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Objective: To identify chromosomal gains and losses in sporadic parathyroid adenomas (PAs). Methods: Fourteen sporadic PAs were studied by comparative genomic hybridization (CGH). Results: The fourteen studied PAs showed chromosomal imbalances. All cases except one exhibited two or more abnormalities. Chromosomal gains were found in all cases, and three cases (21%) also presented chromosomal losses. Genomic amplification was not observed. Chromosome 9 was involved in ten cases. Recurrent genetic gain was found on 9p22-24 and on 9q34, each in 6 of 14 cases (43%). Other recurrent gains included Xq26 in 6 PAs (43%) and 4q21-28 and 8p22 -23, each in 4 of 14 cases (29%). Regions of recurrent genetic loss involved whole chromosome 11 and 20q12-13, each in 2 of 14 cases (14%). Conclusions: Our findings show chromosomal imbalances in all sporadic PAs studied by CGH, partly confirming previous reports, with the exception that we observed more chromosomal gains than losses. Several regions (9p22 -24, 9q34, Xq26, 4q21-28, and 8p22 -23) probably deserve further investigation in order to discard the presence of genes involved in parathyroid tumorigenesis.

This paper discusses and analyses the parallel operation of Uninterruptible Power Supplies (UPS) units when loaded through long wiring cables having non-negligible inductance and resistance. This scenario is often encountered in practice, as the UPS power supplies are often located far from the load they are actually powering. The analysis demonstrates how long cable connections between the power supply system and the load deeply modify the behavior of the single UPS unit. More precisely, it is shown how the cable inductance interacts with the UPS closed-loop output impedance modifying the control loop gain, ultimately generating resonance phenomena which deteriorate or even compromise system stability and performances if suitable provisions are not taken at the design stage. Simulation and experimental results carried out on two paralleled three-phase, 40kVA UPS units based on voltage-source inverters topologies confirm the validity of the theoretical discussion and the practical relevance of the phenomenon

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