A smooth subducting seafloor usually leads to a smooth megathrust, which promotes great earthquakes. We present a case study at the northern Manila Trench to emphasize that the process depends also ...on sediment accretion and deformation. Here, a very rugged igneous basement is hidden beneath a smooth sediment cover on the incoming seafloor. Seismic imaging indicates that most of the sediment is scraped off at the trench, resulting in an uneven décollement interrupted by partially exposed subducted seamounts. New thermal models confirm the presence of large frictional heating, also consistent with a rough and strong megathrust. Our findings in conjunction with the low degree of megathrust locking reported in the literature are compatible with the notion of strong creep. Consequent implications to regional seismic and tsunami hazards call for further investigations, especially with new seafloor geodetic monitoring and improved paleoseismic studies.
Plain Language Summary
Great earthquakes, usually accompanied with large tsunamis, tend to occur in subduction zones where the megathrust fault is smooth. In appraising the potential of such great earthquakes, it is customary to use the ruggedness of the incoming seafloor before subduction to represent the roughness of the megathrust. In this work, we conduct a case study at the northern Manila Trench subduction zone to demonstrate that a smooth incoming seafloor does not always lead to a smooth megathrust. If the seafloor smoothness owes to a thick sediment cover, a rugged basement hidden beneath the sediment can still lead to a rough megathrust if most of the sediment is scraped off when the seafloor is subducted. We show seismic imaging results that indicate sediment scraping‐off at the trench to expose basement relief such as seamounts. The lack of a very smooth megathrust suggests lower potential for great earthquakes, but an accurate assessment of regional seismic and tsunami hazards requires other independent observations that help to constrain strain accumulation across the trench and earthquake history.
Key Points
Seismic imaging shows that rugged igneous basement hidden beneath smooth sediment on subducting seafloor can lead to rough megathrust
Thermal modeling constrained by heat flow observations indicates large frictional heating, consistent with a very rough megathrust
Possibility of a strong‐creep megathrust raises scientific questions in assessing seismic and tsunami hazards at northern Manila Trench
Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and ...sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.
•Dual detection modes were realized for Hg2+ sensing.•Cytotoxicity of sulfur dots was evaluated.•Endocytosis mechanism concerning sulfur dots was established.•Cellular tracking of mercury ions was ...realized.
As the standard for heavy metal sensing systems increases, it becomes more important to find out new self-indicating materials as alternatives. The traditional design of optical probe contains receptor and fluorophore as two moieties. Here a novel sulfur quantum dot as the intrinsic fluorescent sensor has been established and the signal transduction involves interaction of mercury ions with sulfur atoms which belongs to the internal system of the fluorophore. Its analytical performances can be assessed by fluorometric and colorimetric titrations simultaneously and the detection limits for Hg2+ ions are determined to be 65 nM and 1.86 μM respectively. In the presence of sulfur dots, very low cytotoxicity has been verified in two cell lines (HeLa and K562) via both cell counting kit-8 method and flow cytometry. For the first time, four sorts of chemical inhibitors have been employed to clarify the endocytosis mechanism based on sulfur quantum dots. The collected results indicate that clathrin and lipid raft mediated endocytosis play as primary roles in the internalization processes. It has been found that sulfur dots are located in the cytoplasm with intense blue emissions and the cellular tracking of mercury ions has been realized.
Aiming at the tool position optimization problems in flank milling of non-developable ruled surface with conical tools, a new method based on immune particle swarm optimization (IPSO) and least ...squares (LS) is proposed. The geometric features of the non-developable ruled surface are analyzed and the error measurement function under each tool position is used as the objective function of the intelligent algorithm. It means that the sum of the distances from the discrete points on the axis of the conical tool to the design surface is the minimum by adjusting the cutter axis and the offset distance to the design surface. The initial tool position is determined by two-point offset method. On this basis, the objective function is optimized by the immune particle swarm optimization algorithm to obtain the optimized tool position. Since the geometric decomposition method is adopted, the optimization is essentially a local optimization, so the least squares method is further used for global optimization, and the overall optimized tool position is obtained. The simulation results show that the machining error is reduced by 86% and the validity of the method is verified by machining experiments finally.
•A novel ternary lanthanide system was assembled.•Electrospinning technique was employed to control microstructure.•Emission evolution was observed in the presence of HCl.
The generation of novel ...optical sensing structures through the lanthanide coordination has been a key scientific endeavor. The design of molecular indicator for chemical response is derived from the assembly of a polymeric-based ternary europium (III) complex system (Eu(NTA)3L/PVA (NTA = 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dione, L = 2-(4-(4-(allyloxy)phenyl)-6-(pyridin-2-yl)pyridin-2-yl)pyridine, PVA = poly(vinyl acetate)). The electrospinning technique has been employed to create a nanometer scale membrane and this functional film with ultrafine fibers (diameter of about 110 nm) exhibits intense red light at 618 nm under ultra-violet excitation of 340 nm. The luminescent signal transduction involves the interaction of hydrogen chloride (HCl) with the organic ligand. The strong acidity of the analyte induces dissociation of complex network and the evolution of emission from red to blue has been observed. The fabricated nanosensor demonstrates rapid response time (<2 s) and the detection limit has been calculated to be 3.0 ppm. This effective strategy for achieving lanthanide complex-encapsulated polymer fibers will contribute to the development of new intelligent photonic devices.
Abstract
Poly (3-hexylthiophene) (P3HT) is one of the most attractive hole transport materials (HTMs) for the pursuit of stable, low-cost, and high-efficiency perovskite solar cells (PSCs). However, ...the poor contact and the severe recombination at P3HT/perovskite interface lead to a low power conversion efficiency (PCE). Thus, we construct a molecular bridge, 2-((7-(4-(bis(4-methoxyphenyl)amino)phenyl)−10-(2-(2-ethoxyethoxy)ethyl)−10H-phenoxazin-3-yl)methylene)malononitrile (MDN), whose malononitrile group can anchor the perovskite surface while the triphenylamine group can form π−π stacking with P3HT, to form a charge transport channel. In addition, MDN is also found effectively passivate the defects and reduce the recombination to a large extent. Finally, a PCE of 22.87% has been achieved with MDN-doped P3HT (M-P3HT) as HTM, much higher than the efficiency of PSCs with pristine P3HT. Furthermore, MDN gives the un-encapsulated device enhanced long-term stability that 92% of its initial efficiency maintain even after two months of aging at 75% relative humidity (RH) follow by one month of aging at 85% RH in the atmosphere, and the PCE does not change after operating at the maximum power point (MPP) under 1 sun illumination (~45
o
C in N
2
) over 500 hours.
A transparent, conductive, and flexible electrode is demonstrated. It is based on an inexpensive and easily manufacturable metallic network formed by depositing metals onto a template film. This ...electrode shows excellent electro‐optical properties, with the figure of merit ranging from 300 to 700, and transmittance from 82% (~4.3 Ω sq–1) to 45% (~0.5 Ω sq–1).
Combining multi‐channel seismic reflection and gravity modeling, this study has investigated the crustal structure of the northwestern South China Sea margin. These data constrain a hyper‐extended ...crustal area bounded by basin‐bounding faults corresponding to an aborted rift below the Xisha Trough with a subparallel fossil ridge in the adjacent Northwest Sub‐basin. The thinnest crust is located in the Xisha Trough, where it is remnant lower crust with a thickness of less than 3 km. Gravity modeling also revealed a hyper‐extended crust across the Xisha Trough. The postrift magmatism is well developed and more active in the Xisha Trough and farther southeast than on the northwestern continental margin of the South China Sea; and the magmatic intrusion/extrusion was relatively active during the rifting of Xisha Trough and the Northwest Sub‐basin. A narrow continent‐ocean transition zone with a width of ∼65 km bounded seaward by a volcanic buried seamount is characterized by crustal thinning, rift depression, low gravity anomaly and the termination of the break‐up unconformity seismic reflection. The aborted rift near the continental margin means that there may be no obvious detachment fault like that in the Iberia‐Newfoundland type margin. The symmetric rift, extreme hyper‐extended continental crust and hotter mantle materials indicate that continental crust underwent stretching phase (pure‐shear deformation), thinning phase and breakup followed by onset of seafloor spreading and the mantle‐lithosphere may break up before crustal‐necking in the northwestern South China Sea margin.
Key Points
Multichannel seismic reflection and satellite gravity data in the northwestern South China Sea
Seismic images and gravity modeling indicate a hyper‐extended continental margin
Mantle‐lithosphere may break up before crustal‐necking in the northwestern South China Sea margin
Achieving high power conversion efficiencies (PCEs) in ferroelectric photovoltaics (PVs) is a longstanding challenge. Although recently ferroelectric thick films, composite films, and bulk crystals ...have all been demonstrated to exhibit PCEs >1%, these systems still suffer from severe recombination because of the fundamentally low conductivities of ferroelectrics. Further improvement of PCEs may therefore rely on thickness reduction if the reduced recombination could overcompensate for the loss in light absorption. Here, a PCE of up to 2.49% (under 365-nm ultraviolet illumination) was demonstrated in a 12-nm Pb(Zr0.2Ti0.8)O3 (PZT) ultrathin film. The strategy to realize such a high PCE consists of reducing the film thickness to be comparable with the depletion width, which can simultaneously suppress recombination and lower the series resistance. The basis of our strategy lies in the fact that the PV effect originates from the interfacial Schottky barriers, which is revealed by measuring and modeling the thickness-dependent PV characteristics. In addition, the Schottky barrier parameters (particularly the depletion width) are evaluated by investigating the thickness-dependent ferroelectric, dielectric and conduction properties. Our study therefore provides an effective strategy to obtain high-efficiency ferroelectric PVs and demonstrates the great potential of ferroelectrics for use in ultrathin-film PV devices.An approach to boost the power conversion efficiencies (PCEs) of ferroelectric photovoltaics (PVs) is proposed based on the Schottky barrier effect. This approach leverages the thinning of a ferroelectric film to somewhere close to the depletion width, which can simultaneously suppress the recombination and lower the series resistance. Using this approach, we achieve a PCE up to 2.49% (under 365-nm ultraviolet illumination) in the 12-nm Pb(Zr0.2Ti0.8)O3 ultrathin films. Our study provides insightful guidance on how to design and tailor the ferroelectric films to achieve high PCEs, and also demonstrates the great potential of ferroelectrics for use in ultrathin-film PV devices.
Modern optoelectronics needs development of new materials characterized not only by high optical transparency and electrical conductivity, but also by mechanical strength, and flexibility. Recent ...advances employ grids of metallic micro- and nanowires, but the overall performance of the resulting material composites remains unsatisfactory. In this work, we propose a new strategy: application of natural scaffoldings perfected by evolution. In this context, we study two bio-inspired networks for two specific optoelectronic applications. The first network, intended for solar cells, light sources and similar devices, has a quasi-fractal structure and is derived directly from a chemically extracted leaf venation system. The second network is intended for touch screens and flexible displays, and is obtained by metalizing a spider's silk web. We demonstrate that each of these networks attain an exceptional optoelectonic and mechanical performance for its intended purpose, providing a promising direction in the development of more efficient optoelectronic devices.
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