Turbulence in boundary flow of superfluid 4He triggered by free vortex rings

The transition to turbulence in the boundary flow of superfluid 4He is investigated using a vortex-free vibrating wire. At high wire vibration velocities, we found that stable alternating flow around the wire enters a turbulent phase triggered by free vortex rings. Numerical simulations of vortex dynamics demonstrate that vortex rings can attach to the surface of an oscillating obstacle and expand unstably due to the boundary flow of the superfluid, forming turbulence. Experimental investigations indicate that the turbulent phase continues even after stopping the injection of vortex rings, which is also confirmed by the simulations.     

Oligodeoxyribonucleotide synthesis by use of S,S-diphenyl deoxyribonucleoside 3'-phosphorodithioates and bifunctional condensing reagents in the phosphotriester approach

Four kinds of arenedisulphonyl chlorides as condensing reagents for oligodeoxyribonucleotide synthesis have been synthesised and their condensing abilities were examined in the synthesis of thymidylyl(3'-5') thymidine. Among them, mesitylenedisulphonyl chloride (MDS) and isodurenedisulphonyl chloride (DDS) proved to be effective for condensation and for separation of the product from the 5'-sulphonated by-product formed simultaneously. This paper describes detailed studies on the selective removal of one of two phenylthio groups by means of phosphinates from S,S-diphenyl deoxyribonucleoside 3'-phosphorodithioate derivatives, which were successfully used as the starting building units for the liquid phase synthesis of a dodecadeoxyribonucleotide, dCATTATTAATAC.     

Magnetic two-dimensional system: Manganese stearate

Magnetic susceptibility of a quasi two-dimensional magnet manganese stearate is measured between 0.05 – 80 K by a Hartshorn bridge method. The molar susceptibility follows the Curie-Weiss law in high temperature range: χ_m = 4.8/ (T + 40) (emu/mol). A transition to weak-ferromagnetic ordered state occurs at about 0.5 K, where the susceptibility maximum is observed. _χH + σ measured by the use of SQUID magnetometer indicates the appearance of spontaneous magnetization below 0.5 K. A preliminary study of a monolayer structure gives a shift of the maximum of _χH + σ to about 0.3 K.     

Phosphotriester approach to oligothymidylate synthesis utilizing a simple thymidine unit and a new type of condensing agents

DMTrTp(SPh)₂ was proposed as a simplest “nucleotide unit” for the synthesis of olygothymidylates. One phenylthio group was removed selectively and rapidly from dithiol-esters by 1 M pyridinium hypophosphonate. Two kinds of arenedisulfonyl chlorides were newly prepared and utilized as promising condensing agents.