Steady-State Magnetohydrodynamic Flow Around an Unmagnetized Conducting Sphere

The non-collisional interaction between conducting obstacles and magnetized plasma winds can be found in different scenarios, from the interaction occurring between regions inside galaxy clusters to the interaction between the solar wind and Mars, Venus, active comets or even the interaction between Titan and the Saturnian's magnetospheric flow. These objects generate, through several current systems, perturbations in the streaming magnetic field leading to its draping around the obstacle's effective conducting surface. Recent observational results suggest that several properties associated with the magnetic field draping, such as the location of the polarity reversal layer of the induced magnetotail, are affected by variations in the conditions of the streaming magnetic field. To improve our understanding of these phenomena, we perform a characterization of several magnetic field draping signatures by analytically solving an ideal problem in which a perfectly conducting magnetized plasma (with frozen-in magnetic field conditions) flows around a spherical body for various orientations of the streaming magnetic field. In particular, we compute the shift of the inverse polarity reversal layer as the orientation of the background magnetic field is changed.Comment: Preprint submitted to Astrophysical Journa

La certificazione di qualità per il sistema di gestione aziendale: il caso Intersonda S.r.l.

L’obiettivo alla base del presente lavoro è quello di indagare il reale significato della qualità in azienda, i presupposti da cui questa ha origine e le sue linee di sviluppo future, in particolare per quanto attiene l’applicazione della stessa ai sistemi di gestione aziendale, in linea con quanto disposto dalla norma internazionale UNI EN ISO 9001:2008. Si tratta di un tema dibattuto negli anni che si rinnova continuamente in seguito all'evoluzione delle modalità di organizzazione e svolgimento dell’attività economica. Per approfondire al meglio queste tematiche il lavoro viene suddiviso in due parti: la prima puramente teorica, la seconda legata ad un caso pratico. In quest’ultima sezione viene infatti analizzata la società Intersonda S.r.l., focalizzando particolarmente l’attenzione sul suo sistema di gestione e il suo livello di adeguamento alla normativa di riferimento

The ULF wave foreshock boundary: Cluster observations

The interaction of backstreaming ions with the incoming solar wind in the upstream region of the bow shock gives rise to a number of plasma instabilities from which ultra-low frequency (ULF) waves can grow. Because of their finite growth rate, the ULF waves are spatially localized in the foreshock region. Previous studies have reported observational evidences of the existence of a ULF wave foreshock boundary, which geometrical characteristics are very sensitive to the interplanetary magnetic field (IMF) cone angle. The statistical properties of the ULF wave foreshock boundary is examined in detail using Cluster data. A new identification of the ULF wave foreshock boundary is presented using specific and accurate criterion for a precises determination of boundary crossings. The criterion is based on the degree of IMF rotation as Cluster crosses the boundary. The obtained ULF wave foreshock boundary is compared with previous results reported in the literature as well as with theoretical predictions. Also, we examined the possible connexion between the foreshock boundary properties and the ion emission mechanisms at the bow shock

Acute effects of aerobic exercise on feelings of energy in relation to age and gender

A crossover experiment was performed to determine whether age and sex, or their interaction, affect the impact of acute aerobic exercise on Vigor-Activity (VA). We also tested whether changes in VA mediated exercise effects on performance on various cognitive tasks. Sixty eight physically inactive volunteers participated in exercise and TV-watching control conditions. They completed the Vigor-Activity subscale of the Profile of Mood States immediately prior to and 2 minutes after the intervention in each condition. They also performed the Trail Making Test 3 minutes after the intervention in each condition. Statistical analyses produced a condition × age × sex interaction characterized by a higher mean VA 10 gain value in the exercise condition (compared to the VA gain value in the TV-watching condition) for young female participants only. In addition, the mediational analyses revealed that changes in VA fully mediated the effects of exercise on TMT-Part A performance

Reconstrução de sinal de medida em sistema de medida de pressão em células vegetais.

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