Biaryl-based anion receptors bearing thiourea groups: fluoride anion receptor

The synthesis, characterization and binding studies with anions for biaryl-based anion receptors bearing thiourea groups have been described. The results revealed that receptors (1 and 2) showed good selectivity and binding affinity for F^?, and among them binaphthyl-based receptor (1a) showed the best binding affinity for F^? in comparison to other tested anions (Cl^?, Br^?, I^?, $ {\text{NO}}_{3}^{ - } ,\;{\text{HSO}}_{4}^{ - } , $ AcO^? and $ {\text{H}}_{2} {\text{PO}}_{4}^{ - } $ ). This is probably due to the fact that the moderate rigidity of binaphthyl skeleton in 1a is able to provide the better geometry of two thiourea groups for incorporating F^? into the binding pocket. The higher basicity of F^? also participated in this selectivity.     

Bayes-optimal solution to inverse halftoning based on statistical mechanics of the Q-Ising model

On the basis of statistical mechanics of the Q-Ising model, we formulate the Bayesian inference to the problem of inverse halftoning, which is the inverse process of representing gray-scales in images by means of black and white dots. Using Monte Carlo simulations, we investigate statistical properties of the inverse process, especially, we reveal the condition of the Bayes-optimal solution for which the mean-square error takes its minimum. The numerical result is qualitatively confirmed by analysis of the infinite-range model. As demonstrations of our approach, we apply the method to retrieve a grayscale image, such as standard image Lena, from the halftoned version. We find that the Bayes-optimal solution gives a fine restored grayscale image which is very close to the original. In addition, based on statistical mechanics of the Q-Ising model, we are sucessful in constructing a practically useful method of inverse halftoning using the Bethe approximation.      

Association of polybutadiene living anions in cyclohexane

Simultaneous measurements of static and dynamic light scattering were made for cyclohexane solutions of living polybutadiene (PB) anion to characterize PB components existing in the solutions. There were two relaxation modes in the relaxation time spectra obtained by dynamic light scattering. The static structure factor and hydrodynamic radius of the major fast relaxation component obtained are explained by the unimer‐tetramer equilibrium model. The same model is also consistent with the data of the propagation reaction rate of the PB living anion in cyclohexane. The slow relaxation component is only minor (less than 1 wt %), but has a large radius of gyration of ca. 200 nm, and is assigned to aggregates consisting of a huge number of PB living anion chains. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1401–1407, 2005     

Systematic studies on structural parameters for nanotubular assembly of hexa-peri-hexabenzocoronenes

Thirteen different hexa-peri-hexabenzocoronenes (HBCs) I-III were newly synthesized, and their self-assembling behaviors were investigated. Taking into account also the reported behaviors of amphiphilic HBCs, some structural parameters of HBC essential for the tubular assembly were revealed. Points to highlight include (1) the importance of two phenyl groups attached to one side of the HBC unit, (2) essential roles of long paraffinic side chains on the other side of the phenyl groups, and (3) no necessity of hydrophilic oligo(ethylene glycol) side chains. The hierarchical nanotubular structure, rendered by virtue of a synchrotron radiation technique, was virtually identical to our previous proposal, where the nanotubes are composed of helically coiled bilayer tapes with a tilting angle of approximately 45 degrees. Each tape consists of pi-stacked HBC units, where the inner and outer HBC layers are connected by interdigitation of paraffinic side chains. The coiled structure is most likely caused by a steric congestion of the phenyl groups attached to the HBC unit, whose tilting direction may determine the handedness of the helically chiral nanotube.     

An instant cell recognition system using a microfabricated coordinate standard chip useful for combinable cell observation with multiple microscopic apparatuses

Disposable coordinate standard (CS) chips were fabricated by the ejection of melted polystyrene into a metal mold. The CS chip surface was divided into four parts different in height and width. The edge lines of these parts could be recognized as straight lines 2 mum in width in the microscope view and used as the X and Y axes for the culture dish. The CS chip was attached on the bottom of a culture dish outside. Then the dish was set on the microscope stage and moved by means of a motorized automatic stage. The X-Y coordinates of many single-cells in a culture dish were registered, respectively. Once registered, any single-cell could instantly be brought to the center of the microscope view even after displacing the dish from the stage for a while and setting it again on the stage. Therefore, experimenters can easily search any single-cell in any culture dish on any microscope at any time. Such a system is remarkably useful for various modes of single-cell experiment and named "Suguwaculture," which means "instantly" ("sugu" in Japanese) + "recognizable" ("wakaru" in Japanese) + "culture" (during culture).     

Selective iodinated dipyrrolyldiketone BF2 complexes as potential building units for oligomeric systems

Selective iodination at the alpha-pyrrole positions of dipyrrolyldiketone BF(2) complexes is a key procedure to afford mono- and bisiodinated derivatives as the starting materials of the coupling reactions for various utility molecules and covalently linked oligomer systems. Iodination can also be applied to the phenylene-bridging receptor dimer to obtain the derivatives selectively iodinated at the terminal alpha-pyrrole position(s).     

Relating conformation and photophysics in single MEH-PPV chains

We use a novel fluorescence polarization microscope in combination with molecular dynamics calculations to determine the conformation of individual isolated chains of the conjugated polymer MEH-PPV. We found a narrow distribution of defect cylinder conformations in a poor-solvent matrix and two types of defect coil conformations in a good-solvent matrix. The conformations were related to photophysical properties of MEH-PPV by measuring fluorescence intermittency on the same chains. We obtained direct evidence that the photophysics is determined by the chain conformations and that small changes in the polymer microscopic structure can qualitatively affect the photophysical properties.     

Charge-Segregated Stacking Structure with Anisotropic Electric Conductivity in NIR-Absorbing and Emitting Positively Charged π-Electronic Systems

Squarylium-based π-electronic cation with an augmented dipole was synthesized by methylation of zwitterionic squarylium. The cation formed various ion pairs in combination with anions, and the ion pairs exhibited distinct photophysical properties in the dispersed state, ascribed to the formation of J- and H-aggregates. The ion pairs provided solid-state assemblies based on cation stacking. It is noteworthy that complete segregation of cations and anions was observed in a pseudo-polymorph of the ion pair with pentacyanocyclopentadienide as a π-electronic anion. In the crystalline state, the ion pairs exhibited photophysical properties and electric conductivity derived from cation stacking. In particular, the charge-segregated ion-pairing assembly induces an electric conductive pathway along the stacking axis. The charge-segregated mode and fascinating properties were derived from the reduced electrostatic repulsion between adjacent π-electronic cations via dipole–dipole interactions.     

Improvement of image sticking on liquid crystal displays with polymer layers produced from mixed monomers

As a model of polymer-sustained-alignment liquid crystal display (PSA-LCD), the LC cells having the polymer layers produced from the homopolymers and copolymers of 4,4?-dimethacryloyl-oxy-biphenyl (4,4?-DMABiph) and 2,6-dimethacryloyl-oxy-naphthalene (2,6-DMANaph) were prepared and investigated image sticking phenomenon with evaluations of residual direct current voltage (V_rDC) and difference in pre-tilt angle before and after application of alternate current (AC) voltage (Δtilt). The V_rDC was effectively improved by adding a small amount of 2,6-DMANaph to 4,4?-DMABiph because the concentrations of radicals and ions in the LC layer were decreased due to increase in the rate constant of the polymerisation with the addition of 2,6-DMANaph under UV light exposure. The Δtilt was proportionally increased with increasing the weight ratio of 2,6-DMANaph in the mixed monomers of 4,4?-DMABiph and 2,6-DMANaph. We confirmed that the range of the weight ratio for 2,6-DMANaph in the mixed monomers of 4,4?-DMABiph and 2,6-DMANaph from 10 to 25 wt% was useful for obtaining the small level of image sticking in the PSA-LCD.     

Determination of isophorone in food samples by solid-phase microextraction coupled with gas chromatography-mass spectrometry

A simple and sensitive method for the determination of isophorone in food samples was developed by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Isophorone was separated within 10 min by GC-MS using a DB-1 capillary column and detected with selective ion monitoring mode. The HS-SPME using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber provided effective sample enrichment, and was carried out by fiber exposition at 60 degrees C for 45 min. The extracted isophorone was easily desorbed by fiber exposition in the injection port of a capillary GC-MS system, and carryover was not observed. Using this method, the calibration curve of isophorone was linear in the range 20-1000 pg/mL, with a correlation coefficient 0.9996 (n = 18), and the detection limit (S/N = 3) was 0.5 pg/mL. The HS-SPME/GC-MS method showed 25,000-fold higher sensitivity than the direct injection method (1 microL injection). The within-day and between-day precisions (relative standard deviations) at the concentration of 1 ng/mL isophorone were 3.9% and 6.1% (n=5), respectively. This method was successfully applied to the analysis of food samples without interference peaks. The recoveries of isophorone spiked into food sample were above 84% for a 50 or 500 pg/mL spiking concentration. The analytical results of the contents of isophorone in various food samples were presented.