Dynamics of seismogenic volcanic extrusion at Mount St Helens in 2004-05

The 2004-05 eruption of Mount St Helens exhibited sustained, near-equilibrium behaviour characterized by relatively steady extrusion of a solid dacite plug and nearly periodic shallow earthquakes. Here we present a diverse data set to support our hypothesis that these earthquakes resulted from stick-slip motion along the margins of the plug as it was forced incrementally upwards by ascending, solidifying, gas-poor magma. We formalize this hypothesis with a dynamical model that reveals a strong analogy between behaviour of the magma-plug system and that of a variably damped oscillator. Modelled stick-slip oscillations have properties that help constrain the balance of forces governing the earthquakes and eruption, and they imply that magma pressure never deviated much from the steady equilibrium pressure. We infer that the volcano was probably poised in a near-eruptive equilibrium state long before the onset of the 2004-05 eruption.     

术语学1990

术语学的基础术语(Termino1ogy),一个学科领域内概念和订名的结构化集合体,是术语科学的研究主题。术语科学的研究对象是概念及其描述、概念体系、术语、概念和术语的对应等,而术语工作的实践集中体现在制订术语方面。术语编纂(Terminography)涉及术语的记录、处理和存取的所有方面。术语的基本元素是概念,概念可以由术语或其它标示符(例如图形符号、字母数字代码、条码、公式等)表达。概念是一种基本的工具,用来处理客观事物的多样性和多变性,自然界中有物质客体或非物质性的客体,人们可以直接理解它们,也可以将其放入不同的分类范畴中加以理解,这就是概念形成的起点(抽象),并导致了信息的稠密化。从认识论的观点来看,概念作为认识客体的“思想单元”;从逻辑学的观念来看,概念作为知识排序的“知识单元”;概念还可作为知识传播的“交流单元”。概念从不孤立地存在,它们总是在现存的概念基础上发展。因此,术语学家认为概念体系是非常重要的,学科专家们则把这些体系看作是其专业领域的知识基础。术语工作的方法50年代,应用语言学的分支学科(首先是专业语言研究和教学法)“发现”了术语工作,从此之后,相继有两种方法论的方法应用于术语科学：——基于学科领域或面向专家的术语工作,源于自然科学和工程技术,有很强的约定俗成倾向;——基于语言学的,面向专业语言(LSP,language for special purporse)的术语工作,普遍存在于人文科学和社会科学,居支配地位的是其描绘性特点。两种方法相互补充且并不矛盾,它们都需要统一的甚至标准化的原则与方法。对于已存在于自然科学和工程技术中的数百万概念和有限的术语元,现今没有那种语言能对所有概念赋予语学形式的订名,在某些领域,多数概念被赋予非语言学形式的订名,在有些情况,概念的描述也常常用非语言学形式的表达所补充,甚至于取代。术语科学和术语编纂学的结构术语科学由下列学科组成：——概念学;——概念表述的理论(包括概念特征的非自然语言表述);——订名理论(应用于术语学的符号学);——术语的有序理论(概念体系的结构及概念间的关系);——(术语的)客体理论。术语编纂,尤其是计算机化的术语编纂,已经与信息和文献工作的某些方面结合,并且进一步发展成术语文献工作(即,术语工作和文献工作的结合)。近些年来,人们已经需要借助于术语编纂的方法来处理概念的动态变化。这就是术语知识工程的起点,处理概念逻辑层的知识。基于这种方法的初级复杂系统已经在各种组织内实现,它们能提供信息与知识处理中常提到的那种硬件软件“一体化”的解决办法,然而,这种解决方法很难达到。术语学的应用上述发展不仅有益于工业化国家,而且更有益于发展中国家。应用这些方法和术语学知识工程体系,能设计出计算机化知识传播系统,这种系统提供了成本低、效率高的系统化知识传播。这种知识传播的过程伴随着所要求的“人类资本”培训,而这种培训又导致了各经济部门自我支持的动态变化。由于这个原因,在术语研究、术语编纂、术语学知识工程领域每年都有一个或几个重要的国际学术会议、研讨会、专家会以及国家水平的其它学术活动。许多国家成立了专门研究术语问题的科技协会。建立在术语学知识工程基础上发展知识工业的第一步骤也由此开始。术语工作网络与合作在术语研究领域内活动和出版物的增加表明该领域内对信息的需求非常大,国际术语情报中心(Infoterm)以及支持国际术语情报中心并与之合作的其它术语机构不能满足这种激增的需求。为了避免事倍功半,应当加强在术语工作领域内的集中合作。学科专家的责任信息和知识是人类共有的财产,两者都是超越国界的,因为没有哪一个国家对一个学科领域知识和技术水平的发展能承担全部责任。此外,世界上的全部知识只是部分地被记录下来,人们能获得的只是其中一部分所谓“信息危机”不完全是由于文献数量增加而引起的,而是由于这些文献之间缺乏有序性,尤其是缺乏可存取性。传统的信息系统存取方法已逐渐过时。文献检索语言,例如分类体系、叙词表、索引语言等不得不附加另外更先进的工具做补充。因为术语以系统的方式表示了某一学科领域的概念,所以它们可以用来直接存取文献中人们所需要的信息。信息和知识的处理,需要高质量的术语作为工具,这些术语只能由学科专家确立。从某种程度上说,专家在术语工作中遇到的一些方法论或实际问题可以通过计算机解决。在计算机辅助术语工作中,不得不考虑下列问题。——术语的形成——定义的制订——概念的协调——源资料信息的处理——非语言概念表述的处理经验已经表明,只有学科专家能估计他们自己需要的信息,并指明有关计算机辅助术语工作的要求。学科专家的主要责任是提供可靠的术语,尤其是为那些知识发展中显示出某种程度“动态稳定”的学科领域提供可靠的术语并为下列用户服务。——科学团体。使用系统化的术语导致了学科领域内的透明性和明晰性,从而使科学团体的交流得以加强,这既防止了重复劳动又促进了整个学科领域的发展;——其他用户群。积极从事于交叉学科和跨语言知识传播的用户,尤其是信息和文献工作专家,翻译和口译员,科学新闻工作者等。忽视术语工作的重要性,会使专业交流遇到障碍,因为低质量的术语(包含许多同义词、多义词等)和低效率的文献管理工具为专业交流增加了很多不便。因此,为了完成无歧义和高效率的知识传播,要求学科专家——使用已存在的术语工具(工具参考书、计算机系统等)解决术语问题;——详尽阐述本学科领域的术语工作指南;——在本学科领域确立术语;——在实践经验的基础上详细说明对计算机系统的要求;——在国家和国际层次上协调每一学科内的术语工作;——在其所在组织和工作机构内,提高对术语问题的认识。(金万平 译,陈宇飞 校)(据TermNet News,4990,No.24)     

Rational general solutions of higher order algebraic odes

This paper generalizes the method of Ngô and Winkler (2010, 2011) for finding rational general solutions of a first order non-autonomous algebraic ordinary differential equation (AODE) to the case of a higher order AODE, provided a proper parametrization of its solution hypersurface. The authors reduce the problem of finding the rational general solution of a higher order AODE to finding the rational general solution of an associated system. The rational general solutions of the original AODE and its associated system are in computable 1-1 correspondence. The authors give necessary and sufficient conditions for the associated system to have a rational solution based on proper reparametrization of invariant algebraic space curves. The authors also relate invariant space curves to first integrals and characterize rationally solvable systems by rational first integrals.     

Changes in patterns of ecdysteroid secretion by the ring gland ofDrosophila in relation to the sterol composition of the diet

Summary Brain-ring glands fromDrosophila larvae reared on a defined diet containing campesterol (24-methyl-cholesterol) as the major sterol, secreted-in addition to ecdysone-a compound identified previously as a 24-methyl analogue, 20-deoxy-makisterone A. Using ergosterol or cholesterol as the sterol component of the diet, only ecdysone was detectable in cultures of brain-ring glands.     

Homology between P-glycoprotein and a bacterial haemolysin transport protein suggests a model for multidrug resistance

Increased expression of P-glycoprotein, a plasma membrane glycoprotein of relative molecular mass (Mr) 170,000 (170K), occurs in a wide variety of cell lines that exhibit pleiotropic resistance to unrelated drugs. The presence of P-glycoprotein in human cancers refractory to chemotherapy suggests that tumour cells with multidrug resistance can arise during malignant progression. We have discovered striking homology between P-glycoprotein and the HlyB protein, a 66K Escherichia coli membrane protein required for the export of haemolysin (protein of Mr 107K). P-glycoprotein can be viewed as a tandem duplication of the HlyB protein. The hydropathy profiles of the two proteins are similar and reveal an extensive transmembrane region resembling those found in pore-forming plasma membrane proteins. The C-terminal region of P-glycoprotein and the HlyB protein contain sequences homologous to the nucleotide-binding domains of a group of closely related bacterial ATP-binding proteins. We propose a model for multidrug resistance in which P-glycoprotein functions as an energy-dependent export pump to reduce intracellular levels of anticancer drugs.     

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Diffusion loading conditions determine recovery of protein synthesis in electroporated P3X63 Ag8 cells

Summary Using the suspension cell line P3X63 Ag8 we have studied the impact of the composition of the diffusion medium on cellular protein synthesis under standard electroporation conditions in TBS-Na. This buffer contains the high saline concentration usually present in electroporation-mediated DNA transfection. Electroporation in the presence of TBS-Na resulted in an immediate shut-off of protein synthesis, even though both FITC-dextran (M_r 40 kD) and Semliki Forest virus core protein (M_r 33 kD) were incorporated efficiently into the cytoplasm across the electropores at 0°C. Subsequent resealing of the pores was completed after a 5-min incubation at 37°C. When compared with control cells, overall protein synthesis of electroporated cells recovered slowly to resume a 30% activity after 1 h of incubation at 37°C. We have determined optimal conditions for diffusion loading (which necessitates the presence of ATP, GTP, amino acids, K⁺, Mg²⁺, and Ca²⁺) and resealing (in the presence of K⁺, Mg²⁺, and Ca²⁺), leading to a full and lasting recovery of protein synthesis within 5 min after pore closure.     

Exponentially Smoothing the Skewed Laplace Distribution for Value‐at‐Risk Forecasting

Value‐at‐risk (VaR) is a standard measure of market risk in financial markets. This paper proposes a novel, adaptive and efficient method to forecast both volatility and VaR. Extending existing exponential smoothing as well as GARCH formulations, the method is motivated from an asymmetric Laplace distribution, where skewness and heavy tails in return distributions, and their potentially time‐varying nature, are taken into account. The proposed volatility equation also involves novel time‐varying dynamics. Back‐testing results illustrate that the proposed method offers a viable, and more accurate, though conservative, improvement in forecasting VaR compared to a range of popular alternatives. Copyright © 2013 John Wiley & Sons, Ltd.