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Sample records for cambrian impact hypothesis

  1. The Cambrian impact hypothesis

    CERN Document Server

    Zhang, Weijia

    2008-01-01

    After a thorough research on the circumstantial changes and the great evolution of life in the Cambrian period, the author propounds such a hypothesis: During the Late Precambrian, about 500-600Ma, a celestial body impacted the Earth. The high temperature ended the great glaciation, facilitated the communication of biological information. The rapid change of Earth environment enkindled the genesis-control system, and released the HSP-90 variations. After the impact, benefited from the protection of the new ozone layer and the energy supplement of the aerobic respiration, those survived underground life exploded. They generated carapaces and complex metabolism to adjust to the new circumstance of high temperature and high pressure. This article uses a large amount of analyses and calculations, and illustrates that this hypothesis fits well with most of the important incidences in astronomic and geologic discoveries.

  2. Testing the Cambrian explosion hypothesis by using a molecular dating technique

    OpenAIRE

    Bromham, L.; Rambaut, A; Fortey, R; Cooper, A.; Penny, D

    1998-01-01

    Molecular studies have the potential to shed light on the origin of the animal phyla by providing independent estimates of the divergence times, but have been criticized for failing to account adequately for variation in rate of evolution. A method of dating divergence times from molecular data addresses the criticisms of earlier studies and provides more realistic, but wider, confidence intervals. The data are not compatible with the Cambrian explosion hypothesis as an explanation for the or...

  3. Possible impact event in the Late Cambrian

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The repeated investigation of the Batyrbay section has been done by the authors. Today we see increasing of interest to revising of volumes and boundaries of Stages and Series in the Cambrian and Ordovician,as well as to the events of this time. In this work the description of iron spherules and particles, found in the deep-water limestone layer of the conodont Cordylodus primitivus Zone in the middle Upper Cambrian of the Batyrbay section, Malyi Karatau of South Kazakhstan, and formed during the time of global sea-level changes known as a world-wide Lange Ranch Eustatic event, have been done. From our point of view, finds of iron spherules and particles may evidence about new unknown yet Event of cosmic origin, i.e. falling of a meteorite on Earth in the middle Late Cambrian.

  4. Brent Spar abandonment - impact hypothesis

    International Nuclear Information System (INIS)

    This report describes the predicted fate of the Brent Spar storage and offloading platform following its proposed deep sea abandonment. Based on the characteristics of the Brent Spar and the contents of the buoy this ''Impact Hypothesis'' uses currently available knowledge of the North East Atlantic deep sea environment. Three scenarios based on possible outcomes are considered, incllcuding the release of metals into the water following corrosion of the structure. (UK)

  5. Cambrian fans

    OpenAIRE

    Reading, Nathan; Speyer, David E.

    2006-01-01

    For a finite Coxeter group W and a Coxeter element c of W, the c-Cambrian fan is a coarsening of the fan defined by the reflecting hyperplanes of W. Its maximal cones are naturally indexed by the c-sortable elements of W. The main result of this paper is that the known bijection cl_c between c-sortable elements and c-clusters induces a combinatorial isomorphism of fans. In particular, the c-Cambrian fan is combinatorially isomorphic to the normal fan of the generalized associahedron for W. Th...

  6. A Blind Test of the Younger Dryas Impact Hypothesis

    Science.gov (United States)

    Holliday, Vance

    2016-01-01

    The Younger Dryas Impact Hypothesis (YDIH) states that North America was devastated by some sort of extraterrestrial event ~12,800 calendar years before present. Two fundamental questions persist in the debate over the YDIH: Can the results of analyses for purported impact indicators be reproduced? And are the indicators unique to the lower YD boundary (YDB), i.e., ~12.8k cal yrs BP? A test reported here presents the results of analyses that address these questions. Two different labs analyzed identical splits of samples collected at, above, and below the ~12.8ka zone at the Lubbock Lake archaeological site (LL) in northwest Texas. Both labs reported similar variation in levels of magnetic micrograins (>300 mg/kg >12.8ka and <11.5ka, but <150 mg/kg 12.8ka to 11.5ka). Analysis for magnetic microspheres in one split, reported elsewhere, produced very low to nonexistent levels throughout the section. In the other split, reported here, the levels of magnetic microspherules and nanodiamonds are low or nonexistent at, below, and above the YDB with the notable exception of a sample <11,500 cal years old. In that sample the claimed impact proxies were recovered at abundances two to four orders of magnitude above that from the other samples. Reproducibility of at least some analyses are problematic. In particular, no standard criteria exist for identification of magnetic spheres. Moreover, the purported impact proxies are not unique to the YDB. PMID:27391147

  7. The impact of inflation targeting: Testing the good luck hypothesis

    OpenAIRE

    Ravenna, Federico

    2007-01-01

    Over the last twenty years the level and volatility of inflation decreased across industrial countries. The inflation behaviour can be explained by a shift in monetary policy or by a lucky period of low volatility in business cycle shocks. To test theluck hypothesis we examine the inflation experience of Canada, one of the earliest and most successful adopter of an inflation targeting monetary policy. We Kalman-filter the historical structural shocks consistent with an estimated DSGE model, b...

  8. Cambrian paleomagnetism of the Llano Uplift, Texas

    Science.gov (United States)

    Watts, Doyle R.; van der Voo, Rob; Reeve, Scott C.

    1980-10-01

    Late Cambrian sandstones and limestones sampled from various members of the Riley and Wilberns formations of the Llano uplift show a progression of paleomagnetic pole positions as a function of age. The members, ages, and poles are the following for the Riley Formation: the Hickory Sandstone, Lower Dresbachian, 34°N, 145°E; the Cap Mountain Limestone, Dresbachian, 33°N, 140°E; the Lion Mountain Limestone, Upper Dresbachian, 24°N, 146°E. For, the Wilberns Formation they are the following: the Welge Sandstone/Morgan Creek Limestone, Lower and Middle Franconian, 24°N, 151°E; and the Point peak Shale, Upper Franconian, 6°N, 159°E. These poles are based on thermal, chemical, and alternating field demagnetizations and on vector analysis. Most directions are interpreted to be of reversed polarity, but the Cap Mountain Limestone also yielded normal polarity directions; all directions resided in hematite with blocking temperatures up to 680°C. Almost all Cambrian poles appear to fall in a broad streak between the equator at about 155°E (e.g., the poles from the Tapeats Sandstone and from the Late Cambrian Point Peak Shale of the Wilberns Formation) and about 60°N, 90°E, where Cambrian poles have been obtained by Elston and Bressler (1977) and French et al. (1977). Although, at the present time, partial to complete remagnetization or nondipole behavior of the geomagnetic field are adequate ad hoc hypotheses to explain some of the data, it is suggested that the simplest and most unifying hypothesis to explain all data involves a Cambrian loop of apparent polar wander with respect to North America. This loop occurs before the middle Late Cambrian, with the poles from the Llano uplift falling on the return track.

  9. Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis

    Science.gov (United States)

    Pigati, Jeffrey S.; Latorre, Claudio; Rech, Jason A.; Betancourt, Julio L.; Martinez, Katherine E.; Budahn, James R.

    2012-01-01

    The Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America at 12.9 ka, initiating the Younger Dryas cold event, the extinction of many North American megafauna, and the demise of the Clovis archeological culture. Although the exact nature and location of the proposed impact or explosion remain unclear, alleged evidence for the fallout comes from multiple sites across North America and a site in Belgium. At 6 of the 10 original sites (excluding the Carolina Bays), elevated concentrations of various "impact markers" were found in association with black mats that date to the onset of the Younger Dryas. Black mats are common features in paleowetland deposits and typically represent shallow marsh environments. In this study, we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern United States and the Atacama Desert of northern Chile. At 10 of 13 sites, we found elevated concentrations of iridium in bulk and magnetic sediments, magnetic spherules, and/or titanomagnetite grains within or at the base of black mats, regardless of their age or location, suggesting that elevated concentrations of these markers arise from processes common to wetland systems, and not a catastrophic extraterrestrial impact event.

  10. The Cambrian explosion.

    Science.gov (United States)

    Briggs, Derek E G

    2015-10-01

    The sudden appearance of fossils that marks the so-called 'Cambrian explosion' has intrigued and exercised biologists since Darwin's time. In On the Origin of Species, Darwin made it clear that he believed that ancestral forms 'lived long before' their first fossil representatives. While he considered such an invisible record necessary to explain the level of complexity already seen in the fossils of early trilobites, Darwin was at a loss to explain why there were no corresponding fossils of these earlier forms. In chapter 9 of the Origin, entitled 'On the imperfection of the geological record', he emphasized the 'poorness of our palaeontological collections' and stated categorically that 'no organism wholly soft can be preserved'. Fortunately much has been discovered in the last 150 years, not least multiple examples of Cambrian and Precambrian soft-bodied fossils. We now know that the sudden appearance of fossils in the Cambrian (541-485 million years ago) is real and not an artefact of an imperfect fossil record: rapid diversification of animals coincided with the evolution of biomineralized shells. And although fossils in earlier rocks are rare, they are not absent: their rarity reflects the low diversity of life at this time, as well as the low preservation potential of Precambrian organisms (see Primer by Butterfield, in this issue). PMID:26439348

  11. Tubicolous enteropneusts from the Cambrian period.

    Science.gov (United States)

    Caron, Jean-Bernard; Morris, Simon Conway; Cameron, Christopher B

    2013-03-28

    Hemichordates are a marine group that, apart from one monospecific pelagic larval form, are represented by the vermiform enteropneusts and minute colonial tube-dwelling pterobranchs. Together with echinoderms, they comprise the clade Ambulacraria. Despite their restricted diversity, hemichordates provide important insights into early deuterostome evolution, notably because of their pharyngeal gill slits. Hemichordate phylogeny has long remained problematic, not least because the nature of any transitional form that might serve to link the anatomically disparate enteropneusts and pterobranchs is conjectural. Hence, inter-relationships have also remained controversial. For example, pterobranchs have sometimes been compared to ancestral echinoderms. Molecular data identify enteropneusts as paraphyletic, and harrimaniids as the sister group of pterobranchs. Recent molecular phylogenies suggest that enteropneusts are probably basal within hemichordates, contrary to previous views, but otherwise provide little guidance as to the nature of the primitive hemichordate. In addition, the hemichordate fossil record is almost entirely restricted to peridermal skeletons of pterobranchs, notably graptolites. Owing to their low preservational potentials, fossil enteropneusts are exceedingly rare, and throw no light on either hemichordate phylogeny or the proposed harrimaniid-pterobranch transition. Here we describe an enteropneust, Spartobranchus tenuis (Walcott, 1911), from the Middle Cambrian-period (Series 3, Stage 5) Burgess Shale. It is remarkably similar to the extant harrimaniids, but differs from all known enteropneusts in that it is associated with a fibrous tube that is sometimes branched. We suggest that this is the precursor of the pterobranch periderm, and supports the hypothesis that pterobranchs are miniaturized and derived from an enteropneust-like worm. It also shows that the periderm was acquired before size reduction and acquisition of feeding tentacles, and

  12. Impact of criticism of null-hypothesis significance testing on statistical reporting practices in conservation biology.

    Science.gov (United States)

    Fidler, Fiona; Burgman, Mark A; Cumming, Geoff; Buttrose, Robert; Thomason, Neil

    2006-10-01

    Over the last decade, criticisms of null-hypothesis significance testing have grown dramatically, and several alternative practices, such as confidence intervals, information theoretic, and Bayesian methods, have been advocated. Have these calls for change had an impact on the statistical reporting practices in conservation biology? In 2000 and 2001, 92% of sampled articles in Conservation Biology and Biological Conservation reported results of null-hypothesis tests. In 2005 this figure dropped to 78%. There were corresponding increases in the use of confidence intervals, information theoretic, and Bayesian techniques. Of those articles reporting null-hypothesis testing--which still easily constitute the majority--very few report statistical power (8%) and many misinterpret statistical nonsignificance as evidence for no effect (63%). Overall, results of our survey show some improvements in statistical practice, but further efforts are clearly required to move the discipline toward improved practices. PMID:17002771

  13. Cambrian explosion triggered by geosphere-biosphere feedbacks

    Science.gov (United States)

    von Bloh, Werner; Bounama, Christine; Franck, Siegfried

    2003-09-01

    A new hypothesis for the cause of the Cambrian explosion is presented. For that the evolution of the planet Earth is described by the co-evolution of the geosphere-biosphere system. Here we specify our previously published Earth system model for the long-term carbon cycle by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. They are characterized by different global temperature tolerance windows. The biotic enhancement of silicate weathering by complex multicellular life adds an additional feedback to the system and triggers the Cambrian explosion. The Cambrian explosion is characterized by a sudden increase of biomass and a rapid cooling, which amplified the spread of complex multicellular life. Cooling events in the Neoproterozoic, however, could force a premature appearance of complex multicellular life.

  14. Sortable elements and Cambrian lattices

    OpenAIRE

    Reading, Nathan

    2005-01-01

    We show that the Coxeter-sortable elements in a finite Coxeter group W are the minimal congruence-class representatives of a lattice congruence of the weak order on W. We identify this congruence as the Cambrian congruence on W, so that the Cambrian lattice is the weak order on Coxeter-sortable elements. These results exhibit W-Catalan combinatorics arising in the context of the lattice theory of the weak order on W.

  15. Trilobite biogeography and Cambrian tectonic models

    Science.gov (United States)

    Burrett, Clive; Richardson, Robert

    1980-03-01

    The biogeographic patterns of Cambrian trilobites are almost impossible to explain on an Early Palaeozoic Pangaea but may be explained by relative movements of several continental blocks separated by wide ocean basins. Realms, regions, provinces and sub-provinces are recognised by progressively agglomerating 450 faunal lists, based on 1371 genera, distributed through eleven time segments. The agglomerating method proposed, is a simple one that may be performed by hand or computer and provides Medial Cambrian results similar to those of Jell (1974) who used principal components and cluster analyses. Simplified results are obtained when time segments are combined or when only the largest list from each 10° (lat. × long.) tessera is used or when only illustrated papers are used or when only lists containing ⩾ 3, 5 or 10 genera are used. The program was also run with all of the presumably planktonic miomerids removed resulting in smaller, better defined provinces with few links between tectonic blocks. The number of polymerid-only realms is three in Albertella Zone times, four in Glossopleura Zone and Eluinia/Conaspis Zone times and five in all other time segments. The average five realms recognised tend to be restricted to one (or rarely two) of the major tectonic blocks: America (excluding Boston and maritime Canada), Europe (including Morocco), Siberia, China and Australia. The existence of the American realm in Argentina through most of the Cambrian and the unlikelihood of a dismembered Gondwanaland necessitates using the latitudinal control hypothesis of Palmer (1972). This hypothesis places the European realm in high palaeolatitudes, the American realm in low palaeolatitudes in the Southern Hemisphere, the Australian realm in low palaeolatitudes in the Northern Hemisphere and the Siberian realm in temperate palaeolatitudes in the Southern Hemisphere. When the miomerids are included, connections between the peripheral ocean-facing regions of one tectonic block

  16. Tropical shoreline ice in the late Cambrian: Implications for earth's climate between the Cambrian Explosion and the Great Ordovician Biodiversification Event

    Science.gov (United States)

    Runkel, Anthony C.; MacKey, T.J.; Cowan, Clinton A.; Fox, David L.

    2010-01-01

    Middle to late Cambrian time (ca. 513 to 488 Ma) is characterized by an unstable plateau in biodiversity, when depauperate shelf faunas suffered repeated extinctions. This poorly understood interval separates the Cambrian Explosion from the Great Ordovician Biodiversification Event and is generally regarded as a time of sustained greenhouse conditions. We present evidence that suggests a drastically different climate during this enigmatic interval: Features indicative of meteoric ice are well preserved in late Cambrian equatorial beach deposits that correspond to one of the shelf extinction events. Thus, the middle to late Cambrian Earth was at least episodically cold and might best be considered a muted analogue to the environmental extremes that characterized the Proterozoic, even though cooling in the two periods may have occurred in response to different triggers. Such later Cambrian conditions may have significantly impacted evolution preceding the Ordovician radiation.

  17. Density Variations in Quartz As a Key for Deciphering Impact-Related Ultrasonic Sounding (Rajlich's Hypothesis)?

    Science.gov (United States)

    Mestan, J.; Alvarez Polanco, E. I.

    2014-12-01

    Ultrasound is a form of mechanical energy with a frequency greater than ≈ 20 kHz (upper human hearing limit). It is used in many scientific as well as industrial fields. Most modern applications of ultrasound utilize sources which are either piezoelectric or magnetostrictive (Benwell et Bly 1987). A meteorite impact has been considered to be an ultrasound source during last years (Rajlich 2011). Rajlich (2014) is coming with a hypothesis that white planes made of microcavities in Bohemian quartz have their origin in an impact-related ultrasonic sounding. The Bohemian Massif has been considered to be one of the largest impact craters in whole of the world (Papagiannis et El-Baz 1988, Papagiannis 1989, Rajlich 2014). Rajlich's hypothesis implies a liquid behavior of quartz during the impact event. We state that then there have to exist planes of slightly higher density than their surroundings together with planes of microcavities. They should intersect each other without mutual influencing (as in a case of planes made of microcavities). Because physics of ultrasound during an impact event is a brand new and unknown field, we try to choose a simple way of its cognition. It is possible to take the sine wave and set 3 requirements. (1) There exist some surroundings of points of peak amplitudes. (2) These surroundings are of higher density (compression) or lower density (rarefaction) than the mean density of quartz. (3) The difference between the higher/lower and surrounding density is measurable. There was done an experimental study of Bohemian quartz using QCT bone densitometry at the Radiology Munich. Quartz with a size of ≈ 5 x 8 cm absorbed too much RTG radiation (kV 140, mAs 330), which made a picture of internal structure impossible. We propose another techniques and appeal to other scientists to face this challenge. If Bohemian quartz has a harmonically distributed density, we consider it to be a support for Rajlich's hypothesis. AcknowledgementsWe would like

  18. Airburst Impact Origin Hypothesis of Taihu Lake Basin in Southeast of China in Around 7000 Years ago

    Science.gov (United States)

    Xie, Z.; Zuo, S.

    2013-08-01

    The paper is to report investigation on unique morphology, occurrence, distribution, and mineralogy of siderite concretions found in Taihu Lake, Southeast of China, and discuss airburst impact origin hypothesis of Taihu Lake basin in ~7000 years ago.

  19. Late Pleistocene Megafaunal Extinction Consistent With YDB Impact Hypothesis at Younger Dryas Onset

    Science.gov (United States)

    Kennett, J. P.; Kennett, D. J.

    2008-12-01

    At least 35 mammal and 19 bird genera became extinct across North America near the end of the Pleistocene. Modern increases in stratigraphic and dating resolution suggest that this extinction occurred relatively rapidly near 12.9 ka (11 radiocarbon kyrs). Within the context of a long-standing debate about its cause, Firestone et al., (2007) proposed that this extinction resulted from an extraterrestrial (ET) impact over North America at 12.9 ka. This hypothesis predicts that the extinction of most of these animals should have occurred abruptly at 12.9 ka. To test this hypothesis, we have critically examined radiocarbon ages and the extinction stratigraphy of these taxa. From a large data pool, we selected only radiocarbon dates with low error margins with a preference for directly dated biological materials (e.g., bone, dung, etc.) and modern chemical purification techniques. A relatively small number of acceptable dates indicate that at least 16 animal genera and several other species became extinct close to 12.9 ka. These taxa include the most common animals of the late Pleistocene such as horses, camels, and mammoths. Also, the remains of extinct taxa are reportedly found up to, but not above, the base of a widely distributed carbon-rich layer called the black mat. This stratum forms an abrupt, major biostratigraphic boundary at the Younger Dryas onset (12.9 ka), which also contains multiple ET markers comprising the impact layer (the YDB). Surviving animal populations were abruptly reduced at the YDB (e.g., Bison), with major range restrictions and apparent evolutionary bottlenecks. The abruptness of this major extinction is inconsistent with the hypotheses of human overkill and climatic change. We argue that extinction ages older than 12.9 ka for many less common species result from the Signor-Lipps effect, but the impact hypothesis predicts that as new dates are acquired, they will approach ever closer to 12.9 ka. The megafaunal extinction is strongly

  20. Cambrian trace fossil Zoophycos from the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Doucek, J.; Mikuláš, Radek

    2014-01-01

    Roč. 65, č. 6 (2014), s. 403-409. ISSN 1335-0552 R&D Projects: GA ČR GA205/09/1521 Institutional support: RVO:67985831 Keywords : Cambrian * Bohemian Massif * Železné hory * ichnology * marine settings * Zoophycos Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.761, year: 2014

  1. Measurements of iridium and the meteoric impact hypothesis at cretaceous end

    International Nuclear Information System (INIS)

    Both instrumental and radiochemical neutron activation analysis methods were developed for trace-element determination, such as iridium and gold, for application in cosmochemistry. The magnitude of the determined concentrations is in the range of parts per billion. In the instrumental method 1.5 grams of sample were submitted to irradiation by 1013 thermal neutrons.cm-2.s-1 during 32 hours. The gamma spectrometry is carried out with 10 to 12 hours counting time after 40 days of decay. In the radiochemical analysis a method of radiochemical separation of noble metals based on tellurium coprecipitation is implanted for iridium and gold determinations. As an application of the instrumental neutron activation analysis, preliminary iridium concentrations are measured for the first time in sedimentary rocks collected in the Brazilian territory. These techniques for determinations of iridium will be useful to check the asteroid impact hypothesis, which is supposed to be the cause of the great Cretaceous/Tertiary mass extinction, using samples collected in the South Hemisphere. (Author)

  2. Causes of the Cambrian Explosion.

    OpenAIRE

    Smith, M P; Harper, D.A.T.

    2013-01-01

    In the last decade, at least thirty individual hypotheses have been invoked to explain the Cambrian Explosion, ranging from starbursts in the Milky Way to intrinsic genomic reorganization and developmental patterning. It has been noted (1) that recent hypotheses fall into three categories: a) developmental/genetic, b) ecologic and c) abiotic environmental, with geochemical hypotheses forming an abundant and distinctive subset of the last. With a few notable exceptions, a significant majority ...

  3. Possible Impact at Precambrian-Cambrian Boundary and Its Influence on Biosphere%前寒武纪-寒武纪界线附近的撞击假说及其对生物圈的影响

    Institute of Scientific and Technical Information of China (English)

    张维加; Daniel P.Connelly; 俞杭杰

    2010-01-01

    HAPCIS陨击坑的基底构造实地分析也表明了前寒武纪末曾经存在过陨击事件.最后笔者利用计算机模拟了大气圈变化.模拟分两步进行,首先从岩石热分解得出需要的温度与压强数据,而后将数据作为参数用于模拟.数据结果表明撞击区域的大气温度在4 000 K左右,压强为5 600 Bar.撞击增加了大气中二氧化碳和氧气的含量,并强化了臭氧层.这些含量的变化与地质上的记录一致.%After a thorough research on the Earth' s circumstantial changes and the great evolution of life in the Cambrian period, the authors propound such a hypothesis: During the Late Precambrian, about 500 ~ 600 Ma, a celestial body impacted the Earth. The high temperature ended the great glaciation, facilitated the communication of biological information. The rapid change of Earth environment enkindled the genesis-control system, and released the HSP-90 variations. After the impact, benefited from the protection of the new ozone layer and the energy supplement of the aerobic respiration, those survived underground life exploded. They generated carapaces and complex metabolism to adjust to the new circumstance of high temperature and high pressure. That' s the Cambrian explosion. This article uses a large amount of analyses and calculations, and illustrates that this hypothesis fits well with most of the important incidences in astronomic and geologic discoveries.

  4. Upper Cambrian chitons (Mollusca, polyplacophora) from Missouri, USA

    Science.gov (United States)

    Pojeta, J., Jr.; Vendrasco, M.J.; Darrough, G.

    2010-01-01

    Numerous new specimens reveal a greater presence of chitons in Upper Cambrian rocks than previously suspected. Evidence is presented showing that the chiton esthete sensory system is present in all chiton species in this study at the very beginning of the known polyplacophoran fossil record. The stratigraphic occurrences and paleobiogeography of Late Cambrian chitons are documented. The 14 previously-named families of Cambrian and Ordovician chitons are reviewed and analyzed. Aulochitonidae n. fam. is defined, based on Aulochiton n. gen.; A. sannerae n. sp. is also defined. The long misunderstood family Preacanthochitonidae and its type genus Preacanthochiton Bergenhayn, 1960, are placed in synonymy with Mattheviidae and Chelodes Davidson & King, 1874, respectively; Eochelodes Marek, 1962, also is placed in synonymy with Chelodes, and Elongata Stinchcomb & Darrough, 1995, is placed in synonymy with Hemithecella Ulrich & Bridge, 1941. At the species level, H. elongata Stinchcomb & Darrough, 1995, and Elongata perplexa Stinchcomb & Darrough, 1995, are placed in synonymy with H. eminensis Stinchcomb & Darrough, 1995. The Ordovician species H. abrupta Stinchcomb & Darrough, 1995, is transferred to the genus Chelodes as C. abrupta (Stinchcomb & Darrough, 1995). The Ordovician species Preacanthochiton baueri Hoare & Pojeta, 2006, is transferred to the genus Helminthochiton as H. ? baueri (Hoare & Pojeta, 2006). The Ordovician species H. marginatus Hoare & Pojeta, 2006, is transferred to the genus Litochiton as L. marginatus (Hoare & Pojeta, 2006). Matthevia walcotti Runnegar, Pojeta, Taylor, & Collins, 1979, is treated as a synonym of Hemithecella expansa Ulrich & Bridge, 1941. In addition, other multivalved Cambrian mollusks are discussed; within this group, Dycheiidae n. fam. is defined, as well as Paradycheia dorisae n. gen. and n. sp. Cladistic analysis indicates a close relationship among the genera here assigned to the Mattheviidae, and between Echinochiton Pojeta

  5. The base of the Cambrian in Morocco

    Science.gov (United States)

    Sdzuy, K.; Geyer, G.

    The paper summarizes problems of datings of Latest Precambrian to Early Cambrian rocks of Morocco. The known palaeontological data are reviewed briefly. Characteristics and correlatability of the earliest trilobites of Morocco are discussed. Additional remarks concern the appearance of hard part animals at the beginning of the Cambrian.

  6. Biological and Molecular Geochemical Evidence for Dinoflagellate Ancestors in the Upper Sinian-Cambrian

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Dinoflagellates are single celled organisms that reflect the ecological conditions in modem oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c.240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4α-methyl-24-ethylcholestane and triaromatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian.

  7. Relationship between the Neoproterozoic snowball Earth and Cambrian explosion

    Science.gov (United States)

    Maruyama, S.; Yoshihara, A.; Isozaki, Y.

    2007-12-01

    Origin of snowball Earth has been debated in terms of greenhouse gas (e.g., Hoffman and Schrag), obliqueness of Earth's rotation axis (Williams, 1975), true polar wander (Evans, 2003), Galactic cosmic ray radiation (Shaviv and Veizer, 2003; Svensmark, 2006), or weakened geomagnetism (Maruyama and Yoshihara, 2003). A major difficulty for the greenhouse gas hypothesis is the on-off switch causing decrease and increase of appropriate amounts of CO2 by plume- and plate tectonics, and also in available amount of CO2 in atmosphere to be consistent with the observations. In contrast, the cosmic ray radiation models due to the star burst peaked at 2.5- 2.1 Ga and 1.4-0.8 Ga can explain on-off switch more easily than the greenhouse gas model. Cosmic ray radiations, however, must be modified by the geomagnetic intensity, fluctuating 150"% to cause the snowball Earth. Time difference between the Neoproterozoic snowball Earth and Cambrian explosion is as large as 250 millions years, and this refuses their direct close-relationship. Role of frequent mass extinctions, i.e., 8 times during 100 m.y. from 585 Ma to 488 Ma, during the Ediacaran and Cambrian, has been proposed (Zhu et al., 2007). This frequency is one order of magnitude higher compared to that in the post-Ordovician time. Yet, the Cambrian explosion cannot be explained by mass extinction which replaced the vacant niches shortly after the mass extinction and never created a new animal with a new body plan. A new model proposed herein is derived from weakened geomagnetism and resultant extensive cosmic radiation to alter gene and genome for a long period over advancement of low magnetic intensity and cosmic radiations (Svensmark, 2006) from 1.2-0.8Ga. As to the new body plans of animals, it took an appreciably long time to prepare all 34 genometypes before the apparent Cambrian explosion. Geochemically extreme conditions and widened shallow marine environment on continental shelf by the return-flow of sweater into

  8. Phosphate Biomineralization of Cambrian Microorganisms

    Science.gov (United States)

    McKay, David S.; Rozanov, Alexei Yu.; Hoover, Richard B.; Westall, Frances

    1998-01-01

    As part of a long term study of biological markers (biomarkers), we are documenting a variety of features which reflect the previous presence of living organisms. As we study meteorites and samples returned from Mars, our main clue to recognizing possible microbial material may be the presence of biomarkers rather than the organisms themselves. One class of biomarkers consists of biominerals which have either been precipitated directly by microorganisms, or whose precipitation has been influenced by the organisms. Such microbe-mediated mineral formation may include important clues to the size, shape, and environment of the microorganisms. The process of fossilization or mineralization can cause major changes in morphologies and textures of the original organisms. The study of fossilized terrestrial organisms can help provide insight into the interpretation of mineral biomarkers. This paper describes the results of investigations of microfossils in Cambrian phosphate-rich rocks (phosphorites) that were found in Khubsugul, Northern Mongolia.

  9. Did Gamma Ray Burst Induce Cambrian Explosion?

    OpenAIRE

    Chen, Pisin; Ruffini, Remo

    2014-01-01

    One longstanding mystery in bio-evolution since Darwin's time is the origin of the Cambrian explosion that happened around 540 million years ago (Mya), where an extremely rapid increase of species occurred. Here we suggest that a nearby GRB event ~500 parsecs away, which should occur about once per 5 Gy, might have triggered the Cambrian explosion. Due to a relatively lower cross section and the conservation of photon number in Compton scattering, a substantial fraction of the GRB photons can...

  10. Diversity partitioning during the Cambrian radiation

    OpenAIRE

    Na, Lin; Kiessling, Wolfgang

    2015-01-01

    Many mechanisms of the Cambrian Explosion have been proposed, but rigorous quantitative analyses of biodiversity dynamics are scarce, although they may shed light on important factors. Using a comprehensive database and sampling standardization, we dissect global diversity patterns. The trajectories of within-community, between-community, and global diversity during the main phase of the Cambrian radiation revealed a low-competition model, which was probably governed by niche contraction and ...

  11. Is a Cambrian Explosion Coming for Robotics?

    OpenAIRE

    Gill A. Pratt

    2015-01-01

    About half a billion years ago, life on earth experienced a short period of very rapid diversification called the "Cambrian Explosion." Many theories have been proposed for the cause of the Cambrian Explosion, one of the most provocative being the evolution of vision, allowing animals to dramatically increase their ability to hunt and find mates. Today, technological developments on several fronts are fomenting a similar explosion in the diversification and applicability of robotics. Many of ...

  12. Globalization and Environment: Can Pollution Haven Hypothesis alone explain the impact of Globalization on Environment?

    OpenAIRE

    Dinda, Soumyananda

    2006-01-01

    The economic literature on trade and environment seeks empirically test hypotheses about how trade affects the environment. It is important to resolve current policy debates. Applying panel data technique we examine the impacts of globalization on pollution level, pollution intensity and relative change of pollution for the developed (OECD), developing (Non-OECD) country groups, and the world as a whole. This paper examines the factor endowment and pollution haven hypotheses th...

  13. Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis

    OpenAIRE

    Israde-Alcántara, Isabel; Bischoff, James L.; Domínguez-Vázquez, Gabriela; Li, Hong-Chun; DeCarli, Paul S.; Bunch, Ted E.; Wittke, James H.; Weaver, James C.; Firestone, Richard B.; West, Allen; Kennett, James P.; Mercer, Chris; Xie, Sujing; Richman, Eric K.; Kinzie, Charles R.

    2012-01-01

    We report the discovery in Lake Cuitzeo in central Mexico of a black, carbon-rich, lacustrine layer, containing nanodiamonds, microspherules, and other unusual materials that date to the early Younger Dryas and are interpreted to result from an extraterrestrial impact. These proxies were found in a 27-m-long core as part of an interdisciplinary effort to extract a paleoclimate record back through the previous interglacial. Our attention focused early on an anomalous, 10-cm-thick, carbon-rich ...

  14. Consequences of exotic host use: impacts on Lepidoptera and a test of the ecological trap hypothesis.

    Science.gov (United States)

    Yoon, Su'ad; Read, Quentin

    2016-08-01

    Investigating the effects of invasive species on native biodiversity is one of the most pressing challenges in ecology. Our goal in this study was to quantify the effects of invasive plants on butterfly and moth communities. In addition, we sought to elucidate the fitness consequences of non-native hosts on lepidopterans. We conducted a meta-analysis on a total of 76 studies which provided data on larval performance, survival, oviposition preference, abundance, and species richness of Lepidoptera on native and exotic plants. Overwhelmingly, we found that performance and survival were reduced for larvae developing on exotic hosts, relative to native hosts. At the community level, alien plant invasion was associated with a reduction in the overall abundance and richness of lepidopteran communities. We found that lepidopterans did not show strong oviposition preference for native hosts. This result suggests that many invasive plant species may decrease lepidopteran abundance by providing a target for oviposition where larvae have a relatively poor chance of survival. Among studies that tested both survival and preference on exotic hosts, 37.5 % found evidence for novel hosts that could function as ecological traps (the figure was 18 % when considering studies that only assayed larval performance). Thus, although the majority of novel hosts included in our analyses are not likely to act as ecological traps, the potential clearly exists for this effect, and the role of ecological traps should be considered along with other aspects of global change impacting natural communities. PMID:26820566

  15. An Early Cambrian tunicate from China.

    Science.gov (United States)

    Shu, D G; Chen, L; Han, J; Zhang, X L

    2001-05-24

    Like the Burgess Shales of Canada, the Chengjiang Lagerstätte from the Lower Cambrian of China is renowned for the detailed preservation as fossils of delicate, soft-bodied creatures, providing an insight into the Cambrian explosion. The fossils of possible hemichordate chordates and vertebrates have attracted particular attention. Tunicates, or urochordates, comprise the most basal chordate clade, and details of their evolution could be important in understanding the sequence of character acquisition that led to the emergence of chordates and vertebrates. However, definitive fossils of tunicates from the Cambrian are scarce or debatable. Here we report a probable tunicate Cheungkongella ancestralis from the Chengjiang fauna. It resembles the extant ascidian tunicate genus Styela whose morphology could be useful in understanding the origin of the vertebrates. PMID:11373678

  16. Collective behavior in an early Cambrian arthropod.

    Science.gov (United States)

    Hou, Xian-Guang; Siveter, Derek J; Aldridge, Richard J; Siveter, David J

    2008-10-10

    Examples that indicate collective behavior in the fossil record are rare. A group association of specimens that belong to a previously unknown arthropod from the Chengjiang Lagerstätte, China, provides evidence that such behavior was present in the early Cambrian (about 525 million years ago), coincident with the earliest extensive diversification of the Metazoa, the so-called Cambrian explosion event. The chainlike form of these specimens is unique for any arthropod, fossil or living, and most likely represents behavior associated with migration. PMID:18845748

  17. Cambrian Research in the New Century—the Fourth International Symposium on the Cambrian System

    Institute of Scientific and Technical Information of China (English)

    Peng Shanchi; Zhu Maoyan; L.E.Babcock

    2006-01-01

    @@ The International Subcomission on Cambrian Stratigraphy (ISCS) of the International Commission on Stratigraphy (ICS)held its Fourth International Symposium on the Cambrian System in Nanjing, the capital city of Jiangsu Province, China, on 18-24August, 2005. The Symposium was held in conjunction with the Tenth Field Conference of the Cambrian Stage Subdivision Working Group of the ISCS. Technical sessions were held in the conference center of Southeast University, and hosted by the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, the Geological Institute, Chinese Academy of Geological Sciences, and Guizhou University. Associated with the meeting were five field excursions to classical Cambrian localities in North China and South China.

  18. A highly redox-heterogeneous ocean in South China during the early Cambrian (˜529-514 Ma): Implications for biota-environment co-evolution

    Science.gov (United States)

    Jin, Chengsheng; Li, Chao; Algeo, Thomas J.; Planavsky, Noah J.; Cui, Hao; Yang, Xinglian; Zhao, Yuanlong; Zhang, Xingliang; Xie, Shucheng

    2016-05-01

    The "Cambrian Explosion" is known for rapid increases in the morphological disparity and taxonomic diversity of metazoans. It has been widely proposed that this biological event was a consequence of oxygenation of the global ocean, but this hypothesis is still under debate. Here, we present high-resolution Fe-S-C-Al-trace element geochemical records from the Jinsha (outer shelf) and Weng'an (outer shelf) sections of the early Cambrian Yangtze Platform, integrating these results with previously published data from six correlative sections representing a range of water depths (Xiaotan, Shatan, Dingtai, Yangjiaping, Songtao, and Longbizui). The integrated iron chemistry and redox-sensitive trace element data suggest that euxinic mid-depth waters dynamically coexisted with oxic surface waters and ferruginous deep waters during the earliest Cambrian, but that stepwise expansion of oxic waters commenced during Cambrian Stage 3 (∼ 521- 514 Ma). Combined with data from lower Cambrian sections elsewhere, including Oman, Iran and Canada, we infer that the global ocean exhibited a high degree of redox heterogeneity during the early Cambrian, consistent with low atmospheric oxygen levels (∼ 10- 40% of present atmospheric level, or PAL). A large spatial gradient in pyrite sulfur isotopic compositions (δ34Spy), which vary from a mean of - 12.0 ‰ in nearshore areas to + 22.5 ‰ in distal deepwater sections in lower Cambrian marine units of South China imply low concentrations and spatial heterogeneity of seawater sulfate, which is consistent with a limited oceanic sulfate reservoir globally. By comparing our reconstructed redox chemistry with fossil records from the lower Cambrian of South China, we infer that a stepwise oxygenation of shelf and slope environments occurred concurrently with a gradual increase in ecosystem complexity. However, deep waters remained anoxic and ferruginous even as macrozooplankton and suspension-feeding mesozooplankton appeared during

  19. Developmental sequence of Cambrian embryo Markuelia

    Institute of Scientific and Technical Information of China (English)

    DONG XiPing

    2007-01-01

    Based on more exquisitely preserved specimens of Markuelia hunanensis recently recovered from Middle and Upper Cambrian in western Hunan and in the light of Synchrotron radiation X-ray tomographic microscopy, the developmental sequence from cleavage through organogenesis to the pre-hatching of Cambrian embryo Markuelia, especially the developmental sequence during the pre-hatching stage, i.e. from the earliest period when the scalids and tail spines only took shape to the latest period (just about hatching), is established. This developmental sequence provides a pattern of embryonic development during the pre-hatching stage, which has not been established in the living scalidophorans (priapulids, Ioriciferans and kinorhynchs). Thus, it not only enriches our knowledge on the embryonic development of the extant descendants of Markuelia, but also opens a new window to the evolution and development of the animal.

  20. A new formal perspective on 'Cambrian explosions'.

    Science.gov (United States)

    Wallace, Rodrick

    2014-01-01

    The 'Cambrian explosion' 500 Myr ago saw a relatively sudden proliferation of organism Bauplan and ecosystem niche structure that continues to haunt evolutionary biology. Here, adapting standard methods from information theory and statistical mechanics, we model the phenomenon as a noise-driven phase transition, in the context of deep-time relaxation of current path-dependent evolutionary constraints. The result is analogous to recent suggestions that multiple 'explosions' of increasing complexity in the genetic code were driven by rising intensities of available metabolic free energy. In the absence of severe path-dependent lock-in, 'Cambrian explosions' are standard features of blind evolutionary process, representing outliers in the ongoing routine of evolutionary punctuated equilibrium. PMID:24439546

  1. The notion of the Cambrian pananimalia genome.

    OpenAIRE

    Ohno, S.

    1996-01-01

    The toil by photosynthesizing cyanobacteria and blue-green algae of nearly three billion years appeared to have finally resulted in the sufficient accumulation of molecular oxygen. So, the stage was set for the emergence, at the ocean bottom, of diverse animals that were consumers of molecular oxygen. It now appears that this Cambrian explosion, during which nearly all the extant animal phyla have emerged, was of an astonishingly short duration, lasting only 6-10 million years. Inasmuch as on...

  2. Oxygen Requirements for the Cambrian Explosion

    Institute of Scientific and Technical Information of China (English)

    Xingliang Zhang; Linhao Cui

    2016-01-01

    Hypoxic tolerance experiments may be helpful to constrain the oxygen requirement for animal evolution. Based on literature review, available data demonstrate that fishes are more sensitive to hypoxia than crustaceans and echinoderms, which in turn are more sensitive than annelids, whilst mollusks are the least sensitive. Mortalities occur where O2 concentrations are below 2.0 mg/L, equivalent to saturation with oxygen content about 25% PAL (present atmospheric level). Therefore, the minimal oxygen requirement for maintaining animal diversity since Cambrian is determined as 25% PAL. The traditional view is that a rise in atmospheric oxygen concentrations led to the oxygenation of the ocean, thus triggering the evolution of animals. Geological and geochemical studies suggest a constant increase of the oxygen level and a contraction of anoxic oceans during Ediacaran–Cambrian transition when the world oceans experienced a rapid diversification of metazoan lineages. However, fossil first appearances of animal phyla are obviously asynchronous and episodic, showing a sequence as:basal metazoans>lophotrochozoans>ecdysozoans and deuterostomes. According to hitherto known data of fossil record and hypoxic sensitivity of animals, the appearance sequence of different animals is broadly consistent with their hypoxic sensitivity:animals like molluscs and annelids that are less sensitive to hypoxia appeared earlier, while animals like echinoderms and fishes that are more sensitive to hypoxia came later. Therefore, it is very likely that the appearance order of animals is corresponding to the increasing oxygen level and/or the contraction of anoxic oceans during Ediacaran–Cambrian transition.

  3. Did Gamma Ray Burst Induce Cambrian Explosion?

    CERN Document Server

    Chen, Pisin

    2014-01-01

    One longstanding mystery in bio-evolution since Darwin's time is the origin of the Cambrian explosion that happened around 540 million years ago (Mya), where an extremely rapid increase of species occurred. Here we suggest that a nearby GRB event ~500 parsecs away, which should occur about once per 5 Gy, might have triggered the Cambrian explosion. Due to a relatively lower cross section and the conservation of photon number in Compton scattering, a substantial fraction of the GRB photons can reach the sea level and would induce DNA mutations in organisms protected by a shallow layer of water or soil, thus expediting the bio-diversification. This possibility of inducing genetic mutations is unique among all candidate sources for major incidents in the history of bio-evolution. A possible evidence would be the anomalous abundance of certain nuclear isotopes with long half-lives transmuted by the GRB photons in geological records from the Cambrian period. Our notion also imposes constraints on the evolution of ...

  4. Did gamma ray burst induce Cambrian explosion?

    Science.gov (United States)

    Chen, Pisin; Ruffini, R.

    2015-06-01

    One longstanding mystery in bio-evolution since Darwin's time is the origin of the Cambrian explosion that happened around 540 million years ago (Mya), where an extremely rapid increase of species occurred. Here we suggest that a nearby GRB event 500 parsecs away, which should occur about once per 5 Gy, might have triggered the Cambrian explosion. Due to a relatively lower cross section and the conservation of photon number in Compton scattering, a substantial fraction of the GRB photons can reach the sea level and would induce DNA mutations in organisms protected by a shallow layer of water or soil, thus expediting the bio-diversification. This possibility of inducing genetic mutations is unique among all candidate sources for major incidents in the history of bio-evolution. A possible evidence would be the anomalous abundance of certain nuclear isotopes with long half-lives transmuted by the GRB photons in geological records from the Cambrian period. Our notion also imposes constraints on the evolution of exoplanet organisms and the migration of panspermia.

  5. Yochelcionella (Mollusca, Helcionelloida) from the lower Cambrian of North America

    OpenAIRE

    Atkins C J; Peel J S

    2008-01-01

    Five named species of the helcionelloid mollusc genus Yochelcionella Runnegar & Pojeta, 1974 are recognized from the lower Cambrian (Cambrian Series 2) of North America: Yochelcionella erecta (Walcott, 1891), Y. americana Runnegar &Pojeta, 1980, Y. chinensis Pei, 1985, Y. greenlandica Atkins & Peel, 2004 and Y. gracilis Atkins & Peel, 2004, linking lower Cambrian o...

  6. Arachnostega Bertling, 1992 in the Drumian (Cambrian) sediments of the Teplá-Barrandian region (Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Fatka, O.; Mikuláš, Radek; Szabad, M.; Micka, V.; Valent, M.

    2011-01-01

    Roč. 61, č. 4 (2011), s. 367-381. ISSN 0001-5709 R&D Projects: GA ČR GA205/06/0395; GA ČR GA205/09/1521 Institutional research plan: CEZ:AV0Z30130516 Keywords : Cambrian * Teplá-Barrandian region * ichnofossils * Jince Formation * Buchava Formation * Arachnostega * Cambrian (Czech Republic) Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.565, year: 2011 https://geojournals.pgi.gov.pl/agp/article/view/9705

  7. High continental weathering rate during Early Cambrian: Evidence from Os isotopic composition of Early Cambrian Ocean

    Science.gov (United States)

    Jiang, S.-Y.; Yang, J.-H.; Ling, H.-F.; Feng, H.-Z.; Chen, Y.-Q.; Chen, J.-H.

    2003-04-01

    The paleo-ocean environmental change during the Precambrian-Cambrian transition is a key issue related to the causes for an explosive radiation of different metazoan phyla during Early Cambrian. The chemical and isotopic compositions of marine sediments and chemical precipitates such as carbonates, phosphorites, siliceous rocks, and black shales record the changing composition and physical conditions of the seawater in which these rocks accumulated. Organic carbon-rich black shales from marine environments are commonly enriched in a number of trace elements such as Ni, Mo, V, Co, Cr, Au, U, As, Pb, Zn, Cu, Re, and platinum-group-elements (PGE). Recent researches have demonstrated that Re-Os isotopes and PGE contents in black shales are useful proxies for seawater chemistry. It is believed that Re and Os in orgainc-carbon rich black shales are mostly hydrogeneous in origin which were largely sequestered from seawater at the time of deposition. In South China, the Lower Cambrian black shale sequence of the Niutitang Formation (and lateral equivalents) exists broadly several thousands kilometers. The lowermost sequence of this formation contain a thin sulfide ore horizon with an apparently unique and extreme case of metal enrichments such as Mo, Ni, Se, Re, Os, As, Hg, Sb, Ag, Au, Pt, and Pd. In this study, we conducted a preliminary investigation of Re-Os isotopes and Plantium Group Element (PGE) distribution patterns of the balck shales and intercalated Ni-Mo polymetallic sulfide bed from Guizhou and Hunan Provinces. The high rOs(t) values of the black shales indicate that the Early Cambrian ocean in Yangtze Platform had a highly radiogenic Os, possibly as a result of high continental weathering rate at that time. The Ni-Mo polymetallic sulfide ores within the black shales have lower rOs(t) values than the black shales, and they show similar REE and PGE patterns as the hydrothermal siliceous rocks within the Lower Cambrian strata, which suggest that the Ni

  8. Early colonization of metazoans in the deep-water: Evidences from the lowermost Cambrian black shales of South China

    Science.gov (United States)

    Zhu, M.-Y.; Yang, A.-H.; Zhang, J.-M.; Li, G.-X.; Yang, X.-L.

    2003-04-01

    Diversity of metazoans is high in the deep-water of the present ocean. But it is unknown that when the metazoans began to colonize in the deep-water and what kinds of metazoans first colonized in the deep-water since origin and radiation of metazoans during the Precambrian-Cambrian transition interval. Up to the present, colonization of the deep-sea began in the Ordovician. Although it is suggested that animals were penetrated into the intermediate water depth during the Precambrian, evidences support such suggestion are based on the problematic Ediacaran-grade fossils. However, almost fossil materials that support the Cambrian Explosion hypothesis were discovered from the lowermost Cambrian shallow-water deposits. The abundant earliest Cambrian mineralized small shelly fossils (SSF) are globally from the shallow-water deposits, and the well-known Chengjiang fauna that may records most complete features of metazoans in the ocean after the Cambrian Explosion, occurs as well in the shallow basin near an old land on the Yangtze Platform. In order to understand ecology of the Cambrian Explosion time interval and how happened of the onshore-offshore trends of metazoans, we focused our attention on collecting fossils in the lowermost Cambrian deposits under the varied facies on the Yangtze Platformm during recent years. Investigations of the shallow-water carbonate facies and the oxygen-depleted deep-water black shale facies revealed additional biological and ecological information that are not recorded in the Chengjiang fauna in the siliclastic shallow-water facies. Here we report our discovery of a particular fossil association from more than 10 sections in the deep-water black shales (Qiongzhusian) in the out shelf and slope area of the Yangtze Platform. The fossil association is composed of pelagic and sessile organisms, including abundant sponges, 3 types of bivalved arthropods, 3 types of tubular animals and few problematic organisms. The fossils have either

  9. The Cambrian “explosion”: Slow-fuse or megatonnage?

    OpenAIRE

    Conway Morris, Simon

    2000-01-01

    Clearly, the fossil record from the Cambrian period is an invaluable tool for deciphering animal evolution. Less clear, however, is how to integrate the paleontological information with molecular phylogeny and developmental biology data. Equally challenging is answering why the Cambrian period provided such a rich interval for the redeployment of genes that led to more complex bodyplans.

  10. The impact of seasonality on niche breadth, distribution range and species richness: a theoretical exploration of Janzen's hypothesis.

    Science.gov (United States)

    Hua, Xia

    2016-07-27

    Being invoked as one of the candidate mechanisms for the latitudinal patterns in biodiversity, Janzen's hypothesis states that the limited seasonal temperature variation in the tropics generates greater temperature stratification across elevations, which makes tropical species adapted to narrower ranges of temperatures and have lower effective dispersal across elevations than species in temperate regions. Numerous empirical studies have documented latitudinal patterns in species elevational ranges and thermal niche breadths that are consistent with the hypothesis, but the theoretical underpinnings remain unclear. This study presents the first mathematical model to examine the evolutionary processes that could back up Janzen's hypothesis and assess the effectiveness of limited seasonal temperature variation to promote speciation along elevation in the tropics. Results suggest that trade-offs in thermal tolerances provide a mechanism for Janzen's hypothesis. Limited seasonal temperature variation promotes gradient speciation not due to the reduction in gene flow that is associated with narrow thermal niche, but due to the pleiotropic effects of more stable divergent selection of thermal tolerance on the evolution of reproductive incompatibility. The proposed modelling approach also provides a potential way to test a speciation model against genetic data. PMID:27466445

  11. Cambrian Fossil Embryos from Western Hunan,South China

    Institute of Scientific and Technical Information of China (English)

    DONG Xiping

    2009-01-01

    The exquisitely preserved fossil embryos of Markuelia recovered from the limestones of the Middle Cambrian Haoqiao Formation and Upper Cambrian Bitiao formation in western Hunan,South China are described and illustrated in detail for the first time.A new species Markuelia elegans sp.nov.is established based mainly on embryos from the Upper Cambrian.A few of animal's resting eggs,which are comparable with those of the Ediacaran Doushantuo Formation,have been also found in the Upper Cambrian of western Hunan.The membrane of oue egg from the uppermost Cambrian has been replaced by pyrite and the overgrowth of the pyrite crystals exhibits a unique inorganic reducing conditions promoted the excellent preservation for the Markuelia specimens.The study of Markuelia provides not only constraint on the anatomy,affinity,embryonic development and phylogenetic significance of this wormlike animal and but also opens a new window onto the evolution and development of the earliest animals.

  12. Paleoecologic Implications of Ichnofossils Associated with Slightly Skeletonized Body Fossils, Middle Cambrian of the Barrandian Area, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Mikuláš, Radek; Fatka, O.; Szabad, M.

    2012-01-01

    Roč. 19, č. 4 (2012), s. 199-210. ISSN 1042-0940 R&D Projects: GA ČR GA205/09/1521 Institutional support: RVO:67985831 Keywords : Middle Cambrian * ichnofossils * slightly skeletonized fauna * Barrandian area Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.727, year: 2012

  13. Remagnetized cratonic Cambrian strata from southern Nevada

    Science.gov (United States)

    Gillett, Stephen L.

    1982-08-01

    Stratigraphic sections of Cambrian strata in southeastern Nevada are akin to thin, cratonic facies exposed in the Grand Canyon; their structural setting is much more complicated, however, from Mesozoic and Cenozoic tectonism. Paleomagnetic samples from two sections through these strata appear to have been completely remagnetized. Coarse-grained, lightcolored sandstone from the Tapeats Sandstone yields scattered magnetizations, residing in hematite, that appear to reflect protracted diagenetic acquisition of remanence. A hematitic sandstone in the Bright Angel Shale yields relatively consistent `Paleozoic' directions of magnetization, but petrographic study shows that the hematite results from diagenetic oxidation, and stratigraphic arguments suggest that the oxidation was not penecontemporaneous. Gray limestones of the Jangle and Muav Limestones yield a magnetization, residing in magnetite, that may reflect late Tertiary remagnetization, being imposed during uplift related to the onset of Basin and Range deformation. In any case, this magnetization differs greatly in direction from a hematite magnetization reported from slightly younger Muav Limestone in the Grand Canyon. Both the sampling sites also appear to have been tectonically rotated, but whether this rotation is true or a geometric artifact of the tilt correction cannot be determined from the present data. These results suggest that paleomagnetic data from rocks as old as Cambrian must be scrutinized very carefully before their magnetizations can be accepted as penecontemporaneous, and such scrutiny must include geologic data.

  14. Segmentation, metamerism and the Cambrian explosion.

    Science.gov (United States)

    Couso, Juan Pablo

    2009-01-01

    Data on the molecular and genetic basis of animal development, and on genome sequences, have been challenging our established assumptions about animal evolution for the last decade. Recent such data in animals of particular phylogenetic importance beg us to take another look at whether similarities in developmental and genetic mechanisms in current animals are the product of a common inheritance (homology) or convergent evolution (analogy). The evolution of segmentation, in particular whether segmentation and metameric bodies have arisen just once or several times in evolution, is a prime concern. Segmentation and metamerism are striking developmental and body organisations that exist, in varying degrees, in many complex animals, but the traditional view holds that this is the result of convergent evolution. Here, I review recent palenotological and developmental information and conclude that a metameric body plan is not only a likely ancestral character of bilaterian animals, but also a possible trigger for the Cambrian explosion in body morphology and complexity. This conclusion is supported by the phylogenetic distribution and prevalence of metameric phyla in the Cambrian, and the similarity of the genomes and segmentation mechanisms across current bilaterian phyla. PMID:19247939

  15. Geosphere-Biosphere Feedbacks as a Trigger for the Cambrian explosion

    Science.gov (United States)

    von Bloh, W.; Bounama, C.; Franck, S.

    2003-12-01

    A new hypothesis for the cause of the Cambrian explosion is presented. The Cambrian explosion 542 Myr ago is characterized by a sudden increase of biomass and a rapid cooling, which amplified the spread of complex multicellular life. The evolution of the planet Earth is described by the co-evolution of the geosphere-biosphere system. A conceptual model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, continental biosphere, the kerogen, as well as the aggregated reservoir ocean and atmosphere is presented. In this study the evolution of the mean global surface temperature, the biomass, and reservoir sizes over the whole history and future of the Earth under a maturing Sun is investigated. Here we specify our previously published Earth system model (Franck et al., 2002) by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. They are characterized by different temperature tolerance windows and biotic amplification factors of silicate weathering. The biotic enhancement of weathering by complex multicellular life adds an additional feedback to the system and triggers the Cambrian explosion. The Cambrian explosion was mainly driven by extrinsic environmental causes, i.e. a gradual cooling of the Earth. The Cambrian explosion was so rapid because of a positive feedback between the spread of biosphere, increased silicate weathering, and a consequent cooling of the climate. The environment itself has been actively changed by the biosphere maintaining the temperature conditions for its existence. Furthermore, it can be shown that the coupled geosphere-biosphere system exhibit s bistability: there exist two stable model solutions for a certain interval of the biotic enhancement factor, one solution with and one without complex multicellular life. In particular, cooling events in the Neoproterozoic, could force a premature appearance of complex multicellular life

  16. Upper Cambrian (Furongian) biostratigraphy in Scandinavia revisited

    DEFF Research Database (Denmark)

    Nielsen, Arne Thorshøj; Weidner, Thomas; Terfelt, Fredrik;

    2014-01-01

    , 73–87], are resurrected and elevated to superzonal rank. These superzones are usually readily recognized in the field, even by non-specialists, and for general correlation and mapping the more wide-ranging biozones are considerably more practicable than the very detailed zonation (formerly......, Parabolina and Leptoplastus (super)zones as well as the recently introduced Acerocarina Superzone ( = Acerocare Zone of older literature) are maintained and formalized. The Protopeltura praecursor, Peltura minor and Peltura scarabaeoides zones are abandoned and replaced by two new units, named the...... Protopeltura and Peltura superzones, respectively. Accordingly, all Furongian superzones have a uniform naming style referring to a characteristic genus. The six Furongian superzones currently comprise 27 trilobite zones. The Paradoxides forchhammeri Superzone (Cambrian Series 3) is extended upwards to the...

  17. The Venus Hypothesis

    CERN Document Server

    Cartwright, Annabel

    2016-01-01

    Current models indicate that Venus may have been habitable. Complex life may have evolved on the highly irradiated Venus, and transferred to Earth on asteroids. This model fits the pattern of pulses of highly developed life appearing, diversifying and going extinct with astonishing rapidity through the Cambrian and Ordovician periods, and also explains the extraordinary genetic variety which appeared over this period.

  18. At the Origin of Animals: The Revolutionary Cambrian Fossil Record

    OpenAIRE

    Budd, Graham E.

    2013-01-01

    The certain fossil record of animals begins around 540 million years ago, close to the base of the Cambrian Period. A series of extraordinary discoveries starting over 100 years ago with Walcott’s discovery of the Burgess Shale has accelerated in the last thirty years or so with the description of exceptionally-preserved Cambrian fossils from around the world. Such deposits of “Burgess Shale Type” have been recently complemented by other types of exceptional preservation. Together with a rema...

  19. An Early Cambrian problematic fossil: Vetustovermis and its possible affinities

    OpenAIRE

    Chen, Jun-Yuan; Huang, Di-Ying; Bottjer, David J.

    2005-01-01

    The Early Cambrian problematic fossil Vetustovermis (Glaessner 1979 Alcheringa 3, 21–31) was described as an annelid or arthropod. Anatomical analysis of 17 new specimens from the Lower Cambrian Maotianshan Shale at Anning, Kunming (South China) does not support its affinities with annelids or arthropods. Anatomical features instead resemble other animal groups including modern flatworms, nemertines and molluscs. The presence of a pelagic slug-like form and ventral foot, as well as a head wit...

  20. Global standard names for the Lowermost Cambrian Series and Stage

    Institute of Scientific and Technical Information of China (English)

    Ed Landing; Shanchi Peng; Loren E.Babcock; Gerd Geyer; Malgorzata Moczydlowska-Vidal

    2007-01-01

    @@ The GSSP marking the base of the Cambrian System was ratified by the IUGS in 1992.Ratification of the GSSP point at the base of the Trichophycus pedum Ichnozone in the Fortune Head section,eastern Newfoundland,Canada,automatically defined the conterminant base of the lowermost series and stage of the Cambrian although names for those subdivisions were not proposed at the time of the decision.

  1. Reconstruction of early Cambrian ocean chemistry from Mo isotopes

    Science.gov (United States)

    Wen, Hanjie; Fan, Haifeng; Zhang, Yuxu; Cloquet, Christophe; Carignan, Jean

    2015-09-01

    The Neoproterozoic-Cambrian transition was a key time interval in the history of the Earth, especially for variations in oceanic and atmospheric chemical composition. However, two conflicting views exist concerning the nature of ocean chemistry across the Precambrian-Cambrian boundary. Abundant geochemical evidence suggests that oceanic basins were fully oxygenated by the late Ediacaran, while other studies provide seemingly conflicting evidence for anoxic deep waters, with ferruginous conditions [Fe(II)-enriched] persisting into the Cambrian. Here, two early Cambrian sedimentary platform and shelf-slope sections in South China were investigated to trace early Cambrian ocean chemistry from Mo isotopes. The results reveal that early Cambrian sediments deposited under oxic to anoxic/euxinic conditions have δ98/95Mo values ranging from -0.28‰ to 2.29‰, which suggests that early Cambrian seawater may have had δ98/95Mo values of at least 2.29‰, similar to modern oceans. The heaviest and relatively homogeneous δ98/95Mo values were recorded in siltstone samples formed under completely oxic conditions, which is considered that Mn oxide-free shuttling was responsible for such heavy δ98/95Mo value. Further, combined with Fe species data and the accumulation extent of Mo and U, the variation of δ98/95Mo values in the two studied sections demonstrate a redox-stratified ocean with completely oxic shallow water and predominantly anoxic (even euxinic) deeper water having developed early on, which eventually became completely oxygenated. This suggests that oceanic circulation at the time became reorganized, and such changes in oceanic chemistry may have been responsible for triggering the "Cambrian Explosion" of biological diversity.

  2. Tectonic Events May Have Triggered the Cambrian Explosion

    Science.gov (United States)

    Wendel, JoAnna

    2014-11-01

    Major geological changes causing sea level rise at the start of the Cambrian period (540-490 million years ago) could have kick-started the Cambrian Explosion—a geological time period when most major phyla of life suddenly appeared in the fossil record. A paper published in the November issue of Geology (doi:10.1130/G35886.1) proposes a new geological mechanism for this event.

  3. Pulse of atmospheric oxygen during the late Cambrian

    OpenAIRE

    Saltzman, Matthew R.; Young, Seth A.; Kump, Lee R.; Gill, Benjamin C.; Lyons, Timothy W.; Runnegar, Bruce

    2011-01-01

    A rise in atmospheric O2 has been linked to the Cambrian explosion of life. For the plankton and animal radiation that began some 40 million yr later and continued through much of the Ordovician (Great Ordovician Biodiversification Event), the search for an environmental trigger(s) has remained elusive. Here we present a carbon and sulfur isotope mass balance model for the latest Cambrian time interval spanning the globally recognized Steptoean Positive Carbon Isotope Excursion (SPICE) that i...

  4. Primitive soft-bodied cephalopods from the Cambrian.

    Science.gov (United States)

    Smith, Martin R; Caron, Jean-Bernard

    2010-05-27

    The exquisite preservation of soft-bodied animals in Burgess Shale-type deposits provides important clues into the early evolution of body plans that emerged during the Cambrian explosion. Until now, such deposits have remained silent regarding the early evolution of extant molluscan lineages-in particular the cephalopods. Nautiloids, traditionally considered basal within the cephalopods, are generally depicted as evolving from a creeping Cambrian ancestor whose dorsal shell afforded protection and buoyancy. Although nautiloid-like shells occur from the Late Cambrian onwards, the fossil record provides little constraint on this model, or indeed on the early evolution of cephalopods. Here, we reinterpret the problematic Middle Cambrian animal Nectocaris pteryx as a primitive (that is, stem-group), non-mineralized cephalopod, based on new material from the Burgess Shale. Together with Nectocaris, the problematic Lower Cambrian taxa Petalilium and (probably) Vetustovermis form a distinctive clade, Nectocarididae, characterized by an open axial cavity with paired gills, wide lateral fins, a single pair of long, prehensile tentacles, a pair of non-faceted eyes on short stalks, and a large, flexible anterior funnel. This clade extends the cephalopods' fossil record by over 30 million years, and indicates that primitive cephalopods lacked a mineralized shell, were hyperbenthic, and were presumably carnivorous. The presence of a funnel suggests that jet propulsion evolved in cephalopods before the acquisition of a shell. The explosive diversification of mineralized cephalopods in the Ordovician may have an understated Cambrian 'fuse'. PMID:20505727

  5. Investigating the Goldilocks Hypothesis: The Non-Linear Impact of Positive Trait Change on Well-Being

    OpenAIRE

    Martin, Chris C.; Keyes, Corey L. M.

    2015-01-01

    This paper attempts to reconcile two perspectives on the impact of positive trait change. The first perspective views positive trait change as salubrious because it reflects the process of self-enhancement, whereas the second perspective views positive change as costly because it disrupts the self-verification process. We propose that benefits and costs accrue at discrete rates, such that moderate positive trait change is more beneficial than too little and too much positive change. This cons...

  6. Marine Redox Conditions in the Early Cambrian Ocean:Insights from the Lower Cambrian Phosphorite Deposits, South China

    Institute of Scientific and Technical Information of China (English)

    Haifeng Fan; Hanjie Wen; Xiangkun Zhu

    2016-01-01

    ABSTRACT:It is generally considered that a significant change in oceanic redox conditions occurred during the Ediacaran–Cambrian transition. However, there are currently two major conflicting views on the degree of oxygenation of deep water (oxic vs. ferruginous) during this interval. To date, the oxygenation conditions of the Early Cambrian ocean have not been well constrained. The oxygenation magnitude and mechanism of the Early Cambrian ocean could be critical to the significant biological evolution of the“Cambrian Explosion”. To constrain the Early Cambrian oceanic redox environment, we conducted an integrated study on iron and sulfur isotopes and redox-sensitive elements (Mo, U, and V) of Lower Cambrian phosphorite deposits from two shallow sections (Meishucun and Gezhongwu) and a deeper water section (Zunyi) from the Yangtze Platform, South China. The near zero δ56Fe values from the two shallow sections studied here reflect oxic conditions in the lower phosphorite deposition. An obvious positive shift inδ56Fe and redox-sensitive element content was observed in the middle parts of the two shallow water sections, which might reflect loss of light iron by dissimilatory iron reduction during early diagenesis under suboxic shallow water in the platform. However, the highly positiveδ56Fe values in the deep section could reflect a lower oxidation degree of dissolved Fe(II) under anoxic deep water. The data suggest redox-stratified oceanic conditions during the Early Cambrian, in which completely oxygenated shallow water (platform) coexisted with anoxic deep water (slope). We propose that prolonged upwelling of dissolved organic carbon (DOC)-, Fe(II)- and phosphorus-rich anoxic deep water in a redox-stratified ocean could have increased exchange with the open ocean, resulting in major phosphorite deposition in oxic-suboxic conditions. The progressive oxygenation of the ocean may have facilitated the Early Cambrian biotic diversification.

  7. PNAS Plus: Independent evaluation of conflicting microspherule results from different investigations of the Younger Dryas impact hypothesis

    Science.gov (United States)

    LeCompte, Malcolm A.; Goodyear, Albert C.; Demitroff, Mark N.; Batchelor, Dale; Vogel, Edward K.; Mooney, Charles; Rock, Barrett N.; Seidel, Alfred W.

    2012-10-01

    Firestone et al. sampled sedimentary sequences at many sites across North America, Europe, and Asia [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 106:16016-16021]. In sediments dated to the Younger Dryas onset or Boundary (YDB) approximately 12,900 calendar years ago, Firestone et al. reported discovery of markers, including nanodiamonds, aciniform soot, high-temperature melt-glass, and magnetic microspherules attributed to cosmic impacts/airbursts. The microspherules were explained as either cosmic material ablation or terrestrial ejecta from a hypothesized North American impact that initiated the abrupt Younger Dryas cooling, contributed to megafaunal extinctions, and triggered human cultural shifts and population declines. A number of independent groups have confirmed the presence of YDB spherules, but two have not. One of them [Surovell TA, et al. (2009) Proc Natl Acad Sci USA 104:18155-18158] collected and analyzed samples from seven YDB sites, purportedly using the same protocol as Firestone et al., but did not find a single spherule in YDB sediments at two previously reported sites. To examine this discrepancy, we conducted an independent blind investigation of two sites common to both studies, and a third site investigated only by Surovell et al. We found abundant YDB microspherules at all three widely separated sites consistent with the results of Firestone et al. and conclude that the analytical protocol employed by Surovell et al. deviated significantly from that of Firestone et al. Morphological and geochemical analyses of YDB spherules suggest they are not cosmic, volcanic, authigenic, or anthropogenic in origin. Instead, they appear to have formed from abrupt melting and quenching of terrestrial materials.

  8. Lithofacies palaeogeography of the Cambrian in Tarim area

    Institute of Scientific and Technical Information of China (English)

    FENG Zengzhao; BAO Zhidong; WU Maobing; JIN Zhenkui; SHI Xiaozhang

    2007-01-01

    The Tarim area in this paper refers to the present Tarim Basin and its surrounding mountains, bounded on the north by the Middle Tianshan Mountains, on the south by the Kunlun Mountains, on the west by the national boundary of China, and on the east by the Altun Mountains. It covers an area of more than 1 000 000 km2. Based on the quantitative and qualitative data from the stratigraphy and petrology of outcrop and well sections, and according to the single factor analysis and multifactor comprehensive mapping method,the single factor maps of the Lower, Middle and Upper Cambrian, and the lithofacies palaeogeography maps of the Early, Middle and Late Cambrian of the Tarim area, are com-piled. The most important character of these lithofacies pal-aeogeography maps is quantification, I.e. The determination of each palaeogeography unit based on accurate quantitativedata and the quantitative single factor maps. The study marksthe first time that this quantitative method has been appliedin the Tarim area. In the Early Cambrian, the present TarimBasin was mainly a carbonate platform, in which there werepenebank, dolostone flats, and gypsum-halite lake. The South Tianshan Basin and East Tarim Basin were siliceous rock-limestone-mudstone basins. The Kunlun Platform was situ-ated in the south, where there were two small lands. The AltunLand was situated in the southeast. In the Middle and Late Cambrian, the framework of lithofacies palaeogeography was similar to that in the Early Cambrian; the land area was gradually reduced; the basin area was enlarged; while the Tarim Carbonate Platform changed little. The transgression continued from the Early Cambrian to the Late Cambrian.

  9. Explaining the Cambrian "Explosion" of Animals

    Science.gov (United States)

    Marshall, Charles R.

    2006-05-01

    The Cambrian "explosion" is a unique episode in Earth history, when essentially all the animal phyla first appear in the fossil record. A variety of environmental, developmental (genetic), and ecological explanations for this complex and somewhat protracted event are reviewed, with a focus on how well each explains the observed increases in disparity and diversity, the time of onset of the radiation, its duration, and its uniqueness. The increase in disparity (the origin of the phyla) and diversity are best understood as being the result of the interplay of the combinatorial bilaterian developmental system and the increase in the number of needs the first bilaterians had to meet as complex ecological interactions developed. The time of onset is constrained by the evolution of the environment, whereas its duration appears to be controlled primarily by rates of developmental innovation. The uniqueness of the event is either due to ensuing developmental limitation, to ecological saturation, or simply to the exhaustion of ecologically viable morphologies that could be produced by the nascent bilaterian developmental system.

  10. The possible impact of persistent virus infection on the function of the RNAi machinery in insects: a hypothesis

    Directory of Open Access Journals (Sweden)

    LucSwevers

    2013-11-01

    Full Text Available RNAi experiments in insects are characterized by great variability in efficiency; for instance beetles and locusts are very amenable to dsRNA-mediated gene silencing, while other insect groups, most notably lepidopterans, are more refractory to RNAi. Several factors can be forwarded that could affect the efficiency of RNAi, such as the composition and function of the intracellular RNAi machinery, the mechanism of dsRNA uptake, the presence of dsRNA- and siRNA-degrading enzymes and non-specific activation of the innate immune response. In this essay, we investigate the evidence whether persistent infection with RNA viruses could be a major factor that affects the response to exogenous dsRNA in insects. The occurrence of RNA viruses in different insect groups will be discussed, as well as several mechanisms by which viruses could interfere with the process of RNAi. Finally, the impact of RNA virus infection on the design of dsRNA-based insect control strategies will be considered.

  11. The evolution of associative learning: A factor in the Cambrian explosion.

    Science.gov (United States)

    Ginsburg, Simona; Jablonka, Eva

    2010-09-01

    The Cambrian explosion is probably the most spectacular diversification in evolutionary history, and understanding it has been a challenge for biologists since the time of Darwin. We propose that one of the key factors that drove this great diversification was associative learning. Although the evolutionary emergence of associative learning required only small modifications in already existing memory mechanisms and may have occurred in parallel in several groups, once this type of learning appeared on the evolutionary scene, it led to extreme diversifying selection at the ecological level: it enabled animals to exploit new niches, promoted new types of relations and arms races, and led to adaptive responses that became fixed through genetic accommodation processes. This learning-based diversification was accompanied by neurohormonal stress, which led to an ongoing destabilization and re-patterning of the epigenome, which, in turn, enabled further morphological, physiological, and behavioral diversification. Our hypothesis combines several previous ideas about the dynamics of the Cambrian explosion and provides a unifying framework that includes both ecological and genomic factors. We conclude by suggesting research directions that would clarify the timing and manner in which associative learning evolved, and the effects it had on the evolution of nervous systems, genomes, and animal morphology. PMID:20558182

  12. A suspension-feeding anomalocarid from the Early Cambrian.

    Science.gov (United States)

    Vinther, Jakob; Stein, Martin; Longrich, Nicholas R; Harper, David A T

    2014-03-27

    Large, actively swimming suspension feeders evolved several times in Earth's history, arising independently from groups as diverse as sharks, rays and stem teleost fishes, and in mysticete whales. However, animals occupying this niche have not been identified from the early Palaeozoic era. Anomalocarids, a group of stem arthropods that were the largest nektonic animals of the Cambrian and Ordovician periods, are generally thought to have been apex predators. Here we describe new material from Tamisiocaris borealis, an anomalocarid from the Early Cambrian (Series 2) Sirius Passet Fauna of North Greenland, and propose that its frontal appendage is specialized for suspension feeding. The appendage bears long, slender and equally spaced ventral spines furnished with dense rows of long and fine auxiliary spines. This suggests that T. borealis was a microphagous suspension feeder, using its appendages for sweep-net capture of food items down to 0.5 mm, within the size range of mesozooplankton such as copepods. Our observations demonstrate that large, nektonic suspension feeders first evolved during the Cambrian explosion, as part of an adaptive radiation of anomalocarids. The presence of nektonic suspension feeders in the Early Cambrian, together with evidence for a diverse pelagic community containing phytoplankton and mesozooplankton, indicate the existence of a complex pelagic ecosystem supported by high primary productivity and nutrient flux. Cambrian pelagic ecosystems seem to have been more modern than previously believed. PMID:24670770

  13. Rates of phenotypic and genomic evolution during the Cambrian explosion.

    Science.gov (United States)

    Lee, Michael S Y; Soubrier, Julien; Edgecombe, Gregory D

    2013-10-01

    The near-simultaneous appearance of most modern animal body plans (phyla) ~530 million years ago during the Cambrian explosion is strong evidence for a brief interval of rapid phenotypic and genetic innovation, yet the exact speed and nature of this grand adaptive radiation remain debated. Crucially, rates of morphological evolution in the past (i.e., in ancestral lineages) can be inferred from phenotypic differences among living organisms-just as molecular evolutionary rates in ancestral lineages can be inferred from genetic divergences. We here employed Bayesian and maximum likelihood phylogenetic clock methods on an extensive anatomical and genomic data set for arthropods, the most diverse phylum in the Cambrian and today. Assuming an Ediacaran origin for arthropods, phenotypic evolution was ~4 times faster, and molecular evolution ~5.5 times faster, during the Cambrian explosion compared to all subsequent parts of the Phanerozoic. These rapid evolutionary rates are robust to assumptions about the precise age of arthropods. Surprisingly, these fast early rates do not change substantially even if the radiation of arthropods is compressed entirely into the Cambrian (~542 mega-annum [Ma]) or telescoped into the Cryogenian (~650 Ma). The fastest inferred rates are still consistent with evolution by natural selection and with data from living organisms, potentially resolving "Darwin's dilemma." However, evolution during the Cambrian explosion was unusual (compared to the subsequent Phanerozoic) in that fast rates were present across many lineages. PMID:24035543

  14. Magmatism in a Cambrian Laurentian Plate Rift

    Science.gov (United States)

    Gilbert, M. C.

    2008-12-01

    Evidences of the Cambrian Southern Oklahoma Aulacogen extend over 1000km from about Dallas out to the Uncompahgre Plateau in SW Colorado. The signature of this originally extensional feature can be traced geophysically, and in some places at the present surface, petrologically and temporally, by the presence of mafic rock. It appears to have been the intracontinental third arm of a plume-generated? triple junction which helped to dismember the southern part of Laurentia on the final break-up of a Neoproterozoic supercontinent. Other parts of Laurentia rifted away and are now found in the Precordillera of Argentina. Rift magmatism appears to have been concentrated nearer the plate edge during the breakup. Perhaps as much as 40,000 km3 of mostly subaerial silicic volcanics and shallow-seated granites overlay and filled the top of the rift in the area of SW Oklahoma. The rift fill below the silicic rocks is large, layered mafic complexes and smaller, layered, hydrous gabbros, the whole set appearing as a shallow AMCG complex. Unusually, direct rift sediments are not obvious. Furthermore, silicic and mafic rocks have identical Nd signatures. Finally, about 20 Ma after rifting ceased and later into the Paleozoic during sea incursion, overlying sediments are thickened 4X compared to equivalent units 100's of kms to the rift sides. This rift appears distinct from most modern rifts. Conclusions are 1) This was a hot, narrow rift; 2) Basaltic magmatism , not sedimentation, filled the rift; 3) Magmatic intensity varied along the rift strike; 4) Silicic rocks were generated mostly directly from new mantle-derived basalt liquids through fractionation, not melting of older crustal rocks; 5) Laurentian lithosphere was weak allowing centering of the Early/Middle Paleozoic large "Oklahoma" basin (pre-Anadarko) over the rift.

  15. Proterozoic and early Cambrian protists: evidence for accelerating evolutionary tempo

    Science.gov (United States)

    Knoll, A. H.

    1994-01-01

    In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was part of a broader radiation of "higher" eukaryotic phyla. Observed diversity levels for protistan microfossils increased significantly at this time, as did turnover rates. Coincident with the Cambrian radiation of marine invertebrates, protistan microfossils again doubled in diversity and rates of turnover increased by an order of magnitude. Evidently, the Cambrian diversification of animals strongly influenced evolutionary rates, within clades already present in marine communities, implying an important role for ecology in fueling a Cambrian explosion that extends across kingdoms.

  16. A vanished history of skeletonization in Cambrian comb jellies.

    Science.gov (United States)

    Ou, Qiang; Xiao, Shuhai; Han, Jian; Sun, Ge; Zhang, Fang; Zhang, Zhifei; Shu, Degan

    2015-07-01

    Ctenophores are traditionally regarded as "lower" metazoans, sharing with cnidarians a diploblastic grade of organization. Unlike cnidarians, where skeletonization (biomineralization and sclerotization) evolved repeatedly among ecologically important taxa (for example, scleractinians and octocorals), living ctenophores are characteristically soft-bodied animals. We report six sclerotized and armored ctenophores from the early Cambrian period. They have diagnostic ctenophore features (for example, an octamerous symmetry, oral-aboral axis, aboral sense organ, and octaradially arranged ctene rows). Unlike most modern counterparts, however, they lack tentacles, have a sclerotized framework, and have eight pairs of ctene rows. They are resolved as a monophyletic group (Scleroctenophora new class) within the ctenophores. This clade reveals a cryptic history and sheds new light on the early evolution of this basal animal phylum. Skeletonization also occurs in some other Cambrian animal groups whose extant members are exclusively soft-bodied, suggesting the ecological importance of skeletonization in the Cambrian explosion. PMID:26601209

  17. U-Pb zircon ages and structural development of metagranitoids of the Teplá crystalline complex: evidence for pervasive Cambrian plutonism within the Bohemian massif (Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Dörr, W.; Fiala, Jiří; Vejnar, Zdeněk; Zulauf, G.

    1998-01-01

    Roč. 87, č. 1 (1998), s. 135-149. ISSN 0016-7835 R&D Projects: GA AV ČR KSK1012601 Grant ostatní: DFG(DE) Zu73/1-3 Keywords : Cambrian plutonism * U-Pb analyses * Bohemian massif Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.841, year: 1998

  18. Darwin's dilemma: the realities of the Cambrian ‘explosion’

    OpenAIRE

    Conway Morris, Simon

    2006-01-01

    The Cambrian ‘explosion’ is widely regarded as one of the fulcrum points in the history of life, yet its origins and causes remain deeply controversial. New data from the fossil record, especially of Burgess Shale-type Lagerstätten, indicate, however, that the assembly of bodyplans is not only largely a Cambrian phenomenon, but can already be documented in fair detail. This speaks against a much more ancient origin of the metazoans, and current work is doing much to reconcile the apparent dis...

  19. Cephalic and appendage morphology of the Cambrian arthropod Sidneyia inexpectans Walcott, 1911

    DEFF Research Database (Denmark)

    Stein, Martin

    2013-01-01

    evidence for variability of head segment counts in Cambrian arthropods, and to falsify the hypothesis of a head with three postantennular segments in the euarthropod ground pattern. Restudy of a substantial amount of material of S. inexpectans shows that previous interpretations of a short head were based...... understood, but the exopod seemed to differ from that of other artiopodans, except for the shared presence of lamellae. The head was considered to comprise only the ocular and antennular segments, these being covered entirely on the ventral side by a large doublure. This short head was often taken as an...... at least two postantennular appendage bearing segments. The appendage morphology is shown to be consistent with artiopodan affinities. The exopod is of the bilobate flap-like type with lamellae inserting on the proximal portion, earlier proposed as a potential autapomorphy of Artiopoda. Reinforcement...

  20. Preliminary notes on soft-bodied fossil concentrations from the Early Cambrian Chengjiang deposits

    Institute of Scientific and Technical Information of China (English)

    HAN Jian; SHU Degan; ZHANG Zhifei; LIU Jianni; ZHANG Xingliang; YAO Yang

    2006-01-01

    The efforts of labor-intensive collecting in the Early Cambrian Chengjiang deposits in eastern Yunnan Province, China led to the discovery of many horizons containing exceptionally well preserved soft-bodied fossil concentrations, many of which can be assigned to either monospecific concentrations or paucispecific concentrations. The features of these fossil concentrations support the hypothesis that frequent storm events producing tempestites mainly contributed to the preservation of abundant softbodied fossils in the Chengjiang deposits, and indicate that the balance of the ecological web in this region was probably frequently destroyed or upset by such storm events during that geological time. Animals in a fossil assemblage in such fossil concentrations probably occupied similar ecological biotopes.

  1. Provenance shift in Cambrian mid-Baltica: detrital zircon chronology of Ediacaran–Cambrian sandstones in Estonia

    Directory of Open Access Journals (Sweden)

    Yukio Isozaki

    2014-12-01

    Full Text Available In order to clarify the tectono-sedimentary history of Paleozoic Baltica, age spectra of detrital zircon grains from the Ediacaran (Kotlin Regional Stage and Lower Cambrian sandstones (lowermost Lontova and Lükati formations in western Estonia in central Baltica were analyzed by LA-ICPMS. The abundant occurrence of Archean to Mesoproterozoic (2800–1000 Ma zircon grains was confirmed in all samples. The new data provided the following information on the provenance of siliciclastic material as well as a major change in the sedimentary regime of the Paleo-Baltic basin during the Early Cambrian: (1 the Ediacaran–Lower Cambrian Paleo-Baltic basin received abundant terrigenous clastics from the core of Baltica underlain by the Archean–Mesoproterozoic crystalline crust, (2 the exposed surface area of the 1600 Ma Rapakivi granites apparently was more extensive during the Ediacaran–Early Cambrian than at present, (3 a major re-organization of the basin geometry occurred in the middle Early Cambrian (ca 530–515 Ma in central Baltica, inducing a change in the sediment supply system, (4 in contrast to the total absence of Neoproterozoic detrital zircon grains before the middle Early Cambrian, their sudden appearance at this time, together with consistent occurrence at least until the mid-Devonian, suggests a significant uplift event located in southeast Baltica and/or in a more easterly land domain (e.g., in Sarmatia, (5 possible sources for the Neoproterozoic zircon grains include the peripheral mobile belts with pan-African signatures around Baltica, e.g., the so-called Gondwanan fragments along the Tornquist margin to the southwest and the Timanian belt along the northeastern margin.

  2. Beyond Correlation in the Detection of Climate Change Impacts: Testing a Mechanistic Hypothesis for Climatic Influence on Sockeye Salmon (Oncorhynchus nerka) Productivity

    Science.gov (United States)

    Tillotson, Michael D.; Quinn, Thomas P.

    2016-01-01

    Detecting the biological impacts of climate change is a current focus of ecological research and has important applications in conservation and resource management. Owing to a lack of suitable control systems, measuring correlations between time series of biological attributes and hypothesized environmental covariates is a common method for detecting such impacts. These correlative approaches are particularly common in studies of exploited fish species because rich biological time-series data are often available. However, the utility of species-environment relationships for identifying or predicting biological responses to climate change has been questioned because strong correlations often deteriorate as new data are collected. Specifically stating and critically evaluating the mechanistic relationship(s) linking an environmental driver to a biological response may help to address this problem. Using nearly 60 years of data on sockeye salmon from the Kvichak River, Alaska we tested a mechanistic hypothesis linking water temperatures experienced during freshwater rearing to population productivity by modeling a series of intermediate, deterministic relationships and evaluating temporal trends in biological and environmental time-series. We found that warming waters during freshwater rearing have profoundly altered patterns of growth and life history in this population complex yet there has been no significant correlation between water temperature and metrics of productivity commonly used in fisheries management. These findings demonstrate that pairing correlative approaches with careful consideration of the mechanistic links between populations and their environments can help to both avoid spurious correlations and identify biologically important, but not statistically significant relationships, and ultimately producing more robust conclusions about the biological impacts of climate change. PMID:27123845

  3. Dr. Cooper Curtice - Unknown worker in interpreting the Cambrian of Alabama

    Science.gov (United States)

    Yochelson, E.L.; Osborne, W.E.

    1999-01-01

    Cooper Curtice was an assistant to C. D. Walcott from 1883-1886. In 1885, he spent four months, mostly in Alabama, measuring sections of Paleozoic rocks and searching for fossils, mainly in the Cambrian. In 1888, Walcott concurred with foreign authorities that the rocks called Middle Cambrian in North America were Early Cambrian in age and vice versa, requiring a new interpretation of Cambrian strata. Curtice returned to Alabama for geologic investigations in 1892, and again briefly with Walcott in 1895. Since that time Cambrian stratigraphy in the southeastern United States has remained virtually unchanged.

  4. New Evidence for Pre-Cambrian Development of Complex Animals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Much mystery surrounds the sudden and mushrooming appearance of animals in the fossil record about 540 million years ago. Known as the "Cambrian explosion," the change took place from zero evidence to all the basic types of creatures in today's world within a few million years.

  5. Nonbiomineralized carapaces in Cambrian seafloor landscapes (Sirius Passet, Greenland)

    DEFF Research Database (Denmark)

    Mangano, M. Gabriela; Bromley, Richard Granville; Harper, David A.T.; Nielsen, Arne Thorshøj; Smith, M. Paul; Vinther, Jakob

    2012-01-01

    Widespread microbial mats and the absence of significant bioturbation resulted in a poorly developed mixed layer and extensive cohesive substrates during the Ediacaran-Cambrian transition. Large nonbiomineralized arthropod carapaces overprinted with trails, interconnected burrow systems, narrow-c...... served as the primary food for small macrofauna and meiofauna....

  6. Fossils, molecules and embryos: new perspectives on the Cambrian explosion

    Science.gov (United States)

    Valentine, J. W.; Jablonski, D.; Erwin, D. H.

    1999-01-01

    The Cambrian explosion is named for the geologically sudden appearance of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals. Earlier indications of metazoans are found in the Neoproterozic; minute trails suggesting bilaterian activity date from about 600 million years ago. Larger and more elaborate fossil burrows appear near 543 million years ago, the beginning of the Cambrian Period. Evidence of metazoan activity in both trace and body fossils then increased during the 13 million years leading to the explosion. All living phyla may have originated by the end of the explosion. Molecular divergences among lineages leading to phyla record speciation events that have been earlier than the origins of the new body plans, which can arise many tens of millions of years after an initial branching. Various attempts to date those branchings by using molecular clocks have disagreed widely. While the timing of the evolution of the developmental systems of living metazoan body plans is still uncertain, the distribution of Hox and other developmental control genes among metazoans indicates that an extensive patterning system was in place prior to the Cambrian. However, it is likely that much genomic repatterning occurred during the Early Cambrian, involving both key control genes and regulators within their downstream cascades, as novel body plans evolved.

  7. A vanished history of skeletonization in Cambrian comb jellies

    OpenAIRE

    Ou, Qiang; Xiao, Shuhai; Han, Jian; Sun, Ge; Zhang, Fang; Zhang, Zhifei; Shu, Degan

    2015-01-01

    Ctenophores are traditionally regarded as “lower” metazoans, sharing with cnidarians a diploblastic grade of organization. Unlike cnidarians, where skeletonization (biomineralization and sclerotization) evolved repeatedly among ecologically important taxa (for example, scleractinians and octocorals), living ctenophores are characteristically soft-bodied animals. We report six sclerotized and armored ctenophores from the early Cambrian period. They have diagnostic ctenophore features (for exam...

  8. A New Landmark for Exploration of the Cambrian Explosion

    Institute of Scientific and Technical Information of China (English)

    Zhao Baohua; Song Jianlan; Guo Haiyan

    2002-01-01

    @@ New studies suggest that the Kaili Biota in southwestern China's Guizhou Province could be the third revealing evidence for the spectacular Cambrian Explosion of life about 530 million years ago, next to the Burgess Shale Biota of Canada, found in 1909,and the Chengjiang Biota, brought to light in Yunnan Province, China,in 1984.

  9. Oceanic anoxia at the Precambrian-Cambrian boundary

    Science.gov (United States)

    Kimura, Hiroto; Watanabe, Yoshio

    2001-11-01

    The Precambrian-Cambrian (PC-C) boundary separates fossils representing two discrete evolutionary phases: the Neoproterozoic soft-bodied Ediacarian biotas and Cambrian small shelly faunas. The biological discontinuity is suspected to have been a result of mass extinction; however, recent discoveries of the Ediacarian biotas in Cambrian sediments have led to an understanding that the faunal change was gradual through the PC-C transition. Th/U ratios, which are high in oxidizing conditions and low in reducing conditions, show a considerable positive correlation with δ13C values at all studied sites of the PC-C boundary. This correlation indicates that reported δ13C variation across the PC-C boundary from numerous localities corresponds to redox variation in the depositional environment. The negative δ13C anomaly that occurs worldwide at the PC-C boundary, therefore, corresponds to the widespread development of an oxygen-deficient shallow marine environment. This finding suggests that widespread oceanic oxygen deficiency, which has been interpreted to reflect Phanerozoic mass extinction events, also occurred immediately before the Cambrian explosion.

  10. Brachiopods hitching a ride: an early case of commensalism in the middle Cambrian Burgess Shale

    Science.gov (United States)

    Topper, Timothy P.; Holmer, Lars E.; Caron, Jean-Bernard

    2014-10-01

    Ecological interactions, including symbiotic associations such as mutualism, parasitism and commensalism are crucial factors in generating evolutionary novelties and strategies. Direct examples of species interactions in the fossil record generally involve organisms attached to sessile organisms in an epibiont or macroboring relationship. Here we provide support for an intimate ecological association between a calcareous brachiopod (Nisusia) and the stem group mollusc Wiwaxia from the Burgess Shale. Brachiopod specimens are fixed to Wiwaxia scleritomes, the latter showing no signs of decay and disarticulation, suggesting a live association. We interpret this association as the oldest unambiguous example of a facultative ectosymbiosis between a sessile organism and a mobile benthic animal in the fossil record. The potential evolutionary advantage of this association is discussed, brachiopods benefiting from ease of attachment, increased food supply, avoidance of turbid benthic conditions, biofoul and possible protection from predators, suggesting commensalism (benefiting the symbiont with no impact for the host). While Cambrian brachiopods are relatively common epibionts, in particular on sponges, the association of Nisusia with the motile Wiwaxia is rare for a brachiopod species, fossil or living, and suggests that symbiotic associations were already well established and diversified by the ``middle'' (Series 3, Stage 5) Cambrian.

  11. The Lower Cambrian of Scandinavia: Depositional environment, sequence stratigraphy and palaeogeography

    Science.gov (United States)

    Nielsen, Arne Thorshøj; Schovsbo, Niels Hemmingsen

    2011-08-01

    impact related. Sequences are defined as transgressive-regressive depositional cycles bounded by maximum regressive surfaces and their correlative conformities. Sea-level rises are identified by fining-upward lithologies, cratonwards shifts in facies and depocentres, formation of widespread thin lime- and ironstones as well as precipitation of phosphorite and glaucony; the latter formed at remarkably shallow depth in comparison with the modern world. Sea-level falls are identified by coarsening-upwards lithologies, basinwards shifts in facies and gaps in the sedimentary record relating to non-deposition/erosion during falling stage and lowstand. Due to the pronounced clastic starvation neither lowstand nor highstand system tracts are developed subsequent to the earliest transgressive phases and eustasy was the primary control on depth changes. The Lower Cambrian comprises two supersequences (2nd order sequences), separated by regional subaerial unconformities reflecting the Rispebjerg Lowstand (new name) and the Hawke Bay Event. The Rispebjerg Lowstand was likely glacio-eustatic. Supersequence 1 (Rovnian-Lontovan-Dominopolian-'Ljubomlian') comprises about nine 3rd order sequences but the exact number of sequences in the Lontovan is unsettled. Supersequence 2 (Vergalian-Rausvian-lower Kibartian) comprises five sequences. Two or more subsequences (new term = 4th order sequences) are recognized in all sequences but long-distance correlation is usually difficult. The sequence stratigraphical resolution of the Lower Cambrian is more than twice as high as the acritarch biozonation. Baltica became intensively peneplained during the Neoproterozoic and was by and large completely flat at the dawn of the Cambrian. The profound Early Cambrian sea-level rise, comprising a series of individual 3rd order drowning events, was associated with step-wise transgression of Baltoscandia and concomitantly the sedimentary supply declined. The sequence stratigraphical analysis indicates onset

  12. Compilation and network analyses of cambrian food webs.

    Directory of Open Access Journals (Sweden)

    Jennifer A Dunne

    2008-04-01

    Full Text Available A rich body of empirically grounded theory has developed about food webs--the networks of feeding relationships among species within habitats. However, detailed food-web data and analyses are lacking for ancient ecosystems, largely because of the low resolution of taxa coupled with uncertain and incomplete information about feeding interactions. These impediments appear insurmountable for most fossil assemblages; however, a few assemblages with excellent soft-body preservation across trophic levels are candidates for food-web data compilation and topological analysis. Here we present plausible, detailed food webs for the Chengjiang and Burgess Shale assemblages from the Cambrian Period. Analyses of degree distributions and other structural network properties, including sensitivity analyses of the effects of uncertainty associated with Cambrian diet designations, suggest that these early Paleozoic communities share remarkably similar topology with modern food webs. Observed regularities reflect a systematic dependence of structure on the numbers of taxa and links in a web. Most aspects of Cambrian food-web structure are well-characterized by a simple "niche model," which was developed for modern food webs and takes into account this scale dependence. However, a few aspects of topology differ between the ancient and recent webs: longer path lengths between species and more species in feeding loops in the earlier Chengjiang web, and higher variability in the number of links per species for both Cambrian webs. Our results are relatively insensitive to the exclusion of low-certainty or random links. The many similarities between Cambrian and recent food webs point toward surprisingly strong and enduring constraints on the organization of complex feeding interactions among metazoan species. The few differences could reflect a transition to more strongly integrated and constrained trophic organization within ecosystems following the rapid

  13. THE FRACTAL MARKET HYPOTHESIS

    OpenAIRE

    FELICIA RAMONA BIRAU

    2012-01-01

    In this article, the concept of capital market is analysed using Fractal Market Hypothesis which is a modern, complex and unconventional alternative to classical finance methods. Fractal Market Hypothesis is in sharp opposition to Efficient Market Hypothesis and it explores the application of chaos theory and fractal geometry to finance. Fractal Market Hypothesis is based on certain assumption. Thus, it is emphasized that investors did not react immediately to the information they receive and...

  14. New Vetulicoliids from the Lower Cambrian Guanshan Fauna,Kunming

    Institute of Scientific and Technical Information of China (English)

    LUO Huilin; FU Xiaoping; HU Shixue; LI Yong; CHEN Liangzhong; YOU Ting; LIU Qi

    2005-01-01

    The Guanshan Fauna, a soft-bodied fauna intermediate between the Chengjiang Fauna and the Kaili Fauna and also the Burgess Shale Fauna stratigraphically, consists of trilobites, trilobitoides, Tuzoia, Vetulicola, Paleoscolex, brachiopods and sponges. The discovery and research of this fauna is of great significance in understading the "Cambrian Explosion" and the evolution of early life. The occurrence of vetulicoliids from the Guanshan Fauna not only adds new members to the taxonomic list, but also provides new information to the evolution of this animal group. This paper describe Vetulicola gantoucunensis Luo, Fu et Hu sp. nov. from the Lower Cambrian Wulongqing Formation in the Kunming area. Also presented are the amended description of Vetulicola and the comparisons with related genera within Vetulicoliids. The affinity, distribution, as well as evolution of vetulicoliids are discussed.

  15. New and extraordinary Early Cambrian sponge spicule assemblage from China

    Science.gov (United States)

    Zhang, Xi-Guang; Pratt, Brian R.

    1994-01-01

    The fossil record of siliceous sponges, compared with that of other skeleton- secreting Metazoa, is poorly known, based as it is on disarticulated spicules and sporadically preserved body fossils. Abundant spicules recovered from Lower Cambrian strata in Shaanxi, China, essentially double the known morphological diversity of siliceous sponges for that interval of geologic time. These fossils, along with a comparable coeval fauna from South Australia, have a remarkably modern aspect, thereby demonstrating that the principal siliceous sponge groups and styles of body architecture were established quickly in the earliest Phanerozoic as part of the Cambrian "explosion" and that they inhabited a variety of low-energy, relatively deep water settings. The similarity of spicule shape and variation to that of younger assemblages reflects a conservative architecture for the siliceous sponges.

  16. Cambrian extensional tectonics and magmatism within the Southern Oklahoma aulacogen

    Science.gov (United States)

    McConnell, D. A.; Gilbert, M. C.

    1990-03-01

    The tectonic evolution of the Southern Oklahoma aulacogen is partially constrained by the petrological consequences of a bimodal igneous suite associated with the Cambrian rift. Mineralogical and compositional layers and erosional surfaces are recognized as initially subplanar, subhorizontal markers. The progressive rotation of these horizons can be explained by uniform-sense normal faulting. Magmatism, confined to the aulacogen trend, elevated the thermal gradient producing a crustal strength-anisotropy. This ensured the localization of the extension throughout the Cambrian rifting event. The presence of a substantial volume of mafic igneous rocks within the crust along the aulacogen's trend suggests that crustal attenuation was compensated for by the addition of mantle derived material during extension.

  17. THE FRACTAL MARKET HYPOTHESIS

    Directory of Open Access Journals (Sweden)

    FELICIA RAMONA BIRAU

    2012-05-01

    Full Text Available In this article, the concept of capital market is analysed using Fractal Market Hypothesis which is a modern, complex and unconventional alternative to classical finance methods. Fractal Market Hypothesis is in sharp opposition to Efficient Market Hypothesis and it explores the application of chaos theory and fractal geometry to finance. Fractal Market Hypothesis is based on certain assumption. Thus, it is emphasized that investors did not react immediately to the information they receive and of course, the manner in which they interpret that information may be different. Also, Fractal Market Hypothesis refers to the way that liquidity and investment horizons influence the behaviour of financial investors.

  18. Contributions to the Proterozoic and Cambrian Evolution of Eukaryotes

    OpenAIRE

    Dong, Lin

    2007-01-01

    This thesis makes several contributions to improve our understanding of Proterozoic-Cambrian evolution of eukaryote life. Chapter 1 provides, for the first time, a quantitative characterization of the evolutionary trends of Proterozoic macroalgae. The analysis reveals that morphological disparity of Paleoproterozoic macroalgae was low but increased in the Mesoproterozoic and Ediacaran, with a plateau in between. There was also a significant increase in thallus surface/volume ratio and maxi...

  19. Did homeobox gene duplications contribute to the Cambrian explosion?

    OpenAIRE

    Holland, Peter W. H.

    2015-01-01

    The Cambrian explosion describes an apparently rapid increase in the diversity of bilaterian animals around 540–515 million years ago. Bilaterian animals explore the world in three-dimensions deploying forward-facing sense organs, a brain, and an anterior mouth; they possess muscle blocks enabling efficient crawling and burrowing in sediments, and they typically have an efficient ‘through-gut’ with separate mouth and anus to process bulk food and eject waste, even when burrowing in sediment. ...

  20. Comparison between Input Hypothesis and Interaction Hypothesis

    Institute of Scientific and Technical Information of China (English)

    李佳

    2012-01-01

      Krashen’s Input hypothesis and Long’s Interaction hypothesis are both valuable research results in the field of language acquisition and play a significant role in language teaching and learning instruction. Through comparing them, their similarities lie in same goal and basis, same focus on comprehension and same challenge the traditional teaching concept. While the differences lie in Different ways to make exposure comprehensible and different roles that learners play. It is meaningful to make the compari⁃son because the results can be valuable guidance and highlights for language teachers and learners to teach or acquire a new lan⁃guage more efficiently.

  1. Armored kinorhynch-like scalidophoran animals from the early Cambrian.

    Science.gov (United States)

    Zhang, Huaqiao; Xiao, Shuhai; Liu, Yunhuan; Yuan, Xunlai; Wan, Bin; Muscente, A D; Shao, Tiequan; Gong, Hao; Cao, Guohua

    2015-01-01

    Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorsoventral muscles, and ganglia. Molecular clock estimates suggest that kinorhynchs may have diverged in the Ediacaran Period. Remarkably, no kinorhynch fossils have been discovered, in sharp contrast to priapulids and loriciferans that are represented by numerous Cambrian fossils. Here we describe several early Cambrian (~535 million years old) kinorhynch-like fossils, including the new species Eokinorhynchus rarus and two unnamed but related forms. E. rarus has characteristic scalidophoran features, including an introvert with pentaradially arranged hollow scalids. Its trunk bears at least 20 annuli each consisting of numerous small rectangular plates, and is armored with five pairs of large and bilaterally placed sclerites. Its trunk annuli are reminiscent of the epidermis segments of kinorhynchs. A phylogenetic analysis resolves E. rarus as a stem-group kinorhynch. Thus, the fossil record confirms that all three scalidophoran phyla diverged no later than the Cambrian Period. PMID:26610151

  2. Early-Middle Cambrian Palynomorph Microfossils and Related Geochemical Events in South China

    Institute of Scientific and Technical Information of China (English)

    Leiming Yin; Chunjiang Wang; Yuanlong Zhao; Zhiji Ou

    2016-01-01

    The earliest Cambrian acritarch ‘Asteridium–Heliosphaeridium–Comasphaeridium’ assemblage and the Early Cambrian (‘Chiungchussuan’) acritarch ‘Skiagia ornate–Fimbriaglomerella membranacea’ assemblage in South China can be correlated with assemblages from synchronous strata elsewhere in the world. Recent geochemical study and biomarker evidence further confirm a biostratigraphic change between Cambrian Series 2 and Series 3 and support the recognition of a major geological and biotic event during this time interval.

  3. First report of Crumillospongia (Demospongea) from the Cambrian of Europe (Murero biota, Spain)

    OpenAIRE

    García-Bellido D C; Dies Álvarez M E; Gámez Vintaned J A Liñán E; Gozalo R

    2011-01-01

    The demosponge genus Crumillospongia, originally described from the Burgess Shale (middle Cambrian of Canada), has only been cited from lower and middle Cambrian localities of North America and China. The taxon is now also described from uppermost lower Cambrian rocks of the Murero Lagerstätte (Zaragoza Province, NE Spain). Crumillospongia mureroensis sp. nov. is a small to medium sized sack-shaped to elongate demosponge characterized by the presence of d...

  4. Lower Cambrian polychaete from China sheds light on early annelid evolution

    OpenAIRE

    Liu, Jianni; Ou, Qiang; Han, Jian; Li, Jinshu; Wu, Yichen; Jiao, Guoxiang; He, Tongjiang

    2015-01-01

    We herein report a fossilized polychaete annelid, Guanshanchaeta felicia gen. et sp. nov., from the Lower Cambrian Guanshan Biota (Cambrian Series 2, stage 4). The new taxon has a generalized polychaete morphology, with biramous parapodia (most of which preserve the evidence of chaetae), an inferred prostomium bearing a pair of appendages, and a bifid pygidium. G. felicia is the first unequivocal annelid reported from the Lower Cambrian of China. It represents one of the oldest annelids among...

  5. Cambrian small shelly fossils from the Çal Tepe Formation, Taurus Mountains, Turkey

    OpenAIRE

    Sarmiento, Graciela N.; Fernández Remolar, David Carlos; Göncüoglu, M. Cemal

    2001-01-01

    [EN] Lower and Middle Cambrian carbonate rocks of the Çal Tepe Formation, cropping out in the western Taurus Mountains, yielded a large number of microfossil remains. Small shelly fossils from a single level in the upper Lower Cambrian represent a high diversity biota that could be related to the «Cambrian explosion». Microfossil association from the lower Middle Cambrian sediments of the Çal Tepe Formation is taxonomically very reduced and a dominant taxon is Hadimopanella GEDIK. Th...

  6. Cambrian small shelly fossils from the Çal Tepe Formation, Taurus Mountains, Turkey

    OpenAIRE

    Sarmiento, Graciela; Fernández Remolar, David Carlos; Göncüoglu, M. Cemal

    2001-01-01

    Lower and Middle Cambrian carbonate rocks of the Çal Tepe Formation, cropping out in the western Taurus Mountains, yielded a large number of microfossil remains. Small shelly fossils from a single level in the upper Lower Cambrian represent a high diversity biota that could be related to the «Cambrian explosion». Microfossil association from the lower Middle Cambrian sediments of the Çal Tepe Formation is taxonomically very reduced and a dominant taxon is Hadimopanella GEDIK. This sudden chan...

  7. Antarctica, supercontinents and the palaeogeography of the Cambrian 'explosion'

    Science.gov (United States)

    Dalziel, Ian

    2014-05-01

    Laurentia is bordered by latest Precambrian-Cambrian rifted margins and must therefore have been located within a Precambrian supercontinent. Geochronologic and geochemical evidence indicates that it was attached to parts of the East Antarctic craton within the Rodinian supercontinent in the late Mesoproterozoic. The Mawson craton of Antarctica rifted from the proto-Pacific margin of Laurentia during the Neooproterozoic, colliding with the present 'southern cone' of Laurentia at ~600 Ma along the Shackleton Range suture zone as Gondwana and Laurentia amalgamated to form the ephemeral Pannotia supercontinental assembly at the end of the Precambrian. The abrupt appearance of almost all animal phyla in the fossil record is often colloquially referred to as the Cambrian 'explosion' of life on Earth. It is also named 'Darwin's dilemma,' as he appreciated that this seemingly mysterious event posed a major problem for his theory of evolution by natural selection. It coincided with a time of major marine transgression over all the continents. Although the metazoan 'explosion' is now seen as more protracted than formerly recognized, it is still regarded one of the most critical events in the history of the biosphere. One of the most striking aspects of the earliest Cambrian fossils is geographic differentiation. In particular, the first benthic trilobite faunas on Laurentia, ancestral North America, and the newly amalgamated southern supercontinent of Gondwana are distinctly different. This has led to the suggestion of an unknown vicariant event intervening between an ancestral trilobite clade and higher members that are represented in the fossil record, possibly one related to the breakup of a supercontinent. Igneous rocks along the Panthalassic margin of Gondwana, including South America, southernmost Africa and the Ellsworth-Whitmore crustal block of Antarctica, and along the proto-Appalachian margin of Laurentia indicate that final separation of Laurentia from

  8. Generalized Riemann Hypothesis

    OpenAIRE

    Agélas, Léo

    2012-01-01

    9 pages (Generalized) Riemann Hypothesis (that all non-trivial zeros of the (Dirichlet L-function) zeta function have real part one-half) is arguably the most important unsolved problem in contemporary mathematics due to its deep relation to the fundamental building blocks of the integers, the primes. The proof of the Riemann hypothesis will immediately verify a slew of dependent theorems ([BRW], [SA]). In this paper, we give a proof of Generalized Riemann Hypothesis which implies the proo...

  9. The Riemann Hypothesis

    OpenAIRE

    Jabbarov, Ilgar Sh.

    2007-01-01

    The Riemann Hypothesis is a conjecture made in 1859 by the great mathematician Riemann that all the complex zeros of the zeta function $\\zeta(s)$ lie on the `critical line' ${Rl} s= 1/2$. Our analysis shows that the assumption of the truth of the Riemann Hypothesis leads to a contradiction. We are therefore led to the conclusion that the Riemann Hypothesis is not true.

  10. The "Speculative Efficiency" Hypothesis

    OpenAIRE

    John F. O. Bilson

    1980-01-01

    The hypothesis that forward prices are the best unbiased forecast of future spot prices is often presented in the economic and financial analysis of futures markets. This paper considers the hypothesis independently of its implications for rational expectations or market efficiency and in order to stress this fact, the term "speculative efficiency" is used to characterize the state envisaged under the hypothesis. If a market is subject to efficient speculation, the supply of speculative funds...

  11. Life Origination Hydrate Hypothesis (LOH-Hypothesis

    Directory of Open Access Journals (Sweden)

    Victor Ostrovskii

    2012-01-01

    Full Text Available The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis, according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides, DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their “thermodynamic front” guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor.

  12. Oxygen-isotope trends and seawater temperature changes across the Late Cambrian Steptoean positive carbon-isotope excursion (SPICE event)

    Science.gov (United States)

    Elrick, M.; Rieboldt, S.; Saltzman, M.; McKay, R.M.

    2011-01-01

    The globally recognized Late Cambrian Steptoean positive C-isotope excursion (SPICE) is characterized by a 3???-5??? positive ??13C shift spanning <4 m.y. Existing hypotheses suggest that the SPICE represents a widespread ocean anoxic event leading to enhanced burial/preservation of organic matter (Corg) and pyrite. We analyzed ??18O values of apatitic inarticulate brachiopods from three Upper Cambrian successions across Laurentia to evaluate paleotemperatures during the SPICE. ??18O values range from ~12.5??? to 16.5???. Estimated seawater temperatures associated with the SPICE are unreasonably warm, suggesting that the brachiopod ??18O values were altered during early diagenesis. Despite this, all three localities show similar trends with respect to the SPICE ??13C curve, suggesting that the brachiopod apatite preserves a record of relative ??18O and temperature changes. The trends include relatively high ??18O values at the onset of the SPICE, decreasing and lowest values during the main event, and an increase in values at the end of the event. The higher ??18O values during the global extinction at the onset of the SPICE suggests seawater cooling and supports earlier hypotheses of upwelling of cool waters onto the shallow shelf. Decreasing and low ??18O values coincident with the rising limb of the SPICE support the hypothesis that seawater warming and associated reduced thermohaline circulation rates contributed to decreased dissolved O2 concentrations, which enhanced the preservation/burial of Corg causing the positive ??13C shift. ?? 2011 Geological Society of America.

  13. Trace fossils accompanying possible "Ediacaran organisms" in the Middle Cambrian sediments of the St. Petersburg Region, Russia

    Czech Academy of Sciences Publication Activity Database

    Natalin, N. M.; Mikuláš, Radek; Dronov, A. V.

    2010-01-01

    Roč. 60, č. 1 (2010), s. 71-75+[2]. ISSN 0001-5709 R&D Projects: GA ČR GA205/04/0151; GA ČR GA205/09/1521 Institutional research plan: CEZ:AV0Z30130516 Keywords : Skolithos ichnofacies * Edicarian-like organism * Middle Cambrian * shallow-marine * Baltic Shied * ichnology (Russia) Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.779, year: 2010 https://geojournals.pgi.gov.pl/agp/article/view/9821/8355

  14. Moulting in the lobopodian Onychodictyon from the lower Cambrian of Greenland

    DEFF Research Database (Denmark)

    Topper, Timothy P.; Skovsted, Christian B.; Peel, John S.; Harper, David A. T.

    2013-01-01

    A number of lobopodian taxa from the Cambrian display pairs of sclerotized plates symmetrically positioned along the dorsum of the animal, predominantly above the walking appendages. Most genera were described from complete body fossils exquisitely preserved in the famous Cambrian Lagerstatten, b...

  15. Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians.

    Science.gov (United States)

    Caron, Jean-Bernard; Smith, Martin R; Harvey, Thomas H P

    2013-09-22

    Burgess Shale-type deposits are renowned for their exquisite preservation of soft-bodied organisms, representing a range of animal body plans that evolved during the Cambrian 'explosion'. However, the rarity of these fossil deposits makes it difficult to reconstruct the broader-scale distributions of their constituent organisms. By contrast, microscopic skeletal elements represent an extensive chronicle of early animal evolution--but are difficult to interpret in the absence of corresponding whole-body fossils. Here, we provide new observations on the dorsal spines of the Cambrian lobopodian (panarthropod) worm Hallucigenia sparsa from the Burgess Shale (Cambrian Series 3, Stage 5). These exhibit a distinctive scaly microstructure and layered (cone-in-cone) construction that together identify a hitherto enigmatic suite of carbonaceous and phosphatic Cambrian microfossils--including material attributed to Mongolitubulus, Rushtonites and Rhombocorniculum--as spines of Hallucigenia-type lobopodians. Hallucigeniids are thus revealed as an important and widespread component of disparate Cambrian communities from late in the Terreneuvian (Cambrian Stage 2) through the 'middle' Cambrian (Series 3); their apparent decline in the latest Cambrian may be partly taphonomic. The cone-in-cone construction of hallucigeniid sclerites is shared with the sclerotized cuticular structures (jaws and claws) in modern onychophorans. More generally, our results emphasize the reciprocal importance and complementary roles of Burgess Shale-type fossils and isolated microfossils in documenting early animal evolution. PMID:23902914

  16. Community structure and composition of the Cambrian Chengjiang biota

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on previously published species data(228 species in over 18 phyla) and field sampling(114 species and 18406 individuals) in the Chengjiang-Haikou-Anning area,we analyzed quantitatively the paleocommunity composition and structure of the Cambrian Chengjiang biota(Cambrian Series 2,eastern Yunnan,China).Arthropods dominate the community both in species diversity(species:37%) and in abundance(individuals:51.8%).Priapulids(individuals:22.6%) and brachiopods(individuals:16.3%) follow in abundance rank.The arthropod Kunmingella douvillei(26.2%),the priapulid Cricocosmia jinning-ensis(15.4%),and the brachiopod Diandongia pista(11%) are the three most abundant species.Ecological analyses show that the community was dominated by epifaunal organisms(species:63%,individuals:68.4%) followed by infaunal organisms(species:11.9%,individuals:25.9%),nektobenthic organisms(species:11.5%,individuals:2.6%),and pelagic organisms(species:5.3%,individuals:3.1%).The diverse feeding strategies,dominated by suspension feeders(species:35.6%,individuals:26.1%) and hunter/scavengers(species:31.1%,individuals:40.4%),indicate the former existence of a complex food chain and intense competition.Epifaunal vagrant omnivores(28.2%),infaunal vagrant hunter/scavengers(19.8%),epifaunal sessile suspension feeders(17.7%),and epifaunal vagrant hunter/scavengers(15.3%) were the most abundant ecological groups,represented primarily by arthropods,poriferans,priapulids,and brachiopods.Ecological group analyses reveal that the early Cambrian Chengjiang biota is similar in community patterns and functional relations to modern biotas in shallow marine settings.

  17. Did homeobox gene duplications contribute to the Cambrian explosion?

    Science.gov (United States)

    Holland, Peter W H

    2015-01-01

    The Cambrian explosion describes an apparently rapid increase in the diversity of bilaterian animals around 540-515 million years ago. Bilaterian animals explore the world in three-dimensions deploying forward-facing sense organs, a brain, and an anterior mouth; they possess muscle blocks enabling efficient crawling and burrowing in sediments, and they typically have an efficient 'through-gut' with separate mouth and anus to process bulk food and eject waste, even when burrowing in sediment. A variety of ecological, environmental, genetic, and developmental factors have been proposed as possible triggers and correlates of the Cambrian explosion, and it is likely that a combination of factors were involved. Here, I focus on a set of developmental genetic changes and propose these are part of the mix of permissive factors. I describe how ANTP-class homeobox genes, which encode transcription factors involved in body patterning, increased in number in the bilaterian stem lineage and earlier. These gene duplications generated a large array of ANTP class genes, including three distinct gene clusters called NK, Hox, and ParaHox. Comparative data supports the idea that NK genes were deployed primarily to pattern the bilaterian mesoderm, Hox genes coded position along the central nervous system, and ParaHox genes most likely originally specified the mouth, midgut, and anus of the newly evolved through-gut. It is proposed that diversification of ANTP class genes played a role in the Cambrian explosion by contributing to the patterning systems used to build animal bodies capable of high-energy directed locomotion, including active burrowing. PMID:26605046

  18. Nomenclature of Cambrian epochs and series based on GSSPs-Comments on an alternative proposal by Rowland and Hicks

    Institute of Scientific and Technical Information of China (English)

    Shanchi Peng; Loren E. Babcock; Gerd Geyer; Malgorzata Moczydlowska

    2006-01-01

    @@ In this issue, Rowland & Hicks advocate a nomenclature for the four epochs of the Cambrian Period that carries over the terms Early, Middle, and Late Cambrian from previous usage (but with new definitions) and introduces a non-geographically-based term, Ichnocambrian, for the earliest Cambrian epoch.

  19. A Precambrian-Cambrian oil play in southern Utah

    Energy Technology Data Exchange (ETDEWEB)

    Lillis, P.G.; Palacas, J.G.; Warden, A. [Geological Survey, Denver, CO (United States)

    1995-06-01

    The potential of the Precambrian Chuar Group as a petroleum source rock in southern Utah and northern Arizona resulted in the drilling of two wildcat wells in 1994. Both wells penetrated the Cambrian Tapeats Sandstone (the target reservoir rock) and presumably Precambrian rocks. The first well, Burnett Federal 36-1, was drilled east of Kanab, Utah (sec.36, T.34S., R.3W.) to a total depth of 5,365 ft and encountered Precambrian (?) reddish-brown sedimentary rocks at 4,790 ft. The Tapeats Sandstone had live oil shows and minor CO{sub 2} (?) gas shows. The second well, BHP Federal 28-1, was drilled near Capitol Reef (sec.28, T.33S., R.7E.) to a total depth of 6,185 ft and encountered the Tapeats Sandstone at 5,922 ft and Precambrian (?) phyllite at 6,125 ft. The upper Paleozoic rocks had abundant live oil/tar shows, and the Cambrian Bright Angel Shale and Tapeats Sandstone had numerous oil shows. There were no gas shows in the well except for a large CO{sub 2} gas kick in the Tapeats Sandstone. A drill-stem test from 5,950 to 6,185 ft yielded mostly CO{sub 2} (92%) and nitrogen gas (6%) and minor amounts of helium, argon, hydrogen, and methane. The {delta}{sup 13}C of the CO{sub 2} is -3.9 per mil PDB. The chemical composition of the extracted oil in the Cambrian sandstones is significantly different than oils produced from the Upper Valley field (upper Paleozoic reservoirs) and the tar sands that are widespread throughout southern and central Utah. However, the oil composition is similar in several aspects to the composition of some of the Precambrian Chuar Group bitumen extracts from the Grand Canyon area in Arizona. The encouraging features of both wells are the good reservoir characteristics and oil shows in the Tapeats Sandstone. In the BHP well the oil appears to be a new oil type, possibly derived from Precambrian or Cambrian source rocks.

  20. The Cambrian explosion triggered by critical turning point in genome size evolution.

    Science.gov (United States)

    Li, Dirson Jian; Zhang, Shengli

    2010-02-01

    The Cambrian explosion is a grand challenge to science today and involves multidisciplinary study. This event is generally believed as a result of genetic innovations, environmental factors and ecological interactions, even though there are many conflicts on nature and timing of metazoan origins. The crux of the matter is that an entire roadmap of the evolution is missing to discern the biological complexity transition and to evaluate the critical role of the Cambrian explosion in the overall evolutionary context. Here, we calculate the time of the Cambrian explosion by a "C-value clock"; our result quite fits the fossil records. We clarify that the intrinsic reason of genome evolution determined the Cambrian explosion. A general formula for evaluating genome size of different species has been found, by which the genome size evolution can be illustrated. The Cambrian explosion, as a major transition of biological complexity, essentially corresponds to a critical turning point in genome size evolution. PMID:20074549

  1. Syn-rift unconformities punctuating the lower-middle Cambrian transition in the Atlas Rift, Morocco

    Science.gov (United States)

    Álvaro, J. Javier; Ezzouhairi, Hassan; Clausen, Sébastien; Ribeiro, M. Luisa; Solá, Rita

    2015-04-01

    The Cambrian Tamdroust and Bab n'Ali Volcanic Complexes represent two magmatic episodes developed in the latest Ediacaran-Cambrian Atlas Rift of Morocco. Their rifting pulses were accompanied by accumulation of volcanosedimentary edifices (dominated by effusive lava flows in the former and explosive acidic aprons in the latter) associated with active tilting and uplift. Sealing of their peneplaned horst-and-graben palaeotopographies led to the onset of distinct onlapping geometries and angular discordances capping eroded basements ranging from the Ediacaran Ouarzazate Supergroup to the Cambrian Asrir Formation. Previous interpretations of these discordances as pull-apart or compressive events are revised here and reinterpreted in an extensional (rifting) context associated with active volcanism. The record of erosive unconformities, stratigraphic gaps, condensed beds and onlapping patterns across the traditional "lower-middle Cambrian" (or Cambrian Series 2-3) transition of the Atlas Rift must be taken into consideration for global chronostratigraphic correlation based on their trilobite content.

  2. Comparison between Input Hypothesis and Interaction Hypothesis

    Institute of Scientific and Technical Information of China (English)

    宗琦

    2016-01-01

    Second Language Acquisition has received more and more attention since 1950s when it becomes an autonomous field of research. Linguists have carried out many theoretical and empirical studies with a sharp purpose to promote Second Language Acquisition. Krashen’s Input Hypothesis and Long’s Interaction Hypothesis are most influential ones among the studies. They both play important roles in language teaching and learning. The paper will present an account of the two great theories, includ-ing the main claims, theoretical foundations as well as some related empirical works and try to investigate commons and differ-ences between them, based on literature and empirical studies. The purpose of writing this paper is to provide a clear outline of the two theories and point out how they are interrelated yet separate predictions about how second language are learned. It is meaningful because the results can be valuable guidance and highlights for language teachers and learners to teach or acquire a language better.

  3. A specific hygiene hypothesis.

    Science.gov (United States)

    Shunsheng Han, Cliff

    2016-08-01

    Allergic diseases have reached epidemic proportions in Western populations in the last several decades. The hygiene hypothesis proposed more than twenty years ago has helped us to understand the epidemic and has been verified with numerous studies. However, translational measures deduced from these studies to prevent allergic diseases have not proven effective. Recent studies on immigrants' allergies and any potential association between oral infection and allergic diseases prompt me to propose a specific hygiene hypothesis to explain how oral hygiene practices might have contributed to the uprising of hay fever, the most common allergic disease. The historic oral hygiene level in US is closely associated with the emerging allergic epidemic. Future studies to test the hypothesis are needed and verification of the hypothesis can potentially yield highly effective measures to prevent allergic diseases. PMID:27372876

  4. Experimental taphonomy and the anatomy and diversity of the earliest fossil vertebrates (Chengjiang Biota, Cambrian, China)

    Science.gov (United States)

    Purnell, Mark; Gabbott, Sarah; Murdock, Duncan; Cong, Peiyun

    2016-04-01

    The oldest fossil vertebrates are from the Lower Cambrian Chengjiang biota of China, which contains four genera of fish-like, primitive vertebrates: Haikouichthys, Myllokunmingia, Zhongjianichthys and Zhongxiniscus. These fossils play key roles in calibrating molecular clocks and informing our view of the anatomy of animals close to the origin of vertebrates, potentially including transitional forms between vertebrates and their nearest relatives. Despite the evident importance of these fossils, the degree to which taphonomic processes have affected their anatomical completeness has not been investigated. For example, some or all might have been affected by stemward slippage - the pattern observed in experimental decay of non-biomineralised chordates in which preferential decay of synapomorphies and retention of plesiomorphic characters would cause fossil taxa to erroneously occupy more basal positions than they should. This hypothesis is based on experimental data derived from decay of non-biomineralised chordates under laboratory conditions. We have expanded this analysis to include a broader range of potentially significant environmental variables; we have also compared and combined the results of experiments from several taxa to identify general patterns of chordate decay. Examination of the Chengjiang vertebrates in the light of these results demonstrates that, contrary to some assertions, experimentally derived models of phylogenetic bias are applicable to fossils. Anatomical and phylogenetic interpretations of early vertebrates that do not take taphonomic biases into account risk overestimating diversity and the evolutionary significance of differences between fossil specimens.

  5. Original molluscan radula: comparisons among Aplacophora, Polyplacophora, Gastropoda, and the Cambrian fossil Wiwaxia corrugata.

    Science.gov (United States)

    Scheltema, Amélie H; Kerth, Klaus; Kuzirian, Alan M

    2003-08-01

    As the original molluscan radula is not known from direct observation, we consider what the form of the original radula may have been from evidence provided by neomenioid Aplacophora (Solenogastres), Gastropoda, Polyplacophora, and the Cambrian fossil Wiwaxia corrugata (Matthews). Conclusions are based on direct observation of radula morphology and its accessory structures (salivary gland ducts, radular sac, anteroventral radular pocket) in 25 species and 16 genera of Aplacophora; radula morphogenesis in Aplacophora; earliest tooth formation in Gastropoda (14 species among Prosobranchia, Opisthobranchia, and Pulmonata); earliest tooth formation in four species of Polyplacophora; and the morphology of the feeding apparatus in W. corrugata. The existence of a true radula membrane and of membranoblasts and odontoblasts in neomenioids indicates that morphogenesis of the aplacophoran radula is homologous to that in other radulate Mollusca. We conclude from p redness of salivary gland ducts, a divided radular sac, and a pair of anteroventral pockets that the plesiomorphic state in neomenioids is bipartite, formed of denticulate bars that are distichous (two teeth per row) on a partially divided or fused radula membrane with the largest denticles lateral, as occurs in the genus Helicoradomenia. The tooth morphology in Helicoradomenia is similar to the feeding apparatus in W. corrugata. We show that distichy also occurs during early development in several species of gastropods and polyplacophorans. Through the rejection of the null hypothesis that the earliest radula was unipartite and had no radula membrane, we conclude that the original molluscan radula was similar to the radula found in Helicoradomena species. PMID:12833382

  6. Neoproterozoic Land Colonisation, Rising Oxygen, Global Cooling and the Cambrian Explosion

    Science.gov (United States)

    Lenton, T. M.; Watson, A. J.

    2004-12-01

    The Neoproterozoic (1000-542 Ma BP) was a time of severe glaciations and a major transition from microscopic to macroscopic life forms. We develop the hypothesis that a rise in atmospheric oxygen in the Neoproterozoic was driven by the biological colonization of the land surface. If early forms of photosynthetic land life selectively weathered continental rock in order to extract nutrients, this would have led to an increase in the flux of biologically available phosphorus to the ocean. We show that recent models for coupled biogeochemical cycles, despite differences in the feedback mechanisms represented, predict this would lead to a rise in atmospheric oxygen concentration, consistent with biological and geochemical evidence. Increased weathering of silicate rocks would also have caused a decline in atmospheric carbon dioxide, which could have been a causal factor in the Neoproterozoic glaciations. A rise in oxygen may have provided a necessary condition for the evolution of animals with hard skeletons seen in the Cambrian explosion. Furthermore, an increase in phosphorus supply to the ocean may have driven an increase in the phosphorus content of marine primary producers. This would have represented an increase in food quality for grazing animals, which have a high phosphorus requirement, and may thus have removed a further limitation on their evolutionary radiation.

  7. Development, triploblastism, physics of wetting and the Cambrian explosion.

    Science.gov (United States)

    Fleury, Vincent

    2013-09-01

    The Cambrian explosion is characterized by the sudden outburst of organized animal plans, which occurred circa 530 M years ago. Around that time, many forms of animal life appeared, including several which have since disappeared. There is no general consensus about "why" this happened, and why it had any form of suddenness. However, all organized animal plans share a common feature: they are triploblastic, i.e., composed of 3 layers of tissue, endoderm, ectoderm and mesoderm. I show here that, within simple hypotheses, the formation of the mesoderm has intrinsically a physical exponential dynamics, leading rapidly to triploblastism, and eventually, to animal formation. A novel physico-mathematical framework including epithelium-mesenchyme transition, visco-elastic constitutive equations, and conservation laws, is presented which allows one to describe gastrulation as a self-wetting phenomenon of a soft solid onto itself. This phenomenon couples differentiation and migration during gastrulation, and leads in a closed form to an exponential scaling law for the formation of the mesoderm. Therefore, the Cambrian explosion might have started, actually, by a true viscoelastic "explosion": the exponential run-away of mesenchymal cells. PMID:23959076

  8. Preservational Pathways of Corresponding Brains of a Cambrian Euarthropod.

    Science.gov (United States)

    Ma, Xiaoya; Edgecombe, Gregory D; Hou, Xianguang; Goral, Tomasz; Strausfeld, Nicholas J

    2015-11-16

    The record of arthropod body fossils is traceable back to the "Cambrian explosion," marked by the appearance of most major animal phyla. Exceptional preservation provides crucial evidence for panarthropod early radiation. However, due to limited representation in the fossil record of internal anatomy, particularly the CNS, studies usually rely on exoskeletal and appendicular morphology. Recent studiesshow that despite extreme morphological disparities, euarthropod CNS evolution appears to have been remarkably conservative. This conclusion is supported by descriptions from Cambrian panarthropods of neural structures that contribute to understanding early evolution of nervous systems and resolving controversies about segmental homologies. However, the rarity of fossilized CNSs, even when exoskeletons and appendages show high levels of integrity, brought into question data reproducibility because all but one of the aforementioned studies were based on single specimens. Foremost among objections is the lack of taphonomic explanation for exceptional preservation of a tissue that some see as too prone to decay to be fossilized. Here we describe newly discovered specimens of the Chengjiang euarthropod Fuxianhuia protensa with fossilized brains revealing matching profiles, allowing rigorous testing of the reproducibility of cerebral structures. Their geochemical analyses provide crucial insights of taphonomic pathways for brain preservation, ranging from uniform carbon compressions to complete pyritization, revealing that neural tissue was initially preserved as carbonaceous film and subsequently pyritized. This mode of preservation is consistent with the taphonomic pathways of gross anatomy, indicating that no special mode is required for fossilization of labile neural tissue. PMID:26526373

  9. Ouachita trough: Part of a Cambrian failed rift system

    Science.gov (United States)

    Lowe, Donald R.

    1985-11-01

    Pre-flysch (Cambrian-Mississippian) strata of the Ouachita Mountains of Arkansas and Oklahoma include two main sandstone lithofacies: (1) a craton-derived lithofacies made up largely of mature medium- to coarse-grained quartzose and carbonate detritus and, in some units, sediment eroded from exposed basement rocks and (2) an orogen-derived facies made up mainly of fine-grained quartzose sedimentary and metasedimentary debris and possibly, in lower units, a volcaniclastic component. Paleocurrent and distribution patterns indicate that detritus of facies I in the Benton uplift was derived from north and detritus of facies II throughout the Ouachitas was derived from south and east of the depositional basin. Overall sedimentological results suggest that the Ouachita trough was a relatively narrow, two-sided basin throughout most and probably all of its existence and never formed the southern margin of the North American craton. Regional comparisons suggest that it was one of several basins, including the Southern Oklahoma aulacogen, Reelfoot Rift, Illinois Basin, and Rome trough, that formed as a Cambrian failed rift system 150 to 250 m.y. after initial rifting along the Appalachian margin of the North American craton.

  10. From snowball earth to the cambrian explosion: the interpretative potential of the isotope record

    Science.gov (United States)

    Shields, G.

    2003-04-01

    generally been overstated in the literature. Sulphur isotopes have been a less visible but just as important component of Proterozoic-Phanerozoic interpretations. After all it is partly δ34S data that have provided crucial, non-palaeontological supporting evidence for a rise in surface oxygenation during the mid-Neoproterozoic. Intriguingly, sometime during the latest Neoproterozoic, seawater sulphate δ34S rose to all-time highest values by the Precambrian-Cambrian boundary. Some proponents of the Snowball Earth hypothesis have surmised that global glaciations would have caused massive fluctuations in seawater sulphate δ34S and recently published carbonate-bound sulphate δ34S data appear to support this idea. However, it first needs to be demonstrated that such data indeed represent faithfully seawater isotopic composition. Isotope stratigraphy across the Proterozoic-Phanerozoic transition is in a state of exciting flux with many mutually conflicting correlation schemes and interpretations. Plainly more work is needed in order to reach a satisfactory consensus. However, what is also needed, is more focus, perhaps within the auspices of a global working group, keeping well in mind that although more data would be welcome, the single most important advance would be more secure age dating.

  11. Fossil Association from the Lower Cambrian Yanjiahe Formation in the Yangtze Gorges Area, Hubei, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Junfeng; Tsuyoshi KOMIYA; LI Yong; HAN Jian; ZHANG Xingliang; ZHANG Zhifei; OU Qiang; LIU Jianni; SHU Degan; Shigenori MARUYAMA

    2008-01-01

    Apart from previously reported Small Shelly Fossils (SSFs), a macroscopic fossil assemblage, comprising abundant algae, cone-shaped tubular fossil forms, and probable impressions of a megascopic metazoan, comes from the Lower Cambrian Yanjiahe Formation in the Yangtze Gorges area of western Hubei Province, south China. The visible fossils are preserved in thin-laminated siltstone or muddy siltstone intercalated between 8-15 mm-thick carbonate deposits, probably representing sedimentary settings of a constrained local depression in the shallow water carbonate platform during the Early Cambrian Meishucunian Stage. The macroscopic fossil association provides significant fossil evidence about the evolution of life from the late Precambrian to the 'Cambrian explosion' interval.

  12. Sponge fossil assemblage from the Early Cambrian Hetang Formation in southern Anhui

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhe; HU Jie; ZHOU Chuanming; XIAO Shuhai; YUAN Xunlai

    2004-01-01

    Abundant well-preserved large articulated sponge fossils and isolated spicules have been reported from the Early Cambrian Hetang Formation, southern Anhui Province. This unique epifaunal fossil assemblage dominated by articulated sponge fossils is called the Xidi Sponge Fauna.The sponge fauna lived in a quiet oxygenic environment below the storm wave base. Bloom of phytoplankton and rapid sedimentation rate resulted in the deposition of the black shales. Sufficient food supply, lack of other competitors,abundant ecological niches, and demand for oxygen during early Cambrian were in favor of the diversification and evolution of large sponges in the Early Cambrian.

  13. The Qualitative Similarity Hypothesis

    Science.gov (United States)

    Paul, Peter V.; Lee, Chongmin

    2010-01-01

    Evidence is presented for the qualitative similarity hypothesis (QSH) with respect to children and adolescents who are d/Deaf or hard of hearing. The primary focus is on the development of English language and literacy skills, and some information is provided on the acquisition of English as a second language. The QSH is briefly discussed within…

  14. Pulse of atmospheric oxygen during the late Cambrian.

    Science.gov (United States)

    Saltzman, Matthew R; Young, Seth A; Kump, Lee R; Gill, Benjamin C; Lyons, Timothy W; Runnegar, Bruce

    2011-03-01

    A rise in atmospheric O(2) has been linked to the Cambrian explosion of life. For the plankton and animal radiation that began some 40 million yr later and continued through much of the Ordovician (Great Ordovician Biodiversification Event), the search for an environmental trigger(s) has remained elusive. Here we present a carbon and sulfur isotope mass balance model for the latest Cambrian time interval spanning the globally recognized Steptoean Positive Carbon Isotope Excursion (SPICE) that indicates a major increase in atmospheric O(2). We estimate that this organic carbon and pyrite burial event added approximately 19 × 10(18) moles of O(2) to the atmosphere (i.e., equal to change from an initial starting point for O(2) between 10-18% to a peak of 20-28% O(2)) beginning at approximately 500 million years. We further report on new paired carbon isotope results from carbonate and organic matter through the SPICE in North America, Australia, and China that reveal an approximately 2‰ increase in biological fractionation, also consistent with a major increase in atmospheric O(2). The SPICE is followed by an increase in plankton diversity that may relate to changes in macro- and micronutrient abundances in increasingly oxic marine environments, representing a critical initial step in the trophic chain. Ecologically diverse plankton groups could provide new food sources for an animal biota expanding into progressively more ventilated marine habitats during the Ordovician, ultimately establishing complex ecosystems that are a hallmark of the Great Ordovician Biodiversification Event. PMID:21368152

  15. A Protocol for Diagnosing the Effect of Calibration Priors on Posterior Time Estimates: A Case Study for the Cambrian Explosion of Animal Phyla.

    Science.gov (United States)

    Battistuzzi, Fabia U; Billing-Ross, Paul; Murillo, Oscar; Filipski, Alan; Kumar, Sudhir

    2015-07-01

    We present a procedure to test the effect of calibration priors on estimated times, which applies a recently developed calibration-free approach (RelTime) method that produces relative divergence times for all nodes in the tree. We illustrate this protocol by applying it to a timetree of metazoan diversification (Erwin DH, Laflamme M, Tweedt SM, Sperling EA, Pisani D, Peterson KJ. 2011. The Cambrian conundrum: early divergence and later ecological success in the early history of animals. Science 334:1091-1097.), which placed the divergence of animal phyla close to the time of the Cambrian explosion inferred from the fossil record. These analyses revealed that the two maximum-only calibration priors in the pre-Cambrian are the primary determinants of the young divergence times among animal phyla in this study. In fact, these two maximum-only calibrations produce divergence times that severely violate minimum boundaries of almost all of the other 22 calibration constraints. The use of these 22 calibrations produces dates for metazoan divergences that are hundreds of millions of years earlier in the Proterozoic. Our results encourage the use of calibration-free approaches to identify most influential calibration constraints and to evaluate their impact in order to achieve biologically robust interpretations. PMID:25808541

  16. A review of the Late Cambrian (Furongian) palaeogeography in the western Mediterranean region, NW Gondwana

    Science.gov (United States)

    Álvaro, J. Javier; Ferretti, Annalisa; González-Gómez, Cristina; Serpagli, Enrico; Tortello, M. Franco; Vecoli, Marco; Vizcaïno, Daniel

    2007-11-01

    The Cambrian-Ordovician transition of the western Mediterranean region (NW Gondwana) is characterized by the record of major erosive unconformities with gaps that range from a chronostratigraphic stage to a series. The hiatii are diachronous and involved progressively younger strata along the Gondwanan margin, from SW (Morocco) to NE (Montagne Noire). They can be related to development of a multi-stage rifting (further North), currently connected to the opening of the Rheic Ocean, and concomitant erosion on southern rift shoulders. The platforms of this margin of Gondwana occupied temperate-water, mid latitudes and were dominated by siliciclastic sedimentation, while carbonate factories were only episodically active in the Montagne-Noire platform. The Upper Cambrian is devoid of significant gaps in the southern Montagne Noire and the Iberian Chains. There, the sedimentation took place in a transgressive-dominated depositional system, with common offshore deposits and clayey substrates, and was bracketed by two major regressive trends. The Late Cambrian is also associated with the record of volcanic activity ( e.g., in the Cantabrian and Ossa-Morena zones, and the northern Montagne Noire), and widespread development of a tectonic instability that led to the episodic establishment of palaeotopographies and record of slope-related facies associations. Several immigration events are recognized throughout the latest Middle Cambrian, Late Cambrian and Tremadocian. The trilobites show a stepwise replacement of Acado-Baltic-type families ( e.g., the conocoryphid-paradoxidid-solenopleurid assemblage) characterized by: (i) a late Languedocian (latest Middle Cambrian) co-occurrence of Middle Cambrian trilobite families with the first anomocarid, dorypygid and proasaphiscid invaders; (ii) a Late Cambrian immigration replacing previous faunas, composed of trilobites (aphelaspidids, catillicephalids, ceratopygids, damesellids, eulomids, idahoiids, linchakephalids, lisariids

  17. Ichnofossil from the Cambrian succession of Parahio Valley, Spiti Basin, India: Their stratigraphic and paleoenvironmental significance

    Science.gov (United States)

    Pandey, Shivani; Parcha, Suraj Kumar

    2013-04-01

    The Spiti Basin exposes an excellent section of Neoproterozoic- Cretaceous rocks in the Tethyan Himalaya of Himachal Pradesh. The diverse assemblage of ichnofossils is present in the Cambrian succession of Parahio Valley in the Spiti Basin. In the present study nineteen ichnofossils are reported from the Cambrian succession of Parahio Valley. The ichnofossils includes Bergaueria, Chondrites, Cruziana, Didymaulichnus, Dimorphichnus, Diplichnites, Helminthorhaphe, Merostomichnites, ?Monocraterion, Monomorphichnus, Nereites, Palaeopascichnus, Palaeophycus, Phycodes, Planolites, Rusophycus, Skolithos, Scolicia, Treptichnus etc. along with annelid worm, burrow and scratch marks. The described ichnofossil assemblage indicates that the ichnocenosis is dominated by a high behavioral diversity ranging from suspension to deposit feeders. It seems that the ichnofauna present in the Cambrian succession of this section were mostly produced by trilobite and arthropods, whereas some of them were produced by crustacean, priapulid worm, polychaetes and polyphyletic vermiforms. The distribution pattern of ichnofossils shows increase in taxonomic and morphological diversity up in the section. It further indicates that the availability of nutrients significantly increased their abundance as well as spatial distribution during Cambrian. The presence of Chondrites, Treptichnus, and Phycodes at the basal part of the Cambrian indicates shallow to deep environment with anaerobic condition. Whereas, the complex forms like Rusophycus, Cruziana, Monomorphichnus and Nereites represent shelf to slope environment. The appearance of Skolithos in the upper part reflects well oxygenated high energy condition. The environmental changes in the Parahio Valley during Cambrian period was distinctly marked by an anaerobic to aerobic condition and by a faunal change from endobenthic, soft - bodied, deposit feeders to epibenthic grazers. The present ichnofossils indicates that these sediments were

  18. Discovery of hydrothermal venting community at the base of Cambrian barite in Guizhou Province, Western China:Implication for the Cambrian biological explosion

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The barite deposit in the Niutitang Formation of Lower Cambrian, in Tianzhu County, Guizhou Province, western China, is a superlarge barite deposit with about 2 × 109 tons of reserves: Mineral, petrological and geochemical studies reveal that this barite deposit belongs to a hydrothermal sedimentary deposit. Microscopic observations indicate that a lot of algae, sponge spicules and tube-type fossils are well-preserved in this barite section, and moreover, those fossils share most characteristics of the deep-sea hydrothermal venting community in the modern Pacific. We suggest that the hydrothermal venting community was thriving in hydrothermal vent in early Cambrian, and it is of great significance for elucidating the geological background of the "Cambrian explosion".

  19. The Keystone Pathogen Hypothesis

    OpenAIRE

    Hajishengallis, George; Darveau, Richard P; Curtis, Michael A.

    2012-01-01

    Recent studies have highlighted the importance of the human microbiome in host health and disease. However, for the most part the mechanisms by which the microbiome mediates disease, or protection from it, remain poorly understood. The “keystone pathogen” hypothesis holds that certain low-abundance microbial pathogens can orchestrate inflammatory disease by remodelling a normally benign microbiota into a dysbiotic one. In this Opinion, we critically assess the available literature in support ...

  20. Testing the Schumpeterian Hypothesis

    OpenAIRE

    Zoltan J. Acs; Audretsch, David B

    1988-01-01

    The late Joseph Schumpeter had opposing views about economic development. In his earlier work, he argued that innovation is promoted by the presence of entrepreneurs outside the firm. Later, he argued that innovation activity is promoted by large firms, for whom the innovation process in endogenous. This paper uses a direct measure of innovation to test the later Schumpeterian hypothesis. The authors find support for bo th the early and later Schumpeterian hypotheses about innovation.

  1. Early Cambrian origin of modern food webs: evidence from predator arrow worms

    OpenAIRE

    Vannier, J; Steiner, M.; Renvoisé, E; Hu, S.-X.; Casanova, J.-P

    2006-01-01

    Although palaeontological evidence from exceptional biota demonstrates the existence of diverse marine communities in the Early Cambrian (approx. 540–520 Myr ago), little is known concerning the functioning of the marine ecosystem, especially its trophic structure and the full range of ecological niches colonized by the fauna. The presence of a diverse zooplankton in Early Cambrian oceans is still an open issue. Here we provide compelling evidence that chaetognaths, an important element of mo...

  2. The Precambrian–Cambrian nonconformity at the Ercall Quarries, The Wrekin, Shropshire, UK

    OpenAIRE

    Pringle, JK; Stimpson, IG

    2013-01-01

    The Precambrian–Cambrian boundary is iconic, marking the first appearance of shelly fauna in the fossil record, and opening the Phanerozoic Eon. In England and Wales, the transition from predominantly Precambrian igneous rocks to Cambrian sedimentary strata is generally unconformable. An exceptional exposure of this transition can be observed in the Ercall Quarries in Shropshire, a classic locality in all senses of the word.

  3. Exceptionally preserved brachiopods from the Chengjiang Lagerstatte (Yunnan, China) : Perspectives on the Cambriane explosion of metazoans

    OpenAIRE

    Zhang, Zhifei; Holmer, L. E.

    2013-01-01

    The Cambrian explosion was coined to describe the geologically sudden appearance of numerous bilaterian body plans (Phyla) around the Ediacaran-Cambrian transition, around 565-520 million years ago. Many explanations and conjectures have been postulated in order to explain the pattern and duration of this explosive radiation of many different phyla of early metazoans. Here, we focus on the evolution of a phylum of marine suspension-feeding animals – the brachiopods, as exemplified by the exce...

  4. The Genetic Response to Snowball Earth: Role of HSP90 in the Cambrian Explosion

    OpenAIRE

    Baker, Michael E.

    2006-01-01

    The events that shaped the Cambrian explosion from 545 to 530 myr ago, when multicellular animals suddenly appeared in the fossil record, are not fully understood. It is likely that the evolution of new transcription factors and other signal transduction proteins that regulated developmental networks were important in the emergence of diverse animal phyla seen in the Cambrian. I propose that one or both extensive glaciations that ended about 670 myr and 635 myr ago were important in the evo...

  5. The C-value enigma and timing of the Cambrian explosion

    OpenAIRE

    Li, Dirson Jian; Zhang, Shengli

    2008-01-01

    The Cambrian explosion is a grand challenge to science today and involves multidisciplinary study. This event is generally believed as a result of genetic innovations, environmental factors and ecological interactions, even though there are many conflicts on nature and timing of metazoan origins. The crux of the matter is that an entire roadmap of the evolution is missing to discern the biological complexity transition and to evaluate the critical role of the Cambrian explosion in the overall...

  6. A sclerite-bearing stem group entoproct from the early Cambrian and its implications

    OpenAIRE

    Zhifei Zhang; Holmer, Lars E.; Skovsted, Christian B; Glenn A. Brock; Graham E. Budd; Dongjing Fu; Xingliang Zhang; Degan Shu; Jian Han; Jianni Liu; Haizhou Wang; Aodhán Butler; Guoxiang Li

    2013-01-01

    The Lophotrochozoa includes disparate tentacle-bearing sessile protostome animals, which apparently appeared in the Cambrian explosion, but lack an uncontested fossil record. Here we describe abundant well preserved material of Cotyledion tylodes Luo et Hu, 1999, from the Cambrian (Series 2) Chengjiang deposits, reinterpreted here as a stem-group entoproct. The entoproct affinity is supported by the sessile body plan and interior soft anatomy. The body consists of an upper calyx and a lower e...

  7. Mesoamerican cosmovision: an hypothesis.

    Science.gov (United States)

    Franch, J. A.

    In the present conference the author explains a new hypothesis to interpret the cosmogonic vision of the people and the cultures from the Mesoamerican area during the precolumbian period. The hypothesis at issue consists in irregular octahedrical form, or as two pyramids jointed by the base in such a manner that the celestial pyramid has thirteen heavens in the form of platforms in such a way that the zenith is the seventh platform; on the contrary, the infraworld pyramid has nine platforms. The sequence of the heavens comes to an end in the number 13 heaven, or the West side of the world, that is to say the Omeyocan or the Tamoanchan, whereas the ninth infraworld is the Apochcalocan. This is the point of the intercommunication between the celestial world and the infraworld, the place of Death and Birth. In order to develop that hypothesis the author has a great number of ethnographic testimonies taken from Totonacs, Tzotziles, Mayas and, along with this, from Southamerican areas, as it is the case of the Kogi, of Colombia. The author has also considered the evidence that proceeds from the ancient codices as well as numerous samples of sculptures and reliefs, especially from the Aztec culture.

  8. Lower Cambrian polychaete from China sheds light on early annelid evolution

    Science.gov (United States)

    Liu, Jianni; Ou, Qiang; Han, Jian; Li, Jinshu; Wu, Yichen; Jiao, Guoxiang; He, Tongjiang

    2015-06-01

    We herein report a fossilized polychaete annelid, Guanshanchaeta felicia gen. et sp. nov., from the Lower Cambrian Guanshan Biota (Cambrian Series 2, stage 4). The new taxon has a generalized polychaete morphology, with biramous parapodia (most of which preserve the evidence of chaetae), an inferred prostomium bearing a pair of appendages, and a bifid pygidium. G. felicia is the first unequivocal annelid reported from the Lower Cambrian of China. It represents one of the oldest annelids among those from other early Paleozoic Lagerstätten including Sirius Passet from Greenland (Vinther et al., Nature 451: 185-188, 2008) and Emu Bay from Kangaroo island (Parry et al., Palaeontology 57: 1091-1103, 2014), and adds to our increasing roll of present-day animal phyla recognized in the early Cambrian Guanshan Biota. This finding expands the panorama of the Cambrian `explosion' exemplified by the Guanshan Biota, suggesting the presence of many more fossil annelids in the Chengjiang Lagerstätte and the Kaili Biota. In addition, this new taxon increases our knowledge of early polychaete morphology, which suggests that polychaete annelids considerably diversified in the Cambrian.

  9. Hydrogen sulphide release to surface waters at the Precambrian/Cambrian boundary.

    Science.gov (United States)

    Wille, Martin; Nägler, Thomas F; Lehmann, Bernd; Schröder, Stefan; Kramers, Jan D

    2008-06-01

    Animal-like multicellular fossils appeared towards the end of the Precambrian, followed by a rapid increase in the abundance and diversity of fossils during the Early Cambrian period, an event also known as the 'Cambrian explosion'. Changes in the environmental conditions at the Precambrian/Cambrian transition (about 542 Myr ago) have been suggested as a possible explanation for this event, but are still a matter of debate. Here we report molybdenum isotope signatures of black shales from two stratigraphically correlated sample sets with a depositional age of around 542 Myr. We find a transient molybdenum isotope signal immediately after the Precambrian/Cambrian transition. Using a box model of the oceanic molybdenum cycle, we find that intense upwelling of hydrogen sulphide-rich deep ocean water best explains the observed Early Cambrian molybdenum isotope signal. Our findings suggest that the Early Cambrian animal radiation may have been triggered by a major change in ocean circulation, terminating a long period during which the Proterozoic ocean was stratified, with sulphidic deep water. PMID:18509331

  10. The Cambrian Evolutionary Explosion: Novel Evidence from Fossils Studied by X-ray Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jun-Yuan [Nanjing University, China

    2011-06-01

    The Cambrian explosion (from 542 million years to 488 million years ago) is one of the greatest mysteries in evolutionary biology. It wasn't until this period that complex organisms became common and diverse. the magnitude of the event can be understood based on the contrast between the biota and the degree of diversity of the fossils from both sides. great advances have been made in Cambrian palaeontology over the past century, especially the discovery of the well-preserved soft-bodied fauna from the Middle Cambrian Burgess Shale and the Lower Cambrian Maotianshan Shale deposits. The Cambrian side of the "Cambrian explosion" is richly illustrated and contrasts greatly with the Precambrian side. The study of these extraordinarily preserved fossil biota is extremely difficult. A major challenge is 3-D reconstruction and determining the patter of the cell organization in Weng'an embryos and their buried structures in Maotianshan Shale fossils. This talk will show that two recent technological approaches, propagation phase contrast synchrotron x-ray microtomography and microtomography, provide unique analytical tools that permit the nondestructive computational examination and visualization of the internal and buried characters in virtual sections in any plane, and virtual 3-D depictions of internal structures.

  11. The Ordovician Radiation: A Follow-up to the Cambrian Explosion?

    Science.gov (United States)

    Droser, Mary L; Finnegan, Seth

    2003-02-01

    There was a major diversification known as the Ordovician Radiation, in the period immediately following the Cambrian. This event is unique in taxonomic, ecologic and biogeographic aspects.While all of the phyla but one were established during the Cambrian explosion, taxonomic increases during the Ordovician were manifest at lower taxonomic levels although ordinal level diversity doubled. Marine family diversity tripled and within clade diversity increases occurred at the genus and species levels. The Ordovician radiation established the Paleozoic Evolutionary Fauna; those taxa which dominated the marine realm for the next 250 million years. Community structure dramatically increased in complexity. New communities were established and there were fundamental shifts in dominance and abundance.Over the past ten years, there has been an effort to examine this radiation at different scales. In comparison with the Cambrian explosion which appears to be more globally mediated, local and regional studies of Ordovician faunas reveal sharp transitions with timing and magnitudes that vary geographically. These transitions suggest a more episodic and complex history than that revealed through synoptic global studies alone.Despite its apparent uniqueness, we cannot exclude the possibility that the Ordovician radiation was an extension of Cambrian diversity dynamics. That is, the Ordovician radiation may have been an event independent of the Cambrian radiation and thus requiring a different set of explanations, or it may have been the inevitable follow-up to the Cambrian radiation. Future studies should focus on resolving this issue. PMID:21680422

  12. Partitioning of Cr, V, and Mn between mantles and cores of differentiated planetesimals - Implications for giant impact hypothesis of lunar origin

    International Nuclear Information System (INIS)

    The partition coefficients of Cr, V, and Mn between metallic Fe and the mineral phases present in the mantle of a giant planetesimal have been determined in the 1500-2000 C range at 3-25 GPa, in order to ascertain whether the formation of an Fe core within a differentiated giant planetesimal could have caused depletions of Cr, V, and Mn in the Mars-sized planetesimal hypothesized as the basis for lunar formation after impact with the earth. The results obtained indicate that the formation of such an Fe core would have led to no such depletion; Cr, V, and Mn are depleted relative to Mg in the earth mantle to a degree comparable to the lunar depletion factor, suggesting that the protolunar material was primarily derived from the earth's mantle. 36 refs

  13. The evolutionary and genetic origins of consciousness in the Cambrian Period over 500 million years ago

    Directory of Open Access Journals (Sweden)

    Todd E Feinberg

    2013-10-01

    Full Text Available Vertebrates evolved in the Cambrian Period before 520 million years ago, but we do not know when or how consciousness arose in the history of the vertebrate brain. Here we propose multiple levels of isomorphic or somatotopic neural representations as an objective marker for sensory consciousness. All extant vertebrates have these, so we deduce that consciousness extends back to the group’s origin. The first conscious sense may have been vision. Then vision, coupled with additional sensory systems derived from ectodermal placodes and neural crest, transformed primitive reflexive systems into image forming brains that map and perceive the external world and the body’s interior. We posit that the minimum requirement for sensory consciousness and qualia is a brain including a forebrain (but not necessarily a developed cerebral cortex/pallium, midbrain and hindbrain. This brain must also have 1 hierarchical systems of intercommunicating, isomorphically organized, processing nuclei that extensively integrate the different senses into representations that emerge in upper levels of the neural hierarchy; and 2 a widespread reticular formation that integrates the sensory inputs and contributes to attention, awareness, and neural synchronization. We propose a two-step evolutionary history, in which the optic tectum was the original center of multi-sensory conscious perception (as in fish and amphibians: step 1, followed by a gradual shift of this center to the dorsal pallium or its cerebral cortex (in mammals, reptiles, birds: step 2. We address objections to the hypothesis and call for more studies of fish and amphibians. In our view, the lamprey has all the neural requisites and is likely the simplest extant vertebrate with sensory consciousness and qualia. Genes that pattern the proposed elements of consciousness (isomorphism, neural crest, placodes have been identified in all vertebrates. Thus, consciousness is in the genes, some of which are

  14. The geobiology of the extremely enriched polymetallic sulfides in the black shale of the lower Cambrian Niutitang formation, Southwestern China

    OpenAIRE

    Xu, Jun; 徐俊

    2014-01-01

    The Precambrian-Cambrian transition is a period with enormous geological and biological changes. There is a wide distribution of black shale sequence in the Late Sinian and Early Cambrian strata along the passive southern margin of the Yangtze Platform in South China. The remarkable polymetallic sulfide extremely enriched ore layer is embedded at the bottom of the Lower Cambrian Niutitang Formation, but its genesis remains highly disputable. Known mechanisms can hardly explain the extreme enr...

  15. A Study on the Input Hypothesis and Interaction Hypothesis

    Institute of Scientific and Technical Information of China (English)

    李雪清

    2016-01-01

    In Second Language Acquisition theory, input and interaction are considered as two key factors greatly influencing the learners’acquisition rate and quality, and therefore input and interaction research has been receiving increasing attention in re-cent years. Among the large amount of research, Krashen’s input hypothesis and Long’s interaction hypothesis are perhaps most influential theories, from which most of input and interaction studies have developed. Input hypothesis claims that compre-hensible input is the only one way to acquire language, whereas interaction hypothesis argues that interaction is necessary for language acquisition. Therefore,this thesis attempts to conduct a descriptive analysis between input hypothesis and interaction hypothesis, based on their basic ideas, theoretical basis, comparisons and empirical work. It concludes that input hypothesis and interaction hypothesis succeed in interpreting the process of language acquisition to some extent, and offer both theoretical and practical inspirations on second language teaching.

  16. Nonlinear geosphere-biosphere interactions and the Cambrian explosion

    Science.gov (United States)

    von Bloh, W.; Bounama, C.; Franck, S.

    2003-04-01

    A conceptual model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, continental biosphere, the kerogen , as well as the aggregated reservoir ocean and atmosphere is presented. In this study the evolution of the mean global surface temperature, the biomass, and reservoir sizes over the whole history and future of the Earth under a maturing Sun is investigated. Reasonable values for the present distribution of carbon in the surface reservoirs of the Earth are obtained and a pronounced global minimum of mean surface temperature at the present state of the Earth is found. Furthermore, three different biosphere types are introduced: procaryotes, eucaryotes, and higher metazoa. They all differ in their temperature tolerance interval and their biogenic enhancement of silicate rock weathering. Around 500 Myr in the past we find a rise of higher metazoa caused by the nonlinear feedback between biosphere and climate. Biotic amplifying of weathering provides and maintains the environment of higher life forms. Such a mechanism may explain the so-called Cambrian explosion.

  17. Open artery hypothesis: the impact of late recanalization of infarct related artery on myocardial perfusion. A prospective randomized study -preliminary data

    International Nuclear Information System (INIS)

    -up than those with persistently occluded coronary artery after myocardial infarction. These findings suggest that late recanalization was associated with less myocardial injury and may have significant impact on clinical prognosis

  18. The qualitative similarity hypothesis.

    Science.gov (United States)

    Paul, Peter V; Lee, Chongmin

    2010-01-01

    Evidence is presented for the qualitative similarity hypothesis (QSH) with respect to children and adolescents who are d/Deaf or hard of hearing. The primary focus is on the development of English language and literacy skills, and some information is provided on the acquisition of English as a second language. The QSH is briefly discussed within the purview of two groups of cognitive models: those that emphasize the cognitive development of individuals and those that pertain to disciplinary or knowledge structures. It is argued that the QSH has scientific merit with implications for classroom instruction. Future research should examine the validity of the QSH in other disciplines such as mathematics and science and should include perspectives from social as well as cognitive models. PMID:20415280

  19. Water Taxation and the Double Dividend Hypothesis

    OpenAIRE

    Nicholas Kilimani

    2014-01-01

    The double dividend hypothesis contends that environmental taxes have the potential to yield multiple benefits for the economy. However, empirical evidence of the potential impacts of environmental taxation in developing countries is still limited. This paper seeks to contribute to the literature by exploring the impact of a water tax in a developing country context, with Uganda as a case study. Policy makers in Uganda are exploring ways of raising revenue by taxing environmental goods such a...

  20. Rapid Polar Wander in North America During the Early Cambrian: Paleomagnetic and Magnetostratigraphic Constraints from the Peurto Blanco Volcanics from Caborca, and the Tapeats Sandstone of the Grand Canyon.

    Science.gov (United States)

    Kirschvink, J. L.; Elston, D. P.; Petterson, R.; Hagadorn, J. W.; Raub, T. D.; Evans, D. A.; Rose, E. C.; Weiss, B. P.; Barr, T. D.

    2006-12-01

    rich sediments along the Cordilleran margin of North America as compared to the Appalachian margin, predicts the observed age transgression in the appearance of archaeocyathid faunas across the North American craton, and supports the hypothesis of one or more rapid true polar wander events during Ediacaran and Cambrian time.

  1. Multi-hypothesis distributed stereo video coding

    DEFF Research Database (Denmark)

    Salmistraro, Matteo; Zamarin, Marco; Forchhammer, Søren

    2013-01-01

    stereo sequences, exploiting an interpolated intra-view SI and two inter-view SIs. The quality of the SI has a major impact on the DVC Rate-Distortion (RD) performance. As the inter-view SIs individually present lower RD performance compared with the intra-view SI, we propose multi-hypothesis decoding...... for robust fusion and improved performance. Compared with a state-of-the-art single side information solution, the proposed DVC decoder improves the RD performance for all the chosen test sequences by up to 0.8 dB. The proposed multi-hypothesis decoder showed higher robustness compared with other...

  2. Ichnology of the Early Cambrian Tal Group, Mussoorie Syncline, Lesser Himalaya, India

    Indian Academy of Sciences (India)

    Meera Tiwari; S K Parcha; Rajita Shukla; Harshita Joshi

    2013-12-01

    The Lesser Himalayan sequence is considered as one of the best developed sections of Cambrian successions, exposed in five different synclines. Mussoorie Syncline, being one of the five synclines, exposes the Cambrian Tal Group. This paper describes nine ichnotaxa, viz., Dimorphichnus isp., ?Diplichnites isp., Monomorphichnus isp., Nereites isp., Palaeopasichnus isp., Palaeophycus isp., Planolites montanus, Planolites isp., Skolithos isp., Treptichnus isp. from the Dhaulagiri Formation of the Tal Group. A detailed analysis of the ichnofossils indicates that the entire succession of Tal Group reflects shallow marine conditions in general and Mussoorie Syncline in particular. The above ichnofossil assemblage along with earlier ichnofossils and other faunal occurrences substantiates the assignment of Early Cambrian age to the Dhaulagiri Formation.

  3. The onset of the 'Ordovician Plankton Revolution' in the late Cambrian

    DEFF Research Database (Denmark)

    Servais, Thomas; Perrier, Vincent; Danelian, Taniel;

    2016-01-01

    The 'Great Ordovician Biodiversification Event' comprises the rapid diversification of marine organisms during the Ordovician Period. It is now clear that this adaptive radiation started for some organisms already in the Cambrian and continued for others beyond the end of the Ordovician, making...... the 'Great Ordovician Biodiversification Event' part of a long-term late Proterozoic and Early Palaeozoic radiation, that in part is expressed by the fossil record as the 'Cambrian Explosion.' A significant diversification of different groups of the plankton is observed in the late Cambrian-Early Ordovician...... interval, leading to the subsequent 'Ordovician Plankton Revolution.' The possible causes of this 'plankton revolution' are currently debated. They include changes in palaeoclimate, palaeogeography or tectonic and volcanic activity, as well as a modified nutrient supply. In this context, the Steptoean...

  4. Ichnology of the Early Cambrian Tal Group, Mussoorie Syncline, Lesser Himalaya, India

    Science.gov (United States)

    Tiwari, Meera; Parcha, S. K.; Shukla, Rajita; Joshi, Harshita

    2013-12-01

    The Lesser Himalayan sequence is considered as one of the best developed sections of Cambrian successions, exposed in five different synclines. Mussoorie Syncline, being one of the five synclines, exposes the Cambrian Tal Group. This paper describes nine ichnotaxa, viz., Dimorphichnus isp., ? Diplichnites isp., Monomorphichnus isp., Nereites isp., Palaeopasichnus isp., Palaeophycus isp., Planolites montanus, Planolites isp., Skolithos isp., Treptichnus isp. from the Dhaulagiri Formation of the Tal Group. A detailed analysis of the ichnofossils indicates that the entire succession of Tal Group reflects shallow marine conditions in general and Mussoorie Syncline in particular. The above ichnofossil assemblage along with earlier ichnofossils and other faunal occurrences substantiates the assignment of Early Cambrian age to the Dhaulagiri Formation.

  5. Cambrian Sequence Stratigraphy and Sea Level Cycles of North China Platform

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The Cambrian of the North China platform consists chiefly of shallow water deposits and shows the sedimentary characters of an epicontinental sea basin. Controlled mainly by global sea level changes and sedimentary influx, the depositional sequences all exhibit as composite sequences. From bottom upward, 14 sequences (3rd order) are recognized, which may be grouped into 5 sequence sets and further into 2 mesosequences (2nd order). It is suggested herein that the Cambrian/Ordovician boundary may better be set at the MFS (maximum flooding surface) of the sequence OSq1, above which the conodont Cordylodus lindstroemi occurs. This position is about 40 m above the traditional Cambrian/Ordovician boundary and is within the Yeli Formation.

  6. Sponge spicules in phosphorites of the Early Cambrian Gezhongwu Formation, Zhijin, Guizhou

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; QIAN Yi; ZHANG Jie; ZHANG Weihua; JIANG Lijun; GAO Hui

    2004-01-01

    Phosphorites occurring at the bottom of the Cambrian system contain abundant small shelly fossils, which are the product of the first episode of life explosion in the Cambrian. It was previously reported that the small shelly fossils are dominated by hyolithids, olivooids, zhijinitids, conodontomorphs, yubelichitids, camenitids and algae, with minor amounts of sponge fossils. Large amounts of sponge spicules, diverse in form, have been found for the first time in the Gezhongwu Formation phosphorites at Shixing, Zhijin County, Guizhou Province, of which such spicules as diaxon-triactins, diaxon-tetractins, pentaxon-pentactins and hexon-hexactins account for 30%. These spicules constitute the sponge clastic phosphorites made up of sponge clastics. Meanwhile, it is also expected that the radiation and diversity of sponge animals started as early as in the earliest Early Cambrian. Habit and burying environment of sponge animal are discussed in the paper.

  7. MicroRNAs and metazoan macroevolution: insights into canalization, complexity, and the Cambrian explosion.

    Science.gov (United States)

    Peterson, Kevin J; Dietrich, Michael R; McPeek, Mark A

    2009-07-01

    One of the most interesting challenges facing paleobiologists is explaining the Cambrian explosion, the dramatic appearance of most metazoan animal phyla in the Early Cambrian, and the subsequent stability of these body plans over the ensuing 530 million years. We propose that because phenotypic variation decreases through geologic time, because microRNAs (miRNAs) increase genic precision, by turning an imprecise number of mRNA transcripts into a more precise number of protein molecules, and because miRNAs are continuously being added to metazoan genomes through geologic time, miRNAs might be instrumental in the canalization of development. Further, miRNAs ultimately allow for natural selection to elaborate morphological complexity, because by reducing gene expression variability, miRNAs increase heritability, allowing selection to change characters more effectively. Hence, miRNAs might play an important role in shaping metazoan macroevolution, and might be part of the solution to the Cambrian conundrum. PMID:19472371

  8. Articulated Wiwaxia from the Cambrian Stage 3 Xiaoshiba Lagerstätte

    Science.gov (United States)

    Yang, Jie; Smith, Martin R.; Lan, Tian; Hou, Jin-Bo; Zhang, Xi-Guang

    2014-04-01

    Wiwaxia is a bizarre metazoan that has been interpreted as a primitive mollusc and as a polychaete annelid worm. Extensive material from the Burgess Shale provides a detailed picture of its morphology and ontogeny, but the fossil record outside this lagerstätte is scarce, and complete wiwaxiids are particularly rare. Here we report small articulated specimens of Wiwaxia foliosa sp. nov. from the Xiaoshiba fauna (Cambrian Stage 3, Hongjingshao Formation, Kunming, south China). Although spines are absent, the fossils' sclerites - like those of W. corrugata - are symmetrically arranged in five distinct zones. They form rows across the body, and were individually added and shed throughout growth to retain an approximately symmetrical body shape. Their development pattern suggests a molluscan affinity. The basic body plan of wiwaxiids is fundamentally conserved across two continents through Cambrian Stages 3-5 - revealing morphological stasis in the wake of the Cambrian explosion.

  9. A sclerite-bearing stem group entoproct from the early Cambrian and its implications.

    Science.gov (United States)

    Zhang, Zhifei; Holmer, Lars E; Skovsted, Christian B; Brock, Glenn A; Budd, Graham E; Fu, Dongjing; Zhang, Xingliang; Shu, Degan; Han, Jian; Liu, Jianni; Wang, Haizhou; Butler, Aodhán; Li, Guoxiang

    2013-01-01

    The Lophotrochozoa includes disparate tentacle-bearing sessile protostome animals, which apparently appeared in the Cambrian explosion, but lack an uncontested fossil record. Here we describe abundant well preserved material of Cotyledion tylodes Luo et Hu, 1999, from the Cambrian (Series 2) Chengjiang deposits, reinterpreted here as a stem-group entoproct. The entoproct affinity is supported by the sessile body plan and interior soft anatomy. The body consists of an upper calyx and a lower elongate stalk with a distal holdfast. The soft anatomy includes a U-shaped gut with a mouth and aboral anus ringed by retractable marginal tentacles. Cotyledion differs from extant entoprocts in being larger, and having the calyx and the stalk covered by numerous loosely-spaced external sclerites. The description of entoprocts from the Chengjiang biota traces the ancestry of yet another lophotrochozoan phylum back to the Cambrian radiation, and has important implications for the earliest evolution of lophotrochozoans. PMID:23336066

  10. Biodiversity and taphonomy of the Early Cambrian Guanshan biota,eastern Yunnan

    Institute of Scientific and Technical Information of China (English)

    Michael; STEINER

    2010-01-01

    The Guanshan biota from eastern Yunnan(Cambrian Series 2,early Stage 4) is a Burgess Shale-type fossil biota with abundant exceptionally preserved soft-bodied fossils after the discovery of the well-known Cambrian Chengjiang fauna and Kaili biota in South China.The geological settings,sedimentology,taphonomy,and the fossil assemblage of the Guanshan biota are briefly summarized here.The Guanshan biota consists of about 60 taxa belonging to more than 10 metazoan groups and algae,among which the lobopods,eldonids,hyolithids with helens,and green algae are reported for the first time.The common occurrence of soft-bodied preservation in many groups,notably the trilobites and brachiopods,makes the Guanshan biota a significant fossil lagersttte for understanding the metazoan evolution during Cambrian explosion and taphonomy of the Burgess Shale-type fossils.

  11. Geochemistry of the Ediacaran-Early Cambrian transition in Central Iberia: Tectonic setting and isotopic sources

    Science.gov (United States)

    Fuenlabrada, José Manuel; Pieren, Agustín P.; Díez Fernández, Rubén; Sánchez Martínez, Sonia; Arenas, Ricardo

    2016-06-01

    A complete Ediacaran-Early Cambrian stratigraphic transition can be observed in the southern part of the Central Iberian Zone (Iberian Massif). Two different stratigraphic units, underlying Ordovician series, display geochemical and Sm-Nd isotopic features in agreement with an evolving geodynamic setting. Pusa Shales (Early Cambrian) rest unconformably on greywackes of the Lower Alcudian Formation (Late Ediacaran). Both sequences present minor compositional variations for major and trace element contents and similar REE patterns, close to those of PAAS (Post Archean Australian Shale). Trace element contents and element ratios suggest mixed sources, with intermediate to felsic igneous contributions for both units. Tectonic setting discrimination diagrams for the Ediacaran greywackes indicate that these turbiditic series were deposited in a sedimentary basin associated with a mature active margin (volcanic arc). However, the compositions of the Cambrian shales fit better with a more stable context, a back-arc or retro-arc setting. εNd(T) and TDM ages are compatible with dominance of a similar cratonic source for both sequences, probably the West Africa Craton. εNd565 values for the Ediacaran greywackes (- 3.0 to - 1.4) along with TDM ages (1256-1334 Ma) imply a significant contribution of juvenile material, probably derived from the erosion of the volcanic arc. However, εNd530 values in the Cambrian shales (- 5.2 to - 4.0) together with older TDM ages (1444-1657 Ma), suggest a higher contribution of cratonic isotopic sources, probably derived from erosion of the adjacent mainland. Coeval with the progressive cessation of arc volcanism along the peri-Gondwanan realm during the Cambrian, there was a period of more tectonic stability and increasing arrival of sediments from cratonic areas. The geochemistry of the Ediacaran-Cambrian transition in Central Iberia documents a tectonic switch in the periphery of Gondwana, from an active margin to a more stable context

  12. Comparative analysis of methods used to define eustatic variations in outcrop: Late Cambrian interbasinal sequence development

    Energy Technology Data Exchange (ETDEWEB)

    Osleger, D. (Univ. of California, Riverside (United States)); Read, J.F. (Virginia Polytechnic Inst. and State Univ., Blacksburg (United States))

    1993-03-01

    Interbasinal correlation of Late Cambrian cyclic carbonates from the Appalachian and Cordilleran passive margins, the Texas craton, and the southern Oklahoma aulacogen defines six major third-order depositional sequences. Graphic correlation of biostratigraphically-constrained strata was used to establish equivalency of stratigraphic sequences between the individual sections. Relatively isochronous biomere boundaries were used as time datums for lithostratigraphic correlation. Although the individual sections are composed of different types of meter-scale cycles and component lithofacies that reflect the various environmental settings of the localities, the overall upward-shallowing character of individual sequences is evident. The sequences are: late Cedaria, mid-Crepicephalus, late Crepicephalus, Aphelaspis to earliest Elvinia, Elvinia to early Saukia, and Saukia to the Cambrian-Ordovician boundary. Interbasinal correlation of stratigraphic sequences permits an evaluation of quantitative techniques for determining accommodation history. Correlation of Fischer plots of cyclic successions from separate basins supports a eustatic control of Late Cambrian sequence development. R2/R3 curves derived from subsidence analysis of the Late Cambrian sections provide good resolution of the second- and third-order scales of accommodation change, and interbasinal correlations of R2/R3 curves also support eustatic control on sequence development. Comparing the accomodation curves and subsidence analysis with paleobathymetric trends of Late Cambrian cyclic strata suggests that the curves may approximate the form of the eustatic sealevel signal. A composite eustatic sealevel curve for Late Cambrian time in North America was created by qualitatively combining the accommodation curves defined by the different techniques for each of the four localities. 129 refs., 16 figs., 3 tabs.

  13. The equivalence of the Riemann Hypothesis and the Density Hypothesis

    CERN Document Server

    Cheng, Yuan-You Fu-Rui

    2008-01-01

    The Riemann zeta function is defined as $\\zeta(s)=\\sum\\sb{n=1}\\sp{\\infty} \\frac{1}{n\\sp{s}}$ for $\\Re(s)>1$ and extended to a regular function on the whole complex plane deleting its unique pole at $s=1$ with the residue 1. The Riemann hypothesis asserts that all non-trivial zeros for $\\zeta(s)$ lie on the line $\\Re(s)=1/2$. The density hypothesis is a related "weaker" conjecture about the estimate of the number of zeros for the Riemann zeta function on the right half side of the so-called critical strip $0\\le \\Re(s)\\le 1$; it is trivial that the Riemann hypothesis implies the density hypothesis. In this article, we prove that the (quasi) Riemann hypothesis and the (quasi) density hypothesis are equivalent.

  14. Discovery of sponge body fossils from the late Meishucunian (Cambrian) at Jinsha, Guizhou, south China

    Institute of Scientific and Technical Information of China (English)

    YANG Xinglian; ZHAO Yuanlong; WANG Yue; WANG Pingli

    2005-01-01

    Here we report discovery of a sponge body fossil Triticispongia sp. from the base of lower Cambrian Niutitang Formation at Jinsha, Guizhou. Stratigraphically, the fossil horizon is located below Ni-Mo ore layer with the Niutitang Biota above, and is equivalent to the late Meishucunian. The species is global in shape with skeletons composed of stauractins and monaxons. Triticispongia sp. reported here may be the earliest sponge body fossils of Cambrian, which provides new informationfor understanding early evolution and radiation of sponge animals.

  15. Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) 'The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia'.

    Science.gov (United States)

    Briggs, Derek E G

    2015-04-19

    Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a 'weird wonder' (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750235

  16. Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) ‘The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia’

    Science.gov (United States)

    Briggs, Derek E. G.

    2015-01-01

    Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a ‘weird wonder’ (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750235

  17. Combined Microfacies-Log-Analysis of Cambrian and Ordovician Carbonate Rocks (Upper Cambrian, Western Hills, Bejing; TZ-162 well, Tarim Basin, Western China)

    OpenAIRE

    Wang, Anjia

    2014-01-01

    The Tarim Basin in northwestern China is the second largest petroleum field in China. The reservoirs are predominantly Palaeozoic (Devonian, Ordovician, and Cambrian) carbonate rocks buried at a depth of 5000 m – 6000 m. Ordovician carbonate rocks are one of the main topics in recent hydrocarbon drilling projects. This great depth and a complex inhomogeneous geological and tectonic development results in many problems in hydrocarbon exploration and production. The Ordovician sequence is do...

  18. Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) ‘The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia’

    OpenAIRE

    Briggs, Derek E G

    2015-01-01

    Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a ‘weird wonder’ (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved ...

  19. Is the Aluminum Hypothesis Dead?

    OpenAIRE

    Lidsky, Theodore I.

    2014-01-01

    The Aluminum Hypothesis, the idea that aluminum exposure is involved in the etiology of Alzheimer disease, dates back to a 1965 demonstration that aluminum causes neurofibrillary tangles in the brains of rabbits. Initially the focus of intensive research, the Aluminum Hypothesis has gradually been abandoned by most researchers. Yet, despite this current indifference, the Aluminum Hypothesis continues to attract the attention of a small group of scientists and aluminum continues to be viewed w...

  20. Active Learning and Hypothesis Testing /

    OpenAIRE

    Naghshvar, Mohammad

    2013-01-01

    This dissertation considers a generalization of the classical hypothesis testing problem. Suppose there are M hypotheses of interest among which only one is true. A Bayesian decision maker is responsible to collect observation samples so as to enhance his information about the true hypothesis in a speedy manner while accounting for the penalty of wrong declaration. In contrast to the classical hypothesis testing problem, at any given time, the decision maker can choose one of the available se...

  1. Antiaging therapy: a prospective hypothesis

    OpenAIRE

    Shahidi Bonjar MR; Shahidi Bonjar L

    2015-01-01

    Mohammad Rashid Shahidi Bonjar,1 Leyla Shahidi Bonjar2 1School of Dentistry, Kerman University of Medical Sciences, Kerman Iran; 2Department of Pharmacology, College of Pharmacy, Kerman University of Medical Sciences, Kerman, Iran Abstract: This hypothesis proposes a new prospective approach to slow the aging process in older humans. The hypothesis could lead to developing new treatments for age-related illnesses and help humans to live longer. This hypothesis has no previous docum...

  2. Geochronological Constraints on Neoproterozoic Glaciations, the first appearance of Metazoans, and the Cambrian Explosion.

    Science.gov (United States)

    Bowring, S.; Condon, D.; Ramezani, J.; Myrow, P.; Landing, E.

    2004-05-01

    Studies of Neoproterozoic climate fluctuations, plate reconstructions, biological evolution and their interrelationships have been hindered by a lack of high-precision geochronological constraints. The correlation and estimates of duration for Neoproterozoic glaciations has relied on physical/chemo-stratigraphy, and thermal subsidence models respectively. New geochronological constraints from Neoproterozoic successions worldwide have sharpened the debate as to the number, synchroneity, and duration of glacial episodes and the relationship, if any, between Metazoan evolution and global glaciation(s). Crucial to the debate are correct interpretation of geochronological data that range from U-Pb zircon studies of intercalated volcanic ash-beds, U-Pb detrital zircon studies, Re-Os from black shales, Rb-Sr from clay-rich rocks, U-Pb and Pb-Pb from carbonates and phosphates, and Lu-Hf from phosphates. Development of a highly resolved Neoproterozoic timescale will require integration and cross-calibration of multiple dating techniques and consideration of what is actually being recorded by each chronometer. A review of available geological and geochronological data indicate that there were at least three and perhaps as many as five periods of Neoproterozoic glacial deposition including rocks from United States (Idaho and Virginia), Newfoundland and the Northwest Territories of Canada, Namibia, and Oman. What must be evaluated is how the paleogeographic distribution of glaciated regions varied with time during the Neoproterozoic. Do Neoproterozoic glacial successions distributed worldwide record a small number of globally synchronous, long-lived glaciations, or numerous diachronous glacial epochs, or a combination of both? At present, the duration of only one glacial deposit, the ca 581 Ma Gaskiers Formation (Newfoundland), is known and it is on the order of 1 Ma, at odds with a long-lived global glaciation predicted by the snowball Earth hypothesis. Other major issues are

  3. 寒武纪早期大气-海洋氧含量与生命大爆发%Atmosphere-Ocean Oxygen Levels and Biotic Explosion in the Early Cambrian

    Institute of Scientific and Technical Information of China (English)

    李超; 金承胜

    2015-01-01

    寒武纪早期(541~510,Ma)地球环境与这一时期生命大爆发之间的关系一直是地球生物学研究的热点问题之一。本文系统总结了目前寒武纪早期大气-海洋氧含量与这一时期生命辐射之间关系的3种假说:大气-海洋的氧含量增加导致了寒武纪生命大爆发;寒武纪生命大爆发导致了大气-海洋氧化以及二者之间没有因果关系。3种假说均有相应的支持证据,但也存在与寒武纪早期海洋化学记录、与现代海洋观察不符和上述假说均未考虑寒武纪早期生命演化所展示的时空差异性等问题。在上述3种假说的基础之上,本文通过对寒武纪构造活动、陆源输入、海洋化学和生命演化等最新资料的综合讨论和分析表明:寒武纪早期地球环境与生命辐射之间很可能是相互作用与协同演化关系,而非简单的单向关系。%The relationship between the Earth environment and the biotic explosion in early Cambrian (ca.541 -5 10,Ma) is one top geobiological issue.Here,we systematically summarized three major hypotheses for the relationship between the atmosphere-ocean oxygen level and the biotic evolution in early Cambrian,including that (1)increasing oxygenation of at-mosphere and ocean caused the Cambrian explosion,(2)the emergence and evolution of lives resulted in oxygenation of atmosphere and ocean,(3)the atmosphere-ocean oxygen level and the evolution of lives are not interrelated.Although each hypothesis is supported by specific evidences,these hypotheses show significantly inconsistent with partial ocean chemistry records in early Cambrian and investigations of lives in modern ocean analogues.In addition,the spatiotemporal heterogeneity of early Cambrian life evolution is not considered in these hypotheses.By synthesizing these major hypotheses with available data on Cambrian tectonic activities,terrestrial fluxes,ocean chemistry and life evolution patterns,we dis

  4. On the evolution and histology of some Cambrian protoconodonts, paraconodonts and primitive euconodonts

    Institute of Scientific and Technical Information of China (English)

    DONG Xiping

    2004-01-01

    Previous reports on the morphological evolution of protoconodonts and paraconodonts are reviewed. The evolutionary trends exhibited by species of the protoconodont genus Gapparodus and the paraconodont genus Westergaadodina are discussed. Based on the present study on histology, genus Paibiconus is protoconodont, while genus Yongshunella is paraconodont (fig. 1 (a)). However, the nature of Huayuanodontus has not been fully understood so far.Recently, the transitional form New Gen. Sensu Miller, 1980 of late Late Cambrian has been found in Hunan Province, South China. It is considered as the Sister-Group of Proconodontus.Moreover, another kind of transitional form of middle Late Cambrian and late Late Cambrian between Prooneotodus rotundatus and Proconodontus, which looks like Prooneotodus rotundatus in gross morphology, but has anterior and posterior costae, has also been found in Hunan,South China. This kind of transitional form is believed to be probably the real intermediate link between Prooneotodus rotundatus and Proconodontus, and Prooneotodus rotundatus is most probably the ancestor of Proconodontus. The two transitional forms noted above are all euconodonts by the study of their histology. Unlike the euconodonts of Post-Cambrian, the evolutionary relationships among the species of protoconodonts, paraconodonts and the primitive euconodonts could not be made clear without the histological study on them.

  5. The sudden appearance of diverse animal body plansduring the Cambrian explosion.

    Science.gov (United States)

    Chen, Jun-Yuan

    2009-01-01

    Beautifully preserved organisms from the Lower Cambrian Maotianshan Shale in central Yunnan, southern China, document the sudden appearance of diverse metazoan body plans at phylum or subphylum levels, which were either short-lived or have continued to the present day. These 530 million year old fossil representatives of living animal groups provide us with unique insight into the foundations of living animal groups at their evolutionary roots. Among these diverse animal groups, many are conservative, changing very little since the Early Cambrian. Others, especially Panarthropoda (superphylum), however, evolved rapidly, with origination of novel body plans representing different evolutionary stages one after another in a very short geological period of Early Cambrian time. These nested body plans portray a novel big picture of pararthropod evolution as a progression of step-wise changes both in the head and the appendages. The evolution of the pararthropods displays how the head/trunk boundary progressively shifted to the posterior, and how the simple annulated soft uniramous appendages progressively changed into stalked eyes in the first head appendages, into whip-like sensorial and grasping organs in the second appendage, and into jointed and biramous bipartite limbs in the post-antennal appendages. Haikouella is one of most remarkable fossils representing the origin body plan of Cristozoa, or crest animals (procraniates+craniates). The anatomy of Early Cambrian crest animals, including Haikouella and Yunnanozoon, contributes to novel understanding and discussion for the origins of the vertebrate brain, neural crest cells, branchial system and vertebrae. PMID:19557680

  6. Gut contents as direct indicators for trophic relationships in the Cambrian marine ecosystem.

    Science.gov (United States)

    Vannier, Jean

    2012-01-01

    Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5) Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways. PMID:23300612

  7. Progress and significance in research on the early Middle Cambrian Kaili Biota, Guizhou Province,China

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Important progress in research on the Kaili Biota has been made recently. Many interesting components from Chengjiang Biota and Burgess Shale Biota have been discovered, e.g. Microdictyon of lobopodia; Ottoia, Palaeoscolex of worms; Naraoia, Marrella of Trilobitioidea, Mollisonia, anamalocarids and other non-trilobite arthropods; and new sorts of echinoder-mas, macroalage fossils and so on. Recent work on the Kaili Biota has resulted in the following developments: (i) an increase in the number of animal genera, up to more than 100 genera in total, so that the Kaili Biota has become the third most diverse of the Burgess Shale-type Biota after the Burgess Shale and Chengjiang Biotas; and (ii) the most noteworthy fossils in the Kaili Biota are echinoderms, non-trilobite arthropods and soft-bodied medusiform fossils, especially the most diverse echinoderms. The progress provides envidence for the biodiversity of marine organisms presented after the "Cambrian Explosion" and serves as a link between the earlist Cambrian Chengjiang Biota and late early Middle Cambrian Burgess Shale Biota. It is of great significance in the reconstruction of the Cambrian palaeoplate, palaeongeography and in research on taphonomy.

  8. Gut contents as direct indicators for trophic relationships in the Cambrian marine ecosystem.

    Directory of Open Access Journals (Sweden)

    Jean Vannier

    Full Text Available Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut contents of Ottoia prolifica, an abundant priapulid worm from the middle Cambrian (Stage 5 Burgess Shale biota. I identify the undigested exoskeletal remains of a wide range of small invertebrates that lived at or near the water sediment interface such as hyolithids, brachiopods, different types of arthropods, polychaetes and wiwaxiids. This set of direct fossil evidence allows the first detailed reconstruction of the diet of a 505-million-year-old animal. Ottoia was a dietary generalist and had no strict feeding regime. It fed on both living individuals and decaying organic matter present in its habitat. The feeding behavior of Ottoia was remarkably simple, reduced to the transit of food through an eversible pharynx and a tubular gut with limited physical breakdown and no storage. The recognition of generalist feeding strategies, exemplified by Ottoia, reveals key-aspects of modern-style trophic complexity in the immediate aftermath of the Cambrian explosion. It also shows that the middle Cambrian ecosystem was already too complex to be understood in terms of simple linear dynamics and unique pathways.

  9. The distribution of the oil derived from Cambrian source rocks in Lunnan area, the Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    There are great differences in biomarks between Cambrian oil and Middle-Upper Ordoviclan oil. In this stuty, the authors analyzed 40 oils found in Lunnan area by GC-MS and calculated the content of Cambrian oil in the 40 oils according to the steroid indexes of typical oil mixture and match experiment. The results show that it is a general phenomenon in Ordovician reservoir that the oil derived from Cambrian source rock mixed with the oil derived from Middle-Upper Ordovician source rock in Lunnan area, the mixture degree of the two oils is lower in Carboniferous reservoir than in Ordovician reservoir, and the oils kept in Triassic reservoir have single source, Middle-Upper Ordovician source rock. The mixture oils mainly composed of Cambrian oil (>50%) distributed in Sangtamu fault zone, and the oils found in Lunnan fault zone are Middle-Upper Ordovician oil. This distribution of oils in Lunnan area is owing to that Lunnan fault zone is located in anticline axis part, Lunnan fault zone underwent serious erosion, and the oils from Cambrian source rock accumulated in Lunnan fault zone were degraded completely during Caledonian-Hercynian movement. But the Cambrian oil accumulated in Sangtamu fault zone was not degraded completely and some of them were left for the location of Sangtamu fault zone is lower than Lunnan fault zone. Later, the oil derived from Middle-Upper Ordovician source rock mixed with the remained Cambrian oil, and the mixture oil formed in Sangtamu fault zone.

  10. A Puzzle About Stalnaker's Hypothesis

    NARCIS (Netherlands)

    Douven, Igor; Dietz, Richard

    2011-01-01

    According to Stalnaker's Hypothesis, the probability of an indicative conditional, Pr(phi -> psi), equals the probability of the consequent conditional on its antecedent, Pr(phi -> psi). While the hypothesis is generally taken to have been conclusively refuted by Lewis' and others' triviality argume

  11. Geological features of Sinian-Early Cambrian intracratonic rift of the Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Guoqi Wei

    2015-01-01

    Full Text Available With the major breakthrough in Sinian-Cambrian gas exploration in the Sichuan Basin, the geologic understanding on this formation has changed. One change concerns the discovery of a nearly SN negative structure in the west of Gaoshiti-Moxi area, but there is controversy over the nature, boundary features and distribution scope, sedimentary features, formation stage and evolution of the structure [11–14]. Since the negative structure belt is closely related to the formation of the Anyue Sinian-Cambrian giant gas field, it is necessary to get a better understanding of its geological features in order to guide the gas exploration in Sinian-Cambrian of the Sichuan Basin in the future. Through an analysis of the drilling data of Sinian-Cambrian in this area, an observation of outcrop profiles and the use of 27000 km 2D seismic data and latest drilling data (Well Gaoshi 17, and in combination with regional structure background, the boundary and distribution scope, sedimentary features and evolution of the Mianzhu-Changning rift in craton were investigated. The results showed that: ① the rift in overall SN direction had a steep and fairly stable eastern boundary, and gentler western boundary with variable positions in different stages; ② at the end of Sinian Deng2 member, the rift was a nearly symmetrical depression with an area of 3 × 104 km2; ③ at the end of Deng4 member, it was a fault depression which was steep in the east and gentle in the west controlled by its eastern boundary fault with an area of 8 × 104 km2; and ④ the evolution of the rift can be divided into four stages: embryonic stage in Deng1-Deng2, formation stage in Deng3-Deng4, filling and subsidence stage in Early Cambrian Maidingping-Qiongzhusi Formation, shrinkage and disappearing stage in Early Cambrian Canglangpu-Longwangmiao Formation. Through the study, it was concluded that both sides of the rift are in good Sinian-Cambrian gas-reservoir-forming conditions

  12. Timing and evolution of ocean anoxic event during Early Cambrian in south China

    Science.gov (United States)

    Yang, J.; Jiang, S.; Pi, D.; Ling, H.

    2008-12-01

    The Precambrian/Cambrian (PC-C) interval is one of the most interesting intervals in the evolution of life because of the sudden diversification of animals with mineralized skeletons, known as "Cambrian Explosion". The Yangtze Platform in south China is one of the best occurrences that can provide excellent insights into the palaeo-environmental and biological changes across the PC-C boundary. Our study show that the ocean anoxia were widespread during the Early Cambrian period, however, the start of this anoxic event was not from the PC-C boundary (i.e., 542 Ma), but some 7 Ma later (~535 Ma) when the Niutitang Formation black rock series (black phosphorite, chert, and black shale) deposited along a thousand kilometer long NEE zone in the transitional facies in the Yangtze Platform, while the major Cambrian radiation (Changjiang fauna) took place during 521-511 Ma. During the Niutitang period, the depositional environment of the Early Cambrian sedimentary sequence in south China have evolved from an initial oxic/dysoxic to a major anoxic/euxinic environment, and then back to dysoxic/oxic environment. A Ni-Mo sulfide layer occurred in the lower part of the Niutitang black shales which contains extremely enrichments of many metals, and can serve as a marker layer in south China when the depositional environment turned into euxinic condition. Re-Os isotope study of the sulfide ores and host black shales show an age of 535 Ma. Initial Os isotopic compositions, Mo isotopic compositions, and rare earth elements and Pt group element geochemistry suggest involvement of submarine hydrothermal fluids during the metal enrichments in black shale.

  13. Hypothesis Designs for Three-Hypothesis Test Problems

    OpenAIRE

    Xiaolong Pu; Yan Li

    2010-01-01

    As a helpful guide for applications, the alternative hypotheses of the three-hypothesis test problems are designed under the required error probabilities and average sample number in this paper. The asymptotic formulas and the proposed numerical quadrature formulas are adopted, respectively, to obtain the hypothesis designs and the corresponding sequential test schemes under the Koopman-Darmois distributions. The example of the normal mean test shows that our methods are quite efficient and s...

  14. The absorber hypothesis of electrodynamics

    OpenAIRE

    De Luca, Jayme

    2008-01-01

    We test the absorber hypothesis of the action-at-a-distance electrodynamics for globally-bounded solutions of a finite-particle universe. We find that the absorber hypothesis forbids globally-bounded motions for a universe containing only two charged particles, otherwise the condition alone does not forbid globally-bounded motions. We discuss the implication of our results for the various forms of electrodynamics of point charges.

  15. An Early Cambrian archaeocyath–trilobite fauna in limestone erratics from the Upper Carboniferous Fitzroy Tillite Formation, Falkland Islands

    OpenAIRE

    Stone, P; Thomson, M.R.A; Rushton, A.W.A.

    2012-01-01

    Rare clasts of limestone contained in the uppermost Carboniferous Fitzroy Tillite Formation of the Falkland Islands contain a rich Cambrian fauna of archaeocyaths together with a radiocyath and a few trilobites. Neither Cambrian strata nor limestone are present in the indigenous rock succession and the clasts are regarded as exotic erratics, introduced during the Permo-Carboniferous glaciation of southern Gondwana, prior to its Mesozoic break-up. Nineteen archaeocyath taxa have been identifie...

  16. Paleoproterozoic mojaveprovince in northwestern Mexico? Isotopic and U-Pb zircon geochronologic studies of precambrian and Cambrian crystalline and sedimentary rocks, Caborca, Sonora

    Science.gov (United States)

    Lang, Farmer G.; Bowring, S.A.; Matzel, J.; Maldonado, G.E.; Fedo, C.; Wooden, J.

    2005-01-01

    Whole-rock Nd isotopic data and U-Pb zircon geochronology from Precambrian crystalline rocks in the Caborca area, northern Sonora, reveal that these rocks are most likely a segment of the Paleoproterozoic Mojave province. Supporting this conclusion are the observations that paragneiss from the ??? 1.75 Ga Bamori Complex has a 2.4 Ga Nd model age and contains detrital zircons ranging in age from Paleo- proterozoic (1.75 Ga) to Archean (3.2 Ga). Paragneisses with similar age and isotopic characteristics occur in the Mojave province in southern California. In addition, "A-type" granite exposed at the southern end of Cerro Rajon has ca 2.0 Ga Nd model age and a U-Pb zircon age of 1.71 Ga, which are similar to those of Paleoproterozoic granites in the Mojave province. Unlike the U.S. Mojave province, the Caborcan crust contains ca. 1.1 Ga granite (Aibo Granite), which our new Nd isotopic data suggest is largely the product of anatexis of the local Precambrian basement. Detrital zircons from Neoproterozoic to early Cambrian miogeoclinal arenites at Caborca show dominant populations ca. 1.7 Ga, ca. 1.4 Ga, and ca. 1.1 Ga, with subordinate Early Cambrian and Archean zircons. These zircons were likely derived predominately from North American crust to the east and northeast, and not from the underlying Caborcan basement. The general age and isotopic similarities between Mojave province basement and overlying miogeoclinal sedimentary rocks in Sonora and southern California is necessary, but not sufficient, proof of the hypothesis that Sonoran crust is allochthonous and was transported to its current position during the Mesozoic along the proposed Mojave-Sonora megashear. One viable alternative model is that the Caborcan Precambrian crust is an isolated, autochthonous segment of Mojave province crust that shares a similar, but not identical, Proterozoic geological history with Mojave province crust found in the southwest United States ?? 2005 Geological Society of America.

  17. Eocrinoid echinoderms from the Lower Cambrian Guanshan Fauna in Wuding, Yunnan, China

    Institute of Scientific and Technical Information of China (English)

    HU ShiXue; LUO HuiLin; HOU ShuGuang; Bernd-Dietrich ERDTMANN

    2007-01-01

    This is a brief report of a new occurrence of eocrinoids from the Early Cambrian Wulongqing Formation in Yunnan, China. The eocrinoids from the Guanshan fauna are among the earliest known eocrinoids. Different from many other Early and Middle Cambrian eocrinoids, the Guanshan eocrinoids are characterized by the absence of sutural pores and epispires, the long and spiral brachioles, the extremely long stalk, and the ratio of the length of the stalk versus that of the calyx. The discovery of the eocrinoids from the Guanshan fauna not only provides new information to the investigation of the early evolution of this animal group, but also shed new light on the occurrence and migration of early eocrinoids.

  18. Lower Cambrian yolk-pyramid embryos from Southern Shaanxi,China

    Institute of Scientific and Technical Information of China (English)

    CHEN Junyuan; Andreas BRAUN; Dieter WALOSZEK; PENG Qingqing; Andreas MAAS

    2004-01-01

    Phosphatized globules with radially arranged pillars were recently recorded from the Lower Cambrian phosphate deposit, Ningqiang, Shaanxi by Yue and Bengtson. These authors interpreted the globules as blastula stage of embryos and the pillars as blastomeres. On the basis of new additional material, we reinterpret these structures as yolk-pyramid stages of possible arthropod eggs. The 20 embryos under present study range from 380 μm to 600 μm in diameter and contain about 120 pyramids. Some embryos having a higher number of pyramids are tentatively interpreted as slightly later developmental stages of the same animal. These 543-million-year-old embryos may push back the evolutionary history of the arthropods to a deeper time and also suggest that one important pattern of arthropod development was already present at the beginning of the Cambrian.

  19. Experimental mineralization of crustacean eggs: new implications for the fossilization of Precambrian-Cambrian embryos

    Science.gov (United States)

    Hippler, D.; Hu, N.; Steiner, M.; Scholtz, G.; Franz, G.

    2012-05-01

    Phosphatized globular microfossils from the Ediacaran and lower Cambrian of South China represent an impressive record of early animal evolution and development. However, their phylogenetic affinity is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are crucial for a reliable interpretation of their phylogenetic position. We conducted phosphatization experiments on eggs of the marbled crayfish Procambarus that indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope. Our experiments replicated the different preservational stages of degradation observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4 · 2H2O) and calcite. The mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment were likely similar during fossilization of Cambrian embryos.

  20. Rise to modern levels of ocean oxygenation coincided with the Cambrian radiation of animals.

    Science.gov (United States)

    Chen, Xi; Ling, Hong-Fei; Vance, Derek; Shields-Zhou, Graham A; Zhu, Maoyan; Poulton, Simon W; Och, Lawrence M; Jiang, Shao-Yong; Li, Da; Cremonese, Lorenzo; Archer, Corey

    2015-01-01

    The early diversification of animals (∼ 630 Ma), and their development into both motile and macroscopic forms (∼ 575-565 Ma), has been linked to stepwise increases in the oxygenation of Earth's surface environment. However, establishing such a linkage between oxygen and evolution for the later Cambrian 'explosion' (540-520 Ma) of new, energy-sapping body plans and behaviours has proved more elusive. Here we present new molybdenum isotope data, which demonstrate that the areal extent of oxygenated bottom waters increased in step with the early Cambrian bioradiation of animals and eukaryotic phytoplankton. Modern-like oxygen levels characterized the ocean at ∼ 521 Ma for the first time in Earth history. This marks the first establishment of a key environmental factor in modern-like ecosystems, where animals benefit from, and also contribute to, the 'homeostasis' of marine redox conditions. PMID:25980960

  1. Cambrian spiral-plated echinoderms from Gondwana reveal the earliest pentaradial body plan.

    Science.gov (United States)

    Smith, Andrew B; Zamora, Samuel

    2013-08-22

    Echinoderms are unique among animal phyla in having a pentaradial body plan, and their fossil record provides critical data on how this novel organization came about by revealing intermediate stages. Here, we report a spiral-plated animal from the early Cambrian of Morocco that is the most primitive pentaradial echinoderm yet discovered. It is intermediate between helicoplacoids (a bizarre group of spiral-bodied echinoderms) and crown-group pentaradiate echinoderms. By filling an important gap, this fossil reveals the common pattern that underpins the body plans of the two major echinoderm clades (pelmatozoans and eleutherozoans), showing that differential growth played an important role in their divergence. It also adds to the striking disparity of novel body plans appearing in the Cambrian explosion. PMID:23804624

  2. A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora.

    Science.gov (United States)

    Yang, Jie; Ortega-Hernández, Javier; Gerber, Sylvain; Butterfield, Nicholas J; Hou, Jin-Bo; Lan, Tian; Zhang, Xi-guang

    2015-07-14

    We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion. PMID:26124122

  3. Mineralogy and Chemistry of Coronadite from Middle Cambrian Manganese Deposits at Wadi Dana, Southern Jordan

    OpenAIRE

    Ahmad Al-Malabeh; Tayel El-Hasan

    2009-01-01

    Coronadite was reported from the upper-most horizons of the Middle Cambrian sediments at two locations in Wadi Dana, central Wadi Araba and Jordan. The unit is composed of dolomite, limestone and shale. Geochemical investigations show appreciable variations in Mn, Pb, Fe, K and Ba contents in the coronadite between the two studied sites. Pb was found to increase downward in both sites in spite of the lateral distance between them. Fe does not vary vertically, but its concentration decreases e...

  4. Precambrian-Cambrian Sedimentology, Stratigraphy, and Paleontology in the Great Basin (Western United States)

    OpenAIRE

    Sappenfield, Aaron Dale

    2015-01-01

    Thick accumulations of Neoproterozoic and early Phanerozoic strata are distributed throughout much of the arid continental interior of western North America, providing an expansive and well-exposed archive of this important time in Earth’s history. The information presented herein supplements evaluations regarding the utility and limitations of this archive by providing an integrated sedimentological, paleontological, and geochronological description for Precambrian-Cambrian strata exposed i...

  5. The Middle Cambrian fossil Pikaia and the evolution of chordate swimming

    OpenAIRE

    Lacalli Thurston

    2012-01-01

    Abstract Conway Morris and Caron (2012) have recently published an account of virtually all the available information on Pikaia gracilens, a well-known Cambrian fossil and supposed basal chordate, and propose on this basis some new ideas about Pikaia’s anatomy and evolutionary significance. Chief among its chordate-like features are the putative myomeres, a regular series of vertical bands that extends the length of the body. These differ from the myomeres of living chordates in that boundari...

  6. Cambrian Series 3 carbonate platform of Korea dominated by microbial-sponge reefs

    Science.gov (United States)

    Hong, Jongsun; Lee, Jeong-Hyun; Choh, Suk-Joo; Lee, Dong-Jin

    2016-07-01

    Metazoans have been considered as negligible components of Cambrian Series 3 and Furongian microbial-dominated reefs, in contrast to their presence in earlier Terreneuvian-Cambrian Series 2 microbial-archaeocyath reefs. However, recent discoveries of sponges in Cambrian Series 3-Furongian reefs of Australia, China, Iran, USA, and Korea have raised question regarding their contribution in terms of carbonate platform development, which have never been assessed. This study examines Cambrian Series 3 deposits of the Daegi Formation, Korea to elucidate this question. The 100-m-thick middle part of the Daegi Formation is dominated by boundstone facies, which occupies 45% of the study interval, as well as bioclastic wackestone to packstone, bioclastic grainstone, and ooid packstone to grainstone facies. The Daegi reefs are primarily thrombolitic in composition, with 90% (n = 26/29) of the reefs containing an average of 9% sponges in aerial percentage calculated from thin sections. Lithistid sponges composed of peloidal fabrics, some desma spicules, and spicule networks commonly occupy the interstitial space in microbial clusters, are encrusted by mesoclots and Epiphyton, and are surrounded by micrite. Subordinate non-lithistid demosponges occur within clusters of microbial elements. The middle Daegi Formation can be largely subdivided into shoal environment dominated by grainstone to packstone facies and shallow subtidal platform interior environment located behind shoal with wackestone to packstone facies. The microbial-sponge reefs mainly developed around platform interior as patch reefs. The current study indicates that metazoans in the form of lithistid and non-lithistid demosponges are nearly ubiquitously incorporated in Daegi reefs and contributed greatly to the formation of microbial-sponge reefs as well as carbonate platform during the time. Study of these microbial-sponge reefs and their distribution within the carbonate platform may help us to understand how

  7. Cambrian and Ordovician Fossil-Lagerstätten in the Barrandian area

    Czech Academy of Sciences Publication Activity Database

    Fatka, O.; Budil, P.; Kraft, P.; Mergl, M.; Mikuláš, Radek; Valent, M.; Lajblová, K.; Rak, Š.; Steinová, M.; Szabad, M.; Micka, V.; Aubrechtová, M.; Lajbl, L.; Nohejlová, M.; Vodička, J.

    2012-01-01

    Roč. 18, č. 1 (2012), s. 22-25. ISSN 1212-6209. [Congress of CGS and SGS. Moninec, 2011.09.22-2011.09.25] R&D Projects: GA ČR GA205/06/0395; GA ČR GA205/09/1521 Institutional research plan: CEZ:AV0Z30130516 Keywords : Cambrian * Ordovician * Fossil-Lagerstätten Subject RIV: DB - Geology ; Mineralogy http://www.sci.muni.cz/gap/casop/

  8. Cambrian spiral-plated echinoderms from Gondwana reveal the earliest pentaradial body plan

    OpenAIRE

    Smith, Andrew B.; Zamora, Samuel

    2013-01-01

    Echinoderms are unique among animal phyla in having a pentaradial body plan, and their fossil record provides critical data on how this novel organization came about by revealing intermediate stages. Here, we report a spiral-plated animal from the early Cambrian of Morocco that is the most primitive pentaradial echinoderm yet discovered. It is intermediate between helicoplacoids (a bizarre group of spiral-bodied echinoderms) and crown-group pentaradiate echinoderms. By filling an important ga...

  9. Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians

    OpenAIRE

    Caron, Jean-Bernard; Smith, Martin R; Harvey, Thomas H. P.

    2013-01-01

    Burgess Shale-type deposits are renowned for their exquisite preservation of soft-bodied organisms, representing a range of animal body plans that evolved during the Cambrian ‘explosion’. However, the rarity of these fossil deposits makes it difficult to reconstruct the broader-scale distributions of their constituent organisms. By contrast, microscopic skeletal elements represent an extensive chronicle of early animal evolution—but are difficult to interpret in the absence of corresponding w...

  10. Decoding the fossil record of early lophophorates : Systematics and phylogeny of problematic Cambrian Lophotrochozoa

    OpenAIRE

    Butler, Aodhán D.

    2015-01-01

    The evolutionary origins of animal phyla are intimately linked with the Cambrian explosion, a period of radical ecological and evolutionary innovation that begins approximately 540 Mya and continues for some 20 million years, during which most major animal groups appear. Lophotrochozoa, a major group of protostome animals that includes molluscs, annelids and brachiopods, represent a significant component of the oldest known fossil records of biomineralised animals, as disclosed by the enigmat...

  11. Articulated Wiwaxia from the Cambrian Stage 3 Xiaoshiba Lagerstätte.

    OpenAIRE

    Yang, J.; Smith, M. R.; Lan, T.; Hou, J.-B.; Zhang, X.-G.

    2014-01-01

    Wiwaxia is a bizarre metazoan that has been interpreted as a primitive mollusc and as a polychaete annelid worm. Extensive material from the Burgess Shale provides a detailed picture of its morphology and ontogeny, but the fossil record outside this lagerstätte is scarce, and complete wiwaxiids are particularly rare. Here we report small articulated specimens of Wiwaxia foliosa sp. nov. from the Xiaoshiba fauna (Cambrian Stage 3, Hongjingshao Formation, Kunming, south China). Although spines ...

  12. A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora

    OpenAIRE

    Yang, Jie; Ortega-Hernández, Javier; Gerber, Sylvain; Butterfield, Nicholas J.; Hou, Jin-bo; Lan, Tian; Zhang, Xi-guang

    2015-01-01

    Paleozoic lobopodians constitute a diverse assemblage of worm-like organisms that are known from various exceptional fossil deposits and were among the earliest animals to develop skeletonized body parts for protection. Here, we describe Collinsium ciliosum gen. et sp. nov., an armored lobopodian from the early Cambrian Xiaoshiba Lagerstätte (South China). Collinsium belongs to an extinct clade of superarmored lobopodians characterized by supernumerary dorsal spines, and specialized limbs for...

  13. Gut Contents as Direct Indicators for Trophic Relationships in the Cambrian Marine Ecosystem

    OpenAIRE

    Vannier, Jean

    2012-01-01

    Present-day ecosystems host a huge variety of organisms that interact and transfer mass and energy via a cascade of trophic levels. When and how this complex machinery was established remains largely unknown. Although exceptionally preserved biotas clearly show that Early Cambrian animals had already acquired functionalities that enabled them to exploit a wide range of food resources, there is scant direct evidence concerning their diet and exact trophic relationships. Here I describe the gut...

  14. Response to "Discussion on the systematic position of the Early Cambrian priapulomorph worms"

    Institute of Scientific and Technical Information of China (English)

    HAN Jian; HU Shixue

    2006-01-01

    @@ Due to the combination of complex states of preservation and taphonomies in Chengjiang fossils, Huang et al.[1] expressed different opinions to those of Han et al.[2] on the morphology and systematic position of the fossil priapulomorph worms (Priapulomorpha) based on their additional materials. These diverse opinions are critical in any investigation of the diversity of the Introverta in the Cambrian explosion. However, some of their ideas need to be discussed in further detail.

  15. Can fast early rates reconcile molecular dates with the Cambrian explosion?

    OpenAIRE

    Bromham, L D; Hendy, M D

    2000-01-01

    Molecular dates consistently place the divergence of major metazoan lineages in the Precambrian, leading to the suggestion that the 'Cambrian explosion' is an artefact of preservation which left earlier forms unrecorded in the fossil record. While criticisms of molecular analyses for failing to deal with variation in the rate of molecular evolution adequately have been countered by analyses which allow both site-to-site and lineage-specific rate variation, no analysis to date has allowed the ...

  16. Adaptive walks in a gene network model of morphogenesis: insights into the Cambrian explosion

    OpenAIRE

    Sole, Ricard V.; Fernandez, Pau; Kauffman, Stuart A.

    2003-01-01

    The emergence of complex patterns of organization close to the Cambrian boundary is known to have happened over a (geologically) short period of time. It involved the rapid diversification of body plans and stands as one of the major transitions in evolution. How it took place is a controversial issue. Here we explore this problem by considering a simple model of pattern formation in multicellular organisms. By modeling gene network-based morphogenesis and its evolution through adaptive walks...

  17. Modern optics in exceptionally preserved eyes of Early Cambrian arthropods from Australia

    Science.gov (United States)

    Lee, Michael S. Y.; Jago, James B.; García-Bellido, Diego C.; Edgecombe, Gregory D.; Gehling, James G.; Paterson, John R.

    2011-06-01

    Despite the status of the eye as an ``organ of extreme perfection'', theory suggests that complex eyes can evolve very rapidly. The fossil record has, until now, been inadequate in providing insight into the early evolution of eyes during the initial radiation of many animal groups known as the Cambrian explosion. This is surprising because Cambrian Burgess-Shale-type deposits are replete with exquisitely preserved animals, especially arthropods, that possess eyes. However, with the exception of biomineralized trilobite eyes, virtually nothing is known about the details of their optical design. Here we report exceptionally preserved fossil eyes from the Early Cambrian (~515 million years ago) Emu Bay Shale of South Australia, revealing that some of the earliest arthropods possessed highly advanced compound eyes, each with over 3,000 large ommatidial lenses and a specialized `bright zone'. These are the oldest non-biomineralized eyes known in such detail, with preservation quality exceeding that found in the Burgess Shale and Chengjiang deposits. Non-biomineralized eyes of similar complexity are otherwise unknown until about 85 million years later. The arrangement and size of the lenses indicate that these eyes belonged to an active predator that was capable of seeing in low light. The eyes are more complex than those known from contemporaneous trilobites and are as advanced as those of many living forms. They provide further evidence that the Cambrian explosion involved rapid innovation in fine-scale anatomy as well as gross morphology, and are consistent with the concept that the development of advanced vision helped to drive this great evolutionary event.

  18. Paleobiology of the Early Cambrian Yanjiahe Formation in Hubei Province of South China

    OpenAIRE

    Broce, Jesse

    2013-01-01

    Fossils recovered from limestones of the lower Cambrian (Stage 2-3) Yanjiahe Formation in Hubei Province, South China, recovered using acetic acid maceration, fracturing, and thin sectioning techniques were examined using a combination of analytical techniques, including energy dispersive spectroscopic (EDS) elemental mapping and micro-focus X-ray computed tomography (micro-CT). One important fossil recovered and analyzed with these techniques is a fossilized embryo. Fossilized animal embryos...

  19. Formation of the 'Great Unconformity' as a trigger for the Cambrian explosion.

    Science.gov (United States)

    Peters, Shanan E; Gaines, Robert R

    2012-04-19

    The transition between the Proterozoic and Phanerozoic eons, beginning 542 million years (Myr) ago, is distinguished by the diversification of multicellular animals and by their acquisition of mineralized skeletons during the Cambrian period. Considerable progress has been made in documenting and more precisely correlating biotic patterns in the Neoproterozoic-Cambrian fossil record with geochemical and physical environmental perturbations, but the mechanisms responsible for those perturbations remain uncertain. Here we use new stratigraphic and geochemical data to show that early Palaeozoic marine sediments deposited approximately 540-480 Myr ago record both an expansion in the area of shallow epicontinental seas and anomalous patterns of chemical sedimentation that are indicative of increased oceanic alkalinity and enhanced chemical weathering of continental crust. These geochemical conditions were caused by a protracted period of widespread continental denudation during the Neoproterozoic followed by extensive physical reworking of soil, regolith and basement rock during the first continental-scale marine transgression of the Phanerozoic. The resultant globally occurring stratigraphic surface, which in most regions separates continental crystalline basement rock from much younger Cambrian shallow marine sedimentary deposits, is known as the Great Unconformity. Although Darwin and others have interpreted this widespread hiatus in sedimentation on the continents as a failure of the geologic record, this palaeogeomorphic surface represents a unique physical environmental boundary condition that affected seawater chemistry during a time of profound expansion of shallow marine habitats. Thus, the formation of the Great Unconformity may have been an environmental trigger for the evolution of biomineralization and the 'Cambrian explosion' of ecologic and taxonomic diversity following the Neoproterozoic emergence of animals. PMID:22517163

  20. Cyclostratigraphy of Late Cambrian cyclic carbonates: an interbasinal field and modelling study, U.S.A.

    OpenAIRE

    Osleger, David Allen

    1995-01-01

    An interbasinal study of Late Cambrian cyclic carbonate successions in the Appalachian and Cordilleran passive margins, the Texas cratonic embayment and the southern Oklahoma aulacogen has provided controls on the simultaneous development of peritidal to subtidal meter-scale cycles and the larger scale depositional sequences on which they are superimposed. Fining-upward peritidal cycles grade seaward into coarsening-upward, shallow to deep subtidal cycles that form a continuum across...

  1. Discussion of the Porter hypothesis

    International Nuclear Information System (INIS)

    In the reaction to the long-range vision of RMNO, published in 1996, The Dutch government posed the question whether a far-going and progressive modernization policy will lead to competitive advantages of high-quality products on partly new markets. Such a question is connected to the so-called Porter hypothesis: 'By stimulating innovation, strict environmental regulations can actually enhance competitiveness', from which statement it can be concluded that environment and economy can work together quite well. A literature study has been carried out in order to determine under which conditions that hypothesis is endorsed in the scientific literature and policy documents. Recommendations are given for further studies. refs

  2. Thoughts on the Riemann hypothesis

    OpenAIRE

    Chaitin, G J

    2003-01-01

    The simultaneous appearance in May 2003 of four books on the Riemann hypothesis (RH) provoked these reflections. We briefly discuss whether the RH should be added as a new axiom, or whether a proof of the RH might involve the notion of randomness.

  3. Why is construction of an Ediacaran-Cambrian global paleogeography so difficult?

    Science.gov (United States)

    Evans, D. A.; Raub, T. D.; Maloof, A. C.

    2004-05-01

    The foremost answer to the above question is that high-precision global biostratigraphy extends only to Early Cambrian time. A more challenging issue concerns paleomagnetic data from the Ediacaran (proposed terminal Proterozoic period) and earliest Cambrian intervals: each paleocontinent's apparent polar wander path shows a large spread in poles, intriguingly distributed around a great circle (excepting Baltica, see below), and implying rates of paleolatitude translation or rotation far exceeding typical values from the Cenozoic. Oscillatory true polar wander (TPW) has been proposed to explain these great-circle distributions, but as more data are gathered the number of required episodes increases steadily. Another mechanism to explain such jumpy datasets is a persistently nonaxial geomagnetic field, with greatly amplified paleosecular variation; however, such an interpretation is unattractive to many geodynamicists. A third approach to explain the anomalous data is to discount them altogether; this is unsatisfactory because some of the most reliable results (e.g., Grenville dykes B component and Bunyeroo Formation pole) must be discarded in order to simplify the paths. We propose a new technique for Ediacaran-Cambrian continental reconstruction, which uses these intriguing great circle pole paths regardless of how they were generated. Each paleocontinent's path yields a best-fit great circle and corresponding pole. In the TPW interpretation, that pole describes the long-lived, common (equatorial) axis to the oscillatory rotations. Given that age constraints on the poles is generally so poor, we may reconstruct each continent to this axis with azimuthal freedom. This is topologically identical to the longitudinal degeneracy of standard paleomagnetic reconstructions, but in the case of TPW uncertainties in positions along the great circle represent uncertainties in paleolatitudes, hence climate zones. Analysis of the global Ediacaran-Cambrian paleomagnetic database

  4. The Cambrian Explosion of Popular 3D Printing

    OpenAIRE

    Juan Luis Chulilla Cano

    2011-01-01

    The unexpected appearance of 3D printing has caught many of technology analyst by surprise. In this paper we aim to provide a social context to the feedback loops that have generated this rapid evolution of technologies and skills involved in 3D printing, as well as and online communities related with 3D printing and the impact of this evolution on media an popular imaginary… and our near future.

  5. The Cambrian Explosion of Popular 3D Printing

    Directory of Open Access Journals (Sweden)

    Juan Luis Chulilla Cano

    2011-12-01

    Full Text Available The unexpected appearance of 3D printing has caught many of technology analyst by surprise. In this paper we aim to provide a social context to the feedback loops that have generated this rapid evolution of technologies and skills involved in 3D printing, as well as and online communities related with 3D printing and the impact of this evolution on media an popular imaginary… and our near future.

  6. Trajectory probability hypothesis density filter

    OpenAIRE

    García-Fernández, Ángel F.; Svensson, Lennart

    2016-01-01

    This paper presents the probability hypothesis density (PHD) filter for sets of trajectories. The resulting filter, which is referred to as trajectory probability density filter (TPHD), is capable of estimating trajectories in a principled way without requiring to evaluate all measurement-to-target association hypotheses. As the PHD filter, the TPHD filter is based on recursively obtaining the best Poisson approximation to the multitrajectory filtering density in the sense of minimising the K...

  7. Remarks upon neutrino mixing hypothesis

    International Nuclear Information System (INIS)

    It is shown that various versions of the neutrino mixing hypothesis and theoretical descriptions are in contradiction with generally accepted facts and principles. The possible alternative formulation of the neutrino oscillation theory there is also presented and it is shown under what conditions this theory reproduces the known oscillation probability formula. In our approach (flavor) neutrinos are Dirac particles. In the case of Majorana neutrinos, or the nonrelativistic neutrinos (i.e. relic neutrinos), the problem could be more complicated. (Authors)

  8. Hypothesis Formation, Paradigms, and Openness

    Directory of Open Access Journals (Sweden)

    Conrad P. Pritscher

    2008-01-01

    Full Text Available A part of hypothesis formation, while necessary for scientific investigation, is beyond direct observation. Powerful hypothesis formation is more than logical and is facilitated by mind­opening. As Percy Bridgeman, Nobel laureate, said, science is: “Nothing more than doing one's damnedest with one's mind, no holds barred.” This paper suggests more open schooling helps generate more open hypothesizing which helps one do one's damnedest with one's mind. It is hypothesized that a more open process of hypothesis formation may help schools and society forge new ways of living and learning so that more people more often can do their damnedest with their mind. This writing does not offer a new paradigm but rather attempts to elaborate on the notion that new paradigms are difficult to form without openness to what was previously quasi­unthinkable. More on these topics and issues is included in the author's Reopening Einstein's Thought: About What Can't Be Learned From Textbooks ­­to be published by Sense Publishers in June 2008.

  9. A new U/Pb date for the basal Meishucun section and implications for the age of the Cambrian explosion

    Science.gov (United States)

    Brooks, B. J.; Crowley, J. L.; Bowring, S. A.; Cervato, C.; Jin, Y.

    2006-12-01

    The Early Cambrian of southern China has long been recognized to record the spectacular transition from microscopic small shelly fossils to a fauna characterized by large, diverse higher bilaterians during part of the Early Cambrian evolutionary explosion. Understanding the timing and rate of this evolutionary transition has been aided through the integration of U/Pb geochronology into Cambrian fossil biozones, which has established strong tie-points between platforms. The Meishucun section (Yunnan, China) is one of the units that best preserves what could be considered the prelude to the Cambrian explosion. Several attempts at dating volcanic horizons within this section have resulted in U/Pb zircon dates that range from 538 to 525 Ma, making correlations to sections further afield problematic. This new high-precision U/Pb date of 533 Ma for Meishucun's Bed 5 is in broad agreement but considerably more precise than previous U/Pb ages. This indicates that the low diversity fauna of the Anabarites trisulcatus--Protohertzina anabarica zone persisted for no less than the first 9 m.y. of the Cambrian in China, and sets an additional lower bracket age for the emergence of higher bilaterians (e.g. trilobites, soft-bodied fauna).

  10. A Cambrian micro-lobopodian and the evolution of arthropod locomotion and reproduction

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The evolutionary success of arthropods, the most abundant and diverse animal group, is mainly based on their segmented body and jointed appendages, features that had evolved most likely already before the Cambrian. The first arthropod-like animals, the lobopodians from the Early Cambrian, were unsclerotized and worm-like, and they had unjointed tubular legs. Here we describe the first three-dimensionally preserved Cambrian lobopodian. The material presented of Orstenotubulus evamuellerae gen. et sp. nov. is the smallest and youngest of a lobopodian known. O. evamuellerae shows strikingly detailed similarities to Recent tardigrades and/or onychophorans in its cellular-structured cuticle and the telescopic spines. It also shows similarities to other, longer known lobopodians, but which are ten times as large as the new form. These similarities include the finely annulated body and legs, which is characteristic also for Recent onychophorans, and paired humps continuing into spines situated dorsally to the leg insertions, a feature lacking in the extant forms. The morphology of O. evamuellerae not only elucidates our knowledge about lobopodians, but also aids in a clearer picture of the early evolution of arthropods. An example is the single ventral gonopore between a limb pair of O. evamuellerae, which indicates that a single gonopore, as developed in onychophorans, tardigrades, pentastomids, myriapods and insects, might represent the plesiomorphic state for Arthropoda, while the paired state in chelicerates and crustaceans was convergently achieved. Concerning life habits, the lateral orientation of the limbs and their anchoring spines of the new lobopodian imply that early arthropods were crawlers rather than walkers.

  11. Molecular Fossils for Understanding Biodiversity During the Neoproterozoic-Cambrian Transition in China

    Science.gov (United States)

    Pi, Y.; Tuo, J.; McFadden, K.; Xiao, S.; Zhang, C. L.

    2005-12-01

    Neoproterozoic-Cambrian rocks in South China contain an extraordinary fossil record, including exceptionally well preserved animal embryos, acritarchs, and multi-cellular algae. The goal of this study was to evaluate the microbial diversity associated with these remarkably preserved fossil assemblages at the Neoproterozoic-Cambrian transition. Rock samples of 520-632 Ma in age were collected in the Yangtze Gorges area and southern Anhui Province, China. Samples were powdered and extracted for organic biomarkers. The content of bitumen A accounted for 4-16% of the rock material and most of it (49-79%) was asphaltenes. Saturated and aromatic hydrocarbons accounted for 2-6% and 1-3%, respectively. Analysis using GC-MS indicated the predominance of n-alkanes and less abundant isoprenoid alkanes in the saturated fractions. The n-alkanes were characterized by homologues dominated by C15-C17, which is consistent with the result of high thermal-evolution (Brocks et al., 2003. GCA 67:4321-4335). Hopanoids were present in less abundance and ranged from C29 to C32. A smaller amount of heavy-molecular-weight n-alkanes (C23-C39) was also detected, which indicated a source of high plants and must be contamination from younger organic matter. Still, patterns of variation can be detected among these samples. For example, the ratio of pristane to phytane was all greater than 1.0 except for one sample (JLW9.3) from Yangtze Gorges area. The results indicate that sample JLW9.3 might have been deposited in a reducing environment whereas the other samples might have been formed in relatively oxidative environments. The overall results, however, suggest that rock samples from the Neoproterozoic-Cambrian transition in China have gone through significant metamorphism; thus, understanding of microbial communities using molecular biomarkers in such altered rocks needs to be cautiously executed.

  12. The Urbilateria: Insights From Comparative Developmental Biology Into The Cambrian Radiation

    Science.gov (United States)

    Erwin, D. H.

    2004-12-01

    A critical issue in understanding the patterns of morphological and developmental evolution during the Cambrian radiation of animal body plans is the morphological complexity of the last common ancestor of the two great bilaterian clades, the protostomes and deuterostomes. Often known as the Urbilateria or the protostome-deuterostome ancestor (PDA) this node in metazoan phylogeny distinguishes the sponges and cnidarians from the bilaterian clades. Highly conserved developmental genes and complexes suggests that the PDA was a relatively complex organism, with dorsal-ventral and anterior-posterior patterning, eyes, appendages, heart, central nervous system, segmentation and other relatively complex morphological features. If this view of the PDA is correct, it has important implications for understanding the Cambrian radiation, for such a complex animal is likely to leave traces in the sedimentary record even if it lacked a durable skeleton. However, this interpretation of conserved developmental sequences may overestimate the extent to which homologies of developmental sequences implies morphological conservation. In other words, does the presence of the Nkx 2.5 gene in the PDA necessitate the presence of a heart, or simple the appearance of contractile muscles? If the latter, then the PDA may have been a much less complex organism. This latter view of developmental evolution suggests the PDA possessed a developmental toolkit, but that the specific implementation of these tools in specific body plans occurred after the PDA, within specific clades. Moreover, this view also strongly suggests that changes in the physical environment, or in ecological relationships, was primarily responsible for the evolutionary innovations seen in the Cambrian, rather than developmental innovations.

  13. Preliminary basin analysis of late Proterozoic-Cambrian post-rift strata, southeast Idaho thrust belt

    Energy Technology Data Exchange (ETDEWEB)

    Link, P.K.; Jansen, S.T.; Halimdihardja, P.; Lande, A.C.; Zahn, P.D.

    1987-08-01

    Strata of the Brigham Group in the Paris-Putnam plate of the southeastern Idaho thrust belt span the late Proterozoic-Cambrian boundary and consist of quartzose sandstone with subordinate pebble conglomerate and siltstone. The Brigham Group is overlain by fossiliferous Cambrian carbonate units that represent the transition from siliciclastic to carbonate deposition in the Cordilleran miogeocline. The Brigham Group contains four stratigraphic sequences bounded by regional disconformities. The lower sequence includes strata below the Brigham group (upper member, Pocatello Formation), plus the Papoose Creek Formation and most of the overlying Caddy Canyon Quartzite. This sequence is dominantly marine with shoreface and braided fluvial strata at the top. The first sequence is overlain disconformably by offshore sub-wave base marine strata of the upper Caddy Canyon Quartzite and Inkom Formation. This second sequence is entirely marine and is composed dominantly of siltstone with sandstone-filled channels. The third sequence comprises the Mutual Formation, an entirely braided fluvial and lacustrine unit. The fourth sequence (Sauk sequence) locally overlies the Mutual Formation with an erosional unconformity and consists of dominantly marine strata of the Camelback Mountain Quartzite, Gibson Jack Formation, Windy Pass Argillite, Twin Knobs Formation, and Sedgwick peak Quartzite. Correlations of these sequences to the McCoy Creek Group of eastern Nevada suggests uniform conditions of sea level and subsidence across the late Proterozoic-Cambrian Cordilleran miogeocline. This preliminary synthesis suggests the Brigham and McCoy Creek Groups are post-rift deposits, as indicated by regional persistence of facies, paleocurrents, and quartzose petrology.

  14. COGNITIVE INTERPRETATION OF INPUT HYPOTHESIS

    Institute of Scientific and Technical Information of China (English)

    WangHongyue; RenLiankui

    2004-01-01

    Krashen's Input Hypothesis, together with its earlier version, the Monitor Model is an influential theory in Second Language Acquisition research. In his studies, Krashen, on the one hand, emphasizes the part '“ comprehensible input” plays in learning a second language, on the other hand, he simply defines“comprehensible input” as “a little beyond the learner's current level”. What input can be considered as“a little beyond the learner's current level ”? Krashen gives no furtherexplanation. This paper tries to offer a more concrete and more detailed interpretation with Ausubel's Cognitive Assimilation theory.

  15. In search of the hypothesis.

    Science.gov (United States)

    Kaufman, J S; Cooper, R S

    1995-01-01

    Epidemiologic studies of racial differences sorely lack sound and explicit hypotheses. Race is a social convention, not a biological concept. Its careless use in epidemiology demonstrates a failure to generate appropriate hypotheses to study its role in health. Studies of hypertension in blacks illustrate the point. Two underlying pitfalls plague hypothesis generation: directionality involving the null and alternative hypotheses and circularity, where efforts to understand social factors have the effect of emphasizing racial differences. The proper prescription is to identify explicitly the hypotheses of interest, including their origins and implication. Images p662-a p665-a PMID:8570813

  16. Antiaging therapy: a prospective hypothesis

    Directory of Open Access Journals (Sweden)

    Shahidi Bonjar MR

    2015-01-01

    Full Text Available Mohammad Rashid Shahidi Bonjar,1 Leyla Shahidi Bonjar2 1School of Dentistry, Kerman University of Medical Sciences, Kerman Iran; 2Department of Pharmacology, College of Pharmacy, Kerman University of Medical Sciences, Kerman, Iran Abstract: This hypothesis proposes a new prospective approach to slow the aging process in older humans. The hypothesis could lead to developing new treatments for age-related illnesses and help humans to live longer. This hypothesis has no previous documentation in scientific media and has no protocol. Scientists have presented evidence that systemic aging is influenced by peculiar molecules in the blood. Researchers at Albert Einstein College of Medicine, New York, and Harvard University in Cambridge discovered elevated titer of aging-related molecules (ARMs in blood, which trigger cascade of aging process in mice; they also indicated that the process can be reduced or even reversed. By inhibiting the production of ARMs, they could reduce age-related cognitive and physical declines. The present hypothesis offers a new approach to translate these findings into medical treatment: extracorporeal adjustment of ARMs would lead to slower rates of aging. A prospective “antiaging blood filtration column” (AABFC is a nanotechnological device that would fulfill the central role in this approach. An AABFC would set a near-youth homeostatic titer of ARMs in the blood. In this regard, the AABFC immobilizes ARMs from the blood while blood passes through the column. The AABFC harbors antibodies against ARMs. ARM antibodies would be conjugated irreversibly to ARMs on contact surfaces of the reaction platforms inside the AABFC till near-youth homeostasis is attained. The treatment is performed with the aid of a blood-circulating pump. Similar to a renal dialysis machine, blood would circulate from the body to the AABFC and from there back to the body in a closed circuit until ARMs were sufficiently depleted from the blood. The

  17. A hypothesis on neutrino helicity

    CERN Document Server

    Sahin, I

    2016-01-01

    It is firmly established by experimental results that neutrinos are almost 100\\% longitudinally polarized and left-handed. It is also confirmed by neutrino oscillation experiments that neutrinos have tiny but non-zero masses. Since the helicity is not a Lorentz invariant quantity for massive particles, neutrinos can not be strictly left-handed. On the other hand, it is generally assumed that ultrarelativistic massive fermions can be described well enough by the Weyl equations. We discuss the validity of this assumption and propose a new hypothesis according to which neutrinos can be described by pure helicity states although they are not massless.

  18. A Molecular–Structure Hypothesis

    Directory of Open Access Journals (Sweden)

    Jan C. A. Boeyens

    2010-11-01

    Full Text Available The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its extension into four-dimensional space-time. It is concluded that a quantum molecule only has structure in four dimensions and that classical (Newtonian structure, which occurs in three dimensions, cannot be simulated by quantum-chemical computation.

  19. A Molecular–Structure Hypothesis

    Science.gov (United States)

    Boeyens, Jan C. A.

    2010-01-01

    The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its extension into four-dimensional space-time. It is concluded that a quantum molecule only has structure in four dimensions and that classical (Newtonian) structure, which occurs in three dimensions, cannot be simulated by quantum-chemical computation. PMID:21151437

  20. Vermicular fossils in the Early Cambrian Xidashan Formation in the Quruqtagh region of Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    YANG Ruidong; ZHANG Chuanlin; SONG Guoqi; LUO Xinrong

    2006-01-01

    Large amounts of vermicular fossils and a minor amount of sponge animal fossils have been found in the Early Cambrian Xidashan Formation in the region of Quruqtagh, Xinjiang. Vermicular fossils are generally more than 50 mm long and 0.3-1.4 mm wide; their wrinkled lamellae are microfine with 3-10 pieces within the length of every each millimeter. The fossils are considered to be Sabellidites cambriensis Sokolov (1965). The Xidashan Formation is the highest stratum in which Sabellidites occur, as has been so far reported.

  1. Organic carbon isotopes of the Sinian and Early Cambrian black shales on Yangtze Platform, China

    Institute of Scientific and Technical Information of China (English)

    李任伟; 卢家烂; 张淑坤; 雷加锦

    1999-01-01

    Organic matter of the Sinian and early Cambrian black shales on the Yangtze Platform belongs to the light carbon group of isotopes with the δ13C values from - 27 % to -35 % , which are lower than those of the contemporaneously deposited carbonates and phosphorites. A carbon isotope-stratified paleooceanographic model caused by upwelling is proposed, which can be used not only to interpret the characteristics of organic carbon isotopic compositions of the black shales, but also to interpret the paleogeographic difference in the organic carbon isotope compositions of various types of sedimentary rocks.

  2. Early Cambrian phosphatized blastula-and gastrula-stage animal fossils from southern Shaanxi

    Institute of Scientific and Technical Information of China (English)

    HUA Hong; CHEN Zhe; ZHANG Luyi

    2004-01-01

    Marine invertebrate animal embryos and their early developmental products are of great significance to the study of taxonomy and phylogeny of early animals. A great number of phosphatized globular fossils were collected from the early Cambrian Kuanchuanpu Member (upper Dengying Formation), southern Shaanxi, and a nearly complete developmental sequence--from a fertilized egg, via blastodisc formation, blastula development, blastodisc enlargement toward gastrulae, to tissue differentiation--can be discerned in this collection. This discovery provides unmatchable material for studies on the origin, taxonomy, radiation,and ontogeny of early metazoans.

  3. Neo proterozoic Cambrian in Uruguay: Dom Feliciano belt against Cuchilla Dionisio Terrane

    International Nuclear Information System (INIS)

    After an exhaustive bibliographic research about the subject, its was detected two opinion groups that beleive different evolution processes during Neoproterozoic Cambrian period in Uruguay.One of them beleives that litho-structural arrangement was generated in an unique Wilson cycle, the other one, supports that the genesis of nowaday structure is a tangential collision near 520 Ma; this point of view coincides with authors thinking 62 papers were consulted and many geological as some geochronological unpublished data were used in the analysis of the subject

  4. Origin and variability of the late Precambrian-Cambrian Athel Silicilyte, South Oman Salt Basin

    OpenAIRE

    Al Rajaibi, Ibrahim Mohamed amur

    2011-01-01

    The Precambrian-Cambrian Athel Silicilyte is an enigmatic chert unit of up to 390 m thick found as slabs (each slab typically 2 × 6 km across) entrapped within salt domes at a depth of 4-5 km in the South Oman Salt Basin. This formation is a prolific self-charged reservoir with high porosity (up to 34 %) and high oil saturation (80 %). Despite its economic value, the origin and the variability of this formation are not fully understood. This study therefore aims to investigate the variability...

  5. Rise to modern levels of ocean oxygenation coincided with the Cambrian radiation of animals.

    OpenAIRE

    Chen, X.; Ling, HF; Vance, D.; Shields-Zhou, GA; Zhu, M.; Poulton, SW; Och, LM; Jiang, SY; Li, D.; Cremonese, L; Archer, C.

    2015-01-01

    The early diversification of animals (∼630 Ma), and their development into both motile and macroscopic forms (∼575–565 Ma), has been linked to stepwise increases in the oxygenation of Earth's surface environment. However, establishing such a linkage between oxygen and evolution for the later Cambrian ‘explosion' (540–520 Ma) of new, energy-sapping body plans and behaviours has proved more elusive. Here we present new molybdenum isotope data, which demonstrate that the areal extent of oxygenat...

  6. A molecular and isotopic study of palaeoenvironmental conditions through the middle Cambrian in the Georgina Basin, central Australia

    Science.gov (United States)

    Pagès, Anais; Schmid, Susanne; Edwards, Dianne; Barnes, Stephen; He, Nannan; Grice, Kliti

    2016-08-01

    The Cambrian period marks an important point in Earth's history with profound changes in the ocean's biogeochemistry and the occurrence of the most significant evolutionary event in the history of life, the Cambrian explosion. The Cambrian explosion is described as a succession of complex cycles of extinctions and radiations. This study integrates biomarkers and their compound-specific stable carbon isotopes to investigate the palaeoenvironmental depositional conditions in middle Cambrian (Series 3) sedimentary rocks (Thorntonia Limestone, Inca Formation and Currant Bush Limestone) from two drillholes in the Undilla Sub-basin in the eastern Georgina Basin, central Australia. The occurrence of photic zone euxinia (PZE) was detected throughout these three formations by the identification of green sulfur bacteria Chlorobiaceae-derived biomarkers, including a series of 2,3,6-aryl isoprenoids and the intact biomarker isorenieratane. Pulses of enhanced PZE conditions were detected in two core intervals (90-110 mKB, Currant Bush Limestone and 170-200 mKB, Inca Formation) by an increase in the 2,3,6-aryl isoprenoids and C19 biphenyl concentrations. These enhanced PZE conditions were followed by blooms of phytoplankton, as demonstrated by the increase in algal-derived biomarker (i.e. pristane, phytane and the C19n-alkane) concentrations and compound-specific isotopes. These observations confirm that palaeoenvironmental conditions were similar to those reported for the Permian/Triassic and Triassic/Jurassic mass extinction events. The sterane distributions varied across the three formations reflecting possible changes in the phytoplanktonic communities through time. Although a rise in atmospheric oxygen during the Cambrian has been previously associated with the rapid evolution of metazoans, the ecological challenges related to widespread anoxia must have had a major influence on the evolution of life in Cambrian oceans.

  7. Cambrian Evolutionary Radiation: Context, correlation, and chronostratigraphy—Overcoming deficiencies of the first appearance datum (FAD) concept

    Science.gov (United States)

    Landing, Ed; Geyer, Gerd; Brasier, Martin D.; Bowring, Samuel A.

    2013-08-01

    Use of the first appearance datum (FAD) of a fossil to define a global chronostratigraphic unit's base can lead to intractable correlation and stability problems. FADs are diachronous—they reflect species' evolutionary history, dispersal, biofacies, preservation, collection, and taxonomy. The Cambrian Evolutionary Radiation is characterised by diachronous FADs, biofacies controls, and provincialism of taxa and ecological communities that confound a stable Lower Cambrian chronostratigraphy. Cambrian series and stage definitions require greater attention to assemblage zone successions and non-biostratigraphic, particularly carbon isotope, correlation techniques such as those that define the Ediacaran System base. A redefined, basal Cambrian Trichophycus pedum Assemblage Zone lies above the highest Ediacaran-type biotas (vendobionts, putative metazoans, and calcareous problematica such as Cloudina) and the basal Asteridium tornatum-Comasphaeridium velvetum Zone (acritarchs). This definition and the likely close correspondence of evolutionary origin and local FAD of T. pedum preserves the Fortune Head, Newfoundland, GSSP of the Cambrian base and allows the presence of sub-Cambrian, branched ichnofossils. The sub-Tommotian-equivalent base of Stage 2 (a suggested "Laolinian Stage") should be defined by the I'/L4/ZHUCE δ13C positive peak, bracketed by the lower ranges of Watsonella crosbyi and Aldanella attleborensis (molluscs) and the Skiagia ornata-Fimbrioglomerella membranacea Zone (acritarchs). The W. crosbyi and A. attleborensis FADs cannot define a Stage 2 base as they are diachronous even in the Newfoundland "type" W. crosbyi Zone. The Series 2 base cannot be based on a species' FAD owing to the provincialism of skeletalised metazoans in the Terreneuvian-Series 2 boundary interval and global heterochrony of the oldest trilobites. A Series 2 and Stage 3 (a suggested "Lenaldanian Series" and "Zhurinskyan Stage," new) GSSP base is proposed at the Siberian lower

  8. Isotopic compositions of small shelly fossil Anabarites from Lower Cambrian in Yangtze Platform of South China: Implications for palaeocean temperature

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Anabarites belong to small shelly fossils (SSF), which occur widely in the Lower Cambrian strata of Yangtze Platform in South China. They are phosphate shell in composition and represent the earliest stage of the Cambrian bioradiation of Bilateria, the socalled "Cambrian Explosion". In this study, we attempted to separate Anabarites fossils from Lower Cambrian dolostones, and we obtained samples of both the fossils (SSF) and the granular phosphates (GP). Isotopic analyses were performed on samples of SSF, GP, and matrix dolostone (DH-23). The results showed that the δ30 Si values of the quartz filling in fossils celoms, and the siliceous materials in granular phosphates are -0.6‰ and -0.7‰, which is different from normal sedimentary siliceous rocks from the Lower Cambrian strata (0-0.7‰) as reported by Li et al., but is consistent with the data for siliceous rocks and cherts of submarine hydrothermal origin. It is likely that a later hydrothermal replacement could have taken place in the SSF-bearing sedimentary rocks. The oxygen isotope values of the phosphate of SSF and GP are 16.8‰ and 17.0‰, respectively. These are significantly higher than the Neoproterozoic phosphate ores (10.9‰-13.9‰) as reported by Ling et al., hence, late diagenesis and hydrothermal replacement may not have caused a significant change in the oxygen isotope compositions of the small shelly fossils, and the calculated temperatures (25.4-26.3 ℃ ) for palaeo-seawater using a SSF phosphate oxygen isotope thermometer are therefore considered here as the upper limit of seawater temperature in the Early Cambrian ocean of the Yangtze Platform.

  9. The Debt Overhang Hypothesis: Evidence from Pakistan

    Directory of Open Access Journals (Sweden)

    Shah Muhammad Imran

    2016-04-01

    Full Text Available This study investigates the debt overhang hypothesis for Pakistan in the period 1960-2007. The study examines empirically the dynamic behaviour of GDP, debt services, the employed labour force and investment using the time series concepts of unit roots, cointegration, error correlation and causality. Our findings suggest that debt-servicing has a negative impact on the productivity of both labour and capital, and that in turn has adversely affected economic growth. By severely constraining the ability of the country to service debt, this lends support to the debt-overhang hypothesis in Pakistan. The long run relation between debt services and economic growth implies that future increases in output will drain away in form of high debt service payments to lender country as external debt acts like a tax on output. More specifically, foreign creditors will benefit more from the rise in productivity than will domestic producers and labour. This suggests that domestic labour and capital are the ultimate losers from this heavy debt burden.

  10. A hypothesis of earth quake

    CERN Document Server

    Tsai, Yeong-Shyeong

    2008-01-01

    Without a model, it is impossible for a geophysicist to study the possibility of forecasting earth quakes. In order to make a simple model, we make a hypothesis of earth quakes. The hypothesis is: (i) There are two kinds of earth quakes, one is the triggered breaking (earth quake), the other is spontaneous breaking (earth quake). (ii) Most major quakes in continental plates Eurasian Plate, North America Plate, South America Plate, Africa Plate and Australia Plate are triggered breaking. (iii) These triggered quakes are triggered by the movements of high pressure centers and low pressure centers of the atmosphere on continental plates. (iv) How can the movements of the high pressure centers trigger a quake? It depends on the extent of the high pressure center and the speed of the movement. Here, we stress high pressure center instead of low pressure center because it is dominated by high pressure center mostly. Of course, the boundary of the plates must have stored enough energy to have quakes, that is, near t...

  11. Sinian-Cambrian stratigraphic framework for shallow- to deep-water environments of the Yangtze Platform: an integrated approach

    Institute of Scientific and Technical Information of China (English)

    ZHU Maoyan; ZHANG Junming; Michael STEINER; YANG Aihua; LI Guoxiang; Bernd D. ERDTMANN

    2003-01-01

    The Sinian (Terminal Proterozoic) and Early Cambrian shallow- to deep-water sequences of the Yangtze Platform were investigated. Based on integrated lithostratigraphic, biostratigraphic, and other approaches, the shallow-water sequence from the base of the Sinian (base of the Doushantuo Formation) to the top of the Qiongzhusian (top of the Yu'anshan Formation) was subdivided into 12 stratigraphic intervals. These 12 intervals were applied in turn to the subdivision and correlation of the sequences present in various facies of the Yangtze Platform. The high-resolution stratigraphic framework here developed can serve as a time frame for ongoing multidisciplinary analyses of the "Cambrian explosion".

  12. The hexagon hypothesis: Six disruptive scenarios.

    Science.gov (United States)

    Burtles, Jim

    2015-01-01

    This paper aims to bring a simple but effective and comprehensive approach to the development, delivery and monitoring of business continuity solutions. To ensure that the arguments and principles apply across the board, the paper sticks to basic underlying concepts rather than sophisticated interpretations. First, the paper explores what exactly people are defending themselves against. Secondly, the paper looks at how defences should be set up. Disruptive events tend to unfold in phases, each of which invites a particular style of protection, ranging from risk management through to business continuity to insurance cover. Their impact upon any business operation will fall into one of six basic scenarios. The hexagon hypothesis suggests that everyone should be prepared to deal with each of these six disruptive scenarios and it provides them with a useful benchmark for business continuity. PMID:26420396

  13. Experimental mineralization of crustacean eggs: new implications for the fossilization of Precambrian–Cambrian embryos

    Directory of Open Access Journals (Sweden)

    D. Hippler

    2012-05-01

    Full Text Available Phosphatized globular microfossils from the Ediacaran and lower Cambrian of South China represent an impressive record of early animal evolution and development. However, their phylogenetic affinity is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are crucial for a reliable interpretation of their phylogenetic position. We conducted phosphatization experiments on eggs of the marbled crayfish Procambarus that indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope. Our experiments replicated the different preservational stages of degradation observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4 · 2H2O and calcite. The mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment were likely similar during fossilization of Cambrian embryos.

  14. Mantle insulation beneath the West African craton during the Precambrian-Cambrian transition

    Science.gov (United States)

    Doblas, Miguel; López-Ruiz, José; Cebriá, José-María; Youbi, Nasrrddine; Degroote, Eugenio

    2002-09-01

    At the time of the Precambrian-Cambrian transition, the West African craton underwent widespread magmatism, hydrothermal activity, and thermal rejuvenation. This tectonothermal event gave rise to an anorogenic “ring of fire” along the rim of this craton, following the Pan-African Brasiliano belt that was reactivated by extension and transtension. The thermal phenomena were due to the progressive peripheral release of mantle heat that had built up beneath this craton because of strong insulating conditions. The West African craton at the Precambrian-Cambrian transition can thus be envisioned in terms of a gigantic pressure-cooker with a thick blanketing lithospheric lid. These insulation processes triggered an unusually hot mantle that was channeled by edge-driven convection toward the peri West African craton extensional corridors and released through magmatic pressure-relief valves. Massive ice melting and outgassing of volcanic CO2 gave rise to a planet-scale sea-level rise, a greenhouse effect, and the end of the icehouse snowball Earth. These processes played an important role in the Phanerozoic explosion of life on Earth.

  15. Preliminary estimate of crustal extension during Cambrian rifting in the southern midcontinent

    Energy Technology Data Exchange (ETDEWEB)

    McConnell, D.A.; Gilbert, M.

    1985-01-01

    The Southern Oklahoma Aulacogen is a prominent rift extending 500+ km NW into the southern Midcontinent from the probably Cambrian plate margin. The biomodal igneous floor of the rift has been strongly structurally inverted and is now partially exposed in the core of the Wichita Mountains. Utilizing structural and stratigraphic patterns, and character of the igneous sequence, the style of tectonism and magnitude of displacement can be inferred for the initiation of the rift. Five possible extensional pulses can be related to specific igneous features although these could be part of one continuous episode lasting from about 565 to 525 mybp. Pennsylvanian transpressive faults are assumed to be reactivated Cambrian normal faults (and they may even have an earlier parentage). Using known thickness of continuous rhyolite (1.4 km), an initial width of 60 km, and a half-graben configuration, an estimate of extension is possible independent of bounding fault dip. For a brittle-ductile transition between 10 to 15 km, the brittle extension in the upper crust varies between 8-5%. Using the minimum mafic volume needed within the ductile lower crust (40,000 km/sup 3/), and a total crustal thickness of 35 to 45 km, the lower crust was extended 8-6% to 10-7%. The upper and lower crustal estimates of extension are in good agreement confirming a relatively shallow brittle-ductile transition. This is consistent with concomitant igneous activity and an enhanced geothermal gradient.

  16. The paleomagnetism of the salt pseudomorph beds of middle cambrian age from the salt range, West Pakistan

    NARCIS (Netherlands)

    Wensink, H.

    1972-01-01

    Oriented cores for a paleomagnetic investigation were collected from ten sites in the sedimentary redbeds of the Salt Pseudomorph Beds of Middle Cambrian age m the Salt Range near Khcwra. All samples were subjected to progressive, thermal demagnetization procedures which revealed the characteristic

  17. The paleomagnetism of the Salt Pseudomorph Beds of Middle Cambrian age from the Salt Range, West Pakistan

    NARCIS (Netherlands)

    Wensink, H.

    1972-01-01

    Oriented cores for a paleomagnetic investigation were collected from ten sites in the sedimentary redbeds of the Salt Pseudomorph Beds of Middle Cambrian age in the Salt Range near Khewra. All samples were subjected to progressive, thermal demagnetization procedures which revealed the characteristic

  18. Diversification of skeletal microstructures of organisms through the interval from the latest Precambrian to the Early Cambrian

    Institute of Scientific and Technical Information of China (English)

    FENG; Weimin(冯伟民); CHEN; Zhe(陈哲); SUN; Weiguo(孙卫国)

    2003-01-01

    Research on early skeletal fossils of southern Shaanxi Province and eastern Yunnan Province shows that the interval from the latest Precambrian to the Early Cambrian was an important period of significant changes in biomineralization of various organisms. The latest Precambrian skeletal fossils, represented by Cloudina, are characterized by cone-in-cone structures, relatively high content of organic matter, and various shell shapes with obvious plastic deformation. In the Early Cambrian the skeletal organisms, consisting of phosphatic, carbonate and siliceous minerals, began to appear in great abundance and to distribute widely. Moreover, microstructure of these skeletal organisms appeared to have been diversified, for example, main types of recent molluscan microstructures, such as prismatic, lamello-fibrillar and regular foliated structures, were already developed at that time; fibrous structures further diversified, such as lamello-fibrillas indicative of mollusks and fibre bundles of hyoliths; there were at least two layers in a shell. This shows that biologically controlled biomineralization had played the main role in the Early Cambrian and it laid a key foundation for formation of the true shell of diverse invertebrates, giving rise to the "Cambrian explosion".

  19. Estimation of porosity of Khewra sandstone of cambrian age by using helium porosimeter and its application in reservoir evaluation

    International Nuclear Information System (INIS)

    Estimation of petrophysical properties of the rock formations played decisive role in all the processes of petroleum exploration. The Cambrian sequence is well established as reservoir rocks in the various parts of the world from where petroleum is being tapped. The Cambrian sequence has been encountered in the Potwar area and limited petroleum is being produced from the Adhi Oil Field. The Khewra Sandstone of the Cambrian sequence is outcropped in the Khewra Gorge, Salt Range Pakistan below an unconformity qf the Tobra Formation. For the assessment of porosity and reservoir characterization Helium Porosimeter has been used, six samples Qf the upper horizon were collected from various locations of the Khewra Gorge and the Khewra Choha Sadden Shah road side section; cores were prepared from these samples according to the instrument standard. The results of this study revealed that the upper horizon Qf the Khewra Sandstone Formation has good porosity ranging from 18.76% to 21.07%, porosity varied in different parts of the formation. These results are in good agreement with the internationally reported values for petroleum reservoir of the Cambrian sandstone. (author)

  20. The structure and sedimentary sequence of intracratonic rift from Late Sinian to Early Cambrian in the Sichuan Basin, South China

    Science.gov (United States)

    Gu, Zhidong; Zhang, Baomin; Lu, Weihu; Zhai, Xiufen; Jiang, Hua

    2016-04-01

    Sichuan Basin is located in the northwest of Upper Yangtze craton of South China, and there is developed an intracratonic rift from Late Sinian to Early Cambrian in the middle of Sichuan Basin, and the paper systematically discusses the structure and sedimentary sequence of the intracratonic rift based on the fields, drilling and seismic data, and so on. Detailed structural interpretation of 2D and 3D seismic profiles displays the development of two stages of intracratonic rift due to regional extension with the depth of 2000m, and plane distribution of intracratonic rift presents the V-pattern from the northwest to the southeast in the middle of Sichuan Basin with the width from 100km to 20km. The drilling data from the intracratonic rift shows the obvious thinning of Upper Sinian and thickening of Lower Cambrian. And field outcrops situated in the intracratonic rift reveal that the Upper Sinian is mainly composed of siliceous rock, shale and carbonate, with the thickness of less than 100m, but the thickness of Upper Sinian on the platform reaches 1000m by contrast; They also reveals that Lower Cambrian is mainly composed of shale, mudstone, and siltstone with the development of gravity current, and the thickness of Lower Cambrian reaches 2000m. The formation of intracratonic rift may be initiated by pre-existing basement weakness zone and deep mantle dynamics.

  1. Glauconitic deposits at Julegård on the south coast of Bornholm, Denmark dated to the Cambrian

    DEFF Research Database (Denmark)

    Clemmensen, Lars B; Bromley, Richard Granville; Holm, Paul Martin

    2011-01-01

    the deposits belong to the Lower Cambrian Norretorp Member of the Læså Formation. The shallow marine deposits are strongly bioturbated, but only a single ichnoassociation is represented. The ichnogenus is referable to either Trichophycus Miller and Dyer, 1878 or Teichichnus Seilacher, 1955. Rare...

  2. Decoupled evolution of soft and hard substrate communities during the Cambrian Explosion and Great Ordovician Biodiversification Event.

    Science.gov (United States)

    Buatois, Luis A; Mángano, Maria G; Olea, Ricardo A; Wilson, Mark A

    2016-06-21

    Contrasts between the Cambrian Explosion (CE) and the Great Ordovician Biodiversification Event (GOBE) have long been recognized. Whereas the vast majority of body plans were established as a result of the CE, taxonomic increases during the GOBE were manifested at lower taxonomic levels. Assessing changes of ichnodiversity and ichnodisparity as a result of these two evolutionary events may shed light on the dynamics of both radiations. The early Cambrian (series 1 and 2) displayed a dramatic increase in ichnodiversity and ichnodisparity in softground communities. In contrast to this evolutionary explosion in bioturbation structures, only a few Cambrian bioerosion structures are known. After the middle to late Cambrian diversity plateau, ichnodiversity in softground communities shows a continuous increase during the Ordovician in both shallow- and deep-marine environments. This Ordovician increase in bioturbation diversity was not paralleled by an equally significant increase in ichnodisparity as it was during the CE. However, hard substrate communities were significantly different during the GOBE, with an increase in ichnodiversity and ichnodisparity. Innovations in macrobioerosion clearly lagged behind animal-substrate interactions in unconsolidated sediment. The underlying causes of this evolutionary decoupling are unclear but may have involved three interrelated factors: (i) a Middle to Late Ordovician increase in available hard substrates for bioerosion, (ii) increased predation, and (iii) higher energetic requirements for bioerosion compared with bioturbation. PMID:27247396

  3. Decoupling of body-plan diversification and ecological structuring during the Ediacaran-Cambrian transition: evolutionary and geobiological feedbacks.

    Science.gov (United States)

    Mángano, M Gabriela; Buatois, Luis A

    2014-04-01

    The rapid appearance of bilaterian clades at the beginning of the Phanerozoic is one of the most intriguing topics in macroevolution. However, the complex feedbacks between diversification and ecological interactions are still poorly understood. Here, we show that a systematic and comprehensive analysis of the trace-fossil record of the Ediacaran-Cambrian transition indicates that body-plan diversification and ecological structuring were decoupled. The appearance of a wide repertoire of behavioural strategies and body plans occurred by the Fortunian. However, a major shift in benthic ecological structure, recording the establishment of a suspension-feeder infauna, increased complexity of the trophic web, and coupling of benthos and plankton took place during Cambrian Stage 2. Both phases were accompanied by different styles of ecosystem engineering, but only the second one resulted in the establishment of the Phanerozoic-style ecology. In turn, the suspension-feeding infauna may have been the ecological drivers of a further diversification of deposit-feeding strategies by Cambrian Stage 3, favouring an ecological spillover scenario. Trace-fossil information strongly supports the Cambrian explosion, but allows for a short time of phylogenetic fuse during the terminal Ediacaran-Fortunian. PMID:24523279

  4. Memory in astrocytes: a hypothesis

    Directory of Open Access Journals (Sweden)

    Caudle Robert M

    2006-01-01

    Full Text Available Abstract Background Recent work has indicated an increasingly complex role for astrocytes in the central nervous system. Astrocytes are now known to exchange information with neurons at synaptic junctions and to alter the information processing capabilities of the neurons. As an extension of this trend a hypothesis was proposed that astrocytes function to store information. To explore this idea the ion channels in biological membranes were compared to models known as cellular automata. These comparisons were made to test the hypothesis that ion channels in the membranes of astrocytes form a dynamic information storage device. Results Two dimensional cellular automata were found to behave similarly to ion channels in a membrane when they function at the boundary between order and chaos. The length of time information is stored in this class of cellular automata is exponentially related to the number of units. Therefore the length of time biological ion channels store information was plotted versus the estimated number of ion channels in the tissue. This analysis indicates that there is an exponential relationship between memory and the number of ion channels. Extrapolation of this relationship to the estimated number of ion channels in the astrocytes of a human brain indicates that memory can be stored in this system for an entire life span. Interestingly, this information is not affixed to any physical structure, but is stored as an organization of the activity of the ion channels. Further analysis of two dimensional cellular automata also demonstrates that these systems have both associative and temporal memory capabilities. Conclusion It is concluded that astrocytes may serve as a dynamic information sink for neurons. The memory in the astrocytes is stored by organizing the activity of ion channels and is not associated with a physical location such as a synapse. In order for this form of memory to be of significant duration it is necessary

  5. The oxidative hypothesis of senescence

    Directory of Open Access Journals (Sweden)

    Gilca M

    2007-01-01

    Full Text Available The oxidative hypothesis of senescence, since its origin in 1956, has garnered significant evidence and growing support among scientists for the notion that free radicals play an important role in ageing, either as "damaging" molecules or as signaling molecules. Age-increasing oxidative injuries induced by free radicals, higher susceptibility to oxidative stress in short-lived organisms, genetic manipulations that alter both oxidative resistance and longevity and the anti-ageing effect of caloric restriction and intermittent fasting are a few examples of accepted scientific facts that support the oxidative theory of senescence. Though not completely understood due to the complex "network" of redox regulatory systems, the implication of oxidative stress in the ageing process is now well documented. Moreover, it is compatible with other current ageing theories (e.g., those implicating the mitochondrial damage/mitochondrial-lysosomal axis, stress-induced premature senescence, biological "garbage" accumulation, etc. This review is intended to summarize and critically discuss the redox mechanisms involved during the ageing process: sources of oxidant agents in ageing (mitochondrial -electron transport chain, nitric oxide synthase reaction- and non-mitochondrial- Fenton reaction, microsomal cytochrome P450 enzymes, peroxisomal β -oxidation and respiratory burst of phagocytic cells, antioxidant changes in ageing (enzymatic- superoxide dismutase, glutathione-reductase, glutathion peroxidase, catalase- and non-enzymatic glutathione, ascorbate, urate, bilirubine, melatonin, tocopherols, carotenoids, ubiquinol, alteration of oxidative damage repairing mechanisms and the role of free radicals as signaling molecules in ageing.

  6. The First Paleomagnetic data from the Cambrian basalts of Henrietta Island (De Long Archipelago, Arctic Ocean)

    Science.gov (United States)

    Metelkin, D. V.; Zhdanova, A.; Vernikovskiy, V. A.; Matushkin, N. Y.

    2015-12-01

    Henrietta Island in De Long archipelago (East-Siberian sea) still remains poorly studied geologically but last investigations show that its volcano-sedimentary sequences can help reconstruct tectonic evolution of East Russian Arctic in Early Paleozoic stage. The deposits lying on Precambrian basements are deformed to varying degrees and intruded by mafic dykes.The study was carried out on two basaltic lava flows whose 40Ar/39Ar age is 520.6±9.5 Ma. Previously the age of these basalts was assumed Cretaceous. According to available data the underlaying sediments contain zircons with Cambrian and Ordovician ages but all boundaries between these basalts and other strata are tectonic. So we suppose the age of basalts as Middle Cambrian but more precise geochronological data are required. All magnetic measurements were performed at the Laboratory of Geodynamics and Paleomagnetism of Institute of Petroleum Geology and Geophysics (Novosibirsk). Basalt samples has relatively high magnetic susceptibility values varying from 5x10-4 to 180x10-4SI units. NRM values range is from 3 to 170 mA/m. Petromagnetic parameters including also coercive characteristics point at the good potentially preserving primary magnetization. Stepwise thermal demagnetization permits to isolate characteristic components of magnetization and calculate mean directions in two lava flows: 1. Ds=294.3°, Is=29.1°, K=81.1, α95=5.1; 2. Ds=301.0°, Is=28.3°, K=34.4, α95=7.9). The mean paleomagnetic pole has coordinates: Plat=20.9°, Plong = 42.6°, dp/dm=14.3/7.9. Paleolatitude was defined as 15.3° but the question of the hemisphere for De Long Islands is open yet. In case of south hemisphere in Middle Cambrian according to available paleomagnetic data De Long islands could be placed close to Taimyr margin of Siberia and in case of northern hemisphere they may be located near south (in present-day coordinates) margin of Siberia. The work was supported by grant RFBR 14-05-31399 and Russian Research Fund

  7. Lower Cambrian Black Rock Series and Associated Stratiform Deposits in Southern China

    Institute of Scientific and Technical Information of China (English)

    陈南生; 范德廉; 等

    1990-01-01

    Widespread in more than ten provinces of southern China are the Lower Cambrian black argillaceous-arenaceous rock series consisting of black carbonaceous shales,black carbonaceousargillo-siliceous rocks,black carbonaceous silicolite and black silicolite and black carbonaceous argillaceous siltstone.The Ni,Mo,V,Cu,U,Ba,Ag,P contents of these series are usually several to tens of times higher than their average values in shales.As viewed from lithological sequence,element association and evolution,these black series can be diveided into two types.There occur a variety of deposits in the black rock series,such as phosphorite deposits,Ni-Mo-V polymetal deposits and "Stone coal" seams.According to ore composition,texture and structure,the phosphorite deposits fall into three types,i.e.,thick-bedded,lenticular and nodular,The Ni-Mo-V polymetal deposits,V deposits and reworked sedimentary CU-U-Cd polymetal deposits in terms of their element assiciation and ore genesis.As for the stratiform deposits in the black rock series,three mineralization stages have been recognized,i.e.,the formation of phosphorite deposits,of Ni-Mo polymetal deposits and of V-Cu-U-Cd polymetal deposits as well as of ":stone coal" seams.Evidence strongly suggests that lower organisms have played an important role in mineralization. Our studies indicate that the Lower Cambrian black argillaceous-arenaceous rock series in southern China and their associated stratiform deposits occur generally in the basal parts of a big sedimentary cycle,i.e.,the initial period of a transgression,or in the fine detrital-siliceous formation between two carbonate formatons,formed in a humid climatic zone between two arid ones.As for the environment of deposition,it is suggested that the Lower Cambrian black argillaceous-arenaceous rock series and associated stratiform deposits(excluding thick-bedded phosphorite deposits)were formed mainly in a restricted and poorly-fed sea basin of stagnant shallow water containing

  8. Female Survival Advantage Relates to Male Inferiority Rather Than Female Superiority: A Hypothesis Based on the Impact of Age and Stroke Severity on 1-Week to 1-Year Case Fatality in 40,155 Men and Women

    DEFF Research Database (Denmark)

    Olsen, T.S.; Andersen, Klaus Kaae

    2010-01-01

    until death or censoring. Case fatality (stratified by 1 week, 1 month, 3 months, and 1 year) in men and women was correlated with age and stroke severity. Adjustment for cardiovascular risk factors was performed by means of multivariate regression analysis. Results: A total of 20,854 (51.9%) men and 19......,301 (48.1%) women were registered. Women were significantly older than men at the time of stroke (74.5 vs 69.7 years, respectively; P <0.001) and had signficantly more severe strokes, as expressed by the mean SSS score (39.6 vs 43.3; P <0.001). Stratification of 1-week to 1-year case fatality according to...... patients with severe as well as mild strokes, but not in those younger than age 50 years. Conclusions: Our findings dispute the effects of female sex hormones as the underlying cause of female survival superiority over men. Instead, we propose the hypothesis that the progressive deficiency of male sex...

  9. The feeling of agency hypothesis: a critique

    DEFF Research Database (Denmark)

    Grünbaum, Thor

    2015-01-01

    A dominant view in contemporary cognitive neuroscience is that low-level, comparator-based mechanisms of motor control produce a distinctive experience often called the feeling of agency (the FoA-hypothesis). An opposing view is that comparator-based motor control is largely non-conscious and not...... associated with any particular type of distinctive phenomenology (the simple hypothesis). In this paper, I critically evaluate the nature of the empirical evidence researchers commonly take to support FoA-hypothesis. The aim of this paper is not only to scrutinize the FoA-hypothesis and data supposed to...... support it; it is equally to argue that experimentalists supporting the FoA-hypothesis fail to establish that the experimental outcomes are more probable given the FoA-hypothesis than given the simpler hypothesis....

  10. The anatomy, taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans

    Science.gov (United States)

    Dong, X.-P.; Bengtson, S.; Gostling, N.J.; Cunningham, J.A.; Harvey, T.H.P.; Kouchinsky, A.; Val'Kov, A.K.; Repetski, J.E.; Stampanoni, M.; Marone, F.; Donoghue, P.C.J.

    2010-01-01

    Markuelia is a vermiform, annulated introvertan animal known as embryonic fossils from the Lower Cambrian to Lower Ordovician. Analysis of an expanded and revised dataset for Introverta shows that the precise position of Markuelia within this clade is dependent on the taxa included. As a result, Markuelia is assigned to the scalidophoran total group to reflect uncertainty as to whether it is a stem-scalidophoran or a stem-priapulid. The taxonomy of the genus is revised to provide an improved taxonomic framework for material assigned to Markuelia. Five species are recognized: M. secunda Val'kov, M. hunanensis Dong and Donoghue, M. lauriei Haug et al., M. spinulifera sp. nov. and M. waloszeki sp. nov. Finally, the preservation of Markuelia is evaluated in the light of both the taphonomy of the fossil embryos themselves and the experimental taphonomy of the priapulid Priapulus caudatus, which has been proposed as both a close relative and an anatomical analogue of Markuelia. ?? The Palaeontological Association.

  11. Ediacarian sponge spicule clusters from southwestern Mongolia and the origins of the Cambrian fauna

    Science.gov (United States)

    Brasier, Martin; Green, Owen; Shields, Graham

    1997-04-01

    Carbon and strontium isotopic data are used to show that the earliest sponge spicule clusters and associated phosphatic sediments (with Anabarites) from southwestern Mongolia are of Ediacarian age. Spicule morphologies include bundles of oxeas arranged in three-dimensional quadrules, linked together at junctions by tetracts, pentacts, hexacts, or polyactines. All are referred to the Phylum Porifera, Class Hexactinellida. These sponge spicules provide the oldest remains that can be assigned without question to an extant phylum, and also the first firm evidence for filter feeding and metazoan silica biomineralization in the fossil record. It is suggested that siliceous and phosphatic members of the “Cambrian fauna” may have had their origins in eutrophic and outer shelf facies of the Late Proterozoic.

  12. Petrographic and geochemical composition of kerogen in the Furongian (U. Cambrian) Alum Shale, central Sweden

    DEFF Research Database (Denmark)

    Sanei, H.; Petersen, H. I.; Schovsbo, N. H.; Jiang, C.; Goodsite, M. E.

    2014-01-01

    degradation of labile kerogen by radiation from uranium-rich minerals. The higher degree of aromaticity in Alum shale suggests lower than expected oil-proneness. The results of this study suggest that the Alum Shale is a gas-prone source producing aromatic hydrocarbon mixtures with an unexpectedly low......This paper presents an integrated geochemical and petrological study of the Hällekis-1 core from the Furongian (upper Cambrian) Alum shales in central Sweden to characterise organic matter composition, depositional environment, and potential hydrocarbon generation capability. The results show that...... organic-rich Alum Shale (TOC: 8.9-28.0. wt.%) contains mainly immature, predominantly algal-derived kerogen with unusually reduced hydrocarbon generation potential as suggested by relatively low Hydrogen Index (HI) values (HI: 251-471. mg HC/g TOC) and high degree of aromaticity. In the absence of thermal...

  13. Ferroan dolomite cement in Cambrian sandstones: burial history and hydrocarbon generation of the Baltic sedimentary basin

    DEFF Research Database (Denmark)

    Sliaupa, S.; Cyziene, J.; Molenaar, Nicolaas;

    2008-01-01

    The conditions and timing of carbonate cementation in Cambrian sandstones of the Baltic sedimentary basin were determined by oxygen and carbon stable isotope and chemical data in combination with optical and cathodoluminescence petrographic studies. Studied samples represent a range in present...... burial depth from 340 to 2150 m. The carbonate cement is dominantly ferroan dolomite that occurs as dispersed patches of poikilotopic crystals. Temperatures of dolomite precipitation, based on delta O-18 values, range from 27 degrees C in the shallow buried to 95 degrees C in the deep buried sandstones....... The burial history modelling points to development of most of the dolomite cement during rapid Silurian-Devonian subsidence and Carboniferous-early Permian uplift. A wide range of precipitation temperatures indicate that temperature was not a major factor in triggering the carbonate cementation. Dolomite...

  14. Extensive Cambrian braidplain sedimentation: Insights from the southwestern Cordillera, U. S. A

    Energy Technology Data Exchange (ETDEWEB)

    Fedo, C.M. (Virginia Polytechnic Inst. and State Univ., Blacksburg (United States)); Prave, A.R. (City College of New York, NY (United States))

    1991-02-01

    The Lower to Middle Cambrian time-transgressive coarse terrigenous clastic rocks that form the basal part of the Cordilleran cratonal (Tapeats Sandstone) to miogeoclinal (Wood Canyon Formation, Zabriskie Quartzite) succession have long been though of as products of marine sediment dispersion processes. The authors' recent facies analyses and reinterpretation suggest, instead, that those strata record an extensive continental braidplain which interacted with marine environments. Marine deposits are distinguished by the presence of trace fossils and abundant wave- and tide-influenced sedimentary structures. The most abundant braidplain facies are those assigned a fluvial origin. Coarser, more poorly sorted deposits are feldspathic, whereas finer, better sorted deposits are quartzitic. Beds typically are wedge- and channel-shaped and their width ranges inversely to grain size; channels in conglomeratic layers are relatively narrow (< 20 m wide), whereas those in sand-dominated intervals are shallow (< 1 m) and wide (tens of meters) with broadly concave-up bases. Trough cross-strata and flat laminations are common with planar cross-strata less common. Basal lags and cyclic arrangement of sedimentary structures are rare, although thinning- and fining-upward intervals are developed locally. Paleocurrent indicators across the entire region are west directed and of low variance. They suggest that the dominant mode of sediment transport was by down-channel migrating dunes and that subordinate processes included sheet flow (flat laminated sandstones) and eolian deflation (textural bimodality). These consistent paleocurrent directions attest to the remarkable longevity (Early through Middle Cambrian) of an extensive, westward-draining fluvial system.

  15. Evidence for microbial dissolution of pyrite from the Lower Cambrian oolitic limestone, South China

    Directory of Open Access Journals (Sweden)

    W. Liu

    2011-03-01

    Full Text Available The oxidative dissolution of the sulphide mineral pyrite (FeS2 has been of significant interest since it affects global geochemical cycles, generates acid mine drainage, and is used in industrial metal extraction. Several different groups of prokaryotes are known to catalyze the dissolution of pyrite and use the free energy generated from the oxidation, which may result in the dissolution of the mineral and the precipitation of the secondary ferric iron minerals either on the cell surface or is separated from the cells. However, straightforward evidence for such metabolic process in the ancient sediments is rare. Here we report pyrite crystals from the Lower Cambrian oolitic limestones that show indications of microbial erosion in various degrees. Erosion pits and tubular micro-tunnels with characteristic shapes and sizes in our samples are generally similar to those obtained from the laboratory studies on the oxidative dissolution of pyrite by iron-oxidizing bacteria. Diagenetic examination demonstrates that the bioerosion predates the consolidation of the limestone. In addition, bacillus-sized and -shaped microfossils encrusted with iron oxides are present in our samples, which are very likely to be fossilized sheaths produced by iron-oxidizing bacteria. Our findings indicate that the microbial oxidative dissolution of pyrite existed in the Cambrian shallow marine carbonate sediments. Furthermore, we suggest that characteristic pitting patterns on the pyrite crystals from ancient sediments are an important clue to trace the evolution of life, in particular, the evolution of metabolism like microbial iron oxidation in the remote past on our planet, independent of biomarkers, isotopic signals and body fossils as well.

  16. Origin of northern Gondwana Cambrian sandstone revealed by detrital zircon SHRIMP dating

    Science.gov (United States)

    Avigad, D.; Kolodner, K.; McWilliams, M.; Persing, H.; Weissbrod, T.

    2003-01-01

    Voluminous Paleozoic sandstone sequences were deposited in northern Africa and Arabia following an extended Neoproterozoic orogenic cycle that culminated in the assembly of Gondwana. We measured sensitive high-resolution ion microprobe (SHRIMP) U-Pb ages of detrital zircons separated from several Cambrian units in the Elat area of southern Israel in order to unravel their provenance. This sandstone forms the base of the widespread siliciclastic section now exposed on the periphery of the Arabian-Nubian shield in northeastern Africa and Arabia. Most of the detrital zircons we analyzed yielded Neoproterozoic concordant ages with a marked concentration at 0.55–0.65 Ga. The most likely provenance of the Neoproterozoic detritus is the Arabian-Nubian shield; 0.55–0.65 Ga was a time of posttectonic igneous activity, rift-related volcanism, and strike-slip faulting there. Of the zircons, 30% yielded pre-Neoproterozoic ages grouped at 0.9–1.1 Ga (Kibaran), 1.65–1.85 Ga, and 2.45–2.7 Ga. The majority of the pre-Neoproterozoic zircons underwent Pb loss, possibly as a consequence of the Pan-African orogeny resetting their provenance. Rocks of the Saharan metacraton and the southern Afif terrane in Saudi Arabia (∼1000 km south of Elat) are plausible sources of these zircons. Kibaran basement rocks are currently exposed more than 3000 km south of Elat (flanking the Mozambique belt), but the shape of the detrital zircons of that age and the presence of feldspar in the host sandstone are not fully consistent with such a long-distance transport. Reworking of Neoproteorozoic glacial detritus may explain the presence of Kibaran detrital zircons in the Cambrian of Elat, but the possibility that the Arabian-Nubian shield contains Kibaran rocks (hitherto not recognized) should also be explored.

  17. Detrital zircon geochronology of Neoproterozoic to Middle Cambrian miogeoclinal and platformal strata: Northwest Sonora, Mexico

    Science.gov (United States)

    Gross, E.L.; Stewart, John H.; Gehreis, G.E.

    2000-01-01

    Eighty-five detrital zircon grains from Mesoproterozoic and/or Neoproterozoic to Middle Cambrian sedimentary strata in northwest Sonora, Mexico, have been analyzed to determine source terranes and provide limiting depositional ages of the units. The zircon suites from the Mesoproterozoic and/or Neoproterozoic El Alamo Formation and El Aguila unit yield ages between 1.06 Ga and 2.67 Ga, with predominant ages of 1.1 to 1.2 Ga. Zircons from the Lower? and Middle Cambrian Bolsa Quartzite show age groups from 525 Ma to 1.63 Ga, with a dominant population of 1.1 to 1.2 Ga grains. Grains older than 1.2 Ga in the samples were most likely derived from basement terranes and ???1.4 Ga granitic bodies of the southwest U.S. and northwest Mexico. It is also possible that the sediments were transported from the south, although source rocks of the appropriate age are not presently exposed south of the study area in northern Mexico. Three possibilities for the dominant 1.1 to 1.2 Ga grains include derivation from: (I) exposures of the Grenville belt in southern North America, (2) local 1.1-1.2 Ga granite bodies, or (3) a southern source, such as the Oaxaca terrane, that was subsequently rifted away. Sampling of additional units in the western U.S. and northern Mexico may help resolve the ambiguity surrounding the source of the 1.1 to 1.2 Ga grains.

  18. The Meers Fault in Southern Oklahoma: Holocene Movements on a Fault with Pennsylvanian and Cambrian Linages

    Science.gov (United States)

    Keller, G. R.; Holland, A. A.; Luza, K.; Oldow, J. S.; Crain, K.

    2011-12-01

    The Meers fault and subparallel fault strands in southern Oklahoma is the southernmost element of the complex and massive (>10 km of throw) frontal fault zone that forms the boundary between the Anadarko basin, which is the deepest intra-continental basin in the United States, and the uplifted Cambrian igneous rocks of the Wichita Mountains. The Wichita uplift is evidence of extraordinary Pennsylvanian intra-plate deformation along the trend of the Southern Oklahoma aulacogen, which is a classic example of a failed and massively inverted rift. The Meers Fault is the best-documented Holocene fault scarp east of Colorado and probably represents reactivation of a Pennsylvanian oblique thrust that in turn is likely to be an inverted Cambrian normal fault. The magnitude of these structures is shown on images from 3-D industry seismic reflection data ~25 km northwest of the northwestern mapped extent of the Meers fault that indicate the Pennsylvanian structure, or a northern strand of it, has a reverse throw of ~6km at depth. The fault displays a conspicuous and continuous scarp that is at least 25 km long and is evident in air photos and 1:100,000 scale geologic mapping, but this feature is not well mapped in detail beyond the area of trenching studies conducted in the 1980's. In the Holocene, 3-5 m of vertical surface displacement has been documented and left-lateral strike slip displacement on the fault is 2-3 times greater than the vertical displacement. During this movement, Quaternary soils along the fault were folded and ruptured, and the scarp has dammed small gullies where fine-grained alluvium has collected and has been used in the dating efforts. The most recent movement occurred (1100-1300 y ago) with a variety of earlier events having been proposed. As such, this fault represents one of the highest potential seismic hazards in the central/eastern United States.

  19. Geodatabase of the datasets used to represent the four aquifer subunits of the Cambrian-Ordovician aquifer system, Illinois, Iowa, Michigan, Minnesota, and Wisconsin

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This geodatabase includes spatial datasets that represent the Cambrian-Ordovician aquifer system in the States of Wisconsin, Michigan, Minnesota, Iowa, and...

  20. Reassessing the Trade-Off Hypothesis

    DEFF Research Database (Denmark)

    Rosas, Guillermo; Manzetti, Luigi

    2015-01-01

    Do economic conditions drive voters to punish politicians that tolerate corruption? Previous scholarly work contends that citizens in young democracies support corrupt governments that are capable of promoting good economic outcomes, the so-called trade-off hypothesis. We test this hypothesis based...... duped by good economic performance. However, we find some evidence for a weaker form of the trade-off hypothesis: presidential disapproval among corruption victims might be more pronounced in contexts of high inflation and high unemployment....

  1. Validity of Linder Hypothesis in Bric Countries

    Directory of Open Access Journals (Sweden)

    Rana Atabay

    2016-03-01

    Full Text Available In this study, the theory of similarity in preferences (Linder hypothesis has been introduced and trade in BRIC countries has been examined whether the trade between these countries was valid for this hypothesis. Using the data for the period 1996 – 2010, the study applies to panel data analysis in order to provide evidence regarding the empirical validity of the Linder hypothesis for BRIC countries’ international trade. Empirical findings show that the trade between BRIC countries is in support of Linder hypothesis.

  2. "The Chengjiang Fauna and the Cambrian Explosion" Sponsord by NSFC won the first-class award of National Natural Sciences Award

    Institute of Scientific and Technical Information of China (English)

    Liu Y.; Yao Y.P.

    2004-01-01

    @@ "The Chengjiang Fauna and the Cambrian explosion'' sponsord by NSFC won the first-class award of National Natural Sciences Award. The Awarding ceremony was held in the Great Hall of the People in Beijing on February 20, 2004. "The Chengjiang Fauna and the Cambrian explosion" was sponsord by NSFC and carried out by several groups led by Prof. Chen Junyuan of the Nanjing Institute of Geology and Palaeontology,CAGS, Prof. Hou Xianguang of Yunnan University and Prof.

  3. The significance of 24-norcholestanes, triaromatic steroids and dinosteroids in oils and Cambrian-Ordovician source rocks from the cratonic region of the Tarim Basin, NW China

    Science.gov (United States)

    Li, Meijun; Wang, T.-G.; Lillis, Paul G.; Wang, Chunjiang; Shi, Shengbao

    2012-01-01

    Two oil families in Ordovician reservoirs from the cratonic region of the Tarim Basin are distinguished by the distribution of regular steranes, triaromatic steroids, norcholestanes and dinosteroids. Oils with relatively lower contents of C28 regular steranes, C26 20S, C26 20R + C27 20S and C27 20R regular triaromatic steroids, dinosteranes, 24-norcholestanes and triaromatic dinosteroids originated from Middle–Upper Ordovician source rocks. In contrast, oils with abnormally high abundances of the above compounds are derived from Cambrian and Lower Ordovician source rocks. Only a few oils have previously been reported to be of Cambrian and Lower Ordovician origin, especially in the east region of the Tarim Basin. This study further reports the discovery of oil accumulations of Cambrian and Lower Ordovician origin in the Tabei and Tazhong Uplifts, which indicates a potential for further discoveries involving Cambrian and Lower Ordovician sourced oils in the Tarim Basin. Dinosteroids in petroleum and ancient sediments are generally thought to be biomarkers for dinoflagellates and 24-norcholestanes for dinoflagellates and diatoms. Therefore, the abnormally high abundance of these compounds in extracts from the organic-rich sediments in the Cambrian and Lower Ordovician and related oils in the cratonic region of the Tarim Basin suggests that phytoplankton algae related to dinoflagellates have appeared and might have flourished in the Tarim Basin during the Cambrian Period. Steroids with less common structural configurations are underutilized and can expand understanding of the early development history of organisms, as well as define petroleum systems.

  4. The financing constraints hypothesis and inventory investment decisions of firms

    OpenAIRE

    Cunha, Jorge; Paisana, António

    2010-01-01

    In the last two decades there was an increasing interest of researchers on the impact of financing constraints on investment expenses of firms. However, the vast empirical literature that followed focused, mainly, on fixed investment and less attention has been given to the effect of financing constraints on inventory investment decisions of firms (Hubbard, 1998). The present paper aims to shed some light on this relationship by testing the financing constraints hypothesis on inventory invest...

  5. Le volcanisme cambrien du Maroc central : implications géodynamiquesThe Central Morocco Cambrian volcanism: geodynamic implications

    Science.gov (United States)

    Ouali, Houssa; Briand, Bernard; Bouchardon, Jean-Luc; Capiez, Paul

    2003-05-01

    In southeastern Central Morocco, the Bou-Acila volcanic complex is considered of Cambrian age. In spite of low-grade metamorphic effect, initial volcanic texture and mineralogy can be recognized and volcanic rocks are dominated by dolerites and porphyric dolerites. The initial mineralogy is composed of plagioclases, pyroxenes and dark minerals. A secondary mineral assemblage is composed of albite, epidote, chlorite and calcite. According to their immobile elements compositions, the southeastern central Morocco metavolcanites are of within-plate continental tholeiites. This volcanism and those recognized in many other areas in Morocco confirm a Cambrian extensive episode within the Gondwana supercontinent. To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).

  6. Paleomagnetism of the Cambrian Sediments in Bornholm (Denmark) and Southern Sweden and Implications for Paleogeography of Baltica

    Science.gov (United States)

    Lewandowski, M.; Abrahamsen, N.

    2001-12-01

    In Bornholm the Phanerozoic sedimentary succession overlying Precambrian basement starts with the Lower Cambrian (ca. 545 Ma) Nekso Sandstone Fm (NSF) that, in the earlier paleomagnetic analyses, have yielded characteristic magnetization (ChRM) similar to the Permian direction for Baltica. Here, we present paleomagnetic results from other Lower Cambrian formations in Bornholm (Balka Sandstone, Broens Odde siltstone) and in southern Sweden (Hardebega, Mickwitzia and Lingula Sandstones). Lithologically, most of these formations are very similar to the NSF and they are all considered stratigraphically younger. The intention was to check, whether a Permian paleomagnetic overprint occured on a regional scale and could it be attributed to secondary magnetic phases originating from fluids, which possibly traveled laterally along the contact between the basement and the Lower Cambrian sediments. In this report we show results of this regional test, followed by a comprehensive re-analysis of our Nekso data, including new results obtained after supplementary sampling and new petrologic information, which appeared recently. We have found that the NSF possessed a unique ChRM. The well-grouped and stable characteristic magnetization of the Nekso Sandstone contrasts with fairly chaotic, soft and badly preserved magnetization of the Balka, the Hardeberga, the Mickwitzia and the Lingulid sandstones of Bornholm and southern Sweden. A regional geological context, including the inferred diagenetic evolution of Lower Cambrian sediments, points to a syndepositional/early diagenetic origin of the characteristic remanence of the Nekso Sandstone, revealing a stable remanence applicable for plate tectonic interpretations. Similarity of the characteristic remanence of the NSF to the Permian direction for Baltica has been confirmed, but it is supposed to be casual, because of lack of any sign of a regional Permian remagnetization within the other Cambrian deposits of Southern Scandinavia

  7. A New Arthropod, Guangweicaris Luo, Fu et Hu gen. nov.from the Early Cambrian Guanshan Fauna, Kunming, China

    Institute of Scientific and Technical Information of China (English)

    LUO Huilin; FU Xiaoping; HU Shixue; LI Yong; HOU Shuguang; YOU Ting; PANG Jiyuan; LIU Qi

    2007-01-01

    The Guanshan Fauna is a soft-bodied fauna dominated by arthropods (including trilobites,trilobitoides, Tuzoia, Isoxys, and bradorids) in association with priapulids, brachiopods,anomalocaridids, vetulicoliids, sponges, chancellorids, and echinoderms. This paper reports and describes a new arthropod from the yellowish green mudstone at the lower part of the Wulongqing Formation, Canglangpuan Stage, Lower Cambrian in Kunming, Yunnan, China. The stratigraphic and geographic distribution, classification, fossil preservation, life style of this new arthropod and comparisons with other fossil arthropods are also discussed in details. The discovery and research of the non-mineralized arthropod, Guangweicaris Luo, Fu et Hu gen. nov. from the Guanshan Fauna adds new members to the taxonomic list and provides new information to the evolution of early arthropods.Furthermore, this study would shed new light into the "Cambrian Explosion" and the evolution of early life.

  8. The Interaction Hypothesis: A Literature Review

    Science.gov (United States)

    Tran, Thu Hoang

    2009-01-01

    This paper will examine the interaction hypothesis (IH) in second language acquisition (SLA). To begin with a short discussion of the confusing terms in SLA such as theory, model, hypothesis, and construct will be done so as to help readers easily understand theories in the field of SLA and related concepts. Next, what the IH is, and who proposed…

  9. The Interaction Hypothesis: A Critical Evaluation.

    Science.gov (United States)

    Ellis, Rod

    The oral interaction hypothesis, proposed by Long and investigated by Pica, in second language (L2) acquisition is critiqued. The interaction hypothesis advances two major claims about the role of interaction in L2 acquisition: (1) comprehensible input is necessary for L2 acquisition; and (2) modifications to the interactional structure of…

  10. A Model of the Relative Income Hypothesis

    Science.gov (United States)

    Sanders, Shane

    2010-01-01

    James Duesenberry's (1949) relative income hypothesis holds substantial empirical credibility, as well as a rich set of implications. Although present in the pages of leading economics journals, the hypothesis has become all but foreign to the blackboards of economics classrooms. To help reintegrate the concept into the undergraduate economics…

  11. The demosponge Leptomitus cf. L. lineatus, first occurence from the Middle Cambrian of Spain (Murero Formation, Western Iberian Chain)

    OpenAIRE

    García-Bellido, Diego

    2003-01-01

    The Middle Cambrian Murero Formation in the Iberian Chain (NE Spain) has yielded a small collection of softbodied fossils (palaeoscolecid worms, onychophorans, algae), a host of fossils from organisms with mineralized skeletons such as trilobites and brachiopods, and some trace fossils. This paper deals with the description of the only specimen of the demosponge Leptomitus known so far from Spain and its association with the brachiopod Micromitra, showing a probable case of commensalism by th...

  12. Decoupling of body-plan diversification and ecological structuring during the Ediacaran–Cambrian transition: evolutionary and geobiological feedbacks

    OpenAIRE

    Mángano, M. Gabriela; Luis A. Buatois

    2014-01-01

    The rapid appearance of bilaterian clades at the beginning of the Phanerozoic is one of the most intriguing topics in macroevolution. However, the complex feedbacks between diversification and ecological interactions are still poorly understood. Here, we show that a systematic and comprehensive analysis of the trace-fossil record of the Ediacaran–Cambrian transition indicates that body-plan diversification and ecological structuring were decoupled. The appearance of a wide repertoire of behav...

  13. On gamma-ray bursts and their biological effects :a case for an extrinsic trigger of the Cambrian explosion ?

    CERN Document Server

    Horváth, J E

    2003-01-01

    We discuss some the effects of local gamma-ray bursts on the earth's atmosphere. A rough calculation of the fraction of ozone destruction by catalytic $NO_{x}$ cycles is given, which in turn serves to argue how the large flux of gammas from these events would have indirectly provoked major extinction of living organisms. We give specific examples of these features, and tentatively identify the Cambrian explosion seen in the actual fossil record as an event caused by a GRB.

  14. A new vetulicolian from Australia and its bearing on the chordate affinities of an enigmatic Cambrian group

    OpenAIRE

    García-Bellido, Diego C.; Lee, Michael S. Y.; Gregory D. Edgecombe; Jago, James B; Gehling, James G; Paterson, John R

    2014-01-01

    Background Vetulicolians are one of the most problematic and controversial Cambrian fossil groups, having been considered as arthropods, chordates, kinorhynchs, or their own phylum. Mounting evidence suggests that vetulicolians are deuterostomes, but affinities to crown-group phyla are unresolved. Results A new vetulicolian from the Emu Bay Shale Konservat-Lagerstätte, South Australia, Nesonektris aldridgei gen. et sp. nov., preserves an axial, rod-like structure in the posterior body region ...

  15. The Sirius Passet Lagerstatte : silica death masking opens the window on the earliest matground community of the Cambrian explosion.

    OpenAIRE

    Strang, K.M.; Armstrong, H.A.; Harper, D.A.T.; Trabucho-Alexandre, João P.

    2016-01-01

    The Sirius Passet Lagerstätte (SP), Peary Land, North Greenland, occurs in black slates deposited at or just below storm wave base. It represents the earliest Cambrian microbial mat community with exceptional preservation, predating the Burgess Shale by 10 million years. Trilobites from the SP are preserved as complete, three-dimensional, concave hyporelief external moulds and convex epirelief casts. External moulds are shown to consist of a thin veneer of authigenic silica. The casts are for...

  16. Discussions on the sedimentary-tectonic event and tectonic setting of the North Tarim Basin in Cryogenian-Cambrian

    Science.gov (United States)

    Zhou, X. B.; Li, J. H.; Li, W. S.

    2012-04-01

    Across the Tarim Basin, limited surface outcrops of Cryogenian to Cambrian sedimentary succession are completely exposed in the vicinity of Aksu area(Northwest Tarim), Kuruktag(Northeast Tarim)and Southwest Tarim, thus provides a unique, well preserved and accessible means by which to study the early development of the north Tarim Basin. Based on the field geological investigation in the northwestern and northeastern of Tarim Basin, with the referencing of paleomagnetism mapping and previous research, basin evolution process in Cryogenian-Cambrian is discussed according to sedimentary-tectonic event and other evidences. The major lithological types of Cryogenian-Cambrian system in Northeast Tarim are: tillite, clastic rocks(rich in organic matter) and carbonate ,with interbeds of volcanic rocks while in Northwest Tarim, the calstic rocks and carbonate are the common rock type, with tillite and volcanic interbeds in a small amount. The north margin of Tarim Block, which was a part of Rodinia supercontinent, neighboring the northwestern margin of Australia, was deeply rifted in Cryogenian-Ediacaran and developed into two rifts in the northwestern and northeastern margin, while formed a thick layer of the rift-passive margin deposits and the layer in the northwestern rift was not completely developed as the northeastern. The deepest rift-passive magin sediment which can be observed is Cryogenian-Middle Ordovician strata, and the period can be divided into Cryogenian faulted period (supercontinent rifting stage) and Ediacaran-Middle Ordovician subsidence period (plate drifting stage).

  17. Molecular fossils and sources of Cambrian heavy oil of Well Tadong-2 in theTarim Basin, Xinjiang, China

    Institute of Scientific and Technical Information of China (English)

    TANG Youjun; ZAN Ling

    2009-01-01

    Research on the molecular fossil characteristics of heavy oil from Well Tadong-2 is of great importance to constrain the source of marine crude oils in the Tarim Basin, Xinjiang, China. The authors synthetically applied the isotope mass spectrograph, chromatography and chromatography-mass spectrography to the studies of molecular fossil characteristics of heavy oil from Well Tadong-2 in the Tarim Basin, and the results obtained revealed that heavy oil from Well Tadong-2 is characterized by high gammacerane, high C28 sterane, low rearranged sterane and high C27-triaromatic steroid, these characteristics are similar to those of Cambrian-Lower Ordovician source rocks, demonstrating that Cambrian crude oils came from Cambrian-Lower Ordovician source rocks; condensed compounds (fluoranthene, pyrene, benzo[a]anthracene, bow, benzo fluoranthene, benzopyrene) of high abundance were detected in heavy oil from Well Tadong-2, and the carbon isotopic values of whole oil are evidently heavy, all the above characteristics revealed that hydrocarbons in the crude oils became densified in response to thermal alteration.

  18. Sm-Nd isotopic compositions of Cambrian-Ordovician strata at the Jinggangshan area in Jiangxi Province:Tectonic implications

    Institute of Scientific and Technical Information of China (English)

    SHEN WeiZhou; LING HongFei; SHU LiangShu; ZHANG FangRong; XIANG Lei

    2009-01-01

    Whole-rock Sm-Nd Isotopes were investigated for Cambrian-Ordovician strata from the Jinggangshan area beTween the Yangtze Block and Cathysla Block in South China. These strata were deposited as a greatly thick unit of muddy-sandy laminas with intercalated carbonate and organic carbon-bearing layers. They have low ε(t) values of -13.9 to -7.9 and old Nd model ages of 1842 to 2375 Ma. In t-tdiagram, they are far away from the concordant line but fall within the evolution zone of the Proterozoic crust of South China. This indicates that the Cambrian-Ordovician strata are mainly composed of mat-ters eroded from ancient Paleoproterozoic crust that may mainly consist of continental-derived detrital sediments with high maturity in the Cathyaia Block. However, the Ordovician Jueshangou Formation and Dui'erehi Formation have ε(t) values of -10.5 and -7.9 at the higher end of the above range and Nd model ages of 1842 to 2059 Ma at the lower end of the above range. This suggests involvement of more detritus that were eroded from the relatively juvenile crust from Late Paleoproterozoic to the Early Neoproterozoic. All the Nd model ages for the Cambrian-Ordovlcian sedimentary rocks in the Cathysia Block and the southeastern margin of the Yangtze Block are older than 1800 Ma, suggesting that no material from the Early Paleozoic depleted mantle-derived magmas was involved in these regions.

  19. Ichnofossils and their significance in the Cambrian successions of the Parahio Valley in the Spiti Basin, Tethys Himalaya, India

    Science.gov (United States)

    Parcha, S. K.; Pandey, Shivani

    2011-11-01

    The Spiti Basin exposes well preserved Cambrian successions in the Tethys Himalaya. The present ichnofossil assemblage is reported from the Debsakhad Member of the Kunzum La Formation. The ichnofossils includes the ichnogenera Bergaueria, Chondrites, Cruziana, Didymaulichnus, Dimorphichnus, Diplichnites, Helminthorhaphe, Merostomichnites, ?Monocraterion, Monomorphichnus, Nereites, Palaeopascichnus, Palaeophycus, Phycodes, Planolites, Rusophycus, Skolithos, Scolicia, Treptichnus, etc. along with annelid worm, burrow and scratch marks. These ichnogenera can be assigned to cubichnial, repichnial, pascichnial to fodinichnial behaviors. The ichnofossils reported from this section provide evidence regarding the developmental patterns during the early phase of life. In absence of trilobites, the present assemblage of ichnofossils is very significant in assigning the age of the Debsakhad Member. The abundance of ichnofossils in sandstone, siltstone and in shale beds indicate that the ichnocenosis is dominated by a high behavioral diversity ranging from the suspension to deposit feeders. Three lithofacies were observed in this section, they show a vertical disposition, which further reflects general upward coarsening trend. Ichnofossils are mostly produced by arthropods along with crustacean, polychaetes and polyphyletic vermiforms. Due to the paucity of body fossil, as well as microbiota in the lowermost beds of the Debsakhad Member, the Precambrian-Cambrian boundary could not be demarcated. However, the presence of Treptichnus and Phycodes can be considered as a horizon marker for the beginning of Lower Cambrian in this section.

  20. Quartz cementation mechanisms between adjacent sandstone and shale in Middle Cambrian, West Lithuania

    Science.gov (United States)

    Zhou, Lingli; Friis, Henrik

    2013-04-01

    Quartz is an important cementing material in siliciclastic sandstones that can reduce porosity and permeability severely. For efficiently predicting and extrapolating petrophysical properties such as porosity and permeability, the controls on the occurrence and the degree of quartz cementation need to be better understood. Because it is generally difficult to identify specific sources for quartz cement, many models attempting to explain quartz cementation conclude that external sources of silica are needed to explain the observed quantity of quartz cement, such as the mass transfer between sandstone and shale. Cambrian sandstones in Lithuania have abundant quartz cement which has significant effect on reservoir properties. The detrital quartz grains have been dissolved extensively along the shale-quartz contacts zones, making it a natural laboratory to study the influence of mass transfer between sandstone and shale to quartz cementation on petrophysical properties and reservoir quality. Our Cambrian shale samples in west Lithuania are mainly silty shale or siltstone (sample locations vary from 330 to 2090 m of burial depth). They are composed of quartz, clay and traces of feldspars, sericite, calcite, and pyrite. The clay minerals are mainly illite, with variable content of kaolinite and traces of chlorite. In the sandstone lamina, authigenic illite occurs as pore-filling cement which was composed of fibrous illite; pore-filling kaolinite is generally well crystallized and occurs as hexagonal plates arranged in booklets; quartz overgrowth are obvious in these sandstone laminas, especially in the contact zones between sandstone and shale. Dolomite and pyrite cementation are also present in some sandstone laminas but with few quartz overgrowth. Depositional facies and architecture played an important role in the precipitation of silica. Three different possible sources are distinguished for the quartz overgrowths in the intercalated sandstones: 1) Pressure

  1. A Euxinic-Wedge Model for Mo Cycling in the Early Cambrian Oceans

    Science.gov (United States)

    Li, C.; Cheng, M.; Zhou, L.; Algeo, T. J.; Jin, C. S.; Lei, L. D.; Feng, L. J.; Jiang, S. Y.

    2015-12-01

    Ocean redox conditions during the early Cambrian, a critical period in Earth history marked by rapid evolution of animals, are uncertain. Previous studies have suggested well oxic conditions based on Mo isotopes and stratified, anoxic deep waters based on Fe-S-C and trace metal data. The Niutitang Formation (529-514 Ma) at Yangjiaping (South China) consists of a lower black shale member (LM, 0-18 m) and an upper gray silty shale member (UM, 24-80 m). The LM is moderately to strongly enriched in Mo, U and V, and heterogeneous in Mo-isotopic compositions (δ98Mo = ‒0.65‰ to +2.14‰), while the UM shows lesser enrichment of Mo, U and V, higher Mo/U ratios, and intermediate and more uniform δ98Mo (+1.16‰ to +1.71‰). The metal data and previously reported Fe-speciation data suggest a redox change from dominantly euxinic conditions for the LM to suboxic or weakly anoxic-euxinic conditions for the UM, consistent with a shift of the chemocline from the water column to the sediment during a eustatic fall. We propose an "euxinic wedge" model for the δ98Mo patterns observed here. In this model, the early Cambrian ocean exhibited a lateral transition from ferruginous conditions in nearshore areas to euxinic conditions at mid-depths and back to ferruginous conditions in offshore areas. This pattern was the result of terrigenous Fe-Mnox reduction, sulfate resupply via rivers, and hydrothermal inputs of reactive Fe into the deep basin. Within this framework, sedimentary δ98Mo variation in the study units can be explained through the combined effects of Mo isotopic fractionation associated with Fe-Mnox adsorption and depth-dependent H2S concentrations. Importantly, the heaviest δ98Mo values, which were previously interpreted to reflect full oxygenation, can be explained by the operation of a globally widespread Fe-Mn particulate shuttle that removed large quantities of isotopically light Mo to the sediment, leaving seawater enriched in 98Mo.

  2. Reconstructing redox conditions of mesoproterozoic-early Cambrian seawater using δ98/95Mo

    International Nuclear Information System (INIS)

    Full text: Mo isotope composition of seawater is determined by its relative removal in oxic and anoxic sinks as Mo isotope fractionates during its removal from seawater in oxic sediments whereas it remains invariable during its precipitation in reducing sediments. Hence, Mo isotope composition of reducing sediments can be used to track the temporal variation in redox condition of the global ocean. In this study an attempt is being made to reconstruct the redox conditions during Mesoproterozoic-Early Cambrian period using δ98/95∼Mo in black shales from Vindhyan and Outer belt of Lesser Himalaya. This time span witnessed the important evolutionary changes in the early earth such as rise in atmospheric oxygen and changes in the biosphere. Samples processed for this study were collected from Bijaigarh Shales of Kaimur formation of the Vindhyan and Lower Tal formation of the Lesser Himalaya. The depositional ages of these formations was estimated to be -1200 Ma and -540 Ma for Bijaigarh and Tal formations respectively. Mo isotope composition of black shales were determined by their complete acid digestion in presence of 97Mo-100Mo double spike followed by column chromatography separation. Mo isotope composition in purified samples were analysed using Finnigan Neptune MC-ICP-MS at Physical Research Laboratory. δ98/95% Mo measured in Bijaigarh Shales indicate variation from 0.4 to 1.35% with concentration ranging from 1.6-34 ppm whereas the Tal black shales display variability of 0.3-1.5%0 with concentration 16-80 ppm. In general, higher 09%sMo in Bijaigarh shales are associated with higher Mo concentration indicating the dominance of seawater Mo. Lower δ99/95%Mo in some samples could result from detrital component. Based on these data it can be inferred that Mesoproterozoic ocean was more anoxic compared to that of Early Cambrian and the contemporary ocean. More work is underway to track and further quantify the anoxicity of the ocean with time

  3. Carbon isotope fluctuations through the neoproterozoic-lower cambrian Birmania basin, Rajasthan, India

    International Nuclear Information System (INIS)

    The paleogeographic reconstruction of the end phase of Neoproterozoic assumes a significance due to the fact that the interactions between the biosphere and the atmosphere, hydrosphere and geosphere during this period of time strongly influenced the evolution of life and initiated a remarkable phase of organic evolution well documented in the rocks of this age (Banerjee and Majumdar, 1999). Time related changes in these carbon reservoirs and processes during the end Proterozoic have played an important role in the evolution of the environment and of life (Des Marais, 1997). Brasier (1992) discussed at length various factors that pushed shallow marine ecosystem of the late Neoproterozoic-Cambrian towards P-limitation and suggested that nitrate fixation, density stratification and massive removal of P in the sediments were responsible for the formation of phosphatic deposits within this time interval. East Gondwana assembly of continents provide fine examples of stratigraphic successions in which the ideas related to oceanic stratification, phosphate deposition, enhanced organic production and carbon isotope fluctuations can be verified and correlated from continent to continent (Banerjee and Majumdar, 1999). The Birmania basin is an oval shaped isolated remnant of the Marwar basin (Neo-proterozoic-Early Palaeozoic) located in the heart of the Thar desert of western Rajasthan, India. It is underlain by Malani Igneous Suite of rocks which range in age from 780 to 680Ma (Rathore et al., 1999).The Birmania basin comprises around 900 metre thick sedimentary sequence of siliciclastic, carbonate and phosphorite facies. These sequences are unconformably overlain by La-thi conglomerate of Jurassic age in north-ern flank of the basin. Global Neoproterozoic glacial activity in the western Rajasthan is also reported and is represented by Pokaran Boulder Bed, few kms away from study area. The Pokaran Boulder Bed overlies the Malani Igneous Suite and is mainly consist of boulders

  4. Knowledge dimensions in hypothesis test problems

    Science.gov (United States)

    Krishnan, Saras; Idris, Noraini

    2012-05-01

    The reformation in statistics education over the past two decades has predominantly shifted the focus of statistical teaching and learning from procedural understanding to conceptual understanding. The emphasis of procedural understanding is on the formulas and calculation procedures. Meanwhile, conceptual understanding emphasizes students knowing why they are using a particular formula or executing a specific procedure. In addition, the Revised Bloom's Taxonomy offers a twodimensional framework to describe learning objectives comprising of the six revised cognition levels of original Bloom's taxonomy and four knowledge dimensions. Depending on the level of complexities, the four knowledge dimensions essentially distinguish basic understanding from the more connected understanding. This study identifiesthe factual, procedural and conceptual knowledgedimensions in hypothesis test problems. Hypothesis test being an important tool in making inferences about a population from sample informationis taught in many introductory statistics courses. However, researchers find that students in these courses still have difficulty in understanding the underlying concepts of hypothesis test. Past studies also show that even though students can perform the hypothesis testing procedure, they may not understand the rationale of executing these steps or know how to apply them in novel contexts. Besides knowing the procedural steps in conducting a hypothesis test, students must have fundamental statistical knowledge and deep understanding of the underlying inferential concepts such as sampling distribution and central limit theorem. By identifying the knowledge dimensions of hypothesis test problems in this study, suitable instructional and assessment strategies can be developed in future to enhance students' learning of hypothesis test as a valuable inferential tool.

  5. Replacement of benthic communities in two Neoproterozoic-Cambrian subtropical-to-temperate rift basins, High Atlas and Anti-Atlas, Morocco

    Science.gov (United States)

    Clausen, Sébastien; Álvaro, J. Javier; Zamora, Samuel

    2014-10-01

    The ‘Cambrian explosion’ is often introduced as a major shift in benthic marine communities with a coeval decline of microbial consortia related to the diversification of metazoans and development of bioturbation (‘Agronomic Revolution’). Successive community replacements have been reported along with ecosystem diversification and increase in guild complexity from Neoproterozoic to Cambrian times. This process is recorded worldwide but with regional diachroneities, some of them directly controlled by the geodynamic conditions of sedimentary basins. The southern High Atlas and Anti-Atlas of Morocco record development of two rifts, Tonian (?) - early Cryogenian and latest Ediacarian-Cambrian in age, separated by the onset of the Pan-African Orogeny. This tectonically controlled, regional geodynamic change played a primary control on pattern and timing of benthic ecosystem replacements. Benthic communities include microbial consortia, archaeocyathan-thromboid reefal complexes, chancelloriid-echinoderm-sponge meadows, and deeper offshore echinoderm-dominated communities. Microbial consortia appeared in deeper parts of the Tonian (?) - early Cryogenian fluvio-deltaic progradational rift sequences, lacustrine environments of the Ediacaran Volcanic Atlasic Chain (Ouarzazate Supergroup) and the Ediacaran-Cambrian boundary interval, characterized by the peritidal-dominated Tifnout Member (Adoudou Formation). They persisted and were largely significant until Cambrian Age 3, as previous restricted marine conditions precluded the immigration of shelly metazoans in the relatively shallow epeiric parts of the Cambrian Atlas Rift. Successive Cambrian benthic communities were replaced as a result of distinct hydrodynamic and substrate conditions, which allow identification of biotic (e.g., antagonistic relationships between microbial consortia and echinoderms, and taphonomic feedback patterns in chancelloriid-echinoderm-sponge meadows) and abiotic (e.g., rifting

  6. Early Cambrian eodiscoid trilobites of the Yangtze Platform and their stratigraphic implications

    Institute of Scientific and Technical Information of China (English)

    YANG Aihua; ZHU Maoyan; ZHANG Junming; LI Guoxiang

    2003-01-01

    Analysis of the taxonomy and stratigraphic distribution of the Early Cambrian eodiscoid trilobites of the Yangtze Platform indicates that species of Tsunyidiscus and Hupeidiscus can be used for biostratigraphic correlation. T. aclis occurs only in the lower Qiongzhusian, T. armatus occurs in the lower and middle Qiongzhusian, while T. niutitangensis and T. tingi occur mainly in the middle and upper Qiongzhusian, with only T. tingi extending upward into the lower Canglangpuian. H. orientalis first appears in the upper Qiongzhusian, reaching peak abundance in the lower Canglangpuian and becoming extinct above the Drepanuroides Zone. Biostratigraphic and lithostratigraphic correlations indicate that the limestone in the lower part of the Mingxinsi Formation, the Upper Member of Jiumenchong Formation, and the upper part of the Middle Member of the Huangbailing Formation, can be correlated with each other as Hupediscus, an index fossil of the lower Canglangpuian, is abundant in all these units. The lower part of the Niutitang and Jiumenchong formations in eastern Guizhou, which mainly represent Qiongzhusian strata, can be correlated with the Lower Member of the Huangbailing Formation. The basal part of the Niutitang Formation, which may be equivalent to the Upper Meishucunian Shiyantou Formation in eastern Yunnan, is very condensed. Well-preserved sponge faunas and non-mineralized fossils in the lower part of the Niutitang and Hetang formations are not older than Qiongzhusian in age.

  7. The newly-developed Cambrian biostratigraphic succession and chronostratigraphic scheme for South China

    Institute of Scientific and Technical Information of China (English)

    PENG ShanChi

    2009-01-01

    Biostratigraphy and chronostratigraphy are common means of subdividing rock strata.The biostratigraphic succession and chronostratigraphic scheme are regarded as the basis for the subdivision and correlation of regional and global stratigraphic units.This paper reviews research on the biostratigraphy and chronostratigraphy carried out in the Jiangnan Slope Belt,South China since 1978,and,in particular,the biostratigraphic succession and chronostratigraphic scheme developed in the last decade.The updated biostratigraphic succession of South China includes 36 biozones,the base of each of which is defined by the first appearance of a single taxon (index fossil),and a poorly fossiliferous interzone.The updated chronostratigraphic scheme of South China comprises 4 series and 10 stages,embracing 3 global chronostratigraphic units,the Guzhangian Stage,Furongian Series,and Paibian Stage,and 2 GSSPa,all of which are erected in northwestern Hunan and 2 International Tie Points recognized in sections also in northwestern Hunan and each was accepted by the International Subcommission on Cambrian Stratigraphy for defining the base of the global stage.The biostratigraphic and chronostratigraphic systems are recognized as Chinese standards both domestically and worldwide.Future research is suggested for improving the two sets of stratigraphic standards.

  8. Body Size Evolution in Conodonts from the Cambrian through the Triassic

    Science.gov (United States)

    Schaal, E. K.; Morgan, D. J.; Payne, J.

    2013-12-01

    The size of an organism exercises tremendous control over its physiology, life history, and ecology, yet the factors that influence body size evolution remain poorly understood. One major limitation is the lack of appropriate datasets spanning long intervals of evolutionary time. Here, we document size trends in conodonts (tooth-like microfossils from marine chordates) because they evolved rapidly and are known to change size during intervals of environmental change. By measuring photographs from the Catalogue of Conodonts (Ziegler 1982), we compiled a database of conodont P1 element measurements for 575 species and subspecies from the Cambrian through Triassic periods. Because tooth size correlates with body size in conodont animals and their extant relatives, conodont element length can serve as a proxy for the size of the conodont animal. We find that mean and maximum size across species increased during the early Paleozoic, peaked during the Devonian-Mississippian, and then generally decreased until conodonts went extinct at the end of the Triassic. We used regression analyses to compare conodont mean size trends to potential environmental predictors, such as changing atmospheric pO2, atmospheric pCO2, and sea level. Conodont size exhibited poor correlation with these environmental factors, suggesting that conodont evolution may have been more strongly influenced by other environmental covariates or ecological variables such as predation and competition.

  9. Phylogeny and evolutionary significance of vermiform animals from the Early Cambrian Chengjiang Lagersttte

    Institute of Scientific and Technical Information of China (English)

    David; BAINES

    2010-01-01

    The Early Cambrian Chengjiang Biota of China has preserved many species of vermiform animals in exquisite detail,which provide a unique window into the origin and early evolution of different vermiform phyla.This article reviews and discusses the forty-five Chengjiang vermiform animals discovered so far,and specifically comments on the phylogeny,modes of life,evolutionary significance as well as existing debates concerning the Chengjiang priapulid and lobopodian phyla.This article analyzes existing problems with Chengjiang vermiform morphological research and highlights various factors that affect the final preserved fossil morphology,including taphonomy and shape change caused by vermiform movement,as well as proposing that Anningvermis multispinosa and Corynetis brevis are synonymous.Chengjiang vermiform animals displayed a great diversity of morphologies and ecological roles,which is significant for understanding the origin and evolution of early metazoans;the potential for future research is enormous but needs to be broadened by interdisciplinary work involving taphonomy,geochemistry,cladistics,and genetics.

  10. Preservation and phylogeny of Cambrian ecdysozoans tested by experimental decay of Priapulus.

    Science.gov (United States)

    Sansom, Robert S

    2016-01-01

    The exceptionally preserved Cambrian fossil record provides unique insight into the early evolutionary history of animals. Understanding of the mechanisms of exceptional soft tissue preservation frames all interpretations of the fauna and its evolutionary significance. This is especially true for recent interpretations of preserved nervous tissues in fossil ecdysozoans. However, models of soft tissue preservation lack empirical support from actualistic studies. Here experimental decay of the priapulid Priapulus reveal consistent bias towards rapid loss of internal non-cuticular anatomy compared with recalcitrant cuticular anatomy. This is consistent with models of Burgess Shale-type preservation and indicates that internal tissues are unlikely to be preserved with fidelity if organically preserved. This pattern, along with extreme body margin distortion, is consistent with onychophoran decay, and is therefore resolved as general for early ecdysozoans. Application of these patterns to phylogenetic data finds scalidophoran taxa to be very sensitive to taphonomically informed character coding, but not panarthropodan taxa. Priapulid decay also have unexpected relevance for interpretation of myomeres in fossil chordates. The decay data presented serve not only as a test of models of preservation but also a framework with which to interpret ecdysozoan fossil anatomies, and the subsequent evolutionary inferences drawn from them. PMID:27595908

  11. Geochemical investigations on some of the Infra Cambrian Acid intrusive and volcanic rocks in Iran

    International Nuclear Information System (INIS)

    Geochemical investigations on some of the acid intrusive and volcanic rocks of Iran, which are attributed to the Infra cambrian, have been carried out to reveal their possible genetic relationships. These igneous rocks include: Do ran, Shah-Bolaghi, Sarve-Jahan, NE Ardakan - Yazd (Darbastegoon), south Mahabad, Bornavard (Tak nar), Zarigan, Narigan, Chardormaloo granites, Rizo and De zoo micro granites and volcanic rocks, Ga chin rhyolites (Bandar-Abass), and Ghareh-Dash (east of Sae en-De j). These intrusive s, except south Mahabad granodiorite, belong to the class of the alkali feldspathic granite to granitic rocks. Most of these rocks are hololeucocratic and devoid of ferro magnesian minerals. The volcanic rocks are mainly felsic (Rhyolite and Quartz porphyra) associated with vacillation's rocks. These suites of rocks plot on the chemical diagrams in sub alkaline field. Regarding to variations of Na2O, K2O and Ca O contents, they can further be subdivided into sodi c, potas sic, sodi-potas sic and sodi-calci c subgroups. The normalized values (MORB and chondritic) of their trace elements on the spider diagrams overlap each other indicates that some genetic relations ships exist among samples of white Doran Granite, Shahbolaghi, Sarve-Jahan and some Darbastegoon, in one hand, and Taknar, Narigan Granites, Gachin, Rizoo and Dezoo Rhyolites, on the other hand. The overlap also shows that the mentioned igneous bodies have been originated from continental crust and the samples of each groups, at least belong to a distinct tectonic al regime

  12. The importance of preadapted genomes in the origin of the animal bodyplans and the Cambrian explosion.

    Science.gov (United States)

    Marshall, Charles R; Valentine, James W

    2010-05-01

    The genomes of taxa whose stem lineages branched early in metazoan history, and of allied protistan groups, provide a tantalizing outline of the morphological and genomic changes that accompanied the origin and early diversifications of animals. Genome comparisons show that the early clades increasingly contain genes that mediate development of complex features only seen in later metazoan branches. Peak additions of protein-coding regulatory genes occurred deep in the metazoan tree, evidently within stem groups of metazoans and eumetazoans. However, the bodyplans of these early-branching clades are relatively simple. The existence of major elements of the bilaterian developmental toolkit in these simpler organisms implies that these components evolved for functions other than the production of complex morphology, preadapting the genome for the morphological differentiation that occurred higher in metazoan phylogeny. Stem lineages of the bilaterian phyla apparently required few additional genes beyond their diploblastic ancestors. As disparate bodyplans appeared and diversified during the Cambrian explosion, increasing complexity was accommodated largely through changes in cis-regulatory networks, accompanied by some additional gene novelties. Subsequently, protein-coding genic richness appears to have essentially plateaued. Some genomic evidence suggests that similar stages of genomic evolution may have accompanied the rise of land plants. PMID:19930449

  13. The sexual competition hypothesis for eating disorders

    OpenAIRE

    Abed, Riadh T.

    1998-01-01

    A hypothesis is presented for eating disorders that contends that these syndromes together with the phenomenon of the pursuit of thinness are manifestations of female intra-sexual competition. It is argued that the present-day environment of Western coutries presnts a range of conditions that have led to the overactivation or disruption of the archaic female sexual strategy of maximising 'mate value'. The hypothesis deals with the ultimate level of causation and is therefore compatible with a...

  14. The discovered preference hypothesis - an empirical test

    DEFF Research Database (Denmark)

    Lundhede, Thomas; Ladenburg, Jacob; Olsen, Søren Bøye

    Using stated preference methods for valuation of non-market goods is known to be vulnerable to a range of biases. Some authors claim that these so-called anomalies in effect render the methods useless for the purpose. However, the Discovered Preference Hypothesis, as put forth by Plott [31], offers...... decays as respondents evaluate more and more choice sets. This finding supports the Discovered Preference Hypothesis interpretation and explanation of starting point bias....

  15. Inadequacies of TPR and Krashen's Input Hypothesis

    Institute of Scientific and Technical Information of China (English)

    Meng Meng; LI Laifa

    2008-01-01

    In this paper,the rationale of TPR and the Input Hypothesis of Krashen which justifies practices of TPR are reviewed and criticized in the light of evidence from teachers'observation of a long-term TPR project.It is argued that the effectiveness of TPR is compromised by its inadequate attention to the complexity of classroom interactions and children's cognition.The Input Hypothesis is believed that it oversimplified the cognitive dynamics of language learning.

  16. The Efficient Market Hypothesis: A Survey

    OpenAIRE

    Meredith Beechey; David Gruen; James Vickery

    2000-01-01

    The efficient market hypothesis states that asset prices in financial markets should reflect all available information; as a consequence, prices should always be consistent with ‘fundamentals’. In this paper, we discuss the main ideas behind the efficient market hypothesis, and provide a guide as to which of its predictions seem to be borne out by empirical evidence, and which do not. In examining the empirical evidence, we concentrate on the stock and foreign exchange markets. The efficient ...

  17. The Efficient Market Hypothesis and Its Critics

    OpenAIRE

    Burton G. Malkiel

    2003-01-01

    Revolutions often spawn counterrevolutions and the efficient market hypothesis in finance is no exception. The intellectual dominance of the efficient-market revolution has more been challenged by economists who stress psychological and behaviorial elements of stock-price determination and by econometricians who argue that stock returns are, to a considerable extent, predictable. This survey examines the attacks on the efficient market hypothesis and the relationship between predictability an...

  18. Bootstraping the general linear hypothesis test

    OpenAIRE

    Delicado, Pedro; Río, Manuel del, 1690-1766

    1993-01-01

    We discuss the use of bootstrap methodology in hypothesis testing, focusing on the classical F-test for linear hypotheses in the linear model. A modification of the F-statistics which allows for resampling under the null hypothesis is proposed. This approach is specifically considered in the one-way analysis of variance model. A simulation study illustrating the behaviour of our proposal is presented.

  19. Particle creation and Dirac's large numbers hypothesis

    International Nuclear Information System (INIS)

    Reference is made to cosmologies based on Dirac's large numbers hypothesis (Nature 139:323 (1937) and Proc. Roy. Soc. A333:403 (1973)). Dirac suggested that continuous creation of matter is required. Two modes of particle creation have been proposed and cosmological models corresponding to each mode have been studied. It is here shown that, within the context of the large numbers hypothesis, the number of particles in the Universe varies as expected (N proportional to t2) so that particle creation is unnecessary. Some undesirable features of cosmologies based on the large numbers hypothesis are also discussed. In order to appreciate fully the results presented for cosmologies based on the large numbers hypothesis a review is made of the corresponding relationship in conventional cosmologies in which the gravitational constant G does not vary with time. It is found, amongst other things that there is no nucleosynthesis in cosmologies based on the large numbers hypothesis, making the large and uniform abundance of He inexplicable. Another undesirable finding with the large numbers hypothesis is the extremely steep decline in the number of particles in the Universe with increasing temperature. Yet another undesirable finding concerns the scattering of photons by electrons in the early Universe; there is no way to establish thermodynamic equilibrium between the photons and electrons, and the black body spectrum of the background radiation is without explanation. (U.K.)

  20. Aminoglycoside antibiotics and autism: a speculative hypothesis

    Directory of Open Access Journals (Sweden)

    Manev Hari

    2001-10-01

    Full Text Available Abstract Background Recently, it has been suspected that there is a relationship between therapy with some antibiotics and the onset of autism; but even more curious, some children benefited transiently from a subsequent treatment with a different antibiotic. Here, we speculate how aminoglycoside antibiotics might be associated with autism. Presentation We hypothesize that aminoglycoside antibiotics could a trigger the autism syndrome in susceptible infants by causing the stop codon readthrough, i.e., a misreading of the genetic code of a hypothetical critical gene, and/or b improve autism symptoms by correcting the premature stop codon mutation in a hypothetical polymorphic gene linked to autism. Testing Investigate, retrospectively, whether a link exists between aminoglycoside use (which is not extensive in children and the onset of autism symptoms (hypothesis "a", or between amino glycoside use and improvement of these symptoms (hypothesis "b". Whereas a prospective study to test hypothesis "a" is not ethically justifiable, a study could be designed to test hypothesis "b". Implications It should be stressed that at this stage no direct evidence supports our speculative hypothesis and that its main purpose is to initiate development of new ideas that, eventually, would improve our understanding of the pathobiology of autism.

  1. A Proof for the Riemann Hypothesis

    CERN Document Server

    Cheng, Yuan-You Fu-Rui

    2008-01-01

    The Riemann zeta function $\\zeta(s)$ is defined by $\\zeta(s) =\\sum\\sb{n=1}\\sp{\\infty} \\tfrac{1}{n\\sp{s}}$ for $\\Re(s)>1$ and can be extended to a regular function on the whole complex plane deleting its unique pole at $s=1$. The Riemann hypothesis is a conjecture made by Riemann in 1859 asserting that all non-trivial zeros for $\\zeta(s)$ lie on the line $\\Re(s)=\\tfrac{1}{2}$, which is equivalent to the prime number theorem in the form of $\\pi(x)-\\Li(x) =O(x\\sp{{1/2}+\\epsilon})$ for any positive $\\epsilon$, where $\\pi(x) =\\sum\\sb{p\\le x} 1$ with the sum runs through the set of primes is the prime counting function and $\\Li(x) =\\int\\sb{2}\\sp{x} \\tfrac{1}{\\log v}\\dd v$ is Gauss' logarithmic integral function. In this article, it gives a proof for the density hypothesis and so that settles the long time due justification for the Riemann hypothesis from the equivalence of the density hypothesis and the Riemann hypothesis proved recently in \\cite{CY2}, which in turn gives a prime number theorem stated as above.

  2. Population Structure, Life Strategies and Systematics of Phosphatocope Ostracods from the Middle Cambrian of Bornholm

    Directory of Open Access Journals (Sweden)

    I. Hinz-Schallreuter

    1998-01-01

    Full Text Available She Middle Cambrian Borregård Member of Bornholm which is the stratigraphical equivalent to the Baltoscandian Exsulans Limestone yielded a rich and comparatively diverse ostracod fauna in its upper part. It comprises eight species out of four genera. They belong to three known subfamilies that are redefined on the basis of special characters of the contact margin. An ontogenetic character unknown from typical ostracods is documented in several species: during early ontogeny the gestalt (l:h ratio develops constantly in becoming increasingly longer until the so-called ontogenetical turning point (OTP from which the direction of growth focusses on carapace height. This phenomenon may be explained by changes in body morphology. The Borregård association represents an ecologic community type differing from other yet recorded Middle Cambrian communities in the Baltoscandic region. Apart from Vestrogothia longispinosa which is a common faunal element in Baltoscandian ostracod faunas, the yet recorded species of Bidimorpha are unknown from other Baltoscandian occurrences. Vice versa, the known species of Bidimorpha described from Swedish occurrences have not been recognized in the rich Borregård community. Similarly, Falites insula and Hesslandona abdominalis may be of local significance, too, but the respective records from contemporaneous Swedish localities are insufficient in this respect, yet. Due to specific morphological adaptations, the four genera are assumed to represent different benthic life strategies. New taxa are: Bidimorpha arator n. sp., Bidimorpha labiator n. sp., Bidimorpha sexspinosa n. sp., Falites insula n. sp., Hesslandona abdominalis n. sp., Vestrogothia herrigi n. sp. and Vestrogothia minilaterospinata n. sp. Aus dem mittelkambrischen Borregård Member von Bornholm, einem zeitlichen Äquivalent des baltoskandischen Exsulanskalkes, wurde eine reiche und vergleichsweise diverse Ostrakodenfauna gewonnen. Sie umfaßt 8 Arten aus

  3. Krashen's Input Hypothesis and Affective Filter Hypothesis ’Enlighten-ment to the Vocational English Teaching

    Institute of Scientific and Technical Information of China (English)

    LI Chun-xia

    2013-01-01

    The Krashen's second language acquisition theory have two important assumptions:input hypothesis and the affective filter hypothesis. They can guide and inspire vocational teaching, because they start from the student's learning situation, guide teachers to adjust their teaching methods, and provide better service for teaching and learning. This paper mainly analyzes the Krashen's input hypothesis and the affective filter hypothesis’enlightenment to the vocational English teaching.

  4. From Cycles to Sequences: Sequence Stratigraphy and Relative Sea Level Change for the Late Cambrian of the North China Platform

    Institute of Scientific and Technical Information of China (English)

    MEI Mingxiang; MA Yongsheng; DENG Jun; CHEN Huijun

    2005-01-01

    In the Late Cambrian, the North China Platform was a typical carbonate ramp platform. The Upper Cambrian of the northern part of the North China Platform is famous for the development of bioherm limestones and storm calcirudites and can be divided from bottom to top into the Gushan, Changshan and Fengshan formations. In this set of strata, the deep-ramp mudstone and marls and the shallow-ramp packstones and grainstones constitute many carbonate meter-scale cycles of subtidal type. More tidal-flat dolomites are developed in the Upper Cambrian of the southern margin of the North China platform, in which limestone and dolomite beds also constitute many carbonate meter-scale cycles of the peritidal type. These cycles are marked by a variety of litho-facies successions. There are regularly vertical stacking patterns of meter-scale cycles in long-term third-order sequences, which is the key to discerning such sequences. Thirdorder sequence is marked by a particular sedimentary-facies succession that is the result of the environment-changing process of deepening and shoaling, which is genetically related to third-order sea level changes. Furthermore, four thirdorder sequences can be grouped in the Upper Cambrian of the North China Platform. The main features of these four thirdorder sequences in the northern part of the platform can be summarized as follows: firstly, sequence-boundaries are characterized by drowning unconformities; secondly, the sedimentary-facies succession is generally constituted by one from deep-ramp facies to shallow-ramp facies; thirdly, a succession of "CS (?)+HST" (i.e., "condensed section and highstand system") forms these four third-order sequences. The chief features for the third-order sequences in the southern part of the North China Platform comprises: more dolomites are developed in the HSTs of third-order sequences and also developed more carbonate meter-scale cycles of peritidal types; the sedimentary-facies succession of the third

  5. Effects of fracture reactivation and diagenesis on fracture network evolution: Cambrian Eriboll Formation, NW Scotland

    Science.gov (United States)

    Hooker, J. N.; Eichhubl, P.; Xu, G.; Ahn, H.; Fall, A.; Hargrove, P.; Laubach, S.; Ukar, E.

    2011-12-01

    The Cambrian Eriboll Formation quartzarenites contain abundant fractures with varying degrees of quartz cement infill. Fractures exist that are entirely sealed; are locally sealed by bridging cements but preserve pore space among bridges; are mostly open but lined with veneers of cement; or are devoid of cement. Fracture propagation in the Eriboll Formation is highly sensitive to the presence of pre-existing fractures. Fracture reactivation occurs in opening mode as individual fractures repeatedly open and are filled or bridged by syn-kinematic cements. As well, reactivation occurs in shear as opening of one fracture orientation coincides with shear displacement along pre-existing fractures of different orientations. The tendency for pre-existing fractures to slip varies in part by the extent of cement infill, yet we observe shear and opening-mode reactivation even among sealed fractures. Paleotemperature analysis of fluid inclusions within fracture cements suggests some fractures now in outcrop formed deep in the subsurface. Fractures within the Eriboll Formation may therefore affect later fracture propagation throughout geologic time. With progressive strain, fault zones develop within fracture networks by a sequence of opening-mode fracture formation, fracture reactivation and linkage, fragmentation, cataclasis, and the formation of slip surfaces. Cataclasite within fault zones is commonly more thoroughly cemented than fractures in the damage zone or outside the fault zone. This variance of cement abundance is likely the result of (1) continued exposure of freshly broken quartz surfaces within cataclasite, promoting quartz precipitation, and (2) possibly more interconnected pathways for mass transfer within the fault zone. Enhanced cementation of cataclasite results in strengthening or diagenetic strain hardening of the evolving fault zone. Further slip is accommodated by shear localization along discrete slip surfaces. With further linkage of fault segments

  6. The Middle Cambrian fossil Pikaia and the evolution of chordate swimming

    Directory of Open Access Journals (Sweden)

    Lacalli Thurston

    2012-07-01

    Full Text Available Abstract Conway Morris and Caron (2012 have recently published an account of virtually all the available information on Pikaia gracilens, a well-known Cambrian fossil and supposed basal chordate, and propose on this basis some new ideas about Pikaia’s anatomy and evolutionary significance. Chief among its chordate-like features are the putative myomeres, a regular series of vertical bands that extends the length of the body. These differ from the myomeres of living chordates in that boundaries between them (the myosepta are gently curved, with minimal overlap, whereas amphioxus and vertebrates have strongly overlapping V- and W-shaped myomeres. The implication, on biomechanical grounds, is that myomeres in Pikaia exerted much less tension on the myosepta, so the animal would have been incapable of swimming as rapidly as living chordates operating in the fast-twitch mode used for escape and attack. Pikaia either lacked the fast-twitch fibers necessary for such speeds, having instead only slow-twitch fibers, or it had an ancestral fiber type with functional capabilities more like modern slow fibers than fast ones. The first option is supported by the sequence of development in zebrafish, where both myoseptum formation and fast fiber deployment show a dependence on slow fibers, which develop first. For Pikaia, the absence of fast fibers has both behavioral and anatomical implications, which are discussed. Among the latter is the possibility that a notochord may not have been needed as a primary stiffening device if other structures (for example, the dorsal organ could perform that role.

  7. Depositional and diagenetic variability within the Cambrian Mount Simon Sandstone: Implications for carbon dioxide sequestration

    Science.gov (United States)

    Bowen, B.B.; Ochoa, R.I.; Wilkens, N.D.; Brophy, J.; Lovell, T.R.; Fischietto, N.; Medina, C.R.; Rupp, J.A.

    2011-01-01

    The Cambrian Mount Simon Sandstone is the major target reservoir for ongoing geologic carbon dioxide (CO2) sequestration demonstrations throughout the midwest United States. The potential CO2 reservoir capacity, reactivity, and ultimate fate of injected CO2 depend on textural and compositional properties determined by depositional and diagenetic histories that vary vertically and laterally across the formation. Effective and efficient prediction and use of the available pore space requires detailed knowledge of the depositional and diagenetic textures and mineralogy, how these variables control the petrophysical character of the reservoir, and how they vary spatially. Here, we summarize the reservoir characteristics of the Mount Simon Sandstone based on examination of geophysical logs, cores, cuttings, and analysis of more than 150 thin sections. These samples represent different parts of the formation and depth ranges of more than 9000 ft (>2743 m) across the Illinois Basin and surrounding areas. This work demonstrates that overall reservoir quality and, specifically, porosity do not exhibit a simple relationship with depth, but vary both laterally and with depth because of changes in the primary depositional facies, framework composition (i.e., feldspar concentration), and diverse diagenetic modifications. Diagenetic processes that have been significant in modifying the reservoir include formation of iron oxide grain coatings, chemical compaction, feldspar precipitation and dissolution, multiple generations of quartz overgrowth cementation, clay mineral precipitation, and iron oxide cementation. These variables provide important inputs for calculating CO2 capacity potential, modeling reactivity, and are also an important baseline for comparisons after CO2 injection. Copyright ??2011. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  8. Enigmatic Connection Between Rhyolites and Shallow Granites in a Cambrian Rift

    Science.gov (United States)

    Gilbert, M. C.

    2007-12-01

    The Cambrian Southern Oklahoma Aulacogen (SOA) exposes shallow-seated, A-type sheet granites emplaced on top of layered mafic bodies and under cover of A-type rhyolites, this gabbro-rhyolite boundary being a crustal magma trap. Granites and rhyolites appear to overlap in age, although rhyolites built up first, with the rhyolite pile thickening as later granites coarsened texturally to medium-grained types from earlier fine-grained sheets. Outcrop relations + widespread subsurface data, including regional gravity, indicate rhyolite volume exceeds granite volume. Both silicic and mafic members of the SOA sequence have the same positive Nd signature showing a fundamental genetic relationship between the rifting process and the development of new crust in the SOA. Major element geochemistry of rhyolites (~76% SiO2) and granites (73-76% SiO2) is similar, as are many trace element abundances and signatures. However, some indices are different: Zr in rhyolites is ~600-700ppm, in granites ~300-500; Zr/Nb in rhyolites 8-11, in granites 4-8; K/Rb in rhyolites 300's, in granites 200's. In only one locality can a continuous connection between fine-grained granite and a texturally rhyolitic lobe be seen. Thus, it is clear that none of the rhyolites and granites are directly related at their emplacement level. Conclusions: 1)Silicic magma, both rhyolitic and granitic, was fractionated from mafic sources in the middle rift crust. 2)Magma driving pressures for silicic liquids must have been higher for those becoming rhyolites than for those that became granites. 3)These differences imply that rhyolitic magma generally came from a deeper depth in the mid-crust, although the ultimate mafic sources may have been similar. 4)More generally as this case shows, spatially near, and chemically similar, rhyolite and granite bodies in the same tectonic setting may not be directly related.

  9. The neural rejuvenation hypothesis of cocaine addiction.

    Science.gov (United States)

    Dong, Yan; Nestler, Eric J

    2014-08-01

    A leading hypothesis guiding current molecular and cellular research into drug addiction conceptualizes key aspects of addiction as a form of memory in which common neuroplasticity mechanisms that mediate normal learning and memory processes are 'hijacked' by exposure to drugs of abuse to produce pathologic addiction-related memories. Such addiction-related memories are particularly robust and long-lasting and once formed are less amenable to updating. Here we propose a neural rejuvenation hypothesis of cocaine addiction. According to this hypothesis, repeated exposure to drugs of abuse induces some plasticity mechanisms normally associated with brain development within the reward circuitry that mediate the highly efficient and unusually stable memory abnormalities that characterize addiction. PMID:24958329

  10. Proterozoic sequences and their implications for precamorian and cambrian geologic evolution of Western Kentucky: Evidence from seismic-reflection data

    Science.gov (United States)

    Drahovzal, J.A.

    1997-01-01

    Analyses of two seismic-reflection lines in western Kentucky indicate the presence of two Proterozoic, unconformity-bounded sequences. One is autochthonous and of probable Late Proterozoic age; the other is allochthonous and of probable Middle Proterozoic age. Reflector patterns and apparent relationships to similar sequences elsewhere in the region suggest that the two sequences are of continental-rift origin. The two Proterozoic sequences lie beneath and adjacent to rocks of the Cambrian rift sequence in the Rough Creek Graben. The oldest sequence, the pre-Grenville sequence, was apparently folded and thrust faulted by the Grenville compressional event, implying that it is older than ???0.975 Ga (Middle Proterozoic). Two seismic-reflection pattern types are present in the western Kentucky data that may relate to the Middle Run (lithic arenite) and volcanic sequences defined farther east near the Grenville Front. The presence of imbricate, thrust-belt geometries in the pre-Grenville sequence extends the known westward limit of Grenville compressional structures into western Kentucky. The younger, post-Grenville sequence is less deformed and was apparently formed after the Grenville compressional event; several lines of evidence indicate that it is Late Proterozoic (0.7 to 0.6 Ga) in age. This probable siliciclastic and volcanic-rift sequence is represented by only thin remnants in western Kentucky and has no equivalent near the Grenville Front in southwestern Ohio and central Kentucky. Rocks of the better documented Cambrian rifting event belong to the thick, pre-Knox sequence in the Rough Creek Graben of western Kentucky and lie unconformably above these earlier sequences. A previously undocumented, northward-thickening interval within the lower part of the Cambrian pre-Knox sequence is recognized north of the Rough Creek Graben.

  11. Geochemical comparison of a Cambrian alginite potential source rock, and hydrocarbons from the Colville/Tweed Lake area, Northwest Territories

    Energy Technology Data Exchange (ETDEWEB)

    Wielens, J.B.W.; Fowler, M.G.; Brooks, P.W. (Inst. of Sedimentary and Petroleum Geology, Calgary, AB (Canada)); Dick, H. Von der (Canadian Hunter Exploration Ltd., Calgary, AB (Canada)); Monnier, F. (Chevron Oil Field Research, CA (USA))

    1990-06-01

    The reservoir for gas discoveries in the Colville/Tweed Lake area is the Lower Cambrian Mount Clark sandstone. Heavy oils are also found in this area in Cretaceous formations for which no source rock has previously been assigned. A comparison and correlation of reservoir and oil seep hydrocarbons is presented, and a potential source rock discussed. The gasoline range composition of Tweed Lake condensate shows an unusual distribution, distinguished by a very high abundance of n-alkanes and iso-alkanes and an extremely low abundance of benzene and toluene. The C{sub 15+} saturate fraction gas chromatograms of the condensate and of bitumens found with the Mount Clark reservoir also show many similarities to Ordovidian oils sourced from kukersite intervals. Geochemical screening of samples from several wells indicates that only the Middle Cambrian Mount Cap Formation is sufficiently organic-rich to be a probable source rock. Microscopic examination of one particularly rich interval shows dominance by alginite of a species resembling Gloeocapsomorpha prisca, the predominant contributor to kukersites. The organic matter is Type I, known to generate hydrocarbons at higher maturities. Organic geochemical investigations indicate that a source rock similar to this sample is responsible for the hydrocarbons in the Mount Clark reservoirs. The actual source rocks must be present in areas which have not been drilled to date. Bitumens recovered from surface seeps in the area are very biodegraded and cannot be correlated with any specific source rock, but they were not derived from the Cambrian source rock. 24 refs., 7 figs., 3 tabs.

  12. Paleomagnetic results from the Cambrian and Ordovician sediments of Bornholm (Denmark) and Southern Sweden and paleogeographical implications for Baltica

    Science.gov (United States)

    Lewandowski, Marek; Abrahamsen, Niels

    2003-11-01

    If apparent polar wander paths (APWP) cross, the question arises how to prove the older magnetization to be primary and not just a younger overprint. This problem is typically met in areas affected by percolating mineralizing fluids and/or heating due to a younger regional igneous activity. The Permian magnetic overprint is the classical example. Earlier paleomagnetic studies over the Lowermost Cambrian Nekso Sandstone Fm (NSF) of Bornholm (Denmark) yielded a characteristic remanent magnetization (ChRM) similar to the Permian directions for Baltica. Since a possible reason could be a chemical overprint, we checked whether this phenomenon did take place on a regional scale. Some samples therefore were collected from other Lower Cambrian clastics of Bornholm and Southern Scandinavia. In result we show that the well-grouped and stable ChRM of the NSF contrasts with fairly chaotic, soft, and badly preserved magnetizations of the Balka, Hardeberga, Mickwitzia, and Lingulid sandstones of Bornholm and Southern Sweden, thus not indicating widespread paleomagnetic overprint. We demonstrate that the ChRM of the NSF is most probably of syndepositional/early diagenetic origin and its similarity to the Permian direction for Baltica is only casual. We propose a normal polarity and a near-equatorial position on the Southern Hemisphere for Baltica in the early Cambrian time, as well as a more complicated trend of the APWP for this paleocontinent than envisaged by other authors. Paleomagnetic results from the Arenigian limestones of the Laesaa Formation (Bornholm) that yield excellently defined but most probably only secondary components are also presented.

  13. Self-recognition and Ca2+-dependent carbohydrate-carbohydrate cell adhesion provide clues to the cambrian explosion.

    Science.gov (United States)

    Fernàndez-Busquets, Xavier; Körnig, André; Bucior, Iwona; Burger, Max M; Anselmetti, Dario

    2009-11-01

    The Cambrian explosion of life was a relatively short period approximately 540 Ma that marked a generalized acceleration in the evolution of most animal phyla, but the trigger of this key biological event remains elusive. Sponges are the oldest extant Precambrian metazoan phylum and thus a valid model to study factors that could have unleashed the rise of multicellular animals. One such factor is the advent of self-/non-self-recognition systems, which would be evolutionarily beneficial to organisms to prevent germ-cell parasitism or the introduction of deleterious mutations resulting from fusion with genetically different individuals. However, the molecules responsible for allorecognition probably evolved gradually before the Cambrian period, and some other (external) factor remains to be identified as the missing triggering event. Sponge cells associate through calcium-dependent, multivalent carbohydrate-carbohydrate interactions of the g200 glycan found on extracellular proteoglycans. Single molecule force spectroscopy analysis of g200-g200 binding indicates that calcium affects the lifetime (+Ca/-Ca: 680 s/3 s) and bond reaction length (+Ca/-Ca: 3.47 A/2.27 A). Calculation of mean g200 dissociation times in low and high calcium within the theoretical framework of a cooperative binding model indicates the nonlinear and divergent characteristics leading to either disaggregated cells or stable multicellular assemblies, respectively. This fundamental phenomenon can explain a switch from weak to strong adhesion between primitive metazoan cells caused by the well-documented rise in ocean calcium levels at the end of Precambrian time. We propose that stronger cell adhesion allowed the integrity of genetically uniform animals composed only of "self" cells, facilitating genetic constitutions to remain within the metazoan individual and be passed down inheritance lines. The Cambrian explosion might have been triggered by the coincidence in time of primitive animals

  14. A Hypothesis on Production of Tachyons

    OpenAIRE

    Kowalczynski, J. K.

    1999-01-01

    An exact solution of the Einstein--Maxwell equations yields a general relativistic picture of the tachyonic phenomenon, suggesting a hypothesis on the tachyon creation. The hypothesis says that the tachyon is produced when a neutral and very heavy (over 75 GeV/c^2) subatomic particle is placed in electric and magnetic fields that are perpendicular, very strong (over 6.9 x 10^17 esu/cm^2 or oersted), and the squared ratio of their strength lies in the interval (1,5]. Such conditions can occur ...

  15. SMARANDACHE HYPOTHESIS: EVIDENCES, IMPLICATIONS AND APPLICATIONS

    OpenAIRE

    Motta, Leonardo

    2000-01-01

    In 1972, Smarandache proposed that there is not a limit speed on the nature, based on the EPR-Bell (Einstein, Podolsky, Rosen, Bell) paradox. Although it appears that this paradox was solved recently, there are many other evidences that guide us to believe that Smarandache Hypothesis is right on quantum mechanics and even on the new unification theories. If Smarandache Hypothesis turns to be right under any circumstance, some concepts of modern physics would have to be ...

  16. Interaction Hypothesis and Spoken English Teaching

    Institute of Scientific and Technical Information of China (English)

    郭菲菲

    2013-01-01

    Spoken English is one of the most practical skill that students need to obtain.However there exist many problems in Spoken English Teaching in China ,one of the most serious problem is that it lacks sufficient practice.According to the interaction hypothesis (Long, Gass), second language acquisition occurs when learners interact in conversation with native speakers and/or each other.Based on this hypothesis,the author presents some new insights for improving Spoken English Teaching and discusses its enlightenment in Spoken English Teaching Classroom.

  17. Trilobites from the Çal Tepe Formation (Cambrian), Near Seydişehir, Central Taurides, Southwestern Turkey

    OpenAIRE

    DEAN, WILLIAM T.

    2005-01-01

    The type section of the Çal Tepe Formation, near Seydişehir, is reviewed. The basal dolomite member is unfossiliferous, but the succeeding black limestone member (24 m), light-grey limestone member (10.15 m), and red nodular limestone member (46.7 m) are subdivided into thirty-seven numbered, often fossiliferous beds. Trilobites from the black limestone member, late Early Cambrian, exhibit affinities with Morocco, Spain and northwestern Europe; they include one new genus and species (Pamphyli...

  18. High-Precision U-Pb Geochronology and Correlation: An example Using the Neoproterozic-Cambrian Transition

    Science.gov (United States)

    Bowring, S. A.; Grotzinger, J. P.; Amthor, J.; Martin, M. E.

    2001-05-01

    The precise, global correlation of Precambrian and Paleozoic sedimentary rocks can be achieved using temporally calibrated chemostratigraphic records. This approach is essential for determining rates and causes of environmental and faunal change, including mass extinctions. For example, The Neoproterozoic is marked by major environmental change, including periods of global glaciation, large fluctuations in the sequestration of carbon and major tectonic reorganization followed by the explosive diversification of animals in the earliest Cambrian. The extreme climatic change associated with these glaciations have been implicated as a possible trigger for the Cambrian explosion. The recognition of thin zircon-bearing air-fall ash in Neoproterozoic and Cambrian rocks has allowed the establishment of a high-precision temporal framework for animal evolution and is helping to untangle the history of glaciations. In some cases analytical uncertainties translate to age uncertainties of less than 1 Ma and when integrated with chemostratigraphy, the potential for global correlations at even higher resolution. Progress in the global correlation of Neoproterozoic strata has been achieved through the use of C and Sr isotope chemostratigraphy although it has been hampered by a lack of precise geochronological and faunal control. For example, the period from ca 800-580 Ma is characterized by at least two and perhaps as many as four glacial events that are interpreted by many to be global glaciations on a "Snowball Earth". A lack of precise chronological constraints on the number and duration of glaciations, multiple large excursions in the carbon isotopic record, and an absence of detailed biostratigraphy have complicated global correlation and hindered our understanding of this important period of Earth history. However, the ongoing integration of chemostratigraphic and geochronological data are improving temporal resolution and detailed correlations. These data are critical for

  19. Detrital zircon U-Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico

    Science.gov (United States)

    Gehrels, G.E.; Stewart, John H.

    1998-01-01

    One hundred and eighty two individual detrital zircon grains from Cambrian through Permian miogeoclinal strata, Ordovician eugeoclinal rocks, and Triassic post-orogenic sediments in northwestern Sonora have been analyzed. During Cambrian, Devonian, Permian, and Triassic time, most zircons accumulating along this part of the Cordilleran margin were shed from 1.40-1.45 and 1.62-1.78 Ga igneous rocks that are widespread in the southwestern United States and northwestern Mexico. Zircons with ages of approximately 1.11 Ga are common in Cambrian strata and were apparently shed from granite bodies near the sample site. The sources of 225-280 Ma zircons in our Triassic sample are more problematic, as few igneous rocks of these ages are recognized in northwestern Mexico. Such sources may be present but unrecognized, or the grains could have been derived from igneous rocks of the appropriate ages to the northwest in the Mojave Desert region, to the east in Chihuahua and Coahuila, or to the south in accreted(?) arc-type terranes. Because the zircon grains in our Cambrian and Devonian to Triassic samples could have accumulated in proximity to basement rocks near their present position or in the Death Valley region of southern California, our data do not support or refute the existence of the Mojave-Sonora megashear. Ordovician strata of both miogeoclinal and eugeoclinal affinity are dominated by >1.77 Ga detrital zircons, which are considerably older than most basement rocks in the region. Zircon grains in the miogeoclinal sample were apparently derived from the Peace River arch area of northwestern Canada and transported southward by longshore currents. The eugeoclinal grains may also have come from the Peace River arch region, with southward transport by either sedimentary or tectonic processes, or they may have been shed from off-shelf slivers of continents (perhaps Antarctica?) removed from the Cordilleran margin during Neoproterozoic rifting. It is also possible that the

  20. Does Portuguese economy support crude oil conservation hypothesis?

    International Nuclear Information System (INIS)

    This paper examines cointegration relationships and Granger causality nexus in a trivariate framework among oil consumption, economic growth and international oil price in Portugal. For this purpose, we employ two Granger causality approaches: the Johansen cointegration test and vector error correction model (VECM) and the Toda–Yamamoto approaches. Cointegration test proves the existence of a long run equilibrium relationship among these variables and VECM and Toda–Yamamoto Granger causality tests indicate that there is bidirectional causality between crude oil consumption and economic growth (feed back hypothesis). Therefore, the Portuguese economy does not support crude oil conservation hypothesis. Consequently, policymakers should consider that implementing oil conservation and environmental policies may negatively impact on the Portuguese economic growth. - Highlights: ► We examine Granger causality among oil consumption, GDP and oil price in Portugal. ► VECM and Toda–Yamamoto tests found bidirectional causality among oil and GDP. ► Portuguese economy does not support the crude oil conservation hypothesis.

  1. From Basin Black Shales to Platform Carbonate Rocks: A Study on Sequence Stratigraphy for the Lower Cambrian of the Upper-Yangtze Region in South China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the Upper-Yangtze region, especially in Guizhou Province and its adjacent areas, the Lower Cambrian is well developed and is marked by a succession from black shales of the basin facies to carbonate rocks of the platform facies. The drowning event of the platform occurring at the turn from Sinian to Cambrian resulted in a set of black shales, i.e. the Niutitang Formation, which makes up the bottom part of the Lower Cambrian. With the shoaling of the sedimentary environment, a set of carbonate rocks, i.e. the Qingxudong Formation, was formed in the top part of the Lower Cambrian. Thus, the Lower Cambrian in the study area makes up one second-order sequence that can be further subdivided into five third-order sequences, and forms a regularly cyclic succession of transgression-regression. There is a regularly vertical stacking pattern for the third-order sequences in the second-order sequence. From bottom to top, the succession of the "CS (condensed section)+HST (high-stand system tract)" of the third-order sequences is changed into the succession of the "TST (transgressive system tract)+CS+HST". Correspondingly, the drowning-type sequence boundary is changed into the exposure-type one. Therefore, both the second-order and the third-order sequences have similar sedimentary-facies architectures. A concomitant with these temporal changes,the Lower Cambrian with a thickness of 1000 m that contains five third-order sequences is changed into a condensed succession that cannot identify third-order sequences toward the southeast with the deepening of the sedimentary environment. According to the elementary features of the third-order sequences, i.e. the regularity o sedimentary-facies successions in space and the synchronism of sedimentary-environment changes in time, the detailed division of the third-order sequences at main logged sections in different paleogeographical background becomes the basis to establish the sequence-stratigraphic framework that can demonstrate

  2. Paleoceangraphic significance of redox-sensitive metals of black shales in the basal Lower Cambrian Niutitang Formation in Guizhou Province,South China

    Institute of Scientific and Technical Information of China (English)

    YANG Jinghong; JIANG Shaoyong; LING Hongfei; FENG Hongzhen; CHEN Yongquan; CHEN Jianhua

    2004-01-01

    Black shales of the Lower Cambrian Niutitang Formation occur widely on the Yangtze Platform. In this study, we analyzed black shales from two sections (Zhongnan and Zhijin) in Guizhou Province. The redox-sensitive metal concentration and distribution of black shales from the two sections provide good evidence for the anoxic conditions of the basal Cambrian ocean on the Yangtze Platform. Our geochemical data suggest that the black shales from the Zhongnan section may have deposited in a more strongly anoxic environment than the black shales in the Zhijin section.

  3. "The Chengjiang Fauna and the Cambrian Explosion" Sponsord by NSFC won the first-class award of National Natural Sciences Award

    Institute of Scientific and Technical Information of China (English)

    Liu; Y.; Yao; Y.P.

    2004-01-01

      "The Chengjiang Fauna and the Cambrian explosion'' sponsord by NSFC won the first-class award of National Natural Sciences Award. The Awarding ceremony was held in the Great Hall of the People in Beijing on February 20, 2004. "The Chengjiang Fauna and the Cambrian explosion" was sponsord by NSFC and carried out by several groups led by Prof. Chen Junyuan of the Nanjing Institute of Geology and Palaeontology,CAGS, Prof. Hou Xianguang of Yunnan University and Prof.……

  4. Vacuum counterexamples to the cosmic censorship hypothesis

    International Nuclear Information System (INIS)

    In cylindrically symmetric vacuum spacetimes it is possible to specify nonsingular initial conditions such that timelike singularities will (necessarily) evolve from these conditions. Examples are given; the spacetimes are somewhat analogous to one of the spherically symmetric counterexamples to the cosmic censorship hypothesis

  5. Empagliflozin's Fuel Hypothesis: Not so Soon.

    Science.gov (United States)

    Lopaschuk, Gary D; Verma, Subodh

    2016-08-01

    The EMPA-REG OUTCOME trial (Zinman et al., 2015) established cardioprotective effects of empagliflozin in high-risk diabetic patients, but the underlying mechanisms remain elusive. A recent hypothesis proposed that increased ketone oxidation contributed to the effect, but several caveats indicate that the role of myocardial ketone oxidation is far from clear. PMID:27508868

  6. Some Thoughts on Sapir-Whorf Hypothesis

    Institute of Scientific and Technical Information of China (English)

    杨慧芳

    2010-01-01

    @@ The relationship between language and thought has long been discussed by scholars since Plato's time and various hypotheses have been made concerning it.The most provocative one is the Sapir-Whorf hypothesis.Although it appeared very reasonable and had been very popular for a time,more and more arguments can be found to challenge its validity.

  7. A Philosophical Critique of Null Hypothesis Testing.

    Science.gov (United States)

    Orey III, Michael A.; And Others

    1989-01-01

    An attempt is made to clarify the philosophical foundations of the debate over research methodology appropriate for psychology in particular and the utility of null hypothesis testing in general. The article also relates the debate to education and suggests that the debate is far from settled. (IAH)

  8. Joint production and price uncertainty: hypothesis tests

    OpenAIRE

    Alghalith, Moawia

    2006-01-01

    This paper extends the existing estimation methods to allow empirical estimation and hypothesis testing under joint production and price uncertainty. Our approach modifies and expands the use of duality theory. Furthermore, our approach does not require the specification or estimation of the production/cost function. We apply the methodology to the U.S. manufacturing sector.

  9. Hypothesis on the nature of atmospheric UFOs

    Science.gov (United States)

    Mukharev, L. A.

    1991-08-01

    A hypothesis is developed according to which the atmospheric UFO phenomenon has an electromagnetic nature. It is suggested that an atmospheric UFO is an agglomeration of charged atmospheric dust within which there exists a slowly damped electromagnetic field. This field is considered to be the source of the observed optical effects and the motive force of the UFO.

  10. The (not so immortal strand hypothesis

    Directory of Open Access Journals (Sweden)

    Cristian Tomasetti

    2015-03-01

    Significance: Utilizing an approach that is fundamentally different from previous efforts to confirm or refute the immortal strand hypothesis, we provide evidence against non-random segregation of DNA during stem cell replication. Our results strongly suggest that parental DNA is passed randomly to stem cell daughters and provides new insight into the mechanism of DNA replication in stem cells.

  11. A Flexible Non Linear Model to Test the Expectation Hypothesis of Interest Rates

    OpenAIRE

    Jean-michel Sahut

    2014-01-01

    Conventional approaches to examining the expectation hypothesis of interest rates assume a parametric linear specification among variables. In contrast, this paper tests the hypothesis using a flexible nonlinear inference approach proposed by Hamilton (2001). We examine the impact of the nonlinearity of interest rates to explain the variability of risk premia on market rates. It is assumed that the term structure of interest rates can be identified by two factors, the risk-free rate and its v...

  12. Fractal Markets Hypothesis and the Global Financial Crisis: Scaling, Investment Horizons and Liquidity

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav

    2012-01-01

    Roč. 15, č. 6 (2012), 1250065-1-1250065-13. ISSN 0219-5259 R&D Projects: GA ČR GA402/09/0965 Grant ostatní: GA UK(CZ) 118310; SVV(CZ) 265 504 Institutional support: RVO:67985556 Keywords : fractal markets hypothesis * scaling * fractality * investment horizons * efficient markets hypothesis Subject RIV: AH - Economics Impact factor: 0.647, year: 2012 http://library.utia.cas.cz/separaty/2012/E/kristoufek-fractal markets hypothesis and the global financial crisis scaling investment horizons and liquidity.pdf

  13. Organic Carbon Isotopic Evolution during the Ediacaran-Cambrian Transition Interval in Eastern Guizhou, South China: Paleoenvironmental and Stratigraphic Implications

    Institute of Scientific and Technical Information of China (English)

    YANG Xinglian; ZHU Maoyan; GUO Qingjun; ZHAO Yuanlong

    2007-01-01

    Secular variations of carbon isotopic composition of organic carbon can be used in the study of global environmental variation, the carbon cycle, stratigraphic delimitation, and biological evolution, etc. Organic carbon isotopic analysis of the Nangao and Zhalagou sections in eastern Guizhou reveals a negative excursion near the Precambrian-Cambrian boundary that correlates with a distinct carbonate carbon isotopic negative excursion at this boundary globally. Our results also demonstrate that several alternating positive and negative shifts occur in the Meishucunian, and an obvious negative anomaly appears at the boundary between the Meishucunian and Qiongzhusian. The isotope values are stable in the middle and lower parts but became more positive in the upper part of the Qiongzhusian. Evolution of organic carbon isotopes from the two sections in the deepwater facies can be well correlated with that of the carbonate carbon isotopes from the section in the shallow water facies. Integrated with other stratigraphic tools, we can precisely establish a lower Cambrian stratigraphic framework from shallow shelf to deep basin of the Yangtze Platform.

  14. Experimental mineralization of crustacean eggs leads to surprising tissue conservation: new implications for the fossilization of Precambrian-Cambrian embryos

    Directory of Open Access Journals (Sweden)

    D. Hippler

    2011-12-01

    Full Text Available Phosphatized globular microfossils from the Ediacaran and Lower Cambrian of South China represent an impressive record of early animal evolution and development, however their affinity based on putative embryonic metazoan, bacterial and inorganic features is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are therefore crucial for a reliable interpretation of their phylogenetic position. Taphonomic experiments on eggs of the marbled crayfish indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope, producing different preservational stages of degradation resembling the various decay stages observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4·2H2O over calcite as the dominating mineral phase. Although the endochorional envelope was not preserved, experiments resulted in exceptional preservation of the embryonic tissue at the cellular level. Thus our findings suggest that the mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment and during fossilization of Cambrian embryos were likely operating at a similar rationale.

  15. Cambrian magmatism, Variscan high-grade metamorphism and imposed greenschist facies shearing in the Central Sredna Gora basement units (Bulgaria

    Directory of Open Access Journals (Sweden)

    Lazarova Anna

    2015-12-01

    Full Text Available Gneisses from the deep structural levels of the European Variscan Belt are well exposed in the Central Sredna Gora in Bulgaria. In general, migmatites predominate, but unmigmatized domains (or domains with incipient migmatization are also documented in this area. This paper presents new structural, petrographic and U-Pb isotope geochronological data from such an unmigmatized part of the Variscan high-grade metamorphic basement (the Koprivshtitsa Unit. A predominant part of this unit represents an alternation of metagranitoids and metabasites. The protolith crystallization age of the metagranitoids is constrained at 491.5 ± 7.6 Ma by U-Pb laser ablation method on zircons. This age coincides with the previously available Late Cambrian protolith ages of metabasic rocks that crop out within the adjacent migmatitic unit. The Korpivshtitsa Unit comprises also lesser orthogneisses with Late Neoproterozoic protoliths. Based on the available local and regional paleogeographic reconstruction schemes, we suggest that the Upper Cambrian magmatic rocks intruded Upper Neoproterozoic crust during the initial opening stages of the Rheic Ocean or a related basin. Subsequently, both were involved in the Variscan high-grade deformation. The contact of the Koprivshitsa Unit with the migmatitic part of the metamorphic complex coincides with a north-vergent greenschist facies thrust zone – the Chuminska Shear Zone. The exact time of the shearing is still not well constrained but it clearly postdates the Variscan high-temperature metamorphism of the gneisses.

  16. Experimental mineralization of crustacean eggs leads to surprising tissue conservation: new implications for the fossilization of Precambrian-Cambrian embryos

    Science.gov (United States)

    Hippler, D.; Hu, N.; Steiner, M.; Scholtz, G.; Franz, G.

    2011-12-01

    Phosphatized globular microfossils from the Ediacaran and Lower Cambrian of South China represent an impressive record of early animal evolution and development, however their affinity based on putative embryonic metazoan, bacterial and inorganic features is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are therefore crucial for a reliable interpretation of their phylogenetic position. Taphonomic experiments on eggs of the marbled crayfish indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope, producing different preservational stages of degradation resembling the various decay stages observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4·2H2O) over calcite as the dominating mineral phase. Although the endochorional envelope was not preserved, experiments resulted in exceptional preservation of the embryonic tissue at the cellular level. Thus our findings suggest that the mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment and during fossilization of Cambrian embryos were likely operating at a similar rationale.

  17. Isotopic evolution of the terminal Neoproterozoic and early Cambrian carbon cycle on the northern Yangtze Platform, South China

    Institute of Scientific and Technical Information of China (English)

    GUO Qingjun; LIU Congqiang; Harald STRAUSS; Tatiana GOLDBERG

    2003-01-01

    Profound geotectonic, climatic and biological changes occur during the terminal Neoproterozoic and its transition into the early Cambrian. These are reflected in temporal variations of the chemical and isotopic composition of seawater. We are studying a sequence of sedimentary rocks at the Shatan section, northern Yangtze Platform, Sichuan Province of China. This succession comprises, in ascending stratigraphic order, predominantly calcareous sediments of the Sinian upper Dengying Formation and black shales of the lower Cambrian Guojiaba Formation (time equivalent of Niutitang Fm.). Paleoenvironmental setting represents shallow-water shelf deposits. The objective of our study is to provide temporal records for the isotopic compositions of organic and carbonate carbon throughout this time interval. Organic carbon isotope values display a range between -35.8‰ and -30.1‰ with clear stratigraphic variations. Carbonate carbon isotope data vary between -3.5‰ and +0.5‰. These secular variations are interpreted to reflect perturbations of the global carbon cycle, specifically changes in the fractional burial of organic carbon. However, local conditions have further affected the isotopic signals.

  18. Proterozoic-Cambrian detrital zircon and monazite ages from the Anakie lnlier, central Queensland: Grenville and Pacific-Gondwana signatures

    International Nuclear Information System (INIS)

    The Anakie Metamorphic Group is a complexly deformed, dominantly metasedimentary succession in central Queensland. Metamorphic cooling is constrained to ca 500 Ma by previously published K-Ar ages. Detrital-zircon SHRIMP U-Pb ages from three samples of greenschist facies quartz-rich psammites (Bathampton Metamorphics), west of Clermont, are predominantly in the age range 1300-1000Ma (65-75%). They show that a Grenville-aged orogenic belt must have existed in northeastern Australia, which is consistent with the discovery of a potential Grenville source farther north. The youngest detrital zircons in these samples are ca 580 Ma, indicating that deposition may have been as old as latest Neoproterozoic. Two samples have been analysed from amphibolite facies pelitic schist from the western part of the inlier (Wynyard Metamorphics). One sample contains detrital monazite with two age components of ca 580-570 Ma and ca 540 Ma. The other sample only has detrital zircons with the youngest component between 510Ma and 700Ma (Pacific-Gondwana component), which is consistent with a Middle Cambrian age for these rocks. These zircons were probably derived from igneous activity associated with rifting events along the Gondwanan passive margin. These constraints confirm correlation of the Anakie Metamorphic Group with latest Neoproterozoic - Cambrian units in the Adelaide Fold Belt of South Australia and the Wonominta Block of western New South Wales. Copyright (2001) Geological Society of Australia

  19. Phylogenomic insights into the cambrian explosion, the colonization of land and the evolution of flight in arthropoda.

    Science.gov (United States)

    Wheat, Christopher W; Wahlberg, Niklas

    2013-01-01

    The timing of the origin of arthropods in relation to the Cambrian explosion is still controversial, as are the timing of other arthropod macroevolutionary events such as the colonization of land and the evolution of flight. Here we assess the power of a phylogenomic approach to shed light on these major events in the evolutionary history of life on earth. Analyzing a large phylogenomic dataset (122 taxa, 62 genes) with a Bayesian-relaxed molecular clock, we simultaneously reconstructed the phylogenetic relationships and the absolute times of divergences among the arthropods. Simulations were used to test whether our analysis could distinguish between alternative Cambrian explosion scenarios with increasing levels of autocorrelated rate variation. Our analyses support previous phylogenomic hypotheses and simulations indicate a Precambrian origin of the arthropods. Our results provide insights into the 3 independent colonizations of land by arthropods and suggest that evolution of insect wings happened much earlier than the fossil record indicates, with flight evolving during a period of increasing oxygen levels and impressively large forests. These and other findings provide a foundation for macroevolutionary and comparative genomic study of Arthropoda. PMID:22949483

  20. The GAIA Hypothesis and Chaos in Daisyworld.

    Science.gov (United States)

    Flynn, Cathal Michael

    1993-01-01

    To correctly model the climate it is necessary to include the effects of the biosphere. The Gaia hypothesis claims that the earth's living matter, air, oceans, and land form a complex system which has the capacity to regulate the earth's climate. A model developed by Lovelock and Watson to demonstrate the Gaia hypothesis is explained and the results of their work are reviewed. Only steady state behavior is observed in the Daisyworld model. The work of Zeng et al. on the presence of chaos in Daisyworld is reviewed as an introduction to our own work. The presence of oscillatory and even chaotic behavior in this Daisyworld model brings into question the Gaia hypothesis. We develop a model of two-dimensional crystal growth called Crystalworld. The Crystalworld model is similar to the Daisyworld model in that there is a coupling between the growing entities and their environment via temperature. The results of this model are similar to that of the Daisyworld model. We present the results of another modified model of Daisyworld which we developed. This modified model takes into account the finite response time of the daisies to changes in the planet's climatic conditions. With a generation time introduced into the model equations, while retaining the differential equation format, it is found that the system can show oscillatory and chaotic behavior. These results show that any climate-biosphere model must contain a time delay and that such a time delay leads to behavior which contradicts the Gaia hypothesis. In order to determine the effects of introducing more species we develop a model with two species of daisies and a parasite species. For this Parasite-Daisyworld model steady state, periodic and chaotic behavior is found. A comparison between the results of this model and that of Zeng et al. is made. The results of the Parasite-Daisyworld model show that increasing the number of species does not lead to increased regulation. This contradicts the Gaia hypothesis and

  1. A hypothesis on production of tachyons

    International Nuclear Information System (INIS)

    An exact solution of the Einstein-Maxwell equations yields a general relativistic picture of the tachyonic phenomenon, suggesting a hypothesis on the tachyon creation. The hypothesis says that the tachyon is produced when a neutral and very heavy (over 75 GeV/c2) subatomic particle is placed in electric and magnetic fields that are perpendicular, very strong (over 6.9 x 1017 esu/cm2 or oersted), and the squared ratio of their strength lies in the interval (1,5]. Such conditions can occur when non positive subatomic particles of high energy strike atomic nuclei other than the proton. The kinematical relations for the produced tachyon are given. Previous searches for tachyons in air showers and some possible causes of their negative results are discussed. Experiments with the use of the strongest colliders and improvements in the air shower experiments are suggested. An unfortunate terminology is also discussed. (Authors)

  2. Testing the Markov hypothesis in fluid flows

    Science.gov (United States)

    Meyer, Daniel W.; Saggini, Frédéric

    2016-05-01

    Stochastic Markov processes are used very frequently to model, for example, processes in turbulence and subsurface flow and transport. Based on the weak Chapman-Kolmogorov equation and the strong Markov condition, we present methods to test the Markov hypothesis that is at the heart of these models. We demonstrate the capabilities of our methodology by testing the Markov hypothesis for fluid and inertial particles in turbulence, and fluid particles in the heterogeneous subsurface. In the context of subsurface macrodispersion, we find that depending on the heterogeneity level, Markov models work well above a certain scale of interest for media with different log-conductivity correlation structures. Moreover, we find surprising similarities in the velocity dynamics of the different media considered.

  3. Optimality of Binning for Distributed Hypothesis Testing

    CERN Document Server

    Rahman, Md Saifur

    2011-01-01

    We study a hypothesis testing problem in which data is compressed distributively and sent to a detector that seeks to decide between two possible distributions for the data. The aim is to characterize all achievable encoding rates and exponents of the type 2 error probability when the type 1 error probability is at most a fixed value. For related problems in distributed source coding, schemes based on random binning perform well and often optimal. For distributed hypothesis testing, however, the use of binning is hindered by the fact that the overall error probability may be dominated by errors in binning process. We show that despite this complication, binning is optimal for a class of problems in which the goal is to "test against conditional independence." We then use this optimality result to give an outer bound for a more general class of instances of the problem.

  4. Exploring heterogeneous market hypothesis using realized volatility

    Science.gov (United States)

    Chin, Wen Cheong; Isa, Zaidi; Mohd Nor, Abu Hassan Shaari

    2013-04-01

    This study investigates the heterogeneous market hypothesis using high frequency data. The cascaded heterogeneous trading activities with different time durations are modelled by the heterogeneous autoregressive framework. The empirical study indicated the presence of long memory behaviour and predictability elements in the financial time series which supported heterogeneous market hypothesis. Besides the common sum-of-square intraday realized volatility, we also advocated two power variation realized volatilities in forecast evaluation and risk measurement in order to overcome the possible abrupt jumps during the credit crisis. Finally, the empirical results are used in determining the market risk using the value-at-risk approach. The findings of this study have implications for informationally market efficiency analysis, portfolio strategies and risk managements.

  5. Multi-agent sequential hypothesis testing

    KAUST Repository

    Kim, Kwang-Ki K.

    2014-12-15

    This paper considers multi-agent sequential hypothesis testing and presents a framework for strategic learning in sequential games with explicit consideration of both temporal and spatial coordination. The associated Bayes risk functions explicitly incorporate costs of taking private/public measurements, costs of time-difference and disagreement in actions of agents, and costs of false declaration/choices in the sequential hypothesis testing. The corresponding sequential decision processes have well-defined value functions with respect to (a) the belief states for the case of conditional independent private noisy measurements that are also assumed to be independent identically distributed over time, and (b) the information states for the case of correlated private noisy measurements. A sequential investment game of strategic coordination and delay is also discussed as an application of the proposed strategic learning rules.

  6. The Efficient Market Hypothesis: Empirical Evidence

    OpenAIRE

    Martin Victor Sewell

    2012-01-01

    The efficient market hypothesis (EMH) has been the central proposition of finance since the early 1970s and is one of the most well-studied hypotheses in all the social sciences, yet, surprisingly, there is still no consensus, even among financial economists, as to whether the EMH holds. Five statistical analyses are conducted in an attempt to explicate such apparently contrary convictions.  An analysis of daily, weekly, monthly and annual Dow Jones Industrial Average log returns found that f...

  7. Competitive Environment Hypothesis in Turkish Banking System

    OpenAIRE

    Alper Aslan; Kemal Koksal; Oguz Ocal

    2011-01-01

    TThis paper investigates the persistence of profit in Turkish banking system for the period of 2004:1 – 2009:4 by focusing net income after tax to total equity (ROE) as profit measures by utilizing panel unit root tests. We found that competition among surviving banks is high in the Turkish Banking System for the period 2004:1 – 2009:4 which means that competitive environment hypothesis is valid in Turkish banking system.

  8. Around LTD hypothesis in motor learning.

    OpenAIRE

    Hirano, Tomoo

    2014-01-01

    Long-term depression (LTD) at parallel fiber-Purkinje neuron synapses has been regarded as a primary cellular mechanism for motor learning. However, this hypothesis has been challenged. Demonstration of normal motor learning under LTD-suppressed conditions suggested that motor learning can occur without LTD. Synaptic plasticity mechanisms other than LTD have been found at various synapses in the cerebellum. Animals may achieve motor learning using several types of synaptic plasticity in the c...

  9. Quantum effects and hypothesis of cosmic censorship

    International Nuclear Information System (INIS)

    It is shown that filamentary characteristics with linear mass of less than 1025g/cm distort slightly the space-time at distances, exceeding Planck ones. Their formation doesn't change vacuum energy and doesn't lead to strong quantum radiation. Therefore, the problem of their occurrence can be considered within the framework of classical collapse. Quantum effects can be ignored when considering the problem of validity of cosmic censorship hypothesis

  10. The vascular depression hypothesis: An update

    OpenAIRE

    Sneed, Joel R.; Culang-Reinlieb, Michelle E.

    2011-01-01

    Since being proposed as a unique subtype of late-life depression (LLD), the vascular depression hypothesis has received considerable research attention. Although this effort has generated considerable empirical support for the validity of the subtype, fundamental questions remain including how the illness is defined, whether cerebrovascular disease and executive dysfunction (ED) define two separate entities or one underlying subtype, and whether ED is responsible for poor response to antidepr...

  11. The social brain hypothesis of schizophrenia

    OpenAIRE

    Burns, Jonathan

    2006-01-01

    The social brain hypothesis is a useful heuristic for understanding schizophrenia. It focuses attention on the core Bleulerian concept of autistic alienation and is consistent with well-replicated findings of social brain dysfunction in schizophrenia as well as contemporary theories of human cognitive and brain evolution. The contributions of Heidegger, Merleau-Ponty and Wittgenstein allow us to arrive at a new "philosophy of interpersonal relatedness", which better reflects...

  12. The Neural Rejuvenation Hypothesis of Cocaine Addiction

    OpenAIRE

    Dong, Yan; Nestler, Eric J.

    2014-01-01

    A leading hypothesis guiding current molecular and cellular research of drug addiction conceptualizes key aspects of addiction as a form of memory, in which common neuroplasticity mechanisms that mediate normal learning and memory processes are “hijacked” by exposure to drugs of abuse to produce pathologic addiction-related memories. Such addiction-related memories are particularly robust and long-lasting and once formed, less amenable to updating. Here, we propose the Neural Rejuvenation Hyp...

  13. Sea otter health: Challenging a pet hypothesis.

    Science.gov (United States)

    Lafferty, Kevin D

    2015-12-01

    A recent series of studies on tagged sea otters (Enhydra lutris nereis) challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to Toxoplasma gondii in central California. Counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. Ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of disease transmission. PMID:26155464

  14. Sea otter health: Challenging a pet hypothesis

    Directory of Open Access Journals (Sweden)

    Kevin D. Lafferty

    2015-12-01

    Full Text Available A recent series of studies on tagged sea otters (Enhydra lutris nereis challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to Toxoplasma gondii in central California. Counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. Ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of disease transmission.

  15. Sea otter health: Challenging a pet hypothesis

    OpenAIRE

    Lafferty, Kevin D.

    2015-01-01

    A recent series of studies on tagged sea otters (Enhydra lutris nereis) challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to Toxoplasma gondii in central California. Counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. Ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of...

  16. Testing the single-state dominance hypothesis

    Energy Technology Data Exchange (ETDEWEB)

    Álvarez-Rodríguez, R. [Universidad Politécnica de Madrid, Avda. Juan Herrera 4, E-28040 Madrid (Spain); Moreno, O.; Moya de Guerra, E. [Universidad Complutense de Madrid, Avda. Complutense, E-28040 Madrid (Spain); Sarriguren, P. [Instituto de Estructura de la Materia (CSIC), Serrano 123, E-28006 Madrid (Spain); Šimkovic, F. [Comenius University, SK-842 15 Bratislava (Slovakia); Faessler, A. [University of Tübingen, D-72076 Tübingen (Germany)

    2013-12-30

    We present a theoretical analysis of the single-state dominance hypothesis for the two-neutrino double-beta decay process. The theoretical framework is a proton-neutron QRPA based on a deformed Hartree-Fock mean field with BCS pairing correlations. We focus on the decays of {sup 100}Mo, {sup 116}Cd and {sup 128}Te. We do not find clear evidences for single-state dominance within the present approach.

  17. Somatotropic function: the somatomedin hypothesis revisited.

    Science.gov (United States)

    Etherton, T D

    2004-01-01

    The discovery in 1922 that an alkaline extract of the anterior pituitary can increase growth and change carcass composition of rats led to the discovery of growth hormone (somatotropin, ST). Since the early studies, much has been learned about the biological effects of ST. The advent of recombinant DNA technology has led to the commercial development of ST-based products for animal agriculture. Administration of porcine ST (pST) at maximally effective doses (approximately 100 microg x kg BW(-1) x d(-1)) to growing pigs for 30 to 77 d increases average daily gain approximately 10 to 20%, improves productive efficiency (i.e., the ratio of body weight gain to feed consumed) 13 to 33%, decreases lipid accretion rates by as much as approximately 80%, and stimulates protein deposition (muscle growth) by as much as 70%. These responses are associated with a decrease in feed intake of approximately 10 to 15%. The effects of ST are mediated directly and indirectly. The indirect effects of ST are mediated by the somatomedin (insulin-like growth factor-I). The discovery of somatomedin led to the introduction of the somatomedin hypothesis, which explained the basis of ST action. Since the discovery of the somatomedins, there have been several modifications of the hypothesis developed to accommodate the evolution in understanding of how ST and IGF-I affect a diverse array of biological events. This review will summarize the history of ST and the evolution of the somatomedin hypothesis. PMID:15471803

  18. Predictions from high scale mixing unification hypothesis

    Indian Academy of Sciences (India)

    Rahul Srivastava

    2016-02-01

    Starting with ‘high scale mixing unification’ hypothesis, we investigate the renormalization group evolution of mixing parameters and masses for both Dirac and Majorana-type neutrinos. Following this hypothesis, the PMNS mixing parameters are taken to be identical to the CKM ones at a unifying high scale. Then, they are evolved to a low scale using MSSM renormalization group equations. For both types of neutrinos, the renormalization group evolution naturally results in a non-zero and small value of leptonic mixing angle 13. One of the important predictions of this analysis is that, in both cases, the mixing angle 23 turns out to be non-maximal for most of the parameter range. We also elaborate on the important differences between Dirac and Majorana neutrinos within our framework and how to experimentally distinguish between the two scenarios. Furthermore, for both cases, we also derive constraints on the allowed parameter range for the SUSY breaking and unification scales, for which this hypothesis works. The results can be tested by the present and future experiments.

  19. A test of the orthographic recoding hypothesis

    Science.gov (United States)

    Gaygen, Daniel E.

    2003-04-01

    The Orthographic Recoding Hypothesis [D. E. Gaygen and P. A. Luce, Percept. Psychophys. 60, 465-483 (1998)] was tested. According to this hypothesis, listeners recognize spoken words heard for the first time by mapping them onto stored representations of the orthographic forms of the words. Listeners have a stable orthographic representation of words, but no phonological representation, when those words have been read frequently but never heard or spoken. Such may be the case for low frequency words such as jargon. Three experiments using visually and auditorily presented nonword stimuli tested this hypothesis. The first two experiments were explicit tests of memory (old-new tests) for words presented visually. In the first experiment, the recognition of auditorily presented nonwords was facilitated when they previously appeared on a visually presented list. The second experiment was similar, but included a concurrent articulation task during a visual word list presentation, thus preventing covert rehearsal of the nonwords. The results were similar to the first experiment. The third experiment was an indirect test of memory (auditory lexical decision task) for visually presented nonwords. Auditorily presented nonwords were identified as nonwords significantly more slowly if they had previously appeared on the visually presented list accompanied by a concurrent articulation task.

  20. 40Ar/39Ar dating of exceptional concentration of metals by weathering of Precambrian rocks at the Precambrian–Cambrian boundary

    DEFF Research Database (Denmark)

    Parnell, John; Mark, Darren F.; Frei, Robert; Fallick, Anthony E.; Ellam, Rob M.

    2014-01-01

    peneplanation. An 40Ar/39Ar age of 542.62 ± 0.38 Ma (1 sigma, full external precision, Renne et al., 2011) for metalliferous alteration clays in Scotland shows that this event occurred immediately prior to the Precambrian–Cambrian boundary. A negative δ53Cr isotopic signature for the clay is consistent with...

  1. Substrate as test of behaviour and as the ichnotaxonomical problem: predation and scavenging traces on trilobite exosceletons, Middle Cambrian, Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Mikuláš, Radek; Fatka, O.; Szabad, M.

    Moscow : PIN RAN, 2010. s. 39-40. [Workshop on Ichnotaxonomy /4./. 21.06.2010-26.06.2010, Moscow - St. Petersburg] R&D Projects: GA ČR GA205/09/1521 Institutional research plan: CEZ:AV0Z30130516 Keywords : Cambrian * ichnology * ichnotaxonomy * ichnofossils * predation traces * scavening traces * palaeontology Subject RIV: DB - Geology ; Mineralogy

  2. The discrediting of the monoamine hypothesis

    Directory of Open Access Journals (Sweden)

    Uncini T

    2012-02-01

    Full Text Available Marty Hinz1, Alvin Stein2, Thomas Uncini31Clinical Research, NeuroResearch Clinics, Inc, Cape Coral, FL, 2Stein Orthopedic Associates, Plantation, FL, 3Fairview University Medical Center, Hibbing, MN, USABackground: The monoamine hypothesis has been recognized for over half a century as a reference point to understanding electrical dysfunction associated with disease states, and/or regulatory dysfunction related to synaptic, centrally acting monoamine concentrations (serotonin, dopamine, norepinephrine, and epinephrine.Methods: Organic cation transporters (OCT are a primary force controlling intracellular and extracellular (including synaptic concentrations of centrally acting monoamines and their amino acid precursors. A new type of research was analyzed in this paper (previously published by the authors relating to determining the functional status of the nutritionally driven organic cation transporters. It was correlated with the claims of the monoamine hypothesis.Results: Results of laboratory assays from subjects not suffering from a hyperexcreting tumor show that centrally acting monoamine concentrations are indistinguishable in subjects with and without disease symptoms and/or regulatory dysfunction. Analysis of centrally acting monoamine concentrations in the endogenous state reveals a significant difference in day-to-day assays performed on the same subject with and without monoamine-related disease symptoms and/or regulatory dysfunction. The day-to-day difference renders baseline testing in the endogenous state non-reproducible in the same subject.Conclusion: It is asserted that the monoamine hypothesis, which claims that low synaptic levels of monoamines are a primary etiology of disease, is not a valid primary reference point for understanding chronic electrical dysfunction related to the centrally acting monoamines. Furthermore, the "bundle damage theory" is a more accurate primary model for understanding chronic dysfunction. The

  3. IMPACTS !

    CERN Multimedia

    2008-01-01

    (Photo courtesy of Don Davis / NASA)The University of Geneva (UNIGE) and the Ecole Polytechnique Fédérale of Lausanne (EPFL) are organising the 4th series of public lectures on astronomy, on the theme of "Impacts". The schedule is as follows: Il y a 100 ans : une explosion dans la Tunguska – Dr. Frédéric COURBIN, EPFL Les impacts sur Terre – Prof. Didier Queloz, UNIGE La fin des dinosaures – Dr. Stéphane Paltani, UNIGE Wednesday 7 May 2008, from 7.00 p.m. to 9.00 p.m. Auditoire CO1, EPFL, Ecublens Thursday 08 May 2008, from 7.00 p.m. to 9.00 p.m. Auditoire Rouiller, Uni-Dufour, Genève All 3 lectures will be givent each evening! Admission free Information: 022 379 22 00

  4. Germanium/silicon of the Ediacaran-Cambrian Laobao cherts: Implications for the bedded chert formation and paleoenvironment interpretations

    Science.gov (United States)

    Dong, Lin; Shen, Bing; Lee, Cin-Ty A.; Shu, Xu-jie; Peng, Yang; Sun, Yuanlin; Tang, Zhuanhong; Rong, Hong; Lang, Xianguo; Ma, Haoran; Yang, Fan; Guo, Wen

    2015-03-01

    Sedimentary strata of the terminal Ediacaran (635-542 Ma) to early Cambrian (542-488 Ma) Laobao-Liuchapo bedded cherts in the South China Block include the Ediacaran Oxidation Event and the Cambrian explosion. Understanding the origin and depositional environment of the bedded cherts may provide insight into how the Earth's surface environment changed between the Proterozoic and Phanerozoic. We measured major and trace element compositions and Ge/Si ratios of the Laobao cherts from northern Guangxi province. The Laobao cherts were deposited in the deep basinal environment of the South China Block. We show that the composition of the Laobao cherts is determined by a mixture of four components: quartz, clay, carbonate, and pyrite/iron-oxide. The quartz component is the dominant component of the Laobao cherts. The maximum estimated Ge/Si of the quartz component is between 0.4 and 0.5 μmol/mol, which is close to the Ge/Si of modern seawater and biogenic silica but 1 order of magnitude lower than that of hydrothermal fluids. These Ge/Si systematics suggest that normal seawater rather than mid-ocean ridge hydrothermal fluids is the primary Si source for the Laobao cherts. The Ge/Si of the clay component varies between 1 and 10 μmol/mol, which is comparable to the Ge/Si of typical marine clays, but 10-100 times lower than that of chert nodules from early Ediacaran beds (the Doushantuo Formation) predating the terminal Ediacaran Laobao cherts studied here. Our observations indicate that the clay component Ge/Si ratio decreased from the early Ediacaran to the late Ediacaran. We speculate that high Ge/Si ratios in clays reflect the preferential chelation of Ge by dissolved organic compounds adsorbed onto clays. If so, this suggests that the decrease in Ge/Si ratio of the clay component in the Ediacaran signifies a decrease in the total dissolved organic carbon content of seawater toward the Ediacaran-Cambrian transition, consistent with oxidation of the oceans during the

  5. The Parental Co-Immunization Hypothesis

    OpenAIRE

    Portela, Miguel; Schweinzer, Paul

    2013-01-01

    We attempt to answer a simple empirical question: does having children make a parent live longer? The hypothesis we o ffer is that a parent's immune system is refreshed by a child's infections at a time when their own protection starts wearing thin. With the boosted immune system, the parent has a better chance to fend off whatever infections might strike when old and weak. Thus, parenthood is rewarded in individual terms. Using the O ffice for National Statistics Longitudinal Study (ONS-LS)...

  6. On Multiple Hypothesis Testing with Rejection Option

    CERN Document Server

    Grigoryan, Naira; Voloshynovskiy, Svyatoslav; Koval, Oleksiy

    2011-01-01

    We extend existing results on multiple hypothesis testing (HT) in view of rejection option. The model has many different applications. Errors in testing of M hypotheses regarding the source distribution with an option of rejecting all those hypotheses are considered. The source is discrete and arbitrarily varying (AVS). The tradeoffs among error probability exponents/reliabilities are investigated and the optimal decision strategies are outlined. Then the main result is specialized for discrete memoryless sources (DMS) and studied further. Geometric interpretations of the optimal decision schemes are given for the current and known bounds in multi-HT for AVS.

  7. Statistical hypothesis testing with SAS and R

    CERN Document Server

    Taeger, Dirk

    2014-01-01

    A comprehensive guide to statistical hypothesis testing with examples in SAS and R When analyzing datasets the following questions often arise:Is there a short hand procedure for a statistical test available in SAS or R?If so, how do I use it?If not, how do I program the test myself? This book answers these questions and provides an overview of the most commonstatistical test problems in a comprehensive way, making it easy to find and performan appropriate statistical test. A general summary of statistical test theory is presented, along with a basicdescription for each test, including the

  8. Interstellar colonization and the zoo hypothesis

    Energy Technology Data Exchange (ETDEWEB)

    Jones, E.M.

    1978-01-01

    Michael Hart and others have pointed out that current estimates of the number of technological civilizations arisen in the Galaxy since its formation is in fundamental conflict with the expectation that such a civilization could colonize and utilize the entire Galaxy in 10 to 20 million years. This dilemma can be called Hart's paradox. Resolution of the paradox requires that one or more of the following are true: we are the Galaxy's first technical civilization; interstellar travel is immensely impractical or simply impossible; technological civilizations are very short-lived; or we inhabit a wildnerness preserve. The latter is the zoo hypothesis. (GHT)

  9. Set theory and the continuum hypothesis

    CERN Document Server

    Cohen, Paul J

    2008-01-01

    This exploration of a notorious mathematical problem is the work of the man who discovered the solution. The independence of the continuum hypothesis is the focus of this study by Paul J. Cohen. It presents not only an accessible technical explanation of the author's landmark proof but also a fine introduction to mathematical logic. An emeritus professor of mathematics at Stanford University, Dr. Cohen won two of the most prestigious awards in mathematics: in 1964, he was awarded the American Mathematical Society's Bôcher Prize for analysis; and in 1966, he received the Fields Medal for Logic.

  10. Efficient Market Hypothesis in European Stock Markets

    OpenAIRE

    Borges, Maria Rosa

    2008-01-01

    This paper reports the results of tests on the weak-form market efficiency applied to stock market indexes of France, Germany, UK, Greece, Portugal and Spain, from January 1993 to December 2007. We use a serial correlation test, a runs test, an augmented Dickey-Fuller test and the multiple variance ratio test proposed by Lo and MacKinlay (1988) for the hypothesis that the stock market index follows a random walk. The tests are performed using daily and monthly data for the whole period and fo...

  11. Interstellar colonization and the zoo hypothesis

    International Nuclear Information System (INIS)

    Michael Hart and others have pointed out that current estimates of the number of technological civilizations arisen in the Galaxy since its formation is in fundamental conflict with the expectation that such a civilization could colonize and utilize the entire Galaxy in 10 to 20 million years. This dilemma can be called Hart's paradox. Resolution of the paradox requires that one or more of the following are true: we are the Galaxy's first technical civilization; interstellar travel is immensely impractical or simply impossible; technological civilizations are very short-lived; or we inhabit a wildnerness preserve. The latter is the zoo hypothesis

  12. The Kalkarindji Large Igneous Province and the Early-Middle Cambrian Extinction.

    Science.gov (United States)

    Jourdan, Fred; Evins, Lena

    2010-05-01

    Despite being one of the largest large igneous provinces (LIP) on Earth, the recently discovered Kalkarindji LIP, Australia, has received only very little attention (e.g., Glass & Philips, 2005; Evins et al., 2009). This province is located across the Northern Territories and Western Australia and covers a currently known area of ≥ 2.1x106 km² (Evins et al., 2009) with hints that it stretches as far as the southernmost part of South Australia (equivalent to a total area of ≥ 3x106 km²). The province includes flows, intrusions and volcanic tuffs. The age of the province is currently based only on three robust 40Ar/39Ar apparent ages ranging from 504.6 ± 2.5 to 507.5 ± 1.6 Ma (Glass & Philips, 2005; Evins et al., 2009). This province is of particular interest as it seems to coincide with a global anoxic event (Hough et al., 2006) and more importantly, the Early-Middle Cambrian (EMC) extinction where 50% of the genera (e.g. Archeocyaths, Trilobites) went extinct. The age of the EMC extinction has been estimated at ~510 Ma according to the revised timescale of 2009 but so far, attempts to date the extinction level have not yielded any precise date. Considering the now well-established 40K decay constant bias (Min et al., 2000), the 40Ar/39Ar ages obtained so far suggest an emplacement age of the Kalkarindji province between ~509 and ~512 Ma, thus apparently synchronous with the EMC extinction. However, due to the paucity of available ages, it is still not clear if the Kalkarindji LIP was emplaced during only few hundred ka, or rather was more sluggish over few Ma. The Kalkarindji basalts are overlapping thick sulfate-rich evaporite layers and carbonate rocks of the Precambrian central Australia basins. Evaporite and carbonate metamorphism might have been responsible for a significant source of CO2, SO2 and halocarbons as demonstrated for the Siberian traps (Svensen et al., 2009). In addition, the occurrence of pyroclastics eruptions as indicated by the presence

  13. Detrital zircon provenance of Mesoproterozoic to Cambrian arenites in the Western United States and Northwestern Mexico

    Science.gov (United States)

    Stewart, John H.; Gehrels, G.E.; Barth, A.P.; Link, P.K.; Christie-Blick, N.; Wrucke, C.T.

    2001-01-01

    U-Pb isotopic dating of detrital zircon from supracrustal Proterozoic and Cambrian arenites from the western United States and northern Mexico reveal three main age groups, 1.90 to 1.62 Ga, 1.45 to 1.40 Ga, and 1.2 to 1.0 Ga. Small amounts of zircons with ages of 3.1 to 2.5 Ga, 1.57 Ga, 1.32 Ga, 1.26 Ga, 0.7 Ga, and 0.5 Ga are also present. Detrital zircons ranging in age from 1.90 to 1.62 Ga and from 1.45 to 1.40 Ga are considered to have been derived from Proterozoic crystalline basement rocks of these known ages, and probably in part from reworked Proterozoic supracrustal sedimentary rocks, of the western United States. The 1.2 to 1.0 Ga detrital zircon ages from California, Arizona, and Sonora are characterized by distinct spikes (1.11 Ga, in particular) in the age-probability plots. These spikes are interpreted to indicate the influx of zircon from major silicic volcanic fields. Igneous rocks such as the Pikes Peak Granite (1.093 Ga) of Colorado, and the Aibo Granite (1.110 Ga) of Sonora, Mexico, may represent the deeply eroded roots of such volcanic fields. Samples from farther north along the Cordilleran margin that contain abundant 1.2-1.0 Ga detrital zircons do not show spikes in the age distribution, but rather ages spread out across the entire 1.2-1.0 Ga range. These age spectra resemble those for detrital zircons from the Grenville province, which is considered their source. Less common detrital zircons had a variety of sources. Zircons ranging in age from 3.36 to 2.31 Ga were apparently derived from inland parts of the North American continent from Wyoming to Canada. Zircons of about 1.577 Ga are highly unusual and may have had an exotic source; they may have come from Australia and been deposited in North America when Australia and North America were juxtaposed as part of the hypothetical Rodinian supercontinent. Detrital zircon of ??1.320 Ga apparently had the same source as that for tuff (1.320 Ga) in the Pioneer Shale of the Apache Group in Arizona

  14. Learning-Related Changes in Adolescents' Neural Networks during Hypothesis-Generating and Hypothesis-Understanding Training

    Science.gov (United States)

    Lee, Jun-Ki; Kwon, Yongju

    2012-01-01

    Fourteen science high school students participated in this study, which investigated neural-network plasticity associated with hypothesis-generating and hypothesis-understanding in learning. The students were divided into two groups and participated in either hypothesis-generating or hypothesis-understanding type learning programs, which were…

  15. Lack of inhibiting effect of oil emplacement on quartz cementation: Evidence from Cambrian reservoir sandstones, Paleozoic Baltic Basin

    DEFF Research Database (Denmark)

    Molenaar, Nicolaas; Cyziene, Jolanta; Sliaupa, Saulius;

    2008-01-01

    cementation is derived from internal sources. Rather, in spite of large variation in porosity and quartz cement content, a regular pattern of porosity decrease is related to increasing temperature or depth. The observed heterogeneity is due to local factors that influence the precipitation of quartz cement......Currently, the question of whether or not the presence of oil in sandstone inhibits quartz cementation and preserves porosity is still debated. Data from a number of Cambrian sandstone oil fields and dry fields have been studied to determine the effects of oil emplacement on quartz cementation. The......, including sandstone architecture, i.e., distribution of shales within the sandstone bodies, and sandstone thickness. Heterogeneity is inherent to sandstone architecture and to the fact that silica for quartz cementation is derived from heterogeneously distributed local pressure solution. Models predicting...

  16. Speciation of the genus Arthricocephalus Bergeron, 1899 (Trilobita) from the late Early Cambrian and its stratigraphic significance

    Institute of Scientific and Technical Information of China (English)

    YUAN Jinliang; ZHAO Yuanlong; YANG Xinglian

    2006-01-01

    The genus Arthricocephalus Bergeron,1899 is revised, and Halipanktos Balker & Peel, 1997 is suggested here as a senior synonym. The subgenus Arthricocephalus (Arthricocephalites) Chien & Lin in Lu et al., 1974 is considered as a separate genus.Of the 20 previously assigned species of Arthricocephalus ( Arthricocephalus ) Bergeron, 1899, Arthricocephalus ( Arthricocephalites )Chien & Lin in Lu et al., 1974, Arthricocephalus (Euarthricocephalus) Ju, 1983 are lumped into eight species. The speciation trend of Arthricocephalus and Arthricocephalites is demonstrated based on their stratigraphic occurrences. It not only enhances the resolution of the biostatigraphic zonation in the uppermost Lower Cambrian, but also represents a potential candidate to define the Duyunian stage. The base of the stage is suggested at the first appearance datum (FAD) of Arthricocephalus chauveaui Bergeron, 1899 within the evolutionary lineage from Ar. jiangkouensis Yin in Yin & Li, 1978 to Ar. chauveaui in a global scale.

  17. Late Ediacaran-Cambrian structures and their reactivation during the Variscan and Alpine cycles in the Anti-Atlas (Morocco)

    Science.gov (United States)

    Soulaimani, A.; Michard, A.; Ouanaimi, H.; Baidder, L.; Raddi, Y.; Saddiqi, O.; Rjimati, E. C.

    2014-10-01

    The post-Pan-African evolution of the northern border of the West African Craton is largely controlled by the remobilisation of Late Neoproterozoic basement faults. The Upper Ediacaran volcanic and volcano-sedimentary sequences of the Ouarzazate Group show dramatic and rapid thickness changes, consistent with active extensional faulting associated with post-orogenic collapse and incipient continental rifting. The geometry and kinematics of these faults differ from west to east in the Anti-Atlas. N- to NE-trending faults dominate in western Anti-Atlas in response to E-W to NW-SE pure extension, while a transtensive opening regime characterize the central (Bou Azzer) and eastern (Saghro-Ougnate) Anti-Atlas. The marine incursion in the west-central Anti-Atlas during the late Ediacaran-Early Cambrian occurred without major geodynamical break between the continental Ouarzazate Group and marine sediments of the Adoudou Fm. Extensional tectonics went on during the Early Cambrian, being concentrated in the western and central parts of the belt. From Middle Cambrian to Lower Devonian and mainly due to thermal subsidence, the Anti-Atlas basement was buried under marine sediments with dominant south-derived detrital input. Basement faults control the distribution of subsiding versus shallow areas. During the Middle-Late Devonian, the dislocation of the Saharan platform occurred, mainly in the eastern Anti-Atlas where Precambrian faults were also remobilized during the Early Carboniferous. During the Variscan orogeny, the Paleozoic series of the Anti-Atlas basin were involved in folding tectonics, concomitant with the uplift of Proterozoic basement blocks bounded by inherited basement faults. The pre-existing rift-related faults were variably inverted across the Anti-Atlas. In the westernmost part of the belt, Variscan shortening induced positive inversions along the remobilized basement faults, but in some cases, some faults preserved an apparently normal throw. Some hidden

  18. Source tracing of noble metal elements in Lower Cambrian black rock series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-element- ore-deposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.

  19. Source tracing of noble metal elements in Lower Cambrian black rock series of Guizhou-Hunan Provinces, China

    Institute of Scientific and Technical Information of China (English)

    李胜荣; 高振敏

    2000-01-01

    The Lower Cambrian black rock series of South China is abnormally rich in noble metal elements. According to the concentrations, the ratios, the relations, the distribution and partition patterns of noble metal elements, the authors think that the noble metals and other elements are neither directly from extraterrestrial materials, nor from the products of normal marine sedimentation. The abnormal enrichment of noble metal elements is closely related with hydrothermal fluid that flew out on the sea floor through deep cycling and reaction with Proterozoic ultramafic-mafic igneous rocks forming noble metal rich fluid. It is possible to form industrial multiple-element-ore-deposits, especially hydrothermal type platinum-group-element-ore-deposits in the region with strong hydrothermal action.

  20. Chengjiang fauna & the Cambrian taxonomic explosion%澄江动物群与寒武纪大爆发

    Institute of Scientific and Technical Information of China (English)

    赵生才

    1998-01-01

    @@ 1984年,中国学者在云南澄江寒武纪地层发现一批丰富多彩的古化石群,迅速在世界上引起强烈反响,美国据世界一些著名科学家联合建议,将此列入本世纪最惊人的发现之一.德国古生物学家赛拉赫(Seilacher)等著名学者认为,"寒武纪大爆发(Cambrian Explosion)"是生命历史中最伟大、但也是了解最少的一次生物事件,而中国澄江动物群拥有解开这个谜的线索.

  1. A New Ichnogenus Kailidiscus Produced by Attachment from the Middle Cambrian Kaili Formation in Taijiang, Guizhou Province, China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Over 190 specimens of an attachment ichnofossil Kailidiscus (n. ichnogen.) have been found in the Kaili Bitoa, a Burgess Shale-type biota, from the middle Kaili Formation (early Middle Cambrian) in Taijiang County, Guizhou Province, southern China. Kailidiscus is an epichnia with a circular to oval attachment platform, on which there is a carbonaceous film probably formed by the body of the living organism. Structures such as a marginal furrow, an inner and outer marginal ride, many convex fold-ridges, and a large caved peripheral furrow on the attachment platform may be the result of basal tissues of a sessile organism that wrinkled to increase the attachment's surface area. The Kailidiscus organism may have been a sessile cnidarian attached to the muddy seafloor. Kailidiscus organisms lived in relatively quiet water,and were buried by a sudden influx of sediment.

  2. Pathogenesis of and unifying hypothesis for idiopathic pouchitis.

    LENUS (Irish Health Repository)

    Coffey, J Calvin

    2009-04-01

    Ileal pouch-anal anastomosis is the procedure of choice in the surgical management of refractory ulcerative colitis. Pouchitis affects up to 60% of patients following ileal pouch-anal anastomosis for ulcerative colitis. It overlaps significantly with ulcerative colitis such that improvements in our understanding of one will impact considerably on the other. The symptoms are distressing and impinge significantly on patients\\' quality of life. Despite 30 years of scientific and clinical investigation, the pathogenesis of pouchitis is unknown; however, recent advances in molecular and cell biology make a synergistic hypothesis possible. This hypothesis links interaction between epithelial metaplasia, changes in luminal bacteria (in particular sulfate-reducing bacteria), and altered mucosal immunity. Specifically, colonic metaplasia supports colonization by sulfate-reducing bacteria that produce hydrogen sulfide. This causes mucosal depletion and subsequent inflammation. Although in most cases antibiotics lead to bacterial clearance and symptom resolution, immunogenetic subpopulations can develop a chronic refractory variant of pouchitis. The aims of this paper are to discuss proposed pathogenic mechanisms and to describe a novel mechanism that combines many hypotheses and explains several aspects of pouchitis. The implications for the management of both pouchitis and ulcerative colitis are discussed.

  3. Pathogenesis of and unifying hypothesis for idiopathic pouchitis.

    LENUS (Irish Health Repository)

    Coffey, J Calvin

    2012-02-01

    Ileal pouch-anal anastomosis is the procedure of choice in the surgical management of refractory ulcerative colitis. Pouchitis affects up to 60% of patients following ileal pouch-anal anastomosis for ulcerative colitis. It overlaps significantly with ulcerative colitis such that improvements in our understanding of one will impact considerably on the other. The symptoms are distressing and impinge significantly on patients\\' quality of life. Despite 30 years of scientific and clinical investigation, the pathogenesis of pouchitis is unknown; however, recent advances in molecular and cell biology make a synergistic hypothesis possible. This hypothesis links interaction between epithelial metaplasia, changes in luminal bacteria (in particular sulfate-reducing bacteria), and altered mucosal immunity. Specifically, colonic metaplasia supports colonization by sulfate-reducing bacteria that produce hydrogen sulfide. This causes mucosal depletion and subsequent inflammation. Although in most cases antibiotics lead to bacterial clearance and symptom resolution, immunogenetic subpopulations can develop a chronic refractory variant of pouchitis. The aims of this paper are to discuss proposed pathogenic mechanisms and to describe a novel mechanism that combines many hypotheses and explains several aspects of pouchitis. The implications for the management of both pouchitis and ulcerative colitis are discussed.

  4. The alliance hypothesis for human friendship.

    Directory of Open Access Journals (Sweden)

    Peter DeScioli

    Full Text Available BACKGROUND: Exploration of the cognitive systems underlying human friendship will be advanced by identifying the evolved functions these systems perform. Here we propose that human friendship is caused, in part, by cognitive mechanisms designed to assemble support groups for potential conflicts. We use game theory to identify computations about friends that can increase performance in multi-agent conflicts. This analysis suggests that people would benefit from: 1 ranking friends, 2 hiding friend-ranking, and 3 ranking friends according to their own position in partners' rankings. These possible tactics motivate the hypotheses that people possess egocentric and allocentric representations of the social world, that people are motivated to conceal this information, and that egocentric friend-ranking is determined by allocentric representations of partners' friend-rankings (more than others' traits. METHODOLOGY/PRINCIPAL FINDINGS: We report results from three studies that confirm predictions derived from the alliance hypothesis. Our main empirical finding, replicated in three studies, was that people's rankings of their ten closest friends were predicted by their own perceived rank among their partners' other friends. This relationship remained strong after controlling for a variety of factors such as perceived similarity, familiarity, and benefits. CONCLUSIONS/SIGNIFICANCE: Our results suggest that the alliance hypothesis merits further attention as a candidate explanation for human friendship.

  5. Einstein's Revolutionary Light-Quantum Hypothesis

    International Nuclear Information System (INIS)

    Albert Einstein's light-quantum paper was the only one of his great papers of 1905 that he himself called ''very revolutionary''. I sketch his arguments for light quanta, his analysis of the photoelectric effect, and his introduction of the wave-particle duality into physics in 1909. I show that Robert Andrews Millikan, in common with almost all physicists at the time, rejected Einstein's light-quantum hypothesis as an interpretation of his photoelectric-effect experiments of 1915. I then trace the complex experimental and theoretical route that Arthur Holly Compton followed between 1916 and 1922 that led to his discovery of the Compton effect, a discovery that Peter Debye also made virtually simultaneously and independently. Compton's discovery, however, was challenged on experimental grounds by William Duane and on theoretical grounds by Niels Bohr in the Bohr-Kramers-Slater theory of 1924, and only after that theory was disproved experimentally the following year by Walther Bothe and Hans Geiger in Berlin and by Compton and Alfred W. Simon in Chicago was Einstein's light-quantum hypothesis generally accepted by physicists. (author)

  6. Computer diagnosis in cardiology: Oxidative stress hypothesis

    Directory of Open Access Journals (Sweden)

    Ezekiel Uba Nwose

    2009-10-01

    Full Text Available Background: Virtual scanning is one of the emerging technologies in complementary medicine practice. The diagnostic principle is hinged on perception and ultra weak light emission, while the treatment options associated with it includes diet, flash light, exercise and relaxation. However, a mechanism that links the diagnostic and treatment principles has yet to be elucidated. Aims: The objective here is to further explanation of oxidative stress concept as the biochemical basis of the technology. Materials and Methods: Using available literature and basic science textbook, the function of the hypothalamus-pituitary-adrenalin axis as neuro-endocrine physiological system that is strongly linked to the rate of alterations in biochemical processes through to cardiovascular complications is articulated. Results: The hypothesis brings to fore the potential of using the alterations in biochemical processes associated with cognition as tool to validate the Virtual Scanning technology for possible incorporation into clinical practice. Or vice versa to use Virtual Scanning technology to determine the chemiluminescence-related biochemical changes resulting from pathologies that could benefit from relaxation, light therapy, exercise and antioxidant nutrition. Conclusions: This article advances the applicability of cognitive test procedure for indication of the disease(s affecting heart function. The implication for some laboratory indices that are already available in clinical practice is highlighted. Investigation of this hypothesis will help provide clear link between plausible mechanism and the theory proposed.

  7. Computer diagnosis in cardiology: Oxidative stress hypothesis

    Directory of Open Access Journals (Sweden)

    Ezekiel Uba Nwose

    2009-01-01

    Full Text Available Background : Virtual scanning is one of the emerging technologies in complementary medicine practice. The diagnostic principle is hinged on perception and ultra weak light emission, while the treatment options associated with it includes diet, flash light, exercise and relaxation. However, a mechanism that links the diagnostic and treatment principles has yet to be elucidated. Aims: The objective here is to further explanation of oxidative stress concept as the biochemical basis of the technology. Materials and Methods: Using available literature and basic science textbook, the function of the hypothalamus-pituitary-adrenalin axis as neuro-endocrine physiological system that is strongly linked to the rate of alterations in biochemical processes through to cardiovascular complications is articulated. Results: The hypothesis brings to fore the potential of using the alterations in biochemical processes associated with cognition as tool to validate the Virtual Scanning technology for possible incorporation into clinical practice. Or vice versa to use Virtual Scanning technology to determine the chemiluminescence-related biochemical changes resulting from pathologies that could benefit from relaxation, light therapy, exercise and antioxidant nutrition. Conclusions: This article advances the applicability of cognitive test procedure for indication of the disease(s affecting heart function. The implication for some laboratory indices that are already available in clinical practice is highlighted. Investigation of this hypothesis will help provide clear link between plausible mechanism and the theory proposed.

  8. Phosphatized Punctatus with mouthparts and its embryo fossils from the Lower Cambrian of Ningqiang, south Shaanxi, China

    Institute of Scientific and Technical Information of China (English)

    LIU Yunhuan; LI Yong; SHAO Tiequan; ZHU Zhixin; YU Bo; WANG Zhuo; ZHANG Wanqian; LI Rongxi

    2007-01-01

    The appearance of coelenterates marks the real beginning ofmetazoan evolution. It therefore has a prominent position in the origin and evolutionary history of organisms,and is also a pivotal question of evolutionary biology.Punctatus is an extinct, ancient marine animal from the early stage of the Cambrian explosion, occurring at. The lowermost Cambrian of both Kuanchuanpu (Ningqiang, Shaanxi) and Maidiping (Emei, Sichuan) areas. Punctatus has been studied for many years since the discovery of its fragments. System-atic and phylogenetic analysis has long been limited because of the rarity of complete specimens. In order to improve research into Punctatus, more than ten thousand globular fossils were recovered by means of "Chemistry Retting". On the basis of the study of these globular fossils, a series of Punctatus fossils with cone parts and finely preserved soft-tissue mouthparts and fossilized metazoan embryo were recovered. Through research on characteristics such as shape,modality and structure of these fossils symbiotic with Punctatus emeiensis, the author found many possible embryo fossils including the evidence of gastrula-stage animal fossils.The sequence of fetation might have appeared on the corol-liform oral region of Punctatus emeiensis. A study of the soft tissues, functional morphology and the sequence of embryo fossils shows evidence that Punctatus resembles coelenterate polyps in systematic classification. Perhaps it also represents an ancestor of the coelenterate with an original tentacle. A comparison with the real "tentacle animal" found in the Chengjiang Fauna, shows that the original tentacle is very tiny and its function range is limited. This reveals the primi-tive nature of the animal. Although the original tentacle is so small, it does exist, representing the first big step towards the real flexible tentacle with a strong function from the early evolving tentacle.

  9. Giant submarine landslide grooves in the Neoproterozoic/Lower Cambrian Phe Formation, northwest Himalaya: Mechanisms of formation and palaeogeographic implications

    Science.gov (United States)

    Draganits, E.; Schlaf, J.; Grasemann, B.; Argles, T.

    2008-04-01

    Giant groove casts have been found in the upper Proterozoic to Lower Cambrian Phe Formation (Haimanta Group), a siliciclastic sandstone/shale succession in the Tethyan Zone of the Higher Himalaya tectonic unit. The grooves are among the largest linear erosion structures related to submarine mass-movements observed in the geologic record. They are up to 4 m wide, about 0.2 m deep and can be traced for more than 35 m without changing their character. The grooves are straight, subparallel to cross-cutting striations with shallow semi-circular cross-sections and well-defined superimposed minor ridges and grooves. Groove casts exist on the soles of several sandstone beds within a 73 m thick logged section, commonly associated with flute casts. Their characteristics were compared with several other types of ancient and modern submarine linear erosion structures. A sand-rich, non-channelized basin floor depositional environment is inferred from the lithofacies, the combination of sedimentary structures, the lack of coarse-grained pebbly facies, the lateral continuity of beds, and the lack of channel structures. The grooves probably formed by laminar debris flows/concentrated density flows dragging blocks of already lithified sediment across the basin floor. When the bedding is structurally rotated back to horizontal, the groove casts show consistent North-South oriented palaeocurrent trends, with South-directed palaeocurrent directions indicated by flute casts. These palaeocurrent orientations contrast with previous palaeogeographic reconstructions of this area, which propose sediment delivery from the South. We therefore suggest a new "double provenance" model for the spatial relationship of late Proterozoic to Early Cambrian strata of the Himalaya, in which Lesser and Tethyan Himalayan age-equivalent sediment was deposited in a connected basin, where the former received detritus from the South, and the latter from a hitherto unknown source in the North. One possible

  10. The noble gas isotope geochemical composition of chert at the bottom of Cambrian in Tarim Basin,China

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In the Tarim Basin,black shale series at the bottom of Cambrian is one of the important marine facies hydrocarbon source rocks. This research focuses on the analysis of the isotope of noble gas of 11 cherts. The R/Ra ratio of chert in the Keping area is 0.032―0.319,and 40Ar/36Ar is 338―430. In Quruqtagh the R/Ra ratio is 0.44―10.21,and 40Ar/36Ar is 360―765. The R/Ra ratio of chert increases with 40Ar/36Ar from the west to the east accordingly. They have evolved from the crust source area to the mantle source area in a direct proportion. Surplus argon 40ArE in chert is in direct proportion to the R/Ra ratio,indicating that it has the same origin of excess argon as in fluid and mantle source helium. Comparison of the R/Ra ratios between the west and the east shows that the chert in the eastern part formed from the activity system of the bottom hydrothermal venting driven by the mantle source,where the material and energy of crust and mantle had a strong interaction in exchange;whereas in the western part,chert deposited from the floating of hydrothermal plume undersea bottom,which is far away from the centre of activities of the hydrothermal fluid of ocean bottom. In addition,from noble gas isotope composition of chert,it is suggested that the ocean anoxia incident happened at the black shale of the Cambrian bottom probably because of the large-scaled ocean volcanoes and the followinghydrothermal activities.

  11. The geological significance of the boundary between the Fort Sill and Signal Mountain Formations in the lower Arbuckle Group (Cambrian)

    Energy Technology Data Exchange (ETDEWEB)

    Hosey, R.; Donovan, R.N. (Texas Christian Univ., Ft Worth, TX (United States). Geology Dept.)

    1993-02-01

    During the upper Cambrian, a transgression inundated the Southern Oklahoma aulacogen enveloping a landscape that consisted of hills of Cambrian-aged rhyolite up to 350 m in height. Initial deposits on this topography--the Reagan Formation--consist of siliciclastics that were deposited as alluvium and succeeding tidally-influenced marine sandstones and shales. The siliciclastics grains are made up of local rhyolite, quartz and authigenic glauconite. The overlying Honeycreek Formation is defined by the addition of carbonated detritus in the form of tidally-influenced pelmatozoan grainstones. The passage from the Honeycreek to the overlying Fort Sill Formation of the Arbuckle Group is marked by the incoming of beds of lime mudstone and the gradual disappearance of grainstones and siliciclastics. The contact between the Fort Sill and the overlying thinly-bedded dark grey bioclastic limestones of the Signal Mountain Formation is one of the most distinctive horizons in the Arbuckle Group. The contact evidently marks a substantial change in depositional environment. In detail the contact is sharp and shows evidence of minor erosion, although no karsting has been detected. The authors suggest that the contact surface records a regression, perhaps associated with dolomitization and followed by some erosion. A regression is also indicated by the local occurrence of a laminated tidal flat unit with traces of evaporites that outcrops in the far west of the Slick Hills immediately below the formation contact. They suggest that the Signal Mountains as a transgressive unit, incorporating siliciclastics transported into the area during the regression. It has been suggested that the unconformity reflects localized tectonism associated with the evolution of the Southern Oklahoma aulacogen. On the other hand the surface may correlate with a craton--wide Sauxian' hiatus.

  12. A novel hypothesis splitting method implementation for multi-hypothesis filters

    DEFF Research Database (Denmark)

    Bayramoglu, Enis; Ravn, Ole; Andersen, Nils Axel

    2013-01-01

    The paper presents a multi-hypothesis filter library featuring a novel method for splitting Gaussians into ones with smaller variances. The library is written in C++ for high performance and the source code is open and free1. The multi-hypothesis filters commonly approximate the distribution...... transformations better, if the covariances of the individual hypotheses are sufficiently small. We propose a look-up table based method to calculate a set of Gaussian hypotheses approximating a wider Gaussian in order to improve the filter approximation. Python bindings for the library are also provided for fast...

  13. Minimax hypothesis testing for curve registration

    CERN Document Server

    Collier, Olivier

    2011-01-01

    This paper is concerned with the problem of goodness-of-fit for curve registration, and more precisely for the shifted curve model, whose application field reaches from computer vision and road traffic prediction to medicine. We give bounds for the asymptotic minimax separation rate, when the functions in the alternative lie in Sobolev balls and the separation from the null hypothesis is measured by the l2-norm. We use the generalized likelihood ratio to build a nonadaptive procedure depending on a tuning parameter, which we choose in an optimal way according to the smoothness of the ambient space. Then, a Bonferroni procedure is applied to give an adaptive test over a range of Sobolev balls. Both achieve the asymptotic minimax separation rates, up to possible logarithmic factors.

  14. The Gaia hypothesis: Can it be tested?

    Science.gov (United States)

    Kirchner, James W.

    1989-05-01

    The Gaia hypothesis' central theme is that biological processes homeostatically maintain, on a planetary scale, geochemical and climatic conditions favorable for life. A number of distinct hypotheses have been proposed, spanning a range from the self-evident to the highly speculative. The self-evident forms of Gaia reiterate the well-documented fact that biological processes are critical to biogeochemical cycles, adding the straightforward (though important) point that the coupling between biotic and physical processes should create feedback loops. The speculative forms of Gaia assert that biological processes regulate the physical environment, keeping Earth's climate and surface geochemistry stable and favorable for life. As metaphors, these versions of Gaia are intriguing, untestable, and, if taken literally as a basis for research, potentially misleading. As hypotheses, they are ill-defined, unparsimonious, and unfalsifiable.

  15. The oxidative stress hypothesis in Alzheimer's disease.

    Science.gov (United States)

    Padurariu, Manuela; Ciobica, Alin; Lefter, Radu; Serban, Ionela Lacramioara; Stefanescu, Cristinel; Chirita, Roxana

    2013-12-01

    Oxidative stress may be involved in many somatic and psychiatric pathological states including dementia. The hypothesis of oxidative stress involvement in dementia is supported by much scientific data through biochemical, genetic and molecular studies. Thus, there are many reports of an increased level of the markers for oxidative damage, alterations in the specific activity of the antioxidant system, mutations in specific genes, mitochondrial disturbances and also several connections between oxidative stress and amyloid plaques. Despite these evidence and clinical approaches in using antioxidant therapy in dementia treatment, studies have failed to prove a clear benefit for antioxidant treatment in dementia. Hence, there is a need for further research regarding antioxidant therapy in very early stages of dementia. PMID:24247053

  16. A critical examination of the bioplasma hypothesis.

    Science.gov (United States)

    Quickenden, T I; Tilbury, R N

    1986-01-01

    The hypothesis of Zon (Physiol. Chem. and Physics 11, 501-506 (1979); 12, 357-364 (1980] that regions of semiconduction within living organisms may exhibit plasma behaviour is shown to be most unlikely. Although charge carrier concentrations may be acceptable, calculated Debye lengths are shown to be only marginally acceptable and calculated plasma frequencies are not sufficiently high to ensure that charge carrier motions are governed by electrical and magnetic forces rather than hydrodynamic considerations. For the latter reason, conventional semiconductors do not exhibit plasma behaviour except close to absolute zero and if they are free from impurities and lattice disorder. The experimental evidences presented for the existence of biological plasma (bioplasma) from the areas of Kirlian photography, mitogenetic radiation, acupuncture and studies of biological fields, are largely explainable in conventional terms without invoking the existence of biological plasma. PMID:3809263

  17. On the immunostimulatory hypothesis of cancer

    Directory of Open Access Journals (Sweden)

    Juan Bruzzo

    2011-12-01

    Full Text Available There is a rather generalized belief that the worst possible outcome for the application of immunological therapies against cancer is a null effect on tumor growth. However, a significant body of evidence summarized in the immunostimulatory hypothesis of cancer suggests that, upon certain circumstances, the growth of incipient and established tumors can be accelerated rather than inhibited by the immune response supposedly mounted to limit tumor growth. In order to provide more compelling evidence of this proposition, we have explored the growth behavior characteristics of twelve murine tumors -most of them of spontaneous origin- arisen in the colony of our laboratory, in putatively immunized and control mice. Using classical immunization procedures, 8 out of 12 tumors were actually stimulated in "immunized" mice while the remaining 4 were neither inhibited nor stimulated. Further, even these apparently non-antigenic tumors could reveal some antigenicity if more stringent than classical immunization procedures were used. This possibility was suggested by the results obtained with one of these four apparently non-antigenic tumors: the LB lymphoma. In effect, upon these stringent immunization pretreatments, LB was slightly inhibited or stimulated, depending on the titer of the immune reaction mounted against the tumor, with higher titers rendering inhibition and lower titers rendering tumor stimulation. All the above results are consistent with the immunostimulatory hypothesis that entails the important therapeutic implications -contrary to the orthodoxy- that, anti-tumor vaccines may run a real risk of doing harm if the vaccine-induced immunity is too weak to move the reaction into the inhibitory part of the immune response curve and that, a slight and prolonged immunodepression -rather than an immunostimulation- might interfere with the progression of some tumors and thus be an aid to cytotoxic therapies.

  18. Biostatistics Series Module 2: Overview of Hypothesis Testing

    OpenAIRE

    Avijit Hazra; Nithya Gogtay

    2016-01-01

    Hypothesis testing (or statistical inference) is one of the major applications of biostatistics. Much of medical research begins with a research question that can be framed as a hypothesis. Inferential statistics begins with a null hypothesis that reflects the conservative position of no change or no difference in comparison to baseline or between groups. Usually, the researcher has reason to believe that there is some effect or some difference which is the alternative hypothesis. The researc...

  19. Do scientific advancements lean on the shoulders of giants? A bibliometric investigation of the Ortega hypothesis.

    Directory of Open Access Journals (Sweden)

    Lutz Bornmann

    Full Text Available BACKGROUND: In contrast to Newton's well-known aphorism that he had been able "to see further only by standing on the shoulders of giants," one attributes to the Spanish philosopher Ortega y Gasset the hypothesis saying that top-level research cannot be successful without a mass of medium researchers on which the top rests comparable to an iceberg. METHODOLOGY/PRINCIPAL FINDINGS: The Ortega hypothesis predicts that highly-cited papers and medium-cited (or lowly-cited papers would equally refer to papers with a medium impact. The Newton hypothesis would be supported if the top-level research more frequently cites previously highly-cited work than that medium-level research cites highly-cited work. Our analysis is based on (i all articles and proceedings papers which were published in 2003 in the life sciences, health sciences, physical sciences, and social sciences, and (ii all articles and proceeding papers which were cited within these publications. The results show that highly-cited work in all scientific fields more frequently cites previously highly-cited papers than that medium-cited work cites highly-cited work. CONCLUSIONS/SIGNIFICANCE: We demonstrate that papers contributing to the scientific progress in a field lean to a larger extent on previously important contributions than papers contributing little. These findings support the Newton hypothesis and call into question the Ortega hypothesis (given our usage of citation counts as a proxy for impact.

  20. Hypothesis of demodicidosis rosacea flushing etiopathogenesis.

    Science.gov (United States)

    Robledo, Mary Ann; Orduz, Mariana

    2015-04-01

    Most of the patients with erythematotelangiectatic rosacea are characterized by flushing, oedema and telangiectasia. The etiopathogenesis of the flushing in rosacea patients is unknown. Clinically the flushing in rosacea is similar to the "Asian flushing syndrome". Most Asians have an overactive alcohol dehydrogenase (ADH) that tends to break down alcohol into acetaldehyde faster. People with "Asians flushing syndrome" have a genetic disorder with the Aldehyde Dehydrogenase 2(∗)2 (ALDH2(∗)2) allele. This is the reason why they do not metabolize very well the acetaldehyde that comes from the alcohol, which means that acetaldehyde takes much longer to clear from their blood. ALDH2 enzyme is primarily responsible for oxidation of acetaldehyde derived from ethanol metabolism, as well as oxidation of various other endogenous and exogenous aldehydes. Acetaldehyde produces the vasodilatation in the "Asian flushing syndrome". The antibodies against the GroEl chaperonin protein, a 62-kDa heat shock protein were found in the Bacillus oleronius isolated from Demodex mites, in rosacea patients. The GroEl chaperonin protein is a protein that plays a key role in normal folding of ALDH2. If the GroEl chaperonin antibodies found in patients with rosacea, cross react with the human GroEl chaperonin protein, they will not fold normally the ALDH2, and then the enzyme will not metabolize the acetaldehyde. Many of the patients with rosacea have a concomitant infection with Helicobacter pylori in their stomach. The H.pylori produces high amounts of acetaldehyde, which comes from their metabolism of ethanol or carbohydrates. As a result, high amounts of acetaldehyde will circulate for longer time in the blood, until the liver CYP2E1(p450) enzyme system finally metabilizes the acetaldehyde, during that period of time the patients will experience a flushing as well as the people with the "Asian flushing syndrome" suffer when they drink ethanol. To prove the hypothesis it is necessary

  1. Proposed GSSP for the base of Cambrian Stage 9, coinciding with the first appearance of Agnostotes orientalis, at Duibian, Zhejiang, China

    Institute of Scientific and Technical Information of China (English)

    Loren; E.; BABCOCK; Gabriella; BAGNOLI

    2009-01-01

    Exposed in natural outcrops near the Duibian Village, Jiangshan County, Zhejiang Province, China, the Duibian B section is proposed as the boundary stratotype for the base of an unnamed stage termed provisionally Cambrian Stage 9. The proposed position of the GSSP is 108.12 m above the base of the Huayansi Formation, at a horizon coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis. This horizon coincides also with the first appearance of the cosmopoli-tan polymerid trilobite Irvingella angustilimbata. The section fulfills all the requirements for a GSSP, and the horizon can be constrained not only by the primary stratigraphic marker (A. orientalis) but also with secondary biostratigraphic, chemostratigraphic, and sequence-stratigraphic correlation tools. The first appearance of A. orientalis is one of the most readily recognizable levels in Cambrian, and can be correlated with precision to all paleocontinents.

  2. A Unified Relevance Retrieval Model by Eliteness Hypothesis

    CERN Document Server

    Gorla, Jagadeesh; Wang, Jun

    2011-01-01

    We propose an "Eliteness hypothesis" for information retrieval. Based on the hypothesis, we define two methods to formulate a relevance model and derive a unified probabilistic relevance ranking function. The hypothesis is tested by evaluating a simple ranking function, derived from unified ranking function with some assumptions, on TREC-8 ad-hoc task collection.

  3. A nonparametric hypothesis test via the Bootstrap resampling

    OpenAIRE

    Temel, Tugrul

    2011-01-01

    This paper adapts an already existing nonparametric hypothesis test to the bootstrap framework. The test utilizes the nonparametric kernel regression method to estimate a measure of distance between the models stated under the null hypothesis. The bootstraped version of the test allows to approximate errors involved in the asymptotic hypothesis test. The paper also develops a Mathematica Code for the test algorithm.

  4. Contribution of Oxygenic Photosynthesis to Palaeo-Oceanic Organic Carbon Sink Fluxes in Early Cambrian Upper Yangtze Shallow Sea:Evidence from Black Shale Record

    Institute of Scientific and Technical Information of China (English)

    Kunyu Wu; Tingshan Zhang; Yang Yang; Yuchuan Sun; Daoxian Yuan

    2016-01-01

    ABSTRACT:The extensive transgression that occurred on the Yangtze Plate in Early Cambrian led to a massive organic carbon pool in the Niutitang Formation. A black shale core section from 3 251.08 to 3 436.08 m beneath the Earth’s surface was studied to estimate the contribution of oxygenic photosyn-thesis to organic carbon sink fluxes in Early Cambrian Upper Yangtze shallow sea. Results indicate that the oxygenic photosynthesis played the most important role in carbon fixation in Early Cambrian. Or-ganic carbon sink was mainly contributed by photosynthetic microorganisms, e.g., cyanobacteria, algae and archaea. The Niutitang Formation was formed in a deep anoxic marine shelf sedimentary envi-ronment at a sedimentation rate of ~0.09±0.03 mm/yr. The initial TOC abundance in Niutitang shale ranged from 0.18%to 7.09%, with an average of 2.15%. In accordance with the sedimentation rate and initial TOC abundance, organic carbon sink fluxes were calculated and found to range from 0.21 to 8.10×103 kg/km2·yr-1, especially the organic carbon sink fluxes in depth between 3 385 and 3 470 m range from 3.80 to 8.10×103 kg/km2·yr-1, with an average of~6.03×103 kg/km2·yr-1, which is much high-er than that of contemporary marine sediments. The organic carbon sink fluxes of Niutitang shale are equal to 0.56 to 21.61×103 kg/km2·yr-1 net oxygen emitted into the Early Cambrian ocean and atmos-phere, this emitted oxygen may have significantly promoted the oxygen level of the Earth’s surface and diversification of metazoans.

  5. Impulse Control Disorders - The Continuum Hypothesis.

    Science.gov (United States)

    Stenberg, Georg

    2016-01-01

    The group Parkinson Inside Out is composed of health professionals and academic researchers who have been diagnosed with Parkinson's Disease. In our discussions we try to make use of both our inside perspective as patients, and our outside perspective as professionals. In this paper, we apply the two perspectives to the Impulse Control Disorders. These impulsive behaviour patterns are thought to be relatively uncommon side effects of some of the medication used in dopamine replacement therapy. The phenomenon is usually described as relatively rare (dopamine replacement therapy. They result from difficulties in decision making engendered by variations in dopamine accessibility in the reward centre of the brain. Only in a minority do the consequences grow to the damaging proportions of a disorder, but most patients are probably affected to some degree. Seeing, and measuring, decision difficulties as a continuous dimension, rather than as a discrete category, brings increased possibilities for early detection and continuous monitoring. With reliable measures of the propensity for impulsive decision making, it may become possible to both reap the benefits and avoid the dangers of the dopamine agonists. We point to ways of empirically testing our continuity hypothesis. PMID:27031861

  6. Environmental Kuznets Curve Hypothesis. A Survey

    International Nuclear Information System (INIS)

    The Environmental Kuznets Curve (EKC) hypothesis postulates an inverted-U-shaped relationship between different pollutants and per capita income, i.e., environmental pressure increases up to a certain level as income goes up; after that, it decreases. An EKC actually reveals how a technically specified measurement of environmental quality changes as the fortunes of a country change. A sizeable literature on EKC has grown in recent period. The common point of all the studies is the assertion that the environmental quality deteriorates at the early stages of economic development/growth and subsequently improves at the later stages. In other words, environmental pressure increases faster than income at early stages of development and slows down relative to GDP growth at higher income levels. This paper reviews some theoretical developments and empirical studies dealing with EKC phenomenon. Possible explanations for this EKC are seen in (1) the progress of economic development, from clean agrarian economy to polluting industrial economy to clean service economy; (2) tendency of people with higher income having higher preference for environmental quality, etc. Evidence of the existence of the EKC has been questioned from several corners. Only some air quality indicators, especially local pollutants, show the evidence of an EKC. However, an EKC is empirically observed, till there is no agreement in the literature on the income level at which environmental degradation starts declining. This paper provides an overview of the EKC literature, background history, conceptual insights, policy and the conceptual and methodological critique

  7. Knowledge-based economy hypothesis revisited

    Directory of Open Access Journals (Sweden)

    Kaurin Dragoljub

    2009-01-01

    Full Text Available At the theoretical level, within the context of developed countries such as the UK and USA, the paradigm of the emerging 'knowledge economy' is becoming prevalent in sociology, and social sciences more broadly. Leading social scientists see this as a crucial development. This paper challenges the view about the emergence of this new type of economy and looks at the intersection of economics and the sociology of education. Central questions to be addressed here are whether we need a radically new approach to education in the light of the recent developments? Should broad and humanistic goals be subjected to the needs of economy and the labour market? How can we best approach educational planning? Are we witnessing the emergence of the economy of the highly skilled? Are there examples that represent a countervailing power to this hypothesis? Are there instances where we can witness the 'low skills' agenda? In essence, the paper is geared to investigating how these questions can be answered or deflected.

  8. The social brain hypothesis of schizophrenia.

    Science.gov (United States)

    Burns, Jonathan

    2006-06-01

    The social brain hypothesis is a useful heuristic for understanding schizophrenia. It focuses attention on the core Bleulerian concept of autistic alienation and is consistent with well-replicated findings of social brain dysfunction in schizophrenia as well as contemporary theories of human cognitive and brain evolution. The contributions of Heidegger, Merleau-Ponty and Wittgenstein allow us to arrive at a new "philosophy of interpersonal relatedness", which better reflects the "embodied mind" and signifies the end of Cartesian dualistic thinking. In this paper I review the evolution, development and neurobiology of the social brain - the anatomical and functional substrate for adaptive social behaviour and cognition. Functional imaging identifies fronto-temporal and fronto-parietal cortical networks as comprising the social brain, while the discovery of "mirror neurons" provides an understanding of social cognition at a cellular level. Patients with schizophrenia display abnormalities in a wide range of social cognition tasks such as emotion recognition, theory of mind and affective responsiveness. Furthermore, recent research indicates that schizophrenia is a disorder of functional and structural connectivity of social brain networks. These findings lend support to the claim that schizophrenia represents a costly by-product of social brain evolution in Homo sapiens. Individuals with this disorder find themselves seriously disadvantaged in the social arena and vulnerable to the stresses of their complex social environments. This state of "disembodiment" and interpersonal alienation is the core phenomenon of schizophrenia and the root cause of intolerable suffering in the lives of those affected. PMID:16946939

  9. Minireview: Organizational hypothesis: instances of the fingerpost.

    Science.gov (United States)

    Breedlove, S Marc

    2010-09-01

    There is now compelling evidence that the ratio of the length of the second digit divided by the length of the fourth digit (2D:4D) is affected by prenatal androgens in humans. This ratio is greater in females than males from fetal life through adulthood, correlates with polymorphism in the androgen receptor gene in men, is feminine in XY androgen insensitivity syndrome, and masculinized in congenital adrenal hyperplasia. Using 2D:4D as a correlate, researchers have found evidence that prenatal androgens affect many sexually differentiated human behaviors, including sexual orientation in women (but not in men), attention deficit disorder, autism, eating disorders, aggression, and risk-taking. In each case, lower 2D:4D, indicative of greater prenatal androgen stimulation, is associated with behavior more commonly displayed by males than females. The correlation between 2D:4D and prenatal androgen stimulation is too imperfect to accurately predict the phenotype of a particular individual, even in terms of sex. However, digit ratio is the best available retrospective marker of average differences in prenatal androgen stimulation between groups of people, and/or correlations of prenatal androgen stimulation with particular behaviors and characteristics within a group. Thus digit ratios offer a valid test of the organizational hypothesis that androgens act early in life to masculinize various human behaviors. PMID:20631003

  10. Bayesian Hypothesis Testing for Planet Finding

    Science.gov (United States)

    Braems, I.; Kasdin, N. J.

    2003-12-01

    One of the most important performance metrics of any space planet finding system is integration time. The time needed to make a positive detection of an extrasolar planet determines the number of systems we can observe for the life of the mission and the stability requirements of the spacecraft and optical control systems. Most astronomical detection approaches rely on fairly simple signal-to-noise calculations and a threshold determined by the ability of the human eye to extract the planet image from the background (usually a signal-to-noise ratio of five). In this paper we present an alternative approach to detection using Bayesian hypothesis testing. This optimal approach provides a quantitative measure of the probability of detection under various conditions and integration times (such as known or unknown background levels) and under different prior assumptions. We also show how the technique allows for a much higher probability of detection for shorter integration times than the previous photometric approaches. We gratefully acknowledge the support of the Jet Propulsion Laboratory of the National Aeronautics and Space Administration for this work and Institut National de Recherche en Informatique et Automatique (INRIA) for its support of Ms. Braems.

  11. The Stem Cell Hypothesis of Aging

    Directory of Open Access Journals (Sweden)

    Anna Meiliana

    2010-04-01

    Full Text Available BACKGROUND: There is probably no single way to age. Indeed, so far there is no single accepted explanation or mechanisms of aging (although more than 300 theories have been proposed. There is an overall decline in tissue regenerative potential with age, and the question arises as to whether this is due to the intrinsic aging of stem cells or rather to the impairment of stem cell function in the aged tissue environment. CONTENT: Recent data suggest that we age, in part, because our self-renewing stem cells grow old as a result of heritable intrinsic events, such as DNA damage, as well as extrinsic forces, such as changes in their supporting niches. Mechanisms that suppress the development of cancer, such as senescence and apoptosis, which rely on telomere shortening and the activities of p53 and p16INK4a may also induce an unwanted consequence: a decline in the replicative function of certain stem cells types with advancing age. This decrease regenerative capacity appears to pointing to the stem cell hypothesis of aging. SUMMARY: Recent evidence suggested that we grow old partly because of our stem cells grow old as a result of mechanisms that suppress the development of cancer over a lifetime. We believe that a further, more precise mechanistic understanding of this process will be required before this knowledge can be translated into human anti-aging therapies. KEYWORDS: stem cells, senescence, telomere, DNA damage, epigenetic, aging.

  12. Spectral analysis and the Riemann hypothesis

    Science.gov (United States)

    Lachaud, Gilles

    2003-11-01

    The explicit formulas of Riemann and Guinand-Weil relate the set of prime numbers with the set of nontrivial zeros of the zeta function of Riemann. We recall Alain Connes' spectral interpretation of the critical zeros of the Riemann zeta function as eigenvalues of the absorption spectrum of an unbounded operator in a suitable Hilbert space. We then give a spectral interpretation of the zeros of the Dedekind zeta function of an algebraic number field K of degree n in an automorphic setting. If K is a complex quadratic field, the torical forms are the functions defined on the modular surface X, such that the sum of this function over the "Gauss set" of K is zero, and Eisenstein series provide such torical forms. In the case of a general number field, one can associate to K a maximal torus T of the general linear group G. The torical forms are the functions defined on the modular variety X associated to G, such that the integral over the subvariety induced by T is zero. Alternately, the torical forms are the functions which are orthogonal to orbital series on X. We show here that the Riemann hypothesis is equivalent to certain conditions bearing on spaces of torical forms, constructed from Eisenstein series, the torical wave packets. Furthermore, we define a Hilbert space and a self-adjoint operator on this space, whose spectrum equals the set of critical zeros of the Dedekind zeta function of K.

  13. The Analysis of Fisher Hypothesis in Terms of Turkish Economy Through Alternative Interest Rates

    Directory of Open Access Journals (Sweden)

    Fuat Lebe

    2016-06-01

    Full Text Available The purpose of this study is to analyze the relationship between the interest rate and inflation rate in the context of Fisher hypothesis (1930 by using the data regarding Turkish Economy Differing from the available literature, the validity of Fisher hypothesis for Turkey was assessed according to the alternative interest rates (rediscount interest rate, deposit interest rate and the monetary policy interest rate. The long-term relationship among variables was analyzed via ARDL bound test. As a result of this analysis, it was determined that a stronger Fisher impact is valid for Turkish economy when the monetary interest rate is based as interest rate.

  14. AN APPLICATION OF THE INPUT HYPOTHESIS TO THE TEACHING OF COLLEGE ENGLISH READING

    Institute of Scientific and Technical Information of China (English)

    LiNa

    2004-01-01

    The present paper is a teaching experiment, during whichKrashen' Input Hypothesis was integrated with the context ofChina's college English teaching, and three aspects wereemphasized: increasing the comprehensible input, emphasizingvocabulary and structure, and lowering the students' affectivelevel. The results after a one-term teaching experiment indicatedthat the experimental class significantly outperformed thecontrol class, which proved that Krashen' Input Hypothesis hassome positive impact on our foreign language teaching. Theauthor points out, in the meantime, that we should by nomeans mechanically adopt it. The paper then puts forwardseveral implications for China's English teaching.

  15. An Evaluation of the Contractionary Devaluation Hypothesis

    OpenAIRE

    Bebczuk, Ricardo Néstor; Galindo, Arturo; Panizza, Ugo

    2006-01-01

    Recent empirical and theoretical literature on the impact of real exchange rate devaluations on economic performance questions the traditional expansionary effect generated within standard Mundell-Fleming models. Contractionary devaluations may arise when firms face maturity or currency mismatches that, when faced with real exchange rate depreciations, lead to balance-sheet effects that erode firms' wealth and lead to an output contraction. While some authors show that the standard Mundell-Fl...

  16. Age-specific reproductive success: evidence for the selection hypothesis.

    Science.gov (United States)

    Mauck, R A; Huntington, C E; Grubb, T C

    2004-04-01

    Age-specific reproductive success has been demonstrated in many species. Three hypotheses have been raised to explain this general phenomenon: the experience hypothesis based on age-specific reproductive experience, the effort hypothesis based on age-specific reproductive effort, and the selection hypothesis based on progressive disappearance of phenotypes due to variation in individual productivity and survival. We used data from a long-term study of Leach's storm-petrels (Oceanodroma leucorhoa) to present a single test of mutually exclusive predictions about the relationship between early breeding success and longevity. There should be no correlation between early breeding success and longevity under the experience hypothesis, a negative correlation under the effort hypothesis, and a positive correlation under the selection hypothesis. We found a significant (P seabirds, strongly suggesting that low-productivity parents were also less likely to survive early breeding. These data provide some of the strongest support to date for the selection hypothesis. PMID:15154562

  17. Fungiculture or Termite Husbandry? The Ruminant Hypothesis.

    Science.gov (United States)

    Nobre, Tânia; Aanen, Duur K

    2012-01-01

    We present a new perspective for the role of Termitomyces fungi in the mutualism with fungus-growing termites. According to the predominant view, this mutualism is as an example of agriculture with termites as farmers of a domesticated fungus crop, which is used for degradation of plant-material and production of fungal biomass. However, a detailed study of the literature indicates that the termites might as well be envisioned as domesticates of the fungus. According to the "ruminant hypothesis" proposed here, termite workers, by consuming asexual fruiting bodies not only harvest asexual spores, but also lignocellulolytic enzymes, which they mix with foraged plant material and enzymes of termite and possibly bacterial origin. This mixture is the building material of the fungus garden and facilitates efficient degradation of plant material. The fungus garden thus functions as an external rumen for termites and primarily the fungi themselves benefit from their own, and gut-derived, lignocellulolytic enzymes, using the termites to efficiently mix these with their growth substrate. Only secondarily the termites benefit, when they consume the degraded, nitrogen-enriched plant-fungus mixture a second time. We propose that the details of substrate use, and the degree of complementarity and redundancy among enzymes in food processing, determine selection of horizontally transmitted fungal symbionts at the start of a colony: by testing spores on a specific, mechanically and enzymatically pre-treated growth substrate, the termite host has the opportunity to select specific fungal symbionts. Potentially, the gut-microbiota thus influence host-fungus specificity, and the selection of specific fungal strains at the start of a new colony. We argue that we need to expand the current bipartite insect-biased view of the mutualism of fungus-growing termites and include the possible role of bacteria and the benefit for the fungi to fully understand the division of labor among

  18. A Hypothesis for Bacteriophage DNA Packaging Motors

    Directory of Open Access Journals (Sweden)

    Philip Serwer

    2010-08-01

    Full Text Available The hypothesis is presented that bacteriophage DNA packaging motors have a cycle comprised of bind/release thermal ratcheting with release-associated DNA pushing via ATP-dependent protein folding. The proposed protein folding occurs in crystallographically observed peptide segments that project into an axial channel of a protein 12-mer (connector that serves, together with a coaxial ATPase multimer, as the entry portal. The proposed cycle begins when reverse thermal motion causes the connector’s peptide segments to signal the ATPase multimer to bind both ATP and the DNA molecule, thereby producing a dwell phase recently demonstrated by single-molecule procedures. The connector-associated peptide segments activate by transfer of energy from ATP during the dwell. The proposed function of connector/ATPase symmetry mismatches is to reduce thermal noise-induced signaling errors. After a dwell, ATP is cleaved and the DNA molecule released. The activated peptide segments push the released DNA molecule, thereby producing a burst phase recently shown to consist of four mini-bursts. The constraint of four mini-bursts is met by proposing that each mini-burst occurs via pushing by three of the 12 subunits of the connector. If all four mini-bursts occur, the cycle repeats. If the mini-bursts are not completed, a second cycle is superimposed on the first cycle. The existence of the second cycle is based on data recently obtained with bacteriophage T3. When both cycles stall, energy is diverted to expose the DNA molecule to maturation cleavage.

  19. Pb-Pb isotope dating of black shales from the Lower Cambrian Niutitang Formation, Guizhou Province, South China

    Institute of Scientific and Technical Information of China (English)

    CHEN Yongquan; JIANG Shaoyong; LING Hongfei; FENG Hongzhen; YANG Jinghong; CHEN Jianhua

    2003-01-01

    The Lower Cambrian black shales of the Niutitang Formation and their lateral equivalents occur widely on the Yangtze Platform, South China. In this study, we examine two sections of the Niutitang Formation in Guizhou Province. We employ a stepwise acid-leaching technique to obtain Pb-isotope compositions of the black shales. At the Zhongnan section, the black shales display large Pb isotope variations, with 206Pb/204Pb of 20.5396~33.5709, and 207Pb/204Pb of 15.8407~16.5782. In contrast, Pb isotope data show a relatively limited range in 206Pb/204Pb (18.2797~18.5972) and 207Pb/204Pb (15.6813~15.7159) at the Zhijin section. Data for all acid-leached black shale samples from the two sections yield a Pb-Pb isochron age of 531±24 Ma. This age may represent the sedimentary age of the black shales. The initial Pb-isotope composition of the black shales falls near the upper-crust evolution curve in a Zartman Pb-Pb evolution diagram. Hence, it is likely that the Pb in the black shales may have been derived from an upper continental crustal source.

  20. Morphology and function in the Cambrian Burgess Shale megacheiran arthropod Leanchoilia superlata and the application of a descriptive matrix

    Directory of Open Access Journals (Sweden)

    Haug Joachim T

    2012-08-01

    Full Text Available Abstract Background Leanchoilia superlata is one of the best known arthropods from the middle Cambrian Burgess Shale of British Columbia. Here we re-describe the morphology of L. superlata and discuss its possible autecology. The re-description follows a standardized scheme, the descriptive matrix approach, designed to provide a template for descriptions of other megacheiran species. Results Our findings differ in several respects from previous interpretations. Examples include a more slender body; a possible hypostome; a small specialised second appendage, bringing the number of pairs of head appendages to four; a further sub-division of the great appendage, making it more similar to that of other megacheirans; and a complex joint of the exopod reflecting the arthropod’s swimming capabilities. Conclusions Different aspects of the morphology, for example, the morphology of the great appendage and the presence of a basipod with strong median armature on the biramous appendages indicate that L. superlata was an active and agile necto-benthic predator (not a scavenger or deposit feeder as previously interpreted.

  1. Exceptionally preserved Cambrian trilobite digestive system revealed in 3D by synchrotron-radiation X-ray tomographic microscopy.

    Directory of Open Access Journals (Sweden)

    Mats E Eriksson

    Full Text Available The Cambrian 'Orsten' fauna comprises exceptionally preserved and phosphatised microscopic arthropods. The external morphology of these fossils is well known, but their internal soft-tissue anatomy has remained virtually unknown. Here, we report the first non-biomineralised tissues from a juvenile polymerid trilobite, represented by digestive structures, glands, and connective strands harboured in a hypostome from the Swedish 'Orsten' fauna. Synchrotron-radiation X-ray tomographic microscopy enabled three-dimensional internal recordings at sub-micrometre resolution. The specimen provides the first unambiguous evidence for a J-shaped anterior gut and the presence of a crop with a constricted alimentary tract in the Trilobita. Moreover, the gut is Y-shaped in cross section, probably due to a collapsed lumen of that shape, another feature which has not previously been observed in trilobites. The combination of anatomical features suggests that the trilobite hypostome is functionally analogous to the labrum of euarthropods and that it was a sophisticated element closely integrated with the digestive system. This study also briefly addresses the preservational bias of the 'Orsten' fauna, particularly the near-absence of polymerid trilobites, and the taphonomy of the soft-tissue-harbouring hypostome.

  2. New observations of the lobopod-like worm Facivermis from the Early Cambrian Chengjiang Lagerst(a)tte

    Institute of Scientific and Technical Information of China (English)

    LIU Jianni; HAN Jian; SIMONETTA A. M.; HU Shixue; ZHANG Zhifei; YAO Yang; SHU Degan

    2006-01-01

    Facivermis yunnanicus (Hou & Chen, 1989), from the Early Cambrian Chengjiang Lagerst(a)tte, a worm-like fossil with 5 pairs of tentacles and a perceived shrunken end, has been regarded as related to polychaetes, later it has been variously interpreted as lobopods, Pentastoma and lophophorates. Newly discovered complete specimens by the ELI field team show that the taxon has, in addition to the 5 pairs of appendages, a pear-shaped trunk end bearing two or three circles of hooks. Accordingly, based on these important morphological characters, reconsideration of its affinities is provided and the taxonomy is remedied herein. Because the five pairs of appendages of Facivermis yunnanicus resemble the appendages of the fore-trunk of lobopod Miraluolishania (Liu & Shu, 2004), it seems that they are homologous structures. Therefore, the affinities of Facivermis are regarded here as being close to the lobopods, in addition, the lobe-like appendages of Facivermis are very crucial to exploring the origin of the appendages of lobopods and arthropods.

  3. The Guarguaraz Complex and the Neoproterozoic-Cambrian evolution of southwestern Gondwana: Geochemical signatures and geochronological constraints

    Science.gov (United States)

    López de Azarevich, Vanina L.; Escayola, Mónica; Azarevich, Miguel B.; Pimentel, Márcio M.; Tassinari, Colombo

    2009-12-01

    The Guarguaraz Complex, in western Argentina, comprises a metasedimentary assemblage, associated with mafic sills and ultramafic bodies intruded by basaltic dikes, which are interpreted as Ordovician dismembered ophiolites. Two kinds of dikes are recognized, a group associated with the metasediments and the other ophiolite-related. Both have N-MORB signatures, with ɛNd between +3.5 and +8.2, indicating a depleted source, and Grenville model ages between 0.99 and 1.62 Ga. A whole-rock Sm-Nd isochron yielded an age of 655 ± 76 Ma for these mafic rocks, which is compatible with cianobacteria and acritarchae recognized in the clastic metasedimentary platform sequences, that indicate a Neoproterozoic (Vendian)-Cambrian age of deposition. The Guarguaraz metasedimentary-ophiolitic complex represents, therefore, a remnant of an oceanic basin developed to the west of the Grenville-aged Cuyania terrane during the Neoproterozoic. The southernmost extension of these metasedimentary sequences in Cordón del Portillo might represent part of this platform and not fragments of the Chilenia terrane. An extensional event related to the fragmentation of Rodinia is represented by the mafic and ultramafic rocks. The Devonian docking of Chilenia emplaced remnants of ocean floor and slices of the Cuyania terrane (Las Yaretas Gneisses) in tectonic contact with the Neoproterozoic metasediments, marking the Devonian western border of Gondwana.

  4. Characteristics of sulfur species and their implications in Lower Cambrian black shales from southern margin of Yangtze Platform

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    There are different sulfur forms in the black shales from theEarly Cambrian of the Yangtze platform. With its emphasis on pyrite and organosulfur, this paper discusses their distribution and formation. The research shows that sulfur phases take regular variations laterally as well as vertically in the research areas. In western researched profile with high terrigenous supply at the time it formed, there exists a larger amount of pyrite and less organosulfur, and pyrite amount declines while organosulfur content increases upwards along the profile. This black shale profile is characterized by relatively light sulfur isotope composition with evolution trend of becoming heavier both for pyrite and organosulfur from bottom to top along the profile. Opposite situation occurs in eastern profiles which were located farther away from terrigenous land. Here pyrite amount obviously decreases and organic matter has combined more sulfur, although these two kinds of sulfur species take similar trend in content variation along profiles to that for western profile. At the same time more 34S is accumulated in sulfur species of black shale samples from eastern profile, and sulfur isotope composition gradually turns lighter from bottom to top. In combination with other information of iron, organic carbon contents and petrographic features, it can be established that sea-level change, supply of terrigenous matters, tectonic background and natures of paleoceanic chemistry have exerted great influence on the distribution of sulfur species in these black shales.

  5. A submarine welded ignimbrite-crystal-rich sandstone facies association in the Cambrian Tyndall Group, western Tasmania, Australia

    Science.gov (United States)

    White, Matthew J.; McPhie, Jocelyn

    1997-04-01

    Three occurrences of rhyolitic welded ignimbrite are intercalated within a submarine, below-storm-wave-base sedimentary succession in the Cambrian Tyndall Group, Mount Read Volcanics, western Tasmania. These occurrences are closely associated with very thick crystal-rich sandstone facies that is present at this stratigraphic level throughout the Tyndall Group. This facies is interpreted to comprise deposits from syn-eruptive, crystal-rich, submarine sediment gravity flows that were generated by interaction of subaerial pyroclastic flows with seawater. Removal of fine ash and pumice from the submarine flows by hydraulic sorting and flotation resulted in marked crystal enrichment in the deposits. Rapid, essentially syn-eruptive aggradation of crystal-rich sand led to temporary shoaling so that in some cases, subsequent pyroclastic flows deposited welded ignimbrite in shallow marine or possibly subaerial settings (e.g., Zig Zag Hill welded ignimbrite). Breccia units composed of welded ignimbrite clasts and crystal-rich matrix (e.g., Comstock and Anthony Road ignimbrite breccias) imply that some welded ignimbrite was submerged, providing clasts to syn-eruptive, submarine, crystal-rich sediment gravity flows. One example of welded ignimbrite (Cradle Mountain Link Road) may have been deposited in an entirely below-storm-wave-base environment. The distinctive facies association of welded ignimbrite, crystal-rich sandstone and ignimbrite-clast breccia in the Tyndall Group exemplifies the submarine record of a major rhyolitic explosive eruption in the source volcanic terrane.

  6. The earliest-known ancestors of Recent Priapulomorpha from the Early Cambrian Chengjiang Lagerst(``a)tte

    Institute of Scientific and Technical Information of China (English)

    HAN Jian; SHU Degan; ZHANG Zhifei; LIU Jianni

    2004-01-01

    The taxonomy of an early ancestor of Recent Priapulidae, Xiaoheiqingella peculiaris (= Yunnanpriapulus halteroformis Huang et al., 2004) from the Early Cambrian Chengjiang fossil LagerstStte, is revised. Morphological characters comprise a pair of caudal appendages rather than a single appendage flanking the trunk end and a possible urogenital duct found inside the preanal region. An additional extremely rare fossil priapulid worm, Paratubiluchus bicaudatus gen. nov., sp. nov. is also described herein. Its diagnostic characters are: an introvert bearing 25 longitudinal rows of scalids, a distinct neck region, no annulus on the oval trunk, and a pair of caudal appendages. The proportion of body parts is similar in size to that of loricate larvae of Recent priapulids and larva-formed Palaeopriapulitidae. Taking account of the features of Xiaoheiqingella, bicaudal appendages are considered to be a synapomorphy of Priapulidae and Tubiluchidae. Paratubiluchus gen. nov. is most likely a candidate for the ancestor of the Tubiluchidae; it probably originated from a larva-formed priapulid with 25 rows of scalids, thus representing an intermediate link between the priapulids in mature-form and the priapulids with Iorica.

  7. Does the Slow-Growth, High-Mortality Hypothesis Apply Below Ground?

    Science.gov (United States)

    Hourston, James E; Bennett, Alison E; Johnson, Scott N; Gange, Alan C

    2016-01-01

    Belowground tri-trophic study systems present a challenging environment in which to study plant-herbivore-natural enemy interactions. For this reason, belowground examples are rarely available for testing general ecological theories. To redress this imbalance, we present, for the first time, data on a belowground tri-trophic system to test the slow growth, high mortality hypothesis. We investigated whether the differing performance of entomopathogenic nematodes (EPNs) in controlling the common pest black vine weevil Otiorhynchus sulcatus could be linked to differently resistant cultivars of the red raspberry Rubus idaeus. The O. sulcatus larvae recovered from R. idaeus plants showed significantly slower growth and higher mortality on the Glen Rosa cultivar, relative to the more commercially favored Glen Ample cultivar creating a convenient system for testing this hypothesis. Heterorhabditis megidis was found to be less effective at controlling O. sulcatus than Steinernema kraussei, but conformed to the hypothesis. However, S. kraussei maintained high levels of O. sulcatus mortality regardless of how larval growth was influenced by R. idaeus cultivar. We link this to direct effects that S. kraussei had on reducing O. sulcatus larval mass, indicating potential sub-lethal effects of S. kraussei, which the slow-growth, high-mortality hypothesis does not account for. Possible origins of these sub-lethal effects of EPN infection and how they may impact on a hypothesis designed and tested with aboveground predator and parasitoid systems are discussed. PMID:27571368

  8. Testing Happiness Hypothesis among the Elderly

    Directory of Open Access Journals (Sweden)

    Rossi Máximo

    2008-08-01

    Full Text Available We use a rich data set that allows us to test different happiness hypotheses employing four methodological approaches. We find that older people in Uruguay have a tendency to report themselves happy when they are married, when they have higher standards of health and when they earn higher levels of income or they consider that their income is suitable for their standard of living. On the contrary, they report lower levels of happiness when they live alone and when their nutrition is insufficient. We also find that education has no clear impact on happiness. We think that our study is a contribution to the study of those factors that can explain happiness among the elderly in Latin American countries. Future work will focus on enhanced empirical analysis and in extending our study to other countries.

  9. Economic Risk Assessment using the Fractal Market Hypothesis

    OpenAIRE

    Blackledge, Jonathan; Rebow, Marek

    2010-01-01

    This paper considers the Fractal Market Hypothesi (FMH) for assessing the risk(s) in developing a financial portfolio based on data that is available through the Internet from an increasing number of sources. Most financial risk management systems are still based on the Efficient Market Hypothesis which often fails due to the inaccuracies of the statistical models that underpin the hypothesis, in particular, that financial data are based on stationary Gaussian processes. The FMH considered in...

  10. On the Nature and Role of Hypothesis Tests.

    OpenAIRE

    McLean, A

    2001-01-01

    Hypothesis testing is widely regarded as an essential part of statistics, but it s use in research has led to considerable controversy in a number of disciplines, especially psychology, with a number of commentators suggesting it should not be used at all. A root cause of this controversy was the overenthusiastic adoption of hypothesis testing, based on a greatly exaggerated view of its role in research. A second cause was confusion between the two forms of hypothesis testing developed by Fis...

  11. Multi-Task Classification Hypothesis Space with Improved Generalization Bounds

    OpenAIRE

    Li, Cong; Georgiopoulos, Michael; Anagnostopoulos, Georgios C.

    2013-01-01

    This paper presents a RKHS, in general, of vector-valued functions intended to be used as hypothesis space for multi-task classification. It extends similar hypothesis spaces that have previously considered in the literature. Assuming this space, an improved Empirical Rademacher Complexity-based generalization bound is derived. The analysis is itself extended to an MKL setting. The connection between the proposed hypothesis space and a Group-Lasso type regularizer is discussed. Finally, exper...

  12. APPLICABILITY OF DAMAGE DEFINITION BASED ON HYPOTHESIS OF STRAIN EQUIVALENCE

    Institute of Scientific and Technical Information of China (English)

    鞠杨; 谢和平

    2000-01-01

    The hypothesis of strain equivalence is used to measure damage in materials. The physical meaning of the elastic modulus of damaged materials defined in the hypothesis is discussed in this paper. The inapplicability of the hypothesis to be used to determine the damage and its evolution in elasto-plastic materials are analyzed. It is emphasized that the method in which the relaxed modulus is taken as the deformed modulus, i.e. the elastic modulus defined in the hypothesis, is only applicable for measuring the damage in elastic materials. A new damage variable is proposed, which is applicable for both elastic and elastoplastic materials.

  13. A new `hidden colour hypothesis' in hadron physics

    Indian Academy of Sciences (India)

    Afsar Abbas

    2006-05-01

    A new `hidden colour hypothesis' within the framework of QCD, as an extension of and in keeping with the spirit of the `colour singlet hypothesis' is hereby proposed. As such it should play a role in a consistent description of exotic hadrons, such as diquonia, pentaquarks, dibaryons etc. How these exotic hadrons are affected by this new hypothesis is discussed here. This new hypothesis suggests that the experimentalists may not be looking for single exotics but for composites of two or more of the same.

  14. Reconstruction of Cambrian Global Paleo-plates and Paleogeography%寒武纪全球板块构造与古地理环境再造

    Institute of Scientific and Technical Information of China (English)

    周肖贝; 李江海; 王洪浩; 李文山

    2014-01-01

    基于古地磁数据对寒武纪全球古板块进行再造,并叠加更新的寒武纪全球大地构造背景和岩相古地理分布等要素,编制了寒武纪全球古板块再造图、古地理图、全球岩相及烃源岩分布图。寒武纪全球板块以冈瓦纳超大陆、劳伦古陆、西伯利亚板块和波罗的板块为主,多集中位于南半球,冈瓦纳超大陆快速向南漂移,其他板块主要向北漂移,并伴随逆时针旋转。寒武纪整体处于海平面及温度的上升时期,全球板块多为陆表海环境,有利于早寒武世的富有机质沉积,为寒武纪生命大爆发提供了良好条件。但此时气候带梯度不高,干旱气候带广泛分布,下要中寒武统多蒸发盐岩。冈瓦纳超大陆北部主要为碳酸盐岩沉积,南部多为砂岩沉积,东部边缘多火山活动,在中部的西侧边缘地区碳酸盐岩沉积和砂岩沉积物中一般有较好的油气和烃源岩。劳伦古陆沉积具有环带特征,其外侧为碳酸盐岩沉积。西伯利亚板块早要中寒武世主要以巨厚的膏盐岩沉积为主,晚期沉积仅为几百米厚的碳酸盐岩,整体处于被动陆缘沉积的构造背景,这促进了该板块中储层和盖层的发育。波罗的板块纬度相对偏高,主要为砂岩和页岩沉积。%The global maps of Cambrian plate tectonics, plaeogeography, lithofaices and source rock distribution are compiled up for reconstructing Cambrian global paleo-plates on the basis of the paleomagnetic data and the updating data of the Cambrian global tectonics, lithofacies paleogeography and source rocks. Cambrian plates can be divided into four parts including Gondwana, Laurentia, Siberia and Baltica. They were generally distributed in the southern hemisphere and drifted northwards with contrarotating rotation except the southwards drifting Gondwana supercontinent. Owing to rising of global sea level eustacy and temperature for a long time

  15. Biogenic gas in the Cambrian-Ordovcian Alum Shale (Denmark and Sweden)

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, H.M.; Wirth, R.; Biermann, S.; Arning, E.T. [Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ, Potsdam (Germany); Krueger, M.; Straaten, N. [BGR Hannover (Germany); Bechtel, A. [Montanuniv. Leoben (Austria); Berk, W. van [Technical Univ. of Clausthal (Germany); Schovsbo, N.H. [Geological Survey of Denmark and Greenland - GEUS, Copenhagen (Denmark); Crabtree, Stephen [Gripen Gas (Sweden)

    2013-08-01

    Shale gas is mainly produced from thermally mature black shales. However, biogenic methane also represents a resource which is often underestimated. Today biogenic methane is being produced from the Upper Devonian Antrim Shale in the Michigan Basin which was the most successfully exploited shale gas system during the 1990-2000 decade in the U.S.A. before significant gas production from the Barnett Shale started (Curtis et al., 2008). The Cambro-Ordovician Alum Shale in northern Europe has thermal maturities ranging from overmature in southern areas (Denmark and southern Sweden) to immature conditions (central Sweden). Biogenic methane is recorded during drilling in central Sweden. The immature Alum Shale in central Sweden has total organic carbon (TOC) contents up to 20 wt%. The hydrogen index HI ranges from 380 to 560 mgHC/gTOC at very low oxygen index (OI) values of around 4 mg CO{sub 2}/gTOC, Tmax ranges between 420 - 430 C. The organic matter is highly porous. In general, the Alum Shale is a dense shale with intercalated sandy beds which may be dense due to carbonate cementation. Secondary porosity is created in some sandy beds due to feldspar dissolution and these beds serve as gas conduits. Methane production rates with shale as substrate in the laboratory are dependent on the kind of hydrocarbon-degrading microbial enrichment cultures used in the incubation experiments, ranging from 10-620 nmol/(g*d). In these experiments, the CO{sub 2} production rate was always higher than for methane. Like the northern part of North America, also Northern European has been covered by glaciers during the Pleistocene and similar geological processes may have developed leading to biogenic shale gas formation. For the Antrim Shale one hypothesis suggests that fresh waters, recharged from Pleistocene glaciation and modern precipitation, suppressed basinal brine salinity along the northern margins of the Michigan Basin to greater depths and thereby enhancing methanogenesis

  16. Implications of Krashen’s Input Hypothesis and Affective Filter Hypothe-sis in College English Teaching

    Institute of Scientific and Technical Information of China (English)

    张妮

    2014-01-01

    American linguist Krashen proposed the input hypothesis and affective filter hypothesis which has influenced linguistic world deeply. These two assumptions play an important role in improving learners' language ability in the process of second lan⁃guage acquisition. Applying two hypothesis theories to college English teaching, teachers ’aim is to establish a new mode of lan⁃guage teaching and improve the efficiency of college English teaching.

  17. A mechanistic investigation of the oxygen fixation hypothesis and oxygen enhancement ratio

    OpenAIRE

    Grimes, David Robert; Partridge, Mike

    2015-01-01

    The presence of oxygen in tumours has substantial impact on treatment outcome; relative to anoxic regions, well-oxygenated cells respond better to radiotherapy by a factor 2.5–3. This increased radio-response is known as the oxygen enhancement ratio. The oxygen effect is most commonly explained by the oxygen fixation hypothesis, which postulates that radical-induced DNA damage can be permanently ‘fixed’ by molecular oxygen, rendering DNA damage irreparable. While this oxygen effect is importa...

  18. Fractal Markets Hypothesis and the Global Financial Crisis: Wavelet Power Evidence

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav

    2013-01-01

    Roč. 3, č. 10 (2013), 2857-1-2857-12. ISSN 2045-2322 R&D Projects: GA ČR GA402/09/0965 Grant ostatní: GA ČR(CZ) GAP402/11/0948 Institutional support: RVO:67985556 Keywords : fractal markets hypothesis * investment horizons * wavelets Subject RIV: AH - Economics Impact factor: 5.078, year: 2013 http://library.utia.cas.cz/separaty/2013/E/kristoufek-0397560.pdf

  19. How Null Hypothesis Significance Testing May Impede Further Progress Within Psychology

    OpenAIRE

    Tveit, Håvard

    2014-01-01

    In 2005, Ioannidis revitalised a long-lasting debate concerning whether or not null hypothesis significance testing may serve to uphold accessibility related biases, and in effect the file drawer problem as well. Though several authors have argued that significance testing may consequentially impede further progress within the medical and behavioural sciences, it has had little impact on the general consensus, and significance testing is still the most common approach to analyze and interpret...

  20. Social Comparison and Performance: Experimental Evidence on the Fair Wage-Effort Hypothesis

    OpenAIRE

    Simon Gaechter; Christian Thoeni

    2009-01-01

    We investigate the impact of wage comparisons for worker productivity. We present three studies which all use three-person gift-exchange experiments. Consistent with Akerlof and Yellen's (1990) fair wage-effort hypothesis we find that disadvantageous wage discrimination leads to lower efforts while advantageous wage discrimination does not increase efforts on average. Two studies allow us to measure wage comparison effects at the individual level. We observe strongly heterogeneous wage compar...

  1. Social Comparison and Performance: Experimental Evidence on the Fair Wage-Effort Hypothesis

    OpenAIRE

    Gächter, Simon; Thöni, Christian

    2010-01-01

    We investigate the impact of wage comparisons for worker productivity. We present three studies which all use three-person gift-exchange experiments. Consistent with Akerlof and Yellen's (1990) fair wage-effort hypothesis we find that disadvantageous wage discrimination leads to lower efforts while advantageous wage discrimination does not increase efforts . Two studies allow us to measure wage comparison effects at the individual level. We observe strongly heterogeneous wage comparison effec...

  2. Dynamical agents' strategies and the fractal market hypothesis

    Czech Academy of Sciences Publication Activity Database

    Vácha, Lukáš; Vošvrda, Miloslav

    2005-01-01

    Roč. 14, č. 2 (2005), s. 172-179. ISSN 1210-0455 Grant ostatní: GA UK(CZ) 454/2004/A EK/FSV Institutional research plan: CEZ:AV0Z10750506 Keywords : efficient market hypothesis * fractal market hypothesis * agent's investment horizons Subject RIV: AH - Economics

  3. Teacher Satisfaction and Dissatisfaction: Herzberg's 'Two-Factor' Hypothesis Revisited.

    Science.gov (United States)

    Nias, Jennifer

    1981-01-01

    Discusses a study undertaken to evaluate perceptions of job satisfaction and dissatisfaction among 100 graduates trained to teach in primary schools. Weighs findings in light of a hypothesis (Herzberg's two-factor hypothesis) which states that causes of job satisfaction are substantially independent of those determining job dissatisfaction.…

  4. From Grammatical Gender to Sapir-Whorf Hypothesis

    Institute of Scientific and Technical Information of China (English)

    王皓

    2015-01-01

    <正>Comment on Vigliocco,G.et al.(2005)and Review on SapirWhorf Hypothesis Does language shape thought?The question derived from Sapir-Whorf Hypothesis has never been easy to answer with certainty.Nevertheless,the attempts and trials of tackling this question seldom stops.The Vigliocco et al.paper"Grammatical

  5. The Role of Hypothesis in Constructive Design Research

    DEFF Research Database (Denmark)

    Bang, Anne Louise; Krogh, Peter; Ludvigsen, Martin;

    2012-01-01

    nuanced and solid perspective on how to keep constructive design research on track, this paper offers a model for understanding the role of hypothesis in constructive design research. The model allows for understanding the hypothesis’s relation to research motivation, questions, experiments, evaluation...... central position of the hypothesis as a key-governing element even in artistic led research processes....

  6. An Analysis of Input Hypothesis in English Teaching

    Institute of Scientific and Technical Information of China (English)

    赖菲菲

    2016-01-01

    Input plays a significant role in the process of foreign language teaching and learning. One of the most important studies about input is Krashen's Input Hypothesis, which emphasizes the importance of comprehensive input in foreign language teaching and learning. This paper aims to study the significance of Input Hypothesis and its application to English teaching.

  7. Inflation uncertainty and a test of the Friedman hypothesis

    OpenAIRE

    R. W. Hafer

    1985-01-01

    This paper tests Friedman's (1977) hypothesis that increases in inflation uncertainty, ceteris paribus, may yield higher levels of unemployment. Tests are made using quarterly measures of inflation uncertainty taken from the ASA-NBER survey. Using the 1972-1984 period, we find general support for the hypothesis.

  8. Assess the Critical Period Hypothesis in Second Language Acquisition

    Science.gov (United States)

    Du, Lihong

    2010-01-01

    The Critical Period Hypothesis aims to investigate the reason for significant difference between first language acquisition and second language acquisition. Over the past few decades, researchers carried out a series of studies to test the validity of the hypothesis. Although there were certain limitations in these studies, most of their results…

  9. The Critical Period Hypothesis: A Coat of Many Colours

    Science.gov (United States)

    Singleton, David

    2005-01-01

    Research on age-related effects in L2 development often invokes the idea of a critical period--the postulation of which is customarily referred to as the Critical Period Hypothesis. This paper argues that to speak in terms of the Critical Period Hypothesis is misleading, since there is a vast amount of variation in the way in which the critical…

  10. New Hypothesis for SOFC Ceramic Oxygen Electrode Mechanisms

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Chatzichristodoulou, Christodoulos; Graves, Christopher R.;

    2016-01-01

    A new hypothesis for the electrochemical reaction mechanism in solid oxide cell ceramic oxygen electrodes is proposed based on literature including our own results. The hypothesis postulates that the observed thin layers of SrO-La2O3 on top of ceramic perovskite and other Ruddlesden-Popper struct...

  11. Age Dedifferentiation Hypothesis: Evidence form the WAIS III.

    Science.gov (United States)

    Juan-Espinosa, Manuel; Garcia, Luis F.; Escorial, Sergio; Rebollo, Irene; Colom, Roberto; Abad, Francisco J.

    2002-01-01

    Used the Spanish standardization of the Wechsler Adult Intelligence Scale III (WAIS III) (n=1,369) to test the age dedifferentiation hypothesis. Results show no changes in the percentage of variance accounted for by "g" and four group factors when restriction of range is controlled. Discusses an age indifferentation hypothesis. (SLD)

  12. Mazur’s Hypothesis on Technology Controversy and Media

    NARCIS (Netherlands)

    Gutteling, Jan M.

    2005-01-01

    In the early 1980s, Allan Mazur published his hypothesis on the direct relation between media coverage and public reaction toward technological issues. This hypothesis stated, ‘the rise in reaction against a scientific technology appears to coincide with a rise in quantity of media coverage, suggest

  13. Geochemical characteristics of organic matter-rich strata of lower Cambrian in Tarim Basin and its origin

    Institute of Scientific and Technical Information of China (English)

    CHEN; Jianfa; SUN; Shengli; LIU; Wenhui; ZHENG; Jianjing

    2004-01-01

    The organic matter-rich strata of the Yurtusi Formation of Lower Cambrian are wildly spread and steady in the Tarim Basin, in which cherts are developed, companied with phosphorite. Al/(Al+Fe+Mn) ratio and Si/(Si+Al+Fe) ratio of cherts range from 0.0023 to 0.0046 and 0.965 to 0.98, respectively, suggesting that cherts are formed in submarine hydrothermal activity and far away from terrestrial. Trace elements, such as As, Hg, Pb, Zn, Cu, Co, P, V, Ba, etc., are markedly rich in organic matter-rich sedimentary rocks of which Ba/Sr ratios are between 21.2 and 158.1. Compared with modern hydrothermal sediments, their Ba/Sr ratios are similar, it indicates that the organic matter-rich strata have the geochemical feature of submarine hydrothermal sediments. The total content of rare earth elements (ЕREE) in cherts is from 8.81 to 56.682 μg/g, on average 31.41 μg/g and the ΕREE of cherts is between continental margin chert's and abyssal chert's. The LREE/HREE ratio of cherts varies from 1.01 to 3.56, which reveals the characteristics of hydrothermal sediments. There is positive correlation between the total organic content (TOC) and Ba/Sr ratio which is geochemical index of submarine hydrothermal activity, which indicates that the submarine hydrothermal activity obviously influences the richness of organic matter in the Yurtusi Formation.

  14. Maps showing petroleum exploration intensity and production in major Cambrian to Ordovician reservoir rocks in the Anadarko Basin

    Science.gov (United States)

    Henry, Mitch; Hester, Tim

    1996-01-01

    The Anadarko basin is a large, deep, two-stage Paleozoic basin (Feinstein, 1981) that is petroleum rich and generally well explored. The Anadarko basin province, a geogrphic area used here mostly for the convenience of mapping and data management, is defined by political boundaries that include the Anadarko basin proper. The boundaries of the province are identical to those used by the U.S. Geological Survey (USGS) in the 1995 National Assessment of United Stated Oil and Gas Resources. The data in this report, also identical to those used in the national assessment, are from several computerized data bases including Nehring Research Group (NRG) Associates Inc., Significant Oil and Gas Fields of the United States (1992); Petroleum Information (PI), Inc., Well History Control System (1991); and Petroleum Information (PI), Inc., Petro-ROM: Production data on CD-ROM (1993). Although generated mostly in response to the national assessment, the data presented here arc grouped differently and arc displayed and described in greater detail. In addition, the stratigraphic sequences discussed may not necessarily correlate with the "plays" of the 1995 national assessment. This report uses computer-generated maps to show drilling intensity, producing wells, major fields, and other geologic information relevant to petroleum exploration and production in the lower Paleozoic part of the Anadarko basin province as defined for the U.S. Geological Survey's 1995 national petroleum assessment. Hydrocarbon accumulations must meet a minimum standard of 1 million barrels of oil (MMBO) or 6 billion cubic feet of gas (BCFG) estimated ultimate recovery to be included in this report as a major field or revoir. Mapped strata in this report include the Upper Cambrian to Lower Ordovician Arbuckle and Low Ordovician Ellenburger Groups, the Middle Ordovician Simpson Group, and the Middle to Upper Ordovician Viola Group.

  15. A transgression-regression event during the deposition of the Upper Cambrian Honey Creek formation in the southern Oklahoma aulacogen

    Energy Technology Data Exchange (ETDEWEB)

    McElmoyl, C.; Donovan, R.N. (Texas Christian Univ., Ft. Worth, TX (United States). Geology Dept.)

    1993-02-01

    The transgression that inundated the Southern Oklahoma aulacogen during the upper Cambrian enveloped a landscape that consisted of hills of rhyolite up to 350 m in high. Initial deposits on this topography have been interpreted as alluvium. These, together with succeeding tidally-influenced marine siliciclastics form the Reagan Formation. The siliciclastics grains are made up of fragments of local origin (i.e., rhyolite), quartz (derived from a distal source) and authigenic glauconite. The upward passage from the Reagan to the Honeycreek Formation is defined by the addition to the siliciclastics of carbonate detritus in the form of tidally-influenced grainstones, mostly composed of pelmatozoan fragments. The passage from the Honeycreek to the overlying Fort Sill Formation of the Arbuckle Group is marked by the incoming of beds of lime mudstone and the gradual disappearance of grainstones and siliciclastics. Evidence of the existence of rhyolite topography (i.e., an archipelago) can be detected to within 50 m of the top of the Fort Sill. While the overall facies pattern undoubtedly records a widespread transgression, a newly-discovered slightly angular unconformity within the lower part of the Honeycreek is best interpreted as a record of a temporary regression. Three distinctive lithologies are involved in this relationship: the lowest beds are light grey cross-bedded pelmatozoan grainstones with minor amounts of quartz and rhyolite grains. Syntaxial cements at the base of this unit are homogenous under cathode luminescence, while cements near the top display up to 27 zones of reflectance, interpreted as a fluctuating marine-meteoric groundwater imprint. The overlying bed is a red-brown mud-supported limestone that contains abundant angular rhyolite pebbles and a rich trilobite fauna. Some of the pebbles are coated by pelmatozoans.

  16. Cambrian Magmatism Along the Southern Laurentian Margin: New Petrologic Constraints from Well Cuttings in the Southern Oklahoma Aulacogen (USA)

    Science.gov (United States)

    Hobbs, J. M.; Brueseke, M. E.; Mertzman, S. A.; Puckett, R. E., Jr.

    2014-12-01

    Magmatism in the Southern Oklahoma aulacogen (SOA) is associated with >250,000 km3 of early Cambrian aged mafic-silicic intrusives and effusive products possibly related to the opening of the Iapetus Ocean. In the vicinity of the Arbuckle Mts., thick mafic to intermediate lava packages interbedded with rhyolite lavas and sedimentary strata are exposed in the subsurface and penetrated by oil and gas exploration wells. We have sampled cuttings from six wells exposed along the strike of the SOA with the aim of petrographically, geochemically, and isotopically characterizing the rocks to better understand their tectonomagmatic affinity. Cuttings were observed under a binocular microscope to ensure textural homogeneity; XRF bulk chemistry from these samples show that they are relatively unaltered based on analytical totals and alteration indices. The samples plot as basalts to andesites (e.g., 47-64 wt. % SiO2) and are primarily tholeiitic. On discrimination diagrams, these samples fall in "intraplate" fields, consistent with continental basalt volcanism, including flood basalt eruptions. These lavas show Zr/Nb values ranging from 6.8 to 11.1, K/Nb values ranging from 300-600, and Ba/Nb values ranging from 10-20, which are similar to EM1 OIB. The samples also show trace element patterns consistent with OIB-like mantle sources when normalized to primitive mantle, and similar geochemical traits to the Roosevelt Gabbros that crop out along strike of the SOA in the Wichita Mts.. Sr, Nd, and Pb isotope analysis is ongoing. Chemostratigraphic variations show the possibility of several lava packages. The geochemical analyses of the SOA lava flows provide insight into how these magmas formed as well as what tectonic regime (e.g., lower-mantle derived plume, upper-mantle extension, or "leaky" transform fault) produced the volcanism that affected the southern margin of Laurentia during the formation of the SOA; we favor the involvement of a deep mantle plume.

  17. Further evidence for epidemiological transition hypothesis for elderly suicides

    Directory of Open Access Journals (Sweden)

    Ajit Shah

    2011-01-01

    Full Text Available BACKGROUND: A developmental model of epidemiological transition for elderly suicide rates with four sequential stages has been developed to simultaneously explain cross-national variations in elderly suicide rates, trends over time for elderly suicide rates and age-associated trends in suicides rates reported in the literature. This model was supported by demonstration of a curvilinear (inverted U-shaped curve relationship between elderly suicide rates and socio-economic status fitting the quadratic equation Y = A + BX - CX2 (where Y is the suicide rate, X is the socio-economic status and A,B, and C are constants in both sexes. However, this relationship was derived from a cross-sectional study and, therefore, only an association can be inferred. One way to substantiate this further would be to examine the above curvilinear relationship between suicide rates and socio-economic status in a series of younger age-bands because a large part of the epidemiological transition hypothesis was contingent upon the impact of socio-economic status, through a series of mechanisms, on life expectancy. It was hypothesized that the curvilinear (inverted U-shaped curve relationship between suicide rates and socio-economic status would be absent in younger age-bands and may be present in the younger age-bands closer to the older age-bands (i.e. 45-54 years and 55-64 years. METHODS: The curvilinear relationship between suicide rates in five age-bands 15-24 years to 55-64 years in both sexes and gross national domestic product (GDP, a measure of socio-economic status, fitting the above quadratic equation was examined with curve estimation regression model using data from the World Health Organization. RESULTS: In males in the age-bands 35-44 years, 45-54 years and 55-64 years there was a statistically significant curvilinear (inverted U-shaped curve relationship with GDP and fitted the quadratic equation Y = A + BX - CX2; this relationship was absent in males in

  18. The origin of increased salinity in the Cambrian-Vendian aquifer system on the Kopli Peninsula, northern Estonia

    Science.gov (United States)

    Karro, Enn; Marandi, Andres; Vaikmäe, Rein

    Monitoring of the confined Cambrian-Vendian aquifer system utilised for industrial water supply at Kopli Peninsula in Tallinn over 24 years reveals remarkable changes in chemical composition of groundwater. A relatively fast 1.5 to 3.0-fold increase in TDS and in concentrations of major ions in ed groundwater is the consequence of heavy pumping. The main sources of dissolved load in Cambrian-Vendian groundwater are the leaching of host rock and the other geochemical processes that occur in the saturated zone. Underlying crystalline basement, which comprises saline groundwater in its upper weathered and fissured portion, and which is hydraulically connected with the overlying Cambrian-Vendian aquifer system, is the second important source of ions. The fractured basement and its clayey weathering crust host the Ca-Cl type groundwater, which is characterised by high TDS values (2-20 g/L). Intensive water ion accelerates the exchange of groundwaters and increases the area of influence of pumping. Chemical and isotopic studies of groundwater indicate an increasing contribution of old brackish water from the crystalline basement and rule out the potential implication of an intrusion of seawater into aquifer. L'origine de la salinité croissante dans le système aquifère du Cambrien-Vendien dans la péninsule de Kopli, nord de l'Estonie Le suivi à long terme du système aquifère captif du Cambrien-Vendien utilisé pour l'approvisionnement d'eaux industrielles dans la Péninsule de Kopli, nord de l'Estonie, révèle de remarquables changements dans la composition chimique des eaux souterraines. Une augmentation de facteur 1.5 à 3 de la TDS et des concentrations en ions majeurs dans l'eau souterraine est la conséquence de pompages intensifs. Les sources principales des charges dissoutes dans les eaux de l'aquifère du Cambrien-Vendien sont le lessivage des roches et d'autres phénomènes géochimiques ayant lieu dans la zone saturée. Le soubassement rocheux cristallin

  19. Sulfur and Oxygen Isotopes of Sulfate Extracted from Early Cambrian Phosphorite Nodules:Implications for Marine Redox Evolution in the Yangtze Platform

    Institute of Scientific and Technical Information of China (English)

    Wenlang Qiao; Xianguo Lang; Yongbo Peng; Kaiyuan Jiang; Wu Chen; Kangjun Huang; Bing Shen

    2016-01-01

    ABSTRACT:Phosphorite nodule beds are discovered in the black shale of basal Niutitang Formation throughout the Yangtze Platform in South China, recording an important phosphorite-generation event. Platform-wide phosphorite precipitation requires special oceanographic and geochemical conditions, thus the origin of the Niutitang phosphorite nodules may provide valuable information about the ocean chemistry in the Early Cambrian. In this study, we measured sulfur and oxygen isotopic compositions of sulfate extracted from phosphorite nodules collected from the basal Niutitang Formation. Phosphorite associated sulfate (PAS) is a trace amount of sulfate that incorporates into crystal lattice during phosphorite precipitation, accordingly PAS records the geochemical signals during phosphorite nodule formation. Sulfur isotopic composition of PAS (δ34SPAS) ranges from -1.16‰ to +24.48‰(mean=+8.19‰, n=11), and oxygen isotopic value (δ18OPAS) varies between -5.3‰ and +26.3‰(mean=+7.0‰, n=8). Most phosphorite nodules have low δ34SPAS and low δ18OPAS values, suggesting PAS mainly derived from anaerobic oxidation of H2S within suboxic sediment porewater. We propose that phosphate was delivered to the Yangtze Platform by a series of upwelling events, and was scavenged from seawater with the precipitation of FeOOH. The absorbed phosphate was released into suboxic porewater by the reduction of FeOOH at the oxic-suboxic redox boundary in sediments, and phosphorite nodule precipitated by the reaction of phosphate with Ca2+ diffused from the overlying seawater. The platform-wide deposition of phosphorite nodules in the basal Niutitang Formation implies the bottom water might be suboxic or even oxic, at least sporadically, in Early Cambrian. We speculate that the intensified ocean circulation as evident with frequent occurrences of upwelling events might be the primary reason for the episodic oxidation of the Yangtze Platform in Early Cambrian.

  20. Zn-Pb Ores of Mississippi Valley Type in the Lycksele-Storuman District, Northern Sweden: A Possible Rift-Related Cambrian Mineralisation Event

    Directory of Open Access Journals (Sweden)

    Kjell Billström

    2012-06-01

    Full Text Available The epigenetic Zn-Pb deposits in the Lycksele-Storuman ore district, northern Sweden, are hosted by Paleoproterozoic basement near the margin of the Caledonian mountains. A paleogeographic reconstruction suggests that platform sediments, including Cambrian shales, overlaid the mineralised basement. The mineralisation type, containing sphalerite, galena, calcite and fluorite, is confined to veins and breccias and interpreted to be of Mississippi Valley Type (MVT style. There is no appreciable wall rock alteration. Fluid inclusion work reveals coexisting aqueous and hydrocarbon fluids. Ore deposition is interpreted to have occurred during mixing of two fluids; a cool (

  1. A highly diverse trilobite fauna with Avalonian affinities from the Middle Cambrian Acidusus atavus Zone (Drumian Stage) of Bornholm, Denmark

    DEFF Research Database (Denmark)

    Weidner, Thomas; Nielsen, Arne Thorshoj

    2014-01-01

    A newly collected trilobite fauna from the lowermost part of the Alum Shale Formation at Øleå, Bornholm, Denmark, demonstrates the presence of a thin but richly fossiliferous Middle Cambrian Acidusus atavus Zone (Paradoxides paradoxissimus Superzone). The lower part of the zone (the Tomagnostus...... designation and reillustration of relevant lectotypes. The abundance of polymerid trilobites in comparison with nearby Scania, southern Sweden, where 25 agnostid and nine polymerid species have been reported from equivalent strata, is indicative of a less dysoxic environment in the Bornholm area, which was...

  2. Limitations of metazoan 18S rRNA sequence data : implications for reconstructing a phylogeny of the animal kingdom and inferring the reality of the cambrian explosion

    OpenAIRE

    Abouheif, Ehab; Zardoya, Rafael; Meyer, Axel

    1998-01-01

    We document the phylogenetic behavior of the 18S rRNA molecule in 67 taxa from 28 metazoan phyla and assess the effects of among-site rate variation on reconstructing phylogenies of the animal kingdom. This empirical assessment was undertaken to clarify further the limits of resolution of the 18S rRNA gene as a phylogenetic marker and to address the question of whether 18S rRNA phylogenies can be used as a source of evidence to infer the reality of a Cambrian explosion. A notable degree of am...

  3. Three-step modernization of the ocean:Modeling of carbon cycles and the revolution of ecological systems in the Ediacaran/Cambrian periods

    Institute of Scientific and Technical Information of China (English)

    Miyuki Tahata; Yusuke Sawaki; Yuichiro Ueno; Manabu Nishizawa; Naohiro Yoshida; Toshikazu Ebisuzaki; Tsuyoshi Komiya; ,Shigenori Maruyama

    2015-01-01

    Important ecological changes of the Earth (oxidization of the atmosphere and the ocean) increase in nutrient supply due to the break-up of the super continent (Rodinia) and the appearance of multi-cellular organisms (macroscopic algae and metazoan) took place in the Ediacaran period, priming the Cambrian explosion. The strong perturbations in carbon cycles in the ocean are recorded as excursions in carbonate and organic carbon isotope ratio (d13Ccarb and d13Corg) from the Ediacaran through early Cambrian periods. The Ediacaraneearly Cambrian sediment records of d13Ccarb and d13Corg, obtained from the drill-core samples in Three Gorges in South China, are compared with the results of numerical simulation of a sim-ple one-zone model of the carbon cycle of the ocean, which has two reservoirs (i.e., dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The fluxes from the reservoirs are assumed to be proportional to the mass of the carbon reservoirs. We constructed a model, referred to here as the Best Fit Model (BFM), which reproduce d13Ccarb and d13Corg records in the Ediacaraneearly Cambrian period noted above. BFM reveals that the Shuram excursion is related to three major changes in the carbon cycle or the global ecological system of the Earth:(1) an increase in the coefficient of remineralization by a factor of ca. 100, possibly corresponding to a change in the dominant metabolism from anaerobic respiration to aerobic respiration, (2) an increase of carbon fractionation index from 25&to 33&, possibly corresponding to the change in the primary producer from rock-living cyanobacteria to free-living macro algae, and (3) an in-crease in the coefficient of the organic carbon burial by a factor of ca. 100, possibly corresponding to the onset of a biological pump driven by the flourishing metazoan and zooplankton. The former two changes took place at the start of the Shuram excursion, while the third occurred at the end of the Shuram excursion. The other

  4. Evaluating the primary and/or diagenetic origin of rare earth element abundances in Ediacaran to early Cambrian phosphate deposits, Yangtze Platform (South China) by LA-ICPMS

    Science.gov (United States)

    Hippler, Dorothee; Klügel, Andreas; Biedermann, Nicole; Guo, Qingjun; Franz, Gerhard

    2014-05-01

    The Precambrian-Cambrian time interval represents one of the greatest phosphogenic episodes in Earth's history with giant and well-preserved phosphate deposits occurring on the Yangtze Platform in South China. We investigated concentrations of rare earth elements (REE) and yttrium of shallow and deep-water sedimentary phosphate deposits of the Ediacaran Doushantou Formation and the early Cambrian Zhongyicun Formation by using LA-ICP mass spectrometry. The aim is to examine the temporal and spatial variability of seawater chemistry in conjunction with the conditions of phosphate formation and the evaluation of the extent of diagenetic modification. The mineralogical and textural composition of the samples was pre-screened using SEM and XRD, and polished thick sections were prepared for subsequent high-resolution LA-ICPMS analyses. Overall concentrations in REE range between 18 and 657 ppm, with elevated concentrations (> 200 ppm) in apatite from the deep-water phosphate deposits. REE+Y patterns of shallow-water phosphate deposits exhibit the evolution from flat shale-like to gently inclined seawater-derived patterns, with the early Cambrian phosphate deposits revealing distinct negative Ce- and positive Y-anomalies indicative for oxygenated surface waters. REE+Y patterns of phosphate deposits of the deep-water facies are flat to highly enriched in MREE, which is manifested in variably pronounced concave-down patterns. In detail, these patterns display different Ce-anomalies, as well as small positive Eu-anomalies. We propose that REE+Y patterns of Ediacaran and early Cambrian sedimentary phosphate deposits can inherit both primary and secondary signatures reflecting either seawater composition or diagenetic modification and fluid flow. The combination of imaging techniques and in-situ LA-ICPMS thereby enables a more sophisticated examination of the potential sources and processes than whole rock determinations. Placing the results in stratigraphic order and assuming

  5. Krashen’s Input Hypothesis and Affective Filter Hypothesis and Their Enlightenment to English Teaching in China

    Institute of Scientific and Technical Information of China (English)

    许琴

    2012-01-01

      “The Input Hypothesis”and“The Affective Filter Hypothesis”are the most important branches of the“Monitor Theory”declared by the famous American linguist Krashen in 1980s. This thesis is based on Krashen’s Input Hypothesis and Affective Filter Hypothesis, aiming to provide an applicable guide for foreign language teachers and learners in China.

  6. Les microbialites de l'Anti-Atlas occidental (Maroc) : marqueurs stratigraphiques et témoins des changements environnementaux au Cambrien inférieur Stratigraphic and environmental significance of the Lower-Cambrian western Anti-Atlasic microbialites (Morocco)

    Science.gov (United States)

    Benssaou, Mohammed; Hamoumi, Naima

    2004-02-01

    Three microbialite forms are recognized in the Lower-Cambrian succession of Irherm area in the western Anti-Atlas (Morocco). Stromatolites, which correspond to non-calcified shallow marine laminated microbialites, are well developed in the basal Lower-Cambrian succession. Occurrence of calcified microbial thrombolites, in the middle part of this succession, reflects an increasing sea level from the peritidal zone to the subtidal environment. In the upper part of this succession, a second increasing water depth event and the development of branching archaeocyathan reefal framework lead to dendritic microbialite emergence. To cite this article: M. Benssaou, N. Hamoumi, C. R. Geoscience 336 (2004).

  7. The linear hypothesis - an idea whose time has passed

    International Nuclear Information System (INIS)

    The linear no-threshold hypothesis is the basis for radiation protection standards in the United States. In the words of the National Council on Radiation Protection and Measurements (NCRP), the hypothesis is: open-quotes In the interest of estimating effects in humans conservatively, it is not unreasonable to follow the assumption of a linear relationship between dose and effect in the low dose regions for which direct observational data are not available.close quotes The International Commission on Radiological Protection (ICRP) stated the hypothesis in a slightly different manner: open-quotes One such basic assumption ... is that ... there is ... a linear relationship without threshold between dose and the probability of an effect. The hypothesis was necessary 50 yr ago when it was first enunciated because the dose-effect curve for ionizing radiation for effects in humans was not known. The ICRP and NCRP needed a model to extrapolate high-dose effects to low-dose effects. So the linear no-threshold hypothesis was born. Certain details of the history of the development and use of the linear hypothesis are presented. In particular, use of the hypothesis by the U.S. regulatory agencies is examined. Over time, the sense of the hypothesis has been corrupted. The corruption of the hypothesis into the current paradigm of open-quote a little radiation, no matter how small, can and will harm youclose quotes is presented. The reasons the corruption occurred are proposed. The effects of the corruption are enumerated, specifically, the use of the corruption by the antinuclear forces in the United States and some of the huge costs to U.S. taxpayers due to the corruption. An alternative basis for radiation protection standards to assure public safety, based on the weight of scientific evidence on radiation health effects, is proposed

  8. Environmental regulation and competitiveness: Empirical evidence on the Porter Hypothesis from European manufacturing sectors

    International Nuclear Information System (INIS)

    This paper investigates the “weak” and “strong” versions of Porter Hypothesis (PH) focusing on the manufacturing sectors of 17 European countries between 1997 and 2009. The hypothesis that well-crafted and well-enforced regulation would benefit both the environment and the firm was originally proposed by Porter (1991) and Porter and van der Linde (1995). To date, the literature has analyzed the impact of environmental regulation on innovation and on productivity mostly in separate analyses and focusing on the USA. The few existing contributions on Europe study the effect of environmental regulation either on green innovation or on performance indicators such as exports. We instead look at overall innovation and productivity impacts. First, focusing on overall innovative activity allows us to account for potential opportunity costs of induced innovations. Second, productivity impacts are arguably the most relevant indicators for the “strong” PH. As a proxy of environmental policy stringency we use pollution abatement and control expenditures (PACE), one of the few sectoral level indicators available. We remedy upon its main drawback, namely potential endogeneity, by adopting an instrumental variable estimation approach. We find evidence of a positive impact of environmental regulation on the output of innovation activity, as proxied by patents, thus providing support in favor of the “weak” PH. This result is in line with most of the literature. On the other front, we find no evidence in favor of the “strong” PH, as productivity appears to be unaffected by the degree of pollution control and abatement efforts. -- Highlights: •Weak and strong Porter Hypothesis. •Panel of manufacturing sectors of 17 European countries between 1997 and 2009. •Look at overall innovation and productivity impacts. •Pollution abatement & control expenditures proxy of environmental policy stringency. •Account for potential endogeneity of PACE by adopting

  9. Vehicle Detection Based on Probability Hypothesis Density Filter

    Science.gov (United States)

    Zhang, Feihu; Knoll, Alois

    2016-01-01

    In the past decade, the developments of vehicle detection have been significantly improved. By utilizing cameras, vehicles can be detected in the Regions of Interest (ROI) in complex environments. However, vision techniques often suffer from false positives and limited field of view. In this paper, a LiDAR based vehicle detection approach is proposed by using the Probability Hypothesis Density (PHD) filter. The proposed approach consists of two phases: the hypothesis generation phase to detect potential objects and the hypothesis verification phase to classify objects. The performance of the proposed approach is evaluated in complex scenarios, compared with the state-of-the-art. PMID:27070621

  10. Biostatistics series module 2: Overview of hypothesis testing

    Directory of Open Access Journals (Sweden)

    Avijit Hazra

    2016-01-01

    Full Text Available Hypothesis testing (or statistical inference is one of the major applications of biostatistics. Much of medical research begins with a research question that can be framed as a hypothesis. Inferential statistics begins with a null hypothesis that reflects the conservative position of no change or no difference in comparison to baseline or between groups. Usually, the researcher has reason to believe that there is some effect or some difference which is the alternative hypothesis. The researcher therefore proceeds to study samples and measure outcomes in the hope of generating evidence strong enough for the statistician to be able to reject the null hypothesis. The concept of the P value is almost universally used in hypothesis testing. It denotes the probability of obtaining by chance a result at least as extreme as that observed, even when the null hypothesis is true and no real difference exists. Usually, if P is < 0.05 the null hypothesis is rejected and sample results are deemed statistically significant. With the increasing availability of computers and access to specialized statistical software, the drudgery involved in statistical calculations is now a thing of the past, once the learning curve of the software has been traversed. The life sciences researcher is therefore free to devote oneself to optimally designing the study, carefully selecting the hypothesis tests to be applied, and taking care in conducting the study well. Unfortunately, selecting the right test seems difficult initially. Thinking of the research hypothesis as addressing one of five generic research questions helps in selection of the right hypothesis test. In addition, it is important to be clear about the nature of the variables (e.g., numerical vs. categorical; parametric vs. nonparametric and the number of groups or data sets being compared (e.g., two or more than two at a time. The same research question may be explored by more than one type of hypothesis test

  11. A new hypothesis about plant bio-invasion

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Although both the generalpurpose genotype hypothesis and the hypothesis about the evolution of invasiveness predict that invasive species are characterized by particular traits that confer invasiveness, what these traits are still remains unclear. A theory put forward by a CAS botanist and colleagues suggests that the success of an invasive plant in a new habitat is due to the allocation of more nitrogen to its photosynthesis. As reported in a recent issue of Oecologia, the hypothesis has been supported by their research on the metabolic comparison between an invasive shrub and five native plants.

  12. Vehicle Detection Based on Probability Hypothesis Density Filter.

    Science.gov (United States)

    Zhang, Feihu; Knoll, Alois

    2016-01-01

    In the past decade, the developments of vehicle detection have been significantly improved. By utilizing cameras, vehicles can be detected in the Regions of Interest (ROI) in complex environments. However, vision techniques often suffer from false positives and limited field of view. In this paper, a LiDAR based vehicle detection approach is proposed by using the Probability Hypothesis Density (PHD) filter. The proposed approach consists of two phases: the hypothesis generation phase to detect potential objects and the hypothesis verification phase to classify objects. The performance of the proposed approach is evaluated in complex scenarios, compared with the state-of-the-art. PMID:27070621

  13. Occurrence of Highly Mature Organic Matter in Marine Black Shale Petroleum Source Rocks of Basal Cambrian from Northern Tarim Basin, China

    Institute of Scientific and Technical Information of China (English)

    YU Bingsong (于炳松); Hailiang DONG; CHEN Jianqiang (陈建强); CHEN Xiaolin (陈晓林); LIANG Shiyou (梁世友)

    2004-01-01

    More and more evidence indicates that organic matter (OM) in immature organic-rich sediments and sedimentary rocks is chemically adsorbed onto the outer surfaces of minerals and into interlayer (inner) surfaces of smectitic clay minerals in the form of amorphous molecular-scale carbon. But there have been few reports about the occurrence of highly mature OM in marine black shales (petroleum source rocks). The occurrence of highly mature OM in the black shales of basal Cambrian from northern Tarim Basin is studied in this paper. Based on the comprehensive analyses of total organic carbon contents (TOC), maximum thermolysis temperatures (T max ) of OM, mineral surface areas (MSA), and scanning electronic microscopic (SEM) and transmission electronic microscopic (TEM) observations of the black shales, it is concluded that the highly mature OM in the marine black shales of the basal Cambrian from northern Tarim Basin occurs in particulates ranging in size from 1 to 5 μm in diameter. Through the contrast of the occurrence of the highly mature OM in the black shales with that of the immature ones in modern marine continental margin sediments, some scientific problems are proposed, which are worth to study further in detail.

  14. An Ediacaran–Cambrian thermal imprint in Rajasthan, western India: Evidence from 40Ar-39Ar geochronology of the Sindreth volcanics

    Indian Academy of Sciences (India)

    Archisman Sen; Kanchan Pande; Hetu C Sheth; Kamal Kant Sharma; Shraboni Sarkar; A M Dayal; Harish Mistry

    2013-12-01

    The Sindreth Group exposed near Sirohi in southern Rajasthan, western India, is a volcanosedimentary sequence. Zircons from Sindreth rhyolite lavas and tuffs have yielded U–Pb crystallization ages of ∼768–761 Ma, suggesting that the Sindreth Group is a part of the Malani magmatic event. Earlier 40Ar-39Ar studies of other Malani volcanic and plutonic rocks yielded disturbed argon release spectra, ascribed to a ∼550 Ma thermal event possibly related to the Pan-African orogeny. To test and confirm this possibility, we dated two whole-rock and three feldspar separate samples of the Sindreth volcanics by the 40Ar-39Ar method. All samples yield disturbed argon release spectra suggesting radiogenic argon loss and with plateau segments at 550 Ma or 490 Ma. We interpret these as events of argon loss at 550–490 Ma related to an Ediacaran–Cambrian thermal event, possibly related to the Malagasy orogeny. The combined older and new 40Ar-39Ar results are significant in showing that whereas Ediacaran–Cambrian magmatic and metamorphic events are well known from many parts of India, they left thermal imprints in much of Trans-Aravalli Rajasthan as well. The overall evidence is consistent with a model of multiphase assembly of Gondwanaland from separate continental landmasses.

  15. Phosphatized rare star-like mouth disc of Punctatus and its functional morphology from the earliest Cambrian of the South Shaanxi China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Meishucun stage is the prelude in decipher-ing the Cambrian Explosion. In this prominent stage, rapid radioactive evolution and body-plan innovation have taken place and different associations of organism have been shaped. In this paper we report several 3D-preserved rare star-like fossils with finely preserved soft tissues which were recovered from the Kuanchuanpu Member of the Dengying Formation in South Shaanxi, China in 2003. By studying on functional morphology and analogy with mouthpart of Punctatus, there are evidences that this star-like organism approaches the coelenterates in systematic classification and the centre of star-like organism is its mouth. The appearance of coelenterates marks the real beginning of metazoan evolution. Therefore, it has the prominent position in the origin and evolutionary history of organisms. Perhaps the star-like organism represents the early types of coelenterate with original tentacles. These new materials provide new evidence for the origin, evolution and the functional evolution of the metazoan during the early stage of the Cambrian Explosion.

  16. Research progress and prospects of Cambrian medusae from South China%寒武纪水母化石研究现状与展望

    Institute of Scientific and Technical Information of China (English)

    韩健; 李国祥; 久保田信; 王星; 欧强

    2014-01-01

    We introduced the fossil records of medusa in brief and discussed the radial symmetry, body plan, life history, and exoskeleton of ancestral medusae. It is hypothesized that major clades of superclass medusa should have derived prior to that of ballerinas at the dawn of Cambrian explosion. The Cambrian medusae should be classified as sessile benthic and pelagic forms.%简述了水母的早期化石记录,并根据华南寒武系发现的立方水母干群化石,讨论了祖先型水母的辐射对称、躯体构型、生活史、生活习性,以及外骨骼的形成特征,推测水母类在寒武纪大爆发初期先于两侧对称动物基本完成其高级分类单元的宏演化。寒武纪的水母在生活习性上可以分为底栖固着型和游泳型两种。

  17. On a Misconception Involving Point Collocation and the Rayleigh Hypothesis

    DEFF Research Database (Denmark)

    Christiansen, Søren; Kleinman, Ralph E.

    1996-01-01

    It is shown that the Rayleigh hypothesis does notgovern convergence of the simple point collocationapproach to the numerical solutions of scatteringby a sinusoidal grating. A recently developed numerical technique, interval arithmetic, is employed to perform some decisive numerical experiments wh...

  18. Cross-system log file analysis for hypothesis testing

    NARCIS (Netherlands)

    Glahn, Christian

    2008-01-01

    Glahn, C. (2008). Cross-system log file analysis for hypothesis testing. Presented at Empowering Learners for Lifelong Competence Development: pedagogical, organisational and technological issues. 4th TENCompetence Open Workshop. April, 10, 2008, Madrid, Spain.

  19. Temporal surrogates of spatial turbulent statistics the Taylor hypothesis revisted

    CERN Document Server

    Lvov, V S; Procaccia, I; L'vov, Victor S.; Pomyalov, Anna; Procaccia, Itamar

    1999-01-01

    The Taylor hypothesis which allows surrogating spatial measurements requiring many experimental probes by time series from one or two probes is examined on the basis of a simple analytic model of turbulent statistics. The main points are as follows: (i) The Taylor hypothesis introduces systematic errors in the evaluation of scaling exponents. (ii) When the mean wind $\\bar{V}_0$ is not infinitely larger than the root-mean-square longitudinal turbulent fluctuations $v_T$, the effective Taylor advection velocity $V_{ad}$ should take the latter into account. (iii) When two or more probes are employed the application of the Taylor hypothesis and the optimal choice of the effective advecting wind $V_{ad}$ need extra care. We present practical considerations for minimizing the errors incurred in experiments using one or two probes. (iv) Analysis of the Taylor hypothesis when different probes experience different mean winds is offered.

  20. Hypothesis Testing Using the Films of the Three Stooges

    Science.gov (United States)

    Gardner, Robert; Davidson, Robert

    2010-01-01

    The use of The Three Stooges' films as a source of data in an introductory statistics class is described. The Stooges' films are separated into three populations. Using these populations, students may conduct hypothesis tests with data they collect.