物种分布模型(Species distribution models,SDMs)是基于物种的生态位要求,通过将物种已知的分布数据和对应地区的环境数据联系起来,以预测该物种在不同时间和空间下的地理分布的一种数学工具。它为地史时期生物地理分布的重建、生物生...物种分布模型(Species distribution models,SDMs)是基于物种的生态位要求,通过将物种已知的分布数据和对应地区的环境数据联系起来,以预测该物种在不同时间和空间下的地理分布的一种数学工具。它为地史时期生物地理分布的重建、生物生态特征的分析及生物与地球环境协同演化研究等提供了一种新的途径。此方法具有研究精度高、预测效果好及应用广泛等优点,尤其适合开展高精度的古生物地理、古生态及生物宏演化等相关研究。文章着重介绍物种分布模型的基本原理及建模流程,在此基础上以笔石种Tang yagraptus typicus Mu作为建模实例进一步说明物种分布建模的详细步骤,最后概述此方法在古生物研究中的适用性及存在的问题。展开更多
In this work,we study a new(2+1)-dimensional generalized breaking soliton equation which admits the Painleve property for one special set of parameters.We derive multiple soliton solutions,traveling wave solutions,and...In this work,we study a new(2+1)-dimensional generalized breaking soliton equation which admits the Painleve property for one special set of parameters.We derive multiple soliton solutions,traveling wave solutions,and periodic solutions as well.We use the simplified Hirotas method and a variety of ansatze to achieve our goal.展开更多
The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a...The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs.展开更多
The supercontinent cycle has had a profound effect on the Earth＇s evolution since the Late Archean but our understanding of the forces responsible for its operation remains elusive.Supercontinents appear to form by t...The supercontinent cycle has had a profound effect on the Earth＇s evolution since the Late Archean but our understanding of the forces responsible for its operation remains elusive.Supercontinents appear to form by two end-member processes：extroversion,in which the oceanic lithosphere surrounding the supercontinent（exterior ocean） is preferentially subducted（e.g.Pannotia）,and introversion in which the oceanic lithosphere formed between dispersing fragments of the previous supercontinent（interior ocean） is preferentially subducted（e.g.Pangea）.Extroversion can be explained by ＂top-down＂ geodynamics, in which a supercontinent breaks up over a geoid high and amalgamates above a geoid low. Introversion,on the other hand,requires that the combined forces of slab-pull and ridge push（which operate in concert after supercontinent break-up） must be overcome in order to enable the previously dispersing continents to turn inward.Introversion may begin when subduction zones are initiated along boundaries between the interior and exterior oceans and become trapped within the interior ocean.We speculate that the reversal in continental motion required for introversion may be induced by slab avalanche events that trigger the rise of superplumes from the core-mantle boundary.展开更多
The Global boundary Stratotype Section and Point （GSSP） for the base of the Hirnantian Stage （the uppermost of the Ordovician System） is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangj...The Global boundary Stratotype Section and Point （GSSP） for the base of the Hirnantian Stage （the uppermost of the Ordovician System） is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North section. The section is located near Wangjiawan village, 42 km north of Yichang city （western Hubei, China）, at 30° 58′56″N and 111° 25′10″E. The GSSP level coincides with the first appearance of the graptolite species Normalograptus extraordinarius （Sobolevskaya）. Secondary markers include the onset of a positive carbon-isotope excursion, and a slightly earlier first appearance of Normalograptus ojsuensis （ Koren and Mikhailova ）. The Wangjiawan North section possesses continuity of sedimentation and biozonation with completeness of exposures, abundant and well-preserved graptolites and shelly fossils, i. e. the Hirnantia- Dalmanitina shelly fauna which is a key element for recognition of the Hirnantian Stage. The Wangjiawan North, South and Riverside sections possess favorable facies and widespread correlation potential, are free from structure complication, metamorphism and other alteration, and have good accessibility. The Riverside section in particular possesses amenability to isotopic age determination. The beginning of the Hirnantian was followed by a global episode of a major extinction event, which happened in the Diceratograptus mirus Subzone. The proposal was voted by the International Subcommission on Ordovician Stratigraphy in October, 2004, approved by the International Commission on Stratigraphy in February, 2006, and ratified by the International Union of Geological Sciences in May, 2006.展开更多
The supercontinent cycle, by which Earth history is seen as having been punctuated by the episodic assembly and breakup of supercontinents, has influenced the rock record more than any other geologic phenomena, and it...The supercontinent cycle, by which Earth history is seen as having been punctuated by the episodic assembly and breakup of supercontinents, has influenced the rock record more than any other geologic phenomena, and its recognition is arguably the most important advance in Earth Science since plate tectonics. It documents fundamental aspects of the planet＇s interior dynamics and has charted the course of Earth＇s tectonic, climatic and biogeochemical evolution for billions of years. But while the widespread realization of the importance of supercontinents in Earth history is a relatively recent development, the supercontinent cycle was first proposed thirty years ago and episodicity in tectonic processes was recognized long before plate tectonics provided a potential explanation for its occurrence. With interest in the supercontinent cycle gaining momentum and the literature expanding rapidly, it is instructive to recall the historical context from which the concept developed. Here we examine the supercontinent cycle from this perspective by tracing its development from the early recognition of long-term epi- sodicity in tectonic processes, through the identification of tectonic cycles following the advent of plate tectonics, to the first realization that these phenomena were the manifestation of episodic superconti- nent assembly and breakup.展开更多
The Rheic Ocean was one of the most important oceans of the Paleozoic Era. It lay between Laurentia and Gondwana from the Early Ordovician and closed to produce the vast Ouachita- Alleghanian-Variscan orogen during th...The Rheic Ocean was one of the most important oceans of the Paleozoic Era. It lay between Laurentia and Gondwana from the Early Ordovician and closed to produce the vast Ouachita- Alleghanian-Variscan orogen during the assembly of Pangea. Rifting began in the Cambrian as a continua- tion of Neoproterozoic orogenic activity and the ocean opened in the Early Ordovician with the separation of several Neoproterozoic arc terranes from the continental margin of northern Gondwana along the line of a former suture. The rapid rate of ocean opening suggests it was driven by slab pull in the outboard Iapetus Ocean. The ocean reached its greatest width with the closure of Iapetus and the accretion of the peri- Gondwanan arc terranes to Laurentia in the Silurian. Ocean closure began in the Devonian and continued through the Mississippian as Gondwana sutured to Laurussia to form Pangea. The ocean consequently plays a dominant role in the Appalachian-Ouachita orogeny of North America, in the basement geology of southern Europe, and in the Paleozoic sedimentary, structural and tectonothermal record from Middle America to the Middle East. Its closure brought the Paleozoic Era to an end.展开更多
Methylmercury（MeHg） bioaccumulation is a growing concern in ecosystems worldwide. The absorption of solar radiation by dissolved organic matter（DOM） and other photoreactive ligands can convert MeHg into less toxic...Methylmercury（MeHg） bioaccumulation is a growing concern in ecosystems worldwide. The absorption of solar radiation by dissolved organic matter（DOM） and other photoreactive ligands can convert MeHg into less toxic forms of mercury through photodemethylation. In this study, spectral changes and photoreactivity of DOM were measured to assess the potential to control photoreactions and predict in situ MeHg concentration. Water samples collected from a series of lakes in southwestern Nova Scotia in June, August, and September were exposed to controlled ultraviolet-A（UV-A） radiation for up to 24 hr. Dissolved organic matter photoreactivity, measured as the loss of absorbance at 350 nm at constant UV-A irradiation, was positively dependent on the initial DOM concentration in lake waters（r^2=0.94）. This relationship was consistent over time with both DOM concentration and photoreactivity increasing from summer into fall across lakes. Lake in situ MeHg concentration was positively correlated with DOM concentration and likely catchment transport in June（r = 0.77） but not the other sampling months. Despite a consistent seasonal variation in both DOM and Fe, and their respective correlations with MeHg, no discernable seasonal trend in MeHg was observed. However, a 3-year dataset from the 6 study lakes revealed a positive correlation between DOM concentration and both Fe（r = 0.91） and MeHg concentrations（r = 0.51） suggesting a more dominant landscape mobility control on MeHg.The DOM-MeHg relationships observed in these lakes highlights the need to examine DOM photoreactivity controls on MeHg transport and availability in natural waters particularly given future climate perturbations.展开更多
The East African Orogen involves a collage of Proterozoic microcontinents and arc terranes that became wedged between older cratonic blocks during the assembly of Gondwana.The Ediacaran-Cambrian Ambalavao and Maevaran...The East African Orogen involves a collage of Proterozoic microcontinents and arc terranes that became wedged between older cratonic blocks during the assembly of Gondwana.The Ediacaran-Cambrian Ambalavao and Maevarano Suites in Madagascar were emplaced during the waning orogenic stages and consist of weakly deformed to undeformed plutonic rocks and dykes of mainly porphyritic granite but also gabbro,diorite and charnockite.U-Pb geochronological data date emplacement of the Ambalavao Suite to between ca.580 Ma and 540 Ma and the Maevarano Suite to between ca.537 Ma and522 Ma.Major and trace element concentrations are consistent with emplacement in a syn-to postcollisional tectonic setting as A-type(anorogenic) suites.Oxygen(δ^(18)O of 5.27‰-7.45‰) and hafnium(ε(Hf)(t) of-27.8 to-12.3) isotopic data from plutons in the Itremo and Antananarivo Domains are consistent with incorporation of an ancient crustal source.More primitive δ^(18)O(5.27‰-5.32‰) andε(Hf)(t)(+0.0 to+0.2) isotopic values recorded in samples collected from the Ikalamavony Domain demonstrate the isotopic variation of basement sources present in the Malagasy crust.The Hf isotopic composition of Malagasy zircon are unlike more juvenile Ediacaran-Cambrian zircon sou rces elsewhere in the East African Orogen and,as such,Madagascar represents a distinct and identifiable detrital zircon source region in Phanerozoic sedimentary provenance studies.Taken together,these data indicate that high-T crustal anatexis,crustal assimilation and interaction of crustal material with mantle-derived melts were the processes operating during magma emplacement.This magmatism was coeval with polyphase deformation throughout Madagascar during the amalgamation of Gondwana and magmatism is interpreted to reflect lithospheric delamination of an extensive orogenic plateau.展开更多
An extended form of the modified Kadomtsev-Petviashvili （mKP） equation is investigated. The simplified form of the Hirota bilinear method established by Hereman and Nuseir is employed. Multi-front wave solutions are...An extended form of the modified Kadomtsev-Petviashvili （mKP） equation is investigated. The simplified form of the Hirota bilinear method established by Hereman and Nuseir is employed. Multi-front wave solutions are formally derived to the extended mKP equation and the mKP equation. The results show that the extension terms do not kill the integrability of the mKP equation.展开更多
To examine the pro- and anti-oxidant properties of nitric oxide (NO) production in alcoholic liver disease, we compared the effects of ethanol pretreatment (24 hrs, 100 mM concentration in a dedicated CO2 incubator) o...To examine the pro- and anti-oxidant properties of nitric oxide (NO) production in alcoholic liver disease, we compared the effects of ethanol pretreatment (24 hrs, 100 mM concentration in a dedicated CO2 incubator) on the induction of inducible NO synthase and its activity in a cell culture system. We employed two types of liver cells as models for the intact liver parenchyma: the rat hepatoma cell FTO2B and rat hepatocytes in primary culture. Cells were incubated with a combination of cytokines (IFN-γ, TNF-α, IL-β) and LPS in the presence or absence of (85 - 93 mM) ethanol in the culture media. At series of time intervals, production of nitric oxide was measured as the accumulation of nitrite and nitrate, using Griess assay. The results revealed that 1) total NO formation was attenuated by ethanol in hepatocytes (ca. 50%) but augmented in FTO2B cells (ca. 37%) and 2) both pretreatment and co-treatment with ethanol were necessary for maximal ethanol effect. These results indicate that the effects of ethanol on inflammatory processes, such as induction of NO synthesis, are cell-type specific.展开更多
Pancreatic cancer is a highly aggressive disease with a very high mortality rate among all human cancers. The poor prognosis is in part due to intrinsic resistance to the apoptosis-inducing effects of radio- and chemo...Pancreatic cancer is a highly aggressive disease with a very high mortality rate among all human cancers. The poor prognosis is in part due to intrinsic resistance to the apoptosis-inducing effects of radio- and chemotherapy. To find alternative cell death pathways that can bypass the apoptotic resistance of pancreatic cancer cells, we examined the role of the novel anoikis effector Bit1 (Bcl-2 inhibitor of transcription) in the survival and apoptotic resistance of pancreatic cancer cells. Bit1 is a mitochondrial protein that induces a caspase-independent apoptosis upon its release into the cytosol following loss of integrin-mediated attachment to extracellular matrix (anoikis). In this report, we observed that ectopic expression of Bit1 in the cytosol reduced viability and induced caspase-independent apoptosis in human pancreatic cancer cell lines, Miapaca-2 and PANC-1. While increased expression of mitochondrial Bit1 in these cells did not induce apoptosis under attached conditions, detachment significantly induced higher level of apoptosis in mitochondrial Bit1-transfected cells than in control transfected cells. Conversely, downregulation of endogenous Bit1 in PANC-1 cells further enhanced their anoikis resistance. Furthermore, exogenous expression of mitochondrial Bit1 in Miapaca-2 cells inhibited their anchorage-independent growth and enhanced their sensitivity to etoposide-mediated apoptosis. Mechanistically, we found that the Bit1 apoptosis function is in part dependent on the groucho related Amino-terminal Enhancer of Split (AES) expression and is abrogated by the transcriptional corepressor TLE1 protein. Consistent with our in vitro findings that Bit1 is an effector of apoptosis in pancreatic tumor cells, we find that Bit1 is significantly downregulated in a fraction of advanced stages of human pancreatic carcinoma tissues. Taken together, these findings indicate that the Bit1-apoptotic pathway can be targeted to trigger cell death in pancreatic cancer cells and implicate Bit1 as a novel therapeutic agent in attenuating pancreatic chemoresistance.展开更多
Cyber-physical systems(CPS)are increasingly commonplace,with applications in energy,health,transportation,and many other sectors.One of the major requirements in CPS is that the interaction between cyber-world and man...Cyber-physical systems(CPS)are increasingly commonplace,with applications in energy,health,transportation,and many other sectors.One of the major requirements in CPS is that the interaction between cyber-world and man-made physical world(exchanging and sharing of data and information with other physical objects and systems)must be safe,especially in bi-directional communications.In particular,there is a need to suitably address security and/or privacy concerns in this human-in-the-loop CPS ecosystem.However,existing centralized architecture models in CPS,and also the more general IoT systems,have a number of associated limitations,in terms of single point of failure,data privacy,security,robustness,etc.Such limitations reinforce the importance of designing reliable,secure and privacy-preserving distributed solutions and other novel approaches,such as those based on blockchain technology due to its features(e.g.,decentralization,transparency and immutability of data).This is the focus of this special issue.展开更多
A large member of lump chain solutions of the(2+1)-dimensional Bogoyavlenskii-Kadomtsev-Petviashvili(BKP)equation are constructed by means of theτ-function in the form of Grammian.The lump chains are formed by period...A large member of lump chain solutions of the(2+1)-dimensional Bogoyavlenskii-Kadomtsev-Petviashvili(BKP)equation are constructed by means of theτ-function in the form of Grammian.The lump chains are formed by periodic arrangement of individual lumps and travel with distinct group and velocities.An analytical method related dominant regions of polygon is developed to analyze the interaction dynamics of the multiple lump chains.The degenerate structures of parallel,superimposed,and molecular lump chains are presented.The interaction solutions between lump chains and kink-solitons are investigated,where the kink-solitons lie on the boundaries of dominant region determined by the constant term in theτ-function.Furthermore,the hybrid solutions consisting of lump chains and individual lumps controlled by the parameter with high rank and depth are investigated.The analytical method presented in this paper can be further extended to other integrable systems to explore complex wave structures.展开更多
基金中国科学院知识创新工程重要方向项目(KZCX2-EW-111)国家自然科学基金(40839910)+3 种基金美国自然科学基金(EAR0418790)资助地质生物多样性数据库项目(Geobiodiversity Databasewww.geobio-diversity.com)IGCP591项目"The Early to Middle Paleozoic Revolution"系列成果之一
基金中国科学院知识创新工程方向性项目(KZCX2-EW-111)美国自然科学基金(EAR 0418790)+4 种基金国家自然科学基金(4122100141290260和41202004)的联合资助地质生物多样性数据库项目(Geobiodiversity Databasewww.geobiodiversity.com)IGCP591项目"The Early to Middle Paleozoic Revolution"系列成果之一
文摘物种分布模型(Species distribution models,SDMs)是基于物种的生态位要求,通过将物种已知的分布数据和对应地区的环境数据联系起来,以预测该物种在不同时间和空间下的地理分布的一种数学工具。它为地史时期生物地理分布的重建、生物生态特征的分析及生物与地球环境协同演化研究等提供了一种新的途径。此方法具有研究精度高、预测效果好及应用广泛等优点,尤其适合开展高精度的古生物地理、古生态及生物宏演化等相关研究。文章着重介绍物种分布模型的基本原理及建模流程,在此基础上以笔石种Tang yagraptus typicus Mu作为建模实例进一步说明物种分布建模的详细步骤,最后概述此方法在古生物研究中的适用性及存在的问题。
基金This work was partially supported by National Natural Science Foundation of China(No. 10471078)Doctoral Foundation of the Education committee of China(No. 2004042204)Supported by an NSERC grant Canada
文摘In this work,we study a new(2+1)-dimensional generalized breaking soliton equation which admits the Painleve property for one special set of parameters.We derive multiple soliton solutions,traveling wave solutions,and periodic solutions as well.We use the simplified Hirotas method and a variety of ansatze to achieve our goal.
文摘The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs.
基金the continuing support of the Natural Sciences and Engineering Research Council,Canada through Discovery and Research Capacity grantsRDN is supported by National Science Foundation grant EAR-0308105+1 种基金a Baker Award from Ohio Universitya contribution to the International Geoscience Program,IGCP Project 597
文摘The supercontinent cycle has had a profound effect on the Earth＇s evolution since the Late Archean but our understanding of the forces responsible for its operation remains elusive.Supercontinents appear to form by two end-member processes：extroversion,in which the oceanic lithosphere surrounding the supercontinent（exterior ocean） is preferentially subducted（e.g.Pannotia）,and introversion in which the oceanic lithosphere formed between dispersing fragments of the previous supercontinent（interior ocean） is preferentially subducted（e.g.Pangea）.Extroversion can be explained by ＂top-down＂ geodynamics, in which a supercontinent breaks up over a geoid high and amalgamates above a geoid low. Introversion,on the other hand,requires that the combined forces of slab-pull and ridge push（which operate in concert after supercontinent break-up） must be overcome in order to enable the previously dispersing continents to turn inward.Introversion may begin when subduction zones are initiated along boundaries between the interior and exterior oceans and become trapped within the interior ocean.We speculate that the reversal in continental motion required for introversion may be induced by slab avalanche events that trigger the rise of superplumes from the core-mantle boundary.
文摘The Global boundary Stratotype Section and Point （GSSP） for the base of the Hirnantian Stage （the uppermost of the Ordovician System） is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North section. The section is located near Wangjiawan village, 42 km north of Yichang city （western Hubei, China）, at 30° 58′56″N and 111° 25′10″E. The GSSP level coincides with the first appearance of the graptolite species Normalograptus extraordinarius （Sobolevskaya）. Secondary markers include the onset of a positive carbon-isotope excursion, and a slightly earlier first appearance of Normalograptus ojsuensis （ Koren and Mikhailova ）. The Wangjiawan North section possesses continuity of sedimentation and biozonation with completeness of exposures, abundant and well-preserved graptolites and shelly fossils, i. e. the Hirnantia- Dalmanitina shelly fauna which is a key element for recognition of the Hirnantian Stage. The Wangjiawan North, South and Riverside sections possess favorable facies and widespread correlation potential, are free from structure complication, metamorphism and other alteration, and have good accessibility. The Riverside section in particular possesses amenability to isotopic age determination. The beginning of the Hirnantian was followed by a global episode of a major extinction event, which happened in the Diceratograptus mirus Subzone. The proposal was voted by the International Subcommission on Ordovician Stratigraphy in October, 2004, approved by the International Commission on Stratigraphy in February, 2006, and ratified by the International Union of Geological Sciences in May, 2006.
基金R.D.N. acknowledges NSF Grant EAR-0308105J.B.M. acknowledges N.S.E.R.C.(Canada) Discovery and Research Capacity grants for continuing supportcontribution to IGCP 597
文摘The supercontinent cycle, by which Earth history is seen as having been punctuated by the episodic assembly and breakup of supercontinents, has influenced the rock record more than any other geologic phenomena, and its recognition is arguably the most important advance in Earth Science since plate tectonics. It documents fundamental aspects of the planet＇s interior dynamics and has charted the course of Earth＇s tectonic, climatic and biogeochemical evolution for billions of years. But while the widespread realization of the importance of supercontinents in Earth history is a relatively recent development, the supercontinent cycle was first proposed thirty years ago and episodicity in tectonic processes was recognized long before plate tectonics provided a potential explanation for its occurrence. With interest in the supercontinent cycle gaining momentum and the literature expanding rapidly, it is instructive to recall the historical context from which the concept developed. Here we examine the supercontinent cycle from this perspective by tracing its development from the early recognition of long-term epi- sodicity in tectonic processes, through the identification of tectonic cycles following the advent of plate tectonics, to the first realization that these phenomena were the manifestation of episodic superconti- nent assembly and breakup.
基金an outcome of IGCP Project 497:The Rheic Ocean:its origin,evolution and correlatives.RDN acknowledges NSF grant EAR-0308105G.G-A.acknowledges Spanish Education and Science Ministry Vroject Grant CGL2009- 1367(O.D.R.E.Ⅱ)+2 种基金JDK acknowledges CONACyT(Project CB- 2005-1:24894)PAPIIT(IN 100108-3)grantsJBM acknowledges N.S.E.R.C.Discovery and Research Capacity grants for continuing support
文摘The Rheic Ocean was one of the most important oceans of the Paleozoic Era. It lay between Laurentia and Gondwana from the Early Ordovician and closed to produce the vast Ouachita- Alleghanian-Variscan orogen during the assembly of Pangea. Rifting began in the Cambrian as a continua- tion of Neoproterozoic orogenic activity and the ocean opened in the Early Ordovician with the separation of several Neoproterozoic arc terranes from the continental margin of northern Gondwana along the line of a former suture. The rapid rate of ocean opening suggests it was driven by slab pull in the outboard Iapetus Ocean. The ocean reached its greatest width with the closure of Iapetus and the accretion of the peri- Gondwanan arc terranes to Laurentia in the Silurian. Ocean closure began in the Devonian and continued through the Mississippian as Gondwana sutured to Laurussia to form Pangea. The ocean consequently plays a dominant role in the Appalachian-Ouachita orogeny of North America, in the basement geology of southern Europe, and in the Paleozoic sedimentary, structural and tectonothermal record from Middle America to the Middle East. Its closure brought the Paleozoic Era to an end.
基金provided from the National Science and Engineering Council (NSERC) of Canada in the form of a discovery grant (#341960-2013)Canada Research Chair (#950-203477)an NSERC CREATE (#371177-2010)scholarship to S.J.K
文摘Methylmercury（MeHg） bioaccumulation is a growing concern in ecosystems worldwide. The absorption of solar radiation by dissolved organic matter（DOM） and other photoreactive ligands can convert MeHg into less toxic forms of mercury through photodemethylation. In this study, spectral changes and photoreactivity of DOM were measured to assess the potential to control photoreactions and predict in situ MeHg concentration. Water samples collected from a series of lakes in southwestern Nova Scotia in June, August, and September were exposed to controlled ultraviolet-A（UV-A） radiation for up to 24 hr. Dissolved organic matter photoreactivity, measured as the loss of absorbance at 350 nm at constant UV-A irradiation, was positively dependent on the initial DOM concentration in lake waters（r^2=0.94）. This relationship was consistent over time with both DOM concentration and photoreactivity increasing from summer into fall across lakes. Lake in situ MeHg concentration was positively correlated with DOM concentration and likely catchment transport in June（r = 0.77） but not the other sampling months. Despite a consistent seasonal variation in both DOM and Fe, and their respective correlations with MeHg, no discernable seasonal trend in MeHg was observed. However, a 3-year dataset from the 6 study lakes revealed a positive correlation between DOM concentration and both Fe（r = 0.91） and MeHg concentrations（r = 0.51） suggesting a more dominant landscape mobility control on MeHg.The DOM-MeHg relationships observed in these lakes highlights the need to examine DOM photoreactivity controls on MeHg transport and availability in natural waters particularly given future climate perturbations.
基金output of ARC Future Fellowship grant FT120100340
文摘The East African Orogen involves a collage of Proterozoic microcontinents and arc terranes that became wedged between older cratonic blocks during the assembly of Gondwana.The Ediacaran-Cambrian Ambalavao and Maevarano Suites in Madagascar were emplaced during the waning orogenic stages and consist of weakly deformed to undeformed plutonic rocks and dykes of mainly porphyritic granite but also gabbro,diorite and charnockite.U-Pb geochronological data date emplacement of the Ambalavao Suite to between ca.580 Ma and 540 Ma and the Maevarano Suite to between ca.537 Ma and522 Ma.Major and trace element concentrations are consistent with emplacement in a syn-to postcollisional tectonic setting as A-type(anorogenic) suites.Oxygen(δ^(18)O of 5.27‰-7.45‰) and hafnium(ε(Hf)(t) of-27.8 to-12.3) isotopic data from plutons in the Itremo and Antananarivo Domains are consistent with incorporation of an ancient crustal source.More primitive δ^(18)O(5.27‰-5.32‰) andε(Hf)(t)(+0.0 to+0.2) isotopic values recorded in samples collected from the Ikalamavony Domain demonstrate the isotopic variation of basement sources present in the Malagasy crust.The Hf isotopic composition of Malagasy zircon are unlike more juvenile Ediacaran-Cambrian zircon sou rces elsewhere in the East African Orogen and,as such,Madagascar represents a distinct and identifiable detrital zircon source region in Phanerozoic sedimentary provenance studies.Taken together,these data indicate that high-T crustal anatexis,crustal assimilation and interaction of crustal material with mantle-derived melts were the processes operating during magma emplacement.This magmatism was coeval with polyphase deformation throughout Madagascar during the amalgamation of Gondwana and magmatism is interpreted to reflect lithospheric delamination of an extensive orogenic plateau.
文摘An extended form of the modified Kadomtsev-Petviashvili （mKP） equation is investigated. The simplified form of the Hirota bilinear method established by Hereman and Nuseir is employed. Multi-front wave solutions are formally derived to the extended mKP equation and the mKP equation. The results show that the extension terms do not kill the integrability of the mKP equation.
文摘To examine the pro- and anti-oxidant properties of nitric oxide (NO) production in alcoholic liver disease, we compared the effects of ethanol pretreatment (24 hrs, 100 mM concentration in a dedicated CO2 incubator) on the induction of inducible NO synthase and its activity in a cell culture system. We employed two types of liver cells as models for the intact liver parenchyma: the rat hepatoma cell FTO2B and rat hepatocytes in primary culture. Cells were incubated with a combination of cytokines (IFN-γ, TNF-α, IL-β) and LPS in the presence or absence of (85 - 93 mM) ethanol in the culture media. At series of time intervals, production of nitric oxide was measured as the accumulation of nitrite and nitrate, using Griess assay. The results revealed that 1) total NO formation was attenuated by ethanol in hepatocytes (ca. 50%) but augmented in FTO2B cells (ca. 37%) and 2) both pretreatment and co-treatment with ethanol were necessary for maximal ethanol effect. These results indicate that the effects of ethanol on inflammatory processes, such as induction of NO synthesis, are cell-type specific.
文摘Pancreatic cancer is a highly aggressive disease with a very high mortality rate among all human cancers. The poor prognosis is in part due to intrinsic resistance to the apoptosis-inducing effects of radio- and chemotherapy. To find alternative cell death pathways that can bypass the apoptotic resistance of pancreatic cancer cells, we examined the role of the novel anoikis effector Bit1 (Bcl-2 inhibitor of transcription) in the survival and apoptotic resistance of pancreatic cancer cells. Bit1 is a mitochondrial protein that induces a caspase-independent apoptosis upon its release into the cytosol following loss of integrin-mediated attachment to extracellular matrix (anoikis). In this report, we observed that ectopic expression of Bit1 in the cytosol reduced viability and induced caspase-independent apoptosis in human pancreatic cancer cell lines, Miapaca-2 and PANC-1. While increased expression of mitochondrial Bit1 in these cells did not induce apoptosis under attached conditions, detachment significantly induced higher level of apoptosis in mitochondrial Bit1-transfected cells than in control transfected cells. Conversely, downregulation of endogenous Bit1 in PANC-1 cells further enhanced their anoikis resistance. Furthermore, exogenous expression of mitochondrial Bit1 in Miapaca-2 cells inhibited their anchorage-independent growth and enhanced their sensitivity to etoposide-mediated apoptosis. Mechanistically, we found that the Bit1 apoptosis function is in part dependent on the groucho related Amino-terminal Enhancer of Split (AES) expression and is abrogated by the transcriptional corepressor TLE1 protein. Consistent with our in vitro findings that Bit1 is an effector of apoptosis in pancreatic tumor cells, we find that Bit1 is significantly downregulated in a fraction of advanced stages of human pancreatic carcinoma tissues. Taken together, these findings indicate that the Bit1-apoptotic pathway can be targeted to trigger cell death in pancreatic cancer cells and implicate Bit1 as a novel therapeutic agent in attenuating pancreatic chemoresistance.
文摘Cyber-physical systems(CPS)are increasingly commonplace,with applications in energy,health,transportation,and many other sectors.One of the major requirements in CPS is that the interaction between cyber-world and man-made physical world(exchanging and sharing of data and information with other physical objects and systems)must be safe,especially in bi-directional communications.In particular,there is a need to suitably address security and/or privacy concerns in this human-in-the-loop CPS ecosystem.However,existing centralized architecture models in CPS,and also the more general IoT systems,have a number of associated limitations,in terms of single point of failure,data privacy,security,robustness,etc.Such limitations reinforce the importance of designing reliable,secure and privacy-preserving distributed solutions and other novel approaches,such as those based on blockchain technology due to its features(e.g.,decentralization,transparency and immutability of data).This is the focus of this special issue.
基金Project supported by the National Natural Science Foundation of China(Grant No.12101572)the Research Project Supported by Shanxi Scholarship Council of China(Grant No.2020-105)。
文摘A large member of lump chain solutions of the(2+1)-dimensional Bogoyavlenskii-Kadomtsev-Petviashvili(BKP)equation are constructed by means of theτ-function in the form of Grammian.The lump chains are formed by periodic arrangement of individual lumps and travel with distinct group and velocities.An analytical method related dominant regions of polygon is developed to analyze the interaction dynamics of the multiple lump chains.The degenerate structures of parallel,superimposed,and molecular lump chains are presented.The interaction solutions between lump chains and kink-solitons are investigated,where the kink-solitons lie on the boundaries of dominant region determined by the constant term in theτ-function.Furthermore,the hybrid solutions consisting of lump chains and individual lumps controlled by the parameter with high rank and depth are investigated.The analytical method presented in this paper can be further extended to other integrable systems to explore complex wave structures.
