The Kelvin-Helmholtz Instability (KHI) can drive waves at the magnetopause. These waves can grow to form rolled-up vortices and facilitate transfer of plasma into the magnetosphere. To investigate ...the persistence and frequency of such waves at the magnetopause we have carried out a survey of all Double Star 1 magnetopause crossings, using a combination of ion and magnetic field measurements. Using criteria originally used in a Geotail study made by Hasegawa et al. (2006) (forthwith referred to as H2006), 17 candidate events were identified from the entire TC-1 mission (covering 623 orbits where the magnetopause was sampled), a majority of which were on the dayside of the terminator. The relationship between density and shear velocity was then investigated, to identify the predicted signature of a rolled up vortex from H2006 and all 17 events exhibited some level of rolled up behavior. The location of the events had a clear dawn-dusk asymmetry, with 12 (71 %) on the post noon, dusk flank suggesting preferential growth in this region.
Abstract
The reinforcing effects of zeolites in poly(dimethylsiloxane) (PDMS) elastomers were characterized using two preparative approaches. In the first, end-functionalized polymer chains were ...blended into the zeolite, and were then endlinked into the required network structure. The second approach represented an attempt to force some chains through the cavities, by blending the monomer itself into the zeolite and then polymerizing it to obtain the PDMS elastomer. The two types of zeolite-filled PDMS were characterized using stress-strain measurements in elongation, equilibrium swelling, and small-angle X-ray scattering. The second synthetic approach did seem to give improvements in mechanical properties, particularly when the average cavity size of the zeolite particles was relatively large. Ascribing the observed improvements in reinforcement at least partly to the threading of some PDMS chains through the zeolites was supported by the results obtained in the swelling and scattering experiments.
High quality poly（5-cyanoindole） （P5CI） films were electrosynthesized by direct anodic oxidation of 5-cyanoindole on stainless steel sheet in the mixed electrolytes of boron trifluoride diethyl ...etherate （BFEE） and diethyl ether （EE） （by volume 1：1） ＋ 0,05 mol L^-1 Bu4NBF4. The film formed can be peeled off the electrode into freestanding films, The addition of EE into BFEE can improve the solubility of monomer. P5CI films obtained from this medium showed excellent electrochemical behavior with conductivity of 10^-2 S cm^-1, Structural studies showed that the polymerization of 5-cyanoindole occurred at the 2,3 position. As-formed P5CI films were thoroughly soluble in strong polar organic solvent dimethyl sulfoxide （DMSO） while partly soluble in tetrahydrofuran （THF） or acetone. Fluorescence spectral studies indicated that P5CI was a good blue-ight emitter.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The Kelvin-Helmholtz (K-H) instability of a tangential discontinuity in compressible plasmas is reexamined within the framework of a linear MHD treatment. The properties of the surface modes for ...general plasma conditions are characterized, providing a full description of the wave properties, including the critical velocities, linear growth rates, wave vectors, and phase velocities. Previous work in the area is reviewed. The dispersion relation is solved, pointing out that there are two kinds of unstable surface waves called fast and slow waves. It is shown that both waves are K-H unstable over limited ranges of relative flow speeds between the lower and upper critical velocities. Both critical velocities and growth rates are evaluated numerically for some typical parameters. It is also shown that if the flow speed exceeds the upper critical velocity of the fast wave, the wave vector of the fast wave changes from complex to real, reflecting a change of the unstable fast surface wave into stable MHD body waves.
The title compound, C 20 H 12 F 6 N 2 S 2 , is a new asymmetric photochromic diarylethene which contains 3-thienyl substituents. The distance between the two reactive C atoms in the molecule is 3.677 ...(8) Å. The dihedral angles between the central cyclopentene ring and the two thiophene rings are 47.6 (2) and 49.2 (2)°.
