Two-photon absorption properties of azulenyl compounds having a conjugated ketone backbone

Two-photon absorption (TPA) properties of newly synthesized conjugated ketone derivatives that include nonalternant azulenyl moieties in the pi-conjugation system, alpha,alpha'-bis(1-azulenylidene)cyclopentanone (1Az), alpha,alpha'-bis(2-azulenylidene)cyclopentanone (2Az), and alpha,alpha'-bis(6-azulenylidene)cyclopentanone (6Az) are reported. TPA spectra of these azulenyl compounds were measured using the open-aperture Z-scan method with a femtosecond laser. The TPA cross section at the peak position (sigma(2)peak) of 1Az was found to be the largest among the three azulenyl compounds, which is almost 7 times larger than that of the alpha,alpha'-bis(1-naphthylidene)cyclopentanone (1Nph), an alternant isomer of 1Az with the same number of pi-electrons. The small detuning energies of the azulenyl compounds compared to those of 1Nph were responsible for the large TPA cross sections. We report that a compound having an azulenyl moiety can be a promising TPA material.     

时间分辨与偏振红外光谱研究电场诱导下手性反铁电液晶的 …

手性反铁电液晶分子中的各个不同片段、不同基团在电场诱导下展现不同的取向与取向分布。在交变电场的作用下,分子中各个部分的翻转动力学行为也表现的不同。     

Effects of blowing or suction on the laminar boundary layer flow over a rotating cone

The effects of suction or blowing at the surface of a rotating cone in a quiet fluid on the skin friction and heat transfer are described. The equations which govern the fluid motion and thermal energy transfer are transformed by the boundary layer approximations and the resulting equations are solved under the condition that the suction or blowing velocity varies as x ⁿ (x: distance measured from the apex of the cone, n: arbitrary constant). The solutions are obtained as a perturbation from the basic laminar flow of an incompressible viscous fluid over the impermeable rotating cone. Detailed numerical calculations are performed for the case of an isothermal rotating cone with uniform blowing or suction, i.e. n=0, the Prandtl number being 0.72. Results are given for the shear stress, heat transfer and velocity and temperature fields. It is shown from the analysis that suction sharply increases the circumferential shear stress and the heat transfer at the surface.Nomenclature c proportional constant - C _fx dimensionless skin friction factor, _x /(V ²) - C _fx0 dimensionless skin friction factor for an impermeable cone - C _fy dimensionless circumferential skin friction factor, _y /(V ²) - C _fy0 dimensionless circumferential skin friction factor for an impermeable cone - c _p specific heat at constant pressure - f _k function of - g _k function of - h heat transfer coefficient, q/(T _w–T ) - k thermal conductivity of fluid - n arbitrary constant - Nu _x local Nusselt number, hx/k - Nu _x0 local Nusselt number for an impermeable cone - Pr Prandtl number - q heat transfer rate - r radius of a circular cross section of the cone, x sin - R _x Reynolds number, Vx/ - T temperature - T _w surface temperature of the cone - T temperature of the surrounding fluid - u fluid velocity in x-direction - v fluid velocity in y-direction - V circumferential velocity at the cone surface, r - w fluid velocity in z-direction - x coordinate along meridional section - y coordinate along a circular cross section - z coordinate perpendicular to both x and y - perturbation parameter, cx ⁿ /(x sin )^1/2 - dimensionless z-coordinate, z( sin /)^1/2 - _k function of - kinematic viscosity - density of fluid - _x skin friction in x-direction - _y circumferential skin friction - stream function - angular speed of the cone     

Melting heat transfer along a horizontal heated tube immersed in a fluidized liquid ice bed

An experimental study was performed to determine the melting heat transfer characteristics along a horizontal heated circular tube immersed in a solid-air-liquid three-phase fluidized liquid ice bed. A mixture of fine ice particles and ethylene glycol acqueous solution was adopted as the liquid ice for the test. Measurements were carried out for a range of parameters such as airflow rate, heated tube diameter, and initial concentration of acqueous binary solution. It was found that the heat transfer coefficient for the fluidized liquid ice bed might be more than 20 times as large as that for the fixed liquid ice bed.     

Design of a poly(L‐histidine)‐carbohydrate conjugate for a new pH‐sensitive drug carrier

A poly(L ‐histidine) (PLH)‐carbohydrate conjugate has been synthesized as a new macromolecule extracting pH‐dependent properties of PLH with imidazole groups. Because of poor water solubility at physiological pH, the application of PLH with a pK_a around 6.0 has been limited in spite of the native possession of the pH‐dependent property change at endosomal pH. Although the PLH modified with aliphatic primary amino groups suddenly precipitated out of the aqueous medium above pH 6.0 as a result of the deprotonation of the imidazole groups, the water solubility of PLH was improved at physiological pH by the conjugation of the aminated PLH with hydrophilic maltopentaose. The resulting PLH‐maltopentaose conjugates and metalloporphyrins formed the complexes which varied their assembling structure below pH 6.0. The PLH‐maltopentaose would be the fundamental compound for designing various drug carriers with the pH sensitivity at endosomal pH. Copyright © 2004 John Wiley & Sons, Ltd.     

Determination of Sub-ppb Cadmium in Urine by Solid-Phase Extraction and Inductively Coupled Plasma-Mass Spectrometry

In order to determine low levels of Cd in urine samples, we tried to remove Mo interference using ICP-MS with a dynamic reaction-cell technique, but failed due to the low sensitivity and the variance with the standards. We then performed solid-phase extraction (SPE) before the ICP-MS measurement. A commercially available chelating resin, NOBIAS PA-1, was used for SPE, and could effectively remove Mo from urine samples, permitting the accurate determination of Cd by ICP-MS. This SPE-ICP-MS method gave 0.012 microg Cd L(-1) as the method limit of quantification, and the mean recovery of Cd spiked with 0.0505 and 5.05 microg L(-1) was 93.1 and 97.6%, respectively.     

Unusual temperature dependence of enantioselectivity in asymmetric reductions by chiral NADH models

[reaction: see text] Unusual stereoselectivity changes, i.e., enhancement and inversion of enantioselectivity with increasing temperature, were observed in the asymmetric reduction of methyl benzoylformate with chiral 1,4-dihydropyridines possessing amino acid residues as ligating chiral auxiliaries. The differential activation parameters, DeltaDeltaH(S-R) and DeltaDeltaS(S-R), obtained from the Eyring plots demonstrate that the entropy term controls the enantiodifferentiating step, accounting for the observed unique temperature dependencies.     

New dimeric and monomeric chromanones,gonytolides D–G,isolated from the fungus Gonytrichum sp.

In the course of the screening of innate immune regulators from natural resources, we isolated new dimeric and monomeric chromanones, gonytolides D–G (4–7), from Gonytrichum sp. along with a known innate immune promoter, gonytolide A (1). The structures of these compounds were determined by spectral analysis, chemical conversion, and biogenetic consideration. The compounds 4–7 were evaluated on the innate immune response, indicating that the 8,8′-linked bischromanone rings were crucial for innate immune-promoting activity.     

Defects in semiconductors observed by positron annihilation

The origin of the effect of defects on positron annihilation in semiconductors has been studied. The electron-positron momentum densities in elemental semiconductors (Si and Ge), III-V compound semiconductors (GaAs, InP and GaSb), diamond and the proton irradiated Si were investigated by a full-scale use of the two-dimensional angular correlation of positron annihilation radiations (2D-ACAR). The obtained results showed, as a whole, good agreement with the electron momentum distribution of the fully occupied Jones zone with a small exception for the fact that the low density channels are running along the three principal axes. This anisotropy was strong in elemental semiconductors, while it was weakened in compound semiconductors. This anisotropy and its dependence on the material were found to be generally understood by the incorporation of crystal symmetry. The anisotropy will be discussed by group theory in conjunction to the effect of defects on positron annihilation.