An inexpensive and continuous radon progeny detector for indoor air-quality monitoring

A silicon photodiode-based inexpensive detector working as a counter and spectrometer for alpha particles has been conceived, designed, constructed and analyzed in depth. Monte Carlo simulations by means of MCNPX ver. 2.7.0 code have been carried out to select the most suitable sensitive element for the intended applications. The detecting unit has been coupled to an Arduino board and tested for low-rate alpha-particle counting and spectroscopy. Results demonstrate a maximum count rate of 4000 s-1, an energy resolution corresponding to a full width at half maximum of 160 keV over the entire energy range of measured alpha (namely 4 ÷ 6.5 MeV), and the sensitive element’s intrinsic efficiency of about 100%. Being the detector capable of distinguishing alpha energy associated to decays of radon daughters, its applications include 222Rn progeny monitoring. The air sampling system has been realized by a volumetric micro-pump forcing the air-flow through a millipore filter. By knowing the air-flow rate processed and the corresponding alpha energy spectrum measured, the concentrations of 218Po, 214Po and 210Po are determined. The potential alpha energy concentration-in-air is inferred, and effective dose evaluated. Calibration and testing measurements have been carried out by comparing the obtained results to the outputs of professional and expensive radon progeny monitor. The detector capability of “following” radon progeny concentration-in-air vs. time has been demonstrated. The device studied here can be configured as a prototype for an inexpensive radon progeny sensor to be potentially suitable for indoor air-monitoring in residential buildings, evaluating people’s exposures to radon and initiating corrective actions (e.g., mechanical ventilation) if necessary

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

Palliation of complex cardiac anomalies with subaortic obstruction: New operative approach

AbstractThe modified Fontan operation for complex cardiac anomalies associated with subaortic obstruction entails a high surgical risk. It is likely that ventricular hypertrophy secondary to chronic pressure overload plays a significant role. This problem was approached with a new type of palliative operation comprising both a proximal pulmonary artery to ascending aorta anastomosis and a bidirectional cavopulmonary anastomosis.This operation was performed in six children ranging in age from 26 to 63 months. There was one intraoperative death due to hemorrhage. In one patient, a pulmonary to aorta conduit caused compression of the right coronary artery; the problem was solved by lengthening the conduit with a second period of cardiopulmonary bypass.The five survivors experienced an uneventful postoperative course. Repeat cardiac catheterization in these five patients showed low pressure in the cavopulmonary system (mean 10 mm Hg), absence of a gradient at rest between the systemic ventricle and aorta and fair arterial oxygenation (mean 82%). A technetium-99m perfusion lung scan visualized a slight prevalence of pulmonary blood flow ipsilateral to the shunt in three cases, whereas in one case preferential flow to the right lung was associated with a narrowing at the site of the cavopulmonary anastomosis. Mild hypoperfusion of the anterior pulmonary segments was observed in two cases.Both pressure and volume overload are abolished with this procedure and a satisfactory oxygenation is provided. Low venous pressure in the coronary, hepatic and renal areas as well as the short bypass time may explain the smoothness of the postoperative course in our patients. It is conceivable that oxygenation can be improved by a modified Fontan operation at a lower operative risk than is obtained with a single stage procedure because of regression of ventricular hypertrophy. Long-term follow-up indicates the value of this operation as a form of definitive palliation

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

Indoor radon survey in university buildings: a case study of Sapienza - University of Rome

The indoor radon concentration in underground workplaces pertaining to Sapienza – University of Rome have been monitored since the 90’s according to prescription of Italian Legislative Decree 230/95. In the last years, the recommendations contained in the Council Directive 2013/59/Euratom have shifted the focus to all indoor exposure situations by promoting actions to identify workplaces and dwellings with radon concentrations exceeding the reference level of 300 Bq/m3. In response to the upcoming transposition into national legislation, Sapienza has promoted the first Italian survey addressing workplaces in university buildings, regardless of the position with respect to the ground floor. The survey has interested more than three hundred workplaces, i.e. administration and professors’ offices, research and educational laboratories, conference rooms and classrooms, distributed in fifteen different buildings. Places monitored are strongly heterogeneous in terms of users’ habit, occupancy pattern and building characteristics. The influence of these parameters into seasonal variation have been addressed by organizing the survey in four quarters. The indoor radon concentration is measured by solid state nuclear track detectors, CR39. The aim of the paper is to present features, methods and intermediate results of the survey. The work, relying on the analysis of previous measurements interesting underground workplaces, focuses on methodology followed during all the preliminary and preparatory phases: active measurements by ionization chamber radon continuous monitor, radon progeny equilibrium factor estimations by radon daughters monitor, strategies for occupants’ awareness, positioning protocol and provisions to maximize representativity of results

Optimal stochastic modelling with unitary quantum dynamics

Identifying and extracting the past information relevant to the future behaviour of stochastic processes is a central task in the quantitative sciences. Quantum models offer a promising approach to this, allowing for accurate simulation of future trajectories whilst using less past information than any classical counterpart. Here we introduce a class of phase-enhanced quantum models, representing the most general means of causal simulation with a unitary quantum circuit. We show that the resulting constructions can display advantages over previous state-of-art methods - both in the amount of information they need to store about the past, and in the minimal memory dimension they require to store this information. Moreover, we find that these two features are generally competing factors in optimisation - leading to an ambiguity in what constitutes the optimal model - a phenomenon that does not manifest classically. Our results thus simultaneously offer new quantum advantages for stochastic simulation, and illustrate further qualitative differences in behaviour between classical and quantum notions of complexity.Comment: 9 pages, 5 figure

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

Who was thrombogenic: the stent or the doctor?

In 1986, when pioneers such as Jacques Puel and Ulrich Sigwart implanted the first coronary Wallstents, no guidelines were available to determine the treatment after stenting. From the experience acquired with mechanical prosthetic heart valves, it was inferred that chronic anticoagulation with coumarins was indicated. When the first cases of subacute occlusion were encountered, the anticoagulation regimen was further reinforced. The use of heparin, dextran, or thrombolytic agents during the procedure followed by warfarin, aspirin, sulphinpyrazone, and dipyridamole did not eliminate subacute thrombosis, which occurred in 18% of the first 117 stents implanted and was responsible for a higher incidence of hemorrhagic complications and prolonged hospital stay

Managerial Ability, Players’ Cultural Diversity, and Sporting and Economic Performance in English Soccer

We use a large homemade database on professional soccer in England to estimate the relevance of managerial ability on performance and the managerial skills in keeping up cultural diversity. The team manager faces a set of very complex tasks. Not only he is the head coach of the soccer team, thus influencing sporting performance, but he can also have an impact on performance, by improving economic efficiency or by limiting the organization innovation in order to foster the creation of organizational routines. The sporting competitive advantage translates into economic and financial performance; therefore the manager is a dominant voice in the financial viability of the club, too. We also measure the impact of cultural diversity: attendance appreciates home-grown and talented players, and dislikes cultural diversity