STK33 plays an important positive role in the development of human large cell lung cancers with variable metastatic potential Ping Wang, Hongzhong Cheng, Jianqiang Wu, Anrun Yan and Libin Zhang Acta Biochim Biophys Sin 2015, 47: 214–223; doi: 10.1093/abbs/gmu136 Department of Thoracic Surgery, First People's Hospital of Yunnan Province, Kunming 650031, China Serine/threonine kinase 33 (STK33) is a novel protein that has attracted considerable interest in recent years. Previous research has revealed that STK33 expression plays a special role in cancer cell proliferation. However, the mechanisms of STK33 induction of cancer cells remain largely unknown. In this study, it is demonstrated that STK33 expression varies in NL9980 and L9981 cells which are homogeneous cell lines with similar genetic backgrounds. STK33 can promote cell migration and invasion and suppress p53 gene expression in the NL9980 and L9981 cells. In addition, this protein also promotes epithelial–mesenchymal transition (EMT). Moreover, STK33 knockdown decreases tumor-related gene expression and inhibits cell migration, invasion, and EMT, suggesting that STK33 may be a mediator of signaling pathways that are involved in cancer. In conclusion, our results suggest that STK33 may be an important prognostic marker and a therapeutic target for the metastatic progression of human lung cancer. 图例: STK33诱导Snail、Slug、Twist、FoxC2基因的表达 全文: http://abbs.oxfordjournals.org/content/47/3/214.full.pdf+html
Abstract. Considering the time-delayed feedback and environmental perturbations in spin-crossover system, we construct a stochastic delayed differential equation to study the state transitions from the low spin (LS) state to the high spin (HS) state in spin-crossover solids. It is shown that the delayed feedback and noise can induce optical bistability and state transitions. The mean first-passage time (MFPT) of the transition from the LS state to the HS state as the function of the noise intensity exhibits a maximum, and the noise-enhanced stability is observed. However the MFPT decreases with increase of the delayed feedback intensity, thus the delayed feedback accelerates the conversion from the LS state to the HS state. 该成果发表在Eur. Phys. J. B (2013)上，DOI: 10.1140/epjb/e2013-40179-y 清样版本： 2013epjb.pdf
The Cultures of Energy research group at Rice University seeks a one-year postdoctoral fellow for the 2013-14 academic year. Over the past two years, Cultures of Energy has worked to incubate multi-disciplinary humanistic collaboration and scholarly inquiry on matters of energy and environmental transition. A key goal of the research group is to establish humanistic and social scientific scholarship as a dynamic and integral part of public debate over energy choices and energy futures. The 2013/14 postdoctoral fellow will play an active role in the process of establishing the first research center in the world devoted specifically to cultivating energy and environmental research in the humanities and social sciences. Rice University has recently announced a five-year cross-campus Energy and Environment Initiative (E2I) within which Cultures of Energy is a founding research cluster. More details on Cultures of Energy can be found at http://www.culturesofenergy.com We seek excellent scholars whose research and teaching interests focus on energy and energy transitions or on the environmental impacts of energy use such as climate change. We welcome applicants from any discipline or interdiscipline in the human sciences including, but not limited to, anthropology, art history, history, literary studies, philosophy, religious studies, sociology and the arts. The fellow will take part in a faculty working group, help organize a campus-wide speakers series, and design and teach two courses, one semester-long introductory-level undergraduate course on energy and environmental humanities and one upper-level seminar course in her or his home discipline. The fellow will receive $50,000 per year, benefits eligibility, and a $5,000 allowance for research and relocation. The closing date for applications is March 31 st , 2013. Please send all application materials electronically to dcb2@rice.edu Required application materials: · Cover letter (2-3 pages) describing research interests and experience, in language appropriate for a multi-disciplinary panel of reviewers, and a teaching plan for the postdoctoral year. · CV · 2 letters of reference to be sent directly to dcb2@rice.edu Eligibility: · Applicants should have received a PhD between July 1, 2009 and June 30, 2013. · Fellowship recipients cannot have accepted or currently hold a tenure-track position. · Rice University is an Affirmative Action/Equal Opportunity employer. Scholars who are members of traditionally under-represented groups are encouraged to apply. · There is no citizenship requirement or restriction for this fellowship. Non-U.S. nationals are welcome to apply. · Employment eligibility verifications requested upon hire.
By Andrei Shleifer Professor of Economics, Harvard University Twenty years ago, communist countries began their shift towards capitalism. What do we know now that we didn’t know then? Harvard's Andrei Shleifer, the Russian-born, American-trained economist, provides his answers and their relevance for contemporary policymakers. Recently, I was asked by the organisers of the IIASA conference to mark the 20 th anniversary of the beginning of economic reforms in Eastern Europe and former Soviet Union to comment on the lessons of transition. The assignment presumably refers to the things that I learned – as an economist – that are different from what I believed initially. Such a recollection free from hindsight bias is challenging, but I tried. This list might be useful to future reformers, although there are not so many communist countries left. Some of the issues are however relevant not just for communist countries; the problems of heavily statist economies are similar. So here is my top-seven list. First, in all countries in Eastern Europe and the former Soviet Union, economic activity shrunk at the beginning of transition, in some very sharply. In many countries, economic decline started earlier, but still continued. In Russia, the steepness and the length of the decline (almost a decade) was a big surprise. Countries with the biggest trade shocks (such as Poland and Czechoslovakia) experienced the mildest declines. To be sure, the true declines were considerably milder than what was officially recorded – unofficial economies expanded, communist countries exaggerated their GDPs, defence cuts, and so on – but this does not take away from the basic fact that declines occurred and were surprising. These declines contradicted at least the simple economic theory that a move to free prices should immediately improve resource allocation. The main lesson of this experience is for reformers not to count on an immediate return to growth. Economic transformation takes time. Second, the decline was not permanent. Following these declines, recovery and rapid growth occurred nearly everywhere. Over 20 years, living standards in most transition countries have increased substantially for most people, although the official GDP numbers show much milder improvements and are inconsistent with just about any direct measure of the quality of life (again raising questions about communist GDP calculations). As predicted, capitalism worked and living standards improved enormously. One must say, however, that for a time things looked glum. So lesson learned: have faith – capitalism really does work. Third, the declines in output nowhere led to populist revolts – as many economists had feared. Surely reform governments were thrown out in some countries, but not by populists. Instead of populism, politics in many countries came to be dominated by new economic elites, the so-called oligarchs, who combined wealth with substantial political influence. From the perspective of 1992, this came as a huge surprise. Ironically, in some countries in Eastern Europe populism appeared 20 years after transition started, after huge improvements in living standards were absolutely obvious. Indeed, people in all transition countries were unhappy with transition: they were unhappy even in countries with rapidly improving quality of life (and this itself is another surprise and major puzzle – something for future reformers to keep in mind). But the lesson is clear: a reformer should fear not populism but capture of politics by the new elites. Fourth, economists and reformers overstated both their ability to sequence reforms, and the importance of particular tactical choices, eg , in privatisation. In retrospect, many of the theories that animated the discussion of reform – whether institutions should be built first, whether companies should be prepared for privatisation by the government, whether voucher privatisation or mutual fund privatisation is better, whether case by case privatisations might work – look quaint. Reformers nearly everywhere, including in Russia, had a vastly overstated sense of control. Politics and competence frequently intervened and dictated to a large extent most of the tactical choices. Still, most countries, despite different choices, ended up with largely similar outcomes (notable and sad exceptions are Belarus, Uzbekistan, and Turkmenistan). In various forms, all had privatisation and macroeconomic stabilisation as well as legal and institutional reform to support a market economy. Lesson learned: do not over-plan the move to markets, but, more importantly, do not delay in the hope of having a tidier reform later. Fifth, economists have greatly exaggerated the benefits of incentives by themselves, without changes in people. Economic theory of socialism has put way too much weight on incentives, and way too little on human capital. Winners in the communist system turned out not to be so good in a market economy. Transition to markets is accomplished by new people, not by old people with better incentives. I realised this and wrote about it in the mid-1990s, but the lesson both in firms and in politics in profound: you cannot teach an old dog new tricks, even with incentives. Sixth, it is important not to overestimate the long-run consequences of macroeconomic crises and even debt defaults. Russia experienced a major crisis in 1997–98, which some extremely knowledgeable observers said would set it back by 20 years, yet it began growing rapidly in 1999–2000. Similar stories apply elsewhere, from East Asia to Argentina. Debt restructurings do not necessarily make permanent scars. This experience bears a profound lesson for reformers, who are always intimidated by the international financial community: do not panic about crises; they blow over fast. Seventh, it is much easier to forecast economic than political evolution. Although nearly all transition countries have eventually converged to some form of capitalism, there has been a broader range of political experiences, from full democracies, to primitive dictatorships, to just about everything in between. There appears a strong geographic pattern in this, with countries further West, especially those involved with the European Union, becoming clearly democratic, and countries further East remaining generally more authoritarian. For countries in the middle, including Russia and Ukraine, the political paths over the 20 years have wiggled around. Lesson learned: middle-income countries eventually slouch toward democracy, but not nearly in as direct or consistent a way as they move toward capitalism.
Prof Hu, distinguished speakers, students, ladies and gentlemen: Today's topic, "Education in transition", is central to the mission of Asian universities, indeed all universities. Our world is in transition. You might say that it is in a state of rapid change, or you would say that it is in turmoil. Either way, big change is the order of the day: changes in the economic system and changes in demand for new skills. Parents and students may expect that a university education will prepare students for a cushy job. But I am sorry to say that this is a misunderstanding of the purpose of higher education, especially in a world that is changing before our very eyes. I would say that education in general, and university education in particular, is "preparation for change" because we cannot have a static education for a fast-changing world. The job market is a very different today, compared to your parents' days. Few jobs now last a lifetime. Instead, people change jobs, employers or even occupations almost as often as they change their fashion. Old jobs are lost to the market and new jobs are being created every day. Some jobs go overseas. Others simply disappear. So, how do we prepare for change in Hong Kong through our education system? This is where the 334 reform comes in. For the non-HK people in the audience, 334 means that HK will go from a three year university system, to a four year university program with high school education being shortened from 7 to 6 years. 334 is not just about changing the number of years at each level. It is an opportunity to rethink our approach to education, to break free from our obsession with static examination learning and passive memory learning. Instead, students are asked to learn how to learn, to learn analytically and creatively. For centuries, students in Asia were taught to memorize and regurgitate, to respect scholarship and accept the authority of famous people. People in the West often compare us unfavorably with Western education which puts a premium on inquiry learning and creativity. Don't get me wrong. There are some things that Asian people do right. We Asians value education greatly. We believe that education will better our lives and our society. Asian students are also known for their discipline and drive. By now, you have all heard about our "Tiger Moms". But discipline and a belief in education alone will not bring out the best in each individual. At HKUST, we ask ourselves, "What kind of graduates do we want to produce? "Well, the ideal graduate is someone who asks a lot of questions, who is curious about things, who never takes anything for granted and who is prepared and has the experience and confidence to learn anything new. Someone who is not curious will not discover new things. Einstein famously said: "I have no special talents. I am only very curious." Well, I think he was a bit too modest but talent without curiosity and drive will not go far. But curiosity alone is not enough. We must learn by doing, often through trial and error. Some wise educator once said: "We remember 10% of what we hear, 20% of what we see, and 80% of what we do." This is why in designing our new undergraduate curriculum, we make an effort to offer opportunities for doing research at the undergraduate level under the guidance and mentorship of some our leading researchers. Our famous Undergraduate Research Opportunities Program is responsible for sending 50 of our graduates every year into Ph.D. programs in world-leading universities, many with full scholarships. There is another change: to move away from early specialization. Previously, our admission is discipline-based. Now it is school-based. Applicants can wait till their second year before deciding on their majors and all students share a common core program which is broad-based. Students can explore "Signature Courses" from other Schools. Your minor may turn out to spark your life-long interest or become your career. Two of the Nobel Laureates who came to lecture at our university this year became world-famous experts in a subject they took only as a minor in university. We offer multidisciplinary programs such as environmental studies, and biomedical engineering. Our business majors can learn some ST and our ST students can pick up some business and management skills. You have no doubt heard of the complaint that students are often unable to find work in the discipline in which they are trained. We have two responses to that. First, remember I already said that the purpose of university education is not just vocational training and many successful people built their careers in fields other than their university majors. Their successes are often helped by the general skills, logical thinking, the experience and confidence in having learned a subject in depth, and broad and global perspectives. Our second response is to train our students to create their own jobs and jobs for others, to pursue their passion as entrepreneurs. Over the years, our Entrepreneurship Center has helped 46 start-ups, giving them market advice and connections, and even steering them to angel investors. Our first PhD is now the founder and chairman of a tech company that is listed in the Hong Kong Stock Exchange. Just last week, he had a one-on-one with the legendary former GE CEO Jack Welch in a forum held at this very Convention Center. Finally, education is not just about yourself. The duty of the educated is to serve the society that gives you that privilege. That is why community service and engagement is part of our ideal student profile. We have two service learning programs: CONNECT and REDBIRD. To date, over 3,000 students have taken part in one or the other. So you can see that they are not just token projects. Ladies and gentlemen, no jobs are safe and permanent in this new global order. The wise graduate is one who sees opportunities in difficulties and future trends. That is the new leader for tomorrow. I hope those are graduates that HKUST will produce. Thank you. 原文见 http://www.ust.hk/eng/about/speeches_20110915-130.htm
《Automated Composition of Nondeterministic Stateful Services》， Giuseppe De Giacomo and Fabio Patrizi WS-FM 2009, Abstract. This paper addresses the automated composition of nondeterministic available services modeled as transition systems. Nondeterminism stems naturally when the results of client-service interactions cannot be foreseen, and calls for specific orchestration strategies able to deal with partial controllability. We show how to build a set of orchestrators, by resorting to a variant of the simulation relation’s formal notion, by exploiting recent results on LTL formulas’ synthesis and by reducing our technique to the search for a safety game winning strategy. The resulting technique is sound, complete and optimal w.r.t. computational complexity, and generates all possible solutions at once. 个人点评： 个人以为作者先将 Web Service用 transition systems 形式化，再转化时序逻辑（博弈 game），最后用TLA验证 Automated Composition of Nondeterministic Stateful Services.pdf beamer_Automated_Composition_Nondeterministic_Stateful_services.pdf beamer_Automated_Composition_Nondeterministic_Stateful_services.tex
地幔转换带不连续面地震成像结果指示夏威夷西部存在热地幔 Seismic imaging of transition zone discontinuities suggests hot mantle west of Hawaii Q. Cao 1 , * , R. D. van der Hilst 1 , * , M. V. de Hoop 2 , and S.-H. Shim 1 太平洋中部夏威夷热点通常都被认为是来自深部地幔物质穿越上地幔在地表形成的，但是要在地震学上对plume进行严格的约束却是比较困难的事情。来自美国麻省理工大学（MIT）的van der Hilst研究小组（ http://quake.mit.edu/hilstgroup/robspage/ ），通过地球物理方法，对夏威夷周围地区地幔转换带的结构（不连续面深度，转换带厚度）进行了研究，并对转换带边界的异常进行了讨论分析，他们认为这些异常是由于高温条件下的地幔矿物相变(橄榄石和石榴石体系相变)形成的，但是这些热物质并不是来自于下地幔，这与传统地球化学研究观点是不同的。这一研究成果发表在2011年5月27日最新一期Science杂志上。 (延伸阅读)： Hawaii heat source debated ： http://www.sciencenews.org/view/generic/id/74845/title/Hawaii_heat_source_debated Science原文链接： http://www.sciencemag.org/content/332/6033/1068.full Supporting Online Material ： www.sciencemag.org/cgi/content/full/332/6033/1068/DC1 PDF文档： http://quake.mit.edu/hilstgroup/robspage/PapersPDF/2011Science_Hawaii_I.pdf 全文翻译：周春银 夏威夷热点 (hotspot) 通常被认为是由来自地幔深部的热物质形成的，但是要通过地震学方法来探测这样一个热柱却是很困难的。为了研究这样的热异常，我们利用 SS 波逆散射方法对太平洋中部之下的地震不连续面进行了成像，这些不连续面我们可以用地幔岩成分的地幔中的橄榄石和石榴石的相变来解释。 在夏威夷西部地幔转换带中出现的 800-2000 km 的热异常 (ΔT max ~300-400 K) ，说明这些热物质并不是从下地幔通过较细的垂直热柱 (plume) 上升上来的，而是在其进入流向夏威夷或者其他岛屿地区的热流之前就已堆积在转换带底部。这说明夏威夷熔岩的地球化学特征并不能直接约束下地幔(地球化学)域。 地幔柱 (mantle plume) 仍然是地球深部研究 (studies of Earth’s deep interior, SEDI) 中尚未完全解决的问题，作为与地幔柱有关的热点活动的原型，夏威夷长期以来都是争论的焦点。在运动的太平洋板块下面有一个来自下地幔的细细的热柱 (1-5) ，这样的经典观点已经被广泛运用于夏威夷熔岩 (6-7) 、地幔柱 - 板块相互作用 (8) 以及对流地幔风对地幔柱形态和海山链发育的影响作用 (9,10) 等方面的研究。深源地幔柱的经典一直都受到质疑，但是，仍有一些其他的代表性的解释，如来自转换带底部附近热边界处的上升流 (11) 和浅部地幔过程 (12) 。有关传说中的地幔柱的存在、定位和起源深度的层析成像证据仍然是比较模糊的 (13-17)(SOM text 1) 。 与深源地幔柱相关的温度异常会影响到矿物相边界 ( 压力引起的 ) 的深度，这可以通过地震波的反射或转换来确定 (18) 。非常重要的成像目标为在 410km 和 660km 深度附近 (Mg,Fe) 2 SiO 4 体系的橄榄石 - 瓦兹利石相变和后尖晶石相变 (19) 。由于他们具有相反的克拉伯龙斜率 (Clapeyron slope) ，高温将会使前者下降而使后者抬升 (SOM text 2) 。接收函数方法研究 (P-S 转换 ) 显示在夏威夷西南部 (20-22) 以及夏威夷岛链 (23) 之下存在较薄的地幔转换带。这表明存在高温环境，但是这些异常在侧向上的范围还难于确定，因为在岛屿及其周围地区地震台网还不够。 在超出接收函数方法之外，转换带不连续面可以利用下面的 S d S 反射 (d 是反射深度 ) 来成像确定，它在远离研究区域之外作为接收器面反射 SS 波的前驱波 (precursors) 而到达 (Fig.1) 。传统方法通过沿大范围 (10 -20 ) 区域叠加镜像 ( 像镜子一样 )SS 反射来提高较弱的信号 (24-28) 。这样的平均化会导致较低的空间分辨率，但是还并未得到夏威夷之下明显的 410 和 660km 不连续面 (SOM text 1) 。本文我们使用了 SS 波场的三维 (3D) 逆散射方法，以及被称为 GRT(generalized Radon transform)(29)(SOM text 3) 的方法 ( 改自碳氢化合物勘探方法 ) 。这也会产生数据冗余，但是不再在立体空间 (bins) 内叠加静态相，它结合了与单一成像点散射波相关的信号。利用 SS 前驱波进行 GRT 成像的可行性最早是在一个远离已知的热上涌和下降的大洋区域得到证明的 (30) 。 Fig. 1 Left: (Top) Map of study region (175° to 214°E; 12° to 26°N; Mercator projection, perspective view); (middle) geographical distribution of ~170,000 surface mid-points of SS waves (the darker the shading, the denser the coverage (SOM text 3.2); (bottom) path geometry of underside reflections at the surface ( SS ) and an upper-mantle discontinuity ( S 410 S or S 660 S ); precursor stack showing signal associated with S 660 S , S 410 S , and SS waves . Right: (Top) Geographical distribution of ~4800 sources (red symbols) and ~2250 receivers (blue) from which data are used, and which produces the data coverage shown on the left; (bottom) schematic view of ray geometry of SS , S 410 S, and S 660 S sampling the upper-mantle transition zone below the imaging area (UM, upper mantle; TZ, transition zone; LM, lower mantle). 我们利用 SS 波场 ~170000 宽频带 (20-50s) 记录来对夏威夷及其附近区域的转换带进行成像，这些记录来自于太平洋地区附近总共 ~2250 地震台站 ~4800 次地震记录 ( 震级 m b 5.2, 震源深度 75km)(Fig.1, SOM text 3.1) 。数据覆盖在大多数研究区域都是足够的，但是向西南方向会降低 (SOM fig.S6, C and F) 。在 250-950 km 深度范围、 0.5×0.5 经纬度格子内 GRT 得到弹性差异的 1D 剖面 (SOM text 3.2 and 3.3) 。这些图像，经过 3D 地幔不均一性 ( 利用不同的层析成像模型 ) 和 SS 反射点深度区域变化的校正，可以在与接收函数方法相当的辐射分辨率条件下确定边界。这些紧密隔开的反射剖面显示了 410km 和 660km 不连续面的深度变化 (topography) ，并阐明了在其他深度可能会被当作噪声而处理的构造。我们利用抽样分析来了解这些成像结果的可靠性 (SOM text 3.5) 。 3D 成像的横截剖面如穿过夏威夷的剖面 (Fig.2) 显示了多个散射水平面。除了 410km 附近和 650-700km 深度范围内的反射体之外，在大约 350 、 500 、 550 以及 800-900km 深度附近也有散射产生。大多数都是连续的并具有明显的 topography ，但是有些仍然是断断续续的或者分散的。我们这里主要关注转换带的通常边界。在 Fig.2B 中我们追踪横截剖面中的 410km 和 660km 不连续面，从所有网格点选取的深度得出不连续面深度 (Fig.3A and B) 、转换带厚度 (Fig.3C) 和深度相关性 (Fig.3D) 图像。 Fig. 2 Seismic section (E-W) across Hawaii (see Fig. 3 for section location). ( A ) Seismic image superimposed on tomographically inferred wave-speed variations ( 13 ). ( B ) Enlargement of image between 370- and 760-km depth, with interpretation of 410 (dashed green line), 520 (blue), and 660 (red) discontinuities. The depth profiles are corrected for 3D mantle heterogeneity (from tomography) and for the depth to the ocean floor where SS reflections occur. Inverse scattering does not assume contiguous reflectors (SOM text 3.2), but alignment suggests lateral continuity. Interfaces appear as a pulse with sidelobes, the width of which depends on frequency of the data and the angle at which image points are sampled ( 30 ). Horizontal resolution (which depends on illumination) is estimated to be on the order of a few hundred kilometers in the center of the study region (degrading to ~500 km toward the southwest owing to reduced sampling). I, II, and III mark regions discussed in the main text. The image gathers at 190°E and 200°E (highlighted in section on the right) are discussed in SOM text 3.3 and fig. S7). 410km 不连续面深度变化于 395-430km 之间 ( 侧向范围 500-750km) ， 660km 不连续面深度变化于 640-705km 之间 ( 侧向上更平滑一些 ) 。夏威夷下面之下及以东 ( 区域 I) ， 660km 不连续面比全球平均值 (~650km) 略浅一点。夏威夷和 165 W 之间 ( 区域 II) ， 660km 不连续面更加异常 (~640km) ，这证实了 P-S 转换的观测结果 (20-23) ，但是将异常延伸到比原来更向西的区域。 167 W-179 W 之间 ( 区域 III) ， 410km 不连续面达到了 430km 而 660km 不连续面出现在异常深度 (~700km) 。 180 以西区域界面接近全球平均深度 (29) 。 410km 和 660km 不连续面的区域平均深度分别为 413km 和 665km ，后者在区域 III 中具有较大值。转换带在夏威夷之下以及西北部较薄而在区域 III 中较厚 (Fig.3C) 。 410km 和 660km 不连续面在区域 I 和 II 中呈负相关关系，而在区域 III 中呈正相关关系 (Fig.3D) 。 Fig. 3 Discontinuity depths, transition zone thickness, and depth correlations in the study region. ( A ) Topographic map of 410 (regional average 413 km) and ( B ) 660 (regional average 665 km). Thick black solid line depicts location of E-W cross section in Fig. 2 , and thin black line in (B) indicates the location (at 700-km depth) of the mantle plume identified in ( 16 ); see also fig. S2B. I, II, and III mark the regions discussed in the main text. ( C ) The difference between 410 and 660 depths suggests that a relatively thin transition zone (passing through Hawaii) surrounds a thick transition (between 180° and 195°E, Region III). ( D ) Correlation between 410 and 660 depth variations (in regions where 410 and 660 topography exceeds 2.5 and 5 km, respectively). Interface depths are (weakly) negatively correlated beneath Hawaii, but conspicuous positive correlation appears in region III. In (A) to (C), regions where the 410 or 660 could not be identified unambiguously are left blank, and light shading indicates areas of relatively poor data coverage. 有两种类型的人为因素会影响成像的质量和准确性。首先，如果体积波速与我们用来作走时计算的值不同时，边界深度就会出现偏离 (Something text 3.4) 。这一效应非常小而难于解释区域 II 和 III 内较大的深度变化，但也可能存在某种平衡 (trade-off) 。在空间上连续的深度变化达 10km 或以上则被认为是有意义的 (30) ，但是作为保守的解释，对界面深度的估计被当作上限。其次，较稀疏的采样 ( 如夏威夷西部 ) 会降低降噪作用和空间分辨率。目测显示收集的图像 (Something text 3.3) 在大多数研究区域都是可靠的，抽样表明在区域 I 、 II 和 III 内一级观测在 95%(2σ) 自信度条件下都是可靠的 (SOM text 3.5) 。但是夏威夷西部部分深部构造处于在目前有效数据条件下可分辨的边缘。 即使存在这些不确定性因素，一级观测仍表明，夏威夷位于一个由异常较深的 410km 和 660km 不连续面以及很厚的转换带 ( 区域 III) 所构成区域东缘之上，周围是较浅的 660km 不连续面和减薄的转换带 ( 区域 I,II) 。这一预料之外的结构复杂性表明，夏威夷及其周缘地区下地幔上部边界处存在着较大的温度变化 ( 以及可能的成分变化 ) 。为了估算转换带顶部 (ΔT 410 ) 和底部 (ΔT 660 ) 的原位 (in situ) 地幔温度，我们使用的是地幔岩成分地幔中橄榄石和石榴石相变的压力 - 温度关系 ( 即克拉伯龙斜率 Γ)(SOM text 2) 。在这里并不需要非地幔岩成分来解释一级观测结果。 我们首先利用 (Mg,Fe) 2 SiO 4 橄榄石相变来解释观测结果，即橄榄石 - 瓦兹利石相变 (31) ，瓦兹利石 - 林伍德石相变 (32) ，林伍德石 - 钙钛矿 + 铁方镁石相变 ( 后尖晶石相变 ) (33) 。根据这些斜率所得到的温度地图显示，在夏威夷下面及以东地区 ( 区域 I) 存在较弱的扰动 (ΔT 410 ≈ΔT 660 ≈150K) ，但是更远的西部存在较大的异常。如果认为区域 II 较浅的 660km 不连续面是后尖晶石相变边界的上拱引起的，那么可以得到 ΔT 660 ≈300K ，与前人估计 (20,21) 一致，而较低的 ΔT 410 则说明比较明显的异常仅仅局限于转换带底部。但是 3D 结构却是很复杂的，更北地区较深的 410km 不连续面和较浅的 660km 不连续面则说明夏威夷岛链下面上地幔中具有很高的温度 (23) 。 较深的 660km 不连续面 ( 区域 III) 仍然是难于解释的谜团。对于上述 Γ p-sp 来说， 640-700km 之间的后尖晶石相变深度变化意味着温差达 ~850K 。在远离板块边缘的地区存在这样巨大的梯度是不现实的。如果 660km 不连续面之上 ( 或下 ) 波速比 3D 地幔校正中根据层析成像所推测的值要更低 ( 或高 ) ，那么 660km 不连续面可能会被高估。也有可能存在某些平衡，但是用这种方法来解释所有信号特征则需要一些似是而非的地震波和 ( 可能 ) 热异常 (SOM text 3.4) 。对于 Γ p-sp 、 ΔT 660 和上地幔波速真实值来说，后尖晶石相变并不能很好的解释 700km 深度附近的界面。 较大的 410km 和 520km 不连续面深度说明区域 III 转换带温度升高。多顶砧 (multi-anvil) 实验结果 (34-36) 证明，在高温条件下存在不同的相关系以及 Al 分配作用会增加后石榴石相变 (post-garnet transitions) 时的 ( 地震波 ) 突变。这类实验都是非常具有挑战性的，但是相关系的一些重要方面，如该正克拉伯龙斜率 (Γ p-gt ) 的大小、化学成分对其位置的影响以及 ( 相对于后尖晶石相变而言 ) 后石榴石相变的地震学可探测性 (seismic detectability) ，仍然不是特别清楚 (SOM text 2) 。后石榴石相变可能存在于热地幔中比正常地幔后尖晶石相变更深的位置，这已经被用来解释深部 660km 不连续面的发现 (24,27) 。我们的图像则描述了从后尖晶石相变 ( 区域 II) 到后石榴石 ( 区域 III) 的侧向变化。考虑到可能存在的某种平衡 (trade-off) 以及克拉伯龙斜率和 ( 地幔岩中 )Al 2 O 3 含量的不确定性，对后石榴石相变的 ΔT 660 的估计仍然带有很多不确定性，但是 Γ p-gt =3.0 MPa/K (37) 将会产生一个 450K 的上限 ( 下限由区域 II 后尖晶石相变温度所确定 ) 。 夏威夷西部地幔 660km 深度附近是很热的，该区域至少有 800km 宽 ( 如果局限于区域 II) ，但是也可能宽达 2000km ( 如果包括区域 III) ，该界面说明热物质在下地幔顶部堆积并扩散开来，热点火山作用可以由转换带底部的次级上升流 (5,38)(SOM text 5) 提供物质来源 (Fig.4) 。这与夏威夷西南下地幔地幔柱的层析成像观点 (16,17) 是不同的，但是目前还没有可用的走时数据来解释地幔中连续的地幔柱似的结构和不同深度的分散的异常 (SOM text 1) 。 Fig. 4 Cartoon of broad anomaly near base of the transition zone west of Hawaii, superimposed on a scattering image ( Fig. 2 ). Green, blue, and red lines depict interfaces near depths of 410, 520, and 660 km. The deep 410 and 520 west of Hawaii suggest higher-than-average temperatures (Δ T 410 ≈ 200 K) in the upper mantle and transition zone, but with current data coverage we cannot distinguish between a large single anomaly and multiple smaller ones. Updoming of the 660 beneath region II is consistent with elevation of post-spinel transition in hot mantle regions (with Δ T 660 ≈ 300 K), whereas deepening to ~700 km beneath III (red dashed line) may indicate change of dominant transition system to garnet (with Δ T 660, max ≈ 450 K). The positive Clapeyron slope of the latter may aid flux of lower mantle material into the transition zone (thin red arrows). Pathways of flow from the deep anomaly to Earth’s surface are not resolved by the data used, but Hawaii volcanism may result from upwellings from the (edge of the) broad anomaly (for instance, just east of Hawaii, region I, Fig. 3 ). 不连续面层析成像反应的是局部环境，其自身并不能确定热异常的来源、寿命和深度范围。但是温度差异以及地表火山作用所需要的持续热流 ( 如果他们的确是相关的话 ) 表明这并不是一个孤立的、短暂的结构，它可以从下面如通过热柱或者大尺度 ( 热化学的 ) 地幔穹窿来更新 (5) 。如果存在联系，由转换带产生的短暂的失稳特征将有助于解释夏威夷 - 皇帝海山链演化 ( 随年代推进 ) 过程中的不规则性 (10) 。此外，主要相变体系在侧向上的变化可以影响上下地幔之间的物质交换。根据后石榴石相变的宽度、每个高温相变的密度差异 ( 即尖晶石相 ↔ 石榴石 + 镁方铁矿 ↔ 钙钛矿 + 镁方铁矿 ) 、 Γ p-gt 的值和化学成分的综合作用，后石榴石相变可以促进次级上升流的形成，因而也有助于形成区域 III 上地幔温度的提高、正大地水准面异常以及可能的远离海山链的深海测量特征的富集。最后，任何在 660km 不连续面处的下地幔流动临时富集都表明存在管流或者说地幔柱的成带分布 (7,39-41) 肯定是浅部地幔现象，而地表熔岩的同位素特征并不能用来构建下地幔中的地球化学域。 References and Notes 1. J. T. Wilson , Can. J. Phys. 42 , 893 (1963). 2. W. J. Morgan, Convection plumes in the lower mantle. Nature 230 , 42 (1971). doi:10.1038/230042a0 CrossRef 3. G. F. Davies, Ocean bathymetry and mantle convection 1. Large-scale flow and hotspots. J. 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电影《Lie to Me》3x06，Beyond Belief，以一个“励志/心理调适”之类的活动为背景，讲述一个故事。 下面这个图是它的7个precept（戒条）： The Seven Transitions，可以看成是这个所谓“科学重构 模式 ”（Scientific Re-Pattern）的7大步骤： 认识到你的精神上的不和谐 - Recognize/Accept spiritual dissonance Re-align our environment - 与环境重新相调适 Breakdown problem "Negtive patterning" - 解决问题，消除“负模式” Become nothing. Embrace the void.- 把自己“空”起来；拥抱这个“空” Substitute solution - negate the void. "Positive Re-Patterning." - 替换解决方案：取空的反面：正模式 Release of Negative Patterning. Fire/Pain of Release.- 消除负模式，释放痛苦获得解放 Self-Deliver and Re-Environmentalize. Self Recreation and Freedom. Share new knowledge with others - 自我实现，重建环境，自我娱乐，自由。和他人共享知识。 上面的翻译不太地道 -- 不过我觉得原文也不太地道，因为毕竟是为了拍电影临时凑的。 不过也有些道理。 问题是， 这些貌似很合理的心理辅导，背后如果有一个类似邪教的运作机构，就非常地“不地道”了。需要防范。 现在的商业社会，什么陷阱都有，也算是一个时代的悲哀。 更悲哀的是：这个机构，也确实帮助了许多人。 ——why？可能是这个社会不能帮助他们。 附：我从网上找了一个更为权威一些的类似东西：（我只读了标题），放在这里仅供参考： 原文： http://www.transitionus.org/initiatives/7-principles The 7 Principles of Transition 1. Positive Visioning Transition Initiatives are based on a dedication to the creation of tangible, clearly expressed and practical visions of the community in question beyond its present‐day dependence on fossil fuel. Our primary focus is not campaigning against things, but rather on creating positive, empowering possibilities and opportunities. The generation of new stories and myths are central to this visioning work. 2. Help People Access Good Information and Trust Them to Make Good Decisions Transition initiatives dedicate themselves, through all aspects of their work, to raising awareness of peak oil and climate change and related issues such as critiquing economic growth. In doing so they recognize the responsibility to present this information in ways which are playful, articulate, accessible and engaging, and which enable people to feel enthused and empowered rather than powerless Transition initiatives focus on telling people the closest version of the truth that we know in times when the information available is deeply contradictory. The messages are non‐directive, respecting each person’s ability to make a response that is appropriate to their situation. 3. Inclusion and Openness Successful Transition Initiatives need an unprecedented coming together of the broad diversity of society. They dedicate themselves to ensuring that their decision making processes and their working groups embody principles of openness and inclusion. This principle also refers to the principle of each initiative reaching the community in its entirety, and endeavoring, from an early stage, to engage their local business community, the diversity of community groups and local government authorities. It makes explicit the principle that there is no room for ‘them and us’ thinking in the challenge of energy descent planning. 4. Enable Sharing and Networking Transition Initiatives dedicate themselves to sharing their successes, failures, insights and connections at the various scales across the Transition network, so as to more widely build up a collective body of experience. 5. Build Resilience This stresses the fundamental importance of building resilience i.e. the capacity of our businesses, communities and settlements to withstand shock. Transition initiatives commit to building resilience across a wide range of areas (food, economics, energy etc) and also on a range of scales (from the local to the national) as seems appropriate ‐ and to setting them within an overall context of the need to do everything we can to ensure environmental resilience. 6. Inner and Outer Transition The challenges we face are not just caused by a mistake in our technologies but are a direct result of our world view and belief system. The impact of the information about the state of our planet can generate fear and grief ‐ which may underlie the state of denial that many people are caught in. Psychological models can help us understand what is really happening and avoid unconscious processes sabotaging change. E.g. addictions models, models for behavioral change. This principle also honors the fact that Transition thrives because it enables and supports people to do what they are passionate about, what they feel called to do. 7. Subsidiarity: self‐organization and decision making at the appropriate level This final principle embodies the idea that the intention of the Transition model is not to centralize or control decision making, but rather to work with everyone so that it is practiced at the most appropriate, practical and empowering level, and in such a way that it models the ability of natural systems to self organize.
地幔深部 Fe 的自旋态转换以及富 Fe 硅酸盐熔体 下地幔底部核幔边界之上可能存在着高密度的熔体，这些熔体由于特别富集Fe而比周围地幔物质密度更大，从而可以在这样的极端环境下保持重力稳定。Fe在下地幔中的分配行为伴随着下地幔中Fe的自旋态的转换，即从高自旋态向低自旋态转换，这种行为在下地幔矿物钙钛矿和铁方镁石中已经被广泛观测到。如果这种高低度的富Fe熔体可以在下地幔底部核幔边界之上稳定存在，那么就可能在地球形成演化过程中产生厚达1000km的高密度熔体层，这对于地球内部物质的分异演化以及现在下地幔底部超低速带(ULVZs )的解释具有重要的揭示意义。这一成果发表在最新一期2011年5月12日《Nature》杂志上，正是由发现后钙钛矿(post-perovskite)的日本科学家Kei Hirose小组利用激光加热金刚石压砧(LHDAC)完成了相关实验。（译者注） Nature原文链接： http://www.nature.com/nature/journal/v473/n7346/full/nature09940.html Supplementary Information (5.1M)： http://www.nature.com/nature/journal/v473/n7346/extref/nature09940-s1.pdf PDF文档下载： 2011-Nature- Spin crossover and iron-rich silicate melt in the Earth’s deep mantle .pdf 熔体与同成分的硅酸盐固相相比具有更大的体积。但是在高压条件下这一差距将会缩小，并且现在普遍推测具有这样一种可能性，那就是，在地球内部（以及其他类地天体）高压条件下大量富集重元素 Fe的熔体比固相密度更大 (1,2)。这些致密硅酸盐熔体在下地幔底部的出现，将会对其物理化学演化产生重要影响，并可以提供一个统一模型来解释核幔边界区所观测到的一些特征 (3)。最近的理论计算 (4)以及在浅部地幔条件下对 (Mg,Fe)SiO 3 钙钛矿和熔体之间 Fe的分配关系的估计(5-7)表明， 在地球最深部地幔高压条件下熔体比固相密度更大 ，这与冲击波实验分析结果一致(8)。本文我们将 Fe分配关系测量扩大到整个地幔压力范围，发现 在大于 ~76 GPa压力时有一个明显突变，导致 Fe在熔体中的强烈富集 。随后对 (Mg 0.95 Fe 0.05 )SiO 3 玻璃的 X光发射光谱分析显示在大约 70 GPa时有一个自旋态突降 (spin collapse)，这表明所观测到的 Fe分配关系的变化可以用硅酸盐熔体中 Fe的自旋态转换 (从高自旋态到低自旋态 )来解释。这些结果意味着 在下地幔 ~1800 km深度条件下 (Mg,Fe)SiO 3 液相比共存的固相密度更大 。在地球刚形成早期，由增生作用 (accretion)和内部分异 (internal differentiation)所释放的热量可以在固体地幔下面形成一个厚达 1000 km的致密熔体层。我们也推测 (Mg,Fe)SiO 3 钙钛矿在深部地幔条件下处于液相线状态，致密岩浆的分异结晶作用 (fractional crystallization)会逐渐向富 Fe贫 Si成分演化，这与地震学上对核幔边界区结构的推测是一致的 。 我们的熔融实验是在激光加热金刚石压砧 (laser-heated diamond-anvil cell, DAC) 上进行的，样品总体成分为 (Mg 0.89 ,Fe 0.11 ) 2 SiO 4 ，压力条件为 20-159 GPa 。为了避免出现异常热扩散，加热时间控制到比较短 ( 见补充材料 ) ，但是这也使我们难于测量熔融温度。不过实验中温度的上下限可以分别由 Mg 2 SiO 4 液相线温度以及天然橄榄岩的固相线温度来给出 ( 见 Methods 以及补充材料图 1) 。从 DAC 回收的样品用高分辨率场发射电子探针显微分析仪 (FE-EPMA) 进行了分析。回收样品显示同心结构，这反映了加热过程中的温度分布 (Fig.1) ，与常见的多顶砧实验 (5-7) 中所观测的结构类似。我们在样品中间温度最高部分总是观测到一个斑点 (pocket) ，它具有非化学计量比的成分，我们将其看作是淬火局部熔体 (quenched partial melt) 。该淬火熔体的 ( Mg+Fe)/Si 摩尔比随压力增加而增大 ，从 36 GPa 时的 1.50 到 159 GPa 时的 2.56( 补充材料图 2) 。该熔体斑点被一个单相固体层 ( 铁方镁石或者钙钛矿，视压力条件不同 ) 所包围，我们认为这是在降温过程中最先结晶的相 ( 液相线相 )(5,7) 。 Figure 1: Backscattered electron images and X-ray maps for Si, Mg and Fe for samples recovered from high-pressure melting experiments. a , At 32 GPa, when ferropericlase (Fp) is the liquidus phase; b , at 76 GPa, when perovskite (Pv) is the crystalline phase in contact with the quenched melt pocket; and c , at 159 GPa in the stability field of post-perovskite (PPv). Quenched melt was found at the centre of the sample, where the temperature was highest. Metallic iron was observed at the edge of the laser-heated area in all samples, where a strong temperature gradient existed 28 . It was also found in the melt pocket, but only above 36 GPa where the liquidus phase was perovskite or post-perovskite. Arrows in a represent the directions of the laser beams for heating. See Supplementary Information for the valence state of iron in the partial melt. 在本研究中，在 20-36 GPa 时液相线相是铁方镁石 (ferropericlase) ，在更高压力下则逐渐被钙钛矿所取代 ( 在 36 GPa 时两者同时都与熔体池接触 ) (Fig.1) 。考虑到样品中 Mg/Si 比值的差异 (7) ，这与橄榄岩成分物质的观测结果 (5) 一致，其中在 31 GPa 以上条件下液相线相从铁方镁石变成钙钛矿。尽管实验中并没有做物相鉴定，但是在 143-159 GPa 条件下的实验中应该会形成后钙钛矿 (post-perovskite) 。在 36 GPa 时液相线相从铁方镁石向钙钛矿的转变表明，共熔 (eutectic) 熔体成分在高压条件下更加富 Mg 。这与熔体中 (Mg+Fe)/Si 摩尔比随压力增加而增大的现象是一致的 ( 补充材料图 2) ，尽管熔体成分与熔融程度也是相关的。 Figure 2: Change in Fe-Mg distribution coefficient and calculated density profiles. a , K D = (Fe Pv /Mg Pv )/(Fe melt /Mg melt ) between perovskite (blue circles) or post-perovskite (red squares) and melt; the values drop sharply at pressures above 76 GPa, probably due to the effect of the spin crossover of iron in silicate melt (see Fig. 3 ). Previous experimental datum obtained at 25 GPa using a multi-anvil apparatus is shown by a grey circle 6 . Error bars were estimated from uncertainties (1 σ ) in both solid and liquid compositions. b , Density of the (Mg,Fe)SiO 3 liquid coexisting with (Mg 0.92 Fe 0.08 )SiO 3 perovskite calculated for 4,000 K using the newly obtained Fe-Mg partitioning data. Data for (Mg 0.86 Fe 0.14 ) O ferropericlase 29 , Ca-perovskite 30 and PREM 19 are also shown for comparison. Liq, liquid; Fp, ferro-periclase; CaPv, calcium silicate perovskite; MgPv, magnesium silicate perovskite. 钙钛矿 / 后钙钛矿和熔体之间的 Fe-Mg 分配系数 K D = ( / )/( / ) ，在 36-159 GPa 压力范围内均得到测定 (Fig.2a) ，其中钙钛矿 / 后钙钛矿为液相线相。尽管淬火熔体斑点含有多价态的 Fe(Fig.1b,c) ，但是我们将高温下所有的 Fe 均看作为 Fe 2+ ( 见补充材料 ) 。 K D 值在 73 GPa 以下几乎保持恒定不变 ( 大约 0.22-0.29) 。这与前人在含 Al 橄榄岩总体成分 (5-7) 中的测量结果 (~0.4) 相比要低一些，但是与不含 Al 的橄榄岩物质 (6) 在 25 GPa 条件下所获得的 K D =0.304 ± 0.035 非常一致。在含 Al 体系中高 K D 值应该是由于钙钛矿中的高 Fe 3+ 含量引起的 ( 见 ref.9) 。另一方面， K D 在 76 GPa 时会突降到 0.07±0.02(Fig.2a) 。随后一直到 159 GPa 则几乎保持恒定在 0.06-0.08 。 Figure 3: Evolution of X-ray emission spectra of (Mg 0.95 Fe 0.05 )SiO 3 glass with increasing pressure. Measurements were conducted at 300 K. All spectra are normalized to transmitted intensity, and shifted so that the weighted average of main (Kβ) plus satellite (Kβ′) emission lines is set to 7,058 eV. The satellite peak decreased slightly at 59 GPa and completely disappeared at 77 GPa, indicating the spin crossover of iron. 为了研究 76 GPa 以上条件下 Fe 在熔体中强烈富集的原因，我们在 300 K 、 8-85 GPa 条件下对 (Mg 0.95 Fe 0.05 )SiO 3 玻璃进行了 X 光发射光谱分析 (Fig.3) 。在低压下， Fe 的 Kβ ′ 峰 (satellite peak) 在 7045 eV 非常明显，指示玻璃样品中的高自旋态的 Fe 2+ 。这一峰在 59 GPa 时会减弱，而在 77 GPa 时会消失。这表明了二价 Fe 中的自旋态转换。因为玻璃是液态的一个很好的类似物，这样一个 Fe 的高自旋向低自旋态的转换也可以在相似压力条件下的熔体中产生，因此为熔体中所观测到的 Fe 富集的突变而提供了一种解释 ( 见 refs. 10, 11) 。确实在我们的玻璃样品中所观测到的自旋态转换的压力范围与 K D 急剧变化的压力 (Fig.2a) 是相符的。我们的熔体比 (Mg 0.95 Fe 0.05 )SiO 3 玻璃具有更高的 Mg/Si 比值以及 FeO 含量；但是 Mg 2 SiO 4 流体中所计算的平均 Mg-O 和 Si-O 配位数 (12) 与下地幔压力条件下 MgSiO 3 流体中的值 (13) 非常相近。因此，与 Mg/Fe-O 配位相关的自旋态转换压力不会伴随着熔体中 Mg/Si 比值从 1 变化到 2 而产生明显偏移。理论研究 (14,15) 表明，当 Fe 浓度很低时 ( 低于 ~20%) ， Fe 含量并不会改变自旋态转换的压力范围，因为 Fe-Fe 相互作用是可以忽略的。多顶砧实验 (16) 结果表明，在自旋态转换开始时，钙钛矿和铁方镁石之间 Fe 的分配会产生急剧变化，这与我们的观测具有可比性。 Figure 4: Evolution and crystallization of dense melts in the deep mantle. a , During Earth's early history, any melts that form below ~1,800 km depth sink and accumulate at the base of the mantle, while any crystals that form owing to cooling of this dense magma will rise upward into the solid mantle. b , Fe-poor perovskite crystallization leaves a residual liquid enriched in FeO and depleted in SiO 2 , and crystals forming from this evolved liquid may become dense enough to form thermo-chemical piles at the base of the solid mantle. c , The final stage of crystallization involves a composition close to wüstite, leaving behind a very dense thin layer that is consistent with the seismic properties inferred inside ULVZs. White arrows indicate schematic flow patterns in the convecting solid mantle. Fe 分配关系的巨大变化表明在 1800 km 深度以下熔体会变得更加致密。我们计算了与 (Mg 0.92 Fe 0.08 )SiO 3 钙钛矿 ( 地幔岩下地幔的代表成分 (16,17)) 达到平衡的 (Mg,Fe)SiO 3 流体， 在 4000K 条件下随压力变化的密度 (Fig.2b) 。为简化起见，在 75 GPa 以下我们使用 K D =0.25 ，在更高压力下我们使用 K D =0.07 。 MgSiO 3 流体的摩尔体积根据最近的第一性原理计算结果 (4) 获得， Fe 的作用对于流体相和固相 ( 钙钛矿 ) 假设是相同的 (4,18) 。但是 (Mg,Fe)SiO 3 熔体在 75 GPa 以下时与任何典型下地幔矿物相比都是具有浮力的，而在更高压条件下则会突然变得密度更大。在地幔底部与初始参考地球模型 (PREM)(19) 的差距达到 8% 。本实验中熔体的 Mg/Si 比值比 MgSiO 3 高 ( 补充材料图 2) 。根据前人的冲击波压缩实验 (8) ，这种高 (Mg+Fe)/Si 熔体可能比上面所讨论的 (Mg,Fe)SiO 3 熔体密度更大，从而表明熔体和固体之间的密度转换可能发生在比 1800 km 更浅的深度。尽管有关熔体在地幔底部的详细情况并不是十分清楚，但是我们的结果为下地幔中可能存在的厚达 1000 km 的稳定熔体层提供了约束条件 (Fig.4) 。 Labresse 等 (3) 已经提出了一个模型，在地球形成不久所产生的致密熔体，可以构成一个相当大的“基底岩浆海” (basal magma ocean, BMO) ，它在几十亿年中缓慢结晶，其速率由上覆固体地幔中相对缓慢的固相对流所控制。我们的实验结果为固体地幔下高达 1000 km 的 BMO 的重力稳定性提供了一个新的物理证据，并且上面所推测的最大的可能厚度与 BMO 假说在广范围来说是一致的。例如，一个 1000 km 厚的 BMO 可以构成地幔 1/4 的质量；分异结晶作用以及冷却过程中残余流体中热量所产生的不相容元素 ( 如 U,Th) 的隔离，可以解释“丢失”的球粒陨石成分，这些物质可能被隔离在地幔中的某个储库中 (20) 。我们的实验结果也可以帮助我们对 BMO 的性质以及其化学演化过程随时间的变化做进一步的推测。 正如上文所提到的，我们的结果说明， (Mg,Fe)SiO 3 钙钛矿是从熔体中最先结晶出来的相，并具有较广的 (Mg+Fe)/Si 比值；对于核幔边界条件下 (Mg+Fe)/Si≈2.5 的贫 Si 熔体来说依然是这样的 ( 补充材料 Fig.2) 。这充分说明， BMO 冷却过程主要是以钙钛矿的结晶作用为特点，其他的相如 (Mg,Fe)O 镁方铁矿 (magnesiowustite) 只在相对较晚的时期结晶。另外， BMO 中形成的钙钛矿晶体将会相对亏损 Fe ，并漂浮到 1800 km 深度以下的岩浆区的顶部 (Fig.4) ，因为其 Fe/Mg 分配 K D 值较低。由此，我们可以推断残余岩浆将会向富 FeO 贫 SiO 2 成分演化 ( 即接近于方铁矿的成分 ) ，随时间密度变得更大，而且可能会保留相当量的不相容挥发性物质。 经过如上文所讨论的分异结晶演化，同样也可以影响从 BMO 所形成的堆积岩的成分。尤其是当从越来越富 Fe 的岩浆中结晶出来时，堆积岩会随时间变得更加富 Fe 密度更大。这些高密度堆积岩最终将可以保持稳定而不会被地幔对流所带走，并在地幔底部集中形成热化学堆积 (Fig.4) 。这些致密固体物质的堆积，大约比平均地幔密度高 2-3% 并构成 ~2% 的总体地幔体积，可以解释太平洋和非洲地区 (21) 下面地幔底部两个巨大的低剪切波速省 (low-sheaer-wave velocity provinces, LLSVPs) ；这些高密度物质的富 Fe 成分与这些异常 (22) 大小是一致的。 BMO 中更高程度的结晶作用也可以在核幔边界之上的薄层中产生一些高密度残余体补丁，这将可以解释超低速带 (ultralow-velocity zones, ULVZs)(23) 的出现以及地震波速特征。这些物质在地质历史时期里可以保持在或接近固相线，因为参与流体将会隔离不相容物质，相应地也会降低熔融温度。那么后期富方铁矿的堆积岩从富 Fe 贫 Si 熔体中结晶出来将会产生一个高密度固相层，即使没有熔体 (24) ，其地震波特征同样与来自 ULVZ 的地震反射仍然是一致的。 BMO 模型以及我们实验所推测的成分演化过程，与两种可能性都是相容的。另外一种可能，有助于解释为什么不同地区的 ULVZs 并不总是显示相同的地震特征 (25) ，那就是在一些 ULVZs 中间隙中的熔体已经完全抽干，留下一个强烈富集方铁矿的不含熔体的固相岩石。在另外一些 ULVZs 中，由于周围地幔中存在不同的动力学条件，上覆地幔流粘度耦合作用所产生的这些糊状残余体的连续扰动，将会阻止岩石的固结和熔体的分离 (26) 。不含熔体富集方铁矿的 ULVZ 和固有的糊状的 ULVZ 之间，我们所预计观测到的主要区别就是，剪切波速的降低幅度，在糊状 ULVZs 中降低幅度更大 (27) 。 参考文献： Stolper, E., Walker, D., Hager, B. 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科学家发现碳在地球深部新的赋存状态 New host for carbon in the deep Earth 最近法国科学家在研究中发现一种新的含C高压相，这种含C高压相具有相当的稳定性，与理论计算所预测的结构非常一致，这对于认识C在地球深部的赋存状态以及地球内部的碳循环具有一定的意义。这一成果发表在2011年3月29日美国科学院院报PNAS上： http://www.pnas.org/content/108/13/5184 PDF下载： 2011-PNAS-New host for carbon in the deep Earth.pdf 以下是全文翻译：（原文中有太多的化学式，难于在编辑器中一一编辑，请见谅；所有化学式以公式请参考原文。） 全球地球化学碳循环包含地球内部和表层碳的交换。碳通过俯冲作用主要以碳酸盐形式再循环进入地幔中，通过火山作用主要以 CO2 形式释放到大气中。所以碳酸盐的稳定性以及脱碳酸盐化作用和熔融作用对于认识全球碳循环具有重要意义。由此，我们需要认识一直到核幔边界条件下这些矿物的热动力学性质和相图。但是含 C 矿物在这些条件下的性质仍然不太清楚。本文我们报道了在 1800km 以下条件下存在一种新的 Mg-Fe 含 C 化合物。它具有由共角 (CO4)4- 四面体所构成的三元环结构，与第一性原理量子计算所预测的结构 (Oganov et al.,2008) 非常接近。该碳酸盐高压相可以通过如下 Fe(II) 和 (CO3)2- 的晶内反应： 4FeO + CO2 → 2Fe2O3 + C ，来聚集大量的 Fe(III) 。这将会形成由新的高压相 + 磁铁矿 + 纳米金刚石所组成的矿物组合。 关键词： diamond, Earth mantle, phase transition, experimental petrology, redox interaction 碳酸盐是主要的含 C 矿物，能够通过大洋岩石圈深俯冲作用进入到地幔中 (1) 。俯冲下去的成分与原始的 C 一同被认为对下地幔 C 储库具有重要作用 (2,3) 。因为在深部地幔矿物中 C 的溶解度极低 (4,5) ，因此 C 有可能以单独的相存在，如碳酸盐或者金刚石。有些研究表明碳酸镁 ( 菱镁矿 ) 是方解石和白云石消失之后 C 在深部的主要赋存方式 (6-8) 。另外一些模型认为与橄榄岩达到平衡以后的碳酸盐将会在下地幔被还原成金刚石 (9) 。但是，如同在上地幔所观测到的，下地幔氧化还原状态的不均匀性很有可能也存在：例如，俯冲带是由能够在很长时间尺度都保持稳定的更加氧化的矿物所组成的 (10) 。也有观点认为氧化和还原矿物可以在地球深部共存，如富 CO2 的金伯利岩浆可以将金刚石携带至地表来 (11,12) ，并且在来自下地幔的金刚石中发现了碳酸盐包裹体 (13,14) 。有关碳酸盐稳定性的高压实验表明菱形结构的 MgCO3 菱镁矿可以稳定至 115 GPa 、 2000-3000K ，而它在高压下会形成一种新的结构 (8) 。但是，第一性原理计算预测菱镁矿在 82 GPa 会转变成由 (CO4)4- 四面体所构成的新相，在 160 GPa 会转变成类似辉石的结构。考虑到地幔中平均 Fe/Mg 摩尔比为 0.12 ，那么碳酸盐的成分可能是介于菱镁矿和 FeCO3 菱铁矿之间，这两相可以形成连续的固熔体。目前含铁碳酸盐的相变研究很少。菱铁矿可以稳定至至少 47 GPa 和 2000K(18) ，在常温下可以稳定至 90 GPa(19) 。总之，菱铁矿和菱镁矿端元的结构特征是相似的，因为 Fe(II) 和 Mg 原子之间大小不匹配可以由 Fe(II) 中的自旋态转换来补偿 (19,20) 。 结果 Result 对于 MgCO3 和 MgO+CO2 组合，高压含 C 化合物的稳定性是一致的。在两种情况下，在类似温压条件下 ( 大约 80 GPa ， 2400K) 所获取的 X 光衍射 (XRD) 图像中出现了新的峰，这些峰并不是已知的 MgO 和 CO2 氧化物或者菱镁矿结构的峰。这些峰指示在该压力范围内一种新的稳定结构。 MgO+CO2 组合在 82 GPa 、 2350 ± 150K 条件下典型的 XRD 图像如图 1A 所示。淬火到室温之后该高压相会转变回低压菱镁矿结构。对回收样品的 EELS (Electron energy loss spectroscopy) 分析结果与原位 (in situ) 观测结果是一致的。图 1B 显示自 MgO+CO2 组合回收样品在碳 K-edge 所获取的 EELS 图谱。 290.3 eV 处尖锐的峰指示 (CO3)2-(21) 。另外，根据 EELS 分析所得出的化学成分指示为 MgCO3 成分。所以，该高压相是菱镁矿的一种等化学多晶体。 图 1. (A) X-ray diffraction pattern of a sample obtained from the transformation of periclase in CO2 confining medium at 82 GPa and 2,350 ± 150 K. Crosses represent observed data after subtraction of the background and the solid line represents the profile refinement. For this refinement we used an assemblage of untransformed periclase (Upper), platinum (Middle), and the new high-pressure phase (Lower). Residual between observations and fit is shown below the spectrum. (B) C K-edge EELS spectrum done on the recovered sample. 大于 80 GPa 时，天然富菱铁矿样品在 1850-2300 K 会发生相变，生成与上述 MgCO3 样品类似的 XRD 图像，同时还有一种铁氧化物 ( 图 2A) 。这表示形成了一种 Mg-Fe 系列的含 C 高压相。与 MgCO3 端元不同地是，该高压含铁结构是可淬火的 (quenchable) 。随后对回收样品的 TEM 分析显示有三种不同相对存在：未相变的 (Fe0.75Mg0.25)CO3 菱铁矿、高压相和一种铁氧化物 ( 图 2B) 。图 2C 中显示在铁 L2,3 dege 所获取的 EELS 图像；部分图谱与残余菱铁矿晶体结构比较吻合，与在相同能量分辨率条件下所获取的含 Fe(II) 相的图谱比较相似 (22) 。菱镁矿的出现同样也由 EELS 分析所确认。该高压相 Fe L2,3 edge 处的结构显示处理含 Fe(III) 矿物的明显结构 (22,23) ，并且根据参考文献 24 所作的定量分析表明至少 3/4 的铁是以 Fe(III) 氧化态形式存在的。根据碳 K-edge 的 EELS 数据 ( 图 2D) 确认残余菱铁矿的存在，并显示未相变的碳酸盐的峰偏移到 290.7 eV 处的特征。 287.5 eV 处的小峰指示一氧化碳 (CO)(25) 可能以包裹体 / 纳米泡形式存在，形成了该高压相的独特显微结构 ( 图 2B) 。如下面所讨论的，这些包裹体是在碳酸盐高压相形成过程中生成的。 EELS 测量表明元素比值与初始碳酸盐有所不同： Fe/C ~0.61 ± 0.07 ， Fe/O ~0.22 ± 0.02 。 图 2. (A) X-ray diffraction pattern collected at 80 GPa and room temperature of siderite transformed at 1,850–2,300 K. Crosses represent observed diffraction data after subtraction of the background and solid line the profile refinement. For the refinement we used an assemblage of high-pressure polymorph of magnetite (37) (Upper), untransformed siderite (space group R-3c) (Middle), and the new high-pressure phase (Lower). Residual between observations and fit is shown below the spectrum. (B) STEM high-angle annular dark field showing the untransformed siderite (Sid), the iron oxide (Mt for magnetite), and the transformed carbonate (HP carb.) appearing as a dark gray uniform matrix in the left side of the image. (C) EELS spectra collected on the recovered sample. These spectra provide qualitative information on the Fe(III)/ Σ Fe ratio of each phase (23, 24) and noticeable features have been indicated by small bars and can be compared with reference siderite, magnetite, and Fe(III) oxide (22). Spectrum collected on the untransformed carbonate shows a high intensity peak of 707.7 eV that indicates the main iron speciation to be Fe(II). In the case of the iron oxide, the broad L3 peak at 707–709 eV with no splitting is characteristic of magnetite, whereas the L2 shows many subsplitting and an intermediate energy position between pure ferric and ferrous iron that is typical of a mixed valence of magnetite (23). The spectrum collected in the new phase shows a L3 line at higher energy loss than in carbonate groups with a fine structure indicating the main iron speciation to be Fe(III). (D) C K-edge spectra collected in the untransformed and transformed carbonate phases. In the case of siderite relic, the peak at 290.3 eV corresponds to planar (CO3)2- carbonate groups. In the spectrum collected in the transformed carbonate, the slightly broader peak at 290.7 eV is attributed to the tetrahedral (CO4)4- forming rings of (C3O9)6-. Presence of CO can also be detected in intimate association with the new phase. (Mg0.6,Fe0.4)O+CO2 在 105 GPa 、 ~2850 K 条件下的相变会形成一个由未反应的 (Mg0.6,Fe0.4)O 、菱镁矿的高压相和相同的新高压相所组成的组合。这一组合已经由 XRD 所观测到并进一步由 ATEM 所确认 ( 图 3A) 。纳米金刚石也由电子衍射和碳 K-edge EELS 图谱所鉴别出来 ( 图 3B) 图 3. (A) TEM image of the recovered sample from the ferropericlase + CO2 experiment. Magnetite (Mt), high-pressure carbon-bearing phase (HP carb.), ferropericlase (FP), and nanodiamonds (D) are present. (B) C K-edge EELS spectrum of nanodiamonds observed in the recovered sample. The spectrum presents the absorption edge at 289 eV and the dip at 303 eV is characteristic of diamond C K-edge (38, 39). 讨论 Discussion 对高温高压下 XRD 图像分析可以鉴定高压含 C 结构。 XRD 图像与在该压力范围内理论计算所得到的菱镁矿的 phase II 相 ( 空间群为 C2/m) 是一致的 (15) 。但是当使用另一个晶体对称性更低一些的 P21/c 空间群时，拟合的质量会得到明显提高。这一结构见图 4 所示，它由共角的三个 (CO4)4- 四面体组所构成，这样组成了 (C3O9)6- 环。晶格常数为： MgO+CO2 在 P=82 GPa 、 T=2350 ±150K 条件下： a=8.39 , b=6.41 , c=6.82 , β =105.49 (V=354.7 3 ) ； MgCO3 在 P=85 GPa 、 T=2400 ±150K 条件下： a=8.37 , b=6.37 , c=6.80 , β =104.57 (V=351.7 3 ) 。对于后者，假设每个晶胞化学式单位为 12 (15) ，得到的密度为 4.76 g/cm3 ，与相同 P-T 条件下的低压结构具有 +10% 的密度差异。因为有相对较小的 Fe(III) 原子的加入，这种新的含铁相的晶格体积比富镁端元的要小 10% ： (Mg0.6Fe0.4)O+CO2 在 P=105 GPa 、 T=2850 ±150K 条件下： a=7.72 , b=6.41 , c=6.57 , β =101.31 (V=319.0 3 ) ； (Mg0.25Fe0.75)CO3 在 P=80 GPa 、室温 条件下： a=7.83 , b=6.37 , c=6.73 , β =101.97 (V=328.9 3 ) 。 图 4. Structure of the new high-pressure phase in space group P21/c related to phase II of magnesite proposed by theoretical calculation (15). (CO4)4- tetrahedra appear in green and magnesium atoms are shown as violet spheres. 对于这种新的高压相由于没有现成的 EELS 图谱做参考，我们对该未知的电子态密度进行了密度泛函理论 (DFT) 计算。 Mg 态密度显示在大约 5 eV 费米能级之上有个很窄的峰，对应着碳的 K-edge 以及它的“分子”类型 (CO3)2-( 图 5) 。由这种高压含 C 新相所得到的态密度并没有任何 (CO3)2- 峰，但是在高能区 (7-11 eV) 有一个很宽的带 (band) 。晶体密度在 80 GPa 时为 4.79 g/cm3 。 (C3O9)6- 环的几何形态见图 5 右边所示。 为了解四面体 (C3O9)6- 环在减压时是如何变化的，在常温常压条件下该结构得到松弛。结果如下图所示 ( 密度为 3.60 g/cm3),C-O 键会变长。从 80 GPa 到 0 GPa C-O-C 角从大约 10-112 变到 115-118 ，这些值与已知的四面体的畸变 (distortion) 是一致得 (15) 。这些结构变化对于态密度具有重要影响。的确，正如对低密度结构的预测，整体态密度会向低能方向偏移。这些出现的窄峰对应着四面体 (C3O9)6- 环，其分子结构特征与高压实验样品的 EELS 分析结果非常相似 ( 即 290.7 eV 附近的峰 ) 图 5. DFT calculations for electronic density of state of the carbon atoms (p orbital symmetry). This unoccupied density of state roughly corresponds to the excitation probed by EELS at the C K-edge (excitonic effects are neglected in the calculation). 在含铁实验中，大量的 Fe(III) 进入到这种新结构中。实验中未见 Pt 的出现，因此 Pt 对该氧化还原反应没有影响。 Fe(III) 形成的氧化还原配对 (partner) 最终可能是 Fe(0) ，就像在高压硅酸盐如钙钛矿中观测到的一样 (9) 。但是 Fe(0) 可能只是一个过渡配对，因为在回收样品中并未观测到 Fe(0) 的存在证据。我们认为 Fe(III) 的加入更可能是由于一个氧化碳配对。我们由此认为铁的氧化是通过下面的化学反应由如 (CO3)2- 或 CO2 这样的含 C 分子结构的部分还原作用来平衡的： 20(Mg0.25Fe(II)0.75)CO3 = 20Mg0.25Fe(III)0.3(C3O9)0.2333 + 3Fe3O4 + 6CO 该反应指示含 Fe(III) 新相中的元素比值为 Fe/C ~0.43 ， Fe/O ~0.14 ，与对回收样品的 EELS 估算值非常吻合。 结论 Conclusion 我们的研究证明，在近于下地幔地温 P-T 条件下 CO2 和其他氧化物的重新作用可以形成一种新的高压含 C 相。这表明这种新相具有较高的稳定性而不会分解为简单氧化物。同样，新高压相中 Fe(III) 的出现指示部分 C 的还原，如以上化学反应。这表明在下地幔条件下 C 的氧化态和还原态可以共存。这种性质可能是由于该含 C 相具有较强的热动力学稳定性。但是若这种新相真在下地幔深部存在的话，那么碳酸盐必须能够在深俯冲中保存下来。尽管根据下地幔矿物组合推测下地幔为还原条件 (9) ，但是如果与周围地幔隔离开来碳酸盐是可以在深部保持稳定的，例如在相对低温的俯冲板片中，由局部矿物组合所控制的氧逸度会相对较高一些 (10,26) 。残留的部分碳酸盐可以被搬运到 1800 km 深度以下，并转变成这种新的含 Fe(III) 相。 参考文献： ↵ Sleep NH, Zahnle K (2001) Carbon dioxide cycling and implications for climate on ancient Earth. 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标签: transition
