Studies on the chemical synthesis of potential antimetabolites. 30. Regioselective introduction of a chlorine atom into the imidazo[4,5-b]pyridine nucleus

Reactions of some imidazo[4,5-b]pyridine 4-oxides with phosphoryl chloride are described. Treatment of N-1-substituted imidazo[4,5-b]pyridine 4-oxides with phosphoryl chloride led to the predominant formation of 7-chloro derivatives. This feature was successfully applied to the preparation of a chloroimidazo[4,5-b]pyridine nucleoside, which served as an important precursor of 1-deazaadenosine.     

A novel kinetic method for the speciation of cadmium in river water by micro solvent extraction with dithizone.

Cadmium species in river water were kinetically extracted with dithizone by varying the extraction time. The obtained extraction curve showed a three-stage stepwise profile that reflected the rate of the ligand substitution reaction between the dithizone and cadmium species. Corresponding to each stage, we divided these extracted cadmium species into three groups: "highly labile", "moderately labile" and "slowly labile" species.     

Tris(2-methyl-8-quinolinolato)gallium(III) as a fluorescent probe for sensitive silanol-testing.

The peak shape of tris(2-methyl-8-quinolinolato)gallium(III) by reversed-phase high-performance liquid chromatography was found to be very sensitive to trace amounts of silanol groups on the surface of octadecylsylanized silica gel (ODS silica gel). The variation of the peak of the gallium(III) complex can be used as a probe of the residual silanol groups in an ODS column. The chromatographic peak parameters of the complex were compared with the silanol activities output by some silanol-detecting tests using nitrogen-containing compounds as probes. The comparison was performed with several commercially available ODS columns and laboratory-packed columns in which the amount of silanol groups was controlled by mixing fully endcapped ODS materials and a non-endcapped ODS material. The peak height was the most effective parameter among the peak parameters, and much more sensitive than the silanol-detecting tests using nitrogen-containing compounds, in detecting a trace amount of silanol groups that could not be detected by other silanol-detecting tests.     

Tris(2-methyl-8-quinolinolato)iron(III) as a novel spectrophotometric probe for silanol detection.

Tris(2-methyl-8-quinolinolato)iron(III) was proposed as a sensitive spectrophotometric silanol-detecting probe based on the coordination ability of silanol groups on the surface of octadecylsylanized silica gel (ODS silica gel) for reversed-phase high-performance liquid chromatography. A peak of the iron(III) complex on a chromatogram abruptly collapsed as the silanol content in an ODS column increased, indicating that the iron(III) complex could sense trace amounts of silanol groups. The change of the peak parameters, such as the peak height and the peak area was highly related to the output of some nitrogen-containing compounds used as silanol-detecting probes as a function of the silanol content in an ODS column. The response of the peak height of the iron(III) complex to the silanol content was much more sensitive than the response of the nitrogen-containing probes, and was comparable to that of tris(2-methyl-8-quinolinolato)gallium(III), which had been proposed as a fluorometric silanol-detecting probe based on the coordination ability of the silanol groups.     

Analysis of E1 and E2 radiative α-capture and giant multipole resonances

Experimental data on E1 and E2 radiative α-capture are analyzed by taking account of direct and semidirect processes as well as the compound process. Observed excitation functions for these reactions are reasonably well reproduced assuming the reactions take place mainly through giant multipole resonances. It is shown that the compound process dominates in the lower energy region especially for E1 capture whereas in the higher energy region direct and semidirect captures are the major processes especially for E2 capture. Several interesting results are obtained on α-particle spectroscopic factors of target ground states and on spreading widths and isospin-mixing coefficients of the giant multipole resonance states. The data are shown to be consistent with the existence of the isoscalar giant quadrupole resonances. The applicability of direct and semidirect capture theories to α-capture is examined.     

Blue-to-red chromatic sensor composed of gold nanoparticles conjugated with thermoresponsive copolymer for Thiol sensing

We describe the first determination of thiol compounds with gold nanocomposites composed of gold nanoparticles and thermoresponsive copolymers having polyamino groups. The gold nanocomposites, which are used as a chromatic sensor, reveal chromatic change from blue to red with thermal stimuli, heating followed by cooling the solution. The blue-to-red chromatic change results from disassembly of the gold nanocomposites, which arises from shrinkage of the thermoresponsive copolymers bound to the gold nanoparticle surfaces due to the phase transition induced by thermal stimuli. The disassembly is inhibited by addition of thiol compounds through displacement of the adhered thermoresponsive copolymers. The detached copolymers no longer influence morphological change of the gold nanocomposites. Corresponding with increase of concentration of the thiol compounds, a solution of the gold nanocomposites after the thermal stimuli shows chromatic change, which was quantified with the a* value in L*a*b* chromatic coordinates. A linear relationship between the a* value and concentration of cysteine, examined as a bio-important thiol, is obtained below 7x10(-6) mol dm(-3), estimating a detection limit defined as 3sigma of the blank to be 2.8x10(-7) mol dm(-3). The chromatic sensor of the gold nanocomposites is applied to the determination of cysteine in commercial supplements containing ascorbic acid, which seriously interferes with redox-based determination of cysteine. Analytical results obtained with the chromatic sensor are identical to those obtained with HPLC.     

Thermal-induced growth of gold nanoparticles conjugated with thermoresponsive polymer without chemical reduction

The growth of gold nanoparticles without chemical reduction of gold (III) ions was achieved by the disruption of thermoresponsive polymers conjugated with the gold nanoparticles through the phase transition of the polymers. When a solution of gold nanoparticles coated with thermoresponsive polymers was heated, chains of the thermoresponsive polymers were disrupted because of dehydration, resulting in the fusion of gold nanoparticles to form larger nanoparticles. The evolution of the extinction band around 550 nm evidenced the formation of these large (post-fusion) gold nanoparticles, which were characterized by transmission electron microscope (TEM) and dynamic light scattering (DLS). TEM images verified the formation of the large gold nanoparticles having particle sizes of 80-100 nm, whereas DLS indicated the existence of large nanoparticles with hydrodynamic diameters exceeding 200 nm. The deposition did not require the addition of reductants or trivalent gold ions for the formation of the large gold nanoparticles. Both the heating and the solution conditions were studied to elucidate the mechanism of the formation of large gold nanoparticles.     

Numerical analysis of a rib optical waveguide with trapezoidal cross section

Dispersion relations and field distributions in rib optical waveguides with several sizes of trapezoidal cross sections are investigated by using a new highly accurate numerical method, which is based on the Rayleigh principle and on the least-squares method.     

Typed Quantum Logic

The aim of this paper was to lift traditional quantum logic to its higher order version with the help of a type-theoretic method. A higher order axiomatic system is defined explicitly and then a sound and complete class of models is given. This is an attempt to provide a quantum counterpart of classical set theory or intuitionistic topos.