Thermomagnetic history effects in niobium and its implication for H c1 in highT c superconductors

The existence of a remanent magnetization (M _rem) on switching off the field of a field cooled (FC) sample of a highT _c superconductor is often reported. It has recently been argued thatM _rem should equal the difference in FC and zero field cooled (ZFC) magnetizations (M _FC —M _ZFC) in hard superconductors and this has been demonstrated to hold in single crystals of YBCO at 4.2K over a limited range ofH values. We report the detailed magnetization measurements under various thermomagnetic histories (of whichM _rem is one special case) on two specimens of Nb, which show different extents of flux trapping. We find that there are in general three regions inH, T space, corresponding toM _rem+M _ZFC−M _FC=0,M _rem<(M _FC−M _ZFC) andM _rem>(M _FC−M _ZFC). At anyT, the equality holds forH<H _c1(T), and forH→H _c2 (M _FC−M _ZFC) asymptotically vanishes and thereM _rem>(M _FC−M _ZFC). We show that there exists an intermediate region in all hard superconductors, whereM _rem<(M _FC−M _ZFC). The range over which this situation persists, however, depends on the degree of irreversibility in a sample. We can explain qualitatively all the history dependent magnetization data in terms of the critical state model. We point out an inconsistency in an earlier analysis to determineH _c1(T) from such data in YBCO. We also propose a new criterion for putting limits onH _c1(T) in hard superconductors.     

Cross-flow induced vibrations in a tube bank—Turbulent buffeting and fluid elastic instability

Experimental results are reported for a wind tunnel study of cross-flow induced vibrations in a tube bank. The rotated triangular array had a pitch ratio of 1·375 and consisted of 19 flexibly mounted tubes surrounded by 116 rigid, removable tubes. The natural frequency and damping of the flexibly mounted tubes could be carefully controlled. Details of the experimental facility and the vortex shedding behaviour of the tube bank were reported in the first of these two companion papers. The turbulent buffeting and fluid elastic response are treated in this second paper. The effects on the fluid elastic threshold of the motion of surrounding tubes, damping and number of upstream rows of tubes are discussed.     

The effect of the order of Gauss quadrature on the free vibrations of plates in fluid

In this paper two types of approach are used for the dynamic analysis of plates in fluid. The first approach is based on the classical thin plate theory. The second approach is based on the modified thin plate theory in which transverse shear has been included. The analysis also includes the compressibility effect of the fluid. The results obtained with the second approach are closer to the practical results than those obtained by any other approach provided both the shear and interaction matrices are evaluated with low-order Gauss quadrature. It is also shown that in problems of infinite regions the use of infinite elements coupled with finite elements not only gives accurate results but also economises on computation time and storage.     

Detection of the difference between two images: An improved method

The method for the detection of the difference between two images, proposed by the authors, can be modified to improve the signal/noise ratio. An amplitude distribution proportional to cos²? is obtained in the Fourier plane using three exposures in the ratio 1 : 2 : 1. In the neighbourhood of ? = Π/2 the gradient of this distribution is one order of magnitude inferior to that of cos? obtained with two equal exposures. Consequently a wider slit can be used as a filter. A further improvement can be obtained if the number of exposures is increased.     

Genetically encoded pH sensor for tracking surface proteins through endocytosis

Traffic cam: a tandem dye prepared from a FRET acceptor and a fluorogenic donor functions as a cell surface ratiometric pH indicator, which upon internalization serves to follow protein trafficking during endocytosis. This sensor was used to analyze agonist-dependent internalization of β(2)-adrenergic receptors. It was also used as a surrogate antigen to reveal direct surface-to-endosome antigen transfer between dendritic cells (not shown).     

Light outcoupling efficiency enhancement in organic light emitting diodes using an organic scattering layer

Crystallized 4,7‐diphyenyl‐1,10‐phenanthroline (BPhen) films deposited by convenient vacuum thermal evaporation technique have been found to be an efficient means to extract the substrate wave guided light in organic light emitting diodes (OLEDs). The optimized BPhen film working as organic scattering layer was successfully used with OLEDs for light outcoupling efficiency improvement. Enhancement of 26%, 15% and 6% in efficiency of the blue, green and red OLEDs were obtained, respectively. The achievement was found to be advantageous in terms of simplicity of fabrication method and feasibility for large area OLED applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new lithium alkoxide accelerated diastereoselective cyanation of ketones

[reaction: see text] A remarkably general lithium heteroatom assisted TMSCN or TBSCN addition to aldehydes and ketones has been discovered. The process provides excellent selectivities and high rates. Conformationally constrained ketones such as camphor, fenchone, and nopinone give excellent diastereoselectivities with TMSCN. Reduction of 2 provided diastereopure amino alcohol 3 in good yield. alpha- and beta-Methyl cyclohexanones with TBSCN-LiOR afford high diastereoselectivities and yields.