The European Alps are the site where classic geologic concepts such as nappe theory, continental subduction and slab breakoff have been first proposed. However, the deep tectonic structure of the ...Alps has long been poorly constrained by independent geophysical evidence. This review paper summarizes the main results of the CIFALPS passive seismic experiment, that was launched by Chinese, French and Italian scientists in the 2010s to provide new insights on the deep tectonic structure of the Alpine region. The application of a wide range of tomographic methods to the analysis of a single fossil subduction zone makes the CIFALPS experiment a potential reference case for the analysis of other orogenic belts. Major results include: (i) the first seismic evidence of European continental crust subducted into the Adriatic upper mantle, beneath the place where coesite was first recognized in continental (U)HP rocks in the Alps; (ii) evidence of a major involvement of the mantle wedge during (U)HP rock exhumation; (iii) evidence of a serpentinized plate interface favoring continental subduction; (iv) evidence of a continuous slab beneath the Western and Central Alps, ruling out the classic model of slab breakoff magmatism; (v) evidence of a polyphase development of anisotropic fabrics in the Alpine mantle, either representing active mantle flows or fossil fabrics inherited from previous rifting stages. Detection of these major tectonic features allows to propose interpretive geologic cross‐sections at the scale of the lithosphere and upper mantle, providing a baseline for future analyses of active continental margins.
Plain Language Summary
The European Alps are the site where classic geologic concepts such as nappe theory, continental subduction, and slab breakoff have been first proposed. However, the deep tectonic structure of the Alps has long been poorly constrained by independent geophysical evidence. This review paper summarizes the main results of the CIFALPS passive seismic experiment, which allows us to propose an updated image of the deep structure of the Alps at the scale of the lithosphere and the upper mantle. The concepts and ideas summarized in this article provide a baseline for further advances in the fields of Alpine tectonics and in the analysis of active continental margins more generally.
Key Points
Summary of the main results of the CIFALPS seismic experiment provides new insights on the deep tectonic structure of the Alpine region
Application of a wide range of tomographic methods and joint interpretation with geological and petrophysical data
Interpretive geologic cross‐sections at the scale of the lithosphere and the upper mantle
SUMMARY
In previous publications, we presented a general framework, which we called ‘box tomography’, that allows the coupling of any two different numerical seismic wave propagation solvers, ...respectively outside and inside a target region, or ‘box’. The goal of such hybrid wavefield computations is to reduce the cost of computations in the context of full-waveform inversion for structure within the target region, when sources and/or receivers are located at large distances from the box. Previously, we had demonstrated this approach with sources and receivers outside the target region in a 2-D acoustic spherical earth model, and demonstrated and applied this methodology in the 3-D spherical elastic Earth in a continental scale inversion in which all stations were inside the target region. Here we extend the implementation of the approach to the case of a 3-D global elastic earth model in the case where both sources and stations are outside the box. We couple a global 3-D solver, SPECFEM3D_GLOBE, for the computation of the wavefield and Green’s functions in a reference 3-D model, with a regional 3-D solver, RegSEM, for the computation of the wavefield within the box, by means of time-reversal mirrors. We briefly review key theoretical aspects, showing in particular how only the displacement is needed to be stored at the boundary of the box. We provide details of the practical implementation, including the geometrical design of the mirrors, how we deal with different sizes of meshes in the two solvers, and how we address memory-saving through the use of B-spline compression of the recorded wavefield on the mirror. The proposed approach is numerically efficient but also versatile, since adapting it to other solvers is straightforward and does not require any changes in the solver codes themselves, as long as the displacement can be recovered at any point in time and space. We present benchmarks of the hybrid computations against direct computations of the wavefield between a source and an array of stations in a realistic geometry centred in the Yellowstone region, with and without a hypothetical plume within the ‘box’, and with a 1-D or a 3-D background model, down to a period of 20 s. The ultimate goal of this development is for applications in the context of imaging of remote target regions in the deep mantle, such as, for example, Ultra Low Velocity Zones.
•Ability of post-and-beam timber frames to resist progressive collapse was studied.•Compressive arch and catenary actions under large deformations were reported.•Currently used and tested connectors ...cannot resist progressive collapse alone.•A proposed novel connector could represent a solution to robust timber buildings.•To resist progressive collapse, alternate load paths must be found.
Mid-rise to tall mass timber buildings, which are constructed from engineered solid wood products, such as Laminated Veneer Lumber (LVL), Glued laminated timber (Glulam) and Cross Laminated Timber (CLT), have recently gained international popularity. As the height of timber buildings increases, so do the consequences of a progressive collapse event. While collapse mechanisms of concrete and steel buildings have been widely researched, limited studies have been carried out on mass timber buildings. This paper presents and discusses the experimental results performed on a series of 2D timber frame substructures, used in post-and-beam mass timber buildings and scaled down to fit the purpose of this research, under a middle column removal scenario. The behaviour of the frames and the ability of three types of commercially available beam-to-column connections and a proposed non-commercial novel connection, to develop catenary action under large deformations are reported. Furthermore, the system capacity in terms of the uniformly distributed pressure is also discussed. The test results showed that only the proposed connector was able to sustain the design pressure in international design specifications if no dynamic increase factor was considered, and therefore presented a potential solution to improve the robustness of post-and-beam timber buildings.
Abstract Radio observations of pulsars offer a potential method to probe the intricate microstructure in the turbulent interstellar medium. Here we report on a high-resolution dynamic spectral ...analysis of the “swooshing pulsar” B0919+06 observed with the Five-hundred-meter Aperture Spherical radio Telescope over multiple epochs and with the ultrawideband receiver on the Parkes radio telescope. For all observations, the dynamic scintillation spectra, two-dimensional autocovariance functions, and secondary spectra are presented. At 1250 MHz, the decorrelation bandwidth, diffraction timescale, and the drift rate are determined to be Δ ν d = 25.89 ± 7.55 MHz, Δ τ d = 14.42 ± 3.98 minutes, and dt / d ν = 0.07 ± 0.14 minutes MHz −1 , respectively. The frequency dependencies of the scintillation parameters exhibit single power-law spectral behaviors, indicating that the electron density fluctuations in the interstellar medium approximately follow the Kolmogorov spectrum. The secondary spectra exhibit two distinct parabolic arcs with well-determined curvatures of 0.002 and 0.02 s 3 for the outer and inner arcs, respectively. The locations of the scattering screens are approximately determined to be 157.3 and 726.0 pc, respectively, from the pulsar for isotropic scattering. The inner scintillation arc is present contemporaneously over a wide frequency range, indicating that the scintillation arc is a broadband phenomenon. The arc curvature scales with observing frequency as a power law with an index of −2.05 ± 0.05, which implies that the scattering screen spans a physical distance from 689.7 to 883.3 pc from the pulsar.
With the transition of the medical model from the traditional biomedical model to the biopsychosocial one, there is a growing trend and requirement for oral operations that prioritize comfort, pain ...management, minimally invasive techniques, and visualization. Consequently, demands for comfortable dental treatments among individuals are increasing. However, initial periodontal therapy is often accompanied by pain, and patients' reactions to pain range from nervousness to dental fear, such as irritability, hyperventilation, even nausea, vomiting, and refusal to cooperate, which make the implementation of initial periodontal therapy difficult or even impossible. This article will focus on three key steps: firstly, the preparation of the clinic, the acquisition of patients' trust and the implementation of preventive sedation before treatment; secondly, the use of comfort operation and nursing, psychological intervention measures, local anesthesia, and sedation techniques during treatment; thirdly, the health educ
A novel, time-resolved interferometric technique is presented that allows the reconstruction of the complex electric field output of a swept source laser in a single-shot measurement. The power of ...the technique is demonstrated by examining a short cavity swept source designed for optical coherence tomography (OCT) applications with a spectral width of over 100 nm. The novel analysis allows a time-resolved real-time characterization of the roll-off, optical spectrum, linewidth, and coherence properties of a dynamic, rapidly swept laser source.
Abstract
We have carried out a detailed study of polarimetric individual pulse emission from the pulsar J1701−3726 (B1658−37), observed at 1369 MHz using the Parkes 64 m radio telescope. The ...single-pulse sequences reveal the presence of the three major emission phenomena of pulse nulling, mode changing, and subpulse drifting. Trimodal distribution of the pulse energy is present, implying one population of nulls and two others of emission in the phase window. The mean flux density of the normal mode is almost two times that of the abnormal mode. Our data show that, for PSR J1701−3726, 64% of the time was spent in the normal mode and 12% was in the abnormal mode. The single pulses show the presence of two distinct periodic modulations using a fluctuation spectral analysis. About 24% of the nulls are found to create alternating bunches of nulls and bursts in a quasiperiodic manner with a longer periodicity of 48 ± 4 rotational periods. Additionally, the pulsar presents a steady even–odd modulated feature with a stationary longitude within the pulse window. The ramifications for constraining the viewing geometry and understanding the radio emission mechanisms are discussed.
Abstract
We have carried out a detailed study of individual pulse emission from the pulsar J2022+5154 (B2021+51), observed at 2250 MHz using the Jiamusi 66 m radio telescope. We have investigated the ...modulations in single-pulse behavior using fluctuation spectral analysis, which shows the presence of two prominent periodicities, around 5 and 40 rotation periods, respectively. The shorter periodicity is associated with the phenomenon of subpulse drifting. In the absence of aliasing, the emission pattern is demonstrated to consist of eight subbeams, which rotate around the magnetic axis in about 45 periods. In addition to subpulse drifting, the pulsar also shows the presence of periodic amplitude modulation with a longer periodicity in the single-pulse sequence. The pulsar joins a select group that shows the presence of periodic phase-modulated drifting as well as amplitude-modulated drifting. This provides further evidence for the two phenomena being distinct from each other with different physical origins.
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