Discovery of a geomorphological analog to Martian araneiforms in the Qaidam Basin, Tibetan Plateau

Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars.A gas erosion process driven by the seasonal sublimation of CO_(2) ice was proposed as an explanation for their formation,which cannot occur on Earth due to the high climatic temperature.In this study,we propose an alternative mechanism that attrib-utes the araneiform formation to the erosion of upwelling salt water from the subsurface,relying on the identification of the first terrestrial analog found in a playa of the Qaidam Basin on the northern Tibetan Plateau.Morphological analysis indicates that the structures in the Qaidam Basin have fractal features comparable to araneiforms on Mars.A numerical model is developed to investigate the araneiform formation driven by the water-diffusion mechanism.The simulation res-ults indicate that the water-diffusion process,under varying ground conditions,may be responsible for the diverse aranei-form morphologies observed on both Earth and Mars.Our numerical simulations also demonstrate that the orientations of the saltwater diffusion networks are controlled by pre-existing polygonal cracks,which is consistent with observations of araneiforms on Mars and Earth.Our study thus suggests that a saltwater-related origin of the araneiform is possible and has significant implications for water searches on Mars.

Aseismic ridge subduction and flat subduction:Insights from three-dimensional numerical models

Flat subduction can significantly influence the distribution of volcanism,stress state,and surface topography of the overriding plate.However,the mechanisms for inducing flat subduction remain controversial.Previous two-dimensional(2-D)numerical models and laboratory analogue models suggested that a buoyant impactor(aseismic ridge,oceanic plateau,or the like)may induce flat subduction.However,three-dimensional(3-D)systematic studies on the relationship between flat subduction and buoyant blocks are still lacking.Here,we use a 3-D numerical model to investigate the influence of the aseismic ridge,especially its width(which is difficult to consider in 2-D numerical models),on the formation of flat subduction.Our model results suggest that the aseismic ridge needs to be wide and thick enough to induce flat subduction,a condition that is difficult to satisfy on the Earth.We also find that the subduction of an aseismic ridge parallel to the trench or a double aseismic ridge normal to the trench has a similar effect on super-wide aseismic ridge subduction in terms of causing flat subduction,which can explain the flat subduction observed beneath regions such as Chile and Peru.

Analytical and numerical simulations of uplift processes at the Tibet-Sichuan boundary

Previous studies have shown that the uplift of Tibetan plateau started in response to the collision of Indian plate and Eurasian plate. During this process, the crust of Tibetan plateau has been greatly thickened which leads to significant elevations. The elevation gradient is extremely large at the east boundary of Tibetan plateau where Longmenshan fault exists, dropping from 4500 to 500 m within a distance of 100 km, while it is more gentle at the south and north sides of Sichuan basin. Such a difference of elevation gradient has been explained with a crustal channel flow model. However, pre- vious crustal flow models consider the thickness of the lower crust as a constant which is highly simplified. Therefore, it is essential to build a more realistic crustal flow model, in which the thickness of the lower crust is variable and dependent on the inflow velocity of crustal materials. Here we build up both analytical and numerical models to study the mechanism and process of the uplift of Tibetan plateau at the eastern boundary. The results of the analytical model show that if the thickness of the lower crust can vary during the uplift process, the lower crustal viscosity of the Sichuan basin needs to be 1022 Pas to fit the observed elevation gradient. Such a viscosity is one-order magnitude larger than the previous results. Numerical model results further show that the state of stresses at the plateau boundary changes during uplift processes. Such a stress state change may cause the formation of different fault types in the Longmenshan fault area during its uplift history.

用于密集波分复用光纤传输系统的路由选择机制研究（英文）

为了提高密集波分复用光纤传输的Qos质量,提出了一种基于蚁群优化算法的Qos单播路由选择机制。该算法根据动态的光路连接请求,通过蚁群分类来构建主光路和备用光路,从而将主从复用技术引起的阻塞率降到最低。此外,为了解决局部最优解问题,通过设置遗传因子对蚁群算法进行了优化。NS2仿真实验结果显示,相比传统的路由选择算法,提出的Qo S单播路由选择具有较好的可行性和全局最优化能力,能够有效降低阻塞率从而提高网络资源的利用率。

Thermal structure of continental subduction zone: high temperature caused by the removal of the preceding oceanic slab

The thermal structure of the continental subduction zone can be deduced from high-pressure and ultra-high-pressure rock samples or numerical simulation.However,petrological data indicate that the temperature of subducted continental plates is generally higher than that derived from numerical simulation.In this paper,a two-dimensional kinematic model is used to study the thermal structure of continental subduction zones,with or without a preceding oceanic slab.The results show that the removal of the preceding oceanic slab can effectively increase the slab surface temperature of the continental subduction zone in the early stage of subduction.This can sufficiently explain the difference between the cold thermal structure obtained from previous modeling results and the hot thermal structure obtained from rock sample data.

Professor Yumao Du's Experience in Treating Chronic Nephritis

Chronic nephritis is a common clinical kidney disease,with insidious onset and long course,which can eventually develop into chronic renal failure.In Chinese medicine,it belongs to the categories of"edema,""back pain""deficiency,"and epertigo."Professor Du Yumao is a well-known Chinese medicine doctor and a well-known nephropathy expert in China.He has rich clinical experience and unique insights into the treatment of chronic nephritis.He believes that insufficient kidney yin is the key to this disease,and water dampness and blood stasis are important pathological factors.Appropriate change of method according to the situation and flexible use of medicine often lead to good clinical outcomes.

Progress in the numerical modeling of mantle plumes

The mantle plume model, as an integral part of the Earth’s internal convection system, is complementary to the theory of plate tectonics. They together constitute the key configuration of material circulation and energy transport in the Earth’s interior. Seismology, high-temperature and high-pressure mineralogy, geology, and geodynamic numerical modeling have conducted comprehensive studies on the mantle plume model since it was proposed. In particular, numerical simulation, which investigates the dynamic processes of mantle plumes by establishing a theoretical model, provides a quantitative description of possible mantle plume evolution and the responses of the Earth’s interior and surface, which can be used to explain observations and experimental results from other disciplines. Thus, it is one of the most important means to study plume dynamics. This paper summarizes the research progress in numerical modeling of mantle plumes in past decades, including the origin of mantle plumes, seismological evidence for the existence of plumes, interactions between mantle plumes and the lithosphere, mid-ocean ridges, subduction zones, and the mantle transition zone, as well as the relationship between plumes and large low shear wave velocity provinces. The theoretical results of numerical modeling combined with observations from other disciplines enable us to deeply understand the dynamic process of mantle plumes. With the continuing development of numerical methodology and the improvement of high-performance computing, geodynamic numerical modeling will become a more accurate and efficient approach for studying mantle plume dynamics and related frontier problems in geosciences.

Progress in numerical modeling of subducting plate dynamics

The core concerns of plate tectonics theory are the dynamics of subducting plates, which can be studied by integrating multidisciplinary fields such as seismology, mineral physics, rock geochemistry, geological formation studies, sedimentology,and numerical simulations. By establishing a theoretical model and solving it with numerical methods, one can replicate the dynamic effects of a subducting plate, quantifying its evolution and the surface response. Simulations can also explain the observations and experimental results of other disciplines. Therefore, numerical models are among the most important tools for studying the dynamics of subducting plates. This paper provides a review on recent advances in the numerical modeling of subducting plate dynamics. It covers various aspects, namely, the origin of plate tectonics, the initiation process and thermal structure of subducting slab, and the main subduction slab dynamics in the upper mantle, mantle transition zone, and lower mantle. The results of numerical models are based on the theoretical equations of mass, momentum, and energy conservation. To better understand the dynamic progress of subducting plates, the simulation results must be verified in comparisons with the results from natural observations by geology, geophysics and geochemistry. With the substantial increase in computing power and continuous improvement of simulation methods, numerical models will become a more accurate and efficient means of studying the frontier issues of Earth sciences, including subducting plate dynamics.

黄瓜苋科凝集素基因的表达分析与逆境调控

凝集素是一类具有特异性糖结合活性的蛋白质,通常具有1个或多个非催化的糖结合结构域。凝集素在植物对病原菌的防御反应中发挥重要作用。由于其抗细菌、真菌、病毒和昆虫等的活性,凝集素在农业和生物医药领域都具有很大的应用潜力。作为最小的凝集素家族之一,苋科凝集素的研究较少。该文通过对重要经济作物黄瓜(Cucumissativus)的基因组进行分析,对16种苋科凝集素基因在黄瓜基因组中的分布和位置进行研究,并分析相关基因的外显子/内含子组成。进一步通过启动子分析,阐明了苋科凝集素基因对非生物胁迫的响应情况。最后,通过实时荧光定量PCR,检测了黄瓜中4种苋科凝集素基因对低温、高盐、干旱和ABA处理的响应情况。研究结果可为揭示苋科凝集素的生理功能及其在植物胁迫响应中的作用提供参考。

A Parallel Computational Model for Three-Dimensional,Thermo-Mechanical Stokes Flow Simulations of Glaciers and Ice Sheets

This paper focuses on the development of an efficient,three-dimensional,thermo-mechanical,nonlinear-Stokes flow computational model for ice sheet simulation.The model is based on the parallel finite element model developed in[14]which features high-order accurate finite element discretizations on variable resolution grids.Here,we add an improved iterative solution method for treating the nonlinearity of the Stokes problem,a new high-order accurate finite element solver for the temperature equation,and a new conservative finite volume solver for handling mass conservation.The result is an accurate and efficient numerical model for thermo-mechanical glacier and ice-sheet simulations.We demonstrate the improved efficiency of the Stokes solver using the ISMIP-HOM Benchmark experiments and a realistic test case for the Greenland ice-sheet.We also apply our model to the EISMINT-II benchmark experiments and demonstrate stable thermo-mechanical ice sheet evolution on both structured and unstructured meshes.Notably,we find no evidence for the“cold spoke”instabilities observed for these same experiments when using finite difference,shallow-ice approximation models on structured grids.