Silo collapse under granular discharge.

We investigate, at a laboratory scale, the collapse of cylindrical shells of radius R and thickness t induced by a granular discharge. We measure the critical filling height for which the structure fails upon discharge. We observe that the silos sustain filling heights significantly above an estimation obtained by coupling standard shell-buckling and granular stress distribution theories. Two effects contribute to stabilize the structure: (i) below the critical filling height, a dynamical stabilization due to granular wall friction prevents the localized shell-buckling modes to grow irreversibly; (ii) above the critical filling height, collapse occurs before the downward sliding motion of the whole granular column sets in, such that only a partial friction mobilization is at play. However, we notice also that the critical filling height is reduced as the grain size d increases. The importance of grain size contribution is controlled by the ratio d/√[Rt]. We rationalize these antagonist effects with a novel fluid-structure theory both accounting for the actual status of granular friction at the wall and the inherent shell imperfections mediated by the grains. This theory yields new scaling predictions which are compared with the experimental results.

[The psychological aspects of pregnancy]. / Aspetti psicologici della gravidanza.

Pregnancy is a stage of maturation crisis which, like other moments of crisis in a woman's life (adolescence and menopause), is characterised by phases of regression, the weakness of mental defences and transformation of the image of self. When there are conflicts with femininity, the experience of pregnancy may be complicated and unease may be expressed in somatic symptoms such as nausea and vomit, and may even lead to the onset of pathologies such as hypertension, miscarriage and pre-term labour. This has led to the term "psychological" risk pregnancy being used over the past 20 years.

[Injuries in pregnancy]. / Traumi in gravidanza.

From a review of the literature on this subject it emerges that around 6-7% of women are injured during the course of pregnancy. Road accidents, falls and domestic accidents are the most frequent events: it is therefore important to provide pregnant women with information to prevent such events which may endanger both maternal and fetal health.

Chromosome heteromorphisms and early recurrent abortions.

In order to identify the role played by heterochromatic polymorphisms in miscarriage, an analysis was carried out on 257 couples, 137 of them with two or more abortions and 120 serving as a control. All couples were taken from two Italian populations: 77 cases and 70 controls came from an exogamic population whilst 60 cases and 50 controls came from an almost endogamic one. Out of the 137 cases, six couples in the exogamic and five in the endogamic groups were excluded because at least one partner had balanced chromosomal aberrations. Four controls from the exogamic group were also excluded for the same reason. The remaining 126 cases were analysed to detect the presence of chromosomal heteromorphism in one or both partners. The results suggested that chromosomal heteromorphism does not induce miscarriage. In fact, only one heteromorphism, inv(9)(p11q12), seems to be marginally related to recurrent abortion and only in the exogamic population. In addition no differences were found in the distribution of chromosomal heteromorphism in the couples analysed in relation to the number of abortions, i.e. two or more than two.