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Many experiments on high-temperature superconductors have shown paramagnetic behavior when the sample is field cooled. The paramagnetism was attributed to a d-wave order parameter creating pi-junctions in the samples. However, the same effect was later discovered in traditional low-temperature superconductors and conventional Josephson-junction arrays which are s wave. By simulating both conventional and mixed pi/conventional Josephson-junction arrays we determine that differences exist which may be sufficient to clearly identify the presence of pi junctions. In particular, the pi junctions cause a symmetry breaking providing a measurable signature of their presence.

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Annihilation cross-sections sigma(ann) for antineutrons on some nuclei (C, Al, Cu, Sn and Pb) at three antineutron momenta (180, 240 and 280 MeV/c) were measured at LEAR (CERN) with the OBELIX spectrometer. A behaviour sigma(ann) = = sigma0A(nu) has been found with nu almost-equal-to 2/3. The data are discussed following some models for antineutron-nucleus interaction

The magnetic behavior of Multiply Connected Superconductors (MCS) can be described analyzing the simplest loop structures containing Josephson junctions: conventional loops with all conventional Josephson junctions and π-loops with an odd subset of πjunctions. These last are unconventional Josephson junctions in which the coupling has the reversed sign and appears in the ceramic materials as consequence of d-pairing. Among MCS the magnetic behavior of large β two-dimensional Josephson Junction Arrays (JJA) is based on the single loop behavior. Solving full mutual inductance Josephson junction square array equations with and without π-loops show that the mutual inductance coupling influence the distribution of π/conventional loops without altering substantially their single loop magnetization. The JJA mean magnetic behavior in low field can be recovered using a simple energy approach based on the single loop solutions avoiding the solution of the array full equations. Also we draw some consequences on the behavior of more complex MCS as high-T C ceramics and their observed paramagnetic susceptibilities (Paramagnetic Meissner Effect).

LTC Josephson junction arrays (JJA) have recently gained interest as a model for the study of magnetization in superconductor materials. The presence of paramagnetic Meissner effect in such devices when field-cooled makes them an excellent candidate to discriminate between the different explanations given for such phenomenon. On the other hand, the understanding of the JJA physics is not simple due to the interplay between the non-linear behaviour of Josephson devices and the mutual induction effects in large JJA. The use of a SQUID microscope (SSM) to catch the magnetic image of the array is a distinctive feature of the experiment. So a study of SQUID read-out based on the actual JJA magnetic behaviour is needed in order to have a correct picture of what is going on. In this paper, using a simple way to reconstruct the complex array far-field viewed by the SQUID, we study how the flux read-out is dependent on array resolution, distance, tilting and noise for the typical situations in which arrays are found.

In last years the return current, i.e., the value of the bias current where an

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