西藏琼嘉岗伟晶岩型锂矿矿物包裹体形成过程及其对熔-流体特征的指示

西藏琼嘉岗伟晶岩型锂矿是喜马拉雅地区发现的首例具有工业价值的伟晶岩型锂矿床,该矿床的发现证实了喜马拉雅地区具有成为我国稀有金属战略基地的潜力,也为喜马拉雅地区寻找伟晶岩型锂矿床提供了指示意义。本研究主要针对琼嘉岗锂矿花岗岩和伟晶岩中三种主要副矿物独居石、磷灰石和锆石中的矿物包裹体进行扫描电镜分析,确定矿物包裹体种类、频率以及产状(与裂隙关系),结合磷灰石中长石包裹体电子探针分析,综合指示琼嘉岗锂矿熔-流体性质及演化过程。研究表明:(1)琼嘉岗锂矿独居石、磷灰石和锆石中主要发育硅酸盐、氧化物、磷酸盐以及少量硫化物包裹体,其中填充裂隙和穿切裂隙的富稀土矿物独居石和磷灰石包裹体均由热液蚀变形成,而锆石放射性损伤强烈的区域中发育的远离裂隙的晶质铀矿和方钍石包裹体的形成也和流体作用相关;(2)电气石白云母花岗岩的磷灰石中发育钶钽铁矿以及烧绿石包裹体表明早期花岗岩岩浆富集铌和钽,稀有金属包裹体的数量以及类型也对高演化的花岗岩和伟晶岩是否具有稀有金属成矿潜力以及矿化类型具有一定指示意义;(3)锂辉石伟晶岩磷灰石中发育异常高且变化大的An值的斜长石包裹体,它们分别记录了磷灰石在结晶时对早期富钙熔体的捕获以及熔体的分异过程。本文的研究结果还表明副矿物中矿物包裹体的种类以及元素组成可以为高演化花岗岩-伟晶岩体系的熔-流体特征及演化提供指示意义。

ResoNet:Robust and Explainable ENSO Forecasts with Hybrid Convolution and Transformer Networks

Recent studies have shown that deep learning(DL)models can skillfully forecast El Niño–Southern Oscillation(ENSO)events more than 1.5 years in advance.However,concerns regarding the reliability of predictions made by DL methods persist,including potential overfitting issues and lack of interpretability.Here,we propose ResoNet,a DL model that combines CNN(convolutional neural network)and transformer architectures.This hybrid architecture enables our model to adequately capture local sea surface temperature anomalies as well as long-range inter-basin interactions across oceans.We show that ResoNet can robustly predict ENSO at lead times of 19 months,thus outperforming existing approaches in terms of the forecast horizon.According to an explainability method applied to ResoNet predictions of El Niño and La Niña from 1-to 18-month leads,we find that it predicts the Niño-3.4 index based on multiple physically reasonable mechanisms,such as the recharge oscillator concept,seasonal footprint mechanism,and Indian Ocean capacitor effect.Moreover,we demonstrate for the first time that the asymmetry between El Niño and La Niña development can be captured by ResoNet.Our results could help to alleviate skepticism about applying DL models for ENSO prediction and encourage more attempts to discover and predict climate phenomena using AI methods.

Linkage Between European and East Asian Heatwaves on Synoptic Scales

Concurrent extreme weather events in geographically distant areas potentially cause high-end risks for societies.By using network analysis,the present study managed to identify significant nearly-simultaneous occurrences of heatwaves between the grid cells in East Asia and Eastern Europe,even though they are geographically far away from each other.By further composite analysis,this study revealed that hot events first occurred in Eastern Europe,typically with a time lag of3-4 days before the East Asian heatwave events.An eastward propagating atmospheric wave train,known as the circumglobal teleconnection(CGT)pattern,bridged the sequent occurrences of extreme events in these two remote regions.Atmospheric blockings,amplified by surface warming over Eastern Europe,not only enhanced local heat extremes but also excited a CGT-like pattern characterized by alternative anomalies of high and low pressures.Subsequent downstream anticyclones in the middle and upper troposphere reduced local cloud cover and increased downward solar radiation,thereby facilitating the formation of heatwaves over East Asia.Nearly half of East Asian heatwave events were preceded by Eastern European heatwave events in the 10-day time range before East Asian heatwave events.This investigation of heatwave teleconnection in the two distant regions exhibits strong potential to improve the prediction accuracy of East Asian heatwaves.

Differential roles of C-3 and C-6 phosphate monoesters in affecting potato starch properties

The effects of starch phosphate monoester content(SPC),namely C-3(C3P)and C-6 phosphate monoesters(C6P),on the starch properties were investigated using four potato starches with varied SPC/C3P/C6P and two nonphosphorylated maize starches with a similar range of amylose content(AC)as controls.The starch property results showed that a higher SPC is associated with lower turbidity,storage and loss modulus after storage,and water solubility,but higher swelling power(SP)and pasting viscosities.These findings suggested that SPC inhibited molecular rearrangement during storage and starch leaching during heating,and enhanced swelling and viscosities due to increased hydration and water uptake caused by the repulsion effect of phosphate groups and a less ordered crystalline structure.Increased SPC also resulted in lower resistant starch(RS)content in a native granular state but higher RS after retrogradation.Pearson correlations further indicated that SPC/C3P/C6P were positively correlated with peak(r^(2)=0.925,0.873 and 0.930,respectively),trough(r^(2)=0.994,0.968 and 0.988,respectively),and final viscosities(r^(2)=0.981,0.968 and 0.971,respectively).Notably,SPC,mainly C3P,exhibited a significantly positive correlation with SP(r^(2)=0.859)and setback viscosity(r^(2)=0.867),whereas SPC,mainly C6P,showed a weak positive correlation with RS after retrogradation(r^(2)=0.746).However,SPC had no significant correlations with water solubility,turbidity and rheology properties,which were more correlated with AC.These findings are helpful for the food industry to select potato starches with desired properties based on their contents of SPC,C3P,or C6P.

Correcting Climate Model Sea Surface Temperature Simulations with Generative Adversarial Networks:Climatology,Interannual Variability,and Extremes

Climate models are vital for understanding and projecting global climate change and its associated impacts.However,these models suffer from biases that limit their accuracy in historical simulations and the trustworthiness of future projections.Addressing these challenges requires addressing internal variability,hindering the direct alignment between model simulations and observations,and thwarting conventional supervised learning methods.Here,we employ an unsupervised Cycle-consistent Generative Adversarial Network(CycleGAN),to correct daily Sea Surface Temperature(SST)simulations from the Community Earth System Model 2(CESM2).Our results reveal that the CycleGAN not only corrects climatological biases but also improves the simulation of major dynamic modes including the El Niño-Southern Oscillation(ENSO)and the Indian Ocean Dipole mode,as well as SST extremes.Notably,it substantially corrects climatological SST biases,decreasing the globally averaged Root-Mean-Square Error(RMSE)by 58%.Intriguingly,the CycleGAN effectively addresses the well-known excessive westward bias in ENSO SST anomalies,a common issue in climate models that traditional methods,like quantile mapping,struggle to rectify.Additionally,it substantially improves the simulation of SST extremes,raising the pattern correlation coefficient(PCC)from 0.56 to 0.88 and lowering the RMSE from 0.5 to 0.32.This enhancement is attributed to better representations of interannual,intraseasonal,and synoptic scales variabilities.Our study offers a novel approach to correct global SST simulations and underscores its effectiveness across different time scales and primary dynamical modes.

Alexa,let's train now!——A systematic review and classification approach to digital and home-based physical training interventions aiming to support healthy cognitive aging

Background:There is mounting evidence that regular physical activity is an important prerequisite for healthy cognitive aging.Consequently,the finding that almost one-third of the adult population does not reach the recommended level of regular physical activity calls for further public health actions.In this context,digital and home-based physical training interventions might be a promising alternative to center-based intervention programs.Thus,this systematic review aimed to summarize the current state of the literature on the effects of digital and home-based physical training interventions on adult cognitive performance.Methods:In this pre-registered systematic review(PROSPERO;ID:CRD42022320031),5 electronic databases(PubMed,Web of Science,Psyclnfo,SPORTDiscus,and Cochrane Library)were searched by 2 independent researchers(FH and PT)to identify eligible studies investigating the effects of digital and home-based physical training interventions on cognitive performance in adults.The systematic literature search yielded 8258 records(extra17 records from other sources),of which 27 controlled trials were considered relevant.Two reviewers(FH and PT)independently extracted data and assessed the risk of bias using a modified version of the Tool for the assEssment of Study qualiTy and reporting in EXercise(TESTEX scale).Results:Of the 27 reviewed studies,15 reported positive effects on cognitive and motor-cognitive outcomes(i.e.,performance improvements in measures of executive functions,working memory,and choice stepping reaction test),and a considerable heterogeneity concerning study-related,population-related,and intervention-related characteristics was noticed.A more detailed analysis suggests that,in particular,interventions using online classes and technology-based exercise devices(i.e.,step-based exergames)can improve cognitive performance in healthy older adults.Approximately one-half of the reviewed studies were rated as having a high risk of bias with respect to completion adherence(≤85%)and monitoring of the level of regular physical activity in the control group.Conclusion:The current state of evidence concerning the effectiveness of digital and home-based physical training interventions is mixed overall,though there is limited evidence that specific types of digital and home-based physical training interventions(e.g.,online classes and step-based exergames)can be an effective strategy for improving cognitive performance in older adults.However,due to the limited number of available studies,future high-quality studies are needed to buttress this assumption empirically and to allow for more solid and nuanced conclusions.

Comparison of carotenoid,chlorophyll concentrations and their biosynthetic transcript levels in different coloured cauliflower

Carotenoids and chlorophylls are among the most widely distributed pigments in nature that play essential roles in the photosynthetic apparatus and confer diverse colours in plants.Among all vegetables,cauliflower(Brassica oleracea L.ssp.var.botrytis)is rich in phytochemicals and is an important crop grown all over the world.This study investigates carotenoid and chlorophyll concentrations in differently pigmented cultivars and elucidates the role of transcriptional regulation of carotenoid accumulation including lutein andβ-carotene.Here,we characterised changes in pigments by UHPLC-DAD-ToF-MS and changes in transcript levels of carotenoid metabolic genes by qRT-PCR in florets and leaves of orange(‘Jaffa'and‘Sunset'),purple(‘Di Sicilia Violetto'and‘Graffiti'),green(‘Trevi')and white(‘Clapton')cultivars.Transcript levels of all carotenoid metabolic genes showed different transcript level patterns in the leaves and florets.Compared to the other cultivars,the orange cultivars had the highest levels ofβ-carotene in the florets and lutein in the leaves resulting in changes lutein/β-carotene ratios.In the green cultivar,higher transcript levels were also found,especially for phytoene synthase and phytoene desaturase genes of the core biosynthesis pathway.However,no increased carotenoid concentrations were observed,possibly due to a higher carotenoid turnover induced by the carotenoid cleavage dioxygenase 4 in the green cultivar.In the white(‘Clapton')and purple(‘Di Sicilia Violetto'and‘Graffiti')cultivars the phytoene desaturase transcript levels as well as carotenoid concentrations were low.Chlorophyll concentrations changed in trend comparable to the carotenoid concentrations and were only significantly lower in the leaves of the orange cultivar‘Jaffa'.Also,the chlorophyll a/b ratio changed in‘Jaffa'.In florets the highest chlorophylls concentrations were observed for the green cultivar(‘Trevi')and the purple cultivar(‘Di Sicilia Violetto').Taken together,the study demonstrates the complex source-sink relationship of carotenoid accumulation in different coloured cauliflower.

奈妥匹坦帕洛诺司琼预防化疗引起的恶心呕吐:从临床试验到日常临床实践

化疗引起的恶心呕吐(CINV)是众多抗癌药物治疗中常见的不良事件,不仅会对患者生活质量带来负面影响,还有可能影响化疗效果。目前,指南建议的止吐方案可以预防大部分癌症患者的CINV。但临床医师并不能始终遵循指南建议,患者也常常难以坚持医师处方的治疗。因此需要采取一些提高指南依从性的方法。奈妥匹坦帕洛诺司琼(NEPA)是首个也是唯一一个固定剂量复方止吐药,由奈妥匹坦(口服)/福奈妥匹坦(静脉给药)与帕洛诺司琼(PALO)组成。NEPA可以联合地塞米松组成三联止吐方案,这是用于高致吐性化疗(HEC)患者和部分中致吐性化疗(MEC)患者预防CINV的推荐方案。因此,NEPA止吐治疗操作简单便捷,可能有助于提高指南依从性。本综述对CINV进行了概括,评价了在临床试验和真实实践中积累的NEPA止吐效果及安全性方面的证据,同时也评价了在关键临床试验之外的环境下,即日常临床环境中使用NEPA进行止吐的初步证据。此外,本文还评述了化疗期间使用NEPA控制恶心症状和提高患者生活质量,这是癌症患者管理中面临的两个大挑战。

Shoaling Internal Solitary Waves and the Formation of Boluses

An internal solitary wave of elevation in a two-layer density stratified system of an incompressible, viscous and homogeneous fluid was studied. The run-up of a wave of elevation encountering different slopes was investigated numerically based on solving the continuity, Navier-Stokes and convective-diffusion equations within the Boussinesq approximation. The commercial software COMSOL Multiphysics was used to conduct the numerical simulations. For gradual shoals, a bolus formed that transported dense fluid up the shoal. The bolus disappeared when it reached its maximum height on the slope due to the draining of the dense fluid. Various shoal angles were simulated to detect the critical angle above which a bolus does not form. An angle of 30 or less resulted in the formation of a bolus. In addition, the simulations demonstrated that the size of the bolus induced by shallower slopes was larger and that the vertical height traveled by the bolus was insensitive to the slope of the shoal.

Ground-based and additional science support for SMILE

The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions,and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere.Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission.Here,we describe current community efforts to prepare for SMILE,and the benefits and context various experiments that have explicitly expressed support for SMILE can offer.A dedicated group of international scientists representing many different experiment types and geographical locations,the Ground-based and Additional Science Working Group,is facilitating these efforts.Preparations include constructing an online SMILE Data Fusion Facility,the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar,and the consideration of particular observing strategies and spacecraft conjunctions.We anticipate growing interest and community engagement with the SMILE mission,and we welcome novel ideas and insights from the solar-terrestrial community.

黄河头道拐段冰输移及堆积过程数值模拟

头道拐河段因其特殊的河道形态及地理位置而成为黄河内蒙古段最易形成冰坝的河段,研究该河段河冰输移及堆积过程是理解内蒙古段河冰过程及卡冰结坝作用机理的关键。本文基于耦合的二维有限元水动力学模型和DPM(Discrete Parcel Method)河冰动力学模型,模拟了黄河头道拐河段2020—2021年冬季封河过程并进行了验证,讨论了不同水力条件、上游流凌密集度及河道形态对封河过程的影响。结果表明:相比于官牛犋弯道,河道弯曲率大、束窄程度高的什四份子弯道更易形成卡冰,且流量越小,卡冰作用越明显,冰盖向上游发展速度越快。河道流凌密集度小于0.4时,各种流量下研究河段未发生卡冰;流凌密集度增大至0.4,表面流冰首先在弯曲率系数较大的什四份子弯道处形成卡冰,随着流凌密集度和流量的进一步增大,下潜并输移到下游的流凌也会在官牛犋弯道形成卡冰,因此,头道拐河段形成卡冰的流凌密集度临界条件为0.4。应用冰水耦合二维动力学模型可以很好地模拟天然河道河冰输移、堆积过程中河道的水力特性、冰厚增长及封河形态,揭示了影响河冰过程的相关因素及作用机理,为黄河内蒙古段防凌减灾工作提供技术支撑。

树脂柱串联法分离地质样品中Sr-Nd-U

Sr、Nd、U等同位素体系被广泛应用于地球表生过程中年代测定及物源示踪等研究,高效地分离这些同位素体系,对于推广这些同位素方法的应用具有重要现实意义。若要同时分析地质样品中Sr、Nd、U三种元素的同位素,现有方法往往需要消解两份样品,一份用于Sr-Nd而另一份用于U的分离提纯。这种方法不但增加了样品用量,而且需要多次蒸干溶液转换介质,既延长了分离流程也增加了样品被污染的风险。为了提高样品利用率和分析效率,本文通过将树脂柱串联改进了分离流程,提出一种仅需消解一份样品,便可同时提取Sr、Nd、U三种元素的新方法。本方法中Sr的分离采用Sr特效树脂,包含Nd在内的稀土元素(REE)的分离采用AG50W-X8树脂,U的分离采用UTEVA特效树脂。实验中将三种树脂柱串联,采用3mol/L硝酸淋洗液淋洗,同步进行平衡树脂、上样、洗杂志,避免了蒸干操作。分离后的淋出液使用电感耦合等离子体质谱仪(ICP-MS)测试元素含量。结果表明:U的回收率接近99.9%,Sr的回收率超过90%,Nd的回收率超过80%;同时三种树脂柱串联的分离流程,主要基体元素(K、Ca、Na、Ba、Fe、Rb等)的去除率均超过99%,降低了对Sr、Nd、U高精度同位素分析的干扰;REE中的Sm则可以通过后续使用Ln树脂等进一步去除。此外,本文还交换了Sr特效树脂和UTEVA树脂的位置,比对两种不同串联顺序对分离结果的影响,结果表明两种树脂柱串联顺序对目标元素的分离并无显著影响。使用该方法可以有效地实现Sr、Nd、U的分离,在减少操作步骤的同时节省约一半的样品用量,提高了同位素分析效率。

Mutual impact of true triaxial stress, borehole orientation and bedding inclination on laboratory hydraulic fracturing of Lushan shale

Unconventional resources like shale gas has been the focus of intense research and development for two decades. Apart from intrinsic geologic factors that control the gas shale productivity (e.g. organic matter content, bedding planes, natural fractures, porosity and stress regime among others), external factors like wellbore orientation and stimulation design play a role. In this study, we present a series of true triaxial hydraulic fracturing experiments conducted on Lushan shale to investigate the interplay of internal factors (bedding, natural fractures and in situ stress) and external factors (wellbore orientation) on the growth process of fracture networks in cubic specimens of 200 mm in length. We observe relatively low breakdown pressure and fracture propagation pressure as the wellbore orientation and/or the maximum in situ stress is subparallel to the shale bedding plane. The wellbore orientation has a more prominent effect on the breakdown pressure, but its effect is tapered with increasing angle of bedding inclination. The shale breakdown is followed by an abrupt response in sample displacement, which reflects the stimulated fracture volume. Based on fluid tracer analysis, the morphology of hydraulic fractures (HF) is divided into four categories. Among the categories, activation of bedding planes (bedding failure, BF) and natural fractures (NF) significantly increase bifurcation and fractured areas. Under the same stress regime, a horizontal wellbore is more favorable to enhance the complexity of hydraulic fracture networks. This is attributed to the relatively large surface area in contact with the bedding plane for the horizontal borehole compared to the case with a vertical wellbore. These findings provide important references for hydraulic fracturing design in shale reservoirs.

不同温度条件下含流体砂岩裂隙摩擦特性的试验研究

砂岩储层中由流体注入导致的地震活动与砂岩断层(裂隙)的摩擦行为有关.为了揭示不同温度条件下含流体砂岩裂隙的摩擦特性,在温度范围为25°C~140°C和有效法向应力范围为4~12 MPa的试验条件下,本文分别对干燥、水饱和以及注CO_(2)锯切砂岩裂隙进行了速度分级加载试验.试验结果表明:(1)对于干燥砂岩裂隙,增大有效法向应力和升高温度均能增大裂隙的初始摩擦系数,而改变有效法向应力对裂隙摩擦稳定性影响不明显,仅升高温度会略微降低其摩擦稳定性;(2)对于水饱和砂岩裂隙,裂隙的初始摩擦系数同样会随着有效法向应力的增大而增大,但会受到升温的弱化作用,而增大有效法向应力和升高温度均能降低裂隙的摩擦稳定性;(3)对于注CO_(2)砂岩裂隙,裂隙的初始摩擦系数受有效法向应力和温度变化的影响与水饱和砂岩裂隙相反,但裂隙的摩擦稳定性仅会随着温度的升高而降低,受有效法向应力的影响不明显.因此,砂岩裂隙的摩擦特性受有效法向应力、温度和注入流体类型的共同影响.该试验结果对理解流体注入诱发地震有一定的指示作用.

The effects of plyometric jump training on lower-limb stiffness in healthy individuals:A meta-analytical comparison

Purpose:This study aimed to examine the effects of plyometric jump training(PJT)on lower-limb stiffness.Methods:Systematic searches were conducted in PubMed,Web of Science,and Scopus.Study participants included healthy males and females who undertook a PJT programme isolated from any other training type.Results:There was a small effect size(ES)of PJT on lower-limb stiffness(ES=0.33,95%confidence interval(95%CI):0.07-0.60,z=2.47,p=0.01).Untrained individuals exhibited a larger ES(ES=0.46,95%CI:0.08-0.84,p=0.02)than trained individuals(ES=0.15,95%CI:-0.23 to 0.53,p=0.45).Interventions lasting a greater number of weeks(>7 weeks)had a larger ES(ES=0.47,95%CI:0.06-0.88,p=0.03)than those lasting fewer weeks(ES=0.22,95%CI:-0.12 to 0.55,p=0.20).Programmes with<2 sessions per week exhibited a larger ES(ES=0.39,95%CI:0.01-0.77,p=0.04)than programmes that incorporated>2 sessions per week(ES=0.20,95%CI:-0.10 to 0.50,p=0.18).Programmes with<250 jumps per week(ES=0.50,95%CI:0.02-0.97,p=0.04)showed a larger effect than programmes with250-500 jumps per week(ES=0.36,95%CI:0.00-0.72,p=0.05).Programmes with>500 jumps per week had negative effects(ES=-0.22,95%CI:-1.10 to 0.67,p=0.63).Programmes with>7.5 jumps per set showed larger effect sizes(ES=0.55,95%CI:0.02-1.08,p=0.04)than those with<7.5 jumps per set(ES=0.32,95%CI:0.01-0.62,p=0.04).Conclusion:PJT enhances lower-body stiffness,which can be optimised with lower volumes(<250 jumps per week)over a relatively long period of time(>7 weeks).

Fixed-time group consensus of second-order multi-agent systems based on event-triggered control

The problem of fixed-time group consensus for second-order multi-agent systems with disturbances is investigated.For cooperative-competitive network,two different control protocols,fixed-time group consensus and fixed-time eventtriggered group consensus,are designed.It is demonstrated that there is no Zeno behavior under the designed eventtriggered control.Meanwhile,it is proved that for an arbitrary initial state of the system,group consensus within the settling time could be obtained under the proposed control protocols by using matrix analysis and graph theory.Finally,a series of numerical examples are propounded to illustrate the performance of the proposed control protocol.

A GDPR Compliant Approach to Assign Risk Levels to Privacy Policies

Data privacy laws require service providers to inform their customers on how user data is gathered,used,protected,and shared.The General Data ProtectionRegulation(GDPR)is a legal framework that provides guidelines for collecting and processing personal information from individuals.Service providers use privacy policies to outline the ways an organization captures,retains,analyzes,and shares customers’data with other parties.These policies are complex and written using legal jargon;therefore,users rarely read them before accepting them.There exist a number of approaches to automating the task of summarizing privacy policies and assigning risk levels.Most of the existing approaches are not GDPR compliant and use manual annotation/labeling of the privacy text to assign risk level,which is time-consuming and costly.We present a framework that helps users see not only data practice policy compliance with GDPR but also the risk levels to privacy associated with accepting that policy.The main contribution of our approach is eliminating the overhead cost of manual annotation by using the most frequent words in each category to create word-bags,which are used with Regular Expressions and Pointwise Mutual Information scores to assign risk levels that comply with the GDPR guidelines for data protection.We have also developed a web-based application to graphically display risk level reports for any given online privacy policy.Results show that our approach is not only consistent with GDPR but performs better than existing approaches by successfully assigning risk levels with 95.1%accuracy after assigning data practice categories with an accuracy rate of 79%.

地球系统复杂性研究综述

本文旨在全面回顾统计物理学、复杂系统科学(如临界现象、网络理论、渗流、临界点分析和熵)以及机器学习等方法在复杂地球系统研究和应用方面的最新进展.这些方法的整合,为理解地球系统的动力学,提供了新的见解和视角.通过运用这些方法,可以更好地建模、分析地球系统中的相互关系和非线性效应,揭示系统的复杂行为和临界性质.

Numerical Studies of Magnetic Reconnection and Heating Mechanisms for the Ellerman Bomb

An Ellerman Bomb(EB)is a kind of small scale reconnection event,which is ubiquitously formed in the upper photosphere or the lower chromosphere.The low temperature(<10,000 K)and high density(~1019–1022)plasma there makes the magnetic reconnection process strongly influenced by partially ionized effects and radiative cooling.This work studies the highβmagnetic reconnection near the solar temperature minimum region based on high-resolution 2.5D magnetohydrodynamics simulations.The time-dependent ionization degree of hydrogen and helium are included to realize more realistic diffusivities,viscosity and radiative cooling in simulations.Numerical results show that the reconnection rate is smaller than 0.01 and decreases with time during the early quasi-steady stage,then sharply increases to a value above 0.05 in the later stage as the plasmoid instability takes place.Both the large value ofηen(magnetic diffusion caused by the electron-neutral collision)and the plasmoid instability contribute to the fast magnetic reconnection in the EB-like event.The interactions and coalescence of plasmoids strongly enhance the local compression heating effect,which becomes the dominant mechanism for heating in EBs after plasmoid instability appears.However,the Joule heating contributed byηen can play a major role to heat plasmas when the magnetic reconnection in EBs is during the quasi-steady stage with smaller temperature increases.The results also show that the radiative cooling effect suppresses the temperature increase to a reasonable range,and increases the reconnection rate and generation of thermal energy.

Cenozoic Age Counterclockwise Rotation in the Northwest End of the Sierras Pampeanas, Argentina

Investigations into the Andean orocline revealed a counterclockwise rotation of about 37° in the north and a clockwise rotation of about 29° in the south. This rotation would have started in the Eocene because the Nazca and South American plates converged. The transition zone between the Puna and the Sierras Pampeanas has a clockwise rotation pattern. Our new data show that the NE convergence of the Nazca and South American plates caused the counterclockwise rotation around the NW end of the Sierras Pampeanas. The temperature rise during a magmatic activity at 13 Ma would have favored a counterclockwise rotation of the mountain blocks of about 20° on a detachment zone within 10 to 15 km of depth. These range rotations generated local stress tensors trending NE and NW, facilitating the development of valleys, basins, mineralized dikes, mineral deposits, and alluvial fans separated from their origin. The Atajo fault shows both ductile and brittle characteristics. A mylonitic belt from the Sierra de Aconquija was juxtaposed on the rocks of the Ovejería Block and the Farallón Negro Volcanic Complex by reverse vertical displacement, and a dextral horizontal component of displacement resulted in curvatures that gave rise to pull-apart basins and step over features. The Santa Maria Valley, Campo del Arenal, Hualfín Valley, and Pipanaco salt flat most likely constituted a vast early Miocene basin rarely interrupted by low feature relief.