Palladium(0)-catalyzed tandem cyclization of allenenes: direct construction of tricyclic heterocycles through aromatic C--H activation

Palladium(0)-catalyzed tandem cyclization of allenenes is described. Treatment of allenenes with an aryl halide, potassium carbonate, and catalytic [Pd(PPh(3))(4)] in dioxane afforded tri- or tetracyclic heterocycles in moderate to good yields through insertion of arylpalladium(II) halide into the allenic moiety, intramolecular carbopalladation, and aromatic C--H bond activation. The substituent on the olefin terminus has proven to be essential for the success of the tandem cyclization. The reaction with heterocyclic aryl halides such as iodopyrazine or 4-bromo-1-methylindole afforded tri- or tetracyclic heteroaromatic products in good yields.     

Regioselective photolabeling of glycoprotein A in membranes

We have developed a chemical method for directly identifying the amino acid residues of the transmembrane domain of a protein that are located right in the center of the membrane. Glycophorin A (GPA), the major sialoglycoprotein of human erythrocytes, was the first membrane protein whose primary sequence was elucidated, but its three-dimensional structure is still not known. GPA has been reconstituted into liposomes formed from dimyristoylphosphatidylcholine, dimyristoylphosphatidylserine, cholesterol, and a bola-amphiphilic phospholipidic photoactivatable probe (radioactive probe 1) by a detergent-mediated method. Electron microscopy confirmed the formation of spherical vesicular structures, and sucrose-density gradients revealed that the proteoliposomes comprised only one membrane fraction. Proteinase-K digestion of GPA in the proteoliposomes suggested that the orientation of GPA in reconstituted proteoliposomes was virtually identical to that observed in natural erythrocyte membranes. After photo-irradiation of the reconstituted proteoliposomes and in situ tryptic digestion, the photolabeled amino acid residues were analyzed by Edman degradation and their radioactivity was measured. Val80 and Met81, which had been assumed to be located near the center of the transmembrane domain of GPA, were indeed highly selectively photolabeled by probe 1. The new method might be applied to analyze the three-dimensional arrangement of the transmembrane domain of protein complexes that are made up from several subunits.     

Magnetoresistance of untwinned YBa(2)Cu(3)O(y) single crystals in a wide range of doping: anomalous hole-doping dependence of the coherence length

Magnetoresistance (MR) in the a-axis resistivity of untwinned YBa(2)Cu(3)O(y) single crystals is measured for a wide range of doping ( y = 6.45-7.0). The y dependence of the in-plane coherence length xi(ab) estimated from the fluctuation magnetoconductance indicates that the superconductivity is anomalously weakened in the 60-K phase; this observation, together with the Hall coefficient and the a-axis thermopower data which suggest the hole doping to be 12% for y approximately equal to 6.65, gives evidence that the origin of the 60-K plateau is the 1/8 anomaly. At high temperatures, the normal-state MR data show signatures of the Zeeman effect on the pseudogap in underdoped samples.     

Low-temperature electronic heat transport in La2-xSrxCuO4 single crystals: unusual low-energy physics in the normal and superconducting states

The thermal conductivity kappa is measured in a series of La2-xSrxCuO4 (0 < or = x < or = 0.22) single crystals down to 90 mK to elucidate the evolution of the residual electronic thermal conductivity kappa(res), which probes the extended quasiparticle states in the d-wave gap. We found that kappa(res)/T grows smoothly, except for a 1/8 anomaly, above x approximately 0.05, and shows no discontinuity at optimum doping, indicating that the behavior of kappa(res)/T is not governed by the metal-insulator crossover in the normal state; as a result, kappa(res)/T is much larger than what the normal-state resistivity would suggest in the underdoped region, which highlights the peculiarities in the low-energy physics in the cuprates.     

Spectral Based Color Correction Technique Compatible with Standard RGB System

A spectral turn method is presented as a spectral based color correction method compatible with the standard RGB system by applying the idea of a multi-spectral method. The multi-spectral based color reproduction technique has been proposed for providing independent color of device and viewing conditions. However, it is difficult to replace the RGB devices with high cost multi-spectral devices since the latter have advanced only to the laboratory level. In the proposed method, the standard RGB values are converted into spectral information, then returned to RGB values for different viewing conditions. This process provides more accurate reproduction than the conventional forward process of the color reproduction. An experiment of psychophysical color matching was performed to evaluate the technique. The mixed chromatic adaptation model was applied to the method in the experiment, and the results showed the effectiveness of the proposed method.     

Analog Integrated Circuit for Motion Detection against Moving Background Based on the Insect Visual System

A network for displaying the velocity signal of a target edge which has larger velocity than the background was proposed and designed based on an insect visual system. In the insect visual system, the velocity signals generated by the background are inhibited by the signals generated by averaging the velocity signals from each cell and can only display the velocity signals of the target. The proposed network was constructed with simple analog circuits. The measured results of the test chip fabricated with the 1.2$mUm complementary metal-oxide-semiconductor (CMOS) process showed that the edge detection circuit inserted to the first stage of the proposed network can detect the edge position. It was apparent from the measured results of the test circuit constructed with discrete metal-oxide-semiconductor (MOS) transistors that the proposed unit circuit constructing the network can generate the velocity signals by inputting the edge signals. The results with the simulation program with integrated circuit emphasis (SPICE) showed that the proposed network can only display the velocity signals of the target edges but not those of the background. Thus, it was clarified that the various motion directions of the target can be detected independent of the background by using the proposed network.