The analysis of a combined data set, totaling 3.6 × 10(14) stopped muons on target, in the search for the lepton flavor violating decay μ(+) → e(+)γ is presented. The data collected by the MEG ...experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 × 10(-13) (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.
Summary
In this study, numerical investigation is performed on a realistic source-to-site earthquake scenario, with the aim to assess the role of complex 3-D geological structures on the predicted ...wavefield. With this respect, the paper pointedly targets the seismic response of nuclear power plants in near-field conditions and the verification of some simplified assumptions commonly adopted for earthquake ground motion prediction and site effects analysis. To this purpose, the Kashiwazaki-Kariwa Nuclear Power Plant (Japan) is assumed as reference case-study. In 2007, the nuclear site and its surroundings were struck by the Niigata-Ken Chūetsu-Oki seismic sequence, which caused some of the peak ground motion design limits to be largely overpassed. The dense observation network deployed at the site recorded a highly incoherent and impulsive earthquake ground motion. Many studies argued that the intricate syncline-anticline geology lying underneath the nuclear facility was highly responsible of the observed seismic response. Therefore, a physics-based numerical model of the epicentral area is built-up (≈60 km wide) and tested for small aftershocks, so to discount the effect of extended source on the synthetic site-response. The numerical model (based on the Spectral Element Method) reproduces the source-to-site wave propagation by embracing the effects of the surface topography along with the presence of the Japan Sea (i.e. the bathymetry, the coastline and the fluid–solid interaction). Broad-band (0–5 Hz) synthetic waveforms are obtained for two different aftershocks, located at the two opposite sides of the nuclear facility, aiming to assess the influence of the incidence angle the radiated wave field impinges the foldings beneath it. The effect of the folding presence is assessed by comparing it to a subhorizontally layered geology, in terms of numerical outcome, and by highlighting the differences with respect to the observations. The presence of an intricate geology effectively unveils the reason behind the observed ground motion spatial variability within a relatively small area, stressing its crucial role to properly reproduce the modification the wavefield undergoes during its propagation path towards the surface. The accuracy of the numerical exercise is discussed along with its results, to show the high-fidelity of these deterministic earthquake ground motion predictions.
In this paper, physics-based numerical simulation (PBS) is employed to render a broad-band (0–10 Hz) realization of the near-field seismic response of the experimental nuclear site of Cadarache, ...located nearby the active Middle Durance Fault (southeastern France). The sensitivity of the earthquake numerical model to geological features is investigated by comparison with geophysical measurements and past aftershock and by highlighting the amplification induced by the soft sediments below Cadarache. The blind prediction of an MW6 target earthquake is approached by synthesizing four different finite-fault scenarios. The outcome is compared to the standard ground motion prediction equations (GMPEs), unveiling a possible GMPE overestimation of the pseudospectral acceleration ordinates at short natural periods, supporting the actual need to integrate synthetic and empirical predictions when direct observations are not available.
Describing diffraction of atomic and molecular projectiles at fast grazing incidence presents a real challenge for quantum theoretical simulations due to the high incidence energy (100eV–1keV) used ...in experiments. This is one of the main reasons why most theoretical simulations performed to date are based on reduced dimensional models. Here we analyze two alternatives to reduce the computational effort, while preserving the real dimensionality of the system. First, we show that grazing incidence conditions are already fulfilled for incidence angles ⩽5°, i.e., incidence angles higher than those typically used in experiments. Thus, accurate comparisons with experiment can be performed considering diffraction at grazing incidence, but with smaller total incidence energies, whilst keeping the same experimental normal energy in the calculations. Second, we show that diffraction probabilities obtained at fast grazing incidence are fairly well reproduced by simulations performed at slow normal incidence. This latter approach would allow one to simulate several experimental spectra, measured at the same normal incidence energy for several incidence crystallographic directions, with only one calculation. This approach requires to keep the full dimensionality of the system.
Abstract This study retrospectively analyses paranasal sinus complications following displacement of oral implants in the maxillary sinus treated according to clinical situation by functional ...endoscopic sinus surgery (FESS), an intraoral approach, or a combination of both procedures. Over 5 years, 27 patients (13 male; 14 female), aged 27–73 years (mean 53.9 years), underwent treatment for postoperative complications involving the paranasal sinuses following displacement of oral implants in the maxillary sinuses. According to the complication (implant displacement, implant displacement with or without reactive sinusitis and/or with or without associated oro-antral communication), patients were treated with FESS, intraoral approach to the sinus, or FESS associated with an intraoral approach. Follow up lasted for at least 1 year with clinical and radiographic controls. 26 patients recovered completely; one patient underwent re-intervention with FESS and an intraoral approach 2 years after implant removal, due to persistent signs and symptoms of maxillary sinusitis and oro-antral communication. Postoperative recovery after the second procedure was followed by complete recovery. The results demonstrate that a rational choice of surgical protocol for the treatment of complications involving the paranasal sinuses following displacement of implants in the maxillary sinuses may lead to reliable results.
The scope of this paper is to give an insight into the advantages of a new, all-embracing, modeling approach of a strong ground motion scenario, by carrying out a source-to-structure analysis at ...regional scale, accounting explicitly for the uncertainties related to the databases and the models. To this end, a suitable case-study is represented by the 2007 Mw6.6 Niigata-Ken Chūetsu-Oki seismic sequence (west Japan), that damaged the Kashiwazaki Kariwa Nuclear Power Plant. This study describes the effect of the wave propagation path within the Earth's crust on the seismic response of nuclear reactor buildings located nearby a seismogenic source. The multiscale problem is de-coupled into three steps: (1) a parallel simulation of seismic-wave propagation throughout the Earth's crust at regional scale (≈ 60 km wide, major 3-D geological interfaces found below the nuclear site), reliable up to 5.0 Hz; (2) a mid hybridization step consisting in enriching the synthetic wave-field at high frequency (up to 30 Hz), employing an Artificial Neural Network to predict the short-period (SP) spectral ordinates; (3) a high-resolution structural dynamic analysis, introducing the hybrid broad-band synthetics as input wave-motion. A simplified stress-test is performed, by simulating two small point-wise aftershocks at different source-site position. The impact of the underground 3-D geology on the structural components is finally quantified, by injecting the obtained broad-band time-histories in a Soil-Structure Interaction (SSI) model of the nuclear reactor building. The good fit obtained in terms of amplification factor at different recording stations assures the high-fidelity of the holistic philosophy endorsed.
•Source-to-structure simulation of nuclear power plant seismic response.•3D physics-based earthquake simulation (PBS) at regional scale (60 km) up to fmax=5Hz.•Realistic simulation of ground motion spatial variability due to 3D folding geology.•Hybrid broad-band wave-motion by coupling PBS with Artificial Neural Networks (ANN).•SSI analysis of reactor building injecting broad-band synthetics (PBS + ANN).
We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton-flavor-violating decay μ(+)e(+)γ. The ...likelihood analysis of the combined data sample, which corresponds to a total of 1.8×10(14) muon decays, gives a 90% C.L. upper limit of 2.4×10(-12) on the branching ratio of the μ(+)→e(+)γ decay, constituting the most stringent limit on the existence of this decay to date.
Realistic physics-based 3D earthquake simulation for source-to-structure wave propagation consists of a powerful numerical tool for seismic response prediction of critical structures submitted to ...high safety standards. Structural response considering soil-structure interaction (SSI) is usually estimated by Finite Element Method (FEM) approach, as it is considered as the most flexible numerical approach for nonlinear structural dynamics. However, current engineering practice considers seismic input motion as vertically incident plane waves, despite the fact that this assumption excludes wave passage effects for large infrastructures and surface waves appearing from possible local basin effects. In this framework, a realistic input excitation needs to be defined as an input excitation of the FEM model, accounting for (i) a realistic dynamic excitation, (ii) wave propagation path in the regional scale, and (iii) local site-effects. The Domain Reduction Method (DRM), which allows for the imposition of a 3D complex incident wave field as an input to the SSI model, is adapted and examined here in a Spectral Element Method (SEM) - FEM weak coupling approach. The weak coupling is verified at first for a canonical case-study and for an increasing complexity of the dynamic excitation: (i) double-couple point-source and (ii) extended fault. An optimization approach, based on the decimation of SEM output signal, is then examined in order to decrease the computational burden by maintaining the same accuracy of the final solution. The SEM-FEM weak coupling is then used to study the SSI problem, where the impact of the reduced domain size on structural response is examined at first. The current study shows that a reduced domain of dimension greater than
, where
is the maximum wavelength, is sufficient for a proper representation of structural response. For a fixed size model, structural and soil responses are then examined for a hypothetical case-study.
A rotaxane is described in which a macrocycle moves reversibly between two hydrogen-bonding stations after a nanosecond laser pulse. Observation of transient changes in the optical absorption ...spectrum after photoexcitation allows direct quantitative monitoring of the submolecular translational process. The rate of shuttling was determined and the influence of the surrounding medium was studied: At room temperature in acetonitrile, the photoinduced movement of the macrocycle to the second station takes about 1 microsecond and, after charge recombination (about 100 microseconds), the macrocycle shuttles back to its original position. The process is reversible and cyclable and has properties characteristic of an energy-driven piston.
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