Phase-Slip Statistics of a Single Isolated Flux-Biased Superconducting Ring.

We describe measurements of the thermally activated transitions between fluxoid states of a single isolated superconducting ring. We compare these measurements with theoretical predictions in which all of the relevant parameters are determined via independent characterization of the same ring. This no-free-parameters comparison shows qualitative agreement over a wide range of temperatures. We discuss possible origins for the remaining discrepancies between the data and theory, in particular the choice of model for the superconducting order parameter's damping.

Fatigue in Sjogren's syndrome: relationship with fibromyalgia, clinical and biologic features.

More than two third of patients with primary Sjögren's syndrome (SS) report fatigue. Despite its clinical relevance, only a few studies have examined the relationship of fatigue with the presence of an overlapping Fibromyalgia (FM) and other clinical and biological variables. The aim of this study was to assess the relationship between fatigue and SS disease activity and damage, FM, widespread pain, and mood disorders; finally, the possible correlation between fatigue and a panel of cytokines likely to drive the immunopathological process of the disease has been examined. Thirty-five female patients with primary SS were consecutively enrolled; for each patient the Sjögren's Syndrome Disease Damage Index (SSDDI) and the Sjögren's Syndrome Disease Activity Index (SSDAI) were calculated. Patients rated pain, fatigue and disease activity using a 100-mm VAS and completed Health Assessment Questionnaire (HAQ), the Zung depression (ZSDS) and anxiety scales (ZSAS). 30/35 patients (85.7%) felt unduly tired and the same percentage of patients suffered with pain in more than one area of the body. 7 patients satisfied ACR criteria for FM, representing 20% of the whole cohort and 23% of SS patients with fatigue. No differences were found in disease duration, SSDDI, SSDAI, ZSDS and ZSAS among SS patient with or without FM. In the whole group, fatigue VAS correlated with HAQ, ZSAS, ZSDS and pain VAS but not with age, disease duration, presence and severity of arthritis, SSDDI, SSDAI, or cytokines. In conclusion, an overlapping FM can contribute to, but does not entirely account for fatigue in Italian patients with primary SS.

Deterministic phase slips in mesoscopic superconducting rings.

The properties of one-dimensional superconductors are strongly influenced by topological fluctuations of the order parameter, known as phase slips, which cause the decay of persistent current in superconducting rings and the appearance of resistance in superconducting wires. Despite extensive work, quantitative studies of phase slips have been limited by uncertainty regarding the order parameter's free-energy landscape. Here we show detailed agreement between measurements of the persistent current in isolated flux-biased rings and Ginzburg-Landau theory over a wide range of temperature, magnetic field and ring size; this agreement provides a quantitative picture of the free-energy landscape. We also demonstrate that phase slips occur deterministically as the barrier separating two competing order parameter configurations vanishes. These results will enable studies of quantum and thermal phase slips in a well-characterized system and will provide access to outstanding questions regarding the nature of one-dimensional superconductivity.

Fabrication and characterization of large arrays of mesoscopic gold rings on large-aspect-ratio cantilevers.

We have fabricated large arrays of mesoscopic metal rings on ultrasensitive cantilevers. The arrays are defined by electron beam lithography and contain up to 10(5) rings. The rings have a circumference of 1 µm, and are made of ultrapure (6N) Au that is deposited onto a silicon-on-insulator wafer without an adhesion layer. Subsequent processing of the SOI wafer results in each array being supported at the end of a free-standing cantilever. To accommodate the large arrays while maintaining a low spring constant, the cantilevers are nearly 1 mm in both lateral dimensions and 100 nm thick. The extreme aspect ratio of the cantilevers, the large array size, and the absence of a sticking layer are intended to enable measurements of the rings' average persistent current ⟨I⟩ in the presence of relatively small magnetic fields. We describe the motivation for these measurements, the fabrication of the devices, and the characterization of the cantilevers' mechanical properties. We also discuss the devices' expected performance in measurements of ⟨I⟩.