organized dye assembly with a given size and particular orientation. In this review, we evaluate the spectroscopic behavior of the H-type aggregate based on molecular exciton theory and compare it with actual dye assembly with DNA duplex. Furthermore, we demonstrate the importance of coherent interactions on the observed optical properties of dyes assembled in a DNA duplex.