6,991 research outputs found
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
Monolithic zirconia and digital impression: case report
The aim of this study is to present a clinical case of a full arch prosthetic rehabilitation on natural teeth, combining both digital work-flow and monolithic zirconi
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
Phase structure of a generalized Nambu Jona-Lasinio model with Wilson fermions in the mean field or large -expansion
We analyze the vacuum structure of a generalized lattice Nambu--Jona-Lasinio
model with two flavors of Wilson fermions, such that its continuum action is
the most general four-fermion action with 'trivial' color interactions, and
having a symmetry in the chiral limit. The phase structure
of this model in the space of the two four-fermion couplings shows, in addition
to the standard Aoki phases, new phases with , in
close analogy to similar results recently suggested by some of us for lattice
QCD with two degenerate Wilson fermions. This result shows how the phase
structure of an effective model for low energy QCD cannot be entirely
understood from Wilson Chiral Perturbation Theory, based on the standard QCD
chiral effective Lagrangian approach.Comment: 24 pages, 3 figures, sent to Nuclear Physics
Defining directorsâ conflict of interests in code of ethics
We propose a definition of directorsâ conflict of interests (CoI) by critically reviewing the academic literature. Then, we present an exploratory study, based on a content analysis of the leading Italian listed companies that sought to empirically assess the directorsâ CoI definitions provided by corporate codes of ethics. We found that despite the presence of CoI statement within corporate codes of ethics, CoI definition is often absent, when present it is not always clear, and differs widely among firms. The consequence is that CoI recognition could be not easy and remedies to prevent and resolve directorsâ CoI lose their practical utility
Energy and economic analysis of a residential Solar Organic Rankine plant
To answer the actual energy, water, economic, social and environmental challenges, renewable, distributed power plants need to
be developed. Among renewables, solar tri-generative power plants can be a solution where there is big low temperature
heating/cooling demand and small electricity demand, like many residential and industrial utilities. In this case, solar thermal
plants can produce thermal energy with low cost and high efficiency. The higher temperature heat not needed by the user can be
exploited via Organic Rankine Cycle to produce electrical energy and desalinized water via reverse osmosis. The present paper
analyses, via TRNSYS simulation, a system composed of 50 m2
of CPC solar thermal collectors, 3 m3
of thermal storage, a
synthetic heat transfer fluid, 3 kWe ORC, 8 kWth absorber, 200 l/h direct reverse osmosis desalination device. The system is able
to produce power, heating/cooling and fresh water needs for a residential house. Although systemâs components are well known
technologies, the integration to a efficient and economic working system is still a challenge. Global energy and economic
analyses have been performed. Low temperature heating/cooling terminals allow to increase not only the use of thermal energy
but also the ORCand absorber efficiency. ORC-Absorber configuration and relative fluids and temperatures are central.
Government support and/or cost reduction of 30% are necessary to have positive NPV and acceptable PBT and IR
Towards Drift Correction in Chemical Sensors Using an Evolutionary Strategy
Gas chemical sensors are strongly affected by the so-called drift, i.e., changes in sensors' response caused by poisoning and aging that may significantly spoil the measures gathered. The paper presents a mechanism able to correct drift, that is: delivering a correct unbiased fingerprint to the end user. The proposed system exploits a state-of-the-art evolutionary strategy to iteratively tweak the coefficients of a linear transformation. The system operates continuously. The optimal correction strategy is learnt without a-priori models or other hypothesis on the behavior of physical-chemical sensors. Experimental results demonstrate the efficacy of the approach on a real problem
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