Numerical Simulation of the Effects of Wedge Subduction on the Lithospheric Thermal Structure and the Seismogenic Zone South of Chile Triple Junction

In contrast to common subduction, the young and thin part of the Antarctic Plate subducts first to the south of the Chile Triple Junction (CTJ), followed by the old and thick part, corresponding to wedge subduction. A finite element model was used to simulate the wedge subduction of the Antarctic Plate and to compare it with the slab subduction of the Nazca Plate. The results show that the CTJ is not only a wedge subduction boundary but also an important factor controlling the lithospheric thermal structure of the overriding plate. The computed heat flow curves are consistent with the data observed near the trench of the two selected profiles. The different slab dips to the north and south of the CTJ are considered to be caused by wedge subduction. When the slabs are young and at the same age, the deep dip of the Antarctic slab is 22° smaller than the Nazca slab. Southward from the CTJ, the slab age of the wedge subduction increases, which leads to a larger slab dip, a colder slab, and a wider seismogenic zone. The effect of the slab age of wedge subduction on the focal depth is smaller than that of the convergence rate. A 4.8-cm/year difference in convergence rate of the wedge subduction results in an 11-km difference in the width of the seismogenic zone and a 10-km difference in the depth of the downdip limit. Among these controlling factors, the convergence rate plays a major role in the different focal depths south and north of the CTJ.

Numerical Analysis of Stapes Prosthesis Constraining in the Case of Otosclerosis

In the case of otosclerosis, it has been noticed that even though there are a variety of different prostheses on the market, due to the anatomical characteristics, it is not always possible to restore excellent mobility to the ossicles and the prosthesis. On the one hand, this happens because the incus long process and the prosthesis create difficult angles. On the other hand, incus necrosis is among the most common causes of the loss of stability to the prosthesis and stapedectomy failure. The aim of this research is to suggest an improvement for stapes prosthesis stability and numerically evaluate the impact of the prosthesis constraining to its dynamical behavior. Numerical 3D models of a standard as well as a modified (adjustable angled) stapes prosthesis were created in order to achieve this aim. Consequently, the modal analysis has been performed to evaluate the mechanical behavior of the prosthesis, assuming that the piston (thick part) would be made of Teflon, and the thin part, fixated on the incus long process, would be made from titanium alloy. Finally, the numerical analysis has been conducted by changing the boundary conditions in respect of the prosthesis constraining, where the attached stapes prosthesis connects to the ossicular chain. Subsequently, there were two hypotheses raised for the prosthesis loop constraining. The first is that during the surgery, the prosthesis is perfectly crimped with certain looseness. The second is that the prosthesis is outgrown by the tissues over time and thus becomes over-constrained. Then, the analyzed standard stapes prosthesis does not fulfil its functions because of the over-constraining that develops over time. An improvement for the standard stapes prosthesis, i.e., a modified stapes prosthesis (adjustable angled), that has been proposed in this research allows avoidance of the negative effects of the over-constrained standard stapes prosthesis that appear over time. Moreover, the proposed modified prosthesis helps to regain hearing when the angle between the incus long process and prosthesis is unfavorable.

Seismic Site Response of A Large Deep-seated Rock Slope Revealed by Field Monitoring and Geophysical Methods

Shidaguan Slope (hereinafter short for SDG Slope) is an unstable rock slope with an area of 30.78×104 m2 and a deformation depth of 30-70 m in Maoxian County, Sichuan Province, China. Three seismometers (P2-P4) with high sensitivity were installed at different locations on the unstable part of the slope. P2 and P3 were almost at the same elevation (2221 m and 2247 m), while P4 was the lowest (at 2140 m). Another seismometer (P1) sat in a stable location at a higher elevation (2373 m). 99 shallow earthquakes were analyzed. According to the peak acceleration ratios of three seismometers (P2-P4) on the unstable part and another seismometer (P1) on the stable part, the points at lower elevations showed greater seismic amplification (with the amplification coefficient of 2.64-3.51) than one at a higher elevation. And points at relatively thinner part (23 m thick) of unstable slope showed greater seismic amplification than ones at thick part (60-75 m thick). The same rule was also found in studying the site-epicenter azimuth and earthquake magnitude data. Based on the relationship between amplification coefficient and resistivity and rock core, the seismic response amplification was affected by the lithofacies difference. The lithofacies with resistivity values of 50-100 Ohm.m and RQD values of 0-50 % incurred seismic response amplification, which was restrained by the below lithofacies with resistivity values of 10-50 Ohm.m and ROD values of 0 %. When building on slope areas, the lithofacies difference should be taken into full consideration.

First direct identification of the barlens vertical structure in galaxy models

Applying spectral dynamics methods to one typical N-body model with a barlens, we dissect the modelled bar into separate components supported by completely different types of orbits. We identify at least four components: a narrow elongated bar, a boxy bar, and two components contributing to the barlens. We analyse the vertical structure of all components that make up the thick part of the bar, which has a boxy/peanut shape (B/P bulge). We show that the ‘peanut’ shape is mainly due to the orbits that assemble the boxy part of the face-on bar. We associate the X-shape with the narrow and elongated bar. The wider part of the barlens with square-like isophotes contributes to the boxy shape of the B/P bulge when we observe the galaxy edge-on. However, the part of the barlens with rounded isophotes in the face-on view is a rather flat structure in the vertical direction without any significant off-centre protrusions. Thus, for the first time, we demonstrate that the rounded face-on barlens cannot be entirely associated with the B/P bulge.

Studying electric double layer under sorption of gold on activated carbons from thiocarbamide solutions

The purpose of the article is to research the mechanism of gold-thiocarbamide complex sorption by activated carbons by studying the properties of the resulting electric double layer. The study of the electric double layer of coal sorption surface is conducted using a polar conductometric method based on the simultaneous use of polarization dependences on direct current and conductometric measurements on alternating current. It is shown that the sorption of thiocarbamide complexes of gold occurs more intensively at the cathodic values of sorbent potentials. Dependence of the adsorption value on the potential is actually linear in the negative region from 0.05 to 0.2 V. The absolute value of goldthiocarbamide sorption at the negative sorbent potential of 0.2 V coincides with the maximum values of the polarization current for direct current and conductivity for alternating current. The electrochemical reduction reaction of thiocarbamide compounds results in the formation of neutral thiocarbamide molecules, it might be the reason for gold deposition in a metallic form on the surface of the carbon sorbent. Neutralization of active compounds in the electric double layer creates conditions for the activation of positively charged gold ions directing to the negatively charged sorbent surface. The anodic region of sorbent polarization is characterized by the maximum values of gold ion sorption at the positive potential of 0.2 V. In this case the sorbent surface should be recharged, since in the same region of the potential the maximum AC conductivity is observed. Such conditions should lead to the destruction of the thick part of the electric double layer and, consequently, create favorable sorption conditions. The conducted studies allowed to derive a conclusion that the sor ption of gold-thiocarbamide complexes by activated carbons is significantly influenced by the sorbent potential. The use of the polar conductometric method for studying the electric double layer makes it possible to explain the features of given compound sorption on activated carbons.

uGMRT HI 21-cm absorption observations of two extremely inverted spectrum sources

We report the detection of HI 21-cm absorption in a member of the rare and recently discovered class of compact radio sources: extremely inverted spectrum extragalactic radio sources (EISERS). The EISERS conceivably form a special subclass of the inverted spectrum radio galaxies since the spectral index of the optically thick part of the spectrum for these sources crosses the synchrotron self-absorption limit of α = +2.5 (S(ν) ∝ να). We searched for HI absorption in two EISERS using the recently upgraded Giant Metrewave Radio Telescope (uGMRT) and detected an absorption feature in one of them. The strong associated HI absorption detected against the source J1209−2032 (z = 0.4040) implies an optical depth of 0.178 ± 0.02, corresponding to an HI column density of 34.8 ± 2.9 × 1020 cm−2, for an assumed HI spin temperature of 100 K and covering factor of 1. This is among the highest known optical depth and HI column densities found for compact radio sources of peaked spectrum type and supports the free-free absorption model for the steeply inverted radio spectrum of this source. For the other source, J1549+5038 (z = 2.171), no HI absorption was detected in our observations.

Variability and parsec-scale radio structure of candidate compact symmetric objects

ABSTRACT We report results on multiepoch Very Large Array (VLA) and pc-scale Very Long Baseline Array (VLBA) observations of candidate compact symmetric objects (CSOs) from the faint sample of high-frequency peakers. New VLBA observations could resolve the radio structure in about 42 per cent of the observed sources, showing double components that may be either mini-lobes or core-jet structures. Almost all the sources monitored by the VLA show some variability on time-scale of a decade, and only one source does not show any significant variation. In 17 sources, the flux density changes randomly as it is expected in blazars, and in four sources the spectrum becomes flat in the last observing epoch, confirming that samples selected in the GHz regime are highly contaminated by beamed objects. In 16 objects, the pc-scale and variability properties are consistent with a young radio source in adiabatic expansion, with a steady decrease of the flux density in the optically thin part of the spectrum, and a flux density increase in the optically thick part. For these sources, we estimate dynamical ages between a few tens to a few hundred years. The corresponding expansion velocity is generally between 0.1c and 0.7c, similar to values found in CSOs with different approaches. The fast evolution that we observe in some CSO candidates suggests that not all the objects would become classical Fanaroff–Riley radio sources.

CFD Analysis of Mechanisms Underlying the Porosity-reducing Effect of Atomized Flows in High-pressure Die Cast Products

In high-pressure die casting, attention has been paid to the J factor, which is defined by the speed of the metal injected at the gate and the shape of the gate. In casting experiments using a piston die, the porosity of the product can be reduced by increasing the J factor such that the metal flow passing through the gate forms an atomized flow. To clarify the underlying mechanisms, we developed a system for simulating a two-phase flow of air and aluminum by large-scale calculations of turbulent flow. During the development of the system, we injected metal into an open space and performed imaging to confirm the state of the atomized flow. The system was then verified by reproducing the atomized flow. The analysis results visualized the many small turbulent vortices generated in the thick part far from the gate. We demonstrated that the change from small to longitudinal vortices promoted entrainment of air into the aluminum and increased the efficiency of air expulsion outside the die through an increase in the J factor.

Recurrence of quadratic differentials for harmonic measure

We consider random walks on the mapping class group that have finite first moment with respect to the word metric, whose support generates a non-elementary subgroup and contains a pseudo-Anosov map whose invariant Teichmüller geodesic is in the principal stratum of quadratic differentials. We show that a Teichmüller geodesic typical with respect to the harmonic measure for such random walks, is recurrent to the thick part of the principal stratum. As a consequence, the vertical foliation of such a random Teichmüller geodesic has no saddle connections.