Precise measurement of the 222Rn half-life: a probe to monitor the stability of radioactivity

We give the results of a study on the 222Rn decay we performed in the Gran Sasso Laboratory (LNGS) by detecting the gamma rays from the radon progeny. The motivation was to monitor the stability of radioactivity measuring several times per year the half-life of a short lifetime (days) source instead of measuring over a long period the activity of a long lifetime (tens or hundreds of years) source. In particular, we give a possible reason of the large periodical fluctuations in the count rate of the gamma rays due to radon inside a closed canister which has been described in literature and which has been attributed to a possible influence of a component in the solar irradiation affecting the nuclear decay rates. We then provide the result of four half-life measurements we performed underground at LNGS in the period from May 2014 to January 2015 with radon diffused into olive oil. Briefly, we did not measure any change of the 222Rn half-life with a 8*10^-5 precision. Finally, we provide the most precise value for the 222Rn half-life: 3.82146(16){stat}(4){syst} days.Comment: Accepted for publication in Physics Letters B, 6 pages, 6 figure

Search for correlations between solar flares and decay rate of radioactive nuclei

The deacay rate of three different radioactive sources 40K, 137Cs and natTh has been measured with NaI and Ge detectors. Data have been analyzed to search for possible variations in coincidence with the two strongest solar flares of the years 2011 and 2012. No significant deviations from standard expectation have been observed, with a few 10-4 sensitivity. As a consequence, we could not find any effect like that recently reported by Jenkins and Fischbach: a few per mil decrease in the decay rate of 54Mn during solar flares in December 2006.Comment: 5 pages, 3 figure

The value relevance of effective investor relations

In this study, we test formally the market value of investor relations (IR) activity employing the annual Investor Relations Magazine Best Overall IR Awards data from 2000 to 2002 to proxy for the quality of firm investor relations. We find firms perceived by survey respondents to have effective IR strategies have significantly higher market value, and, also, earn superior abnormal returns, both before and after the award nominations. We also find that, not surprisingly, higher analyst following is associated with more nominations, suggesting analysts tend to favor the stocks they follow, although being nominated for best overall IR is also consistent with a significant increase in analyst following in the following year. Finally, in line with effective IR leading to lower information risk, liquidity of nominated firms, measured by stock turnover, increases in the year subsequent to the award nominations. Overall, our evidence is consistent with good IR successfully reducing the risk to investors associated with high information asymmetry, as predicted by information risk and agency theories

Clustering stock market companies via chaotic map synchronization

A pairwise clustering approach is applied to the analysis of the Dow Jones index companies, in order to identify similar temporal behavior of the traded stock prices. To this end, the chaotic map clustering algorithm is used, where a map is associated to each company and the correlation coefficients of the financial time series are associated to the coupling strengths between maps. The simulation of a chaotic map dynamics gives rise to a natural partition of the data, as companies belonging to the same industrial branch are often grouped together. The identification of clusters of companies of a given stock market index can be exploited in the portfolio optimization strategies.Comment: 12 pages, 3 figure

Hausdorff clustering of financial time series

A clustering procedure, based on the Hausdorff distance, is introduced and tested on the financial time series of the Dow Jones Industrial Average (DJIA) index.Comment: 9 pages, 3 figure

A Bayesian Networks Approach to Operational Risk

A system for Operational Risk management based on the computational paradigm of Bayesian Networks is presented. The algorithm allows the construction of a Bayesian Network targeted for each bank using only internal loss data, and takes into account in a simple and realistic way the correlations among different processes of the bank. The internal losses are averaged over a variable time horizon, so that the correlations at different times are removed, while the correlations at the same time are kept: the averaged losses are thus suitable to perform the learning of the network topology and parameters. The algorithm has been validated on synthetic time series. It should be stressed that the practical implementation of the proposed algorithm has a small impact on the organizational structure of a bank and requires an investment in human resources limited to the computational area

Search for time modulations in the decay rate of 40K and 232Th

Time modulations at per mil level have been reported to take place in the decay constant of about 15 nuclei with period of one year (most cases) but also of about one month or one day. In this paper we give the results of the activity measurement of a 40K source and a 232Th one. The two experiments have been done at the Gran Sasso Laboratory during a period of about 500 days, above ground (40K) and underground (232Th) with a target sensitivity of a few parts over 10^5. We also give the results of the activity measurement at the time of the X-class solar flares which took place in May 2013. Briefly, our measurements do not show any evidence of unexpected time dependence in the decay rate of 40K and 232Th.Comment: version accepted for publication (Astroparticle Physics

Cancer rate of the indeterminate lesions at low or high risk according to italian system for reporting of thyroid FNA

Background: Italian consensus for the classification and reporting of thyroid cytology (ICCRTC) has been used in almost all Italian institutions since 2014. High reliability of ICCRTC in classifying low and high risk indeterminate nodules (Tir 3A and Tir 3B, respectively) was demonstrated. Here we reviewed our casuistry of thyroid indeterminate lesions to analyze the histologic outcome. Methods: All lesions undergone FNA and final histology at S. Andrea Hospital of Rome after a cytologic assessment of Tir 3A and Tir 3B, according to ICCRTC, were included in the study. Results: A number of 157 indeterminate FNA was found after the introduction of ICCRTC. Of these, 75 undergone surgery and were finally included for the study. At histology we found a 33.3% of cancers and a 67.7% of benign lesions. Out of the overall series, 25 were classified as Tir 3A and 50 as Tir 3B. Cancer rate observed in Tir 3A (1/25, 4%) was significantly (p = 0.0002) lower than that of Tir 3B (24/50, 48%). No significant difference was found in age and size between the two subcategories. Conclusions: We confirm in our series that Italian consensus for the classification and reporting of thyroid cytology allows to discriminate indeterminate lesions at low and high risk of malignancy