An experimental study of intermodulation effects in an atomic fountain frequency standard

The short-term stability of passive atomic frequency standards, especially in pulsed operation, is often limited by local oscillator noise via intermodulation effects. We present an experimental demonstration of the intermodulation effect on the frequency stability of a continuous atomic fountain clock where, under normal operating conditions, it is usually too small to observe. To achieve this, we deliberately degrade the phase stability of the microwave field interrogating the clock transition. We measure the frequency stability of the locked, commercial-grade local oscillator, for two modulation schemes of the microwave field: square-wave phase modulation and square-wave frequency modulation. We observe a degradation of the stability whose dependence with the modulation frequency reproduces the theoretical predictions for the intermodulation effect. In particular no observable degradation occurs when this frequency equals the Ramsey linewidth. Additionally we show that, without added phase noise, the frequency instability presently equal to 2x10-13 at 1s, is limited by atomic shot-noise and therefore could be reduced were the atomic flux increased

Economic resources and the first child in Italy: A focus on income and job stability

At the turn of the twentieth century Italy registered a lowest-low fertility level, i.e., a total fertility rate of 1.26 children per woman in 2000. In this paper we investigate whether and how in that period economic resources and, in particular, income and job stability were linked with couples’ decisions to enter parenthood. With this aim, we use data from ECHP and carry out a longitudinal analysis on a sample of childless married couples to study the transition to their first child. Results show that the couples’ employment arrangement played some role in first child rates, with the single earner arrangement experiencing the highest first birth rates. We also find that employed women with labour income have much lower first birth rates than non-working women, while no evidence is found for male earnings and other sources of income. As concerns job instability, we find evidence that it was not significantly linked with the transition to first time parenthood during the investigated period.event history analysis, income, job stability, transition to first child

Leaving home, family support and intergenerational ties in Italy: Some regional differences

In Italy conditions at leaving home are characterized by high age at exit, high proximity with parents and widespread intergenerational support, showing important regional differences. According to the "familistic" approach such conditions spread from strong intergenerational ties. Proximity and support are considered proxies of ties’ strength so that different regional proximity and support correspond to different ties’ intensities. The study aims at analyzing similarities and differences about parent-child ties, proximity and support in selected Italian regions, Liguria, Umbria, Sicily and Sardinia. Results show important differences among regions with respect to proximity and support, suggesting different intensity of intergenerational ties.family ties, intergenerational proximity, intergenerational support, regional comparison

Is firm growth proportional? An appraisal of firm size distribution

The aim of this paper is to shed light on the phenomenon of firm growth, analyzing the evolution of young firms within some selected industries. We find that the firm size distribution is fairly skewed to the right during the infancy stage, whereas it converges towards a more symmetric distribution, via selection mechanisms, with the passing of time.