Pervasive Crustal Volcanic Mush in the Highly Stretched Sunda Plate Margin of Northern Sumatra

Arc volcanism, crustal deformation, and their interplay are poorly understood in northwestern Sumatra. Traditional receiver function H-κ stacking studies constrain the variations in crustal thickness and Vp/Vs ratio in volcanic zones but rarely estimate the melt fractions. Here, we propose a H-Φ stacking method, a variant of the H-κ stacking method, and apply it to the dense nodal array data from Aceh, northern Sumatra, to estimate crustal thickness, Vp/Vs ratio, and melt fraction. Most results show considerably high Vp/Vs ratios (∼1.98) and melt fractions (up to 19%), indicating pervasive crustal magmatic mush. The northwestern edge of the Aceh crust is much thinner (∼22 km) than extended crust globally, reflecting a highly stretched crust due to tectonic processes governing the opening of the Andaman Sea. This thin crust and high melt fractions explain the Bouguer gravity anomaly, and partly explain the northward migration of Quaternary volcanics.Ministry of Education (MOE)Published versionThis research is jointly supported by the National Natural Science Foundation of China (42288201) and the Ministry of Education, Singapore, under its MOE Academic Research Fund Tier 3 (Award MOE-MOET32021-0002)

Seismic receiver function H-Phi stacking to estimate crustal thickness and melt fraction

<p>This package includes H-Phi stacking and virtual station stacking codes used in Feng et al. (2023, GRL, Accepted). The H-Phi stacking can provide estimations of crustal thickness and melt fraction using teleseismic receiver functions (RF). The virtual station stacking is used to group short-period seismic RF records to increase the signal-to-noise ratio. H-Phi stacking is implemented by C, and virtual station stacking is written in Python. H-Phi stacking has been successfully tested on both MacOS and Ubuntu. Users can follow the readme instruction in the package to achieve a simple attempt. </p&gt

Crack Propagation and Fragmentation Characteristics of Single-Flawed Sandstone Samples under Different Loading Conditions

Red sandstone specimens with preexisting single flaw were taken as the research object in the static and dynamic loading tests. A hydraulic press was used for the uniaxial compression experiment, and SHPB was used for the impact test. The corresponding static and dynamic stress-strain curves were obtained. The crack propagation of rock samples under different loading conditions was obtained using the camera system. The crack propagation, compressive strength, and energy characteristics of samples under quasi-static and dynamic impact loading were analyzed. The findings show that the crack initiation, development, and final fracture mode of the samples are closely related to the inclination angle of preexisting flaw and strain rate. Compared with samples under static loading, tensile and shear mixed cracks, layer separation cracks, and more far-field cracks appeared in the samples under dynamic loading. With the increase of the peak of incident wave during the SHPB test, the samples with preexisting flaw change from tensile crack to X-shaped shear failure in the range of medium strain rate. Under different loading conditions, the compressive strength of samples with 45° crack is the lowest. The energy dissipation density and energy dissipating rate of the single-flawed specimens feature a rising trend with the increasing peak of incident wave, and the influence of the inclination angle of preexisting flaw on the energy dissipation is significant for a given peak of incident wave. The strength, energy dissipation, and fractal dimension of the specimens are positively correlated with each other under different strength impact loading. As the peak of incident wave increases, the inclination angle of preexisting flaw has more significant influence on the interrelation of these three parameters

A new method to estimate slab dip direction using receiver functions and its application in revealing slab geometry and a diffuse plate boundary beneath Sumatra

While dip direction is a fundamental parameter of slab geometry, it is rarely estimated quantitatively. Here, we develop a new method, Dip Direction Searching (DDS), of receiver functions (RFs) that reduces the uncertainty of slab dip direction estimation from tens to several degrees. DDS can also resolve the thickness and depth of a dipping structure. We then apply DDS to the RFs in the Sumatran subduction zone. Travel time differences of the converted phases from the upper and lower (oceanic Moho) boundaries of the dipping low-velocity layer (LVL) along the plate interface show a thickness of 10–14 km. The results also show increased dip direction of the slab Moho from 47 ± 5.3° in southern Sumatra to 70 ± 10.7° in northern Sumatra, indicating a complicated slab geometry and internal deformation along strike. Similar dip directions are obtained for the upper and lower LVL boundaries beneath Nias and Enggano forearc islands in the north and south, whereas we find a larger discrepancy of ∼14–23° beneath Siberut and Pagai in between. The thicker LVL with a non-negligible difference in the dip directions of its upper and lower bounds in the center of Sumatra is interpreted as a partially serpentinized mantle layer above the oceanic crust, forming a distinct channel atop the subducting slab. Our results provide basic observational constraints on the structure and geometry of the oceanic slab and associated subduction processes. Both synthetics and data analyses also indicate DDS can be applied in other subduction zones and for other dipping interfaces.Ministry of Education (MOE)National Research Foundation (NRF)Published versionThis research is jointly supported by the National Natural Science Foundation of China (Grant 42288201), the Strategic Priority Research Program (A) of Chinese Academy of Sciences (Grant XDA20070302) and Singapore MOE tier-2 Grant (MOE2019-T2-1-182 (S)). This research was supported by the Earth Observatory of Singapore via its funding from the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative. This work comprises EOS contribution number 522. M. Feng thanks the Chinese Scholarship Council for scholarship fund

Steroid nuclear receptor coactivator 2 controls immune tolerance by promoting induced Treg differentiation via up-regulating Nr4a2

Steroid nuclear receptor coactivator 2 (SRC2) is a member of a family of transcription coactivators. While SRC1 inhibits the differentiation of regulatory T cells (Tregs) critical for establishing immune tolerance, we show here that SRC2 stimulates Treg differentiation. SRC2 is dispensable for the development of thymic Tregs, whereas naive CD4+ T cells from mice deficient of SRC2 specific in Tregs (SRC2fl/fl/Foxp3YFP-Cre) display defective Treg differentiation. Furthermore, the aged SRC2fl/fl/Foxp3YFP-Cre mice spontaneously develop autoimmune phenotypes including enlarged spleen and lung inflammation infiltrated with IFNγ-producing CD4+ T cells. SRC2fl/fl/Foxp3YFP-Cre mice also develop severer experimental autoimmune encephalomyelitis (EAE) due to reduced Tregs. Mechanically, SRC2 recruited by NFAT1 binds to the promoter and activates the expression of Nr4a2, which then stimulates Foxp3 expression to promote Treg differentiation. Members of SRC family coactivators thus play distinct roles in Treg differentiation and are potential drug targets for controlling immune tolerance

Novel Dental Adhesive with Biofilm-Regulating and Remineralization Capabilities

The mechanical properties and anti-caries effect of a novel anti-caries adhesive containing poly (amidoamine) dendrimer (PAMAM) and dimethylaminododecyl methacrylate (DMADDM) were investigated for the first time. Microtensile bond strength and surface charge density were measured for the novel anti-caries adhesives. Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii were chosen to form three-species biofilms. Lactic acid assay, MTT (3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, exopolysaccharide staining and live/dead staining were performed to study anti-biofilm effect of the adhesive. The TaqMan realtime polymerase chain reaction was used to study the proportion change in three-species biofilms of different groups. The Scanning Electron Microscope (SEM) was used to observe the remineralization effect of PAMAM and DMADDM. The results showed that incorporating PAMAM and DMADDM into adhesive had no adverse effect on the dentin bond strength. The 1% PAMAM and 5% DMADDM adhesive group showed anti-biofilm properties and developed a healthier biofilm with a lower chance of inducing dental caries. Combination of 1% PAMAM and 5% DMADDM solution maintained remineralization capability on dentin, similar to that using 1% PAMAM alone. In conclusion, the adhesive containing PAMAM and DMADDM had strong antimicrobial properties and biological remineralization capabilities, and is promising for anti-caries clinical applications

Novel Cavity Disinfectants Containing Quaternary Ammonium Monomer Dimethylaminododecyl Methacrylate

This study was set to assess the possible benefits of novel cavity disinfectants with 5% dimethylaminododecyl methacrylate (DMADDM); and compare the effectiveness of saliva microbial-aging method with water-aging in measuring the changing of resin–dentin bond strength. Three cavity disinfectants were tested: 0.2% Chlorhexidine (CHX); 5% DMADDM; and 5% DMADDM + 0.2% CHX. Microtensile bond strength (μTBS) test was performed after microbial-aging with saliva microbial or water aging for one month. Hydroxyproline (HYP), the production of collagen degradation, was measured spectrophotometrically. Additionally, the antibacterial effects of each reagent were evaluated. The 5% DMADDM exerted the least percentage of resin–dentin bond strength loss after one month microbial-aging (p < 0.05). There were no statistically significant differences of bond strength decrease after one month water aging among the tested groups (p > 0.05). Microbial-aging method yield more drop of bond strength than water aging in all groups except 5% DMADDM (p < 0.05). Meanwhile, 5% DMADDM had the same matrix metalloproteinases (MMPs) inhibitory effects as the other two agents (p > 0.05), but much stronger antibacterial capability than 0.2% CHX (p < 0.05). This indicated that a cavity disinfectant with 5% DMADDM is promising for improving the stability of resin–dentin bonds in appearance of saliva biofilm; and the saliva microbial-aging method is more promising for studying the durability of resin–dentin bonds than water aging