Search results for "decay"
showing 10 items of 2087 documents
Memory effects and coverage dependence of surface diffusion in a model adsorption system
1999
We study the coverage dependence of surface diffusion coefficients for a strongly interacting adsorption system O/W(110) via Monte Carlo simulations of a lattice-gas model. In particular, we consider the nature and emergence of memory effects as contained in the corresponding correlation factors in tracer and collective diffusion. We show that memory effects can be very pronounced deep inside the ordered phases and in regions close to first and second order phase transition boundaries. Particular attention is paid to the details of the time dependence of memory effects. The memory effect in tracer diffusion is found to decay following a power law after an initial transient period. This beha…
Characterization of water mobility in dry and wetted roasted coffee using low-field proton nuclear magnetic resonance
2007
Abstract Roasted and ground coffee was studied by low-field 1 H nuclear magnetic resonance at various water contents and temperatures. The spin–spin relaxation times ( T 2 ) were measured with single pulse free induction decay (FID) and Carr–Purcell–Meiboom–Gill (CPMG) sequences. Four relaxing components were distinguished: the solid population was observed with FID sequence at T 2s ∼9 μs; the other three populations, measured with the CPMG sequence, corresponded to an apolar phase, the coffee oil, and two polar phases. The two polar populations, observed at T 2m ∼6 ms and ∼27 ms (for coffee with 50% water content at 90 °C) were attributed to water in cell wall polymers and in water filling…
Biodiversity of wood-decay fungi in Italy
2011
Abstract Current knowledge about Italian wood-decay fungi (Basidiomycota and Ascomycota) is surveyed: 1582 taxa belonging to Ascomycota (341) and Basidiomycota (1241) have been reported, including 23 species new to science of Basidiomycota described from Italy within the last five years. Evaluating diversity of wood-decay fungi can provide a more accurate estimation of species richness for fungi which are an important functional component of ecosystems. Aphyllophoroid and Ascomycota species play an important role in habitat conservation and management. Sardinia, Sicily, the Alps and the Apennines are “hot spots” for wood-decay Basidiomycota in Italy.
Beta Decay Studies of Neutron Rich Nuclei Using Total Absorption Gamma-ray Spectroscopy and Delayed Neutron Measurements
2010
International audience; A complete characterisation of the β-decay of neutron-rich nuclei can be obtained from the measurement of β-delayed gamma rays and, whenever the process is energetically possible, β-delayed neutrons. The accurate determination of the β-intensity distribution and the β-delayed neutron emission probability is of great relevance in the fields of reactor technology and nuclear astrophysics. A programme for combined measurements using the total absorption gamma-ray spectroscopy technique and both neutron counters and neutron time-of-flight spectrometers is presented.
Commissioning of the BRIKEN beta-delayed neutron detector for the study of exotic neutron-rich nuclei
2017
Beta-delayed neutron emission (Beta-n) is a form of radioactive decay in which an electron, an anti-neutrino and one or more neutrons are emitted. This process arises if the energy window of the decay Q_Beta is greater than the neutron separation energy S n of the daughter. The probability in each decay of emitting neutrons is called the Pn value. This form of decay plays a key role in the synthesis of chemical elements in the Universe via the rapid neutron capture process, or r-process. The r-process proceeds far from the valley of nuclear stability, and leads to very neutron-rich nuclei that then decay to the line of stability. Most of these nuclei are ßn emitters. The initial abundance d…
Search for heavy neutral lepton production in K+ decays to positrons
2020
A search for heavy neutral lepton ($N$) production in $K^+\to e^+N$ decays using the data sample collected by the NA62 experiment at CERN in 2017--2018 is reported. Upper limits of the extended neutrino mixing matrix element $|U_{e4}|^2$ are established at the level of $10^{-9}$ over most of the accessible heavy neutral lepton mass range 144--462 MeV/$c^2$, with the assumption that the lifetime exceeds 50 ns. These limits improve significantly upon those of previous production and decay searches. The $|U_{e4}|^2$ range favoured by Big Bang Nucleosynthesis is excluded up to a mass of about 340 MeV/$c^2$.
Discovery potential of xenon-based neutrinoless double beta decay experiments in light of small angular scale CMB observations
2013
The South Pole Telescope (SPT) has probed an expanded angular range of the CMB temperature power spectrum. Their recent analysis of the latest cosmological data prefers nonzero neutrino masses, with Sigma m(nu) = (0.32 +/- 0.11) eV. This result, if con firmed by the upcoming Planck data, has deep implications on the discovery of the nature of neutrinos. In particular, the values of the effective neutrino mass m(beta beta) involved in neutrinoless double beta decay (beta beta 0 nu) are severely constrained for both the direct and inverse hierarchy, making a discovery much more likely. In this paper, we focus in xenon-based beta beta 0 nu experiments, on the double grounds of their good perfo…
(Standard model) universe dominated by the right matter
2009
14 pages, 3 figures. References on late time enthropy release included, several points clarified. PACS numbers: 14.60.Pq, 98.80.Cq. ArXiv pre-print available at http://arxiv.org/abs/0806.4389
Neutrino masses and their ordering: global data, priors and models
2018
We present a Bayesian analysis of the combination of current neutrino oscillation, neutrinoless double beta decay and CMB observations. Our major goal is to carefully investigate the possibility to single out one neutrino mass ordering, Normal Ordering or Inverted Ordering, with current data. Two possible parametrizations (three neutrino masses versus the lightest neutrino mass plus the two oscillation mass splittings) and priors (linear versus logarithmic) are examined. We find that the preference for NO is only driven by neutrino oscillation data. Moreover, the values of the Bayes factor indicate that the evidence for NO is strong only when the scan is performed over the three neutrino ma…
A White Paper on keV sterile neutrino Dark Matter
2017
We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved - cosmology, astrophysics, nuclear, and particle physics - in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrin…