Reconstruction of pitchfork bifurcation with exogenous disturbances based on equivalent-input-disturbance approach

Nonlinear Dynamics - Reconstructing a pitchfork bifurcation that is destroyed by an exogenous disturbance is important to control it. This paper extends the equivalent-input-disturbance (EID)...     

Sulfur-containing silsesquioxane hybrids with high refractive index and high Abbe number

Novel sulfur-containing silsesquioxane nanoparticles, (R_S–SiO_1.5) _n , having uniform size distribution, good solubility, and relatively high refractive index were synthesized by hydrolytic condensation of a triethoxysilane precursor derived from glycidol, followed by the esterification with sulfur-containing acid chlorides. Esterification of the water-soluble silsesquioxane nanoparticles with 3-(methylthio)propionyl chloride afforded silsesquioxane hybrid with a high density of chemically bonded peripheral methyl thioether groups, which was characterized by ¹H, ¹³C NMR, Fourier transform infrared spectroscopy, and thermogravimetric analysis measurements. The resulting product was soluble in various organic solvents, such as CHCl₃, acetone, tetrahydrofuran, dimethyl formamide, and dimethyl sulfoxide. The size of the sulfur-containing nanoparticles evaluated by X-ray diffraction was 2.1 nm. Transmission electron microscopy, gel permeation chromatography, and dynamic light scattering measurements indicated the formation of the nanoparticles having relatively narrow size distribution with an average particle diameter of less than 3 nm without aggregation. The sulfur content of the methyl thioether-containing silsesquioxane hybrid analyzed by elemental analysis was 16.1 %, which led to relatively high refractive index (n _D?=?1.588) and high Abbe number (34.4). Two sulfur-containing silsesquioxane hybrids with peripheral thiophene and phenyl thioether moieties were also obtained by the same procedure, and resulting hybrids showed high refractive indices of 1.605 and 1.627, and Abbe numbers of 31.8 and 24.3, respectively.     

Enantio- and diastereoselective cyclopropanation with tert-butyl α-diazopropionate catalyzed by dirhodium(II) tetrakis[N-tetrabromophthaloyl-(S)-tert-leucinate]

The first successful example of a catalytic asymmetric cyclopropanation with α-diazopropionates is described. The cyclopropanation reaction of 1-aryl-substituted and related conjugated alkenes with tert-butyl α-diazopropionate has been achieved by catalysis with dirhodium(II) tetrakis[N-tetrabromophthaloyl-(S)-tert-leucinate], Rh₂(S-TBPTTL)₄, providing the corresponding cyclopropane products containing a quarternary stereogenic center in good to high yields and with high diastereo- and enantioselectivities (trans:cis = 90:10 to >99:1, 81-93% ee).     

Studies of the isotopomer determination method for the hydrogen-deuterium exchange of methane. Introduction of methane by a pulse in a deuterium stream at high temperature

The H/D exchange reactions of methane in a deuterium stream using a fixed bed flow reactor were studied. In order to precisely determine the ratio of the exchanged products by a quadrupole mass spectrometry, a new method of corrections for the fragmentation peaks was developed.     

Preparation and crystal structure analysis of CeCuOS

A single phase of CeCuOS was prepared by sulfurization of starting materials, CeO₂+Cu₂S, and subsequent post-annealing in evacuated silica tubes. The crystal structure of the CeCuOS single phase was examined by the Rietveld analysis. The shrinkage of the unit-cell volume for CeCuOS was obviously observed in the series of LnCuOS (Ln=La-Nd) oxysulfides. The examination of interatomic distances revealed that Ce-S distances in CeCuOS are shorter than those predicted from the lanthanide contraction and this short Ce-S bond length is responsible for the unit-cell-volume shrinkage of CeCuOS. The origin of the shrinkage is discussed in the viewpoints of the Ce valence and interatomic distances along with the results of magnetic measurements.     

Spectroscopic Determination of Charge Formation Efficiency of Organic Photovoltaic Cells

The internal quantum efficiency (Φ_IQ) of an organic photovoltaic (OPV) cell is governed by plural processes, i.e., the carrier formation process at the D/A interface and the carrier transfer process toward the collector electrode. Then, Φ_IQ can be decomposed into the carrier formation (Φ_CF) and carrier transfer efficiencies (Φ_CT). By combination of femtosecond time-resolved and electrochemical spectroscopies, we determined absolute values of Φ_CF of F8T2/PC₇₁BM, P3HT/PCBM, and PTB7/PC₇₁BM solar cells. We found that Φ_CF at 400 nm of the F8T2/PC₇₁BM cell is higher than those of the P3HT/PCBM, and PTB7/PC₇₁BM cells, although Φ_IQ at 400 nm is the lowest.     

Comprehensive analysis of short peptides in sera from patients with IgA nephropathy

We analyzed serum short peptides comprehensively to know whether they were useful to characterize IgA nephropathy (IgAN). Serum samples from 26 patients with untreated IgAN and 25 healthy donors were tested. Short peptides with molecular weights of ～7 kDa, purified from the serum samples by magnetic‐beads‐based weak cation exchange, were detected by mass spectrometry. Then the peptide peaks detected were subjected to the multivariate data analysis by SIMCA‐P+® containing principal component analysis (PCA) and orthogonal partial‐least‐squares‐discriminate analysis (OPLS‐DA). A total of 92 peptide peaks were detected in the tested serum samples. The OPLS‐DA analysis revealed that the profile of all the peptide peak intensities discriminated the IgAN group and the healthy group completely with a high R2 value (0.919) and a high Q2 value (0.861). Further, the profile of only five peptide peaks was found to discriminate the two groups. By tandem mass spectrometry and database searching, three of the five peptides which increased in the IgAN group were identified as fragments of fibrinogen alpha chain, and the two peptides which increased in the healthy group were identified as fragments of complement C3f and kininogen‐1 light chain. Taken together, the profile of the serum short peptides would be useful to discriminate IgAN and healthy conditions. Further, the five peptides may be candidate serum markers for IgAN and may be related to pathogenesis of IgA. Copyright © 2009 John Wiley & Sons, Ltd.     

Self-Assembling Properties of 6-O- and 6′-O-Alkylsucrose Mixtures Having Different Chain Lengths Under Aqueous Conditions

The self-assembling properties of the 6-O- and 6′-O-alkylsucrose mixtures with different chain lengths including octyl, decyl, dodecyl, and tetradecyl under aqueous conditions were studied and compared with those of the 6-O- and 6′-O-hexadecylsucrose mixture previously reported. The title compounds were synthesized from sucrose in five steps. The results of scanning and transmission electron microscopes, powder X-ray diffraction, and dynamic light scattering measurements indicated that the self-assembling properties of octyl, decyl, and dodecyl derivatives were completely different from those of the 6-O- and 6′-O-hexadecylsucrose mixture. The three derivatives reported here primarily formed lamellar planes, which further induced the formation of vesicle-type particles under aqueous conditions, whereas the previous derivatives primarily formed spherical micelles in water, which further assembled according to face-centered cubic organization by a drying process from the aqueous dispersion. It was also found that the 6-O- and 6′-O-tetradecylsucrose mixture showed concentration-induced micelle-lamellar transition behavior in an aqueous dispersion. Furthermore, the mixing of a regioisomer, 6′-O-hexadecylsucrose, with 6-O-hexadecylsucrose induced different self-assembling properties from that of 6-O-hexadecylsucrose alone, but this effect did not appear in the self-assembling of the 6-O- and 6′-O-octylsucrose mixture.     

Abnormalities of cerebral blood flow in multiple sclerosis: A pseudocontinuous arterial spin labeling MRI study

Arterial spin labeling (ASL) is a noninvasive technique that can measure cerebral blood flow (CBF). To our knowledge, there is no study that examined regional CBF of multiple sclerosis (MS) patients by using this technique. The present study assessed the relationship between clinical presentations and functional imaging data in MS using pseudocontinuous arterial spin labeling (pCASL). Twenty-seven patients with MS and 24 healthy volunteers underwent magnetic resonance imaging and pCASL to assess CBF. Differences in CBF between the two groups and the relationships of CBF values with the T2-hyperintense volume were evaluated. Compared to the healthy volunteers, reduced CBF was found in the bilateral thalami and right frontal region of the MS patients. The volume of the T2-hyperintense lesion was negatively correlated with regional CBF in some areas, such as both thalami. Our results suggest that demyelinated lesions in MS mainly have a remote effect on the thalamus and that the measurement of CBF using ASL could be an objective marker for monitoring disease activity in MS.     

Dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate]: a new chiral Rh(II) catalyst for enantioselective amidation of C---H bonds

Dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], characterized by substitution of chlorine atoms for four hydrogen atoms on the phthalimido group in the parent dirhodium(II) complex has been found to be well suited for enantioselective amidation of benzylic C---H bonds with [(4-nitrophenyl)sulfonylimino]phenyliodinane. The observed enantioselectivity of up to 84% ee is the highest reported to date for dirhodium(II) complex-catalyzed C---H amidations.