The Kondo Effect in the Unitary Limit

We observe a strong Kondo effect in a semiconductor quantum dot when a small magnetic field is applied. The Coulomb blockade for electron tunneling is overcome completely by the Kondo effect and the conductance reaches the unitary-limit value. We compare the experimental Kondo temperature with the theoretical predictions for the spin-1/2 Anderson impurity model. Excellent agreement is found throughout the Kondo regime. Phase coherence is preserved when a Kondo quantum dot is included in one of the arms of an Aharonov-Bohm ring structure and the phase behavior differs from previous results on a non-Kondo dot.Comment: 10 page

SiGe quantum dots for fast hole spin Rabi oscillations

We report on hole g-factor measurements in three terminal SiGe self-assembled quantum dot devices with a top gate electrode positioned very close to the nanostructure. Measurements of both the perpendicular as well as the parallel g-factor reveal significant changes for a small modulation of the top gate voltage. From the observed modulations we estimate that, for realistic experimental conditions, hole spins can be electrically manipulated with Rabi frequencies in the order of 100MHz. This work emphasises the potential of hole-based nano-devices for efficient spin manipulation by means of the g-tensor modulation technique

Polar cap absorption events of November 2001 at Terra Nova Bay, Antarctica

Polar cap absorption (PCA) events recorded during November 2001 are investigated by observations of ionospheric absorption of a 30MHz riometer installed at Terra Nova Bay (Antarctica), and of solar proton flux, monitored by the NOAA-GOES8 satellite in geo-synchronous orbit. During this period three solar proton events (SPE) on 4, 19 and 23 November occurred. Two of these are among the dozen most intense events since 1954 and during the current solar cycle (23rd), the event of 4 November shows the greatest proton flux at energies >10MeV. Many factors contribute to the peak intensity of the two SPE biggest events, one is the Coronal Mass Ejection (CME) speed, other factors are the ambient population of SPE and the shock front due to the CME. During these events absorption peaks of several dB (~20dB) are observed at Terra Nova Bay, tens of minutes after the impact of fast halo CMEs on the geomagnetic field. </p><p style="line-height: 20px;"> Results of a cross-correlation analysis show that the first hour of absorption is mainly produced by 84–500MeV protons in the case of the 4 November event and by 15–44MeV protons for the event of 23 November, whereas in the entire event the contribution to the absorption is due chiefly to 4.2–82MeV (4 November) and by 4.2–14.5MeV (23 November). Good agreement is generally obtained between observed and calculated absorption by the empirical flux-absorption relationship for threshold energy <i>E<sub>0</sub></i>=10MeV. From the residuals one can argue that other factors (e.g. X-ray increases and geomagnetic disturbances) can contribute to the ionospheric absorption.<br><br><b>Key words.</b> Ionosphere (Polar Ionosphere, Particle precipitation) – Solar physics (Flares and mass ejections

Riometry at the Italian Antarctic station of Terra Nova Bay

A solid-state riometer has been installed at Terra Nova Bay (74-420S and 164-060E) during the IX Italian Antarctic expedition (1993/1994) to provide, in the frame of the geophysical observatories, studies on the ionospheric absorption in the lower part of the ionosphere. This kind of measurements will integrate the already existing active vertical ionospheric sounding and the magnetic absolute vector observations, with the objective of investigating the state of the ionosphere-magnetosphere coupling. In order to evaluate the base disturbance to the riometer, a remote campaign has been performed at McCarthy Ridge, rather far from the base station, where no anthropic noise is expected. Preliminary data analysis confirms the good quality of the Antarctic riometer observations

Development of a measurement platformon a light airplane and analysis of airborne measurementsin the atmospheric boundary layer

In the present paper we provide an overview of a long term research project aimed at setting up a suitable platform for measurements in the atmospheric boundary layer on a light airplane along with some preliminary results obtained from fi eld campaigns at selected sites. Measurements of air pressure, temperature and relative humidity have been performed in various Alpine valleys up to a height of about 2500 m a.m.s.l. By means of GPS resources and specifi c post-processing procedures careful positioning of measurement points within the explored domain has been achieved. The analysis of collected data allowed detailed investigation of atmospheric vertical structures and dynamics typical of valley environment, such as morning transition from ground based inversion to fully developed well mixed convective boundary layer. Based on data collected along fl ights, 3D fi elds of the explored variables have been detected and identifi ed through application of geostatistical techniques (Kriging). The adopted procedures allowed evaluation of the intrinsic statistical structure of the spatial distribution of measured quantities and the estimate of the values of the same variable at unexplored locations by suitable weighted average of data recorded at close locations. Results thus obtained are presented and discussed

Fertility decline and the emergence of excess female survival in post-reproductive ages in Italy

In Italy, at least in the cohorts born up to the beginning of the twentieth century, women's mortality in post-reproductive ages was influenced by fertility, with large progenies (and, to a lesser extent, childlessness) leading to markedly lower survival chances. This relationship proved strong enough to affect the female-to-male ratio in old age as fertility declined. In this paper, we show that various measures of extra female survival at high ages are closely connected to the fertility transition in Italy, and to its peculiar historical and geographical evolution