Vortical flow in thermo-acoustic devices

Taconis oscillation in a closed long tube with large thermal gradient is studied by numerical calculation of the 2D compressible Navier-Stokes equations. The both ends of tube are hot (T = T_H), and the center of side wall is cold (T = T_C). We analyze the pressure amplitude p_amp and the time averaged temperature T_m in the closed tube. p_amp is almost homogenous in the tube cross section, however, T_m is not homogenous in the central cold region. We also observe two steady states at the same temperature ratio θ = T_H/T_C. It is important to analyze the effects of the boundary layer in this cold region on Taconis oscillations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dispersion of gold nanoparticles above the poly(methyl methacrylate) surface by the use of fluoroalkyl end-capped oligomeric aggregates

Nanometer size-controlled gold particles were prepared under mild conditions by reducing the corresponding metal precursor in the presence of self-assembled molecular aggregates formed by fluoroalkyl end-capped N-(1,1-dimethyl-3-oxobutyl)acrylamide oligomers. The stable gold nanoparticles protected by these fluorinated molecular aggregates were applied to the dispersion above the poly(methyl methacrylate) film surface.     

Sampling measurement of soft-x-ray-pulse shapes by femtosecond sequential ionization of Kr+ in an intense laser field

We propose a sampling technique for measuring the shape of ultrashort soft-x-ray pulses. The technique uses the transient state of Kr+ ions that is produced by the femtosecond sequential evolution of Kr ions during optical-field-induced ionization as an ultrafast x-ray-absorption sampling gate. We demonstrate the technique by measuring the pulse shape of the 51st harmonic (15.6 nm) generated by a 100-fs titanium:sapphire laser pulse. The measured pulse duration is 220 fs. Our experimental result confirms that the sequential evolution of Kr+ ions from neutral Kr to Kr2+ is the dominant contribution to the ionization process from the aspect of time-domain measurement.     

Bemerkung über die Erstarrungszeit der umkehrbaren Sol-Gel-Umwandlung

Ohne Zusammenfassung Herrn Prof. Dr. Shun-ichiro Imamura, Kyoto Universit?t, sprechen wir an dieser Stelle für seine wertvollen Ratschl?ge unseren besten Dank aus.     

On the stability of Cartan embeddings of compact symmetric spaces

Dedicated to Professor Tadashi Nagano on his sixtieth birthday     

A characterization of ℵ1-free abelian groups and its application to the chase radical

A groupA is an ℵ₁-free abelian group iffA is a subgroup of the Boolean power Z^(B) for some complete Boolean algebraB. The Chase radicalvA=Σ{C≦A: Hom(C, Z)=0 &C is countable). The torsion class {A:vA=A} is not closed under uncountable direct products.