Noise characteristics and instabilities of long Josephson junctions

Journal ArticleIn a magnetic field, current biased long Josephson junctions exhibit the dynamics of fluxon motion which are affected by fluctuations. These consist of telegraph noise at voltage steps and instabilities due to chaotic behavior. Results on long junctions with McCumber number fic ranging from 10 to 100 show such behavior. The telegraph noise is driven by thermal fluctuations. Modeling of our junctions using a perturbed sine-Gordon equation shows the chaotic regions and the periodic ones

Femtosecond dynamics of quasi-particles in YBa2Cu3O7-δ superconductor films

Journal ArticleWe have studied the transient electronic response of YBa2Cu30y . 5 epitaxialy grown HTC superconductor thin films in the femtosecond time domain, using transient photoinduced reflectivity (∆R) with 60 fsec time resolution. For temperatures T>TC only a bolometric signal was observed with ∆R>0. For T0. The results for T<TC are explained in terms of quasi-particle (QP) electronic response giving ∆R<0. Thus the femtosecond rise time is interpreted as avalanche multiplication of QP across the gap 2A and the subsequent picosecond relaxation as QP recombination. The QP optical response is explained within the two fluid model

Quasiparticle relaxation in a high-Tc superconductor

Journal ArticleRecent measurements by Eesley et al. [1] of transient reflectivity in superconducting Tl2Ba2Ca2Cu30io were interpreted as evidence for order-parameter relaxation in the vicinity of Tc, which was analyzed in terms of BCS weak coupling for A(r)/A(0). In this Comment we question this interpretation based on experimental evidence that laser pulse heating can mask the effect. Eesley et al. have shown [1] that the relaxation time TS in the superconducting state increases dramatically as TC is approached; a similar increase was observed previously in YBa2Cu307 [2,3] and in Bi2Sr2Ca2Cu20io [3]. From a detailed temperature dependence at various power levels Eesley et al. inferred [1] that in the temperature range (Tc ? T)/Tc ? 0.15 the relaxation time varies as rs oc T?(T)-1 with a BCS-type ?(T)/?(0), similar to that in the usual low-temperature superconductors [4]

Transient aeroelastic response control of a shipboard rotor during engagements by active Gurney flaps

No abstract available

The Circumstellar Extinction of Planetary Nebulae

We analyze the dependence of circumstellar extinction on core mass for the brightest planetary nebulae (PNe) in the Magellanic Clouds and M31. We show that in all three galaxies, a statistically significant correlation exists between the two quantities, such that high core mass objects have greater extinction. We model this behavior, and show that the relation is a simple consequence of the greater mass loss and faster evolution times of high mass stars. The relation is important because it provides a natural explanation for the invariance of the [O III] 5007 planetary nebula luminosity function (PNLF) with population age: bright Population I PNe are extinguished below the cutoff of the PNLF. It also explains the counter-intuitive observation that intrinsically luminous Population I PNe often appear fainter than PNe from older, low-mass progenitors.Comment: 12 pages, 2 figures, accepted for ApJ, April 10, 199

Loop Dynamics of Thymidine Diphosphate-Rhamnose 3\u27-\u3cem\u3eO\u3c/em\u3e-Methyltransferase (CalS11), an Enzyme in Calicheamicin Biosynthesis

Structure analysis and ensemble refinement of the apo-structure of thymidine diphosphate (TDP)-rhamnose 3\u27-O-methyltransferase reveal a gate for substrate entry and product release. TDP-rhamnose 3\u27-O-methyltransferase (CalS11) catalyses a 3\u27-O-methylation of TDP-rhamnose, an intermediate in the biosynthesis of enediyne antitumor antibiotic calicheamicin. CalS11 operates at the sugar nucleotide stage prior to glycosylation step. Here, we present the crystal structure of the apo form of CalS11 at 1.89 Å resolution. We propose that the L2 loop functions as a gate facilitating and/or providing specificity for substrate entry or promoting product release. Ensemble refinement analysis slightly improves the crystallographic refinement statistics and furthermore provides a compelling way to visualize the dynamic model of loop L2, supporting the understanding of its proposed role in catalysis

Publisher Correction: An engineered human Fc domain that behaves like a pH-toggle switch for ultra-long circulation persistence.

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