Flow Friedel–Crafts alkylation of 1-adamantanol with arenes using HO-SAS as an immobilized acid catalyst

In this communication flow Friedel–Crafts alkylation was studied using hydroxy-substituted sulfonic acid-functionalized silica as a catalyst and 1-adamantanol as a model substrate. The reaction of 1-adamantanol ( 1a ) with toluene ( 2a ) proceeded well with 5 min of residence time at 120°C to give good yield of 1-tolyladamantane ( 3a ) as a 1:9 mixture of meta and para isomers. When the flow synthesis was carried out over 2.5 hr of running time, the collected five fractions contain the product 3a in 97–92% yields, suggesting the durability of the catalyst.     

A rosette cooling cell: More effective container for solubilization of single-walled carbon nanotubes under probe-type ultrasonic irradiation

Probe-type ultrasonication has been employed for surfactant-aided solubilization, or individualization, of single-walled carbon nanotubes (SWNTs). The resulting solution can be used not only for spectroscopic analyses such as absorption, photoluminescence, and circular dichroism, but also for separation by density gradient ultracentrifugation, dielectrophoresis, chromatography, and polymer wrapping. In spite of its importance, the sonochemical processing of SWNTs has not been considered seriously. Herein, we report on a more efficient cooling cell for probe-type ultrasonication. As compared with a conventional cylindrical cell, the concentration of the SWNTs solubilized in water was found to be almost double in a rosette cooling cell after ultracentrifugation. The efficiency of a rosette cell can be attributed to the higher efficiency in circulation and cooling of the SWNT dispersion as well as enhancement of the cavitation process.     

Modification of the physicochemical properties of minocycline hydrochloride ointment with cyclodextrines for optimum treatment of bedsore

Modification to find the best physicochemical properties of minocycline hydrochloride ointment for optimum treatment of bedsore was investigated by coformulating various types of cyclodextrins (CyD) in the ointment base. It was found that the drug release rate from the ointment base was modified according to the preparation method of ointment base and the type of CyD admixed. The physicochemical properties, such as viscosity, elution volume, water absorption of ointment base were also modified by those factors. The mechanism of physicochemical modification with CyD was explained by the structural change of ointment base and the change of surface tension of emulsifying agent solution with the CyD. The stability of ointment was investigated by confirming the reproducibility of drug release rate after storage at ambient and cooled temperature conditions. In conclusion, a fused mixed ointment with beta-CyD was found to be preferable for treatment of bedsore, because of the improved drug release rate, lowered viscosity and increased elution volume of the resultant ointment.     

Superconductor-insulator transition in a two-dimensional array of resistively shunted small josephson junctions

Using a scattering technique based on a parametrized linear combination of atomic orbitals Hamiltonian, we calculate the ballistic quantum conductance of multiwall carbon nanotubes. We find that interwall interactions not only block some of the quantum conductance channels, but also redistribute the current nonuniformly over individual tubes across the structure. Our results provide a natural explanation for the unexpected integer and noninteger conductance values reported for multiwall nanotubes by Stefan Frank et al. [Stefan Frank et al., Science 280, 1744 (1998)].     

Ion-extraction by a crown ether with a photoresponsive carboxylate cap.

A new photoresponsive crown ether (I) with an azobenzene-4-oxyacetate function was synthesized. The photo-isomerized cis-(1) extracted K⁺ ion more selectively than trans-(I) and the thermal cis-trans isomerization was suppressed by added metal ions.     

Redox-switched crown ethers monocrown-biscrown interconversion coupled with redox of a thiol-disulfide couple

To give a redox-switch function to crown ethers, 4′-mercaptomono-benzo-15-crown-5 (CrSH) and its oxidized disulfide form (CrSSCr) were synthesized. The solvent extraction proved that the ion affinity of CrSH is generally greater than that of CrSSCr.     

A copper-free Sonogashira coupling reaction in ionic liquids and its application to a microflow system for efficient catalyst recycling

[reaction: see text] The PdCl2(PPh3)2-catalyzed Sonogashira coupling reaction, in good to high yields, was performed in an ionic liquid ([BMIm][PF6]) in the absence of a copper salt. The use of an ionic liquid allows for the facile separation and recycling of the catalyst. The application of the above reaction in a microflow system in conjunction with an IMM micromixer was also successful.     

Preferential extraction of left- or right-handed single-walled carbon nanotubes by use of chiral diporphyrin nanotweezers

Handedness- and diameter-based separation of single-walled carbon nanotubes was achieved through preferential extraction of 76-CoMoCAT with 2,6-pyridylene-bridged chiral diporphyrin nanotweezers.     

Band-structure-dependent demagnetization in the Heusler alloy Co₂Mn(1-x)FexSi

We investigate the ultrafast demagnetization for two Heusler alloys (Co?Mn(1-x)FexSi) with a different lineup of the minority band gap and the Fermi level. Even though electronic spin-flip transitions are partially blocked by the band gap in one compound, the respective magnetization dynamics, as measured by the time-resolved Kerr effect, are remarkably similar. Based on a dynamical model that includes momentum and spin-dependent carrier scattering, we show that the magnetization dynamics are dominated by hole spin-flip processes, which are not influenced by the gap.