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1

Time-scale calibration by U-Pb geochronology: Examples from the Triassic Period  

NASA Astrophysics Data System (ADS)

U-Pb zircon geochronology, pioneered by Tom Krogh, is a cornerstone for the calibration of the time scale. Before Krogh's innovations, U-Pb geochronology was essentially limited by laboratory blank Pb (typically hundreds of nanograms) inherent in the then existing zircon dissolution and purification methods. The introduction of high pressure HF dissolution combined with miniature ion exchange columns (1) reduced the blank by orders of magnitude and allowed mass-spectrometric analyses of minute amounts of material (picograms of Pb and U). Krogh also recognized the need for minimizing the effects of Pb loss, and the introduction of the air-abrasion technique was the method of choice for two decades (2), until the development of the combined annealing and chemical abrasion technique resulted in essentially closed system zircons (3). These are the prerequisite for obtaining precise (permil-level) and accurate radio-isotopic ages of individual zircons contained in primary volcanic ash deposits, which are primary targets for the calibration of the time scale if they occur within fossil bearing sediments. A prime example is the calibration of the Triassic time scale which improved significantly using these techniques. The ages for the base and the top of the Triassic are constrained by U-Pb ages to 252.3 (4) and 201.5 Ma (5), respectively. These dates also constrain the ages of major extinction events at the Permian-Triassic and Triassic-Jurassic boundaries, and are statistically indistinguishable from ages obtained for the Siberian Traps and volcanic products from the Central Atlantic Magmatic Province, respectively, suggesting a causal link. Ages for these continental volcanics, however, are mostly from the K-Ar (40Ar/39Ar) system which requires accounting and correcting for a systematic bias of ca 1 % between U-Pb and 40Ar/39Ar isotopic ages (the 40Ar/39Ar ages being younger) (6). Robust U-Pb age constraints also exist for the Induan- Olenekian boundary (251.2 Ma, (7)) and the Early-Middle Triassic (Olenekian-Anisian) boundary (247.2 Ma, (8, 9)), resulting in a surprisingly short duration of the Early Triassic which has implications for the timing of biotic recovery and major changes in ocean chemistry during this time. Furthermore, the Anisian-Ladinian boundary is constrained to 242.0 Ma by new U-Pb and 40Ar/39Ar ages. Radio-isotopic ages for the Late Triassic are scarce and the only reliable and biostratigraphically controlled age is from an upper Carnian tuff dated to 230.9 Ma (10), yielding a duration of more than 35 Ma for the Late Triassic. The resulting time-scale is at odds with the most recent compilation (11) but arguably more accurate because it is entirely based on U-Pb analyses applied to closed-system zircons with uncertainties at the permil level or better. 1. T. E. Krogh, Geochimica et Cosmochimica Acta 37, 485 (1973); 2. T. E. Krogh, Geochimica et Cosmochimica Acta 46, 637 (1982); 3. J. M. Mattinson, Chemical Geology 220, 47 (2005); 4. R. Mundil, K. R. Ludwig, I. Metcalfe, P. R. Renne, Science 305, 1760 (2004); 5. U. Schaltegger, J. Guex, A. Bartolini, B. Schoene, M. Ovtcharova, Earth and Planetary Science Letters 267, 266 (2008); 6. R. Mundil, P. R. Renne, K. K. Min, K. R. Ludwig, in Eos Trans. AGU, Fall Meet. Suppl. (2006), vol. 87(52), pp. V21A-0543; 7. T. Galfetti et al., Earth and Planetary Science Letters 258, 593 (2007). 8. M. Ovtcharova et al., Earth and Planetary Science Letters 243, 463 (2006). 9. J. Ramezani et al., Earth and Planetary Science Letters 256, 244 (2007). 10. S. Furin et al., Geology 34, 1009 (2006); 11. J. G. Ogg, in A Geologic Time Scale 2004 F. M. Gradstein, J. G. Ogg, A. G. Smith, Eds. (University Press, Cambridge, 2004) pp. 271-306.

Mundil, R.

2009-05-01

2

Magnetostratigraphic dating of the proposed Rhaetian GSSP at Steinbergkogel (Upper Triassic, Austria): Implications for the Late Triassic time scale  

E-print Network

by cyclostratigraphic control on the marine Pizzo Mondello (Italy) section, where a combination of long period The Late Triassic period is characterized by increasingenvironmental stress that eventually culminated and Rhaetian stages. The GSSP defining the base of the Hettangian (base Jurassic) was formally accepted by ICS

Utrecht, Universiteit

3

High-precision U-Pb zircon geochronological constraints on the End-Triassic Mass Extinction, the late Triassic Astronomical Time Scale and geochemical evolution of CAMP magmatism  

NASA Astrophysics Data System (ADS)

Mass extinction events that punctuate Earth's history have had a large influence on the evolution, diversity and composition of our planet's biosphere. The approximate temporal coincidence between the five major extinction events over the last 542 million years and the eruption of Large Igneous Provinces (LIPs) has led to the speculation that climate and environmental perturbations generated by the emplacement of a large volume of magma in a short period of time triggered each global biologic crisis. Establishing a causal link between extinction and the onset and tempo of LIP eruption has proved difficult because of the geographic separation between LIP volcanic deposits and stratigraphic sequences preserving evidence of the extinction. In most cases, the uncertainties on available radioisotopic dates used to correlate between geographically separated study areas often exceed the duration of both the extinction interval and LIP volcanism by an order of magnitude. The "end-Triassic extinction" (ETE) is one of the "big five" and is characterized by the disappearance of several terrestrial and marine species and dominance of Dinosaurs for the next 134 million years. Speculation on the cause has centered on massive climate perturbations thought to accompany the eruption of flood basalts related to the Central Atlantic Magmatic Province (CAMP), the most aerially extensive and volumetrically one of the largest LIPs on Earth. Despite an approximate temporal coincidence between extinction and volcanism, there lacks evidence placing the eruption of CAMP prior to or at the initiation of the extinction. Estimates of the timing and/or duration of CAMP volcanism provided by astrochronology and Ar-Ar geochronology differ by an order of magnitude, precluding high-precision tests of the relationship between LIP volcanism and the mass extinction, the causes of which are dependent upon the rate of magma eruption. Here we present high precision zircon U-Pb ID-TIMS geochronologic data for eight CAMP flows and sills from the eastern U.S. and Morocco. These data are used first to independently test the astronomically calibrated time scale and sediment accumulation rates within the Triassic-Jurassic rift basins along the eastern North America. The U-Pb, paleontological, magnetostratigraphic and astronomical data are combined to constrain the onset and duration of the CAMP and clarify the temporal relationship between the CAMP and the ETE. The dataset together allows more precise estimates of eruptive volume per unit time, a requirement for rigorous evaluation of climate-driven models for the extinction.

Blackburn, T. J.; Olsen, P. E.; Bowring, S. A.; McLean, N. M.; Kent, D. V.; Puffer, J. H.; McHone, G.; Rasbury, T.

2012-12-01

4

Early Triassic magnetic polarity time scale—integration of magnetostratigraphy, ammonite zonation and sequence stratigraphy from stratotype sections (Canadian Arctic Archipelago)  

NASA Astrophysics Data System (ADS)

Stratotypes defining the stages of the Early Triassic (Griesbachian, Dienerian, Smithian and Spathian) are located on Ellesmere and Axel Heiberg islands in the northern Canadian Arctic. Ammonite-rich horizons are within a clastic outer shelf-to-slope facies of thick progradational wedges of mudstones and siltstones. Three sections were sampled for magnetostratigraphy and interpreted for transgressive and regressive pulses of sedimentation. Using the ammonite zonation as a guide, the transgressive-regressive cycles and magnetostratigraphies have been correlated among the sections and to the published Triassic sequence stratigraphy time scale, thus enabling definition of the magnetic polarity pattern for the upper Griesbachian to Smithian stages in multiple sections. The magnetic polarity and associated sequence stratigraphy pattern for the lower Griesbachian and for the Spathian were derived from single sections. The Griesbachian and Dienerian stages each have two pairs of normal- and reversed-polarity chrons; the Smithian is predominantly of normal polarity, and the Spathian is predominantly of reversed polarity. This magnetic polarity time scale may help to resolve age correlations of North American redbed facies and to define the Permian-Triassic boundary. After correction for variable structural orientations, the mean directions of magnetization from the three sites converge at 296° declination, 57° inclination ( k = 60, ? 95 = 16.5° ; equivalent pole = 41°N, 161°E; paleolatitude = 38°N), which is consistent with the pole derived from nearby Early Permian volcanics and supports a postulated post-Early Triassic, pre-Tertiary counterclockwise rotation of this region with respect to cratonic North America.

Ogg, James G.; Steiner, Maureen B.

1991-10-01

5

A 70 million year astronomical time scale for the deep-sea bedded chert sequence (Inuyama, Japan): Implications for Triassic-Jurassic geochronology  

NASA Astrophysics Data System (ADS)

The astronomical time scale (ATS) has provided high-resolution geochronology. However, the early Mesozoic ATS is still under construction partly due to the lack of continuous pelagic sequences of the early Mesozoic. Here we present ca. ?70 Myr long ATS constructed from the early Mesozoic deep-sea bedded chert sequence exposed in the Inuyama area, central Japan. The sedimentary rhythms of bedded chert display a full range of climatic precession related cycles; ?20-kyr cycle as a chert-shale couplet and ?100-, 405-, 2000- to 4000-, and 10,000-kyr cycles as chert bed thickness variation. The newly established ATS (Inuyama-ATS) is tuned by 405-kyr eccentricity cycle and is anchored at the end-Triassic radiolarian extinction level as 201.4±0.2 Ma. This Inuyama-ATS gives ages consistent with the radiometric ages projected to the Inuyama deep-sea sequence using biostratigraphy and carbon isotope stratigraphy. The Inuyama-ATS provides the age constraints for the Triassic and Jurassic stage boundaries, which support the “Long-Norian” option of Muttoni et al. (2004). Because the deep-sea bedded chert sequence covers a long time interval before the Cretaceous, the ATS for the bedded chert will serve as a template for the astrochronology of Mesozoic and older ages.

Ikeda, Masayuki; Tada, Ryuji

2014-08-01

6

Patterns of Reef Ecosystem Recovery Indicate That Adverse Early Triassic Ocean Conditions Extended into Middle Triassic Time  

NASA Astrophysics Data System (ADS)

The pattern of reef ecosystem recovery from the end-Permian extinction is poorly constrained due to the limited stratigraphic, spatial, and geographic range of reef buildups in Early Triassic and Anisian (early Middle Triassic) strata. In this study, we combined field studies and petrographic analysis to examine the pattern of reef evolution in latest Permian to Late Triassic carbonate platforms in the Nanpanjiang Basin of South China, an area of extensive shallow-water carbonate deposition in the tropical eastern Tethys. We find that early Mesozoic reef recovery in the eastern Tethys was a five-step process: (1) in the immediate aftermath of extinction, calcimicrobial biostromes (P/T boundary microbialites) developed in shallow-water platform settings; (2) in late Induan time, biohermal stromatolites developed in platform interior settings; (3) in latest Spathian time, large-scale Tubiphytes, microbial, and cement reefs lacking skeletal metazoans initiated on the margins and steep upper slopes of carbonate platforms, signaling the return of reefs to platform-margin settings; (4) in the Aegean or Bithynian (early Anisian), diminutive (mm-scale) calcareous sponges and calcareous algae appeared in the Tubiphytes reef, marking the reappearance of skeletal metazoans and calcareous algae to reefs in the eastern Tethys; and (5) in the late Anisian, the appearance of scleractinian corals coincided with increased abundance, size, and diversity of metazoan and algal reef builders. Early Mesozoic reefs of the eastern Tethys were dominated by microbes, Tubiphytes, and early-marine cements until the late Anisian, several million years into the Middle Triassic. The appearance of small metazoan buildups in Early Triassic strata in other parts of the world indicates that potential reef-building organisms were present much earlier. The limited stratigraphic range of those buildups, however, reinforces the interpretation that episodic environmental disturbances such as euxinia, high temperatures, and acidification impacted biotic recovery during Early Triassic time. Our findings of protracted early Mesozoic reef recovery suggest that the causal links between environmental disturbance and biotic recovery extended into Middle Triassic time.

Kelley, B. M.; Yu, M.; Lehrmann, D. J.; Jost, A. B.; Lau, K. V.; Li, X.; Schaal, E. K.; Payne, J.

2013-12-01

7

Status Report on the 40Ar/39Ar and U/Pb Dating of Tuffs in the Dewey Lake Formation of West Texas Towards Constraining the Permo-Triassic Magnetostratigraphic Time Scale  

NASA Astrophysics Data System (ADS)

A detailed magnetic polarity time scale for the Permo-Triassic Boundary interval, critical for correlating events in marine and terrestrial paleoenvironments, is not yet well-established. Recently, late Permian magnetostratigraphic studies have been reported for non-marine sections in Europe and South Africa (Szurlies et al., 2003; Nawrocki, 2004; Ward et al., 2005). However, these sections are devoid of index fossil suitable for correlation with marine successions and also lack age constraints from radioisotopic dating methods. In other words, it is dubious to correlate these magnetostratigraphic data with the GSSP Permo-Triassic boundary and mass extinction. The Dewey Lake red beds formation of West Texas, believed to be the youngest Permian formation in North America, has yielded high-quality paleomagnetic data (Molina-Garza et al., 1989; Steiner, 2001) and contains several silicic tuffs potentially enabling high-resolution calibration of the magnetic polarity time scale in this critical age range. The tuffs have yet to be placed into a regional stratigraphic or magnetostratigraphic framework, and it is unclear exactly how many distinct eruptive units are represented by the 7 distinct samples collected to date from widely separated (>160 km) localities. 40Ar/39Ar (sanidine and biotite) and U/Pb (zircon) studies reveal that all 7 sampled tuffs were probably erupted within several hundred ka of the Permo-Triassic boundary as dated at the Meishan GSSP section (Renne et al., 1995; Mundil et al., 2004) but results thus far are inadequate to convincingly resolve age differences between the various samples. U/Pb dating of some samples is severely challenged by Pb-loss from the zircons despite application of the Mattinson (2005) annealing/chemical abrasion technique. 40Ar/39Ar data have been obtained from as many as four different irradiations in order to reduce neutron fluence related error. We observe the familiar ~1% bias between U/Pb and 40Ar/39Ar ages. Biotite microprobe data, zircon U/Th TIMS data, and the absence of sanidine from some samples serve to help correlate or distinguish some samples despite irresolvable age differences; existing data suggest that 4 distinct tuffs are present in the Dewey Lake Formation. Resolving their ages convincingly will require further work, but it is clear from our results combined with previous magnetostratigraphic data that magnetic polarity reversals were relatively frequent in the latest Permian. Thus the uniqueness of correlations elsewhere with the Permo-Triassic boundary based on magnetostratigraphy alone are not well-founded.

Chang, S.; Renne, P. R.; Mundil, R.

2007-12-01

8

Integrative stratigraphy during extreme environmental changes and biotic recovery time: The Early Triassic in Indian Himalaya  

NASA Astrophysics Data System (ADS)

The understanding of extreme environmental changes as major extinction events, perturbations of global biogeochemical cycles or rapid climate shifts is based on a precise timing of the different events. But especially in such moving environments exact correlations are difficult to establish what underlines the necessity of an integrated stratigraphy by using all tools at disposition. A Lower Triassic section at Mud in the Spiti Valley (Western Himalaya, India) is a candidate section for the GSSP of the Induan-Olenekian Boundary (IOB). The succession was deposited in a deep-shelf setting on the southern margin of the Neotethys Ocean. The section contains abundant fossils allowing a very precise regional biostratigraphy and displays no signs of sedimentary breaks. Analysis of pelagic faunas proves a significant, two-step radiation phase in ammonoids and conodonts close to the Induan-Olenekian boundary. These diversifications are coupled with a short-termed positive ?13Ccarb excursion of global evidence. The Spiti ?13Ccarb excursion displays, however, different amplitude and biostratigraphic position than in other relevant sections for this time interval. In this study, we analyzed ?13Ccarb, ?13Corg, and ?15Norg as well as major, trace, and REE concentrations for a 16-m-thick interval spanning the mid-Griesbachian to early Spathian substages, to better constrains the chain of events. Prior to the first radiation step, high difference gradient between the ?13Ccarb values of tempestite beds with shallow carbonate and carbonate originated in deeper water is interpreted as a sign of a stratified water column. This effect disappears with the onset of better oxygenated conditions at the time of the ammonoid-conodont radiation, which correspond as well to ?13Ccarb, ?13Corg and ?15Norg positive excursions. A decrease in Mo and U concentrations occurring at the same point suggests a shift toward locally less reducing conditions. The second step coincided with the change from terrigenous to almost pure carbonate sedimentation. This new set of data demonstrates from on hand the rapidity of radiation of the pelagic fauna in the aftermath of the Permian-Triassic extinction as soon as environmental conditions were favourable again. On the other hand, it demonstrates that bathymetry, for example, but also other local factors, could have had a significant impact in the timing of these radiations and may hamper solid worldwide correlations.

Richoz, Sylvain; Krystyn, Leopold; Algeo, Thomas; Bhargava, Om

2014-05-01

9

Timing is everything: ecological vs. evolutionary pacing of Triassic-Jurassic carbon cycle disruptions  

NASA Astrophysics Data System (ADS)

Eruption of Earth's largest flood basalt, the Central Atlantic Magmatic Province (CAMP) has been proposed as the trigger for a major carbon cycle disruption at the Triassic-Jurassic mass extinction interval at ~201 Ma. Inferred from negative excursions in the carbon isotopic composition (?13C) of carbonate and organic matter, this perturbation has been linked to massive dissociation of isotopically light, methane-rich gas hydrates caused by volcanogenic CO2-induced global warming. However, both the sequence and duration of the CAMP eruptions relative to the carbon cycle perturbation remain circumstantial and indirect, because the data have been from stratigraphic sections far from the flood basalts and without accumulation rate constraints. Here we use a record of atmospheric (?13C) from specific molecules (nC25 - nC32 n-alkanes) diagnostic of terrestrial plant leaf waxes from astronomically-paced cyclical lacustrine strata in which CAMP flood basalts are interbedded to directly examine the relationship between the (?13C) excursions and their durations. We show that the flood basalts postdate the abrupt start of a ~400 ky negative excursion coincident with the initiation of the mass extinction event, but predate a protracted 1.5 m.y. negative excursion. Based on a modified BLAG carbon cycle model, the timing and long durations of our (?13C) excursions are incompatible with CAMP-triggered gas hydrate release. Instead, we suggest that the (?13C) pattern is more consistent with a catastrophically-triggered functional reorganization of the biosphere, part of which involved the ascent of dinosaurs to ecological dominance, playing out over evolutionary time.

Whiteside, J. H.; Olsen, P. E.; Eglinton, T. I.

2007-12-01

10

Recognising ocean acidification in deep time: An evaluation of the evidence for acidification across the Triassic-Jurassic boundary  

NASA Astrophysics Data System (ADS)

While demonstrating ocean acidification in the modern is relatively straightforward (measure increase in atmospheric CO2 and corresponding ocean chemistry change), identifying palaeo-ocean acidification is problematic. The crux of this problem is that the rock record is a constructive archive while ocean acidification is essentially a destructive (and/or inhibitory) phenomenon. This is exacerbated in deep time without the benefit of a deep ocean record. Here, we discuss the feasibility of, and potential criteria for, identifying an acidification event in deep time. Furthermore, we investigate the evidence for ocean acidification during the Triassic-Jurassic (T-J) boundary interval, an excellent test case because 1) it occurs in deep time, beyond the reach of deep sea drilling coverage; 2) a potential trigger for acidification is known; and 3) it is associated with one of the 'Big Five' mass extinctions which disproportionately affected modern-style invertebrates. Three main criteria suggest that acidification may have occurred across the T-J transition. 1) The eruption of the Central Atlantic Magmatic Province (CAMP) and the associated massive and rapid release of CO2 coincident with the end-Triassic mass extinction provide a suitable trigger for an acidification event (full carbonate undersaturation in the surface ocean is possible but improbable). 2) Tentative evidence for a global paucity of carbonate across the end-Triassic mass extinction versus the adjacent stratigraphy is consistent with a predicted sedimentary response to acidification. 3) The end-Triassic mass extinction was particularly selective against acid-sensitive organisms (more so than perhaps any other extinction event) and temporarily eliminated coral reefs. Therefore multiple lines of evidence are consistent with a T-J ocean acidification event within our current resolution to recognise such events in deep time. The conclusion that the end-Triassic extinction was influenced by acidification implies that short-term acidification perturbations may have long-term effects on ecosystems, a repercussion that has previously not been established. Although anthropogenic emissions are more rapid than any event in the geologic record, events such as the T-J can serve as partial analogues for the present anthropogenic carbon release. Since the T-J was such a pronounced crisis for both modern-style marine invertebrates and scleractinian reefs, it is of particular interest in terms of informing projections about the effects of modern ocean acidification.

Greene, Sarah E.; Martindale, Rowan C.; Ritterbush, Kathleen A.; Bottjer, David J.; Corsetti, Frank A.; Berelson, William M.

2012-06-01

11

Geological Time Scale  

NSDL National Science Digital Library

This document describes how geologic time is approached in discussions of geologic topics. The uses of relative time and absolute time are compared, and a geologic time scale is provided to represent both concepts. References are provided.

12

Position of the Triassic-Jurassic boundary and timing of the end-Triassic extinctions on land: Data from the Moenave Formation on the southern Colorado Plateau, USA  

USGS Publications Warehouse

Strata of the Moenave Formation on and adjacent to the southern Colorado Plateau in Utah-Arizona, U.S.A., represent one of the best known and most stratigraphically continuous, complete and fossiliferous terrestrial sections across the Triassic-Jurassic boundary. We present a synthesis of new biostratigraphic and magnetostratigraphic data collected from across the Moenave Formation outcrop belt, which extends from the St. George area in southwestern Utah to the Tuba City area in northern Arizona. These data include palynomorphs, conchostracans and vertebrate fossils (including footprints) and a composite polarity record based on four overlapping magnetostratigraphic sections. Placement of the Triassic-Jurassic boundary in strata of the Moenave Formation has long been imprecise and debatable, but these new data (especially the conchostracans) allow us to place the Triassic-Jurassic boundary relatively precisely in the middle part of the Whitmore Point Member of the Moenave Formation, stratigraphically well above the highest occurrence of crurotarsan body fossils or footprints. Correlation to marine sections based on this placement indicates that major terrestrial vertebrate extinctions preceded marine extinctions across the Triassic-Jurassic boundary and therefore were likely unrelated to the Central Atlantic Magmatic Province (CAMP) volcanism. ?? 2011 Elsevier B.V.

Lucas, S. G.; Tanner, L. H.; Donohoo-Hurley, L. L.; Geissman, J. W.; Kozur, H. W.; Heckert, A. B.; Weems, R. E.

2011-01-01

13

Timing of the Permian-Triassic biotic crisis: implications from new zircon U/Pb age data (and their limitations)  

NASA Astrophysics Data System (ADS)

The most profound biotic crisis in the Earth's history, causing the near extinction of both terrestrial and marine life, occurred at the end of the Permian period about 253 Myr ago and marks the Paleozoic-Mesozoic era boundary. The cause of this event is still a matter of vigorous debate, with both brief and catastrophic as well as gradual mechanisms having been proposed. Similar to a recent landmark study, this study uses the U-Pb method on zircons from the uppermost Permian/lowermost Triassic ash fall deposits at Meishan (Zhejiang Province, SE China) in order to examine time and rate constraints for these events. The results of both this study and previous work show that for these ash layers, the effects of Pb loss are combined with varying amounts and sources of inheritance, resulting in an age scatter which prohibits the extraction of a statistically robust age in many cases. Though the effects of Pb loss on the zircons analyzed in this study were reduced by leaching the grains in hydrofluoric acid (as opposed to commonly applied air abrasion) prior to analysis, the presence within a single ash layer of multiple generations of older xenocrysts (in many cases only slightly older than the depositional age) has made quantitative interpretation even more difficult. When these combined phenomena bias individual zircon ages by less than a percent, they are extremely difficult to deconvolute, and, if multi-grain analyses are used, can become impossible to recognize (because of the resulting age averaging). Monte Carlo simulations using actual measurements of individual zircon crystals show that age excursions due to Pb loss and xenocrystic contamination for the Meishan bentonites are easily homogenized to the point of undetectability when replicate analyses of multi-grain zircon samples are compared. Thus this study uses only high-precision analyses of single crystals, whether from our work or that of previous studies. Three main conclusions have emerged. First, our data require a significant increase in the age of the Permian-Triassic boundary by more than 2 myr compared to the previous study, which shifts the age to a value older than 253 Ma. Second, neither our data nor those from previous work can confirm or negate the possibility of a very abrupt biotic crisis. Third, even large suites of very high-quality, single-zircon U-Pb analyses for these tuffs cannot, in most cases, yield objective, reliable, and robust dates with accuracies at the sub-myr level - though the temptation to perform arbitrary selection of subsets of the analyses for that purpose is almost irresistible. The last conclusion is not an indictment of zircon U/Pb dating in general (other rocks and other zircon populations can - and do - behave very differently), and further technical advances will likely improve our ability to prepare grains or sub-grains of adequately enhanced quality for analysis. Consequently, the results of the present study strongly suggest that for problems requiring time-scale accuracy, inferences from zircon U-Pb dating must be based on sufficiently large suites of single-crystal or crystal domain, high-precision analyses (<1% error) that are realistically interpreted.

Mundil, Roland; Metcalfe, Ian; Ludwig, Kenneth R.; Renne, Paul R.; Oberli, Felix; Nicoll, Robert S.

2001-04-01

14

Integration on time scales  

Microsoft Academic Search

In this paper we study the process of Riemann and Lebesgue integration on time scales. The relationship of the Riemann and Lebesgue integrals is considered and a criterion for Riemann integrability is established.

Gusein Sh. Guseinov

2003-01-01

15

GSA Geologic Time Scale  

NSDL National Science Digital Library

This Geological Society of America (GSA) site contains a detailed geologic time scale as an educational resource. It may be downloaded to a larger size, and includes all Eras, Eons, Periods, Epochs and ages as well as magnetic polarity information.

1999-01-01

16

The Geologic Time Scale  

NSDL National Science Digital Library

This site contains a large, easy to read, detailed geologic time scale for the Phanerozoic Eon (544 million years ago - Present). This is the period of time, also known as an eon, between the end of the Precambrian and today. The Phanerozoic begins with the start of the Cambrian period, 544 million years ago. It encompasses the period of abundant, complex life on Earth. The chart includes the Era, Period or System, and the Epoch or Series and features a brief description of each.

17

Time scales in LISA  

E-print Network

The LISA mission is a space interferometer aiming at the detection of gravitational waves in the [$10^{-4}$,$10^{-1}$] Hz frequency band. In order to reach the gravitational wave detection level, a Time Delay Interferometry (TDI) method must be applied to get rid of (most of) the laser frequency noise and optical bench noise. This TDI analysis is carried out in terms of the coordinate time corresponding to the Barycentric Coordinate Reference System (BCRS), TCB, whereas the data at each of the three LISA stations is recorded in terms of each station proper time. We provide here the required proper time versus BCRS time transformation. We show that the difference in rate of station proper time versus TCB is of the order of $5 10^{-8}$. The difference between station proper times and TCB exhibits an oscillatory trend with a maximum amplitude of about $10^{-3}$ s.

S. Pireaux

2007-03-23

18

Geologic time scale bookmark  

USGS Publications Warehouse

This bookmark, designed for use with U.S. Geological Survey activities at the 2nd USA Science and Engineering Festival (April 26–29, 2012), is adapted from the more detailed Fact Sheet 2010–3059 "Divisions of Geologic Time." The information that it presents is widely sought by educators and students.

U.S. Geological Survey

2012-01-01

19

The Triassic-Jurassic boundary in eastern North America  

NASA Technical Reports Server (NTRS)

Rift basins of the Atlantic passive margin in eastern North America are filled with thousands of meters of continental rocks termed the Newark Supergroup which provide an unprecedented opportunity to examine the fine scale structure of the Triassic-Jurassic mass extinction in continental environments. Time control, vital to the understanding of the mechanisms behind mass extinctions, is provided by lake-level cycles apparently controlled by orbitally induced climate change allowing resolution at the less than 21,000 year level. Correlation with other provinces is provided by a developing high resolution magnetostratigraphy and palynologically-based biostratigraphy. A large number of at least local vertebrate and palynomorph extinctions are concentrated around the boundary with survivors constituting the earliest Jurassic assemblages, apparently without the introduction of new taxa. The palynofloral transition is marked by the dramatic elimination of a relatively high diversity Triassic pollen assemblage with the survivors making up a Jurassic assemblage of very low diversity overwhelmingly dominated by Corollina. Based principally on palynological correlations, the hypothesis that these continental taxonomic transitions were synchronous with the massive Triassic-Jurassic marine extinctions is strongly corroborated. An extremely rapid, perhaps catastrophic, taxonomic turnover at the Triassic-Jurassic boundary, synchronous in continental and marine realms is hypothesized and discussed.

Olsen, P. E.; Comet, B.

1988-01-01

20

Deep Time: The Geologic Time Scale  

NSDL National Science Digital Library

This page examines the issues involved in teaching students about the geologic time scale. There are suggestions for tackling troublesome issues in class as well as activities that can be used to clarify how geoscientists look at deep time. Five main concepts with which students struggle when thinking about Deep Time are addressed here: imagining or comprehending big numbers; the difference between relative and numerical age; the concept of "timescales"; the ways we know about the age of the Earth and other materials; and resolving perceived issues with religious beliefs.

Wenner, Jennifer M.

2011-04-25

21

Time Scales in Evolutionary Dynamics  

Microsoft Academic Search

Evolutionary game theory has traditionally assumed that all individuals in a population interact with each other between reproduction events. We show that eliminating this restriction by explicitly consid- ering the time scales of interaction and selection leads to dramatic changes in the outcome of evolution. Examples include the selection of the inefficient strategy in the Harmony and Stag-Hunt games, and

Carlos P. Roca; Angel Sanchez

2006-01-01

22

Time Scales in Evolutionary Dynamics  

Microsoft Academic Search

Evolutionary game theory has traditionally assumed that all individuals in a\\u000apopulation interact with each other between reproduction events. We show that\\u000aeliminating this restriction by explicitly considering the time scales of\\u000ainteraction and selection leads to dramatic changes in the outcome of\\u000aevolution. Examples include the selection of the inefficient strategy in the\\u000aHarmony and Stag-Hunt games, and the

Carlos P. Roca; Jose A. Cuesta; Angel Sánchez

2006-01-01

23

Applying tracer techniques to determine recharge rate, groundwater age and travel times in Permo-Triassic sandstones.  

NASA Astrophysics Data System (ADS)

The Eden Valley in East Cumbria is underlain by Permo-Triassic sandstone, the major aquifer in Northwest England. Rising nitrate trends in some boreholes has prompted collaborative research into flow systems and timescales in the area. The use of slurry and artificial fertilisers following agricultural intensification during the 1980s is believed to be responsible for the rise in nitrate concentrations. The broad aim of this research is to enable prediction of future nitrate concentrations at abstraction boreholes and in groundwater discharge to surface water. The approach taken has been to study groundwater processes along a 4km transect (approximating a groundwater flowline) in order to estimate groundwater travel timescales through the sandstone and thin superficial Till . A combination of porewater sampling during borehole coring, discrete interval sampling using a borehole packer system, geophysical logging and imaging were employed to develop physical and hydrochemical profiles. Separate tracer techniques were used to estimate recharge rates at different parts of the transect. Tracers used were: deuterium and bromide through Till, nitrate, chloride and tritium through the unsaturated zone and CFCs and SF6 within the saturated zone. Tracer profiles in Till demonstrated a correspondence between Till thickness, type of cultivation and recharge rate. In the thick unsaturated zone of the sandstone they suggested relatively rapid groundwater recharge rates. Key fractures or fracture zones in the saturated sandstone were identified and sampled. The hydrochemistry (particularly nitrate) of samples from discrete intervals in the profiles exhibited a remarkably good relationship with the proportion of modern water (and year of recharge) for example, the age of groundwater increasing to c. 1950 towards the bottom of a 90m borehole. This work demonstrates that the combination of discrete sampling and dating of groundwater is a powerful tool in characterising groundwater movement and timescales in boreholes and hence in parts of aquifers where pollution is most significant. With timescales and processes better constrained, a more reliable prediction of nitrate (and other) trends can be made.

Butcher, Andrew; Gallagher, Alexander; Darling, W. George; Gooddy, Daren; Burke, Sean

2010-05-01

24

Time scales in cognitive neuroscience  

PubMed Central

Cognitive neuroscience boils down to describing the ways in which cognitive function results from brain activity. In turn, brain activity shows complex fluctuations, with structure at many spatio-temporal scales. Exactly how cognitive function inherits the physical dimensions of neural activity, though, is highly non-trivial, and so are generally the corresponding dimensions of cognitive phenomena. As for any physical phenomenon, when studying cognitive function, the first conceptual step should be that of establishing its dimensions. Here, we provide a systematic presentation of the temporal aspects of task-related brain activity, from the smallest scale of the brain imaging technique's resolution, to the observation time of a given experiment, through the characteristic time scales of the process under study. We first review some standard assumptions on the temporal scales of cognitive function. In spite of their general use, these assumptions hold true to a high degree of approximation for many cognitive (viz. fast perceptual) processes, but have their limitations for other ones (e.g., thinking or reasoning). We define in a rigorous way the temporal quantifiers of cognition at all scales, and illustrate how they qualitatively vary as a function of the properties of the cognitive process under study. We propose that each phenomenon should be approached with its own set of theoretical, methodological and analytical tools. In particular, we show that when treating cognitive processes such as thinking or reasoning, complex properties of ongoing brain activity, which can be drastically simplified when considering fast (e.g., perceptual) processes, start playing a major role, and not only characterize the temporal properties of task-related brain activity, but also determine the conditions for proper observation of the phenomena. Finally, some implications on the design of experiments, data analyses, and the choice of recording parameters are discussed. PMID:23626578

Papo, David

2013-01-01

25

Early Triassic seawater sulfate drawdown  

NASA Astrophysics Data System (ADS)

The marine sulfur cycle is intimately linked to global carbon fluxes, atmospheric composition, and climate, yet relatively little is known about how it responded to the end-Permian biocrisis, the largest mass extinction of the Phanerozoic. Here, we analyze carbonate-associated-sulfate (CAS) from three Permo-Triassic sections in South China in order to document the behavior of the C-S cycle and its relationship to marine environmental changes during the mass extinction and its aftermath. We find that ?34SCAS varied from +9‰ to +44‰ at rates up to 100‰ Myr-1 during the Griesbachian-Smithian substages of the Early Triassic. We model the marine sulfur cycle to demonstrate that such rapid variation required drawdown of seawater sulfate concentrations to ?4 mM and a reduction in its residence time to ?200 kyr. This shorter residence time resulted in positive covariation with ?13Ccarb due to strong coupling of the organic carbon and pyrite burial fluxes. Carbon and sulfur isotopic shifts were associated with contemporaneous changes in climate, marine productivity, and microbial sulfate reduction rates, with negative shifts in ?13Ccarb and ?34SCAS linked to warming, decreased productivity, and reduced sulfate reduction. Sustained cooling during the Spathian re-invigorated oceanic overturning circulation, reduced marine anoxia, and limited pyrite burial. As seawater sulfate built to higher concentrations during the Spathian, the coupling of the marine C and S cycles came to an end and a general amelioration of marine environmental conditions set the stage for a recovery of invertebrate faunas. Variation in seawater sulfate during the Early Triassic was probably controlled by climate change, possibly linked to major eruptive phases of the Siberian Traps.

Song, Huyue; Tong, Jinnan; Algeo, Thomas J.; Song, Haijun; Qiu, Haiou; Zhu, Yuanyuan; Tian, Li; Bates, Steven; Lyons, Timothy W.; Luo, Genming; Kump, Lee R.

2014-03-01

26

The Planck Scale Underpinning for Space Time  

E-print Network

We provide a rationale for the Planck scale being the minimum scale in the universe, as also its specific numerical values. In the process we answer the question of why the Planck scale is $10^{20}$ times the Compton scale of elementary particles. These considerations show how the Planck scale provides an underpinning for space time.

Burra G. Sidharth

2005-09-03

27

The Sail-Backed Reptile Ctenosauriscus from the Latest Early Triassic of Germany and the Timing and Biogeography of the Early Archosaur Radiation  

PubMed Central

Background Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3–247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains. Methodology/Principal Findings We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the ‘sail’ of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation. Conclusions/Significance Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian–Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which appear to have been the first global radiation of archosaurs. PMID:22022431

Butler, Richard J.; Brusatte, Stephen L.; Reich, Mike; Nesbitt, Sterling J.; Schoch, Rainer R.; Hornung, Jahn J.

2011-01-01

28

Triassic in Iran  

Microsoft Academic Search

Summary  Except of the Nakhlak and Aghdarband regions, Lower and Middle Triassic strata in Iran consist almost exclusively of carbonate\\u000a rocks built on vast platforms along the shelves of the Paleo- and Neotethys. The depositional environments varied from shallow\\u000a shelf sea to lagoonal and near-shore tidal flats, becoming even evaporitic towards the coastal regions of the Persian Gulf.\\u000a During the early

Kazem Seyed-Emami

2003-01-01

29

Improving the Geologic Time Scale (Jean Baptiste Lamarck Medal Lecture)  

NASA Astrophysics Data System (ADS)

The Geologic Time Scale (GTS) provides the framework for the physical, chemical and biological processes on Earth. The time scale is the tool "par excellence" of the geological trade, and insight in its construction, strength, and limitations enhances its function and its utility. Earth scientists should understand how time scales are constructed and its myriad of physical and abstract data are calibrated, rather than merely using ages plucked from a convenient chart or card. Calibration to linear time of the succession of events recorded in the rocks on Earth has three components: (1) the standard stratigraphic divisions and their correlation in the global rock record, (2) the means of measuring linear time or elapsed durations from the rock record, and (3) the methods of effectively joining the two scales, the stratigraphic one and the linear one. Under the auspices of the International Commission on Stratigraphy (ICS), the international stratigraphic divisions and their correlative events are now largely standardized, especially using the GSSP (Global Stratigraphic Section and Point) concept. The means of measuring linear time or elapsed durations from the rock record are objectives in the EARTH TIME and GTS NEXT projects, that also are educating a new generation of GTS dedicated scientists. The U/Pb, Ar/Ar and orbital tuning methods are intercalibrated, and external error analysis improved. Existing Ar/Ar ages become almost 0.5% older, and U/Pb ages stratigraphically more realistic. The new Os/Re method has potential for directly dating more GSSP's and its correlative events. Such may reduce scaling uncertainty between the sedimentary levels of an age date and that of a stage boundary. Since 1981, six successive Phanerozoic GTS have been published, each new one achieving higher resolution and more users. The next GTS is scheduled for 2011/2012, with over 50 specialists taking part. New chapters include an expanded planetary time scale, sequence stratigraphy, Osmium, Carbon and Oxygen stratigraphy, the Cryogenian period, history of the plants, hominid prehistory, and last but not least the Anthropocene. The Cambrian Period is radically improved with 10 standard stages and detailed trilobite biochronology. Ordovician now has a stable international stages and graptolites scale. The integration of a refined 100 and 400 ka sedimentary cycles scale and a truly high-resolution U/Pb ages scale for the Mississippian is a major step towards the global Carboniferous GTS. The Devonian GTS leaves to be desired with lack of firm definitions for its upper boundary, and the long Emsian stage; it also lacks age dates. Its stages scaling is disputed. The Rhaetian and Norian stages in the Triassic and the Berriasian stage in the Cretaceous urgently require lower boundary definitions, and also boundary age dates. The single ~400 ka eccentricity component is very stable and can extend orbital tuning from the Cenozoic well into the Mesozoic portion of the GTS. Jurassic and Cretaceous now have long orbitally tuned segments. A completely astronomical-tuned Geological Time Scale (AGTS) for the Cenozoic is within reach showing unprecedented accuracy, precision and resolution. Burdigalian in the Miocene, and Lutetian, Bartonian and Priabonian stages in the Eocene still require formal definition. The K/T boundary will become about 0.5 ± 0.1 Ma older. After 25 years of research and authorship in the GTS it behoves me to especially thank my colleagues James Ogg, Frits Agterberg, John McArthur and Roger Cooper for longstanding collaboration. As a final note I urge construction of more regional time scales(like developed ‘down under') calibrated to the standard global GTS, to scale regional rock units.

Gradstein, Felix M.

2010-05-01

30

Modeling orbital changes on tectonic time scales  

NASA Technical Reports Server (NTRS)

Geologic time series indicate significant 100 ka and 400 ka pre-Pleistocene climate fluctuations, prior to the time of such fluctuations in Pleistocene ice sheets. The origin of these fluctuations must therefore depend on phenomena other than the ice sheets. In a previous set of experiments, we tested the sensitivity of an energy balance model to orbital insolation forcing, specifically focusing on the filtering effect of the Earth's geography. We found that in equatorial areas, the twice-yearly passage of the sun across the equator interacts with the precession index to generate 100 ka and 400 ka power in our modeled time series. The effect is proportional to the magnitude of land in equatorial regions. We suggest that such changes may reflect monsoonal variations in the real climate system, and the subsequent wind and weathering changes may transfer some of this signal to the marine record. A comparison with observed fluctuations of Triassic lake levels is quite favorable. A number of problems remain to be studied or clarified: (1) the EBM experiments need to be followed up by a limited number of GCM experiments; (2) the sensitivity to secular changes in orbital forcing needs to be examined; (3) the possible modifying role of sedimentary processes on geologic time series warrants considerably more study; (4) the effect of tectonic changes on Earth's rotation rate needs to be studied; and (5) astronomers need to make explicit which of their predictions are robust and geologists and astronomers have to agree on which of the predictions are most testable in the geologic record.

Crowley, Thomas J.

1992-01-01

31

How severe is the modern biotic crisis?—A comparison of global change and biotic crisis between Permian-Triassic transition and modern times  

NASA Astrophysics Data System (ADS)

A comparison of the modern condition with the Permian-Triassic Boundary (PTB) times was made to estimate how severe the modern biotic crisis is. About the global changes, the two periods are correlative in carbon dioxide concentration and carbon isotope negative excursion, UV strengthening, temperature increase, ocean acidification, and weathering enhancement. The following tendencies of biotic crises are also correlative: acceleration of extinction rates accompanied by parabolic curve of extinction with a turning interval representing the critical crisis; decline of the three main ecosystems: reefs, tropical rain forests and marine phytoplankton. It is also interesting to note that certain leading organism in both periods undergo accelerated evolution during the crisis. The comparison shows that the modern crisis is about at the turning point from decline to decimation. The extinction curve is now parabolic, and the extinction rate has been accelerated, but the decimation is not yet in real. This is also justified by the modern situation of the three main ecosystems. Modern biotic decline may worsen into decimation and mass extinction but may also get better and recover to ordinary evolution. Since human activities are the main cause of the deterioration of environments and organisms, mankind should be responsible and able to strive for the recovery of the crisis. For the future of mankind, Homo sapiens may become extinct, i.e., disappear without leaving descendants, or evolve into a new and more advanced species, i.e., disappear but leave descendants. For a better future, mankind should be conscious of the facing danger and act as a whole to save biodiversity and harmonize with the environments.

Yin, Hongfu; He, Weihong; Xie, Shucheng

2011-03-01

32

Introduction to the time scale problem  

SciTech Connect

As motivation for the symposium on extended-scale atomistic methods, I briefly discuss the time scale problem that plagues molecular dynamics simulations, some promising recent developments for circumventing the problem, and some remaining challenges.

Voter, A. F.

2002-01-01

33

Two-time-scale Wonham filters  

Microsoft Academic Search

This paper is concerned with a two-time-scale approximation of Wonham filters. A main feature is that the underlying hidden Markov chain has a large state space. To reduce computational complexity, we develop two-time-scale approach. Under time scale separation, we divide the state space of the Markov chain into a number of groups such that the chain jumps rapidly within each

Q. Zhang; G. Yin; J. B. Moore

2007-01-01

34

Scaling Behavior of Hydrologic Time Series  

NASA Astrophysics Data System (ADS)

An important area of research in hydrologic modeling is the issue of scaling of certain deterministic properties at various spatial and temporal scales. The complexity for modeling of most systems is because hydrologic processes scale nonlinearly; that is, the moments (e.g. the mean and variance) obtained at one scale may be significantly different from those obtained at a larger or smaller scale. Improvements in hydrologic modeling that include the tenants of scaling in the relevant processes would be novel, and likely lead to a stronger predictive approach than are currently available. Fractal-based scale invariant approach for analyzing long-term time series data can provide insight into the scaling issue as a quantitative approach for evaluating temporal scale in hydrologic time series. The main objective of this research is to study the effects of deterministic trends, mainly seasonality of hydrologic time series on scaling parameter. Different hydrologic time series (rainfall and runoff) from various locations are investigated. Two hydrologic time series, one with the raw hydrologic time series data and another by removing the seasonality are compared. The comparison of untransformed and deseasonalized data series showed that there is no statistically significant value to deseasonalize the data, although the data series appears to shift toward random scaling after deseasonalization.

Koirala, S. R.

2012-12-01

35

movements in Triassic theropod dinosaurs. Nature 339, 141144 (1999). 8. Gierlinski, G. Avialian theropod tracks from the Early Jurassic strata of Poland. Zubia 14, 7987 (1996).  

E-print Network

theropod tracks from the Early Jurassic strata of Poland. Zubia 14, 79­87 (1996). 9. Rainforth, E. C. Late Triassic­Early Jurassic dinosaur ichnofaunas, eastern North America and Southern Africa. J. Vert. Paleo. 21, Jurassic and Cretaceous time scale. SEPM Spec. Publ. 54, 95­126 (1995). 16. Kent, D. V. & Olsen, P. E

Gribble, Paul

36

Scaling exponents estimation from time-scale energy distributions  

Microsoft Academic Search

It is shown using some examples that the problem of estimating the evolution of scaling exponents characterizing locally a self-similar process can be efficiently handled within the general framework of time-scale energy distributions related to the wavelength transform. As is implicit from the structure of the estimators considered, the proposed methodology is dependent on the degree of nonstationarity of such

P. Goncalves; P. Flandrin

1992-01-01

37

Kalman plus weights: a time scale algorithm  

NASA Technical Reports Server (NTRS)

KPW is a time scale algorithm that combines Kalman filtering with the basic time scale equation (BTSE). A single Kalman filter that estimates all clocks simultaneously is used to generate the BTSE frequency estimates, while the BTSE weights are inversely proportional to the white FM variances of the clocks. Results from simulated clock ensembles are compared to previous simulation results from other algorithms.

Greenhall, C. A.

2001-01-01

38

Microbialites and geochemistry of the Early Triassic enigma?  

NASA Astrophysics Data System (ADS)

The Permian-Triassic mass extinction, 252 Myr ago, is the most devastating global-scale event ever recorded. Ecological and environmental changes during this interval are commonly assumed to be associated with numerous perturbations (i.e. productivity changes, acidification, redox changes, eustatism) that still remain elusive. The present study focus on the relationships between the redox conditions within the water column, the successive sedimentary deposits and marine community turnovers. Our study is based on new Early Triassic sections from the western USA Basin that preserve diversified reefs and bioaccumulations that contain microbialites and various benthic and pelagic organisms (e.g. serpulids, bivalves, ostracods, gastropods, cephalopods). Such a sedimentary prisitine record provides interesting new prospects to decipher the relationships between lithology, microbial structures and the geochemistry of the water column. Three outcrops were studied: the Mineral Mountains, the Confusion Range and the Pahvant Range, that record a general transgressive trend from proximal to distal deposits during the Smithian substage. Continental to open marine conditions are deduced from sedimentological studies and are related to variations of the microbialite meso- and micro-structures over a short time scale. Hydrodynamics and bathymetry are shown to be the major parameters that influence the morphology and distribution of these microbialites. Additionally to the study of the different microbialites structures and associated depositional environments, the chemiotratigraphic record of both carbon isotopes and major elements indicate a complex and a wide range of variations at short time scale. Carbon isotopes vary from -5 to 2 ‰PDB and FeHR/FeT ratio, after iron speciation, indicate a broad range of variation between 0.1 and 1.5. On the one hand, these analyses suggest potential transient oxygen depletion within the water column. On the other hand, fluctuations of these geochemical proxies seem to be influenced by lithology. We thus suggest that biogeochemical cycles of carbon and iron in the studied sections were influenced by the paleo-bathymetry and the distal to proximal polarity between the three locations. A second order control on the water column geochemistry is also probably the consequence of the microbially-induced carbonate precipitation. This study suggests that the Early Triassic paleoenvironments with the western USA basin were highly variable in terms of sedimentology and geochemistry, but also suggest a low oxygen concentration within the water column during the Smithian substage.

Bour, Ivan; Vennin, Emmanuelle; Thomazo, Christophe; Brayard, Arnaud; Olivier, Nicolas; Escarguel, Gilles; Bylund, Kevin G.; Jenks, Jim; Stephen, Daniel A.

2013-04-01

39

A New Time-Scale for Tunneling  

E-print Network

We study the tunneling through an oscillating delta barrier. Using time periodicity of the model, the time-dependent Schr\\"odinger equation is reduced to a simple but infinite matrix equation. Employing Toeplitz matrices methods, the infinite matrix is replaces by a $3\\times 3$ matrix, allowing an analytical solution. Looking at the frequency dependence of the transmissionamplitudes, one observes a new time scale which dominates the tunneling dynamics. This time scale differs from the one previously introduced by B\\"uttiker and Landauer. The relation between these two is discussed.

E. Eisenberg; Y. Ashkenazy

1996-10-25

40

Mouse Activity across Time Scales: Fractal Scenarios  

PubMed Central

In this work we devise a classification of mouse activity patterns based on accelerometer data using Detrended Fluctuation Analysis. We use two characteristic mouse behavioural states as benchmarks in this study: waking in free activity and slow-wave sleep (SWS). In both situations we find roughly the same pattern: for short time intervals we observe high correlation in activity - a typical 1/f complex pattern - while for large time intervals there is anti-correlation. High correlation of short intervals ( to : waking state and to : SWS) is related to highly coordinated muscle activity. In the waking state we associate high correlation both to muscle activity and to mouse stereotyped movements (grooming, waking, etc.). On the other side, the observed anti-correlation over large time scales ( to : waking state and to : SWS) during SWS appears related to a feedback autonomic response. The transition from correlated regime at short scales to an anti-correlated regime at large scales during SWS is given by the respiratory cycle interval, while during the waking state this transition occurs at the time scale corresponding to the duration of the stereotyped mouse movements. Furthermore, we find that the waking state is characterized by longer time scales than SWS and by a softer transition from correlation to anti-correlation. Moreover, this soft transition in the waking state encompass a behavioural time scale window that gives rise to a multifractal pattern. We believe that the observed multifractality in mouse activity is formed by the integration of several stereotyped movements each one with a characteristic time correlation. Finally, we compare scaling properties of body acceleration fluctuation time series during sleep and wake periods for healthy mice. Interestingly, differences between sleep and wake in the scaling exponents are comparable to previous works regarding human heartbeat. Complementarily, the nature of these sleep-wake dynamics could lead to a better understanding of neuroautonomic regulation mechanisms. PMID:25275515

Lima, G. Z. dos Santos; Lobão-Soares, B.; do Nascimento, G. C.; França, Arthur S. C.; Muratori, L.; Ribeiro, S.; Corso, G.

2014-01-01

41

Gondwana's climate history inferred from the palynological record of South Africa's coal deposits: the Early Triassic wet intermezzo  

NASA Astrophysics Data System (ADS)

Permian-Triassic coals of the South African Karoo Basin play a central role in the study and interpretation of Gondwana's climate history and related vegetational changes in time and space. The palynological record of the coal-bearing formations reveals major phases of climate amelioration succeeding the Permo-Carboniferous Gondwana glaciations. Subsequent to the melting of the Dwyka ice, cold to cool-temperate climate conditions prevailed during the Early Permian and a continuous change to hot and dry climate conditions of the Late Permian and Triassic was inferred from sedimentological and palaeontological data so far. The here presented new palynological and geochemical data from the Early Triassic Molteno coal (Stormberg Group) point to a short-term switch from dry to wet climate conditions. To date, this wet intermezzo of Gondwana's early Mesozoic climate history has been overlooked in the Molteno coal of the Karoo Basin. The spore/pollen ratios, used as a proxy for humidity changes, indicate a significant climatic change corresponding to a prominent C-isotope excursion. Ongoing studies will provide a detailed palynological inventory of the Early Triassic coal deposits on an intra-Gondwanic scale, contributing to the interpretation of early Mesozoic palaeoclimates.

Götz, Annette E.

2013-04-01

42

Chronology of fluctuating sea levels since the triassic  

SciTech Connect

Advances in sequence stratigraphy and the development of depositional models have helped explain the origin of genetically related sedimentary packages during sea level cycles. These concepts have provided the basis for the recognition of sea level events in subsurface data and in outcrops of marine sediments around the world. Knowledge of these events has led to a new generation of Mesozoic and Cenozoic global cycle charts that chronicle the history of sea level fluctuations during the past 250 million years in greater detail than was possible from seismic-stratigraphic data alone. An effort has been made to develop a realistic and accurate time scale and widely applicable chronostratigraphy and to integrate depositional sequences documented in public domain outcrop sections from various basins with this chronostratigraphic framework. A description of this approach and an account of the results, illustrated by sea level cycle charts of the Cenozoic, Cretaceous, Jurassic, and Triassic intervals, are presented.

Haq, B.U.; Hardenbol, J.; Vail, P.R.

1987-03-06

43

The Geologic Time Scale in Historical Perspective  

NSDL National Science Digital Library

This brief discussion of the development of the Geologic Time Scale begins with Nicolas Steno in 1669 whose ideas have become known as the principles of original horizontal deposition and superposition. Next are James Hutton in 1795 and Charles Lyell in the early 1800s who supported the principle of uniformitarianism. The work of William Smith and the principle of faunal succession is also noted. The site goes on to explain how and why the scale is divided as it is.

44

Brownian motion at short time scales  

E-print Network

Brownian motion has played important roles in many different fields of science since its origin was first explained by Albert Einstein in 1905. Einstein's theory of Brownian motion, however, is only applicable at long time scales. At short time scales, Brownian motion of a suspended particle is not completely random, due to the inertia of the particle and the surrounding fluid. Moreover, the thermal force exerted on a particle suspended in a liquid is not a white noise, but is colored. Recent experimental developments in optical trapping and detection have made this new regime of Brownian motion accessible. This review summarizes related theories and recent experiments on Brownian motion at short time scales, with a focus on the measurement of the instantaneous velocity of a Brownian particle in a gas and the observation of the transition from ballistic to diffusive Brownian motion in a liquid.

Tongcang Li; Mark G. Raizen

2012-11-07

45

Sedimentology, stratigraphy, and micropalaeontology of the Upper Triassic reefal series in Eastern Sulawesi (Indonesia)  

Microsoft Academic Search

An Upper Triassic (Upper Norian-Rhaetian) carbonate complex, composed of open marine to reefal deposits, has been investigated for the first time in Eastern Sulawesi. The age is based on the occurrence of benthic foraminifera, and also of the Upper Sevatian to Rhaetian conodont Misikella posthernsteini Kozur and Mock. Palynological assemblages contain Upper Triassic-Lower Jurassic palynomorphs. The scleractinian coral Retiophyllia seranica

Rossana Martini; Daniel Vachard; Louisette Zaninetti; Simonetta Cirilli; Jean-Jacques Cornée; Bernard Lathuilière; Michel Villeneuve

1997-01-01

46

The time scale of evolutionary innovation.  

PubMed

A fundamental question in biology is the following: what is the time scale that is needed for evolutionary innovations? There are many results that characterize single steps in terms of the fixation time of new mutants arising in populations of certain size and structure. But here we ask a different question, which is concerned with the much longer time scale of evolutionary trajectories: how long does it take for a population exploring a fitness landscape to find target sequences that encode new biological functions? Our key variable is the length, L, of the genetic sequence that undergoes adaptation. In computer science there is a crucial distinction between problems that require algorithms which take polynomial or exponential time. The latter are considered to be intractable. Here we develop a theoretical approach that allows us to estimate the time of evolution as function of L. We show that adaptation on many fitness landscapes takes time that is exponential in L, even if there are broad selection gradients and many targets uniformly distributed in sequence space. These negative results lead us to search for specific mechanisms that allow evolution to work on polynomial time scales. We study a regeneration process and show that it enables evolution to work in polynomial time. PMID:25211329

Chatterjee, Krishnendu; Pavlogiannis, Andreas; Adlam, Ben; Nowak, Martin A

2014-09-01

47

The hippocampus, time, and memory across scales.  

PubMed

A wealth of experimental studies with animals have offered insights about how neural networks within the hippocampus support the temporal organization of memories. These studies have revealed the existence of "time cells" that encode moments in time, much as the well-known "place cells" map locations in space. Another line of work inspired by human behavioral studies suggests that episodic memories are mediated by a state of temporal context that changes gradually over long time scales, up to at least a few thousand seconds. In this view, the "mental time travel" hypothesized to support the experience of episodic memory corresponds to a "jump back in time" in which a previous state of temporal context is recovered. We suggest that these 2 sets of findings could be different facets of a representation of temporal history that maintains a record at the last few thousand seconds of experience. The ability to represent long time scales comes at the cost of discarding precise information about when a stimulus was experienced--this uncertainty becomes greater for events further in the past. We review recent computational work that describes a mechanism that could construct such a scale-invariant representation. Taken as a whole, this suggests the hippocampus plays its role in multiple aspects of cognition by representing events embedded in a general spatiotemporal context. The representation of internal time can be useful across nonhippocampal memory systems. PMID:23915126

Howard, Marc W; Eichenbaum, Howard

2013-11-01

48

Time scales in tidal disruption events  

NASA Astrophysics Data System (ADS)

We explore the temporal structure of tidal disruption events pointing out the corresponding transitions in the lightcurves of the thermal accretion disk and of the jet emerging from such events. The hydrodynamic time scale of the disrupted star is the minimal time scale of building up the accretion disk and the jet and it sets a limit on the rise time. This suggest that Swift J1644+57, that shows several flares with a rise time as short as a few hundred seconds could not have arisen from a tidal disruption of a main sequence star whose hydrodynamic time is a few hours. The disrupted object must have been a white dwarf. A second important time scale is the Eddington time in which the accretion rate changes form super to sub Eddington. It is possible that such a transition was observed in the light curve of Swift J2058+05. If correct this provides interesting constraints on the parameters of the system.

Piran, T.; Krolik, J.

2012-12-01

49

Filling the Triassic Geochronologic Gap: A Continuous Cored Record of Continental Environmental Change in Western North America  

NASA Astrophysics Data System (ADS)

The Triassic Period (252.2-201.6 Ma) is bracketed by two mass extinctions, witnessed the evolution of the major groups of modern tetrapods, saw giant bolide impacts, and was typified by generally high atmospheric CO2 and a lack of ice at the poles. Testing hypotheses relevant to these major features of the Triassic, as well as problems related to the Earth system in general, requires temporally well-defined records of environmental and biotic change, especially in terrestrial environments, which until recently were lacking. The NSF and ICDP funded ~500 m long core at Petrified Forest National Park, scheduled to be drilled in Fall, 2013, is part of an interdisciplinary, multi-institutional, Colorado Plateau Coring Project, and is a major step towards providing a network of such records. The core will recover virtually the entire pre-Owl-Rock-Member Late Triassic age Chinle and underlying Early-Middle Triassic age Moenkopi formations. A core is required despite excellent outcrop and a long and distinguished history of study because of ambiguities in local correlation, a lack of constraints on the temporal duration and resolution of biotic events, and an inability to make clear global correlations. Specifically, by integrating a densely sampled paleomagnetic record with high-resolution radioisotopic ages in unquestioned superposition, the new core will allow us to test at least five sets of hypotheses: (1) were marine and continental biotic turnover events in the Late Triassic coupled? (2) was there high faunal provinciality during the existence of the supercontinent of Pangea?; (3) is the time scale of the Newark basin astronomically calibrated GPTS for the Triassic accurate, particularly for the Norian age part that is relevant for mapping the chaotic evolution of the Solar System, as well as global correlations?; (4) is the supposed Carnian-Norian boundary in the Chinle actually a late middle Norian extinction coinciding with the 215.5 Ma Manicouagan impact?; (5) is the stratigraphic record in the Triassic a reflection of changes in local climate due to plate motion through climate belts or changes in global climate driven by other processes, such as CO2 fluctuations? The Petrified Forest core will thus be key to unambiguous testing of these ideas, and observations from it promise to fundamentally change the certainty and specificity of the questions that relate the rich surface record from the Chinle and Moenkopi to Earth system processes.

Olsen, P. E.; Kent, D. V.; Geissman, J. W.; Mundil, R.; Gehrels, G. E.; Irmis, R. B.; Whiteside, J. H.; Schaller, M. F.

2013-12-01

50

EDITORIAL: Special issue on time scale algorithms  

Microsoft Academic Search

This special issue of Metrologia presents selected papers from the Fifth International Time Scale Algorithm Symposium (VITSAS), including some of the tutorials presented on the first day. The symposium was attended by 76 persons, from every continent except Antarctica, by students as well as senior scientists, and hosted by the Real Instituto y Observatorio de la Armada (ROA) in San

Demetrios Matsakis; Patrizia Tavella

2008-01-01

51

Assessing the record and causes of Late Triassic extinctions  

USGS Publications Warehouse

Accelerated biotic turnover during the Late Triassic has led to the perception of an end-Triassic mass extinction event, now regarded as one of the "big five" extinctions. Close examination of the fossil record reveals that many groups thought to be affected severely by this event, such as ammonoids, bivalves and conodonts, instead were in decline throughout the Late Triassic, and that other groups were relatively unaffected or subject to only regional effects. Explanations for the biotic turnover have included both gradualistic and catastrophic mechanisms. Regression during the Rhaetian, with consequent habitat loss, is compatible with the disappearance of some marine faunal groups, but may be regional, not global in scale, and cannot explain apparent synchronous decline in the terrestrial realm. Gradual, widespread aridification of the Pangaean supercontinent could explain a decline in terrestrial diversity during the Late Triassic. Although evidence for an impact precisely at the boundary is lacking, the presence of impact structures with Late Triassic ages suggests the possibility of bolide impact-induced environmental degradation prior to the end-Triassic. Widespread eruptions of flood basalts of the Central Atlantic Magmatic Province (CAMP) were synchronous with or slightly postdate the system boundary; emissions of CO2 and SO2 during these eruptions were substantial, but the contradictory evidence for the environmental effects of outgassing of these lavas remains to be resolved. A substantial excursion in the marine carbon-isotope record of both carbonate and organic matter suggests a significant disturbance of the global carbon cycle at the system boundary. Release of methane hydrates from seafloor sediments is a possible cause for this isotope excursion, although the triggering mechanism and climatic effects of such a release remain uncertain. ?? 2003 Elsevier B.V. All rights reserved.

Tanner, L.H.; Lucas, S.G.; Chapman, M.G.

2004-01-01

52

Scaling in the Timing of Extreme Events  

E-print Network

Extreme events can come either from point processes, when the size or energy of the events is above a certain threshold, or from time series, when the intensity of a signal surpasses a threshold value. We are particularly concerned by the time between these extreme events, called respectively waiting time and quiet time. If the thresholds are high enough it is possible to justify the existence of scaling laws for the probability distribution of the times as a function of the threshold value, although the scaling functions are different in each case. For point processes, in addition to the trivial Poisson process, one can obtain double-power-law distributions with no finite mean value. This is justified in the context of renormalization-group transformations, where such distributions arise as limiting distributions after iterations of the transformation. Clear connections with the generalized central limit theorem are established from here. The non-existence of finite moments leads to a semi-parametric scaling...

Corral, Alvaro

2014-01-01

53

The end-triassic mass extinction event  

NASA Technical Reports Server (NTRS)

The end-Triassic is the least studied of the five major episodes of mass extinction recognized in the Phanerozoic, and the Triassic-Jurassic boundary is not precisely defined in most parts of the world, with a paucity of good marine sections and an insufficiency of biostratigraphically valuable fossils. Despite these limitations it is clear that there was a significant episode of mass extinction, affecting many groups, in the Late Norian and the existing facts are consistent with it having taken place at the very end of the period. The best record globally comes from marine strata. There was an almost complete turnover of ammonites across the T-J boundary, with perhaps no more than one genus surviving. About half the bivalve genera and most of the species went extinct, as did many archaeogastropods. Many Paleozoic-dominant brachiopods also disappeared, as did the last of the conodonts. There was a major collapse and disappearance of the Alpine calcareous sponge. Among terrestrial biota, a significant extinction event involving tetrapods was recognized. With regard to possible environmental events that may be postulated to account for the extinctions, there is no evidence of any significant global change of climate at this time. The existence of the large Manicouagan crater in Quebec, dated as about late or end-Triassic, has led to the suggestion that an impact event might be implicated, but so far despite intensive search no unequivocal iridium anomaly or shocked quartz was discovered. On the other hand there is strong evidence for significant marine regression in many parts of the world. It is proposed therefore that the likeliest cause of the marine extinctions is severe reduction in habitat area caused either by regression of epicontinental seas, subsequent widespread anoxia during the succeeding transgression, or a combination of the two.

Hallam, A.

1988-01-01

54

Short-time scale behavior modeling within long-time scale fuel cycle evaluations  

SciTech Connect

Typically, short-time and long-time scales in nuclear energy system behavior are accounted for with entirely separate models. However, long-term changes in system characteristics do affect short-term transients through material variations. This paper presents an approach to consistently account for short-time scales within a nuclear system lifespan. The reported findings and developments are of significant importance for small modular reactors and other nuclear energy systems operating in autonomous modes. It is necessary to simulate the short time-scale kinetic behavior of the reactor as well as the long time-scale dynamics that occur with fuel burnup. The former is modeled using the point kinetics equations, while the latter is modeled by the Bateman equations. (authors)

Johnson, M.; Tsvetkov, P. [Dept. of Nuclear Engineering, Texas A and M Univ., 3133 TAMU, College Station, TX 77843 (United States); Lucas, S. [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States)

2012-07-01

55

Cell water dynamics on multiple time scales.  

PubMed

Water-biomolecule interactions have been extensively studied in dilute solutions, crystals, and rehydrated powders, but none of these model systems may capture the behavior of water in the highly organized intracellular milieu. Because of the experimental difficulty of selectively probing the structure and dynamics of water in intact cells, radically different views about the properties of cell water have proliferated. To resolve this long-standing controversy, we have measured the (2)H spin relaxation rate in living bacteria cultured in D(2)O. The relaxation data, acquired in a wide magnetic field range (0.2 mT-12 T) and analyzed in a model-independent way, reveal water dynamics on a wide range of time scales. Contradicting the view that a substantial fraction of cell water is strongly perturbed, we find that approximately 85% of cell water in Escherichia coli and in the extreme halophile Haloarcula marismortui has bulk-like dynamics. The remaining approximately 15% of cell water interacts directly with biomolecular surfaces and is motionally retarded by a factor 15 +/- 3 on average, corresponding to a rotational correlation time of 27 ps. This dynamic perturbation is three times larger than for small monomeric proteins in solution, a difference we attribute to secluded surface hydration sites in supramolecular assemblies. The relaxation data also show that a small fraction ( approximately 0.1%) of cell water exchanges from buried hydration sites on the microsecond time scale, consistent with the current understanding of protein hydration in solutions and crystals. PMID:18436650

Persson, Erik; Halle, Bertil

2008-04-29

56

Time sequence and time scale of intermediate mass fragment emission  

SciTech Connect

Semiperipheral collisions in the {sup 124}Sn+{sup 64}Ni reaction at 35 MeV/nucleon were studied using the forward part of the Charged Heavy Ion Mass and Energy Resolving Array. Nearly completely determined ternary events involving projectilelike fragments (PLF), targetlike fragments (TLF), and intermediate mass fragments (IMF) were selected. A new method of studying the reaction mechanism, focusing on the analysis of the correlations between relative velocities in the IMF+PLF and IMF+TLF subsystems, is proposed. The relative velocity correlations provide information on the time sequence and time scale of the neck fragmentation processes leading to production of IMFs. It is shown that the majority of light IMFs are produced within 40-80 fm/c after the system starts to reseparate. Heavy IMFs are formed at times of about 120 fm/c or later and can be viewed as resulting from two-step (sequential) neck rupture processes.

De Filippo, E.; Pagano, A.; Cardella, G.; Lanzano, G.; Papa, M.; Pirrone, S.; Politi, G. [INFN, Sezione di Catania and Dipartimento di Fisica e Astronomia, Universita di Catania (Italy); Wilczynski, J. [A. Soltan Institute for Nuclear Studies, Swierk/Warsaw (Poland); Amorini, F.; Anzalone, A.; Baran, V.; Bonasera, A.; Cavallaro, S.; Colonna, M.; Di Toro, M.; Giustolisi, F.; Iacono-Manno, M.; La Guidara, E.; Lanzalone, G.; Maiolino, C. [INFN, Laboratori Nazionali del Sud and Dipartimento di Fisica e Astronomia, Universita di Catania (Italy)] [and others

2005-04-01

57

Time scale analysis of ISTTOK probe data  

SciTech Connect

Magnetic and turbulent activity in a tokamak plasma discharge may evolve in a complex trend during the discharge. In the ISTTOK tokamak, characterised by a short 30ms pulse duration, particle confinement of the order 0.3 ms and typical burst-like activity, the analysis of the time scales involved in the plasma activity is even more demanding. In this work, use is made of the Empirical Mode Decomposition (EMD) method as a tool for turbulence and MHD instability analysis obtained with Langmuir and magnetic probes, respectively. The time evolution of the energy content and wavenumber characterisation of fluctuating potential, edge plasma density and perturbed magnetic fields is investigated, with special emphasis on discharges where both limiter and electrode biasing were used to induce local sheared electric fields, thus affecting turbulence and consequently particle confinement.

Coelho, R.; Alves, D.; Silva, C. [Associacao Euratom/IST, Centro de Fusao Nuclear, 1049-001 Lisboa (Portugal)

2008-04-07

58

Convergence of Unilateral Laplace Transforms on Time Scales  

Microsoft Academic Search

A time scale is any closed subset of the real line. Continuous time and discrete time are special cases. The unilateral Laplace\\u000a transform of a signal on a time scale subsumes the continuous-time unilateral Laplace transform, and the discrete-time unilateral\\u000a z-transform as special cases. The regions of convergence (ROCs) time scale Laplace transforms are determined by the time scale’s\\u000a graininess.

John M. Davis; Ian A. Gravagne; Robert J. Marks

2010-01-01

59

A NEW SHRIMP (DECAPODA, DENDROBRANCHIATA, PENAEOIDEA) FROM THE MIDDLE TRIASSIC OF YUNNAN, SOUTHWEST CHINA  

E-print Network

the type species, Aeger tipularius from the Jurassic Solnhofen Plattenkalk, in having a long, smooth of the marine ecosystem between Eastern and Western Tethys. INTRODUCTION THE TRIASSIC Period was a pivotal time

Benton, Michael

60

CO2 and the end-Triassic mass extinction.  

PubMed

The end of the Triassic period was marked by one of the largest and most enigmatic mass-extinction events in Earth's history and, with few reliable marine geochemical records, terrestrial sediments offer an important means of deciphering environmental changes at this time. Tanner et al. describe an isotopic study of Mesozoic fossil soils which suggests that the atmospheric concentration of carbon dioxide (pCO2) across the Triassic-Jurassic boundary was relatively constant (within 250 p.p.m.v.), but this is inconsistent with high-resolution evidence from the stomatal characters of fossil leaves. Here I show that the temporal resolution of the fossil-soil samples may have been inadequate for detecting a transient rise in pCO2. I also show that the fossil-soil data are consistent with a large increase in pCO2 across the Triassic-Jurassic boundary when variations in the stable carbon isotope (denoted as delta13C) in terrestrial plant leaves are taken into account. These factors suggest that the linkage between pCO2, global warming and the end-Triassic mass extinction remains intact. PMID:11807542

Beerling, David

2002-01-24

61

Interest point detection and scale selection in space-time  

E-print Network

by maximising a scale-normalised space-time Laplacian operator over both spatial scales and temporal scales that the resulting approach is truly scale invariant with respect to both spatial scales and temporal scales of the data in both the spatial and the temporal directions. For example, consider scenes with a person

Lindeberg, Tony

62

Time Horizon and Social Scale in Communication  

NASA Astrophysics Data System (ADS)

In 2009 our center (CRED) published a first version of The Psychology of Climate Change Communication. In it, we attempted to summarize facts and concepts from psychological research that could help guide communication. While this work focused on climate change, most of the ideas are at least partly applicable for communication about a variety of natural hazards. Of the many examples in this guide, I mention three. Single-action bias is the human tendency to stop considering further actions that might be needed to deal with a given hazard, once a single action has been taken. Another example is the importance of group affiliation in motivating voluntary contributions to joint action. A third concerns the finding that group participation enhances understanding of probabilistic concepts and promotes action in the face of uncertainty. One current research direction, which goes beyond those included in the above publication, focuses on how time horizons arise in the thinking of individuals and groups, and how these time horizons might influence hazard preparedness. On the one hand, individuals sometimes appear impatient, organizations look for immediate results, and officials fail to look beyond the next election cycle. Yet under some laboratory conditions and in some subcultures, a longer time horizon is adopted. We are interested in how time horizon is influenced by group identity and by the very architecture of planning and decision making. Institutional changes, involving long-term contractual relationships among communities, developers, insurers, and governments, could greatly increase resilience in the face of natural hazards. Communication about hazards, in the context of such long-term contractual relationships might look very different from communication that is first initiated by immediate threat. Another new direction concerns the social scale of institutions and of communication about hazards. Traditionally, insurance contracts share risk among a large number of insurees: each contributes a small premium toward a fund that is adequate to cover the large losses that occasionally occur. Participatory processes are needed that extend risk sharing to larger social scales and that reduce adversarial relationships between insurers, insurees, insurance regulators, and governments that intervene or fail to intervene on an ad hoc rather than a contractual basis.

Krantz, D. H.

2010-12-01

63

Permian-Triassic thermal anomaly of the active margin of South America as a result of plate kinematics reorganization  

NASA Astrophysics Data System (ADS)

From Permian to Triassic times, tectonic plate reorganization provoked Pangaea breakup, counterclockwise rotation of Gondwana, closing of the Paleo-Tethys Ocean and opening of the Neo-Tethys oceanic realm. Meanwhile, the switch from arc volcanism to widespread S-type magmatism along the western South American active margin around 275-265 Ma is symptomatic of the onset of a large-scale Permian-Triassic thermal anomaly (PTTA)affecting the whole margin. Here we report metamorphic and U-Pb geochronological results from the El Oro metamorphic complex in the forearc zone of southwestern Ecuador, which recorded the last step, at 230-225 Ma, of the PTTA. The change in the drift direction of Gondwana from north to east at ca. 270 Ma was related to plate reorganization and provoked the verticalization of the subducted Panthalassa slab. As the slab verticalized, strong heat advection produced a high heat flow beneath the active margin inducing the development of a huge thermal anomaly responsible for the PTTA, which lasted 30 Ma. This voluminous magmatic activity culminated at the Permian-Triassic boundary, and may have contributed to the degradation of life conditions on the Earth surface.

Riel, Nicolas; Jaillard, Etienne; Guillot, Stéphane; Martelat, Jean-Emmanuel; Braun, Jean

2013-04-01

64

Uncertainty, entropy, scaling and hydrological stochastics. 2. Time dependence of hydrological processes and time scaling  

Microsoft Academic Search

The well-established physical and mathematical principle of maximum entropy (ME), is used to explain the distributional and autocorrelation properties of hydrological processes, including the scaling behaviour both in state and in time. In this context, maximum entropy is interpreted as maximum uncertainty. The conditions used for the maximization of entropy are as simple as possible, i.e. that hydrological processes are

DEMETRIS KOUTSOYIANNIS

65

A method to diagnose sources of annular mode time scales  

Microsoft Academic Search

Stratospheric annular mode time scales linked to local temperature variationsTropospheric annular mode time scales linked to surface pressure variationsSurface pressure-temperature cross correlations are weak but highly persistent

Lawrence R. Mudryk; Paul J. Kushner

2011-01-01

66

Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic  

PubMed Central

The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm. PMID:23129649

Onoue, Tetsuji; Sato, Honami; Nakamura, Tomoki; Noguchi, Takaaki; Hidaka, Yoshihiro; Shirai, Naoki; Ebihara, Mitsuru; Osawa, Takahito; Hatsukawa, Yuichi; Toh, Yosuke; Koizumi, Mitsuo; Harada, Hideo; Orchard, Michael J.; Nedachi, Munetomo

2012-01-01

67

Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic.  

PubMed

The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm. PMID:23129649

Onoue, Tetsuji; Sato, Honami; Nakamura, Tomoki; Noguchi, Takaaki; Hidaka, Yoshihiro; Shirai, Naoki; Ebihara, Mitsuru; Osawa, Takahito; Hatsukawa, Yuichi; Toh, Yosuke; Koizumi, Mitsuo; Harada, Hideo; Orchard, Michael J; Nedachi, Munetomo

2012-11-20

68

A multiple time scale solution for the Chapman mechanism  

SciTech Connect

The rate equations representing the Chapman mechanism are solved analytically in the Multiple Time Scale Approximation by the exploitation of their stiffness. The widely different time scales of the reactions in the mechanism can be used to disentangle their effects on the solution. The reactions which bring oxygen into equilibrium with ozone are responsible for the overall stiffness, because their time scales are on the extreme ends of time scale spectrum for the reactions comprising the Chapman mechanism. Since catalytic cycles have similar equilibration reactions which may have time scales bordering the time scales of other reactions involving the catalysts, the method of multiple time scales can also be used to cured the stiffness in the rate equations governing these cycles. These analytical solutions may be incorporated into a numerical algorithm to improve its efficiency for the computation of the rate equations governing the chemistry of the atmosphere.

Chang, B.

1994-06-01

69

A Quaternary Geomagnetic Instability Time Scale  

NASA Astrophysics Data System (ADS)

Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought. Rather, during the Quaternary period, they occur nearly three times as often as full polarity reversals. I will address analytical issues, including the size and consistency of system blanks, that have led to the recognition of minor (1%) discrepencies between the 40Ar/39Ar age for a particular reversal or excursion and the best astrochronologic estimates from ODP sediment cores. For example, re-analysis of lava flows from Haleakala volcano, Maui that record in detail the Matuyama-Brunhes polarity reversal have been undertaken with blanks an order of magntitude smaller and more stable than was common a decade ago. Using the modern astrochronologic calibration of 28.201 Ma for the age of the Fish Canyon sanidine standard, results thus far yield an 40Ar/39Ar age of 772 × 11 ka for the reversal that is identical to the most precise and accurate astrochronologic age of 773 × 2 ka for this reversal from ODP cores. Similarly, new dating of sanidine in the Cerro Santa Rosa I rhyolite dome, New Mexico reveals an age of 932 × 5 ka for the excursion it records, in perfect agreement with astrochronologically dated ODP core records. Work underway aims at refining the 40Ar/39Ar ages that underpin the entire GITS by further eliminating the bias between the radioisotopic and astrochronologically determined ages for several reversals and excursions.

Singer, B. S.

2013-12-01

70

Phreatomagmatic eruption during the buildup of a Triassic carbonate platform (Oman Exotics): eruptive style, associated deformations, and implications on CO2 release by volcanism  

E-print Network

1 Phreatomagmatic eruption during the buildup of a Triassic carbonate platform (Oman Exotics@ujf-grenoble.fr; francois.chauvet@ujf-grenoble.fr Abstract Oman exotics represent remnants of a Triassic carbonate platform in Oman, emphasizing on small- and large-scale deformations of lithified and unlithified s

Paris-Sud XI, Université de

71

Stratigraphy and correlation of Upper Triassic strata between west Texas and eastern New Mexico  

SciTech Connect

Lithostratigraphy and vertebrate biochronology allow precise correlation of Upper Triassic strata between west Texas and eastern New Mexico. Upper Triassic strata are well exposed in west Texas from Oldham to Scurry counties, and are assigned to the Dockum Formation of the Chinle Group. Fossil vertebrates from the Camp Springs and Tecovas Members are of late Carnian age, whereas those from the Copper Member are of early Norian age. Upper Triassic strata in east-central New Mexico, across the Llano Estacado from the west Texas outcrops, correlate as follows: Camper Springs = lower Santa Rose; Tecovas = upper Santa Rosa/Garita Creek; Trujillo = Trujillo ('Cuervo'); Cooper = lower Bull Canyon. Upper Triassic strata in southeastern New Mexico and in Howard and adjacent counties in Texas are the lower Santa Rosa/Camper Springs overlain by mudstones and sandstones that contain late Carnian vertebrates and are informally termed upper member of Dockum Formation. Available data refute several long-held ideas about the Upper Triassic of west Texas. These data demonstrate that: (1) there is a pervasive unconformity at the base of the Dockum Formation that represents much of Triassic time; (2) the Trujillo Member is not correlative with the Santa Rosa of eastern New Mexico: Trujillo is a medial Dockum unit, whereas Santa Rosa is at the base of the Upper Triassic section; (3) very little Dockum mudrock was deposited in lakes; and (4) Dockum rivers flowed almost exclusively to the north, northwest, and west, so there was no closed depositional basin in west Texas during the Late Triassic.

Lucas, S.G. (New Mexico Museum of Natural History, Albuquerque (United States)); Anderson, O.J. (New Mexico Bureau of Mines and Mineral Resources, Socorro (United States))

1992-04-01

72

A late Triassic impact ejecta layer in southwestern Britain.  

PubMed

Despite the 160 or so known terrestrial impact craters of Phanerozoic age, equivalent ejecta deposits within distal sedimentary successions are rare. We report a Triassic deposit in southwestern Britain that contains spherules and shocked quartz, characteristic of an impact ejecta layer. Inter- and intragranular potassium feldspar from the deposit yields an argon-argon age of 214 +/- 2.5 million years old. This is within the age range of several known Triassic impact craters, the two closest of which, both in age and location, are Manicouagan in northeastern Canada and Rochechouart in central France. The ejecta deposit provides an important sedimentary record of an extraterrestrial impact in the Mesozoic that will help to decipher the number and effect of impact events, the source and dynamics of the event that left this distinctive sedimentary marker, and the relation of this ejecta layer to the timing of extinctions in the fossil record. PMID:12434010

Walkden, Gordon; Parker, Julian; Kelley, Simon

2002-12-13

73

A Late Triassic Impact Ejecta Layer in Southwestern Britain  

NASA Astrophysics Data System (ADS)

Despite the 160 or so known terrestrial impact craters of Phanerozoic age, equivalent ejecta deposits within distal sedimentary successions are rare. We report a Triassic deposit in southwestern Britain that contains spherules and shocked quartz, characteristic of an impact ejecta layer. Inter- and intragranular potassium feldspar from the deposit yields an argon-argon age of 214 +/- 2.5 million years old. This is within the age range of several known Triassic impact craters, the two closest of which, both in age and location, are Manicouagan in northeastern Canada and Rochechouart in central France. The ejecta deposit provides an important sedimentary record of an extraterrestrial impact in the Mesozoic that will help to decipher the number and effect of impact events, the source and dynamics of the event that left this distinctive sedimentary marker, and the relation of this ejecta layer to the timing of extinctions in the fossil record.

Walkden, Gordon; Parker, Julian; Kelley, Simon

2002-12-01

74

Paleophysiology of Permian and Triassic Seed Plants  

E-print Network

study of leaf economics of Permian Glossopteris leaves reveals that the plant possessed deciduous leaves and adaptations to continuous light environments. Analysis of Permian and Triassic leaf hydraulic conductance demonstrates that leaf venation density...

Schwendemann, Andrew Benjamin

2012-08-31

75

Scale-Time Kernels and Models  

Microsoft Academic Search

Receptive eld sensitivity proles of visual front-end cells in the LGN and V1 area in intact animals can be measured with increas- ing accuracy, both in the spatial and temporal domain. This urges the need for mathematical models. Scale-space theory, as a theory of (mul- tiscale) apertures as operators on observed data, is concerned with the mathematical modeling of front-end

Bart M. Ter Haar Romeny; Luc Florack; Mads Nielsen

2001-01-01

76

Observation time scale, free-energy landscapes, and molecular symmetry  

E-print Network

Observation time scale, free-energy landscapes, and molecular symmetry David J. Walesa,1 and Peter structures that interconvert on a given time scale are lumped together, the corresponding free-energy surface that are connected by free-energy barriers below a certain threshold. We illustrate this time dependence for some

Salamon, Peter

77

Early Triassic Marine Biotic Recovery: The Predators' Perspective  

PubMed Central

Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent. PMID:24647136

Scheyer, Torsten M.; Romano, Carlo; Jenks, Jim; Bucher, Hugo

2014-01-01

78

Osmium isotope evidence for a large Late Triassic impact event  

PubMed Central

Anomalously high platinum group element concentrations have previously been reported for Upper Triassic deep-sea sediments, which are interpreted to be derived from an extraterrestrial impact event. Here we report the osmium (Os) isotope fingerprint of an extraterrestrial impact from Upper Triassic chert successions in Japan. Os isotope data exhibit a marked negative excursion from an initial Os isotope ratio (187Os/188Osi) of ?0.477 to unradiogenic values of ?0.126 in a platinum group element-enriched claystone layer, indicating the input of meteorite-derived Os into the sediments. The timing of the Os isotope excursion coincides with both elevated Os concentrations and low Re/Os ratios. The magnitude of this negative Os isotope excursion is comparable to those found at Cretaceous–Paleogene boundary sites. These geochemical lines of evidence demonstrate that a large impactor (3.3–7.8?km in diameter) produced a global decrease in seawater 187Os/188Os ratios in the Late Triassic. PMID:24036603

Sato, Honami; Onoue, Tetsuji; Nozaki, Tatsuo; Suzuki, Katsuhiko

2013-01-01

79

Time\\/scale-adjusted dyadic wavelet packet bases  

Microsoft Academic Search

This paper generalizes the dyadic wavelet packet bases (DWP), developed by Coifman and Wickerhauser, to time\\/scale-adjusted DWP bases. These generalized DWP bases provide more flexibility in matching the time-scale characteristics of the input signal. Development of these generalized bases is achieved by combining the previously defined time-invariant DWP bases of Pesquet, Krim, Carfantan, and Proakis with a generalized scale sampling.

Stephen P. del Marco

1996-01-01

80

A Real-Time Framework for Video Time and Pitch Scale Modification  

Microsoft Academic Search

A framework is presented which addresses the issues related to the real-time implementation of synchronized video and audio time-scale and pitch-scale modification algorithms. It allows for seamless real-time transition between continually varying, independent time-scale and pitch-scale parameters arising as a result of manual or automatic intervention. We illuminate the problems which arise in a real-time context as well as provide

Ivan Damnjanovic; Dan Barry; David Dorran; Joshua D. Reiss

2010-01-01

81

Local-time effect on small space-time scale  

E-print Network

The paper presents an investigation of local-time effect - one of the manifestations of macroscopic fluctuations phenomena. Was shown the existence of the named effect for longitudinal distance between locations of measurements up to 500 meters. Also a structure of intervals distribution in neighborhood of local-time peak was studied and splitting of the peak was found out. Obtained results lead to conclusion about sharp anisotropy of space-time.

V. A. Panchelyuga; V. A. Kolombet; M. S. Panchelyuga; S. E. Shnoll

2006-10-18

82

General Entanglement Scaling Laws from Time Evolution  

NASA Astrophysics Data System (ADS)

We establish a general scaling law for the entanglement of a large class of ground states and dynamically evolving states of quantum spin chains: we show that the geometric entropy of a distinguished block saturates, and hence follows an entanglement-boundary law. These results apply to any ground state of a gapped model resulting from dynamics generated by a local Hamiltonian, as well as, dually, to states that are generated via a sudden quench of an interaction as recently studied in the case of dynamics of quantum phase transitions. We achieve these results by exploiting ideas from quantum information theory and tools provided by Lieb-Robinson bounds. We also show that there exist noncritical fermionic systems and equivalent spin chains with rapidly decaying interactions violating this entanglement-boundary law. Implications for the classical simulatability are outlined.

Eisert, Jens; Osborne, Tobias J.

2006-10-01

83

Milankovitch and sub-Milankovitch cycles of the Early Triassic Daye Formation, South China and their geochronological and paleoclimatic implications  

NASA Astrophysics Data System (ADS)

The most profound mass extinction in the Phanerozoic occurred at the end of the Permian, with global loss of nearly 90% of marine invertebrate species and 70% of terrestrial vertebrate genera. Recent studies suggested that volcanisms represented by the Siberian Trap were most likely cause of the end-Permian extinction. The post-extinction periods in the Early Triassic was characterized by low biodiversity, reduced abundance and size of invertebrates, hiatus in coal deposition, anomalously high sediment fluxes, and large perturbations of the carbon cycle, which have been interpreted as the consequence of persistently unfavorable environmental conditions. However, the time framework for the Early Triassic geological, biological and geochemical events is traditionally established by conodont biostratigraphy, but the absolute duration of condont biozones are not well constrained. In this study, a rock magnetic cyclostratigraphy, based on high-resolution analysis (2440 samples) of magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) intensity variations, was developed for the 55.1-m-thick, Early Triassic Daye Formation at the Daxiakou section, Hubei province in South China. The Daye Formation shows exceptionally well-preserved lithological cycles with alternations of thin-bedded mudstone, marl and limestone, which are closely tracked by the MS and ARM variations. Power spectral, wavelet and amplitude modulation (AM) analysis of the ARM and MS series reveal strong evidence for the presence of Milankovitch to sub-Milankovitch frequencies dominated by precession index signal and 4-5 ka cycles. Cycles expressed by variations in MS and ARM were likely controlled by the input of fine-grained detrital magnetite, which in turn may be driven by astronomically induced changes in monsoon intensity in the equatorial eastern Tethys during the Early Triassic greenhouse period. On the basis of the 100-ka tuning results, the astronomically constrained duration of the Induan stage is 1.162 Ma, with the Griesbachian and Dienerian substage of 491ka and 671 ka, respectively. The new astronomical time scale also provides time constraints for the conodont and bivalve biozones, the carbonate carbon isotope (?13C) records and magnetic polarity zones of the Lower Triassic Daye Formation. Time constraints for the conodont biozones include 34 ka for Hindeodus parvus , 24 ka for Isarcicella stachei-I. isarcica, 367 ka for Neogondolella planate-Ng. carinata, 66 ka for Neogondolella discreta, 255 ka for Neospathodus kummeli and 416 ka for Neospathodus dieneri. The Early Smithian negative ?13C shift near the Indun/Olenekian boundary may have happened within 430 ka. Global comparison indicates that Milankovitch and 4-5 ka sub-Milankovitch forcing depositional rhythms may have been common in tropical and sub-tropical carbonate platforms during Early and Middle Triassic time. The ultimate control on the 4-5 ka cycles may have been millennial-scale fluctuations in solar insolation.

Wu, H.; Zhang, S.; Feng, Q.; Jiang, G.; Li, H.; Yang, T.

2011-12-01

84

Improved phase vocoder time-scale modification of audio  

Microsoft Academic Search

The phase vocoder is a well established tool for time scaling and pitch shifting speech and audio signals via modification of their short-time Fourier transforms (STFTs). In contrast to time-domain time-scaling and pitch-shifting techniques, the phase vocoder is generally considered to yield high quality results, especially for large modification factors and\\/or polyphonic signals. However, the phase vocoder is also known

Jean Laroche; Mark Dolson

1999-01-01

85

Permo-Triassic vertebrate extinctions: A program  

NASA Technical Reports Server (NTRS)

Since the time of the Authors' study on this subject, a great deal of new information has become available. Concepts of the nature of extinctions have changed materially. The Authors' conclusion that a catastrophic event was not responsible for the extinction of vertebrates has modified to the extent that hypotheses involving either the impact of a massive extra-terrestrial body or volcanism provide plausible but not currently fully testable hypotheses. Stated changes resulted in a rapid decrease in organic diversity, as the ratio of origins of taxa to extinctions shifted from strongly positive to negative, with momentary equilibrium being reached at about the Permo-Triassic boundary. The proximate causes of the changes in the terrestrial biota appear to lie in two primary factors: (1) strong climatic changes (global mean temperatures, temperature ranges, humidity) and (2) susceptibility of the dominant vertebrates (large dicynodonts) and the glossopteris flora to disruption of the equlibrium of the world ecosystem. The following proximate causes have been proposed: (1) rhythmic fluctuations in solar radiation, (2) tectonic events as Pangea assembled, altering land-ocean relationships, patterns of wind and water circulation and continental physiography, (3) volcanism, and (4) changes subsequent to impacts of one or more massive extra terrestrial objects, bodies or comets. These hypotheses are discussed.

Olson, E. C.

1988-01-01

86

THE AERODYNAMICS OF THE BRITISH LATE TRIASSIC KUEHNEOSAURIDAE  

E-print Network

THE AERODYNAMICS OF THE BRITISH LATE TRIASSIC KUEHNEOSAURIDAE by KOEN STEIN* , COLIN PALMER been limited. Here, we provide a thorough aerodynamic analysis of both genera of British kuehneosaur words: Kuehneosauridae, Diapsida, Late Triassic, glid- ing, aerodynamics. The Kuehneosauridae

Benton, Michael

87

Permian–Triassic boundary magnetostratigraphy from the Southern Alps (Italy)  

Microsoft Academic Search

Palaeomagnetic investigations of Permian–Triassic boundary sections in the Dolomites provided a magnetostratigraphy for the uppermost part of the Permian Bellerophon Formation to the Lower Triassic Werfen Formation. Magnetite was the dominant magnetic component in most of the samples, while the presence of hematite was characteristic for the Tesero horizon, which is regarded as the immediate Permian–Triassic boundary layer. The palaeomagnetic

Robert Scholger; Hermann J. Mauritsch; Rainer Brandner

2000-01-01

88

TriassicJurassic boundary events: Problems, progress, possibilities 1. Problems  

E-print Network

As for most geological period boundaries, the Triassic­Jurassic (T­J) transition, 200 million years agoEditorial Triassic­Jurassic boundary events: Problems, progress, possibilities 1. Problems to reconstruct past events, a physical record of their passing is essential. Here again the Triassic­Jurassic

McRoberts, Christopher A.

89

Water Peak Suppression: Time-Frequency vs TimeScale Approach  

Microsoft Academic Search

Wavelets are the most popular time-scale analysis tool. A well-known application of wavelets in nuclear magnetic resonance spectroscopy is water peak extraction\\/suppression. However, spectroscopists are more familiar with frequency than scale. So, from a spectroscopist point of view, a time-scale analysis tool (i.e., wavelets) is not natural and a time-frequency approach would be much more satisfactory. We explain a time-frequency

Jean-Pierre Antoine; Alain Coron; Jean-Marie Dereppe

2000-01-01

90

Liquidity Spillover in International Stock Markets through Distinct Time Scales  

PubMed Central

This paper identifies liquidity spillovers through different time scales based on a wavelet multiscaling method. We decompose daily data from U.S., British, Brazilian and Hong Kong stock markets indices in order to calculate the scale correlation between their illiquidities. The sample is divided in order to consider non-crisis, sub-prime crisis and Eurozone crisis. We find that there are changes in correlations of distinct scales and different periods. Association in finest scales is smaller than in coarse scales. There is a rise on associations in periods of crisis. In frequencies, there is predominance for significant distinctions involving the coarsest scale, while for crises periods there is predominance for distinctions on the finest scale. PMID:24465918

Righi, Marcelo Brutti; Vieira, Kelmara Mendes

2014-01-01

91

Liquidity spillover in international stock markets through distinct time scales.  

PubMed

This paper identifies liquidity spillovers through different time scales based on a wavelet multiscaling method. We decompose daily data from U.S., British, Brazilian and Hong Kong stock markets indices in order to calculate the scale correlation between their illiquidities. The sample is divided in order to consider non-crisis, sub-prime crisis and Eurozone crisis. We find that there are changes in correlations of distinct scales and different periods. Association in finest scales is smaller than in coarse scales. There is a rise on associations in periods of crisis. In frequencies, there is predominance for significant distinctions involving the coarsest scale, while for crises periods there is predominance for distinctions on the finest scale. PMID:24465918

Righi, Marcelo Brutti; Vieira, Kelmara Mendes

2014-01-01

92

Triassic actinopterygian fishes: the recovery after the end-Permian crisis.  

PubMed

In the last 15 years, the discovery of several new actinopterygian fish faunas from the Early and Middle Triassic of the Tethys, cast new light on the timing, speed and range of their recovery after the end-Permian crisis. In addition to several new taxa having been described, the stratigraphical and geographical record of many others have been greatly extended. In fact, most of the new fossiliferous sites are in southern China, thus at the Eastern end of the Tethys, and furthermore a few are somewhat older (Chaohu, Panxian, Luoping) than the major classical Western Tethys sites (Monte San Giorgio). Following these new finds, it is possible to have a better definition of the Triassic recovery stages. Indeed, after a quite short phase till the end of the Smithian (Olenekian, Early Triassic) in which a rather consistent fauna was present all around the Pangea coasts, a major radiation occurred in the Early-Middle Anisian after the new Middle Triassic fish fauna already appeared in the late Early Triassic, thus occuring well before what was previously supposed from the Alps localities. Furthermore, the new assemblages from southern China point to an early broader differentiation among the basal neopterygians rather than in the 'subholosteans', the group that was then dominant in the Western Tethys since the Late Anisian. It stands that during the Norian a new basal neopterygian radiation gave rise to several new branches that dominated the remaining part of the Mesozoic. PMID:24148549

Tintori, Andrea; Hitij, Tomaž; Jiang, Dayong; Lombardo, Cristina; Sun, Zuoyu

2014-08-01

93

Simple models and time scales in the dynamo effect  

Microsoft Academic Search

The dynamo effect has been studied for 50 years, starting from the simple homopolar dynamo of Bullard. Numerical calculations on simple models, such as the crossed dynamos of Rikitake, display large oscillations and brutal reversals. The present Note puts emphasis on time scales. One scale ?1, purely electromagnetic, describes inductive decay (the frequency at which the skin depth is the

Philippe Nozières

2008-01-01

94

EXPLOITING MULTIPLE TIME SCALE PROPERTIES FOR FAST SIMULATION ALGORITHMS  

Microsoft Academic Search

Adaptive step size algorithms are presented making use of the muliple time scale character of power systems. The pa- per analyzes methods using multiple step sizes simultane- ously (multirate methods) and methods adapting the inte- gration step size in time. The resulting algorithm covers transients of all time ranges, from electromagnetic to elec- tromechanical phenomena.

Markus Poller; Martin Schmieg

95

Modes and emergent time scales of embayed beach dynamics  

NASA Astrophysics Data System (ADS)

In this study, we use a simple numerical model (the Coastline Evolution Model) to explore alongshore transport-driven shoreline dynamics within generalized embayed beaches (neglecting cross-shore effects). Using principal component analysis (PCA), we identify two primary orthogonal modes of shoreline behavior that describe shoreline variation about its unchanging mean position: the rotation mode, which has been previously identified and describes changes in the mean shoreline orientation, and a newly identified breathing mode, which represents changes in shoreline curvature. Wavelet analysis of the PCA mode time series reveals characteristic time scales of these modes (typically years to decades) that emerge within even a statistically constant white-noise wave climate (without changes in external forcing), suggesting that these time scales can arise from internal system dynamics. The time scales of both modes increase linearly with shoreface depth, suggesting that the embayed beach sediment transport dynamics exhibit a diffusive scaling.

Ratliff, Katherine M.; Murray, A. Brad

2014-10-01

96

A variable resolution radio-frequency spectrometer employing time scaling  

Microsoft Academic Search

The effective resolution of a constant resolution filter spectrometer is varied by employing a time-scaling stage between data acquisition and spectral computation. For low-input data rates multiplexing can be introduced to analyze several signals simultaneously.

J. L. Yen; S. KITAOKA; Komukai Toshiba-cho; H. IIZUKA

1970-01-01

97

Kibble-Zurek mechanism and finite-time scaling  

NASA Astrophysics Data System (ADS)

The Kibble-Zurek (KZ) mechanism has been applied to a variety of systems ranging from low-temperature Bose-Einstein condensations to grand unification scales in particle physics and cosmology and from classical phase transitions to quantum phase transitions. Here, we show that finite-time scaling (FTS) provides a detailed improved understanding of the mechanism. In particular, the finite time scale, which is introduced by the external driving (or quenching) and results in FTS, is the origin of the division of the adiabatic regimes from the impulse regime in the KZ mechanism. The origin of the KZ scaling for the defect density, generated during the driving through a critical point, is not that the correlation length ceases growing in the nonadiabatic impulse regime, but rather, is that it is taken over by the effective finite length scale corresponding to the finite time scale. We also show that FTS accounts well for and improves the scaling ansatz proposed recently by Liu, Polkovnikov, and Sandvik, [Phys. Rev. B 89, 054307 (2014), 10.1103/PhysRevB.89.054307]. Further, we show that their universal power-law scaling form applies only to some observables in cooling but not to heating. Even in cooling, it is invalid either when an appropriate external field is present. However, this finite-time-finite-size scaling calls for caution in application of FTS. Detailed scaling behaviors of the FTS and finite-size scaling, along with their crossover, are explicitly demonstrated, with the dynamic critical exponent z being estimated for two- and three-dimensional Ising models under the usual Metropolis dynamics. These values of z are found to give rise to better data collapses than the extant values do in most cases but take on different values in heating and cooling in both two- and three-dimensional spaces.

Huang, Yingyi; Yin, Shuai; Feng, Baoquan; Zhong, Fan

2014-10-01

98

Diffusion Time-Scale of Porous Pressure-Sensitive Paint  

NASA Technical Reports Server (NTRS)

Pressure-sensitive paint (PSP) is an optical pressure sensor that utilizes the oxygen quenching of luminescence. PSP measurements in unsteady aerodynamic flows require fast time response of the paint. There are two characteristic time-scales that are related to the time response of PSP. One is the luminescent lifetime representing an intrinsic physical limit for the achievable temporal resolution of PSP. Another is the time-scale of oxygen diffusion across the PSP layer. When the time-scale of oxygen diffusion is much larger than the luminescent lifetime, the time response of PSP is controlled by oxygen diffusion. In a thin homogenous polymer layer where diffusion is Fickian, the oxygen concentration 1021 can be described by the diffusion equation in one-dimension.

Liu, Tianshu; Teduka, Norikazu; Kameda, Masaharu; Asai, Keisuke

2001-01-01

99

Two-Time-Scale Approximation for Wonham Filters  

Microsoft Academic Search

Abstract—This paper is concerned with approximation of Wonham filters. A focal point is that the underlying hidden Markov chain has a large state space. To reduce computational complexity, a two-time-scale approach is developed. Under time scale separation, the state space of the underlying Markov chain is divided into a number of groups such that the chain jumps rapidly within each

Qing Zhang; Gang George Yin; Johb B. Moore

2007-01-01

100

Large Deviations for Two-Time-Scale Diffusions, with Delays  

SciTech Connect

We consider the problem of large deviations for a two-time-scale reflected diffusion process, possibly with delays in the dynamical terms. The Dupuis-Ellis weak convergence approach is used. It is perhaps the most intuitive and simplest for the problems of concern. The results have applications to the problem of approximating optimal controls for two-time-scale systems via use of the averaged equation.

Kushner, Harold J., E-mail: hjk@dam.brown.ed [Brown University, Applied Math (United States)

2010-12-15

101

Time scale for point-defect equilibration in nanostructures  

SciTech Connect

Molecular dynamics simulations of high-temperature annealing are performed on nanostructured materials enabling direct observation of vacancy emission from planar defects (i.e., grain boundaries and free surfaces) to populate the initially vacancy-free grain interiors on a subnanosecond time scale. We demonstrate a universal time-length scale correlation that governs these re-equilibration processes, suggesting that nanostructures are particularly stable against perturbations in their point-defect concentrations, caused for example by particle irradiation or temperature fluctuations.

Millett, Paul C.; Wolf, Dieter; Desai, Tapan [Materials Science Department, Idaho National Laboratory, Idaho Falls, Idaho 83415 (United States); Yamakov, Vesselin [National Institute of Aerospace, Hampton, Virginia 23693 (United States)

2008-10-20

102

Time Scales of Observation and Ontological Levels of Reality  

Microsoft Academic Search

My goal is to conceive how the reality would look like for hypothetical creatures that supposedly perceive on time scales\\u000a much faster or much slower than that of us humans. To attain the goal, I propose modelling in two steps. At step one, we have\\u000a to single out a unified parameter that sets time scale of perception. Changing substantially the

Alexey Alyushin

2010-01-01

103

Signatures of discrete scale invariance in Dst time series  

NASA Astrophysics Data System (ADS)

Self-similar systems are characterized by continuous scale invariance and, in response, the existence of power laws. However, a significant number of systems exhibits discrete scale invariance (DSI) which in turn leads to log-periodic corrections to scaling that decorate the pure power law. Here, we present the results of a search of log-periodic corrections to scaling in the squares of Dst index increments which are taken as proxies of the energy dissipation rate in the magnetosphere. We show that Dst time series exhibit DSI and discuss the consequence of this feature, as well as the possible implications of Dst DSI on space weather forecasting efforts.

Balasis, Georgios; Papadimitriou, Constantinos; Daglis, Ioannis A.; Anastasiadis, Anastasios; Athanasopoulou, Labrini; Eftaxias, Konstantinos

2011-07-01

104

Phenomenology of scale-dependent space-time dimension  

E-print Network

Loop-mediated processes characterized by dynamical scale M indirectly measure space-time dimension d at this scale. Assuming the latter to be scale-dependent d=d(L) and taking as examples B-oscillations and muon (g-2) experimental results we address the question about constraints put by this data on 4-d(L). It is shown that sensitivity is lost for 1/L around 350 GeV, and any value of d(L) between 2 and 5 at this scale is compatible with the data.

V. I. Shevchenko

2009-03-03

105

Biogeochemistry of the Triassic-Jurassic Boundary  

NASA Astrophysics Data System (ADS)

New biostratigraphic and biogeochemical data are presented from Triassic-Jurassic (Tr-J) boundary sections at Kennecott Point, Queen Charlotte Islands (QCI), Canada, Muller Canyon, Nevada, USA, and Marokopa Beach, New Zealand. The New Zealand record shows two negative excursions in ?13Corg of approximately 2‰ associated with the Tr-J transition. The QCI and Nevada boundary sections show a consistent isotopic trend indicative of multiple major perturbations to the carbon cycle: one negative excursion in ?13Corg of 2‰ at the boundary and one positive excursion of 3 to 5‰ following the boundary. The post-Tr-J boundary positive excursion is especially prominent in boundary sections from QCI, where the high organic content of the black shales makes the rocks suitable for a survey of lipid biomarkers. New GC-MS data are presented from this locality, revealing changes in the distribution and abundance of alkanes, hopanes, and steranes across the Tr-J transition. Litho-, bio- and chemostratigraphy from these boundary localities do not support a single impact cause for the late Triassic extinctions, although impact events such as the Manicouagan may well have exerted significant stress on a biosphere still recovering from the Permian-Triassic mass extinction. The data support the idea of a degraded late Triassic environment persisting for millions of years and characterized by low atmospheric oxygen and high carbon dioxide associated with Central Atlantic Magmatic Province volcanism. Global warming and sea level change may have led to destabilization of seafloor methane hydrates and runaway greenhouse conditions.

Williford, K. H.; Ward, P. D.; Garrison, G. H.

2006-12-01

106

Early ornithischian dinosaurs: the Triassic record  

Microsoft Academic Search

Ornithischian dinosaurs are one of the most taxonomically diverse dinosaur clades during the Mesozoic, yet their origin and early diversification remain virtually unknown. In recent years, several new Triassic ornithischian taxa have been proposed, mostly based upon isolated teeth. New discoveries of skeletal material of some of these tooth taxa indicate that these teeth can no longer be assigned to

Randall B. Irmis; William G. Parker; Sterling J. Nesbitt; Jun Liu

2007-01-01

107

Middle Triassic source rocks in north Lombardy  

SciTech Connect

Using molecular geochemistry techniques, we established that the Perledo-Verenna and Meride Formations (Middle Triassic, southern Alps) represent the source rocks of the Gaggiano and Villafortuna deep oil fields discovered 40 km northwest of Milan. To find the geological factors which control the areal extent thickness and organic matter distribution relative to these sequences, a sedimentological and geochemical study was undertaken.

Gnaccolini, M.; Gaetani, M.; Mattavelli, L.; Leoni, C.; Poliani, G.; Riva, A.

1988-08-01

108

Characteristic Time Scales of Characteristic Magmatic Processes and Systems  

NASA Astrophysics Data System (ADS)

Every specific magmatic process, regardless of spatial scale, has an associated characteristic time scale. Time scales associated with crystals alone are rates of growth, dissolution, settling, aggregation, annealing, and nucleation, among others. At the other extreme are the time scales associated with the dynamics of the entire magmatic system. These can be separated into two groups: those associated with system genetics (e.g., the production and transport of magma, establishment of the magmatic system) and those due to physical characteristics of the established system (e.g., wall rock failure, solidification front propagation and instability, porous flow). The detailed geometry of a specific magmatic system is particularly important to appreciate; although generic systems are useful, care must be taken to make model systems as absolutely realistic as possible. Fuzzy models produce fuzzy science. Knowledge of specific time scales is not necessarily useful or meaningful unless the hierarchical context of the time scales for a realistic magmatic system is appreciated. The age of a specific phenocryst or ensemble of phenocrysts, as determined from isotopic or CSD studies, is not meaningful unless something can be ascertained of the provenance of the crystals. For example, crystal size multiplied by growth rate gives a meaningful crystal age only if it is from a part of the system that has experienced semi-monotonic cooling prior to chilling; crystals entrained from a long-standing cumulate bed that were mechanically sorted in ascending magma may not reveal this history. Ragged old crystals rolling about in the system for untold numbers of flushing times record specious process times, telling more about the noise in the system than the life of typical, first generation crystallization processes. The most helpful process-related time scales are those that are known well and that bound or define the temporal style of the system. Perhaps the most valuable of these times comes from the observed durations and rates of volcanism. There can be little doubt that the temporal styles of volcanism are the same as those of magmatism in general. Volcano repose times, periodicity, eruptive fluxes, acoustic emission structures, lava volumes, longevity, etc. must also be characteristic of pluton-dominated systems. We must therefore give up some classical concepts (e.g., instantaneous injection of crystal-free magma as an initial condition) for any plutonic/chambered system and move towards an integrated concept of magmatism. Among the host of process-related time scales, probably the three most fundamental of any magmatic system are (1) the time scale associated with crystal nucleation (J) and growth (G) (tx}=C{1(G3 J)-{1}/4; Zieg & Marsh, J. Pet. 02') along with the associated scales for mean crystal size (L) and population (N), (2) the time scale associated with conductive cooling controlled by a local length scale (d) (tc}=C{2 d2/K; K is thermal diffusivity), and (3) the time scale associated with intra-crystal diffusion (td}=C{3 L2/D; D is chemical diffusivity). It is the subtle, clever, and insightful application of time scales, dovetailed with realistic system geometry and attention paid to the analogous time scales of volcanism, that promises to reveal the true dynamic integration of magmatic systems.

Marsh, B. D.

2004-05-01

109

Geomagnetic secular variations at the Permo-Triassic boundary  

NASA Astrophysics Data System (ADS)

Study of changes in geomagnetic secular variations through geological time is essential to document the Earth's magnetic field evolution and provides an important constraint for geodynamo modeling. Moreover, knowledge of the secular variations value for any specific geological epoch (paleosecular variations - PSV) may give an additional tool to constrain the duration of emplacement and cooling of various magmatic bodies including flows, dykes and sills. In this report we present the result of study of the PSV at the Permo-Triassic boundary (~252 Ma), based on the paleomagnetic data, obtained from numerous (N>100) volcanic flows of the Siberian traps exposed in series of sections located in Norilsk and Maymecha-Kotuy regions in the North-West and North of the Siberian platform. Our data, taken together with similar data from other regions (Sementau, East Kazakhstan; Emeichan, China) indicates that the amplitude of PSV at the Permo-Triassic boundary was about the same or a little lower than in Late Cenozoic during last 5 milllions years. The low (comparing with expected one) value of PSV recorded in several large sills from Angara-Bratsk region (southern Siberian platform) indicates that these sills was formed very fast during the time interval less than, at least, several thousand years. Especially this conclusion is interesting for so called Tolstomyss sill, which, in fact, represents a huge field of associated tuffs, sills, dykes and volcanics, extended over the distance more than 200 km. This result can be considered as a further indication of very fast emplacement of the Siberian traps and their link with the Permo-Triassic catastrophe.

Pavlov, Vladimir; Veselovskiy, Roman; Fetisova, Anna; Latyshev, Anton; Fluteau, Frederic

2014-05-01

110

On the time scale of energy transport in the sun  

NASA Astrophysics Data System (ADS)

It is pointed out that the time scale of energy transport in the Sun is the Kelvin Helmholtz time scale, of order 3×107 years, roughly 100 times longer than the photon-diffusion time estimated by Mitalas and Sills (1992). The difference corresponds to a factor U gas/U rad, the ratio of thermal energy density to radiation energy density. Thus the heat transport, even when mediated by photons, is slowed down by the large heat capacity of the star. A numerical example calculation is presented.

Stix, Michael

2003-01-01

111

Supraregional seismites in Triassic - Jurassic boundary strata  

NASA Astrophysics Data System (ADS)

The end-Triassic mass extinction event (201.564 Ma) was synchronous with the earliest volcanic phase during the emplacement of the Central Atlantic Magmatic Province (CAMP), a large igneous province (LIP) formed during the initial breakup of Pangea. Volcanic degassing of CO2 and other volatile gases, and/or thermogenic methane, from the CAMP is generally regarded as the main cause of the end-Triassic biotic crisis. However, discrepancies in the durations of the ETE (50 Kyrs) and the CAMP volcanism (600 Kyrs) as well as temporal offsets between carbon cycle perturbations and biotic turnovers suggest a more complex scenario that require further studies of the temporal succession of events in Triassic-Jurassic (TJ) boundary strata. Here, we present and examine multiple episodes of soft-sediment deformation (seismite) within uppermost Rhaetian marine and terrestrial strata of Denmark, Sweden and Germany. These seismites are stratigraphically constrained by palynology and C-isotopes to the latest Rhaetian, and are synchronous to the single seismite layer from the UK, which similarly predates the T/J boundary, and has been explained by an extraterrestrial bolide impact. Instead, we argue that the multiple episodes of soft-sediment deformation, interbedded by undisturbed strata, were formed from repeated intense earthquake activity restricted to an interval within the latest Rhaetian bracketed by two negative excursions in ?13C and also containing palynological evidence for deforestation and fern proliferation. The fact that these biotic changes coincide with repeated seismic activity has implications for the end-Triassic extinction and the CAMP scenario. We discuss the temporal position of the seismites in regards to other end-Triassic events, and argue that their supraregional distribution in pre-TJ-boundary strata of NW Europe may be linked to intensified earthquake activity during CAMP emplacement, rather than an extraterrestrial impact.

Lindström, Sofie; Pedersen, Gunver K.; van de Schootbrugge, Bas; Johansson, Leif; Petersen, Henrik I.; Dybkjær, Karen; Weibel, Rikke; Hansen, Katrine H.; Erlström, Mikael; Alwmark, Carl; Nielsen, Lars Henrik; Oschmann, Wolfgang; Tegner, Christian

2014-05-01

112

Simple models and time scales in the dynamo effect  

NASA Astrophysics Data System (ADS)

The dynamo effect has been studied for 50 years, starting from the simple homopolar dynamo of Bullard. Numerical calculations on simple models, such as the crossed dynamos of Rikitake, display large oscillations and brutal reversals. The present Note puts emphasis on time scales. One scale ?, purely electromagnetic, describes inductive decay (the frequency at which the skin depth is the size of the system), the other ? is magnetohydrodynamic, controlling the exchanges of kinetic and magnetic energies. Usually ???: a clear separation of time scales makes the physics much more transparent. We show why sharp reversals must be expected, starting either from the slow or from the fast time scale. Such a comparison clarifies the issue. To cite this article: P. Nozières, C. R. Physique 9 (2008).

Nozières, Philippe

2008-09-01

113

Evolution of a Permo-Triassic sedimentary melange, Grindstone terrane, east-central Oregon  

USGS Publications Warehouse

Perceives the Grindstone rocks to be a sedimentary melange composed of Paleozoic limestone slide and slump blocks that became detached from a carbonate shelf fringing a volcanic knoll or edifice in Late Permian to Middle Triassic time and were intermixed with Permian and Triassic slope to basinal clastic and volcaniclastic rocks in a forearc basin setting. Paleogeographic affinities of the Grindstone limestone faunas and volcaniclastic debris in the limestone and clastic rocks all indicate deposition in promixity to an island-arc system near the North American craton. -from Authors

Blome, C.D.; Nestell, M.K.

1991-01-01

114

Time scale construction from multiple sources of information (Invited)  

NASA Astrophysics Data System (ADS)

Geological age estimates are provided by diverse chronometers, such as radiometric measurements, astrochronology, and the spacing of magnetic anomalies recorded on mid-ocean ridges by seafloor spreading. These age estimates are affected by errors that can be systematic (e.g., biased radiometric dates due to imperfect assumptions) or random (e.g., imprecise recording of astronomical cycles in sedimentary records). Whereas systematic errors can be reduced by improvements in technique and calibration, uncertainties due to random errors will always be present and need to be dealt with. A Bayesian framework can be used to construct an integrated time scale that is based on several uncertain sources of information. In this framework, each piece of data and the final time scale have an associated probability distribution that describes their uncertainty. The key calculation is to determine the uncertainty in the time scale from the uncertain data that constrain it. In practice, this calculation can be performed by Monte Carlo sampling. In Markov chain Monte Carlo algorithms, the time scale is iteratively perturbed and the perturbed time scale is accepted or rejected depending on how closely it fits the data. The final result is a large ensemble of possible time scales that are consistent with all the uncertain data; while the average of this ensemble defines a 'best' time scale, the ensemble variability quantifies the time scale uncertainty. An example of this approach is the M-sequence (Late Jurassic-Early Cretaceous, ~160-120 Ma) MHTC12 geomagnetic polarity time scale (GPTS) of Malinverno et al. (2012, J. Geophys. Res., B06104, doi:10.1029/2012JB009260). Previous GPTSs were constructed by interpolating between dated marine magnetic anomalies while assuming constant or smoothly varying spreading rates. These GPTSs were typically based on magnetic lineations from one or a few selected spreading centers, and an undesirable result is that they imply larger spreading rate fluctuations on other ridges. On the other hand, the Monte Carlo algorithm used in MHTC12 makes it easy to sample GPTSs that result in small spreading rate variations over multiple spreading centers (in the Western Pacific, North Atlantic, and Indian Ocean NW of Australia). MHTC12 also accounts for the duration of five polarity chrons estimated from floating astrochronologies (CM0r through CM3r). A Bayesian framework and Monte Carlo sampling offer a useful strategy to construct time scales that incorporate different types of chronological information, have a quantified uncertainty, and can be easily updated with additional data that may become available in the future.

Malinverno, A.

2013-12-01

115

The Late Permian - Early Triassic Evolution of the Western Barents Sea  

NASA Astrophysics Data System (ADS)

The Permian-Triassic boundary was temporarily associated with formation of the Siberian Traps Large Igneous Province. Major Late Permian and Early Triassic subsidence is documented by seismic reflection data in the East Barents Basin. Further west, basin subsidence and an abrupt change from carbonate and evaporite deposition to clastic sedimentation is recorded by industry seismic and well data in the south and onshore Svalbard in the north. The Permian-Triassic boundary is commonly not preserved either due to non-deposition or erosion, but could be locally preserved in depocenters. A major northwestward prograding clastic delta sourced from the Uralian hinterland reached the Norwegian (western) part of the Barents Sea in the earliest Triassic (Induan). We suggest that the large-scale changes in paleoenviroment, vertical motions, and sedimentary processes in the Barents Sea region were strongly influenced by large-scale changes in mantle dynamics and paleoclimate caused by the Siberian Traps igneous event. By analogy with other Large Igneous Provinces, such as the North Atlantic Volcanic Province, regional uplift and subsidence associated with a rising mantle plume may precede the arrival of the plume at the base of the lithosphere with 10's of millions of years. In contrast, the paleoenvironmental changes and the associated extinction were mainly caused by rapid intrusion of magma into sedimentary basins and voluminous igneous eruptions.

Planke, S.; Svensen, H.; Faleide, J.; Myklebust, R.

2013-12-01

116

The "terminal Triassic catastrophic extinction event" in perspective: a review of carboniferous through Early Jurassic terrestrial vertebrate extinction patterns  

USGS Publications Warehouse

A catastrophic terminal Triassic extinction event among terrestrial vertebrates is not supported by available evidence. The current model for such an extinction is based on at least eight weak or untenable assumptions: (1) a terminal Triassic extinction-inducing asteroid impact occurred, (2) a terminal Triassic synchronous mass extinction of terrestrial vertebrates occurred, (3) a concurrent terminal Triassic marine extinction occurred, (4) all terrestrial vertebrate families have similar diversities and ecologies, (5) changes in familial diversity can be gauged accurately from the known fossil record, (6) extinction of families can be compared through time without normalizing for changes in familial diversity through time, (7) extinction rates can be compared without normalizing for differing lengths of geologic stages, and (8) catastrophic mass extinctions do not select for small size. These assumptions have resulted in unsupportable and (or) erroneous conclusions. Carboniferous through Early Jurassic terrestrial vertebrate families mostly have evolution and extinction patterns unlike the vertebrate evolution and extinction patterns during the terminal Cretaceous event. Only the Serpukhovian (mid Carboniferous) extinction event shows strong analogy to the terminal Cretaceous event. Available data suggest no terminal Triassic extinction anomaly, but rather a prolonged and nearly steady decline in the global terrestrial vertebrate extinction rate throughout the Triassic and earliest Jurassic. ?? 1992.

Weems, R.E.

1992-01-01

117

Plate tectonic controls on atmospheric CO2 levels since the Triassic  

NASA Astrophysics Data System (ADS)

Climate trends on time-scales of 10's to 100's of millions of years are controlled by changes in solar luminosity, continent distribution and atmosphere composition. Plate tectonics affect geography, but also atmosphere composition through volcanic degassing of CO2 at subduction zones and mid-ocean ridges. So far, such degassing estimates were based on reconstructions of ocean floor production for the last 150 Million years (Myr) and indirectly, through sea level inversion before 150 Myr. Here we quantitatively estimate CO2 degassing by reconstructing lithosphere subduction evolution, using recent advances in combining global plate reconstructions and present-day structure of the mantle. First, we estimate that since the Triassic (250-200 Myr) until Present, the total paleo-subduction zone length reached up to ~200% of the present-day value. Comparing our subduction zone lengths with previously reconstructed ocean-crust production rates over the past 140 Myr suggests average global subduction rates have been constant, ~6 cm/year: Higher ocean-crust production is associated with longer total subduction length. We compute a Strontium isotope record based on subduction zone length, which agrees well with geological records supporting the validity of our approach: The total subduction zone length is proportional to the summed arc- and ridge volcanic CO2 production and thereby to global volcanic degassing at plate boundaries. We therefore use our degassing curve as input for the GEOCARBSULF model to estimate atmospheric CO2 levels since the Triassic. Our calculated CO2 levels for the mid-Mesozoic differ from previous modeling results and are more consistent with available proxy data.

van der Meer, Douwe; Zeebe, Richard; van Hinsbergen, Douwe; Sluijs, Appy; Spakman, Wim; Torsvik, Trond

2014-05-01

118

Multiple-time scales analysis of physiological time series under neural control  

NASA Technical Reports Server (NTRS)

We discuss multiple-time scale properties of neurophysiological control mechanisms, using heart rate and gait regulation as model systems. We find that scaling exponents can be used as prognostic indicators. Furthermore, detection of more subtle degradation of scaling properties may provide a novel early warning system in subjects with a variety of pathologies including those at high risk of sudden death.

Peng, C. K.; Hausdorff, J. M.; Havlin, S.; Mietus, J. E.; Stanley, H. E.; Goldberger, A. L.

1998-01-01

119

Magnetostratigraphy of Permian/Triassic boundary sequences in the Cis-Urals, Russia: No evidence for a major temporal hiatus  

NASA Astrophysics Data System (ADS)

During the last five years there has been considerable doubt over the age of the continental uppermost Permian Russian stages, the Kazanian and Tatarian. Traditionally they have been regarded as Late Permian but were re-dated as Middle Permian in the 2004 international time scale, despite fossil evidence that the Tatarian, at least, is Late Permian. These debated ages are tested by magnetostratigraphic study of five sections spanning the Permian Triassic Boundary (PTB) of the SE Urals in the Orenburg region of Russia. The Upper Permian and Lower Triassic of this region have a well documented vertebrate fauna whose evolution has a significant bearing on our understanding of the PTB mass extinction event. If the Tatarian is viewed as Mid Permian, then the Late Permian in Russia is marked by a 9-10 Ma stratigraphic gap. The palaeomagnetic data yield a distinct series of polarity zones that provide clear local and regional correlation and are readily tied to a recently compiled global magnetostratigraphic record. On the basis of this correlation the sampled sections span the upper Guadalupian to Induan stages without any obvious break, so confirming the traditional view that the Tatarian is Late Permian in age. Anomalies in the magnetic inclination are consistent with sediment compaction (inclination shallowing, a common phenomenon of red beds) but declination anomalies between these sites and elsewhere in Russia may suggest localised vertical axis rotation.

Taylor, Graeme K.; Tucker, Christopher; Twitchett, Richard J.; Kearsey, Timothy; Benton, Michael J.; Newell, Andrew J.; Surkov, Mikhail V.; Tverdokhlebov, Valentin P.

2009-04-01

120

Palaeoenvironments and palaeotectonics of the arid to hyperarid intracontinental latest Permian- late Triassic Solway basin (U.K.)  

NASA Astrophysics Data System (ADS)

The late Permian to late Triassic sediments of the Solway Basin consist of an originally flat-lying, laterally persistent and consistent succession of mature, dominantly fine-grained red clastics laid down in part of a very large intracontinental basin. The complete absence of body or trace fossils or palaeosols indicates a very arid (hyperarid) depositional environment for most of the sediments. At the base of the succession, thin regolith breccias and sandstones rest unconformably on basement and early Permian rift clastics. Overlying gypsiferous red silty mudstones, very fine sandstones and thick gypsum were deposited in either a playa lake or in a hypersaline estuary, and their margins. These pass upwards into thick-bedded, multi-storied, fine- to very fine-grained red quartzo-felspathic and sublithic arenites in which even medium sand is rare despite channels with clay pebbles up to 30 cm in diameter. Above, thick trough cross-bedded and parallel laminated fine-grained aeolian sandstones (deposited in extensive barchanoid dune complexes) pass up into very thick, multicoloured mudstones, and gypsum deposited in marginal marine or lacustrine sabkha environments. The latter pass up into marine Lower Jurassic shales and limestones. Thirteen non-marine clastic lithofacies are arranged into five main lithofacies associations whose facies architecture is reconstructed where possible by analysis of large exposures. The five associations can be compared with the desert pavement, arid ephemeral stream, sabkha, saline lake and aeolian sand dune environments of the arid to hyperarid areas of existing intracontinental basins such as Lake Eyre and Lake Chad. The accommodation space in such basins is controlled by gradual tectonic subsidence moderated by large fluctuations in shallow lake extent (caused by climatic change and local variation) and this promotes a large-scale layer-cake stratigraphy as exemplified in the Solway basin. Here, the dominant fine-grained mature sandstones above the local basal reg breccias suggest water-reworking of wind-transported sediment, as in the northern part of the Lake Chad basin. Growth faulting occurs in places in the Solway basin, caused by underlying evaporite movement, but these faults did not significantly affect pre-late Triassic sedimentation and did not expose pre-Permian units above the basal breccias. There is no evidence of post-early Permian rifting anywhere during deposition of the late Permian to middle Triassic British succession although the succession is often interpreted with a rift-basin model. The arid to hyperarid palaeoclimate changed little during deposition of the Solway basin succession, in contrast to Lakes Eyre and Chad: and this is attributed to tectonic and palaeolatitude stability. Unlike the later Mesozoic- Cenozoic, only limited plate movements took place during the Triassic in western Europe, palaeolatitude changed little, and the Solway Basin remained in the northern latitudinal desert belt from early to mid-Triassic times. However, the influence of the early Triassic impoverished biota on environmental interpretations needs further study.

Brookfield, Michael E.

2008-10-01

121

Planck Scale Physics, Pregeometry and the Notion of Time  

E-print Network

Recent progress in quantum gravity and string theory has raised interest among scientists to whether or not nature behaves discretely at the Planck scale. There are two attitudes twoards this discretenes i.e. top-down and bottom-up approach. We have followed up the bottom-up approach. Here we have tried to describe how macroscopic space-time or its underlying mesoscopic substratum emerges from a more fundamental concept. The very concept of space-time, causality may not be valid beyond Planck scale. We have introduced the concept of generalised time within the framework of Sheaf Cohomology where the physical time emrges around and above Planck scale. The possible physical amd metaphysical implications are discussed.

S. Roy

2003-11-04

122

Multiple time scales from hard local constraints: Glassiness without disorder  

NASA Astrophysics Data System (ADS)

While multiple time scales generally arise in the dynamics of disordered systems, we find multiple time scales in the absence of disorder in a simple model with hard local constraints. The dynamics of the model, which consists of local collective rearrangements of various scales, is not determined by the smallest scale but by a length l* that grows at low energies. In real space we find a hierarchy of fast and slow regions: Each slow region is geometrically insulated from all faster degrees of freedom, which are localized in fast pockets below percolation thresholds. A tentative analogy with structural glasses is given, which attributes the slowing down of the dynamics to the growing size of mobile elementary excitations, rather than to the size of some domains.

Cépas, O.

2014-08-01

123

Deviations from uniform power law scaling in nonstationary time series  

NASA Technical Reports Server (NTRS)

A classic problem in physics is the analysis of highly nonstationary time series that typically exhibit long-range correlations. Here we test the hypothesis that the scaling properties of the dynamics of healthy physiological systems are more stable than those of pathological systems by studying beat-to-beat fluctuations in the human heart rate. We develop techniques based on the Fano factor and Allan factor functions, as well as on detrended fluctuation analysis, for quantifying deviations from uniform power-law scaling in nonstationary time series. By analyzing extremely long data sets of up to N = 10(5) beats for 11 healthy subjects, we find that the fluctuations in the heart rate scale approximately uniformly over several temporal orders of magnitude. By contrast, we find that in data sets of comparable length for 14 subjects with heart disease, the fluctuations grow erratically, indicating a loss of scaling stability.

Viswanathan, G. M.; Peng, C. K.; Stanley, H. E.; Goldberger, A. L.

1997-01-01

124

Common scaling patterns in intertrade times of U. S. stocks  

NASA Astrophysics Data System (ADS)

We analyze the sequence of time intervals between consecutive stock trades of thirty companies representing eight sectors of the U.S. economy over a period of 4 yrs. For all companies we find that: (i) the probability density function of intertrade times may be fit by a Weibull distribution, (ii) when appropriately rescaled the probability densities of all companies collapse onto a single curve implying a universal functional form, (iii) the intertrade times exhibit power-law correlated behavior within a trading day and a consistently greater degree of correlation over larger time scales, in agreement with the correlation behavior of the absolute price returns for the corresponding company, and (iv) the magnitude series of intertrade time increments is characterized by long-range power-law correlations suggesting the presence of nonlinear features in the trading dynamics, while the sign series is anticorrelated at small scales. Our results suggest that independent of industry sector, market capitalization and average level of trading activity, the series of intertrade times exhibit possibly universal scaling patterns, which may relate to a common mechanism underlying the trading dynamics of diverse companies. Further, our observation of long-range power-law correlations and a parallel with the crossover in the scaling of absolute price returns for each individual stock, support the hypothesis that the dynamics of transaction times may play a role in the process of price formation.

Ivanov, Plamen Ch.; Yuen, Ainslie; Podobnik, Boris; Lee, Youngki

2004-05-01

125

How was the Triassic Songpan-Ganzi basin filled? A provenance study  

USGS Publications Warehouse

The Triassic Songpan-Ganzi complex comprises >200,000 km2 of 5-15 km thick turbiditic sediments. Although surrounded by several magmatic and orogenic belts, the Triassic high- and ultrahigh-pressure Qinling-Tongbai-Hong'an-Dabie (QTHD) orogen, located several hundred kilometers to the east, was proposed as its major source. Middle to Late Triassic samples from the northern and southern Songpan-Ganzi complex, studied using detrital white mica 40Ar/39Ar ages, Si-in-white mica content, and detrital zircon U/Pb ages, suggest that the northern Songpan-Ganzi deposystem obtained detritus from the north: the north China block, east Kunlun, northern Qaidam, Qilian, and western Qinling; the southern Songpan-Ganzi deposystem was supplied from the northeasterly located Paleozoic QTHD area throughout the Ladinian and received detritus from the Triassic Hong'an-Dabie orogen during the Carnian, indicative of exhumation of the orogen at that time. The QTHD orogen fed the Norian samples in the southeastern southern Songpan-Ganzi deposystem, signifying long drainage channels along the western margin of the south China block. An additional supply from the Emeishan magmatic province and/or the Yidun arc is suggested by the paucity of white mica in the southern Songpan-Ganzi deposystem. Mica ages of Rhaetian sediments from the northwestern Sichuan basin best correlate with those of the Triassic QTHD orogen. Our Si-in-white mica data demonstrate that the high- and ultrahigh-pressure rocks of the Hong'an-Dabie Shan were not exposed in the Middle to Late Triassic. Copyright 2007 by the American Geophysical Union.

Enkelmann, E.; Weislogel, A.; Ratschbacher, L.; Eide, E.; Renno, A.; Wooden, J.

2007-01-01

126

Investigating the Geologic Time Scale: Creating posters to Display Trends in Geologic Time  

NSDL National Science Digital Library

This observational inquiry activity involving careful descriptions of rocks and fossil including age will be used to create a scalar accurate geologic time scale. Students will observe and learn that the geologic time scale was created based on changes in fossil, rock, and atmospheric changes.

Atkins, Kim

127

Physics in space-time with scale-dependent metrics  

NASA Astrophysics Data System (ADS)

We construct three-dimensional space R?3 with the scale-dependent metric and the corresponding Minkowski space-time M?,?4 with the scale-dependent fractal (DH) and spectral (DS) dimensions. The local derivatives based on scale-dependent metrics are defined and differential vector calculus in R?3 is developed. We state that M?,?4 provides a unified phenomenological framework for dimensional flow observed in quite different models of quantum gravity. Nevertheless, the main attention is focused on the special case of flat space-time M1/3,14 with the scale-dependent Cantor-dust-like distribution of admissible states, such that DH increases from DH=2 on the scale ??0 to DH=4 in the infrared limit ??0, where ?0 is the characteristic length (e.g. the Planck length, or characteristic size of multi-fractal features in heterogeneous medium), whereas DS?4 in all scales. Possible applications of approach based on the scale-dependent metric to systems of different nature are briefly discussed.

Balankin, Alexander S.

2013-10-01

128

Palynological assemblages of non-marine rocks at the Permian Triassic boundary, western Guizhou and eastern Yunnan, South China  

NASA Astrophysics Data System (ADS)

Marine and non-marine facies of the Permian-Triassic boundary stratigraphic set (PTBST) are well developed in South China. Palynological assemblages enable subdivision and correlation of the Permian-Triassic boundary (PTB) rocks. Three palynological assemblages are recognized across the PTBST in two terrestrial PTB sections in western Guizhou and eastern Yunnan, South China. Assemblage 1 (Xuanwei Formation) is a Late Permian palynological assemblage dominated by ferns and pteridosperms, with minor gymnosperms. Most taxa are typical long-ranging Paleozoic forms, but the appearance of Lueckisporites confirms a Late Permian age for this assemblage. Assemblage 2 (PTBST) is marked by an abrupt decrease in palynomorph abundance and diversity, and thriving fungal/algal(?) spores. Assemblage 2 is still dominated by ferns and pteridosperms, with a few gymnosperms, but is characterized by a mixed palynoflora containing both Late Permian and Early Triassic elements. Most taxa are typical Late Permian ones also found in Assemblage 1, however, some taxa of Early Triassic aspect, e.g. Lundbladispora and Taeniaesporites, appeared for the first time. In Assemblage 3 (top Xuanwei Formation and Kayitou Formation), the proportion of gymnosperm pollen increases rapidly, exceeding that of ferns and pteridosperms, but the abundance of palynomorphs is still low. Typical Early Triassic taxa (such as Lundbladispora, Aratrisporites and Taeniaesporites) are present in greater abundance and confirms an Early Triassic age for this assemblage.

Peng, Yuanqiao; Yu, Jianxin; Gao, Yongqun; Yang, Fengqing

2006-12-01

129

Mantle plume: The invisible serial killer — Application to the Permian–Triassic boundary mass extinction  

Microsoft Academic Search

The Earth experienced a severe mass extinction at the Permian–Triassic boundary (PTB) about 252 million years ago. This biological catastrophe was accompanied by major changes in geochemical composition of the atmosphere and ocean and the appearance of sedimentary features which had not occurred since the Precambrian time. The eruption of the largest continental flood basalt, the Siberian Traps, overlapped this mass

Ezat Heydari; Nasser Arzani; Jamshid Hassanzadeh

2008-01-01

130

Floral changes across the Triassic\\/Jurassic boundary linked to flood basalt volcanism  

Microsoft Academic Search

One of the five largest mass extinctions of the past 600million years occurred at the boundary of the Triassic and Jurassic periods, 201.6million years ago. The loss of marine biodiversity at the time has been linked to extreme greenhouse warming, triggered by the release of carbon dioxide from flood basalt volcanism in the central Atlantic Ocean. In contrast, the biotic

B. van de Schootbrugge; T. M. Quan; S. Lindström; W. Püttmann; C. Heunisch; J. Pross; J. Fiebig; R. Petschick; H.-G. Röhling; S. Richoz; Y. Rosenthal; P. G. Falkowski

2009-01-01

131

A time scale for electrical screening in pulsed gas discharges  

NASA Astrophysics Data System (ADS)

The Maxwell time is a typical time scale for the screening of an electric field in a medium with a given conductivity. We introduce a generalization of the Maxwell time that is valid for gas discharges: the ionization screening time, that takes the growth of the conductivity due to impact ionization into account. We present an analytic estimate for this time scale, assuming a planar geometry, and evaluate its accuracy by comparing with one- and three-dimensional numerical simulations. We investigate the minimum plasma density required to prevent the growth of streamers with local field enhancement, and we discuss the effects of photoionization and electron detachment on ionization screening. Our results can help to understand the development of pulsed discharges, for example nanosecond pulsed discharges at atmospheric pressure or halo discharges in the lower ionosphere.

Teunissen, Jannis; Sun, Anbang; Ebert, Ute

2014-09-01

132

A time scale for electrical screening in pulsed gas discharges  

E-print Network

The Maxwell time is a typical time scale for the screening of an electric field in a medium with a given conductivity. We introduce a generalization of the Maxwell time that is valid for gas discharges: the \\emph{ionization screening time}, that takes the growth of the conductivity due to impact ionization into account. We present an analytic estimate for this time scale, assuming a planar geometry, and evaluate its accuracy by comparing with numerical simulations in 1D and 3D. We investigate the minimum plasma density required to prevent the growth of streamers with local field enhancement, and we discuss the effects of photoionization and electron detachment on ionization screening. Our results are especially relevant for the description of nanosecond pulsed discharges.

Teunissen, Jannis; Ebert, Ute

2014-01-01

133

Sedimentary record of Late Triassic transpressional tectonics of the Longmenshan thrust belt, SW China  

NASA Astrophysics Data System (ADS)

Sedimentary data from field and borehole investigations allow reconstruction of the southwesterly variations of proximal sedimentary processes along the Longmenshan thrust belt during Late Triassic and Early Jurassic times and relating them to the development of a transpression basin. Conglomerates, which are the early indicators of the tectonic activity and orogeny appear for the first time in the second member of the Upper Triassic Xujiahe Formation and crop out only in the northern segment of the Longmenshan thrust belt. They are also present in the central segment in the fourth member of the Xujiahe Formation. In contrast the Early Jurassic Baitianba conglomerates were deposited all along the front of the Longmenshan thrust belt. The contact between the Upper Triassic and Lower Jurassic units is an angular unconformity and or a disconformity in the northern and central segments of the Longmenshan thrust belt, but becomes conformable to the southwest, along the strike. The isopach maps of different stratigraphic units show the along-strike shift of the depocenters with time, the result of southwestward propagating contraction and deformation of the Longmenshan thrust belt. In conjunction with the regional structural analysis and paleocurrent reconstructions, the southwesterly variations of sedimentary processes demonstrate an along-strike kinematic change of tectonic process in the western Sichuan basin from the northeast to the southwest. These data indicates that a transpressional deformation occurred along the Longmenshan thrust belt during the Late Triassic, and was synchronous with the development of the western Sichuan basin, which behaved as a transpressional foreland basin.

Deng, Bin; Liu, Shugen; Jansa, Luba; Cao, Junxing; Cheng, Yang; Li, Zhiwu; Liu, Shun

2012-04-01

134

Appropriate time scales for nonlinear analyses of deterministic jump systems  

NASA Astrophysics Data System (ADS)

In the real world, there are many phenomena that are derived from deterministic systems but which fluctuate with nonuniform time intervals. This paper discusses the appropriate time scales that can be applied to such systems to analyze their properties. The financial markets are an example of such systems wherein price movements fluctuate with nonuniform time intervals. However, it is common to apply uniform time scales such as 1-min data and 1-h data to study price movements. This paper examines the validity of such time scales by using surrogate data tests to ascertain whether the deterministic properties of the original system can be identified from uniform sampled data. The results show that uniform time samplings are often inappropriate for nonlinear analyses. However, for other systems such as neural spikes and Internet traffic packets, which produce similar outputs, uniform time samplings are quite effective in extracting the system properties. Nevertheless, uniform samplings often generate overlapping data, which can cause false rejections of surrogate data tests.

Suzuki, Tomoya

2011-06-01

135

Triassic/Jurassic faulting patterns of Conecuh Ridge, southwest Alabama  

SciTech Connect

Two major fault systems influenced Jurassic structure and deposition on the Conecuh Ridge, southwest Alabama. Identification and dating of these fault systems are based on seismic-stratigraphic interpretation of a 7-township grid in Monroe and Conecuh Counties. Relative time of faulting is determined by fault geometry and by formation isopachs and isochrons. Smackover and Norphlet Formations, both Late Jurassic in age, are mappable seismic reflectors and are thus reliable for seismicstratigraphic dating. The earlier of the 2 fault systems is a series of horsts and grabens that trends northeast-southwest and is Late Triassic to Early Jurassic in age. The system formed in response to tensional stress associated with the opening of the Atlantic Ocean. The resulting topography was a series of northeast-southwest-trending ridges. Upper Triassic Eagle Mills and Jurassic Werner Formations were deposited in the grabens. The later fault system is also a series of horsts and grabens trending perpendicular to the first. This system was caused by tensional stress related to a pulse in the opening of the Gulf of Mexico. Faulting began in Early Jurassic and continued into Late Jurassic, becoming progressively younger basinward. At the basin margin, faulting produced a very irregular shoreline. Submerged horst blocks became centers for shoaling or carbonate buildups. Today, these blocks are exploration targets in southwest Alabama.

Hutley, J.K.

1985-02-01

136

Time Scale Calculus - a new perspectives for synthetic seismogram calculations  

NASA Astrophysics Data System (ADS)

Synthetic, numerically generated seismograms are one of the key factors of any interpretation of recorded seismic data. At the early stage of development, calculation of full seismic waveforms was impossible due to a limited computational resource so we were forced to used only some selected characteristics of seismic waves relatively easy for numerical calculations like first arrival times, maximum amplitude, approximate source spectra, to name a few. Continues development of computational resources as well as progress in numerical techniques has opened possibilities of generation the full, 3-component seismograms incorporating many physically important elements like wave attenuation, anisotropy or randomness of the media. Although achieved results are impressive we still need new numerical methods to tackle existing problems with the synthetic seismogram generation. In this contribution we present a novel approach to discretization of the wave equation which brings together continues and discrete numerical analysis of the seismic waves. The foundations of this new technique, called Time Scale Calculus, have been formulated by Hilger in late eighties and is very dynamically developing. The Time scale calculus, due to its universality seems to have a great potential when practical applications are considered. Thus we have decided to bring the Time Scale calculus concept closer to geophysical, or more precisely to seismological applications. This presentation is intend as a basic introduction to the time scales calculus considered from seismological point of view. We shortly present and discuss the possibility of using the Time Scales (TS) technique for solving the simplest acoustic 2D wave equation keeping in mind its particular applications for mining induced seismicity.

Waskiewicz, Kamil; Debski, Wojciech

2013-04-01

137

A pseudo-Bertrand distribution for time-scale analysis  

Microsoft Academic Search

Using the pseudo-Wigner time-frequency distribution as a guide, we derive two new time-scale representations: the pseudo-Bertrand and the smoothed pseudo-Bertrand distributions. Unlike the Bertrand distribution, these representations support efficient online operation at the same computational cost as the continuous wavelet transform. Moreover, they take advantage of the affine smoothing inherent in the sliding structure of their implementation to suppress cumbersome

P. Goncalves; R. G. Baraniuk

1996-01-01

138

Food Expenditure, Food Preparation Time and Household Economies of Scale  

Microsoft Academic Search

This paper is concerned with the effect of household size on the allocation of household money and time to food consumption. A broad literature has examined household economies of scale. Since food is a private good, it might be expected that larger households, which could economize on shared goods such as housing, would spend more per equivalent household member on

Victoria Vernon

2004-01-01

139

Scaling Task Management in Space and Time: Reducing User Overhead  

E-print Network

on some tasks for days or even months. It is well known that such tasks typically involve severalScaling Task Management in Space and Time: Reducing User Overhead in Ubiquitous at Carnegie Mellon University were supported in part by the Portuguese Ministry of Science and Technology

140

Scaling Task Management in Space and Time: Reducing User Overhead  

E-print Network

expand their computer-supported tasks across multiple locations, and they may work on some tasks for daysScaling Task Management in Space and Time: Reducing User Overhead in Ubiquitous at Carnegie Mellon University were supported in part by the Portuguese Ministry of Science and Technology

141

Speech Compensation for Time-Scale-Modified Auditory Feedback  

ERIC Educational Resources Information Center

Purpose: The purpose of this study was to examine speech compensation in response to time-scale-modified auditory feedback during the transition of the semivowel for a target utterance of /ija/. Method: Each utterance session consisted of 10 control trials in the normal feedback condition followed by 20 perturbed trials in the modified auditory…

Ogane, Rintaro; Honda, Masaaki

2014-01-01

142

Measuring Change over Time with a Rasch Rating Scale Model.  

ERIC Educational Resources Information Center

When measures are taken on the same individual over time, it is difficult to determine whether observed differences are the result of changes in the person or changes in other facets of the measurement situation (e.g. interpretation of items or use of rating scale). This paper describes a method for disentangling changes in persons from changes in…

Wolfe, Edward W.; Chiu, Chris W. T.

143

GNSS observations of deep convective time scales in the Amazon  

NASA Astrophysics Data System (ADS)

In the tropics, understanding the shallow-to-deep transition and organization of convection on the mesoscale is made difficult due the paucity of long-term high spatial/temporal resolution data. In this paper, data from the world's first long-term equatorial Global Navigational Satellite System meteorological station in Manaus (Central Amazon) is used to create a new metric, a water vapor convergence time scale, to characterize the temporal evolution of deep convection over a tropical continental region. From 3.5 years of data, 320 convective events were analyzed using a compositing analysis. Results reveal two characteristic time scales of water vapor convergence; an 8 h time scale of weak convergence and 4 h timescale of intense water vapor convergence associated with the shallow-to-deep convection transition. The 4 h shallow-to-deep transition time scale is particularly robust, regardless of convective intensity, seasonality, or nocturnal versus daytime convection. This new result provides a useful metric for both high resolution and global climate models to replicate.

Adams, D. K.; Gutman, Seth I.; Holub, Kirk L.; Pereira, Dulcineide S.

2013-06-01

144

Behavioral Programming, Decentralized Control, and Multiple Time Scales  

E-print Network

Behavioral Programming, Decentralized Control, and Multiple Time Scales David Harel, Assaf Marron, Guy Wiener Weizmann Institute of Science {first name.last name}@weizmann.ac.il Gera Weiss Ben Gurion University of the Negev geraw@cs.bgu.ac.il Abstract Behavioral programming is a recently proposed approach

Weiss, Gera

145

Separation of time scales in the HCA model for sand  

NASA Astrophysics Data System (ADS)

Separation of time scales is used in a high cycle accumulation (HCA) model for sand. An important difficulty of the model is the limited applicability of the Miner's rule to multiaxial cyclic loadings applied simultaneously or in a combination with monotonic loading. Another problem is the lack of simplified objective HCA formulas for geotechnical settlement problems. Possible solutions of these problems are discussed.

Niemunis, Andrzej; Wichtmann, Torsten

2014-10-01

146

Time Flies When You're Learning About Scale!  

NSDL National Science Digital Library

Not many students would forget to say "Dinosaurs!" if you mention the Jurassic period, yet the word scale only conjures up ideas of measuring objects. Most students automatically think of measuring mass, volume, or distance, and not necessarily time. In t

Taylor, Amy R.; Jones, M. G.; Falvo, Michael R.

2009-04-01

147

Stellar differential rotation and coronal time-scales  

NASA Astrophysics Data System (ADS)

We investigate the time-scales of evolution of stellar coronae in response to surface differential rotation and diffusion. To quantify this, we study both the formation time and lifetime of a magnetic flux rope in a decaying bipolar active region. We apply a magnetic flux transport model to prescribe the evolution of the stellar photospheric field, and use this to drive the evolution of the coronal magnetic field via a magnetofrictional technique. Increasing the differential rotation (i.e. decreasing the equator-pole lap time) decreases the flux rope formation time. We find that the formation time is dependent upon the lap time and the surface diffusion time-scale through the relation ?_Form ? ?{?_Lap?_Diff}. In contrast, the lifetimes of flux ropes are proportional to the lap time (?Life??Lap). With this, flux ropes on stars with a differential rotation of more than eight times the solar value have a lifetime of less than 2 d. As a consequence, we propose that features such as solar-like quiescent prominences may not be easily observable on such stars, as the lifetimes of the flux ropes which host the cool plasma are very short. We conclude that such high differential rotation stars may have very dynamical coronae.

Gibb, G. P. S.; Jardine, M. M.; Mackay, D. H.

2014-10-01

148

Feather-like development of Triassic diapsid skin appendages  

NASA Astrophysics Data System (ADS)

Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquama’s appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument.

Voigt, Sebastian; Buchwitz, Michael; Fischer, Jan; Krause, Daniel; Georgi, Robert

2009-01-01

149

Evolution of Bulk Scale Factor in Warped Space-time  

E-print Network

In this work the role of extra dimensions in the accelerated universe through the scenario of higher-dimensional Friedmann-Robertson-Walker (FRW) cosmology has been studied. For this purpose, we first consider warped space-time in the standard flat brane scenario as the modified form of Robertson-Walker (RW) metric in five-dimension (5D) space-time and then the variation of the bulk scale factor (warp factor), with respect to both space-like and time-like extra dimensions is obtained. Finally, it is shown that both of two types of extra dimensions are important in this scenario and also the bulk scale factor plays two different roles.

M. Mohsenzadeh; E. Yusofi

2012-02-22

150

P3.11 ESTIMATION OF THE INTEGRAL TIME SCALE WITH TIME SERIES MODELS  

Microsoft Academic Search

Climate- and regional models solve the dynamics of the atmosphere with a resolution ? of 10 km or more. They use parameterizations to incorporate the effects of turbu- lence in the atmospheric boundary layer (ABL). Fluxes, entrainment and dissipation are associated with charac- teristic time-scales T. They are often constructed from characteristic length scales L for these quantities (tem- perature,

Stijn de Waele; Arjan van Dijk; Piet Broersen; Peter Duynkerke

151

Sublinear scaling for time-dependent stochastic density functional theory  

E-print Network

A stochastic approach to time-dependent density functional theory (TDDFT) is developed for computing the absorption cross section and the random phase approximation (RPA) correlation energy. The core idea of the approach involves time-propagation of a small set of stochastic orbitals which are fi?rst projected on the occupied space and then propagated in time according to the time-dependent Kohn-Sham equations. The evolving electron density is exactly represented when the number of random orbitals is in?finite, but even a small number (? 16) of such orbitals is enough to obtain meaningful results for absorption spectrum and the RPA correlation energy per electron. We implement the approach for silicon nanocrystals (NCs) using real-space grids and ?find that the overall scaling of the algorithm is sublinear with computational time and memory.

Gao, Yi; Baer, Roi; Rabani, Eran

2014-01-01

152

Continental weathering in the Early Triassic in Himalayan Tethys, central Nepal: Implications for abrupt environmental change on the northern margin of Gondwanaland  

NASA Astrophysics Data System (ADS)

The geochemistry of Triassic mudstones in the Himalayan Tethys sequence, central Nepal, was studied with respect to changes in sedimentary facies, grain size, and source rocks. The Triassic sedimentary facies of mudstone and carbonates show deposition in offshore to hemiplegic environments. The rare earth element (REE) pattern of the Permian and Triassic mudstones suggests uniformity correlatable to average shale. The major element geochemistry of the Early Triassic Griesbachian-early Smithian mudstones indicates a sediment supply from strongly weathered sources with the chemical index of alteration (CIA) values of 76-81. However, the mudstones in the late Smithian show weakly weathered sources with CIA values of 68-74. The lower part of the Middle Triassic Anisian mudstones return to Early Triassic paleoweathering levels. There are no significant relationships among lithofacies, the grain size of the sediments, and CIA values. Thus, the abrupt change of the degree of paleoweathering in the Early Triassic, late Smithian time, suggests a dramatic decrease in continental weathering, which is related to a predominantly arid climate in the northern marginal area of Gondwana.

Yoshida, Kohki; Kawamura, Toshio; Suzuki, Shigeyuki; Regmi, Amar Deep; Gyawali, Babu Ram; Shiga, Yuka; Adachi, Yoshiko; Dhital, Megh Raj

2014-01-01

153

The length and time scales of water's glass transitions  

NASA Astrophysics Data System (ADS)

Using a general model for the equilibrium dynamics of supercooled liquids, I compute from molecular properties the emergent length and time scales that govern the nonequilibrium relaxation behavior of amorphous ice prepared by rapid cooling. Upon cooling, the liquid water falls out of equilibrium whereby the temperature dependence of its relaxation time is predicted to change from super-Arrhenius to Arrhenius. A consequence of this crossover is that the location of the apparent glass transition temperature depends logarithmically on cooling rate. Accompanying vitrification is the emergence of a dynamical length-scale, the size of which depends on the cooling rate and varies between angstroms and tens of nanometers. While this protocol dependence clarifies a number of previous experimental observations for amorphous ice, the arguments are general and can be extended to other glass forming liquids.

Limmer, David T.

2014-06-01

154

Reduction of nonautonomous population dynamics models with two time scales.  

PubMed

The purpose of this work is reviewing some reduction results to deal with systems of nonautonomous ordinary differential equations with two time scales. They could be included among the so-called approximate aggregation methods. The existence of different time scales in a system, together with some long-term features, are used to build up a simpler system governed by a lesser number of state variables. The asymptotic behavior of the latter system is then used to describe the asymptotic behaviour of the former one. The reduction results are stated in two particular but important cases: periodic systems and asymptotically autonomous systems. The reduction results are illustrated with the help of simple spatial SIS epidemic models including either periodic or asymptotically autonomous terms. PMID:24838547

Marvá, Marcos; Bravo de la Parra, Rafael

2014-09-01

155

A study of Venus rotation at short time scale  

NASA Astrophysics Data System (ADS)

Venus which can be considered as the twin sister of the Earth in view of its global characteristics (size, density) has been the subject of many investigations to understand its slow retrograde rotation (243d) and its rather small obliquity (2°.63). Many of these studies concern the evolution of Venus rotation at very long time scales. Here we present a complete model of Venus precession and nutation based on Hamiltonian formalism for short times scales. We apply a theoretical framework already used by Kinoshita (1977) for the rigid Earth. After calculating the effects due to the gravitational tide exerted by the Sun, we also evaluate the indirect planetary effects due to the perturbation of the planets. We compare our results with those obtained by Souchay et al. (1999) on the Earth. At last we present the prospect for future studies among which are the polhody, the effects of the atmosphere and of the core-mantle interaction.

Cottereau, L.; Souchay, J.

2009-12-01

156

The Permo-Triassic Extinction  

NSDL National Science Digital Library

This website covers details about the Permian extinction, which occurred about 250 million years ago. It contains a paleontological overview of the extinction, discussing the life present at that time, evidence for the extinction, and what types of lifeforms disappeared. Other sections discuss various theories about what caused the mass-extinction including volcanism, impacts, climate change, glaciation, Pangea and other proposed theories.

157

TimeScale Feature Extractions for Emotional Speech Characterization  

Microsoft Academic Search

Abstract,Emotional,speech,characterization,is,an important issue for the understanding,of interaction. This article discusses the time-scale analysis problem in feature extraction for emotional speech processing. We describe a computational,framework,for combining,segmental,and supra-segmental features for emotional,speech detection. The statistical fusion is based on the estimation of local a posteriori class probabilities and the overall decision employs,weighting factors directly related to the duration of the individual speech

Mohamed Chetouani; Ammar Mahdhaoui; Fabien Ringeval

2009-01-01

158

Solar Irradiance Variations on Active Region Time Scales  

NASA Technical Reports Server (NTRS)

The variations of the total solar irradiance is an important tool for studying the Sun, thanks to the development of very precise sensors such as the ACRIM instrument on board the Solar Maximum Mission. The largest variations of the total irradiance occur on time scales of a few days are caused by solar active regions, especially sunspots. Efforts were made to describe the active region effects on total and spectral irradiance.

Labonte, B. J. (editor); Chapman, G. A. (editor); Hudson, H. S. (editor); Willson, R. C. (editor)

1984-01-01

159

Scale dependence of the directional relationships between coupled time series  

NASA Astrophysics Data System (ADS)

Using the cross-correlation of the wavelet transformation, we propose a general method of studying the scale dependence of the direction of coupling for coupled time series. The method is first demonstrated by applying it to coupled van der Pol forced oscillators and coupled nonlinear stochastic equations. We then apply the method to the analysis of the log-return time series of the stock values of the IBM and General Electric (GE) companies. Our analysis indicates that, on average, IBM stocks react earlier to possible common sector price movements than those of GE.

Shirazi, Amir Hossein; Aghamohammadi, Cina; Anvari, Mehrnaz; Bahraminasab, Alireza; Rahimi Tabar, M. Reza; Peinke, Joachim; Sahimi, Muhammad; Marsili, Matteo

2013-02-01

160

Scaling Brain Size, Keeping Timing: Evolutionary Preservation of Brain Rhythms  

PubMed Central

Despite the several-thousand-fold increase of brain volume during the course of mammalian evolution, the hierarchy of brain oscillations remains remarkably preserved, allowing for multiple-time-scale communication within and across neuronal networks at approximately the same speed, irrespective of brain size. Deployment of large-diameter axons of long-range neurons could be a key factor in the preserved time management in growing brains. We discuss the consequences of such preserved network constellation in mental disease, drug discovery, and interventional therapies. PMID:24183025

Buzsáki, György; Logothetis, Nikos; Singer, Wolf

2014-01-01

161

Two-time-scale population evolution on a singular landscape  

NASA Astrophysics Data System (ADS)

Under the effect of strong genetic drift, it is highly probable to observe gene fixation or gene loss in a population, shown by singular peaks on a potential landscape. The genetic drift-induced noise gives rise to two-time-scale diffusion dynamics on the bipeaked landscape. We find that the logarithmically divergent (singular) peaks do not necessarily imply infinite escape times or biological fixations by iterating the Wright-Fisher model and approximating the average escape time. Our analytical results under weak mutation and weak selection extend Kramers's escape time formula to models with B (Beta) function-like equilibrium distributions and overcome constraints in previous methods. The constructed landscape provides a coherent description for the bistable system, supports the quantitative analysis of bipeaked dynamics, and generates mathematical insights for understanding the boundary behaviors of the diffusion model.

Xu, Song; Jiao, Shuyun; Jiang, Pengyao; Ao, Ping

2014-01-01

162

5nsec Dead time multichannel scaling system for Mössbauer spectrometer  

NASA Astrophysics Data System (ADS)

A PC programmable and fast multichannel scaling module has been designed to use a commercial Mössbauer spectrometer. This module is based on a 10 single chip 8 bits microcomputer (MC6805) and on a 35 fast ALU, which allows a high performance and low cost system. The module can operate in a stand-alone mode. Data analysis are performed in real time display, on XT/AT IBM PC or compatibles. The channels are ranged between 256 and 4096, the maximum number of counts is 232-1 per channel, the dwell time is 3 ?sec and the dead time between channels is 5 nsec. A friendly software display the real time spectrum and offers menues with different options at each state.

Verrastro, C.; Trombetta, G.; Pita, A.; Saragovi, C.; Duhalde, S.

1991-11-01

163

Arthropods in amber from the Triassic Period.  

PubMed

The occurrence of arthropods in amber exclusively from the Cretaceous and Cenozoic is widely regarded to be a result of the production and preservation of large amounts of tree resin beginning ca. 130 million years (Ma) ago. Abundant 230 million-year-old amber from the Late Triassic (Carnian) of northeastern Italy has previously yielded myriad microorganisms, but we report here that it also preserves arthropods some 100 Ma older than the earliest prior records in amber. The Triassic specimens are a nematoceran fly (Diptera) and two disparate species of mites, Triasacarus fedelei gen. et sp. nov., and Ampezzoa triassica gen. et sp. nov. These mites are the oldest definitive fossils of a group, the Eriophyoidea, which includes the gall mites and comprises at least 3,500 Recent species, 97% of which feed on angiosperms and represents one of the most specialized lineages of phytophagous arthropods. Antiquity of the gall mites in much their extant form was unexpected, particularly with the Triassic species already having many of their present-day features (such as only two pairs of legs); further, it establishes conifer feeding as an ancestral trait. Feeding by the fossil mites may have contributed to the formation of the amber droplets, but we find that the abundance of amber during the Carnian (ca. 230 Ma) is globally anomalous for the pre-Cretaceous and may, alternatively, be related to paleoclimate. Further recovery of arthropods in Carnian-aged amber is promising and will have profound implications for understanding the evolution of terrestrial members of the most diverse phylum of organisms. PMID:22927387

Schmidt, Alexander R; Jancke, Saskia; Lindquist, Evert E; Ragazzi, Eugenio; Roghi, Guido; Nascimbene, Paul C; Schmidt, Kerstin; Wappler, Torsten; Grimaldi, David A

2012-09-11

164

Arthropods in amber from the Triassic Period  

PubMed Central

The occurrence of arthropods in amber exclusively from the Cretaceous and Cenozoic is widely regarded to be a result of the production and preservation of large amounts of tree resin beginning ca. 130 million years (Ma) ago. Abundant 230 million-year-old amber from the Late Triassic (Carnian) of northeastern Italy has previously yielded myriad microorganisms, but we report here that it also preserves arthropods some 100 Ma older than the earliest prior records in amber. The Triassic specimens are a nematoceran fly (Diptera) and two disparate species of mites, Triasacarus fedelei gen. et sp. nov., and Ampezzoa triassica gen. et sp. nov. These mites are the oldest definitive fossils of a group, the Eriophyoidea, which includes the gall mites and comprises at least 3,500 Recent species, 97% of which feed on angiosperms and represents one of the most specialized lineages of phytophagous arthropods. Antiquity of the gall mites in much their extant form was unexpected, particularly with the Triassic species already having many of their present-day features (such as only two pairs of legs); further, it establishes conifer feeding as an ancestral trait. Feeding by the fossil mites may have contributed to the formation of the amber droplets, but we find that the abundance of amber during the Carnian (ca. 230 Ma) is globally anomalous for the pre-Cretaceous and may, alternatively, be related to paleoclimate. Further recovery of arthropods in Carnian-aged amber is promising and will have profound implications for understanding the evolution of terrestrial members of the most diverse phylum of organisms. PMID:22927387

Schmidt, Alexander R.; Jancke, Saskia; Lindquist, Evert E.; Ragazzi, Eugenio; Roghi, Guido; Nascimbene, Paul C.; Schmidt, Kerstin; Wappler, Torsten; Grimaldi, David A.

2012-01-01

165

Scale and time dependence of serial correlations in word-length time series of written texts  

NASA Astrophysics Data System (ADS)

This work considered the quantitative analysis of large written texts. To this end, the text was converted into a time series by taking the sequence of word lengths. The detrended fluctuation analysis (DFA) was used for characterizing long-range serial correlations of the time series. To this end, the DFA was implemented within a rolling window framework for estimating the variations of correlations, quantified in terms of the scaling exponent, strength along the text. Also, a filtering derivative was used to compute the dependence of the scaling exponent relative to the scale. The analysis was applied to three famous English-written literary narrations; namely, Alice in Wonderland (by Lewis Carrol), Dracula (by Bram Stoker) and Sense and Sensibility (by Jane Austen). The results showed that high correlations appear for scales of about 50-200 words, suggesting that at these scales the text contains the stronger coherence. The scaling exponent was not constant along the text, showing important variations with apparent cyclical behavior. An interesting coincidence between the scaling exponent variations and changes in narrative units (e.g., chapters) was found. This suggests that the scaling exponent obtained from the DFA is able to detect changes in narration structure as expressed by the usage of words of different lengths.

Rodriguez, E.; Aguilar-Cornejo, M.; Femat, R.; Alvarez-Ramirez, J.

2014-11-01

166

GLOBAL TRIASSIC TETRAPOD BIOSTRATIGRAPHY AND BIOCHRONOLOGY: 2007 STATUS  

Microsoft Academic Search

The global Triassic timescale based on tetrapod biochronology remains a robust tool for both global and regional age assignment and correlation. The Lootsbergian and Nonesian land-vertebrate faunachrons (LVFs) are of Early Triassic age; cross correlation of part of the Lootsbergian to the Olenekian and all or part of the Nonesian to the Anisian lacks support. In the South African Karoo

SPENCER G. LUCAS; ADRIAN P. HUNT; ANDREW B. HECKERT; JUSTIN A. SPIELMANN

2007-01-01

167

Time scaling with efficient time-propagation techniques for atoms and molecules in pulsed radiation fields  

SciTech Connect

We present an ab initio approach to solving the time-dependent Schroedinger equation to treat electron- and photon-impact multiple ionization of atoms or molecules. It combines the already known time-scaled coordinate method with a high-order time propagator based on a predictor-corrector scheme. In order to exploit in an optimal way the main advantage of the time-scaled coordinate method, namely, that the scaled wave packet stays confined and evolves smoothly toward a stationary state, of which the squared modulus is directly proportional to the electron energy spectra in each ionization channel, we show that the scaled bound states should be subtracted from the total scaled wave packet. In addition, our detailed investigations suggest that multiresolution techniques like, for instance, wavelets are the most appropriate ones to represent the scaled wave packet spatially. The approach is illustrated in the case of the interaction of a one-dimensional model atom as well as atomic hydrogen with a strong oscillating field.

Hamido, Aliou; Frapiccini, Ana Laura; Piraux, Bernard [Institute of Condensed Matter and Nanosciences, Universite Catholique de Louvain, Batiment de Hemptinne, 2, chemin du cyclotron, B-1348 Louvain-la Neuve (Belgium); Eiglsperger, Johannes [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Physik Departement, Technische Universitaet Muenchen, D-85747 Garching (Germany); Madronero, Javier [Physik Departement, Technische Universitaet Muenchen, D-85747 Garching (Germany); Mota-Furtado, Francisca; O'Mahony, Patrick [Department of Mathematics, Royal Holloway, University of London, Egham, TW20 0EX Surrey (United Kingdom)

2011-07-15

168

Tethys- and Atlas-related deformations in the Triassic Basin, Algeria  

SciTech Connect

Petroleum provinces of Algeria can be divided into Paleozoic and Mesozoic domains. Paleozoic basins are located on the Gondwanaland paleo-continent where the last significant tectonic episode is ascribed to the Late Paleozoic Hercynian Orogeny. Mesozoic basins are located on the south margin of the Neo-Tethyan seaway. These basins were subject to varying degrees of contractional deformation during the Cenozoic Atlas Orogeny. The Triassic Basin of Algeria is a Tethyan feature located above portions of the Paleozoic Oued M`ya and Ghadames Basins. Paleozoic strata are deeply truncated at the Hercynian Unconformity on a broad arch between the older basins. This is interpreted to reflect rift margin rebound during Carboniferous time. Continental Lower Triassic sediments were deposited in a series of northeast trending basins which opened as the Neo-Tethys basin propagated from east to west between Africa and Europe. Middle Triassic marine transgression from the east resulted in evaporate deposition persisting through the Early Jurassic. Passive margin subsidence associated with carbonate marine deposition continued through the Early Cretaceous. Several zones of coeval wrench deformation cross the Atlas and adjoining regions. In the Triassic Basin, inversion occurred before the end of the Early Cretaceous. This episode created discrete uplifts, where major hydrocarbon accumulations have been discovered, along northeast trending lineaments. During the Eocene, the main phase of the Atlas Orogeny produced low amplitude folding of Jurassic and Cretaceous sediments. The folds detach within the Triassic-Jurassic evaporate interval. Many of these folds have been tested without success, as the deeper reservoirs do not show structural closure.

Jackson, J.S.; Moore, S.R.; Quarles, A.I. [ARCO International Oil and Gas Company, Plano, TX (United States)

1995-08-01

169

Parallel trends in organic and inorganic carbon isotopes across the Permian/Triassic boundary  

SciTech Connect

Stable carbon isotope ratios in both inorganic and organic reservoirs have been widely applied to model environmental and sedimentological changes on a global scale. Most studies dealing with major extinction events have used the record of inorganic carbon. In this paper the authors report the relation between shifts in carbon-13 content of organic matter and coexisting carbonate fractions at a major extinction event, the Permian/Triassic boundary. They found that both [delta][sup 13]C[sub carb] and [delta][sup 13]C[sub org] of the surface ocean varied dramatically across the boundary, but the fractionation [Delta][sup 13]C between organic matter and carbonate remained constant. This result appreciably restricts the interpretation of changes in the carbon cycle during this critical interval. The new data are best explained by a combination of two mechanisms for variation in [delta][sup 13]C[sub carb]: (1) burial and erosion of organic carbon, with a long time constant; and (2) sequestration of organic carbon into shallow and deep oceanic reservoirs, with a shorter time constant. For application to their case, the first mechanism is limited by possible buildup of marine pCO[sub 2], which would increase the isotopic fractionation factor. The second mechanism is limited in application to short-term transient variations in [delta][sup 13]C. Modeling of the carbon cycle and its variations of [delta][sup 13]C must take both mechanisms into account.

Magaritz, M. (Weizmann Inst., Rehovot (Israel)); Krishnamurthy, R.V. (California Inst. of Technology, Pasadena (United States)); Holser, W.T. (Univ. of Oregon, Eugene (United States) Cornell Univ., Ithaca, NY (United States))

1992-12-01

170

The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania.  

PubMed

The rise of dinosaurs was a major event in vertebrate history, but the timing of the origin and early diversification of the group remain poorly constrained. Here, we describe Nyasasaurus parringtoni gen. et sp. nov., which is identified as either the earliest known member of, or the sister-taxon to, Dinosauria. Nyasasaurus possesses a unique combination of dinosaur character states and an elevated growth rate similar to that of definitive early dinosaurs. It demonstrates that the initial dinosaur radiation occurred over a longer timescale than previously thought (possibly 15 Myr earlier), and that dinosaurs and their immediate relatives are better understood as part of a larger Middle Triassic archosauriform radiation. The African provenance of Nyasasaurus supports a southern Pangaean origin for Dinosauria. PMID:23221875

Nesbitt, Sterling J; Barrett, Paul M; Werning, Sarah; Sidor, Christian A; Charig, Alan J

2013-02-23

171

Terrestrial Waters and Sea Level Variations on Interannual Time Scale  

NASA Technical Reports Server (NTRS)

On decadal to multi-decadal time scales, thermal expansion of sea waters and land ice loss are the main contributors to sea level variations. However, modification of the terrestrial water cycle due to climate variability and direct anthropogenic forcing may also affect sea level. For the past decades, variations in land water storage and corresponding effects on sea level cannot be directly estimated from observations because these are almost non-existent at global continental scale. However, global hydrological models developed for atmospheric and climatic studies can be used for estimating total water storage. For the recent years (since mid-2002), terrestrial water storage change can be directly estimated from observations of the GRACE space gravimetry mission. In this study, we analyse the interannual variability of total land water storage, and investigate its contribution to mean sea level variability at interannual time scale. We consider three different periods that, each, depend on data availability: (1) GRACE era (2003-2009), (2) 1993-2003 and (3) 1955-1995. For the GRACE era (period 1), change in land water storage is estimated using different GRACE products over the 33 largest river basins worldwide. For periods 2 and 3, we use outputs from the ISBA-TRIP (Interactions between Soil, Biosphere, and Atmosphere-Total Runoff Integrating Pathways) global hydrological model. For each time span, we compare change in land water storage (expressed in sea level equivalent) to observed mean sea level, either from satellite altimetry (periods 1 and 2) or tide gauge records (period 3). For each data set and each time span, a trend has been removed as we focus on the interannual variability. We show that whatever the period considered, interannual variability of the mean sea level is essentially explained by interannual fluctuations in land water storage, with the largest contributions arising from tropical river basins.

Llovel, W.; Becker, M.; Cazenave, A.; Jevrejeva, S.; Alkama, R.; Decharme, B.; Douville, H.; Ablain, M.; Beckley, B.

2011-01-01

172

Many roads to synchrony: Natural time scales and their algorithms  

NASA Astrophysics Data System (ADS)

We consider two important time scales—the Markov and cryptic orders—that monitor how an observer synchronizes to a finitary stochastic process. We show how to compute these orders exactly and that they are most efficiently calculated from the ?-machine, a process's minimal unifilar model. Surprisingly, though the Markov order is a basic concept from stochastic process theory, it is not a probabilistic property of a process. Rather, it is a topological property and, moreover, it is not computable from any finite-state model other than the ?-machine. Via an exhaustive survey, we close by demonstrating that infinite Markov and infinite cryptic orders are a dominant feature in the space of finite-memory processes. We draw out the roles played in statistical mechanical spin systems by these two complementary length scales.

James, Ryan G.; Mahoney, John R.; Ellison, Christopher J.; Crutchfield, James P.

2014-04-01

173

Role of relaxation time scale in noisy signal transduction  

E-print Network

Intracellular fluctuations, mainly triggered by gene expression, are an inevitable phenomenon observed in living cells. It influences generation of phenotypic diversity in genetically identical cells. Such variation of cellular components is beneficial in some contexts but detrimental in others. To quantify the fluctuations in a gene product, we undertake an analytical scheme for studying few naturally abundant linear as well as branched chain network motifs. We solve the Langevin equations associated with each motif under the purview of linear noise approximation and quantify Fano factor and mutual information. Both quantifiable expressions exclusively depend on the relaxation time (decay rate constant) and steady state population of the network components. We investigate the effect of relaxation time constraints on Fano factor and mutual information to indentify a time scale domain where a network can recognize the fluctuations associated with the input signal more reliably. We also show how input populatio...

Maity, Alok Kumar; Banik, Suman K

2014-01-01

174

Holographic Brownian motion and time scales in strongly coupled plasmas  

NASA Astrophysics Data System (ADS)

We study Brownian motion of a heavy quark in field theory plasma in the AdS/CFT setup and discuss the time scales characterizing the interaction between the Brownian particle and plasma constituents. Based on a simple kinetic theory, we first argue that the mean-free-path time is related to the connected 4-point function of the random force felt by the Brownian particle. Then, by holographically computing the 4-point function and regularizing the IR divergence appearing in the computation, we write down a general formula for the mean-free-path time, and apply it to the STU black hole which corresponds to plasma charged under three U(1)R-charges. The result indicates that the Brownian particle collides with many plasma constituents simultaneously.

Atmaja, Ardian Nata; de Boer, Jan; Shigemori, Masaki

2014-03-01

175

From Permo-Triassic lithospheric thinning to Jurassic rifting at the Adriatic margin: Petrological and geochronological record in Valtournenche (Western Italian Alps)  

NASA Astrophysics Data System (ADS)

Slices of polycyclic metasediments (marbles and meta-cherts) are tectonically amalgamated with the polydeformed basement of the Dent Blanche tectonic system along a major Alpine shear zone in the Western Alps (Becca di Salé area, Valtournenche Valley). A combination of techniques (structural analysis at various scales, metamorphic petrology, geochronology and trace element geochemistry) was applied to determine the age and composition of accessory phases (titanite, allanite and zircon) and their relation to major minerals. The results are used to reconstruct the polyphase structural and metamorphic histories, comprising both pre-Alpine and Alpine cycles. The pre-Alpine evolution is associated with low-pressure high-temperature metamorphism related to Permo-Triassic lithospheric thinning. In meta-cherts, microtextural relations indicate coeval growth of allanite and garnet during this stage, at ~ 300 Ma. Textures of zircon also indicate crystallisation at HT conditions; ages scatter from 263 to 294 Ma, with a major cluster of data at ~ 276 Ma. In impure marble, U-Pb analyses of titanite domains (with variable Al and F contents) yield apparent 206Pb/238U dates range from Permian to Jurassic. Chemical and isotopic data suggest that titanite formed at Permian times and was then affected by (extension-related?) fluid circulation during the Triassic and Jurassic, which redistributed major elements (Al and F) and partially opened the U-Pb system. The Alpine cycle lead to early blueschist facies assemblages, which were partly overprinted under greenschist facies conditions. The strong Alpine compressional overprint disrupted the pre-Alpine structural imprint and/or reactivated earlier structures. The pre-Alpine metamorphic record, preserved in these slices of metasediments, reflects the onset of the Permo-Triassic lithospheric extension to Jurassic rifting.

Manzotti, Paola; Rubatto, Daniela; Darling, James; Zucali, Michele; Cenki-Tok, Bénédicte; Engi, Martin

2012-08-01

176

Problems of correlation of South African and South American tetrapod faunas across the Permian-Triassic boundary  

NASA Astrophysics Data System (ADS)

The best record of continental tetrapod faunas crossing the Permo-Triassic boundary (PTB) is found in the Karoo Basin of South Africa. Similar records are not known elsewhere among the former Gondwanan land masses, but it was recently proposed on the basis of palaeontological evidence that the Buena Vista Formation of Uruguay preserves a South American record of continental PTB tetrapods. The Buena Vista Formation was previously correlated to the Lower Triassic (Olenekian) Sanga do Cabral Formation of Brazil on the basis of lithostratigraphic evidence, but recent collecting in the former unit has produced a tetrapod fauna that is distinct to that documented for the latter. The unequivocal tetrapod fossils that have been described thus far from the Buena Vista Formation include indeterminate mastodonsaurid temnospondyls, a plagiosauroid temnospondyl, and a procolophonid reptile. The temnospondyls belong to Triassic groups, whereas the procolophonid is allied most closely with Early Triassic taxa from the Karoo Basin. We conclude that there is no compelling palaeontological evidence for placing any part of the Buena Vista Formation in the Permian. A precise placement of the Buena Vista Formation in the Triassic on the basis of its tetrapod fauna is not possible at this time. Accordingly, the Karoo Basin of South Africa remains the only Gondwanan basin that records a PTB tetrapod fauna.

Modesto, Sean P.; Botha-Brink, Jennifer

2010-05-01

177

Scaling in a Continuous Time Model for Biological Aging  

NASA Astrophysics Data System (ADS)

In this paper, we consider a generalization to the asexual version of Penna model for biological aging, where we take a continuous time limit. The genotype associated to each individual is an interval of real numbers over which Dirac ?-functions are defined, representing genetically programmed diseases to be switched on at defined ages of the individual life. We discuss two different continuous limits for the evolution equation and two different mutation protocols, to be implemented during reproduction. Exact stationary solutions are obtained and scaling properties are discussed.

de Almeida, R. M. C.; Thomas, G. L.

178

Multiple scale dynamics in proteins probed at multiple time scales through fluctuations of NMR chemical shifts.  

PubMed

Fluctuations of NMR resonance frequency shifts and their relation with protein exchanging conformations are usually analyzed in terms of simple two-site jump processes. However, this description is unable to account for the presence of multiple time scale dynamics. In this work, we present an alternative model for the interpretation of the stochastic processes underlying these fluctuations of resonance frequencies. Time correlation functions of (15)N amide chemical shifts computed from molecular dynamics simulations (MD) were analyzed in terms of a transiently fractional diffusion process. The analysis of MD trajectories spanning dramatically different time scales (? 200 ns and 1 ms [ Shaw, D. E.; Science 2010, 330, 341 - 346]) allowed us to show that our model could capture the multiple scale structure of chemical shift fluctuations. Moreover, the predicted exchange contribution Rex to the NMR transverse relaxation rate is in qualitative agreement with experimental results. These observations suggest that the proposed fractional diffusion model may provide significative improvement to the analysis of NMR dispersion experiments. PMID:24628040

Calligari, Paolo; Abergel, Daniel

2014-04-10

179

Estimating ventilation time scales using overturning stream functions  

NASA Astrophysics Data System (ADS)

A simple method for estimating ventilation time scales from overturning stream functions is proposed. The stream function may be computed using either geometric coordinates or a generalized vertical coordinate, such as potential density (salinity in our study). The method is tested with a three-dimensional circulation model describing an idealized semi-enclosed ocean basin ventilated through a narrow strait over a sill, and the result is compared to age estimates obtained from a passive numerical age tracer. The best result is obtained when using the stream function in salinity coordinates. In this case, the reservoir-averaged advection time obtained from the overturning stream function in salinity coordinates agrees rather well with the mean age of the age tracer, and the corresponding maximum ages agree very well.

Thompson, Bijoy; Nycander, Jonas; Nilsson, Johan; Jakobsson, Martin; Döös, Kristofer

2014-06-01

180

Infrasonic Observations of Thunderstorms at High Latitudes: Time Scales  

NASA Astrophysics Data System (ADS)

The present work summarizes some results of infrasonic observations of thunderstorms recorded in the Northern Scandinavia by the Swedish-Finnish Infrasound Network (SIN). A lightning in the atmosphere is a source of cylindrical shock waves. When the distance from the source increases, more and more energy is transferred into the low-frequency range through the same mechanism as for shock waves from supersonic aircraft. Frequently, semi-regular sequences of lightning with similar orientation and nearly constant repetition frequency are observed. For that reason the spectrum of time delays between individual strokes is studied. It has been found that the apparent random occurrence of strokes seems be a result of superposition of several processes with slowly varying time scales.

Liszka, L. J.

2008-12-01

181

Generalized dynamic scaling for quantum critical relaxation in imaginary time  

NASA Astrophysics Data System (ADS)

We study the imaginary-time relaxation critical dynamics of a quantum system with a vanishing initial correlation length and an arbitrary initial order parameter M0. We find that in quantum critical dynamics, the behavior of M0 under scale transformations deviates from a simple power law, which was proposed for very small M0 previously. A universal characteristic function is then suggested to describe the rescaled initial magnetization, similar to classical critical dynamics. This characteristic function is shown to be able to describe the quantum critical dynamics in both short- and long-time stages of the evolution. The one-dimensional transverse-field Ising model is employed to numerically determine the specific form of the characteristic function. We demonstrate that it is applicable as long as the system is in the vicinity of the quantum critical point. The universality of the characteristic function is confirmed by numerical simulations of models belonging to the same universality class.

Zhang, Shuyi; Yin, Shuai; Zhong, Fan

2014-10-01

182

Coupling among Electroencephalogram Gamma Signals on a Short Time Scale  

PubMed Central

An important goal in neuroscience is to identify instances when EEG signals are coupled. We employ a method to measure the coupling strength between gamma signals (40–100?Hz) on a short time scale as the maximum cross-correlation over a range of time lags within a sliding variable-width window. Instances of coupling states among several signals are also identified, using a mixed multivariate beta distribution to model coupling strength across multiple gamma signals with reference to a common base signal. We first apply our variable-window method to simulated signals and compare its performance to a fixed-window approach. We then focus on gamma signals recorded in two regions of the rat hippocampus. Our results indicate that this may be a useful method for mapping coupling patterns among signals in EEG datasets. PMID:20811477

McAssey, Michael P.; Hsieh, Fushing; Smith, Anne C.

2010-01-01

183

Exact dynamical coarse-graining without time-scale separation  

NASA Astrophysics Data System (ADS)

A family of collective variables is proposed to perform exact dynamical coarse-graining even in systems without time scale separation. More precisely, it is shown that these variables are not slow in general, yet satisfy an overdamped Langevin equation that statistically preserves the sequence in which any regions in collective variable space are visited and permits to calculate exactly the mean first passage times from any such region to another. The role of the free energy and diffusion coefficient in this overdamped Langevin equation is discussed, along with the way they transform under any change of variable in collective variable space. These results apply both to systems with and without inertia, and they can be generalized to using several collective variables simultaneously. The view they offer on what makes collective variables and reaction coordinates optimal breaks from the standard notion that good collective variable must be slow variable, and it suggests new ways to interpret data from molecular dynamics simulations and experiments.

Lu, Jianfeng; Vanden-Eijnden, Eric

2014-07-01

184

Nonlinear Dynamics of Extended Hydrologic Systems over long time scales  

NASA Astrophysics Data System (ADS)

We often view our knowledge of hydrology and hence of nature as intransient, at least over the time scales over which we study processes we wish to predict and understand. Over the last few decades, this assumption has come under question, largely because of the vocal expression of a changing climate, but also the recurrent demonstration of significant land use change, both of which significantly affect the boundary conditions for terrestrial hydrology that is our forte. Most recently, the concepts of hydromorphology and social hydrology have entered the discussion, and the notion that climate and hydrology influence human action, which in turn shapes hydrology, is being recognized. Finally, as a field, we seem to be coming to the conclusion that the hydrologic system is an open system, whose boundaries evolve in time, and that the hydrologic system, at many scales, has a profound effect on the systems that drive it -- whether they be the ecological and climatic systems, or the social system. What a mess! Complexity! Unpredictability! At a certain level of abstraction, one can consider the evolution of these coupled systems with nonlinear feedbacks and ask what types of questions are relevant in terms of such a coupled evolution? What are their implications at the planetary scale? What are their implications for a subsistence farmer in an arid landscape who may under external influence achieve a new transient hydro-ecological equilibrium? What are the implications for the economy and power of nations? In this talk, I will try to raise some of these questions and also provide some examples with very simple dynamical systems that suggest ways of thinking about some practical issues of feedback across climate, hydrology and human behavior.

Lall, Upmanu

2014-05-01

185

Multiple-time-scale motion in molecularly linked nanoparticle arrays.  

PubMed

We explore the transport of electrons between electrodes that encase a two-dimensional array of metallic quantum dots linked by molecular bridges (such as ?,? alkaline dithiols). Because the molecules can move at finite temperatures, the entire transport structure comprising the quantum dots and the molecules is in dynamical motion while the charge is being transported. There are then several physical processes (physical excursions of molecules and quantum dots, electronic migration, ordinary vibrations), all of which influence electronic transport. Each can occur on a different time scale. It is therefore not appropriate to use standard approaches to this sort of electron transfer problem. Instead, we present a treatment in which three different theoretical approaches-kinetic Monte Carlo, classical molecular dynamics, and quantum transport-are all employed. In certain limits, some of the dynamical effects are unimportant. But in general, the transport seems to follow a sort of dynamic bond percolation picture, an approach originally introduced as formal models and later applied to polymer electrolytes. Different rate-determining steps occur in different limits. This approach offers a powerful scheme for dealing with multiple time scale transport problems, as will exist in many situations with several pathways through molecular arrays or even individual molecules that are dynamically disordered. PMID:23199199

George, Christopher; Szleifer, Igal; Ratner, Mark

2013-01-22

186

Critical time scales for advection-diffusion-reaction processes  

NASA Astrophysics Data System (ADS)

The concept of local accumulation time (LAT) was introduced by Berezhkovskii and co-workers to give a finite measure of the time required for the transient solution of a reaction-diffusion equation to approach the steady-state solution [A. M. Berezhkovskii, C. Sample, and S. Y. Shvartsman, Biophys. J.BIOJAU0006-349510.1016/j.bpj.2010.07.045 99, L59 (2010); A. M. Berezhkovskii, C. Sample, and S. Y. Shvartsman, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.83.051906 83, 051906 (2011)]. Such a measure is referred to as a critical time. Here, we show that LAT is, in fact, identical to the concept of mean action time (MAT) that was first introduced by McNabb [A. McNabb and G. C. Wake, IMA J. Appl. Math.IJAMDM0272-496010.1093/imamat/47.2.193 47, 193 (1991)]. Although McNabb's initial argument was motivated by considering the mean particle lifetime (MPLT) for a linear death process, he applied the ideas to study diffusion. We extend the work of these authors by deriving expressions for the MAT for a general one-dimensional linear advection-diffusion-reaction problem. Using a combination of continuum and discrete approaches, we show that MAT and MPLT are equivalent for certain uniform-to-uniform transitions; these results provide a practical interpretation for MAT by directly linking the stochastic microscopic processes to a meaningful macroscopic time scale. We find that for more general transitions, the equivalence between MAT and MPLT does not hold. Unlike other critical time definitions, we show that it is possible to evaluate the MAT without solving the underlying partial differential equation (pde). This makes MAT a simple and attractive quantity for practical situations. Finally, our work explores the accuracy of certain approximations derived using MAT, showing that useful approximations for nonlinear kinetic processes can be obtained, again without treating the governing pde directly.

Ellery, Adam J.; Simpson, Matthew J.; McCue, Scott W.; Baker, Ruth E.

2012-04-01

187

Bilateral Laplace Transforms on Time Scales: Convergence, Convolution, and the Characterization of Stationary Stochastic Time Series  

Microsoft Academic Search

The convergence of Laplace transforms on time scales is generalized to the bilateral case. The bilateral Laplace transform\\u000a of a signal on a time scale subsumes the continuous time bilateral Laplace transform, and the discrete time bilateral z-transform as special cases. As in the unilateral case, the regions of convergence (ROCs) time scale Laplace transforms are\\u000a determined by the time

John M. Davis; Ian A. Gravagne; Robert J. Marks II

2010-01-01

188

Growth mode of Middle Triassic carbonate platforms in the Western Dolomites (Southern Alps, Italy)  

Microsoft Academic Search

The correlation of carbonate platform and slope sediments with biostratigraphically and radiometrically dated basinal successions in the Western Dolomites allows the reconstruction of the growth of a Middle Triassic carbonate platform (Schlern\\/Rosengarten) over a time interval of approximately five ammonoid zones (Reitzi, Secedensis, Curionii, Gredleri, Archelaus zones). The whole platform evolution had a total duration of <4.7Ma and the growth

F. Maurer

2000-01-01

189

Impacts on Earth in the Late Triassic  

NASA Astrophysics Data System (ADS)

Sprayet al. postulate that five widely dispersed terrestrial impact structures with very similar geological age estimates (about 214 million years ago, in the Late Triassic epoch) are evidence of a multiple impact event. Most notably, the three largest impact structures, Saint Martin in western Canada (~40 km diameter), Manicouagan in eastern Canada (~100 km diameter), and Rochechouart in France (~25 km diameter), plot at virtually the same palaeolatitude in a continental reconstruction. Spray et al. suggest that this apparent crater chain was produced within hours as a series of coaxial projectiles collided in rapid succession with the rotating planet Earth, and drew analogies to the recent collision sequence of fragmented comet Shoemaker-Levy 9 with Jupiter.

Kent, Dennis V.

1998-09-01

190

Reid Roundabout Theorem for Symplectic Dynamic Systems on Time Scales  

SciTech Connect

The principal aim of this paper is to state and prove the so-called Reid roundabout theorem for the symplectic dynamic system (S) z{sup {delta}}= cal S {sub t}z on an arbitrary time scale Bbb T , so that the well known case of differential linear Hamiltonian systems (Bbb T = Bbb R ) and the recently developed case of discrete symplectic systems (Bbb T = Bbb Z ) are unified. We list conditions which are equivalent to the positivity of the quadratic functional associated with (S), e.g. disconjugacy (in terms of no focal points of a conjoined basis) of (S), no generalized zeros for vector solutions of (S), and the existence of a solution to the corresponding Riccati matrix equation. A certain normality assumption is employed. The result requires treatment of the quadratic functionals both with general and separated boundary conditions.

Hilscher, R. [Department of Mathematics, Masaryk University Brno, Janackovo nam. 2a, CZ-66295 Brno (Czech Republic)], E-mail: houska@math.muni.cz

2001-07-01

191

Large-scale structure of time evolving citation networks  

NASA Astrophysics Data System (ADS)

In this paper we examine a number of methods for probing and understanding the large-scale structure of networks that evolve over time. We focus in particular on citation networks, networks of references between documents such as papers, patents, or court cases. We describe three different methods of analysis, one based on an expectation-maximization algorithm, one based on modularity optimization, and one based on eigenvector centrality. Using the network of citations between opinions of the United States Supreme Court as an example, we demonstrate how each of these methods can reveal significant structural divisions in the network and how, ultimately, the combination of all three can help us develop a coherent overall picture of the network's shape.

Leicht, E. A.; Clarkson, G.; Shedden, K.; Newman, M. E. J.

2007-09-01

192

Large-scale structure of time evolving citation networks  

E-print Network

In this paper we examine a number of methods for probing and understanding the large-scale structure of networks that evolve over time. We focus in particular on citation networks, networks of references between documents such as papers, patents, or court cases. We describe three different methods of analysis, one based on an expectation-maximization algorithm, one based on modularity optimization, and one based on eigenvector centrality. Using the network of citations between opinions of the United States Supreme Court as an example, we demonstrate how each of these methods can reveal significant structural divisions in the network, and how, ultimately, the combination of all three can help us develop a coherent overall picture of the network's shape.

Leicht, E A; Shedden, Kerby; Newman, M E J

2007-01-01

193

Control of Systems With Slow Actuators Using Time Scale Separation  

NASA Technical Reports Server (NTRS)

This paper addresses the problem of controlling a nonlinear plant with a slow actuator using singular perturbation method. For the known plant-actuator cascaded system the proposed scheme achieves tracking of a given reference model with considerably less control demand than would otherwise result when using conventional design techniques. This is the consequence of excluding the small parameter from the actuator dynamics via time scale separation. The resulting tracking error is within the order of this small parameter. For the unknown system the adaptive counterpart is developed based on the prediction model, which is driven towards the reference model by the control design. It is proven that the prediction model tracks the reference model with an error proportional to the small parameter, while the prediction error converges to zero. The resulting closed-loop system with all prediction models and adaptive laws remains stable. The benefits of the approach are demonstrated in simulation studies and compared to conventional control approaches.

Stepanyan, Vehram; Nguyen, Nhan

2009-01-01

194

Wood remains from the Late Triassic (Carnian) of Jordan and their paleoenvironmental implications  

NASA Astrophysics Data System (ADS)

During field work in the Triassic of Jordan fossil wood remains have been discovered at five horizons (S-1AR-S-5AR) of the Late Triassic (Carnian) Abu Ruweis Formation in NW Jordan. In most horizons wood remains are too badly preserved to allow for a detailed xylotomic investigation. Only two horizons provided material which exhibited anatomical details: (1) in horizon S-1AR we found rare and rather small fragments of woody charcoal exhibiting cellular details (representing the first macroscopic evidence of paleo-wildfires from the Late Triassic of the Middle East), and (2) in horizon S-5AR surfaces of partly compressed (gagatized) and partly permineralized wood fragments exhibited anatomical details that could be investigated by means of scanning electron microscopy. All wood remains that allow for a detailed investigation show features typical of gymnosperms, but at the moment nothing can be said about a more specific taxonomic affinity of most of the woods, although wood from horizon S-5AR exhibits characteristics of protopinoid wood. Our data provide evidence that gymnospermous woody vegetation cover has existed in the source areas of the sediments deposited in the Abu Ruweis Formation in Jordan and that this woody vegetation occasionally experienced wildfires. This, together with lithological data, provides evidence for a seasonally dry (maybe even arid) climate during deposition of the Abu Ruweis Formation. On a larger scale our findings contribute to the very scarce current knowledge about Late Triassic wildfires on the entire continent Gondwana, from where so far only three records of macro-charcoals, as undisputed evidence of paleo-wildfires, have been published from this period.

Abu Hamad, Abdalla M. B.; Jasper, André; Uhl, Dieter

2014-07-01

195

1. Geologic time scale 2. Local stratigraphic column ( Cambrian Flathead -f , Cambrian Wolsey -w , Cambrian  

E-print Network

for each period of geologic time (e.g. Cambrian ­ west to east transgression; Late Jurassic ­ widespread that you know the geologic time scale, at least to the period level. Knowing the time scale is essential

Polly, David

196

Permian and Triassic microfloral assemblages from the Blue Nile Basin, central Ethiopia  

NASA Astrophysics Data System (ADS)

Palynological investigation was carried out on surface samples from up to 400 m thick continental siliciclastic sediments, here referred to as “Fincha Sandstone”, in the Blue Nile Basin, central Ethiopia. One hundred sixty species were identified from 15 productive samples collected along a continuous road-cut exposure. Six informal palynological assemblage zones have been identified. These assemblage zones, in ascending order, are: “Central Ethiopian Permian Assemblage Zone - CEPAZ I”, earliest Permian (Asselian-Sakmarian); “CEPAZ II”, late Early Permian (Artinskian-Kungurian); CEPAZ III - Late Permian (Kazanian-Tatarian); “CETAZ IV”, Lower Triassic (Olenekian Induan); “CETAZ V”, Middle Triassic (Anisian Ladinian); “CETAZ VI”, Late Triassic (Carnian Norian). Tentative age ranges proposed herein are compared with faunally calibrated palynological zones in Gondwana. The overall composition and vertical distribution of miospores throughout the studied section reveals a wide variation both qualitatively and quantitatively. The high frequency of monosaccate pollen in CEPAZ I may reflect a Glossopterid-dominated upland flora in the earliest Permian. The succeeding zone is dominated by straite/taeniate disaccate pollen and polyplicates, suggesting a notable increase in diversity of glossopterids. The decline in the diversity of taeniate disaccate pollen and the concomitant rise in abundance of non-taeniate disaccates in CEPAZ III may suggest the decline in Glossopteris diversity, though no additional evidence is available to equate this change with End-Permian extinction. More diverse and dominant non-taeniate, disaccate, seed fern pollen assignable to FalcisporitesAlisporites in CETAZ IV may represent an earliest Triassic recovery flora. The introduction of new disaccate forms with thick, rigid sacci, such as Staurosaccites and Cuneatisporites, in CETAZ V and VI may indicate the emergence of new gymnospermous plants that might have favourably adapted to coastal plain wetland environments with the return of humid conditions in the Middle to early Late Triassic. The present data constitute the first paleontologically substantiated record for the existence of Permian strata in the Blue Nile Basin. The new results allow for the first time a reliable biostratigraphic subdivision of the central Ethiopia Karoo and its correlation with coeval strata of adjacent regions in Gondwana. From a phytogeographic point of view, the overall microfloral evidence is in support of the position of central Ethiopia occupying the northern part of the southern Gondwana palynofloral province. In view of palaeoecological and paleoclimatic conditions, the microfloral change from the base to the top of the studied section may indicate a response to shifting climatic belts from warm- and cool-temparate climate in the earliest Permian to progressively drier seasonal conditions at successively higher palaeolatitudes during the Late Permian to Middle Triassic.

Dawit, Enkurie L.

2014-11-01

197

Homogenization of historical time series on a subdaily scale  

NASA Astrophysics Data System (ADS)

Homogeneous long-term climatological time series provide useful information on climate back to the preindustrial era. High temporal resolution of climate data is desirable to address trends and variability in the mean climate and in climatic extremes. For Switzerland, three long (~250 yrs) historical time series (Basel, Geneva, Gr. St. Bernhard) that were hitherto available in the form of monthly means only have recently been digitized (in cooperation with MeteoSwiss) on a subdaily scale. The digitized time series contain subdaily data (varies from 2-5 daily measurements) on temperature, precipitation/snow height, pressure and humidity, as subdaily descriptions on wind direction, wind speeds and cloud cover. Long-term climatological records often contain inhomogeneities due to non climatic changes such as station relocations, changes in instrumentation and instrument exposure, changes in observing schedules/practices and environmental changes in the proximity of the observation site. Those disturbances can distort or hide the true climatic signal and could seriously affect the correct assessment and analysis of climate trends, variability and climatic extremes. It is therefore crucial to detect and eliminate artificial shifts and trends, to the extent possible, in the climate data prior to its application. Detailed information of the station history and instruments (metadata) can be of fundamental importance in the process of homogenization in order to support the determination of the exact time of inhomogeneities and the interpretation of statistical test results. While similar methods can be used for the detection of inhomogeneities in subdaily or monthly mean data, quite different correction methods can be chosen. The wealth of information in a high temporal resolution allows more physics-based correction methods. For instance, a detected radiation error in temperature can be corrected with an error model that incorporates radiation and ventilation terms using the subdaily information on cloud cover and wind from the station. The basic approach will be demonstrated.

Kocen, Renate; Brönnimann, Stefan; Breda, Leila; Spadin, Reto; Begert, Michael; Füllemann, Christine

2010-05-01

198

Triassic-Jurassic mass extinction as trigger for the Mesozoic radiation of crocodylomorphs.  

PubMed

Pseudosuchia, one of the two main clades of Archosauria (Reptilia: Diapsida), suffered a major decline in lineage diversity during the Triassic-Jurassic (TJ) mass extinction (approx. 201 Ma). Crocodylomorpha, including living crocodilians and their extinct relatives, is the only group of pseudosuchians that survived into the Jurassic. We reassess changes in pseudosuchian morphological diversity (disparity) across this time interval, using considerably larger sample sizes than in previous analyses. Our results show that metrics of pseudosuchian disparity did not change significantly across the TJ boundary, contrasting with previous work suggesting low pseudosuchian disparity in the Early Jurassic following the TJ mass extinction. However, a significant shift in morphospace occupation between Late Triassic and Early Jurassic taxa is recognized, suggesting that the TJ extinction of many pseudosuchian lineages was followed by a major and geologically rapid adaptive radiation of crocodylomorphs. This marks the onset of the spectacularly successful evolutionary history of crocodylomorphs in Jurassic and Cretaceous ecosystems. PMID:23536443

Toljagic, Olja; Butler, Richard J

2013-06-23

199

PTB mass extinction and earliest Triassic recovery overlooked? New evidence for a marine origin of Lower Triassic mixed carbonate–siliciclastic sediments (Rogenstein Member), Germany  

Microsoft Academic Search

The Central European Permo-Triassic basin was land-locked with occasional connections to the North Pangaea shelf and Tethys. A thick sequence of siliciclastic fluvial and floodplain sediments separates the Late Permian marine carbonate–evaporite cycles of the Zechstein Basin from marine Middle Triassic marls and carbonates of the Germanic Basin. Within this Latest Permian–Middle Triassic siliciclastic interval, the location of the Permian–Triassic

Oliver Weidlich

2007-01-01

200

Did an Impact Trigger the Permian-Triassic Extinction?  

NSDL National Science Digital Library

NASA Astrobiology Institute news story on new evidence of a 251-million year-old impact crater off the western coast of Australia that may have caused the "Great Dying", the Permian-Triassic extinction event.

Morrison, David

2004-07-16

201

1. Introduction Triassic sediments in the southern UK were  

E-print Network

into the Sherwood Sand- stone Group, which is of Early-Middle Triassic (Olenekian-Anisian) age, overlain by the Mer of granitic and metasedi- mentary lithologies of ages of mostly over 550 Ma. These sources were probably

202

Structural studies of melting on the picosecond time scale.  

PubMed

Ultrafast structural studies of laser-induced melting have demonstrated that the solid-liquid phase transition can take place on a picosecond time scale in a variety of materials. Experimental studies using ångström wavelength X-rays from the sub-picosecond pulse source at Stanford (now retired) on non-thermal melting of semi-conductors, such as indium antimonide, employed the decay of a single Bragg-peak to measure the time component of the phase transition. These materials were found to start melting within one picosecond after the laser pulse. Recent computer simulations have described the thermal melting of ice induced by an infrared laser pulse. Here it was shown that melting can happen within a few picoseconds, somewhat slower than non-thermal melting in semi-conductors. These computer simulations are compatible with spectroscopy experiments on ice-melting, demonstrating that simulations form a very powerful complement to experiments targeting the process of phase-transitions. Here we present an overview of recent experimental and theoretical studies of melting, as well as new simulations of ice-melting where the effect of the size of the crystal on scattering is studied. Based on simulations of a near-macroscopic crystal, we predict the decay of the most intense Bragg peaks of ice following heating by laser pulse, by modeling the scattering from the melting sample in the simulations. PMID:18972022

Spoel, David van der; Maia, Filipe R N C; Caleman, Carl

2008-11-14

203

Gyrokinetic Particle Simulation of Microturbulence in Transport Time Scale  

NASA Astrophysics Data System (ADS)

Recent investigations on Alfven waves in gyrokinetic plasmas and their relationship with those in the MHD theory have enabled us to extend the gyrokinetic particle simulation techniques into the kinetic-MHD regime when the finite-Larmor radius effects are important and the time step restrictions imposed by compressional Alfven waves are not desirable.[1,2] Some of the numerical schemes have already been devised based on their thermodynamic properties.[1,2] Here, we propose to use gyrokinetic particle simulation to study microturbulence in transport time scale. The procedures involve the use of finite-? microturbulence simulation as well as the use of transport coefficients in the steady state for predicting density,temperature and parallel current profile changes, along with the use of perpendicular current information for the establishment of equilibrium magnetic structure. Details will be given. [1] W. W. Lee and H. Qin, Phys. Plasmas, to appear (August 2003). [2] W. W. Lee, J. L. V. Lewandowski, T. S. Hahm, and Z. Lin, Phys. Plasmas 8, 4435 (2001).

Lee, W. W.

2003-10-01

204

Use of a Walk Through Time to Facilitate Student Understandings of the Geological Time Scale  

NASA Astrophysics Data System (ADS)

Students often have difficulties in appreciating just how old the earth and the universe are. While they can simply memorize a number, they really do not understand just how big that number really is, in comparison with other, more familiar student referents like the length of a human lifetime or how long it takes to eat a pizza. (See, e.g., R.D. Trend 2001, J. Research in Science Teaching 38(2): 191-221) Students, and members of the general public, also display such well-known misconceptions as the "Flintstone chronology" of believing that human beings and dinosaurs walked the earth at the same time. (In the classic American cartoon "The Flintstones," human beings used dinosaurs as draft animals. As scientists we know this is fiction, but not all members of the public understand that.) In an interdisciplinary undergraduate college class that dealt with astronomy, cosmology, and biological evolution, I used a familiar activity to try to improve student understanding of the concept of time's vastness. Students walked through a pre-determined 600-step path which provided a spatial analogy to the geological time scale. They stopped at various points and engaged in some pre-determined discussions and debates. This activity is as old as the hills, but reports of its effectiveness or lack thereof are quite scarce. This paper demonstrates that this activity was effective for a general-audience, college student population in the U.S. The growth of student understandings of the geological time scale was significant as a result of this activity. Students did develop an understanding of time's vastness and were able to articulate this understanding in various ways. This growth was monitored through keeping track of several exam questions and through pre- and post- analysis of student writings. In the pre-writings, students often stated that they had "no idea" about how to illustrate the size of the geological time scale to someone else. While some post-time walk responses simply restated what was done in the walk through time, some students were able to develop their own ways of conceptualizing the vastness of the geological time scale. A variety of findings from student understandings will be presented. This work has been supported in part by the Distinguished Scholars Program of the National Science Foundation (DUE-0308557).

Shipman, H. L.

2004-12-01

205

Triassic Leech Cocoon From Antarctica Contains Fossil Bell Animal  

E-print Network

KU ScholarWorks | http://kuscholarworks.ku.edu Triassic Leech Cocoon From Antarctica Contains Fossil Bell Animal 2012 by Benjamin Bomfleur, Hans Kerp, Thomas N. Taylor, Øjvind Moestrup, and Edith L. Taylor This work has been made available.... The original published version can be found at the link below. Bomfleur, B., Kerp, H., Taylor, T., Moestrup, Ø., and Taylor, E. 2012. Triassic Leech Cocoon From Antarctica Contains Fossil Bell Animal. Proceedings of the National Academy of Sciences 109...

Bomfleur, Benjamin; Kerp, Hans; Taylor, Thomas N.; Moestrup, Ø jvind; Taylor, Edith L.

2012-01-01

206

First occurrence of tetrapod footprints from the continental Triassic of the Sidi Said Maachou area (Western Meseta, Morocco)  

NASA Astrophysics Data System (ADS)

The Sidi Said Maachou area in the Moroccan western Meseta preserves a succession, up to 400 m thick, of hitherto poorly studied continental Triassic deposits. Recent detailed geological mapping proposes a lithostratigraphic subdivision of the predominantly red-coloured siliciclastic deposits into three formations. Laminated mudstones and fine-grained sandstones in the upper part of the Oued Oum Er Rbiaa Formation have the most interesting fossil content including plant impressions, rhizoliths, fish scales, and invertebrate and vertebrate traces. These biogenic remains are partially associated with tool marks, microbially induced sedimentary structures, oscillation ripples, desiccation cracks, and halite pseudomorphs, suggesting sedimentation in a playa-like, fluvio-lacustrine system under semiarid conditions. All tetrapod footprints from these beds are assigned to Brachychirotherium parvum and indistinguishable from other occurrences of the ichnogenus in Central Europe and North America. Supposed trackmakers are archosaurs of the crocodile stem-group (Crurotarsi) that were widely spread over Triassic Pangaea. Because Brachychirotherium is only known from Late Triassic (Carnian-Rhaetian) deposits, the same age is attributed to the footprint horizon of the Oued Oum Er Rbiaa Formation. This is the first record of Brachychirotherium on the African continent and the first record of Triassic tetrapod footprints in Morocco outside of the High Atlas.

Hminna, Abdelkbir; Voigt, Sebastian; Klein, Hendrik; Saber, Hafid; Schneider, Jörg W.; Hmich, Driss

2013-04-01

207

Evaluating the uncertainty of predicting future climate time series at the hourly time scale  

NASA Astrophysics Data System (ADS)

A stochastic downscaling methodology is developed to generate hourly, point-scale time series for several meteorological variables, such as precipitation, cloud cover, shortwave radiation, air temperature, relative humidity, wind speed, and atmospheric pressure. The methodology uses multi-model General Circulation Model (GCM) realizations and an hourly weather generator, AWE-GEN. Probabilistic descriptions of factors of change (a measure of climate change with respect to historic conditions) are computed for several climate statistics and different aggregation times using a Bayesian approach that weights the individual GCM contributions. The Monte Carlo method is applied to sample the factors of change from their respective distributions thereby permitting the generation of time series in an ensemble fashion, which reflects the uncertainty of climate projections of future as well as the uncertainty of the downscaling procedure. Applications of the methodology and probabilistic expressions of certainty in reproducing future climates for the periods, 2000 - 2009, 2046 - 2065 and 2081 - 2100, using the 1962 - 1992 period as the baseline, are discussed for the location of Firenze (Italy). The climate predictions for the period of 2000 - 2009 are tested against observations permitting to assess the reliability and uncertainties of the methodology in reproducing statistics of meteorological variables at different time scales.

Caporali, E.; Fatichi, S.; Ivanov, V. Y.

2011-12-01

208

Existence results for time scale boundary value problem  

NASA Astrophysics Data System (ADS)

In this paper, we establish some existence results for positive solutions to a class of singular boundary value problem on time scale by using the Krasnosel'skii fixed point theorem. Two examples are presented as applications. The conditions we used in this paper are different from those in [D.R. Anderson, Eigenvalue intervals for a two-point boundary value problem on a measure chain, J. Comput. Appl. Math. 141 (2002) 57-64; C.J. Chyan, J. Henderson, Eigenvalues problems for nonlinear differential equations on a measure chain, J. Math. Anal. Appl. 245 (2000) 547-559; L.H. Erbe, A. Peterson Positive solutions for nonlinear differential equation on a measure chain, Math. Comput. Modelling 32 (2000) 571-585; L.H. Erbe, H.Y. Wang, On the existence of positive solutions of ordinary differential equations, Proc. Amer. Math. Soc. 120 (1994) 743-748; J. Henderson, H.Y. Wang, Positive solutions for nonlinear eigenvalue problems, J. Math. Anal. Appl. 208 (1997) 252-259; C.H. Hong, C.C. Yeh, Positive solutions for eigenvalue problems on a measure chain, Nonlinear Anal. 51 (2002) 499-507; W.C. Lian; W.F. Wong; C.C. Yeh, On the existence of positive solutions of nonlinear differential equations, Proc. Amer. Math. Soc. 124 (1996) 1117-1126; J. Liang, T.J. Xiao, Z.C. Hao, Positive solutions of singular differential equations on measure chain, Comput. Math. Appl. 49 (2005) 651-663].

Hao, Zhao-Cai; Liang, Jin; Xiao, Ti-Jun

2006-12-01

209

Tectonic implications of Perm-Triassic paleomagnetic results from north and south China  

NASA Astrophysics Data System (ADS)

Late Permian and Early Triassic paleomagnetic results of our own and others show that the North China Block (NCB), South China Block (SCB), and Siberia were not in their present positions relative to each other. Paleomagnetic poles for the NCB that derived from our studies of Permian rocks at several localities in Shanxi and Hebei provinces are concordant with poles from other studies of Permian rocks in Shanxi, Gansu, and Inner Mongolia. In addition, our poles for the Permian Emeishan Basalts and those from many other studies of the same formation over a sizeable portion of the SCB are consistent if we reinterpret the polarity of several of them. Early Triassic poles from both blocks are fairly close to the Late Permian ones, and greatly increase the areal extent covered by the data for the SCB. The equatorial paleolatitudes inferred by the data from both blocks are similar, but the mean declination for the SCB is rotated clockwise more than 60 degrees with respect to that for the NCB. To explain these results we propose a simple tectonic model in which initial collision of the blocks occurred in the Early Triassic near the eastern end of their boundary and progressed westward as the SCB rotated clockwise 67 degrees relative to the NCB. Eastward thinning and eventual disappearance of Triassic marine sediments on the northern margin of the SCB support this model. A simple alternative model involves sinistral movement on a transform fault that wraps around the SCB to the north and west, but evidence for the large Mesozoic displacement (2,500 km minimum) is presently lacking. Jurassic and Cretaceous poles for North and South China and for Siberia are overlapping, but no fold or reversal tests are available for the Jurassic data from China. Thus, the major movements between the three blocks were completed at least by the Late Cretaceous, perhaps during Jurassic time.

Zhao, Xixi; Coe, Robert S.

210

Scale relativity and fractal space-time: Applications to quantum physics, cosmology and chaotic systems  

Microsoft Academic Search

The theory of scale relativity is a new approach to the problem of the origin of fundamental scales and of scaling laws in physics, that consists of generalizing Einstein's principle of relativity (up to now applied to motion laws) to scale transformations. Namely, we redefine space-time resolutions as characterizing the state of scale of the reference system and require that

L. Nottale

1996-01-01

211

Floral changes across the Triassic/Jurassic boundary linked to flood basalt volcanism  

NASA Astrophysics Data System (ADS)

One of the five largest mass extinctions of the past 600million years occurred at the boundary of the Triassic and Jurassic periods, 201.6million years ago. The loss of marine biodiversity at the time has been linked to extreme greenhouse warming, triggered by the release of carbon dioxide from flood basalt volcanism in the central Atlantic Ocean. In contrast, the biotic turnover in terrestrial ecosystems is not well understood, and cannot be readily reconciled with the effects of massive volcanism. Here we present pollen, spore and geochemical analyses across the Triassic/Jurassic boundary from three drill cores from Germany and Sweden. We show that gymnosperm forests in northwest Europe were transiently replaced by fern and fern-associated vegetation, a pioneer assemblage commonly found in disturbed ecosystems. The Triassic/Jurassic boundary is also marked by an enrichment of polycyclic aromatic hydrocarbons, which, in the absence of charcoal peaks, we interpret as an indication of incomplete combustion of organic matter by ascending flood basalt lava. We conclude that the terrestrial vegetation shift is so severe and wide ranging that it is unlikely to have been triggered by greenhouse warming alone. Instead, we suggest that the release of pollutants such as sulphur dioxide and toxic compounds such as the polycyclic aromatic hydrocarbons may have contributed to the extinction.

van de Schootbrugge, B.; Quan, T. M.; Lindström, S.; Püttmann, W.; Heunisch, C.; Pross, J.; Fiebig, J.; Petschick, R.; Röhling, H.-G.; Richoz, S.; Rosenthal, Y.; Falkowski, P. G.

2009-08-01

212

A Group Simulation of the Development of the Geologic Time Scale.  

ERIC Educational Resources Information Center

Explains how to demonstrate to students that the relative dating of rock layers is redundant. Uses two column diagrams to simulate stratigraphic sequences from two different geological time scales and asks students to complete the time scale. (YDS)

Bennington, J. Bret

2000-01-01

213

Geologic history of Florida-Bahama platform, Triassic through Paleocene  

SciTech Connect

This study is based on top-to-bottom examination of samples from 146 wells from the Florida-Bahama platform. Following Triassic graben formation, three different structural configurations develop through time. In the Late Jurassic-Coahuilan, a northwestern and southeastern sedimentary province were separated by the Sarasota arch, located on the west Florida shelf. Modern basin configurations, which began to appear in the Comanchean, were modified by tectonics in Cuba in the early Gulfian. From the Late Jurassic through the Comanchean, the continental margin was occupied by a carbonate complex that restricted marine circulation in some areas. In the southeast, this barrier caused the deposition of lagoonal carbonates and anhydrites; in the north, clastics were deposited. Carbonate-evaporite deposition in the south ended at the close of the Comanchean and was followed by the deposition of chalk and chalky limestone in the Gulfian. During this epoch, the rapid subsidence of the Blake Plateau basin to bathal depths and the collapse of the Florida straits were associated with tectonic activity in northern Cuba. By the middle Gulfian, the Rebecca Shoal barrier reef had appeared on the upthrown northern side of the straits. This barrier reef expanded to encircle the Florida peninsula completely, at which time the Cedar Keys (Paleocene) lagoonal dolomite-anhydrite deposition was initiated.

Winston, G.O.

1988-02-01

214

Studying the Dynamics of Problem Behavior across Multiple Time Scales: Prospects and Challenges.  

ERIC Educational Resources Information Center

As a commentary on the Special Issue, this paper discusses recent advances in the study of change across several time scales. It points out the importance of specifying time scales and putative patterns of change when characterizing problem behavior over developmental time scales. Methods for studying risk and protective mechanisms through…

Howe, George W.

2004-01-01

215

Collisional Time Scales in the Kuiper Disk and Their Implications  

NASA Technical Reports Server (NTRS)

We explore the rate of collisions among bodies in the present-day Kuiper Disk as a function of the total mass and population size structure of the disk. We find that collisional evolution is an important evolutionary process in the disk as a whole, and indeed, that it is likely the dominant evolutionary process beyond approx. 42 AU, where dynamical instability time scales exceed the age of the solar system. Two key findings we report from this modeling work are: that unless the disk's population structure is sharply truncated for radii smaller than approx. 1-2 km, collisions between comets and smaller debris are occurring so frequently in the disk, and with high enough velocities, that the small body (i.e., KM-class object) population in the disk has probably developed into a collisional cascade, thereby implying that the Kuiper Disk comets may not all be primordial, and that the rate of collisions of smaller bodies with larger 100 less R less 400 km objects (like 1992QB(sub 1) and its cohorts) is so low that there appears to be a dilemma in explaining how QB(sub 1)s could have grown by binary accretion in the disk as we know it. Given these findings, it appears that either the present-day paradigm for the formation of Kuiper Disk is failed in some fundamental respect, or that the present-day disk is no longer representative of the ancient structure from which it evolved. This in turn suggests the intriguing possibility that the present-day Kuiper Disk evolved through a more erosional stage reminiscent of the disks around the stars Beta Pictorus, alpha PsA, and alpha Lyr.

Stern, S. Alan

1995-01-01

216

Astronomical timescale calibration for the Permian-Triassic boundary transition interval from global correlation of cyclic marine sequences  

NASA Astrophysics Data System (ADS)

The mass extinctions near the Permian-Triassic boundary (PTB) resulted in the greatest dying of life on Earth. The cause of this catastrophe remains enigmatic. High-resolution chronology is crucial to understanding the recorded pattern of biotic evolution and possible causes for the extinctions. Magnetic susceptibility (MS) data from Shangsi, South China shows evidence for astronomical forcing through the PTB interval, with strong 405-kyr cycling. This allows development of an astrochronology for the PTB interval based on the 405-kyr orbital eccentricity metronome that has been proposed for the Mesozoic timescale. Radioisotope dating combined with the 405-kyr tuned MS series from Shangsi shows that the 405-kyr-cycle predominates throughout the PTB interval. In the Permian segment, ~100-kyr cyclicity dominates, and the 100-kyr-scale MS maxima correlate with high-amplitude precession-scale MS variations. Minima in the ~1.5-Myr, 405-kyr and ~100-kyr cycles converge at 252.6 Ma, approximately 200 kyr before the onset of the main mass extinction near the PTB. In the Triassic aftermath, the recorded astronomical signal is different, with predominant 405-kyr cycles and loss of 100 kyr cyclicity, and appearance of ~33 kyr (obliquity scale) cyclicity; 100-kyr cyclicity strengthens again 2 Myr later. This pattern indicates a change in the response of the depositional environment (or magnetic susceptibility) to astronomical forcing before and after the mass extinction interval. The astrochronology interpolates the timescale between the radioisotopically determined absolute dates; this facilitates estimation of ages for specific events in the PTB crisis, including magnetic reversals, biozone boundaries, and the mass extinctions. An estimated ~700 kyr duration for the Mass Extinction Interval (MEI) at Shangsi based on the 405-kyr tuning is supported by eccentricity-tuned estimates of three other sections in China (Meishan, Huangzhishan, and Heping), and two Alpine sections (Gartnerkofel, Austria and Bulla, Italy) from the eastern and western margins of the Palaeo-Tethys Ocean during PTB time. This suggests that the PTB mass extinctions were not the result of a single catastrophic event. Siberian trap volcanism was largely synchronous with the MEI and appears to be the most likely cause of the mass extinctions; astronomically paced climate change may also have played a role.

Huang, C.; Hinnov, L. A.; Tong, J.; Chen, Z.

2011-12-01

217

Time-resolved and time-scale adaptive measures of spike train synchrony.  

PubMed

A wide variety of approaches to estimate the degree of synchrony between two or more spike trains have been proposed. One of the most recent methods is the ISI-distance which extracts information from the interspike intervals (ISIs) by evaluating the ratio of the instantaneous firing rates. In contrast to most previously proposed measures it is parameter free and time-scale independent. However, it is not well suited to track changes in synchrony that are based on spike coincidences. Here we propose the SPIKE-distance, a complementary measure which is sensitive to spike coincidences but still shares the fundamental advantages of the ISI-distance. In particular, it is easy to visualize in a time-resolved manner and can be extended to a method that is also applicable to larger sets of spike trains. We show the merit of the SPIKE-distance using both simulated and real data. PMID:21129402

Kreuz, Thomas; Chicharro, Daniel; Greschner, Martin; Andrzejak, Ralph G

2011-01-30

218

Real time density functional simulations of quantum scale conductance  

E-print Network

We study electronic conductance through single molecules by subjecting a molecular junction to a time dependent potential and propagating the electronic state in real time using time-dependent density functional theory ...

Evans, Jeremy Scott

2009-01-01

219

Evidence for a late Triassic multiple impact event on Earth  

NASA Astrophysics Data System (ADS)

We present evidence for a multiple impact event that occurred on Earth. Five terrestrial impact structures have been found to possess comparable ages, coincident with the Norian stage of the Triassic period. These craters are Rochechouart (France), Manicouagan and Saint Martin (Canada), Obolon' (Ukraine), and Red Wing (USA). When these impact structures are plotted on a tectonic reconstruction of the North American and Eurasian plates for 214 Myr before present, the three largest structures (Rochechouart, Manicouagan and Saint Martin) are colatitudinal at 22.8 deg and span 43.5 deg of palaeolongitude. These structures may thus represent the remains of a crater chain at least 4462 km long. The Obolon' and Red Wing craters, on the other hand, lie on great circles of identical declination with Rochechouart and Saint Martin, respectively. We therefore suggest that the five impact structures were formed at the same time (within hours) during a multiple impact event caused by a fragmented comet or asteroid colliding with Earth.

Spray, John G.; Kelley, Simon P.; Rowley, David B.

1998-03-01

220

A simple scaling for the minimum instability time-scale of two widely spaced planets  

NASA Astrophysics Data System (ADS)

Long-term instability in multiplanet exosystems is a crucial consideration when confirming putative candidates, analysing exoplanet populations, constraining the age of exosystems and identifying the sources of white dwarf pollution. Two planets that are Hill stable are separated by a wide-enough distance to ensure that they will never collide. However, Hill-stable planetary systems may eventually manifest Lagrange instability when the outer planet escapes or the inner planet collides with the star. We show empirically that for two nearly coplanar Hill-stable planets with eccentricities less than about 0.3, instability can manifest itself only after a time corresponding to x initial orbits of the inner planet, where log10x ˜ 5.2[?/(MJupiter/M?)]-0.18 and ? is the planet-star mass ratio. This relation applies to any type of equal-mass secondaries, and suggests that two low-eccentricity Hill-stable terrestrial-mass or smaller mass planets should be Lagrange stable throughout the main-sequence lifetime of any white dwarf progenitor. However, Hill-stable giant planets are not guaranteed to be Lagrange stable, particularly within a few tens of per cent beyond the critical Hill separation. Our scaling represents a useful `rule of thumb' for planetary population syntheses or individual systems for which performing detailed long-term integrations is unfeasible.

Veras, Dimitri; Mustill, Alexander J.

2013-07-01

221

Long-term oceanic changes prior the end-Triassic mass extinction  

NASA Astrophysics Data System (ADS)

A number of potential causes and kill mechanisms have been proposed for the end-Triassic mass extinction such as palaeoclimatic and sea-level variations, massive volcanism and ocean acidification. Recent analysis of the stomatal index and density of fossil leaves and geochemical research on pedogenic carbonate nodules are suggestive of rising atmospheric CO2 concentration and fluctuating climate in the Rhaetian. It seems therefore probable that the end-Triassic event was preceded by large climatic fluctuations and environmental perturbations in the Rhaetian which might have partly affected the composition and diversity of the terrestrial and marine biota prior to the end-Triassic interval. The Northern Calcareous Alps (NCA) has long been favored for the study of the Rhaetian, since the GSSP of the Triassic/Jurassic (T/J) boundary and other important T/J sections are situated in this region. However, the most famous Rhaetian sections in the NCA are composed of carbonates from the Koessen Formation and were situated in a large isolated intraplatform Basin (the Eiberg Basin), bordered to the south-east by a well-developed coral reef in the NW of the Tethys border. Several Rhaetian sections composed of marls and shales of the Zlambach Formation were deposited at the same time on the other side of this reef, in the oceanic Halstatt Basin, which was in direct connection to the Tethys. Here, we present new results on sedimentology, stable isotope and trace element analysis of both intraplatform and oceanic basin deposits in the NCA. Intraplatform Rhaetian sections from the Koessen Formation bear a few minor intervals of shales with enrichments in organic matter, some of which are associated to carbon isotopic excursions. Oceanic sections from the Hallstatt Basin are characterized at the base by very cyclic marl-limestone alternations. Higher up in the section, sediments progressively turn into pure shale deposits and the top of the Formation is characterized by organic-rich, laminated black shales. This interval of black shales is associated with a 2 per mil negative carbon isotopic excursion and a strong warming as suggested by fluctuations in oxygen isotopes. Forthcoming geochemical and paleontological analysis on these two Formations should help us : (1) better constrain the stratigraphy of the Rhaetian in the NCA by correlating geochemical and climatic events that took place both in the intraplaform (Eiberg) and oceanic (Hallstatt) Basin, (2) decipher localized vs large Tethyan anoxic events and associated carbon-cycle perturbations and (3) constrain the possible influence of Rhaetian climatic perturbations on the biota before the end-Triassic mass extinction.

Clémence, Marie-Emilie; Mette, Wolfgang; Thibault, Nicolas; Korte, Christoph

2014-05-01

222

Permo-Triassic collisional orogenesis and transition to intraplate sinistral shear in southeastern Mongolia  

NASA Astrophysics Data System (ADS)

Southeastern Mongolia is part of a vast accretionary complex involving Paleozoic arc terranes of the Altaid tectonic collage that collided with North China during closure of the Paleo-Asian Ocean. The region also records a complex history of post-collisional polyphase Triassic-Quaternary intraplate deformation. We present new 40Ar/39Ar and U/Pb titanite data that place temporal constraints on the evolution of collisional orogenesis and the transition to intraplate deformation in southeastern Mongolia where highly deformed and metamorphosed Lower-Upper Permian turbidite successions mark final closure of a remnant ocean basin between the Paleozoic arc terranes and the North China block. At Nomgon, the turbidite sequences are structurally bound by deformed metasediments, including marbles, of higher strain and metamorphic grade. 40Ar/39Ar step heating analyses of hornblende from a granitoid and white mica from muscovite schist along the SW and S margins of the turbidites yield plateau ages of 274 and 273 Ma, respectively. White mica from mylonitic rocks along the NW margin of the Nomgon block yielded a 40Ar/39Ar spectrum with a loss profile and 234 Ma weighted mean age. At Bulgan Uul, an offset correlative of the Nomgon section, the transition from marine to terrestrial sedimentation is cross-cut by an intermediate-mafic dike swarm for which hornblende yielded a 245 Ma 40Ar/39Ar plateau age. To the north and structurally below a carbonate klippe, hornblende from the metamorphosed and boudinaged equivalent of the dike gave a 40Ar/39Ar 227 Ma weighted mean age. Biotite from the same boudin and its host gneiss both yield complicated spectra but are consistent with Late Triassic metamorphism and deformation. Late Triassic metamorphic tectonites at Tavan Har record evidence for partial melting at amphibolite-facies conditions and multiple generations of intrusions. Field, petrographic, and U/Pb zircon analyses indicate that the protoliths of the metamorphic tectonites are Paleozoic volcanic and sedimentary sequences. U/Pb titanite data from amphibolites and amphibolite-facies gneisses yield an older population c. 274 Ma, and two younger populations at 244 and 224 Ma. The latter is consistent with 40Ar/39Ar data that constrain the timing of amphibolite-facies sinistral shear in the East Gobi Fault Zone (EGFZ). Taken together and integrated with ongoing studies, these data along strike of the EGFZ suggest that Permian collisional orogenesis in SE Mongolia continued until the Early Triassic and that the transition to intraplate sinistral shear along the NE-trending EGFZ occurred by the Late Triassic (Carnian), dissecting the closed oceanic basin.

Webb, L. E.; Taylor, J. P.; Heumann, M. J.; Johnson, C. L.; Stypula, M.; Kylander-Clark, A. R.

2011-12-01

223

Local scale invariance as dynamical space-time symmetry in phase-ordering kinetics  

E-print Network

The scaling of the spatio-temporal response of coarsening systems is studied through simulations of the 2D and 3D Ising model with Glauber dynamics. The scaling functions agree with the prediction of local scale invariance, extending dynamical scaling to a space-time dynamical symmetry.

Malte Henkel; Michel Pleimling

2003-02-24

224

Reaching extended length scales and time scales in atomistic simulations via spatially parallel temperature-accelerated dynamics  

Microsoft Academic Search

We present a method for performing parallel temperature-accelerated dynamics TAD simulations over extended length scales. In our method, a two-dimensional spatial decomposition is used along with the recently proposed semirigorous synchronous sublattice algorithm of Shim and Amar Phys. Rev. B 71, 125432 2005. The scaling behavior of the simulation time as a function of system size is studied and compared

Yunsic Shim; Jacques G. Amar; B. P. Uberuaga; A. F. Voter

2007-01-01

225

Reaching extended length scales and time scales in atomistic simulations via spatially parallel temperature-accelerated dynamics  

Microsoft Academic Search

We present a method for performing parallel temperature-accelerated dynamics (TAD) simulations over extended length scales. In our method, a two-dimensional spatial decomposition is used along with the recently proposed semirigorous synchronous sublattice algorithm of Shim and Amar [Phys. Rev. B 71, 125432 (2005)]. The scaling behavior of the simulation time as a function of system size is studied and compared

Yunsic Shim; Jacques G. Amar; B. P. Uberuaga; A. F. Voter

2007-01-01

226

A POLYNOMIAL-TIME AFFINE-SCALING METHOD FOR ...  

E-print Network

We develop a natural variant of Dikin's affine-scaling method, first for semidefinite ... displayed for a Klee-Minty cube that given ? > 0, by beginning at a particular interior point .... In section 3 we are thus led to bring duality into the picture, even

2014-10-22

227

The biology of time across different scales Dean V Buonomano  

E-print Network

of large networks of neurons--lack the digital precision of modern clocks. Second, the features required a traffic light will change,or control the circadian fluctuations in sleep-wake cycles. The mechanisms oscillations, such as our sleep-wake cycle. In-between these extremes temporal processing occurs on the scale

Buonomano, Dean

228

Multiple Time Scales And Canards In A Chemical Oscillator  

Microsoft Academic Search

. We present a geometric singular perturbation analysis of a chemicaloscillator. Although the studied three-dimensional model is rather simple its dynamicsare quite complex. In the original scaling the problem has a folded critical manifold whichadditionally becomes tangent to the fast fibers in a region relevant to the dynamics.Thus normal hyperbolicity of the critical manifold is lost in two regions. The

Alexandra Milik Peter Szmolyan

1998-01-01

229

Evidence for recurrent Early Triassic massive volcanism from quantitative interpretation of carbon isotope fluctuations  

Microsoft Academic Search

Carbon cycle disturbance associated with mass extinction at the end of the Permian Period continued through the Early Triassic, an interval of approximately 5 million years. Coincidence of carbon cycle stabilization with accelerated Middle Triassic biotic recovery suggests a link between carbon cycling and biodiversity, but the cause of Early Triassic carbon isotope excursions remains poorly understood. Previous modeling studies have

Jonathan L. Payne; Lee R. Kump

2007-01-01

230

South American Reptiles Found in Virginia: Second Triassic Extinction Constrained in NorthAmerica  

E-print Network

in the period, and an- other great event, the Triassic Jurassic mass ex tinction (201 Ma) closing it (Fig 1 in the Triassic period, with the largest of all extinctions, the Permian-Triassic event (245 Ma), ushering of large lakes, controlled by orbitally induced (Milan- kovitchtype) climate change, with a period

Olsen, Paul E.

231

Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation in the Fundy basin  

E-print Network

Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation] characterized the Triassic as perhaps the most arid period of the Phanerozoic, citing evidence for widespread,5] and the apparent expan- sion of deserts in the Triassic and Early Jurassic to an extent not since repeated [6

Olsen, Paul E.

232

Tectonostratigraphy, Biostratigraphy, and Magnetostratigraphy of Late Triassic-Early Jurassic Red  

E-print Network

Tectonostratigraphy, Biostratigraphy, and Magnetostratigraphy of Late Triassic-Early Jurassic Red Brook Street, Box 1846, Providence Rl 02912, USA Late Triassic-Early Jurassic predominately continental red beds formed during the Triassic/Jurassic rifting of Pangeacrop out over large portions of northern

Olsen, Paul E.

233

CAUSES AND CONSEQUENCES OF THE TRIASSIC-JURASSIC MASS EXTINCTION AS SEEN FROM THE HARTFORD BASIN  

E-print Network

B5-1 CAUSES AND CONSEQUENCES OF THE TRIASSIC-JURASSIC MASS EXTINCTION AS SEEN FROM THE HARTFORD of the most severe mass extinctions of the Phanerozoic, the Triassic-Jurassic event is greater or equal dinosaurs (whose descendants survive as birds) and mammals. The Triassic-Jurassic mass extinction may have

Olsen, Paul E.

234

Triassic-Jurassic faunal and floral transition in the Fundy Basin, Nova  

E-print Network

Triassic-Jurassic faunal and floral transition in the Fundy Basin, Nova Scotia Paul E. Olsen Considered one of the five great mass extinctions of the Phanerozoic, the Triassic- Jurassic event), although dissenters remain (e.g. Hallam, 2002; Tanner et al., 2004). Explanations for the Triassic-Jurassic

Olsen, Paul E.

235

Scaling up dynamic time warping for datamining applications  

Microsoft Academic Search

There has been much recent interest in adapting data mining algorithms to time series databases. Most of these algorithms need to compare time series. Typically some variation of Euclidean distance is used. However, as we demonstrate in this paper, Euclidean distance can be an extremely brittle distance measure. Dynamic time warping (DTW) has been suggested as a technique to allow

Eamonn J. Keogh; Michael J. Pazzani

2000-01-01

236

Lethally Hot Temperatures During the Early Triassic Greenhouse  

NASA Astrophysics Data System (ADS)

Global warming is widely regarded to have played a contributing role in numerous past biotic crises. Here, we show that the end-Permian mass extinction coincided with a rapid temperature rise to exceptionally high values in the Early Triassic that were inimical to life in equatorial latitudes and suppressed ecosystem recovery. This was manifested in the loss of calcareous algae, the near-absence of fish in equatorial Tethys, and the dominance of small taxa of invertebrates during the thermal maxima. High temperatures drove most Early Triassic plants and animals out of equatorial terrestrial ecosystems and probably were a major cause of the end-Smithian crisis.

Sun, Yadong; Joachimski, Michael M.; Wignall, Paul B.; Yan, Chunbo; Chen, Yanlong; Jiang, Haishui; Wang, Lina; Lai, Xulong

2012-10-01

237

Redescription of Bellerophon bittneri (Gastropoda: Triassic) from Wyoming.  

USGS Publications Warehouse

Bellerophon bittneri Newell and Kummel is an Early Triassic bellerophontacean from the Dinwoody Formation in the Wind River Mountains. The available type material consists of one fair, but incomplete, external mold, which resembles a Bellerophon but is actually a Retispira. After repeated search, additional specimens were found at one locality in the southern Wind River Range of Wyoming; Retispira bittneri is redescribed from this new material. Like other Triassic bellerophontaceans, there is nothing unusual about the species apart from occurrence in the Mesozoic; it is clearly congeneric with Permian Retispira from underlying rocks. -Authors

Yochelson, E.L.; Boyd, D.W.; Wardlaw, B.

1985-01-01

238

Macrofossil Evidence For Pleuromeialean Lycophytes From the Triassic of Antarctica  

E-print Network

KU ScholarWorks | http://kuscholarworks.ku.edu Macrofossil Evidence For Pleuromeialean Lycophytes From the Triassic of Antarctica 2010 by Benjamin Bomfleur, Michael Krings, Edith L. Taylor, and Thomas N. Taylor This work has been made available...-203. Published version: http://dx.doi.org/10.4202/app.2010.0022 Terms of Use: http://www2.ku.edu/~scholar/docs/license.shtml Macrofossil evidence for pleuromeialean lycophytes from the Triassic of Antarctica BENJAMIN BOMFLEUR, MICHAEL KRINGS, EDITH L. TAYLOR...

Bomfleur, Benjamin; Krings, Michael; Taylor, Edith L.; Taylor, Thomas N.

2010-01-01

239

Photic zone euxinia during the Permian-triassic superanoxic event.  

PubMed

Carbon and sulfur isotopic data, together with biomarker and iron speciation analyses of the Hovea-3 core that was drilled in the Perth Basin, Western Australia, indicate that euxinic conditions prevailed in the paleowater column during the Permian-Triassic superanoxic event. Biomarkers diagnostic for anoxygenic photosynthesis by Chlorobiaceae are particularly abundant at the boundary and into the Early Triassic. Similar conditions prevailed in the contemporaneous seas off South China. Our evidence for widespread photiczone euxinic conditions suggests that sulfide toxicity was a driver of the extinction and a factor in the protracted recovery. PMID:15661975

Grice, Kliti; Cao, Changqun; Love, Gordon D; Böttcher, Michael E; Twitchett, Richard J; Grosjean, Emmanuelle; Summons, Roger E; Turgeon, Steven C; Dunning, William; Jin, Yugan

2005-02-01

240

Storm-time Observations of Adiabatically-Scaled GOES electrons  

NASA Astrophysics Data System (ADS)

Electron populations in the Earth's radiation belts are subject to many energization and loss processes due to geomagnetic activity. Because satellites are often at fixed energy, they observe particle populations at changing values of the adiabatic invariants, which can result in observational increases and decreases in flux level. We scale geosynchronous phase space densities from GOES satellites for a period encompassing nearly a solar cycle (1995-2006) to a constant value of the first invariant, based on measured energy spectra and magnetic field strengths. We identify changes in the radiation environment during geomagnetic storms using these scaled values and show somewhat different results than previous efforts using unscaled phase space densities do, with relatively more storms showing an increase in phase space density than a decrease. We also observe several examples of sudden energetic electron enhancements during storm main phase, in contrast to the slow recovery phase increases suggested by previous studies using unscaled phase space densities.

Gannon, Jennifer; Elkington, Scot; Onsager, Terry

2010-05-01

241

Global terrestrial biogeochemistry: Perturbations, interactions, and time scales  

SciTech Connect

Global biogeochemical processes are being perturbed by human activity, principally that which is associated with industrial activity and expansion of urban and agricultural complexes. Perturbations have manifested themselves at least since the beginning of the 19th Century, and include emissions of CO{sub 2} and other pollutants from fossil fuel combustion, agricultural emissions of reactive nitrogen, and direct disruption of ecosystem function through land conversion. These perturbations yield local impacts, but there are also global consequences that are the sum of local-scale influences. Several approaches to understanding the global-scale implications of chemical perturbations to the Earth system are discussed. The lifetime of anthropogenic CO{sub 2} in the atmosphere is an important concept for understanding the current and future commitment to an altered atmospheric heat budget. The importance of the terrestrial biogeochemistry relative to the lifetime of excess CO{sub 2} is demonstrated using dynamic, aggregated models of the global carbon cycle.

Braswell, B.H. Jr.

1996-12-01

242

Fractal scaling properties in nonstationary heartbeat time series  

NASA Astrophysics Data System (ADS)

Under healthy conditions, the normal cardiac (sinus) interbeat interval fluctuates in a complex manner. Quantitative analysis using techniques adapted from statistical physics reveals the presence of long-range power-law correlations extending over thousands of heartbeats. This scale-invariant (fractal) behavior suggests that the regulatory system generating these fluctuations is operating far from equilibrium. In contrast, we find that for subjects at high risk of sudden death (e.g. congestive heart failure patients) these long-range correlations break down. Application of fractal scaling analysis and related techniques provides new approaches to assessing cardiac risk and forecasting sudden cardiac death, as well as motivating development of novel physiological models of systems that appear to be ``hetero-dynamic'' rather than ``homeo-static.''

Peng, C.-K.; Havlin, S.; Stanley, H. E.; Goldberger, A. L.

1996-06-01

243

Multiple Time Scales and Canards in a Chemical Oscillator  

Microsoft Academic Search

\\u000a We present a geometric singular perturbation analysis of a chemical oscillator. Although the studied three-dimensional model\\u000a is rather simple, its dynamics are quite complex. In the original scaling the problem has a folded critical manifold which\\u000a additionally becomes tangent to the fast fibers in a region relevant to the dynamics. Thus normal hyperbolicity of the critical\\u000a manifold is lost in

Alexandra Milik; Peter Szmolyan

2001-01-01

244

Detrital zircon provenance of the Late Triassic Songpan-Ganzi complex: Sedimentary record of collision of the North and South China blocks  

USGS Publications Warehouse

Using detrital zircon geochronology, turbidite deposystems fed from distinct sediment sources can be distinguished within the Songpan-Ganzi complex, a collapsed Middle to Late Triassic turbidite basin of central China. A southern Songpan-Ganzi deposystem initially was sourced solely by erosion of the Qinling-Dabie orogen during early Late Triassic time, then by Qinling-Dabie orogen, North China block, and South China block sources during middle to late Late Triassic time. A northern Songpan-Ganzi system was sourced by erosion of the Qinling-Dabie orogen and the North China block throughout its deposition. These separate deposystems were later tectonically amalgamated to form one complex and then uplifted as the eastern Tibet Plateau. ?? 2006 Geological Society of America.

Weislogel, A. L.; Graham, S. A.; Chang, E. Z.; Wooden, J. L.; Gehrels, G. E.; Yang, H.

2006-01-01

245

Time-scale invariance as an emergent property in a perceptron with realistic, noisy neurons  

PubMed Central

In most species, interval timing is time-scale invariant: errors in time estimation scale up linearly with the estimated duration. In mammals, time-scale invariance is ubiquitous over behavioral, lesion, and pharmacological manipulations. For example, dopaminergic drugs induce an immediate, whereas cholinergic drugs induce a gradual, scalar change in timing. Behavioral theories posit that time-scale invariance derives from particular computations, rules, or coding schemes. In contrast, we discuss a simple neural circuit, the perceptron, whose output neurons fire in a clockwise fashion (interval timing) based on the pattern of coincidental activation of its input neurons. We show numerically that time-scale invariance emerges spontaneously in a perceptron with realistic neurons, in the presence of noise. Under the assumption that dopaminergic drugs modulate the firing of input neurons, and that cholinergic drugs modulate the memory representation of the criterion time, we show that a perceptron with realistic neurons reproduces the pharmacological clock and memory patterns, and their time-scale invariance, in the presence of noise. These results suggest that rather than being a signature of higher-order cognitive processes or specific computations related to timing, time-scale invariance may spontaneously emerge in a massively-connected brain from the intrinsic noise of neurons and circuits, thus providing the simplest explanation for the ubiquity of scale invariance of interval timing. PMID:23518297

Buhusi, Catalin V.; Oprisan, Sorinel A.

2013-01-01

246

Scale of Viability and Minimal Time of Crisis  

Microsoft Academic Search

In this paper, we introduce and study the minimal time of a crisis map which measures the minimal time spent outside a given closed domain of constraints by trajectory solutions of a differential inclusion. The interest of such a notion is basically to tackle simultaneously viability and target issues. The main mathematical result characterizes the epigraph of the crisis map

L. Doyen; P. Saint-Pierre

1997-01-01

247

Compile-Time Dynamic Voltage Scaling Settings: Opportunities and Limits  

NSDL National Science Digital Library

The Parapet research group at Princeton University focuses on power-related issues in computer hardware and software design. Citing the importance of power efficiency both in mobile applications as well as in the general goal of shrinking technology sizes on chips, the authors of this paper discuss the role of dynamic voltage scaling (DVS) in managing power during runtime. This interesting technique enables control of "the power consumption by varying a processor's supply voltage...and clock frequency." The paper identifies specific factors that contribute to the effectiveness of DVS and considers the extent to which it can save power.

Malik, Sharad; Martonosi, Margaret; Xie, Fen

248

Scale-Invariant Extinction Time Estimates for Some Singular Diffusion Equations  

E-print Network

Scale-Invariant Extinction Time Estimates for Some Singular Diffusion Equations Yoshikazu Giga that the solution becomes identically zero in finite time. We prove scale-invariant estimates for the extinction and q > 1). Our goal is to prove finite-time extinction, i.e. to show that the solution becomes

249

Geologic Time Scale 2010 1 Minority Science Programs School of Biological Sciences University of California, Irvine  

E-print Network

of Earth's history. By the end of this activity you should be able to: · Understand the magnitude of geologic time · Explain why the geologic time scale is used to show Earth's history. · Describe what early of Earth 4600 4600 ÷ 100 = 46 meters Questions: 1. Why is a time scale used to represent Earth's history

Rose, Michael R.

250

Terrestrial waters and sea level variations on interannual time scale W. Llovel a,  

E-print Network

Terrestrial waters and sea level variations on interannual time scale W. Llovel a, , M. Becker model. For each time span, we compare change in land water storage (expressed in sea level equivalent to multidecadal time scales, thermal expansion of sea waters and land ice loss are the main contributors to sea

Ribes, Aurélien

251

Parametric Timing Analysis and Its Application to Dynamic Voltage Scaling  

E-print Network

of real-time applications to programs with loop-invariant dy- namic loop bounds while retaining tight WCET deployed in safety-critical environ- ments. Examples include avionics, power plants, automobiles, etc

Mueller, Frank

252

Non-clairvoyant Speed Scaling for Weighted Flow Time  

Microsoft Academic Search

\\u000a We study online job scheduling on a processor that can vary its speed dynamically to manage its power. We attempt to extend\\u000a the recent success in analyzing total unweighted flow time plus energy to total weighted flow time plus energy. We first consider\\u000a the non-clairvoyant setting where the size of a job is only known when the job finishes. We

Sze-Hang Chan; Tak-Wah Lam; Lap-Kei Lee

2010-01-01

253

TRIASSIC AND JURASSIC FORMATIONS OF THE NEWARK BASIN  

E-print Network

TRIASSIC AND JURASSIC FORMATIONS OF THE NEWARK BASIN PAUL E. OLSEN Bingham Laboratories, Department of Biology, Yale University, New Haven, Connecticut Abstract Newark Supergroup deposits of the Newark Basin (or lack thereof). Fossils are abundant in the sedimentary formations of the Newark Basin and provide

Olsen, Paul E.

254

Triassic gas potential seen high in Western Canada plains region  

SciTech Connect

This article summarizes results of a recently completed study -- Geological Survey of Canada Bulletin 483 -- of conventional gas resources contained in Triassic strata of the plains portion of the Western Canada basin. The report includes a detailed geological play analysis and numerical assessment of undiscovered gas potential in Part 1, by Bird et al. of the GSC, and an economic analysis, Part 2, by Waghmare et al. of the Energy Sector of Natural Resources Canada in Ottawa. This bulletin on the appraisal of the natural gas potential is part of a series of reports resulting from a comprehensive assessment by GSC of Western Canada gas resources. The Western Canada gas assessment project was divided into seven major play groups on the basis of geological criteria, following major stratigraphic units or structural/tectonic provinces. Each group has a distinct set of geological factors which control size, distribution, and type of hydrocarbon play or reservoir. The major play groups are: the Devonian, Carboniferous-Permian, Triassic, Jurassic to Lower Cretaceous (Mannville), Middle Cretaceous Colorado Group, Upper Cretaceous-Tertiary, and Rocky Mountain foreland belt. About 5% of the discovered in-place gas reserves in the interior plains of Western Canada basin is contained in Triassic rocks. Two-thirds of the discovered in-place gas reserves of the Triassic are contained in the Interior Plains, with the remaining third in Rocky Mountain foreland belt of the Cordilleran Orogen.

Bird, T.D.; Barclay, J.E.; Campbell, R.I.; Lee, P.J. (Geological Survey of Canada, Calgary, Alberta (Canada))

1994-12-05

255

Did an Impact Trigger the Permian-Triassic Extinction?  

NSDL National Science Digital Library

This resource, authored by David Morrison, contains the National Aeronautics and Space Administration's Astrobiology Institute news story on new evidence of a 251-million year-old impact crater off the western coast of Australia that may have caused the "Great Dying", the Permian-Triassic extinction event.

Morrison, David

2009-05-26

256

A new chronology for the end-Triassic mass extinction  

Microsoft Academic Search

The transition from the Triassic to Jurassic Period, initiating the ‘Age of the dinosaurs’, approximately 200Ma, is marked by a profound mass extinction with more than 50% genus loss in both marine and continental realms. This event closely coincides with a period of extensive volcanism in the Central Atlantic Magmatic Province (CAMP) associated with the initial break-up of Pangaea but

M. H. L. Deenen; M. Ruhl; N. R. Bonis; W. Krijgsman; W. M. Kuerschner; M. Reitsma; M. J. van Bergen

2010-01-01

257

Triassic origin and early radiation of multicellular volvocine algae  

E-print Network

Triassic origin and early radiation of multicellular volvocine algae Matthew D. Herron1 , Jeremiah transitions in individuality (ETIs) underlie the water- shed events in the history of life on Earth, including the origins of cells, eukaryotes, plants, animals, and fungi. Each of these events constitutes an increase

258

New Paleoenvironmental and Biotic Records from the Triassic-Jurassic Boundary Interval of the Algarve Basin, Portugal  

NASA Astrophysics Data System (ADS)

Studies of carbonate, bulk organic, and compound-specific stable isotopes of carbon have shown that the Triassic-Jurassic boundary interval (including the end-Triassic mass extinction) displays major, global perturbations to the carbon cycle. These records are instrumental not only in reconstructing environmental change, as they are thought to reflect ecosystem instability and changing atmospheric gas inventories, but, due to their global nature, can be useful tools for stratigraphic correlation. The Algarve Basin, a deformed, extensional basin in the south of Portugal, has potential for yielding insight into the dramatic paleoenvironmental and faunal changes that occurred during the latest Triassic through earliest Jurassic. During this time interval, the basin records an evolution from continental to marginal marine sediments that are interbedded with radioisotopically dated Central Atlantic Magmatic Province (CAMP) basalts, thought to be a major causative agent in the end-Triassic mass extinction. Recent field excavations in the Algarve Basin have documented terrestrial vertebrate remains at multiple horizons, including a rich bone bed densely packed with well-preserved remains of large stereospondyl temnospondyls (skull length up to ~1 meter) positioned close to the Triassic-Jurassic boundary. These stereospondyls may represent some of the latest surviving members of their groups in Europe, and occur in a time interval in which stereospondyl material is scarce and represented primarily by isolated and fragmentary material. Unfortunately, the paleoenvironmental and chronologic framework of the Algarve Basin is not well constrained, despite its importance as a critical record of this time in Earth history. We present a preliminary bulk organic carbon isotope record of early Mesozoic rift-basin sediments from the Algarve Basin. This record exhibits significant variability, but appears to record a trend towards more negative values at the top of the section, though this needs better constraint with further sampling. Although the potential for changes in the source of organic material can be expected to have an effect on the overall signal, the presence of depleted ?13C values in proximity to CAMP basalts relative to stratigraphically lower sections points to the potential for identifying key negative excursions associated with Triassic-Jurassic boundary events in the Algarve Basin.

Kasprak, A. H.; Whiteside, J. H.; Lopes, F. M.; Brusatte, S. L.; Butler, R. J.; Mateus, O.

2010-12-01

259

Uranium comminution ages: Sediment transport and deposition time scales  

NASA Astrophysics Data System (ADS)

The uranium isotope comminution age is determined from the 234U/238U ratio and reflects the timescale associated with the transformation of bedrock to sediment. The comminution age is applicable to Late Pleistocene sediments and measures the amount of time elapsed since sediment generation by mechanical weathering and erosion. The age significance of the 234U/238U ratios is based on physical disruption of the 238U-decay series by recoil loss of 234Th that occurs in mineral grains smaller than 50 ?m. Results from study of fine-grained deep sea sediments in the North Atlantic Ocean, alluvial sediments in California and Australia, and modern glacial outwash are encouraging, but critical aspects of the method require further investigation. Particular issues are the effects of laboratory chemical leaching treatment on sediment samples and estimation of 234U loss rates as a function of grain size. In the North Atlantic marine environment the U isotope variations are inferred to reflect differences in the transport time of the sediment-the time elapsed between the generation of the small sediment particles by glacial action in Iceland and Fennoscandian source areas, and the time of deposition on the seafloor in the North Atlantic Ocean at a drift site south of Iceland. Calculated transport times vary from less than 10 kyr to about 400 kyr, and correlate with provenance and glacial cycles. Application to alluvial sediments in California and Australia suggests that where sediments are glacially-derived and transported short distances, the U comminution age may approximate the sedimentation age, but in larger basins that are not glaciated the sediments retain information about residence/transport times that can extend to ca. 400 kyr. To verify that initial 234U/238U ratios for glacial sediments are close to the secular equilibrium ratio, outwash from several major glaciers around the world was measured and found to be within ± 1% of the accepted equilibrium 234U/238U value.

DePaolo, Donald J.; Lee, Victoria E.; Christensen, John N.; Maher, Kate

2012-11-01

260

Probing Single-Photon Ionization on the Attosecond Time Scale  

SciTech Connect

We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s{sup 2} and from the 3p{sup 6} shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay.

Kluender, K.; Dahlstroem, J. M.; Gisselbrecht, M.; Fordell, T.; Swoboda, M.; Guenot, D.; Johnsson, P.; Mauritsson, J.; L'Huillier, A. [Department of Physics, Lund University, P.O. Box 118, 22100 Lund (Sweden); Caillat, J.; Maquet, A.; Taieeb, R. [Laboratoire de Chimie Physique-Matiere et Rayonnement, Universite Pierre et Marie Curie, 11, Rue Pierre et Marie Curie, 75231 Paris Cedex, 05 (France)

2011-04-08

261

Space Charge Models for Particle Tracking on Long Time Scales  

SciTech Connect

In order to efficiently track charged particles over long times, most tracking codes use either analytic charge distributions or particle-in-cell (PIC) methods based on fast Fourier transforms (FFTs). While useful for theoretical studies, analytic distribution models do not allow accurate simulation of real machines. PIC calculations can utilize realistic space charge distributions, but these methods suffer from the presence of discretization errors. We examine the situation for particle tracking with space charge over long times, and consider possible ideas to improve the accuracy of such calculations.

Holmes, Jeffrey A [ORNL] [ORNL; Cousineau, Sarah M [ORNL] [ORNL; Shishlo, Andrei P [ORNL] [ORNL; Potts III, Robert E [ORNL] [ORNL

2013-01-01

262

Computer Response Time Measurements of Mood, Fatigue and Symptom Scale Items: Implications for Scale Response Time Uses.  

ERIC Educational Resources Information Center

Describes study conducted with U.S. Marine Corps enlisted personnel to measure response time to computer-administered questionnaire items, and to evaluate how measurement of response time might be useful in various research areas. Topics addressed include mood states; the occurrence of straight lining; and experimental effects of sleep loss and…

Ryman, David H.; And Others

1988-01-01

263

Observed Relationships between Large-Scale Tropical Convection and the Tropical Circulation on Subseasonal Time Scales during Northern Hemisphere Winter  

Microsoft Academic Search

The work presented is a correlative study of the interaction between large-scale tropical convection and midlatitude wind anomalies, and the tropical wind field on subseasonal time scales. Outgoing longwave radiation (OLR) is used as a proxy for convection. Correlations are calculated from six years of 5-day averaged data for the December-February (DJF) season. The seasonal cycle and interannual variability are

Brant Liebmann

1987-01-01

264

An analytical framework for quantifying aquifer response time scales associated with transient boundary conditions  

NASA Astrophysics Data System (ADS)

A major challenge in studying coupled groundwater and surface-water interactions arises from the considerable difference in the response time scales of groundwater and surface-water systems affected by external forcings. Although coupled models representing the interaction of groundwater and surface-water systems have been studied for over a century, most have focused on groundwater quantity or quality issues rather than response time. In this study, we present an analytical framework, based on the concept of mean action time (MAT), to estimate the time scale required for groundwater systems to respond to changes in surface-water conditions. MAT can be used to estimate the transient response time scale by analyzing the governing mathematical model. This framework does not require any form of transient solution (either numerical or analytical) to the governing equation, yet it provides a closed form mathematical relationship for the response time as a function of the aquifer geometry, boundary conditions, and flow parameters. Our analysis indicates that aquifer systems have three fundamental time scales: (i) a time scale that depends on the intrinsic properties of the aquifer, (ii) a time scale that depends on the intrinsic properties of the boundary condition, and (iii) a time scale that depends on the properties of the entire system. We discuss two practical scenarios where MAT estimates provide useful insights and we test the MAT predictions using new laboratory-scale experimental data sets.

Jazaei, Farhad; Simpson, Matthew J.; Clement, T. Prabhakar

2014-11-01

265

Space-time scales of internal waves: A progress report  

Microsoft Academic Search

We present a revised model for the distribution of internal wave energy in wave number frequency space. The model is empirical, guided by the following measurements: moored spectra and moored coherences for horizontal and vertical separations (MS, MHC, MVC as functions of frequency), towed spectra and towed vertical and time-lagged coherences (TS, TVC, TLC as functions of horizontal wave number),

Christopher Garrett; Walter Munk

1975-01-01

266

Time scales in the JPL and CfA ephemerides  

Microsoft Academic Search

Over the past decades, the IAU has repeatedly at- tempted to correct its definition of the basic fundamental argu- ment used in the ephemerides. Finally, they have defined a time system which is physically possible, according to the accepted standard theory of gravitation: TCB (\\

E. M. Standish

267

Oil and gas potential of the Triassic in west Siberia  

SciTech Connect

Permian-Triassic rocks are widely spread within the West Siberian basin, and they include volcanics, volcanoclastics, and clastics. Their thickness varies from tens of meters of 3000 m. Recently, three commercial oil pools have been discovered in Triassic effusive-sedimentary rocks. These discoveries, together with other geological and geochemical data, identify the Triassic complex as a major play. Oil-bearing intervals have been found in three different types of sequences; a fourth also may be prospective. The first type is represented by lacustrine-terrigenous sediments, which comprise oil-saturated sandstones interbedded with basalts (the Turin series). Oil influxes were obtained in the Yakhlinskaya and Triyurtin-skaya structures in the Shaim region. The second type is distinguished from the first by the presence of coal-bearing intervals in the upper part. Oil was produced in the Yerofeyev area of the Chelyabinsk garben. The third type differs from the other two by the presence of potassic rhyolites and dacites. Their age is not precisely dated, and supposedly they are of Permian age. The largest oil influxes have been obtained from fractured and eroded rocks of this type in the Rogozhnikovskaya and other places in the Krasnoleninsk region. Rhyodacites often underlie Turin basalts, but locally they occur in the upper part of the series. Triassic and Permian-Trissic rocks of the three types are overlain by Jurassic and Cretaceous rocks with a large break. The fourth type of section is completely terrigenous (Tampei series). It is developed in the northern part of west Siberia. Here Triassic sediments are overlain by the Jurassic complex without a break. According to well-log data, productive horizons occur at Urengoy and Beregovaya (in the Urengoy region).

Bochkarev, V.S.; Kulakhmetov, N.KH.; Nesterov, I.I. (ZapSibNIGNI, Tyumen (Russian Federation))

1993-09-01

268

Experimental investigations of local-time effect existence on laboratory scale and heterogeneity of space-time  

E-print Network

The main subject of the work is experimental investigation of local-time effect existence on laboratory scale, which means longitudinal distances between locations of measurements from tens to one meter. Also short revue of our investigations of local-time effect existence for distances from 15 km to 500 m are presented. Besides investigations of the minimal spatial scale of local-time effect existence the paper presents investigations of the named effect for time domain. In this relation a structure of intervals distribution in neighborhood of local-time peak was studied and splitting of the peak was found out. Further investigations shows second order splitting of local-time peak. From this result arise a supposition that space-time heterogeneity, which following from local-time effect existence probably has fractal character. Obtained results lead to conclusion about sharp anisotropy of space-time.

V. A. Panchelyuga; V. A. Kolombet; M. S. Panchelyuga; S. E. Shnoll

2006-12-06

269

Using Audio Time Scale Modification for Video Browsing  

Microsoft Academic Search

In the IBM CueVideo TM project we study various aspects of fully automated video indexing, browsing and retrieval. The technical aspects include audio processing, speech recognition, image processing and information retrieval. Equally important, however, is exploring user expectations and conducting user studies. We focus on the field of video for Training and Education, including Distributed Learning, Remote Education, and Just-in-Time

Arnon Amir; Dulce B. Ponceleon; Brian Blanchard; Dragutin Petkovic; Savitha Srinivasan; G. Cohen

2000-01-01

270

Time scales of spike-train correlation for neural oscillators with common drive  

SciTech Connect

We examine the effect of the phase-resetting curve on the transfer of correlated input signals into correlated output spikes in a class of neural models receiving noisy superthreshold stimulation. We use linear-response theory to approximate the spike correlation coefficient in terms of moments of the associated exit time problem and contrast the results for type I vs type II models and across the different time scales over which spike correlations can be assessed. We find that, on long time scales, type I oscillators transfer correlations much more efficiently than type II oscillators. On short time scales this trend reverses, with the relative efficiency switching at a time scale that depends on the mean and standard deviation of input currents. This switch occurs over time scales that could be exploited by downstream circuits.

Barreiro, Andrea K.; Shea-Brown, Eric; Thilo, Evan L. [Department of Applied Mathematics, University of Washington, P.O. Box 352420, Seattle, Washington 98195 (United States)

2010-01-15

271

The Triassic dicynodont Kombuisia (Synapsida, Anomodontia) from Antarctica, a refuge from the terrestrial Permian-Triassic mass extinction  

NASA Astrophysics Data System (ADS)

Fossils from the central Transantarctic Mountains in Antarctica are referred to a new species of the Triassic genus Kombuisia, one of four dicynodont lineages known to survive the end-Permian mass extinction. The specimens show a unique combination of characters only present in this genus, but the new species can be distinguished from the type species of the genus, Kombuisia frerensis, by the presence of a reduced but slit-like pineal foramen and the lack of contact between the postorbitals. Although incomplete, the Antarctic specimens are significant because Kombuisia was previously known only from the South African Karoo Basin and the new specimens extend the taxon’s biogeographic range to a wider portion of southern Pangaea. In addition, the new finds extend the known stratigraphic range of Kombuisia from the Middle Triassic subzone B of the Cynognathus Assemblage Zone into rocks that are equivalent in age to the Lower Triassic Lystrosaurus Assemblage Zone, shortening the proposed ghost lineage of this taxon. Most importantly, the occurrence of Kombuisia and Lystrosaurus mccaigi in the Lower Triassic of Antarctica suggests that this area served as a refuge from some of the effects of the end-Permian extinction. The composition of the lower Fremouw Formation fauna implies a community structure similar to that of the ecologically anomalous Lystrosaurus Assemblage Zone of South Africa, providing additional evidence for widespread ecological disturbance in the extinction’s aftermath.

Fröbisch, Jörg; Angielczyk, Kenneth D.; Sidor, Christian A.

2010-02-01

272

The carbon-isotope shift at the Permian\\/Triassic boundary in the southern Alps is gradual  

Microsoft Academic Search

Carbon isotope ratios in marine carbonate rocks have been shown to shift at some of the time boundaries associated with extinction events; for example, Cretaceous\\/Tertiary1 and Ordovician\\/ Silurian2. The Permian\\/Triassic boundary, the greatest extinction event of the Phanerozoic3, is also marked by a large delta13C depletion4,5. New carbon isotope results from sections in the southern Alps show that this depletion

Mordeckai Magaritz; Richard Bart; Aymon Baud; William T. Holser

1988-01-01

273

The carbon and sulfur cycles and atmospheric oxygen from middle Permian to middle Triassic  

NASA Astrophysics Data System (ADS)

The results of a theoretical isotope mass balance model are presented for the time dependence of burial and weathering-plus-degassing fluxes within the combined long-term carbon and sulfur cycles. Averaged data for oceanic ? 13C and ? 34S were entered for every million years from 270 to 240 Ma (middle Permian to middle Triassic) to study general trends across the Permian-Triassic boundary. Results show a drop in the rate of global organic matter burial during the late Permian and a predominance of low values during the early-to-middle Triassic. This overall decrease with time is ascribed mainly to epochs of conversion of high biomass forests to low biomass herbaceous vegetation resulting in a decrease in the production of terrestrially derived organic debris. Additional contributions to lessened terrestrial carbon burial were increased aridity and a drop in sea level during the late Permian which led to smaller areas of low-lying coastal wetlands suitable for coal and peat deposition. Mirroring the drop in organic matter deposition was an increase in the burial of sedimentary pyrite, and a dramatic increase in the calculated global mean ratio of pyrite-S to organic-C. High S/C values resulted from an increase of deposition in marine euxinic basins combined with a decrease in the burial of low-pyrite associated terrestrial organic matter. The prediction of increased oceanic anoxia during the late Permian and early Triassic agrees with independent studies of the composition of sedimentary rocks. Weathering plus burial fluxes for organic carbon and pyrite sulfur were used to calculate changes in atmospheric oxygen. The striking result is a continuous drop in O 2 concentration from ˜30% to ˜13% over a twenty million year period. This drop was brought about mainly by a decrease in the burial of terrestrially derived organic matter. but with a possible contribution from the weathering of older organic matter on land. It must have exerted a considerable influence on animal evolution because of the role of O 2 in respiration. Some examples are the extinction of many vertebrates, loss of giant insects and amphibians, and the restriction of animals to low elevations. It is concluded that the extinction of plants may have contributed to the extinction of animals.

Berner, Robert A.

2005-07-01

274

Filling a 30 Million Year Gap: Radioisotopic Age Constraints for the Late Triassic Timescale  

NASA Astrophysics Data System (ADS)

The Triassic Period records a critical interval of Phanerozoic Earth history, including major paleoenvironmental changes in a greenhouse world, recovery from one mass extinction and the onset of another, and the origin of modern terrestrial ecosystems. Recent efforts have been instrumental in calibrating the timing of these events by producing numerous high resolution radioisotopic ages from Early and Middle Triassic marine strata that facilitate building of a robust 20 Ma chronostratigraphic framework. This contrasts starkly with the Late Triassic (Carnian, Norian, and Rhaetian stages), where ~30 Ma of the timescale is virtually uncalibrated by high-resolution radioisotopic data. This is the only interval of such long duration in the Mesozoic or Cenozoic that remains so poorly constrained by reliable absolute ages, despite the occurrence of major events such as the origin and early diversification of dinosaurs, major reef building episodes in marine ecosystems, key paleoenvironmental changes (e.g., Carnian Pluvial Event), and large extraterrestrial bolide impacts (e.g., Manicouagan). An additional challenge is that the biostratigraphically-defined marine timescale cannot be applied globally, so that other areas (e.g., New Zealand) have independent timescales that cannot be confidently correlated to classic Laurasian sections. All of these problems preclude formulating robust first-order hypotheses about the Late Triassic world. We present new CA-TIMS U-Pb zircon data from volcaniclastic units within both marine and terrestrial strata that aim at calibrating the timescale itself and as a result constrain the timing of some of these major events in Earth history. Several preliminary ages support the hypothesis that the Norian Stage was very long, ~20 Ma. Our new data from marine sequences in New Zealand demonstrate that the timescale divisions there do not correlate directly with biostratigraphic boundaries in the Tethys; specifically, the Ladinian-Carnian boundary is somewhere within the Kaihikuan biozone, and the lower Otamitan biozone is correlative with the mid-Norian. Our new data from the terrestrial Chinle Formation in the southwestern US demonstrate that all of this formation is Norian in age or later, younger than South American sequences it had previously been correlated with. This supports the hypothesis that the rise of dinosaurs was diachronous, occurring later in North America than in Argentina and Brazil. These new ages also constrain a major faunal turnover event in the middle Chinle Fm to the mid-Norian, close in age to the Manicouagan impact event. Correlation and calibration of these major events will be further strengthened by the unambiguous superposition provided by core samples, such as the forthcoming Colorado Plateau Coring Project.

Irmis, R. B.; Mundil, R.

2011-12-01

275

Multiscale Modeling and TimeScale Analysis of a Human Limb  

Microsoft Academic Search

A multi-scale modeling approach is proposed in this paper that assists the user in constructing musculoskeletal system models from sub-models describing various mechanisms on different levels on the length scale. In addition, dynamic time-scale analysis has been performed on the developed multi-scale models of various parts of a human limb: on wrist, elbow and shoulder characterized by different maximal muscle

Csaba Fazekas; ORGY KOZMANN; Katalin M. Hangos

2007-01-01

276

Time scale of magma differentiation in arcs from protactinium-radium isotopic data  

NASA Astrophysics Data System (ADS)

Absolute chronology of magma differentiation processes has been a long-desired goal, given its importance in understanding magma chamber dynamics and its connection to a fundamental understanding of the style and frequency of volcanic eruptions. Broad estimates of the duration of magma differentiation and overall crustal residence times have been made based on a variety of indirect approaches, such as physical models of magma chamber cooling, rates of crystal growth and settling, and long-lived radiogenic isotopes. In contrast, combined 231Pa-235U data may provide a robust measure of the time scale of magma differentiation. Based on 231Pa-235U, 230Th-238U and 226Ra-230Th data from Taal volcano, Luzon Arc, Philippine Archipelago, we show that 231Pa-235U data may provide a robust direct measure of the time scale of magma differentiation. A closed-system magma fractionation model gives a 231Pa-235U differentiation time scale in the range of 30 k.y., while the 226Ra-230Th time scale is considerably younger. The time scales are reconciled if we consider either fluid-mixing or magma-mixing models. The fluid-mixing model gives a time scale of differentiation similar to the 231Pa-235U closed-system time scale and is supported by the 230Th-238U data. The magma-mixing model gives a considerably longer time, in the range of 55 k.y. The combined observations support the robustness of the 231Pa-235U chronology, indicating a differentiation time scale in the range of 30 k.y., although this time scale for other volcanoes may vary depending on size and thermal state of the magma chamber. The 226Ra-230Th closed-system model ages, which yield much younger estimates for magma differentiation, are not likely to reflect time scales of magma differentiation.

Asmerom, Yemane; Dufrane, S. Andrew; Mukasa, Samuel B.; Cheng, Hai; Edwards, R. Lawrence

2005-08-01

277

Permian Triassic palynofloral transition in Chintalapudi area, Godavari Graben, Andhra Pradesh, India  

NASA Astrophysics Data System (ADS)

The entire 606 m-thick sedimentary sequence in borecore MCP-7 from Chintalapudi area, Chintalapudi sub-basin has been lithologically designated as Kamthi Formation. However, the palynological investigation revealed five distinct palynoassemblages, which essentially fall under two groups, one group (Palynoassemblage-I, II and III) having dominance of striate disaccates along with presence of some stratigraphically significant taxa, belongs to Late Permian (Raniganj) palynoflora, while the other group (Palynoassemblages IV and V) shows sharp decline in percentage of characteristic taxa of first group, i.e., striate disaccates, and consequent rise or dominance of taeniate and cingulate cavate spores, belongs to Early Triassic (Panchet) palynoflora. Palynoassemblage-I, II and III (Group I) are characterized by dominance of striate disaccates chiefly, Striatopodocarpites spp. and Faunipollenites spp. along with presence of rare but stratigraphically significant taxa, viz., Gondisporites raniganjensis, Falcisporites nuthaliensis, Klausipollenites schaubergeri, Chordasporites sp., Striomonosaccites, ovatus, Crescentipollenites multistriatus, Verticipollenites debiles, Strotersporites crassiletus, Guttulapollenites hannonicus, G. gondwanensis, Hamiapollenites insolitus, Corisaccites alutus, Lunatisporites ovatus, Weylandites spp. and Vitreisporites pallidus. Palynoassemblage-I is distinguished by significant presence of Densipollenites spp. while Palynoassemblage-II shows significant presence of Crescentipollenites spp. and Palynoassemblage-III differs from the above two assemblages in having significant presence of Guttulapollenites hannonicus. Palynoassemblage-IV (Group II) is characterized by high percentage of taeniate disaccates chiefly Lunatisporites spp., while Palynoassemblage-V (Group II) is characterized by cingulate-cavate trilete spores chiefly, Lundbladispora spp. and Densoisporites spp. Striate disaccates show a sharp decline in these two assemblages. In Chintalapudi area Late Permian and Early Triassic palynoflora has been recorded for the first time indicating existence of Raniganj and Panchet sediments as well. The study further supports the earlier studies of Jha and Srivastava (1996) that Kamthi Formation represents Early Triassic (=Panchet Formation) overlying Raniganj equivalent sediments with a gradational contact.

Jha, Neerja; Chary, M. Basava; Aggarwal, Neha

2012-10-01

278

The lower Triassic microbiolites in Chaohu region, East China and their contribution to the early Triassic recovery  

NASA Astrophysics Data System (ADS)

The lower Triassic is well preserved in Chaohu Region, Anhui Province, East China. It can be divided into Yinkeng Formation (80 meters thick, was formed during the Indian and early Smitian), Helongshan Formation (21 meters thick, was formed during the end Smithian) and Nanlinghu Formation (more than 157 meters thick, was formed during the Spathian) from bottom to top. It is mainly composed of carbonatites such as micrite limestones and nodular limestones, as well as shales and calcareous marls. The lower Triassic in this area has been well researched for more than a decade, and many fossils such as ammonites, bivalves, fishes, ichthyosaurus, conodonts, and ichnofossils have been found, but the microbiolites have been neglected. Microbiolites were mainly outcropped in the Helongshan Formaiton and the lower Nanlinghu Formation. In the lower Helongshan Formaiton, tens microbial mat layers and thin bedded calcareous marl layers formed cyclothems which have been named as nodular limstones. The thin-section observation of the microbial mats indicate that many films and thin-shell bivalve fragments deposited almost horizontally. In the upper Helongshan Formaiton, six microstromatolite bioherm layers were outcropped in the thin bedded calcareous marl layers. The diameter of the stromatolite column is about 2 millimeters, the bioherms are lenticular and no more than 3 centimeters thick in the central, their diameters change from 5 centimeters to 30 centimeters, calcareous marls were deposited around the bioherms, and many ammonoids, bivalves and burrows were found in such layers. The microfacies differentiation of the stromatolites such as the basement, reef core and the capping beds can be recognised clearly in thin sections. Several microstromatolite layers were outcropped in the micritic limestones with a stable thickness of 15 millimeters in the lower Nanlinghu Formation and the stromatolite column look like the ones in the Helongshan Formation. Few microbiolites have been found in the middle and upper Nanlinghu Formation. The macro fossil association of the lower Triassic in Chaohu region is quite different in different Formations. Ammonoids and bivalves can be found in the whole lower Triassic strata, and they are especially dominant in the Yinkeng Formation and lower Helongshan Formaiton, worms and borrowing animals can be found in the middle Helongshan Formation, fishes can be found in the uppermost Helongshan Formation and the lower Nanlinghu Formation, and the oldest ichthyosaurus in the world can be found in the upper Nanlinghu Formation. According to the changing characters of the fossil association in this area, it is indicated that the high-level ecosystem had been formed in this area in the late early Triassic, and the appearance of the microbiolites in the Helongshan Formation might be the milestone for the early Triassic recovery. Though the global recovery process after the Permian-Triassic mass extinction might be postponed to the end of the early Triassic, regional recovery process in Chaohu region might start at the end Smithian and actualized at the middle Spathian. The microbioilites might be the original impetus for the early Triassic recovery. Key words: microbiolites, early Triassic, regional recovery, Chaohu region Acknowledgments This work is supported by the grants from National Natural Science Fundation of China (No. 40902096 and No.J0830522) and the IGCP 572 program. * Corresponding author: zhihai.jia@gmail.com

Jia, Zhihai; Zhang, Liwei; Hong, Tianqiu

2010-05-01

279

Space-time scale sensitivity of the Sacramento model to radar-gage precipitation inputs  

Microsoft Academic Search

Runoff timing and volume biases are investigated when performing hydrologic forecasting at space-time scales different from those at which the model parameters were calibrated. Hydrologic model parameters are inherently tied to the space-time scales at which they were calibrated. The National Weather Service calibrates rainfall runoff models using 6-hour mean areal precipitation (MAP) inputs derived from gage networks. The space-time

Bryce D. Finnerty; Michael B. Smith; Dong-Jun Seo; Victor Koren; Glenn E. Moglen

1997-01-01

280

Fetal development assessed by heart rate patterns—Time scales of complex autonomic control  

Microsoft Academic Search

The increasing functional integrity of the organism during fetal maturation is connected with increasing complex internal coordination. We hypothesize that time scales of complexity and dynamics of heart rate patterns reflect the increasing inter-dependencies within the fetal organism during its prenatal development. We investigated multi-scale complexity, time irreversibility and fractal scaling from 73 fetal magnetocardiographic 30min recordings over the third

Dirk Hoyer; Samuel Nowack; Stephan Bauer; Florian Tetschke; Stefan Ludwig; Liviu Moraru; Anja Rudoph; Ulrike Wallwitz; Franziska Jaenicke; Jens Haueisen; Ekkehard Schleußner; Uwe Schneider

281

Real-time hardware simulation of a small-scale helicopter dynamics  

Microsoft Academic Search

Purpose – The purpose of this paper is to develop a real-time simulation environment for the validation of controller for an autonomous small-scale helicopter. Design\\/methodology\\/approach – The real-time simulation platform is developed based on the nonlinear model of a series of small-scale helicopters. Dynamics of small-scale helicopter is analyzed through simulation. The controller is designed based on the extracted linear

Agus Budiyono; Idris E. Putro; K. Yoon; Gilar B. Raharja; G. B. Kim

2010-01-01

282

Paleoclimate cycles and tectonic controls on fluvial, lacustrine, and eolian strata in upper Triassic Chinle Formation, San Juan basin  

SciTech Connect

Sedimentologic study of the Upper Triassic Chinle Formation in the San Juan basin (SJB) indicates that Late Triassic paleoclimate and tectonic movements influenced the distribution of continental lithofacies. The Shinarump, Monitor Butte, and Petrified Forest Members in the lower part of the Chinle consist of complexly interfingered fluvial, floodplain, marsh, and lacustrine rocks; the Owl Rock and Rock Point Members in the upper part consists of lacustrine-basin and eolian sandsheet strata. Facies analysis, vertebrate and invertebrate paleontology, and paleoclimate models demonstrate that the Late Triassic was dominated by tropical monsoonal circulation, which provided abundant precipitation interspersed with seasonally dry periods. Owl Rock lacustrine strata comprise laminated limestones that reflect seasonal monsoonal precipitation and larger scale, interbedded carbonates and fine-grained clastics that represent longer term, alternating wet and dry climatic cycles. Overlying Rock Point eolian sand-sheet and dune deposits indicate persistent alternating but drier climatic cyclicity. Within the Chinle, upward succession of lacustrine, alternating lacustrine/eolian sand-sheet, and eolian sand-sheet/dune deposits reflects an overall decrease in precipitation due to the northward migration of Pangaea out of low latitudes dominated by monsoonal circulation.

Dubiel, R.F. (Geological Survey, Denver, CO (USA))

1989-09-01

283

Well concentration: a novel scaling limitation factor derived from DRAM retention time and its modeling  

Microsoft Academic Search

A novel scaling limitation factor derived from DRAM retention time and its modeling has been proposed. So far, the well concentration has been optimized from the viewpoint of the scaling of the transistor dimensions. However, it has been found that the DRAM retention time strongly depends on the well concentration. Increase of the well concentration enhances thermionic field emission (TFE)

T. Hamamoto; S. Sugiura; S. Sawada

1995-01-01

284

Time Scale Decomposition of a Class of Generalized Stochastic Petri Net Models  

Microsoft Academic Search

A time-scale decomposition (TSD) algorithm of a class of generalized stochastic Petri net (GSPN) models of systems comprising activities whose duration differ by orders of magnitude is presented. The GSPN model of a system can be decomposed into a hierarchical sequence of aggregated subnets, each of which is valid at a certain time scale. These smaller subnets are solved in

Hany H. Ammar; S. M. Rezaul Islam

1989-01-01

285

On Green's functions and positive solutions for boundary value problems on time scales  

Microsoft Academic Search

In this paper we offer a form of self-adjoint differential equations on time scales so that the associated Green's function is found symmetric in the usual sense. For this purpose together with the delta derivative we employ the nabla derivative as well. We introduce the concepts of Lebesgue delta and nabla integrals on time scales. Next, sign properties of the

F. Merdivenci Atici; G. Sh. Guseinov

2002-01-01

286

Annular mode time scales in the Intergovernmental Panel on Climate Change Fourth Assessment Report models  

E-print Network

Annular mode time scales in the Intergovernmental Panel on Climate Change Fourth Assessment Report in the Intergovernmental Panel on Climate Change Fourth Assessment Report to capture the temporal structure of the annular. Ancukiewicz (2008), Annular mode time scales in the Intergovernmental Panel on Climate Change Fourth

Gerber, Edwin

287

APPLICATION OF THE DYPSA ALGORITHM TO SEGMENTED TIME SCALE MODIFICATION OF SPEECH  

Microsoft Academic Search

This paper presents a method for speech time scale modification. Voiced speech is pseudo-periodic, allowing time scale modification by the repetition or removal of cycles as necessary. However, in the case of unvoiced speech and at the boundaries of voiced speech, no such periodicity exists so the speech should not be modified. To address this issue, the proposed approach is

Mark R. P. Thomas; Jon Gudnason; Patrick A. Naylor

2008-01-01

288

Evolution of Geomagnetic Cutoff Rigidities on Short-and Long-term Time Scales  

Microsoft Academic Search

The magnetic shielding of the Earth from galactic and solar cosmic radiation is dependent on the magnitude and orientation of the Earth's magnetic field. The amount of shielding at a specific location is defined by the geomagnetic cutoff rigidity (RC), which varies on both short- and long-term time scales. On short time scales, the amount of geomagnetic shielding at any

D. F. Smart; M. A. Shea; N. Lifton

2008-01-01

289

Characteristic Variations of Sea Surface Temperature with Multiple Time Scales in the North Pacific  

Microsoft Academic Search

Temporal evolution and spectral structure of sea surface temperature (SST) anomalies in the North Pacific over the last 37 years are investigated on the three characteristic time scales: shorter than 24 months (HF), 24-60 months (ES), and longer than 60 months (DC). The leading empirical-orthogonal function (EOF) for the DC time scale is characterized by a zonally elongated monopole centered

Youichi Tanimoto; Kimio Hanawa; Yoshiaki Toba; Naoto Iwasaka

1993-01-01

290

Signatures of multiple time-scale behaviour in the power spectra of water  

E-print Network

Signatures of multiple time-scale behaviour in the power spectra of water Anirban Mudi are analysed for bulk SPC/E water for a range of temperatures along the 1.0 g/cm3 isochore. Fluctuations in the tagged particle potential energies give rise to 1=f a noise, indicative of multiple time-scale behaviour

Ramaswamy, Ram

291

Thermalisation in metals on a sub-picosecond time scale  

NASA Astrophysics Data System (ADS)

A theoretical model of the transient reflectivity of metals based on dynamics of down-converting electron and phonon cascades is developed in order to interpret recent pump-and-probe experiments in conventional superconductors and proximised structures. We show that the standard two-temperature model is totally inadequate to describe the response to pump excitation in the time domain up to several picoseconds. We also consider in detail the extended pre-equilibration regime for which the two-temperature model apparently does provide a credible description, despite failing to include realistically the essential characteristics of the quasiparticle and phonon spectral distributions. Based on our model we interpret recent experimental data on pump-and-probe studies of Nb films, and we discuss the important features of the down-conversion process in relation to various types of cryogenic detectors.

Kozorezov, A.; Pepe, G.; Golubov, A.; Martin, D.; Wigmore, J. K.

2009-12-01

292

Time scale of an early to mid-Paleozoic orogenic cycle of the long-lived Central Asian Orogenic Belt, Inner Mongolia of China: Implications for continental growth  

NASA Astrophysics Data System (ADS)

We present a detailed, new time scale for an orogenic cycle (oceanic accretion-subduction-collision) that provides significant insights into Paleozoic continental growth processes in the southeastern segment of the long-lived Central Asian Orogenic Belt (CAOB). The most prominent tectonic feature in Inner Mongolia is the association of paired orogens. A southern orogen forms a typical arc-trench complex, in which a supra-subduction zone ophiolite records successive phases during its life cycle: birth (ca. 497-477 Ma), when the ocean floor of the ophiolite was formed; (2) youth (ca. 473-470 Ma), characterized by mantle wedge magmatism; (3) shortly after maturity (ca. 461-450 Ma), high-Mg adakite and adakite were produced by slab melting and subsequent interaction of the melt with the mantle wedge; (4) death, caused by subduction of a ridge crest (ca. 451-434 Ma) and by ridge collision with the ophiolite (ca. 428-423 Ma). The evolution of the magmatic arc exhibits three major coherent phases: arc volcanism (ca. 488-444 Ma); adakite plutonism (ca. 448-438 Ma) and collision (ca. 419-415 Ma) of the arc with a passive continental margin. The northern orogen, a product of ridge-trench interaction, evolved progressively from coeval generation of near-trench plutons (ca. 498-461 Ma) and juvenile arc crust (ca. 484-469 Ma), to ridge subduction (ca. 440-434 Ma), microcontinent accretion (ca. 430-420 Ma), and finally to forearc formation. The paired orogens followed a consistent progression from ocean floor subduction/arc formation (ca. 500-438 Ma), ridge subduction (ca. 451-434 Ma) to microcontinent accretion/collision (ca. 430-415 Ma); ridge subduction records the turning point that transformed oceanic lithosphere into continental crust. The recognition of this orogenic cycle followed by Permian-early Triassic terminal collision of the CAOB provides compelling evidence for episodic continental growth.

Jian, Ping; Liu, Dunyi; Kröner, Alfred; Windley, Brian F.; Shi, Yuruo; Zhang, Fuqin; Shi, Guanghai; Miao, Laicheng; Zhang, Wei; Zhang, Qi; Zhang, Liqao; Ren, Jishun

2008-03-01

293

Metamorphic and volcanic quartz of the siliciclastic Tipuma Formation, West Papua, Indonesia: an insight into Triassic palaeogeography of northern Australia  

NASA Astrophysics Data System (ADS)

The origin and Triassic evolution of the Bird's Head of West Papua has been a subject of active discussion. Many interpretations have been proposed for the Triassic evolution, from active margin to passive margin models. The Bird's Head region is underlain by Australian continental crust and has a relatively complete stratigraphy from Palaeozoic to Recent. The Tipuma Formation is a Mesozoic siliciclastic sequence and a potentially important reservoir. Its sedimentation may record parts of the region's Mesozoic tectonic history, including several phases of rifting. Little is known about the variations in lithologies and their composition, and nothing is known about its provenance. The Tipuma Formation is dominated by red to cream well-bedded mudstone, sandstone and conglomerate. It rests unconformably on the Kemum Formation and is overlain by the Cretaceous Jass Formation. It is difficult to assess the depositional age of the Tipuma Formation due to the absence of fossils. The suggested Triassic age is based solely on its stratigraphic position. The Tipuma Formation was previously thought to be deposited in a stable continental setting. Detrital modes indicate acid plutonic, metamorphic, and recycled sedimentary source rocks for the Tipuma Formation sandstones. Angular volcanic quartz and elongate euhedral zircons suggest a contribution from previously unrecognised contemporaneous acid volcanics. New interpretations suggest that the widespread Permo-Triassic volcanic activity in the Bird's Head was caused by subduction associated with an Andean-type active margin and that the Tipuma Formation was deposited in a fluvial setting close to the volcanic arc. Cathodoluminescence (CL) characteristics of quartz depend on variations in temperature, pressure, and geochemical environment during crystal growth and subsequent events. The CL colour spectra of quartz can be correlated with the formation conditions of the quartz. They can therefore be used as a provenance indicator along with other techniques. Quartz from Tipuma Formation sandstone is dominated by quartz of low-T metamorphic and volcanic origin and only with little plutonic quartz. This strongly suggests an input of detritus derived from contemporaneous acid volcanic rocks and some local low-grade metamorphic rocks. The results confirm assessment based on zircon study of the main contemporaneous volcanic activity, which waned or ceased during deposition of the Middle Member of the Tipuma Formation. Widespread Permo-Triassic volcanic activity in the Bird's Head possibly caused contact metamorphism in the area with uplift and erosion of low-T metamorphic rocks. The Tasman Line continues from Eastern Australia through New Guinea, into the Bird's Head region. At least since the Triassic, the Bird's Head has been part of the Gondwana margin and for the first time, we can provide compelling evidence that volcanic activity has played a major role in this region.

Gunawan, Indra; Hall, Robert; Augustsson, Carita

2013-04-01

294

Updating the planetary time scale: focus on Mars  

USGS Publications Warehouse

Formal stratigraphic systems have been developed for the surface materials of the Moon, Mars, Mercury, and the Galilean satellite Ganymede. These systems are based on geologic mapping, which establishes relative ages of surfaces delineated by superposition, morphology, impact crater densities, and other relations and features. Referent units selected from the mapping determine time-stratigraphic bases and/or representative materials characteristic of events and periods for definition of chronologic units. Absolute ages of these units in some cases can be estimated using crater size-frequency data. For the Moon, the chronologic units and cratering record are calibrated by radiometric ages measured from samples collected from the lunar surface. Model ages for other cratered planetary surfaces are constructed primarily by estimating cratering rates relative to that of the Moon. Other cratered bodies with estimated surface ages include Venus and the Galilean satellites of Jupiter. New global geologic mapping and crater dating studies of Mars are resulting in more accurate and detailed reconstructions of its geologic history.

Tanaka, Kenneth L.; Quantin-Nataf, Cathy

2013-01-01

295

Integration of molecules and new fossils supports a Triassic origin for Lepidosauria (lizards, snakes, and tuatara)  

PubMed Central

Background Lepidosauria (lizards, snakes, tuatara) is a globally distributed and ecologically important group of over 9,000 reptile species. The earliest fossil records are currently restricted to the Late Triassic and often dated to 227 million years ago (Mya). As these early records include taxa that are relatively derived in their morphology (e.g. Brachyrhinodon), an earlier unknown history of Lepidosauria is implied. However, molecular age estimates for Lepidosauria have been problematic; dates for the most recent common ancestor of all lepidosaurs range between approximately 226 and 289 Mya whereas estimates for crown-group Squamata (lizards and snakes) vary more dramatically: 179 to 294 Mya. This uncertainty restricts inferences regarding the patterns of diversification and evolution of Lepidosauria as a whole. Results Here we report on a rhynchocephalian fossil from the Middle Triassic of Germany (Vellberg) that represents the oldest known record of a lepidosaur from anywhere in the world. Reliably dated to 238–240 Mya, this material is about 12 million years older than previously known lepidosaur records and is older than some but not all molecular clock estimates for the origin of lepidosaurs. Using RAG1 sequence data from 76 extant taxa and the new fossil specimens two of several calibrations, we estimate that the most recent common ancestor of Lepidosauria lived at least 242 Mya (238–249.5), and crown-group Squamata originated around 193 Mya (176–213). Conclusion A Early/Middle Triassic date for the origin of Lepidosauria disagrees with previous estimates deep within the Permian and suggests the group evolved as part of the faunal recovery after the end-Permain mass extinction as the climate became more humid. Our origin time for crown-group Squamata coincides with shifts towards warmer climates and dramatic changes in fauna and flora. Most major subclades within Squamata originated in the Cretaceous postdating major continental fragmentation. The Vellberg fossil locality is expected to become an important resource for providing a more balanced picture of the Triassic and for bridging gaps in the fossil record of several other major vertebrate groups. PMID:24063680

2013-01-01

296

Geochronological, isotopic, and geochemical data from Permo-Triassic granitic gneisses and granitoids of the Colombian Central Andes  

NASA Astrophysics Data System (ADS)

New U-Pb SHRIMP ages in zircon, Ar-Ar ages in micas and amphiboles, Nd-Sr isotopes, and major and REE geochemical analyses in granitic gneisses and granitic stocks of the Central Cordillera of Colombia indicate the presence of a collisional orogeny in Permo-Triassic times in the Northern Andes related to the construction of the Pangea supercontinent. The collision is recorded by metamorphic U-Pb SHRIMP ages in inherited zircons around 280 Ma and magmatic U-Pb SHRIMP ages in neoformed zircons around 250 Ma within syntectonic crustal granitic gneisses. Magmatic U-Pb SHRIMP and Ar-Ar Triassic ages around 228 Ma in granitic stocks indicate the presence of late tectonic magmatism related to orogenic collapse and the beginning of the breakup of the supercontinent. During this period, the Central Cordillera of Colombia would have been located between the southern United States and northern Venezuela, in the leading edge of the Gondwana supercontinent.

Vinasco, C. J.; Cordani, U. G.; González, H.; Weber, M.; Pelaez, C.

2006-09-01

297

Time-Dependent Slow-Time-Scale Theory of Free-Running and Phase-Locked Gyrotron Oscillators.  

National Technical Information Service (NTIS)

A time dependent slow time scale theory is developed for the analysis of high power, pulsed gyrotrons. Calculations are carried out to simulate the operation of a 35 GHz hig voltage gyrotron. Both free running and phase locked oscillator configurations ar...

A. W. Fliflet, R. C. Lee, W. M. Manheimer, E. Ott

1988-01-01

298

An Approach to the solutions of time varying linear dynamic systems with multi - point boundary values on time scales  

Microsoft Academic Search

In this work,firstly we consider the solution of an initial value problem (IVP) of a non-homogeneous time varying linear dynamic system on a time scale T.That is N R x t x t x t f t x t A t x ? T ? = + =

Ömer AKIN; Mohammad Taghi; Nurettin DO?AN; H. Hüseyin

299

Exponential stability analysis of large-scale time-delay nonlinear systems with hybrid models  

Microsoft Academic Search

This paper presents one method to deal with the exponential stability problems for a kind of complex large-scale time-delay nonlinear systems with hybrid models. These hybrid large-scale time-delay systems are composed of considerable interconnected time-delay nonlinear subsystems, some of which are described by differential equations and others by Takagi-Sugeno fuzzy models. Novel techniques to cope with the nonlinear interconnection between

Degang Xu; Guiwei Hua; Zhifang Su

2008-01-01

300

The space-time variability and scaling of climate data, climate models and their converge as functions of space-time scale  

NASA Astrophysics Data System (ADS)

Climate models are evaluated by comparing them with other models and (when possible), with climate data: one attempts to match the data and numerics as closely as possible pixel by pixel, time step by time step- i.e. deterministically. As a consequence very little attention has been paid to understanding the space-time statistical properties of the models and data. There is little understanding of the convergence of the model and data to their 'climates' and to each other. In the time domain, there is no objective definition of the distinction between weather and climate in the spatial domain, there is corresponding lack of understanding of climate regions. In order to overcome this, we systematically study the statistics of fluctuations (primarily of temperature but also precipitation and pressure) as function of space and time. For both data and models, we find that in space, that fluctuations increase up to about 5000 km before starting to decrease; this quantitatively defines the typical size of regional climates. In time, we find that fluctuations decrease out to about 10-30 years in the industrial epoch, out to 50 -100 years in the pre-industrial epoch and then starts to increase; this defines the difference between 'macroweather' and the climate. Applying fluctuation analysis to longer time scales, we examine last millennium simulations from four GCMs, we show that control runs only reproduce macroweather. When various (reconstructed) climate forcings are included, in the recent (industrial) period they show global fluctuations strongly increasing at scales >_10-30 yr, which is quite close to the observations. However, in the preindustrial period we find that the multicentennial variabilities are too weak and by analysing the scale dependence of solar and volcanic forcings, we argue that these forcings are unlikely to be sufficiently strong to account for the multicentennial and longer-scale temperature variability. A likely explanation is that the models lack important slow 'climate' processes such as land ice or various biogeochemical processes. This technique can be used to show that the error in estimating the global temperature is about ±0.03K, and this - surprisingly - at any time scale out to over 100 years. Similarly, in space the different surface temperature only start to converge (i.e. to agree with each other) at scales larger than ? 2000 km. The same fluctuation analysis technique can be used to quantify the convergence of the models to the model climates and to the real climate. By comparing different realizations of the NASA GISS model historical simulations (from 1850), we show that in time, they converge to each other (i.e. to the model climate) at the slow rate ?t-0.3; however in space, they diverge up to about 5000km (? ?t0.4) only converging to their climate at larger scales, this 'continental scale' is thus the smallest scale that can be attained by climate models and this likely imposes a fundamental limit on regional skill. By comparing the model to the data (20C reanalysis), we find that the two differ by between ±1 and ±2K at all space and time scales - beyond about 8 months, temporal averaging does not improve agreement, nor does spatial averaging help much. However, if the long tem averages are know and removed - so that one considers anomalies - space-time statistics of the model and the data are remarkably similar. This indicates that the model produces space-time fields of similar type to the data, but that the model and real climates are significantly different.

Lovejoy, Shaun; Elias, Lydia

2014-05-01

301

Modelling soil carbon movement by erosion over large scales and long time periods  

NASA Astrophysics Data System (ADS)

Agricultural intensification accelerates physical erosion rates and the transport of carbon within the landscape. In order to improve understanding of how past, present and future anthropogenic land-use change has and will influence carbon and nutrient cycling, it is necessary to develop quantitative tools that can predict soil erosion and carbon movement at large temporal and spatial scales, that are consistent with the time constants of biogeochemical processes and the spatial scales of land-use change and natural resources. However, representing erosion and its impact on the carbon cycle over large spatial scales and long time periods is challenging. Erosion and sediment transport processes operate at multiple spatial and temporal scales with splash erosion dominating at the sub-plot scale and occurring within seconds, up to gully formation operating at field-catchment scales over days to months. In addition, most erosion production observations are made at the experimental plot scale, where fine time scales and detailed processes dominate. This is coupled with complexities associated with carbon detachment, decomposition and uncertainties surrounding carbon burial rates and stability - all of which occur over widely different temporal and spatial scales. As such, these data cannot be simply scaled to inform erosion and carbon representation at the regional scale, where topography, vegetation cover and landscape organisation become more important controls on sediment fluxes. We have developed a simple energy-based regional scale method of soil erosion modelling, which is integration into a hydro-biogeochemical model that will simulate carbon, nitrogen and phosphorus pools and fluxes across the UK from the industrial revolution to the present day. The model is driven by overland flow, dynamic vegetation cover, soil properties, and topographic distributions and produces sediment production and yield at the 5km grid scale. In this paper we will introduce the modelling approach and examine some of the challenges facing attempts to erosion and carbon transport processes at larger spatial and temporal scales.

Quinton, John; Davies, Jessica; Tipping, Ed

2014-05-01

302

Ophiuroids Discovered in the Middle Triassic Hypersaline Environment  

PubMed Central

Echinoderms have long been considered to be one of the animal phyla that is strictly marine. However, there is growing evidence that some recent species may live in either brackish or hypersaline environments. Surprisingly, discoveries of fossil echinoderms in non-(open)marine paleoenvironments are lacking. In Wojkowice Quarry (Southern Poland), sediments of lowermost part of the Middle Triassic are exposed. In limestone layer with cellular structures and pseudomorphs after gypsum, two dense accumulations of articulated ophiuroids (Aspiduriella similis (Eck)) were documented. The sediments with ophiuroids were formed in environment of increased salinity waters as suggested by paleontological, sedimentological, petrographical and geochemical data. Discovery of Triassic hypersaline ophiuroids invalidates the paleontological assumption that fossil echinoderms are indicators of fully marine conditions. Thus caution needs to be taken when using fossil echinoderms in paleoenvironmental reconstructions. PMID:23185442

Salamon, Mariusz A.; Nied?wiedzki, Robert; Lach, Rafa?; Brachaniec, Tomasz; Gorzelak, Przemys?aw

2012-01-01

303

Using Focused Regression for Accurate Time-Constrained Scaling of Scientific Applications  

SciTech Connect

Many large-scale clusters now have hundreds of thousands of processors, and processor counts will be over one million within a few years. Computational scientists must scale their applications to exploit these new clusters. Time-constrained scaling, which is often used, tries to hold total execution time constant while increasing the problem size along with the processor count. However, complex interactions between parameters, the processor count, and execution time complicate determining the input parameters that achieve this goal. In this paper we develop a novel gray-box, focused median prediction errors are less than 13%. regression-based approach that assists the computational scientist with maintaining constant run time on increasing processor counts. Combining application-level information from a small set of training runs, our approach allows prediction of the input parameters that result in similar per-processor execution time at larger scales. Our experimental validation across seven applications showed that median prediction errors are less than 13%.

Barnes, B; Garren, J; Lowenthal, D; Reeves, J; de Supinski, B; Schulz, M; Rountree, B

2010-01-28

304

A review of selected triassic to Early Cretaceous ferns  

Microsoft Academic Search

After becoming nearly extinct during the Permian, the ferns began a slow recovery during the Triassic as the climate of the\\u000a earth moderated. As a result, a considerable number and variety were present and widely distributed during the Jurassic and\\u000a Early Cretaceous. However, with the rapid expansion of the angiosperms during the Late Cretaceous, the ferns once again became\\u000a reduced

William D. Tidwell; Sidney R. Ash

1994-01-01

305

Piezoresponse force microscopy studies of switching behavior of ferroelectric capacitors on a 100-ns time scale.  

PubMed

Piezoresponse force microscopy is a powerful technique for nm-scale studies but is usually limited by response time. In this Letter, we report the first direct studies of ferroelectric capacitor switching on a submicrosecond time scale. Simultaneous domain imaging and sub-mus transient current measurements establish a direct relationship between polarization P(t) and domain kinetics. Switching times scale with capacitor size over an order of magnitude. Small capacitors, where polarization reversal is dominated by domain wall motion, switch faster at high fields but more slowly at low fields while larger capacitors do the reverse. PMID:18352748

Gruverman, A; Wu, D; Scott, J F

2008-03-01

306

Behavior of carbonate shelf communities in the Upper Triassic of Nevada: Evidence of impact mediated faunal turnover  

SciTech Connect

The carbonate shelf sediments of the Luning and Gabbs Formations of Nevada span the last several million years of the Triassic. This richly fossiliferous sequence provides a relatively continuous record of benthic community behavior during a long interval of global biotic turnover. Upper Carnian-Lower Norian and Upper Norian sea floors in this region were inhabited by a variety of invertebrate communities, all of them mollusc-dominated. Across a range of offshore shelf to basinal environments and throughout repeated community replacements, the most abundant and diverse taxa were infaunal and epifaunal bivalves and ammonites. The sequence of Upper Triassic molluscan communities was interrupted by a Lower or Middle Norian interval of brachiopod-dominated faunas. Although preserved in similar offshore carbonate shelf sediments, these communities are nearly devoid of the infaunal bivalves and ammonites that characterize both older and younger assemblages in the section. This pattern, of a temporary replacement of molluscan communities by brachiopod faunas, mimics that reported for some shelf assemblages across the Cretaceous-Tertiary boundary. That brief resurgence of brachiopods is linked to a sharp drop in marine primary productivity, which suggests that a disruption of planktonic food chains may also have occurred early in the Norian. The timing and pattern of Carnian-Norian faunal and physical events and their resemblance to K/T sequences are consistent with the proposal that an asteroid impact played a role in the Upper Triassic faunal transition.

Hogler, J.A. (Univ. of California, Berkeley, CA (United States). Museum of Paleontology)

1993-04-01

307

Rock-inhabiting fungi originated during periods of dry climate in the late Devonian and middle Triassic.  

PubMed

Non-lichenized rock-inhabiting fungi (RIF) are slow-growing melanized ascomycetes colonizing rock surfaces in arid environments. They possess adaptations, which allow them to tolerate extreme abiotic conditions, such as high UV radiations and extreme temperatures. They belong to two separate lineages, one consisting in the sister classes Dothideomycetes and Arthoniomycetes (Dothideomyceta), and the other consisting in the order Chaetothyriales (Eurotiomycetes). Because RIF often form early diverging groups in Chaetothyriales and Dothideomyceta, the ancestors of these two lineages were suggested to most likely be rock-inhabitants. The lineage of RIF related to the Chaetothyriales shows a much narrower phylogenetic spectrum than the lineage of RIF related to Dothideomyceta, suggesting a much more ancient origin for the latter. Our study aims at investigating the times of origin of RIF using a relaxed clock model and several fossil and secondary calibrations. Our results show that the RIF in Dothideomyceta evolved in the late Devonian, much earlier than the RIF in Chaetothyriales, which originated in the middle Triassic. The origin of the chaetothyrialean RIF correlates well with a period of recovery after the Permian-Triassic mass extinction and an expansion of arid landmasses. The period preceding the diversification of the RIF related to Dothideomyceta (Silurian--Devonian) is also characterized by large arid landmasses, but temperatures were much cooler than during the Triassic. The paleoclimate record provides a good explanation for the diversification of fungi subjected to abiotic stresses and adapted to life on rock surfaces in nutrient-poor habitats. PMID:21944211

Gueidan, Cécile; Ruibal, Constantino; de Hoog, G S; Schneider, Harald

2011-10-01

308

Petroleum systems characterization and ages in the Neuquen Basin (Triassic-to-Tertiary), West-Central Andes, Argentina  

SciTech Connect

The Neuquen Basin, implanted on the western margin of the South American Plate evolved from Late Triassic-Early Jurassic as a set of isolated troughs, some of them connected to the {open_quotes}Pacific Ocean,{close_quotes} to an intra-arc to back-arc marine setting in Early-Late Jurassic. At the present day, a 7-km-thick succession of clastics, carbonates, evaporates, and volcanic rocks is preserved in between the eastern side of the Andean folded belt and the South American hinterland, affected by gentle deformation. On the southeastern margin of the basin occurs a relatively complex structural trend, as a result of the inversion tectonics related to an E-W regional strike-slip, fault. Five source-rock intervals are documented, the oldest consists of dark shales accumulated in a lacustrine environment (L. Triassic-E. Jurassic) and the others contain Type I and II organic matter as a consequence of anoxic conditions associated with marine flooding events that took place during the Jurassic and Early Cretaceous. The presence of numerous reservoir levels (clastics, carbonates, and also sills) and many regional and local seal intervals (shales and evaporates) within the sedimentary pile, combined with a diverse structural style, allowed the oil and gas trapping. Hydrocarbons were generated in various kitchens working at different times, as result of the subsidence regime and geothermal gradient that diversely affected different regions of the Neuquen Basin.

Legarreta, L.; Gulisano, C.A.; Orchuela, I.; Minnti, S.A. [Petrolera Argentina San Jorge, Buenos Aires (Argentina)

1996-08-01

309

The Theory of Scale Relativity: Non-Dieren tiable Geometry and Fractal Space-Time1  

Microsoft Academic Search

The aim of the theory of scale relativity is to derive the physical behavior of a non-dieren tiable and fractal space-time and of its geodesics (with which particles are identied), under the constraint of the principle of the relativity of scales. We mainly study in this contribution the eects induced by internal fractal structures on the motion in standard space.

Laurent NOTTALE

2004-01-01

310

Nanometer-scale recording with transition time at nanosecond D.X. Shia,b,*  

E-print Network

.65 Keywords: Recording; Data storage; Transient conductance; Scanning tunneling microscopy 1. IntroductionNanometer-scale recording with transition time at nanosecond D.X. Shia,b,* , D.C. Baa , S.J. Panga 2001; accepted 23 July 2001 Abstract Recording at a nanometer-scale on 3-phenyl-1-ureidonitrile (CPU

Gao, Hongjun

311

Fine-scale variation in the timing of reproduction in titmice and chickadees  

Microsoft Academic Search

Variation among female songbirds in the timing of clutch initiation has been studied, nearly continu- ously, for at least the last 60 years. Rather than a focus on control of broad timing patterns across sea- sons (Chapter 4), this research has concerned itself with fine-scale adjustment of reproductive timing for strategic breeding purposes. It has benefited from long-term data sets

Scott M. Ramsay; Ken A. Otter

312

Travel-time tomography in shallow water: Experimental demonstration at an ultrasonic scale  

E-print Network

Travel-time tomography in shallow water: Experimental demonstration at an ultrasonic scale Philippe arrays record the transfer matrix in the time domain of the waveguide between each pair of source­receiver trans- ducers. A time-domain, double-beamforming algorithm is simultaneously performed on the source

Paris-Sud XI, Université de

313

The role of topography on catchment-scale water residence time  

Microsoft Academic Search

The age, or residence time, of water is a fundamental descriptor of catchment hydrology, revealing information about the storage, flow pathways, and source of water in a single integrated measure. While there has been tremendous recent interest in residence time estimation to characterize watersheds, there are relatively few studies that have quantified residence time at the watershed scale, and fewer

K. J. McGuire; J. J. McDonnell; M. Weiler; C. Kendall; B. L. McGlynn; J. M. Welker; J. Seibert

2005-01-01

314

Sensitivity of Southern Ocean overturning to wind stress changes: Role of surface restoring time scales  

NASA Astrophysics Data System (ADS)

The influence of different surface restoring time scales on the response of the Southern Ocean overturning circulation to wind stress changes is investigated using an idealised channel model. Regardless of the restoring time scales chosen, the eddy-induced meridional overturning circulation (MOC) is found to compensate for changes of the direct wind-driven Eulerian-mean MOC, rendering the residual MOC less sensitive to wind stress changes. However, the extent of this compensation depends strongly on the restoring time scale: residual MOC sensitivity increases with decreasing restoring time scale. Strong surface restoring is shown to limit the ability of the eddy-induced MOC to change in response to wind stress changes and as such suppresses the eddy compensation effect. These model results are consistent with qualitative arguments derived from residual-mean theory and may have important implications for interpreting past and future observations.

Zhai, Xiaoming; Munday, David R.

2014-12-01

315

Just in Time Clouds: Enabling Highly-Elastic Public Clouds over Low Scale Amortized Resources  

E-print Network

Just in Time Clouds: Enabling Highly-Elastic Public Clouds over Low Scale Amortized Resources, Brazil {rostand.costa, fubica}@lsd.ufcg.edu.br Guido Lemos de Souza Filho2 , Dênio Mariz Sousa2 2 Federal

Cirne, Walfredo

316

The dirt on paleosols: sedimentology and paleoclimate indicators within the upper triassic Chinle Formation, Paria, Utah.  

E-print Network

??The supercontinent Pangea was at its maximum subaerial exposure during the Late Triassic, causing an extreme paleoclimatic state. Seasonal, potentially monsoonal weather patterns affected the… (more)

Crocker, Megan Lynn

2012-01-01

317

RAP: A Real-Time Communication Architecture for Large-Scale Wireless Sensor Networks  

Microsoft Academic Search

Large-scale wireless sensor networks represent a new generation of real-time embedded systems with signifi- cantly different communication constraints from tradi- tional networked systems. This paper presents RAP, a new real-time communication architecture for large- scale sensor networks. RAP provides convenient, high- level query and event services for distributed micro- sensing applications. Novel location-addressed com- munication models are supported by a

Chenyang Lu; Brian M. Blum; Tarek F. Abdelzaher; John A. Stankovic; Tian He

2002-01-01

318

Validating a rapid-update satellite precipitation analysis across telescoping space and time scales  

Microsoft Academic Search

In order to properly utilize remotely sensed precipitation estimates in hydrometeorological applications, knowledge of the\\u000a accuracy of the estimates are needed. However, relatively few ground validation networks operate with the necessary spatial\\u000a density and time-resolution required for validation of high-resolution precipitation products (HRPP) generated at fine space\\u000a and time scales (e.g., hourly accumulations produced on a 0.25° spatial scale). In

Francis Joseph Turk; Byung-Ju Sohn; Hyun-Jong Oh; Elizabeth E. Ebert; Vincenzo Levizzani; Eric A. Smith

2009-01-01

319

A UPb and 40 Ar\\/ 39 Ar time scale for the Jurassic  

Microsoft Academic Search

Published time scales provide discrepant age estimates for Jurassic stage boundaries and carry large uncer - tainties. The U-Pb or 40Ar\\/39Ar dating of volcaniclastic rocks with precisely known stratigraphic age is the preferred method to improve the calibration. A radiometric age database consisting of fifty U-Pb and 40Ar\\/39Ar ages was com- piled to construct a revised Jurassic time scale. Accepted

J. Pálfy; P. L. Smith; J. K. Mortensen

2000-01-01

320

Tectonically controlled magnetic fabrics in the Iberian Triassic basin  

NASA Astrophysics Data System (ADS)

A relationship between the orientation of the magnetic susceptibility ellipsoid and the strain ellipsoid has been demonstrated by using the anisotropy of magnetic susceptibility (AMS) in sedimentary rocks. Studies also interpret an early development of the magnetic fabric, which registers the stress pattern acting during deposition. But this primary fabric can be overwritten by successive deformation phases, and these changes have been registered even in weakly deformed sediments. This work studies the AMS registered in an inverted basin where no penetrative compression-related structures have been recognized. Although inversion took place, strata remain weakly deformed, with shallow dips in most part of the area. Triassic sedimentary rocks from the Castilian Branch of the Iberian Range (NE Spain) are studied. The Castilian Branch started to develop as a rift basin during the Late Permian-Early Triassic with NW-SE and NE-SW faults affecting Upper Permian materials. Buntsandstein red beds accumulated in asymmetric half-grabens with strong thickness variations related to their position within the troughs and highs. After the Mid-Triassic, a marine and transitional sedimentation spanned throughout the Iberian Range (Keuper and Muschelkalk). Jurassic to Upper Cretaceous deposits unconformably covered the Triassic sediments with thickness of a few hundreds of meters. During the Paleogene, tectonic inversion took place, developing gentle folds and steeply-dipping reverse faults, resulting from the reactivation of extensional Triassic faults. The particular lithology of the Buntsandstein red beds also allows determining the influence of ferromagnetic phases in the AMS. We analyzed 815 standard specimens from 55 sites in a KLY-3S Kappabridge (AGICO) susceptometer to obtain the bulk susceptibility and the orientation of the three main eigenvectors of the magnetic ellipsoid. In order to determine the magnetic carriers of the bulk susceptibility, 22 temperature dependent susceptibility curves (from 40 to 700°C) were carried out, combining the susceptometer with a CS-3 furnace. Sites are representative of all the red beds sectors from the Castilian Branch, limited by different extensional structures acting during Triassic rifting. The magnetic susceptibility ranges between 80 and 350 x 10-6 SI. Most of the thermomagnetic curves indicate the presence of a high fraction of hematite as ferromagnetic mineral. In other cases, hematite and phyllosilicates are present in the same proportion, usually coinciding with samples from sites with the lowest susceptibility values. In some cases neoformation of magnetite takes place during heating. Results show kmin always subperpendicular to the bedding plane, according to a sedimentary fabric. kmax indicates four main directions for the magnetic lineation: NW-SE, NNE-SSW and, less represented N-S and E-W. These variations in lineation directions are directly related to several tectonic events, and can be interpreted according to i) the direction of the major extensional structures nearest to each site (suggesting an extensional-influenced origin for the lineation), ii) the geographic position of the basin sectors, depending on their proximity to the inverted faults (that would suggest a partial tectonically-influenced secondary magnetic fabric), iii) the age of the studied rocks, suggesting a stronger influence of extensional features in Early Triassic rocks, progressively diminishing upwards within the sedimentary sequence.

García-Lasanta, C.; Oliva-Urcia, B.; Román-Berdiel, T.; Casas-Sainz, A.; Gil-Peña, I.; Sánchez-Moya, Y.; Sopeña, A.

2012-04-01

321

Time Scales Of Auroral Intensifications Measured By Polar Uvi: Seasonal And Imf Dependence  

NASA Astrophysics Data System (ADS)

The hemispheric power of auroral electron precipitation measured by the Polar Ul- traviolet Imager (UVI) is used to quantify the time scales of auroral intensifications. It is shown that the auroral power during substorms is sustained above pre-onset lev- els for longer time scales during events that occur during southward interplanetary magnetic field (IMF). Furthermore, it is demonstrated that the characteristic time for substorm activity is roughly a factor of three longer for events that occur in darkness than for those when the ionosphere is sunlit. It is shown that the longer time scale of substorms occurring in darkness is sustained by discrete auroral features associated with field-aligned potential drops and inertial Alfven waves. These discrete structures exist for shorter time scales if they are observed at all during substorms that occur in sunlight. These results provide further evidence for the emerging view that the iono- spheric boundary conditions at the foot of auroral field lines play a significant role in determining both the synoptic scale structure of the aurora and its dynamical time scales.

Chua, D.; Parks, G.; Brittnacher, M.; Germany, G.; Spann, J.; Carlson, C.

322

New time-scale criteria for model simplification of bio-reaction systems  

PubMed Central

Background Quasi-steady state approximation (QSSA) based on time-scale analysis is known to be an effective method for simplifying metabolic reaction system, but the conventional analysis becomes time-consuming and tedious when the system is large. Although there are automatic methods, they are based on eigenvalue calculations of the Jacobian matrix and on linear transformations, which have a high computation cost. A more efficient estimation approach is necessary for complex systems. Results This work derived new time-scale factor by focusing on the problem structure. By mathematically reasoning the balancing behavior of fast species, new time-scale criteria were derived with a simple expression that uses the Jacobian matrix directly. The algorithm requires no linear transformation or decomposition of the Jacobian matrix, which has been an essential part for previous automatic time-scaling methods. Furthermore, the proposed scale factor is estimated locally. Therefore, an iterative procedure was also developed to find the possible multiple boundary layers and to derive an appropriate reduced model. Conclusion By successive calculation of the newly derived time-scale criteria, it was possible to detect multiple boundary layers of full ordinary differential equation (ODE) models. Besides, the iterative procedure could derive the appropriate reduced differential algebraic equation (DAE) model with consistent initial values, which was tested with simple examples and a practical example. PMID:18694523

Choi, Junwon; Yang, Kyung-won; Lee, Tai-yong; Lee, Sang Yup

2008-01-01

323

Implications from Paleomagnetic Age Constrains and Petrology Analyses on the Reconstruction of the Triassic Paleosurface in Europe - Examples from Catalonia and the Polish Sudetes (Invited)  

NASA Astrophysics Data System (ADS)

The crystalline basement rocks (such as granites and rhyolithes) of European Variscan massifs often show Permo-Triassic paleomagnetic remagnetizations resulting in underestimated age determinations. These rejuvenated ages are attributed to an alteration of the primary paleomagnetic signal recently carried by the neo-formation of secondary hematite. Hematite forms under oxic conditions. Thus, one may deduce that the remagnetization of the Paleozoic crystalline rocks occurs once the basement rocks are exposed at the Permo-Triassic (paleo)surface. Permo-Triassic remagnetizations are ubiquitous, affecting many emerged Paleozoic rocks in Europe (and beyond) and suggesting a major weathering event under oxic conditions. The extent of the altered zone (> 100 m in depth) points to a sodium enriched groundwater environment. The Na+ enrichment is likely related to the Triassic environment characterized by widespread salt deposits, such as leaching of salt, marine aerosols, periodic/episodic contribution of seawater or evaporative solutions. Under these uncommon shallow conditions the basement rocks containing feldspars (mainly granites and gneisses) suffered an ubiquitous process of alteration consisting in the albitization of feldspars (fsp). The most visible feature of this alteration at outcrop scale is the pervasive red staining of the rock due to the presence of associated Fe-oxide inclusions, which are responsible for the penetrative red colour of the rock. Examination by petrographical microscopy shows that the fsp replacement by albite is pseudomorphic and the shape and optical properties of the parent fsp are preserved in the daughter grain. The composition of the albitized fsp is very constant and close to the albite end-member, displaying values of Ab96-97 in all studied massifs. In cathodoluminescence microscopy, the albitized fsp display a noticeable lack of luminescence, whereas the primary fsp usually show luminescence. The SEM images revealed that secondary albite contains widespread ?m and nm pores. Observations under SEM and HRSEM show that this microporosity is hoisting Fe-oxides inclusions responsible for the red colour. Most of the Fe-oxides tends to concentrate in the larger pores and in the majority of the imaged pores these Fe-oxides appears to be arranged in aggregates of nm size botryoids attached to the pore walls. Demonstrating that the albitized facies are of supergenic origin and that they are bound to the Triassic paleosurface deeply renews the ideas about the evolution of basement areas. The recognition of the Triassic paleosurface on widespread basements in Europe will provide spatio-temporal benchmarks to constrain the ablation of these massifs since the Triassic. This will be a major contribution to the geodynamic modelling of these areas.

Parcerisa, D.; Franke, C.; Fabrega, C.; Yao, K.; Thiry, M.

2013-12-01

324

Two Distinct Time-Scale Regimes of the Effective Temperature for an Aging Colloidal Glass  

E-print Network

Colloidal dispersions of Laponite platelets are known to age slowly from viscous sols to colloidal glasses. We follow this aging process by monitoring the diffusion of probe particles embedded in the sample via dynamic light scattering. Our results show that the time-dependent diffusion of the probe particles scales with their size. This implies that the fluctuation-dissipation theorem can be generalized for this out-of-equilibrium system by replacing the bath temperature with an effective temperature. Simultaneous dynamic rheological measurements reveal that this effective temperature increases as a function of aging time and frequency. This suggests the existence of two regimes: at probed time scales longer than the characteristic relaxation time of the Laponite dispersion, the system thermalizes with the bath, whereas at shorter time scales, the system is out-of-equilibrium with an effective temperature greater than the bath temperature.

D. R. Strachan; G. C. Kalur; S. R. Raghavan

2005-10-27

325

Feedback-Based Dynamic Voltage and Frequency Scaling for Memory-Bound Real-Time Applications  

Microsoft Academic Search

Dynamic voltage and frequency scaling is increasingly being used to reduce the energy requirements of embed- ded and real-time applications by exploiting idle CPU re- sources, while still maintaining all application's real-time characteristics. Accurate predictions of task run-times a re key to computing the frequencies and voltages that en- sure that all tasks' real-time constraints are met. Past wor k

Christian Poellabauer; Leo Singleton; Karsten Schwan

2005-01-01

326

U-Pb single zircon ages and geochemistry of metagranitoid rocks in the Cycladic Blueschists (Evia Island): Implications for the Triassic tectonic setting of Greece  

NASA Astrophysics Data System (ADS)

U-Pb zircon geochronology, geochemical and microstructural analyses were carried out to a metagranitoid suite exposed in the Blueschist unit of the Attic-Cycladic zone on Evia Island. Concordant zircons from three metagranitoid samples yielded ID-TIMS U-Pb single grain ages of 234 ± 1.2 Ma, 232 ± 1 Ma and 214 ± 0.7 Ma, which are interpreted to constrain the intrusion of the igneous protolith in Late Triassic times. These age data in combination with previously published Early-Middle Triassic protolith ages of (meta-)igneous rocks from other Greek islands support magmatic activity in the Cycladic area throughout the Triassic. Major and trace element whole rock analyses reveal that the granitic protolith of the Evia metagranitoid suite is of A-type affinity implying Triassic magmatism in an extensional setting along the northern Gondwanan margin rather than back-arc extension above a subduction zone. Subsequent Alpine subduction and related high-pressure metamorphism led to pervasive non-coaxial fabrics of the Evia metagranitoid, which indicate top-to-the-E(SE) shearing. This Alpine deformation took place under ductile (viscous) conditions at temperatures close to 450-500 °C and differential stresses of 65 + 15/- 10 MPa.

Chatzaras, V.; Dörr, W.; Finger, F.; Xypolias, P.; Zulauf, G.

2013-06-01

327

Global correlations of mid Early Triassic events: The Induan/Olenekian boundary in the Dolomites (Italy)  

NASA Astrophysics Data System (ADS)

The Dolomites (Southern Alps, Italy) are a reference-area for research on the end-Permian mass extinction and its Early Triassic aftermath. The effects on shallow marine benthic biota are recorded in the Werfen Formation, a thick mixed carbonate-siliciclastic sedimentary succession. Only in its lower (Griesbachian) and upper (Spathian) parts, this formation is bio-chronologically constrained by means of conodonts and ammonoids, whilst no significant bioevent occurs in its middle part. This represents an impediment to the biochronologic recognition of the Induan/Olenekian boundary (IOB). The Bulla/Pufels (Val Gardena) succession is a key-section for the P/T boundary and Early Triassic for global correlation due to the abundance of studies on biostratigraphy (mostly on conodonts), magnetostratigraphy and chemostratigraphy carried out there by stratigraphers of various nationalities. Recent chemostratigraphic studies have permitted the recognition of some carbon isotope positive peaks, the strongest of which is considered to approximate the IOB. However, various authors have reached different conclusions on the position of the maximum peak and thus on the IOB location. This leads to important stratigraphic consequences for the calibration of conodont biostratigraphy. The critical revision of the traditional stratigraphic units (litho- and biostratigraphy), under-evaluated in most of the recent literature, and magneto-, chemo- and sequence stratigraphic units allowed herein an integrated stratigraphic scale for the Bulla/Pufels section to be proposed. This contribution highlights the mid Early Triassic Dolomites record for regional and global correlations. The most significant results attained herein regard the different lithostratigraphic subdivisions of the middle Werfen Formation and its consequences on the position of the IOB with respect to the conodont and bivalve biostratigraphy and sequence stratigraphic units. The upper part of the section is attributed herein to the Gastropod Oolite Member, which is represented by the lithozone A, a predominant supratidal episode, and the lower part of the subtidal lithozone B. Between the lithozones A and B, a sequence boundary of 3th order (Sc2/Sc3) is located. The maximum carbon isotope excursion is near this boundary, which therefore approximates the IOB in the Dolomites. This proposal suggests a Dienerian age for the FO of the conodont Pachycladina obliqua, which occurs about 60 m below the stage boundary. No significant biotic event, either for molluscs or conodonts, occurred across this stage boundary.

Posenato, Renato

2008-12-01

328

Nitrogen isotope chemostratigraphy across the Permian-Triassic boundary at Chaotian, Sichuan, South China  

NASA Astrophysics Data System (ADS)

Nitrogen isotopic compositions of upper Permian to lowermost Triassic rocks were analyzed at Chaotian in northern Sichuan, South China, in order to clarify changes in the oceanic nitrogen cycle around the Permian-Triassic boundary (P-TB) including the entire Changhsingian (Late Late Permian) prior to the extinction. The analyzed ca. 40 m thick interval across the P-TB at Chaotian consists of three stratigraphic units: the upper Wujiaping Formation, the Dalong Formation, and the lowermost Feixianguan Formation, in ascending order. The upper Wujiaping Formation, ca. 10 m thick, is mainly composed of dark gray limestone with diverse shallow-marine fossils such as calcareous algae and brachiopods, deposited on the shallow shelf. In contrast, the overlying Dalong Formation, ca. 25 m thick, is mainly composed of thinly bedded black mudstone and siliceous mudstone containing abundant radiolarians, deposited on the relatively deep slope/basin. Absence of bioturbation, substantially high total organic carbon contents (up to 15%), and abundant occurrence of pyrite framboids in the main part of the Dalong Formation indicate deposition under anoxic condition. The lowermost Feixianguan Formation, ca. 5 m thick, is composed of thinly bedded gray marl and micritic limestone with minor fossils such as ammonoids and conodonts, deposited on the relatively shallow slope. ?15NTN values are in positive values around +1 to +2‰ in the upper Wujiaping Formation implying denitrification and/or anammox in the ocean. ?15NTN values gradually decrease to -1‰ in the lower Dalong Formation and are consistently low (around 0‰) in the middle Dalong to lowermost Feixianguan Formation. No clear ?15NTN shift is recognized across the extinction horizon. The consistently low ?15NTN values suggest the enhanced nitrogen fixation in the ocean during the Changhsingian at Chaotian. Composite profiles based on previous and the present studies demonstrate the substantial ?15N variation on a global scale in the late Permian to earliest Triassic; a systematic ?15N difference by low and high latitudes is particularly clarified. Although the enhanced nitrogen fixation throughout the Changhsingian at Chaotian was likely a regional event in northwestern South China, the composite ?15N profiles imply that the sea area in which fixed nitrogen is depleted has gradually developed worldwide in the Changhsingian, possibly acting as a prolonged stress to shallow-marine biota.

Saitoh, Masafumi; Ueno, Yuichiro; Nishizawa, Manabu; Isozaki, Yukio; Takai, Ken; Yao, Jianxin; Ji, Zhansheng

2014-10-01

329

Characteristic Time Scales of Transport Processes for Chemotactic Bacteria in Groundwater: Analysis of Pore-scale to Field-scale Experimental Data  

NASA Astrophysics Data System (ADS)

Many processes contribute to the transport of microorganisms in groundwater environments. One process of interest is chemotaxis, whereby motile bacteria are able to detect and swim toward increasing concentrations of industrial hydrocarbons that they perceive as food sources. By enabling bacteria to migrate to the sources of pollutants that they degrade, chemotaxis has the potential to enhance bioremediation efforts, especially in less permeable zones where contamination may persist. To determine the field conditions under which chemotaxis might be exploited in a bioremediation scheme requires an understanding of the characteristic time scales in the system. We defined a dimensionless chemotaxis number that compares the time over which a bacterial population is exposed to a chemical gradient to the time required for a bacterial population to migrate a significant distance in response to a chemical gradient. The exposure time and the response time are dependent upon the experimental conditions and properties of the bacteria and chemical attractant. Experimental data was analyzed for a range of groundwater flow rates over a wide scope of experimental systems including a single-pore with NAPL source, a microfluidic channel with and without a porous matrix, a laboratory column, a bench-scale microcosm and a field-scale study. Chemical gradients were created transverse to the flow direction. Distributions of chemotactic and nonchemotactic bacteria were compared to determine the extent of migration due to chemotaxis. Under some conditions at higher flow rates, the effect of chemotaxis was diminished to the point of not being detected. The goal of the study was to determine a critical value for the dimensionless chemotaxis number (which is independent of scale) that can be used as a design criterion to ascertain a priori the conditions under which a chemotactic response will impact bacterial transport relative to other processes such as advection and dispersion.

Ford, R. M.

2010-12-01

330

Micro- and nano- second time scale, high power electrical wire explosions in water.  

NASA Astrophysics Data System (ADS)

Experimental and magneto-hydro-dynamic simulation results of micro- and nanosecond time scale underwater electrical Al, Cu and W wires explosions are presented. A capacitor bank with stored energy up to 6 kJ (discharge current up to 80 kA with 2.5 ?s quarter period) was used in microsecond time scale experiments and water forming line generator with current amplitude up to 100 kA and pulse duration of 100 ns were used in nanosecond time scale experiments. Extremely high energy deposition of up to 60 times the atomization enthalpy was registered in nanosecond time scale explosions. A discharge channel evolution and surface temperature were analyzed by streak shadow imaging and using fast photo-diode with a set of interference filters, respectively. Microsecond time scale electrical explosion of cylindrical wire array showed extremely high pressure of converging shock waves at the axis, up to 0.2 MBar. A 1D and 2D magneto-hydro-dynamic simulation demonstrated good agreement with such experimental parameters as discharge channel current, voltage, radius, and temperature.

Grinenko, Alon; Efimov, Sergey; Sayapin, Arkadii; Fedotov, Alexander; Gurovich, Viktor; Krasik, Yakov

2006-10-01

331

Astronomy 102: Black Holes, Time Warps, and the Large-Scale Structure of the Universe  

E-print Network

Astronomy 102: Black Holes, Time Warps, and the Large-Scale Structure of the Universe Fall 2009. Required textbook: Only one, Kip Thorne's Black Holes and Time Warps: Einstein's Outrageous Legacy (Norton of Einstein's theory of relativity, and its application to black holes and the Big Bang. Black holes turn out

332

Quaternary Science Reviews 22 (2003) 16311646 Greenland--Antarctic phase relations and millennial time-scale  

E-print Network

Quaternary Science Reviews 22 (2003) 1631­1646 Greenland--Antarctic phase relations and millennial the south to north time lag. At higher frequencies, in the millennial band, there is no measurable average. All rights reserved. 1. Introduction Millennial time-scale signals in ice and seafloor cores have

Wunsch, Carl

333

The power of time: spatiotemporal scaling of species Peter B. Adler1  

E-print Network

in space and time and raise questions about the diversity estimates currently used by basic researchersREPORT The power of time: spatiotemporal scaling of species diversity Peter B. Adler1 * and William K. Lauenroth1,2 1 Graduate Degree Program in Ecology, Natural Resources, Colorado State University

334

SMEX02: Field scale variability, time stability and similarity of soil moisture  

E-print Network

for intermediate soil moisture range. Time stability analysis showed that an appropriately selected single samplingSMEX02: Field scale variability, time stability and similarity of soil moisture Jennifer M. Jacobsa 2004 Abstract Evaluation of air- or space-borne remote sensors measuring soil moisture requires

Mohanty, Binayak P.

335

Assessment of effective thermal product of surface junction thermocouples on millisecond and microsecond time scales  

Microsoft Academic Search

Surface junction thermocouples are used extensively for transient heat flux measurements, but their accuracy is dependent on the effective thermal product (TP) of the gauge and this can be a function of the time scale of interest. In the present work the response of surface junction k-type thermocouples was investigated experimentally using a water droplet calibration technique (for millisecond times

David R. Buttsworth

2001-01-01

336

Fast Similarity Search in the Presence of Noise, Scaling, and Translation in Time-Series Databases  

Microsoft Academic Search

We introduce a new model of similarity of time se- quences that captures the intuitive notion that two sequences should be considered similar if they have enough non-overlapping time-ordered pairs of subse- quences thar are similar. The model allows the am- plitude of one of the two sequences to be scaled by any suitable amount and its offset adjusted appropriately.

Rakesh Agrawal; King-ip Lin; Harpreet S. Sawhney; Kyuseok Shim

1995-01-01

337

An Open and Scalable Emulation Infrastructure for Large-Scale Real-Time Network Simulations  

E-print Network

based on Virtual Private Network (VPN) customized to function as a gateway that bridges traffic between network aiming to create a large-scale real-time virtual network testbed. Our real- time interactive to the simulated network conditions computed as a result of both real and virtual traffic traversing the network

Liu, Xiaowen "Jason"

338

A REAL-TIME ROBUST SLAM for LARGE-SCALE OUTDOOR ENVIRONMENTS  

E-print Network

1 A REAL-TIME ROBUST SLAM for LARGE-SCALE OUTDOOR ENVIRONMENTS Jianping Xie, Fawzi Nashashibi-mail: garciafavrot@hotmail.com ABSTRACT The problem of simultaneous localization and mapping (SLAM) is still-time reliable SLAM solution with the capability of closing the loop using exclusive laser data. In our algorithm

Paris-Sud XI, Université de

339

Acoustic Emission Monitoring of the Syracuse Athena Temple: Scale Invariance in the Timing of Ruptures  

SciTech Connect

We perform a comparative statistical analysis between the acoustic-emission time series from the ancient Greek Athena temple in Syracuse and the sequence of nearby earthquakes. We find an apparent association between acoustic-emission bursts and the earthquake occurrence. The waiting-time distributions for acoustic-emission and earthquake time series are described by a unique scaling law indicating self-similarity over a wide range of magnitude scales. This evidence suggests a correlation between the aging process of the temple and the local seismic activity.

Niccolini, G.; Carpinteri, A.; Lacidogna, G.; Manuello, A. [Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino (Italy)] [Department of Structural Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)

2011-03-11

340

Can inertial electrostatic confinement work beyond the ion--ion collisional time scale?  

SciTech Connect

Inertial electrostatic confinement (IEC) systems are predicated on a nonequilibrium ion distribution function. Coulomb collisions between ions cause this distribution to relax to a Maxwellian on the ion--ion collisional time scale. The power required to prevent this relaxation and maintain the IEC configuration for times beyond the ion--ion collisional time scale is shown to be greater than the fusion power produced. It is concluded that IEC systems show little promise as a basis for the development of commercial electric power plants. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Nevins, W.M. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

1995-10-01

341

Can inertial electrostatic confinement work beyond the ion-ion collisional time scale?  

SciTech Connect

Inertial electrostatic confinement systems are predicated on a non-equilibrium ion distribution function. Coulomb collisions between ions cause this distribution to relax to a Maxwellian on the ion-ion collisional time-scale. The power required to prevent this relaxation and maintain the IEC configuration for times beyond the ion-ion collisional time scale is shown to be at least an order of magnitude greater than the fusion power produced. It is concluded that IEC systems show little promise as a basis for the development of commercial electric power plants.

Nevins, W.M.

1995-01-01

342

Acoustic emission monitoring of the Syracuse Athena temple: scale invariance in the timing of ruptures.  

PubMed

We perform a comparative statistical analysis between the acoustic-emission time series from the ancient Greek Athena temple in Syracuse and the sequence of nearby earthquakes. We find an apparent association between acoustic-emission bursts and the earthquake occurrence. The waiting-time distributions for acoustic-emission and earthquake time series are described by a unique scaling law indicating self-similarity over a wide range of magnitude scales. This evidence suggests a correlation between the aging process of the temple and the local seismic activity. PMID:21469841

Niccolini, G; Carpinteri, A; Lacidogna, G; Manuello, A

2011-03-11

343

Acoustic Emission Monitoring of the Syracuse Athena Temple: Scale Invariance in the Timing of Ruptures  

NASA Astrophysics Data System (ADS)

We perform a comparative statistical analysis between the acoustic-emission time series from the ancient Greek Athena temple in Syracuse and the sequence of nearby earthquakes. We find an apparent association between acoustic-emission bursts and the earthquake occurrence. The waiting-time distributions for acoustic-emission and earthquake time series are described by a unique scaling law indicating self-similarity over a wide range of magnitude scales. This evidence suggests a correlation between the aging process of the temple and the local seismic activity.

Niccolini, G.; Carpinteri, A.; Lacidogna, G.; Manuello, A.

2011-03-01

344

Coevolution of strategy-selection time scale and cooperation in spatial prisoner's dilemma game  

NASA Astrophysics Data System (ADS)

In this paper, we investigate a networked prisoner's dilemma game where individuals' strategy-selection time scale evolves based on their historical learning information. We show that the more times the current strategy of an individual is learnt by his neighbors, the longer time he will stick on the successful behavior by adaptively adjusting the lifetime of the adopted strategy. Through characterizing the extent of success of the individuals with normalized payoffs, we show that properly using the learned information can form a positive feedback mechanism between cooperative behavior and its lifetime, which can boost cooperation on square lattices and scale-free networks.

Rong, Zhihai; Wu, Zhi-Xi; Chen, Guanrong

2013-06-01

345

Huge (but finite) time scales in slow relaxations: beyond simple aging.  

PubMed

Experiments performed in the last years demonstrated slow relaxations and aging in the conductance of a large variety of materials. Here, we present experimental and theoretical results for conductance relaxation and aging for the case-study example of porous silicon. The relaxations are experimentally observed even at room temperature over time scales of hours, and when a strong electric field is applied for a time tw, the ensuing relaxation depends on tw. We derive a theoretical curve and show that all experimental data collapse onto it with a single time scale as a fitting parameter. This time scale is found to be of the order of thousands of seconds at room temperature. The generic theory suggested is not fine-tuned to porous silicon, and thus we believe the results should be universal, and the presented method should be applicable for many other systems manifesting memory and other glassy effects. PMID:22107656

Amir, Ariel; Borini, Stefano; Oreg, Yuval; Imry, Yoseph

2011-10-28

346

Calibration of the geologic time scale: Cenozoic and Late Cretaceous glauconite and nonglauconite dates compared  

SciTech Connect

Revision of the 1982 time scale of Harland et al. has led to the compilation of 377 isotopic dates for calibration of the Cenozoic to Cretaceous time interval. The results show that the ages of stage boundaries based on glauconite dates are on average about 2 m.y. younger than those based on nonglauconite dates, but for many Cenozoic and Late Cretaceous stages the differences are too small to require special consideration of glauconite dates. Future work may reveal an irreducible systematic difference between glauconite and nonglauconite time scales, but the progress made so far in recognizing those glauconites likely to yield reliable dates for the Cenozoic to Late Cretaceous interval may continue to provide useful time-scale calibration points.

Craig, L.E.; Smith, A.G. (Univ. of Cambridge (England)); Armstrong, R.L. (Univ. of British Columbia, Vancouver (Canada))

1989-09-01

347

A hybrid procedure for MSW generation forecasting at multiple time scales in Xiamen City, China.  

PubMed

Accurate forecasting of municipal solid waste (MSW) generation is crucial and fundamental for the planning, operation and optimization of any MSW management system. Comprehensive information on waste generation for month-scale, medium-term and long-term time scales is especially needed, considering the necessity of MSW management upgrade facing many developing countries. Several existing models are available but of little use in forecasting MSW generation at multiple time scales. The goal of this study is to propose a hybrid model that combines the seasonal autoregressive integrated moving average (SARIMA) model and grey system theory to forecast MSW generation at multiple time scales without needing to consider other variables such as demographics and socioeconomic factors. To demonstrate its applicability, a case study of Xiamen City, China was performed. Results show that the model is robust enough to fit and forecast seasonal and annual dynamics of MSW generation at month-scale, medium- and long-term time scales with the desired accuracy. In the month-scale, MSW generation in Xiamen City will peak at 132.2 thousand tonnes in July 2015 - 1.5 times the volume in July 2010. In the medium term, annual MSW generation will increase to 1518.1 thousand tonnes by 2015 at an average growth rate of 10%. In the long term, a large volume of MSW will be output annually and will increase to 2486.3 thousand tonnes by 2020 - 2.5 times the value for 2010. The hybrid model proposed in this paper can enable decision makers to develop integrated policies and measures for waste management over the long term. PMID:23490364

Xu, Lilai; Gao, Peiqing; Cui, Shenghui; Liu, Chun

2013-06-01

348

Development of lower Triassic wrinkle structures: implications for the search for life on other planets.  

PubMed

Wrinkle structures are microbially mediated sedimentary structures that are a common feature of Proterozoic and earliest Phanerozoic siliciclastic seafloors on Earth and occur only rarely in post-Cambrian strata. These macroscopic microbially induced sedimentary structures are readily identifiable at the outcrop scale, and their recognition on other planetary bodies by landed missions may suggest the presence of past microbial life. Wrinkle structures of the Lower Triassic (Spathian) Virgin Limestone Member of the Moenkopi Formation in the western United States record an occurrence of widespread microbialite formation in the wake of the end-Permian mass extinction, the largest biotic crisis of the Phanerozoic. Wrinkle structures occur on proximal sandy tempestites deposited within the offshore transition. Storm layers appear to have been rapidly colonized by microbial mats and were subsequently buried by mud during fair-weather conditions. Wrinkle structures exhibit flat-topped crests and sinuous troughs, with associated mica grains oriented parallel to bedding, suggestive of trapping and binding activity. Although Lower Triassic wrinkle structures postdate the widespread occurrence of these features during the Proterozoic and Cambrian, they exhibit many of the same characteristics and environmental trends, which suggests a conservation of microbial formational and preservational processes in subtidal siliciclastic settings on Earth from the Precambrian into the Phanerozoic. In the search for extraterrestrial life, it may be these conservative characteristics that prove to be the most useful and robust for recognizing microbial features on other planetary bodies, and may add to an ever-growing foundation of knowledge for directing future explorations aimed at seeking out macroscopic microbial signatures. PMID:19968465

Mata, Scott A; Bottjer, David J

2009-11-01

349

Space and time scales of shoreline change at Cape Cod National Seashore, MA, USA  

USGS Publications Warehouse

Different processes cause patterns of shoreline change which are exhibited at different magnitudes and nested into different spatial and time scale hierarchies. The 77-km outer beach at Cape Cod National Seashore offers one of the few U.S. federally owned portions of beach to study shoreline change within the full range of sediment source and sink relationships, and barely affected by human intervention. 'Mean trends' of shoreline changes are best observed at long time scales but contain much spatial variation thus many sites are not equal in response. Long-term, earlier-noted trends are confirmed but the added quantification and resolution improves greatly the understanding of appropriate spatial and time scales of those processes driving bluff retreat and barrier island changes in both north and south depocenters. Shorter timescales allow for comparison of trends and uncertainty in shoreline change at local scales but are dependent upon some measure of storm intensity and seasonal frequency. Single-event shoreline survey results for one storm at daily intervals after the erosional phase suggest a recovery time for the system of six days, identifies three sites with abnormally large change, and that responses at these sites are spatially coherent for now unknown reasons. Areas near inlets are the most variable at all time scales. Hierarchies in both process and form are suggested.

Allen, J.R.; LaBash, C.L.; List, J.H.

1999-01-01

350

Semantic and acoustic analysis of speech by functional networks with distinct time scales  

PubMed Central

Speech perception requires the successful interpretation of both phonetic and syllabic information in the auditory signal. It has been suggested by Poeppel (2003) that phonetic processing requires an optimal time scale of 25 ms while the time scale of syllabic processing is much slower (150–250ms). To better understand the operation of brain networks at these characteristic time scales during speech perception, we studied the spatial and dynamic properties of EEG responses to five different stimuli: (1) amplitude modulated (AM) speech, (2) AM speech with added broadband noise, (3) AM reversed speech, (4) AM broadband noise, and (5) AM pure tone. Amplitude modulation at gamma band frequencies (40 Hz) elicited steady-state auditory evoked responses (SSAERs) bilaterally over primary auditory cortices. Reduced SSAERs were observed over the left auditory cortex only for stimuli containing speech. In addition, we found over the left hemisphere, anterior to primary auditory cortex, a network whose instantaneous frequencies in the theta to alpha band (4–16 Hz) are correlated with the amplitude envelope of the speech signal. This correlation was not observed for reversed speech. The presence of speech in the sound input activates a 4–16 Hz envelope tracking network and suppresses the 40-Hz gamma band network which generates the steady-state responses over the left auditory cortex. We believe these findings to be consistent with the idea that processing of the speech signals involves preferentially processing at syllabic time scales rather than phonetic time scales. PMID:20580635

Deng, Siyi; Srinivasan, Ramesh

2014-01-01

351

Multi-time step modeling of plume dynamics in nanosecond-scale carbon ablation.  

PubMed

The time span of plume dynamics in laser ablation of carbon ranges from nanoseconds to milliseconds. Multi-time step approach is developed to study the plume dynamics over this entire range with minimum requirements of numerical computational resources. This approach is applied to study one of the important aspects of nanosecond-scale laser ablation, namely the shielding of incident laser beam with previously ejected plumes. Capturing the shielding effect requires smaller than nanosecond-scale time step because of large velocity and pressure gradients in plume. Use of this time step over the entire domain needs enormous amount of computer time to cover the whole time span of plume dynamics. Multi-time step modeling for such an application is therefore useful. In general, for nanosecond-scale laser ablation this shielding is caused by ionized particles and by gas molecules. It is shown for carbon plume resulting from the nanosecond-scale lasers that the degree of ionization is small. Ionization of ablated carbon is estimated by Saha equation for the given initial plume conditions. The shielding of incident laser beam is therefore calculated by normal molecular absorption. The laser-light intensity that reaches the target for subsequent pulses is evaluated. PMID:19198348

Pathak, Kedar; Povitsky, Alex

2008-11-01

352

Provenance of Late Triassic sediments in central Lhasa terrane, Tibet and its implication  

E-print Network

Provenance of Late Triassic sediments in central Lhasa terrane, Tibet and its implication Guangwei online xxxx Handling Editor: G.C. Zhao Keywords: Provenance Late Triassic Lhasa terrane Chronology Hf of the Lhasa terrane prior to Indo-Asian collision. We report new data relevant to the provenance of a Late

Sandiford, Mike

353

Constraints on Early Triassic carbon cycle dynamics from paired organic and inorganic carbon isotope records  

Microsoft Academic Search

Marine anoxia and euxinia are widely cited as a leading cause of the end-Permian mass extinction and a factor limiting recovery during the Early Triassic. Middle Triassic diversification coincided with the waning of anoxia and stabilization of the global carbon cycle, suggesting that environment-ecosystem linkages were important to biological recovery. However, the mechanisms responsible for these phenomena remain poorly constrained.

K. M. Meyer; M. Yu; J. Payne

2010-01-01

354

North-directed Triassic nappes in Northeastern Vietnam (East Bac Bo) Claude Lepvrier a  

E-print Network

1 1 North-directed Triassic nappes in Northeastern Vietnam (East Bac Bo) Claude Lepvrier nappes, including recumbent folds, formed during the Triassic, prior to the unconformable deposition of « preyunnanaises nappes », represented by Middle-Upper Paleozoic foliated limestone resting through a flat

Paris-Sud XI, Université de

355

Stratigraphy and correlation of Upper Triassic strata between west Texas and eastern New Mexico  

Microsoft Academic Search

Lithostratigraphy and vertebrate biochronology allow precise correlation of Upper Triassic strata between west Texas and eastern New Mexico. Upper Triassic strata are well exposed in west Texas from Oldham to Scurry counties, and are assigned to the Dockum Formation of the Chinle Group. Fossil vertebrates from the Camp Springs and Tecovas Members are of late Carnian age, whereas those from

S. G. Lucas; O. J. Anderson

1992-01-01

356

A new chronology for the end-Triassic mass extinction M.H.L. Deenen a,  

E-print Network

from the Triassic to Jurassic Period, initiating the `Age of the dinosaurs', approximately 200 Ma. This event closely coincides with a period of extensive volcanism in the Central Atlantic Magmatic Province. The Triassic­Jurassic (T­J) boundary is recently proposed in the marine record at the first occurrence datum

Utrecht, Universiteit

357

A critical re?evaluation of the Late Triassic dinosaur taxa of North America  

Microsoft Academic Search

The North American Triassic dinosaur record has been repeatedly cited as one of the most complete early dinosaur assemblages. The discovery of Silesaurus from Poland and the recognition that Herrerasaurus and Eoraptor may not be theropods have forced a re?evaluation of saurischian and theropod synapomorphies. Here, we re?evaluate each purported Triassic dinosaur from North America on a specimen by specimen

Sterling J. Nesbitt; Randall B. Irmis; William G. Parker

2007-01-01

358

Correlation of upper Triassic strata between southern Colorado Plateau and southern High Plains, New Mexico  

SciTech Connect

Almost 600 m of Upper Triassic strata are exposed in the Hagan basin. They pertain to the basal Agua Zarca member of the Chinle Formation (as much as 80 m), overlain by about 500 m of mud-rock-dominated red beds of the Petrified Forest Member of the Chinle Formation. The top of the Triassic section here is the 5.5-24 m-thick Correo Sandstone Bed of Chinle Formation, which is disconformably overlain by the medial silty member of the Middle Jurassic Entrada Sandstone. At Lamy, approximately 370 m of Upper Triassic strata represent the westernmost outcrops of the Triassic section typical of the Tucumcari basin. This Triassic section consists of about 140 m of Santa Rosa Formation (divisible into three members) overlain by a mud-rock-dominated section (Chinle Formation) split by a medial sandy interval, the Cuervo member (Trujillo Formation of the Palo Duro basin). The youngest Triassic strata near Lamy are rhythmically bedded sediments of the Redonda Member. Based on lithologic similarity, stratigraphic position, and limited paleontological data, the central New Mexico Upper Triassic strata support for the following correlations (from west to east): (1) Shinarump = Agua Zarca = Santa Rosa; (2) lower Petrified Forest = lower shale member of the Chinle = Tecovas; (3) Sonsela = Poleo = Cuervo = Trujillo; (4) upper Petrified Forest = upper shale member of the Chinle; and (5) Owl Rock = Redonda = Correo. These correlations reflect homotaxis of sedimentary cycles across a broad region of the southern Western Interior during the Late Triassic.

Lucas, S.G. (New Mexico Museum of Natural History, Albuquerque (USA))

1989-09-01

359

Early ta Middle Carnian (Triassic) Flora and Fauna of the Richmond and Taylorsville  

E-print Network

#12;1 Early ta Middle Carnian (Triassic) Flora and Fauna of the Richmond and Taylorsville Basins, Virginia and Maryland, U.S.A. #12;#12;Early ta Middle Carnian (Triassic) Flora and Fauna of the Richlllond Age of the Richmond-Taylorsville Basin Floras 7 Vertebrate Assemblages 14 Taxonomic Treatment

Olsen, Paul E.

360

STRATIGRAPHIC RECORD OF TRIASSIC-JURASSIC COLLISIONAL TECTONICS IN THE BLUE MOUNTAINS PROVINCE,  

E-print Network

STRATIGRAPHIC RECORD OF TRIASSIC-JURASSIC COLLISIONAL TECTONICS IN THE BLUE MOUNTAINS PROVINCE in the Blue Mountains province (BMP) of northeastern Oregon preserve a well studied record of Triassic­Jurassic to Early Jurassic deposits that change up section from (1a) older volcanic and volcaniclastic deposits

Dorsey, Becky

361

Thermal maturity of the Upper Triassic-Middle Jurassic Shemshak Group (Alborz Range, Northern Iran)  

E-print Network

1 Thermal maturity of the Upper Triassic-Middle Jurassic Shemshak Group (Alborz Range, Northern of the Shemshak Group (Upper Triassic-Middle Jurassic) from fifteen localities along the Alborz Range of Northern deeply buried part of the Shemshak Group (i.e., Tazareh section) corresponds to Late Jurassic

Paris-Sud XI, Université de

362

Triassic arc-derived detritus in the Triassic Karakaya accretionary complex was not derived from either the S Eurasian margin (Istanbul terrane) or the N Gondwana margin (Taurides)  

NASA Astrophysics Data System (ADS)

We present new U-Pb zircon source age data for Upper Triassic sandstones of the Istanbul Terrane (S Eurasian margin) and also for Triassic sandstones of the Taurides (N Gondwana margin). The main aim is to detect and quantify the contribution of Triassic magmatism as detritus to either of these crustal blocks. This follows the recent discovery of a Triassic magmatic arc source for the Triassic sandstones of the Palaeotethyan Karakaya subduction-accretion complex (Ustaömer et al. 2013; this meeting). Carboniferous (Variscan) zircon grains also form a significant detrital population, plus several more minor populations. Six sandstone samples were studied, two from the ?stanbul Terrane (Bak?rl?k?ran Formation of the Kocaeli Triassic Basin) and four from the Tauride Autochthon (latest Triassic Üzümdere Formation and Mid-Triassic Kas?mlar Formations; Bey?ehir region). Detrital zircon grains were dated by the laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb method at Goethe University, Frankfurt. Our results do not reveal Triassic detritus in the Üzümdere Formation. The U-Pb age of the analysed zircon grains ranges from 267 Ma to 3.2 Ga. A small fraction of Palaeozoic zircons are Permian (267 to 296 Ma), whereas the remainder are Early Palaeozoic. Ordovician grains (4%) form two age clusters, one at ca. 450 Ma and the other at ca. 474 Ma. Cambrian-aged grains dominate the zircon population, while the second largest population is Ediacaran (576 to 642 Ma). Smaller populations occur at 909-997 Ma, 827-839 Ma, 1.8-2.0 Ga and 2.4-2.6 Ga. The sandstones of the Kas?mlar Formation have similar zircon age cluster to those of the somewhat younger Üzümdere Formation, ranging from 239 Ma to 2.9 Ga. A few grains gave Anisian ages. Cambrian zircon grains are less pronounced than in the Kas?mlar Formation compared to the Üzümdere Formation. The detrital zircon record of Tauride sandstones, therefore, not indicates significant contribution of Triassic or Carboniferous (Variscan) arc sources, in marked contrast to those of the Triassic Karakaya subduction complex. In comparison, the ages of the analysed zircons in the Upper Triassic sandstones of the Istanbul Terrane range from 294 Ma to 3.1 Ga. Triassic zircons are again absent, while Variscan-aged zircons (294 to 339 Ma) dominate the zircon population. Additional zircon populations are dated at 554 to 655 Ma, 0.9 to 1.2 Ga, 1.5 Ga, 1.65 Ga, 2.0 to 2.15 and 2.5 to 2.8 Ga. The Precambrian zircon age spectra are compatible with derivation from an Avalonian/Amazonian/Baltic crustal provenance. In summary, there is no evidence in either the Triassic sandstones of the ?stanbul Terrane or of the Taurides of the Triassic magmatic arc source that dominates the Triassic Karakaya subduction-accretion complex. Where then was the source of the Karakaya arc detritus? A likely option is that the Karakaya subduction-accretion complex is an exotic terrane that was detached from a source magmatic arc and displaced to its present location, probably prior the initial deposition of the Early Jurassic cover sediments. This study was supported by TUBITAK, Project No: 111R015

Ustaömer, Timur; Ayda Ustaömer, Petek; Robertson, Alastair H. F.; Gerdes, Axel; Zulauf, Gernold

2014-05-01

363

Studying Science Teaching Practices in Relation to Learning: Time Scales of Teaching Phenomena  

Microsoft Academic Search

This chapter presents an analysis of the teaching practices in the perspective of relating teaching and learning. This analysis\\u000a involves three time scales: macro (months), meso (about ten minutes) and micro (seconds). Different concepts are involved\\u000a in the meso and micro analyses. The theoretical approaches at the meso scale are mainly based on the notion of chronogenesis that is included

Andrée Tiberghien; Christian Buty

364

Long-time, large-scale properties of the random-force-driven Burgers equation  

Microsoft Academic Search

Statistical properties of solutions of the random-force-driven Burgers equation are investigated by use of the dynamic renormalization group and direct numerical simulations. The agreement between computed and analytical results on both exponents and amplitudes of the correlation functions is good. It is shown that a small-scale noise dominates large-scale, long-time (k approaching O, omega approaching O) behavior of the system

Victor Yakhot; Z.-S. She

1988-01-01

365

Pterosauria from the Late Triassic of Southern Brazil  

NASA Astrophysics Data System (ADS)

A few postcranial remains of a Late Triassic pterosaur from the early Coloradian Caturrita Formation of Rio Grande do Sul are communicated. The general morphology of the coracoid, proximal portion of the humerus, femur, tibia and fibula suggests that it is more primitive than the pterosaurs from the Norian of northern Italy. The morphology and proportions of the different bones support their assignment to a primitive pterosaur. An almost complete maxilla with three teeth is tentatively referred to the same taxon because it was collected at some distance from the postcrania cited above.

Bonaparte, J. F.; Schultz, C. L.; Soares, M. B.

366

A Triassic mygalomorph spider from the northern Vosges, France  

E-print Network

. The fovea in Rosamygale compares with the Theraphosoidea of Eskov and Zonshtein (1990) but, because of the poor recognition of the fovea in the fossils, it could be a transverse pit. Atypids bear characteristically elongate maxillary lobes, which Gertsch... but poor in species. [PlUtonCology, V o L 35, Pari I» 1992, pp. 211-235. * p b j O The Pmlfttofrtttofki] Atsocialios 220 PALAEONTOLOGY, VOLUME 35 TEXT-FIO. 5, Rosamygale grauvogeti gen. et sp. nov. Triassic (Anisian) Grès à Voltaa; northern Vosges...

Selden, Paul A.; Gall, Jean-Claude

1992-01-01

367

Acoustic Emission Monitoring of the Syracuse Athena Temple: Scale Invariance in the Timing of Ruptures  

Microsoft Academic Search

We perform a comparative statistical analysis between the acoustic-emission time series from the ancient Greek Athena temple in Syracuse and the sequence of nearby earthquakes. We find an apparent association between acoustic-emission bursts and the earthquake occurrence. The waiting-time distributions for acoustic-emission and earthquake time series are described by a unique scaling law indicating self-similarity over a wide range of

G. Niccolini; A. Carpinteri; G. Lacidogna; A. Manuello

2011-01-01

368

Linking the information for the control computer to an absolute time scale  

Microsoft Academic Search

The problem, how to operate a satellite laser ranging system under a precise clock control, employing only its own microcomputer and build-in time base, is considered. The investigation shows, that strict adherence to an absolute time scale can be achieved, using only standard tools of the computer's operating system and an easy-to-build interface card between computer and the time base.

A. Rubans; K. Salminsh

1988-01-01

369

Capacitor placement and real time control in large-scale unbalanced distribution systems: Numerical studies  

SciTech Connect

A novel solution algorithm for capacitor placement and real-time control in real large-scale unbalanced distribution systems is evaluated and implemented to determine the number, locations, sizes, types and control schemes of capacitors to be placed on large-scale unbalanced distribution systems. A detailed numerical study regarding the solution algorithm in large scale unbalanced distribution systems is undertaken. Promising numerical results on both 292 bus and 394 bus real unbalanced distribution systems containing unbalanced loads and phasing and various types of transformers are presented. The computational performance for the capacitor control problem under load variations is encouraging.

Wang, J.C.; Chiang, H.D.; Miu, K.N. [Cornell Univ., Ithaca, NY (United States). School of Electrical Engineering; Darling, G. [NYSEG Corp., Binghamton, NY (United States). Distribution System Dept.

1997-04-01

370

First Triassic palaeomagnetic constraints from Junggar (NW China) and their implications for the Mesozoic tectonics in Central Asia  

E-print Network

shows major rotations between the Late Permian and the Late Jurassic­Early Cretaceous. These periods of the Mesozoic Tibetan and the Cenozoic Himalayan collisions. Triassic is a crucial period to understand between the Early and the Late Triassic and between the Late Triassic and the Late Jurassic

Cogne, Jean-Pascal

371

Olsen, et al., 2002 From: McRoberts, C. A. and Olsen, P. E., 2002, Triassic-Jurassic  

E-print Network

Olsen, et al., 2002 From: McRoberts, C. A. and Olsen, P. E., 2002, Triassic-Jurassic Non. #12;p. 13 ASTRONOMICALLY CALIBRATED GPTS FOR THE LATE TRIASSIC AND EARLY JURASSIC BASED ON THE NEWARK Timescale (GPTS) for the Triassic and Early Jurassic based on scientific coring of the Newark basin (NY, NJ

Olsen, Paul E.

372

Et-Touhami, et al., 2002 From: McRoberts, C. A. and Olsen, P. E., 2002, Triassic-Jurassic  

E-print Network

Et-Touhami, et al., 2002 From: McRoberts, C. A. and Olsen, P. E., 2002, Triassic-Jurassic Non MESOZOIC BASALT ERUPTION OVER MOROCCO IMMEDIATELY AFTER THE TRIASSIC-JURASSIC BOUNDARY. Mohammed Et similarities with each other, but also with sequences in the latest Triassic and earliest Jurassic of eastern

Olsen, Paul E.

373

PUBLISHED ONLINE: 13 JULY 2009 | DOI: 10.1038/NGEO577 Floral changes across the Triassic/Jurassic  

E-print Network

ARTICLES PUBLISHED ONLINE: 13 JULY 2009 | DOI: 10.1038/NGEO577 Floral changes across the Triassic/Jurassic occurred at the boundary of the Triassic and Jurassic periods, 201.6 million years ago. The loss of marine volcanism. Here we present pollen, spore and geochemical analyses across the Triassic/Jurassic boundary from

374

Permian to Late Triassic evolution of the Longmen Shan Foreland Basin (Western Sichuan): Model results from both the lithospheric extension and flexure  

NASA Astrophysics Data System (ADS)

The lithosphere was extended during the Permian-Middle Triassic in the Yangtze Craton where the Sichuan Basin located, and then bent due to thrusting of the Longmen Shan orogen, leading to formation of the Longmen Shan Foreland Basin (Western Sichuan) during the Late Triassic Indosinian orogeny. The lateral variation of the lithospheric strength resulted by former differential extension would inevitably influence the subsequent evolution of the foreland basin. In order to investigate this, both extensional and flexural models were applied in modeling Permian-Late Triassic basin evolution. A 2D kinematic extensional model was initially developed along a profile crossing the Yangtze Craton to simulate the lithospheric thermal evolution during the Permian-Middle Triassic. Based on the thermal results, the thermal-rheological structure, as well as the effective elastic thickness of the lithosphere (Te), was then determined. Extension model show that the stretching factors decrease gradually from Songpan-Ganzi to the Sichuan Basin, leading to variable thermal-rheological structure and increased Te from west to east. Taking into account of the Te variation, a flexural model was finally constructed to investigate the evolution of the Longmen Shan Foreland Basin during the Late Triassic spanning the time period c. 227-206 Ma. Three episodes were divided according to the corresponding tectonostratigraphic units. By matching the stratigraphic observations, three phase advance distances eastward of the Longmen Shan along the Qingchuan-Maowen Fault turned out to be 18, 22, and 18 km. It implied a slow and similar thrust advance rate of 3.6 (c.227-222 Ma), 2.2 (c.222-212 Ma), and 3 mm/yr (c.212-206 Ma), respectively.

He, Lijuan

2014-10-01

375

Early Triassic stromatolites in a siliciclastic nearshore setting in northern Perth Basin, Western Australia: Geobiologic features and implications for post-extinction microbial proliferation  

NASA Astrophysics Data System (ADS)

An Early Triassic stromatolite deposit in Gondwana is documented from the Smithian succession of the Lower Triassic Kockatea Shale Formation in the Northampton area, northern Geraldton, Western Australia. Abundant tube-like sheaths of filaments and tiny circular microspherule balls are well preserved in laminae of the Northampton stromatolites, which are characterized by finely laminated domes and digitate high-relief columns. These filament sheaths are superficially analogous to their counterparts of modern stromatolites, and thus are interpreted as putative fossilized filamentous cyanobacteria. Elemental mapping of EDS analysis shows very high contents of both Fe and Si elements as well as common presence of both S and Al elements along the laminae of the stromatolites, suggesting that the stromatolites may have been ferritized or silicified. Both ferritization and silicification may have played a crucial role in the exceptional preservation of the micro-structures in the Northampton stromatolites. The high content of Al along the laminae indicates that the stromatolites may have been influenced by terrigenous fine-grained clastics during their growth. The Northampton stromatolites show several growth modes, initiating on either pebbles/conglomerates or sandy seafloor and building laminar domes and digitate, high-relief columns during an initial transgression period. Steady increase in sea level facilitated the growth of stromatolites. The Early Triassic stromatolites ceased growth due to either rapid rise in sea level or increased clay influx probably sourced from increased weathering on land at that time, or both. The occurrence of the Northampton stromatolites in the siliciclastic succession, in comparison with published records of Early Triassic microbialites, reveals that post-extinction microbialites were widespread in the Smithian. Stromatolites show a broad geographic distribution from low-latitude to southern high-latitude regions of Gondwana and inhabited not only carbonate settings, but also siliciclastic nearshore settings. All features of these Early Triassic stromatolites indicate a microbial bloom in the aftermath of the P-Tr mass extinction.

Chen, Zhong-Qiang; Wang, Yongbiao; Kershaw, Stephen; Luo, Mao; Yang, Hao; Zhao, Laishi; Feng, Yuheng; Chen, Jianbo; Yang, Li; Zhang, Lei

2014-10-01

376

STOCHASTIC STREAMFLOW SIMULATION AT INTERDECADAL TIME SCALES AND IMPLICATIONS TO WATER RESOURCES MANAGEMENT IN THE COLORADO RIVER  

E-print Network

STOCHASTIC STREAMFLOW SIMULATION AT INTERDECADAL TIME SCALES AND IMPLICATIONS TO WATER RESOURCES Simulation at Interdecadal Times Scales and Implications for Water Resources Management in the Colorado River Simulation at Interdecadal Times Scales and Implications for Water Resources Management in the Colorado River

377

Predicting Regional Drought on Sub-Seasonal to Decadal Time Scales  

NASA Technical Reports Server (NTRS)

Drought occurs on a wide range of time scales, and within a variety of different types of regional climates. It is driven foremost by an extended period of reduced precipitation, but it is the impacts on such quantities as soil moisture, streamflow and crop yields that are often most important from a users perspective. While recognizing that different users have different needs for drought information, it is nevertheless important to understand that progress in predicting drought and satisfying such user needs, largely hinges on our ability to improve predictions of precipitation. This talk reviews our current understanding of the physical mechanisms that drive precipitation variations on subseasonal to decadal time scales, and the implications for predictability and prediction skill. Examples are given highlighting the phenomena and mechanisms controlling precipitation on monthly (e.g., stationary Rossby waves, soil moisture), seasonal (ENSO) and decadal time scales (PD and AMO).

Schubert, Siegfried; Wang, Hailan; Suarez, Max; Koster, Randal

2011-01-01

378

Effective Dynamics for a Kinetic Monte-Carlo Model with Slow and Fast Time Scales  

NASA Astrophysics Data System (ADS)

We consider several multiscale-in-time kinetic Monte Carlo models, in which some variables evolve on a fast time scale, while the others evolve on a slow time scale. In the first two models we consider, a particle evolves in a one-dimensional potential energy landscape which has some small and some large barriers, the latter dividing the state space into metastable regions. In the limit of infinitely large barriers, we identify the effective dynamics between these macro-states, and prove the convergence of the process towards a kinetic Monte Carlo model. We next consider a third model, which consists of a system of two particles. The state of each particle evolves on a fast time-scale while conserving their respective energy. In addition, the particles can exchange energy on a slow time scale. Considering the energy of the first particle, we identify its effective dynamics in the limit of asymptotically small ratio between the characteristic times of the fast and the slow dynamics. For all models, our results are illustrated by representative numerical simulations.

Lahbabi, Salma; Legoll, Frédéric

2013-12-01

379

A new time scale based k-epsilon model for near wall turbulence  

NASA Technical Reports Server (NTRS)

A k-epsilon model is proposed for wall bonded turbulent flows. In this model, the eddy viscosity is characterized by a turbulent velocity scale and a turbulent time scale. The time scale is bounded from below by the Kolmogorov time scale. The dissipation equation is reformulated using this time scale and no singularity exists at the wall. The damping function used in the eddy viscosity is chosen to be a function of R(sub y) = (k(sup 1/2)y)/v instead of y(+). Hence, the model could be used for flows with separation. The model constants used are the same as in the high Reynolds number standard k-epsilon model. Thus, the proposed model will be also suitable for flows far from the wall. Turbulent channel flows at different Reynolds numbers and turbulent boundary layer flows with and without pressure gradient are calculated. Results show that the model predictions are in good agreement with direct numerical simulation and experimental data.

Yang, Z.; Shih, T. H.

1992-01-01

380

Enhanced identification and exploitation of time scales for model reduction in stochastic chemical kinetics  

NASA Astrophysics Data System (ADS)

Widely different time scales are common in systems of chemical reactions and can be exploited to obtain reduced models applicable to the time scales of interest. These reduced models enable more efficient computation and simplify analysis. A classic example is the irreversible enzymatic reaction, for which separation of time scales in a deterministic mass action kinetics model results in approximate rate laws for the slow dynamics, such as that of Michaelis-Menten. Recently, several methods have been developed for separation of slow and fast time scales in chemical master equation (CME) descriptions of stochastic chemical kinetics, yielding separate reduced CMEs for the slow variables and the fast variables. The paper begins by systematizing the preliminary step of identifying slow and fast variables in a chemical system from a specification of the slow and fast reactions in the system. The authors then present an enhanced time-scale-separation method that can extend the validity and improve the accuracy of existing methods by better accounting for slow reactions when equilibrating the fast subsystem. The resulting method is particularly accurate in systems such as enzymatic and protein interaction networks, where the rates of the slow reactions that modify the slow variables are not a function of the slow variables. The authors apply their methodology to the case of an irreversible enzymatic reaction and show that the resulting improvements in accuracy and validity are analogous to those obtained in the deterministic case by using the total quasi-steady-state approximation rather than the classical Michaelis-Menten. The other main contribution of this paper is to show how mass fluctuation kinetics models, which give approximate evolution equations for the means, variances, and covariances of the concentrations in a chemical system, can feed into time-scale-separation methods at a variety of stages.

Gómez-Uribe, Carlos A.; Verghese, George C.; Tzafriri, Abraham R.

2008-12-01

381

The Late Triassic Central Patagonian Batholith: Magma hybridization, 40Ar/39Ar ages and thermobarometry  

NASA Astrophysics Data System (ADS)

The Late Triassic Central Patagonian Batholith is a key element in paleogeographic models of West Gondwana just before to the break-up of the supercontinent. The preexisting classification of units of this batholith was mainly based on isotopic and geochemical data. Here we report the results of field mapping and petrography, backed up by three new 40Ar/39Ar biotite ages, which reveal previously unnoticed relationships of the rocks in the batholith. Based on the new information we present a reorganization of units where the batholith is primarily formed by the Gastre and the Lipetrén superunits. The Gastre Superunit is the oldest magmatic suite and is composed of I-type granites which display evidence of felsic and mafic magma interaction. It is formed by 4 second-order units: 1) equigranular hornblende-biotite granodiorites, 2) porphyritic biotite-hornblende monzogranites, 3) equigranular biotitic monzogranites and 4) hornblende quartz-diorites. Emplacement depth of the Gastre Superunit is bracketed between 6 and 11 km (1.8-3 kbar), and the maximum recorded temperatures of emplacement are comprised between 660 and 800 °C. The recalculated Rb/Sr age is 222 ± 3 Ma and the porphyritic biotite-hornblende monzogranites yielded a 40Ar/39Ar age in biotite of 213 ± 5 Ma. On the other hand, the Lipetrén Superunit is made up by fine-grained biotitic monzo- and syenogranites that postdate magma hybridization processes and intrude all the other units. The recalculated Rb/Sr age for this suite is identical to a 40Ar/39Ar age in biotite extracted from one of its monzogranites (206.4 ± 5.3 and 206 ± 4 Ma, respectively). This and the observed textural features suggest very fast cooling related to a subvolcanic emplacement. An independent unit, the “Horqueta Granodiorite”, which has previously been considered as the record of a Jurassic intrusive stage in the Central Patagonian Batholith, gave a 40Ar/39Ar age in biotite of 214 ± 2 Ma. This and the reexamination of available isotopic data allow propose that this granodiorite unit is part of the Late Paleozoic intrusives in the region. The Late Triassic Central Patagonian Batholith is overlain by 190-185 Ma volcano-sedimentary rocks, suggesting that it was exposed sometime between the latest Triassic and earliest Jurassic times, roughly coeval with a major accretionary episode in the southwestern margin of Gondwana.

Zaffarana, Claudia B.; Somoza, Rubén; López de Luchi, Mónica

2014-11-01

382

Seismic analyses of the Triassic in Northern Germany for hydrogeothermal exploitation  

NASA Astrophysics Data System (ADS)

Hydrothermal resources provide a large potential for the energy supply in Germany. However, the risk in reservoir detection is a major obstacle for its commercial utilization. Deep drillholes for a geothermal plant demand financial investments of several ten million Euros, without a comprehensive guarantee that the delivery and temperature of the required energy supply are met. A risk reduction is offered through the application of seismic techniques that have been developed in the oil and gas industry. Yet, in the geothermic business the topic of exploration cost reduction often has a higher priority. This is the reason why the necessity of 3D seismic is being repeatedly questioned. However, a seismic dataset from northern Germany currently being studied reveals a complicated fault zone network that has been partly generated by salt tectonics. It would be unrepresentable without the aid of 3D seismic. For fault detection in particular, time slices of the signal variance with a short time window and few traces have proven their suitability. In northern Germany some strata of the middle and lower Triassic are being regarded as hydrogeothermal reservoirs because of their temperature and permeability. Typically, areal amplitude distributions are being analyzed for anomalies. In the referred dataset, such areal analyses are however degraded by the intercalated complicated fault zone structures. In particular, in large sections of the lower Triassic the fault zone detection with signal variance calculation is also poor because of small seismic reflection amplitudes. It can be concluded that in some cases, 3D seismic offers the only way to recognize the subsurface structures. On the other hand, there are cases where even 3D seismic data needs carefully guided analysis instead of automatic algorithms.

Beilecke, Thies; Buness, Hermann; Musmann, Patrick; Schulz, Rüdiger

2010-05-01

383

Permian and Triassic palaeolatitudes of the Ukrainian shield with implications for Pangea reconstructions  

NASA Astrophysics Data System (ADS)

A collection of 306 oriented samples from 43 Permian and Triassic intrusions from the Ukrainian Shield, the southwest portion of the East European Craton, has yielded valuable palaeomagnetic directions with new ages obtained using the 40Ar/39Ar method. Andesitic intrusions have Late Triassic ages (six dating samples) of 204.2 ± 1.6 Ma to 215.7 ± 2.0 Ma and dual-polarity Dec/Inc = 60.1°/+64.4°, k= 96, ?95= 4.5°, derived from N= 12 sites. Trachyte dykes have an early Artinskian (mid-Early Permian) age (one dating sample) of 282.6 ± 2.6 Ma, and yielded Dec/Inc = 204.3°/-23.8°, k= 27.7, ?95= 6.5°, from N= 19 sites. The palaeolatitude of the trachyte intrusions is 12.4°± 3.7° N. Because the Artinskian and younger Permian palaeopoles obtained from the Gondwana continents are subject to uncertainties, some studies have adopted a palaeopole (at 41°S, 61°E) largely based on results from ˜280 Ma Permian quartzporphyries in the Southern Alps of Italy as proxy to position Gondwana at that time. With this palaeoposition and our new ˜280 Ma palaeolatitude for Baltica, a Pangea A reconstruction cannot be supported. To avoid its inherent continental overlap of Africa and Eurasia, a Pangea B reconstruction has been favoured, wherein Eurasia's southern margin faces the northcoast of South America instead. However, the 280 ± 10 Ma palaeomagnetic data from the Gondwana continents themselves give a mean palaeopole at 30°S, 59°E, which results in a palaeogeographic position of Gondwana that allows a Pangea A type reconstruction. Thus, the choice between Pangea A versus B in the Artinskian hinges on data selection and reliability criteria and the assumptions about tectonic coherence of northern Adria (i.e. the Southern Alps) with Africa in Permian times. A more reliable mid-Early Permian palaeopole from cratonic Gondwana would provide a more definitive conclusion.

Yuan, Kenneth; van der Voo, R.; Bazhenov, M. L.; Bakhmutov, V.; Alekhin, V.; Hendriks, B. W. H.

2011-02-01

384

Synchronous wildfire activity rise and mire deforestation at the triassic-jurassic boundary.  

PubMed

The end-Triassic mass extinction event (?201.4 million years ago) caused major faunal and floral turnovers in both the marine and terrestrial realms. The biotic changes have been attributed to extreme greenhouse warming across the Triassic-Jurassic (T-J) boundary caused by massive release of carbon dioxide and/or methane related to extensive volcanism in the Central Atlantic Magmatic Province (CAMP), resulting in a more humid climate with increased storminess and lightning activity. Lightning strikes are considered the primary source of wildfires, producing charcoal, microscopically recognized as inertinite macerals. The presence of polycyclic aromatic hydrocarbons (PAHs) of pyrolytic origin and allochthonous charcoal in siliciclastic T-J boundary strata has suggested widespread wildfire activity at the time. We have investigated largely autochthonous coal and coaly beds across the T-J boundary in Sweden and Denmark. These beds consist of predominantly organic material from the in situ vegetation in the mires, and as the coaly beds represent a substantial period of time they are excellent environmental archives. We document a remarkable increase in inertinite content in the coal and coaly beds across the T-J boundary. We show estimated burning temperatures derived from inertinite reflectance measurements coupled with palynological data and conclude that pre-boundary late Rhaetian mire wildfires included high-temperature crown fires, whereas latest Rhaetian-Sinemurian mire wildfires were more frequent but dominated by lower temperature surface fires. Our results suggest a major change in the mire ecosystems across the T-J boundary from forested, conifer dominated mires to mires with a predominantly herbaceous and shrubby vegetation. Contrary to the overall regional vegetation for which onset of recovery commenced in the early Hettangian, the sensitive mire ecosystem remained affected during the Hettangian and did not start to recover until around the Hettangian-Sinemurian boundary. Decreasing inertinite content through the Lower Jurassic suggests that fire activity gradually resumed to considerable lower levels. PMID:23077574

Petersen, Henrik I; Lindström, Sofie

2012-01-01

385

Scaling properties of rainfall time-series in the urban area of Rome  

NASA Astrophysics Data System (ADS)

The rainfall fields exhibits a high space-time variability which generates a large degree of uncertainty in modelling the process, thus causing lack of accuracy in many key hydrological problems, such as the forecasting of floods and the management of water resources. The large amount of literature produced in the last thirty years about this issue deals with the development of stochastic models able to represent the non-linearity and intermittence of rainfall in order to perform the downscaling process, i.e. transferring to finer scales the information on rainfall observed or forecasted at large scales. Traditionally, these models are based upon point processes in both the time (e.g. Waymire and Gupta, 1981) and the space-time domain (e.g. Rodriguez-Iturbe et al., 1986). Although this approach is cluster-based so as to model the physical structure of rainfall, its application may involve an inconvenient mathematical complexity and a large number of parameters, leading to several problems in parameter estimation. Another approach to this problem is based on the empirical detection of some regularity in hydrological observations, such as the scale-invariance properties of rainfall (e.g. Lovejoy and Schertzer, 1985). Models following this approach are based upon the assumption of a power law dependence of all statistical moments on the scale of aggregation. That means scaling properties can provide simple relationships to link the statistical distribution of the rainfall process at different spatial and temporal scales, in the ranges of which the power-low assumption can be verified (Marani, 2003). This work focuses on the analysis of the scaling properties of rainfall time series from a high density rain gauge network covering the Rome's urban area. The network consists of 24 sites, and the gauge record at each site has 10-minute time resolution and about 16-year length (1992-2007). The aim of the study is the identification of temporal scaling regimes, their ranges of validity, and the evaluation of the corresponding scaling properties. REFERENCES Lovejoy S. and Schertzer D. Generalized scale invariance in the atmosphere and fractal models of rain. Water Resour. Res., 21(8), 1233-1250, 1985. Marani, M. (2003) On the correlation structure of continuous and discrete point rainfall, Water Resour. Res., 39(5), 1128, doi:10.1029/2002WR001456. Rodriguez-Iturbe I., Cox D. and Eagleson P.S. Spatial modelling of total storm rainfall. Proc. R. Soc. London, A403, 27-50, 1986. Waymire E. and Gupta V.K. The mathematical structure of rainfall representations. Water Resour. Res., 17 (5), 1261-1294, 1981.

Volpi, E.; Napolitano, F.; Lombardo, F.

2009-04-01

386

Doubly stochastic Poisson process models for precipitation at fine time-scales  

NASA Astrophysics Data System (ADS)

This paper considers a class of stochastic point process models, based on doubly stochastic Poisson processes, in the modelling of rainfall. We examine the application of this class of models, a neglected alternative to the widely-known Poisson cluster models, in the analysis of fine time-scale rainfall intensity. These models are mainly used to analyse tipping-bucket raingauge data from a single site but an extension to multiple sites is illustrated which reveals the potential of this class of models to study the temporal and spatial variability of precipitation at fine time-scales.

Ramesh, Nadarajah I.; Onof, Christian; Xie, Dichao

2012-09-01

387

Unification of Small and Large Time Scales for Biological Evolution: Deviations from Power Law  

NASA Astrophysics Data System (ADS)

We develop a unified model that describes both “micro” and “macro” evolutions within a single theoretical framework. The ecosystem is described as a dynamic network; the population dynamics at each node of this network describes the “microevolution” over ecological time scales (i.e., birth, ageing, and natural death of individual organisms), while the appearance of new nodes, the slow changes of the links, and the disappearance of existing nodes accounts for the “macroevolution” over geological time scales (i.e., the origination, evolution, and extinction of species). In contrast to several earlier claims in the literature, we observe strong deviations from power law in the regime of long lifetimes.

Chowdhury, Debashish; Stauffer, Dietrich; Kunwar, Ambarish

2003-02-01

388

IUE program SUGSD: Varability time scale of H Ly-alpha from Uranus  

NASA Technical Reports Server (NTRS)

The scientific motivation for this program was to determine the time scale for the variability of the H Lyman-alpha emission from Uranus. The purpose of this series of observation is to determine its variability on shorter time scales. A series of observations was carried out in coordination with ESA to cover as completely as possible one 24 hour period of the Uranian H Lyman-alpha emission. The observations were obtained on April 23 and 24. Two additional ovservations on April 25 and 26 were obtained to search for longer term trends. A small modulation in the brightness was observed and the results presented.

Durrance, Samuel T.; Clarke, J. T.; Moss, H. W.; Boyer, S.

1988-01-01

389

Local and Catchment-Scale Water Storage Changes in Northern Benin Deduced from Gravity Monitoring at Various Time-Scales  

NASA Astrophysics Data System (ADS)

Water storage changes (WSC) are investigated by the mean of gravity monitoring in Djougou, northern Benin, in the frame of the GHYRAF (Gravity and Hydrology in Africa) project. In this area, WSC are 1) part of the control system for evapotranspiration (ET) processes, a key variable of the West-African monsoon cycle and 2) the state variable for resource management, a critical issue in storage-poor hard rock basement contexts such as in northern Benin. We show the advantages of gravity monitoring for analyzing different processes in the water cycle involved at various time and space scales, using the main gravity sensors available today (FG5 absolute gravimeter, superconducting gravimeter -SG- and CG5 micro-gravimeter). The study area is also part of the long-term observing system AMMA-Catch, and thus under intense hydro-meteorological monitoring (rain, soil moisture, water table level, ET ...). Gravity-derived WSC are compared at all frequencies to hydrological data and to hydrological models calibrated on these data. Discrepancies are analyzed to discuss the pros and cons of each approach. Fast gravity changes (a few hours) are significant when rain events occur, and involve different contributions: rainfall itself, runoff, fast subsurface water redistribution, screening effect of the gravimeter building and local topography. We investigate these effects and present the statistical results of a set of rain events recorded with the SG installed in Djougou since July 2010. The intermediate time scale of gravity changes (a few days) is caused by ET and both vertical and horizontal water redistribution. The integrative nature of gravity measurements does not allow to separate these different contributions, and the screening from the shelter reduces our ability to retrieve ET values. Also, atmospheric corrections are critical at such frequencies, and deserve some specific attention. However, a quick analysis of gravity changes following rain events shows that the values are in accordance with expected ET values (up to about 5mm/day). Seasonal WSC are analyzed since 2008 using FG5 absolute gravity measurements four times a year and since 2010 using the continuous SG time series. They can reach up to 12 microGal (?270mm) and show a clear interannual variability, as can be expected from rainfall variability in the area. This data set allows some estimates of an average specific yield for the local aquifer, together with a scaling factor for Magnetic Resonance Soundings-derived water content.

Hinderer, J.; Hector, B.; Séguis, L.; Descloitres, M.; Cohard, J.; Boy, J.; Calvo, M.; Rosat, S.; Riccardi, U.; Galle, S.

2013-12-01

390

Discovery of a Triassic magmatic arc source for the Permo-Triassic Karakaya subduction complex, NW Turkey  

NASA Astrophysics Data System (ADS)

The Permo-Triassic Karakaya Complex is well explained by northward subduction of Palaeotethys but until now no corresponding magmatic arc has been identified in the region. With the aim of determining the compositions and ages of the source units, ten sandstone samples were collected from the mappably distinct Ortaoba, Hodul, Kendirli and Orhanlar Units. Zircon grains were extracted from these sandstones and >1300 were dated by the U-Pb method and subsequently analysed for the Lu-Hf isotopic compositions by LA-MC-ICPMS at Goethe University, Frankfurt. The U-Pb-Hf isotope systematics are indicative of two different sediment provenances. The first, represented by the Ortaoba, Hodul and Kendirli Units, is dominated by igneous rocks of Triassic (250-220 Ma), Early Carboniferous-Early Permian (290-340 Ma) and Early to Mid-Devonian (385-400 Ma) ages. The second provenance, represented by the Orhanlar Unit, is indicative of derivation from a peri-Gondwanan terrane. In case of the first provenance, the Devonian and Carboniferous source rocks exibit intermediate eHf(t) values (-11 to -3), consistent with the formation at a continental margin where juvenile mantle-derived magmas mixed with (recycled) old crust having Palaeoproterozoic Hf model ages. In contrast, the Triassic arc magma exhibits higher eHf(t) values (-6 to +6), consistent with the mixing of juvenile mantle-derived melts with (recycled) old crust perhaps somewhat rejuvanated during the Cadomian period. We have therefore identified a Triassic magmatic arc as predicted by the interpretation of the Karakaya Complex as an accretionary complex related to northward subduction (Carboniferous and Devonian granites are already well documented in NW Turkey). Possible explanations for the lack of any outcrop of the source magmatic arc are that it was later subducted or the Karakaya Complex was displaced laterally from its source arc (both post 220 Ma). Strike-slip displacement (driven by oblique subduction?) can also explain the presence of two different sandstone source areas as indicated by the combined U-Pb-Hf isotope and supporting petrographic data. This study was supported by TUBITAK, Project no: 111R015

Ayda Ustaömer, Petek; Ustaömer, Timur; Gerdes, Axel; Robertson, Alastair H. F.; Zulauf, Gernold

2014-05-01

391

Evaluation of Self-Sputtering Time-Scale in Pulsed Magnetrons using Time-Resolved OES and Monte Carlo Calculations  

NASA Astrophysics Data System (ADS)

Time-resolved Optical Emission Spectroscopy of Ar+ ions and Cu sputtered atoms in a pulsed DC magnetron discharge shows that the intensities of the exited Cu lines are maintained at almost constant levels for several us after the Ar+ lines intensity has decayed. This effect can be attributed to Cu self-sputtering. To assess the amount of self-sputtering and the time scale of this effect relative to the operating duty-cycle in a pulsed DC magnetron, the return time to the target of the sputtered metal ions has been evaluated through Monte Carlo calculations. The "ON" time of a pulsed DC magnetron plasma at 50kHz, pulse width 2016ns, 2A constant current run and 0.4Pa Ar gas pressure has been modelled for a magnetron with opposed rectangular copper targets. A computer code that simulates 3D charged particles trajectories in 3D electric and magnetic fields has been developed and used to simulate Cu ions trajectories in the plasma bulk. At each time step of 0.02us, the magnetic field is calculated using a routine based on the current sheet model and the cathode sheath thickness is calculated using the Child-Langmuir law and the corresponding I and V waveforms measured values. The return time to target for Cu ions has been evaluated and compared to the time-resolved OES measurements. The consequences of the self-sputtering and confinement time-scales are discussed in connection to the starting energy of Cu ions and the operating duty cycle of the magnetron.

Moiseev, Tamara; Cameron, David

2004-09-01

392

Distinct scalings for mean first-passage time of random walks on scale-free networks with the same degree sequence  

E-print Network

Distinct scalings for mean first-passage time of random walks on scale-free networks with the same is an integral major theme of interest for random walks in the presence of an immobile perfect absorber. In order to achieve this goal, we study random walks on a family of one-parameter denoted by q scale-free networks

Keinan, Alon

393

Hydrological response to climate variability at different time scales: A study in the Ebro basin  

NASA Astrophysics Data System (ADS)

SummaryIn this study we analyzed the response of monthly runoff to precedent climatic conditions at temporal scales of 1-48 months in 88 catchments of the Ebro basin (northeast Spain). The standardized precipitation evapotranspiration index (SPEI) was used to summarize the climatic conditions at different time scales, and was correlated with the standardized streamflow index (SSI) calculated at the mouth of each catchment. The Ebro basin encompasses a gradient from Atlantic to Mediterranean climates, and has remarkable complexity in topography, geology and land cover. The basin is highly regulated by dams, which were built to produce hydropower and supply water for agriculture. These characteristics explain why sub-basins of the Ebro River basin respond in differing ways to precedent climatic conditions. Three main sub-basin groups were distinguished on the basis of the correlation of their streamflow responses to different time scales of the SPEI: (1) sub-basins correlated with short SPEI time scales (2-4 months), which generally corresponded to unregulated headwater areas; (2) sub-basins correlated with long SPEI time scales (10-20 months), where groundwater reserves play a major hydrological role; and (3) sub-basins correlated with medium SPEI time scales (6-10 months). The latter occur in the lower sectors of the Ebro basin and its tributaries, which receive river flows from the other two sub-basins, and where dam regulation has a significant influence on the hydrological characteristics. In addition to the three main sub-basin groups, other streamflow responses associated with seasonal factors were identified, particularly those related to snowpack and the various management strategies applied to reservoirs.

López-Moreno, J. I.; Vicente-Serrano, S. M.; Zabalza, J.; Beguería, S.; Lorenzo-Lacruz, J.; Azorin-Molina, C.; Morán-Tejeda, E.

2013-01-01

394

Hierarchical Dynamics of Ecological Communities: Do Scales of Space and Time Match?  

PubMed Central

Theory posits that community dynamics organize at distinct hierarchical scales of space and time, and that the spatial and temporal patterns at each scale are commensurate. Here we use time series modeling to investigate fluctuation frequencies of species groups within invertebrate metacommunities in 26 boreal lakes over a 20-year period, and variance partitioning analysis to study whether species groups with different fluctuation patterns show spatial signals that are commensurate with the scale-specific fluctuation patterns identified. We identified two groups of invertebrates representing hierarchically organized temporal dynamics: one species group showed temporal variability at decadal scales (slow patterns of change), whilst another group showed fluctuations at 3 to 5-year intervals (faster change). This pattern was consistently found across all lakes studied. A spatial signal was evident in the slow but not faster-changing species groups. As expected, the spatial signal for the slow-changing group coincided with broad-scale spatial patterns that could be explained with historical biogeography (ecoregion delineation, and dispersal limitation assessed through a dispersal trait analysis). In addition to spatial factors, the slow-changing groups correlated with environmental variables, supporting the conjecture that boreal lakes are undergoing environmental change. Taken together our results suggest that regionally distinct sets of taxa, separated by biogeographical boundaries, responded similarly to broad-scale environmental change. Not only does our approach allow testing theory about hierarchically structured space-time patterns; more generally, it allows assessing the relative role of the ability of communities to track environmental change and dispersal constraints limiting community structure and biodiversity at macroecological scales. PMID:23874905

Angeler, David G.; Gothe, Emma; Johnson, Richard K.

2013-01-01

395

Metamorphic and geochronogical study of the Triassic El Oro metamorphic complex, Ecuador: Implications for high-temperature metamorphism in a forearc zone  

NASA Astrophysics Data System (ADS)

In the forearc of the Andean active margin in southwest Ecuador, the El Oro metamorphic complex exhibits a well exposed tilted forearc section partially migmatized. We used Raman spectroscopy on carbonaceous matter (RSCM) thermometry and pseudosections coupled with mineralogical and textural studies to constrain the pressure-temperature (P-T) evolution of the El Oro metamorphic complex during Triassic times. Our results show that anatexis of the continental crust occurred by white-mica and biotite dehydration melting along a 10 km thick crustal domain (from 4.5 to 8 kbar) with increasing temperature from 650 to 700 °C. In the biotite dehydration melting zone, temperature was buffered at 750-820 °C in a 5 km thick layer. The estimated average thermal gradient during peak metamorphism is of 30 °C/km within the migmatitic domain can be partitioned into two apparent gradients parts. The upper part from surface to 7 km depth records a 40-45 °C/km gradient. The lower part records a quasi-adiabatic geotherm with a 10 °C/km gradient consistent with an isothermal melting zone. Migmatites U-Th-Pb geochronology yielded zircon and monazite ages of 229.3 ± 2.1 Ma and 224.5 ± 2.3 Ma, respectively. This thermal event generated S-type magmatism (the Marcabeli granitoid) and was immediately followed by underplating of the high-pressure low-temperature (HP-LT) Arenillas-Panupalí unit at 225.8 ± 1.8 Ma. The association of high-temperature low-pressure (HT-LP) migmatites with HP-LT unit constitutes a new example of a paired metamorphic belt along the South American margin. We propose that in addition to crustal thinning, underplating of the Piedras gabbroic unit before 230 Ma provided the heat source necessary to foster crustal anatexis. Furthermore, its MORB signature shows that the asthenosphere was involved as the source of the heat anomaly. S-type felsic magmatism is widespread during this time and suggests that a large-scale thermal anomaly affected a large part of the South American margin during the late Triassic. We propose that crustal anatexis is related to an anomaly that arose during subduction of the Panthalassa ocean under the South American margin. Slab verticalization or slab break-off can be invoked as the origin of the upwelling of the asthenosphere.

Riel, N.; Guillot, S.; Jaillard, E.; Martelat, J.-E.; Paquette, J.-L.; Schwartz, S.; Goncalves, P.; Duclaux, G.; Thebaud, N.; Lanari, P.; Janots, E.; Yuquilema, J.

2013-01-01

396

Time Scaling of the Rates of Produced Fluids in Laboratory Displacements  

SciTech Connect

In this report, the use of an asymptotic method, based on the time scaling of the ratio of produced fluids, to infer the relative permeability exponent of the displaced phase near its residual saturation, for immiscible displacements in laboratory cores was proposed. Sufficiently large injection rates, the existence of a power law can be detected, and its exponent inferred, by plotting in an appropriate plot the ratio of the flow rates of the two fluids at the effluent for some time after breakthrough.

Laroche, Catherine; Chen, Min; Yortsos, Yanis C.; Kamath, Jairam

2001-02-27

397

Scaling graphs of heart rate time series in athletes demonstrate the VLF, LF and HF regions  

Microsoft Academic Search

Scaling analysis of heart rate time series has emerged as an useful tool for\\u000aassessment of autonomic cardiac control. We investigate the heart rate time\\u000aseries of ten athletes (five males and five females), by applying detrended\\u000afluctuation analysis (DFA). High resolution ECGs are recorded under\\u000astandardized resting conditions over 30 minutes and subsequently heart rate\\u000atime series are extracted

Mathias Baumert; Lars M Brechtel; Juergen Lock; Andreas Voss; Derek Abbott

2006-01-01

398

Landscape behaviour at storm and millennial time scales: How good are landscape evolution models at prediction?  

NASA Astrophysics Data System (ADS)

Landscape evolution models theoretically provide the ability to examine both short and long-term evolution processes. The hydrology and sediment transport components of these models have been largely based on physical principals and well understood theory yet they have not been fully assessed or employed across all environments. They have been recognised as valuable tools with which to explore the short and long-term erosional behaviour of both natural and anthropogenic landscapes. Of particular interest are anthropogenic landscapes (i.e. post-mining landscapes) which often have steeper slopes, unconsolidated materials and a higher erodibility than the undisturbed surface where these models have been used to examine the long-term erosional behaviour usually at millennial scales. Further, such landscapes often have to contain potential contaminants (i.e. radionuclides, acid generating materials) that need to be contained over geological timescales. Here two landscape evolution models (SIBERIA and CAESAR) are used to examine a proposed rehabilitation design for the ERA Ranger mine in the Northern Territory, Australia. The SIBERIA model has been developed to operate at annual timescales and has been calibrated for surface conditions at the site. CAESAR operates at sub-hourly time scales and employs hydrology and sediment characteristics in its calibration. The results demonstrate that despite the different modelling approaches, both SIBERIA and CAESAR produce similar spatial and temporal outcomes with erosion patterns (i.e. gullying) and rates very comparable. As a result of SIBERIA using annual time scales the model run time is significantly quicker than CAESAR however CAESAR can provide important information at the storm scale. Significantly, both models are sensitive to parameterisation with soils evolution (pedogenesis) and vegetation having significant influences on erosion rates. The findings demonstrate the usefulness of landscape evolution models to explore the behaviour of catchments both at short (storm scale) and millennial time scales.

Hancock, G. R.; Coulthard, T. J.; Lowry, J.

2012-12-01

399

COASTAL ENGINEERING 2004, pp.2620-2632. IMPLICATIONS OF MORPHODYNAMIC TIME SCALE  

E-print Network

COASTAL ENGINEERING 2004, pp.2620-2632. 2620 IMPLICATIONS OF MORPHODYNAMIC TIME SCALE FOR COASTAL forcing conditions. 1. Introduction The use of groins for coastal protection has become somewhat tarnished contributed to down-drift erosion. Clearly, our understanding of relevant design parameters needs

US Army Corps of Engineers

400

Integrating dynamic voltage\\/frequency scaling and adaptive body biasing using test-time voltage selection  

Microsoft Academic Search

Adaptive body biasing is a promising technique for address- ing increasing process variability, but it also provides new opportunities for reducing power when combined with dy- namic voltage\\/frequency scaling. Limitations of existing ABB\\/DVFS proposals are explored, and a new scheme, test- time voltage selection (TTVS), is presented. By delaying the mapping between frequency and supply voltage until test, variability information

Alyssa Bonnoit; Sebastian Herbert; Diana Marculescu; Lawrence T. Pileggi

2009-01-01

401

On the timing and mechanism of millennial-scale climate variability during the last glacial cycle  

Microsoft Academic Search

The demonstration that natural climate vari- ability during the last glacial cycle shifted rapidly be- tween remarkable extremes has dramatically revised the understanding of climate change. To further advance our understanding, research continues into the timings, geographic distribution, and nature of the millennial- scale climate extremes, and into the mechanisms for in- tra- and inter-hemispheric transmission of variability through the

E. J. Rohling; P. Challenor; P. A. Mayewski

2003-01-01

402

Development and Preliminary Validation of the Time Management for Exercise Scale  

Microsoft Academic Search

The purpose of this study was to collect preliminary validity evidence for a time management scale for exercise. An initial pool of 91 items was developed from existing literature. Ten exercise\\/health psychologists evaluated each of the items in terms of relevance and representativeness. Forty-nine items met all criteria. Exploratory factor analysis of the initial pool of items with a sample

Laurie-ann M. Hellsten; W. Todd Rogers

2009-01-01

403

Performance Evaluation of Multiple Time Scale TCP Under Self-Similar Traffic  

E-print Network

TCP endows the underlying feedback control with proactivity by bridging the uncertainty gap associatedPerformance Evaluation of Multiple Time Scale TCP Under Self-Similar Traffic Conditions KIHONG PARK control framework to window-based congestion control, in particular, TCP. This is performed by interfacing

Park, Kihong

404

Annular mode time scales in the Intergovernmental Panel on Climate Change Fourth Assessment Report models  

Microsoft Academic Search

The ability of climate models in the Intergovernmental Panel on Climate Change Fourth Assessment Report to capture the temporal structure of the annular modes is evaluated. The vertical structure and annual cycle of the variability is quantified by the e-folding time scale of the annular mode autocorrelation function. Models vaguely capture the qualitative features of the Northern and Southern Annular

E. P. Gerber; L. M. Polvani; D. Ancukiewicz

2008-01-01

405

Optical dating of young coastal dunes on a decadal time scale  

Microsoft Academic Search

We explore the use of quartz optically stimulated luminescence (OSL) dating for reconstructing coastal evolution on a time scale of decades to a few hundred years. Samples are taken from the accretionary south-west coast of Texel, a barrier island just offshore of the northern Netherlands. The ages of dune ridges are known from historical sources; an excellent chronology with a

M. Ballarini; J. Wallinga; A. S. Murray; S. van Heteren; A. P. Oost; A. J. J. Bos; C. W. E. van Eijk

2003-01-01

406

Large volume recycling of oceanic lithosphere over short time scales: geochemical constraints from the Caribbean Large  

E-print Network

Large volume recycling of oceanic lithosphere over short time scales: geochemical constraints from with derivation from recycled oceanic crust, while the depleted lavas are derived from a highly residual source source mantle could have been 9 500 Ma before CLIP formation and interpreted to reflect the recycling

Graham, David W.

407

North Atlantic Multidecadal Climate Variability: An Investigation of Dominant Time Scales and Processes  

E-print Network

- ferred to as the Atlantic multidecadal oscillation (AMO; Kerr 2000). Water from the North Atlantic entersNorth Atlantic Multidecadal Climate Variability: An Investigation of Dominant Time Scales form 12 January 2010) ABSTRACT The issue of multidecadal variability in the North Atlantic has been

Frankcombe, Leela

408

time scale observed in some close binary systems (19), and tidal dissipation (20)  

E-print Network

time scale observed in some close binary systems (19), and tidal dissipation (20) may also cause). At this stage, the core of star A undergoes collapse, and the residual nuclear fuel is ignited to power aware that both tidal and general relativistic ef- fects will be important in this system

Stanley, H. Eugene

409

Detection and diagnosis of changes in the time-scale eigenstructure for vibrating systems  

Microsoft Academic Search

Focuses on techniques used in monitoring machine condition and diagnosing mechanical faults in vibrating mechanical equipment which has varied operational modes and whose dynamic signals are nonstationary. Because of the nonstationary nature of the vibrating system, one has to apply the time-scale transform to capture the nonstationary modes. The autoregressive moving average modeling captures the modal signatures, in particular, the

Ahmed Hambaba; E. Huff; U. Kaul

2001-01-01

410

Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales  

PubMed Central

The majority of numerical models in climatology and geomagnetism rely on deterministic finite-difference techniques and attempt to include as many empirical constraints on the many processes and boundary conditions applicable to their very complex systems. Despite their sophistication, many of these models are unable to reproduce basic aspects of climatic or geomagnetic dynamics. We show that a simple stochastic model, which treats the flux of heat energy in the atmosphere by convective instabilities with random advection and diffusive mixing, does a remarkable job at matching the observed power spectrum of historical and proxy records for atmospheric temperatures from time scales of one day to one million years (Myr). With this approach distinct changes in the power-spectral form can be associated with characteristic time scales of ocean mixing and radiative damping. Similarly, a simple model of the diffusion of magnetic intensity in Earth's core coupled with amplification and destruction of the local intensity can reproduce the observed 1/f noise behavior of Earth's geomagnetic intensity from time scales of 1 (Myr) to 100 yr. In addition, the statistics of the fluctuations in the polarity reversal rate from time scales of 1 Myr to 100 Myr are consistent with the hypothesis that reversals are the result of variations in 1/f noise geomagnetic intensity above a certain threshold, suggesting that reversals may be associated with internal fluctuations rather than changes in mantle thermal or magnetic boundary conditions. PMID:11875208

Pelletier, Jon D.

2002-01-01

411

Nonoscillatory Solutions for System of Neutral Dynamic Equations on Time Scales  

PubMed Central

We will discuss nonoscillatory solutions to the n-dimensional functional system of neutral type dynamic equations on time scales. We will establish some sufficient conditions for nonoscillatory solutions with the property limt?? ?x i(t) = 0, i = 1, 2,…, n. PMID:24757436

Chen, Zhanhe; Wang, Qi; Xi, Hongjian

2014-01-01

412

An Ancient Universe: How Astronomers Know the Vast Scale of Cosmic Time  

NSDL National Science Digital Library

The booklet, An Ancient Universe: How Astronomers Know the Vast Scale of Cosmic Time, is a guide for Teachers, Students and the Public. The booklet was written by a subcommittee of the American Astronomical Society's Astronomy Education Board, and was published in 2004 by the American Astronomical Society with the Astronomical Society of the Pacific.

Society, American A.

2005-06-17

413

Time and space scales of vertical mixing and advection of phytoplankton in the upper ocean  

Microsoft Academic Search

The dependence of phytoplankton photosynthesis on light intensity may be altered by the range and frequency of variations in light intensity recentlv experienced by the organisms. A major source of the fluctuations in light intensity experienced by phytoplankton in the upper ocean is vertical motion. We estimate time and space scales for \\\\Tertical displacements of phytoplankton caused by turbulent mixing,

K. L. DENMAN; A. E. GARGETT

1983-01-01

414

Constrained Optimization Based Control of Real Time Large-Scale Systems: Airjet Object Movement System  

E-print Network

,Fy,) Position Cmd (x,y,) Sensor Fusion 32000 576 Figure 1 Control loop for airjet system. The numbers indicate, and system identification emerge as challenging problems for large- scale system control. In this work* within the control system loop time without losing relevant information. In general, this process

Shang, Yi

415

Practical Stability in terms of Two Measures for Set Differential Equations on Time Scales  

PubMed Central

We present a new comparison principle by introducing a notion of upper quasi-monotone nondecreasing and obtain the practical stability criteria for set valued differential equations in terms of two measures on time scales by using the vector Lyapunov function together with the new comparison principle. PMID:24574876

Wang, Peiguang; Sun, Weiwei

2014-01-01

416

Multi-time multi-scale correlation functions in hydrodynamic turbulence  

NASA Astrophysics Data System (ADS)

High Reynolds numbers Navier-Stokes equations are believed to break self-similarity concerning both spatial and temporal properties: correlation functions of different orders exhibit distinct decorrelation times and anomalous spatial scaling properties. Here, we present a systematic attempt to measure multi-time and multi-scale correlations functions, by using high Reynolds numbers numerical simulations of fully homogeneous and isotropic turbulent flow. The main idea is to set-up an ensemble of probing stations riding the flow, i.e., measuring correlations in a reference frame centered on the trajectory of distinct fluid particles (the quasi-Lagrangian reference frame introduced by Belinicher and L'vov [Sov. Phys. JETP 66, 303 (1987)]). In this way, we reduce the large-scale sweeping and measure the non-trivial temporal dynamics governing the turbulent energy transfer from large to small scales. We present evidences of the existence of the dynamic multiscaling properties of turbulence - first proposed by L'vov et al. [Phys. Rev. E 55, 7030 (1997)] - in which multi-time correlation functions are characterized by an infinite set of characteristic times.

Biferale, Luca; Calzavarini, Enrico; Toschi, Federico

2011-08-01

417

Practical TimeScale Fitting of Self-Similar Traffic with Markov-Modulated Poisson Process  

Microsoft Academic Search

streams. In this paper, we first give some definitions of self- similarity. Then, we propose a fitting method for the self-similar trac in terms of Markov- modulated Poisson process (MMPP). We construct an MMPP as the superposition of two- state MMPPs and fit it so as to match the variance function over several time-scales. Numerical examples show that the variance

Tadafumi Yoshihara; Shoji Kasahara; Yutaka Takahashi

2001-01-01