Non-catalyzed addition of heterocyclic thiols and 5-substituted-1H-tetrazoles to vinyl ethers

The alkylation of 1-substituted 1H-tetrazole-5-thiols and 4-substituted 4 H-1,2,4-triazole-3-thiols with alkyl halides or sulfonates lead to the formation of S-alkylated products regardless of the substituent on the heterocycle. In this work, we found that substituted 1H-tetrazole-5-thiols and 4 H-1,2,4-triazole-3-thiols readily reacted with vinyl ethers in the absence of a catalyst to exclusively form N-substituted 1H-tetrazole-5(4H)-thiones and 1H-1,2,4-triazole-5(4H)-thiones, respectively. Furthermore, the reactions of 5-substituted-1H-tetrazoles with vinyl ethers under the same conditions selectively yielded 2,5-disubstitued tetrazoles.     

Synthesis of spiroindenyl-2-oxindoles by montmorillonite K-10-catalyzed tandem Friedel-Crafts alkenylation/hydroarylation of propargylic alcohols with sterically hindered and electron-rich arenes

Various spiroindenyl-2-oxindoles have been synthesized in a one-pot reaction from isatin-derived propargylic alcohols with sterically hindered and electron-rich arenes such as 2-phenylindole and 1,3,5-trimethoxybenzene. The reaction involved montmorillonite K-10-catalyzed tandem Friedel-Crafts alkenylation and a following hydroarylation of an allene intermediate.     

Parallel capillary-tube-based extension of thermoacoustic theory for random porous media

Thermoacoustic theory is extended to stacks made of random bulk media. Characteristics of the porous stack such as the tortuosity and dynamic shape factors are introduced into the thermoacoustic wave equation in the low reduced frequency approximation. Basic thermoacoustic equations for a bulk porous medium are formulated analogously to the equations for a single pore. Use of different dynamic shape factors for the viscous and thermal effects is adopted and scaling using the dynamic shape factors and tortuosity is demonstrated. Comparisons of the calculated and experimentally derived thermoacoustic properties of reticulated vitreous carbon and aluminum foam show good agreement. A consistent mathematical model of sound propagation in a random porous medium with an imposed temperature is developed. This treatment leads to an expression for the coefficient of the temperature gradient in terms of scaled cylindrical thermoviscous functions.     

State-dependent doubly weighted stochastic simulation algorithm for automatic characterization of stochastic biochemical rare events

In recent years there has been substantial growth in the development of algorithms for characterizing rare events in stochastic biochemical systems. Two such algorithms, the state-dependent weighted stochastic simulation algorithm (swSSA) and the doubly weighted SSA (dwSSA) are extensions of the weighted SSA (wSSA) by H. Kuwahara and I. Mura [J. Chem. Phys. 129, 165101 (2008)]. The swSSA substantially reduces estimator variance by implementing system state-dependent importance sampling (IS) parameters, but lacks an automatic parameter identification strategy. In contrast, the dwSSA provides for the automatic determination of state-independent IS parameters, thus it is inefficient for systems whose states vary widely in time. We present a novel modification of the dwSSA--the state-dependent doubly weighted SSA (sdwSSA)--that combines the strengths of the swSSA and the dwSSA without inheriting their weaknesses. The sdwSSA automatically computes state-dependent IS parameters via the multilevel cross-entropy method. We apply the method to three examples: a reversible isomerization process, a yeast polarization model, and a lac operon model. Our results demonstrate that the sdwSSA offers substantial improvements over previous methods in terms of both accuracy and efficiency.     

A simple and rapid detection of viral protein using RNA oligonucleotide in a biosensor

The monitoring of non-structural viral protein 3 (NS3) has been of considerable interest in developing simple and reliable methods for detection of hepatitis C virus (HCV) for applications in diagnostic medicine. Although enzyme-linked immunosorbent assay (ELISA) is the most general method in HCV detection, using antibody brings problems. This method is temperature-sensitive and requires specific reactions condition. In addition, secondary antibody conjugated with enzyme and fluorescent dye is required. To overcome these bottlenecks, we designed a streptavidin-biotin conjugation method, namely, the RNA oligonucleotide sensor system that could monitor viral protein with detection limit of 500 pg/mL by using biotin-tagged RNA oligonucleotide in forteBio??s Octet optical biosensor system. In this study, we proposed an efficient method for simple and convenient detection of HCV viral protein, with the advantage of target specific monitoring.     

Effect of acute and fractionated irradiation on hippocampal neurogenesis

Ionizing radiation has become an inevitable health concern emanating from natural sources like space travel and from artificial sources like medical therapies. In general, exposure to ionizing radiation such as γ-rays is one of the methods currently used to stress specific model systems. In this study, we elucidated the long-term effect of acute and fractionated irradiation on DCX-positive cells in hippocampal neurogenesis. Groups of two-month-old C57BL/6 female mice were exposed to whole-body irradiation at acute dose (5 Gy) or fractional doses (1 Gy × 5 times and 0.5 Gy × 10 times). Six months after exposure to γ-irradiation, the hippocampus was analyzed. Doublecortin (DCX) immunohistochemistry was used to measure changes of neurogenesis in the subgranular zone (SGZ) of the hippocampal dentate gyrus (DG). The number of DCX-positive cells was significantly decreased in all acute and fractionally irradiation groups. The long-term changes in DCX-positive cells triggered by radiation exposure showed a very different pattern to the short-term changes which tended to return to the control level in previous studies. Furthermore, the number of DCX-positive cells was relatively lower in the acute irradiation group than the fractional irradiation groups (approximately 3.6-fold), suggesting the biological change on hippocampal neurogenesis was more susceptible to being damaged by acute than fractional irradiation. These results suggest that the exposure to γ-irradiation as a long-term effect can trigger biological responses resulting in the inhibition of hippocampal neurogenesis.     

Preparation and characterization of crosslinked proton conducting membranes based on chitosan and PSSA-MA copolymer

Proton conducting crosslinked complex membranes were prepared by blending of a cationic polyelectrolyte, i.e. chitosan (CS) and an anionic polyelectrolyte, i.e. poly(4-styrenesulfonic acid-co-maleic acid) (PSSA-MA). In particular, the dual function of PSSA-MA as a crosslinker and a proton conductor is described. The esterification reaction between –OH of CS and –COOH of PSSA-MA and the complex formation of NH₃⁺ of CS and SO₃^? of PSSA-MA were confirmed using FT-IR spectroscopy. The ion exchange capacity (IEC) of membranes continuously increased with PSSA-MA concentrations, resulting from the increase of ionic groups. However, the membranes exhibited the minimum values of proton conductivity and water uptake at 50–67 wt.% of PSSA-MA due to the effect of crosslinking and complex formation. In addition, a maximum of Young's modulus was achieved at 50 wt.% of PSSA-MA, as revealed by universal testing machine (UTM). Thermogravimetric analysis (TGA) showed that the thermal stability of membranes increased with increasing PSSA-MA concentrations and was the highest at 50 wt.% of PSSA-MA.     

Effect of ethylene carbonate concentration on the conductivity of carbonate-based electrolytes with LiPF6 for Li-ion batteries

A four-probe pouch-type cell was used to study the influence of carbonate-based electrolyte composition on the total conductivity of polyolefin separator impregnated with electrolyte through the electrochemical impedance spectroscopy. A frequency dispersion of separator with electrolyte is found to be dependent on the volume ratio of ethylene carbonate and ethyl methyl carbonate in an electrolyte solution. The origin of high- and low-frequency relaxation processes obtained from the impedance spectra is discussed. A correlation between the direct current resistance of separator with electrolyte and dissociation degree of electrolyte salt is found.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.