Line-shape parameters in infrared bands of sulfur dioxide

This paper presents the calculated results for line-shape parameters in the v₁ and v₃ bands of sulfur dioxide for temperatures between 300 and 1200°K, together with the self-broadening coefficients for some particular rotational lines. The Anderson-Tsao-Curnutte theory was applied to calculate the line half-widths, and a criterion was introduced to determine the line-shape parameters on the basis of a narrow-band model. The calculated results are greatly different from previously assumed values.     

Unconditionally secure key distribution based on two nonorthogonal states

We prove the unconditional security of the Bennett 1992 protocol, by using a reduction to an entanglement distillation protocol initiated by a local filtering process. The bit errors and the phase errors are correlated after the filtering, and we can bound the amount of phase errors from the observed bit errors by an estimation method involving nonorthogonal measurements. The angle between the two states shows a trade-off between accuracy of the estimation and robustness to noises.     

Hydrodynamic radius and intrinsic viscosity of polystyrene in the crossover region from θ to good-solvent conditions

The radius of gyration R_g, the hydrodynamic radius R_h, and the intrinsic viscosity [η] have been measured for polystyrene in cyclohexane (at the θ temperature and 44.5°C), 2-butanone (at 30°C), and toluene (at 30°C) in the molecular weight range 2.38 × 10⁵ ≤ M_w ≤ 5.47 × 10⁶ to elucidate the excluded-volume effects on dynamical behavior in dilute polymer solutions in the crossover region from θ to good-solvent conditions. The results are compared with theoretical predictions of current thermal blob theories and the Pade approximant theory of Tanaka. It is found that the ratio of R_h/R_g decreases with an increase in the excluded-volume effect, following the prediction of the simple blob theory, but that its magnitude is about 15% higher than the theoretical value. Experimental variation of [η] with R_h and/or R_g lies in between predictions of the scaling law and the Pade approximant. The concentration dependence of the diffusion coefficient is also compared with predictions of current theories.     

Chemoselective oxidation with molybdenum catalyst-t-butyl hydroperoxide

Benzyltrimethylammonium tetrabromooxomolybdate is an excellent chemoselective catalyst to oxidize secondary alcohols to ketones, primary alcohols to esters, and aldehydes to acids or esters with t-butyl hydroperoxide.     

Towards beyond-1 GHz solution NMR: internal 2H lock operation in an external current mode

We have commenced a project to develop a beyond-1 GHz solution NMR spectrometer using a HTS coil. Due to a small residual resistance present in the HTS conductor and joint resistance between conductors, a stable persistent current sufficient for NMR measurements is unlikely. Therefore, a current has to be supplied to the HTS coil from an external power supply. The ripple of an external power supply causes a field fluctuation which must be stabilized. In this study we show results of NMR measurements using a 500-600 MHz NMR in such an external current mode: the field fluctuations are stabilized by an internal 2H lock. The field fluctuation from the external power supply comprises a major field fluctuation component at low frequencies, 0.003-0.005 Hz, and superimposed minor field ripples at 2 Hz and 50 Hz. The former limits the time interval of the internal 2H lock, while the latter generates sidebands in the NMR spectrum. Sideband and baseline noise are controlled by appropriate selection of the feedback loop parameters of the lock. The quality of the 1D-solution NMR spectra observed in external current mode is equivalent to that obtained in persistent current mode. However, if the feedback loop time is as short as the gradient pulse width, refocusing of the NMR signal is lost and NMR peaks disappear. The 2D-NOESY and the 2D-HSQC spectra of ubiquitin in an external current mode have been acquired. The quality of the 2D spectra is equivalent to those obtained in persistent current mode; i.e. the internal 2H lock operates stably over an experimental time interval of 40-50 min. To realize a beyond-1 GHz NMR spectrometer, further investigations must be made of (i) the long term stability of a DC power supply, (ii) the enhancement of the compensation field limit for the internal 2H lock, (iii) the extension of the helium refill time interval, and (iv) a method to correct the field homogeneity in the external current mode.     

Total synthesis of the hallucinogenic neoclerodane diterpenoid salvinorin A

Total synthesis of salvinorin A (1), a neoclerodane diterpenoid having the most potent hallucinogenic activity and a selective kappa-opioid agonist, was completed in 20 steps starting from enantiomerically pure hydroxy-Wieland-Miescher ketone 5.     

Development of low cost pulmonary surfactants composed of a mixture of lipids or lipids-peptides using higher aliphatic alcohol or soy lecithin

The artificial pulmonary surfactant composition in the present study is characterized by a lipid mixture system composed of higher aliphatic alcohol, egg yolk phosphatidylcholine (egg PC), soy lecithin and higher aliphatic acid as the major components or a peptide-lipid mixture system composed of a combination of the lipid mixture system to which a peptide is added. Three peptides with amphiphilic surface-staying, membrane spanning, and both properties were designed and synthesized. The evaluation of pulmonary surfactant assay was performed by a hysteresis curve drawn upon the measurement for the surface tension-area curve with the Wilhelmy surface tensometer in vitro and the recovery of lung compliance for the pulmonary surfactant-deficient rat models in vivo. Lipid-mixture systems composed of octadecanol or soy lecithins containing no peptide were favorable hysteresis curves as compared with commercially available Surfacten((R)), but were not prominent. The peptide-lipid mixture systems composed of a combination of the lipid mixture of alkyl alcohol or soy lecithin to which peptides designed were added were desirable hysteresis curves similar to Surfacten((R)) and amphiphilic Hel 13-5 peptide-lipids mixture systems were much more effective than the lipid mixture system. Particularly, the recovery of lung compliance treated with hydrogenated soy lecithin-fractionated soy lecithin PC70-palmitic acid-peptide Hel 13-5 (40:40:17.5:2.5, w/w) was comparable to that with Surfacten((R)). Because the artificial pulmonary surfactant compositions of this study can be prepared at lower costs, they are useful for the treatment of respiratory distress syndrome and acute respiratory distress syndrome as well as for inflammatory pulmonary diseases, dyspnea caused by asthma, etc.