Stable barium compounds in YBa2Cu3Oy superconductors

The stability of various amounts of Ba₃Cu₃In₄O₁₂ (334) or BaTbO₃ (BTO) in a sintered YBa₂Cu₃O_y (YBCO) matrix was examined. Samples with added 334 or BTO exhibited critical temperatures (T_c) above 90 K for up to 20 vol.% addition and improved critical current densities (J_c) under a magnetic field. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analysis indicated that 334 and BTO did not react with the YBCO matrix under the sintering conditions used. The normalized J_c under a magnetic field of 1 T reached a maximum at 14 vol.% of 334 addition and 20 vol.% BTO addition. YBCO thin films with added BTO showed a gradual decrease in the T_c with increasing BTO content. YBCO films with added 334 showed a constant T_c of 87 K up to a 334 content of 4 vol.%.     

Total synthesis of cucurbitoside-like phenolic glycosides by double fluorous and acyl mixture synthesis

The first and simultaneous total syntheses of cucurbitosides A, B, G, and I, seguinosides C and D, and two unnatural analogs were achieved using the technique of fluorous mixture synthesis. The eight precursors of cucurbitoside-like phenolic glycosides were prepared by glycosylation of a mixture of two glucopyranosyl acceptors bearing different fluorous benzyl groups with a mixture of four apiofuranosyl donors bearing benzoyl, 3-methylbutyryl, 4-benzyloxybenzoyl, and 4-nitrobenzoyl groups, followed by a single run of HPLC with serially connected Fluophase^® RP and Inertsil^® ODS-3 columns. Finally, the individual pure disaccharide precursors were detagged to yield the eight cucurbitoside-like phenolic glycosides.     

Access to a stable Si2N2 four-membered ring with non-Kekulé singlet biradical character from a disilyne

The reactions of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with an equivalent amount of trans- and cis-3,3',5,5'-tetramethylazobenzenes produced a Si(2)N(2) four-membered ring biradicaloid [RSi(μ-NAr)(2)SiR] 2 (R = Si(i)Pr[CH(SiMe(3))(2)](2), Ar = 3,5-Me(2)C(6)H(3)), which was isolated as air- and moisture-sensitive dark purple crystals. Compound 2 displays no EPR signal, and the molecular structure of 2 was characterized by NMR spectroscopy and X-ray crystallography, revealing that 2 has a planar centrosymmetric Si(2)N(2) four-membered ring. The Si1-Si1' distance is 2.63380(9) ?, and there is no bond interaction between the Si1 and Si1' atoms of 2. The reactions of 2 with methanol and carbon tetrachloride show that 2 has both closed-shell and radical-type reactivity.     

Rapid detection of a cocaine-binding aptamer using biological nanopores on a chip

This paper describes a methodology for the rapid and highly selective detection of cocaine using a membrane protein channel combined with a DNA aptamer. The DNA aptamer recognizes the cocaine molecule with high selectivity. We successfully detected a low concentration of cocaine (300 ng/mL, the drug test cutoff limit) within 60 s using a biological nanopore embedded in a microchip.     

Tracking of the nuclear wavepacket motion in cyanine photoisomerization by ultrafast pump-dump-probe spectroscopy

Understanding ultrafast reactions, which proceed on a time scale of nuclear motions, requires a quantitative characterization of the structural dynamics. To track such structural changes with time, we studied a nuclear wavepacket motion in photoisomerization of a prototype cyanine dye, 1,1'-diethyl-4,4'-cyanine, by ultrafast pump-dump-probe measurements in solution. The temporal evolution of wavepacket motion was examined by monitoring the efficiency of stimulated emission dumping, which was obtained from the recovery of a ground-state bleaching signal. The dump efficiency versus pump-dump delay exhibited a finite rise time, and it became longer (97 fs → 330 fs → 390 fs) as the dump pulse was tuned to longer wavelengths (690 nm → 950 nm → 1200 nm). This result demonstrates a continuous migration of the leading edge of the wavepacket on the excited-state potential from the Franck-Condon region toward the potential minimum. A slowly decaying feature of the dump efficiency indicated a considerable broadening of the wavepacket over a wide range of the potential, which results in the spread of a population distribution on the flat S(1) potential energy surface. The rapid migration as well as broadening of the wavepacket manifests a continuous nature of the structural dynamics and provides an intuitive visualization of this ultrafast reaction. We also discussed experimental strategies to evaluate reliable dump efficiencies separately from other ultrafast processes and showed a high capability and possibility of the pump-dump-probe method for spectroscopic investigation of unexplored potential regions such as conical intersections.     

Thermogelation of amphiphilic poly(asparagine) derivatives

Thermoresponsive sol–gel transition polymers based on biodegradable poly(amino acid) were synthesized by the reaction of poly(succinimide) with dodecylamine and amino alcohols. The introduction of the hydrophobic amine into the thermoresponsive poly(amino acid)s induced the sol–gel transition in phosphate buffer saline. The effects of the side chain structure, molecular weight, concentration of the polymer, and the additives (inorganic salts and urea) in the solution on the thermoresponsive behaviors were systematically investigated. A relationship between the lowest critical solution temperature (LCST) in the dilute solution and the viscosity reduction of the concentrated solution upon heating was observed. The present poly(amino acid)s showing a thermoresponsive sol–gel transition in aqueous solutions possess immense potential as an injectable biodegradable hydrogel system for various biomedical applications. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and anti-human immunodeficiency virus activity of the skeleton isomers of 3',4'-Di-(O)-(-)-camphanoyl-(+)-khellactone

Optically active structural isomers (1b-f and dst-1b-f) of 3',4'-di-(O)-(-)-camphanoyl-(+)-khellactone (DCK) were synthesized and their anti-human immunodeficiency virus (HIV) activity was investigated. The value of the sensitivity index (SI) of 1b was greater than that of DCK.     

Intensity correlations of thermal light

We demonstrate measurement of normalized Glauber’s intensity correlation functions of different orders using an array photodetector. As the light source, we use a laser beam scattered by a rotating ground-glass disc, which has statistics close to that of thermal light. We compare the measurements of the normalized correlation functions to that of the difference-intensity variance and show that they are in a certain sense complementary. The independence of the variance measurement on the number of temporal modes has been demonstrated for the first time. Different versions of high-order ghost imaging are also realized and characterized quantitatively.     

Effect of irradiation distance on degradation of phenol using indirect ultrasonic irradiation method

Ultrasound is used as degradation of hazardous organic compounds. In this study, indirect ultrasonic irradiation method was applied to the degradation process of phenol, the model hazardous organic compound, and the effects of irradiation distance on radical generation and ultrasonic power were investigated. The chemical effect estimated by KI oxidation dosimetry and ultrasonic power measured by calorimetry fluctuated for the irradiation distance, and there was a relationship between the period of the fluctuation of ultrasonic effect and the wavelength of ultrasound. The degradation of phenol was considered to progress in the zero-order kinetics, before the decomposition conversion was less than 25%. Therefore, the simple kinetic model on degradation of phenol was proposed, and there was a linear relation in the degradation rate constant of phenol and the ultrasonic power inside the reactor. In addition, the kinetic model proposed in this study was applied to the former study. There was a linear relation in the degradation rate constant of phenol and ultrasonic energy in the range of frequency of 20-30 kHz in spite of the difference of equipment and sample volume. On the other hand, the degradation rate constant in the range of frequency of 200-800 kHz was much larger than that of 20-30 kHz in the same ultrasonic energy, and this behaviour was agreed with the former investigation about the dependence of ultrasonic frequency on chemical effect.