External electric field effects on absorption and fluorescence spectra of a fullerene derivative and its mixture with zinc-tetraphenylporphyrin doped in a PMMA film

Electroabsorption and electrofluorescence spectra of a fullerene derivative, C60(C18)2, and its mixture with zinc-tetraphenylporphyrin (ZnTPP) have been measured by using electric field modulation spectroscopy. The change in dipole moment is significant in the electroabsorption spectra both of C60(C18)2 and of a complex composed of C60(C18)2 and ZnTPP, indicating that the excited states both of C60(C18)2 and of a complex between C60(C18)2 and ZnTPP have a large charge-transfer character. The fluorescence quantum yield of C60(C18)2 decreases in the presence of an electric field, which probably arises from the field-induced acceleration of the intramolecular nonradiative process of C60(C18)2 in the fluorescent state. In a mixture between ZnTPP and C60(C18)2, electrofluorescence spectra show the field-induced enhancement for the fluorescence of ZnTPP and the field-induced de-enhancement for the fluorescence both of C60(C18)2 and of the complex between ZnTPP and C60(C18)2. A theoretical analysis clearly shows that the field-induced enhancement of the ZnTPP fluorescence in a mixture results from the field-induced deceleration of the rate of the electron transfer from the excited ZnTPP to C60(C18)2. The standard free energy gap for the photoinduced electron-transfer process is estimated based on the theoretical simulation of the field-dependent fluorescence intensity.     

Magnesium-assisted intramolecular demethylation utilizing carborane C-H geometry

A novel type of demethylation reaction was designed in the Pd-catalyzed coupling reaction of iodocarboranes with several Grignard reagents, CH₃OPhMgBr. 3-Iodo-o-carborane 1 reacted with 2-CH₃OPhMgBr to afford the corresponding phenol compound 4b in 78% yield. However, when compound 1 was reacted with the other Grignard reagents, the corresponding methoxyl compounds 5a and 6a were obtained in excellent yields. 2-Iodo-p-carborane 3 reacted with 2-CH₃OPhMgBr to afford the corresponding phenol 8b in 50% yield and the methoxyl compound 8a in 41% yield. The carborane C-H geometry, which can form an intramolecular C-H?O hydrogen bonding, seems to be an important factor in the demethylation process. To examine the mechanism of the demethylation, compounds 1 and 4a were treated with CH₃MgBr and quenched with D₂O. While the two C-Hs of compound 1 were completely deuterated, compound 4a showed a replacement of one C-H with C-D. Therefore, we propose a mechanism involving intramolecular C-Mg?O interaction instead of intramolecular C-H?O interaction, via the generation of 3-iodo-o-carboranyl(MgBr)₂, 11. Since it is also possible to replace the C-Hs with various metals other than Mg, new applications of carboranes in coordination and metal catalyst chemistry can be expected.     

Mesogenic and magnetic behavior in cobalt(II) and iron(II) compounds with long alkyl chains

Abstract  Metal complexes with long alkyl chains [Co(C16-terpy)₃](BF₄)₂ (1), [Fe(C16-terpy)₂](BF₄)₂ (2), [Co(C16-terpy)₂](BPh₄)₂ (3), [Co(C14-terpy)₂](BF₄)₂ (4), and [Fe(C12C10C5-terpy)₂](BF₄)₂ (5) were synthesized and their physical properties characterized, where C16-terpy, C14-terpy, and C12C10C5-terpy are 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine, 4′-tetradecyloxy-2,2′:6′,2′′-terpyridine, and 4′-5′′′-decyl-1′′′-heptadecyloxy-2,2′:6′,2″-terpyridine, respectively. Complexes 1, 2, and 5 exhibited liquid–crystal properties in the temperature ranges of 371–528 K and 466–556 K, and 88–523 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the Co(II) complexes 1 and 4 exhibited unique spin transitions (T _1/2↓ = 217 K and T _1/2↑ = 260 K for 1 and T _1/2↓ = 250 K and T _1/2↑ = 307 K for 4), so-called ‘reverse spin transition,’ induced by structural phase transitions. Complex 3 exhibited gradual spin-crossover behavior (T _1/2 = 160 K.), and complex 5 exhibited spin transitions (T _1/2↑ = 288 K and T _1/2↓ = 284 K) at the liquid crystal transition temperature. Compounds with multifunction, i.e., magnetic and liquid–crystal properties, are important in the development of molecular materials. Graphical Abstract  

Stability of solitary waves for a system of nonlinear Schrödinger equations with three wave interaction

In this paper we consider a three components system of nonlinear Schrödinger equations related to the Raman amplification in a plasma. We study the orbital stability of scalar solutions of the form (e2iωtφ,0,0)$(e^{2i\omega t}\phi ,0,0)$, (0,e2iωtφ,0)$(0,e^{2i\omega t}\phi ,0)$, (0,0,e2iωtφ)$(0,0,e^{2i\omega t}\phi )$, where φ is a ground state of the scalar nonlinear Schrödinger equation.     

Degradation of fenitrothion by ultrasound/ferrioxalate/UV system

The sonochemical photodegradation of fenitrothion, which is one of phosphorothiate insecticides, was carried out in the presence of Fe(III) and oxalate. The degradation rate was strongly influenced by initial concentrations of Fe(III) and oxalate. An initial fenitrothion concentration of 10 mg L⁻¹ was completely degraded after 30 min at pH 6 under the optimum conditions. Therefore, the photo-Fenton reaction combined with sonication in the presence of oxalate was available around neutral pH. The decrease of TOC as a result of mineralization of fenitrothion was observed during ultrasound (US)/ferrioxalate/UV process. In addition, the formations of nitrite and sulfate ions as end-products were observed during this degradation system. The decomposition of fenitrothion gave two kinds of intermediate products. The degradation mechanism of fenitrothion was proposed on the base of the evidence of the identified intermediates. Based on these results, US/ferrioxalate/UV system could be useful technology for the treatment of wastewater containing fenitrothion.     

Flow measurement around a cycloidal propeller

Abstract  

An experimental investigation was conducted to study the flow around a cycloidal propeller. Flow fields were obtained using a particle image velocimetry system whose data acquisition was synchronized with the propeller’s angular position. The chord-based Reynolds number was Re _c = u _r c/υ = 1.4 × 10⁴, where u _r is the rotational velocity of the propeller and c is the chord length of the airfoil. Flow characteristics such as mean velocity, vorticity and the RMS value of velocity fluctuation were derived from the measurements. The results demonstrated the presence of a downwash around the propeller during the generation of lift. Detailed observations around each airfoil visualized distinct vortex shedding and reattaching flow at certain phase angles of the propeller.     

Evaluating 3D position and velocity of subject in parabolic flight experiment by use of the binocular stereo vision measurement

<正>A practical method for evaluating the three-dimensional(3D) position and velocity of a moving object used in the parabolic flight experiment is developed by using the binocular stereo vision measurement theory. The camera calibration mathematic model without considering the lens distortion is introduced.The direct linear transformation(DLT) algorithm is improved to accomplish the camera calibration.The camera calibration result and optimization algorithm are used to calculate the object's world coordinate from image coordinate.The 3D position and the velocity of the moving object are obtained.The standard uncertainty in estimating the velocity is 0.0024 m/s,which corresponds to 1%level of the velocity of the object in the experiment.The results show that this method is very useful for the parabolic flight experiments.     

Proton transfer in a two-dimensional hydrogen-bonding network: water and hydroxyl on a pt(111) surface

The time scale of proton transfer between H(2)O and OH adsorbed on a Pt(111) surface was determined by a combination of laser-induced thermal desorption (LITD) and microscale x-ray photoelectron spectroscopy (micro-XPS). The patterned distribution OH+H(2)O/H(2)O/OH + H(2)O was initially prepared on the Pt(111) surface by the LITD method and the time evolution of the spatial distribution of H(2)O and OH was observed by the micro-XPS technique. From quantitative analyses based on a diffusion equation, we found two proton-transfer pathways with different time scales of 5.2+/-0.9 ns and 48+/-12 ns at 140 K, which were attributed to direct proton transfer to the neighbor site and H(3)O(+)-mediated transfer to the next-nearest site, respectively.