Observation of Stochastic Resonance in Percolative Josephson Media

Measurements of the electrical response of granular Sn-Ge thin films below the superconducting transition temperature are reported. The addition of an external noise to the magnetic field applied to the sample is found to increase the sample voltage response to a small externally applied ac signal. The gain coefficient for this signal and the signal-to-noise ratio display clear maxima at particular noise levels. We interpret these observations as a stochastic resonance in the percolative Josephson media which occurs close to the percolation threshold.Comment: 4 pages, 5 figure

The Schnitzler syndrome

The Schnitzler syndrome is a rare and underdiagnosed entity which is considered today as being a paradigm of an acquired/late onset auto-inflammatory disease. It associates a chronic urticarial skin rash, corresponding from the clinico-pathological viewpoint to a neutrophilic urticarial dermatosis, a monoclonal IgM component and at least 2 of the following signs: fever, joint and/or bone pain, enlarged lymph nodes, spleen and/or liver, increased ESR, increased neutrophil count, abnormal bone imaging findings. It is a chronic disease with only one known case of spontaneous remission. Except of the severe alteration of quality of life related mainly to the rash, fever and pain, complications include severe inflammatory anemia and AA amyloidosis. About 20% of patients will develop a lymphoproliferative disorder, mainly Waldenström disease and lymphoma, a percentage close to other patients with IgM MGUS. It was exceedingly difficult to treat patients with this syndrome until the IL-1 receptor antagonist anakinra became available. Anakinra allows a complete control of all signs within hours after the first injection, but patients need continuous treatment with daily injections

Superconducting point contacts weakly connecting two superconductors

The present review concerns dc and ac interference phenomena in superconducting point contacts weakly connecting two superconductors. First, the properties of a single superconducting point contact will be discussed. Special attention will be paid to the resistive superconductive region, and its current-voltage characteristic. The point contact will be treated using a two-fluid model in which the total current is the sum of an ideal Josephson supercurrent is( t) = i1 sin Δϕ*(t) and a normal current in = V/Rn = — (ħ/2e) (∂ Δϕ*(t)/∂t)/Rn (i 1 the maximum supercurrent ; Δϕ* the gauge-invariant phase difference ; V the voltage across the point contact and Rn its normal resistance). It appears that small shunt capacitances and series inductances play an important role, even in its dc current-voltage characteristic. Primarily, the two cases for which either the total current i = is + in or the voltage V are constants of time will be discussed. This approach appears to be essential for understanding the modulation in the voltage V(B〉) as a function of an external magnetic field at constant applied current i for a double point contact. Second, the external magnetic field dependence of the critical current (the dc Josephson effect) through a double point contact weakly coupling two superconductors is studied extensively, when the self-induced flux in the enclosed area is taken into account. Its relation with a strongly coupled double point contact, in which flux quantization holds, will be treated. Experimental results will be shown for the critical current of a symmetrical double point contact with such a small enclosed area O = 24 × 10-8 cm2 (L = 1.8 × 10-12 henry, i1 = 185 μA) that flux quantization is very incomplete : (h/2e)/L2i1 ~ 3 > 1) and will be compared with theory. Finally, the properties of double point contacts in the resistive-superconductive region, in relation with both the ac and dc Josephson effects, will be discussed. It is observed that the dc voltage across a double point contact oscillates as a function of the applied magnetic field when a constant current is applied through the double point contact. The complete i — V — B〉 dependence can be represented by a corrugated surface. Two interpretations will be given : when the self-induced flux in the enclosed area is ignored and when it is taken into account respectively. An extension is made by connecting two superconductors by more than two point contacts, which are adjusted on a straight line in such a way that an interference grating is formed

Superconducting point contacts weakly connecting two superconductors

The present review concerns dc and ac interference phenomena in superconducting point contacts weakly connecting two superconductors. First, the properties of a single superconducting point contact will be discussed. Special attention will be paid to the resistive superconductive region, and its current-voltage characteristic. The point contact will be treated using a two-fluid model in which the total current is the sum of an ideal Josephson supercurrent is( t) = i1 sin Δϕ*(t) and a normal current in = V/Rn = — (ħ/2e) (∂ Δϕ*(t)/∂t)/Rn (i 1 the maximum supercurrent ; Δϕ* the gauge-invariant phase difference ; V the voltage across the point contact and Rn its normal resistance). It appears that small shunt capacitances and series inductances play an important role, even in its dc current-voltage characteristic. Primarily, the two cases for which either the total current i = is + in or the voltage V are constants of time will be discussed. This approach appears to be essential for understanding the modulation in the voltage V(B〉) as a function of an external magnetic field at constant applied current i for a double point contact. Second, the external magnetic field dependence of the critical current (the dc Josephson effect) through a double point contact weakly coupling two superconductors is studied extensively, when the self-induced flux in the enclosed area is taken into account. Its relation with a strongly coupled double point contact, in which flux quantization holds, will be treated. Experimental results will be shown for the critical current of a symmetrical double point contact with such a small enclosed area O = 24 × 10-8 cm2 (L = 1.8 × 10-12 henry, i1 = 185 μA) that flux quantization is very incomplete : (h/2e)/L2i1 ~ 3 > 1) and will be compared with theory. Finally, the properties of double point contacts in the resistive-superconductive region, in relation with both the ac and dc Josephson effects, will be discussed. It is observed that the dc voltage across a double point contact oscillates as a function of the applied magnetic field when a constant current is applied through the double point contact. The complete i — V — B〉 dependence can be represented by a corrugated surface. Two interpretations will be given : when the self-induced flux in the enclosed area is ignored and when it is taken into account respectively. An extension is made by connecting two superconductors by more than two point contacts, which are adjusted on a straight line in such a way that an interference grating is formed