A new boundary-type scheme for sensitivity analysis using Trefftz formulation

This paper presents a new boundary-type scheme for a sensitivity analysis of the two-dimensional potential problem by using the Trefftz formulation.

Since the Trefftz method is the boundary-type solution procedure, input data generation is easier than the domain-type solution procedure. Moreover, the physical quantities are expressed by the regular equations, their sensitivities, which is derived from the direct differentiation of the original quantaties, are also regular. Therefore, they can be calculated more easily than the ordinary boundary element method using the singular boundary integral equation. The present schemes are applied to simple numerical examples in order to confirm the validity of the present formulation.     

Controlled intramolecular electron transfers in cyanide-bridged molecular squares by chemical modifications and external stimuli

A series of cyanide bridged Fe-Co molecular squares, [Co(2)Fe(2)(CN)(6)(tp*)(2)(dtbbpy)(4)](PF(6))(2)·2MeOH (1), [Co(2)Fe(2)(CN)(6)(tp*)(2)(bpy)(4)](PF(6))(2)·2MeOH (2), and [Co(2)Fe(2)(CN)(6)(tp)(2)(dtbbpy)(4)](PF(6))(2)·4H(2)O (3) (tp = hydrotris(pyrazol-1-yl)borate, tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate, bpy =2,2'-bipyridine, dtbbpy =4,4'-di-tert-butyl-2,2'-bipyridine), were prepared by the reactions of [Fe(CN)(3)(L)](-) (L = tp or tp*) with Co(2+) and bidentate ligands (bpy or dtbbpy) in MeOH. In the molecular squares, Fe and Co ions are alternately bridged by cyanide ions, forming macrocyclic tetranuclear cores. Variable temperature X-ray structural analyses and magnetic susceptibility measurements confirmed that 1 exhibits two-step charge-transfer induced spin transitions (CTIST) centered at T(1/2) = 275 and 310 K in the solid state. The Fe and Co ions in 1 are the low-spin (LS) Fe(III) and high-spin (HS) Co(II) ions, described here in the high-temperature (HT) phase ([Fe(III)(LS2)Co(II)(HS2)]) at 330 K, while a low-temperature (LT) phase ([Fe(II)(LS2)Co(III)(LS2)]) with LS Fe(II) and Co(III) ions was dominant below 260 K. X-ray structural analysis revealed that in the intermediate (IM) phase at 298 K 1 exhibits positional ordering of [Fe(III)(LS2)Co(II)(HS2)] and [Fe(II)(LS2)Co(III)(LS2)] species with the 2:2 ratio. In photomagnetic experiments on 1, light-induced CTIST from the LT to the HT phase was observed by excitation of Fe(II) → Co(III) intervalence charge transfer (IVCT) band at 5 K and the trapped HT phase thermally relaxed to the LT phase in a two-step fashion. On the other hand, 2 and 3 are in the HT and LT phases, respectively, throughout the entire temperature range measured, and no CTIST was observed. UV-vis-NIR absorption spectral measurements and cyclic voltammetry in solution revealed that the different electronic states in 1-3 are ascribable to the destabilization of iron and cobalt ion d-orbitals by the introduction of methyl and tert-butyl groups to the ligands tp and bpy, respectively. Temperature dependence of UV-vis-NIR spectra confirmed that 1 exhibited a one-step CTIST in butyronitrile, of which T(1/2) varied from 227 to 280 K upon the addition of trifluoroacetic acid.     

Power spectrum and blood flow velocity images obtained by dual-beam backscatter laser Doppler velocimetry

We developed a micro multipoint laser Doppler velocimeter (μ-MLDV) for noninvasive in-vivo measurements of blood flow and we presented the results of demonstrations performed on experimental animals. In this paper, we investigate the validity of power spectrum analysis for determining the flow velocity and the minimum power of the semiconductor laser in the μ-MLDV. Although average velocity is generally estimated from a peak position (f _peak) in the power spectrum, the power spectrum of blood flow included an additional component in the high-frequency region. The conventional method for determining the average velocity of flows of transparent artificial fluids, which involves determining the average velocity from f _peak, is unsuitable for in-vivo measurements of blood flow. The laser power was reduced from 140 to 30mW since 30mW was the minimum power at which images of blood flow velocity in microvessels could be obtained. About 30mW (power density of 15mW/mm²) is the maximum power which can be irradiated to humans. Further reduction in the laser power is necessary before this technique can be applied to humans.     

Syntheses and phosphorescent properties of blue emissive iridium complexes with tridentate pyrazolyl ligands

Novel neutral mixed-ligand Ir(N=C=N)(N=C)X complexes (N=C=N = 1,3-bis(3-methylpyrazolyl)benzene (bpzb), 1,5-dimethyl-2,4-bis(3-methylpyrazolyl)benzene (dmbpzb), and 1,5-difluoro-2,4-bis(3-methylpyrazolyl)benzene (dfbpzb); N=C = 2-phenyl pyridine (ppy); and X = Cl or CN) have been synthesized and characterized. An X-ray single-crystal structure of the complex Ir(dmbpzb)(ppy)Cl shows that the nitrogen atom in the ppy ligand occupied the trans position to the carbon atom in the tridentate N=C=N ligand of dmbpzb with the Ir-C bond length of 1.94(1) A, whereas the coordinating carbon atom occupied the trans position of chlorine. Electrochemical data show that the complexes exhibit an oxidation Ir(III/IV) process in the potential range of +0.5 approximately 0.9 V and two irreversible reductions at approximately -2.6 and -3.0 V against Fc (0)/Fc (+), respectively. All of the Ir(III) complexes do not emit phosphorescence at room temperature, although strong phosphorescence is exhibited at 77 K with the 0-0 transition centered at around 450 nm and lifetimes of 3-14 mus. DFT calculations indicate that the HOMOs are mainly localized on iridium 5dpi and chlorine ppi*, whereas the LUMOs are mainly from the ppy ligand pi* orbitals. The phosphorescence originates from a (3)LC state mixed with the (3)MLCT and (3)XLCT ones. Temperature-dependent lifetime measurements of Ir(dfbpzb)(ppy)Cl reveal the existence of a thermal deactivation process with a low activation energy (1720 cm (-1)) and very high frequency factor (2.3 x 10 (13) s (-1)). An unrestricted density functional theory indicates that the dd state, in which both the Ir-N (pyrazolyl) bond lengths increase considerably, exists almost at the same energy as that for the phosphorescent state. A thorough analysis based on the potential energy surfaces for the T 1 and S 0 states allows us to determine the reaction pathway responsible for this thermal deactivation. The calculated activation energies of 1600 approximately 1800 cm (-1) are in excellent agreement with the observed values.     

Study on line tension of air/hexadecane/aqueous surfactant system

We measured the line tension of the air/hexadecane/aqueous solution of the dodecyltrimethylammonium bromide (DTAB) system as a function of the molality of DTAB aqueous solution at 298.15 K. The experimental values of the line tension were 10^?10 to 10^?12 N, and they coincided with the theoretical estimates. Furthermore, it was found that the line tension changes in sign from positive to negative at around 0.750 mmol kg^?1. This concentration is close to the point of transition from partial to frustrated-complete wetting. Taking into account the profiles of the free energy of the air/water surface, previously developed by Indekeu to understand the interrelationship between the wetting transition and line tension, it is suggested that the sign reversal of the line tension can be attributed to the transition from partial to frustrated-complete wetting.     

Creation of chiral thixotropic gels through a crown-ammonium interaction and their application to a memory-erasing recycle system

A unique class of oligothiophene-based organogelator bearing two crown ethers at both ends was synthesized. This compound could gelatinize several organic solvents, forming one-dimensional fibrous aggregates. From the observation of circular dichroism, it was confirmed that the helical handedness of the fibrous assembly is controllable by the chirality of 1,2-bisammonium guests, thus suggesting that one guest molecule bridges two gelator molecules through the crown-ammonium interaction. Interestingly, we have found that such chirality is created by thermal gelation, whereas it disappears by thixotropic gelation. The new finding implies that the present organogel system is applicable as a reversible switching memory device, featuring memory creation by a heat mode and memory erasing by a mechanical mode.     

Unexpected chiral induction from achiral cationic polythiophene aggregates and its application to the sugar pattern recognition

The aggregates of a cationic polythiophene (PT1) formed in poor solvent in the presence of sugars showed the distinct circular dichroism activity, the intensity being well correlated with the specific optical rotation [α] of sugars: therefore, the present system is useful as a novel sugar structure reading-out method.     

Analysis of vertical coupling between a 2D photonic crystal cavity and a hydrogenated-amorphous-silicon-wire waveguide

We present an efficient means of light extraction from two-dimensional photonic crystal (2D PC) cavities with SiO₂ cladding. We propose a vertically coupled system consisting of a 2D PC cavity and a hydrogenated-amorphous-silicon (a-Si:H)-wire waveguide, which we theoretically investigate using the 3D finite-difference time-domain method. Light can be extracted with an efficiency of greater than 95% to both output ports of the a-Si:H-wire waveguide or extracted with an efficiency of greater than 90% to a single output port of the a-Si:H-wire waveguide with a reflector.