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Sample records for absolute age constraints

  1. Revised Age Constraints on Absolute Age Limits for Mercury's Kuiperian and Mansurian Systems

    NASA Astrophysics Data System (ADS)

    Banks, Maria E.; Zhiyong, Xiao; Braden, Sarah E.; Marchi, Simone S.; Barlow, Nadine G.; Chapman, Clark R.; Fassett, Caleb I.

    2015-11-01

    On the basis of morphologically distinct basin and crater deposits, Mercury’s surface units have been subdivided into five time-stratigraphic systems (youngest to oldest): Kuiperian, Mansurian, Calorian, Tolstojan, and pre-Tolstojan. Approximate age limits were initially suggested for these systems on the basis of the lunar-derived impact-flux history. High-resolution and multi-band image data obtained by the MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) spacecraft were used to catalogue fresh impact craters interpreted to have formed during the Mansurian and Kuiperian systems. Mansurian and Kuiperian craters are characterized as morphologically fresh with crisp morphologies, well-preserved rims, few or no superposed craters, continuous ejecta with radial lineaments, and well-defined secondary craters; Kuiperian craters have bright ray systems while Mansurian craters maintain fresh morphologies but no longer have discernable ray systems.The density of fresh craters in these datasets, along with the recent production and chronology function of Marchi et al. [2009], are used to estimate new limits for the boundaries of the two most recent of Mercury’s systems. Given the effects of strength and other parameters (such as density), we estimate a model age for the population of craters that have formed since the onset of the Mansurian of ~1.9 ±0.3 Gyr. Likewise we estimate a model age for the population of craters that have formed since the onset of the Kuiperian of ~300 ±40 Myr. A particularly good fit for the Mansurian crater size frequency distribution (SFD) was found for the NEO-derived crater distribution. The same is true for the Kuiperian SFD, although the fit is not as robust as for the Mansurian SFD.

  2. Preliminary Monazite U-Th-Total Pb Absolute Age Constraints on Crustal Thickening and Siluro-Devonian Dextral Transpression: Central Appalachian Piedmont, SE Pennsylvania

    NASA Astrophysics Data System (ADS)

    Bosbyshell, H.; Srogi, L.; Pyle, J. M.; Blackmer, G. C.

    2007-12-01

    High grade metamorphic rocks in the Central Appalachian piedmont of SE Pa. occur in at least three distinct lithotectonic belts that are bounded by steeply dipping, NE-striking transcurrent or transpressional shear zones. From NW to SE these belts consist of rocks of Laurentian-, uncertain-, and arc-affinity. The central belt is characterized by basement gneiss-cored nappes and associated shallowly to moderately SE dipping S2 foliation. This belt followed a clockwise metamorphic P-T path; maximum temperatures (T ~ 640 °C at P ~ 0.7 GPa) are associated with syn- to post-S2 garnet growth. An increase in pressure of ~ 0.1 GPa is inferred from post- kinematic high-Ca garnet rims. This paper reports preliminary EPMA results on monazite from two samples, WG- 216 and U-154, from the Glenarm Wissahickon, the metasedimentary cover sequence in the central belt. A few monazite grains from WG-216 exhibit small low-Th cores which give latest Cambrian ages (492 +/- 10 Ma, n = 10; n = # of analyses, all precision is reported as 2 s.e.). All grains in WG-216 contain cores with irregular, patchy zoning that yield late Ordovician ages (454 +/- 6 Ma, n = 31). High-Th, low-Y rims, which yield early Devonian ages (410 +/- 11 Ma, n = 12), are present on monazite inclusions in the outer portions of garnet and staurolite, but are absent in monazite inclusions within microlithons characterized by S1 foliation. High-Th, low-Y rims grow along 001 cleavage in S2 foliation-forming micas, so S2 can be no younger than monazite rims. Similar EPMA monazite results were obtained from U-154, also from the Glenarm Wissahickon. At least one Ordovician core is present (455 +/- 4 Ma, n = 8); pre-S2 matrix monazite and one inclusion in staurolite yield late Silurian ages (422 +/- 4 Ma, n = 29); and one inclusion within outermost garnet yields a Devonian age (415 +/- 8 Ma, n = 8). These results constrain the timing of S2 formation and peak metamorphism in the central belt to the early Devonian. The SE

  3. Age Dependent Absolute Plate and Plume Motion Modeling

    NASA Astrophysics Data System (ADS)

    Heaton, D. E.; Koppers, A. A. P.

    2015-12-01

    Current absolute plate motion (APM) models from 80 - 0 Ma are constrained by the location of mantle plume related hotspot seamounts, in particular those of the Hawaiian-Emperor and Louisville seamount trails. Originally the 'fixed' hotspot hypothesis was developed to explain past plate motion based on linear age progressive intra-plate volcanism. However, now that 'moving' hotspots are accepted, it is becoming clear that APM models need to be corrected for individual plume motion vectors. For older seamount trails that were active between roughly 50 and 80 Ma the APM models that use 'fixed' hotspots overestimate the measured age progression in those trails, while APM models corrected for 'moving' hotspots underestimate those age progressions. These mismatches are due to both a lack of reliable ages in the older portions of both the Hawaii and Louisville seamount trails and insufficient APM modeling constraints from other seamount trails in the Pacific Basin. Seamounts are difficult to sample and analyze because many are hydrothermally altered and have low potassium concentrations. New 40Ar/39Ar Age results from International Ocean Drilling Project (IODP) Expedition 330 Sites U1372 (n=18), U1375 (n=3), U1376 (n=15) and U1377 (n=7) aid in constraining the oldest end of the Louisville Seamount trail. A significant observation in this study is that the age range recovered in the drill cores match the range of ages that were acquired on dredging cruises at the same seamounts (e.g. Koppers et al., 2011). This is important for determining the inception age of a seamount. The sections recovered from IODP EXP 330 are in-situ volcanoclastic breccia and lava flows. Comparing the seismic interpretations of Louisville guyots (Contreras-Reyes et al., 2010), Holes U1372, U1373 and U1374 penetrated the extrusive and volcanoclastic sections of the seamount. The ages obtained are consistent over stratigraphic intervals >100-450 m thick, providing evidence that these seamounts

  4. Passive absolute age and temperature history sensor

    SciTech Connect

    Robinson, Alex; Vianco, Paul T.

    2015-11-10

    A passive sensor for historic age and temperature sensing, including a first member formed of a first material, the first material being either a metal or a semiconductor material and a second member formed of a second material, the second material being either a metal or a semiconductor material. A surface of the second member is in contact with a surface of the first member such that, over time, the second material of the second member diffuses into the first material of the first member. The rate of diffusion for the second material to diffuse into the first material depends on a temperature of the passive sensor. One of the electrical conductance, the electrical capacitance, the electrical inductance, the optical transmission, the optical reflectance, or the crystalline structure of the passive sensor depends on the amount of the second material that has diffused into the first member.

  5. Urey: to measure the absolute age of Mars

    NASA Technical Reports Server (NTRS)

    Randolph, J. E.; Plescia, J.; Bar-Cohen, Y.; Bartlett, P.; Bickler, D.; Carlson, R.; Carr, G.; Fong, M.; Gronroos, H.; Guske, P. J.; Herring, M.; Javadi, H.; Johnson, D. W.; Larson, T.; Malaviarachchi, K.; Sherrit, S.; Stride, S.; Trebi-Ollennu, A.; Warwick, R.

    2003-01-01

    UREY, a proposed NASA Mars Scout mission will, for the first time, measure the absolute age of an identified igneous rock formation on Mars. By extension to relatively older and younger rock formations dated by remote sensing, these results will enable a new and better understanding of Martian geologic history.

  6. Subduction trench migration as a constraint on absolute plate motions since 130 Ma

    NASA Astrophysics Data System (ADS)

    Williams, Simon; Flament, Nicolas; Müller, Dietmar; Butterworth, Nathan

    2015-04-01

    The absolute motions of the lithospheric plates relative to the Earth's deep interior are commonly constrained using observations from paleomagnetism and age-progressive seamount trails. In contrast, a reference frame linking surface plate motions to subducted slab remnants mapped from seismic tomography has recently been proposed. Absolute plate motion (APM) models (or "reference frames") derived using different methodologies, different subsets of hotspots, or differing assumptions of hotspot motion, have contrasting implications for parameters that describe the long term state of the plate-mantle system, such as the balance between advance and retreat of subduction zones, plate velocities, and net lithospheric rotation. Previous studies of contemporary plate motions have used subduction zone kinematics as a constraint on the most likely APM model. Here we use a relative plate motion model to compute these values for the last 130 Myr for a range of alternative reference frames, and quantitatively compare the results. We find that hotspot and tomographic slab-remnant reference frames yield similar results for the last 70 Myr. For the 130-70 Ma period, where hotspot reference frames are less well constrained, these models yield a much more dispersed distribution of slab advance and retreat velocities. By contrast, plate motions calculated using the slab-remnant reference frame, or using a reference frame designed to minimise net rotation, yield more consistent subduction zone kinematics for times older than 70 Ma. Introducing the global minimisation of trench migration rates as a key criterion in the construction of APM models forms the foundation of a new method of constraining APMs (and in particular paleolongitude) in deep geological time.

  7. Uranium isotopic composition and absolute ages of Allende chondrules

    NASA Astrophysics Data System (ADS)

    Brennecka, G. A.; Budde, G.; Kleine, T.

    2015-11-01

    A handful of events, such as the condensation of refractory inclusions and the formation of chondrules, represent important stages in the formation and evolution of the early solar system and thus are critical to understanding its development. Compared to the refractory inclusions, chondrules appear to have a protracted period of formation that spans millions of years. As such, understanding chondrule formation requires a catalog of reliable ages, free from as many assumptions as possible. The Pb-Pb chronometer has this potential; however, because common individual chondrules have extremely low uranium contents, obtaining U-corrected Pb-Pb ages of individual chondrules is unrealistic in the vast majority of cases at this time. Thus, in order to obtain the most accurate 238U/235U ratio possible for chondrules, we separated and pooled thousands of individual chondrules from the Allende meteorite. In this work, we demonstrate that no discernible differences exist in the 238U/235U compositions between chondrule groups when separated by size and magnetic susceptibility, suggesting that no systematic U-isotope variation exists between groups of chondrules. Consequently, chondrules are likely to have a common 238U/235U ratio for any given meteorite. A weighted average of the six groups of chondrule separates from Allende results in a 238U/235U ratio of 137.786 ± 0.004 (±0.016 including propagated uncertainty on the U standard [Richter et al. 2010]). Although it is still possible that individual chondrules have significant U isotope variation within a given meteorite, this value represents our best estimate of the 238U/235U ratio for Allende chondrules and should be used for absolute dating of these objects, unless such chondrules can be measured individually.

  8. Absolute Gravity Datum in the Age of Cold Atom Gravimeters

    NASA Astrophysics Data System (ADS)

    Childers, V. A.; Eckl, M. C.

    2014-12-01

    The international gravity datum is defined today by the International Gravity Standardization Net of 1971 (IGSN-71). The data supporting this network was measured in the 1950s and 60s using pendulum and spring-based gravimeter ties (plus some new ballistic absolute meters) to replace the prior protocol of referencing all gravity values to the earlier Potsdam value. Since this time, gravimeter technology has advanced significantly with the development and refinement of the FG-5 (the current standard of the industry) and again with the soon-to-be-available cold atom interferometric absolute gravimeters. This latest development is anticipated to provide improvement in the range of two orders of magnitude as compared to the measurement accuracy of technology utilized to develop ISGN-71. In this presentation, we will explore how the IGSN-71 might best be "modernized" given today's requirements and available instruments and resources. The National Geodetic Survey (NGS), along with other relevant US Government agencies, is concerned about establishing gravity control to establish and maintain high order geodetic networks as part of the nation's essential infrastructure. The need to modernize the nation's geodetic infrastructure was highlighted in "Precise Geodetic Infrastructure, National Requirements for a Shared Resource" National Academy of Science, 2010. The NGS mission, as dictated by Congress, is to establish and maintain the National Spatial Reference System, which includes gravity measurements. Absolute gravimeters measure the total gravity field directly and do not involve ties to other measurements. Periodic "intercomparisons" of multiple absolute gravimeters at reference gravity sites are used to constrain the behavior of the instruments to ensure that each would yield reasonably similar measurements of the same location (i.e. yield a sufficiently consistent datum when measured in disparate locales). New atomic interferometric gravimeters promise a significant

  9. Observables sensitive to absolute neutrino masses: Constraints and correlations from world neutrino data

    SciTech Connect

    Fogli, G.L.; Lisi, E.; Marrone, A.; Palazzo, A.; Melchiorri, A.; Serra, P.; Silk, J.

    2004-12-01

    In the context of three-flavor neutrino mixing, we present a thorough study of the phenomenological constraints applicable to three observables sensitive to absolute neutrino masses: The effective neutrino mass in Tritium beta-decay (m{sub {beta}}); the effective Majorana neutrino mass in neutrinoless double beta-decay (m{sub {beta}}{sub {beta}}); and the sum of neutrino masses in cosmology ({sigma}). We discuss the correlations among these variables which arise from the combination of all the available neutrino oscillation data, in both normal and inverse neutrino mass hierarchy. We set upper limits on m{sub {beta}} by combining updated results from the Mainz and Troitsk experiments. We also consider the latest results on m{sub {beta}}{sub {beta}} from the Heidelberg-Moscow experiment, both with and without the lower bound claimed by such experiment. We derive upper limits on {sigma} from an updated combination of data from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite and the two degrees Fields (2dF) Galaxy Redshifts Survey, with and without Lyman-{alpha} forest data from the Sloan Digital Sky Survey (SDSS), in models with a nonzero running of the spectral index of primordial inflationary perturbations. The results are discussed in terms of two-dimensional projections of the globally allowed region in the (m{sub {beta}},m{sub {beta}}{sub {beta}},{sigma}) parameter space, which neatly show the relative impact of each data set. In particular, the (in)compatibility between {sigma} and m{sub {beta}}{sub {beta}} constraints is highlighted for various combinations of data. We also briefly discuss how future neutrino data (both oscillatory and nonoscillatory) can further probe the currently allowed regions.

  10. Constraint on Absolute Accuracy of Metacomprehension Assessments: The Anchoring and Adjustment Model vs. the Standards Model

    ERIC Educational Resources Information Center

    Kwon, Heekyung

    2011-01-01

    The objective of this study is to provide a systematic account of three typical phenomena surrounding absolute accuracy of metacomprehension assessments: (1) the absolute accuracy of predictions is typically quite low; (2) there exist individual differences in absolute accuracy of predictions as a function of reading skill; and (3) postdictions…

  11. ABSOLUTE PROPERTIES OF THE ECLIPSING TRIPLE STAR CO ANDROMEDAE: CONSTRAINTS ON CONVECTIVE CORE OVERSHOOTING

    SciTech Connect

    Sandberg Lacy, Claud H.; Torres, Guillermo; Charbonneau, David; Claret, Antonio; O'Donovan, Francis T.; Mandushev, Georgi E-mail: gtorres@cfa.harvard.ed E-mail: claret@iaa.e E-mail: gmand@lowell.ed

    2010-06-15

    Accurate absolute properties have been determined for the eclipsing triple star CO And (F8+F8) based on extensive differential photometry obtained by three robotic observatories and CfA spectroscopy. The eclipsing binary star orbit is circular with a period of 3.655 days. The triple nature of this system is revealed by more than a century of timings of minimum light, and by the presence of third light in the photometric orbits. The masses of the eclipsing pair are 1.289 {+-} 0.007 and 1.264 {+-} 0.007 solar masses, and the corresponding radii are 1.727 {+-} 0.021 and 1.694 {+-} 0.017 solar radii. These stars are synchronously rotating and are near the end of their main-sequence phase, at an age of about 3.6 Gyr. The much fainter widely separated third body appears to have a mass of about 0.8 solar masses. The distance to the system is 377 {+-} 25 pc.

  12. Observational constraints on atmospheric radiaitve feedbacks: absolute accuracy and next-generation observing systems

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Hanssen, L. M.; Mekhontsev, S.; Anderson, J.

    2012-12-01

    The central role of atmospheric radiative feedbacks to understanding and projecting climate change calls for a robust observational system. Recent studies have shown the value of space-based measurements for putting quantitative constraints on a range of radiative feedback processes through a fingerprinting method applied to long-term observational records. More recent work has suggested the value of demonstrably accurate measurements to disentangle model error from observational uncertainties within reanalysis systems, potentially yielding improved representations of feedback processes within just a few years. Both of these methods rely on space-based measurements that can be objectively tested for accuracy on-orbit. A new class of mission has been proposed that incorporates the same type of empirical tests for accuracy as used in the laboratory into a space-based sensor. One example of such a mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO), a new mission suggested by the 2006 National Research Council Decadal Survey. CLARREO includes three sensor types: thermal infrared, microwave, and reflected shortwave. This paper presents a laboratory demonstration of prototype systems for testing the on-orbit accuracy of a thermal infrared sensor for CLARREO. These systems utilize infrared lasers to provide monochromatic light sources to quantitatively determine the optical properties of materials. These infrared optical properties are major determinants of the on-orbit radiometric performance of a thermal infrared sensor. For this reason, reliable quantitative information (including uncertainty) that tracks any changes in relevant infrared materials over the mission lifetime is essential to objective assessment of instrument accuracy. The practicality of mid-infrared lasers for these applications is due to the availability and continued evolution of compact, high-efficiency Quantum Cascade Lasers (QCLs). These lasers can provide over 100 m

  13. GeMS MCAO observations of the Galactic globular cluster NGC 2808: the absolute age

    NASA Astrophysics Data System (ADS)

    Massari, D.; Fiorentino, G.; McConnachie, A.; Bono, G.; Dall'Ora, M.; Ferraro, I.; Iannicola, G.; Stetson, P. B.; Turri, P.; Tolstoy, E.

    2016-02-01

    Context. Globular clusters are the oldest stellar systems in the Milky Way, and they probe the early epoch of the Galaxy formation. However, the uncertainties on their absolute age are still too large to soundly constrain how the Galactic structures have assembled. Aims: The aim of this work is to obtain an accurate estimate of the absolute age of the globular cluster NGC 2808 using deep IR data obtained with the multi-conjugate adaptive optics system operating at the Gemini South telescope (GeMS). Methods: This exquisite photometry, combined with that obtained in V and I-bands with HST, allowed us to detect the faint Main Sequence Knee feature in NGC 2808 colour magnitude diagram. The difference between this point and the main sequence turn-off is a good age estimator that provides ages with unprecedented accuracy. Results: We find that NGC 2808 has an age of t = 10.9 ± 0.7 (intrinsic) ±0.45 (metallicity term) Gyr. A possible contamination by He-enhanced population could make the cluster up to 0.25 Gyr older. Although this age estimate agrees with the age coming from the classical turn-off method (t = 11.0 Gyr), its uncertainty is a factor ~3 better, since it avoids systematics in reddening, distance assumptions, and photometric zero point determination. The final absolute age indicates that NGC 2808 is slightly younger than other Galactic globular clusters with similar metallicity. Tables of the photometry are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A51

  14. Rhenium-osmium isotope constraints on the age of iron meteorites

    USGS Publications Warehouse

    Horan, M.F.; Morgan, J.W.; Walker, R.J.; Grossman, J.N.

    1992-01-01

    Rhenium and osmium concentrations and the osmium isotopic compositions of iron meteorites were determined by negative thermal ionization mass spectrometry. Data for the IIA iron meteorites define an isochron with an uncertainty of approximately ??31 million years for meteorites ???4500 million years old. Although an absolute rhenium-osmium closure age for this iron group cannot be as precisely constrained because of uncertainty in the decay constant of 187Re, an age of 4460 million years ago is the minimum permitted by combined uncertainties. These age constraints imply that the parent body of the IIAB magmatic irons melted and subsequently cooled within 100 million years after the formation of the oldest portions of chondrites. Other iron meteorites plot above the IIA isochron, indicating that the planetary bodies represented by these iron groups may have cooled significantly later than the parent body of the IIA irons.

  15. Rhenium-osmium-isotope constraints on the age of iron meteorites

    NASA Technical Reports Server (NTRS)

    Horan, M. F.; Morgan, J. W.; Walker, R. J.; Grossman, J. N.

    1992-01-01

    Rhenium and osmium concentrations and the osmium isotopic compositions of iron meteorites were determined by negative thermal ionization mass spectrometry. Data for the IIA iron meteorites define an isochron with an uncertainty of approximately +/-31 million years for meteorites about 4500 million years old. Although an absolute rhenium-osmium closure age for this iron group cannot be as precisely constrained because of uncertainty in the decay constant of Re-187, an age of 4460 million years ago is the minimum permitted by combined uncertainties. These age constraints imply that the parent body of the IIAB magmatic irons melted and subsequently cooled within 100 million years after the formation of the oldest portions of chondrites. Other iron meteorites plot above the IIA isochron, indicating that the planetary bodies represented by these iron groups may have cooled significantly later than the parent body of the IIA irons.

  16. Constraints on the Mid-Continent Deformation Gravity Gradient Determined from Co-located GPS and Absolute Gravity Observations

    NASA Astrophysics Data System (ADS)

    James, T. S.; Mazzotti, S.; Mazzotti, S.; Lambert, A.

    2001-12-01

    The deformation gravity gradient (DGG) is the ratio of the time rate of change of surface gravity to vertical crustal velocity. Different processes generate different theoretical predictions of the DGG. Consequently, observational constraints on the DGG are necessary to link crustal uplift observations to satellite-derived observations of the time rate of change of the Earth's gravitational field, which will be generated by upcoming satellite missions such as GRACE. Larson and van Dam (2000) have compared secular gravity trends from 4 sites in interior North America to crustal uplift rates obtained from global point-positioning analyses of GPS observations, and found they agree, assuming a nominal DGG value appropriate to postglacial rebound of -0.15 μ Gal/mm (Wahr et al., 1995). Here we revisit and extend their analysis in order to determine the observational constraints on the DGG in mid-continent North America. We use recently published gravity rates derived from significantly more absolute gravity observations and a different GPS analysis scheme. Lambert et al. (2001) have published secular gravity rates for 7 sites in mid-continent North America, using all available absolute gravity observations and allowing for instrumental offsets. The sites, chosen to sample postglacial rebound, lie on a transect from Churchill, Manitoba, located on Hudson Bay, to North Liberty, Iowa. Four of these sites (Churchill, Flin Flon, Lac du Bonnet, and North Liberty) also feature a nearby GPS station. The GPS observations were analyzed using double differencing with Bernese 4.2, yielding 5 year time series for vertical position. The daily repeatabilities of 5 to 9 mm compare well to the weekly repeatabilities of 7-8 mm reported by Larson and van Dam (2000). A comparison of the vertical rates derived from these time series to the secular solid-surface gravity trends finds a DGG of -0.14 +/- 0.06 μ Gal/mm. This value is in good agreement with model predictions for postglacial

  17. Absolute age of lunar regolith material from the Sea of Fertility

    NASA Technical Reports Server (NTRS)

    Vinogradov, A. P.; Artemov, Y. M.

    1974-01-01

    By averaging the absolute age of lunar regolith materials from the Sea of Fertility for the fine regolith fraction from the core zone V, an age of 4.65 10 to the 9th power + 0.4 10 to the 9th power years was obtained, employing as the primordial Sr-87/Sr-86 ratio 0.69884 (ADOR). Also close to this age value is the age estimate based on the Pb-207/Pb-206 ratio. Using the value 0.69898 (BABI) as a primordial Sr-87/Sr-86 ratio reduces the calculated age of the fine regolith fraction to 4.25 X 10 to the 9th power years. The fine fraction of lunar regolith from the Sea of Fertility is also characterized by a minimum addition of radiogenic Sr-87, a minimum Rb/Sr ratio, and a maximum K/Rb ratio compared with analogous lunar material from other points.

  18. Absolute ages from crater statistics: Using radiometric ages of Martian samples for determining the Martian cratering chronology

    NASA Technical Reports Server (NTRS)

    Neukum, G.

    1988-01-01

    In the absence of dates derived from rock samples, impact crater frequencies are commonly used to date Martian surface units. All models for absolute dating rely on the lunar cratering chronology and on the validity of its extrapolation to Martian conditions. Starting from somewhat different lunar chronologies, rather different Martian cratering chronologies are found in the literature. Currently favored models are compared. The differences at old ages are significant, the differences at younger ages are considerable and give absolute ages for the same crater frequencies as different as a factor of 3. The total uncertainty could be much higher, though, since the ratio of lunar to Martian cratering rate which is of basic importance in the models is believed to be known no better than within a factor of 2. Thus, it is of crucial importance for understanding the the evolution of Mars and determining the sequence of events to establish an unambiguous Martian cratering chronology from crater statistics in combination with clean radiometric ages of returned Martian samples. For the dating goal, rocks should be as pristine as possible from a geologically simple area with a one-stage emplacement history of the local formation. A minimum of at least one highland site for old ages, two intermediate-aged sites, and one very young site is needed.

  19. A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood

    NASA Astrophysics Data System (ADS)

    Bell, Cameron P. M.; Mamajek, Eric E.; Naylor, Tim

    2015-11-01

    We present a self-consistent, absolute isochronal age scale for young ( ≲ 200 Myr), nearby ( ≲ 100 pc) moving groups in the solar neighbourhood based on homogeneous fitting of semi-empirical pre-main-sequence model isochrones using the τ2 maximum-likelihood fitting statistic of Naylor & Jeffries in the MV, V - J colour-magnitude diagram. The final adopted ages for the groups are as follows: 149^{+51}_{-19} {Myr} for the AB Dor moving group, 24 ± 3 Myr for the β Pic moving group (BPMG), 45^{+11}_{-7} {Myr} for the Carina association, 42^{+6}_{-4} {Myr} for the Columba association, 11 ± 3 Myr for the η Cha cluster, 45 ± 4 Myr for the Tucana-Horologium moving group (Tuc-Hor), 10 ± 3 Myr for the TW Hya association and 22^{+4}_{-3} {Myr} for the 32 Ori group. At this stage we are uncomfortable assigning a final, unambiguous age to the Argus association as our membership list for the association appears to suffer from a high level of contamination, and therefore it remains unclear whether these stars represent a single population of coeval stars. Our isochronal ages for both the BPMG and Tuc-Hor are consistent with recent lithium depletion boundary (LDB) ages, which unlike isochronal ages, are relatively insensitive to the choice of low-mass evolutionary models. This consistency between the isochronal and LDB ages instils confidence that our self-consistent, absolute age scale for young, nearby moving groups is robust, and hence we suggest that these ages be adopted for future studies of these groups. Software implementing the methods described in this study is available from http://www.astro.ex.ac.uk/people/timn/tau-squared/.

  20. Accurate radiocarbon age estimation using "early" measurements: a new approach to reconstructing the Paleolithic absolute chronology

    NASA Astrophysics Data System (ADS)

    Omori, Takayuki; Sano, Katsuhiro; Yoneda, Minoru

    2014-05-01

    This paper presents new correction approaches for "early" radiocarbon ages to reconstruct the Paleolithic absolute chronology. In order to discuss time-space distribution about the replacement of archaic humans, including Neanderthals in Europe, by the modern humans, a massive data, which covers a wide-area, would be needed. Today, some radiocarbon databases focused on the Paleolithic have been published and used for chronological studies. From a viewpoint of current analytical technology, however, the any database have unreliable results that make interpretation of radiocarbon dates difficult. Most of these unreliable ages had been published in the early days of radiocarbon analysis. In recent years, new analytical methods to determine highly-accurate dates have been developed. Ultrafiltration and ABOx-SC methods, as new sample pretreatments for bone and charcoal respectively, have attracted attention because they could remove imperceptible contaminates and derive reliable accurately ages. In order to evaluate the reliability of "early" data, we investigated the differences and variabilities of radiocarbon ages on different pretreatments, and attempted to develop correction functions for the assessment of the reliability. It can be expected that reliability of the corrected age is increased and the age applied to chronological research together with recent ages. Here, we introduce the methodological frameworks and archaeological applications.

  1. Reduced Haemodynamic Response in the Ageing Visual Cortex Measured by Absolute fNIRS

    PubMed Central

    Ward, Laura McKernan; Aitchison, Ross Thomas; Tawse, Melisa; Simmers, Anita Jane; Shahani, Uma

    2015-01-01

    The effect of healthy ageing on visual cortical activation is still to be fully explored. This study aimed to elucidate whether the haemodynamic response (HDR) of the visual cortex altered as a result of ageing. Visually normal (healthy) participants were presented with a simple visual stimulus (reversing checkerboard). Full optometric screening was implemented to identify two age groups: younger adults (n = 12, mean age 21) and older adults (n = 13, mean age 71). Frequency-domain Multi-distance (FD-MD) functional Near-Infrared Spectroscopy (fNIRS) was used to measure absolute changes in oxygenated [HbO] and deoxygenated [HbR] haemoglobin concentrations in the occipital cortices. Utilising a slow event-related design, subjects viewed a full field reversing checkerboard with contrast and check size manipulations (15 and 30 minutes of arc, 50% and 100% contrast). Both groups showed the characteristic response of increased [HbO] and decreased [HbR] during stimulus presentation. However, older adults produced a more varied HDR and often had comparable levels of [HbO] and [HbR] during both stimulus presentation and baseline resting state. Younger adults had significantly greater concentrations of both [HbO] and [HbR] in every investigation regardless of the type of stimulus displayed (p<0.05). The average variance associated with this age-related effect for [HbO] was 88% and [HbR] 91%. Passive viewing of a visual stimulus, without any cognitive input, showed a marked age-related decline in the cortical HDR. Moreover, regardless of stimulus parameters such as check size, the HDR was characterised by age. In concurrence with present neuroimaging literature, we conclude that the visual HDR decreases as healthy ageing proceeds. PMID:25909849

  2. Evaluation of the Re-Os Geochronometer in Organic-rich Mudrocks as a Method for Constraining the Absolute Ages of Neoproterozoic Glaciogenic Deposits

    NASA Astrophysics Data System (ADS)

    Kendall, B. S.; Creaser, R. A.; Ross, G. M.

    2002-12-01

    Absolute-age constraints on the Neoproterozoic glaciations are generally poor due to a paucity of suitable plutonic and volcanic igneous rocks that are temporally and spatially related to Neoproterozoic glaciogenic deposits and are amenable to radiometric dating methods. In this study, the Re-Os isotope systematics of dark gray, sulfidic slates from the Old Fort Point Formation (OFP) of the Windermere Supergroup (near Jasper, Alberta) were examined to test the ability of the Re-Os geochronometer to provide an absolute age constraint for a Neoproterozoic glaciogenic deposit. The OFP has been interpreted as the deep water expression of post-glacial sea level rise and therefore is comparable stratigraphically to cap carbonates that immediately overlie glaciogenic deposits worldwide. Despite the relatively low Re (6-16 ppb) and Os (0.07-0.14 ppb) concentrations and total organic contents (~ 0.5% TOC) of the slates compared to other organic-rich mudrocks used in previous Re-Os isotope studies, precise well-fitted Re-Os isochrons have been obtained with two different dissolution methods. An age of 620.8 +/- 8.1 Ma (MSWD = 0.9; initial 187Os/188Os = 0.68 +/- 0.06) is obtained using conventional aqua regia dissolution. Using a method designed to selectively dissolve organic matter alone, an age of 609.0 +/- 8.3 Ma (MSWD = 1.5; initial 187Os/188Os = 0.62 +/- 0.05) is obtained. These absolute age results are in accord with existing age constraints (e.g., stratigraphically younger Hamill Group with a U-Pb zircon age of 569 Ma). The well-defined Re-Os systematics of the OFP slates demonstrates for the first time that the Re-Os system is not disturbed in organic-rich sediments during lower greenschist (-chlorite) grade metamorphic conditions. The whole-rock analysis of each individual sample yields consistently higher initial 187Os/188Os isotope ratios than the corresponding organic matter analysis and suggests that a significant radiogenic detrital Os component is present

  3. Distant Secondary Craters and Age Constraints on Young Martian Terrains

    NASA Technical Reports Server (NTRS)

    McEwen, A.; Preblich, B.; Turtle, E.; Studer, D.; Artemieva, N.; Golombek, M.; Hurst, M.; Kirk, R.; Burr, D.

    2005-01-01

    Are small (less than approx. 1 km diameter) craters on Mars and the Moon dominated by primary impacts, by secondary impacts of much larger primary craters, or are both primaries and secondaries significant? This question is critical to age constraints for young terrains and for older terrains covering small areas, where only small craters are superimposed on the unit. If the martian rayed crater Zunil is representative of large impact events on Mars, then the density of secondaries should exceed the density of primaries at diameters a factor of 1000 smaller than that of the largest contributing primary crater. On the basis of morphology and depth/diameter measurements, most small craters on Mars could be secondaries. Two additional observations (discussed below) suggest that the production functions of Hartmann and Neukum predict too many primary craters smaller than a few hundred meters in diameter. Fewer small, high-velocity impacts may explain why there appears to be little impact regolith over Amazonian terrains. Martian terrains dated by small craters could be older than reported in recent publications.

  4. Redefinition of the crater-density and absolute-age boundaries for the chronostratigraphic system of Mars

    USGS Publications Warehouse

    Werner, S.C.; Tanaka, K.L.

    2011-01-01

    For the boundaries of each chronostratigraphic epoch on Mars, we present systematically derived crater-size frequencies based on crater counts of geologic referent surfaces and three proposed " standard" crater size-frequency production distributions as defined by (a) a simple -2 power law, (b) Neukum and Ivanov, (c) Hartmann. In turn, these crater count values are converted to model-absolute ages based on the inferred cratering rate histories. We present a new boundary definition for the Late Hesperian-Early Amazonian transition. Our fitting of crater size-frequency distributions to the chronostratigraphic record of Mars permits the assignment of cumulative counts of craters down to 100. m, 1. km, 2. km, 5. km, and 16. km diameters to martian epochs. Due to differences in the " standard" crater size-frequency production distributions, a generalized crater-density-based definition to the chronostratigraphic system cannot be provided. For the diameter range used for the boundary definitions, the resulting model absolute age fits vary within 1.5% for a given set of production function and chronology model ages. Crater distributions translated to absolute ages utilizing different curve descriptions can result in absolute age differences exceeding 10%. ?? 2011 Elsevier Inc.

  5. Stratigraphy, structure, absolute age, and paleontology of the upper Pleistocene deposits at Sankaty Head, Nantucket Island, Massachusetts

    USGS Publications Warehouse

    Oldale, Robert N.; Valentine, Page C.; Cronin, T. M.; Spiker, E. C.; Blackwelder, B. W.; Belknap, D.F.; Wehmiller, J. F.; Szabo, B. J.

    1982-01-01

    The Sankaty Head cliff exposes drift of at least two glaciations and interglacial marine deposits. Radiocarbon, amino-acid- racemization, and uranium-thorium analyses were used to determine the absolute ages of the beds. The results indicate that 1) the Sankaty Sand correlates with oxygen-isotope stage 5 (Sangamonian), 2) the underlying drift is older than stage 5 (Illinoian or older) , and 3) the overlying drift is Wisconsinan in age. -from Authors

  6. Using peripheral smear review, age and absolute lymphocyte count as predictors of abnormal peripheral blood lymphocytoses diagnosed by flow cytometry.

    PubMed

    Andrews, Jared M; Cruser, Dan L; Myers, Jerome B; Fernelius, Colby A; Holm, Mitchel T; Waldner, Dale L

    2008-09-01

    Absolute lymphocytosis in the elderly raises the possibility of malignancy and generally warrants further investigation. To better correlate clinical variables with the frequency of neoplastic lymphoid processes in this population, we retrospectively reviewed archived flow cytometric analyses from peripheral blood specimens on patients of 50 years of age and older that had been deemed suspicious for a lymphoproliferative process after peripheral smear review. Age, absolute lymphocyte count (ALC), white blood cell count and relative lymphocyte count were correlated with the results of flow cytometry. Of 71 total cases, 42 (59%) had an abnormal immunophenotype. Independent variables that showed significant differences between normal and abnormal immunophenotype were mean age (p = 0.001) and ALC (p = 0.0032). We combined age and absolute lymphocyte count variables to look for the best possible cutoff values to predict the likelihood of an abnormal immunophenotype. ALC cutoff values of >or=4 x 10(9) cells/L for patients over 67 years of age, and >6.7 x 10(9) cells/L for patients between 50 and 67 years of age, had a high sensitivity for detecting an abnormal immunophenotype. PMID:18798107

  7. Problems determining relative and absolute ages using the small crater population

    NASA Astrophysics Data System (ADS)

    Xiao, Zhiyong; Strom, Robert G.

    2012-07-01

    The small crater populations (diameter smaller than 1 km) are widely used to date planetary surfaces. The reliability of small crater counts is tested by counting small craters at several young and old lunar surfaces, including Mare Nubium and craters Alphonsus, Tycho and Giordano Bruno. Based on high-resolution images from both the Lunar Reconnaissance Orbiter Camera and Kaguya Terrain Camera, small craters in two different diameter ranges are counted for each counting area. Large discrepancies exist in both the cumulative (absolute model ages) and relative plots for the two different size ranges of the same counting areas. The results indicate that dating planetary surfaces using small crater populations is highly unreliable because the contamination of secondaries may invalidate the results of small crater counts. A comparison of the size-frequency distributions of the small crater populations and impact ejected boulders around fresh lunar craters shows the same upturn as typical martian secondaries, which supports the argument that secondaries dominate the small crater populations on the Moon and Mars. Also, the size-frequency distributions of small rayed lunar and martian craters of probable primary origin are similar to that of the Population 2 craters on the inner Solar System bodies post-dating Late Heavy Bombardment. Dating planetary surfaces using the small crater populations requires the separation of primaries from secondaries which is extremely difficult. The results also show that other factors, such as different target properties and the subjective identification of impact craters by different crater counters, may also affect crater counting results. We suggest that dating planetary surfaces using small crater populations should be with highly cautious.

  8. Cosmogenic nuclide age constraints on Middle Stone Age lithics from Niassa, Mozambique

    NASA Astrophysics Data System (ADS)

    Mercader, Julio; Gosse, John C.; Bennett, Tim; Hidy, Alan J.; Rood, Dylan H.

    2012-07-01

    The late phases of the Middle Stone Age (MSA) in the East African Rift System (EARS) are known for their evolutionary shifts and association with bottlenecks, transcontinental expansion, and climatic fluctuations. The chronology of MSA sites contemporaneous with these eco-demographic upheavals is uncertain because of the scarcity of datable sites and the poor understanding of their depositional and erosional histories. We apply terrestrial cosmogenic nuclide dating in a stratigraphic section with a complex exposure history to the study of the Luchamange Beds, a widespread sedimentological unit underlying MSA sites from the shores of Lake Niassa (Mozambican EARS). We use an innovative approach, which may be applicable elsewhere, to calculate their age using a Monte Carlo-based Bayesian model that links depth profiles of 26Al and 10Be, and uses other geomorphic and cosmogenic nuclide age constraints on episodic erosion and burial. The age of the basal Luchamange Beds is 42 + 77/-15 ka, and the MSA occupation on top is 29 + 3/-11 ka. These dates suggest temporal overlap between MSA and the earliest Later Stone Age and diversity in cultural manifestations at the end of the MSA.

  9. Insights from fossil coral U-Th age data from the Last Interglacial: Implications for seawater U-isotope composition and interpretation of absolute ages

    NASA Astrophysics Data System (ADS)

    Dutton, A.; Esat, T. M.

    2011-12-01

    significantly higher than that of modern seawater at sites around the globe, raising the possibility that seawater compositions during the Last Interglacial were also correspondingly higher. Unfortunately, without the traditional U-isotope diagenetic screening criterion it remains difficult to separate out 'altered' corals versus 'unaltered' corals; hence interpretation of the distribution of initial [234U/238U] in this Last Interglacial database requires assumptions about the effects of open-system diagenesis on this distribution. The adopted seawater [234U/238U] value for screening closed-system ages or for calculating ages using an open-system model will ultimately have an effect on the interpretation of the absolute age of the coral(s) in question. Adopting a higher seawater [234U/238U] value than modern seawater will result in an older interpreted age than for the scenario where the modern seawater value is adopted. This observation highlights the need to better characterize past uranium isotope variability in the oceans as we seek to provide increasingly stringent chronological constraints on past sea level change.

  10. 40Ar-39Ar Age Constraints on Volcanism and Tectonism in the Terror Rift of the Ross Sea, Antarctica

    USGS Publications Warehouse

    2007-01-01

    Volcanic sills and dikes inferred from seismic reflection profiles and geophysical studies of the Ross Sea are thought to be related to the rift basins in the region, and their emplacement to be coeval with extension. However, lack of precise geochronology in the Terror Rift of the Ross Sea region has left these inferred relationships poorly constrained and has hindered neotectonic studies, because of the large temporal gaps between seismic reflectors of known ages. New 40Ar/39Ar geochronology presented here for submarine volcanic rocks provides better age constraints for neotectonic interpretations within the Terror Rift. Several samples from seamounts yielded young ages between 156 ± 21 and 122 ± 26 Ka. These ages support interpretations that extension within the Terror Rift was active at least through the Pleistocene. Three evenly spaced samples from the lowermost 100 m of Franklin Island range in age from 3.28 ± 0.04 to 3.73 ± 0.05 Ma. These age determinations demonstrate that construction of a small volcanic edifice such as Franklin Island took at least several hundred thousand years, and therefore that much larger ones in the Erebus Volcanic Province are likely to have taken considerably longer than previously inferred. This warrants caution in applying a limited number of age determinations to define the absolute ages of events in the Ross Sea region

  11. The Aging Mover: A Preliminary Report on Constraints to Action.

    ERIC Educational Resources Information Center

    Williams, Kathleen; Bird, Michael

    1992-01-01

    Examined constraints that might result in locomotion declines in older adults. Videotaped movements of healthy, active females between 20 and 80 years. Those over 60 walked at significantly slower speeds, particularly climbing stairs and used smaller range of speeds than younger individuals. Despite slowing, pattern of coordination between limbs…

  12. Absolute model ages of mantled surfaces in Malea Planum and Utopia Planitia, Mars.

    NASA Astrophysics Data System (ADS)

    Willmes, M.; Hiesinger, H.; Reiss, D.; Zanetti, M.

    2009-04-01

    The surface of Mars is partially covered by a latitude-dependent ice-rich smooth mantle in the middle and high latitudes (±30-60°) [1, 2]. These deposits relate to changes in the obliquity of Mars which have led to major shifts in the Martian climate and repeated global episodes of deposition [3]. The deposits vary in thickness and are usually independent of local geology, topography and elevation. In this study we have determined absolute model ages for the mantled surface units in Utopia Planitia (northern hemisphere) and Malea Planum (southern hemisphere) using crater statistics [4]. These regions show a specific type of mantle degradation called scalloped terrain, and modelled crater retention ages of the easily eroded mantle in these regions reveal the time since the last resurfacing. Images from the High Resolution Imaging Science Experiment (HiRISE) (25-50 cm/pixel spatial resolution) on board the Mars Reconnaissance Orbiter (MRO) were analyzed, continuous areas of smooth mantle were mapped, and small, fresh, unmodified craters were counted. Both regions show degradation features of the mantle in varying degrees. The mantle in Utopia Planitia appears heavily modified by polygonal fractures and scalloped depressions [5]. Scalloped depressions are also found in Malea Planum, but the mantle appears much smoother and less modified by periglacial processes [5, 6]. The study areas totalled 722 km² in Utopia Planitia, and 296 km² in Malea Planum. Model ages for these regions were determined using the chronology function of Hartmann and Neukum [4] and the production function Ivanov [7]. The model ages show that the mantle unit for the area mapped in Utopia Planitia is 0.65 (+0.35/-0.41) to 2.9 (+0.69/-0.75) Myr old and Malea Planum is 3.0 (+1.5/-1.7) to 4.5 (+1.3/-1.4) Myr old, and that both regions represent very recent Amazonian terrain. This is also in agreement with the observed young degradation features described by [6, 8]. We acknowledge that the

  13. Nuclear constraints on the age of the universe

    NASA Technical Reports Server (NTRS)

    Schramm, D. N.

    1983-01-01

    A review is made of how one can use nuclear physics to put rather stringent limits on the age of the universe and thus the cosmic distance scale. The age can be estimated to a fair degree of accuracy. No single measurement of the time since the Big Bang gives a specific, unambiguous age. There are several methods that together fix the age with surprising precision. In particular, there are three totally independent techniques for estimating an age and a fourth technique which involves finding consistency of the other three in the framework of the standard Big Bang cosmological model. The three independent methods are: cosmological dynamics, the age of the oldest stars, and radioactive dating. This paper concentrates on the third of the three methods, and the consistency technique. Previously announced in STAR as N83-34868

  14. Nuclear constraints on the age of the universe

    NASA Technical Reports Server (NTRS)

    Schramm, D. N.

    1982-01-01

    A review is made of how one can use nuclear physics to put rather stringent limits on the age of the universe and thus the cosmic distance scale. The age can be estimated to a fair degree of accuracy. No single measurement of the time since the Big Bang gives a specific, unambiguous age. There are several methods that together fix the age with surprising precision. In particular, there are three totally independent techniques for estimating an age and a fourth technique which involves finding consistency of the other three in the framework of the standard Big Bang cosmological model. The three independent methods are: cosmological dynamics, the age of the oldest stars, and radioactive dating. This paper concentrates on the third of the three methods, and the consistency technique.

  15. Absolute age constraints on the age and tectonics of the Middle and Late Proterozoic Pahrump Group, southern Death Valley, California

    SciTech Connect

    Calzia, J.P. ); Troxel, B.W.

    1993-04-01

    The Pahrump Group unconformably overlies 1.35 Ga granite, is unconformably overlain by the Late Proterozoic Noonday Dolomite, and is divided into the Crystal Spring Formation, the Beck Spring Dolomite, and the Kingston Peak Formation. Contacts between these formations are gradational through several meters of interbedded clastic and carbonate rocks. Lithologic data, sedimentary structures, and fossil assemblages suggest that the Pahrump Group, from middle Crystal Spring to lower Kingston Peak time, was deposited in an intratidal to supratidal environment. Diamictite, volcanic ash, and mono lithologic megabreccia suggest that the middle and the upper members of the Kingston Peak Formation were deposited in a higher energy sedimentary and tectonic environment. Dikes and sills of 1.08 Ga diabase intrude the gneiss and all members of the Crystal Spring Formation; erosional clasts of diabase first appear in the middle Kingston Peak Formation. The diabase sills are up to 450 m thick and have caused at least 20 percent inflation of the Crystal Spring, Beck Spring, and lower Kingston Peak formations. If these sedimentary rocks were deposited at or above wave base, evidence of intraplate rifting or gross stratigraphic inflation is not recorded in the Pahrump stratigraphy until middle and upper Kingston Peak time. Therefore, the stratigraphic and petrologic data suggest that the diabase was emplaced in the Crystal Spring Formation during post-lower but pre-middle Kingston Peak time. The Beck Spring Dolomite and the lower Kingston Peak Formation are older than 1.08 Ga; the contact between the lower and the middle Kingston Peak Formation is a regional disconformity that marks significant changes in the depositional and the tectonic environments of the Pahrump Group at about 1.08 Ga.

  16. Age constraints on fluid inclusions in calcite at Yucca Mountain

    SciTech Connect

    Neymark, Leonid A.; Amelin, Yuri V.; Paces, James B.; Peterman, Zell E.; Whelan, Joseph F.

    2001-04-29

    The {sup 207}Pb/{sup 235}U ages for 14 subsamples of opal or chalcedony layers younger than calcite formed at elevated temperature range between 1.88 {+-} 0.05 and 9.7 {+-} 1.5 Ma with most values older than 6-8 Ma. These data indicate that fluids with elevated temperatures have not been present in the unsaturated zone at Yucca Mountain since about 1.9 Ma and most likely since 6-8 Ma. Discordant U-Pb isotope data for chalcedony subsamples representing the massive silica stage in the formation of the coatings are interpreted using a model of the diffusive loss of U decay products. The model gives an age estimate for the time of chalcedony formation around 10-11 Ma, which overlaps ages of clay minerals formed in tuffs below the water table at Yucca Mountain during the Timber Mountain thermal event.

  17. Predicting Absolute Risk of Type 2 Diabetes Using Age and Waist Circumference Values in an Aboriginal Australian Community

    PubMed Central

    2015-01-01

    Objectives To predict in an Australian Aboriginal community, the 10-year absolute risk of type 2 diabetes associated with waist circumference and age on baseline examination. Method A sample of 803 diabetes-free adults (82.3% of the age-eligible population) from baseline data of participants collected from 1992 to 1998 were followed-up for up to 20 years till 2012. The Cox-proportional hazard model was used to estimate the effects of waist circumference and other risk factors, including age, smoking and alcohol consumption status, of males and females on prediction of type 2 diabetes, identified through subsequent hospitalisation data during the follow-up period. The Weibull regression model was used to calculate the absolute risk estimates of type 2 diabetes with waist circumference and age as predictors. Results Of 803 participants, 110 were recorded as having developed type 2 diabetes, in subsequent hospitalizations over a follow-up of 12633.4 person-years. Waist circumference was strongly associated with subsequent diagnosis of type 2 diabetes with P<0.0001 for both genders and remained statistically significant after adjusting for confounding factors. Hazard ratios of type 2 diabetes associated with 1 standard deviation increase in waist circumference were 1.7 (95%CI 1.3 to 2.2) for males and 2.1 (95%CI 1.7 to 2.6) for females. At 45 years of age with baseline waist circumference of 100 cm, a male had an absolute diabetic risk of 10.9%, while a female had a 14.3% risk of the disease. Conclusions The constructed model predicts the 10-year absolute diabetes risk in an Aboriginal Australian community. It is simple and easily understood and will help identify individuals at risk of diabetes in relation to waist circumference values. Our findings on the relationship between waist circumference and diabetes on gender will be useful for clinical consultation, public health education and establishing WC cut-off points for Aboriginal Australians. PMID:25876058

  18. Towards an absolute chronology for the Aegean iron age: new radiocarbon dates from Lefkandi, Kalapodi and Corinth.

    PubMed

    Toffolo, Michael B; Fantalkin, Alexander; Lemos, Irene S; Felsch, Rainer C S; Niemeier, Wolf-Dietrich; Sanders, Guy D R; Finkelstein, Israel; Boaretto, Elisabetta

    2013-01-01

    The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8(th) century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11(th) century BCE according to the Conventional Aegean Chronology and in the late 12(th) century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11(th) century BCE. PMID:24386150

  19. Constraints on Exposure Ages of Lunar and Asteroidal Regolith Particles

    NASA Technical Reports Server (NTRS)

    Berger, Eve L.; Keller, Lindsay P

    2014-01-01

    Mineral grains in lunar and asteroidal regolith samples provide a unique record of their interaction with the space environment. Exposure to the solar wind results in implantation effects that are preserved in the rims of grains (typically the outermost 100 nm), while impact processes result in the accumulation of vapor-deposited elements, impact melts and adhering grains on particle surfaces. These processes are collectively referred to as space weathering. A critical element in the study of these processes is to determine the rate at which these effects accumulate in the grains during their space exposure. For small particulate samples, one can use the density of solar flare particle tracks to infer the length of time the particle was at the regolith surface (i.e., its exposure age). We have developed a new technique that enables more accurate determination of solar flare particle track densities in mineral grains <50 micron in size that utilizes focused ion beam (FIB) sample preparation combined with transmission electron microscopy (TEM) imaging. We have applied this technique to lunar soil grains from the Apollo 16 site (soil 64501) and most recently to samples from asteroid 25143 Itokawa returned by the Hayabusa mission. Our preliminary results show that the Hayabusa grains have shorter exposure ages compared to typical lunar soil grains. We will use these techniques to re-examine the track density-exposure age calibration from lunar samples reported by Blanford et al. (1975).

  20. Aging increases flexibility of postural reactive responses based on constraints imposed by a manual task

    PubMed Central

    de Lima-Pardini, Andrea Cristina; Coelho, Daniel Boari; Silva, Marina Brito; Azzi, Nametala Maia; Martinelli, Alessandra Rezende; Horak, Fay Bahling; Teixeira, Luis Augusto

    2014-01-01

    This study compared the effect of stability constraints imposed by a manual task on the adaptation of postural responses between 16 healthy elderly (mean age = 71.56 years, SD = 7.38) and 16 healthy young (mean age = 22.94 years, SD = 4.82) individuals. Postural stability was perturbed through unexpected release of a load attached to the participant’s trunk while performing two versions of a voluntary task: holding a tray with a cylinder placed with its flat side down (low constraint) or with its rolling round side down (high constraint). Low and high constraint tasks were performed in alternate blocks of trials. Results showed that young participants adapted muscular activation and kinematics of postural responses in association with previous experience with the first block of manual task constraint, whereas the elderly modulated postural responses based on the current manual constraint. This study provides evidence for flexibility of postural strategies in the elderly to deal with constraints imposed by a manual task. PMID:25520656

  1. Stellar population constraints on the ages of galactic bars

    NASA Astrophysics Data System (ADS)

    James, P. A.; Percival, S. M.

    2016-03-01

    We present a study of the stellar populations within the central regions of four nearby barred galaxies, and use a novel technique to constrain the duration of bar activity. We focus on the star formation `desert', a region within each of these galaxies where star formation appears to have been suppressed by the bar. New Hβ spectroscopic data are presented, and used to produce spectroscopic line indices which are compared with theoretical predictions from population synthesis models for simple stellar populations and temporally truncated star formation histories. This analysis shows that the dearth of star formation activity in these regions appears to have been continuing for at least 1 Gyr, with time-scales of several Gyr indicated for two of the galaxies. This favours models in which strong bars can be long-lived features of galaxies, but our results also indicate a significant diversity in stellar population ages, and hence in the implied histories of bar activity in these four galaxies.

  2. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  3. The Relative and Absolute Ages of Old Globular Clusters in the LCDM Framework

    NASA Astrophysics Data System (ADS)

    Trenti, Michele; Padoan, Paolo; Jimenez, Raul

    2015-08-01

    Old globular clusters (GCs) in the Milky Way have ages of about 13 Gyr, placing their formation time in the reionization epoch. We propose a novel scenario for the formation of these systems based on the merger of two or more atomic cooling halos at high redshift (z\\gt 6). First-generation stars are formed as an intense burst in the center of a minihalo that grows above the threshold for hydrogen cooling (halo mass {M}{{h}}∼ {10}8 {M}ȯ ) by undergoing a major merger within its cooling timescale (∼150 Myr). Subsequent minor mergers and sustained gas infall bring a new supply of pristine gas to the halo center, creating conditions that can trigger new episodes of star formation. The dark-matter halo around the GC is then stripped during assembly of the host-galaxy halo. Minihalo merging is efficient only in a short redshift window, set by the {{Λ }}{CDM} parameters, allowing us to make a strong prediction on the age distribution for old GCs. From cosmological simulations, we derive an average merging redshift < z> =9 and a narrow distribution {{Δ }}z=2, implying average GC age < {t}{age}> =13.0+/- 0.2 {Gyr} including ∼0.2 Gyr of star formation delay. Qualitatively, our scenario reproduces other general old GC properties (characteristic masses and number of objects, metallicity versus galactocentric radius anticorrelation, radial distribution), but unlike age, these generally depend on details of baryonic physics. In addition to improved age measurements, direct validation of the model at z∼ 10 may be within reach with ultradeep gravitationally lensed observations with the James Webb Space Telescope.

  4. The Absolute Age of the Globular Cluster M15 Using Near-infrared Adaptive Optics Images from PISCES/LBT.

    NASA Astrophysics Data System (ADS)

    Monelli, M.; Testa, V.; Bono, G.; Ferraro, I.; Iannicola, G.; Fiorentino, G.; Arcidiacono, C.; Massari, D.; Boutsia, K.; Briguglio, R.; Busoni, L.; Carini, R.; Close, L.; Cresci, G.; Esposito, S.; Fini, L.; Fumana, M.; Guerra, J. C.; Hill, J.; Kulesa, C.; Mannucci, F.; McCarthy, D.; Pinna, E.; Puglisi, A.; Quiros-Pacheco, F.; Ragazzoni, R.; Riccardi, A.; Skemer, A.; Xompero, M.

    2015-10-01

    We present deep near-infrared J, {K}{{s}} photometry of the old, metal-poor Galactic globular cluster M15 obtained with images collected with the LUCI1 and PISCES cameras available at the Large Binocular Telescope (LBT). We show how the use of First Light Adaptive Optics (FLAO) system coupled with the PISCES camera allows us to improve the limiting magnitude by ˜2 mag in {K}{{s}}. By analyzing archival Hubble Space Telescope data, we demonstrate that the quality of the LBT/PISCES color-magnitude diagram is fully comparable with analogous space-based data. The smaller field of view is balanced by the shorter exposure time required to reach a similar photometric limit. We investigated the absolute age of M15 by means of two methods: (i) by determining the age from the position of the main-sequence turnoff (MSTO), and (ii) by the magnitude difference between the MSTO and the well-defined knee detected along the faint portion of the MS. We derive consistent values of the absolute age of M15, that is, 12.9 ± 2.6 Gyr and 13.3 ± 1.1 Gyr, respectively. Observations were carried out using the Large Binocular Telescope at Mount Graham, AZ. The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are the University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; the Ohio State University; and the Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.

  5. Is an absolute level of cortical beta suppression required for proper movement? Magnetoencephalographic evidence from healthy aging.

    PubMed

    Heinrichs-Graham, Elizabeth; Wilson, Tony W

    2016-07-01

    Previous research has connected a specific pattern of beta oscillatory activity to proper motor execution, but no study to date has directly examined how resting beta levels affect motor-related beta oscillatory activity in the motor cortex. Understanding this relationship is imperative to determining the basic mechanisms of motor control, as well as the impact of pathological beta oscillations on movement execution. In the current study, we used magnetoencephalography (MEG) and a complex movement paradigm to quantify resting beta activity and movement-related beta oscillations in the context of healthy aging. We chose healthy aging as a model because preliminary evidence suggests that beta activity is elevated in older adults, and thus by examining older and younger adults we were able to naturally vary resting beta levels. To this end, healthy younger and older participants were recorded during motor performance and at rest. Using beamforming, we imaged the peri-movement beta event-related desynchronization (ERD) and extracted virtual sensors from the peak voxels, which enabled absolute and relative beta power to be assessed. Interestingly, absolute beta power during the pre-movement baseline was much stronger in older relative to younger adults, and older adults also exhibited proportionally large beta desynchronization (ERD) responses during motor planning and execution compared to younger adults. Crucially, we found a significant relationship between spontaneous (resting) beta power and beta ERD magnitude in both primary motor cortices, above and beyond the effects of age. A similar link was found between beta ERD magnitude and movement duration. These findings suggest a direct linkage between beta reduction during movement and spontaneous activity in the motor cortex, such that as spontaneous beta power increases, a greater reduction in beta activity is required to execute movement. We propose that, on an individual level, the primary motor cortices have an

  6. THE DYNAMICAL DISTANCE, RR LYRAE ABSOLUTE MAGNITUDE, AND AGE OF THE GLOBULAR CLUSTER NGC 6266

    SciTech Connect

    McNamara, Bernard J.; McKeever, Jean E-mail: jeanm12@nmsu.edu

    2011-11-15

    The internal proper motion dispersion of NGC 6266 was measured using Hubble Space Telescope Wide Field Planetary Camera 2 images with an epoch difference of eight years. The dispersion was found to be 0.041 {+-} 0.001 arcsec century{sup -1}. This value was then equated to the cluster's radial velocity dispersion of 13.7 {+-} 1.1 km s{sup -1} to yield a distance to NGC 6266 of 7054 {+-} 583 pc. Based on this distance we find that the NGC 6266 RR Lyrae stars have M{sub V} = 0.51 {+-} 0.18 mag. This magnitude is in good agreement with that predicted by the M{sub V} versus [Fe/H] relation found by Benedict et al. Using an average [Fe/H] of -1.25 for NGC 6266, their relation predicts M{sub V} = 0.49 {+-} 0.06. Based on the RR Lyrae M{sub V} versus age relation determined by Chaboyer et al., we estimate that NGC 6266 has an age of 11.4 {+-} 2.2 Gyr.

  7. Age effects on the control of dynamic balance during step adjustments under temporal constraints.

    PubMed

    Nakano, Wataru; Fukaya, Takashi; Kobayashi, Satomi; Ohashi, Yukari

    2016-06-01

    This study investigated the age effects on the control of dynamic balance during step adjustments under temporal constraints. Fifteen young adults and 14 older adults avoided a virtual white planar obstacle by lengthening or shortening their steps under free or constrained conditions. In the anterior-posterior direction, older adults demonstrated significantly decreased center of mass velocity at the swing foot contact under temporal constraints. Additionally, the distances between the 'extrapolated center of mass' position and base of support at the swing foot contact were greater in older adults than young adults. In the mediolateral direction, center of mass displacement was significantly increased in older adults compared with young adults. Consequently, older adults showed a significantly increased step width at the swing foot contact in the constraint condition. Overall, these data suggest that older adults demonstrate a conservative strategy to maintain anterior-posterior stability. By contrast, although older adults are able to modulate their step width to maintain mediolateral dynamic balance, age-related changes in mediolateral balance control under temporal constraints may increase the risk of falls in the lateral direction during obstacle negotiation. PMID:26852293

  8. Borehole magnetostratigraphy, absolute age dating, and correlation of sedimentary rocks, with examples from the Paris Basin, France

    SciTech Connect

    Bouisset, P.M. ); Augustin, A.M. )

    1993-04-01

    Total and CEA have conceived and developed two new logging tools which allow continuous, precise, and accurate in-situ magnetic measurements within weakly magnetized sedimentary rocks encountered in uncased industry drilled wells. The combination of these magnetic measurements permits for the first time continuous determination of natural remanent magnetization (NRM) polarities occurring in the logged section. The resulting well magnetostratigraphic sequence (WMS) which may be recognized from well to well (magnetostratigraphic correlations), may also be correlative to a geomagnetic polarity time scale (GPTS) of reference magnetostratigraphic scale (RMS), given adequate dating tie points and lack of noticeable remagnetizations. Application of this method to the Upper Jurrasic formation in four wells of the Paris basin has yielded promising results for both stratigraphic and near absolute age correlations as well as determination of facies diachronisms. The comparison of results obtained from magnetic measurements and from sequence stratigraphy analysis shows that third-order sequence boundaries may be correlative to geomagnetic reversals, but may also be diachronous in wells 80 km or less apart. The potential of borehole magnetic measurements as presented in this paper is still under investigation. However, these encouraging initial results show that this new investigating and dating method could be of great help in the analysis of subsurface stratigraphy by extending the concepts of magnetostratigraphy from the outcrops and laboratory directly into borehole logging. 81 refs., 18 figs.

  9. General constraints on the age and chemical evolution of the Galaxy

    NASA Technical Reports Server (NTRS)

    Meyer, Bradley S.; Schramm, David N.

    1986-01-01

    The formalism of Schramm and Wasserburg (1970) for determining the mean age of the elements is extended to develop as model-independent a range for the Galaxy's age as possible that takes all nuclear and meteoritic data uncertainties into account. A model-independent upper limit to that age is derived from an expansion of the equation giving the mean age of the elements in moments of the normalized effective nucleosynthesis rate. This limit depends only on the ratio of the mean time of formation of the elements to the total duration of nucleosynthesis, and on model-independent data. It is shown tht the Th-232/U-238. U-235/U-238, and Pu-244/U-238 chronometric pairs can give constraints on the relative rate of nucleosynthesis over the history of the synthesis of the solar system material.

  10. Reassessing The Fundamentals New Constraints on the Evolution, Ages and Masses of Neutron Stars

    NASA Astrophysics Data System (ADS)

    Kızıltan, Bülent

    2011-09-01

    The ages and masses of neutron stars (NSs) are two fundamental threads that make pulsars accessible to other sub-disciplines of astronomy and physics. A realistic and accurate determination of these two derived parameters play an important role in understanding of advanced stages of stellar evolution and the physics that govern relevant processes. Here I summarize new constraints on the ages and masses of NSs with an evolutionary perspective. I show that the observed P-Ṗ demographics is more diverse than what is theoretically predicted for the standard evolutionary channel. In particular, standard recycling followed by dipole spin-down fails to reproduce the population of millisecond pulsars with higher magnetic fields (B > 4 × 108 G) at rates deduced from observations. A proper inclusion of constraints arising from binary evolution and mass accretion offers a more realistic insight into the age distribution. By analytically implementing these constraints, I propose a ``modified'' spin-down age (τ~) for millisecond pulsars that gives estimates closer to the true age. Finally, I independently analyze the peak, skewness and cutoff values of the underlying mass distribution from a comprehensive list of radio pulsars for which secure mass measurements are available. The inferred mass distribution shows clear peaks at 1.35 Msolar and 1.50 Msolar for NSs in double neutron star (DNS) and neutron star-white dwarf (NS-WD) systems respectively. I find a mass cutoff at 2 Msolar for NSs with WD companions, which establishes a firm lower bound for the maximum mass of NSs.

  11. Age constraints from northwest Russia on the global accumulation of carbon during the Palaeoproterozoic Shunga event

    NASA Astrophysics Data System (ADS)

    Martin, A. P.; Condon, D. J.; Prave, A. R.; Lepland, A.; Melezhik, V. A.

    2012-04-01

    The Palaeoproterozoic Shunga event records significant organic-carbon accumulation in sediments correlated between the type-locality in northwest Russia's Onega Basin, the Francevillian series of Gabon, and Indian Palaeoproterozoic sections. The estimated burial of >25 x 10E +10 tonnes of C in the Shunga event is significant and hypotheses have suggested this accumulation as one causal mechanism to the large positive Lomagundi-Jatuli positive carbon isotope excursion (CIE) of marine carbonates. Conversely, is has been suggested that the Shunga event post-dates the termination (at c. 2060 Ma) of the Lomagundi-Jatuli CIE and the two are not overlapping in time. Discrimination between these competing theories requires precise and accurate chronologies for the stratigraphic successions hosting the proxy records. We present new age constraints from a combination of primary volcanic rocks and sedimentary units recording the Shunga event, from the well preserved Palaeoproterozoic sections in the Pechenga Greenstone Belt (Kola craton) and Onega Paleo Basin (Karelia craton) northwest Russia, to further elucidate the unresolved question of timing between the Shunga event and the Lomagundi-Jatuli CIE. Carbon accumulations of the Shunga event are recorded in the Pilgujärvi Sedimentary Formation of the Pechenga Greenstone Belt. Felsic lava flows and pyroclastic rocks, and mafic pyroclastic rocks, in the Pilgujärvi Volcanic Formation overlying the Pilgujärvi sediments yield zircons with concordant U-Pb ages between c. 1970 and 1903 Ma. In the Pilgujärvi Sedimentary Formation detrital zircons yield a minimum age of c. 1922 Ma, equivalent to a minimum c. 1915 Ma age of detrital zircons in the underlying Kolosjoki Sedimentary Formation. Thrust over the main units of the Pechenga Greenstone Belt is a tectonic melange known as the South Pechenga Zone where zircons from an intermediate volcanic rock yield the first age from this zone at c. 1930 Ma. Samples from the Onega Basin are

  12. Linguistic Constraints on Children's Overt Marking of BE by Dialect and Age

    PubMed Central

    Roy, Joseph; Oetting, Janna B.; Moland, Christy Wynn

    2013-01-01

    Purpose Overt marking of BE in nonmainstream adult dialects of English is influenced by a number of linguistic constraints, including the structure's person, number, tense, contractibility, and grammatical function. In the current study, we examined the effects of these constraints on overt marking of BE in children as a function of their nonmainstream English dialect and age. Methods The data were language samples from 62 children, aged four to six years; 24 spoke African American English (AAE) and 38 spoke Southern White English (SWE). Analyses included analysis of variance and logistic regression. Results Rates of overt marking varied by the children's dialect but not their age. Although the person, number, tense, and grammatical function of BE influenced the children's rates of marking, the nature and magnitude of the influence differed by the children's dialect. For AAE-speaking children, contractibility also influenced their marking of BE. Conclusions Consistent with the adult literature, the AAE- and SWE-speaking children marked BE in ways that differed from each other and from what has been documented for child speakers of Mainstream American English. These findings show stability in the use of BE in AAE and SWE that spans different generations and different dialect communities. PMID:23275400

  13. Constraints on the dimensionless age of the Universe from Pan-STARRS supernovae

    NASA Astrophysics Data System (ADS)

    Avelino, Arturo; Kirshner, Robert P.; Scolnic, Daniel

    2014-06-01

    We present the constraints on the dimensionless age of the universe H_o t_o determined from the latest compilation of Type Ia Supernovae (SN Ia) of the Pan-STARRS1 Medium Deep Survey, combined with low-z supernovae from the CfA, Carnegie, and other sources.The cosmological fit to these SN Ia, assuming a spatially flat universe as suggested by Planck, yields a value of H_o t_o = 1.039 +0.04 -0.05.In this talk we briefly discuss the procedure and implications of this result.

  14. Luminescence dating and palaeomagnetic age constraint on hominins from Sima de los Huesos, Atapuerca, Spain.

    PubMed

    Arnold, Lee J; Demuro, Martina; Parés, Josep M; Arsuaga, Juan Luis; Aranburu, Arantza; Bermúdez de Castro, José María; Carbonell, Eudald

    2014-02-01

    Establishing a reliable chronology on the extensive hominin remains at Sima de los Huesos is critical for an improved understanding of the complex evolutionary histories and phylogenetic relationships of the European Middle Pleistocene hominin record. In this study, we use a combination of 'extended-range' luminescence dating techniques and palaeomagnetism to provide new age constraint on sedimentary infills that are unambiguously associated with the Sima fossil assemblage. Post-infrared-infrared stimulated luminescence (pIR-IR) dating of K-feldspars and thermally transferred optically stimulated luminescence (TT-OSL) dating of individual quartz grains provide weighted mean ages of 433 ± 15 ka (thousands of years) and 416 ± 19 ka, respectively, for allochthonous sedimentary horizons overlying the hominin-bearing clay breccia. The six replicate luminescence ages obtained for this deposit are reproducible and provide a combined minimum age estimate of 427 ± 12 ka for the underlying hominin fossils. Palaeomagnetic directions for the luminescence dated sediment horizon and underlying fossiliferous clays display exclusively normal polarities. These findings are consistent with the luminescence dating results and confirm that the hominin fossil horizon accumulated during the Brunhes Chron, i.e., within the last 780 ka. The new bracketing age constraint for the Sima hominins is in broad agreement with radiometrically dated Homo heidelbergensis fossil sites, such as Mauer and Arago, and suggests that the split of the H. neanderthalensis and H. sapiens lineages took place during the early Middle Pleistocene. More widespread numerical dating of key Early and Middle Pleistocene fossil sites across Europe is needed to test and refine competing models of hominin evolution. The new luminescence chronologies presented in this study demonstrate the versatility of TT-OSL and pIR-IR techniques and the potential role they could play in helping to refine evolutionary

  15. Age constraints of the Wassa and Benso mesothermal gold deposits, Ashanti Belt, Ghana, West Africa

    NASA Astrophysics Data System (ADS)

    Parra-Avila, Luis A.; Bourassa, Yan; Miller, John; Perrouty, Stéphane; Fiorentini, Marco L.; Campbell McCuaig, T.

    2015-12-01

    The Ashanti Belt in Ghana hosts numerous multi-million ounce gold deposits and is one of the most richly gold endowed Paleoproterozoic belts of the West African Craton. This work shows that the Wassa mineralized intrusion is part of the Sefwi Group. This unit at Wassa is strongly magnetic and show a distinctly high response in regional magnetic data sets compared to other units of equivalent age within the belt. The unit is inferred to be a lateral extension of an exposed fragment of what defines the substrate to the Tarkwa Basin sediments. The Wassa deposit, located in the eastern limb of the belt, is hosted within mafic to intermediate volcanic flows that are interbedded with minor horizons of volcaniclastics, clastic sediments. The clastic sediments include wackes and magnetite rich sedimentary layers, presumably derived from banded iron formations. The previously described sequence is intruded by syn-volcanic mafic intrusives and felsic porphyries rocks that are all part of the Birimian stratigraphy. Two new key SHRIMP II U-Pb ages were determined as part of this study: a new age of 2191 ± 6 Ma was determined on magmatic zircon grains of the Wassa porphyry host rock, which now represents the oldest known felsic intrusion hosting gold mineralization in the Ashanti Belt region. The Benso gold deposit system, which is located in the eastern limb of the Ashanti Belt approximately 38 km southwest of Wassa is hosted within a series of volcanic units intruded by mafic to intermediate units. A SHRIMP II U-Pb age of 2157 ± 5 Ma was determined from magmatic zircons obtained from a granodiorite of the G-Zone of the Benso deposit. This granodiorite is the main host rock for gold mineralization and thus the age provides an upper constraint for mineral emplacement. The newly determined ages provide an upper constraint for the gold mineralization within this region of the Ashanti Belt. They also support recent structural studies that have interpreted that the Wassa

  16. Changes in the constraints of semantic and syntactic congruity on memory across three age groups.

    PubMed

    Toyota, H

    2001-06-01

    20 college undergraduates, 25 sixth-grade, and 31 second-grade students studied targets embedded in three types of sentence contexts and then performed free recall and cued recall tests. Although there were no differences in performance of free recall among sentence types within each age group, the differences in cued recall among sentence types were observed. For sixth graders and undergraduates, both semantically congruous/syntactically congruous sentences and semantically incongruous/syntactically congruous sentences led to a better cued recall of targets than semantically incongruous/syntactically incongruous sentences. Second graders performed better in a cued recall of targets in semantically congruous/syntactically congruous sentences than for the other two sentence types. The results were interpreted as indicating changes across age groups in constraints of semantic and syntactic congruity on the spreading activation of targets in memory. PMID:11453195

  17. ON A NEW NEAR-INFRARED METHOD TO ESTIMATE THE ABSOLUTE AGES OF STAR CLUSTERS: NGC 3201 AS A FIRST TEST CASE

    SciTech Connect

    Bono, G.; Di Cecco, A.; Sanna, N.; Buonanno, R.; Stetson, P. B.; VandenBerg, D. A.; Calamida, A.; Amico, P.; Marchetti, E.; D'Odorico, S.; Gilmozzi, R.; Dall'Ora, M.; Iannicola, G.; Caputo, F.; Corsi, C. E.; Ferraro, I.; Monelli, M.; Walker, A. R.; Zoccali, M.; Degl'Innocenti, S.

    2010-01-10

    We present a new method to estimate the absolute ages of stellar systems. This method is based on the difference in magnitude between the main-sequence turnoff (MSTO) and a well-defined knee located along the lower main sequence (MSK). This feature is caused by the collisionally induced absorption of molecular hydrogen, and it can easily be identified in near-infrared (NIR) and in optical-NIR color-magnitude diagrams of stellar systems. We took advantage of deep and accurate NIR images collected with the Multi-Conjugate Adaptive Optics Demonstrator temporarily available on the Very Large Telescope and of optical images collected with the Advanced Camera for Surveys Wide Field Camera on the Hubble Space Telescope and with ground-based telescopes to estimate the absolute age of the globular NGC 3201 using both the MSTO and the {delta}(MSTO-MSK). We have adopted a new set of cluster isochrones, and we found that the absolute ages based on the two methods agree to within 1{sigma}. However, the errors of the ages based on the {delta}(MSTO-MSK) method are potentially more than a factor of 2 smaller, since they are not affected by uncertainties in cluster distance or reddening. Current isochrones appear to predict slightly bluer ({approx}0.05 mag) NIR and optical-NIR colors than observed for magnitudes fainter than the MSK.

  18. New Lu-Hf and Pb-Pb age constraints on the earliest animal fossils

    NASA Astrophysics Data System (ADS)

    Barfod, Gry H.; Albarède, Francis; Knoll, Andrew H.; Xiao, Shuhai; Télouk, Philippe; Frei, Robert; Baker, Joel

    2002-07-01

    The Neoproterozoic Doushantuo Formation, South China, preserves a unique assemblage of early multicellular fossils and overlies rocks, which are thought to have formed during an ice age of global extent. The age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the Proterozoic Eon. Until now, direct dating of sedimentary formations such as the Doushantuo has been difficult and associated with large uncertainties. Here, we show that dating of Doushantuo phosphorites by a novel Lu-Hf dating method and conventional Pb-Pb geochronometry independently yield ages of 584±26 Ma and 599.3±4.2 Ma, respectively. These ages are in agreement with bio- and chemostratigraphical observations and show that the Doushantuo animal remains predate diverse Ediacaran fossil assemblages, making them the oldest unambiguous remains of metazoans currently known. Furthermore, the Pb-Pb age for the post-glacial Doushantuo rocks suggests that the Neoproterozoic glaciation in China might predate glacial rocks in Eastern North America commonly associated with the younger (Marinoan) of two major Neoproterozoic glaciations. The combination of Lu-Hf and Pb-Pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on Proterozoic biological and environmental history.

  19. Absolute vs. weight-related maximum oxygen uptake in firefighters: fitness evaluation with and without protective clothing and self-contained breathing apparatus among age group.

    PubMed

    Perroni, Fabrizio; Guidetti, Laura; Cignitti, Lamberto; Baldari, Carlo

    2015-01-01

    During fire emergencies, firefighters wear personal protective devices (PC) and a self-contained breathing apparatus (S.C.B.A.) to be protected from injuries. The purpose of this study was to investigate the differences of aerobic level in 197 firefighters (age: 34±7 yr; BMI: 24.4±2.3 kg.m-2), evaluated by a Queen's College Step field Test (QCST), performed with and without fire protective garments, and to analyze the differences among age groups (<25 yr; 26-30 yr, 31-35 yr, 36-40 yr and >40 yr). Variance analysis was applied to assess differences (p < 0.05) between tests and age groups observed in absolute and weight-related values, while a correlation was examined between QCST with and without PC+S.C.B.A. The results have shown that a 13% of firefighters failed to complete the test with PC+S.C.B.A. and significant differences between QCST performed with and without PC+S.C.B.A. in absolute (F(1,169) = 42.6, p < 0.0001) and weight-related (F(1,169) = 339.9, p < 0.0001) terms. A better correlation has been found in L•min-1 (r=0.67) than in ml•kg-1•min-1 (r=0.54). Moreover, we found significant differences among age groups both in absolute and weight-related values. The assessment of maximum oxygen uptake of firefighters in absolute term can be a useful tool to evaluate the firefighters' cardiovascular strain. PMID:25764201

  20. Bootstrap-Bayesian OSL approach for poorly-bleached sediment sequences tested with dendrochronological age constraints

    NASA Astrophysics Data System (ADS)

    Wallinga, J.; Den Ouden, J.; Cunningham, A. C.; Copini, P.; Versendaal, A. J.; Sass-Klaassen, U. G. W.; Bos, G.; Beerens, A. M. A. J.; Riksen, M. J. P. M.

    2012-04-01

    Optically stimulated luminescence (OSL) dating is widely accepted as a cornerstone dating method for sediments. The method is particularly suitable for aeolian sediments formed between 10 and 100 ka, but is also widely applied to non-ideal deposits. Where light exposure prior to burial is insufficient for complete resetting of the OSL signal in all grains, additional processing is needed to determine accurate burial ages. The Minimum Age Model (MAM; Galbraith et al., 1999) has proven to be very powerful for such analysis, but results on sequences of poorly-bleached samples indicate that MAM uncertainty estimates are too optimistic. We have recently proposed a method to improve MAM uncertainty estimates (Cunningham & Wallinga, 2012). This method involves repeated calculation of the MAM result, with slightly changing input data and model parameters. Resulting uncertainty ranges are wider and more realistic than those of the standard MAM. Moreover, the approach allows construction of probability density distributions of age which can be used for Bayesian modelling (e.g. Oxcal) to combine data of different samples and/or data obtained using other methods. Here we explore the possibilities of the bootstrapped MAM approach combined with Bayesian analysis by detailed investigation of a 2-m thick sequence of aeolian deposits formed during the past 150 years. Processed OSL results on ten samples taken in a vertical sequence compare favourably with dendrochronological age constraints on stem discs taken from buried sections of the tree.

  1. New age constraints for the geodynamic evolution of the Sistan Suture Zone, eastern Iran

    NASA Astrophysics Data System (ADS)

    Bröcker, Michael; Fotoohi Rad, Gholamreza; Burgess, Ray; Theunissen, Stephanie; Paderin, Ilya; Rodionov, Nikolay; Salimi, Zohre

    2013-06-01

    The Sistan Suture Zone (SSZ) in eastern Iran extends as a N-S trending belt over more than 700 km along the border area between Iran and Afghanistan. The SSZ formed as a result of eastward-directed subduction of a Neotethyan ocean basin beneath the Afghan block and includes a tectonic mélange consisting of disrupted meta-ophiolitic rocks within a low-grade matrix of ultramafic, mafic and pelitic schists. Some mélange blocks were affected by eclogite-, blueschist- and/or epidote amphibolite-facies P-T conditions. Understanding of the petrological and geochronological record of these rocks plays a key role in unravelling the geodynamic evolution of the SSZ. The main aim of the present study was to assess the geological significance of previously published 40Ar/39Ar ages (c. 116-139 Ma) which have not provided robust age constraints for geodynamic reconstructions on a regional scale. For this purpose, samples were collected within a NNW-SSE trending belt spanning a distance of c. 120 km that exposes the major occurrences of high-pressure/low temperature rocks and epidote amphibolites. Multi-point Rbsbnd Sr mineral isochrons indicate a regional consistent pattern with ages ranging between c. 83 and c. 87 Ma for eight samples representing different metamorphic grade and widely separated locations (weighted mean = 85.7 ± 0.8 Ma). Additional 40Ar/39Ar dating for five of these samples yielded in most cases ages that are identical to the Rbsbnd Sr results within analytical uncertainty. For one sample the 40Ar/39Ar age of 81.3 ± 1.3 Ma is about 3 myr younger than the corresponding Rbsbnd Sr age. A still younger Rbsbnd Sr age of 78.9 ± 0.5 Ma was determined for a retrograde epidote-biotite assemblage in an overprinted domain of an eclogite. Ion probe Usbnd Pb zircon ages for two eclogites and two meta-acidic rocks from the mélange yielded weighted mean 206Pb/238U ages of 87.3 ± 1.4 Ma, 86.1 ± 1.5 Ma, 88.7 ± 1.4 Ma and 87.2 ± 1.2 Ma, respectively. The results of this

  2. Age constraints for Palaeolithic cave art by U-Th dating of thin carbonate crusts

    NASA Astrophysics Data System (ADS)

    Hoffmann, Dirk; Pike, Alistair; Garcia-Diez, Marcos; Pettitt, Paul; Zilhão, João

    2015-04-01

    U-series dating is an important geochronological tool which is widely applied for instance in speleothem based palaeoclimate research. It has also great potential to provide age constraints for Archaeology, especially for sites or artefacts in cave environments. We present our methods to conduct precise U-Th dating of calcite crusts that formed on top of cave paintings. Recent developments in multi-collector (MC) inductively coupled plasma mass spectrometry (ICPMS) U-series dating greatly improved the precision of this method, and sample sizes needed to obtain reliable results were significantly reduced. Based on these developments the U-series technique can be applied for accurate dating of thin calcite crusts covering cave art at many sites, while taking care not to harm the art underneath. The method provides minimum ages for the covered art and, where possible, also maximum ages by dating the flowstone layer the art is painted on. The U-Th method has been used in a number of recent projects to date calcite precipitates above and occasionally below cave paintings in Spain. Initial results from Cantabria have shown that the earliest dated paintings are older than 41.4 ± 0.6 ka, dating at least to the Early Aurignacian period and present a far longer chronology than that based so far on radiocarbon dating. Here we outline our methodology and the steps we take to demonstrate the reliability of U-Th dates, and present some recent results of our ongoing U-Th dating programme.

  3. The κ Andromedae system: new constraints on the companion mass, system age, and further multiplicity

    SciTech Connect

    Hinkley, Sasha; David, Trevor; Hillenbrand, Lynne A.; Pueyo, Laurent; Faherty, Jacqueline K.; Oppenheimer, Ben R.; Brenner, Douglas; Veicht, Aaron; Nilsson, Ricky; Mamajek, Eric E.; Kraus, Adam L.; Rice, Emily L.; Ireland, Michael J.; Vasisht, Gautam; Cady, Eric; Roberts, Jennifer E.; Zimmerman, Neil; Parry, Ian R.; Beichman, Charles; Dekany, Richard; and others

    2013-12-20

    κ Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 ± 2 AU was recently announced. In this work, we present the first spectrum of the companion, 'κ And B,' using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ∼2000 K as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and T {sub eff} measurements of the host star to argue that the κ And system has an isochronal age of 220 ± 100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of κ And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive. In addition, we use Keck aperture masking interferometry combined with published radial velocity measurements to rule out the existence of any tight stellar companions to κ And A that might be responsible for the system's overluminosity. Further, we show that luminosity enhancements due to a nearly 'pole-on' viewing angle coupled with extremely rapid rotation is unlikely. κ And A is thus consistent with its slightly evolved luminosity class (IV), and we propose here that κ And, with a revised age of 220 ± 100 Myr, is an interloper to the 30 Myr Columba association with which it was previously associated. The photometric and spectroscopic evidence for κ And B combined with our reassessment of the system age implies a substellar companion mass of 50{sub −13}{sup +16} M {sub Jup}, consistent with a brown dwarf rather than a planetary-mass companion.

  4. The κ Andromedae System: New Constraints on the Companion Mass, System Age, and Further Multiplicity

    NASA Astrophysics Data System (ADS)

    Hinkley, Sasha; Pueyo, Laurent; Faherty, Jacqueline K.; Oppenheimer, Ben R.; Mamajek, Eric E.; Kraus, Adam L.; Rice, Emily L.; Ireland, Michael J.; David, Trevor; Hillenbrand, Lynne A.; Vasisht, Gautam; Cady, Eric; Brenner, Douglas; Veicht, Aaron; Nilsson, Ricky; Zimmerman, Neil; Parry, Ian R.; Beichman, Charles; Dekany, Richard; Roberts, Jennifer E.; Roberts, Lewis C., Jr.; Baranec, Christoph; Crepp, Justin R.; Burruss, Rick; Wallace, J. Kent; King, David; Zhai, Chengxing; Lockhart, Thomas; Shao, Michael; Soummer, Rémi; Sivaramakrishnan, Anand; Wilson, Louis A.

    2013-12-01

    κ Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 ± 2 AU was recently announced. In this work, we present the first spectrum of the companion, "κ And B," using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ~2000 K as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and T eff measurements of the host star to argue that the κ And system has an isochronal age of 220 ± 100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of κ And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive. In addition, we use Keck aperture masking interferometry combined with published radial velocity measurements to rule out the existence of any tight stellar companions to κ And A that might be responsible for the system's overluminosity. Further, we show that luminosity enhancements due to a nearly "pole-on" viewing angle coupled with extremely rapid rotation is unlikely. κ And A is thus consistent with its slightly evolved luminosity class (IV), and we propose here that κ And, with a revised age of 220 ± 100 Myr, is an interloper to the 30 Myr Columba association with which it was previously associated. The photometric and spectroscopic evidence for κ And B combined with our reassessment of the system age implies a substellar companion mass of 50^{+16}_{-13} M Jup, consistent with a brown dwarf rather than a planetary-mass companion.

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

    NASA Astrophysics Data System (ADS)

    Irmis, R. B.; Mundil, R.

    2011-12-01

    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

  6. Climate and soil-age constraints on nutrient uplift by plants.

    NASA Astrophysics Data System (ADS)

    Porder, S.; Chadwick, O. A.

    2007-12-01

    We analyzed changes in nutrient availability and elemental losses from the entire weathering zone at 28 sites arrayed across climatic and soil-age gradients on the island of Hawai'i. The sites are located on three basaltic lava flows (10, 170, and 350 ky) each of which crosses a precipitation gradient from <500 to 2,500 mm yr- 1. The results identify a sweet spot of plant nutrient uplift where nutrient cations and phosphorus are retained in upper horizons as a result of plant activity. The gradients also elucidate several abiotic constraints on plant- driven retention of nutrients. At the dry sites (<750 mm yr-1on all three flows, plant slow the loss of nutrient (e.g. potassium) vs. non-nutrient (e.g. sodium) cations, but the effect is small because of low plant cover and productivity. At intermediate rainfall (750 - 1300 mm yr-1) plants substantially enrich both nutrient cations and P in the upper soils, an effect that increases with flow age. In contrast, at high rainfall (>1500 mm yr-1), the effect of plants on nutrient distributions diminishes with soil age and is largely absent after 350 ky of soil development. Unlike the major plant macronutrients, the distribution of the transition metals iron (Fe) and aluminum (Al) is driven more by chemical reactions than by plant uptake. Dry sites exhibit very little movement of either element, even after 350 ky of soil development. However at high rainfall the older flows show substantial Al and Fe translocations, and wet sites on all three flows have increased Al on soil exchange sites. These transition metals are key constituents of the secondary minerals that strongly influence the availability of cations and P to plants. The loss of Fe and Al is highly correlated with the loss of P in the older and wetter sites, and increased Al on exchange sites limits the availability of nutrient cations to plants. Thus redox driven redistribution of Fe and acid solublization of Al place a further abiotic constraint on nutrient

  7. Southernmost Andes and South Georgia Island, North Scotia Ridge: Zircon U-Pb and muscovite {40Ar }/{39Ar } age constraints on tectonic evolution of Southwestern Gondwanaland

    NASA Astrophysics Data System (ADS)

    Mukasa, Samuel B.; Dalziel, Ian W. D.

    1996-11-01

    Zircon U-Pb and muscovite {40Ar }/{39Ar } isotopic ages have been determined on rocks from the southernmost Andes and South Georgia Island, North Scotia Ridge, to provide absolute time constraints on the kinematic evolution of southwestern Gondwanaland, until now known mainly from stratigraphic relations. The U-Pb systematics of four zircon fractions from one sample show that proto-marginal basin magmatism in the northern Scotia arc, creating the peraluminous Darwin granite suite and submarine rhyolite sequences of the Tobifera Formation, had begun by the Middle Jurassic (164.1 ± 1.7 Ma). Seven zircon fractions from two other Darwin granites are discordant with non-linear patterns, suggesting a complex history of inheritances and Pb loss. Reference lines drawn through these points on concordia diagrams give upper intercept ages of ca. 1500 Ma, interpreted as a minimum age for the inherited zircon component. This component is believed to have been derived from sedimentary rocks in the Gondwanaland margin accretionary wedge that forms the basement of the region, or else directly from the cratonic "back stop" of that wedge. Ophiolitic remnants of the Rocas Verdes marginal basin preserved in the Larsen Harbour complex on South Georgia yield the first clear evidence that Gondwanaland fragmentation had resulted in the formation of oceanic crust in the Weddell Sea region by the Late Jurassic (150 ± 1 Ma). The geographic pattern in the observed age range of 8 to 13 million years in these ophiolitic materials, while not definitive, is in keeping with propagation of the marginal basin floor northwestward from South Georgia Island to the Sarmiento Complex in southern Chile. Rocks of the Beagle granite suite, emplaced post-tectonically within the uplifted marginal basin floor, have complex zircon U-Pb systematics with gross discordances dominated by inheritances in some samples and Pb loss in others. Of eleven samples processed, only two had sufficient amounts of zircon for

  8. Using a Novel Absolute Ontogenetic Age Determination Technique to Calculate the Timing of Tooth Eruption in the Saber-Toothed Cat, Smilodon fatalis

    PubMed Central

    Wysocki, M. Aleksander; Feranec, Robert S.; Tseng, Zhijie Jack; Bjornsson, Christopher S.

    2015-01-01

    Despite the superb fossil record of the saber-toothed cat, Smilodon fatalis, ontogenetic age determination for this and other ancient species remains a challenge. The present study utilizes a new technique, a combination of data from stable oxygen isotope analyses and micro-computed tomography, to establish the eruption rate for the permanent upper canines in Smilodon fatalis. The results imply an eruption rate of 6.0 millimeters per month, which is similar to a previously published average enamel growth rate of the S. fatalis upper canines (5.8 millimeters per month). Utilizing the upper canine growth rate, the upper canine eruption rate, and a previously published tooth replacement sequence, this study calculates absolute ontogenetic age ranges of tooth development and eruption in S. fatalis. The timing of tooth eruption is compared between S. fatalis and several extant conical-toothed felids, such as the African lion (Panthera leo). Results suggest that the permanent dentition of S. fatalis, except for the upper canines, was fully erupted by 14 to 22 months, and that the upper canines finished erupting at about 34 to 41 months. Based on these developmental age calculations, S. fatalis individuals less than 4 to 7 months of age were not typically preserved at Rancho La Brea. On the whole, S. fatalis appears to have had delayed dental development compared to dental development in similar-sized extant felids. This technique for absolute ontogenetic age determination can be replicated in other ancient species, including non-saber-toothed taxa, as long as the timing of growth initiation and growth rate can be determined for a specific feature, such as a tooth, and that growth period overlaps with the development of the other features under investigation. PMID:26132165

  9. New geological and palaeontological age constraint for the gorilla-human lineage split.

    PubMed

    Katoh, Shigehiro; Beyene, Yonas; Itaya, Tetsumaru; Hyodo, Hironobu; Hyodo, Masayuki; Yagi, Koshi; Gouzu, Chitaro; WoldeGabriel, Giday; Hart, William K; Ambrose, Stanley H; Nakaya, Hideo; Bernor, Raymond L; Boisserie, Jean-Renaud; Bibi, Faysal; Saegusa, Haruo; Sasaki, Tomohiko; Sano, Katsuhiro; Asfaw, Berhane; Suwa, Gen

    2016-02-11

    The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidation of African ape and human origins, but few fossil assemblages of this period have been reported from sub-Saharan Africa. Since the 1970s, the Chorora Formation, Ethiopia, has been widely considered to contain ~10.5 million year (Myr) old mammalian fossils. More recently, Chororapithecus abyssinicus, a probable primitive member of the gorilla clade, was discovered from the formation. Here we report new field observations and geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7 Ma. The C. abyssinicus fossils are ~8.0 Myr old, forming a revised age constraint of the human-gorilla split. Other Chorora fossils range in age from ~8.5 to 7 Ma and comprise the first sub-Saharan mammalian assemblage that spans this period. These fossils suggest indigenous African evolution of multiple mammalian lineages/groups between 10 and 7 Ma, including a possible ancestral-descendent relationship between the ~9.8 Myr old Nakalipithecus nakayamai and C. abyssinicus. The new chronology and fossils suggest that faunal provinciality between eastern Africa and Eurasia had intensified by ~9 Ma, with decreased faunal interchange thereafter. The Chorora evidence supports the hypothesis of in situ African evolution of the Gorilla-Pan-human clade, and is concordant with the deeper divergence estimates of humans and great apes based on lower mutation rates of ~0.5 × 10(-9) per site per year (refs 13 - 15). PMID:26863981

  10. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  11. Investigation of origin for seawater intrusion using geophysical well logs and absolute ages of volcanic cores in the eastern part of Jeju Island

    NASA Astrophysics Data System (ADS)

    Hwang, Seho; Shin, Jehyun

    2010-05-01

    Jeju located in the southern extremity of Korea is volcanic island, one of best-known tourist attractions in Korea. Jeju Province operates the monitoring boreholes for the evaluation of groundwater resources in coastal area. Major rock types identified from drill cores are trachybasalt, acicular basalt, scoria, hyalocastite, tuff, unconsolidated U formation, and seoguipo formation and so on. Various conventional geophysical well loggings including radioactive logs (natural gamma log, dual neutron log, and gamma-gamma log), electrical log (or electromagnetic induction log), caliper log, fluid temperature/ conductivity log, and televiewer logs have been conducted to identify basalt sequences and permeable zone, and verify seawater intrusion in monitoring boreholes. The conductivity logs clearly show the fresh water-saline water boundaries, but we find it hard to identify the permeable zones because of the mixed groundwater within the boreholes. Temperature gradient logs are mostly related with lithologic boundaries and permeable zones intersected by boreholes of eastern coasts. The wide range of periodic electrical conductivity logging in the deeper depth of monitoring boreholes indicates the possibility of submarine groundwater discharge. However we did not clearly understand the origin of seawater intrusion in the eastern coast until now. So we analysis the electrical conductivity profiles, record of sea-level change and 40Ar/39Ar absolute ages of volcanic rock cores from twenty boreholes in east coast. From comparing absolute ages of volcanic rock cores and sea-level of their ages, we find that the almost ages of depth showing high salinity groundwater are about 100 Ka, and from 130Ka to about 180Ka. The former is after the interglacial period and the latter is illinoian. These results indicate that the abrupt raising of sea level after illinoian formed the regional coast, and the zone of present seawater intrusion also are above the depth of illinoin period. So

  12. Linguistic Constraints on Children's Overt Marking of "BE" by Dialect and Age

    ERIC Educational Resources Information Center

    Roy, Joseph; Oetting, Janna B.; Wynn Moland, Christy

    2013-01-01

    Purpose: Overt marking of "BE" in nonmainstream adult dialects of English is influenced by a number of linguistic constraints, including the structure's person, number, tense, contractibility, and grammatical function. In the current study, the authors examined the effects of these constraints on overt marking of "BE" in…

  13. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  14. Constraints on Statistical Computations at 10 Months of Age: The Use of Phonological Features

    ERIC Educational Resources Information Center

    Gonzalez-Gomez, Nayeli; Nazzi, Thierry

    2015-01-01

    Recently, several studies have argued that infants capitalize on the statistical properties of natural languages to acquire the linguistic structure of their native language, but the kinds of constraints which apply to statistical computations remain largely unknown. Here we explored French-learning infants' perceptual preference for…

  15. Constraints on ages of Taconian and Acadian deformation from zircon evaporation ages of felsic plutons from western Massachusetts

    SciTech Connect

    Williamson, B.F.; Karabinos, P. . Dept. of Geology)

    1993-03-01

    New dates on three felsic plutons constrain the age of Taconian and Acadian deformation in western Massachusetts. The tonalitic Hallockville Pond Gneiss intrudes the Moretown Formation of the Rowe-Hawley belt and shows deformation comparable in degree and orientation to that of the surrounding rocks. The Middlefield Granite, a quartz monzonite, intrudes the Rowe and Moretown Formations at their contact. The Williamsburg Granodiorite, of minimum-melt composition, intrudes Silurian and Devonian formations of the Connecticut Valley Synclinorium, east of the Row-Hawley belt, and contains no obvious deformation fabric. [sup 207]Pb/[sup 206]Pb single-grain zircon evaporation ages for these plutons are as follows: the Hallockville Pond Gneiss, 484 [plus minus] 7 Ma; the Middlefield Granite, 447 [plus minus] 3 Ma (weighted average of 4 grains); and the Williamsburg Granodiorite, 373 [plus minus] 5 Ma (weighted average of 3 grains). The Moretown Formation, presently correlated with the Middle Ordovician Beauceville Formation in Quebec, must be older than 484 Ma (Early Ordovician), the age of the intruding Hallockville Pond Gneiss, which might be related to rocks in the proposed Shelburne Falls arc of similar age (Karabinos and Tucker, 1992). Field relations and the age of the Middlefield Granite show that if the Rowe-Moretown contact is a fault, one interpretation suggested by Stanley and Hatch (1988) and advocated by Ratcliffe et al. (1992), then Taconian thrusting in this area ended by 447 Ma because the pluton is not offset by faults. The 373 Ma age of the unfoliated Williamsburg Granodiorite, together with a U-Pb zircon age on a strongly deformed sill in the Granville dome of 376 [plus minus] 4 Ma, tightly constrains the timing of the main phase of Acadian deformation in western Massachusetts.

  16. The Environment of M85 Optical Transient 2006-1: Constraints on the Progenitor Age and Mass

    NASA Astrophysics Data System (ADS)

    Ofek, E. O.; Kulkarni, S. R.; Rau, A.; Cenko, S. B.; Peng, E. W.; Blakeslee, J. P.; Côté, P.; Ferrarese, L.; Jordán, A.; Mei, S.; Puzia, T.; Bradley, L. D.; Magee, D.; Bouwens, R.

    2008-02-01

    M85 Optical Transient 2006-1 (M85 OT 2006-1) is the most luminous member of the small family of V838 Mon-like objects, whose nature is still a mystery. This event took place in the Virgo Cluster of galaxies and peaked at an absolute magnitude of MI ≈ - 13. Here we present Hubble Space Telescope images of M85 OT 2006-1 and its environment, taken before and after the eruption, along with a spectrum of the host galaxy at the transient location. We find that the progenitor of M85 OT 2006-1 was not associated with any star-forming region. The g- and z-band absolute magnitudes of the progenitor were fainter than about -4 and -6 mag, respectively. Therefore, we can set a lower limit of ~50 Myr on the age of the youngest stars at the location of the progenitor that corresponds to a mass of <7 M⊙. Previously published line indices suggest that M85 has a mean stellar age of 1.6 +/- 0.3 Gyr. If this mean age is representative of the progenitor of M85 OT 2006-1, then we can further constrain its mass to be less than 2 M⊙. We compare the energetics and mass limit derived for the M85 OT 2006-1 progenitor with those expected from a simple model of violent stellar mergers. Combined with further modeling, these new clues may ultimately reveal the true nature of these puzzling events.

  17. The effects of constraint-induced movement therapy for a child less than one year of age.

    PubMed

    Coker, Patty; Lebkicher, Carisa; Harris, Lauren; Snape, Jamie

    2009-01-01

    The aim of this single case study was to determine the effectiveness of a modified version of constraint-induced movement therapy (mCIMT) on a child less than one year of age with a diagnosis of hemiplegic cerebral palsy. A single-subject ABAB design with a 6-month follow-up evaluation used repeated measures of gross and fine motor skills to determine changes at each phase of the study. Measures included the Peabody Developmental Motor Scale-2 (PDMS-2), the Gross Motor Fine Motor Measure-88 (GMFM-88) and videotape analysis of specific motor skills typically seen in children less than one year of age. The child in this study participated in a conventional occupational and physical therapy for 2 hours a week during the 2 baseline phases, A1 and A2, and mCIMT during the 2 intervention phases, B1 and B2. The mCIMT involved constraint of the non-affected limb for 1-hour a day for 30 consecutive days as the child was engaged in developmentally appropriate, task specific activities implemented by therapists and parents. Following participation in this mCIMT, the child demonstrated clinical improvements in both gross and fine motor skills as measured by standardized assessments and videotape analysis of motor behaviors. He was completing developmental motor tasks at his chronological age despite motor deficits resulting from a right-sided hemiparesis. The results of this study supports the use of mCIMT for children less than one year of age and could shift the focus of future research studies to determining the age in which to implement mCIMT before patterns of learned non-use begin to affect the normal development of skilled motor movements in children with hemiplegic CP. PMID:19458426

  18. Cosmogenic Be-10 Constraints of the "Little Ice Age" Glacial Advances in the Eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Li, Y.; Liu, G.; Chen, Y.

    2014-12-01

    The Little Ice Age (LIA) glacial advances, represented as a set of "fresh and bouldery" moraines a few hundred meters downstream from modern glaciers, have been widely recognized in Central Asian highlands. However, few studies have been conducted to constrain the formation ages of these moraines. Glaciers provide critical freshwater supply in Central Asia, so understanding the dynamics of glaciers, especially in the past a few hundreds of years, is of great importance. In a NSF funded project reported here, we aim to constrain the formation ages of these putative LIA moraines in the eastern Tian Shan, China, using cosmogenic 10Be surface exposure dating. Our initial results showed 10Be exposure ages ranging from 0.17±0.10 ka to 0.28±0.10 ka, from 0.38±0.03 ka to 0.86±0.08 ka, and from 0.36±0.04 ka to 0.41±0.10 ka for these moraines from the Bayinbuluke Valley in the Nalati Range, the Turgan Valley in the Karlik Range, and the Daxi Valley in the Tianger Range, respectively. We are currently processing 30 samples for the "LIA" moraines in six valleys located in the Heigou Valley of the Bogeda Range, the Haxilegen Pass in the Borohoro Range, and the Urumqi River headwaters in the Tianger Range. Except for one older age of 5.1±0.6 ka, which might be an outlier, our recently measured four ages range from 0.19±0.04 ka to 0.61±0.10 ka. These ages suggest that these fresh moraines were formed during the LIA, but glaciers might advance to their maximum extents slightly differently in different sites. This work demonstrates the importance of absolute dating in reconstructing past glacial fluctuations, and provides quantitative evidence in assessing the impact of glacier change on the ecosystem and society in recent centuries.

  19. Magnetostratigraphic and geochronological age constraints on the lowermost Beaufort Group, Karoo Basin, South Africa

    NASA Astrophysics Data System (ADS)

    Tohver, E.; Lanci, L.; Wilson, A.; Flint, S.

    2011-12-01

    The Karoo Basin of South Africa is a classic foreland basin sequence, with sedimentation putatively linked to Gondwanide orogenesis in the Cape Fold Belt. Biostratigraphic data for the fluvial to lacustrine sediments of the Beaufort Group have traditionally assigned a late Permian age to these foreland basin sediments on the basis of Glossopteris flora and Dicynodont fauna findings. This age conflicts with recently published U-Pb zircon age data from below the Beaufort Group that suggested a latest Permian, early Triassic age for those rocks. In order to resolve this discrepancy, we undertook a coupled magnetostratigraphic and geochronological study of the lowermost Beaufort Group of South Africa. Volcanic zircons from various tuffaceous horizons were analyzed for U-Pb age by SHRIMP. The youngest population of late Permian zircons are interpreted as the age of volcanic ashfall and sedimentation, with inheritance from pre-existing crust recognized from the presence of ca. 500 Ma and 1000-1100 Ma zircons. The possibility of Pb loss from these youngest grains will be assessed by CA-TIMS work. Magnetostratigraphic sampling was carried out in two separate sedimentary profiles, 169 m and 549 m thick, that are separated by roughly 85 km across depositional strike. Diagnostic patterns of normal and reversed magnetozones allow for the close correlation of these two sections. This pattern, anchored by the U-Pb zircon ages, can be correlated to the Global Polarity Timescale of Ogg et al. (2008), and supports a late Guadalupian age for these sediments.

  20. Social pairing of Seychelles warblers under reduced constraints: MHC, neutral heterozygosity, and age

    PubMed Central

    Wright, David J.; Brouwer, Lyanne; Mannarelli, Maria-Elena; Burke, Terry; Komdeur, Jan

    2016-01-01

    The prevalence and significance of precopulatory mate choice remains keenly debated. The major histocompatibility complex (MHC) plays a key role in vertebrate adaptive immunity, and variation at the MHC influences individual survival. Although MHC-dependent mate choice has been documented in certain species, many other studies find no such pattern. This may be, at least in part, because in natural systems constraints may reduce the choices available to individuals and prevent full expression of underlying preferences. We used translocations to previously unoccupied islands to experimentally reduce constraints on female social mate choice in the Seychelles warbler (Acrocephalus sechellensis), a species in which patterns of MHC-dependent extrapair paternity (EPP), but not social mate choice, have been observed. We find no evidence of MHC-dependent social mate choice in the new populations. Instead, we find that older males and males with more microsatellite heterozygosity are more likely to have successfully paired. Our data cannot resolve whether these patterns in pairing were due to male–male competition or female choice. However, our research does suggest that female Seychelles warblers do not choose social mates using MHC class I to increase fitness. It may also indicate that the MHC-dependent EPP observed in the source population is probably due to mechanisms other than female precopulatory mate choice based on MHC cues. PMID:26792973

  1. Carboniferous age for the East Greenland “Devonian” basin: Paleomagnetic and isotopic constraints on age, stratigraphy, and plate reconstructions

    NASA Astrophysics Data System (ADS)

    Hartz, E. H.; Torsvik, T. H.; Andresen, A.

    1997-08-01

    New paleomagnetic and isotopic data from East Greenland indicate that this classical “Devonian” basin was partly formed in Carboniferous. The basin preserves a stratigraphically linked magnetic reversal pattern of primary character. Paleomagnetic data indicate that the two stratigraphically lowermost intrabasinal angular unconformities, identified on each side of the basin, in fact correlate as one unconformity. This implies a 2 km reduction of the estimated basin thickness, and thus that the unconformity represents a major depositional hiatus. Successions below the unconformity are taken to be Devonian (Givetian) in age, on the basis of correlation with paleomagnetic reference poles. However, we argue that the overlying strata are Carboniferous, rather than Devonian, in age, on the basis of a ca. 336 Ma 40Ar/39Ar extrusive age for a basalt flow and paleomagnetic data. A Carboniferous age for the strata has significant implications for vertebrate evolution; fossils of a terrestial tetrapod, Ichthyostega, are found above the unconformity. Ichthyostega is regarded as the earliest fossil of an animal known to walk on land; however, our data suggest that these dry footsteps are much younger than previously believed. Our results are also significant for plate reconstructions. Paleomagnetic data indicate that the lower part of the basin was deposited at low southerly latitudes. Sediments above our Early Carboniferous unconformity were deposited approximately at lat 4°N, indicating that the continent had drifted northward. A minor pole-longitude misfit between Devonian and Carboniferous poles from East Greenland and North America implies (1) a closer pre Labrador Sea Greenland North America fit; (2) counterclockwise block rotations (10° 15°) of the study area; or (3) a combination of both. The East Greenland “Devonian” basin formed along the Caledonian spine of Euramerica, and counterclockwise block rotation may have occurred between sinistral faults

  2. The Schwartzwalder uranium deposit, II: Age of uranium mineralization and lead isotope constraints on genesis.

    USGS Publications Warehouse

    Ludwig, K. R.; Wallace, A.R.; Simmons, K.R.

    1985-01-01

    Schwartzwalder ores have high amounts of initial (common) Pb that was both variable and relatively radiogenic in its isotope ratios. Assuming the common Pb in these ores to have sources of similar age and similar Th/U, samples with initial Pb isotope ratios are identified - and others with variable initial ratios are normalized - to obtain U-Pb isochrons yielding an early Laramide age of 69.3 + or - 1.1 m.y. for the ores. The initial Pb-isotope systematics indicate local sources of U, dispersed in concentrations <100 ppm, in rocks of 1730 + or - 130 m.y. age. -G.J.N.

  3. Age estimates of globular clusters in the Milky Way: constraints on cosmology.

    PubMed

    Krauss, Lawrence M; Chaboyer, Brian

    2003-01-01

    Recent observations of stellar globular clusters in the Milky Way Galaxy, combined with revised ranges of parameters in stellar evolution codes and new estimates of the earliest epoch of globular cluster formation, result in a 95% confidence level lower limit on the age of the Universe of 11.2 billion years. This age is inconsistent with the expansion age for a flat Universe for the currently allowed range of the Hubble constant, unless the cosmic equation of state is dominated by a component that violates the strong energy condition. This means that the three fundamental observables in cosmology-the age of the Universe, the distance-redshift relation, and the geometry of the Universe-now independently support the case for a dark energy-dominated Universe. PMID:12511641

  4. Siluro-Carboniferous Transpression in Central-Coastal Maine: Constraints From New Chemical Monazite Ages

    NASA Astrophysics Data System (ADS)

    Short, H.; Yates, M.; Johnson, S.

    2004-05-01

    New in-situ chemical age determinations of monazite from several different lithologic units across central and eastern Maine suggest a protracted regional history of dextral transpression, terrane exhumation, fault reactivation, and punctuated metamorphism from the Silurian through the Carboniferous. Acadian-age orogenesis in Maine is considered to be a high-temperature, low-pressure series of events during which the dominant direction of accommodation of convergence switched from orogen-perpendicular to orogen-parallel near the end of the Devonian. New chemical monazite ages suggest this orogenesis involved a significant and long-lived component of transpression at pressures high enough to produce kyanite. A kyanite-bearing schist that occurs along the boundary of the higher-strain, higher-metamorphic-grade Liberty-Orrington belt in the middle of the orogen returns preliminary Late Silurian-Early Devonian ages from both matrix monazite and monazite included in kyanite. These data suggest that the kyanite is contemporaneous with established `Acadian-age' tectonism, and that the Liberty-Orrington belt represents a higher-pressure terrane that was exhumed during Siluro-Devonian time. Late Devonian-Carboniferous monazite ages for grains included in garnet and andalusite from the Liberty-Orrington belt suggest continued metamorphism and fault reactivation. To the east of the Liberty-Orrington belt, preliminary monazite ages of 400 Ma within inclusion trails in cores of staurolite porphyroblasts, 373 Ma from monazite included in andalusite, and 358 Ma for monazite in the dextral matrix emphasizes the protracted transpressive nature of Devonian tectonism in the area. This new monazite work suggests that a geodynamic model incorporating localized exhumation during transpression is a more appropriate model for Acadian-age orogenesis in central-eastern Maine. All analyses were carried out in-situ using the Cameca SX100 electron microprobe at the Department of Earth Sciences

  5. On the age of human footprints in Central Mexico: paleomagnetic constraints

    NASA Astrophysics Data System (ADS)

    Rocha Fernandez, J.; Gogichaishvili, A.; Martin Del Pozo, A.; Urrutia Fucugauchi, J.

    2007-05-01

    Until recently, we thought we knew where ancestral Native Americans came from (central Siberia, then across Beringia), and when they arrived (about 13 000 cal BP, after a trek between the recently separated Canadian ice sheets after Fiedel, 2006). Recent theories of American origins postulate multiple pre-Clovis migrations including Transpacific or coastal voyages by Australians, Melanesians, or Ainu, and even a Transatlantic migrations by Caucasoid Solutreans from Iberia. Thus, timing, route and origin of the first colonization to the Americas remains one of the most important topics in human evolution. Human and animal footprints have been found within the upper bedding surfaces of the Xalnene volcanic ash layer that outcrops in the Valsequillo Basin, south of Puebla, Mexico (Gonzalez et al., 2005). The ash has been dated to at least 40 ka BP. Paleomagnetic investigation yielded an intermediate magnetic polarity for Xalnene ash deposits while nearby Toluquilla volcano is reversely magnetized. Moreover, the absolute geomagnetic paleointensity derived from the volcanic lava flow is significantly reduced with respect to the present day geomagnetic field strength. It is quite possible that the ash as well as volcanic lava flow formed during worldwide observed Laschamp geomagnetic event.

  6. Constraints on the age and evolution of the Galaxy from the white dwarf luminosity function

    NASA Technical Reports Server (NTRS)

    Wood, M. A.

    1992-01-01

    The white dwarf disk luminosity function is explored using observational results of Liebert et al. (1988, 1989) as a template for comparison, and the cooling curves of Wood (1990, 1991) as the input basis functions for the integration. The star formation rate over the history of the Galaxy is found to be constant to within an order of magnitude, and the disk age lies in the range 6-13.5 Gyr, where roughly 40 percent of the uncertainty is due to the observational uncertainties. Using the best current estimates as inputs to the integration, the disk ages range from 7.5 to 11 Gyr, i.e., they are substantially younger than most estimates for the halo globular clusters but in reasonable agreement with those for the disk globular clusters and open clusters. The ages of these differing populations, taken together, are consistent with the pressure-supported collapse models of early spiral Galactic evolution.

  7. Age constraints for Paleoproterozoic glaciation in the Lake Superior Region: Detrital zircon and hydrothermal xenotime ages for the Chocolay Group, Marquette Range Supergroup

    USGS Publications Warehouse

    Vallini, D.A.; Cannon, W.F.; Schulz, K.J.

    2006-01-01

    A geochronological study of the Chocolay Group at the base of the Paleoproterozoic Marquette Range Supergroup in Michigan, Lake Superior Region, is attempted for the first time, Age data from detrital zircon grains and hydrothermal xenotime from the basal glaciogenic formation, the Enchantment Lake Formation, and the stratigraphically higher Sturgeon Quartzite and its equivalent, the Sunday Quartzite, provide maximum and minimum age constraints for the Chocolay Group. The youngest detrital zircon population in the Enchantment Lake Formation is 2317 ?? 6 Ma; in the Sturgeon Quartzite, it is 2306 ?? 9 Ma, and in the Sunday Quartzite, it is 2647 ?? 5 Ma. The oldest hydrothermal xenotime age in the Enchantment Lake Formation is 2133 ?? 11 Ma; in the Sturgeon Quartzite, it is 2115 ?? 5 Ma, and in the Sunday Quartzite, it is 2207 ?? 5 Ma. The radiometric age data in this study implies the depositional age of the Chocolay Group is constrained to ???2.3-2.2 Ga, which proves its correlation with part of the Huronian Supergroup in the Lake Huron Region, Ontario, and reveals the unconformity that separates the Chocolay Group from the overlying Menominee Group is up to 325 million years in duration. The source(s) of the ??? 2.3 Ga detrital zircon populations in the Enchantment Lake Formation and Sturgeon Quartzite remains an enigma because no known rock units of this age are known in the Michigan area. It is speculated that once widespread volcano-sedimentary cover sequences in Michigan were removed or concealed prior to Chocolay Group deposition. The hydrothermal xenotime ages probably reflect basinal hydrothermal fluid flow associated with the period of extension involving rifting and major dyke formation, that affected the North American provinces between 2.2 and 2.1 Ga. ?? 2006 NRC Canada.

  8. Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Li, Yanan; Li, Yingkui; Harbor, Jon; Liu, Gengnian; Yi, Chaolu; Caffee, Marc W.

    2016-04-01

    Presumed Little Ice Age (LIA) glacial advances, represented by a set of fresh, sharp-crested, boulder covered and compact moraines a few hundred meters downstream from modern glaciers, have been widely recognized in the Central Asian highlands. However, few studies have constrained the formation ages of these moraines. We report 31 10Be exposure ages from presumed LIA moraines in six glacial valleys in the Urumqi River headwater area and the Haxilegen Pass area of the eastern Tian Shan, China. Our results reveal that the maximum LIA glacial extent occurred mainly around 430 ± 100 yr, a cold and wet period as indicated by proxy data from ice cores, tree rings, and lake sediments in Central Asia. We also dated a later glacial advance to 270 ± 55 yr. However, 10Be exposure ages on several presumed LIA moraines in front of small, thin glaciers are widely scattered and much older than the globally recognized timing of the LIA. Historical topographic maps indicate that most glaciers were more extensive in the early 1960s, and two of our 10Be sample sites were located close to the ice front at that time. Boulders transported by these small and thin glaciers may be reworked from deposits originally formed prior to the LIA glacial advances, producing apparently old and widely scattered exposure ages due to varied nuclide inheritance. Other published ages indicated an earlier LIA advance around 790 ± 300 yr in the easternmost Tian Shan, but in our study area the more extensive advance around 430 ± 100 yr likely reworked or covered deposits from this earlier event.

  9. Constraints on statistical computations at 10 months of age: the use of phonological features.

    PubMed

    Gonzalez-Gomez, Nayeli; Nazzi, Thierry

    2015-11-01

    Recently, several studies have argued that infants capitalize on the statistical properties of natural languages to acquire the linguistic structure of their native language, but the kinds of constraints which apply to statistical computations remain largely unknown. Here we explored French-learning infants' perceptual preference for labial-coronal (LC) words over coronal-labial words (CL) words (e.g. preferring bat over tab) to determine whether this phonotactic preference is based on the acquisition of the statistical properties of the input based on a single phonological feature (i.e. place of articulation), multiple features (i.e. place and manner of articulation), or individual consonant pairs. Results from four experiments revealed that infants had a labial-coronal bias for nasal sequences (Experiment 1) and for all plosive sequences (Experiments 2 and 4) but a coronal-labial bias for all fricative sequences (Experiments 3 and 4), independently of the frequencies of individual consonant pairs. These results establish for the first time that constellations of multiple phonological features, defining broad consonant classes, constrain the early acquisition of phonotactic regularities of the native language. PMID:25530121

  10. New age constraints for the geodynamic evolution of the Neotethyan Sistan ocean, eastern Iran

    NASA Astrophysics Data System (ADS)

    Broecker, M.; Fotoohi Rad, R.; Burgess, R.; Salimi, Z.

    2012-12-01

    The paleotectonic history of Iran is characterized by the existence of numerous microcontinental blocks which record the fragmentation of a Gondwana-derived crustal segment [1]. Due to the complex interaction between individual blocks and a severe lack of robust geochronologic evidence it has yet not been possible to fully resolve the regional geodynamic framework. Detailed knowledge about the existence and life span of oceanic basins surrounding individual continental segments plays a key role in unravelling the subsequent geotectonic record that has been strongly controlled by various stages of the Arabia-Eurasia collision and the closing of different Tethyan ocean basins. The focus of this study is on the Sistan Suture Zone (SSZ) in eastern Iran which extends as a N-S trending belt over more than 700 km along the border area between Iran and Aghanistan. The SSZ formed as a result of eastward-directed subduction of a Neotethyan ocean basin beneath the Afghan block and includes a tectonic mélange consisting of disrupted meta-ophiolitic rocks within a low-grade matrix of ultramafic, mafic and pelitic schists. Large slabs of ultramafic and mafic rocks record no or only low-grade metamorphism, but some smaller (<200 m) and volumetrically subordinate blocks were affected by eclogite-, blueschist- and/or epidote amphibolite facies P-T conditions. Understanding of the petrological and geochronological record of the HP and amphibolite-facies rocks plays a key role in unravelling the geodynamic evolution of the SSZ. Published Ar-Ar data for such samples indicate a considerable range of apparent ages (ca. 116-139 Ma) for white mica and amphibole [2]. These dates were interpreted to indicate cooling below ca. 350 °C, which led to the conclusion that both HP metamorphism and the epidote-amphibolite-facies stage are older than 125 Ma. The main aim of the present study was to assess the geological significance of this data set in the light of a potential contamination with

  11. Exposure age and ice-sheet model constraints on Pliocene East Antarctic ice sheet dynamics.

    PubMed

    Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki

    2015-01-01

    The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East Antarctic Ice Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand ice sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An ice sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased ice volume. Considering contributions from West Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ∼3 Myr has increased the sea ice cover and inhibited active moisture transport to Antarctica, resulting in reduced ice sheet thickness, at least in coastal areas. PMID:25908601

  12. Exposure age and ice-sheet model constraints on Pliocene East Antarctic ice sheet dynamics

    PubMed Central

    Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki

    2015-01-01

    The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East Antarctic Ice Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand ice sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An ice sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased ice volume. Considering contributions from West Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ∼3 Myr has increased the sea ice cover and inhibited active moisture transport to Antarctica, resulting in reduced ice sheet thickness, at least in coastal areas. PMID:25908601

  13. Exposure age and ice-sheet model constraints on Pliocene East Antarctic ice sheet dynamics

    NASA Astrophysics Data System (ADS)

    Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki

    2015-04-01

    The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East Antarctic Ice Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand ice sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An ice sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased ice volume. Considering contributions from West Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ~3 Myr has increased the sea ice cover and inhibited active moisture transport to Antarctica, resulting in reduced ice sheet thickness, at least in coastal areas.

  14. Quantifying Age-Related Hydraulic and Biochemical Constraints on Tree Photosynthesis in the Southern Appalachian Mountains

    NASA Astrophysics Data System (ADS)

    Missik, J.; Benson, M. C.; Oishi, A. C.; Novick, K. A.; Miniat, C.

    2015-12-01

    Forest carbon accumulation generally declines with age, a trend largely attributed to reductions in gross primary production (GPP). However, for many species, uncertainty remains about the specific mechanisms limiting GPP. We examine both tree hydraulic and biochemical parameters affecting carbon uptake across a successional gradient in the southern Appalachian Mountains, utilizing a chronosequence approach with 5-, 10-, and 85-year old forest stands. We conducted measurements on four of the dominant species in the region: Liriodendron tulipifera, Betula lenta, Acer rubrum, and Quercus alba. To assess biochemical photosynthetic capacity, we estimated Vcmax and Jmax from over 140 gas exchange A/Ci curves. We determined that leaf gas exchange measurements performed on excised branches of A. saccharum, L. tulipifera, and Q. alba significantly underestimated assimilation by 35, 26, and 63% on average, respectively. Therefore, A/Ci measurements were performed on in situ canopy branches, using an 18 m boom lift to access the tallest trees. We examine how these photosynthetic parameters vary with age, height, and foliar nitrogen content among tree species and canopy positions. In order to investigate hydraulic factors driving stomatal behavior and therefore carbon uptake, we collected measurements of mid-day and pre-dawn leaf water potential (ψmd and ψpd) and xylem cavitation vulnerability. Preliminary results suggest that ψmd-ψpd decreases with along the chronosequence in anisohydric species, whereas ψmd-ψpd increases or remains stable with age/height in isohydric species. These data will be analyzed together with site- and species-specific hydraulic vulnerability data to assess whether the hydraulic safety margin changes with tree age/height, and explore how these patterns vary among species representing different xylem anatomies and a range of isohydric/anisohydric water management strategies. These results will provide improved estimates of common parameters in

  15. Constraint on radiocarbon age correction in Lake Biwa environment from the middle to late Holocene

    NASA Astrophysics Data System (ADS)

    Miyata, Y.; Minami, M.; Onbe, S.; Sakamoto, M.; Nakamura, T.; Imamura, M.

    2013-01-01

    Using data from previous studies and newly collected data, we compared the measured radiocarbon ages of molluscan shells, common reed (Phragmites australis) and pine needles (Pinus thunbergii) collected in 1966, 1970, 1990 and 2008 at Lake Biwa in Japan, and of archaeological samples, to examine radiocarbon reservoir effects at Lake Biwa. We also tested for differences in the radiocarbon reservoir effect between species and locations in the lake. The effects of nuclear bomb tests conducted in the 1950s and 1960s are clear, the offset between atmospheric 14C and the Lake Biwa freshwater 14C is larger for this period because the atmospheric 14C is so high. The semiclosed Lake Biwa system is in dynamic equilibrium with the atmosphere, resulting in the 14C content of the water following the changes in atmospheric 14C caused by nuclear testing. The shells collected after 1990 had radiocarbon ages that were 330-450 14C years older than those of the coeval atmosphere. The apparent differences in radiocarbon age (about 300 14C years) between shell fossils and wood samples excavated from the same layer of the submerged Awazu shell midden at Lake Biwa suggest that the radiocarbon reservoir effect also existed in the middle Holocene (the Middle Jomon period, about 5000 years ago). Because the present-day average residence time of Lake Biwa water is 3-6 years, its direct influence on the radiocarbon reservoir effect is small, which suggests that old carbon has been supplied into Lake Biwa.

  16. Theoretical constraints on the precision and age range of rehydroxylation dating

    PubMed Central

    Hare, V. J.

    2015-01-01

    Accurate and precise dating methods are of central importance to archaeology, palaeontology and earth science. This paper investigates the expected precision and age range of rehydroxylation dating, a recently proposed technique for fired clays. An expression for combined measurement uncertainty is presented, which takes into account all significant sources of experimental uncertainty. Numerical simulations are performed for comparison. Combined measurement uncertainties of approximately 5% with respect to the age of the ceramic should be possible given well-designed experiments. In this case, the most significant contribution to combined measurement uncertainty is from effective lifetime temperature. In addition, it is shown that precision should be acceptable for recently fired material (less than 1 year). Mismatch of balance resolution to sample mass results in large variation in combined relative uncertainties, which vary by four orders of magnitude (approx. 1–1160%) across recent experimental studies, rendering some recently reported dates meaningless. It is recommended that this ratio be less than 10−6 for a combined relative uncertainty of less than 1%. The age limits of the technique are set by the value of the rate constant and individual sample mineralogy. This theoretical framework should help future interlaboratory comparison as well as optimizing instrument design. PMID:26064631

  17. Theoretical constraints on the precision and age range of rehydroxylation dating.

    PubMed

    Hare, V J

    2015-04-01

    Accurate and precise dating methods are of central importance to archaeology, palaeontology and earth science. This paper investigates the expected precision and age range of rehydroxylation dating, a recently proposed technique for fired clays. An expression for combined measurement uncertainty is presented, which takes into account all significant sources of experimental uncertainty. Numerical simulations are performed for comparison. Combined measurement uncertainties of approximately 5% with respect to the age of the ceramic should be possible given well-designed experiments. In this case, the most significant contribution to combined measurement uncertainty is from effective lifetime temperature. In addition, it is shown that precision should be acceptable for recently fired material (less than 1 year). Mismatch of balance resolution to sample mass results in large variation in combined relative uncertainties, which vary by four orders of magnitude (approx. 1-1160%) across recent experimental studies, rendering some recently reported dates meaningless. It is recommended that this ratio be less than 10(-6) for a combined relative uncertainty of less than 1%. The age limits of the technique are set by the value of the rate constant and individual sample mineralogy. This theoretical framework should help future interlaboratory comparison as well as optimizing instrument design. PMID:26064631

  18. Constraints on crustal rheology and age of deformation from models of gravitational spreading in Ishtar Terra, Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, Suzanne E.; Soloman, Sean C.

    1992-01-01

    Gravitational spreading is expected to lead to rapid relaxation of high relief due to the high surface temperature and associated weak crust on Venus. In this study, we use new Magellan radar and altimetry data to determine the extent of gravitational relaxation in Ishtar Terra, which contains the highest relief on Venus as well as areas of extremely high topographic slope. Within Ishtar Terra the only mountain belts found on Venus, Akna, Danu, Freyja, and Maxwell Montes, nearly encircle the smooth, high (3-4 km) plateau of Lakshmi Planum. Finite-element models of this process give expected timescales for relaxation of relief and failure at the surface. From these modeling results we attempt to constrain the strength of the crust and timescales of deformation in Ishtar Terra. Below we discuss observational evidence for gravitational spreading in Ishtar Terra, results from the finite-element modeling, independent age constraints, and implications for the rheology and timing of deformation.

  19. New age constraints on the evolution of the Karakorum Fault, West Tibet

    NASA Astrophysics Data System (ADS)

    Valli, F.; Arnaud, N.; Lacassin, R.; Paquette, J.; Leloup, P. H.; Li, H.; Tapponnier, P.; Guillot, S.; Deloule, E.; Maheo, G.; Xu, Z.

    2003-12-01

    Results of detailed mapping and dating of sheared rocks along southern fault-half helps assess the total offset, lifespan, slip-rate and geodynamic importance of the Karakorum Fault (KFZ). South of 33° N, along SW edge of Tashikang-Gar basin, active right-lateral normal faults, belonging to KFZ, exhume metamorphic and magmatic footwall rocks forming the SE termination of Ladakh-Karakorum range. Close to active fault, gneisses and mylonites are affected by strong ductile dextral shear and inter-layered with leucocratic melt veins sheared to various degrees. Several generations of veins are often observed on a same outcrop, with late, weakly deformed veins cutting highly sheared ones. This implies that anatexy and intrusion were coeval with dextral shearing. Direct dating of leucogranites reveals Oligo-Miocene formation ages. U/Pb thermo-ionization dating on zircons yields concordant ages at 22.7+-0.1Ma. Discordant zircons ages are consistent with a poorly defined lower intercept at 32+-3 Ma, and a Proterozoic (1300+-100 Ma) upper intercept. In situ ion microprobe dating of 17 zircons (24 spots) confirms these results. Four mylonite zircons yield comparable, concordant ages ranging between 20 and 25 Ma in their cores and rims, in good agreement with conventional U/Pb dating. Inherited zircon ages range from Paleozoic to Precambrian (ca.1200 Ma). Some of them recrystallized partially during Tertiary deformation, yielding discordant ages, the youngest being 34+-0.8Ma. Cooling was delayed until 12 to 8Ma, at which time very rapid cooling is recorded by 40Ar/39Ar and fission track data. Purely strike-slip ductile shear was thus already in progress along the fault at 23Ma and possibly earlier (ca.34Ma). A marked kinematic change from purely dextral to dextral-normal motion occurred around or just after 12 Ma. Best offset estimate along this main (northern) branch of KFZ is given by correlation of the ophiolite-bearing melange of Shiquanhe with the Shyok suture zone in

  20. Relatively Recent Volcanism on Oahu, Hawaii: New U-series and Paleomagnetic Age Constraints on the Hanauma Bay Eruption

    NASA Astrophysics Data System (ADS)

    Rubin, K. H.; Jurado-Chichay, Z.; Urrutia-Fucugauchi, J.

    2002-12-01

    The Koko Rift Zone (KRZ), eastern Oahu, is generally regarded as among the youngest volcanic features on the island. Previous workers have suggested that the 9 or 10 vents of this rift erupted near-simultaneously. However, K-Ar data in the literature (32-39 ka vs 320 ka) provide only general guidance on the youthfulness of these eruptions. We present new age constraints on KRZ volcanism using deposits of the phreatomagmatic eruption that produced Hanauma Bay (a popular snorkeling spot) and spatially associated lava flows. Numerous continuous basaltic ash units within the walls of Hanauma crater contain lithic fragments of well-preserved coral reef, beach rock, and marine mollusks, indicating that the eruption occurred in a near shore environment. 238U-234U-230Th dating of coral clasts in the deposit demonstrates that the eruption breached reef of MIS stage 7 age (200 +/- 30 ka), thereby ruling out the K-Ar age of 320 ka. U-series nuclides in "normal" MIS 7 coral lithics are indistinguishable from those in the island encircling Waianae Reef of the same age. However, U-series components in some originally aragonitic coral clasts were offset during the eruption when the rims recrystallized to calcite. 87Sr/86Sr, 234U/238U and Sr and U concentration indicate chemical mixing with host basaltic ash during this event, from which potential ages of the eruption can be constructed using isochron methods. More modeling of the data remains to be done but our preliminary estimate places the eruption at less than 100 ka. This result is consistent with new data on paleointensity and paleomagnetic secular variation within the lava flows exposed in or around the crater. This U-series dating approach should prove useful for eruptions in other locales where carbonate bioclast lithics are present in the deposits.

  1. Age and isotopic constraints on pleistocene pluvial episodes in the Western Desert, Egypt.

    SciTech Connect

    Crombie, M. K.; Arvidson, R. E.; Sturchio, N. C.; El Alfy, Z.; Abu Zeid, K.; Environmental Research; Washington Univ.; Egyptian Geological Survey and Mining Authority

    1997-01-01

    North Africa has undergone drastic climatic changes over the past several hundred thousand years. The timing of humid intervals called pluvials was investigated by uranium-series disequilibrium dating of travertines from the Kurkur Oasis, Western Desert, Egypt. The youngest and best dated travertines (70-160 ka) are found in Wadi Kurkur and include spring and lacustrine units exposed as 2 to 3 m high terraces. Travertines having an age of approximately 191-220 ka are exposed by differential erosion as linear mounds produced by spring systems over fracture zones in ancient wadis. The oldest travertines, having ages >260 ka, are extensive, cap limestone units above the oasis, and were deposited in paludal and lacustrine environments. Oxygen isotope ratios were measured for the wadi travertines ({delta}{sup 18}O values ranging from 16.7 to 19.1{per_thousand} SMOW) and for spring mound travertines (18.5-20.5{per_thousand}). Equilibrium oxygen isotope fractionation calculations indicate that the Kurkur travertines were deposited from waters having {delta}{sup 18}O values similar to ancient Western Desert groundwaters ({approx} -11{per_thousand}). The ages of the travertines correspond to times of monsoonal maxima, eustatic sea level high stands and interglacial maxima. Rainfall producing these groundwaters (and travertines) was significantly fractionated during atmospheric transport, in contrast to modern meteoric waters (-2.09{per_thousand}), implying a distant source for the pluvial waters. Increased precipitation, recharge of Western Desert groundwaters, and resultant travertine deposition are interpreted to be consequences of Milankovitch insolation cycle forcing, through enhanced Atlantic and Indian Ocean monsoons during interglacial time periods.

  2. Constraints on the ages of mineralization and deformation in the Oquirrh Mountains, Salt Lake Co. , Utah

    SciTech Connect

    Presnell, R.D. ); Wilson, P.N.; Kroko, C.T.; Parry, W.T. )

    1993-04-01

    The Oquirrh Mountains are the easternmost range in the Basin and Range Province and have experienced several deformational events due to compressional and extensional tectonism. The Oquirrh Mountains contain two major mining districts: Bingham and Mercur. The Bingham porphry copper deposit has been dated at [approximately]39 Ma. The porphyry system contains mineralized NE trending faults which are cut by unmineralized NW trending faults. These two fault sets record two periods of Cenozoic extension in the Oquirrh Mountains: late Eocene and Miocene to recent. The Carlin-type Barneys Canyon gold deposit occurs 7.2 km northeast of the Bingham system on the northern flank of the Copperton anticline. Ages of illite-rich bedding plane gouges formed during growth of the Copperton anticline are late Jurassic. Alteration at Barneys Canyon includes decalcification, weak silicification, and argillization. Argillization consists of illite and kaolinite. The dated illite-rich gouges are gold bearing, have hydrothermal textures and are within the illite-rich argillic alteration zone associated with the orebody. The Carlin-type Mercur gold deposits occur on the east hinge of the Ophir anticline in the southern Oquirrh Mountains. K/Ar ages of illite veins and clay-sized separates range from 122 to 189 Ma and average 160 Ma. Vein attitudes are consistent with formation during growth of the Ophir anticline. Mineralization at Mercur is controlled by high-angle ENE and NNW faults which may have formed during growth of the Ophir anticline. These data suggest that compressional deformation and alteration/mineralization in the Mercur district and at Barneys Canyon are Late Jurassic in age.

  3. Age constraints on the proposed Plio-Pleistocene boundary stratotype at Vrica, Italy.

    USGS Publications Warehouse

    Obradovich, J.D.; Naeser, C.W.; Izett, G.A.; Pasini, G.; Bigazzi, G.

    1982-01-01

    Estimates of the age of the stratotype Plio-Pleistocene boundary in Italy range from 1.65 to 2.5 Myr. We aim here to clarify this dating confusion, and we present new radiometric data on ashes from the proposed stratotype section, Vrica, Italy, which indicate that the Plio-Pleistocene boundary must be less than 2 Myr old. Biostratigraphical criteria - the first appearance datums (FADs) and the last appearance datums (LADs) of planktonic foraminifera and calcareous nannoplankton tied to the magnetic reversal chronology - suggest that this boundary may be nearer to 1.7 Myr.-from Authors

  4. Geologic constraints on kinematic models and age of formation of the Amerasia Basin of the Arctic

    NASA Astrophysics Data System (ADS)

    Miller, E. L.

    2015-12-01

    A wealth of new geologic and geophysical data now exist for the Amerasia Basin, but the details of its age and the nature/kinematics of events that resulted in its formation remain elusive. Basement rock ages, detrital zircon signatures of sedimentary rocks, and sediment dispersal systems have been used to show how parts of the southern margin(s) of the Amerasia Basin (Arctic Alaska-Chukotka, AAC) match their rifted margin counterparts on the Eurasia and Canada side of the Amerasia Basin. Thus we know the approximate finite translations needed to restore the paleogeography of the Arctic, but not the kinematics involved. Important features of the Amerasia Basin that need to be explained in a model for its opening are the age and extent of the high Arctic LIP, the linearity of the strip of continental crust represented by the Lomonosov Ridge, its right angle intersection with the Canadian Arctic margin, and the directional fault patterns mapped bathymetrically and seismically across the Alpha-Lomonosov Ridge and surrounding seafloor. Across AAC, post-Early Cretaceous oroclinal bends provide insight into strike-slip components of deformation involved in opening of the Amerasia Basin: The Chukchi syntax offsets the Brooks Range in a right-lateral sense from Wrangel Island along the Herald Arch; right-lateral motion of Arctic Alaska with respect to the Chukchi Borderland during opening of the Canada Basin; right-lateral shear in Chukotka during 100 Ma magmatism; the tight bend in the northern Verkhoyansk, result of Cretaceous right-lateral shear. The land-based relationships imply a post-Early Cretaceous, younger than Barremian (~130 Ma) age for onset of magmatism and extension related to rifting and formation of the Amerasia Basin. At least two stages of extension are documented, with older E-W extension characterizing the longitude of the New Siberian Islands to Pevek, Russian Arctic, (ca.125 Ma to 100 Ma), with younger N-S extension superimposed on this system (ca

  5. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  6. Impact Constraints on the Age and Origin of the Crustal Dichotomy on Mars

    NASA Technical Reports Server (NTRS)

    Frey, Herbert V.

    2004-01-01

    MOLA data have revealed a large population of 'Quasi-Circular Depressions' (QCDs) with little or no visible expression in image data. These likely buried impact basins have important implications for the age of the lowland crust, how that compares with original highland crust, and when and how the crustal dichotomy may have formed. The buried lowlands are of Early Noachian age, likely slightly younger than the buried highlands but older than the exposed (visible) highland surface. A depopulation of large visible basins at diameters 800 to 1300 km suggests some global scale event early in martian history, maybe related to the formation of the lowlands and/or the development of Tharsis. A suggested early disappearance of the global magnetic field can be placed within a temporal sequence of formation of the very largest impact basins. The global field appears to have disappeared at about the time the lowlands formed. It seems likely the topographic crustal dichotomy was produced very early in martian history by processes which operated very quickly. This and the preservation of large relic impact basins in the northern hemisphere, which themselves can account for the lowland topography, suggest that large impacts played the major role in the origin Mars fundamental crustal feature.

  7. Constraints on the age of the Great Sand Dunes, Colorado, from subsurface stratigraphy and OSL dates

    USGS Publications Warehouse

    Madole, Richard F.; Mahan, Shannon; Romig, Joe H.; Havens, Jeremy C.

    2013-01-01

    The age of the Great Sand Dunes has been debated for nearly 150 yr. Seven ages ranging from Miocene to late Holocene have been proposed for them. This paper presents new information—chiefly subsurface stratigraphic data, OSL dates, and geomorphic evidence—that indicates that the Great Sand Dunes began to form in the latter part of the middle Pleistocene. The dunes overlie a thick wedge of piedmont-slope deposits, which in turn overlies sediment of Lake Alamosa, a paleolake that began to drain about 440 ka. The wedge of piedmont-slope deposits extends westward for at least 23 km and is as much as 60 m thick at a distance of 10 km from the Sangre de Cristo Range. Ostracodes from one well indicate that the eastern shoreline of Lake Alamosa extended to within 4.3 km of where the Great Sand Dunes eventually formed. The time represented by the wedge of piedmont-slope deposits is not known exactly, but the wedge post-dates 440 ka and was in place prior to 130 ka because by then the dunes overlying it were sufficiently close and tall enough to obstruct streams draining from the Sangre de Cristo Range.

  8. Formation waters from Cambrian-age strata, Illinois Basin, USA: Constraints on their origin and evolution

    NASA Astrophysics Data System (ADS)

    Panno, Samuel V.; Hackley, Keith C.; Locke, Randall A.; Krapac, Ivan G.; Wimmer, Bracken; Iranmanesh, Abbas; Kelly, Walton R.

    2013-12-01

    Recently, brine samples from the Cambrian-age Mount Simon Formation (the deepest, most inaccessible sedimentary rock formation of the Illinois Basin) and the overlying Ironton-Galesville Formation were collected as part of a major research effort evaluating the feasibility of sequestration of carbon dioxide in deep geologic formations. Halide and halide/cation ratios (especially Cl/Br and Na/Br ratios) from groundwater samples collected during this investigation suggest that the brines of the Cambrian-age strata formed by the evaporation of seawater well beyond the point of halite precipitation. The Cl/Br and Na/Br ratios, the presence of Mississippi-Valley-Type (MVT) ore mineralization in close proximity to the Illinois Basin, and the tectonic history of the region and the Illinois Basin suggest that components of ore-forming brines and perhaps crystalline basement brine are likely still present within the Mount Simon Formation. Halide and cation/halide ratio plots show that these brines have mixed with and have been diluted by subaerially evaporated seawater, seawater and dilute groundwater. Movement of brines out of the Mount Simon Formation and/or exchange with brines of other formations is constrained by the overlying, siltstone- and shale-rich Eau Claire Formation, a low-permeability layer. The most plausible interpretation of the halide and halide/cation ratio data is that the brines of the Cambrian-age strata were introduced to the Illinois Basin from outside of the basin, perhaps when the Illinois Basin was connected to the Arkoma (Oklahoma and Arkansas) and Black Warrior Basins (Alabama and Mississippi) via the Reelfoot Rift during Cambrian and early Ordovician time. In addition, the presence of some percentage of high NaCl, low Cl/Br brines from the crystalline basement is suggested given the geochemical relationships of the halide and cation/halide ratios and the tectonic history of the Illinois Basin. Finally, halide and cation/halide ratios determined

  9. Age constraints on first versus second language acquisition: evidence for linguistic plasticity and epigenesis.

    PubMed

    Mayberry, Rachel I; Lock, Elizabeth

    2003-12-01

    Does age constrain the outcome of all language acquisition equally regardless of whether the language is a first or second one? To test this hypothesis, the English grammatical abilities of deaf and hearing adults who either did or did not have linguistic experience (spoken or signed) during early childhood were investigated with two tasks, timed grammatical judgement and untimed sentence to picture matching. Findings showed that adults who acquired a language in early life performed at near-native levels on a second language regardless of whether they were hearing or deaf or whether the early language was spoken or signed. By contrast, deaf adults who experienced little or no accessible language in early life performed poorly. These results indicate that the onset of language acquisition in early human development dramatically alters the capacity to learn language throughout life, independent of the sensory-motor form of the early experience. PMID:14642540

  10. Age constraints on the proposed Plio-Pleistocene boundary stratotype at Vrica, Italy

    USGS Publications Warehouse

    Obradovich, J.D.; Naeser, C.W.; Izett, G.A.; Pasini, G.; Bigazzi, G.

    1982-01-01

    Estimates1-4 of the age of the stratotype Plio-Pleistocene boundary in Italy range from 1.65 to 2.5 Myr. We aim here to clarify this dating confusion, and we present new radiometric data on ashes from the proposed stratotype section, Vrica, Italy which indicate that the Plio-Pleistocene boundary must be less than 2 Myr old. Biostratigraphical criteria - The first appearance datums (FADs) and last appearance datums (LADs) of plank-tonic foraminifera and calcareous nannoplankton tied to the magnetic reversal chronology - Suggest that this boundary may be nearer to 1.7 Myr. Attempts to make the boundary far older than this are without basis. ?? 1982 Nature Publishing Group.

  11. Constraints on the formation age and evolution of the Moon from 142Nd-143Nd systematics of Apollo 12 basalts

    NASA Astrophysics Data System (ADS)

    McLeod, Claire L.; Brandon, Alan D.; Armytage, Rosalind M. G.

    2014-06-01

    The Moon likely formed as a result of a giant impact between proto-Earth and another large body. The timing of this event and the subsequent lunar differentiation timescales are actively debated. New high-precision Nd isotope data of Apollo mare basalts are used to evaluate the Low-Ti, High-Ti and KREEP mantle source reservoirs within the context of lunar formation and evolution. The resulting models are assessed using both reported 146Sm half-lives (68 and 103 Myr). The linear relationship defined by 142Nd-143Nd systematics does not represent multi-component mixing and is interpreted as an isochron recording a mantle closure age for the Sm-Nd system in the Moon. Using a chondritic source model with present day μ142Nd of -7.3, the mare basalt mantle source reservoirs closed at 4.45-09+10 Ga (t Sm146=68 Myr) or 4.39-14+16 Ga (t Sm146=103 Myr). In a superchondritic, 2-stage evolution model with present day μNd142 of 0, mantle source closure ages are constrained to 4.41-08+10 (t Sm146=68 Myr) or 4.34-14+15 Ga (t Sm146=103 Myr). The lunar mantle source reservoir closure ages <4.5 Ga may be reconciled by 3 potential scenarios. First, the Moon formed later than currently favored models indicate, such that the lunar mantle closure age is near or at the time of lunar formation. Second, the Moon formed ca. 4.55 to 4.47 Ga and small amounts of residual melts were sustained within a crystallizing lunar magma ocean (LMO) for up to ca. 200 Myr from tidal heating or asymmetric LMO evolution. Third, the LMO crystallized rapidly after early Moon formation. Thus the Sm-Nd mantle closure age represents a later resetting of isotope systematics. This may have resulted from a global wide remelting event. While current Earth-Moon formation constraints cannot exclusively advocate or dismiss any of these models, the fact that U-Pb ages and Hf isotopes for Jack Hills zircons from Australia are best explained by an Earth that re-equilibrated at 4.4 Ga or earlier following the Moon

  12. Microfossil biostratigraphy of prograding Neogene platform-margin carbonates, Bahamas: Age constraints and alternatives

    USGS Publications Warehouse

    Lidz, B.H.; Bralower, T.J.

    1994-01-01

    Benthic and planktic foraminifera and calcareous nannofossils were recovered in shallow-water carbonate rock cores from two continuous boreholes drilled 7.5 km apart on the west platform margin of the Great Bahama Bank. The microfossils define six biostratigraphic units in each hole. One unit in each hole represents a correlative condensed section. Seven foraminiferal biozones are recognized in 11 of the units between the holes: middle Miocene Globorotalia fohsi robusta Zone N12, late Miocene G. acostaensis Zone N16 and G. humerosa Zone N17, early Pliocene G. margaritae evoluta Subzone N19, late Pliocene G. exilis Subzone N21 and, tentatively, G. tosaensis tosaensis Zone N21, and early Pleistocene G. crassaformis viola Subzone N22. The twelfth unit is inferred to be of G. crassaformis viola Subzone N22 age. The oldest unit is onshore, the youngest is offshore. As presently interpreted, the nannofossil and foraminiferal zonations are partially correlative. Although the microfossils unequivocally constrain the series ages of the sediments, the incompleteness of the fossil record allows for alternative biozonal age models within the series. The Miocene and Pliocene biozones are common to both holes, but the greatest similarities between the holes are the significant mixing of middle and late Miocene, and late Miocene-early Pliocene faunas, the greatly condensed intervals at the Miocene/Pliocene boundary, and the early Pliocene influx of deep-water benthic and pelagic foraminifera. Of particular importance is the tentative recognition of late Pliocene G. tosaensis tosaensis Zone N21 in one borehole. Subsequent data not available to this phase of the study indicate that much of the zone is likely missing. Its absence will lend support to speculations of a regional unconformity in the Bahamas. The microfossils indicate that (1) several transgressions occurred from the middle Miocene to at least the earliest Pleistocene (> 11.5-> 0.46 Ma), during which banktop

  13. Age constraints on the evolution of the Quetico belt, Superior Province, Ontario

    NASA Technical Reports Server (NTRS)

    Percival, J. A.; Sullivan, R. W.

    1986-01-01

    Much attention has been focused on the nature of Archean tectonic processes and the extent to which they were different from modern rigid-plate tectonics. The Archean Superior Province has linear metavolcanic and metasediment-dominated subprovinces of similar scale to cenozoic island arc-trench systems of the western Pacific, suggesting an origin by accreting arcs. Models of the evolution of metavolcanic belts in parts of the Superior Province suggest an arc setting but the tectonic environment and evolution of the intervening metasedimentary belts are poorly understood. In addition to explaining the setting giving rise to a linear sedimentary basin, models must account for subsequent shortening and high-temperature, low-pressure metamorphism. Correlation of rock units and events in adjacent metavolcanic and metasedimentary belts is a first step toward understanding large-scale crustal interactions. To this end, zircon geochronology has been applied to metavolcanic belts of the western Superior Province; new age data for the Quetico metasedimentary belt is reported, permitting correlation with the adjacent Wabigoon and Wawa metavolcanic subprovinces.

  14. Improved age constraints for the retreat of the Irish Sea Ice Stream

    NASA Astrophysics Data System (ADS)

    Smedley, Rachel; Chiverrell, Richard; Duller, Geoff; Scourse, James; Small, David; Fabel, Derek; Burke, Matthew; Clarke, Chris; McCarroll, Danny; McCarron, Stephen; O'Cofaigh, Colm; Roberts, David

    2016-04-01

    BRITICE-CHRONO is a large (> 45 researchers) consortium project working to provide an extensive geochronological dataset constraining the rate of retreat of a number of ice streams of the British-Irish Ice Sheet following the Last Glacial Maximum. When complete, the large empirical dataset produced by BRITICE-CHRONO will be integrated into model simulations to better understand the behaviour of the British-Irish Ice Sheet in response to past climate change, and provide an analogue for contemporary ice sheets. A major feature of the British-Irish Ice Sheet was the dynamic Irish Sea Ice Stream, which drained a large proportion of the ice sheet and extended to the proposed southern limit of glaciation upon the Isles of Scilly (Scourse, 1991). This study will focus on a large suite of terrestrial samples that were collected along a transect of the Irish Sea basin, covering the line of ice retreat from the Isles of Scilly (50°N) in the south, to the Isle of Man (54°N) in the north; a distance of 500 km. Ages are determined for both the eastern and western margins of the Irish Sea using single-grain luminescence dating (39 samples) and terrestrial cosmogenic nuclide dating (10 samples). A Bayesian sequence model is then used in combination with the prior information determined for deglaciation to integrate the geochronological datasets, and assess retreat rates for the Irish Sea Ice Stream. Scourse, J.D., 1991. Late Pleistocene stratigraphy and palaeobotany of the Isles of Scilly. Philosophical Transactions of the Royal Society of London B334, 405 - 448.

  15. Deformation mechanism and age constraints of fault zones bordering the Leithagebirge (SE Vienna Basin, Austria).

    NASA Astrophysics Data System (ADS)

    Erkmen, C.; Grasemann, B.; Exner, U.

    2009-04-01

    m thick brittle fault zone forming the SW margin of the Leithagebirge. The ultracataclastic fault core consists of cohesive cataclasites with partly rounded left-over components. The protocataclastic damage zone records several dm- to m-thick vugs, which are covered with cm-thick flowstones. This brittle fault zone is overlain by clastic sediments of Badenian age, which record no evidence of tectonic deformation. We therefore suggest that the exhumation of the Leithagebirge ridge develop prior to the Badenium.

  16. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...

  17. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  18. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  19. Testing LTB void models without the cosmic microwave background or large scale structure: new constraints from galaxy ages

    SciTech Connect

    Putter, Roland de; Verde, Licia; Jimenez, Raul E-mail: liciaverde@icc.ub.edu

    2013-02-01

    We present new observational constraints on inhomogeneous models based on observables independent of the CMB and large-scale structure. Using Bayesian evidence we find very strong evidence for the homogeneous LCDM model, thus disfavouring inhomogeneous models. Our new constraints are based on quantities independent of the growth of perturbations and rely on cosmic clocks based on atomic physics and on the local density of matter.

  20. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. PMID:23586876

  1. The 238U/235U isotope ratio of the Earth and the solar system: Constrains from a gravimetrically calibrated U double spike and implications for absolute Pb-Pb ages

    NASA Astrophysics Data System (ADS)

    Weyer, Stefan; Noordmann, Janine; Brennecka, Greg; Richter, Stephan

    2010-05-01

    The ratio of 238U and 235U, the two primordial U isotopes, has been assumed to be constant on Earth and in the solar system. The commonly accepted value for the 238U/235U ratio, which has been used in Pb-Pb dating for the last ~ 30 years, was 137.88. Within the last few years, it has been shown that 1) there are considerable U isotope variations (~1.3‰) within terrestrial material produced by isotope fractionation during chemical reactions [1-3] and 2) there are even larger isotope variations (at least 3.5‰) in calcium-aluminum-rich inclusions (CAIs) in meoteorites that define the currently accepted age of the solar system [4]. These findings are dramatic for geochronology, as a known 238U/235U is a requirement for Pb-Pb dating, the most precise dating technique for absolute ages. As 238U/235U variations can greatly affect the reported absolute Pb-Pb age, understanding and accurately measuring variation of the 238U/235U ratio in various materials is critical, With these new findings, the questions also arises of "How well do we know the average U isotope composition of the Earth and the solar system?" and "How accurate can absolute Pb-Pb ages be?" Our results using a gravimetrically calibrated 233U/236U double spike IRMM 3636 [5] indicate that the U standard NBL 950a, which was commonly used to define the excepted "natural" 238U/235U isotope ratio, has a slightly lower 238U/235U of 137.836 ± 0.024. This value is indistinguishable from the U isotope compositions for NBL 960 and NBL112A, which have been determined by several laboratories, also using the newly calibrated U double spike IRMM 3636 [6]. These findings provide new implications about the average U isotope composition of the Earth and the solar system. Basalts display a very tight range of U isotope variations (~0.25-0.32‰ relative to SRM 950a). Their U isotope composition is also very similar to that of chondrites [4], which however appear to show a slightly larger spread. Accepting terrestrial

  2. Age constraints on felsic intrusions, metamorphism and gold mineralisation in the Palaeoproterozoic Rio Itapicuru greenstone belt, NE Bahia State, Brazil

    USGS Publications Warehouse

    Mello, E.F.; Xavier, R.P.; McNaughton, N.J.; Hagemann, S.G.; Fletcher, I.; Snee, L.

    2006-01-01

    U-Pb sensitive high resolution ion microprobe mass spectrometer (SHRIMP) ages of zircon, monazite and xenotime crystals from felsic intrusive rocks from the Rio Itapicuru greenstone belt show two development stages between 2,152 and 2,130 Ma, and between 2,130 and 2,080 Ma. The older intrusions yielded ages of 2,152??6 Ma in monazite crystals and 2,155??9 Ma in zircon crystals derived from the Trilhado granodiorite, and ages of 2,130??7 Ma and 2,128??8 Ma in zircon crystals derived from the Teofila??ndia tonalite. The emplacement age of the syntectonic Ambro??sio dome as indicated by a 2,080??2-Ma xenotime age for a granite dyke probably marks the end of the felsic magmatism. This age shows good agreement with the Ar-Ar plateau age of 2,080??5 Ma obtained in hornblendes from an amphibolite and with a U-Pb SHRIMP age of 2,076??10 Ma in detrital zircon crystals from a quartzite, interpreted as the age of the peak of the metamorphism. The predominance of inherited zircons in the syntectonic Ambro??sio dome suggests that the basement of the supracrustal rocks was composed of Archaean continental crust with components of 2,937??16, 3,111??13 and 3,162??13 Ma. Ar-Ar plateau ages of 2,050??4 Ma and 2,054??2 Ma on hydrothermal muscovite samples from the Fazenda Brasileiro gold deposit are interpreted as minimum ages for gold mineralisation and close to the true age of gold deposition. The Ar-Ar data indicate that the mineralisation must have occurred less than 30 million years after the peak of the metamorphism, or episodically between 2,080 Ma and 2,050 Ma, during uplift and exhumation of the orogen. ?? Springer-Verlag 2006.

  3. The absolute path command

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore » provide the absolute path to a relative directory from the current working directory.« less

  4. The absolute path command

    SciTech Connect

    Moody, A.

    2012-05-11

    The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it can provide the absolute path to a relative directory from the current working directory.

  5. Timing of flysch sedimentation in the Ouachita remnant ocean basin: Constraints from U-Pb ages of zircon in subaqueous tuff deposits

    NASA Astrophysics Data System (ADS)

    Shaulis, B. J.; Lapen, T. J.; Casey, J. F.; Staszyc, A.; Newberry, A. S.

    2012-12-01

    New U-Pb ages of zircon from subaqueous tuff in the oldest flysch units deposited in the Ouachita-Marathon remnant ocean basin constrain the absolute timing of orogenic flysch deposition. Zircons from five tuffaceous units distributed throughout the Mississippian Stanley Group in the Ouachita region define its absolute age range and depositional rates (Shaulis et al., 2012, in press). From the lowermost to the uppermost tuff unit analyzed, the weighted averages for the youngest age population range from 328.5 ± 2.7 Ma to 320.7 ± 2.5 Ma. Combined with conodont biostratigraphy, these new zircon ages show sedimentation rates remained low (1-40 m/Ma.) from the end of the Devonian until ~323 Ma. After 323 Ma sedimentation rates increase rapidly to 300-1400 m/Ma and remain high through the deposition of the Pennsylvanian Atoka Formation. The Tesnus Formation (Stanley Group equivalent) in the Marathon region is just 1850 m thick compared to a thickness of ~3000 m for the Stanley Group. The tuffaceous units have only been identified in a single outcrop, but well data from across the region suggest the volcanic units could cover a large area. New U-Pb zircon ages of three tuff units in the Tesnus Formation (320.2 ± 1.7 Ma, 321.5 ± 3.1 Ma, and 321.9 ± 1.7 Ma, lowermost to uppermost) suggest that these tuffs are equivalent to the Mud Creek and Chickasaw Creek tuffs in the Stanley Group. Compared to the Mud Creek and Chickasaw Creek tuffs in the Stanley Group which are separated by nearly 2000 m of sediment, the Tesnus tuffs occur over a much smaller 20 m interval. Based on these proposed tuff correlations, the onset of rapid flysch sedimentation began in the Ouachita region during deposition of the Mud Creek and Chickasaw Creek tuffs (323 Ma) but had not yet begun in the Marathon region during deposition of the age equivalent Tesnus tuffs, where sedimentation rates appear low. This, and dominantly westward paleo-flow indicators (Johnson, 1968), are consistent with a

  6. 'We're in the sandwich': Aged care staff members' negotiation of constraints and the role of the organisation in enacting and supporting an ethic of care.

    PubMed

    Petriwskyj, Andrea; Gibson, Alexandra; Webby, Glenys

    2015-12-01

    Aged care staff are often seen as holding power in care relationships, particularly in client engagement. Such a perception, however, may limit our understanding and analysis of the dynamics and politics within care spaces. This paper uses interview and focus group data from both staff and clients of an Australian aged care provider to identify the positions given to, and taken up by, staff in client engagement. Focusing on one of these positions, in which staff are seen as managing and negotiating constraints, the paper uses an ethic of care lens to examine the context in which engagement - and this position taking - occurs. Findings reflect the importance of the organisational and systemic context to the practice of care ethics and the potential vulnerability and disempowerment of care giving staff. Implications for the support of staff in client engagement and the role of care organisations beyond structures and processes to an active participant in an ethic of care are discussed. PMID:26568218

  7. Ar-40/Ar-39 age constraints for the Jaramillo Normal Subchron and the Matuyama-Brunhes geomagnetic boundary

    NASA Astrophysics Data System (ADS)

    Izett, Glen A.; Obradovich, John D.

    1994-02-01

    Our mid-Pleistocene Ar-40/Ar-39 age recalibration of the geomagnetic polarity timescale is nearly in accord with the oxygen isotope, climate record calibration of the astronomical timescale proposed by Johnson (1982) and Shackleton et al. (1990). Ar-40/Ar-39 ages of a normally magnetized rhyolite dome in the Valles caldera, northern Mexico, yielded a weighted-mean age of 1.004 +/- 0.019 Ma. A K-Ar age of 0.909 +/- 0.019 Ma for this rock by Doell and Dalrymple (1966) was the linchpin for the recognition and calibration of the Jaramillo Normal Subchron (JNS). Other Ar-40/Ar-39 ages from the Valles caldera and Ar-40/Ar-39 ages of Ivory Coast tektites indicate that the JNS began at about 1.11 Ma and ended before 0.92 Ma, probably near 0.97 Ma. The Matuyama-Brunhes boundary occurred between 0.79 Ma and 0.76 Ma on the basis of Ar-40/Ar-39 sanidine ages from (1) three reversely magnetized rhyolite domes of the Valles caldera (0.793 +/- 0.018 Ma, 0.794 +/- 0.007 Ma, and 0.812 +/- 0.023 Ma) and pumice (0.789 +/- 0.006 Ma) from the reversely magnetized Oldest Toba Tuff of Sumatra and (2) pumice (0.764 +/- 0.005 Ma and 0.757 +/- 0.009 Ma) from the lower and upper units of the normally magnetized Bishop Tuff. The age of the boundary may be close to 0.77 Ma as deduced from rates of sedimentation in ancient Lake Bonneville, Utah.

  8. A seismological constraint on the age and geometry of the Ryukyu Subduction Zone in the Vicinity of Taiwan

    NASA Astrophysics Data System (ADS)

    Tseng, Y.; Kuo, B.; Tseng, T.; Chang, Y.

    2012-12-01

    The Huatung basin, a 200 km wide sliver of seafloor, constitutes the westernmost frontier of the Philippine Sea Plate. Paleomagnetic analyses in the 1980's determined the age of the Huatung basin to be about 40 Ma. In 2000, an Ar-Ar dating for rocks dredged from the SE corner of the basin suggested an early-Cretaceous age (~125 Ma), reversing the age contrast with the west Philippine basin to the east. The controversy has remained since. In this study, we use an approximately linear array of broadband stations in Taiwan that points to events in the Aleutian region, and employ a 2-D finite-difference technique to calculate synthetic waveforms for simple slab models that mimic the subduction velocity structure as a function of the age and dip of the slab. Because of the defocusing of waves traveling up-dip the slab from teleseismic sources, the older and thicker the slab (hence the Huatung basin lithosphere), the more diminishing and wide-spreading the amplitude valley along the linear array will appear. We tested different parameters that might effects the modeling: (1) the dip angle, θ, (2) the age of subducting slab, T0, (3) the converted coefficient, ∂V/∂T, and (4) the duration of subduction, TS. The influence of (4) is not in evident, and we focus on the differences between (1) and (3) with different ages of slab. As the results, the best fit of straight slab (θ=45°) occurs around ages 20~30 Ma and converted coefficients -5.4E-5 ~ -7.0E-5. The bended slab models which fit the seismicity well, however, do not yield better fitting than the straight slab model.

  9. U-Pb zircon constraints on the age and provenance of the Rocas Verdes basin fill, Tierra del Fuego, Argentina

    NASA Astrophysics Data System (ADS)

    Barbeau, David L.; Gombosi, David J.; Zahid, Khandaker M.; Bizimis, Michael; Swanson-Hysell, Nicholas; Valencia, Victor; Gehrels, George E.

    2009-12-01

    The Late Jurassic to Early Cretaceous Rocas Verdes basin constitutes one of the most poorly understood components of the southernmost Andes. As a result, accurate reconstructions and interpretations of deformation associated with the Andean orogeny and the kinematics of Scotia arc development also remain poorly constrained. In this data brief, we report U-Pb zircon ages from sandstones of the Rocas Verdes basin fill and from a crosscutting pluton in the southernmost Andes of Argentine Tierra del Fuego. Detrital samples contain predominant Early to early Middle Cretaceous (circa 130-105 Ma) U-Pb zircon age populations, with very small or single-grain middle Mesozoic and Proterozoic subpopulations. A very small subpopulation of Late Cretaceous ages in one sample raises the unlikely possibility that parts of the Rocas Verdes basin are younger than perceived. A sample from a crosscutting syenitic pegmatite yields a crystallization age of 74.7 +2.2/-2.0 Ma. The data presented herein encourage further geochronologic evaluation of the Rocas Verdes basin in order to better constrain the depositional ages and provenance of its contents.

  10. SHRIMP and 40Ar/39Ar age constraints for timing of plutonism and mineralization in the Boulder batholith

    USGS Publications Warehouse

    Lund, K.D.; Aleinikoff, John N.; Kunk, Michael J.; Unruh, Dan M.; Zeihen, G.D.; Hodges, W.C.; du Bray, Edward A.; O'Neill, J Michael

    2002-01-01

    The 66 Ma age for the quartz monzodiorite of Boulder Baldy and consideration of previous dating studies in the region indicate that small ca. 66 Ma plutonic systems may be common in the Boulder batholith region and especially to the east. The approximately 64 Ma porphyry copper systems at Butte and gold mineralization at Miller Mountain are indicative of regionally important mineralizing systems of this age in the Boulder batholith region. Resolution of the age and probable magmatic source of the Butte pre-Main Stage porphyry copper-molybdenum system and of the silver-rich polymetallic quartz vein systems in the northern part of the Boulder batholith documents that these deposits formed from two discrete periods of hydrothermal mineralization related to two discrete magmatic events.

  11. Early Precambrian mantle derived rocks in the southern Prince Charles Mountains, East Antarctica: age and isotopic constraints

    USGS Publications Warehouse

    Mikhalsky, E.V.; Henjes-Kunst, F.; Roland, N.W.

    2007-01-01

    Mafic and ultramafic rocks occurring as lenses, boudins, and tectonic slabs within metamorphic units in the southern Mawson Escarpment display mantle characteristics of either a highly enriched, or highly depleted nature. Fractionation of these mantle rocks from their sources may be as old as Eoarchaean (ca 3850 Ma) while their tectonic emplacement probably occurred prior to 2550 Ma (U-Pb SHRIMP data). These results provide for the first time evidence for Archaean suturing within East Antarctica. Similar upper mantle sources are likely present in the northern Mawson Escarpment. A younger age limit of these rocks is 2200 Ma, as indicated by presumably metamorphic zircon ages while their magmatic age may be constrained by single zircon dates at 2450-2250 Ma. The area of the northern Mawson Escarpment is most likely of ensimatic origin and includes mafic rocks which were derived from distinct mantle source(s) during Palaeoproterozoic time.

  12. Age constraints on Tarkwaian palaeoplacer and lode-gold formation in the Tarkwa-Damang district, SW Ghana

    USGS Publications Warehouse

    Pigois, J.-P.; Groves, D.I.; Fletcher, I.R.; McNaughton, N.J.; Snee, L.W.

    2003-01-01

    Two major epigenetic gold-forming events are recorded in the world-class gold province of southwest Ghana. A pre-Tarkwaian event was the source of the world-class Tarkwa palaeoplacers whereas post-Birimian and Tarkwaian deformation, which was related to the Eburnean orogeny, gave rise to the world-class (e.g. Prestea) to giant (e.g. Obuasi) orogenic gold deposits which have made the region famous for more than 2,500 years. A maximum age of 2133 ?? 4 Ma for Tarkwaian sedimentation is provided by 71 of 111 concordant SHRIMP II U Pb dates from detrital zircons in Tarkwaian clastic rocks from Damang and Bippo Bin, northeast of Tarkwa. The overall data distribution broadly overlaps the relatively poorly constrained ages of Birimian volcanism and associated Dixcove-type granitoid emplacement, indicating syntectonic development of the Tarkwaian sedimentary basin. These zircon ages argue against derivation of the palaeoplacer gold from an orogenic gold source related to the compressional phase of an orogeny significantly older than the Eburnean orogeny. Instead, they suggest that the gold source was either orogenic gold lodes related to an earlier compressional phase of a diachronous Eburnean orogeny or ca. 2200-2100 Ma intrusion-related gold lode. The CO2-rich fluid inclusions in associated vein-quartz pebbles are permissive of either source. At the Damang deposit, an epigenetic, orogenic lode-gold system clearly overprinted, and sulphidised low-grade palaeoplacer hematite magnetite gold occurrences in the Banket Series conglomerate within the Tarkwaian sedimentary sequence. Gold mineralisation is demonstrably post-peak metamorphism, as gold-related alteration assemblages overprint metamorphic assemblages in host rocks. In alteration zones surrounding the dominant, subhorizontal auriferous quartz veins, there are rare occurrences of hydrothermal xenotime which give a SHRIMP U Pb age of 2063 ?? 9 Ma for gold mineralisation. The similar structural timing of epigenetic gold

  13. Mesozoic exhumation in the coastal region of NW Iberia: Preliminary constraints from apatite fission-track cooling ages

    NASA Astrophysics Data System (ADS)

    Alvarez-Marrón, Joaquina; Barbero, Luis; Menéndez-Duarte, Rosana; Fernández, Susana

    2013-04-01

    Apatite fission-track (AFT) ages from the Iberian Massif, along the northern coastal region in Galicia are presented. The study aims at unravelling the exhumation history of this higher topography coastal region, the so-called Rías Altas region, next to the northern Iberian margin. The rough topography region is bound to the south by the WNW-ESE trending As Pontes dextral strike-slip fault zone. This fault was active since ca. 30 Ma (Rupelian) up to ca. 21 Ma (Aquitanian). The area comprises mainly Late Proterozoic to Paleozoic metamorphic and igneous rocks from the hinterland of the Variscan orogen. A N-S AFT ages profile from the coast to the southern block of the As Pontes fault reveal progressively younger ages toward the south with the oldest ages (242 ± 12 Ma) located near the coast and the youngest age being 124 ± 7 Ma. The AFT ages at both sides of the As Pontes fault in samples taken at the same elevation are similar within error (124 ± 7and 127 ± 7 Ma) indicating that this strike-slip fault did not cause significant differential exhumation during Oligocene-Early Miocene times. Another important feature shown by these data is that the age-elevation relationship (AER) is negative, the youngest ages being located at the highest elevation (ca. 1000 m. a. s. l). This agrees with recent published data from the easternmost part of the present study area and is an indication of Post-Early Cretaceous long residence time within the upper 2 or 3 km of the crust at temperatures lower than those of the apatite partial annealing zone (60 to 120°C). We interpret the registered exhumation history as mostly related to rifting processes in Pre-Early Cretaceous times. Possibly recording surface processes associated to the two stage rifting episodes in the Triassic and in the Late Jurassic-Early Cretaceous that culminated with formation of the north Iberian Margin. The negative AER suggests that since Early Cretaceous times the whole area underwent topographic changes

  14. Late Quaternary sedimentological and climate changes at Lake Bosumtwi Ghana: new constraints from laminae analysis and radiocarbon age modeling

    USGS Publications Warehouse

    Shanahan, Timothy M.; Beck, J. Warren; Overpeck, Jonathan T.; McKay, Nicholas P.; Pigati, Jeffrey S.; Peck, John A.; Scholz, Christopher A.; Heil, Clifford W., Jr.; King, John W.

    2012-01-01

    The Lake Bosumtwi sediment record represents one of the longest and highest-resolution terrestrial records of paleoclimate change available from sub-Saharan Africa. Here we report a new sediment age model framework for the last ~ 45 cal kyr of sedimentation using a combination of high-resolution radiocarbon dating, Bayesian age-depth modeling and lamination counting. Our results highlight the practical limits of these methods for reducing age model uncertainties and suggest that even with very high sampling densities, radiocarbon uncertainties of at least a few hundred years are unavoidable. Age model uncertainties are smallest during the Holocene (205 yr) and the glacial (360 yr) but are large at the base of the record (1660 yr), due to a combination of decreasing sample density, larger calibration uncertainties and increases in radiocarbon age scatter. For portions of the chronology older than ~ 35 cal kyr, additional considerations, such as the use of a low-blank graphitization system and more rigorous sample pretreatment were necessary to generate a reliable age depth model because of the incorporation of small amounts of younger carbon. A comparison of radiocarbon age model results and lamination counts over the time interval ~ 15–30 cal kyr agree with an overall discrepancy of ~ 10% and display similar changes in sedimentation rate, supporting the annual nature of sediment laminations in the early part of the record. Changes in sedimentation rates reconstructed from the age-depth model indicate that intervals of enhanced sediment delivery occurred at 16–19, 24 and 29–31 cal kyr, broadly synchronous with reconstructed drought episodes elsewhere in northern West Africa and potentially, with changes in Atlantic meridional heat transport during North Atlantic Heinrich events. These data suggest that millennial-scale drought events in the West African monsoon region were latitudinally extensive, reaching within several hundred kilometers of the Guinea coast

  15. Syn- and post-tectonic granite plutonism in the Sausar Fold Belt, central India: Age constraints and tectonic implications

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Anupam; Das, Kaushik; Hayasaka, Yasutaka; Sarkar, Arindam

    2015-08-01

    Sausar Fold Belt (SFB) in central India forms the southern part of the Central Indian Tectonic Zone (CITZ) - a crustal scale Proterozoic mobile belt dissecting the Indian craton, whose tectonothermal history and age is important for understanding the Proterozoic crustal history of the Indian craton. SFB comprises a gneissic basement (TBG: Tirodi Biotite Gneiss) overlain by a supracrustal sequence of quartzite-pelite-carbonate (SSG: Sausar Group). SSG and TBG are deformed and metamorphosed in greenschist to amphibolite facies. Two phases of granite intrusion are observed in the SSG - a syntectonic foliated granite and a post-tectonic massive granite, with clear structural relationship with the host rocks. Monazite chemical dating (U-Th-total Pb) of the foliated and massive granites yield Neoproterozoic (ca. 945-928 Ma) ages that contradict many earlier geochronological interpretations. Foliated granites and the immediately adjacent TBG show monazite grains with ca. 945 Ma mean age, interpreted as the timing of D2 deformation and amphibolite facies metamorphism of SSG. The post tectonic granites intruded these rocks around 928 Ma, and were largely undeformed. A terminal thermal overprint is found in some monazite grain rims at ca. 785 Ma age. The younger Sausar tectonothermal events have overprinted the adjacent high-grade granulites of Ramakona-Katangi Granulite (RKG) belt, and should not be considered as parts of the same tectonothermal event representing different depth sections only.

  16. Single zircon age constraints on the tectonic juxtaposition of the Archean Abitibi greenstone belt and Pontiac subprovince, Quebec, Canada

    SciTech Connect

    Feng, R.; Kerrich, R. )

    1991-11-01

    Zircons from metasediments and granitoids in the high-grade Lacorne block within the low-grade Archean Abitibi greenstone belt have been dated by single zircon Pb-evaporation technique, yielding {sup 207}Pb/{sup 206}Pb minimum ages. Detrital zircons in the mature clastic metasediments of the Lacorne block display a range of ages from 2,691 {plus minus} 8 Ma to 3,042 {plus minus} 6 Ma. The younger zircon ages thus impose an upper limit for deposition and indicate that the high-grade Lacorne block is not basement to the Abitibi supracrustal sequence (2,747-2,680 Ma). Existence of abundant (69%) older detrital zircons (> 2,750 Ma) suggest in turn that the Abitibi supracrustal rocks are not the source of the Lacorne sediments. Two generations of granitoids occur in the Lacorne block, an early monosodiorite-monzonite-granodiorite-syenite series and a younger S-type garnet-muscovite granite series. This contrasts with granitoid magmatism in the Abitibi greenstone belt which ended at {approximately}2675 Ma. The Pontiac subprovince to the south of the Abitibi greenstone belt shares all of the above features of the Lacorne block, including detrital zircon ages as well as the composition and timing of granitoid magmatism. This is interpreted detrital zircon ages as well as the composition and timing of granitoid magmatism. This is interpreted to indicate that the Lacorne block was originally part of the same tectonic terrane as the Pontiac subprovince. After development of the MMGS magmatism (21,670-2,680 Ma), the Pontiac subprovince locally underthrust the Abitibi greenstone belt, and crustal thickening promoted partial melting of underthrust Pontiac metasediments to form the {approximately}2,644 {plus minus} 13 Ma S-type granites.

  17. 40Ar/39Ar Age Constraints on Caldera Formation of the Emmons Lake Volcanic Center, Alaska Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    Drake, J.; Layer, P. W.; Mangan, M. T.; Miller, T. P.; Waythomas, C. F.

    2001-12-01

    The Emmons Lake Volcanic Center located on the Alaska Peninsula is a large shield/stratovolcano complex composed of basaltic to andesitic lava flows and dacite to rhyolite pyroclastic flows, domes and ashfall. Two caldera forming eruptions in Pleistocene time each produced more than 50 cubic kilometers of silicic ejecta and created a nested depression measuring 20 km long and 10 km wide. We conducted 40Ar/39Ar whole rock dating of units associated with the first caldera forming event, which because of broad geochemical similarities, has been suggested as a possible source of the Old Crow Tephra, dated throughout interior Alaska and the Yukon at about 140 ka. Samples dated ranged in composition from ~62 to 69 wt % SiO2 and contained 2 - 3 wt % K2O. For each sample, 15 specimens, consisting of small ( ~1 mm) whole rock chips, were fused with an argon ion laser. From these analyses, weighted mean and isochron ages were calculated. For all samples, the initial 40Ar/36Ar ratio was indistinguishable from that of the present-day atmosphere (295.5), indicating that these samples do not contain significant quantities of excess argon. The age of a welded tuff interpreted to be from the opening plinian phase of the eruption is 233 +/- 6 ka, and is identical to the age of a post-collapse rheomorphic tuff (234 +/- 5 ka). A lithic fragment from a syn-collapse lag breccia has an age of 419 +/- 9 ka, which we interpret as representing incorporation of older material. Younger tuffs and domes were dated at 99 +/- 7 ka and 16 +/- 10 ka and imply that the complex was active throughout the late Quaternary. Based on these new age data, and subtle but significant trace element differences in glass and Fe-Ti oxide composition, we conclude that the first major caldera building event occurred at approximately 230 ka, and is probably not responsible for the deposition of the Old Crow tephra.

  18. Late Permian age of ammonium-bearing illite in Pennsylvania anthracites: Temporal constraints on coalification in the central Appalachians

    SciTech Connect

    Daniels, E.J.

    1996-12-31

    K/Ar dating of authigenic NH4-bearing illite in coal from the Anthracite region of eastern Pennsylvania yields apparent ages of 253-236 Ma ({+-}8 m.y.). The oldest K/Ar date of 253 Ma ({+-}8 m.y.) is a minimum age for the thermal event associated with anthracite formation and illite authigenesis. This date is probably within {approx}10 m.y. of the time at which coal-bearing rocks experienced peak temperatures, which suggests an age range of 265-255 Ma for this event. Age dates for authigenic NH{sub 4}-bearing illite reflect the approximate age of late-stage coalification (formation of anthracite-rank coal) because this mineral formed only during late-stage coalification (T=200-275{degrees}C) from a kaolinite (potassium-free) precursor, and the K/Ar data suggest that NH{sub 4} does not significantly influence the closure temperature of illite. K/Ar dates, in conjunction with paleomagnetic and vitrinite reflectance data, constrain the thermal pulse and deformation associated with the Alleghanian orogenic episode to a time period of 25-35 m.y., beginning in Early Permian time ({approx}285 Ma) after coal deposition, and concluding by Late Permian time ({approx}260-250 Ma). Syn- and post-folding secondary chemical remanent magnetizations constrain Alleghanian folding in the Central Appalachians to Late Permian time, which coincides with the postulated time range of 265-255 Ma for NH{sub 4}-bearing illite authigenesis and anthracite formation derived from the K/Ar data. The similar time range for anthracite formation and Alleghanian folding is consistent with vitrinite reflectance data that suggests anthracite formation was a syn-folding thermal event.

  19. Late Permian age of ammonium-bearing illite in Pennsylvania anthracites: Temporal constraints on coalification in the central Appalachians

    SciTech Connect

    Daniels, E.J. )

    1996-01-01

    K/Ar dating of authigenic NH4-bearing illite in coal from the Anthracite region of eastern Pennsylvania yields apparent ages of 253-236 Ma ([+-]8 m.y.). The oldest K/Ar date of 253 Ma ([+-]8 m.y.) is a minimum age for the thermal event associated with anthracite formation and illite authigenesis. This date is probably within [approx]10 m.y. of the time at which coal-bearing rocks experienced peak temperatures, which suggests an age range of 265-255 Ma for this event. Age dates for authigenic NH[sub 4]-bearing illite reflect the approximate age of late-stage coalification (formation of anthracite-rank coal) because this mineral formed only during late-stage coalification (T=200-275[degrees]C) from a kaolinite (potassium-free) precursor, and the K/Ar data suggest that NH[sub 4] does not significantly influence the closure temperature of illite. K/Ar dates, in conjunction with paleomagnetic and vitrinite reflectance data, constrain the thermal pulse and deformation associated with the Alleghanian orogenic episode to a time period of 25-35 m.y., beginning in Early Permian time ([approx]285 Ma) after coal deposition, and concluding by Late Permian time ([approx]260-250 Ma). Syn- and post-folding secondary chemical remanent magnetizations constrain Alleghanian folding in the Central Appalachians to Late Permian time, which coincides with the postulated time range of 265-255 Ma for NH[sub 4]-bearing illite authigenesis and anthracite formation derived from the K/Ar data. The similar time range for anthracite formation and Alleghanian folding is consistent with vitrinite reflectance data that suggests anthracite formation was a syn-folding thermal event.

  20. Age constraints on late Mesozoic lithospheric extension and origin of bimodal volcanic rocks from the Hailar basin, NE China

    NASA Astrophysics Data System (ADS)

    Li, Shuang-Qing; Hegner, Ernst; Yang, Yi-Zeng; Wu, Jia-De; Chen, Fukun

    2014-03-01

    Following the amalgamation of the late Mesoproterozoic-Carboniferous Central Asian Orogenic Belt with the Siberian and North China cratons, NE China underwent late Mesozoic lithospheric extension and widespread formation of volcano-sedimentary basins. We report U-Pb zircon ages and geochemical data for mafic and felsic volcanic rocks from the Hailar basin, located about 1000 km north of Beijing. Zircon populations of six felsic rock samples analyzed by laser ablation ICP-MS yielded similar U-Pb age spectra ranging from 158 to 125 Ma. The youngest zircon ages are interpreted as time of magma eruption and the xenocrystic zircon-age spectra as evidence for a protracted melting of lower crust due to the underplating of mantle-derived magmas during lithospheric extension. The volcanic assemblage has a bimodal composition comprising geochemically evolved trachybasalts and felsic volcanic rocks of I- and subordinate A-type compositions. The mafic volcanic rocks have negative Nb-anomalies, high Th/Nb and Ce/Pb ratios, low initial ɛNd values of + 0.4 to + 3.4, and radiogenic Pb and Sr isotopes all interpreted as evidence for the melting of passively upwelling asthenosphere and lithospheric mantle previously modified by plate subduction. The xenocrystic zircon ages and chemical/isotopic data of the felsic rocks support an origin from juvenile crustal protoliths: the data of I-type felsic rocks are consistent with the melting of underplated mafic protoliths and those of the A-type rhyolites support the melting of a crustal source with a composition similar to the I-type felsites with apatite controlling their Nb anomaly. The evidence for the persistent melting of a subduction-modified mantle in NE China is in agreement with a model of an extending coupled upper mantle-crust system due to a retreating Paleo-Pacific trench.

  1. Ice-age Ice-sheet Rheology: Constraints from the Last Glacial Maximum Form of the Laurentide Ice Sheet

    NASA Technical Reports Server (NTRS)

    Peltier, W. Richard; Goldsby, David L.; Kohlstedt, David L.; Tarasov, Lev

    2000-01-01

    State-ot-the-art thermomechanical models of the modern Greenland ice and the ancient Laurenticle ice sheet that covered Canada at the Last Glacial Maximum (LGM) are not able to explain simultaneously the observed forms of these cryospheric structures when the same, anisotropy-enhanced, version of the conventional Glen flow law is employed to describe their rheology. The LGM Laurenticle ice sheet. predicted to develop in response to orbital climate forcing, is such that the ratio of its thickness to its horizontal extent is extremely large compared to the aspect ratio inferred on the basis of surface-geomorphological and solid-earth-geophysical constraints. We show that if the Glen flow law representation of the rheology is replaced with a new rheology based upon very high quality laboratory measurements of the stress-strain-rate relation, then the aspect ratios of both the modern Greenland ice sheet and the Laurenticle ice sheet, that existed at the LGM, are simultaneously explained with little or no retuning of the flow law.

  2. A Novel Method for Predicting Late Genitourinary Toxicity After Prostate Radiation Therapy and the Need for Age-Based Risk-Adapted Dose Constraints

    SciTech Connect

    Ahmed, Awad A.; Egleston, Brian; Alcantara, Pino; Li, Linna; Pollack, Alan; Horwitz, Eric M.; Buyyounouski, Mark K.

    2013-07-15

    Background: There are no well-established normal tissue sparing dose–volume histogram (DVH) criteria that limit the risk of urinary toxicity from prostate radiation therapy (RT). The aim of this study was to determine which criteria predict late toxicity among various DVH parameters when contouring the entire solid bladder and its contents versus the bladder wall. The area under the histogram curve (AUHC) was also analyzed. Methods and Materials: From 1993 to 2000, 503 men with prostate cancer received 3-dimensional conformal RT (median follow-up time, 71 months). The whole bladder and the bladder wall were contoured in all patients. The primary endpoint was grade ≥2 genitourinary (GU) toxicity occurring ≥3 months after completion of RT. Cox regressions of time to grade ≥2 toxicity were estimated separately for the entire bladder and bladder wall. Concordance probability estimates (CPE) assessed model discriminative ability. Before training the models, an external random test group of 100 men was set aside for testing. Separate analyses were performed based on the mean age (≤ 68 vs >68 years). Results: Age, pretreatment urinary symptoms, mean dose (entire bladder and bladder wall), and AUHC (entire bladder and bladder wall) were significant (P<.05) in multivariable analysis. Overall, bladder wall CPE values were higher than solid bladder values. The AUHC for bladder wall provided the greatest discrimination for late bladder toxicity when compared with alternative DVH points, with CPE values of 0.68 for age ≤68 years and 0.81 for age >68 years. Conclusion: The AUHC method based on bladder wall volumes was superior for predicting late GU toxicity. Age >68 years was associated with late grade ≥2 GU toxicity, which suggests that risk-adapted dose constraints based on age should be explored.

  3. The tectonic evolution of Cenozoic extensional basins, northeast Brazil: Geochronological constraints from continental basalt 40Ar/39Ar ages

    NASA Astrophysics Data System (ADS)

    de Souza, Zorano Sérgio; Vasconcelos, Paulo Marcos; Knesel, Kurt Michael; da Silveira Dias, Luiz Gustavo; Roesner, Eduardo Henrique; Cordeiro de Farias, Paulo Roberto; de Morais Neto, João Marinho

    2013-12-01

    The Boa Vista and Cubati Basins, Paraíba, Brazil, are NW-SE extension-related intracratonic basins that resulted from tectonic stresses after the opening of the South Atlantic. These basins contain lacustrine fossiliferous sediments, bentonite beds, and basalt flows that preserve Cenozoic continental records. 40Ar/39Ar ages for six whole-rocks from two distinct basaltic flows underlying the sediments in the Boa Vista basin are 27.3 ± 0.8 and 25.4 ± 1.3 Ma, while three grains from a basaltic flow overlying the sediments yield 22.0 ± 0.2 Ma. The sediments at the nearby Cubati Basin are overlain by a basalt flow with ages of ˜25.4 Ma. Three whole-rocks from an NE-SW-trending trachytic dyke cross cutting the sediments at the Boa Vista Basin yield 40Ar/39Ar ages of ˜12.45 ± 0.06, 12.59 ± 0.07, and 12.58 ± 0.07 Ma. Three whole-rocks from a nearby volcanic plug (Chupador) yield an age of 23.4 ± 0.1 Ma. The geochronological results combined with stratigraphic correlations between the two basins allow bracketing the age of the main sedimentary and bentonic units within the Boa Vista and Cubati Basins between 25.5 ± 1.3 and 24.9 ± 0.1 Ma. The ages, combined with field observations reveal that the formation of the Boa Vista and Cubati basins is associated with mantle-derived magmas channelled through reactivated Precambrian shear zones. Our geochronological results suggest that a temporal link with the Fernando de Noronha and Saint Helena hot spots can be excluded as possible sources of the Boa Vista and Cubati magmas. Rather, the extensional tectonics in the 30-20 Ma interval, long after Gondwana break-up, may be associated with the re-activation of continental-scale shear zones that channelled small batches of mantle-derived magmas.

  4. New SHRIMP zircon age constraints on the evolution of crystalline basement in Eastern Lithuania (East European Craton)

    NASA Astrophysics Data System (ADS)

    Vejelyte, I.; Bogdanova, S.; Yi, K.; Cho, M.

    2012-04-01

    The crystalline crust in Lithuania was formed between ca. 1.9 and 1.8 Ga during the Svecofennian orogeny. Major tectonic domains include the West Lithuanian Granulite Domain and the East Lithuanian Domain occupying either side of the Mid-Lithuanian Suture Zone, and in the southeast the Belarus-Podlasie-Granulite Belt. The study area is situated within the Drūkšiai-Polotsk Deformation Zone (DPDZ) in the East Lithuanian Domain, which is well defined by gravity and magnetic linear anomalies. In this study, zircons separated from two deformed granitoids of the DPDZ were dated using the Sensitive High-Resolution Ion Microprobe (SHRIMP IIe) at the Korea Basic Science Institute (KBSI). The Novikai-1 granite defines two age groups of zircon. One group represents the inherited zircon cores dated at 1907, 1900, and 1887 Ma, respectively. The other comprises the magmatic age of metamictized cores and overgrowth rims that yielded a mean 207Pb/206Pb age of 1793.2±6.5 Ma (n=19, MSWD=2.4). The latter is broadly similar to the zircon 207Pb /206Pb age (1830±20 Ma) of charnockitic rocks in the West Lithuanian Granulite Domain (Claesson et al., 2001) and to 1.81-1.77 Ga of TIB-1 type granitoids in Sweden (Åhäll & Larson 2000; Andersson et al., 2004). This felsic magmatism suggests the development of an active continental margin of the East European Craton in the late Palaeoproterozoic. The Tverečius deformed grandiorite contains well-preserved and oscillatory-zoned zircon grains, which yielded a mean 207Pb/206Pb age of 1542±17 (n=20, MSWD=1.8). This age is consistent with that of the rapakivi granitoids in the Svecofennian domain and of the Mesoproterozoic AMCG granitoids in the Mazury complex, NE Poland (Wiszniewska et al., 2007). Taken together, magmatic activities in the crystalline basement of eastern Lithuania thus correlate well with those in the Baltic Shield, defined by both the Paleoproterozoic orogenic event and the Mesoproterozoic intracratonic extension. This is a

  5. AGE AND MASS CONSTRAINTS FOR A YOUNG MASSIVE CLUSTER IN M31 BASED ON SPECTRAL ENERGY DISTRIBUTION FITTING

    SciTech Connect

    Ma Jun; Wang Song; Wu Zhenyu; Fan Zhou; Yang Yanbin; Zhang Tianmeng; Wu Jianghua; Zhou Xu; Jiang Zhaoji; Chen Jiansheng

    2011-03-15

    VDB0-B195D is a massive, blue star cluster in M31. It was observed as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey using 15 intermediate-band filters covering a wavelength range of 3000-10000 A. Based on aperture photometry, we obtain its spectral energy distribution (SED) as defined by the 15 BATC filters. We apply previously established relations between the BATC intermediate-band and the Johnson-Cousins UBVRI broadband systems to convert our BATC photometry to the standard system. A detailed comparison shows that our newly derived VRI magnitudes are fully consistent with previous results, while our new B magnitude agrees to within 2{sigma}. In addition, we determine the cluster's age and mass by comparing its SED (from 3000 to 20000 A, comprising photometric data in the 15 BATC intermediate bands, optical broadband BVRI, and Two Micron All Sky Survey near-infrared JHK{sub s} data) with theoretical stellar population synthesis models, resulting in age and mass determinations of 60.0 {+-} 8.0 Myr and (1.1-1.6) x 10{sup 5} M{sub sun}, respectively. This age and mass confirms previous suggestions that VDB0-B195D is a young massive cluster in M31.

  6. Age constraints on the dispersal of dinosaurs in the Late Triassic from magnetochronology of the Los Colorados Formation (Argentina)

    PubMed Central

    Kent, Dennis V.; Santi Malnis, Paula; Colombi, Carina E.; Alcober, Oscar A.; Martínez, Ricardo N.

    2014-01-01

    A measured magnetozone sequence defined by 24 sampling sites with normal polarity and 28 sites with reverse polarity characteristic magnetizations was established for the heretofore poorly age-constrained Los Colorados Formation and its dinosaur-bearing vertebrate fauna in the Ischigualasto–Villa Union continental rift basin of Argentina. The polarity pattern in this ∼600-m-thick red-bed section can be correlated to Chrons E7r to E15n of the Newark astrochronological polarity time scale. This represents a time interval from 227 to 213 Ma, indicating that the Los Colorados Formation is predominantly Norian in age, ending more than 11 My before the onset of the Jurassic. The magnetochronology confirms that the underlying Ischigualasto Formation and its vertebrate assemblages including some of the earliest known dinosaurs are of Carnian age. The oldest dated occurrences of vertebrate assemblages with dinosaurs in North America (Chinle Formation) are younger (Norian), and thus the rise of dinosaurs was diachronous across the Americas. Paleogeography of the Ischigualasto and Los Colorados Formations indicates prolonged residence in the austral temperate humid belt where a provincial vertebrate fauna with early dinosaurs may have incubated. Faunal dispersal across the Pangean supercontinent in the development of more cosmopolitan vertebrate assemblages later in the Norian may have been in response to reduced contrasts between climate zones and lowered barriers resulting from decreasing atmospheric pCO2 levels. PMID:24843149

  7. Multiple constraints on the age of a Pleistocene lava dam across the Little Colorado River at Grand Falls, Arizona

    USGS Publications Warehouse

    Duffield, W.; Riggs, N.; Kaufman, D.; Champion, D.; Fenton, C.; Forman, S.; McIntosh, W.; Hereford, R.; Plescia, J.; Ort, M.

    2006-01-01

    The Grand Falls basalt lava flow in northern Arizona was emplaced in late Pleistocene time. It flowed 10 km from its vent area to the Little Colorado River, where it cascaded into and filled a 65-m-deep canyon to form the Grand Falls lava dam. Lava continued ???25 km downstream and ???1 km onto the far rim beyond where the canyon was filled. Subsequent fluvial sedimentation filled the reservoir behind the dam, and eventually the river established a channel along the margin of the lava flow to the site where water falls back into the pre-eruption canyon. The ca. 150 ka age of the Grand Falls flow provided by whole-rock K-Ar analysis in the 1970s is inconsistent with the preservation of centimeter-scale flow-top features on the surface of the flow and the near absence of physical and chemical weathering on the flow downstream of the falls. The buried Little Colorado River channel and the present-day channel are at nearly the same elevation, indicating that very little, if any, regional downcutting has occurred since emplacement of the flow. Newly applied dating techniques better define the age of the lava dam. Infrared-stimulated luminescence dating of silty mudstone baked by the lava yielded an age of 19.6 ?? 1.2 ka. Samples from three noneroded or slightly eroded outcrops at the top of the lava flow yielded 3He cosmogenic ages of 16 ?? 1 ka, 17 ?? 1 ka, and 20 ?? 1 ka. A mean age of 8 ?? 19 ka was obtained from averaging four samples using the 40Ar/39Ar step-heating method. Finally, paleomagnetic directions in lava samples from two sites at Grand Falls and one at the vent area are nearly identical and match the curve of magnetic secular variation at ca. 15 ka, 19 ka, 23 ka, and 28 ka. We conclude that the Grand Falls flow was emplaced at ca. 20 ka. ?? 2006 Geological Society of America.

  8. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the

  9. Constraints on Age of India-Asia Collision and Pre-Collisional Subduction Metamorphism from the Sangsang Region, South Central Tibet

    NASA Astrophysics Data System (ADS)

    Borneman, N.; Hodges, K. V.; Van Soest, M. C.; Wartho, J. A.

    2014-12-01

    A common feature of continental collision zones is the entrainment of ophiolitic and subduction complex rock units. The crystallization and metamorphic ages of these units provide important constraints on both subduction zone evolution and the maximum age of ophiolite obduction. Ophiolites and subduction complexes have been well described in the Yarlung Tsangpo suture zone (YTSZ), but thus far relatively few high-pressure, low-temperature metamorphic assemblages from within the suture zone have been documented and successfully dated. Here we present structural, petrologic, and chronologic data from a recently discovered subduction complex occurrence of high-pressure (blueschist facies) rocks along the YTSZ in south central Tibet (29.31º N, 86.68º E). Mapping of the complex based on ASTER satellite image analysis as well as field work enabled the identification of four major lithostratigaphic units; from structurally highest to lowest, they are: 1) forarc affinity Chengdoi sandstones 2) a variably serpentinized ophiolitic fragment; 3) a structural mélange of blueschist-facies metabasic and metaclastic rocks; and 4) sandstones containing serpentinite and rutile detritus. The second and third of these tectonostratigraphic units are separated by thrust faults, whereas the Chengdoi sandstones unconformably overlie the ophiolitic fragment. We interpret the thrust separating the blueschists from the ophiolites as a paleo-subduction zone that dips northward when the entire section is rotated to restore the Chengdoi formation to horizontal. The subduction complex is further disrupted by oblique faults, including some with apparent normal sense offset that may be pre-collisional, intraoceanic normal faults. U/Pb zircon dating of the blueschist facies metavlocanic rocks implies a ca. 111 Ma protolith age, while a ca. 65 Ma 40Ar/39Ar amphibole date from one blueschist sample is interpreted as representing a close approximation of the timing of high-pressure metamorphism

  10. Magmatism and Eurekan deformation in the High Arctic Large Igneous Province: Age and geological constraints from North Greenland

    NASA Astrophysics Data System (ADS)

    Tegner, C.; Storey, M.; Holm, P. M.; Thorarinsson, S. B.; Zhao, X.; Tappe, S.; Heaman, L.; Knudsen, M. F.

    2013-12-01

    Age, compositional and geological data show the High Arctic Large Igneous Province is unusual on two counts: first, magmatism was prolonged and include an initial tholeiitic phase (130-80 Ma) and a second alkaline phase (85-60 Ma); second, it was subsequently deformed during the Eurekan orogeny. New 40Ar-39Ar and U-Pb dating provides emplacement ages of 71-68 Ma for most of the Kap Washington alkaline volcanics of North Greenland, but with activity continuing down to 61 Ma. A thermal resetting age of 49-47 Ma is also identified in 40Ar-39Ar whole-rock data for trachyte flows. Patch perthite feldspars and coeval resetting of Rb-Sr isotopes by hydrothermal fluids provide further support for thermal overprinting, interpreted as a result of Eurekan compressional tectonism. The formation of the tholeiitic suite (130-80 Ma) appears to be associated with the opening of the Canada Basin and may have involved mantle plume action. Formation of the alkaline suite (85-60 Ma) is attributed to continental rifting in the Lincoln Sea area linked to seafloor spreading in the Labrador Sea and the Baffin Bay. The alkaline and tholeiitic suites of the High Arctic may therefore be unrelated. It is striking that High Arctic volcanism terminates at about the same time (c. 60 Ma) as magmatism in the North Atlantic Large Igneous Province begins. We suggest this is a corollary of a change from extensional to compressional tectonism in the High Arctic. In the period when Greenland moved together with Eurasia (>60 Ma), the separation from North America resulted in rift-related alkaline magmatism in the High Arctic. When Greenland subsequently moved as a separate plate (60-35 Ma), overlapping spreading on both sides pushed it northwards and volcanism in the High Arctic stopped due to compression. Evaluation of plate kinematic models shows that the relative northwards movement of Greenland culminated in the Eocene, coinciding with thermal resetting. We conclude that compression in North

  11. ABSOLUTE POLARIMETRY AT RHIC.

    SciTech Connect

    OKADA; BRAVAR, A.; BUNCE, G.; GILL, R.; HUANG, H.; MAKDISI, Y.; NASS, A.; WOOD, J.; ZELENSKI, Z.; ET AL.

    2007-09-10

    Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy Of {Delta}P{sub beam}/P{sub beam} < 5%. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features proton-proton elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power A{sub N} of this process has allowed us to achieve {Delta}P{sub beam}/P{sub beam} = 4.2% in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of AN in the CNI region (four-momentum transfer squared 0.001 < -t < 0.032 (GeV/c){sup 2}) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.

  12. Origin, age, and paleoclimatic setting of the Late Quaternary deposits in Wadi Feiran, Sinai Peninsula: Geomorphologic, geochronologic, and isotopic constraints

    NASA Astrophysics Data System (ADS)

    Farag, A. Z. A.; Sultan, M.; Forman, S. L.; Krishnamurthy, R. V.

    2015-12-01

    There is considerable debate on the origin, age, and paleoclimatic setting of Late Quaternary deposits within the basement complex of the Sinai Peninsula. Our research in Wadi Feiran focused on documenting the sedimentology, stratigraphy, geochemistry and chronology of Late Quaternary deposits in the Feiran (lat. 28.706 N; long. 33.665; elevation: 715 to 772 m a.m.s.l) and Tarfa (lat. 28.692 N; long. 33.933 E; elevation: 1160 to 1244 m a.m.s.l) oases. Sequence stratigraphy, analysis of remote sensed images, and groundwater levels in these two areas indicate that the investigated deposits are structurally-controlled as they are found in areas with anomalously elevated groundwater levels and upstream from shear zone/wadi intersections. Sediments are largely arenaceous upstream and transition downstream to marly successions. We infer that these sediments were not deposited in lake settings because of the absence of shorelines and associated littoral, sublittoral and deeper water facies, and the presence of rhizoliths, secondary calcite veins and gastropods, all of which suggest deposition in a spring or wetland environment. A short hydrologic residence time and/or deposition in an open water system is supported by the lack of correlation (R = 0.08) between δ18O and δ13C values in carbonate deposits. Our findings are consistent with deposition of sediments by alluvial, fluvial and paludal processes under variable hydrologic conditions and higher water table conditions. Quartz extracts from these sediments yielded optically stimulated luminescence ages between ca. 27 and 11 ka and place these wetter conditions during the last glacial period and extend the "greening" of North Africa further eastward. Our findings are consistent with models which identify the wet periods in the Late Quaternary in the Sinai Peninsula and in North Africa as being glacial periods.

  13. U-Pb ages on single detrital zircon grains from the Witwatersrand Basin, South Africa: Constraints on the age of sedimentation and on the evolution of granites adjacent to the basin

    SciTech Connect

    Robb, L.J. ); Davis, D.W.; Kamo, S.L. )

    1990-05-01

    U-Pb ages of single detrital zircon grains from various stratigraphic horizons in the Dominion and Witwatersrand sequences provide constraints on the maximum age of sedimentation as well as indicating the pattern of age distribution in the (granitoid) source area providing detritus into the basin. Zircon ages in the Dominion sediments range from 3,191-3,105 Ma with a geometric mean ({bar X}) t 3,153 Ma. Those from the lower Witwatersrand sediments (West Rand Group) range from 3,305-3,044 Ma with {bar X} = 3,097 Ma, and zircons in the upper Witwatersrand sediments (Central Rand Group) are between 3,207-2,894 Ma old with {bar X} = 3,053 Ma. Ages of detrital zircons generally decrease upward in the stratigraphic record, and <3,000 Ma old zircons are only found in the Central Rand Group. This trend implies that younger granites may have formed at some time subsequent to lower Witwatersrand deposition, or that continued erosion of the hinterland resulted in the unroofing of successively younger granites. The wide spread of zircon ages (411 Ma) evident in the data set indicates that granites formed virtually continuously between circa 3,300-2.900 Ma in the Witwatersrand source area. Of the zircon ages 45% fall within 30 m.y. of the geometric mean of the total data set, suggesting that a major crust-forming event occurred at 3,073 {plus minus} 30 Ma. Granitoids in the source area can be divided into (i) pre-Dominion basement; (ii) Dominion granites, whose emplacement coincided with the extrusion of Dominion volcanics, and (iii) Randian granites, which were emplaced synchronously with Witwatersrand deposition. This sequence of events supports recent tectonic models that view the Witwatersrand sequence as having been deposited in a foreland basin.

  14. U-Pb geochronology on detrital zircons from FAR-DEEP cores, Fennoscandian Shield - age constraints for events of the Archaean-Palaeoproterozoic transition and provenance

    NASA Astrophysics Data System (ADS)

    Gaertner, C.; Martin, A.; Bahlburg, H.; Lepland, A.; Melezhik, V.; Prave, A. R.; Condon, D. J.; Berndt, J.; Kooijman, E.; Far-Deep Scientists

    2010-12-01

    The Archaean-Palaeoproterozoic transition is marked by several environmental events that were important for the evolution of the Earth system and occurred coeval with plate tectonic reorganisations including the break-up of the supercontinent Kenorland. We applied U-Pb-geochronology on detrital zircons by LA-ICP-MS and ID-TIMS to improve age constraints of these events, recorded in the 2.5-2.0 Ga rock successions of the Fennoscandian Shield and including the Huronian glaciation and the Lomagundi-Jatuli positive excursion of δ13C in sedimentary carbonates. The detrital zircons provided ages ranging from 3.5 to 1.9 Ga with dominant age populations in the range of 2.9-2.5 Ga for most samples. Youngest zircon ages from the Seidorechka Sedimentary and Polisarka formations in the Imandra-Varzuga Greenstone Belt and the Neverskrukk Formation in the Pechenga Greenstone Belt constrain, for the first time, the deposition of glacial diamictites on the Fennoscandian Shield to between 2.43 and 2.2 Ga. Similar ages have been reported for glacial deposits in Canada and South Africa, consistent with a global glaciation at that time. The youngest detrital zircon ages derived from the Kuetsjärvi Sedimentary Fm, containing isotopically heavy carbonates, and from the overlying Kolasjoki Sedimentary Fm in the Pechenga Greenstone Belt indicate that deposition of carbonates corresponding to the Lomagundi-Jatuli δ13C excursion took place between 2.3 Ga and 2.06 Ga, in agreement with previous ages from these formations. Detrital zircon populations of c. 2.06 Ga and c. 1.92 Ga characterise the lower and upper parts of the Kolasjoki Sedimentary Fm, respectively. These units are separated by an unconformity of unknown duration, but the age distributions may indicate a significant hiatus because these are considerably younger than the 2.0-1.97 Ga ages reported from the overlying Pilgujärvi Sedimentary and Volcanic fms. Alternatively, the younger cluster of ages may record deformation

  15. A New age Constraint on Sturtian Glaciation: SHRIMP U-Pb zircon geochronology of Neoproterozoic Altungol Formation in Tarim Basin, NW China

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Li, J.; Li, W.; Wang, H.

    2013-12-01

    Neoproterozoic glaciations with a wide distribution, punctuated the largely ice-free Precambrian world within tropical latitudes, interpreted as evidence record the cold paleoclimate intervals which made a Snowball Earth with the frozen ocean. More recently, Quruqtagh of Northeast Tarim Basin, Northwest China, catches the increasing eyes, not only because of its three or four Neoproterzoic glacial periods in China, but also its tectonic significance for breakup of Rodinia supercontinent. There are many Neoproterozoic glaciation strata exposures in Quruqtagh. The Nanhua System is divided into the Bayisi, Zhaobishan (absent in south aera), Altungol and Tereeken formations. Thick tillites were found in Bayisi, Tereeken and Hankalchough formations, while minor was found in Altungol Formation. After the field investigation of the south Yaerdang Mountain in the South aera, it is suggested that the Altungol Formation in the South aera differs from that the North aera. In the North, it is a set of littoral-neritic clastic facies sediment with few volcanic rocks and marine tillites in the bottom. In South Quruqtagh, it consists of 45m-thick gray-green tillites in the bottom with different size and complex components gravels, volcanic interbed near the top of tillites, overlying strata is cap dolomite of 15m thickness, with abundant drop-stones, the upper is black shales and gray to black thin-interbeded siliceous rock. The reported ages without Altungol glaciation age are all focused on the north Quruqtagh and conversely in South Quruqtagh without reported glaciation age. Based on field investigation of Nanhua System (Cryogenian) in NE Tarim Basin, we offer the first set of Sturtian glaciation age 729.4×6.6Ma, in the form of SHRIMP(sensitive high-resolution ion microprobe) U-Pb zircon age dating of volcanic interbedded near the top of Altungol Formation tillites, South Quruqtagh, which provides a new constraint on the Sturtian glaciation from global perspective. It is a

  16. Neodymium and strontium isotopic study of Australasian tektites - New constraints on the provenance and age of target materials

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Papanastassiou, D. A.; Wasserburg, G. J.; Koeberl, C.

    1992-01-01

    The Nd and Sr isotopic compositions of Australasian tectites (including two flanged Australian tectites, two low-SiO2 Muong Nong-type tectites, and three high-SiO2 Muong Nong-type tectites) and the Nd, Sm, Sr, and Rb concentrations were investigated by isotope-dilution thermal ionization mass spectrometry, and the Sm-Nd and Rb-Sr isotope systematics were used to study the characteristics of the parental material. It is shown that the Nd and Sr isotopic data provide evidence that all Australasian tektites were derived from a single sedimentary formation with a narrow range of stratigraphic ages close to 170 Ma. It is suggested that all of the Australasian tektites were derived from a single impact event and that the australites represent the upper part of a melt sheet ejected at high velocity, whereas the indochinites represent melts formed at a lower level in the target material distributed closer to the area of the impact.

  17. ~100 Ma Lu-Hf eclogite ages from Koralpe and Saualpe (Austroalpine nappes, Austria): New constraints for the kinematics of Eoalpine subduction

    NASA Astrophysics Data System (ADS)

    Miladinova, Irena; Froitzheim, Nikolaus; Nagel, Thorsten; Janák, Marian; Münker, Carsten

    2016-04-01

    The Koralpe and Saualpe complexes are part of the Austroalpine basement nappe system. They represent the largest region in the Eastern Alps exposing high-pressure metamorphic rocks from the Cretaceous Eoalpine orogenic event and also contain the type locality for eclogite. The grade of the Cretaceous metamorphism in the Eastern Alps increases to the southeast, with maximum pressures and temperatures reaching up to 3.5 GPa and 850 °C in the Pohorje Mountains (Janak et al., 2015). The estimated P-T-conditions for the eclogites from Saualpe and Koralpe are 2-2.2 GPa and 600-740 °C (Miller & Thöni 1997, Thöni et al. 2008). Here we present a new Lu-Hf isotopic study of the eclogites from the Hohl locality in the southern Koralpe, and from the Grünburgerbach and Wolfsberger Hütte localities in the southern Saualpe. Two-point isochrones from samples of Hohl and Wolfsberger Hütte based on one whole rock and one garnet separate yield ages of 99.2 ± 1.1 Ma and 101.7 ± 2 Ma, respectively. Two eclogite samples from Grünburgerbach give garnet-omphacite-whole rock ages of 100.3 ± 1 Ma and 101.79 ± 0.92 Ma, identical within error. The garnets in the eclogite from Hohl display a homogenous composition with no zoning of major elements, whereas the garnets of the samples from Grünburgerbach show an enrichment of Mn in the cores and lower contents towards the rims, which indicates prograde garnet growth during increasing P and T. The ages are therefore related to burial during subduction. These new Lu-Hf garnet ages are slightly older than the Lu-Hf garnet age data from Pohorje (~95 Ma; Sandmann et al. 2011, Thöni et al. 2008), which also date burial. If Koralpe/Saualpe and Pohorje would belong to one continuous crustal unit subducted and exhumed "en bloc" in a southeast-dipping subduction zone, the opposite age difference would be expected. Our results show that this is not the case and represent important constraints for a more realistic kinematic model. Janak, M

  18. Identification of possible recent water/lava source fissures in the Cerberus Plains: stratigraphic and crater count age constraints

    NASA Astrophysics Data System (ADS)

    Thomas, Rebecca J.

    2013-04-01

    The Cerberus plains are one of the youngest surfaces on Mars. They are thought to have been formed by lava and/or water flows, but there is considerable debate regarding the source of this material. Much of the material forming the western plains, including the Athabasca Valles outflow channels, appears to have flowed from the region of the Cerberus Fossae graben system [1,2,3] and limited areas forming the eastern plains may have been erupted by low shield volcanoes [4,5]. However, flow of material from west to east is obstructed by a ridge centred on 157°E, 7°N and, prior to this study, vents which might be the source of fluid of a low enough viscosity to form the majority of the flat eastern plains had not been identified. We studied new HiRISE (25cm/px, High Resolution Science Imaging Experiment) images of the ridge between the east and west plains and observed possible source vents for this material: the ridge is cut by a series of pits and fissures which lie at the heads of flows and channels extending towards the surrounding plains. In order to establish the stratigraphic relationships between the vents and plains, this study produced large scale geomorphological maps based on the HiRISE images. The mapping showed that both incised channels and leveed flows extend onto the plain to the south of the ridge and that these were the final phase of plains-forming activity in that region. Conversely, to the north, ridge-sourced deposits only form the plains surface close to the ridge - beyond that, they are overlain by large-scale regional flows that appear to have originated from the direction of Athabasca Valles. In the southeast, a large-scale flow which does not emanate from this ridge forms the plains surface, but there is evidence that the youngest outflow activity from the ridge was contemporaneous with emplacement of this unit. We also performed crater counts to age-date the surfaces and these indicate that plains-forming and ridge-sourced units are of a

  19. Implants as absolute anchorage.

    PubMed

    Rungcharassaeng, Kitichai; Kan, Joseph Y K; Caruso, Joseph M

    2005-11-01

    Anchorage control is essential for successful orthodontic treatment. Each tooth has its own anchorage potential as well as propensity to move when force is applied. When teeth are used as anchorage, the untoward movements of the anchoring units may result in the prolonged treatment time, and unpredictable or less-than-ideal outcome. To maximize tooth-related anchorage, techniques such as differential torque, placing roots into the cortex of the bone, the use of various intraoral devices and/or extraoral appliances have been implemented. Implants, as they are in direct contact with bone, do not possess a periodontal ligament. As a result, they do not move when orthodontic/orthopedic force is applied, and therefore can be used as "absolute anchorage." This article describes different types of implants that have been used as orthodontic anchorage. Their clinical applications and limitations are also discussed. PMID:16463910

  20. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  1. Constraints on the timing of Co-Cu ± Au mineralization in the Blackbird district, Idaho, using SHRIMP U-Pb ages of monazite and xenotime plus zircon ages of related Mesoproterozoic orthogneisses and metasedimentary rocks

    USGS Publications Warehouse

    Aleinikoff, John N.; Slack, John F.; Lund, Karen; Evans, Karl V.; Fanning, C. Mark; Mazdab, Frank K.; Wooden, Joseph L.; Pillers, Renee M.

    2012-01-01

    The Blackbird district, east-central Idaho, contains the largest known Co reserves in the United States. The origin of strata-hosted Co-Cu ± Au mineralization at Blackbird has been a matter of controversy for decades. In order to differentiate among possible genetic models for the deposits, including various combinations of volcanic, sedimentary, magmatic, and metamorphic processes, we used U-Pb geochronology of xenotime, monazite, and zircon to establish time constraints for ore formation. New age data reported here were obtained using sensitive high resolution ion microprobe (SHRIMP) microanalysis of (1) detrital zircons from a sample of Mesoproterozoic siliciclastic metasedimentary country rock in the Blackbird district, (2) igneous zircons from Mesoproterozoic intrusions, and (3) xenotime and monazite from the Merle and Sunshine prospects at Blackbird. Detrital zircon from metasandstone of the biotite phyllite-schist unit has ages mostly in the range of 1900 to 1600 Ma, plus a few Neoarchean and Paleoproterozoic grains. Age data for the six youngest grains form a coherent group at 1409 ± 10 Ma, regarded as the maximum age of deposition of metasedimentary country rocks of the central structural domain. Igneous zircons from nine samples of megacrystic granite, granite augen gneiss, and granodiorite augen gneiss that crop out north and east of the Blackbird district yield ages between 1383 ± 4 and 1359 ± 7 Ma. Emplacement of the Big Deer Creek megacrystic granite (1377 ± 4 Ma), structurally juxtaposed with host rocks in the Late Cretaceous ca. 5 km north of Blackbird, may have been involved in initial deposition of rare earth elements (REE) minerals and, possibly, sulfides. In situ SHRIMP ages of xenotime and monazite in Co-rich samples from the Merle and Sunshine prospects, plus backscattered electron imagery and SHRIMP analyses of trace elements, indicate a complex sequence of Mesoproterozoic and Cretaceous events. On the basis of textural relationships

  2. Relative constraints and evolution

    NASA Astrophysics Data System (ADS)

    Ochoa, Juan G. Diaz

    2014-03-01

    Several mathematical models of evolving systems assume that changes in the micro-states are constrained to the search of an optimal value in a local or global objective function. However, the concept of evolution requires a continuous change in the environment and species, making difficult the definition of absolute optimal values in objective functions. In this paper, we define constraints that are not absolute but relative to local micro-states, introducing a rupture in the invariance of the phase space of the system. This conceptual basis is useful to define alternative mathematical models for biological (or in general complex) evolving systems. We illustrate this concept with a modified Ising model, which can be useful to understand and model problems like the somatic evolution of cancer.

  3. Independent 40Ar/39Ar and 14C age constraints on the last five glacial terminations from the aggradational successions of the Tiber River, Rome (Italy)

    NASA Astrophysics Data System (ADS)

    Marra, F.; Rohling, E. J.; Florindo, F.; Jicha, B.; Nomade, S.; Pereira, A.; Renne, P. R.

    2016-09-01

    We use 13 new 40Ar/39Ar and 4 new 14C datings of volcanic deposits and organic material found within near-coastal aggradational successions deposited by the Tiber River near Rome, Italy, to integrate a larger dataset previously achieved in order to offer independent age constraints to the sea-level fluctuations associated with Late Quaternary glacial cycles during the last 450 ka. Results are compared with the chronologically independently constrained Red Sea relative sea-level curve, and with the astronomically tuned deep-sea benthic δ18O record. We find good agreements for the timings of change, and in several cases for both the amplitudes and timings of change during glacial terminations T-1, T-2, T-3, and T-5. There is one striking exception, namely for glacial termination T-4 that led into interglacial Marine Isotope Stage (MIS) 9. T-4 in our results is dated a full 18 ka earlier than in the Red Sea and deep-sea benthic δ18O records (which are in good agreement with each other in spite of their independent chronological constraints). The observed discrepancy is beyond the scale of the combined age uncertainties. One possible explanation is that the documented aggradation represents an early phase, triggered by a smaller event in the sea-level record, but the thickness of the aggradational sediment sequence then suggests that the amplitude of this earlier sea-level rise is underestimated in the Red Sea and benthic δ18O records. Also, this would imply that the aggradational succession of the main T-4 deglaciation has not yet been located in the study region, which is hard to reconcile with our extensive fieldwork and borehole coverage, unless unlikely non-deposition or complete erosion. Resolving this discrepancy will improve understanding of the timing of deglaciations relative to the orbitally modulated insolation forcing of climate and will require further focused research, both into the nature and chronology of the Tiber sequences of this period, and into

  4. Absolute neutrino mass measurements

    NASA Astrophysics Data System (ADS)

    Wolf, Joachim

    2011-10-01

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2β) searches, single β-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy. Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium β-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope (137Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R&D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2β decay and single β-decay.

  5. Absolute neutrino mass measurements

    SciTech Connect

    Wolf, Joachim

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments in Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.

  6. Absolute dosimetry for extreme-ultraviolet lithography

    NASA Astrophysics Data System (ADS)

    Berger, Kurt W.; Campiotti, Richard H.

    2000-06-01

    The accurate measurement of an exposure dose reaching the wafer on an extreme ultraviolet (EUV) lithographic system has been a technical challenge directly applicable to the evaluation of candidate EUV resist materials and calculating lithography system throughputs. We have developed a dose monitoring sensor system that can directly measure EUV intensities at the wafer plane of a prototype EUV lithographic system. This sensor system, located on the wafer stage adjacent to the electrostatic chuck used to grip wafers, operates by translating the sensor into the aerial image, typically illuminating an 'open' (unpatterned) area on the reticle. The absolute signal strength can be related to energy density at the wafer, and thus used to determine resist sensitivity, and the signal as a function of position can be used to determine illumination uniformity at the wafer plane. Spectral filtering to enhance the detection of 13.4 nm radiation was incorporated into the sensor. Other critical design parameters include the packaging and amplification technologies required to place this device into the space and vacuum constraints of a EUV lithography environment. We describe two approaches used to determine the absolute calibration of this sensor. The first conventional approach requires separate characterization of each element of the sensor. A second novel approach uses x-ray emission from a mildly radioactive iron source to calibrate the absolute response of the entire sensor system (detector and electronics) in a single measurement.

  7. 40Ar 39Ar age constraints on neogene sedimentary beds, Upper Ramparts, half-way Pillar and Canyon village sites, Porcupine river, east-central Alaska

    USGS Publications Warehouse

    Kunk, M.J.; Rieck, H.; Fouch, T.D.; Carter, L.D.

    1994-01-01

    40Ar 39Ar ages of volcanic rocks are used to provide numerical constraints on the age of middle and upper Miocene sedimentary strata collected along the Porcupine River. Intercalated sedimentary rocks north of latitude 67??10???N in the Porcupine terrane of east-central Alaska contain a rich record of plant fossils. The fossils are valuable indicators of this interior region's paleoclimate during the time of their deposition. Integration of the 40Ar 39Ar results with paleomagnetic and sedimentological data allows for refinements in estimating the timing of deposition and duration of selected sedimentary intervals. 40Ar 39Ar plateau age spectra, from whole rock basalt samples, collected along the Upper Ramparts and near Half-way Pillar on the Porcupine River, range from 15.7 ?? 0.1 Ma at site 90-6 to 14.4 ?? 0.1 Ma at site 90-2. With exception of the youngest basalt flow at site 90-2, all of the samples are of reversed magnetic polarity, and all 40Ar 39Ar age spectrum results are consistent with the deposition of the entire stratigraphic section during a single interval of reversed magnetic polarity. The youngest flow at site 90-2 was emplaced during an interval of normal polarity. With age, paleomagnetic and sedimentological data, the ages of the Middle Miocene sedimentary rocks between the basalt flows at sites 90-1 and 90-2 can be assigned to an interval within the limits of analytical precision of 15.2 ?? 0.1 Ma; thus, the sediments were deposited during the peak of the Middle Miocene thermal maximum. Sediments in the upper parts of sites 90-1 and 90-2 were probably deposited during cooling from the Middle Miocene thermal maximum. 40Ar 39Ar results of plagioclase and biotite from a single tephra, collected at sites 90-7 and 90-8 along the Canyon Village section of the Porcupine River, indicate an age of 6.57 ?? 0.02 Ma for its time of eruption and deposition. These results, together with sedimentological and paleomagnetic data, suggest that all of the Upper

  8. Metamorphic and age constraints on tectono-thermal reworking in the western H.U. Sverdrupfjella: A new crustal evolution model for Western Dronning Maud Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Grosch, Eugene; Frimmel, Hartwig; Abu-Alam, Tamer; Košler, Jan

    2014-05-01

    Western Dronning Maud Land (WDML) of East Antarctica is argued to consist of two major crustal domains, namely the low-grade Archaean Kalahari-Grunehogna Craton and the high-grade Maud belt (e.g. Grantham et al., 1995; Jacobs et al. 2008). The geodynamic and tectono-thermal crustal evolution histories of these two proposed domains remain a debated topic in Rodinia and Gondwana reconstructions. In this study we conducted a petrological and metamorphic comparison of Mesoproterozoic metabasic rocks on the eastern margin of the Archaean Grunehogna Craton and the adjacent westernmost Maud Belt, across a major structural discontinuity known as the Pencksökket-Jutulstraumen Discontinuity (PJD). As such we evaluate to what extent the two domains of WDML represent independent crustal growth and metamorphic histories. Metamorphic constraints on low-grade rocks on the eastern Grunehogna craton record greenschist facies conditions of T = 340 ± 25oC and P = 2.9 ± 0.8 kbar. The high-grade PT-constraint of T =700 ± 30oC and P = 9.0 ± 2 kbar for the western extreme of the Maud Belt, derived from garnet-hornblende-plagioclase-quartz geothermobarometry and phase diagram modeling in PERPLEX, is very similar to that reported for the eastern Maud Belt and thus, does not support the concept of a westward decreasing metamorphic field gradient within the Maud Belt as previously proposed. Laser-ablation-ICP-MS U-Pb dating of titanite in a hornblende-plagioclase-quartz symplectite (after garnet breakdown), yielded a Pan-African age for high-grade metamorphism in the westernmost Maud belt, which overlaps with the age of tectonic decompression in the eastern Maud Belt. The new U-Pb age data argues against previous models that invoke only late-Mesoproterozoic high-grade metamorphism in the western Maud Belt. The new petrological data indicate that the inferred sub-glacial boundary (PJD) between the Grunehogna Craton and the Maud Belt, represents a major metamorphic hiatus as a Pan

  9. A more complex deglaciation chronology of Southern Norway than previously thought. New geochronological constraints based on cosmogenic exposure ages of marginal moraines

    NASA Astrophysics Data System (ADS)

    Fredin, Ola; Akçar, Naki; Romundset, Anders; Reber, Regina; Ivy-Ochs, Susan; Kubik, Peter; Høgaas, Fredrik; Schlüchter, Christian

    2015-04-01

    Glacial landforms from the last deglaciation in southern Norway were mapped by the famous glacial geologist Bjørn Andersen already in the early 1950s, using basic aerial photographs and topographic maps. Andersen reconstructed two distinct glacial sub-stages (the Lista stage and Spangereid stage) that were older than the Younger Dryas (YD), and one main glacial stage of assumed YD age (the Ra stage). This interpretation has remained largely untested and is still used in reconstructions of the Fennoscandian ice sheet. However, absolute chronological control has been lacking and only a handful radiocarbon dates has been used to support the deglaciation chronology. In this study we test the reconstruction of Andersen by remapping the whole area using newly aquired LiDAR data (high resolution laser scanning of terrain), together with in-situ cosmogenic nuclide exposure ages of boulders on marginal moraines. The study comprises mapping of more than 6000 km2 of forested and dissected landscape, 53 10Be ages from boulders/bedrock, one cosmogenic 10Be depth profile in a coarse-grained glaciofluvial deposit, and finally one lake record. Our study shows that the oldest of Andersen's glacial stages, the Lista stage right on the outermost Norwegian south coast, should likely be rejected since it consists of consolidated subglacial till and therefore is not an end moraine system. However, our cosmogenic depth profile indicates that this area might have been ice free already by around 19 ka BP, approximately 4000 years earlier than previously thought. At the same time the ice sheet surface slowly lowered, and the first inland hills of about 450 m. asl. became ice free at around 17 ka BP. Ice retreat continued slowly 10-15 km inland and halted as a calving fjord stage at the Spangereid stage with an approximate age of 15 ka BP. Then the deglaciation appears to have been very rapid and the ice front retreated 30-50 km inland to a position inside of the Ra stage, until a readvance

  10. Absolute Identification by Relative Judgment

    ERIC Educational Resources Information Center

    Stewart, Neil; Brown, Gordon D. A.; Chater, Nick

    2005-01-01

    In unidimensional absolute identification tasks, participants identify stimuli that vary along a single dimension. Performance is surprisingly poor compared with discrimination of the same stimuli. Existing models assume that identification is achieved using long-term representations of absolute magnitudes. The authors propose an alternative…

  11. Be Resolute about Absolute Value

    ERIC Educational Resources Information Center

    Kidd, Margaret L.

    2007-01-01

    This article explores how conceptualization of absolute value can start long before it is introduced. The manner in which absolute value is introduced to students in middle school has far-reaching consequences for their future mathematical understanding. It begins to lay the foundation for students' understanding of algebra, which can change…

  12. Absolute Stability Analysis of a Phase Plane Controlled Spacecraft

    NASA Technical Reports Server (NTRS)

    Jang, Jiann-Woei; Plummer, Michael; Bedrossian, Nazareth; Hall, Charles; Jackson, Mark; Spanos, Pol

    2010-01-01

    Many aerospace attitude control systems utilize phase plane control schemes that include nonlinear elements such as dead zone and ideal relay. To evaluate phase plane control robustness, stability margin prediction methods must be developed. Absolute stability is extended to predict stability margins and to define an abort condition. A constrained optimization approach is also used to design flex filters for roll control. The design goal is to optimize vehicle tracking performance while maintaining adequate stability margins. Absolute stability is shown to provide satisfactory stability constraints for the optimization.

  13. Absolute nonlocality via distributed computing without communication

    NASA Astrophysics Data System (ADS)

    Czekaj, Ł.; Pawłowski, M.; Vértesi, T.; Grudka, A.; Horodecki, M.; Horodecki, R.

    2015-09-01

    Understanding the role that quantum entanglement plays as a resource in various information processing tasks is one of the crucial goals of quantum information theory. Here we propose an alternative perspective for studying quantum entanglement: distributed computation of functions without communication between nodes. To formalize this approach, we propose identity games. Surprisingly, despite no signaling, we obtain that nonlocal quantum strategies beat classical ones in terms of winning probability for identity games originating from certain bipartite and multipartite functions. Moreover we show that, for a majority of functions, access to general nonsignaling resources boosts success probability two times in comparison to classical ones for a number of large enough outputs. Because there are no constraints on the inputs and no processing of the outputs in the identity games, they detect very strong types of correlations: absolute nonlocality.

  14. [Geriatrics: an absolute necessity].

    PubMed

    Oostvogel, F J

    1982-02-01

    The medical care for elderly people could be greatly improved. If no specific attention is paid immediately, namely through the various training courses and by way of further and part-time schooling, then this medical care will remain unsatisfactory. This situation worsens continually due to the growing number of elderly people and, within this group, a much higher rate of very aged people. Increasing the care in institutions is altogether unsatisfactory. The problem should be dealt with structurally and the emphasis placed upon prevention and early-diagnosis. There is an urgent need for an integrated method, keeping in mind the limits of the elderly person, from the physical, psychological and social aspects. This demands teamwork in a multidisciplinary system inside as well as outside the institutions. It demands a thorough knowledge of geriatrics based upon gerontology. Geriatricians are urgently needed in this development together with doctors in nursing homes, general practitioners and specialists, so that the necessary care may be established as quickly as possible. PMID:7101393

  15. Aging.

    PubMed

    Park, Dong Choon; Yeo, Seung Geun

    2013-09-01

    Aging is initiated based on genetic and environmental factors that operate from the time of birth of organisms. Aging induces physiological phenomena such as reduction of cell counts, deterioration of tissue proteins, tissue atrophy, a decrease of the metabolic rate, reduction of body fluids, and calcium metabolism abnormalities, with final progression onto pathological aging. Despite the efforts from many researchers, the progression and the mechanisms of aging are not clearly understood yet. Therefore, the authors would like to introduce several theories which have gained attentions among the published theories up to date; genetic program theory, wear-and-tear theory, telomere theory, endocrine theory, DNA damage hypothesis, error catastrophe theory, the rate of living theory, mitochondrial theory, and free radical theory. Although there have been many studies that have tried to prevent aging and prolong life, here we introduce a couple of theories which have been proven more or less; food, exercise, and diet restriction. PMID:24653904

  16. Aging

    PubMed Central

    Park, Dong Choon

    2013-01-01

    Aging is initiated based on genetic and environmental factors that operate from the time of birth of organisms. Aging induces physiological phenomena such as reduction of cell counts, deterioration of tissue proteins, tissue atrophy, a decrease of the metabolic rate, reduction of body fluids, and calcium metabolism abnormalities, with final progression onto pathological aging. Despite the efforts from many researchers, the progression and the mechanisms of aging are not clearly understood yet. Therefore, the authors would like to introduce several theories which have gained attentions among the published theories up to date; genetic program theory, wear-and-tear theory, telomere theory, endocrine theory, DNA damage hypothesis, error catastrophe theory, the rate of living theory, mitochondrial theory, and free radical theory. Although there have been many studies that have tried to prevent aging and prolong life, here we introduce a couple of theories which have been proven more or less; food, exercise, and diet restriction. PMID:24653904

  17. Significance of the whole rock Re-Os ages in cryptically and modally metasomatised cratonic peridotites: Constraints from HSE-Se-Te systematics

    NASA Astrophysics Data System (ADS)

    Luguet, Ambre; Behrens, Melanie; Pearson, D. Graham; König, Stephan; Herwartz, Daniel

    2015-09-01

    the 187Os/188Os signatures, indicating TRD eruption ages identical with those of the SP. By contrast, the PP and GP, which suffered significant BMS ± PGM addition, have 187Os/188Os considerably shifted toward more radiogenic values. As a result, unrealistically young TRD eruption ages are obtained that cannot be used to constrain the time frame of the stabilisation of the cratonic roots and the mechanisms of craton formation. The Se-Te and incompatible HSE (i.e., Pt, Pd) are powerful geochemical tools to assess the robustness of the Re-Os isotopic system in mantle peridotites. Specifically, Se/Te and Pd/Ir ratios provide complementary insights into the complex metasomatic history of mantle peridotites. The Se/Te ratio is very sensitive to Os-free PGM metasomatism producing highly variable Se/Te >15 at low, relatively constant Pd/Ir< 0.4 but does not affect the 187Os/188Os systematics. This contrasts with BMS metasomatism, where Pd/Ir becomes more variable (>0.4), at constant but low Se/Te <10 and which is accompanied by modification of the Os isotopic composition of the host peridotite. As they are sensitive indicators of BMS ± PGM metasomatism, HSE, Se and Te should be systematically considered when investigating the timing of stabilisation of lithospheric mantle and its petrogenetic history. This would allow a more robust assessment of the Re-Os ages obtained and provide firmer constraints on the evolution and formation of Archean cratons and early Earth dynamics.

  18. Age constraints on Jerritt Canyon and other Carlin-type gold deposits in the western United States-relationship to mid-Tertiary extension and magmatism

    USGS Publications Warehouse

    Hofstra, A.H.; Snee, L.W.; Rye, R.O.; Folger, H.W.; Phinisey, J.D.; Loranger, R.J.; Dahl, A.R.; Naeser, C.W.; Stein, H.J.; Lewchuk, M.

    1999-01-01

    Carlin-type gold deposits are difficult to date and a wide range of ages has been reported for individual deposits. Therefore, several methods were employed to constrain the age of the gold deposits in the Jerritt Canyon district. Dated igneous rocks with well-documented crosscutting relationships to ore provided the most reliable constraints. K/Ar and 40Ar/39Ar dates on igneous rocks are as follows: andesite dikes 324 Ma, sericitic alteration in andesite dikes 118 Ma, basalt dikes 40.8 Ma, quartz monzonite dikes 39.2 Ma, and calc-alkaline ignimbrites 43.1 to 40.1 Ma. Of these, only the andesite and basalt dikes are clearly altered and mineralized. The gold deposits are, therefore, younger than the 40.8 Ma basalt dikes. The sericitic alteration in the andesite dikes is unrelated to the gold deposits. A number of dating techniques did not work. K/Ar and 40Ar/39Ar dates on mica from mineralized Ordovician to Devonian sedimentary rocks gave misleading results. The youngest date of 149 Ma from the smallest <0.1-??m-size fraction shows that the temperature (120??-260??C) and duration (?) of hydrothermal activity was insufficient to reset preexisting fine-grained micas in the host rocks. The temperature and duration was also insufficient to anneal fission tracks in zircon from Ordovician quartzites as they yield Middle Proterozoic dates in both mineralized and barren samples. Apatites were too small for fission track dating. Hydrothermal sulfides have pronounced crustal osmium isotope signatures (187Os/188Os(initial) = 0.9-3.6) but did not yield a meaningful isochron due to very low Re and Os concentrations and large analytical uncertainties. Paleomagnetic dating techniques failed because the hydrothermal fluids sulfidized nearly all of the iron in the host rocks leaving no remnant magnetism. When published isotopic dates from other Carlin-type deposits in Nevada and Utah are subject to the rigorous evaluation developed for the Jerritt Canyon study, most deposits can be

  19. Blood pressure targets and absolute cardiovascular risk.

    PubMed

    Odutayo, Ayodele; Rahimi, Kazem; Hsiao, Allan J; Emdin, Connor A

    2015-08-01

    In the Eighth Joint National Committee guideline on hypertension, the threshold for the initiation of blood pressure-lowering treatment for elderly adults (≥60 years) without chronic kidney disease or diabetes mellitus was raised from 140/90 mm Hg to 150/90 mm Hg. However, the committee was not unanimous in this decision, particularly because a large proportion of adults ≥60 years may be at high cardiovascular risk. On the basis of Eighth Joint National Committee guideline, we sought to determine the absolute 10-year risk of cardiovascular disease among these adults through analyzing the National Health and Nutrition Examination Survey (2005-2012). The primary outcome measure was the proportion of adults who were at ≥20% predicted absolute cardiovascular risk and above goals for the Seventh Joint National Committee guideline but reclassified as at target under the Eighth Joint National Committee guideline (reclassified). The Framingham General Cardiovascular Disease Risk Score was used. From 2005 to 2012, the surveys included 12 963 adults aged 30 to 74 years with blood pressure measurements, of which 914 were reclassified based on the guideline. Among individuals reclassified as not in need of additional treatment, the proportion of adults 60 to 74 years without chronic kidney disease or diabetes mellitus at ≥20% absolute risk was 44.8%. This corresponds to 0.8 million adults. The proportion at high cardiovascular risk remained sizable among adults who were not receiving blood pressure-lowering treatment. Taken together, a sizable proportion of reclassified adults 60 to 74 years without chronic kidney disease or diabetes mellitus was at ≥20% absolute cardiovascular risk. PMID:26056340

  20. Absolute transition probabilities of phosphorus.

    NASA Technical Reports Server (NTRS)

    Miller, M. H.; Roig, R. A.; Bengtson, R. D.

    1971-01-01

    Use of a gas-driven shock tube to measure the absolute strengths of 21 P I lines and 126 P II lines (from 3300 to 6900 A). Accuracy for prominent, isolated neutral and ionic lines is estimated to be 28 to 40% and 18 to 30%, respectively. The data and the corresponding theoretical predictions are examined for conformity with the sum rules.-

  1. Constraints on the age and provenance of the Chugach accretionary complex from detrital zircons in the Sitka Graywacke near Sitka, Alaska

    USGS Publications Warehouse

    Haeussler, Peter J.; Gehrels, George E.; Karl, Susan M.

    2006-01-01

    The Sitka Graywacke is the westernmost and youngest unit of the Chugach accretionary complex in southeastern Alaska. Using laser-ablation inductively coupled plasma mass spectroscopy, we obtained 492 detrital-zircon ages on seven typical samples of Sitka Graywacke turbidites, which were collected in a transect across much of the unit near Sitka, Alaska. Individual grains range in age from 66 to 1,802 m.y. The youngest peak ages on relative-probability plots of the western four samples (74, 72, 74, and 74 m.y., from west to east) are distinctly younger than the youngest peak ages of the eastern three samples (105, 103, and 97 m.y., from west to east). These youngest peak ages set maximum depositional ages for each sample. We suggest that these peak ages are not significantly older (within ~5 m.y.) than the depositional age of the Sitka Graywacke because the deposits accumulated in a trench along a convergent margin, where magmatic sources likely continuously introduced juvenile zircons. The differences in the youngest cluster of detrital-zircon ages between the eastern and western sample localities is likely due to both a change in provenance and a fault. The similarity of the youngest peak ages in the Sitka Graywacke to fossil ages in the Valdez Group, in Prince William Sound, implies that the western part of the Sitka Graywacke is correlative with the Valdez Group, as previously inferred. However, the eastern part of the Sitka Graywacke has youngest detrital-zircon ages older than fossil ages in the Valdez Group and younger than fossil ages in the McHugh Complex, which in south-central Alaska is the oldest part of the accretionary complex. The age distribution of zircons in the older, eastern sequence suggests sources along the British Columbia margin. The detrital-zircon ages in the younger, western sequence are similar to igneous ages from south-central Alaska to southern British Columbia. Right-lateral strike slip on various fault systems inboard of the Sitka

  2. Optomechanics for absolute rotation detection

    NASA Astrophysics Data System (ADS)

    Davuluri, Sankar

    2016-07-01

    In this article, we present an application of optomechanical cavity for the absolute rotation detection. The optomechanical cavity is arranged in a Michelson interferometer in such a way that the classical centrifugal force due to rotation changes the length of the optomechanical cavity. The change in the cavity length induces a shift in the frequency of the cavity mode. The phase shift corresponding to the frequency shift in the cavity mode is measured at the interferometer output to estimate the angular velocity of absolute rotation. We derived an analytic expression to estimate the minimum detectable rotation rate in our scheme for a given optomechanical cavity. Temperature dependence of the rotation detection sensitivity is studied.

  3. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  4. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  5. Microphysics-based black carbon aging in a global CTM: constraints from HIPPO observations and implications for global black carbon budget

    NASA Astrophysics Data System (ADS)

    He, Cenlin; Li, Qinbin; Liou, Kuo-Nan; Qi, Ling; Tao, Shu; Schwarz, Joshua P.

    2016-03-01

    We develop and examine a microphysics-based black carbon (BC) aerosol aging scheme that accounts for condensation, coagulation, and heterogeneous chemical oxidation processes in a global 3-D chemical transport model (GEOS-Chem) by interpreting the BC measurements from the HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011) using the model. We convert aerosol mass in the model to number concentration by assuming lognormal aerosol size distributions and compute the microphysical BC aging rate (excluding chemical oxidation aging) explicitly from the condensation of soluble materials onto hydrophobic BC and the coagulation between hydrophobic BC and preexisting soluble particles. The chemical oxidation aging is tested in the sensitivity simulation. The microphysical aging rate is ˜ 4 times higher in the lower troposphere over source regions than that from a fixed aging scheme with an e-folding time of 1.2 days. The higher aging rate reflects the large emissions of sulfate-nitrate and secondary organic aerosol precursors hence faster BC aging through condensation and coagulation. In contrast, the microphysical aging is more than 5-fold slower than the fixed aging in remote regions, where condensation and coagulation are weak. Globally, BC microphysical aging is dominated by condensation, while coagulation contribution is largest over eastern China, India, and central Africa. The fixed aging scheme results in an overestimate of HIPPO BC throughout the troposphere by a factor of 6 on average. The microphysical scheme reduces this discrepancy by a factor of ˜ 3, particularly in the middle and upper troposphere. It also leads to a 3-fold reduction in model bias in the latitudinal BC column burden averaged along the HIPPO flight tracks, with largest improvements in the tropics. The resulting global annual mean BC lifetime is 4.2 days and BC burden is 0.25 mg m-2, with 7.3 % of the burden at high altitudes (above 5 km). Wet scavenging accounts for 80.3 % of global BC

  6. Impaired control of body cooling during heterothermia represents the major energetic constraint in an aging non-human primate exposed to cold.

    PubMed

    Terrien, Jeremy; Zahariev, Alexandre; Blanc, Stephane; Aujard, Fabienne

    2009-01-01

    Daily heterothermia is used by small mammals for energy and water savings, and seems to be preferentially exhibited during winter rather than during summer. This feature induces a trade-off between the energy saved during daily heterothermia and the energy cost of arousal, which can impact energy balance and survival under harsh environmental conditions. Especially, aging may significantly affect such trade off during cold-induced energy stress, but direct evidences are still lacking. We hypothesized that aging could alter the energetics of daily heterothermia, and that the effects could differ according to season. In the gray mouse lemur (Microcebus murinus), a non-human primate species which exhibits daily heterothermia, we investigated the effects of exposures to 25 and 12 degrees C on body composition, energy balance, patterns of heterothermia and water turnover in adult (N = 8) and aged animals (N = 7) acclimated to winter-like or summer-like photoperiods. Acclimation to summer prevented animals from deep heterothermia, even during aging. During winter, adult animals at 12 degrees C and aged animals at 25 degrees C exhibited low levels of energy expenditure with minor modulations of heterothermia. The major effects of cold were observed during winter, and were particularly pronounced in aged mouse lemurs which exhibited deep heterothermia phases. Body composition was not significantly affected by age and could not explain the age-related differences in heterothermia patterns. However, aging was associated with increased levels of energy expenditure during cold exposure, in concomitance with impaired energy balance. Interestingly, increased energy expenditure and depth of heterothermia phases were strongly correlated. In conclusion, it appeared that the exhibition of shallow heterothermia allowed energy savings during winter in adult animals only. Aged animals exhibited deep heterothermia and increased levels of energy expenditure, impairing energy balance

  7. Absolute plate motions since 130 Ma constrained by subduction zone kinematics

    NASA Astrophysics Data System (ADS)

    Williams, Simon; Flament, Nicolas; Dietmar Müller, R.; Butterworth, Nathaniel

    2015-05-01

    The absolute motions of the lithospheric plates relative to the Earth's deep interior are commonly constrained using observations from paleomagnetism and age-progressive seamount trails. In contrast, an absolute plate motion (APM) model linking surface plate motions to subducted slab remnants mapped from seismic tomography has recently been proposed. Absolute plate motion models (or "reference frames") derived using different methodologies, different subsets of hotspots, or differing assumptions of hotspot motion, have contrasting implications for parameters that describe the long term state of the plate-mantle system, such as the balance between advance and retreat of subduction zones, plate velocities, and net lithospheric rotation. Previous studies of contemporary plate motions have used subduction zone kinematics as a constraint on the most likely APM model. Here we use a relative plate motion model to compute these values for the last 130 Myr for a range of alternative reference frames, and quantitatively compare the results. We find that hotspot and tomographic slab-remnant reference frames yield similar results for the last 70 Myr. For the 130-70 Ma period, where hotspot reference frames are less well constrained, these models yield a much more dispersed distribution of slab advance and retreat velocities. By contrast, plate motions calculated using the slab-remnant reference frame, or using a reference frame designed to minimise net rotation, yield more consistent subduction zone kinematics for times older than 70 Ma. Introducing the global optimisation of trench migration characteristics as a key criterion in the construction of APM models forms the foundation of a new method of constraining APMs (and in particular paleolongitude) in deep geological time.

  8. Microphysics-based black carbon aging in a global CTM: constraints from HIPPO observations and implications for global black carbon budget

    NASA Astrophysics Data System (ADS)

    He, C.; Li, Q.; Liou, K. N.; Qi, L.; Tao, S.; Schwarz, J. P.

    2015-11-01

    We develop and examine a microphysics-based black carbon (BC) aerosol aging scheme that accounts for condensation and coagulation processes in a global 3-D chemical transport model (GEOS-Chem) by interpreting the BC measurements from the HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011) using the model. We convert aerosol mass in the model to number concentration by assuming lognormal aerosol size distributions and compute the microphysical BC aging rate explicitly from the condensation of soluble materials onto hydrophobic BC and the coagulation between hydrophobic BC and preexisting soluble particles. The resulting aging rate is ∼ 4 times higher in the lower troposphere over source regions than that from a fixed aging scheme with an e-folding time of 1.2 days. The higher aging rate reflects the large emissions of sulfate-nitrate and secondary organic aerosol precursors hence faster BC aging through condensation and coagulation. In contrast, the microphysical aging is more than fivefold slower than the fixed aging in remote regions, where condensation and coagulation are weak. Globally BC microphysical aging is dominated by condensation, while coagulation contribution is largest over East China, India, and Central Africa. The fixed aging scheme results in an overestimate of HIPPO BC throughout the troposphere by a factor of 6 on average. The microphysical scheme reduces this discrepancy by a factor of ∼ 3, particularly in the middle and upper troposphere. It also leads to a threefold reduction in model bias in the latitudinal BC column burden averaged along the HIPPO flight tracks, with largest improvements in the tropics. The resulting global annual mean BC lifetime is 4.2 days and BC burden is 0.25 mg m-2, with 7.3 % of the burden at high altitudes (above 5 km). Wet scavenging accounts for 80.3 % of global BC deposition. We find that in source regions the microphysical aging rate is insensitive to aerosol size distribution, condensation threshold, and

  9. Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions

    PubMed Central

    Griebeler, Eva Maria; Klein, Nicole; Sander, P. Martin

    2013-01-01

    Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but

  10. Absolute uniqueness of phase retrieval with random illumination

    NASA Astrophysics Data System (ADS)

    Fannjiang, Albert

    2012-07-01

    Random illumination is proposed to enforce absolute uniqueness and resolve all types of ambiguity, trivial or nontrivial, in phase retrieval. Almost sure irreducibility is proved for any complex-valued object whose support set has rank ⩾ 2. While the new irreducibility result can be viewed as a probabilistic version of the classical result by Bruck, Sodin and Hayes, it provides a novel perspective and an effective method for phase retrieval. In particular, almost sure uniqueness, up to a global phase, is proved for complex-valued objects under general two-point conditions. Under a tight sector constraint absolute uniqueness is proved to hold with probability exponentially close to unity as the object sparsity increases. Under a magnitude constraint with random amplitude illumination, uniqueness modulo global phase is proved to hold with probability exponentially close to unity as object sparsity increases. For general complex-valued objects without any constraint, almost sure uniqueness up to global phase is established with two sets of Fourier magnitude data under two independent illuminations. Numerical experiments suggest that random illumination essentially alleviates most, if not all, numerical problems commonly associated with the standard phasing algorithms.

  11. Zircon U-Pb ages and Hf-O isotopic composition of migmatites from the Zanjan-Takab complex, NW Iran: Constraints on partial melting of metasediments

    NASA Astrophysics Data System (ADS)

    Moghadam, Hadi Shafaii; Li, Xian-Hua; Stern, Robert J.; Ghorbani, Ghasem; Bakhshizad, Farzaneh

    2016-01-01

    We study migmatites and other metamorphic rocks in the Zanjan-Takab region of NW Iran and use these results to report the first evidence of Oligocene core complex formation in Iran. Four samples of migmatites associated with paragneisses, including leucosomes and associated para-amphibolite melanosomes were selected for U-Pb dating and Hf-O isotopic analysis. Zircon cores - interpreted as originally detrital zircons - have variable ages that peak at ca. 100-110 Ma, but their sedimentation age - indicated by the youngest 206Pb/238U ages - is ca. 35-40 Ma. New zircons associated with incipient melting occur as overgrowths around zircon cores and/or as newly grown grains. Morphologies and internal structures suggest that rim growth and formation of new zircons were associated with partial melting. All four samples contain zircons with rims that yield 206Pb/238U ages of 28-25 Ma, indicating that partial melting occurred in Late Oligocene time. δ18O values for zircon rims vary between 8.2 and 12.3‰, significantly higher than expected for mantle inputs (δ18O ~ 6‰) and consistent with equilibrium with surface materials. Zircon rims yield εHf(t) between 2.2 and 12.4 and two-stage Hf model ages of ~ 448-562 Ma, indicating that the region is underlain by Cadomian-Caledonian crust. According to the Hf-O isotopic values, the main mechanism forming zircon rims was dissolution of pre-existing detrital zircons with reprecipitation of new zircon shortly thereafter. Oligocene ages indicate that partial melting accompanied core complex formation in the Zanjan-Takab region. Extension, melting, and core complex formation in south-central Iran are Eocene in age, but younger ages of Oligocene-Miocene in NW Iran and Turkey indicate that extension was distributed throughout the region during Cenozoic time.

  12. The AFGL absolute gravity program

    NASA Technical Reports Server (NTRS)

    Hammond, J. A.; Iliff, R. L.

    1978-01-01

    A brief discussion of the AFGL's (Air Force Geophysics Laboratory) program in absolute gravity is presented. Support of outside work and in-house studies relating to gravity instrumentation are discussed. A description of the current transportable system is included and the latest results are presented. These results show good agreement with measurements at the AFGL site by an Italian system. The accuracy obtained by the transportable apparatus is better than 0.1 microns sq sec 10 microgal and agreement with previous measurements is within the combined uncertainties of the measurements.

  13. Absolute limit on rotation of gravitationally bound stars

    SciTech Connect

    Glendenning, N.K.

    1994-03-01

    The authors seek an absolute limit on the rotational period for a neutron star as a function of its mass, based on the minimal constraints imposed by Einstein`s theory of relativity, Le Chatelier`s principle, causality and a low-density equation of state, uncertainties which can be evaluated as to their effect on the result. This establishes a limiting curve in the mass-period plane below which no pulsar that is a neutron star can lie. For example, the minimum possible Kepler period, which is an absolute limit on rotation below which mass-shedding would occur, is 0.33 ms for a M = 1.442 M{circle_dot} neutron star (the mass of PSR1913+16). If the limit were found to be broken by any pulsar, it would signal that the confined hadronic phase of ordinary nucleons and nuclei is only metastable, an extraordinary conclusion.

  14. Evidence for multi-cycle sedimentation and provenance constraints from detrital zircon U-Pb ages: Triassic strata of the Lusitanian basin (western Iberia)

    NASA Astrophysics Data System (ADS)

    Pereira, M. F.; Gama, C.; Chichorro, M.; Silva, J. B.; Gutiérrez-Alonso, G.; Hofmann, M.; Linnemann, U.; Gärtner, A.

    2016-06-01

    Laser ablation ICP-MS U-Pb analyses were conducted on detrital zircons of Triassic sandstone and conglomerate from the Lusitanian basin in order to: i) document the age spectra of detrital zircon; ii) compare U-Pb detrital zircon ages with previous published data obtained from Upper Carboniferous, Ordovician, Cambrian and Ediacaran sedimentary rocks of the pre-Mesozoic basement of western Iberia; iii) discuss potential sources; and iv) test the hypothesis of sedimentary recycling. U-Pb dating of zircons established a maximum depositional age for this deposit as Permian (ca. 296 Ma), which is about sixty million years older compared to the fossil content recognized in previous studies (Upper Triassic). The distribution of detrital zircon ages obtained points to common source areas: the Ossa-Morena and Central Iberian zones that outcrop in and close to the Porto-Tomar fault zone. The high degree of immaturity and evidence of little transport of the Triassic sediment suggests that granite may constitute primary crystalline sources. The Carboniferous age of ca. 330 Ma for the best estimate of crystallization for a granite pebble in a Triassic conglomerate and the Permian-Carboniferous ages (< ca. 315 Ma) found in detrital zircons provide evidence of the denudation of Variscan and Cimmerian granites during the infilling of continental rift basins in western Iberia. The zircon age spectra found in Triassic strata are also the result of recycling from the Upper Carboniferous Buçaco basin, which probably acted as an intermediate sediment repository. U-Pb data in this study suggest that the detritus from the Triassic sandstone and conglomerate of the Lusitanian basin is derived from local source areas with features typical of Gondwana, with no sediment from external sources from Laurussia or southwestern Iberia.

  15. Isotopic age constraints on provenance of exotic terranes, latest Permian collision and fast Late Triassic post-collisional cooling and tectonic exhumation of the Korean collision belt

    NASA Astrophysics Data System (ADS)

    de Jong, Koenraad; Han, Seokyoung; Ruffet, Gilles; Yi, Keewook

    2016-04-01

    The Korean peninsula is located in the eastern margin of the Eurasian continent where major late Palaeozoic to early Mesozoic continental collision zones, like the Central Asian Orogenic Belt and the Central China Orogen, merge with circum-Pacific subduction-accretion systems. We present an integrated view of the Korean collision belt using recent Ar/Ar laser-probe step-heating single grain ages from the uppermost Gyeonggi Massif, central Korea's Palaeoproterozoic high-grade granite-gneiss terrane affected by Permo-Triassic metamorphism, the bordering Hongseong zone and the overlying Imjingang belt and the correlative Taean Formation, as well as SHRIMP isotopic ages of detrital zircons from meta-sandstones from the latter metamorphic marine turbidite sequences. We show that early Paleozoic isolated exotic terranes form part of the collision belt and were reworked in Permo-Triassic time. Age spectra of zircons from mature meta-sandstones in the Misan Formation (Imjingang Belt) and Taean Formation do not match the age distribution of the Gyeonggi Massif, to which both are usually assigned, as they show only subordinate 1.9-1.8 Ga and ~2.5 Ga age modes but dominant 441-426 Ma and 978-919 Ma peaks. Much of the sediment appears to have been derived from distant, exotic middle Paleozoic and Early Neoproterozoic magmatic sources, not present in Gyeonggi or other Korean basement massifs. The youngest concordant zircon ages are: 394, 398 and 402 Ma, showing that both formations are at least of Early Devonian age. Terranes with a substratum with Early Neoproterozoic and Silurian-Devonian granitoids are present in the South Chinese Cathaysia Terrane and in the Qinling Terrane (Central China Orogen). Both formations may, hence, represent the submarine fan part of a routing system and a delta-shelf system originally situated in China. The Taean Formation and Imjingang Belt are thus exotic Paleozoic terranes tectonically emplaced in the Korean collision belt. Muscovite, biotite

  16. U-Pb geochronologic constraints on the age of thrusting, crustal extension, peraluminous plutonism in the Little Rincon Mountains, southern Arizona

    SciTech Connect

    Gehrels, G.E.; Smith, C.H. )

    1991-03-01

    The Little Rincon thrust fault is a mylonitic shear zone that juxtaposes Middle Proterozoic Continental Granodiorite over metasedimentary rocks of Proterozoic and early Paleozoic age. This fault is structurally beneath the San Pedro detachment fault and associated ductile deformational fabrics, which formed during early Oligocene to early Miocene time. A syntectonic leucogranite sill within the Little Rincon shear zone yields a U-Pb concordia-intercept age 66{plus minus}10 Ma for zircon and a concordant age 51{plus minus}2 Ma for fractions composed of monazite and xenotime. This demonstrates that compressional deformation in the Catalina and Rincon mountains is generally coeval with Laramide thrust faults that extend at least from southeastern California to southeastern Arizona. A peraluminous granite pluton that truncates the shear zone but displays extension-related fabrics yields a lower-intercept age 24{plus minus}12 Ma for zircon and an age of 30{plus minus}6 Ma for monazite. This indicates that some peraluminous plutons in the region were emplaced during regional crustal extension.

  17. Metamorphic evolution of the Rechnitz metamorphic core complex in relation to the Neogene Pannonian basin, Eastern Alps: Constraints from Ar-Ar white mica ages

    NASA Astrophysics Data System (ADS)

    Cao, Shuyun; Neubauer, Franz; Genser, Johann; Bernroider, Manfred; Friedl, Gertrude

    2015-04-01

    The exhumation of Cordilleran-type metamorphic core complexes (MCC) is generally related to largely contemporaneous collapse-type sedimentary basins (mainly halfgrabens). Here, we investigate the example of the Rechnitz MCC, which formed by Miocene orogen-parallel extension within the Neogene Pannonian basin. The Rechnitz MCC is located on the South Burgenland basement High within the western part of the Neogene Pannonian basin, with the Styrian basin in the west and the Danube basin in the east. The Rechnitz MCC is metamorphosed within greenschist facies conditions (maximum temperature of 430 °C) ideal for Ar-Ar white mica dating. For the first time, we undertook an extensive survey of 40Ar/39Ar white mica dating combined with microfabrics and electron microprobe compositional data and we compare the new data with major evolutionary stages of adjacent sedimentary basins, mainly based on re-evaluation of existing reflection seismic lines. The internal structure of the Rechnitz window is characterized by two tectonic cover nappes, a lower nappe with distal continental affinity, and an upper nappe representing the infilling of an oceanic basin. Both within greenschist facies metamorphic conditions and few blueschists were found in the northwestern part of the upper nappe. We found a number of distinct white mica age spectra: (1) A sample from the northwesternmost upper nappe yield a staircase pattern ranging from 14.8 ± 0.9 Ma to 41.5 ± 1.0 Ma. We interpret the older age is minimum age of high-pressure metamorphism and the younger age as age of overprint during extensional exhumation. (2) A number of samples from the western part, independent from positions within the nappes yield plateau ages between 20 and maximum 23 Ma and are variably affected by a younger thermal overprint between 13 and 15 Ma. (3) The eastern and lower units show plateau-like patterns with plateau ages of 17 - 19 Ma with a majority at ca. 18 Ma and a single younger outlier at ca. 16 Ma. Some

  18. Zircon U-Pb age constraints on the Paleoproterozoic sedimentary basement of the Ediacaran Porongos Group, Sul-Riograndense Shield, southern Brazil

    NASA Astrophysics Data System (ADS)

    Pertille, Juliana; Hartmann, Léo Afraneo; Philipp, Ruy Paulo

    2015-11-01

    Thick quartzites record significant information on cratonic environments during long geological periods. The capacity to resist weathering and deformation turn the quartzite covers especially useful in the provenance studies of Precambrian basins. Provenance of 194 detrital zircon grains from two samples of thick quartzite cover on the Paleoproterozoic Encantadas Complex displays mostly Paleoproterozoic (95%) and minor Archean (5%) sources. The results indicate that sediments were derived from the La Plata Craton with the maximum depositional age at 2.03 Ga possibly up to 1.7 Ga. In comparison, the adjacent Porongos Group has provenance data of 61 detrital zircon grains indicating mostly Mesoproterozoic (69%), subordinately Paleoproterozoic (26%) and minor Archean ages (5%). Considering previous published data, the Porongos Group is Ediacaran in age and probably chronocorrelated with sedimentary basins from the Tandilia Belt (Argentina). Therefore, the quartzite cover and the Porongos Group require distinct evolution in time and in tectonic environment.

  19. Zircon ages of metamorphic and magmatic rocks within peridotite-bearing mélanges: Crucial time constraints on early Carboniferous extensional tectonics in the Chinese Tianshan

    NASA Astrophysics Data System (ADS)

    Jian, Ping; Kröner, Alfred; Jahn, Bor-ming; Liu, Dunyi; Zhang, Wei; Shi, Yuruo; Ma, Huadong

    2013-07-01

    We dated and geochemically characterized peridotite-bearing mélanges in the Chinese South Tianshan and within the Main Tianshan Shear Zone. The Yushugou-Tonghuashan mélange in the Chinese South Tianshan exposes a tectonic juxtaposition of a diapirically emplaced metaperidotite (predominantly lherzolite) massif with a high-grade metamorphic terrane (ca. 10 km long; protolith age ≥ ca. 445-466 Ma). Metamorphic zircons of a mafic granulite (εNd(t) = 5.0) yielded a weighted mean 206Pb/238U age of 341 ± 8 Ma that we interpret as the time of granulite-facies metamorphism. The youngest zircon rims of an intermediate granulite (εNd(t) = - 4.3) have a mean age of 332 ± 13 Ma that records a retrogressive metamorphic event. These ages determine the timing (ca. 341-332 Ma) of mantle diapirism through continental crust. A dolerite dike (εNd(t) = 2.3) emplaced into metaperidote has a crystallization age of 335 ± 5 Ma, that, on the basis of geochemistry, we interpret as representing E-MORB-OIB magmatism that accompanied mantle diapirism. An undeformed pink granite (εNd(t) = - 3.6) intrudes the mélange matrix and has an emplacement age of 324 ± 5 Ma, thus providing an upper time limit for a tectonic movement that led to mélange formation. The older time limit of deformation (ca. 362-352 Ma) is constrained by the youngest ages of thermo-tectonically modified zircons in a mylonitized metagabbro and a foliated meta-andesite. Magmatic zircons in the meta-andesite (εNd(t) = - 3.3) and a dacite (εNd(t) = - 5.6) have eruption ages of 433 ± 4 Ma and 435 ± 3 Ma that date formation of the mélange matrix. A microgabbro dike (εNd(t) = 10.0) cutting metasediments (i.e. mélange matrix) has an emplacement age of 279 ± 3 Ma and contains abundant zircon xenocrysts ranging in age from Archean to late Paleozoic. Similarly, a dolerite dike, a meta-andesite, an intermediate granulite, and a metagabbro all contain inherited Precambrian to Paleozoic zircons. We accordingly conclude

  20. Roter Kamm Impact Crater, Namibia: Age Constraints from K-Ar, Rb-Sr, Fission Track, 10Be-26Al Studies

    NASA Astrophysics Data System (ADS)

    Koeberl, C.; Klein, J.; Matsuda, J.; Nagao, K.; Reimold, W. U.; Storzer, D.

    1992-07-01

    INTRODUCTION. The Roter Kamm impact crater is located in the Namib Desert in Namibia. The impact occurred in Precambrian granitic-granodioritic orthogneisses of the 1200-900-Ma-old Namaqualand Metamorphic Complex. The granites are invaded by quartz veins and quartz-feldspar-pegmatites. Gariep metasediments probably overlaid the Namaqualand complex at the time of the impact (Reimold and Miller, 1989). Previous estimates for the crater age are not well constrained: regional geology suggests an age of 5-10 Ma, while the only available ^40Ar-^39Ar age (Hartung et al., 1991) is 3.7 Ma. Fission tracks measured in apatites from granites found on or near the crater rim were not completely reset by the impact and suggest an uplift event around 20 Ma ago (Storzer et al., 1990). We are using several approaches to bracket the age of the crater: we have measured melt breccia and pseudotachylite K-Ar ages, and apatite fission track ages in several rim granites. We are comparing Rb-Sr isotope data for rim granites with known ages of regional resetting events (Allsopp et al., 1979). Finally, we are using ^10Be-^26Al measured by accelerator mass spectrometry to determine surface exposure ages for quartz excavated during the impact event. RESULTS AND DISCUSSION. The target rock composition and stratigraphy at Roter Kamm is relatively complicated. Melt breccias formed from pegmatites, gneisses, or schists, while pseudotachylites probably formed from gneissic basement or quartz-feldspar-pegmatites (Reimold and Miller, 1989). Whole rock Rb-Sr data for several granites yield 1498 Ma, and mineral separates from sample URK-M indicate an "age" of 466 Ma; these ages are similar to those of country rocks from the general area of the northwestern Cape/southern Namibia (Allsopp et al., 1979) which indicate two widespread regional resetting events at ca. 700 Ma (related to the Pan-African orogenic deformation), and ca. 500 Ma, related to a subsequent metamorphic event. For K-Ar ages, we

  1. Radioisotopic Age Constraints on Crystallization, Crystal Inheritance, and Eruption of Coso's Pleistocene Rhyolites: Tracking the Evolution of a Silicic Magma System

    NASA Astrophysics Data System (ADS)

    Simon, J. I.; Vazquez, J. A.; Renne, P. R.; Reid, M. R.; Schmitt, A. K.

    2007-12-01

    Radioisotopic dating at Coso provides a direct assessment of the rates at which large silicic magma reservoirs develop and whether upper crustal reservoirs remain thermally viable for protracted amounts of time. We dated a representative suite of Coso extrusions (8 units) ranging in age from ~230 ka to ~56 ka using Ar/Ar techniques, with additional analyses forthcoming. Accurate eruption ages are required to track secular geochemical and petrological changes within the magma system. We also dated zircon from a granodiorite core sample from injection well 46A-19RD and in favorable cases we were able to separate and date accessory minerals (zircon and allanite) from the crystal-poor extrusions. Application of accessory mineral dating is a robust approach for quantifying the time scales associated with physicochemical changes in magmas reservoirs. For example, the age distribution and character of zircons from Coso's ~600 ka Devils Kitchen rhyolite led Miller and Wooden (2004) to suggest that it was emplaced in the crust as a near-solidus crystal mush over an ~200 ka period prior to eruption. Our U-Th ages for zircon and allanite obtained by ion microprobe analysis, when compared to their respective ~115 ka (Dome 24) and ~85 ka (Cactus Peak and Sugarloaf Mountain) Ar/Ar ages, yield near-eruption ages and little evidence of recycled zircon (or allanite) from their older Pleistocene predecessors. Likewise zircon ages in the granodiorite exhibit evidence for a single crystallization event at ~200 ka. However, U-Pb dating of a significant subset of zircon in Coso's ~85 ka rhyolites and in the granodiorite core yield Mesozoic ages between ca. 100 and 200 Ma. The latter includes grains that previously yielded U-Th isotope ages within error of secular equilibrium. Two end-member cases may account for the bimodal distribution of zircon ages and evidence for assimilation and crustal contamination of low temperature (≤800 °C) rhyolite, as well as secular changes in their

  2. Age constraints for the present fault configuration in the Imperial Valley, California - Evidence for northwestward propagation of the Gulf of California rift system

    NASA Technical Reports Server (NTRS)

    Larsen, Shawn; Reilinger, Robert

    1991-01-01

    Releveling and other geophysical data for the Imperial Valley of southern California suggest the northern section of the Imperial-Brawley fault system, which includes the Mesquite Basin and Brawley Seismic Zone, is much younger than the 4 to 5 million year age of the valley itself. A minimum age of 3000 years is calculated for the northern segment of the Imperial fault from correlations between surface topography and geodetically observed seismic/interseismic vertical movements. Calculations of a maximum age of 80,000 years is based upon displacements in the crystalline basement along the Imperial fault, inferred from seismic refraction surveys. This young age supports recent interpretations of heat flow measurements, which also suggest that the current patterns of seismicity and faults in the Imperial Valley are not long lived. The current fault geometry and basement morphology suggest northwestward growth of the Imperial fault and migration of the Brawley Seismic Zone. It is suggested that this migration is a manifestation of the propagation of the Gulf of California rift system into the North American continent.

  3. High-precision 40Ar/ 39Ar age constraints on the basal Lanqi Formation and its implications for the origin of angiosperm plants

    NASA Astrophysics Data System (ADS)

    Chang, Su-chin; Zhang, Haichun; Renne, Paul R.; Fang, Yan

    2009-03-01

    Abundant Mesozoic terrestrial fossils were discovered in the Haifanggou Formation and the overlying Lanqi Formation in northeastern China. The recent discovery of Schmeissneria sinensis from the Haifanggou Formation provides evidence that the origin of angiosperms could be much earlier than previously believed. 92 taxa of plant fossils from the Lanqi Formation provide unique opportunities to understand the floral evolution and its diversification in the Mesozoic. Here we present robust high-precision 40Ar/ 39Ar data of 160.7 ± 0.4 Ma and 158.7 ± 0.6 Ma for two tuffs from the lowest part of the Lanqi Formation near the main outcrop of floral fossils in Beipiao City, Liaoning, China. Our age results indicate the whole Lanqi Formation was deposited in the Late Jurassic; consequently, the underlying Haifanggou Formation and Schmeissneria sinensis are at least Middle Jurassic in age. Besides its importance for floral evolution, our high-precision age results for the basal Lanqi Formation indicate the paleoenvironment in the north margin of the North China Craton was dry and hot in the Late Jurassic. Moreover, the new age data for the basal Lanqi Formation suggest that the unearthed fossils from the Haifanggou Formation and Lanqi Formation should be equivalent to the Daohugou Biota in Inner Mongolia, China.

  4. Age constraints for the present fault configuration in the Imperial Valley, California: Evidence for northwestward propagation of the Gulf of California rift system

    NASA Technical Reports Server (NTRS)

    Larsen, Shawn; Reilinger, Robert

    1990-01-01

    Releveling and other geophysical data for the Imperial Valley of southern California suggest the northern section of the Imperial-Brawley fault system, which includes the Mesquite Basin and Brawley Seismic Zone, is much younger than the 4 to 5 million year age of the valley itself. A minimum age of 3000 years is calculated for the northern segment of the Imperial fault from correlations between surface topography and geodetically observed seismic/interseismic vertical movements. Calculations of a maximum age of 80,000 years is based upon displacements in the crystalline basement along the Imperial fault, inferred from seismic refraction surveys. This young age supports recent interpretations of heat flow measurements, which also suggest that the current patterns of seismicity and faults in the Imperial Valley are not long lived. The current fault geometry and basement morphology suggest northwestward growth of the Imperial fault and migration of the Brawley Seismic Zone. It is suggested that this migration is a manifestation of the propagation of the Gulf of California rift system into the North American continent.

  5. Re-Os and 40Ar/ 39Ar isotope measurements of inclusions in alluvial diamonds from the Ural Mountains: Constraints on diamond genesis and eruption ages

    NASA Astrophysics Data System (ADS)

    Laiginhas, Fernando; Pearson, D. Graham; Phillips, David; Burgess, Ray; Harris, Jeff W.

    2009-11-01

    The Re-Os isotope data for 20 syngenetic sulphide inclusions, recovered from 15 diamonds and the 40Ar/ 39Ar laser probe eruption ages of 7 syngenetic clinopyroxenes recovered from 5 diamonds, all from alluvial placer deposits in the Ural Mountains, have been determined. Six eclogitic sulphide inclusions, two of which coexist in the same diamond, yield an isochron age of 1280 ± 310 Ma (2 σ), with an unusually high initial 187Os/ 188Os ratio of 2.10 ± 0.58 (2 σ). The age is interpreted to date remobilisation of carbon and sulphur, and homogenisation of Os, during rift-related thermal-magmatic events that affected the East European Craton (EEC) at ca. 1.3 Ga. The high initial Os ratio suggests Re-Os evolution over a 100 to 500 Ma period within previously metasomatised lithosphere, most likely the EEC. Five eclogitic clinopyroxenes recovered from four diamonds yielded similar 40Ar/ 39Ar ages averaging 472 ± 28 Ma, which likely approximate the time of source kimberlite/lamproite eruption. This age suggests that the Ural diamonds are not likely to have derived either from the well known diamond-bearing kimberlites of the Siberian craton, nor from presently known Russian and Finnish kimberlite provinces on the EEC. The Urals placer deposits are mainly confined to 397-407 Ma sedimentary rocks along the western side of these mountains, with sediment transportation at that time generally from the north-west. Present evidence suggests the existence of an undiscovered kimberlite/lamproite source, probably on the Volgo-Uralia crustal segment of the EEC, which gave rise to the Urals diamond deposits.

  6. Cosmology with negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Vieira, J. P. P.; Byrnes, Christian T.; Lewis, Antony

    2016-08-01

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion (w < ‑1) with no Big Rip, and their contracting counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.

  7. The Southern Urals Large Igneous Province with an age of approximately 1380 Ma: Precision U-Pb ID-TIMS constraints

    NASA Astrophysics Data System (ADS)

    Ronkin, Yu. L.; Tichomirowa, M.; Maslov, A. V.

    2016-06-01

    The formation of the Large Igneous Province (LIP) approximately 1380 Ma old in the South Urals was related to the Mashak riftogenic event in the Bashkir meganticlinorium, which was synchronous with the emplacement of different magmatic bodies (the Berdyaush pluton of rapakivi granites and associated rocks, the Main dike of the Bakal ore field, and the Medvedev, Guben, and Kusa massifs, among others) localized among sedimentary deposits of the Burzyan and Yurmatin Groups representing Lower and Middle Riphean type units of northern Eurasia. The U-Pb ID-TIMS age of 1379.6 Ma (MSWD = 1.3) obtained with an accuracy of ±2.9 Ma (confidence interval 95%) combined with the available published U-Pb ID-TIMS data constrain the age and duration of the Early-Middle Riphean pulse in the LIP formation in the Southern Urals.

  8. Cadomian vs. Variscan evolution of the Ossa-Morena zone (SW Iberia): field and 40Ar/ 39Ar mineral age constraints

    NASA Astrophysics Data System (ADS)

    Dallmeyer, R. D.; Quesada, C.

    1992-12-01

    Six hornblende and ten muscovite concentrates have been dated from three contrasting tectonic units exposed within the Ossa-Morena zone of the Iberian Massif. These include: (1) the Obejo-Valsequillo domain (north of the Badajoz-Córdoba shear zone); (2) the Sierra Albarrana structural unit (immediately south of the Badajoz-Córdoba shear zone); and (3) the thermal some exposed within the Olivenza-Monesterio antiform (Zafra-Monesterio domain). Hornblende from foliated amphibolite in the Obejo-Valsequillo domain (Siera Negra unit) displays internally discordant 40Ar/ 39Ar age spectra as a result of both intracrystalline contamination with extraneous argon and slight rejuvenation. 36Ar/ 40Ar vs. 39Ar/ 40Ar isotope-correlations are generally well-defined and yield ages of c. 550-560 Ma. These are interpreted to date cooling following late Precambrian-early Paleozoic (Cadomian) tectonothermal activity. This was followed by slight Variscan rejuvenation at c. 375-400 Ma. Muscovite from this unit displays internally discordant age spectra which reflect more extensive Variscan rejuvenation of intracrystalline argon systems which had initially cooled below appropriate blocking temperatures at c. 560 Ma. Hornblende and muscovite from the Sierra Albarrana domain (Sierra Albarrana Group) record 40Ar/ 39Ar plateau and isotope-correlation ages which range between c. 392 Ma and 351 Ma. These results indicate that complete Variscan rejuvenation was followed by relatively rapid post-metamorphic cooling. Hornblende separated from various lithologie elements exposed in the Olivenza-Monesterio Antiform yield variable results. Hornblende within a mafic xenolith in the Monesterio Granodiorite records an isotope-correlation age of c. 553 Ma which is interpreted to date the last cooling through appropriate argon retention temperatures. Hornblende within amphibolite of the Montemolin Series (lower Serie Negra) records internally discordant age spectra which reflect extensive Variscan (c

  9. Improved astronomical age constraints for the middle Miocene climate transition based on high-resolution stable isotope records from the central Mediterranean Maltese Islands

    NASA Astrophysics Data System (ADS)

    Mourik, Anja A.; Abels, Hemmo A.; Hilgen, Frederik J.; Di Stefano, Agata; Zachariasse, Willem Jan

    2011-03-01

    Marine outcrops of the Globigerina Limestone and Blue Clay formations on the Maltese Islands in the central Mediterranean document the middle Miocene climate transition between ˜15 and 13.5 million years ago. Here high-resolution benthic and planktic oxygen isotope records have been constructed for this enigmatic interval in Cenozoic climate evolution. Detailed biostratigraphic correlations to the astronomically tuned La Vedova section in northern Italy allow revision of the tuning of the Blue Clay Formation, constraining the age of the sediments directly above the formation boundary and hence the Mi-3b oxygen isotope event and Serravallian Global Stratotype Section and Point (GSSP). Biostratigraphic age control and cyclic patterns in the benthic carbon isotope record further lead to an astronomically-tuned age model for the Upper Member of the Globigerina Limestone Formation. Start of sedimentation of the Upper Globigerina Limestone is dated at ˜14.95 Ma, and the oldest Blue Clay sediments have a revised astronomical age of 13.76 ± 0.02 Ma. Our data indicates that a hiatus between 13.95 and 13.76 Ma cannot be excluded and could have implications for the Serravallian GSSP currently defined in this section. The global middle Miocene cooling is reflected in the benthic oxygen isotope record, showing a ˜0.6‰ increase (Mi-3b) between ˜13.95 and 13.76 Ma. A divergence between the planktic and benthic oxygen and carbon isotope records after 13.76 Ma could point to a decrease in ventilation, possibly related to increased fresh water influx after the climate transition.

  10. Microfossil assemblages on Tuscaloosa Seamount and their constraints on the age of the Nu´uanu landslide, north of Oahu, HI

    NASA Astrophysics Data System (ADS)

    Morgan, Julia K.; Resig, Johanna M.; Siesser, William G.

    2006-03-01

    The Núuanu submarine landslide, north of the Island of Oahu, is the largest of many debris avalanches along the flanks of the Hawaiian Islands. Several attempts have been made to date the Núuanu landslide and to assess its relationship to the shield-building stage of Kóolau Volcano as an indication of hazards that might be anticipated during the evolution of oceanic volcanoes. Previous age determinations based on magnetostratigraphy and the temporal distribution of turbidites have yielded a range of possible ages. We describe a distinctive fine-grained silty mudstone representing mantling sediment on the largest landslide block within the debris field, Tuscaloosa Seamount. This mudstone contains foraminifera and nannofossil assemblages that yield a micropaleontological age and paleoenvironmental determination for the interval immediately following landslide emplacement. The microfossils constrain the mantling sediment to have been deposited between 2.5 and 3.3 Ma, in offshore, mid- to lower-bathyal (˜1500-3000 m) water depth, consistent with a position on the upper flanks of Tuscaloosa Seamount. These findings indicate that landsliding occurred prior to or near the end of shield building at Kóolau Volcano (2.9 Ma), and may have precipitated dramatic changes in volcano growth and deformation behavior, as well as changes in basalt geochemistry.

  11. Constraints on the Surface Magnetic Fields and Age of a Cool Hypergiant: XMM-Newton X-Ray Observations of VY CMa

    NASA Astrophysics Data System (ADS)

    Montez, Rodolfo, Jr.; Kastner, Joel H.; Humphreys, Roberta M.; Turok, Rebecca L.; Davidson, Kris

    2015-02-01

    The complex circumstellar ejecta of highly evolved, cool hypergiants are indicative of multiple, asymmetric mass-loss events. To explore whether such episodic, non-isotropic mass loss may be driven by surface magnetic activity, we have observed the archetypical cool hypergiant VY CMa with the XMM-Newton X-ray satellite observatory. The hypergiant itself is not detected in these observations. From the upper limit on the X-ray flux from VY CMa at the time of our observations (F X, UL ≈ 8 × 10-14 erg cm-2 s-1, corresponding to log LX /L bol <= -8), we estimate an average surface magnetic field strength fB <= 2 × 10-3 G (where f is the filling factor of magnetically active surface regions). These X-ray results for VY CMa represent the most stringent constraints to date on the magnetic field strength near the surface of a hypergiant. VY CMa's mass loss is episodic, however, and the hypergiant may have been in a state of low surface magnetic activity during the XMM observations. The XMM observations also yield detections of more than 100 X-ray sources within ~15' of VY CMa, roughly 50 of which have near-infrared counterparts. Analysis of X-ray hardness ratios and IR colors indicates that some of these field sources may be young, late-type stars associated with VY CMa, its adjacent molecular cloud complex, and the young cluster NGC 2362. Further study of the VY CMa field is warranted, given the potential to ascertain the evolutionary timescale of this enigmatic, massive star.

  12. Mode and timing of granitoid magmatism in the Västervik area (SE Sweden, Baltic Shield): Sr-Nd isotope and SIMS U-Pb age constraints

    NASA Astrophysics Data System (ADS)

    Kleinhanns, I. C.; Whitehouse, M. J.; Nolte, N.; Baero, W.; Wilsky, F.; Hansen, B. T.; Schoenberg, R.

    2015-01-01

    Observed geochemical and geophysical signatures in the southern Svecofennian domain (SD) and the Transscandinavian Igneous Belt (TIB) are explained through a model of tectonic cycling and episodic south-westward migration of a subduction zone system. The Västervik area is located between these two major tectonic domains and as such has received much attention. Granitoids of the Västervik area were recently re-grouped and classified within the context of this larger regional tectonic model, but a discrepancy between previous relative age estimations and the few available granitoid age determinations was noted. To address this issue, we have dated 13 granitoid samples using a high spatial resolution secondary ion mass spectrometry (SIMS) U-Pb technique. Our new results constrain the intrusion of the majority of granitoids to 1819-1795 Ma, thus placing them into the TIB-1 period. This age range also encompasses our new ages from the central granodiorite belt and the Örö-Hamnö pluton, demonstrating a previous overestimation of older granitoid generations in the Västervik area. Nonetheless, it is shown that Askersund/TIB-0 magmatism, represented by an augen gneiss sample dated to 1846 Ma, is unambiguously present as far south as the Västervik region. The anatectically generated leucogranites reveal TIB-1 ages and, as expected, older inherited zircon derived from the parental metasedimentary Västervik formation. By simple Sr-Nd isotope modeling it is further possible to deduce that most TIB-1 granitoids follow a simple (assimilation-) fractional crystallization petrogenetic trend. The youngest granitoid generation was produced through low-pressure fluid-absent crustal melting. In conclusion, granitoids of the Västervik area fit well into the proposed model for south-westward migration of a subduction zone system active in the Svecofennian domain and represent a new tectonic cycle. It is therefore possible to link the Svecofennian domain and the Transscandinavian

  13. Magmatism along the high Paraguay River at the border of Brazil and Paraguay: A review and new constraints on emplacement ages

    NASA Astrophysics Data System (ADS)

    Comin-Chiaramonti, P.; Gomes, C. B.; De Min, A.; Ernesto, M.; Gasparon, M.

    2015-03-01

    The magmatic rocks from Alto Paraguay (High Paraguay River extensional lineament), western Apa craton, mainly consist of several major circular alkaline complexes and some rhyolitic domes and ignimbrites. The former are characterized by intrusive Na-alkaline rock-types (nepheline syenites and syenites and effusive equivalents) topped by lava flows and ignimbrites. Two main evolved suites were defined using petrochemical and Sr- isotope data: an agpaitic suite in the north and a miaskitic suite in the south. The domes of subalkaline rhyolitic lavas and ignimbrites occur to the north of the alkaline complexes, along the Paraguay River, near the town of Fuerte Olimpo. The emplacement ages of the alkaline complexes were constrained using the K-Ar, Ar-Ar, Rb-Sr and Sm-Nd dating methods on whole rocks and/or mineral separates (amphibole, alkali feldspar and biotite). Ages are quite variable (Upper Permian to Middle Triassic), with average K-Ar and Ar-Ar ages of 248.8 ± 4.8 and 241.8 ± 1.1 Ma, respectively, and Rb-Sr and Sm-Nd age data giving best values from 248 ± 4 to 244 ± 27 Ma and from 256 ± 3 to 257 ± 3 Ma, respectively. In contrast, the Fuerte Olimpo volcanics show a Mesoproterozoic age (1.3 Ga, K-Ar and Ar-Ar radiometric methods; and 1.42 ± 0.24 to 1.30 ± 0.03 Ga, Rb-Sr and Sm-Nd methods, respectively). Rb-Sr systematics (87Sr/86Sr initial ratios ≤ 0.7038) highlight a relatively "primitive" character of the Na-alkaline magmatic source(s), in contrast with the "crustal" values (87Sr/86Sr initial ratio ˜ 0.7105) of the Fuerte Olimpo rhyolites. Thus, magmatism in the Alto Paraguay area is related to two extensional events: a younger event corresponding to the Permian-Triassic alkaline rocks, and an older event connected to the Precambrian volcanic acidic rocks.

  14. Absolute optical surface measurement with deflectometry

    NASA Astrophysics Data System (ADS)

    Li, Wansong; Sandner, Marc; Gesierich, Achim; Burke, Jan

    Deflectometry utilises the deformation and displacement of a sample pattern after reflection from a test surface to infer the surface slopes. Differentiation of the measurement data leads to a curvature map, which is very useful for surface quality checks with sensitivity down to the nanometre range. Integration of the data allows reconstruction of the absolute surface shape, but the procedure is very error-prone because systematic errors may add up to large shape deviations. In addition, there are infinitely many combinations for slope and object distance that satisfy a given observation. One solution for this ambiguity is to include information on the object's distance. It must be known very accurately. Two laser pointers can be used for positioning the object, and we also show how a confocal chromatic distance sensor can be used to define a reference point on a smooth surface from which the integration can be started. The used integration algorithm works without symmetry constraints and is therefore suitable for free-form surfaces as well. Unlike null testing, deflectometry also determines radius of curvature (ROC) or focal lengths as a direct result of the 3D surface reconstruction. This is shown by the example of a 200 mm diameter telescope mirror, whose ROC measurements by coordinate measurement machine and deflectometry coincide to within 0.27 mm (or a sag error of 1.3μm). By the example of a diamond-turned off-axis parabolic mirror, we demonstrate that the figure measurement uncertainty comes close to a well-calibrated Fizeau interferometer.

  15. Geochemistry, geology, and isotopic (Sr, S, and B) composition of evaporites in the Lake St. Martin impact structure: New constraints on the age of melt rock formation

    NASA Astrophysics Data System (ADS)

    Leybourne, Matthew I.; Denison, Rodger E.; Cousens, Brian L.; Bezys, Ruth K.; Gregoire, D. Conrad; Boyle, Dan R.; Dobrzanski, Ed

    2007-03-01

    We report new Sr, S, and B isotopic data for evaporites (gypsum, anhydrite), carbonates, melt rocks, gneisses, and groundwaters recovered in and around the Lake St. Martin (LSM) impact structure, Interlake Region, Manitoba, Canada. The LSM meteorite impacted Devonian to Ordovician carbonates and sandstones of the eastern Williston Basin, resulting in partial melting of underlying Superior Province (~2.5 Ga) gneisses of the Canadian Shield. Overlying the LSM melt rocks are red beds and evaporites (anhydrite/gypsum/glauberite) previously inferred to have been deposited during the Jurassic. The 87Sr/86Sr (lowest values cluster at 0.70836) and δ 34SCDT (+23.7 +/- 0.9‰) of the evaporites, combined with B isotope compositions of associated groundwaters (δ 11BNBS951 = +25 to +28‰), are consistent with evaporite deposition within the impact structure near the edge of an ocean-connected salina. The establishment of a marine origin for the evaporites offers a method of age assignment using the secular variation of S and Sr isotopes in seawater. Comparison of Sr and S isotope results with the seawater curves precludes Jurassic deposition for the evaporites or correlation with Watrous and Amaranth formation evaporites, previously considered correlative with those at LSM. The lowest Sr and mean of S isotope values from the LSM evaporites are similar to seawater in the latest Devonian, consistent with conodonts recovered from carbonate breccia overlying melt rocks, and we suggest this as an alternative age of the evaporites. Data presented here preclude a Jurassic age for the evaporites and therefore for the impact event.

  16. Zircon U-Pb age, geochemical, and Sr-Nd-Pb isotopic constraints on the origin of alkaline intrusions in eastern Shandong Province, China

    NASA Astrophysics Data System (ADS)

    Liu, Shen; Feng, Caixia; Hu, Ruizhong; Gao, Shan; Wang, Tao; Feng, Guangying; Qi, Youqiang; Coulson, Ian M.; Lai, Shaocong

    2013-08-01

    Alkaline intrusions in the eastern Shandong Province consist of quartz monzonite and granite. U-Pb zircon ages, geochemical data, and Sr-Nd-Pb isotopic data for these rocks are reported in the present paper. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb zircon analyses yielded consistent ages ranging from 114.3 ± 0.3 to 122.3 ± 0.4 Ma for six samples of the felsic rocks. The felsic rocks are characterised by a wide range of chemical compositions (SiO2 = 55.14-77.63 wt. %, MgO = 0.09-4.64 wt. %, Fe2O3 = 0.56-7.6 wt. %, CaO = 0.40-5.2 wt. %), light rare earth elements (LREEs) and large ion lithophile elements (LILEs) (i.e., Rb, Pb, U) enrichment, as well as significant rare earth elements (HREEs) and heavy field strength (HFSEs) (Nb, Ta, P and Ti) depletion, various and high (87Sr/86Sr) i ranging from 0.7066 to 0.7087, low ɛ Nd (t) values from -14.1 to -17.1, high neodymium model ages (TDM1 = 1.56-2.38Ga, TDM2 = 2.02-2.25Ga), 206Pb/204Pb = 17.12-17.16, 207Pb/204Pb = 15.44-15.51, and 208Pb/204Pb = 37.55-37.72. The results suggested that these rocks were derived from an enriched crustal source. In addition, the alkaline rocks also evolved as the result of the fractionation of potassium feldspar, plagioclase, +/- ilmenite or rutile and apatite. However, the alkaline rocks were not affected by crustal contamination. Moreover, the generation of the alkaline rocks can be attributed to the structural collapse of the Sulu organic belt due to various processes.

  17. Intraplate Late Jurassic deformation and exhumation in western central Argentina: Constraints from surface data and U-Pb detrital zircon ages

    NASA Astrophysics Data System (ADS)

    Naipauer, Maximiliano; García Morabito, Ezequiel; Marques, Juliana C.; Tunik, Maisa; Rojas Vera, Emilio A.; Vujovich, Graciela I.; Pimentel, Marcio P.; Ramos, Victor A.

    2012-02-01

    Intraplate deformation has been described in several tectonic settings and recently in western central Argentina it has been proposed to explain the complex structural patterns developed between Early Jurassic and Cretaceous times along the Huincul deformation zone. We integrate new field data and detrital zircon ages of the exposed portion of the Huincul High that permit us to quantify the significance of this intraplate deformation in the relief generation. A stratigraphic and structural record of a Jurassic pulsed contractional deformation is derived from field surveys. It is documented through multiple unconformities and growth geometries linked to NE and E-W oriented growth structures extensively developed across the studied region. The pattern of zircon ages from the analyzed Late Jurassic successions indicates that they have a clear provenance from sources located along the Huincul deformation zone. The Tordillo Formation outcrops north of the Huincul High have a dominant provenance from the Andean Jurassic arc; while the Quebrada del Sapo Formation, south of the Huincul High, has a significant input from Late Triassic (220-200 Ma) and Late Permian (280-260 Ma) sources of the axial exposures of the Huincul High. Surface data, combined with detrital zircon ages proved to be a powerful method to confirm the presence of an ancient positive element developed within the southern Neuquén basin. Its genesis falls within the early history of the Huincul deformation zone, where several structural features indicate pulses of growth since Early Jurassic times prior to the main Andean contractional cycle that started in the Late Cretaceous. Therefore, these data document for the first time the importance of the early contractional phases in the relief construction in the southern Central Andes, reinforcing previous hypotheses about pre-Andean intraplate deformation concentrated along this extensive east-west oriented basement weakness zone.

  18. U-series zircon age constraints on the plumbing system and magma residence times of the Changbai volcano, China/North Korea border

    NASA Astrophysics Data System (ADS)

    Zou, Haibo; Fan, Qicheng; Zhang, Hongfu; Schmitt, Axel K.

    2014-07-01

    The Changbai (or Baitoushan, Paektu) volcano on the China/North Korea border is best known for its climactic caldera-forming eruption of 100 km3 of comendite materials 1000 years (1 ka) ago. The polygenetic Changbai volcano also erupted moderate-volume pre-caldera comendite lava at ~ 4 ka and small-volume post-caldera trachyte ignimbrite at ~ 0.3 ka. Here we report 238U-230Th disequilibrium ages of zircons from lavas and ignimbrites of the pre-caldera (~ 4 ka), syn-caldera (1 ka), and post-caldera (~ 0.3 ka) events. The zircon isochron ages are 12.2 ± 1.1 ka (2σ) for the 4-ka comendite lava and 12.2 ± 1.7 ka for the 1-ka comendite ignimbrite. Zircons from the 0.3-ka trachyte ignimbrite exhibit 3 respective peaks at 2.6 ± 1.8 ka, 130 ± 10 ka and > 230 ka. The indistinguishable zircon ages for the 4-ka pre-caldera eruption of comendite lava and the 1-ka caldera-forming eruption of comendite pumice and ignimbrite suggest that the 4-ka lava provides an early sampling of a much larger magma body at depth and thus serves as a kind of petrologic early-warning signal. In addition, the 4-ka lava may represent the lowest-temperature magma in the roof zone of a thermally zoned magma chamber that usually escapes first. The distinctive multi-modal zircon age distributions of the 0.3-ka trachytic eruption, however, reveal that this post-caldera eruption tapped a different magma body and indicate that Changbai's magmatic plumbing system had changed after the 1-ka caldera-forming climactic eruption. Our results suggest very short zircon and magma residence times for the Changbai volcano (8 kyr for the 4-ka eruption, 11-12 kyr for the 1-ka eruption and 2.3 kyr for the 0.3-ka eruption).

  19. Geochemical and VOC-constraints on landfill gas age and attenuation characteristics: A case study from a waste disposal facility in Southern California.

    PubMed

    Hagedorn, Benjamin; Kerfoot, Henry B; Verwiel, Mark; Matlock, Bruce

    2016-07-01

    In this study, a multi-tracer approach was applied to a complex, methane-impacted site in Southern California to (1) distinguish between natural gas and landfill gas (LFG)-derived methane impacts at site perimeter gas probes, (2) estimate the relative age of the LFG at these probes, and (3) document natural attenuation trends during a 3-year monitoring period. Relationships between methane and ethane values suggest that at the majority of probes, methane is from LFG and not from natural gas and that the relative contribution of LFG methane at these probes has increased over the monitoring period. To evaluate whether LFG is attenuating in the subsurface, the relative age of LFG was estimated by comparing readily degraded VOCs that are major constituents in LFG (toluene in this case) with those resistant to degradation (Freons). Time-series data trends are consistent with several probes being impacted by fresh LFG from recent releases that occurred after the update of the local LFG collection and control system (LFGCCS). Data further indicate some probes to be only affected by legacy LFG from a past release that occurred prior to the LFGCCS update and that, because of a lack of oxygen in the subsurface, had not been fully degraded. The outlined attenuation evaluation methodology is potentially applicable to other sites or even groundwater contaminants; however, the assessment is limited by the degree of homogeneity of the LFG source composition and non-LFG-derived toluene inputs to the analyzed samples. PMID:26601889

  20. Sex-Age Related Rumination Behavior of Père David’s Deer under Constraints of Feeding Habitat and Rainfall

    PubMed Central

    Li, Zhongqiu

    2013-01-01

    Extensive studies have been conducted on the rumination behavior of domestic herbivores. However, studies on wild animals are limited, particularly wild animals with specific ruminating parameters. In this study, Père David’s deer, a previously extirpated species, was observed to analyze the effects of sex-age, feeding habitat, and rainfall on rumination behavior in the Dafeng Nature Reserve, China. Rumination behavior was investigated based on four parameters: proportion of bedding time spent chewing, bolus processing time (s/bolus), chewing frequency (chews/bolus), and chewing rate (chews/s). Results showed that all three factors affect rumination behavior. The extent of their effects varied based on the four rumination parameters. Chewing rate and frequency decreased based on sex–age levels, i.e., from fawns to juvenile female, juvenile male, adult female, stag, and harem holder. Therefore, body size played a major role in shaping rumination behavior. Deer found in grasslands could chew faster compared with deer found in woodlands. This result might be caused by the effects of dietary composition and sunlight intensity. A deer spends a longer time ruminating while bedding during rainy days compared with rainless days to maximize energy and nutrition intake and compensate for the loss of feeding time during rainy days. Therefore, rumination behavior is plastic and is shaped by intrinsic and extrinsic factors. PMID:23823072

  1. SHRIMP U-Pb and 40Ar/39Ar age constraints for relating plutonism and mineralization in the Boulder batholith region, Montana

    USGS Publications Warehouse

    Lund, K.; Aleinikoff, J.N.; Kunk, M.J.; Unruh, D.M.; Zeihen, G.D.; Hodges, W.C.; du Bray, E.A.; O'Neill, J. M.

    2002-01-01

    The composite Boulder batholith, Montana, hosts a variety of mineral deposit types, including important silver-rich polymetallic quartz vein districts in the northern part of the batholith and the giant Butte porphyry copper-molybdenum pre-Main Stage system and crosscutting copper-rich Main Stage vein system in the southern part of the batholith. Previous dating studies have identified ambiguous relationships among igneous and mineralizing events. Mineralizing hydrothermal fluids for these types of deposits and magma for quartz porphyry dikes at Butte have all been considered to be late-stage differentiates of the Boulder batholith. However, previous dating studies indicated that the Boulder batholith plutons cooled from about 78 to 72 Ma, whereas copper-rich Main Stage veins at Butte were dated at about 61 Ma. Recent efforts to date the porphyry copper-molybdenum pre-Main Stage deposits at Butte resulted in conflicting estimates of both 64 and 76 Ma for the mineralizing events. Silver-rich polymetallic quartz vein deposits elsewhere in the batholith have not been dated previously. To resolve this controversy, we used the U.S. Geological Survey, Stanford, SHRIMP RG ion mic??roprobe to date single-age domains within zircons from plutonic rock samples and 40Ar/39Ar geochronology to date white mica, biotite, and K-feldspar from mineral deposits. U-Pb zircon ages are Rader Creek Granodiorite, 80.4 ?? 1.2 Ma; Unionville Granodiorite, 78.2 ?? 0.8 Ma; Pulpit Rock granite, 76.5 ?? 0.8 Ma; Butte Granite, 74.5 ?? 0.9 Ma; altered Steward-type quartz porphyry dike (I-15 roadcut), 66.5 ?? 1.0 Ma; altered Steward-type quartz porphyry dike (Continental pit), 65.7 ?? 0.9 Ma; and quartz monzodiorite of Boulder Baldy (Big Belt Mountains), 66.2 ?? 0.9 Ma. Zircons from Rader Creek Granodiorite and quartz porphyry dike samples contain Archean inheritance. The 40Ar/39Ar ages are muscovite, silver-rich polymetallic quartz vein (Basin district), 74.4 ?? 0.3 Ma; muscovite, silver

  2. Upper plate absolute motion and slab-anchor force control on back-arc deformation

    NASA Astrophysics Data System (ADS)

    Heuret, A.; Lallemand, S.

    2003-04-01

    In order to test how the combined effects of overriding plate motion and trench migration can account for the variability of back-arc tectonic regimes, their "normal to the trench" absolute motion components and the strain regime of all oceanic subduction zones were compiled. Strain regime was estimated following Jarrard (1986), in a semiquantitative way. The upper plate absolute motion (Vup) is calculated in the hotspot HS3-NUVEL1A (Gripp and Gordon, 2002) reference frame and trench migration (Vt) from Vup, corrected from deformation rate of back-arc region, mainly given by GPS data. As slabs tend to sink because of their age-related-mass-excess relative to the surrounding mantle, it is generally assumed that most of the trenches have a spontaneous seaward motion (trench rollback). Ages at trench have thus also been compiled ( from Muller et al, 1997) to test a possible control of trench migration with slab age. Our values underline a high control of strain regime by Vup, but inconsistencies still remain with this single parameter. To account for all the observed deformations, trench migration is needed. There are more or less as much subduction zones with seaward Vt as landward ones, and, for 90% of subduction zones, Vt never reach 50 mm/y in the two directions. The expected relation between trench migration and slab age is far to be verified: landward trench migrations exist in many subduction zones, and, among them, many have old slabs. Several examples indicate that the slab tend to follow the trench migration and, so, to move transversely in the surrounding mantle. As a consequence, Vt is close to the "normal to the trench" slab migration and gives informations about the slab anchor force : slabs are not perfectly anchored but their possible motions appear to be limited. This 50 mm/y limitation of slab migration may provide new constraints on the poorly known slab-anchor force. No evidence of age related trench rollback have beeen found. It does not

  3. Multi-proxy constraints on ages of low U-content, young and "dirty" speleothems: Example from southern Portugal cave deposits

    NASA Astrophysics Data System (ADS)

    Ghaleb, Bassam; Veiga-Pires, Christina; Moura, Delminda; Hillaire-Marcel, Claude

    2014-05-01

    Due to uncertainties in 14C activities of cave CO2, radiocarbon measurements in "young" speleothems cannot be straightforwardly used for their dating. U-series isotopes remain their unique tools to set a chronology for carbonate accretion. In cases of pristine carbonate deposits with relatively high U-contents, precise ages can be obtained including for very recent formations (e.g., Shen et al, 2013, Nature). However, this is rarely the case. Speleothems often contain low ppb U-contents, part of this uranium linked to detrital contaminants, thus requiring age corrections. Such corrections turn out to be quite difficult when uncertainties on the isotopic composition of the detrital fraction are in the range of the authigenic U-content and in situ grown daughter 230Th. We will examine here ways to address these issues based on seriated measurements in a late Holocene stalagmite from a cave, near Faro (southern Portugal). Mean contents in 232Th and 238U average respectively 116±28 and 12±10 ppb, with 234U/238U and 230Th/234U activity ratios ranging respectively from 1.241 to 1.293 and 0.065 to 0.115. Whatever the applied correction, 232Th is used as a quantitative marker of the detrital contribution. One way to take into account this contribution is based on the assumption of an isotopically uniform contaminant. With the empirical "crustal model" (Ludwig and Paces, 2002 Geochim.Cosmo.Acta), the contaminating fraction is estimated from the mean crustal isotopic composition. However, the large uncertainty in this estimate discards the use of this model in extreme cases (very low authigenic U and young sample). More recently, Hellstrom, 2006 (Quatern. Gechron.) proposed to calculate a theoretical isotopic composition of the detrital fraction, compatible with stratigraphically ordered of dated speleothem samples. Finally, another approach, which we have tested here, consists in determining the isotopic composition of the finest fraction in soils overlying the carbonated

  4. Zircon U-Pb ages, geochemical and Sr-Nd-Pb-Hf isotopic constraints on petrogenesis of the Tarom-Olya pluton, Alborz magmatic belt, NW Iran

    NASA Astrophysics Data System (ADS)

    Nabatian, Ghasem; Jiang, Shao-Yong; Honarmand, Maryam; Neubauer, Franz

    2016-02-01

    A petrological, geochemical and Sr-Nd-Pb isotopic study was carried out on the Tarom-Olya pluton, Iran, in the central part of the Alpine-Himalayan orogenic belt. The pluton is composed of diorite, monzonite, quartz-monzonite and monzogranite, which form part of the Western Alborz magmatic belt. LA-ICP-MS analyses of zircons yield ages from 35.7 ± 0.8 Ma to 37.7 ± 0.5 Ma, interpreted as the ages of crystallization of magmas. Rocks from the pluton have SiO2 contents ranging from 57.0 to 69.9 wt.%, high K2O + Na2O (5.5 to 10.3 wt.%) and K2O/Na2O ratio of 0.9 to 2.0. Geochemical discrimination criteria show I-type and shoshonitic features for the studied rocks. All investigated rocks are enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs), depleted in high-field strength elements (HFSEs), and show weak or insignificant Eu anomalies (Eu/Eu* = 0.57-1.02) in chondrite-normalized trace element patterns. The Tarom-Olya pluton samples also show depletions in Nb, Ta and Ti typical of subduction-related arc magmatic signatures. The samples have relatively low ISr (0.7047-0.7051) and positive εNd(36 Ma) (+ 0.39 to + 2.10) values. The Pb isotopic ratios show a (206Pb/204Pb)i ratio of 18.49-18.67, (207Pb/204Pb)i ratio of 15.58-15.61 and (208Pb/204Pb)i ratio of 38.33-38.77. The εHf(t) values of the Tarom-Olya pluton zircons vary from - 5.9 to + 8.4, with a peak at + 2 to + 4. The depleted mantle Hf model ages for the Tarom-Olya samples are close to 600 Ma. These isotope evidences indicate contribution of juvenile sources in petrogenesis of the Tarom-Olya pluton. Geochemical and isotopic data suggest that the parental magma of the Tarom-Olya pluton was mainly derived from a sub-continental lithospheric mantle source, which was metasomatized by fluids and melts from the subducted Neotethyan slab with a minor crustal contribution. Subsequent hot asthenospheric upwelling and lithospheric extension caused decompression melting in the final stage of

  5. Improving HST Pointing & Absolute Astrometry

    NASA Astrophysics Data System (ADS)

    Lallo, Matthew; Nelan, E.; Kimmer, E.; Cox, C.; Casertano, S.

    2007-05-01

    Accurate absolute astrometry is becoming increasingly important in an era of multi-mission archives and virtual observatories. Hubble Space Telescope's (HST's) Guidestar Catalog II (GSC2) has reduced coordinate error to around 0.25 arcsecond, a factor 2 or more compared with GSC1. With this reduced catalog error, special attention must be given to calibrate and maintain the Fine Guidance Sensors (FGSs) and Science Instruments (SIs) alignments in HST to a level well below this in order to ensure that the accuracy of science product's astrometry keywords and target positioning are limited only by the catalog errors. After HST Servicing Mission 4, such calibrations' improvement in "blind" pointing accuracy will allow for more efficient COS acquisitions. Multiple SIs and FGSs each have their own footprints in the spatially shared HST focal plane. It is the small changes over time in primarily the whole-body positions & orientations of these instruments & guiders relative to one another that is addressed by this work. We describe the HST Cycle 15 program CAL/OTA 11021 which, along with future variants of it, determines and maintains positions and orientations of the SIs and FGSs to better than 50 milli- arcseconds and 0.04 to 0.004 degrees of roll, putting errors associated with the alignment sufficiently below GSC2 errors. We present recent alignment results and assess their errors, illustrate trends, and describe where and how the observer sees benefit from these calibrations when using HST.

  6. Absolute oral bioavailability of ciprofloxacin.

    PubMed

    Drusano, G L; Standiford, H C; Plaisance, K; Forrest, A; Leslie, J; Caldwell, J

    1986-09-01

    We evaluated the absolute bioavailability of ciprofloxacin, a new quinoline carboxylic acid, in 12 healthy male volunteers. Doses of 200 mg were given to each of the volunteers in a randomized, crossover manner 1 week apart orally and as a 10-min intravenous infusion. Half-lives (mean +/- standard deviation) for the intravenous and oral administration arms were 4.2 +/- 0.77 and 4.11 +/- 0.74 h, respectively. The serum clearance rate averaged 28.5 +/- 4.7 liters/h per 1.73 m2 for the intravenous administration arm. The renal clearance rate accounted for approximately 60% of the corresponding serum clearance rate and was 16.9 +/- 3.0 liters/h per 1.73 m2 for the intravenous arm and 17.0 +/- 2.86 liters/h per 1.73 m2 for the oral administration arm. Absorption was rapid, with peak concentrations in serum occurring at 0.71 +/- 0.15 h. Bioavailability, defined as the ratio of the area under the curve from 0 h to infinity for the oral to the intravenous dose, was 69 +/- 7%. We conclude that ciprofloxacin is rapidly absorbed and reliably bioavailable in these healthy volunteers. Further studies with ciprofloxacin should be undertaken in target patient populations under actual clinical circumstances. PMID:3777908

  7. Constraints on braneworld gravity models from a kinematic limit on the age of the black hole XTE J1118+480.

    PubMed

    Psaltis, Dimitrios

    2007-05-01

    In braneworld gravity models with a finite anti-de Sitter space (AdS) curvature in the extra dimension, the AdS/conformal field theory correspondence leads to a prediction for the lifetime of astrophysical black holes that is significantly smaller than the Hubble time, for asymptotic curvatures that are consistent with current experiments. Using the recent measurements of the position, three-dimensional spatial velocity, and mass of the black hole XTE J1118+480, I calculate a lower limit on its kinematic age of > or =11 Myr (95% confidence). This translates into an upper limit for the asymptotic AdS curvature in the extra dimensions of <0.08 mm, which significantly improves the limit obtained by table top experiments of sub mm gravity. PMID:17501556

  8. Geophysical and geochronological constraints on the extent and age of mafic intrusions in the basement of west Texas and eastern New Mexico

    NASA Astrophysics Data System (ADS)

    Keller, G. Randy; Hills, John M.; Baker, Mark R.; Wallin, E. Timothy

    1989-11-01

    A deep drill hole recently completed on the Central basin platform of west Texas provides a rare look at almost 5 km of basement rocks. Most of the crystalline rocks encountered were basic and ultrabasic in composition. A variety of geophysical data is available from the bore hole and vicinity. The petrographic and geophysical data suggest that a large, layered, basic intrusion was penetrated by the well. Geochronologic (U-Pb) data indicate an age of about 1.1 Ga for this intrusion. This date has significant tectonic implications because it indicates that commonly accepted analogies with the southern Oklahoma aulacogen (550 Ma rifting) are not valid. However, it is interesting to note that this feature formed during another widespread period of rifting (Keweenawan).

  9. Absolute Instability in Coupled-Cavity TWTs

    NASA Astrophysics Data System (ADS)

    Hung, D. M. H.; Rittersdorf, I. M.; Zhang, Peng; Lau, Y. Y.; Simon, D. H.; Gilgenbach, R. M.; Chernin, D.; Antonsen, T. M., Jr.

    2014-10-01

    This paper will present results of our analysis of absolute instability in a coupled-cavity traveling wave tube (TWT). The structure mode at the lower and upper band edges are respectively approximated by a hyperbola in the (omega, k) plane. When the Briggs-Bers criterion is applied, a threshold current for onset of absolute instability is observed at the upper band edge, but not the lower band edge. The nonexistence of absolute instability at the lower band edge is mathematically similar to the nonexistence of absolute instability that we recently demonstrated for a dielectric TWT. The existence of absolute instability at the upper band edge is mathematically similar to the existence of absolute instability in a gyroton traveling wave amplifier. These interesting observations will be discussed, and the practical implications will be explored. This work was supported by AFOSR, ONR, and L-3 Communications Electron Devices.

  10. Provenance and tectonic-paleogeographic evolution: Constraints from detrital zircon U-Pb ages of Late Triassic-Early Jurassic deposits in the northern Sichuan basin, central China

    NASA Astrophysics Data System (ADS)

    Shao, Tongbin; Cheng, Nanfei; Song, Maoshuang

    2016-09-01

    U-Pb ages of 290 new detrital zircons from five Late Triassic-Early Jurassic sandstone samples in the northern Sichuan basin, along with other geological data, are used to constrain the sediment provenance and evaluate tectonic-paleogeographic evolution for the adjacent orogens through/from which these sediments were potentially derived. The Upper Triassic depocenter was located at the front of the Longmen Shan belt, and sediments in the western, southern and eastern Sichuan basin shared the southern North China block (NCB) and Qinling belt with the eastern Songpan-Ganzi terrane of Middle-Upper Triassic via the Longmen Shan belt, whereas the northern part of the basin was fed by dominant South Qinling belt (SQB) and northern Yangtze block and possibly subordinate southern NCB. Also, the youngest population in the northern Sichuan basin has a slightly younger age peak (∼235 Ma) than those (∼270 Ma) in other parts of the basin. During the Early Jurassic, the depocenter was still at the front of the Longmen Shan belt but only northern regions (e.g., SQB and northern Yangtze block) fed the basin. The northern Sichuan basin received less sediments from the southern NCB and more from the SQB and northern Yangtze block during the Early Jurassic than during the Late Triassic. The middle Mesoproterozoic detrital zircons, which likely originated from the North Qinling belt and northern Yangtze block where rocks with these zircons may be unexposed, occur more widely in the Lower Jurassic than in the Upper Triassic. These facts suggest that from the Late Triassic to Early Jurassic, it was increasingly difficult for sediments to transport from the NCB into the northern Sichuan basin and the provenance transferred progressively from the southern NCB to both the SQB and northern Yangtze block, implying the continuous South China block-NCB collision during that time.

  11. Son preference in Indian families: absolute versus relative wealth effects.

    PubMed

    Gaudin, Sylvestre

    2011-02-01

    The desire for male children is prevalent in India, where son preference has been shown to affect fertility behavior and intrahousehold allocation of resources. Economic theory predicts less gender discrimination in wealthier households, but demographers and sociologists have argued that wealth can exacerbate bias in the Indian context. I argue that these apparently conflicting theories can be reconciled and simultaneously tested if one considers that they are based on two different notions of wealth: one related to resource constraints (absolute wealth), and the other to notions of local status (relative wealth). Using cross-sectional data from the 1998-1999 and 2005-2006 National Family and Health Surveys, I construct measures of absolute and relative wealth by using principal components analysis. A series of statistical models of son preference is estimated by using multilevel methods. Results consistently show that higher absolute wealth is strongly associated with lower son preference, and the effect is 20%-40% stronger when the household's community-specific wealth score is included in the regression. Coefficients on relative wealth are positive and significant although lower in magnitude. Results are robust to using different samples, alternative groupings of households in local areas, different estimation methods, and alternative dependent variables. PMID:21302027

  12. Absolute negative mobility of interacting Brownian particles

    NASA Astrophysics Data System (ADS)

    Ou, Ya-li; Hu, Cai-tian; Wu, Jian-chun; Ai, Bao-quan

    2015-12-01

    Transport of interacting Brownian particles in a periodic potential is investigated in the presence of an ac force and a dc force. From Brownian dynamic simulations, we find that both the interaction between particles and the thermal fluctuations play key roles in the absolute negative mobility (the particle noisily moves backwards against a small constant bias). When no the interaction acts, there is only one region where the absolute negative mobility occurs. In the presence of the interaction, the absolute negative mobility may appear in multiple regions. The weak interaction can be helpful for the absolute negative mobility, while the strong interaction has a destructive impact on it.

  13. Geochronology and geochemistry of Eocene-aged volcanic rocks around the Bafra (Samsun, N Turkey) area: Constraints for the interaction of lithospheric mantle and crustal melts

    NASA Astrophysics Data System (ADS)

    Temizel, İrfan; Arslan, Mehmet; Yücel, Cem; Abdioğlu, Emel; Ruffet, Gilles

    2016-08-01

    40Ar-39Ar age, whole-rock chemical, and Sr-Nd isotope data are presented for the post-collisional, Eocene (51.3-44.1 Ma)-aged volcanic rocks from the Bafra (Samsun) area in the western part of the Eastern Pontides (N Turkey) aiming to unravel their sources and evolutionary history. The studied Eocene volcanic rocks can be divided into two groups: analcime-bearing (tephritic lava flows and dykes) and analcime-free (basaltic to trachytic lava flows and basaltic dykes). The analcime-bearing volcanic rocks have a fine-grained porphyritic texture with clinopyroxene phenocrysts, whereas analcime-free volcanic rocks show a variety of textures including hyalo-microlitic microgranular porphyritic, intersertal, trachytic, fluidal, and glomeroporphyritic. The volcanic rocks also show evidence of mineral-melt disequilibrium textures such as sieved, rounded, and corroded plagioclases, partially melted and dissolved clinopyroxenes and poikilitic texture. Petrochemically, the parental magmas of the volcanic rocks evolved from alkaline to calc-alkaline lava suites and include high-K and shoshonitic compositions. They display enrichments in light rare earth and large ion lithophile elements such as Sr, K, and Rb, as well as depletions in high field strength elements such as Nb, Ta, Zr, and Ti, resembling subduction-related magmas. The analcime-bearing and -free volcanic rocks share similar incompatible element ratios and chondrite-normalised rare rearth element patterns, indicating that they originated from similar sources. They also have relatively low to moderate initial 87Sr/86Sr (0.7042-0.7051), high positive εNd(t) values (+ 0.20 to + 3.32), and depleted mantle Nd model ages (TDM1 = 0.63-0.93 Ga, TDM2 = 0.58-0.84 Ga). The bulk-rock chemical and Sr-Nd isotope features as well as the high Rb/Y and Th/Zr, but low Nb/Zr and Nb/Y ratios, indicate that the volcanic rocks were derived from a lithospheric mantle source that had been metasomatised by slab-derived fluids. Trace element

  14. Paleoproterozoic high-sulfidation mineralization in the Tapajós gold province, Amazonian Craton, Brazil: geology, mineralogy, alunite argon age, and stable-isotope constraints

    USGS Publications Warehouse

    Juliani, Caetano; Rye, Robert O.; Nunes, Carmen M.D.; Snee, Lawrence W.; Correa, Rafael H.; Monteiro, Lena V.S.; Bettencourt, Jorge S.; Neumann, Rainer; Neto, Arnaldo A.

    2005-01-01

    The Brazilian Tapajós gold province contains the first evidence of high-sulfidation gold mineralization in the Amazonian Craton. The mineralization appears to be in large nested calderas. The Tapajós–Parima (or Ventuari–Tapajós) geological province consists of a metamorphic, igneous, and sedimentary sequence formed during a 2.10 to 1.87 Ga ocean−continent orogeny. The high-sulfidation mineralization with magmatic-hydrothermal alunite is related to hydrothermal breccias hosted in a rhyolitic volcanic ring complex that contains granitic stocks ranging in age from 1.89 to 1.87 Ga. Cone-shaped hydrothermal breccias, which flare upward, contain vuggy silica and have an overlying brecciated cap of massive silica; the deposits are located in the uppermost part of a ring-structure volcanic cone. Drill cores of one of the hydrothermal breccias contain alunite, natroalunite, pyrophyllite, andalusite, quartz, rutile, diaspore, woodhouseite–svanbergite, kaolinite, and pyrite along with inclusions of enargite–luzonite, chalcopyrite, bornite, and covellite. The siliceous core of this alteration center is surrounded by advanced argillic and argillic alteration zones that grade outward into large areas of propylitically altered rocks with sericitic alteration assemblages at depth. Several occurrences and generations of alunite are observed. Alunite is disseminated in the advanced argillic haloes that envelop massive and vuggy silica or that underlie the brecciated silica cap. Coarse-grained alunite also occurs in branching veins and locally is partly replaced by a later generation of fine-grained alunite. Silicified hydrothermal breccias associated with the alunite contain an estimated reserve of 30 tonnes of gold in rock that grades up to 4.5 g t−1 Au. Seven alunite samples gave 40Ar/39Ar ages of 1.869 to 1.846 Ga, with various degrees of apparent minor Ar loss. Stable isotopic data require a magmatic-hydrothermal origin for the alunite, typical for high

  15. Re-Os and Lu-Hf isotopic constraints on the formation and age of mantle pyroxenites from the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Ackerman, Lukáš; Bizimis, Michael; Haluzová, Eva; Sláma, Jiří; Svojtka, Martin; Hirajima, Takao; Erban, Vojtěch

    2016-07-01

    We report on the Lu-Hf and Re-Os isotope systematics of a well-characterized suite of spinel and garnet pyroxenites from the Gföhl Unit of the Bohemian Massif (Czech Republic, Austria). Lu-Hf mineral isochrons of three pyroxenites yield undistinguishable values in the range of 336-338 Ma. Similarly, the slope of Re-Os regression for most samples yields an age of 327 ± 31 Ma. These values overlap previously reported Sm-Nd ages on pyroxenites, eclogites and associated peridotites from the Gföhl Unit, suggesting contemporaneous evolution of all these HT-HP rocks. The whole-rock Hf isotopic compositions are highly variable with initial εHf values ranging from - 6.4 to + 66. Most samples show a negative correlation between bulk rock Sm/Hf and εHf and, when taking into account other characteristics (e.g., high 87Sr/86Sr), this may be explained by the presence of recycled oceanic sediments in the source of the pyroxenite parental melts. A pyroxenite from Horní Kounice has decoupled Hf-Nd systematics with highly radiogenic initial εHf of + 66 for a given εNd of + 7.8. This decoupling is consistent with the presence of a melt derived from a depleted mantle component with high Lu/Hf. Finally, one sample from Bečváry plots close to the MORB field in Hf-Nd isotope space consistent with its previously proposed origin as metamorphosed oceanic gabbro. Some of the websterites and thin-layered pyroxenites have variable, but high Os concentrations paralleled by low initial γOs. This reflects the interaction of the parental pyroxenitic melts with a depleted peridotite wall rock. In turn, the radiogenic Os isotope compositions observed in most pyroxenite samples is best explained by mixing between unradiogenic Os derived from peridotites and a low-Os sedimentary precursor with highly radiogenic 187Os/188Os. Steep increase of 187Os/188Os at nearly uniform 187Re/188Os found in a few pyroxenites may be connected with the absence of primary sulfides, but the presence of minor

  16. Nd, Sr, Pb, Ar, and O isotopic systematics of Sturgeon Lake kimberlite, Saskatchewan, Canada: constraints on emplacement age, alteration, and source composition

    NASA Astrophysics Data System (ADS)

    Hegner, E.; Roddick, J. C.; Fortier, S. M.; Hulbert, L.

    1995-06-01

    Rb-Sr isotopic dating of phlogopite megacryst samples separated from Sturgeon Lake kimberlite, Saskatchewan, yields a crystallization age of 98±1 Ma (2 σ, MSWD=1.2; 87Sr/86Sr( t)=0.7059). The 40Ar/39Ar analyses of a phlogopite megacryst sample indicate the presence of large amounts of excess 40Ar and yield an excessively old age of ˜410 Ma. Assessment of the Ar data using isotope correlation plots indicates clustering of the data points about a mixing line between the radiogenic 40Ar component at 98 Ma and a trapped component with uniform 36Ar/40Ar and Cl/40Ar. Values of δ 18O as high as +20‰ (VSMOW) for calcite from the groundmass and a whole-rock sample indicate pervasive low-temperature alteration. The δ 13C of matrix carbonate is -11.3‰ (PDB), slightly lighter than typical values from the literature. The δ 18O values of about +5‰ (VSMOW) for brown phlogopite megacrysts may be primary, green phlogopites are interpreted to be an alteration product of the brown variety and are 2‰ heavier. Initial Nd-Sr-Pb isotopic ratios for a whole-rock sample ( ɛ Nd=+0.8; 87Sr/86Sr=0.7063, 206Pb/204Pb=18.67, 207Pb/204Pb=15.54, 208Pb/204Pb=38.97) suggest an affinity with group I kimberlites. Initial ɛ Nd values of +1.7 and +0.5 (87Sr/86Sr( t)=0.7053 and 0.7050) for eclogitic and lherzolitic garnet megacryst samples, and values of 0.0 for two phlogopite megacryst samples reflect an origin from an isotopically evolving melt due to assimilation of heterogeneous mantle. Lilac high-Cr lherzolitic garnet megacrysts give an unusually high ɛ Nd(98. Ma) of +28.6 (87Sr/86Sr=0.7046) indicating a xenocrystic origin probably from the lithospheric mantle. The very radiogenic 87Sr/86Sr and 206Pb/204Pb ratios of the kimberlite are consistent with melting of EM II (enriched) mantle components.

  17. Geochronogy of leucogranites in Yadong region: constraints on the age of the South Tibetan Detachment System in central-eastern Himalaya

    NASA Astrophysics Data System (ADS)

    Liu, Zhi-Chao; Wu, Fu-Yuan; Ji, Wei-Qiang; Wang, Jian-Gang; Liu, Xiao-Chi

    2016-04-01

    . Field relations indicate that after intrusion of the leucogranites, there was no significant movement of the shear zone. Monazite from the main body and dykes were analyzed for Th-Pb isotopes to constrain the time of intrusions. Three samples from the main body of Dingga pluton show fairly homogeneous 208Pb/232Th data, with weighted average dates of 19.3 ± 0.2 Ma, 20.0 ± 0.3 Ma, and 20.8 ± 0.1 Ma, respectively. These dates indicate an Early Miocene emplacement and crystallization age of ca. 20 Ma. Dykes structurally adjacent to the main bodies of Dingga pluton and Gaowu pluton gave final crystallization age of 16.4 ± 0.3 Ma and 16.3 ± 0.3 Ma, respectively. From monazite geochronology and field relationships, we can conclude that the undeformed Dingga and Gaowu leucogranites crosscuted the boundary between the GHS and THS at ca. 20 Ma and ca. 16 Ma, and constrained the end of motion of the STDS in Yadong region at least prior to 20 Ma.

  18. Zircon age and geochemistry of the Tost bimodal volcanic rocks: Constraints on the Early Carboniferous tectonic evolution of the South Mongolia

    NASA Astrophysics Data System (ADS)

    Yang, Shunhu; Miao, Laicheng; Zhang, Fochin; Meng, Qingren; Zhu, Mingshuai; Baatar, Munkhtsengel; Anaad, Chimedtseren

    2016-04-01

    SIMS zircon U-Pb dating, geochemical and Sr-Nd isotopic data are presented for the Late Paleozoic volcanic rocks from Tost area in Mongolia, the southern portion of the Central Asian Orogenic Belt (CAOB). The Tost volcanic rocks show a bimodal feature characterized by a mafic member of basalt and a felsic component of rhyolite, which are temporally and spatially related each other, implying a genetic relationship. Zircon U-Pb isotopic data of the rhyolite constrain the Tost bimodal magmatism occurring from 355 Ma to 320 Ma. The Tost basalt is characterized by high abundances in Th, U and Pb, slightly enriched LREE patterns and low HFSE/LREE ratios. These features, together with their OIB-like isotopic signature ((87Sr/86Sr)i = 0.7039378-0.704397, εNd(t) = 3.55-5.02), suggest that they were likely derived from low-degree partial melting of a metasomatized asthenospheric mantle source with subordinate input of subduction components. The Tost rhyolite, which displays an intimate affinity to Tost basalt, with enrichment in Th, U and Pb, depleted in Nb, Ta and Ti, and gently right-tilted REE patterns, is inferred to be generated by partial melting of a juvenile lower crustal source heated by underplating mafic magmas which rise from asthenosphere during continued rifting. The Tost bimodal volcanic rocks are comparable both in age and composition with those in the East Tianshan, which together constitute an E-W-oriented belt of bimodal volcanic rocks, marking an Early Carboniferous rifting event. Considering regional geology, we propose that the rifting took place in a back-arc extensional setting, probably induced by the subduction of the Dzungaria Ocean between the East Tianshan and Junggar-Kazakhstan plate during the Early Carboniferous.

  19. Chemical, Isotopic and Remote Sensing Constraints on the Age, Origin, and Groundwater Potentiality in the Rub Al Khali Aquifer System, Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Sultan, M.; Sturchio, N. C.; Sefry, S.; Ahmed, M.; AboAbdallah, M.; Emil, M.; Chouinard, K.

    2013-12-01

    The Rub Al Khali (RAK) region of southern Saudi Arabia is underlain by a large aquifer system having three main aquifer groups. Large-scale groundwater flow is recharged mainly from precipitation falling on higher elevations in the southwest Red Sea Hills and flows toward the Arabian Gulf. The average annual precipitation was estimated at 55 x109 m3 from 3-hourly Tropical Rainfall Measuring Mission (TRMM) data acquired (1998-2012) over the RAK and a surface drainage network was delineated across the RAK from digital elevation models. Fourteen groundwater samples were collected from wells in the western portion of the RAK and analyzed for chemical and isotopic compositions. Analysis of the water samples indicate the presence of relatively fresh (Total Dissolved Solids [TDS] ranging from 800-2,800 mg/L in deeper wells) groundwater resource that is suitable for direct use in irrigation and, with minor treatment, for drinking purposes. Major ions are Na, Ca, Cl, SO4 and HCO3. Radiocarbon model ages of the waters span a range from 1,400 to 30,600 years before present. Stable isotopic compositions indicate origin as meteoric precipitation with little or no evaporation except where sampled in open-pit wells. The waters are generally non-radioactive with the exception of samples collected from the Eocene aquifer in the eastern part of the study area; these were found to have 226Ra activities exceeding the US EPA's limit for drinking water. Examination of the inter-annual trends extracted from Gravity Recovery and Climate Experiment (GRACE) monthly (01/2003 - 09/2012) solutions over the RAK system shows near steady conditions. Sustainable use of groundwater in the western RAK is feasible, but requires additional study in the recharge area to quantify the locations and rates of modern recharge.

  20. Geological and 40Ar/39Ar age constraints on late-stage Deccan rhyolitic volcanism, inter-volcanic sedimentation, and the Panvel flexure from the Dongri area, Mumbai

    NASA Astrophysics Data System (ADS)

    Sheth, Hetu C.; Pande, Kanchan

    2014-04-01

    Post-K-Pg Boundary Deccan magmatism is well known from the Mumbai area in the Panvel flexure zone. Represented by the Salsette Subgroup, it shows characters atypical of much of the Deccan Traps, including rhyolite lavas and tuffs, mafic tuffs and breccias, spilitic pillow basalts, and "intertrappean" sedimentary or volcanosedimentary deposits, with mafic intrusions as well as trachyte intrusions containing basaltic enclaves. The intertrappean deposits have been interpreted as formed in shallow marine or lagoonal environments in small fault-bounded basins due to syn-volcanic subsidence. We report a previously unknown sedimentary deposit underlying the Dongri rhyolite flow from the upper part of the Salsette Subgroup, with a westerly tectonic dip due to the Panvel flexure. We have obtained concordant 40Ar/39Ar ages of 62.6 ± 0.6 Ma (2σ) and 62.9 ± 0.2 Ma (2σ) for samples taken from two separate outcrops of this rhyolite. The results are significant in showing that (i) Danian inter-volcanic sedimentary deposits formed throughout Mumbai, (ii) the rock units are consistent with the stratigraphy postulated earlier for Mumbai, (iii) shale fragments known in some Dongri tuffs were likely derived from the sedimentary deposit under the Dongri rhyolite, (iv) the total duration of extrusive and intrusive Deccan magmatism was at least 8-9 million years, and (v) Panvel flexure formed, or continued to form, after 63 Ma, possibly even 62 Ma, and could not have formed by 65-64 Ma as concluded in a recent study.

  1. THE ABSOLUTE MAGNITUDES OF TYPE Ia SUPERNOVAE IN THE ULTRAVIOLET

    SciTech Connect

    Brown, Peter J.; Roming, Peter W. A.; Ciardullo, Robin; Gronwall, Caryl; Hoversten, Erik A.; Pritchard, Tyler; Milne, Peter; Bufano, Filomena; Mazzali, Paolo; Elias-Rosa, Nancy; Filippenko, Alexei V.; Li Weidong; Foley, Ryan J.; Hicken, Malcolm; Kirshner, Robert P.; Gehrels, Neil; Holland, Stephen T.; Immler, Stefan; Phillips, Mark M.; Still, Martin

    2010-10-01

    We examine the absolute magnitudes and light-curve shapes of 14 nearby (redshift z = 0.004-0.027) Type Ia supernovae (SNe Ia) observed in the ultraviolet (UV) with the Swift Ultraviolet/Optical Telescope. Colors and absolute magnitudes are calculated using both a standard Milky Way extinction law and one for the Large Magellanic Cloud that has been modified by circumstellar scattering. We find very different behavior in the near-UV filters (uvw1{sub rc} covering {approx}2600-3300 A after removing optical light, and u {approx} 3000-4000 A) compared to a mid-UV filter (uvm2 {approx}2000-2400 A). The uvw1{sub rc} - b colors show a scatter of {approx}0.3 mag while uvm2-b scatters by nearly 0.9 mag. Similarly, while the scatter in colors between neighboring filters is small in the optical and somewhat larger in the near-UV, the large scatter in the uvm2 - uvw1 colors implies significantly larger spectral variability below 2600 A. We find that in the near-UV the absolute magnitudes at peak brightness of normal SNe Ia in our sample are correlated with the optical decay rate with a scatter of 0.4 mag, comparable to that found for the optical in our sample. However, in the mid-UV the scatter is larger, {approx}1 mag, possibly indicating differences in metallicity. We find no strong correlation between either the UV light-curve shapes or the UV colors and the UV absolute magnitudes. With larger samples, the UV luminosity might be useful as an additional constraint to help determine distance, extinction, and metallicity in order to improve the utility of SNe Ia as standardized candles.

  2. Derivation of Absolute Model Ages for Lunar Lobate Scarps

    NASA Astrophysics Data System (ADS)

    van der Bogert, C. H.; Hiesinger, H.; Banks, M. E.; Watters, T. R.; Robinson, M. S.

    2012-03-01

    Crater size-frequency distribution measurements indicate that the Mandel'shtam and Lee-Lincoln scarps were active as recently as ~91 Ma and ~75 Ma, respectively. These results confirm that lobate scarps are some of the youngest features on the Moon.

  3. Constraints on southern hemisphere tropical climate change during the Little Ice Age and Younger Dryas based on glacier modeling of the Quelccaya Ice Cap, Peru

    NASA Astrophysics Data System (ADS)

    Malone, Andrew G. O.; Pierrehumbert, Raymond T.; Lowell, Thomas V.; Kelly, Meredith A.; Stroup, Justin S.

    2015-10-01

    Improving the late Quaternary paleoclimate record through climate interpretations of low-latitude glacier length changes advances our understanding of past climate change events and the mechanisms for past, present, and future climate change. Paleotemperature reconstructions at low-latitude glaciers are uniquely fruitful because they can provide both site-specific information and enhanced understanding of regional-scale variations due to the structure of the tropical atmosphere. We produce Little Ice Age (LIA) and Younger Dryas (YD) paleoclimate reconstructions for the Huancané outlet glacier of the Quelccaya Ice Cap (QIC) and low-latitude southern hemisphere regional sea surface temperatures (SSTs) using a coupled ice-flow and energy balance model. We also model the effects of long-term changes in the summit temperature and precipitiation rate and the effects of interannual climate variability on the Huancané glacier length. We find temperature to be the dominant climate driver of glacier length change. Also, we find that interannual climate variability cannot adequately explain glacier advances inferred from the geomorphic record, necessitating that these features were formed during past colder climates. To constrain our LIA reconstruction, we incorporate the QIC ice core record, finding a LIA air temperature cooling at the ice cap of between ˜0.7 °C and ˜1.1 °C and ˜0.4 °C and regional SSTs cooling of ˜0.6 °C. For the YD paleoclimate reconstructions, we propose two limits on the precipitation rate, since the ice core record does not extend into the Pleistocene: 1) the precipitation rate scales with the Clausius-Clapeyron relationship (upper limit on cooling) and 2) the precipitation rate increases by 40% (lower limit on cooling), which is an increase about twice as great as the regional increases realized in GCM simulations for the period. The first limit requires ˜1.6 °C cooling in ice cap air temperatures and ˜0.9 °C cooling in SSTs, and the

  4. Direct comparisons between absolute and relative geomagnetic paleointensities: Absolute calibration of a relative paleointensity stack

    NASA Astrophysics Data System (ADS)

    Mochizuki, N.; Yamamoto, Y.; Hatakeyama, T.; Shibuya, H.

    2013-12-01

    Absolute geomagnetic paleointensities (APIs) have been estimated from igneous rocks, while relative paleomagnetic intensities (RPIs) have been reported from sediment cores. These two datasets have been treated separately, as correlations between APIs and RPIs are difficult on account of age uncertainties. High-resolution RPI stacks have been constructed from globally distributed sediment cores with high sedimentation rates. Previous studies often assumed that the RPI stacks have a linear relationship with geomagnetic axial dipole moments, and calibrated the RPI values to API values. However, the assumption of a linear relationship between APIs and RPIs has not been evaluated. Also, a quantitative calibration method for the RPI is lacking. We present a procedure for directly comparing API and RPI stacks, thus allowing reliable calibrations of RPIs. Direct comparisons between APIs and RPIs were conducted with virtually no associated age errors using both tephrochronologic correlations and RPI minima. Using the stratigraphic positions of tephra layers in oxygen isotope stratigraphic records, we directly compared the RPIs and APIs reported from welded tuffs contemporaneously extruded with the tephra layers. In addition, RPI minima during geomagnetic reversals and excursions were compared with APIs corresponding to the reversals and excursions. The comparison of APIs and RPIs at these exact points allowed a reliable calibration of the RPI values. We applied this direct comparison procedure to the global RPI stack PISO-1500. For six independent calibration points, virtual axial dipole moments (VADMs) from the corresponding APIs and RPIs of the PISO-1500 stack showed a near-linear relationship. On the basis of the linear relationship, RPIs of the stack were successfully calibrated to the VADMs. The direct comparison procedure provides an absolute calibration method that will contribute to the recovery of temporal variations and distributions of geomagnetic axial dipole

  5. Inequalities, Absolute Value, and Logical Connectives.

    ERIC Educational Resources Information Center

    Parish, Charles R.

    1992-01-01

    Presents an approach to the concept of absolute value that alleviates students' problems with the traditional definition and the use of logical connectives in solving related problems. Uses a model that maps numbers from a horizontal number line to a vertical ray originating from the origin. Provides examples solving absolute value equations and…

  6. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  7. Monolithically integrated absolute frequency comb laser system

    DOEpatents

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  8. Introducing the Mean Absolute Deviation "Effect" Size

    ERIC Educational Resources Information Center

    Gorard, Stephen

    2015-01-01

    This paper revisits the use of effect sizes in the analysis of experimental and similar results, and reminds readers of the relative advantages of the mean absolute deviation as a measure of variation, as opposed to the more complex standard deviation. The mean absolute deviation is easier to use and understand, and more tolerant of extreme…

  9. Investigating Absolute Value: A Real World Application

    ERIC Educational Resources Information Center

    Kidd, Margaret; Pagni, David

    2009-01-01

    Making connections between various representations is important in mathematics. In this article, the authors discuss the numeric, algebraic, and graphical representations of sums of absolute values of linear functions. The initial explanations are accessible to all students who have experience graphing and who understand that absolute value simply…

  10. Absolute Income, Relative Income, and Happiness

    ERIC Educational Resources Information Center

    Ball, Richard; Chernova, Kateryna

    2008-01-01

    This paper uses data from the World Values Survey to investigate how an individual's self-reported happiness is related to (i) the level of her income in absolute terms, and (ii) the level of her income relative to other people in her country. The main findings are that (i) both absolute and relative income are positively and significantly…

  11. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  12. Luminescence Chronology for the Formation of Glacial Lake Calgary, Southern Alberta, Canada: Age Constraints for the Initiation of the Late Pleistocene Retreat of the Laurentide Ice Sheet from its Western Margin

    NASA Astrophysics Data System (ADS)

    Munyikwa, K.; Rittenour, T. M.

    2014-12-01

    Glacial Lake Calgary in southern Alberta, Canada, was a Late Pleistocene proglacial lake that formed along the southwest margin of the Laurentide Ice Sheet (LIS), dammed by the retreating ice sheet margin. Attempts to constrain the age of the lake using radiocarbon methods have been hampered by the lack of datable organic material. In an effort to apply an alternative chronometer, this study uses two optically stimulated luminescence (OSL) dating approaches to date fine grained sand and silt that were deposited in the lake during its existence. OSL dating determines the depositional ages of sediments by measuring the energy from ionizing radiation that is stored in mineral grains such as quartz and feldspar. Dividing the stored energy, also referred to as the paleodose, by the rate at which the dose accumulated, allows an age to be ascertained. In one method applied in this study, the paleodose stored in the feldspar component of the sediment is determined using normalized infrared stimulated luminescence signals acquired using a portable OSL reader. In the second method, blue optically stimulated luminescence signals obtained from quartz separates from the sediment by employing a regular OSL reader and standard protocols are used to determine the paleodose. After correcting the feldspar data for anomalous fading, the age results from the two dating approaches are compared. The ages signify a time period by which the LIS had retreated from the study area and, hence, serve as constraints for the initiation of the retreat of the ice sheet from its western limit. Advantages and limitations of the dating methods are briefly discussed. Constraining the chronology of the retreat of the LIS from western Canada allows for a better understanding of the driving forces behind ice sheet retreat. Secondly, assigning a temporal scale to the postglacial evolution of the environment of the region permits a better insight into the dynamics of the physical and biological

  13. Internal time marker (Q1) of the Cretaceous super chron in the Bay of Bengal - a new age constraint for the oceanic crust evolved between India and Elan Bank

    NASA Astrophysics Data System (ADS)

    Krishna, K. S.; Ismaiel, M.; Karlapati, S.; Saha, D.; Mishra, J.

    2014-12-01

    Analysis of marine magnetic data of the Bay of Bengal (BOB) led to suggest two different tectonic models for the evolution of lithosphere between India and East Antarctica. The first model explains the presence of M-series (M11 to M0) magnetic anomalies in BOB with a small room leaving for accommodating the crust evolved during the long Cretaceous Magnetic Quiet Period. Second model explains in other way that most part of the crust in BOB was evolved during the quite period together with the possible presence of oldest magnetic chron M1/ M0 in close vicinity of ECMI. It is with this perspective we have reinvestigated the existing and recently acquired magnetic data together with regional magnetic model of BOB for identification of new tectonic constraints, thereby to better understand the evolution of lithosphere. Analysis of magnetic data revealed the presence of spreading anomalies C33 and C34 in the vicinity of 8°N, and internal time marker (Q1) corresponding to the age 92 Ma at 12°N in a corridor between 85°E and Ninetyeast ridges. The new time marker and its location, indeed, become a point of reference and benchmark in BOB for estimating the age of oceanic crust towards ECMI. The magnetic model further reveals the presence of network of fracture zones (FZs) with different orientations. Between 85°E and Ninetyeast ridges, two near N-S FZs, approximately followed 87°E and 89.5°E are found to extend into BOB up to 12°N, from there the FZs reorient in N60°W direction and reach to the continental margin region. Along ECMI two sets of FZs are identified with a northern set oriented in N60°W and southern one in N40°W direction. This suggests that both north and south segments of the ECMI were evolved in two different tectonic settings. The bend in FZs marks the timing (92 Ma) of occurrence of first major plate reorganisation of the Indian Ocean and becomes a very critical constraint for understanding the plate tectonic process in early opening of the

  14. Propagating Resource Constraints Using Mutual Exclusion Reasoning

    NASA Technical Reports Server (NTRS)

    Frank, Jeremy; Sanchez, Romeo; Do, Minh B.; Clancy, Daniel (Technical Monitor)

    2001-01-01

    One of the most recent techniques for propagating resource constraints in Constraint Based scheduling is Energy Constraint. This technique focuses in precedence based scheduling, where precedence relations are taken into account rather than the absolute position of activities. Although, this particular technique proved to be efficient on discrete unary resources, it provides only loose bounds for jobs using discrete multi-capacity resources. In this paper we show how mutual exclusion reasoning can be used to propagate time bounds for activities using discrete resources. We show that our technique based on critical path analysis and mutex reasoning is just as effective on unary resources, and also shows that it is more effective on multi-capacity resources, through both examples and empirical study.

  15. Juvenile accretion (2360-2330 Ma) in the São Francisco Craton, and implications for the Columbia supercontinent: evidence from U-Pb zircon ages, Sr-Nd-Hf and geochemical constraints

    NASA Astrophysics Data System (ADS)

    Teixeira, W.; Ávila, C.

    2012-12-01

    suite is coeval with the Resende Costa pluton. This suite consists of tonalites and trondhjemites with U-Pb crystallization ages of 2356 +3/-2 Ma and 2350 ± 4 Ma, and ɛNd(t) values from +1.0 to +2.1 (TDM = 2.4-2.5 Ga). Chemically, these rocks are metaluminous to slightly peraluminous, with low-Mg#, low-K2O and high-CaO, and varied SiO2 contents (˜62 to 73wt.%). The Lagoa Dourada suite also shows high-Sr/Y ratios (≥41 up to 81), high-(La/Yb)N ratios (≥12 up to 46), and positive Eu/Eu* anomalies, likewise the Resende Costa rocks. From the above, a juvenile accretionary event (2.36-2.33 Ga) is first time defined in the Southern São Francisco craton, correlating well with the early stage of the Itabuna-Salvador-Curaçá belt, according to geologic evidence and isotopic inferences. Roughly contemporary provinces resulted from Early Proterozoic crustal growth are similarly documented in South America and West Africa, Laurentia, Baltica, Siberia, Central Australia, North China and India. From a geodynamic perspective, they are part of a global assembly that took place mainly between 2.0-1.9 Ga - the Columbia Supercontinent - as suggested by geologic correlations, age constraints and paleomagnetic evidences.

  16. Differences in absolute and relative growth between two shell forms of Pinna nobilis (Mollusca: Bivalvia) along the Tunisian coastline

    NASA Astrophysics Data System (ADS)

    Rabaoui, Lotfi; Tlig-Zouari, Sabiha; Katsanevakis, Stelios; Belgacem, Walid; Hassine, Oum Kalthoum Ben

    2011-08-01

    This study investigated the absolute and relative growth patterns of the fan mussel Pinna nobilis along the Tunisian coastline, taking into consideration both the variability among different areas and between the two shell forms "combed" and "straight and wide". Five subpopulations of the species were sampled, one from northern, two from eastern and two from southern Tunisia. Various assumptions on the growth patterns were tested based on an information theory approach and multi-model inference. For absolute growth, the assumption of different growth patterns between the two shell forms of P. nobilis and no difference among subpopulations was the most supported by the data. For the same age, "straight and wide" individuals gained on average greater lengths than the "combed" individuals. The absolute growth of the species was found to be asymptotic and the logistic model was the one most supported by the data. As for the relative growth, apart from the classical allometric model Y = aXb, more complicated models of the form ln Y = f(ln X) that either assumed non-linearities or breakpoints were tested in combination with assumptions for possible differences between the two forms and among subpopulations. Among the eight studied relationships between morphometric characters, the classical allometric model was supported in only two cases, while in all other cases more complicated models were supported. Moreover, the assumption of different growth patterns between the two forms was supported in three cases and the assumption of different growth patterns among subpopulations in four cases. Although precise relationships between the morphometric plasticity of the fan mussel and environmental factors have not been proven in this paper, local small scale constraints might be responsible of the different growth patterns observed in the same locality. A possible co-action of genetic factors should be evaluated in the future.

  17. Constraint monitoring in TOSCA

    NASA Technical Reports Server (NTRS)

    Beck, Howard

    1992-01-01

    The Job-Shop Scheduling Problem (JSSP) deals with the allocation of resources over time to factory operations. Allocations are subject to various constraints (e.g., production precedence relationships, factory capacity constraints, and limits on the allowable number of machine setups) which must be satisfied for a schedule to be valid. The identification of constraint violations and the monitoring of constraint threats plays a vital role in schedule generation in terms of the following: (1) directing the scheduling process; and (2) informing scheduling decisions. This paper describes a general mechanism for identifying constraint violations and monitoring threats to the satisfaction of constraints throughout schedule generation.

  18. Application of U-Th-Pb phosphate geochronology to young orogenic gold deposits: New age constraints on the formation of the Grass Valley gold district, Sierra Foothills province, California

    USGS Publications Warehouse

    Taylor, Ryan D.; Goldfarb, Richard J.; Monecke, Thomas; Fletcher, Ian R.; Cosca, Michael A.; Kelly, Nigel M.

    2015-01-01

    The Grass Valley orogenic gold district in the Sierra Nevada foothills province, central California, the largest historic gold producer of the North American Cordillera, comprises both steeply dipping east-west (E-W) veins located along lithologic contacts in accreted ca. 300 and 200 Ma oceanic rocks and shallowly dipping north-south (N-S) veins hosted by the Grass Valley granodiorite; the latter have yielded about 70 percent of the 13 million ounces of historic lode gold production in the district. The oceanic host rocks were accreted to the western margin of North America between 200 and 170 Ma, metamorphosed to greenschist and amphibolite facies, and uplifted between 175 and 160 Ma. Large-scale magmatism in the Sierra Nevada occurred between 170-140 Ma and 120-80 Ma, with the Grass Valley granodiorite being emplaced during the older episode of magmatism. Uranium-lead isotopic dating of hydrothermal xenotime yielded the first absolute age of 162±5 Ma for the economically more significant N-S veins. The vein-hosted xenotime, as well as associated monazite, are unequivocally of hydrothermal origin as indicated by textural and chemical characteristics, including grain shape, lack of truncated growth banding, lack of a Eu anomaly, and low U and Th concentrations. Furthermore, the crack-seal texture of the veins, with abundant wallrock slivers, suggests their formation as a result of episodic fluid flow possibly related to reoccurring seismic events, rather than a period of fluid exsolution from an evolving magma. The N-S veins are temporally distinct from a younger 153-151 Ma gold event that was previously reported for the E-W veins. Overlapping U-Pb zircon (159.9±2.2 Ma) and 40Ar/39Ar biotite and hornblende (159.7±0.6 to 161.9±1.4 Ma) ages and geothermobarometric calculations indicate that the Grass Valley granodiorite was emplaced at ca. 160 Ma at elevated temperatures (~800°C) within approximately 3 km of the paleosurface and rapidly cooled to the ambient

  19. Absolute optical instruments without spherical symmetry

    NASA Astrophysics Data System (ADS)

    Tyc, Tomáš; Dao, H. L.; Danner, Aaron J.

    2015-11-01

    Until now, the known set of absolute optical instruments has been limited to those containing high levels of symmetry. Here, we demonstrate a method of mathematically constructing refractive index profiles that result in asymmetric absolute optical instruments. The method is based on the analogy between geometrical optics and classical mechanics and employs Lagrangians that separate in Cartesian coordinates. In addition, our method can be used to construct the index profiles of most previously known absolute optical instruments, as well as infinitely many different ones.

  20. Orion Absolute Navigation System Progress and Challenge

    NASA Technical Reports Server (NTRS)

    Holt, Greg N.; D'Souza, Christopher

    2012-01-01

    The absolute navigation design of NASA's Orion vehicle is described. It has undergone several iterations and modifications since its inception, and continues as a work-in-progress. This paper seeks to benchmark the current state of the design and some of the rationale and analysis behind it. There are specific challenges to address when preparing a timely and effective design for the Exploration Flight Test (EFT-1), while still looking ahead and providing software extensibility for future exploration missions. The primary onboard measurements in a Near-Earth or Mid-Earth environment consist of GPS pseudo-range and delta-range, but for future explorations missions the use of star-tracker and optical navigation sources need to be considered. Discussions are presented for state size and composition, processing techniques, and consider states. A presentation is given for the processing technique using the computationally stable and robust UDU formulation with an Agee-Turner Rank-One update. This allows for computational savings when dealing with many parameters which are modeled as slowly varying Gauss-Markov processes. Preliminary analysis shows up to a 50% reduction in computation versus a more traditional formulation. Several state elements are discussed and evaluated, including position, velocity, attitude, clock bias/drift, and GPS measurement biases in addition to bias, scale factor, misalignment, and non-orthogonalities of the accelerometers and gyroscopes. Another consideration is the initialization of the EKF in various scenarios. Scenarios such as single-event upset, ground command, and cold start are discussed as are strategies for whole and partial state updates as well as covariance considerations. Strategies are given for dealing with latent measurements and high-rate propagation using multi-rate architecture. The details of the rate groups and the data ow between the elements is discussed and evaluated.

  1. Absolute magnitudes of trans-neptunian objects

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Alvarez-candal, A.; Pinilla-Alonso, N.; Ortiz, J. L.; Morales, N.; Santos-Sanz, P.; Thirouin, A.

    2015-10-01

    Accurate measurements of diameters of trans- Neptunian objects are extremely complicated to obtain. Radiomatric techniques applied to thermal measurements can provide good results, but precise absolute magnitudes are needed to constrain diameters and albedos. Our objective is to measure accurate absolute magnitudes for a sample of trans- Neptunian objects, many of which have been observed, and modelled, by the "TNOs are cool" team, one of Herschel Space Observatory key projects grantes with ~ 400 hours of observing time. We observed 56 objects in filters V and R, if possible. These data, along with data available in the literature, was used to obtain phase curves and to measure absolute magnitudes by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. In total we obtained 234 new magnitudes for the 56 objects, 6 of them with no reported previous measurements. Including the data from the literature we report a total of 109 absolute magnitudes.

  2. A New Gimmick for Assigning Absolute Configuration.

    ERIC Educational Resources Information Center

    Ayorinde, F. O.

    1983-01-01

    A five-step procedure is provided to help students in making the assignment absolute configuration less bothersome. Examples for both single (2-butanol) and multi-chiral carbon (3-chloro-2-butanol) molecules are included. (JN)

  3. Learning Kinematic Constraints in Laparoscopic Surgery

    PubMed Central

    Huang, Felix C.; Mussa-Ivaldi, Ferdinando A.; Pugh, Carla M.; Patton, James L.

    2012-01-01

    To better understand how kinematic variables impact learning in surgical training, we devised an interactive environment for simulated laparoscopic maneuvers, using either 1) mechanical constraints typical of a surgical “box-trainer” or 2) virtual constraints in which free hand movements control virtual tool motion. During training, the virtual tool responded to the absolute position in space (Position-Based) or the orientation (Orientation-Based) of a hand-held sensor. Volunteers were further assigned to different sequences of target distances (Near-Far-Near or Far-Near-Far). Training with the Orientation-Based constraint enabled much lower path error and shorter movement times during training, which suggests that tool motion that simply mirrors joint motion is easier to learn. When evaluated in physically constrained (physical box-trainer) conditions, each group exhibited improved performance from training. However, Position-Based training enabled greater reductions in movement error relative to Orientation-Based (mean difference: 14.0 percent; CI: 0.7, 28.6). Furthermore, the Near-Far-Near schedule allowed a greater decrease in task time relative to the Far-Near-Far sequence (mean −13:5 percent, CI: −19:5, −7:5). Training that focused on shallow tool insertion (near targets) might promote more efficient movement strategies by emphasizing the curvature of tool motion. In addition, our findings suggest that an understanding of absolute tool position is critical to coping with mechanical interactions between the tool and trocar. PMID:23293709

  4. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed. PMID:19831037

  5. Universal Cosmic Absolute and Modern Science

    NASA Astrophysics Data System (ADS)

    Kostro, Ludwik

    The official Sciences, especially all natural sciences, respect in their researches the principle of methodic naturalism i.e. they consider all phenomena as entirely natural and therefore in their scientific explanations they do never adduce or cite supernatural entities and forces. The purpose of this paper is to show that Modern Science has its own self-existent, self-acting, and self-sufficient Natural All-in Being or Omni-Being i.e. the entire Nature as a Whole that justifies the scientific methodic naturalism. Since this Natural All-in Being is one and only It should be considered as the own scientifically justified Natural Absolute of Science and should be called, in my opinion, the Universal Cosmic Absolute of Modern Science. It will be also shown that the Universal Cosmic Absolute is ontologically enormously stratified and is in its ultimate i.e. in its most fundamental stratum trans-reistic and trans-personal. It means that in its basic stratum. It is neither a Thing or a Person although It contains in Itself all things and persons with all other sentient and conscious individuals as well, On the turn of the 20th century the Science has begun to look for a theory of everything, for a final theory, for a master theory. In my opinion the natural Universal Cosmic Absolute will constitute in such a theory the radical all penetrating Ultimate Basic Reality and will substitute step by step the traditional supernatural personal Absolute.

  6. Strong thermal leptogenesis and the absolute neutrino mass scale

    SciTech Connect

    Bari, Pasquale Di; King, Sophie E.; Fiorentin, Michele Re E-mail: sk1806@soton.ac.uk

    2014-03-01

    We show that successful strong thermal leptogenesis, where the final asymmetry is independent of the initial conditions and in particular a large pre-existing asymmetry is efficiently washed-out, favours values of the lightest neutrino mass m{sub 1}∼>10 meV for normal ordering (NO) and m{sub 1}∼>3 meV for inverted ordering (IO) for models with orthogonal matrix entries respecting |Ω{sub ij}{sup 2}|∼<2. We show analytically why lower values of m{sub 1} require a higher level of fine tuning in the seesaw formula and/or in the flavoured decay parameters (in the electronic for NO, in the muonic for IO). We also show how this constraint exists thanks to the measured values of the neutrino mixing angles and could be tightened by a future determination of the Dirac phase. Our analysis also allows us to place a more stringent constraint for a specific model or class of models, such as SO(10)-inspired models, and shows that some models cannot realise strong thermal leptogenesis for any value of m{sub 1}. A scatter plot analysis fully supports the analytical results. We also briefly discuss the interplay with absolute neutrino mass scale experiments concluding that they will be able in the coming years to either corner strong thermal leptogenesis or find positive signals pointing to a non-vanishing m{sub 1}. Since the constraint is much stronger for NO than for IO, it is very important that new data from planned neutrino oscillation experiments will be able to solve the ambiguity.

  7. Sequestration of atmospheric CO2 in a weathering-derived, serpentinite-hosted magnesite deposit: 14C tracing of carbon sources and age constraints for a refined genetic model

    NASA Astrophysics Data System (ADS)

    Oskierski, H. C.; Dlugogorski, B. Z.; Jacobsen, G.

    2013-12-01

    geochemical signatures indicate that weathering is the integral magnesite mineralisation process at Attunga. Conventional radiocarbon ages of about 50 ka represent a maximum age constraint for the formation of the magnesite deposit during Quaternary weathering. A significant amount of atmospheric CO2 has been sequestered via the biosphere and carbonation of serpentinite at Attunga.

  8. Highly irregular quantum constraints

    NASA Astrophysics Data System (ADS)

    Klauder, John R.; Little, J. Scott

    2006-05-01

    Motivated by a recent paper of Louko and Molgado, we consider a simple system with a single classical constraint R(q) = 0. If ql denotes a generic solution to R(q) = 0, our examples include cases where R'(ql) ≠ 0 (regular constraint) and R'(ql) = 0 (irregular constraint) of varying order as well as the case where R(q) = 0 for an interval, such as a <= q <= b. Quantization of irregular constraints is normally not considered; however, using the projection operator formalism we provide a satisfactory quantization which reduces to the constrained classical system when planck → 0. It is noteworthy that irregular constraints change the observable aspects of a theory as compared to strictly regular constraints.

  9. Absolute isotopic abundances of TI in meteorites

    NASA Astrophysics Data System (ADS)

    Niederer, F. R.; Papanastassiou, D. A.; Wasserburg, G. J.

    1985-03-01

    The absolute isotope abundance of Ti has been determined in Ca-Al-rich inclusions from the Allende and Leoville meteorites and in samples of whole meteorites. The absolute Ti isotope abundances differ by a significant mass dependent isotope fractionation transformation from the previously reported abundances, which were normalized for fractionation using 46Ti/48Ti. Therefore, the absolute compositions define distinct nucleosynthetic components from those previously identified or reflect the existence of significant mass dependent isotope fractionation in nature. The authors provide a general formalism for determining the possible isotope compositions of the exotic Ti from the measured composition, for different values of isotope fractionation in nature and for different mixing ratios of the exotic and normal components.

  10. Molecular iodine absolute frequencies. Final report

    SciTech Connect

    Sansonetti, C.J.

    1990-06-25

    Fifty specified lines of {sup 127}I{sub 2} were studied by Doppler-free frequency modulation spectroscopy. For each line the classification of the molecular transition was determined, hyperfine components were identified, and one well-resolved component was selected for precise determination of its absolute frequency. In 3 cases, a nearby alternate line was selected for measurement because no well-resolved component was found for the specified line. Absolute frequency determinations were made with an estimated uncertainty of 1.1 MHz by locking a dye laser to the selected hyperfine component and measuring its wave number with a high-precision Fabry-Perot wavemeter. For each line results of the absolute measurement, the line classification, and a Doppler-free spectrum are given.

  11. Stimulus probability effects in absolute identification.

    PubMed

    Kent, Christopher; Lamberts, Koen

    2016-05-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of presentation probability on both proportion correct and response times. The effects were moderated by the ubiquitous stimulus position effect. The accuracy and response time data were predicted by an exemplar-based model of perceptual cognition (Kent & Lamberts, 2005). The bow in discriminability was also attenuated when presentation probability for middle items was relatively high, an effect that will constrain future model development. The study provides evidence for item-specific learning in absolute identification. Implications for other theories of absolute identification are discussed. (PsycINFO Database Record PMID:26478959

  12. Absolute calibration in vivo measurement systems

    SciTech Connect

    Kruchten, D.A.; Hickman, D.P.

    1991-02-01

    Lawrence Livermore National Laboratory (LLNL) is currently investigating a new method for obtaining absolute calibration factors for radiation measurement systems used to measure internally deposited radionuclides in vivo. Absolute calibration of in vivo measurement systems will eliminate the need to generate a series of human surrogate structures (i.e., phantoms) for calibrating in vivo measurement systems. The absolute calibration of in vivo measurement systems utilizes magnetic resonance imaging (MRI) to define physiological structure, size, and composition. The MRI image provides a digitized representation of the physiological structure, which allows for any mathematical distribution of radionuclides within the body. Using Monte Carlo transport codes, the emission spectrum from the body is predicted. The in vivo measurement equipment is calibrated using the Monte Carlo code and adjusting for the intrinsic properties of the detection system. The calibration factors are verified using measurements of existing phantoms and previously obtained measurements of human volunteers. 8 refs.

  13. Precise Measurement of the Absolute Fluorescence Yield

    NASA Astrophysics Data System (ADS)

    Ave, M.; Bohacova, M.; Daumiller, K.; Di Carlo, P.; di Giulio, C.; San Luis, P. Facal; Gonzales, D.; Hojvat, C.; Hörandel, J. R.; Hrabovsky, M.; Iarlori, M.; Keilhauer, B.; Klages, H.; Kleifges, M.; Kuehn, F.; Monasor, M.; Nozka, L.; Palatka, M.; Petrera, S.; Privitera, P.; Ridky, J.; Rizi, V.; D'Orfeuil, B. Rouille; Salamida, F.; Schovanek, P.; Smida, R.; Spinka, H.; Ulrich, A.; Verzi, V.; Williams, C.

    2011-09-01

    We present preliminary results of the absolute yield of fluorescence emission in atmospheric gases. Measurements were performed at the Fermilab Test Beam Facility with a variety of beam particles and gases. Absolute calibration of the fluorescence yield to 5% level was achieved by comparison with two known light sources--the Cherenkov light emitted by the beam particles, and a calibrated nitrogen laser. The uncertainty of the energy scale of current Ultra-High Energy Cosmic Rays experiments will be significantly improved by the AIRFLY measurement.

  14. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed. PMID:26022836

  15. Relative and absolute stability in perceived parenting behaviour: a longitudinal study with children and adolescents.

    PubMed

    Carrasco, M A; Rodríguez, M A; Del Barrio, M V; Holgado, F P

    2011-02-01

    Patterns of relative and absolute stability in parental behaviour with children and adolescents are reported. The sample comprised 523 youth (58.7% girls). Data were collected at three time periods: T1 (M age = 11.1 yr.), T2 (M age = 12.2 yr.), and T3 (M age = 13.2 yr.), each separated by one year. According to children's reports, relative consistency was moderate in both mothers and fathers, particularly as regards communication and strict control. In contrast, as children got older, parental rearing practices related to strict control and hostility decreased. There was a similarity between fathers and mothers in terms of relative and absolute stability. Relative stability was affected by the child's sex, the parenting variable, and the time period; however, the patterns of absolute stability reveal no differences by sex. PMID:21526601

  16. Absolute partial photoionization cross sections of ozone.

    SciTech Connect

    Berkowitz, J.; Chemistry

    2008-04-01

    Despite the current concerns about ozone, absolute partial photoionization cross sections for this molecule in the vacuum ultraviolet (valence) region have been unavailable. By eclectic re-evaluation of old/new data and plausible assumptions, such cross sections have been assembled to fill this void.

  17. Solving Absolute Value Equations Algebraically and Geometrically

    ERIC Educational Resources Information Center

    Shiyuan, Wei

    2005-01-01

    The way in which students can improve their comprehension by understanding the geometrical meaning of algebraic equations or solving algebraic equation geometrically is described. Students can experiment with the conditions of the absolute value equation presented, for an interesting way to form an overall understanding of the concept.

  18. Teaching Absolute Value Inequalities to Mature Students

    ERIC Educational Resources Information Center

    Sierpinska, Anna; Bobos, Georgeana; Pruncut, Andreea

    2011-01-01

    This paper gives an account of a teaching experiment on absolute value inequalities, whose aim was to identify characteristics of an approach that would realize the potential of the topic to develop theoretical thinking in students enrolled in prerequisite mathematics courses at a large, urban North American university. The potential is…

  19. Increasing Capacity: Practice Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Dodds, Pennie; Donkin, Christopher; Brown, Scott D.; Heathcote, Andrew

    2011-01-01

    In most of the long history of the study of absolute identification--since Miller's (1956) seminal article--a severe limit on performance has been observed, and this limit has resisted improvement even by extensive practice. In a startling result, Rouder, Morey, Cowan, and Pfaltz (2004) found substantially improved performance with practice in the…

  20. On Relative and Absolute Conviction in Mathematics

    ERIC Educational Resources Information Center

    Weber, Keith; Mejia-Ramos, Juan Pablo

    2015-01-01

    Conviction is a central construct in mathematics education research on justification and proof. In this paper, we claim that it is important to distinguish between absolute conviction and relative conviction. We argue that researchers in mathematics education frequently have not done so and this has lead to researchers making unwarranted claims…

  1. Absolute Points for Multiple Assignment Problems

    ERIC Educational Resources Information Center

    Adlakha, V.; Kowalski, K.

    2006-01-01

    An algorithm is presented to solve multiple assignment problems in which a cost is incurred only when an assignment is made at a given cell. The proposed method recursively searches for single/group absolute points to identify cells that must be loaded in any optimal solution. Unlike other methods, the first solution is the optimal solution. The…

  2. Nonequilibrium equalities in absolutely irreversible processes

    NASA Astrophysics Data System (ADS)

    Murashita, Yuto; Funo, Ken; Ueda, Masahito

    2015-03-01

    Nonequilibrium equalities have attracted considerable attention in the context of statistical mechanics and information thermodynamics. Integral nonequilibrium equalities reveal an ensemble property of the entropy production σ as = 1 . Although nonequilibrium equalities apply to rather general nonequilibrium situations, they break down in absolutely irreversible processes, where the forward-path probability vanishes and the entropy production diverges. We identify the mathematical origins of this inapplicability as the singularity of probability measure. As a result, we generalize conventional integral nonequilibrium equalities to absolutely irreversible processes as = 1 -λS , where λS is the probability of the singular part defined based on Lebesgue's decomposition theorem. The acquired equality contains two physical quantities related to irreversibility: σ characterizing ordinary irreversibility and λS describing absolute irreversibility. An inequality derived from the obtained equality demonstrates the absolute irreversibility leads to the fundamental lower bound on the entropy production. We demonstrate the validity of the obtained equality for a simple model.

  3. Stimulus Probability Effects in Absolute Identification

    ERIC Educational Resources Information Center

    Kent, Christopher; Lamberts, Koen

    2016-01-01

    This study investigated the effect of stimulus presentation probability on accuracy and response times in an absolute identification task. Three schedules of presentation were used to investigate the interaction between presentation probability and stimulus position within the set. Data from individual participants indicated strong effects of…

  4. Precision absolute positional measurement of laser beams.

    PubMed

    Fitzsimons, Ewan D; Bogenstahl, Johanna; Hough, James; Killow, Christian J; Perreur-Lloyd, Michael; Robertson, David I; Ward, Henry

    2013-04-20

    We describe an instrument which, coupled with a suitable coordinate measuring machine, facilitates the absolute measurement within the machine frame of the propagation direction of a millimeter-scale laser beam to an accuracy of around ±4 μm in position and ±20 μrad in angle. PMID:23669658

  5. Geomagnetic paleointensity constraints on eruption timing at the Galapagos Spreading Center

    NASA Astrophysics Data System (ADS)

    Bowles, J. A.; Ab Fatah, A.; Colman, A.; McClinton, J. T.; Sinton, J. M.; White, S. M.; Rubin, K. H.

    2011-12-01

    The intermediate-spreading-rate Galapagos Spreading Center (GSC) experiences decreasing magma supply along axis with increasing distance from the nearby Galapagos hotspot. This allows us to explore the effects of variable magma supply on eruptive frequency, size, and style. Two contrasting sites on the GSC were mapped using high-resolution swath bathymetry, submersible observations, and camera tow photography. Individual eruptive units have been identified on the basis of these data and observations, as well sample geochemistry. In order to construct an eruptive history and to make broader interpretations regarding eruptive processes, it is necessary to place relative and absolute age constraints on these units. We present age determinations derived from geomagnetic paleointensity experiments at one of the study sites, centered at ~91°55'W, where increased magma supply from the hotspot results in an axial high. Due to the near monotonic decrease in geomagnetic paleointensity over the past ~500+ years, it is possible to infer relative age and to place approximate age constraints on eruptive units on the basis of their experimentally-determined paleointensity. Four of the largest identified units have been selected as a test case. Results suggest that the youngest flow is approximately 40 ± 30 years old. This flow unit is ~5 km long by 1 km wide, centered on the rise axis. An older flow (~180 ± 30 years old), also centered along the rise axis, lies to the west and its ~7 km along-axis exposure is interrupted by a large, flat-topped seamount. A number of active hydrothermal chimneys sit atop this flow unit, the heat source for which we infer to be related to the younger flow to the east or to a more recent shallow intrusion. The oldest documented flow is roughly 400 years old and is exposed slightly off-axis to the north of the two younger flows. The paleointensity-derived flow ages are consistent with available geological constraints on relative age. Based on

  6. Creating Positive Task Constraints

    ERIC Educational Resources Information Center

    Mally, Kristi K.

    2006-01-01

    Constraints are characteristics of the individual, the task, or the environment that mold and shape movement choices and performances. Constraints can be positive--encouraging proficient movements or negative--discouraging movement or promoting ineffective movements. Physical educators must analyze, evaluate, and determine the effect various…

  7. Constraint Reasoning Over Strings

    NASA Technical Reports Server (NTRS)

    Koga, Dennis (Technical Monitor); Golden, Keith; Pang, Wanlin

    2003-01-01

    This paper discusses an approach to representing and reasoning about constraints over strings. We discuss how many string domains can often be concisely represented using regular languages, and how constraints over strings, and domain operations on sets of strings, can be carried out using this representation.

  8. Credit Constraints in Education

    ERIC Educational Resources Information Center

    Lochner, Lance; Monge-Naranjo, Alexander

    2012-01-01

    We review studies of the impact of credit constraints on the accumulation of human capital. Evidence suggests that credit constraints have recently become important for schooling and other aspects of households' behavior. We highlight the importance of early childhood investments, as their response largely determines the impact of credit…

  9. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR V335 SERPENTIS

    SciTech Connect

    Lacy, Claud H. Sandberg; Fekel, Francis C.; Claret, Antonio E-mail: fekel@evans.tsuniv.edu

    2012-08-15

    V335 Ser is now known to be an eccentric double-lined A1+A3 binary star with fairly deep (0.5 mag) partial eclipses. Previous studies of the system are improved with 7456 differential photometric observations from the URSA WebScope and 5666 from the NFO WebScope, and 67 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope. From dates of minima, the apsidal period is about 880 years. Accurate (better than 2%) masses and radii are determined from analysis of the two new light curves and the radial velocity curve. Theoretical models match the absolute properties of the stars at an age of about 380 Myr, though the age agreement for the two components is poor. Tidal theory correctly confirms that the orbit should still be eccentric, but we find that standard tidal theory is unable to match the observed asynchronous rotation rates of the components' surface layers.

  10. Constraints in Quantum Geometrodynamics

    NASA Astrophysics Data System (ADS)

    Gentle, Adrian P.; George, Nathan D.; Miller, Warner A.; Kheyfets, Arkady

    We compare different treatments of the constraints in canonical quantum gravity. The standard approach on the superspace of 3-geometries treats the constraints as the sole carriers of the dynamic content of the theory, thus rendering the traditional dynamical equations obsolete. Quantization of the constraints in both the Dirac and ADM square root Hamiltonian approaches leads to the well known problems of time evolution. These problems of time are of both an interpretational and technical nature. In contrast, the geometrodynamic quantization procedure on the superspace of the true dynamical variables separates the issues of quantization from the enforcement of the constraints. The resulting theory takes into account states that are off-shell with respect to the constraints, and thus avoids the problems of time. We develop, for the first time, the geometrodynamic quantization formalism in a general setting and show that it retains all essential features previously illustrated in the context of homogeneous cosmologies.

  11. Absolute plate motion of Africa around Hawaii-Emperor bend time

    NASA Astrophysics Data System (ADS)

    Maher, S. M.; Wessel, P.; Müller, R. D.; Williams, S. E.; Harada, Y.

    2015-06-01

    Numerous regional plate reorganizations and the coeval ages of the Hawaiian Emperor bend (HEB) and Louisville bend of 50-47 Ma have been interpreted as a possible global tectonic plate reorganization at ˜chron 21 (47.9 Ma). Yet for a truly global event we would expect a contemporaneous change in Africa absolute plate motion (APM) reflected by physical evidence distributed on the Africa Plate. This evidence has been postulated to take the form of the Réunion-Mascarene bend which exhibits many HEB-like features, such as a large angular change close to ˜chron 21. However, the Réunion hotspot trail has recently been interpreted as a sequence of continental fragments with incidental hotspot volcanism. Here we show that the alternative Réunion-Mascarene Plateau trail can also satisfy the age progressions and geometry of other hotspot trails on the Africa Plate. The implied motion, suggesting a pivoting of Africa from 67 to 50 Ma, could explain the apparent bifurcation of the Tristan hotspot chain, the age reversals seen along the Walvis Ridge, the sharp curve of the Canary trail, and the diffuse nature of the St. Helena chain. To test this hypothesis further we made a new Africa APM model that extends back to ˜80 Ma using a modified version of the Hybrid Polygonal Finite Rotation Method. This method uses seamount chains and their associated hotspots as geometric constraints for the model, and seamount age dates to determine APM through time. While this model successfully explains many of the volcanic features, it implies an unrealistically fast global lithospheric net rotation, as well as improbable APM trajectories for many other plates, including the Americas, Eurasia and Australia. We contrast this speculative model with a more conventional model in which the Mascarene Plateau is excluded in favour of the Chagos-Laccadive Ridge rotated into the Africa reference frame. This second model implies more realistic net lithospheric rotation and far-field APMs, but

  12. Combined Use of Absolute and Differential Seismic Arrival Time Data to Improve Absolute Event Location

    NASA Astrophysics Data System (ADS)

    Myers, S.; Johannesson, G.

    2012-12-01

    Arrival time measurements based on waveform cross correlation are becoming more common as advanced signal processing methods are applied to seismic data archives and real-time data streams. Waveform correlation can precisely measure the time difference between the arrival of two phases, and differential time data can be used to constrain relative location of events. Absolute locations are needed for many applications, which generally requires the use of absolute time data. Current methods for measuring absolute time data are approximately two orders of magnitude less precise than differential time measurements. To exploit the strengths of both absolute and differential time data, we extend our multiple-event location method Bayesloc, which previously used absolute time data only, to include the use of differential time measurements that are based on waveform cross correlation. Fundamentally, Bayesloc is a formulation of the joint probability over all parameters comprising the multiple event location system. The Markov-Chain Monte Carlo method is used to sample from the joint probability distribution given arrival data sets. The differential time component of Bayesloc includes scaling a stochastic estimate of differential time measurement precision based the waveform correlation coefficient for each datum. For a regional-distance synthetic data set with absolute and differential time measurement error of 0.25 seconds and 0.01 second, respectively, epicenter location accuracy is improved from and average of 1.05 km when solely absolute time data are used to 0.28 km when absolute and differential time data are used jointly (73% improvement). The improvement in absolute location accuracy is the result of conditionally limiting absolute location probability regions based on the precise relative position with respect to neighboring events. Bayesloc estimates of data precision are found to be accurate for the synthetic test, with absolute and differential time measurement

  13. Analysis of Space Tourism Constraints

    NASA Astrophysics Data System (ADS)

    Bonnal, Christophe

    2002-01-01

    Space tourism appears today as a new Eldorado in a relatively near future. Private operators are already proposing services for leisure trips in Low Earth Orbit, and some happy few even tested them. But are these exceptional events really marking the dawn of a new space age ? The constraints associated to the space tourism are severe : - the economical balance of space tourism is tricky; development costs of large manned - the technical definition of such large vehicles is challenging, mainly when considering - the physiological aptitude of passengers will have a major impact on the mission - the orbital environment will also lead to mission constraints on aspects such as radiation, However, these constraints never appear as show-stoppers and have to be dealt with pragmatically: - what are the recommendations one can make for future research in the field of space - which typical roadmap shall one consider to develop realistically this new market ? - what are the synergies with the conventional missions and with the existing infrastructure, - how can a phased development start soon ? The paper proposes hints aiming at improving the credibility of Space Tourism and describes the orientations to follow in order to solve the major hurdles found in such an exciting development.

  14. Absolute and relative dosimetry for ELIMED

    SciTech Connect

    Cirrone, G. A. P.; Schillaci, F.; Scuderi, V.; Cuttone, G.; Candiano, G.; Musumarra, A.; Pisciotta, P.; Romano, F.; Carpinelli, M.; Presti, D. Lo; Raffaele, L.; Tramontana, A.; Cirio, R.; Sacchi, R.; Monaco, V.; Marchetto, F.; Giordanengo, S.

    2013-07-26

    The definition of detectors, methods and procedures for the absolute and relative dosimetry of laser-driven proton beams is a crucial step toward the clinical use of this new kind of beams. Hence, one of the ELIMED task, will be the definition of procedures aiming to obtain an absolute dose measure at the end of the transport beamline with an accuracy as close as possible to the one required for clinical applications (i.e. of the order of 5% or less). Relative dosimetry procedures must be established, as well: they are necessary in order to determine and verify the beam dose distributions and to monitor the beam fluence and the energetic spectra during irradiations. Radiochromic films, CR39, Faraday Cup, Secondary Emission Monitor (SEM) and transmission ionization chamber will be considered, designed and studied in order to perform a fully dosimetric characterization of the ELIMED proton beam.

  15. Probing absolute spin polarization at the nanoscale.

    PubMed

    Eltschka, Matthias; Jäck, Berthold; Assig, Maximilian; Kondrashov, Oleg V; Skvortsov, Mikhail A; Etzkorn, Markus; Ast, Christian R; Kern, Klaus

    2014-12-10

    Probing absolute values of spin polarization at the nanoscale offers insight into the fundamental mechanisms of spin-dependent transport. Employing the Zeeman splitting in superconducting tips (Meservey-Tedrow-Fulde effect), we introduce a novel spin-polarized scanning tunneling microscopy that combines the probing capability of the absolute values of spin polarization with precise control at the atomic scale. We utilize our novel approach to measure the locally resolved spin polarization of magnetic Co nanoislands on Cu(111). We find that the spin polarization is enhanced by 65% when increasing the width of the tunnel barrier by only 2.3 Å due to the different decay of the electron orbitals into vacuum. PMID:25423049

  16. Absolute-magnitude distributions of supernovae

    SciTech Connect

    Richardson, Dean; Wright, John; Jenkins III, Robert L.; Maddox, Larry

    2014-05-01

    The absolute-magnitude distributions of seven supernova (SN) types are presented. The data used here were primarily taken from the Asiago Supernova Catalogue, but were supplemented with additional data. We accounted for both foreground and host-galaxy extinction. A bootstrap method is used to correct the samples for Malmquist bias. Separately, we generate volume-limited samples, restricted to events within 100 Mpc. We find that the superluminous events (M{sub B} < –21) make up only about 0.1% of all SNe in the bias-corrected sample. The subluminous events (M{sub B} > –15) make up about 3%. The normal Ia distribution was the brightest with a mean absolute blue magnitude of –19.25. The IIP distribution was the dimmest at –16.75.

  17. Absolute radiometry and the solar constant

    NASA Technical Reports Server (NTRS)

    Willson, R. C.

    1974-01-01

    A series of active cavity radiometers (ACRs) are described which have been developed as standard detectors for the accurate measurement of irradiance in absolute units. It is noted that the ACR is an electrical substitution calorimeter, is designed for automatic remote operation in any environment, and can make irradiance measurements in the range from low-level IR fluxes up to 30 solar constants with small absolute uncertainty. The instrument operates in a differential mode by chopping the radiant flux to be measured at a slow rate, and irradiance is determined from two electrical power measurements together with the instrumental constant. Results are reported for measurements of the solar constant with two types of ACRs. The more accurate measurement yielded a value of 136.6 plus or minus 0.7 mW/sq cm (1.958 plus or minus 0.010 cal/sq cm per min).

  18. Asteroid absolute magnitudes and slope parameters

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    1991-01-01

    A new listing of absolute magnitudes (H) and slope parameters (G) has been created and published in the Minor Planet Circulars; this same listing will appear in the 1992 Ephemerides of Minor Planets. Unlike previous listings, the values of the current list were derived from fits of data at the V band. All observations were reduced in the same fashion using, where appropriate, a single basis default value of 0.15 for the slope parameter. Distances and phase angles were computed for each observation. The data for 113 asteroids was of sufficiently high quality to permit derivation of their H and G. These improved absolute magnitudes and slope parameters will be used to deduce the most reliable bias-corrected asteroid size-frequency distribution yet made.

  19. Absolute calibration of TFTR helium proportional counters

    SciTech Connect

    Strachan, J.D.; Diesso, M.; Jassby, D.; Johnson, L.; McCauley, S.; Munsat, T.; Roquemore, A.L.; Barnes, C.W. |; Loughlin, M. |

    1995-06-01

    The TFTR helium proportional counters are located in the central five (5) channels of the TFTR multichannel neutron collimator. These detectors were absolutely calibrated using a 14 MeV neutron generator positioned at the horizontal midplane of the TFTR vacuum vessel. The neutron generator position was scanned in centimeter steps to determine the collimator aperture width to 14 MeV neutrons and the absolute sensitivity of each channel. Neutron profiles were measured for TFTR plasmas with time resolution between 5 msec and 50 msec depending upon count rates. The He detectors were used to measure the burnup of 1 MeV tritons in deuterium plasmas, the transport of tritium in trace tritium experiments, and the residual tritium levels in plasmas following 50:50 DT experiments.

  20. Absolute enantioselective separation: optical activity ex machina.

    PubMed

    Bielski, Roman; Tencer, Michal

    2005-11-01

    The paper describes methodology of using three independent macroscopic factors affecting molecular orientation to accomplish separation of a racemic mixture without the presence of any other chiral compounds, i. e., absolute enantioselective separation (AES) which is an extension of a concept of applying these factors to absolute asymmetric synthesis. The three factors may be applied simultaneously or, if their effects can be retained, consecutively. The resulting three mutually orthogonal or near orthogonal directors constitute a true chiral influence and their scalar triple product is the measure of the chirality of the system. AES can be executed in a chromatography-like microfluidic process in the presence of an electric field. It may be carried out on a chemically modified flat surface, a monolithic polymer column made of a mesoporous material, each having imparted directional properties. Separation parameters were estimated for these media and possible implications for the natural homochirality are discussed. PMID:16342798

  1. An absolute measure for a key currency

    NASA Astrophysics Data System (ADS)

    Oya, Shunsuke; Aihara, Kazuyuki; Hirata, Yoshito

    It is generally considered that the US dollar and the euro are the key currencies in the world and in Europe, respectively. However, there is no absolute general measure for a key currency. Here, we investigate the 24-hour periodicity of foreign exchange markets using a recurrence plot, and define an absolute measure for a key currency based on the strength of the periodicity. Moreover, we analyze the time evolution of this measure. The results show that the credibility of the US dollar has not decreased significantly since the Lehman shock, when the Lehman Brothers bankrupted and influenced the economic markets, and has increased even relatively better than that of the euro and that of the Japanese yen.

  2. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  3. Metallic Magnetic Calorimeters for Absolute Activity Measurement

    NASA Astrophysics Data System (ADS)

    Loidl, M.; Leblanc, E.; Rodrigues, M.; Bouchard, J.; Censier, B.; Branger, T.; Lacour, D.

    2008-05-01

    We present a prototype of metallic magnetic calorimeters that we are developing for absolute activity measurements of low energy emitting radionuclides. We give a detailed description of the realization of the prototype, containing an 55Fe source inside the detector absorber. We present the analysis of first data taken with this detector and compare the result of activity measurement with liquid scintillation counting. We also propose some ways for reducing the uncertainty on the activity determination with this new technique.

  4. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1985-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  5. Absolute photoionization cross sections of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Pareek, P. N.

    1982-01-01

    The absolute values of photoionization cross sections of atomic oxygen were measured from the ionization threshold to 120 A. An auto-ionizing resonance belonging to the 2S2P4(4P)3P(3Do, 3So) transition was observed at 479.43 A and another line at 389.97 A. The experimental data is in excellent agreement with rigorous close-coupling calculations that include electron correlations in both the initial and final states.

  6. Silicon Absolute X-Ray Detectors

    SciTech Connect

    Seely, John F.; Korde, Raj; Sprunck, Jacob; Medjoubi, Kadda; Hustache, Stephanie

    2010-06-23

    The responsivity of silicon photodiodes having no loss in the entrance window, measured using synchrotron radiation in the 1.75 to 60 keV range, was compared to the responsivity calculated using the silicon thickness measured using near-infrared light. The measured and calculated responsivities agree with an average difference of 1.3%. This enables their use as absolute x-ray detectors.

  7. Relative errors can cue absolute visuomotor mappings.

    PubMed

    van Dam, Loes C J; Ernst, Marc O

    2015-12-01

    When repeatedly switching between two visuomotor mappings, e.g. in a reaching or pointing task, adaptation tends to speed up over time. That is, when the error in the feedback corresponds to a mapping switch, fast adaptation occurs. Yet, what is learned, the relative error or the absolute mappings? When switching between mappings, errors with a size corresponding to the relative difference between the mappings will occur more often than other large errors. Thus, we could learn to correct more for errors with this familiar size (Error Learning). On the other hand, it has been shown that the human visuomotor system can store several absolute visuomotor mappings (Mapping Learning) and can use associated contextual cues to retrieve them. Thus, when contextual information is present, no error feedback is needed to switch between mappings. Using a rapid pointing task, we investigated how these two types of learning may each contribute when repeatedly switching between mappings in the absence of task-irrelevant contextual cues. After training, we examined how participants changed their behaviour when a single error probe indicated either the often-experienced error (Error Learning) or one of the previously experienced absolute mappings (Mapping Learning). Results were consistent with Mapping Learning despite the relative nature of the error information in the feedback. This shows that errors in the feedback can have a double role in visuomotor behaviour: they drive the general adaptation process by making corrections possible on subsequent movements, as well as serve as contextual cues that can signal a learned absolute mapping. PMID:26280315

  8. Absolute distance measurements by variable wavelength interferometry

    NASA Astrophysics Data System (ADS)

    Bien, F.; Camac, M.; Caulfield, H. J.; Ezekiel, S.

    1981-02-01

    This paper describes a laser interferometer which provides absolute distance measurements using tunable lasers. An active feedback loop system, in which the laser frequency is locked to the optical path length difference of the interferometer, is used to tune the laser wavelengths. If the two wavelengths are very close, electronic frequency counters can be used to measure the beat frequency between the two laser frequencies and thus to determine the optical path difference between the two legs of the interferometer.

  9. Absolute versus relative ascertainment of pedophilia in men.

    PubMed

    Blanchard, Ray; Kuban, Michael E; Blak, Thomas; Cantor, James M; Klassen, Philip E; Dickey, Robert

    2009-12-01

    There are at least two different criteria for assessing pedophilia in men: absolute ascertainment (their sexual interest in children is intense) and relative ascertainment (their sexual interest in children is greater than their interest in adults). The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, 3rd edition (DSM-III) used relative ascertainment in its diagnostic criteria for pedophilia; this was abandoned and replaced by absolute ascertainment in the DSM-III-R and all subsequent editions. The present study was conducted to demonstrate the continuing need for relative ascertainment, particularly in the laboratory assessment of pedophilia. A total of 402 heterosexual men were selected from a database of patients referred to a specialty clinic. These had undergone phallometric testing, a psychophysiological procedure in which their penile blood volume was monitored while they were presented with a standardized set of laboratory stimuli depicting male and female children, pubescents, and adults.The 130 men selected for the Teleiophilic Profile group responded substantially to prepubescent girls but even more to adult women; the 272 men selected for the Pedophilic Profile group responded weakly to prepubescent girls but even less to adult women. In terms of absolute magnitude, every patient in the Pedophilic Profile group had a lesser penile response to prepubescent girls than every patient in the Teleiophilic Profile group. Nevertheless, the Pedophilic Profile group had a significantly greater number of known sexual offenses against prepubescent girls, indicating that they contained a higher proportion of true pedophiles. These results dramatically demonstrate the utility-or perhaps necessity-of relative ascertainment in the laboratory assessment of erotic age-preference. PMID:19901237

  10. Clock time is absolute and universal

    NASA Astrophysics Data System (ADS)

    Shen, Xinhang

    2015-09-01

    A critical error is found in the Special Theory of Relativity (STR): mixing up the concepts of the STR abstract time of a reference frame and the displayed time of a physical clock, which leads to use the properties of the abstract time to predict time dilation on physical clocks and all other physical processes. Actually, a clock can never directly measure the abstract time, but can only record the result of a physical process during a period of the abstract time such as the number of cycles of oscillation which is the multiplication of the abstract time and the frequency of oscillation. After Lorentz Transformation, the abstract time of a reference frame expands by a factor gamma, but the frequency of a clock decreases by the same factor gamma, and the resulting multiplication i.e. the displayed time of a moving clock remains unchanged. That is, the displayed time of any physical clock is an invariant of Lorentz Transformation. The Lorentz invariance of the displayed times of clocks can further prove within the framework of STR our earth based standard physical time is absolute, universal and independent of inertial reference frames as confirmed by both the physical fact of the universal synchronization of clocks on the GPS satellites and clocks on the earth, and the theoretical existence of the absolute and universal Galilean time in STR which has proved that time dilation and space contraction are pure illusions of STR. The existence of the absolute and universal time in STR has directly denied that the reference frame dependent abstract time of STR is the physical time, and therefore, STR is wrong and all its predictions can never happen in the physical world.

  11. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; Bowman, K.; Brindley, H.; Butler, J. J.; Collins, W.; Dykema, J. A.; Doelling, D. R.; Feldman, D. R.; Fox, N.; Huang, X.; Holz, R.; Huang, Y.; Jennings, D.; Jin, Z.; Johnson, D. G.; Jucks, K.; Kato, S.; Kratz, D. P.; Liu, X.; Lukashin, C.; Mannucci, A. J.; Phojanamongkolkij, N.; Roithmayr, C. M.; Sandford, S.; Taylor, P. C.; Xiong, X.

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  12. Absolute properties of the triple star HP Aurigae

    SciTech Connect

    Lacy, Claud H. Sandberg; Burks, Charles L.; Torres, Guillermo; Wolf, Marek E-mail: clburks@email.uark.edu E-mail: wolf@cesnet.cz

    2014-01-01

    New photometric, spectroscopic, and eclipse timing observations of the eclipsing binary star HP Aur allow for very accurate orbital determinations, even in the presence of a third body and transient starspot activity. The eclipsing binary masses are determined to an accuracy of ±0.4% and the radii to ±0.6%. The masses are 0.9543 ± 0.0041 and 0.8094 ± 0.0036 solar masses, and the radii are 1.0278 ± 0.0042 and 0.7758 ± 0.0034 solar radii, respectively. The orbital period in the outer orbit is accurately determined for the first time: 4.332 ± 0.011 yr. A comparison with current theories of stellar evolution shows that the components' absolute properties can be well-matched by the current models at an age of about 7 billion years.

  13. The neurocognitive components of pitch processing: insights from absolute pitch.

    PubMed

    Wilson, Sarah J; Lusher, Dean; Wan, Catherine Y; Dudgeon, Paul; Reutens, David C

    2009-03-01

    The natural variability of pitch naming ability in the population (known as absolute pitch or AP) provides an ideal method for investigating individual differences in pitch processing and auditory knowledge formation and representation. We have demonstrated the involvement of different cognitive processes in AP ability that reflects varying skill expertise in the presence of similar early age of onset of music tuition. These processes were related to different regions of brain activity, including those involved in pitch working memory (right prefrontal cortex) and the long-term representation of pitch (superior temporal gyrus). They reflected expertise through the use of context dependent pitch cues and the level of automaticity of pitch naming. They impart functional significance to structural asymmetry differences in the planum temporale of musicians and establish a neurobiological basis for an AP template. More generally, they indicate variability of knowledge representation in the presence of environmental fostering of early cognitive development that translates to differences in cognitive ability. PMID:18663250

  14. First derivative versus absolute spectral reflectance of citrus varieties

    NASA Astrophysics Data System (ADS)

    Blazquez, Carlos H.; Nigg, H. N.; Hedley, Lou E.; Ramos, L. E.; Sorrell, R. W.; Simpson, S. E.

    1996-06-01

    Spectral reflectance measurements from 400 to 800 nm were taken from immature and mature leaves of grapefruit ('McCarty' and 'Rio Red'), 'Minneola' tangelo, 'Satsuma' mandarin, 'Dancy' tangerine, 'Nagami' oval kumquat, and 'Valencia' sweet orange, at the Florida Citrus Arboretum, Division of Plant Industry, Winter Haven, Florida. Immature and mature leaves of 'Minneola' tangelo had greater percent reflectance in the 400 to 800 nm range than the other varieties and leaf ages measured. The slope of the citrus spectral curves in the 800 nm range was not as sharp as conventional spectrometers, but had a much higher reflectance value than those obtained with a DK-2 spectrometer. Statistical analyses of absolute spectral data yielded significant differences between mature and immature leaves and between varieties. First derivative data analyses did not yield significant differences between varieties.

  15. The Neurocognitive Components of Pitch Processing: Insights from Absolute Pitch

    PubMed Central

    Lusher, Dean; Wan, Catherine Y.; Dudgeon, Paul; Reutens, David C.

    2009-01-01

    The natural variability of pitch naming ability in the population (known as absolute pitch or AP) provides an ideal method for investigating individual differences in pitch processing and auditory knowledge formation and representation. We have demonstrated the involvement of different cognitive processes in AP ability that reflects varying skill expertise in the presence of similar early age of onset of music tuition. These processes were related to different regions of brain activity, including those involved in pitch working memory (right prefrontal cortex) and the long-term representation of pitch (superior temporal gyrus). They reflected expertise through the use of context dependent pitch cues and the level of automaticity of pitch naming. They impart functional significance to structural asymmetry differences in the planum temporale of musicians and establish a neurobiological basis for an AP template. More generally, they indicate variability of knowledge representation in the presence of environmental fostering of early cognitive development that translates to differences in cognitive ability. PMID:18663250

  16. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR HY VIRGINIS

    SciTech Connect

    Sandberg Lacy, Claud H.; Fekel, Francis C. E-mail: fekel@evans.tsuniv.edu

    2011-12-15

    HY Vir is found to be a double-lined F0m+F5 binary star with relatively shallow (0.3 mag) partial eclipses. Previous studies of the system are improved with 7509 differential photometric observations from the URSA WebScope and 8862 from the NFO WebScope, and 68 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope, and the 1 m coude-feed spectrometer at Kitt Peak National Observatory. Very accurate (better than 0.5%) masses and radii are determined from analysis of the new light curves and radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 1.35 Gy.

  17. ABSOLUTE PROPERTIES OF THE TRIPLE STAR CF TAURI

    SciTech Connect

    Lacy, Claud H. Sandberg; Torres, Guillermo; Claret, Antonio E-mail: gtorres@cfa.harvard.edu

    2012-12-01

    CF Tau is now known to be an eclipsing triple star with relatively deep total and annular eclipses. New light and radial velocity curves as well as new times of minima were obtained and used for further modeling of the system. Very accurate (better than 0.9%) masses and radii of the eclipsing pair are determined from analysis of the two new light curves, the radial velocity curve, and the times of minimum light. The mass and luminosity of the distant third component is accurately determined as well. Theoretical models of the detached, evolved eclipsing pair match the observed absolute properties of the stars at an age of about 4.3 Gyr and [Fe/H] = -0.14.

  18. The National Geodetic Survey absolute gravity program

    NASA Astrophysics Data System (ADS)

    Peter, George; Moose, Robert E.; Wessells, Claude W.

    1989-03-01

    The National Geodetic Survey absolute gravity program will utilize the high precision afforded by the JILAG-4 instrument to support geodetic and geophysical research, which involves studies of vertical motions, identification and modeling of other temporal variations, and establishment of reference values. The scientific rationale of these objectives is given, the procedures used to collect gravity and environmental data in the field are defined, and the steps necessary to correct and remove unwanted environmental effects are stated. In addition, site selection criteria, methods of concomitant environmental data collection and relative gravity observations, and schedule and logistics are discussed.

  19. An absolute radius scale for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Nicholson, Philip D.; Cooke, Maren L.; Pelton, Emily

    1990-01-01

    Radio and stellar occultation observations of Saturn's rings made by the Voyager spacecraft are discussed. The data reveal systematic discrepancies of almost 10 km in some parts of the rings, limiting some of the investigations. A revised solution for Saturn's rotation pole has been proposed which removes the discrepancies between the stellar and radio occultation profiles. Corrections to previously published radii vary from -2 to -10 km for the radio occultation, and +5 to -6 km for the stellar occultation. An examination of spiral density waves in the outer A Ring supports that the revised absolute radii are in error by no more than 2 km.

  20. Characterization of the DARA solar absolute radiometer

    NASA Astrophysics Data System (ADS)

    Finsterle, W.; Suter, M.; Fehlmann, A.; Kopp, G.

    2011-12-01

    The Davos Absolute Radiometer (DARA) prototype is an Electrical Substitution Radiometer (ESR) which has been developed as a successor of the PMO6 type on future space missions and ground based TSI measurements. The DARA implements an improved thermal design of the cavity detector and heat sink assembly to minimize air-vacuum differences and to maximize thermal symmetry of measuring and compensating cavity. The DARA also employs an inverted viewing geometry to reduce internal stray light. We will report on the characterization and calibration experiments which were carried out at PMOD/WRC and LASP (TRF).

  1. Absolute calibration of the Auger fluorescence detectors

    SciTech Connect

    Bauleo, P.; Brack, J.; Garrard, L.; Harton, J.; Knapik, R.; Meyhandan, R.; Rovero, A.C.; Tamashiro, A.; Warner, D.

    2005-07-01

    Absolute calibration of the Pierre Auger Observatory fluorescence detectors uses a light source at the telescope aperture. The technique accounts for the combined effects of all detector components in a single measurement. The calibrated 2.5 m diameter light source fills the aperture, providing uniform illumination to each pixel. The known flux from the light source and the response of the acquisition system give the required calibration for each pixel. In the lab, light source uniformity is studied using CCD images and the intensity is measured relative to NIST-calibrated photodiodes. Overall uncertainties are presently 12%, and are dominated by systematics.

  2. Absolute angular positioning in ultrahigh vacuum

    SciTech Connect

    Schief, H.; Marsico, V.; Kern, K.

    1996-05-01

    Commercially available angular resolvers, which are routinely used in machine tools and robotics, are modified and adapted to be used under ultrahigh-vacuum (UHV) conditions. They provide straightforward and reliable measurements of angular positions for any kind of UHV sample manipulators. The corresponding absolute reproducibility is on the order of 0.005{degree}, whereas the relative resolution is better than 0.001{degree}, as demonstrated by high-resolution helium-reflectivity measurements. The mechanical setup and possible applications are discussed. {copyright} {ital 1996 American Institute of Physics.}

  3. Absolute method of measuring magnetic susceptibility

    USGS Publications Warehouse

    Thorpe, A.; Senftle, F.E.

    1959-01-01

    An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved. ?? 1959 The American Institute of Physics.

  4. Absolute Priority for a Vehicle in VANET

    NASA Astrophysics Data System (ADS)

    Shirani, Rostam; Hendessi, Faramarz; Montazeri, Mohammad Ali; Sheikh Zefreh, Mohammad

    In today's world, traffic jams waste hundreds of hours of our life. This causes many researchers try to resolve the problem with the idea of Intelligent Transportation System. For some applications like a travelling ambulance, it is important to reduce delay even for a second. In this paper, we propose a completely infrastructure-less approach for finding shortest path and controlling traffic light to provide absolute priority for an emergency vehicle. We use the idea of vehicular ad-hoc networking to reduce the imposed travelling time. Then, we simulate our proposed protocol and compare it with a centrally controlled traffic light system.

  5. Constraints in Genetic Programming

    NASA Technical Reports Server (NTRS)

    Janikow, Cezary Z.

    1996-01-01

    Genetic programming refers to a class of genetic algorithms utilizing generic representation in the form of program trees. For a particular application, one needs to provide the set of functions, whose compositions determine the space of program structures being evolved, and the set of terminals, which determine the space of specific instances of those programs. The algorithm searches the space for the best program for a given problem, applying evolutionary mechanisms borrowed from nature. Genetic algorithms have shown great capabilities in approximately solving optimization problems which could not be approximated or solved with other methods. Genetic programming extends their capabilities to deal with a broader variety of problems. However, it also extends the size of the search space, which often becomes too large to be effectively searched even by evolutionary methods. Therefore, our objective is to utilize problem constraints, if such can be identified, to restrict this space. In this publication, we propose a generic constraint specification language, powerful enough for a broad class of problem constraints. This language has two elements -- one reduces only the number of program instances, the other reduces both the space of program structures as well as their instances. With this language, we define the minimal set of complete constraints, and a set of operators guaranteeing offspring validity from valid parents. We also show that these operators are not less efficient than the standard genetic programming operators if one preprocesses the constraints - the necessary mechanisms are identified.

  6. Determination of the absolute contours of optical flats

    NASA Technical Reports Server (NTRS)

    Primak, W.

    1969-01-01

    Emersons procedure is used to determine true absolute contours of optical flats. Absolute contours of standard flats are determined and a comparison is then made between standard and unknown flats. Contour differences are determined by deviation of Fizeau fringe.

  7. Constraints complicate centrifugal compressor depressurization

    SciTech Connect

    Key, B. ); Colbert, F.L. )

    1993-05-10

    Blowdown of a centrifugal compressor is complicated by process constraints that might require slowing the depressurization rate and by mechanical constraints for which a faster rate might be preferred. The paper describes design constraints such as gas leaks; thrust-bearing overload; system constraints; flare extinguishing; heat levels; and pressure drop.

  8. Cosmological constraints on the properties of weakly interacting massive particles

    SciTech Connect

    Steigman, G.; Turner, M.S.

    1984-10-01

    Considerations of the age and density of, as well as the evolution of structure in, the Universe lead to constraints on the masses and lifetimes of weakly interacting massive particles (WIMPs). 26 references.

  9. Constraint algebra in bigravity

    SciTech Connect

    Soloviev, V. O.

    2015-07-15

    The number of degrees of freedom in bigravity theory is found for a potential of general form and also for the potential proposed by de Rham, Gabadadze, and Tolley (dRGT). This aim is pursued via constructing a Hamiltonian formalismand studying the Poisson algebra of constraints. A general potential leads to a theory featuring four first-class constraints generated by general covariance. The vanishing of the respective Hessian is a crucial property of the dRGT potential, and this leads to the appearance of two additional second-class constraints and, hence, to the exclusion of a superfluous degree of freedom—that is, the Boulware—Deser ghost. The use of a method that permits avoiding an explicit expression for the dRGT potential is a distinctive feature of the present study.

  10. Standardization of the cumulative absolute velocity

    SciTech Connect

    O'Hara, T.F.; Jacobson, J.P. )

    1991-12-01

    EPRI NP-5930, A Criterion for Determining Exceedance of the Operating Basis Earthquake,'' was published in July 1988. As defined in that report, the Operating Basis Earthquake (OBE) is exceeded when both a response spectrum parameter and a second damage parameter, referred to as the Cumulative Absolute Velocity (CAV), are exceeded. In the review process of the above report, it was noted that the calculation of CAV could be confounded by time history records of long duration containing low (nondamaging) acceleration. Therefore, it is necessary to standardize the method of calculating CAV to account for record length. This standardized methodology allows consistent comparisons between future CAV calculations and the adjusted CAV threshold value based upon applying the standardized methodology to the data set presented in EPRI NP-5930. The recommended method to standardize the CAV calculation is to window its calculation on a second-by-second basis for a given time history. If the absolute acceleration exceeds 0.025g at any time during each one second interval, the earthquake records used in EPRI NP-5930 have been reanalyzed and the adjusted threshold of damage for CAV was found to be 0.16g-set.

  11. Absolute rates of hole transfer in DNA.

    PubMed

    Senthilkumar, Kittusamy; Grozema, Ferdinand C; Guerra, Célia Fonseca; Bickelhaupt, F Matthias; Lewis, Frederick D; Berlin, Yuri A; Ratner, Mark A; Siebbeles, Laurens D A

    2005-10-26

    Absolute rates of hole transfer between guanine nucleobases separated by one or two A:T base pairs in stilbenedicarboxamide-linked DNA hairpins were obtained by improved kinetic analysis of experimental data. The charge-transfer rates in four different DNA sequences were calculated using a density-functional-based tight-binding model and a semiclassical superexchange model. Site energies and charge-transfer integrals were calculated directly as the diagonal and off-diagonal matrix elements of the Kohn-Sham Hamiltonian, respectively, for all possible combinations of nucleobases. Taking into account the Coulomb interaction between the negative charge on the stilbenedicarboxamide linker and the hole on the DNA strand as well as effects of base pair twisting, the relative order of the experimental rates for hole transfer in different hairpins could be reproduced by tight-binding calculations. To reproduce quantitatively the absolute values of the measured rate constants, the effect of the reorganization energy was taken into account within the semiclassical superexchange model for charge transfer. The experimental rates could be reproduced with reorganization energies near 1 eV. The quantum chemical data obtained were used to discuss charge carrier mobility and hole-transport equilibria in DNA. PMID:16231945

  12. Transient absolute robustness in stochastic biochemical networks.

    PubMed

    Enciso, German A

    2016-08-01

    Absolute robustness allows biochemical networks to sustain a consistent steady-state output in the face of protein concentration variability from cell to cell. This property is structural and can be determined from the topology of the network alone regardless of rate parameters. An important question regarding these systems is the effect of discrete biochemical noise in the dynamical behaviour. In this paper, a variable freezing technique is developed to show that under mild hypotheses the corresponding stochastic system has a transiently robust behaviour. Specifically, after finite time the distribution of the output approximates a Poisson distribution, centred around the deterministic mean. The approximation becomes increasingly accurate, and it holds for increasingly long finite times, as the total protein concentrations grow to infinity. In particular, the stochastic system retains a transient, absolutely robust behaviour corresponding to the deterministic case. This result contrasts with the long-term dynamics of the stochastic system, which eventually must undergo an extinction event that eliminates robustness and is completely different from the deterministic dynamics. The transiently robust behaviour may be sufficient to carry out many forms of robust signal transduction and cellular decision-making in cellular organisms. PMID:27581485

  13. Absolute Electron Extraction Efficiency of Liquid Xenon

    NASA Astrophysics Data System (ADS)

    Kamdin, Katayun; Mizrachi, Eli; Morad, James; Sorensen, Peter

    2016-03-01

    Dual phase liquid/gas xenon time projection chambers (TPCs) currently set the world's most sensitive limits on weakly interacting massive particles (WIMPs), a favored dark matter candidate. These detectors rely on extracting electrons from liquid xenon into gaseous xenon, where they produce proportional scintillation. The proportional scintillation from the extracted electrons serves to internally amplify the WIMP signal; even a single extracted electron is detectable. Credible dark matter searches can proceed with electron extraction efficiency (EEE) lower than 100%. However, electrons systematically left at the liquid/gas boundary are a concern. Possible effects include spontaneous single or multi-electron proportional scintillation signals in the gas, or charging of the liquid/gas interface or detector materials. Understanding EEE is consequently a serious concern for this class of rare event search detectors. Previous EEE measurements have mostly been relative, not absolute, assuming efficiency plateaus at 100%. I will present an absolute EEE measurement with a small liquid/gas xenon TPC test bed located at Lawrence Berkeley National Laboratory.

  14. Sentinel-2/MSI absolute calibration: first results

    NASA Astrophysics Data System (ADS)

    Lonjou, V.; Lachérade, S.; Fougnie, B.; Gamet, P.; Marcq, S.; Raynaud, J.-L.; Tremas, T.

    2015-10-01

    Sentinel-2 is an optical imaging mission devoted to the operational monitoring of land and coastal areas. It is developed in partnership between the European Commission and the European Space Agency. The Sentinel-2 mission is based on a satellites constellation deployed in polar sun-synchronous orbit. It will offer a unique combination of global coverage with a wide field of view (290km), a high revisit (5 days with two satellites), a high resolution (10m, 20m and 60m) and multi-spectral imagery (13 spectral bands in visible and shortwave infra-red domains). CNES is involved in the instrument commissioning in collaboration with ESA. This paper reviews all the techniques that will be used to insure an absolute calibration of the 13 spectral bands better than 5% (target 3%), and will present the first results if available. First, the nominal calibration technique, based on an on-board sun diffuser, is detailed. Then, we show how vicarious calibration methods based on acquisitions over natural targets (oceans, deserts, and Antarctica during winter) will be used to check and improve the accuracy of the absolute calibration coefficients. Finally, the verification scheme, exploiting photometer in-situ measurements over Lacrau plain, is described. A synthesis, including spectral coherence, inter-methods agreement and temporal evolution, will conclude the paper.

  15. Absolute Spectrophotometry of 237 Open Cluster Stars

    NASA Astrophysics Data System (ADS)

    Clampitt, L.; Burstein, D.

    1994-12-01

    We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

  16. A Conceptual Approach to Absolute Value Equations and Inequalities

    ERIC Educational Resources Information Center

    Ellis, Mark W.; Bryson, Janet L.

    2011-01-01

    The absolute value learning objective in high school mathematics requires students to solve far more complex absolute value equations and inequalities. When absolute value problems become more complex, students often do not have sufficient conceptual understanding to make any sense of what is happening mathematically. The authors suggest that the…

  17. Using, Seeing, Feeling, and Doing Absolute Value for Deeper Understanding

    ERIC Educational Resources Information Center

    Ponce, Gregorio A.

    2008-01-01

    Using sticky notes and number lines, a hands-on activity is shared that anchors initial student thinking about absolute value. The initial point of reference should help students successfully evaluate numeric problems involving absolute value. They should also be able to solve absolute value equations and inequalities that are typically found in…

  18. 20 CFR 404.1205 - Absolute coverage groups.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 2 2010-04-01 2010-04-01 false Absolute coverage groups. 404.1205 Section... INSURANCE (1950- ) Coverage of Employees of State and Local Governments What Groups of Employees May Be Covered § 404.1205 Absolute coverage groups. (a) General. An absolute coverage group is a...

  19. Use of Absolute and Comparative Performance Feedback in Absolute and Comparative Judgments and Decisions

    ERIC Educational Resources Information Center

    Moore, Don A.; Klein, William M. P.

    2008-01-01

    Which matters more--beliefs about absolute ability or ability relative to others? This study set out to compare the effects of such beliefs on satisfaction with performance, self-evaluations, and bets on future performance. In Experiment 1, undergraduate participants were told they had answered 20% correct, 80% correct, or were not given their…

  20. Incidence of specific absolute neurocognitive impairment in globally intact children with histories of early severe deprivation

    PubMed Central

    Behen, Michael E.; Helder, Emily; Rothermel, Robert; Solomon, Katherine; Chugani, Harry T.

    2008-01-01

    Postnatal deprivation is associated with neurocognitive delay/dysfunction. Although “catch up” in global cognition following adoption has been reported, this study examined the incidence of specific absolute impairment in adopted children with intact global cognitive functioning. Eighty-five children (38 males, mean age=112.8, SD=30.3 months; range 61−209 months) raised from birth in orphanages underwent comprehensive neuropsychological evaluation. Fifty-four were deemed globally intact (IQ>85). Of those deemed globally intact, 46 percent evidenced absolute impairment in at least one domain of functioning. Duration of stay in the orphanage was directly associated with incidence of impairment and number of domains affected. A substantial proportion of participants evidenced persistent, absolute impairment in one or more domains of neurocognitive function despite integrity of basic intellectual functions. PMID:18686074

  1. Absolute calibration of ultraviolet filter photometry

    NASA Technical Reports Server (NTRS)

    Bless, R. C.; Fairchild, T.; Code, A. D.

    1972-01-01

    The essential features of the calibration procedure can be divided into three parts. First, the shape of the bandpass of each photometer was determined by measuring the transmissions of the individual optical components and also by measuring the response of the photometer as a whole. Secondly, each photometer was placed in the essentially-collimated synchrotron radiation bundle maintained at a constant intensity level, and the output signal was determined from about 100 points on the objective. Finally, two or three points on the objective were illuminated by synchrotron radiation at several different intensity levels covering the dynamic range of the photometers. The output signals were placed on an absolute basis by the electron counting technique described earlier.

  2. MAGSAT: Vector magnetometer absolute sensor alignment determination

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.

    1981-01-01

    A procedure is described for accurately determining the absolute alignment of the magnetic axes of a triaxial magnetometer sensor with respect to an external, fixed, reference coordinate system. The method does not require that the magnetic field vector orientation, as generated by a triaxial calibration coil system, be known to better than a few degrees from its true position, and minimizes the number of positions through which a sensor assembly must be rotated to obtain a solution. Computer simulations show that accuracies of better than 0.4 seconds of arc can be achieved under typical test conditions associated with existing magnetic test facilities. The basic approach is similar in nature to that presented by McPherron and Snare (1978) except that only three sensor positions are required and the system of equations to be solved is considerably simplified. Applications of the method to the case of the MAGSAT Vector Magnetometer are presented and the problems encountered discussed.

  3. Absolute geostrophic currents in global tropical oceans

    NASA Astrophysics Data System (ADS)

    Yang, Lina; Yuan, Dongliang

    2016-03-01

    A set of absolute geostrophic current (AGC) data for the period January 2004 to December 2012 are calculated using the P-vector method based on monthly gridded Argo profiles in the world tropical oceans. The AGCs agree well with altimeter geostrophic currents, Ocean Surface Current Analysis-Real time currents, and moored current-meter measurements at 10-m depth, based on which the classical Sverdrup circulation theory is evaluated. Calculations have shown that errors of wind stress calculation, AGC transport, and depth ranges of vertical integration cannot explain non-Sverdrup transport, which is mainly in the subtropical western ocean basins and equatorial currents near the Equator in each ocean basin (except the North Indian Ocean, where the circulation is dominated by monsoons). The identified non-Sverdrup transport is thereby robust and attributed to the joint effect of baroclinicity and relief of the bottom (JEBAR) and mesoscale eddy nonlinearity.

  4. Absolute Measurement of Electron Cloud Density

    SciTech Connect

    Covo, M K; Molvik, A W; Cohen, R H; Friedman, A; Seidl, P A; Logan, G; Bieniosek, F; Baca, D; Vay, J; Orlando, E; Vujic, J L

    2007-06-21

    Beam interaction with background gas and walls produces ubiquitous clouds of stray electrons that frequently limit the performance of particle accelerator and storage rings. Counterintuitively we obtained the electron cloud accumulation by measuring the expelled ions that are originated from the beam-background gas interaction, rather than by measuring electrons that reach the walls. The kinetic ion energy measured with a retarding field analyzer (RFA) maps the depressed beam space-charge potential and provides the dynamic electron cloud density. Clearing electrode current measurements give the static electron cloud background that complements and corroborates with the RFA measurements, providing an absolute measurement of electron cloud density during a 5 {micro}s duration beam pulse in a drift region of the magnetic transport section of the High-Current Experiment (HCX) at LBNL.

  5. Absolute instability of a viscous hollow jet

    NASA Astrophysics Data System (ADS)

    Gañán-Calvo, Alfonso M.

    2007-02-01

    An investigation of the spatiotemporal stability of hollow jets in unbounded coflowing liquids, using a general dispersion relation previously derived, shows them to be absolutely unstable for all physical values of the Reynolds and Weber numbers. The roots of the symmetry breakdown with respect to the liquid jet case, and the validity of asymptotic models are here studied in detail. Asymptotic analyses for low and high Reynolds numbers are provided, showing that old and well-established limiting dispersion relations [J. W. S. Rayleigh, The Theory of Sound (Dover, New York, 1945); S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability (Dover, New York, 1961)] should be used with caution. In the creeping flow limit, the analysis shows that, if the hollow jet is filled with any finite density and viscosity fluid, a steady jet could be made arbitrarily small (compatible with the continuum hypothesis) if the coflowing liquid moves faster than a critical velocity.

  6. Stitching interferometry: recent results and absolute calibration

    NASA Astrophysics Data System (ADS)

    Bray, Michael

    2004-02-01

    Stitching Interferometry is a method of analysing large optical components using a standard "small" interferometer. This result is obtained by taking multiple overlapping images of the large component, and numerically "stitching" these sub-apertures together. We have already reported the industrial use our Stitching Interferometry systems (Previous SPIE symposia), but experimental results had been lacking because this technique is still new, and users needed to get accustomed to it before producing reliable measurements. We now have more results. We will report user comments and show new, unpublished results. We will discuss sources of error, and show how some of these can be reduced to arbitrarily small values. These will be discussed in some detail. We conclude with a few graphical examples of absolute measurements performed by us.

  7. Swarm's Absolute Scalar Magnetometer metrological performances

    NASA Astrophysics Data System (ADS)

    Leger, J.; Fratter, I.; Bertrand, F.; Jager, T.; Morales, S.

    2012-12-01

    The Absolute Scalar Magnetometer (ASM) has been developed for the ESA Earth Observation Swarm mission, planned for launch in November 2012. As its Overhauser magnetometers forerunners flown on Oersted and Champ satellites, it will deliver high resolution scalar measurements for the in-flight calibration of the Vector Field Magnetometer manufactured by the Danish Technical University. Latest results of the ground tests carried out to fully characterize all parameters that may affect its accuracy, both at instrument and satellite level, will be presented. In addition to its baseline function, the ASM can be operated either at a much higher sampling rate (burst mode at 250 Hz) or in a dual mode where it also delivers vector field measurements as a by-product. The calibration procedure and the relevant vector performances will be discussed.

  8. Observables sensitive to absolute neutrino masses. II

    SciTech Connect

    Fogli, G. L.; Marrone, A.; Rotunno, A. M.; Lisi, E.; Melchiorri, A.; Palazzo, A.; Silk, J.; Slosar, A.

    2008-08-01

    In this followup to Phys. Rev. D 75, 053001 (2007) , we report updated constraints on neutrino mass-mixing parameters, in light of recent neutrino oscillation data (KamLAND, SNO, and MINOS) and cosmological observations (WMAP 5-year and other data). We discuss their interplay with the final 0{nu}2{beta} decay results in {sup 76}Ge claimed by part of the Heidelberg-Moscow Collaboration, using recent evaluations of the corresponding nuclear matrix elements, and their uncertainties. We also comment on the 0{nu}2{beta} limits in {sup 130}Te recently set by Cuoricino and on prospective limits or signals from the Karlsruhe tritium neutrino experiment.

  9. L{sup {infinity}} Variational Problems with Running Costs and Constraints

    SciTech Connect

    Aronsson, G.; Barron, E. N.

    2012-02-15

    Various approaches are used to derive the Aronsson-Euler equations for L{sup {infinity}} calculus of variations problems with constraints. The problems considered involve holonomic, nonholonomic, isoperimetric, and isosupremic constraints on the minimizer. In addition, we derive the Aronsson-Euler equation for the basic L{sup {infinity}} problem with a running cost and then consider properties of an absolute minimizer. Many open problems are introduced for further study.

  10. Absolute-dated lake and cave records of the glacial highstand and deglacial regression of Lake Bonneville, Utah, USA

    NASA Astrophysics Data System (ADS)

    McGee, D.; Edwards, R.; Quade, J.; Broecker, W. S.

    2010-12-01

    Lake levels in Utah’s Bonneville Basin declined dramatically during the last deglaciation, likely reflecting changes in the position or intensity of the westerly storm track and increasing summer temperatures over this time period. After a prolonged transgression during the last glacial period, paleolake Bonneville began overflowing its basin at approximately 18 ka and remained hydrologically open until dropping below the overflow threshold (Provo shoreline) sometime between 15.5 and 14 ka. Although previous work has documented the main features of the lake’s history, many questions remain about the precise timing and rate of past lake level changes and their relation to abrupt warm and cold events during the last glacial period and deglaciation. Here we present records from a novel paleohydrological archive: carbonates precipitated within caves flooded by Lake Bonneville. Importantly, the deposits can be precisely dated by U-Th methods with minimal detrital contamination, providing the first high-precision, absolute-dated records of Lake Bonneville’s water balance changes. Additionally, calibrated 14C ages match U-Th ages, showing that Lake Bonneville experienced no measurable reservoir effects and providing an opportunity for improving the 14C calibration between 19 and 26 ka. The deposits appear to reflect periods when a) the lake was above a given cave’s elevation and b) the lake was not overflowing and therefore exceeded calcite/aragonite saturation. The deposits thus record the passage of the lake through each cave’s elevation, the onset and cessation of basin overflow, the isotopic composition of lake water, and changes in lake chemistry between 26 and 13 ka. In Cathedral Cave, the site of the best-studied deposits, carbonate was deposited in four phases, providing precise age constraints on key paleohydrographic events. Phase I (29 ka) is related to a previously unidentified oscillation of lake level above 1352 meters, the cave’s rebound

  11. Transport of absolute angular momentum in quasi-axisymmetric equatorial jet streams

    NASA Technical Reports Server (NTRS)

    Read, P. L.

    1986-01-01

    It is well known that prograde equatorial jet stresses cannot occur in an axisymmetric inviscid fluid, owing to the constraints of local angular momentum conservation. For a viscous fluid, the constraints of mass conservation prevent the formation of any local maximum of absolute angular momentum (m) without a means of transferring m against its gradient (delta m) in the meridional plane. The circumstances under which m can be diffused up-gradient by normal molecular viscosity are derived, and illustrated with reference to numerical simulations of axisymmetric flows in a cylindrical annulus. Viscosity is shown to act so as to tend to expel m from the interior outwards from the rotation axis. Such an effect can produce local super-rotation even in a mechanically isolated fluid. The tendency of viscosity to result in the expulsion of m is shown to be analogous in certain respects to a vorticity-mixing hypothesis for the effects of non-axisymmetric eddies of the zonally-averaged flow. It is shown how the advective and diffusive transport of m by non-axisymmetric eddies can be represented by the Transformed Eulerian Mean meridional circulation and the Eliassen-Palm (EP) flux of Andrews and McIntyre respectively, in the zonal mean. Constraints on the form and direction of the EP flux in an advective/diffusive flow for such eddies are derived, by analogy with similar constraints on the diffusive flux of m due to viscosity.

  12. Dichotomy and perceptual distortions in absolute pitch ability

    PubMed Central

    Athos, E. Alexandra; Levinson, Barbara; Kistler, Amy; Zemansky, Jason; Bostrom, Alan; Freimer, Nelson; Gitschier, Jane

    2007-01-01

    Absolute pitch (AP) is the rare ability to identify the pitch of a tone without the aid of a reference tone. Understanding both the nature and genesis of AP can provide insights into neuroplasticity in the auditory system. We explored factors that may influence the accuracy of pitch perception in AP subjects both during the development of the trait and in later age. We used a Web-based survey and a pitch-labeling test to collect perceptual data from 2,213 individuals, 981 (44%) of whom proved to have extraordinary pitch-naming ability. The bimodal distribution in pitch-naming ability signifies AP as a distinct perceptual trait, with possible implications for its genetic basis. The wealth of these data has allowed us to uncover unsuspected note-naming irregularities suggestive of a “perceptual magnet” centered at the note “A.” In addition, we document a gradual decline in pitch-naming accuracy with age, characterized by a perceptual shift in the “sharp” direction. These findings speak both to the process of acquisition of AP and to its stability. PMID:17724340

  13. High quality absolute paleointensity data from Santa Fe, New Mexico

    NASA Astrophysics Data System (ADS)

    Jones, S. A.; Tauxe, L.; Blinman, E.; Genevey, A.

    2015-12-01

    Preliminary paleointensity experiments were conducted using the IZZI protocol on one hundred and fourteen specimens from fifty-seven baked pottery fragments collected from nine archaeological sites near Santa Fe, New Mexico. Twenty of these fragments passed our weakest selection criteria. Seven additional specimens were made from each passing fragment for further paleointensity experiments. The results of these second experiments indicate that the samples are mildly anisotropic, so anisotropy experiments were conducted to correct for this behavior. Experiments to determine the cooling rate correction will be completed to ensure the robustness of the dataset. Stylistic evidence, historical documentation, dendrochronology, and 14C analyses provide age constraints with up to decade resolution for the VADM results. The twenty pottery fragments analyzed span five distinct time periods between 1300 and 1900 AD. Our new results for each fragment differ slightly from those predicted by the cals3k.4b and arch3k models, suggesting the models require refinement. This is expected because there are few archaeomagnetic constraints on the models from this region. Future pottery fragments and burned adobe fragments from the New Mexico area will be analyzed for paleointensity and combined with our pottery fragment data set to create a high-resolution paleointensity curve for the recent archaeological time in the American Southwest.

  14. A Framework for Dynamic Constraint Reasoning Using Procedural Constraints

    NASA Technical Reports Server (NTRS)

    Jonsson, Ari K.; Frank, Jeremy D.

    1999-01-01

    Many complex real-world decision and control problems contain an underlying constraint reasoning problem. This is particularly evident in a recently developed approach to planning, where almost all planning decisions are represented by constrained variables. This translates a significant part of the planning problem into a constraint network whose consistency determines the validity of the plan candidate. Since higher-level choices about control actions can add or remove variables and constraints, the underlying constraint network is invariably highly dynamic. Arbitrary domain-dependent constraints may be added to the constraint network and the constraint reasoning mechanism must be able to handle such constraints effectively. Additionally, real problems often require handling constraints over continuous variables. These requirements present a number of significant challenges for a constraint reasoning mechanism. In this paper, we introduce a general framework for handling dynamic constraint networks with real-valued variables, by using procedures to represent and effectively reason about general constraints. The framework is based on a sound theoretical foundation, and can be proven to be sound and complete under well-defined conditions. Furthermore, the framework provides hybrid reasoning capabilities, as alternative solution methods like mathematical programming can be incorporated into the framework, in the form of procedures.

  15. Constraint-based scheduling

    NASA Technical Reports Server (NTRS)

    Zweben, Monte

    1991-01-01

    The GERRY scheduling system developed by NASA Ames with assistance from the Lockheed Space Operations Company, and the Lockheed Artificial Intelligence Center, uses a method called constraint-based iterative repair. Using this technique, one encodes both hard rules and preference criteria into data structures called constraints. GERRY repeatedly attempts to improve schedules by seeking repairs for violated constraints. The system provides a general scheduling framework which is being tested on two NASA applications. The larger of the two is the Space Shuttle Ground Processing problem which entails the scheduling of all the inspection, repair, and maintenance tasks required to prepare the orbiter for flight. The other application involves power allocation for the NASA Ames wind tunnels. Here the system will be used to schedule wind tunnel tests with the goal of minimizing power costs. In this paper, we describe the GERRY system and its application to the Space Shuttle problem. We also speculate as to how the system would be used for manufacturing, transportation, and military problems.

  16. Constraint-based scheduling

    NASA Technical Reports Server (NTRS)

    Zweben, Monte

    1993-01-01

    The GERRY scheduling system developed by NASA Ames with assistance from the Lockheed Space Operations Company, and the Lockheed Artificial Intelligence Center, uses a method called constraint-based iterative repair. Using this technique, one encodes both hard rules and preference criteria into data structures called constraints. GERRY repeatedly attempts to improve schedules by seeking repairs for violated constraints. The system provides a general scheduling framework which is being tested on two NASA applications. The larger of the two is the Space Shuttle Ground Processing problem which entails the scheduling of all the inspection, repair, and maintenance tasks required to prepare the orbiter for flight. The other application involves power allocation for the NASA Ames wind tunnels. Here the system will be used to schedule wind tunnel tests with the goal of minimizing power costs. In this paper, we describe the GERRY system and its application to the Space Shuttle problem. We also speculate as to how the system would be used for manufacturing, transportation, and military problems.

  17. Constraint-based scheduling

    NASA Technical Reports Server (NTRS)

    Zweben, Monte

    1991-01-01

    The GERRY scheduling system developed by NASA Ames with assistance from the Lockheed Space Operations Company, and the Lockheed Artificial Intelligence Center, uses a method called constraint based iterative repair. Using this technique, one encodes both hard rules and preference criteria into data structures called constraints. GERRY repeatedly attempts to improve schedules by seeking repairs for violated constraints. The system provides a general scheduling framework which is being tested on two NASA applications. The larger of the two is the Space Shuttle Ground Processing problem which entails the scheduling of all inspection, repair, and maintenance tasks required to prepare the orbiter for flight. The other application involves power allocations for the NASA Ames wind tunnels. Here the system will be used to schedule wind tunnel tests with the goal of minimizing power costs. In this paper, we describe the GERRY system and its applications to the Space Shuttle problem. We also speculate as to how the system would be used for manufacturing, transportation, and military problems.

  18. Protracted construction of gabbroic crust at a slow spreading ridge: Constraints from 206Pb/238U zircon ages from Atlantis Massif and IODP Hole U1309D (30°N, MAR)

    USGS Publications Warehouse

    Grimes, Craig B.; John, Barbara E.; Cheadle, Michael J.; Wooden, Joseph L.

    2008-01-01

    Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon ages of 24 samples from oceanic crust recovered in Integrated Ocean Drilling Program (IODP) Hole U1309D and from the surface of Atlantis Massif, Mid-Atlantic Ridge (MAR) (30°N) document a protracted history of accretion in the footwall to an oceanic detachment fault. Ages for 18 samples of evolved Fe-Ti oxide gabbro and felsic dikes collected 40–1415 m below seafloor in U1309D yield a weighted mean of 1.20 ± 0.03 Ma (mean square of weighted deviates = 7.1). However, the ages range from 1.08 ± 0.07 Ma and 1.28 ± 0.05 Ma indicating crustal construction occurred over a minimum of 100–200 ka. The zircon ages, along with petrologic observations, indicate at least 2 major periods of intrusive activity with age peaks separated by 70 ka. The oldest ages are observed below 600 mbsf, an observation inconsistent with models requiring constant depth melt intrusion beneath a detachment fault. The data are most consistent with a “multiple sill” model whereby sills intrude at random depths below the ridge axis over a length scale greater than 1.4 km. Zircon ages from broadly spaced samples collected along the southern ridge of Atlantis Massif yield a detachment fault slip rate of 28.7 ± 6.7 mm/a and imply significant asymmetric plate spreading (up to 100% on the North American plate) for at least 200 ka during core complex formation.

  19. Structure Constraints in a Constraint-Based Planner

    NASA Technical Reports Server (NTRS)

    Pang, Wan-Lin; Golden, Keith

    2004-01-01

    In this paper we report our work on a new constraint domain, where variables can take structured values. Earth-science data processing (ESDP) is a planning domain that requires the ability to represent and reason about complex constraints over structured data, such as satellite images. This paper reports on a constraint-based planner for ESDP and similar domains. We discuss our approach for translating a planning problem into a constraint satisfaction problem (CSP) and for representing and reasoning about structured objects and constraints over structures.

  20. THE AGES OF 55 GLOBULAR CLUSTERS AS DETERMINED USING AN IMPROVED ΔV{sup HB}{sub TO} METHOD ALONG WITH COLOR-MAGNITUDE DIAGRAM CONSTRAINTS, AND THEIR IMPLICATIONS FOR BROADER ISSUES

    SciTech Connect

    VandenBerg, Don A.; Brogaard, K.; Leaman, R.; Casagrande, L. E-mail: kfb@phys.au.dk E-mail: luca@mso.anu.edu.au

    2013-10-01

    Ages have been derived for 55 globular clusters (GCs) for which Hubble Space Telescope Advanced Camera for Surveys photometry is publicly available. For most of them, the assumed distances are based on fits of theoretical zero-age horizontal-branch (ZAHB) loci to the lower bound of the observed distributions of HB stars, assuming reddenings from empirical dust maps and metallicities from the latest spectroscopic analyses. The age of the isochrone that provides the best fit to the stars in the vicinity of the turnoff (TO) is taken to be the best estimate of the cluster age. The morphology of isochrones between the TO and the beginning part of the subgiant branch (SGB) is shown to be nearly independent of age and chemical abundances. For well-defined color-magnitude diagrams (CMDs), the error bar arising just from the 'fitting' of ZAHBs and isochrones is ≈ ± 0.25 Gyr, while that associated with distance and chemical abundance uncertainties is ∼ ± 1.5-2 Gyr. The oldest GCs in our sample are predicted to have ages of ≈13.0 Gyr (subject to the aforementioned uncertainties). However, the main focus of this investigation is on relative GC ages. In conflict with recent findings based on the relative main-sequence fitting method, which have been studied in some detail and reconciled with our results, ages are found to vary from mean values of ≈12.5 Gyr at [Fe/H] ∼< – 1.7 to ≈11 Gyr at [Fe/H] ∼> –1. At intermediate metallicities, the age-metallicity relation (AMR) appears to be bifurcated: one branch apparently contains clusters with disk-like kinematics, whereas the other branch, which is displaced to lower [Fe/H] values by ≈0.6 dex at a fixed age, is populated by clusters with halo-type orbits. The dispersion in age about each component of the AMR is ∼ ± 0.5 Gyr. There is no apparent dependence of age on Galactocentric distance (R{sub G}) nor is there a clear correlation of HB type with age. As previously discovered in the case of M3 and M13

  1. The Ages of 55 Globular Clusters as Determined Using an Improved \\Delta V^HB_TO Method along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues

    NASA Astrophysics Data System (ADS)

    VandenBerg, Don A.; Brogaard, K.; Leaman, R.; Casagrande, L.

    2013-10-01

    Ages have been derived for 55 globular clusters (GCs) for which Hubble Space Telescope Advanced Camera for Surveys photometry is publicly available. For most of them, the assumed distances are based on fits of theoretical zero-age horizontal-branch (ZAHB) loci to the lower bound of the observed distributions of HB stars, assuming reddenings from empirical dust maps and metallicities from the latest spectroscopic analyses. The age of the isochrone that provides the best fit to the stars in the vicinity of the turnoff (TO) is taken to be the best estimate of the cluster age. The morphology of isochrones between the TO and the beginning part of the subgiant branch (SGB) is shown to be nearly independent of age and chemical abundances. For well-defined color-magnitude diagrams (CMDs), the error bar arising just from the "fitting" of ZAHBs and isochrones is ≈ ± 0.25 Gyr, while that associated with distance and chemical abundance uncertainties is ~ ± 1.5-2 Gyr. The oldest GCs in our sample are predicted to have ages of ≈13.0 Gyr (subject to the aforementioned uncertainties). However, the main focus of this investigation is on relative GC ages. In conflict with recent findings based on the relative main-sequence fitting method, which have been studied in some detail and reconciled with our results, ages are found to vary from mean values of ≈12.5 Gyr at [Fe/H] <~ - 1.7 to ≈11 Gyr at [Fe/H] >~ -1. At intermediate metallicities, the age-metallicity relation (AMR) appears to be bifurcated: one branch apparently contains clusters with disk-like kinematics, whereas the other branch, which is displaced to lower [Fe/H] values by ≈0.6 dex at a fixed age, is populated by clusters with halo-type orbits. The dispersion in age about each component of the AMR is ~ ± 0.5 Gyr. There is no apparent dependence of age on Galactocentric distance (R G) nor is there a clear correlation of HB type with age. As previously discovered in the case of M3 and M13, subtle variations have

  2. Crystallization ages of the A-type magmatism of the Graciosa Province (Southern Brazil): Constraints from zircon U-Pb (ID-TIMS) dating of coeval K-rich gabbro-dioritic rocks

    NASA Astrophysics Data System (ADS)

    Vlach, Silvio R. F.; Siga, Oswaldo; Harara, Ossama M. M.; Gualda, Guilherme A. R.; Basei, Miguel A. S.; Vilalva, Frederico C. J.

    2011-12-01

    Zircon U-Pb (ID-TIMS) ages for gabbro-dioritic rocks and for a monzogranite from the Graciosa Province of A-type granites and syenites, southern Brazil, are presented. Two gabbro-dioritic samples gave concordant ages (580 ± 2, 583 ± 3 Ma), while less precise upper intercept ages were obtained for another one (584 ± 8 Ma) and the monzogranite (585 ± 12 Ma). The best results indicate crystallization ages of the basic-intermediate magmas around 580-583 Ma. Micro-structural evidences and structural relationships between the mafic-intermediate rocks and the much more abundant granites and syenites demonstrate that magmas mingled and partially mixed with one another during emplacement and crystallization. Therefore, the results are representative of the overall magmatism. The extensional A-type magmatism occurred ca. 10-30 Ma after (1) emplacement and crystallization of the high-K calc-alkaline syn- to late-collisional batholiths, (2) peak regional metamorphism, and (3) final amalgamation of the Luis Alves, Curitiba, and Paranaguá terrains. It is suggested that the whole magmatism occurred in a short time interval and there is no evidence of spatial or temporal migration of the magmatic foci. ID-TIMS zircon dating of coeval basic-intermediate rocks may yield better emplacement and crystallization ages than direct dating of granitic and syenitic rocks, which are more susceptible to inheritance and/or late- to post-magmatic disturbances.

  3. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.

  4. Absolute surface energy for zincblende semiconductors

    NASA Astrophysics Data System (ADS)

    Zhang, S. B.; Wei, Su-Huai

    2003-03-01

    Recent advance in nanosciences requires the determination of surface (or facet) energy of semiconductors, which is often difficult due to the polar nature of some of the most important surfaces such as the (111)A/(111)B surfaces. Several approaches have been developed in the past [1-3] to deal with the problem but an unambiguous division of the polar surface energies is yet to come [2]. Here we show that an accurate division is indeed possible for the zincblende semiconductors and will present the results for GaAs, ZnSe, and CuInSe2 [4], respectively. A general trend emerges, relating the absolute surface energy to the ionicity of the bulk materials. [1] N. Chetty and R. M. Martin, Phys. Rev. B 45, 6074 (1992). [2] N. Moll, et al., Phys. Rev. B 54, 8844 (1996). [3] S. Mankefors, Phys. Rev. B 59, 13151 (1999). [4] S. B. Zhang and S.-H. Wei, Phys. Rev. B 65, 081402 (2002).

  5. Climate Absolute Radiance and Refractivity Observatory (CLARREO)

    NASA Technical Reports Server (NTRS)

    Leckey, John P.

    2015-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a mission, led and developed by NASA, that will measure a variety of climate variables with an unprecedented accuracy to quantify and attribute climate change. CLARREO consists of three separate instruments: an infrared (IR) spectrometer, a reflected solar (RS) spectrometer, and a radio occultation (RO) instrument. The mission will contain orbiting radiometers with sufficient accuracy, including on orbit verification, to calibrate other space-based instrumentation, increasing their respective accuracy by as much as an order of magnitude. The IR spectrometer is a Fourier Transform spectrometer (FTS) working in the 5 to 50 microns wavelength region with a goal of 0.1 K (k = 3) accuracy. The FTS will achieve this accuracy using phase change cells to verify thermistor accuracy and heated halos to verify blackbody emissivity, both on orbit. The RS spectrometer will measure the reflectance of the atmosphere in the 0.32 to 2.3 microns wavelength region with an accuracy of 0.3% (k = 2). The status of the instrumentation packages and potential mission options will be presented.

  6. Absolute decay width measurements in 16O

    NASA Astrophysics Data System (ADS)

    Wheldon, C.; Ashwood, N. I.; Barr, M.; Curtis, N.; Freer, M.; Kokalova, Tz; Malcolm, J. D.; Spencer, S. J.; Ziman, V. A.; Faestermann, Th; Krücken, R.; Wirth, H.-F.; Hertenberger, R.; Lutter, R.; Bergmaier, A.

    2012-09-01

    The reaction 126C(63Li, d)168O* at a 6Li bombarding energy of 42 MeV has been used to populate excited states in 16O. The deuteron ejectiles were measured using the high-resolution Munich Q3D spectrograph. A large-acceptance silicon-strip detector array was used to register the recoil and break-up products. This complete kinematic set-up has enabled absolute α-decay widths to be measured with high-resolution in the 13.9 to 15.9 MeV excitation energy regime in 16O; many for the first time. This energy region spans the 14.4 MeV four-α breakup threshold. Monte-Carlo simulations of the detector geometry and break-up processes yield detection efficiencies for the two dominant decay modes of 40% and 37% for the α+12C(g.s.) and a+12C(2+1) break-up channels respectively.

  7. Absolute calibration of forces in optical tweezers

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

    2014-07-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past 15 years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

  8. Absolute spectrophotometry of northern compact planetary nebulae

    NASA Astrophysics Data System (ADS)

    Wright, S. A.; Corradi, R. L. M.; Perinotto, M.

    2005-06-01

    We present medium-dispersion spectra and narrowband images of six northern compact planetary nebulae (PNe): BoBn 1, DdDm 1, IC 5117, M 1-5, M 1-71, and NGC 6833. From broad-slit spectra, total absolute fluxes and equivalent widths were measured for all observable emission lines. High signal-to-noise emission line fluxes of Hα, Hβ, [Oiii], [Nii], and HeI may serve as emission line flux standards for northern hemisphere observers. From narrow-slit spectra, we derive systemic radial velocities. For four PNe, available emission line fluxes were measured with sufficient signal-to-noise to probe the physical properties of their electron densities, temperatures, and chemical abundances. BoBn 1 and DdDm 1, both type IV PNe, have an Hβ flux over three sigma away from previous measurements. We report the first abundance measurements of M 1-71. NGC 6833 measured radial velocity and galactic coordinates suggest that it is associated with the outer arm or possibly the galactic halo, and its low abundance ([O/H]=1.3× 10-4) may be indicative of low metallicity within that region.

  9. Propagating orientation constraints for the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Bose, Ashim; Gerb, Andy

    1994-01-01

    An observing program on the Hubble Space Telescope (HST) is described in terms of exposures that are obtained by one or more of the instruments onboard the HST. Many requested exposures might specify orientation requirements and accompanying ranges. Orientation refers to the amount of roll (in degrees) about the line of sight. The range give the permissible tolerance (also in degrees). These requirements may be (1) absolute (in relation to the celestial coordinate system), (2) relative to the nominal roll angle for HST during that exposure, or (3) relative (in relation to other exposures in the observing program). The TRANSformation expert system converts proposals for astronomical observations with HST into detailed observing plans. Part of the conversion involves grouping exposures into higher level structures based on exposure characteristics. Exposures constrained to be at different orientations cannot be grouped together. Because relative orientation requirements cause implicit constraints, orientation constraints have to be propagated. TRANS must also identify any inconsistencies that may exist so they can be corrected. We have designed and implemented an orientation constraint propagator as part of TRANS. The propagator is based on an informal algebra that facilitates the setting up and propagation of the orientation constraints. The constraint propagator generates constraints between directly related exposures, and propagates derived constraints between exposures that are related indirectly. It provides facilities for path-consistency checking, identification of unsatisfiable constraints, and querying of orientation relationships. The system has been successfully operational as part of TRANS for over seven months. The solution has particular significance to space applications in which satellite/telescope pointing and attitude are constrained and relationships exist between multiple configurations.

  10. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.

    2015-12-01

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  11. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.

    2012-06-05

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  12. The absolute disparity anomaly and the mechanism of relative disparities.

    PubMed

    Chopin, Adrien; Levi, Dennis; Knill, David; Bavelier, Daphne

    2016-06-01

    There has been a long-standing debate about the mechanisms underlying the perception of stereoscopic depth and the computation of the relative disparities that it relies on. Relative disparities between visual objects could be computed in two ways: (a) using the difference in the object's absolute disparities (Hypothesis 1) or (b) using relative disparities based on the differences in the monocular separations between objects (Hypothesis 2). To differentiate between these hypotheses, we measured stereoscopic discrimination thresholds for lines with different absolute and relative disparities. Participants were asked to judge the depth of two lines presented at the same distance from the fixation plane (absolute disparity) or the depth between two lines presented at different distances (relative disparity). We used a single stimulus method involving a unique memory component for both conditions, and no extraneous references were available. We also measured vergence noise using Nonius lines. Stereo thresholds were substantially worse for absolute disparities than for relative disparities, and the difference could not be explained by vergence noise. We attribute this difference to an absence of conscious readout of absolute disparities, termed the absolute disparity anomaly. We further show that the pattern of correlations between vergence noise and absolute and relative disparity acuities can be explained jointly by the existence of the absolute disparity anomaly and by the assumption that relative disparity information is computed from absolute disparities (Hypothesis 1). PMID:27248566

  13. The absolute disparity anomaly and the mechanism of relative disparities

    PubMed Central

    Chopin, Adrien; Levi, Dennis; Knill, David; Bavelier, Daphne

    2016-01-01

    There has been a long-standing debate about the mechanisms underlying the perception of stereoscopic depth and the computation of the relative disparities that it relies on. Relative disparities between visual objects could be computed in two ways: (a) using the difference in the object's absolute disparities (Hypothesis 1) or (b) using relative disparities based on the differences in the monocular separations between objects (Hypothesis 2). To differentiate between these hypotheses, we measured stereoscopic discrimination thresholds for lines with different absolute and relative disparities. Participants were asked to judge the depth of two lines presented at the same distance from the fixation plane (absolute disparity) or the depth between two lines presented at different distances (relative disparity). We used a single stimulus method involving a unique memory component for both conditions, and no extraneous references were available. We also measured vergence noise using Nonius lines. Stereo thresholds were substantially worse for absolute disparities than for relative disparities, and the difference could not be explained by vergence noise. We attribute this difference to an absence of conscious readout of absolute disparities, termed the absolute disparity anomaly. We further show that the pattern of correlations between vergence noise and absolute and relative disparity acuities can be explained jointly by the existence of the absolute disparity anomaly and by the assumption that relative disparity information is computed from absolute disparities (Hypothesis 1). PMID:27248566

  14. Age spectra of detrital zircon of the Jurassic clastic rocks of the Mino-Tanba AC belt in SW Japan: Constraints to the provenance of the mid-Mesozoic trench in East Asia

    NASA Astrophysics Data System (ADS)

    Fujisaki, Wataru; Isozaki, Yukio; Maki, Kenshi; Sakata, Shuhei; Hirata, Takafumi; Maruyama, Shigenori

    2014-07-01

    U-Pb ages of detrital zircon grains were determined from an upper Middle Jurassic siliceous mudstone and two lower Upper Jurassic sandstones of the Mino-Tanba belt, Southwest Japan, by Laser-ablation ICPMS. The age spectra of detrital zircon grains of the three analyzed samples show multiple age clusters: 175-198 Ma (Early Jurassic), 202-284 Ma (Permian to Triassic), 336-431 Ma (Silurian to Carboniferous), and 1691-2657 Ma (Neoarchean to Paleoproterozoic). As per the Precambrian grains, the prominent peak exists around 1800-2000 Ma in all analyzed samples. The age clusters of 175-198 Ma, 202-284 Ma, and 336-431 Ma suggest that pre-Middle Jurassic Japan has exposed older granitic batholiths. The corresponding batholiths occur in the Cathaysian part of South China block. In contrast, the absence of them in modern Japan suggests that these batholiths were totally consumed by post-Jurassic tectonic erosion. The Neoarchean to Paleoproterozoic detrital zircon grains were derived from South China, North China, or possibly both of them; nonetheless, the circumstantial geologic lines of evidence point to South China, in particular to Cathaysia, rather than North China.

  15. Inflationary freedom and cosmological neutrino constraints

    NASA Astrophysics Data System (ADS)

    de Putter, Roland; Linder, Eric V.; Mishra, Abhilash

    2014-05-01

    The most stringent bounds on the absolute neutrino mass scale come from cosmological data. These bounds are made possible because massive relic neutrinos affect the expansion history of the universe and lead to a suppression of matter clustering on scales smaller than the associated free streaming length. However, the resulting effect on cosmological perturbations is relative to the primordial power spectrum of density perturbations from inflation, so freedom in the primordial power spectrum affects neutrino mass constraints. Using measurements of the cosmic microwave background (CMB), the galaxy power spectrum and the Hubble constant, we constrain neutrino mass and number of species for a model-independent primordial power spectrum. Describing the primordial power spectrum by a 20-node spline, we find that the neutrino mass upper limit is a factor 3 weaker than when a power law form is imposed, if only CMB data are used. The primordial power spectrum itself is constrained to better than 10% in the wave vector range k ≈0.01-0.25 Mpc-1. Galaxy clustering data and a determination of the Hubble constant play a key role in reining in the effects of inflationary freedom on neutrino constraints. The inclusion of both eliminates the inflationary freedom degradation of the neutrino mass bound, giving for the sum of neutrino masses Σmν<0.18 eV (at 95% confidence level, Planck+BOSS+H0), approximately independent of the assumed primordial power spectrum model. When allowing for a free effective number of species, Neff, the joint constraints on Σmν and Neff are loosened by a factor 1.7 when the power law form of the primordial power spectrum is abandoned in favor of the spline parametrization.

  16. Asteroseismic constraints for Gaia

    NASA Astrophysics Data System (ADS)

    Creevey, O. L.; Thévenin, F.

    2012-12-01

    Distances from the Gaia mission will no doubt improve our understanding of stellar physics by providing an excellent constraint on the luminosity of the star. However, it is also clear that high precision stellar properties from, for example, asteroseismology, will also provide a needed input constraint in order to calibrate the methods that Gaia will use, e.g. stellar models or GSP_Phot. For solar-like stars (F, G, K IV/V), asteroseismic data delivers at the least two very important quantities: (1) the average large frequency separation < Δ ν > and (2) the frequency corresponding to the maximum of the modulated-amplitude spectrum ν_{max}. Both of these quantities are related directly to stellar parameters (radius and mass) and in particular their combination (gravity and density). We show how the precision in < Δ ν >, ν_{max}, and atmospheric parameters T_{eff} and [Fe/H] affect the determination of gravity (log g) for a sample of well-known stars. We find that log g can be determined within less than 0.02 dex accuracy for our sample while considering precisions in the data expected for V˜12 stars from Kepler data. We also derive masses and radii which are accurate to within 1σ of the accepted values. This study validates the subsequent use of all of the available asteroseismic data on solar-like stars from the Kepler field (>500 IV/V stars) in order to provide a very important constraint for Gaia calibration of GSP_Phot} through the use of log g. We note that while we concentrate on IV/V stars, both the CoRoT and Kepler fields contain asteroseismic data on thousands of giant stars which will also provide useful calibration measures.

  17. Evaluation of the Absolute Regional Temperature Potential

    NASA Technical Reports Server (NTRS)

    Shindell, D. T.

    2012-01-01

    The Absolute Regional Temperature Potential (ARTP) is one of the few climate metrics that provides estimates of impacts at a sub-global scale. The ARTP presented here gives the time-dependent temperature response in four latitude bands (90-28degS, 28degS-28degN, 28-60degN and 60-90degN) as a function of emissions based on the forcing in those bands caused by the emissions. It is based on a large set of simulations performed with a single atmosphere-ocean climate model to derive regional forcing/response relationships. Here I evaluate the robustness of those relationships using the forcing/response portion of the ARTP to estimate regional temperature responses to the historic aerosol forcing in three independent climate models. These ARTP results are in good accord with the actual responses in those models. Nearly all ARTP estimates fall within +/-20%of the actual responses, though there are some exceptions for 90-28degS and the Arctic, and in the latter the ARTP may vary with forcing agent. However, for the tropics and the Northern Hemisphere mid-latitudes in particular, the +/-20% range appears to be roughly consistent with the 95% confidence interval. Land areas within these two bands respond 39-45% and 9-39% more than the latitude band as a whole. The ARTP, presented here in a slightly revised form, thus appears to provide a relatively robust estimate for the responses of large-scale latitude bands and land areas within those bands to inhomogeneous radiative forcing and thus potentially to emissions as well. Hence this metric could allow rapid evaluation of the effects of emissions policies at a finer scale than global metrics without requiring use of a full climate model.

  18. Absolute determination of local tropospheric OH concentrations

    NASA Technical Reports Server (NTRS)

    Armerding, Wolfgang; Comes, Franz-Josef

    1994-01-01

    Long path absorption (LPA) according to Lambert Beer's law is a method to determine absolute concentrations of trace gases such as tropospheric OH. We have developed a LPA instrument which is based on a rapid tuning of the light source which is a frequency doubled dye laser. The laser is tuned across two or three OH absorption features around 308 nm with a scanning speed of 0.07 cm(exp -1)/microsecond and a repetition rate of 1.3 kHz. This high scanning speed greatly reduces the fluctuation of the light intensity caused by the atmosphere. To obtain the required high sensitivity the laser output power is additionally made constant and stabilized by an electro-optical modulator. The present sensitivity is of the order of a few times 10(exp 5) OH per cm(exp 3) for an acquisition time of a minute and an absorption path length of only 1200 meters so that a folding of the optical path in a multireflection cell was possible leading to a lateral dimension of the cell of a few meters. This allows local measurements to be made. Tropospheric measurements have been carried out in 1991 resulting in the determination of OH diurnal variation at specific days in late summer. Comparison with model calculations have been made. Interferences are mainly due to SO2 absorption. The problem of OH self generation in the multireflection cell is of minor extent. This could be shown by using different experimental methods. The minimum-maximum signal to noise ratio is about 8 x 10(exp -4) for a single scan. Due to the small size of the absorption cell the realization of an open air laboratory is possible in which by use of an additional UV light source or by additional fluxes of trace gases the chemistry can be changed under controlled conditions allowing kinetic studies of tropospheric photochemistry to be made in open air.

  19. Absolute Radiometric Calibration of KOMPSAT-3A

    NASA Astrophysics Data System (ADS)

    Ahn, H. Y.; Shin, D. Y.; Kim, J. S.; Seo, D. C.; Choi, C. U.

    2016-06-01

    This paper presents a vicarious radiometric calibration of the Korea Multi-Purpose Satellite-3A (KOMPSAT-3A) performed by the Korea Aerospace Research Institute (KARI) and the Pukyong National University Remote Sensing Group (PKNU RSG) in 2015.The primary stages of this study are summarized as follows: (1) A field campaign to determine radiometric calibrated target fields was undertaken in Mongolia and South Korea. Surface reflectance data obtained in the campaign were input to a radiative transfer code that predicted at-sensor radiance. Through this process, equations and parameters were derived for the KOMPSAT-3A sensor to enable the conversion of calibrated DN to physical units, such as at-sensor radiance or TOA reflectance. (2) To validate the absolute calibration coefficients for the KOMPSAT-3A sensor, we performed a radiometric validation with a comparison of KOMPSAT-3A and Landsat-8 TOA reflectance using one of the six PICS (Libya 4). Correlations between top-of-atmosphere (TOA) radiances and the spectral band responses of the KOMPSAT-3A sensors at the Zuunmod, Mongolia and Goheung, South Korea sites were significant for multispectral bands. The average difference in TOA reflectance between KOMPSAT-3A and Landsat-8 image over the Libya 4, Libya site in the red-green-blue (RGB) region was under 3%, whereas in the NIR band, the TOA reflectance of KOMPSAT-3A was lower than the that of Landsat-8 due to the difference in the band passes of two sensors. The KOMPSAT-3Aensor includes a band pass near 940 nm that can be strongly absorbed by water vapor and therefore displayed low reflectance. Toovercome this, we need to undertake a detailed analysis using rescale methods, such as the spectral bandwidth adjustment factor.

  20. Practical Cleanroom Operations Constraints

    NASA Technical Reports Server (NTRS)

    Hughes, David; Ginyard, Amani

    2007-01-01

    This viewgraph presentation reviews the GSFC Cleanroom Facility i.e., Spacecraft Systems Development and Integration Facility (SSDIF) with particular interest in its use during the development of the Wide Field Camera 3 (WFC3). The SSDIF is described and a diagram of the SSDIF is shown. A Constraint Table was created for consistency within Contamination Control Team. This table is shown. Another table that shows the activities that were allowed during the integration under given WFC3 condition and activity location is presented. Three decision trees are shown for different phases of the work: (1) Hardware Relocation, Hardware Work, and Contamination Control Operations.

  1. Superresolution via sparsity constraints

    NASA Technical Reports Server (NTRS)

    Donoho, David L.

    1992-01-01

    The problem of recovering a measure mu supported on a lattice of span Delta is considered under the condition that measurements are only available concerning the Fourier Transform at frequencies of Omega or less. If Omega is much smaller than the Nyquist frequency pi/Delta and the measurements are noisy, then stable recovery of mu is generally impossible. It is shown here that if, in addition, it is known that mu satisfies certain sparsity constraints, then stable recovery is possible. This finding validates practical efforts in spectroscopy, seismic prospecting, and astronomy to provide superresolution by imposing support limitations in reconstruction.

  2. Lifetime of an ocean island volcano feeder zone: constraints from U-Pb dating on coexisting zircon and baddeleyite, and 40/39Ar age determinations, Fuerteventura, Canary Islands

    USGS Publications Warehouse

    Allibon, James; Ovtcharova, Maria; Bussy, Francois; Cosca, Michael; Schaltegger, Urs; Bussien, Denise; Lewin, Eric

    2011-01-01

    High-precision isotope dilution - thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon and baddeleyite ages from the PX1 vertically layered mafic intrusion Fuerteventura, Canary Islands, indicate initiation of magma crystallization at 22.10 ± 0.07 Ma. The magmatic activity lasted a minimum of 0.52 Ma. 40Ar/39Ar amphibole dating yielded ages from 21.9 ± 0.6 to 21.8 ± 0.3, identical within errors to the U-Pb ages, despite the expected 1% theoretical bias between 40Ar/39Ar and U-Pb dates. This overlap could result from (i) rapid cooling of the intrusion (i.e., less than the 0.3 to 0.6 Ma 40Ar/39Ar age uncertainties) from closure temperatures (Tc) of zircon (699-988 °C) to amphibole (500-600 °C); (ii) lead loss affecting the youngest zircons; or (iii) excess argon shifting the plateau ages towards older values. The combination of the 40Ar/39Ar and U/Pb datasets implies that the maximum amount of time PX1 intrusion took to cool below amphibole Tc is 0.8 Ma, suggesting PX1 lifetime of 520,000 to 800,000 Ma. Age disparities among coexisting baddeleyite and zircon (22.10 ± 0.07/0.08/0.15 Ma and 21.58 ± 0.15/0.16/0.31 Ma) in a gabbro sample from the pluton margin suggest complex genetic relationships between phases. Baddeleyite is found preserved in plagioclase cores and crystallized early from low silica activity magma. Zircon crystallized later in a higher silica activity environment and is found in secondary scapolite and is found close to calcite veins, in secondary scapolite that recrystallised from plagioclase. close to calcite veins. Oxygen isotope δ18O values of altered plagioclase are high (+7.7), indicating interaction with fluids derived from host-rock carbonatites. The coexistence of baddeleyite and zircon is ascribed to interaction of the PX1 gabbro with CO2-rich carbonatite-derived fluids released during contact metamorphism.

  3. Mid-infrared absolute spectral responsivity scale based on an absolute cryogenic radiometer and an optical parametric oscillator laser

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Shi, Xueshun; Chen, Haidong; Liu, Yulong; Liu, Changming; Chen, Kunfeng; Li, Ligong; Gan, Haiyong; Ma, Chong

    2016-06-01

    We are reporting on a laser-based absolute spectral responsivity scale in the mid-infrared spectral range. By using a mid-infrared tunable optical parametric oscillator as the laser source, the absolute responsivity scale has been established by calibrating thin-film thermopile detectors against an absolute cryogenic radiometer. The thin-film thermopile detectors can be then used as transfer standard detectors. The extended uncertainty of the absolute spectral responsivity measurement has been analyzed to be 0.58%–0.68% (k  =  2).

  4. Planck 2015 constraints on reionization history

    NASA Astrophysics Data System (ADS)

    Tristram, Matthieu

    2015-08-01

    On behalf of the Planck collaboration, we will show the tightest constraints on cosmic reionization extracted from the CMB polarization at low multipole by Planck.The CMB large scales polarization data can gives strong constraints on the reionization history through the measurement of the reionization optical depth. The Thomson optical depth measured is significantly smaller than previously estimated from CMB polarization data. This result reduces the tension between CMB based analyses and constraints from other astrophysical sources. It highlights the necessity of a deep revision of our view on the history of reionization and the dark age. We also combine constraints from low and high l, in particular from the amplitude of the kinetic Sunyaev Zeld’ovitch effect (kSZ), to derive the time and duration of the reionization epoch. In addition, using both a new two-stage parametrization of the ionization fraction, closer to recent self-regulated simulations, and a non parametric reconstruction, we estimate a more realistic beginning, end, and duration of Reionization.

  5. Uplift of the southern margin of the Central Anatolian Plateau (CAP): age constraints from the youngest marine deposits capping the central Tauride Units in the Gülnar district (Mersin, southern Turkey)

    NASA Astrophysics Data System (ADS)

    Ogretmen, Nazik; Cipollari, Paola; Frezza, Virgilio; Faranda, Costanza; Gliozzi, Elsa; Yıldırım, Cengiz; Radeff, Giuditta; Cosentino, Domenico

    2016-04-01

    In the Gülnar district (Mersin, southern Turkey), Neogene marine deposits unconformably overlie the basement units of the Central Taurides. The age of these marine deposits was classically used to constrain the uplift of the CAP southern margin and, according to the age of the marine deposits cropping out in the Ermenek Basin (Başyayla section), a post-Tortonian age was recently suggested for this event. Indeed, the stratigraphy of the subsiding Adana-Cilicia Basin, to the south of the uplifted CAP southern margin, provides evidence of even younger age (end of the Messinian, ca. 5.45 Ma). Moreover, the stratigraphical architecture of the marine deposits capping the CAP southern margin, which shows an unconformity surface within the late Neogene marine succession, was recently used for defining a multi-phased uplift of the CAP southern margin, with a second uplift phase in the early Calabrian (ca. 1.6 Ma). In the Gülnar area, we sampled the highest marine deposits of the upper Neogene succession that unconformably overlie the basement units of the Central Taurides (Gülnar E section). Biostratigraphical investigations carried out on calcareous nannofossils, benthic and planktonic foraminifera, and ostracods reveal that the Gülnar E section represents the youngest marine deposits, as far known, preserved on top of the uplifted CAP southern margin. These deposits, which unconformably overlie the shallow-water limestones of the Mut Formation (middle-late Miocene), consist mainly of clays and calcareous beds showing a shallowing-upward trend. Five sapropel layers characterize the grey clays of the lowermost part of the section, with an additional possible anoxic event between the second and third sapropel. A spectacular thick slumped-horizon qualifies the uppermost portion of the study section. The Calabrian age of the Gülnar E section is well constrained by the occurrence of different marker species from both calcareous nannofossils and foraminifera. The

  6. Geochemical, zircon U-Pb dating and Sr-Nd-Hf isotopic constraints on the age and petrogenesis of an Early Cretaceous volcanic-intrusive complex at Xiangshan, Southeast China

    NASA Astrophysics Data System (ADS)

    Yang, Shui-Yuan; Jiang, Shao-Yong; Jiang, Yao-Hui; Zhao, Kui-Dong; Fan, Hong-Hai

    2011-01-01

    The Late Mesozoic geology of Southeast China is characterized by extensive Jurassic to Cretaceous magmatism consisting predominantly of granites and rhyolites and subordinate mafic rocks, forming a belt of volcanic-intrusive complexes. The Xiangshan volcanic-intrusive complex is located in the NW region of the belt and mainly contains the following lithologies: rhyodacite and rhyodacitic porphyry, porphyritic lava, granite porphyry with mafic microgranular enclaves, quartz monzonitic porphyry, and lamprophyre dyke. Major and trace-element compositions, zircon U-Pb dating, and Sr-Nd-Hf isotopic compositions have been investigated for these rocks. The precise SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the emplacement of various magmatic units at Xiangshan took place within a short time period of less than 2 Myrs. The stratigraphically oldest rhyodacite yielded a zircon U-Pb age of 135 ± 1 Ma and the overlying rhyodacitic porphyry has an age of 135 ± 1 Ma. Three porphyritic lava samples yielded zircon U-Pb ages of 136 ± 1 Ma, 132 ± 1 Ma, and 135 ± 1 Ma, respectively. Two subvolcanic rocks (granite porphyry) yielded zircon U-Pb ages of 137 ± 1 Ma and 137 ± 1 Ma. A quartz monzonitic porphyry dyke, which represented the final stage of magmatism at Xiangshan, also yielded a zircon U-Pb age of 136 ± 1 Ma. All these newly obtained precise U-Pb ages demonstrate that the entire magmatic activity at Xiangshan was rapid and possibly took place at the peak of extensional tectonics in SE China. The geochemical data indicate that all these samples from the volcanic-intrusive complex have an A-type affinity. Sr-Nd-Hf isotopic data suggest that the Xiangshan volcanic-intrusive complex derived mainly from remelting of Paleo-Mesoproterozoic crust without significant additions of mantle-derived magma. However, the quartz monzonitic porphyry, which has zircon Hf model ages older than the whole-rock Nd model ages, and which has ɛNd(T) value higher than the other rocks

  7. Symbolic Constraint Maintenance Grid

    NASA Technical Reports Server (NTRS)

    James, Mark

    2006-01-01

    Version 3.1 of Symbolic Constraint Maintenance Grid (SCMG) is a software system that provides a general conceptual framework for utilizing pre-existing programming techniques to perform symbolic transformations of data. SCMG also provides a language (and an associated communication method and protocol) for representing constraints on the original non-symbolic data. SCMG provides a facility for exchanging information between numeric and symbolic components without knowing the details of the components themselves. In essence, it integrates symbolic software tools (for diagnosis, prognosis, and planning) with non-artificial-intelligence software. SCMG executes a process of symbolic summarization and monitoring of continuous time series data that are being abstractly represented as symbolic templates of information exchange. This summarization process enables such symbolic- reasoning computing systems as artificial- intelligence planning systems to evaluate the significance and effects of channels of data more efficiently than would otherwise be possible. As a result of the increased efficiency in representation, reasoning software can monitor more channels and is thus able to perform monitoring and control functions more effectively.

  8. Absolute properties of the eclipsing binary star AP Andromedae

    SciTech Connect

    Sandberg Lacy, Claud H.; Torres, Guillermo; Fekel, Francis C.; Muterspaugh, Matthew W. E-mail: gtorres@cfa.harvard.edu E-mail: matthew1@coe.tsuniv.edu

    2014-06-01

    AP And is a well-detached F5 eclipsing binary star for which only a very limited amount of information was available before this publication. We have obtained very extensive measurements of the light curve (19,097 differential V magnitude observations) and a radial velocity curve (83 spectroscopic observations) which allow us to fit orbits and determine the absolute properties of the components very accurately: masses of 1.277 ± 0.004 and 1.251 ± 0.004 M {sub ☉}, radii of 1.233 ± 0.006 and 1.1953 ± 0.005 R {sub ☉}, and temperatures of 6565 ± 150 K and 6495 ± 150 K. The distance to the system is about 400 ± 30 pc. Comparison with the theoretical properties of the stellar evolutionary models of the Yonsei-Yale series of Yi et al. shows good agreement between the observations and the theory at an age of about 500 Myr and a slightly sub-solar metallicity.

  9. Absolute paleointensity from Hawaiian lavas younger than 35 ka

    USGS Publications Warehouse

    Valet, J.-P.; Tric, E.; Herrero-Bervera, E.; Meynadier, L.; Lockwood, J.P.

    1998-01-01

    Paleointensity studies have been conducted in air and in argon atmosphere on nine lava flows with radiocarbon ages distributed between 3.3 and 28.2 ka from the Mauna Loa volcano in the big island of Hawaii. Determinations of paleointensity obtained at eight sites depict the same overall pattern as the previous results for the same period in Hawaii, although the overall average field intensity appears to be lower. Since the present results were determined at higher temperatures than in the previous studies, this discrepancy raises questions regarding the selection of low versus high-temperature segments that are usually made for absolute paleointensity. The virtual dipole moments are similar to those displayed by the worldwide data set obtained from dated lava flows. When averaged within finite time intervals, the worldwide values match nicely the variations of the Sint-200 synthetic record of relative paleointensity and confirm the overall decrease of the dipole field intensity during most of this period. The convergence between the existing records at Hawaii and the rest of the world does not favour the presence of persistent strong non-dipole components beneath Hawaii for this period.

  10. ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR BF DRACONIS

    SciTech Connect

    Sandberg Lacy, Claud H.; Torres, Guillermo; Fekel, Francis C.; Sabby, Jeffrey A.; Claret, Antonio E-mail: gtorres@cfa.harvard.edu E-mail: jsabby@siue.edu

    2012-06-15

    BF Dra is now known to be an eccentric double-lined F6+F6 binary star with relatively deep (0.7 mag) partial eclipses. Previous studies of the system are improved with 7494 differential photometric observations from the URSA WebScope and 9700 from the NFO WebScope, 106 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope and the 1 m coude-feed spectrometer at Kitt Peak National Observatory, and 31 accurate radial velocities from the CfA. Very accurate (better than 0.6%) masses and radii are determined from analysis of the two new light curves and four radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 2.72 Gyr and [Fe/H] = -0.17, and tidal theory correctly confirms that the orbit should still be eccentric. Our observations of BF Dra constrain the convective core overshooting parameter to be larger than about 0.13 H{sub p}. We find, however, that standard tidal theory is unable to match the observed slow rotation rates of the components' surface layers.

  11. Supplementary and Enrichment Series: Absolute Value. Teachers' Commentary. SP-25.

    ERIC Educational Resources Information Center

    Bridgess, M. Philbrick, Ed.

    This is one in a series of manuals for teachers using SMSG high school supplementary materials. The pamphlet includes commentaries on the sections of the student's booklet, answers to the exercises, and sample test questions. Topics covered include addition and multiplication in terms of absolute value, graphs of absolute value in the Cartesian…

  12. Supplementary and Enrichment Series: Absolute Value. SP-24.

    ERIC Educational Resources Information Center

    Bridgess, M. Philbrick, Ed.

    This is one in a series of SMSG supplementary and enrichment pamphlets for high school students. This series is designed to make material for the study of topics of special interest to students readily accessible in classroom quantity. Topics covered include absolute value, addition and multiplication in terms of absolute value, graphs of absolute…

  13. Novalis' Poetic Uncertainty: A "Bildung" with the Absolute

    ERIC Educational Resources Information Center

    Mika, Carl

    2016-01-01

    Novalis, the Early German Romantic poet and philosopher, had at the core of his work a mysterious depiction of the "absolute." The absolute is Novalis' name for a substance that defies precise knowledge yet calls for a tentative and sensitive speculation. How one asserts a truth, represents an object, and sets about encountering things…

  14. Absolute Humidity and the Seasonality of Influenza (Invited)

    NASA Astrophysics Data System (ADS)

    Shaman, J. L.; Pitzer, V.; Viboud, C.; Grenfell, B.; Goldstein, E.; Lipsitch, M.

    2010-12-01

    Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent re-analysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here we show that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. In addition, we show that variations of the basic and effective reproductive numbers for influenza, caused by seasonal changes in absolute humidity, are consistent with the general timing of pandemic influenza outbreaks observed for 2009 A/H1N1 in temperate regions. Indeed, absolute humidity conditions correctly identify the region of the United States vulnerable to a third, wintertime wave of pandemic influenza. These findings suggest that the timing of pandemic influenza outbreaks is controlled by a combination of absolute humidity conditions, levels of susceptibility and changes in population mixing and contact rates.

  15. Absolute Pitch: Effects of Timbre on Note-Naming Ability

    PubMed Central

    Vanzella, Patrícia; Schellenberg, E. Glenn

    2010-01-01

    Background Absolute pitch (AP) is the ability to identify or produce isolated musical tones. It is evident primarily among individuals who started music lessons in early childhood. Because AP requires memory for specific pitches as well as learned associations with verbal labels (i.e., note names), it represents a unique opportunity to study interactions in memory between linguistic and nonlinguistic information. One untested hypothesis is that the pitch of voices may be difficult for AP possessors to identify. A musician's first instrument may also affect performance and extend the sensitive period for acquiring accurate AP. Methods/Principal Findings A large sample of AP possessors was recruited on-line. Participants were required to identity test tones presented in four different timbres: piano, pure tone, natural (sung) voice, and synthesized voice. Note-naming accuracy was better for non-vocal (piano and pure tones) than for vocal (natural and synthesized voices) test tones. This difference could not be attributed solely to vibrato (pitch variation), which was more pronounced in the natural voice than in the synthesized voice. Although starting music lessons by age 7 was associated with enhanced note-naming accuracy, equivalent abilities were evident among listeners who started music lessons on piano at a later age. Conclusions/Significance Because the human voice is inextricably linked to language and meaning, it may be processed automatically by voice-specific mechanisms that interfere with note naming among AP possessors. Lessons on piano or other fixed-pitch instruments appear to enhance AP abilities and to extend the sensitive period for exposure to music in order to develop accurate AP. PMID:21085598

  16. Karst Water System Investigated by Absolute Gravimetry

    NASA Astrophysics Data System (ADS)

    Quinif, Y.; Meus, P.; van Camp, M.; Kaufmann, O.; van Ruymbeke, M.; Vandiepenbeeck, M.; Camelbeeck, T.

    2006-12-01

    The highly anisotropic and heterogeneous hydrogeological characteristics of karst aquifers are difficult to characterize and present challenges for modeling of storage capacities. Little is known about the surface and groundwater interconnection, about the connection between the porous formations and the draining cave and conduits, and about the variability of groundwater volume within the system. Usually, an aquifer is considered as a black box, where water fluxes are monitored as input and output. However, water inflow and outflow are highly variable and cannot be measured directly. A recent project, begun in 2006 sought to constrain the water budget in a Belgian karst aquifer and to assess the porosity and water dynamics, combining absolute gravity (AG) measurements and piezometric levels around the Rochefort cave. The advantage of gravity measurements is that they integrate all the subsystems in the karst system. This is not the case with traditional geophysical tools like boring or monitoring wells, which are soundings affected by their near environment and its heterogeneity. The investigated cave results from the meander cutoff system of the Lomme River. The main inputs are swallow holes of the river crossing the limestone massif. The river is canalized and the karst system is partly disconnected from the hydraulic system. In February and March 2006, when the river spilled over its dyke and sank into the most important swallow hole, this resulted in dramatic and nearly instantaneous increases in the piezometric levels in the cave, reaching up to 13 meters. Meanwhile, gravity increased by 50 and 90 nms-2 in February and March, respectively. A first conclusion is that during these sudden floods, the pores and fine fissures were poorly connected with the enlarged fractures, cave, and conduits. With a rise of 13 meters in the water level and a 5% porosity, a gravity change of 250 nms-2 should have been expected. This moderate gravity variation suggests either a

  17. Absolute pitch in Costa Rica: Distribution of pitch identification ability and implications for its genetic basis.

    PubMed

    Chavarria-Soley, Gabriela

    2016-08-01

    Absolute pitch is the unusual ability to recognize a pitch without an external reference. The current view is that both environmental and genetic factors are involved in the acquisition of the trait. In the present study, 127 adult musicians were subjected to a musical tone identification test. Subjects were university music students and volunteers who responded to a newspaper article. The test consisted of the identification of 40 piano and 40 pure tones. Subjects were classified in three categories according to their pitch naming ability: absolute pitch (AP), high accuracy of tone identification (HA), and non-absolute pitch (non-AP). Both the percentage of correct responses and the mean absolute deviation showed a statistically significant variation between categories. A very clear pattern of higher accuracy for white than for black key notes was observed for the HA and the non-AP groups. Meanwhile, the AP group had an almost perfect pitch naming accuracy for both kinds of tones. Each category presented a very different pattern of deviation around the correct response. The age at the beginning of musical training did not differ between categories. The distribution of pitch identification ability in this study suggests a complex inheritance of the trait. PMID:27586721

  18. Absolute radiometric calibration of advanced remote sensing systems

    NASA Technical Reports Server (NTRS)

    Slater, P. N.

    1982-01-01

    The distinction between the uses of relative and absolute spectroradiometric calibration of remote sensing systems is discussed. The advantages of detector-based absolute calibration are described, and the categories of relative and absolute system calibrations are listed. The limitations and problems associated with three common methods used for the absolute calibration of remote sensing systems are addressed. Two methods are proposed for the in-flight absolute calibration of advanced multispectral linear array systems. One makes use of a sun-illuminated panel in front of the sensor, the radiance of which is monitored by a spectrally flat pyroelectric radiometer. The other uses a large, uniform, high-radiance reference ground surface. The ground and atmospheric measurements required as input to a radiative transfer program to predict the radiance level at the entrance pupil of the orbital sensor are discussed, and the ground instrumentation is described.

  19. Testing the quasi-absolute method in photon activation analysis

    SciTech Connect

    Sun, Z. J.; Wells, D.; Starovoitova, V.; Segebade, C.

    2013-04-19

    In photon activation analysis (PAA), relative methods are widely used because of their accuracy and precision. Absolute methods, which are conducted without any assistance from calibration materials, are seldom applied for the difficulty in obtaining photon flux in measurements. This research is an attempt to perform a new absolute approach in PAA - quasi-absolute method - by retrieving photon flux in the sample through Monte Carlo simulation. With simulated photon flux and database of experimental cross sections, it is possible to calculate the concentration of target elements in the sample directly. The QA/QC procedures to solidify the research are discussed in detail. Our results show that the accuracy of the method for certain elements is close to a useful level in practice. Furthermore, the future results from the quasi-absolute method can also serve as a validation technique for experimental data on cross sections. The quasi-absolute method looks promising.

  20. Learning in the temporal bisection task: Relative or absolute?

    PubMed

    de Carvalho, Marilia Pinheiro; Machado, Armando; Tonneau, François

    2016-01-01

    We examined whether temporal learning in a bisection task is absolute or relational. Eight pigeons learned to choose a red key after a t-seconds sample and a green key after a 3t-seconds sample. To determine whether they had learned a relative mapping (short→Red, long→Green) or an absolute mapping (t-seconds→Red, 3t-seconds→Green), the pigeons then learned a series of new discriminations in which either the relative or the absolute mapping was maintained. Results showed that the generalization gradient obtained at the end of a discrimination predicted the pattern of choices made during the first session of a new discrimination. Moreover, most acquisition curves and generalization gradients were consistent with the predictions of the learning-to-time model, a Spencean model that instantiates absolute learning with temporal generalization. In the bisection task, the basis of temporal discrimination seems to be absolute, not relational. PMID:26752233

  1. Constraints on ice volume changes of the East Antarctic Ice Sheet and Ross Ice Shelf since the LGM based on cosmogenic exposure ages from Darwin-Hatherton outlet glaciers.

    NASA Astrophysics Data System (ADS)

    Fink, David; Joy, Kurt; Storey, Bryan

    2013-04-01

    At the Last Glacial Maximum and during Termination-1 (~20-10 ka), marine evidence indicates that the grounding line of the West Antarctic Ice Sheet (WAIS) advanced northwards into the Ross Ice Shelf (RIS), blocking drainage of the Darwin and Hatherton outlet glaciers through the Transantarctic Mountains (TM) resulting in significant downstream thickening of glacier profiles. These outlet glaciers provide geological and glaciological records of EAIS expansion through the TMs as well as WAIS fluctuations which together suggest an LGM thickness of ~800 m lager than today at their confluence with the Ross Embayment. About 80 cosmogenic 10Be and 26Al exposure ages of erratics from 3 locations flanking the Hatherton Glacier (Dubris Valley near the EAIS source region, from Lake Wellman at its midpoint and Diamond Hill at its terminus) taken along transects covering 800 m in differential elevation from ice-sheet contact to mountain peaks documents 2.5 Ma of ice volume evolution of the Hatherton allowing a reconstruction of its quaternary paleo-ice surface. Pleistocene ice thickness is some 800 to 400 meters thicker between 2.5 to 0.5 Ma years ago than today . However at all 3 locations, exposure ages of mapped glacial drifts younger than 0.5 Ma at lower elevations down to current ice margin did not show any evidence for a distinct LGM advance. At Lake Wellman a cluster of mid-elevation moraine boulders from the Britannia Drift, previously taken to demarcate the LGM advance, have exposure ages ranging from 30 to 40 ka. At Dubris Valley, the same drift returned ages of 120-125 ka. At Diamond Hill, the confluence of the Darwin Glacier and RIS, two transects were sampled that cover an altitude range of 1100 meters. Cosmogenic dates show a similar trend to that seen further upvalley - the WAIS was approximately 900 meters thicker than the current Rose Ice Shelf configuration at ~1.5Ma and with only minor advances in the last 10ka and an absence of any LGM ages. The absence of a

  2. Zirconolite, zircon and monazite-(Ce) U-Th-Pb age constraints on the emplacement, deformation and alteration history of the Cummins Range Carbonatite Complex, Halls Creek Orogen, Kimberley region, Western Australia

    NASA Astrophysics Data System (ADS)

    Downes, Peter J.; Dunkley, Daniel J.; Fletcher, Ian R.; McNaughton, Neal J.; Rasmussen, Birger; Jaques, A. Lynton; Verrall, Michael; Sweetapple, Marcus T.

    2016-04-01

    In situ SHRIMP U-Pb dating of zirconolite in clinopyroxenite from the Cummins Range Carbonatite Complex, situated in the southern Halls Creek Orogen, Kimberley region, Western Australia, has provided a reliable 207Pb/206Pb age of emplacement of 1009 ± 16 Ma. Variably metamict and recrystallised zircons from co-magmatic carbonatites, including a megacryst ~1.5 cm long, gave a range of ages from ~1043-998 Ma, reflecting partial isotopic resetting during post-emplacement deformation and alteration. Monazite-(Ce) in a strongly foliated dolomite carbonatite produced U-Th-Pb dates ranging from ~900-590 Ma. Although the monazite-(Ce) data cannot give any definitive ages, they clearly reflect a long history of hydrothermal alteration/recrystallisation, over at least 300 million years. This is consistent with the apparent resetting of the Rb-Sr and K-Ar isotopic systems by a post-emplacement thermal event at ~900 Ma during the intracratonic Yampi Orogeny. The emplacement of the Cummins Range Carbonatite Complex probably resulted from the reactivation of a deep crustal structure within the Halls Creek Orogen during the amalgamation of Proterozoic Australia with Rodinia over the period ~1000-950 Ma. This may have allowed an alkaline carbonated silicate magma that was parental to the Cummins Range carbonatites, and generated by redox and/or decompression partial melting of the asthenospheric mantle, to ascend from the base of the continental lithosphere along the lithospheric discontinuity constituted by the southern edge of the Halls Creek Orogen. There is no evidence of a link between the emplacement of the Cummins Range Carbonatite Complex and mafic large igneous province magmatism indicative of mantle plume activity. Rather, patterns of Proterozoic alkaline magmatism in the Kimberley Craton may have been controlled by changing plate motions during the Nuna-Rodinia supercontinent cycles (~1200-800 Ma).

  3. Plate interactions of Laurussia and Gondwana during the formation of Pangea- Constraints by U-Pb LA-SF-ICP-MS detrital zircon ages of Devonian and Early Carboniferous siliciclastics of the Rheinisches Schiefergebirge (Rhenohercynian zone, Central European

    NASA Astrophysics Data System (ADS)

    Eckelmann, Katja; Nesbor, Heinz-Dieter; Königshof, Peter; Linnemann, Ulf; Hofmann, Mandy; Lange, Jan-Michael; Sagawe, Anja

    2013-04-01

    The Rhenohercynian zone of the Central European Variscides contains top-NW thrusted rock complexes in the area of the Hörre nappe. Further to the north, par-authochthonous volcano-sedimentary complexes of the Lahn and Dill-Eder synclines occur. In our paper, a representative data set of U-Pb LA-SF ICP-MS ages of 1228 detrital zircon grains of Devonian and Lower Carboniferous sandstones from both areas is presented. The data constrain the Middle to Upper Devonian and the Lower Carboniferous siliciclastic and volcano-sedimentary complexes of the Hörre nappe to be allochtonous. The cluster of U-Pb ages of detrital zircon grains point to a provenance of the debris from the Saxo-Thuringian zone and rock complexes of the Mid-German Crystalline zone, which were formerly related to the latter one. A long-distance top-NW directed transport of the nappe complex in the Hörre nappe is required by our new data set. The zircon populations derived from the Saxo-Thuringian zone are representative for a Gondwanan hinterland and characterised by age clusters of ~530-700 Ma, ~1,8-2.2 Ga, ~2.5-2.7 Ga, and ~3.0-3.4 Ga. In a palaeogeographic view, the Saxo-Thuringian zone formed during Devonian to Lower Carboniferous time at the southern margin of the Rheic Ocean. A Lower Devonian sandstone sample from the par-authochtonous Lahn-Dill-Eder syncline shows a provenance, which is representative for Laurussia. Most of that debris seems to be derived from Baltica and Avalonia, two important parts of Laurussia. U-Pb zircon ages cluster at ~ 400-450 Ma, 540-650 Ma, 1.0-1.2 Ga, ~1.4-1.5 Ga, ~1.7-2.2 Ga, and 2.3-2.9 Ga. In terms of a palaeogeographic relation, these samples represent a sedimentary unit which was deposited at the northern margin of the Rheic Ocean at the edge of Laurussia facing to the south. Our data set constrains a top-SE directed subduction of the oceanic crust of the Rheic Ocean during its final closure and the formation of supercontinent Pangea.

  4. 40Ar-39Ar age constraint on deformation and brittle-ductile transition of the Main Central Thrust and the South Tibetan Detachment zone from Dhauliganga valley, Garhwal Himalaya, India

    NASA Astrophysics Data System (ADS)

    Sen, Koushik; Chaudhury, Reetam; Pfänder, Jörg

    2015-08-01

    40Ar-39Ar data from two sets of mylonitic two-mica granites present in the Main Central Thrust (MCT) and one leucogranite from the South Tibetan Detachment (STD) of Dhauliganga valley, Garhwal Himalaya are presented. The MCT and the STD bound the High Himalayan Crystallines (HHC) and are believed to facilitate its extrusion. Field evidence of ductile deformation in the form of tight isoclinal folding and brittle deformation in the form of back thrusts and transverse fractures are observed. The STD zone shows evidence of pervasive migration of leucogranitic melt through north dipping extensional shear zones. The ∼19.5 Ma old Malari Leucogranite, present adjacent to the STD zone, experienced ductile and brittle deformation related to the tectonics of the STD. Muscovite analysis from the Malari leucogranite gives a cooling age of ∼15.2 Ma suggesting that ductile deformation in the STD zone may have ceased by ∼15 Ma. 40Ar-39Ar chronology of biotite from two mylonitic granites of the MCT yields cooling ages of 10.8 Ma and 9.7 Ma, which we correlate with activity of the MCT at ∼10 Ma that caused rapid exhumation of the HHC. 40Ar-39Ar ages of 6.4 Ma and 6.2 Ma from white mica represent newly crystallized white mica post-dating biotite cooling and indicate late stage deformation. It is inferred that, as the HHC wedge started to exhume and erode rapidly along the MCT zone at ∼10 Ma, the taper angle of the Himalayan wedge decreased to a 'sub-critical' stage. To regain the critical taper angle, the wedge underwent internal deformation in the form of back thrusts and duplex structures. Comparison of our data with earlier results from other sections of the MCT helps us envisage that the ∼6 Ma white mica ages can be correlated with this internal deformation event and also with the transition of deformation regime in the MCT zone from ductile to brittle.

  5. Detrital zircon U-Pb ages of the Proterozoic metaclastic-sedimentary rocks in Hainan Province of South China: New constraints on the depositional time, source area, and tectonic setting of the Shilu Fe-Co-Cu ore district

    NASA Astrophysics Data System (ADS)

    Wang, Zhilin; Xu, Deru; Hu, Guocheng; Yu, Liangliang; Wu, Chuanjun; Zhang, Zhaochong; Cai, Jianxin; Shan, Qiang; Hou, Maozhou; Chen, Huayong

    2015-12-01

    The Shilu Fe-Co-Cu ore district, located at Hainan Province of South China, is well known for high-grade hematite-rich Fe ores and also two Precambrian host successions, i.e. the Shilu Group and the overlying Shihuiding Formation. This district has been interpreted as a banded iron formation (BIF) deposit-type, but its depositional time, source area and depositional setting have been in debate due to poor geochronological work. Detrital zircon U-Pb dating aided by cathodoluminescence imaging has been carried out on both the Shilu Group and Shihuiding Formation. Most of the zircon grains from both the successions are subrounded to rounded in morphology and have age spectra between 2000 Ma and 900 Ma with two predominant peaks at ca. 1460-1340 Ma and 1070 Ma, and three subordinate peaks at ca. 1740-1660 Ma, 1220 Ma and 970 Ma. The similar age distribution suggests the same depositional system for both successions. Linked to the geological and paleontological signatures, the Shihuiding Formation is better re-interpreted as the top, i.e. Seventh member of the Shilu Group, rather than a distinct Formation. The youngest statistical zircon age peaks for both successions, i.e. ca. 1070-970 Ma may define the maximum depositional time of the Shilu Group and interbedded BIFs. At least two erosional sources are required for deposition of the studied detrital zircons, with one proximal to provide the least abraded zircons and the other distal or recycled to offer the largely abraded zircons. The predominance of rounded or subrounded zircons over angular zircons probably implies a relatively stable tectonic setting during deposition. Given the Precambrian tectonics of Hainan Island, a retro-arc foreland basin is proposed for the deposition of the Shilu Group and interbedded BIFs. In comparison with those from the South China and other typical Grenvillian orogens, the detrital zircon age populations reveal that Hainan Island had crystalline basement similar to neither the Yangtze

  6. Neural constraints on learning

    PubMed Central

    Sadtler, Patrick T.; Quick, Kristin M.; Golub, Matthew D.; Chase, Steven M.; Ryu, Stephen I.; Tyler-Kabara, Elizabeth C.; Yu, Byron M.; Batista, Aaron P.

    2014-01-01

    Motor, sensory, and cognitive learning require networks of neurons to generate new activity patterns. Because some behaviors are easier to learn than others1,2, we wondered if some neural activity patterns are easier to generate than others. We asked whether the existing network constrains the patterns that a subset of its neurons is capable of exhibiting, and if so, what principles define the constraint. We employed a closed-loop intracortical brain-computer interface (BCI) learning paradigm in which Rhesus monkeys controlled a computer cursor by modulating neural activity patterns in primary motor cortex. Using the BCI paradigm, we could specify and alter how neural activity mapped to cursor velocity. At the start of each session, we observed the characteristic activity patterns of the recorded neural population. These patterns comprise a low-dimensional space (termed the intrinsic manifold, or IM) within the high-dimensional neural firing rate space. They presumably reflect constraints imposed by the underlying neural circuitry. We found that the animals could readily learn to proficiently control the cursor using neural activity patterns that were within the IM. However, animals were less able to learn to proficiently control the cursor using activity patterns that were outside of the IM. This result suggests that the existing structure of a network can shape learning. On the timescale of hours, it appears to be difficult to learn to generate neural activity patterns that are not consistent with the existing network structure. These findings offer a network-level explanation for the observation that we are more readily able to learn new skills when they are related to the skills that we already possess3,4. PMID:25164754

  7. Neural constraints on learning.

    PubMed

    Sadtler, Patrick T; Quick, Kristin M; Golub, Matthew D; Chase, Steven M; Ryu, Stephen I; Tyler-Kabara, Elizabeth C; Yu, Byron M; Batista, Aaron P

    2014-08-28

    Learning, whether motor, sensory or cognitive, requires networks of neurons to generate new activity patterns. As some behaviours are easier to learn than others, we asked if some neural activity patterns are easier to generate than others. Here we investigate whether an existing network constrains the patterns that a subset of its neurons is capable of exhibiting, and if so, what principles define this constraint. We employed a closed-loop intracortical brain-computer interface learning paradigm in which Rhesus macaques (Macaca mulatta) controlled a computer cursor by modulating neural activity patterns in the primary motor cortex. Using the brain-computer interface paradigm, we could specify and alter how neural activity mapped to cursor velocity. At the start of each session, we observed the characteristic activity patterns of the recorded neural population. The activity of a neural population can be represented in a high-dimensional space (termed the neural space), wherein each dimension corresponds to the activity of one neuron. These characteristic activity patterns comprise a low-dimensional subspace (termed the intrinsic manifold) within the neural space. The intrinsic manifold presumably reflects constraints imposed by the underlying neural circuitry. Here we show that the animals could readily learn to proficiently control the cursor using neural activity patterns that were within the intrinsic manifold. However, animals were less able to learn to proficiently control the cursor using activity patterns that were outside of the intrinsic manifold. These results suggest that the existing structure of a network can shape learning. On a timescale of hours, it seems to be difficult to learn to generate neural activity patterns that are not consistent with the existing network structure. These findings offer a network-level explanation for the observation that we are more readily able to learn new skills when they are related to the skills that we already

  8. Late Jurassic-Early Cretaceous radiolarian age constraints from the sedimentary cover of the Amasia ophiolite (NW Armenia), at the junction between the Izmir-Ankara-Erzinçan and Sevan-Hakari suture zones

    NASA Astrophysics Data System (ADS)

    Danelian, T.; Asatryan, G.; Galoyan, Gh.; Sahakyan, L.; Stepanyan, J.

    2016-01-01

    The Amasia ophiolite, situated at the northernmost corner of Armenia, is part of the Sevan-Hakari suture zone which links with the Izmir-Ankara-Erzinçan suture zone in northern Turkey. Three new radiolarian assemblages have been extracted from siliceous sedimentary rocks that accumulated on the Amasia ophiolite in an oceanic setting. Two of these assemblages were extracted from red-brownish bedded cherts overlying basaltic lavas; one of these is likely to be middle Oxfordian to early Kimmeridgian in age, while the second correlates with the Berriasian. Similar time-equivalent lava-chert sequences have been dated recently using radiolarians from the Stepanavan, Vedi and Sevan ophiolite units, where they are considered to relate to submarine volcanic activity in the back-arc marginal basin in which the Armenian ophiolites were formed. The third radiolarian assemblage, of late Barremian age, was extracted from a more than 15-m-thick volcaniclastic-chert sequence. The related volcanic activity is likely to have been subaerial and probably relates to the formation of an oceanic volcanic plateau; no Cretaceous subaerial volcanism has been previously recorded in the Lesser Caucasus area.

  9. Early Carboniferous (Viséan) emplacement of the collisional Kłodzko-Złoty Stok granitoids (Sudetes, SW Poland): constraints from geochemical data and zircon U-Pb ages

    NASA Astrophysics Data System (ADS)

    Mikulski, Stanisław Z.; Williams, Ian S.; Bagiński, Bogusław

    2013-06-01

    Sensitive high-resolution ion microprobe zircon U-Pb dating and geochemical data of igneous rocks from the composite Kłodzko-Złoty Stok (KZS) Granite Pluton, Sudetic Block, indicate that the granitoids represent an Early Carboniferous Viséan phase of Variscan metaluminous, high-K, I-type, syn-collisional granite magmatism within the Saxothuringian Zone of the Central European Variscides. Igneous zircon records hypabyssal magmatism that produced various granitoids and lamprophyre (spessartite) emplaced from ca. 340 to 331 Ma. The KZS granitoids have compositions ranging from granodiorite to monzonite, low A/CNK ratios (<1), and are associated with abundant mafic members. Most of them are alkaline, highly potassic, and moderately evolved. The major and trace element contents of the KZS granitoids suggest geochemical heterogeneity, and the hybrid nature of magmas derived from a range of sources in the middle crust, with a strong input of material from the upper mantle. Mixing of magmas of mantle origin with high-K material from partly melted continental crust was probably a more important factor than fractional crystallization, in controlling the evolution of the magmas. The mean Pb-U ages of the main population of igneous zircon from a quartz monzodiorite (Żelazno) and hornblende monzonite (Droszków) are 340.2 ± 2.5 Ma and 339.5 ± 3.1 Ma, respectively. A slightly younger biotite-hornblende granodiorite from Chwalisław, 336.7 ± 2.5 Ma, was cut by a spessartite dyke at 333.1 ± 3.1 Ma. This indicates that mafic magmas were immediately intruded into fractured, probably incompletely solidified, granodiorites. The lamprophyric dyke also contains igneous zircon of Neoproterozoic age, 566.3 ± 6.4 Ma, typical of the crust in the Saxothuringian Zone. Tonalite from Ptasznik Hill near Droszków is of similar age to the spessartite, 331.5 ± 2.6 Ma. High REE contents in the tonalite and its igneous zircon indicate advanced differentiation of granitic magma, producing a

  10. Petrogenesis of the Yaochong granite and Mo deposit, Western Dabie orogen, eastern-central China: Constraints from zircon U-Pb and molybdenite Re-Os ages, whole-rock geochemistry and Sr-Nd-Pb-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Xu, Zhaowen; Qiu, Wenhong; Li, Chao; Yu, Yang; Wang, Hao; Su, Yang

    2015-05-01

    The Dabie orogen is among the most famous continent-continent collisional orogenic belts in the world, and is characterized by intensive post-collisional extension, magmatism and Mo mineralization. However, the genetic links between the mineralization and the geodynamic evolution of the orogen remain unresolved. In this paper, the Yaochong Mo deposit and its associated granitic stocks were investigated to elucidate this issue. Our new zircon U-Pb ages yielded an Early Cretaceous age (133.3 ± 1.3 Ma) for the Yaochong granite, and our molybdenite Re-Os dating gave a similar age (135 ± 1 Ma) for the Mo deposit. The Yaochong stock is characterized by high silica and alkali but low Mg, Fe and Ca. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: Rb, K, Th and U), but strongly depleted in heavy REEs, and high field strength elements (HFSEs: Nb, Ta, Ti and Y). The Yaochong granite has initial 87Sr/86Sr ratios of 0.7087-0.7096, and Pb isotopic ratios of (206Pb/204Pb)i = 16.599-16.704, (207Pb/204Pb)i = 15.170-15.618 and (208Pb/204Pb)i = 36.376-38.248. The granite has εNd(t) of -18.0 to -16.3 and εHf(t) values of -26.5 to -20.0. All these data indicate that the Yaochong granite is a high-K calc-alkaline fractionated I-type granite, and may have originated from partial melting of the thickened Yangtze continental crust. The Mo ores also show low radiogenic Pb isotopes similar to the Yaochong stock. Medium Re content in molybdenite (21.8-74.8 ppm) also suggests that the ore-forming materials were derived from the thickened lower crust with possibly minor mixing with the mantle. Similar to the Eastern Dabie orogen, the thickened crust beneath the Western Dabie orogen may also have experienced tectonic collapse, which may have exerted fundamental geodynamic controls on the two-stage Mo mineralization in the region.

  11. 10Be dating of the Main Terrace level in the Amblève valley (Ardennes, Belgium): new age constraint on the archaeological and palaeontological filling of the Belle-Roche palaeokarst

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Bourlès, Didier L.; Braucher, Régis; Siame, Lionel; Cordy, Jean-Marie; Demoulin, Alain

    2014-05-01

    It is still disputed whether very old archaeological and palaeontological remains found in the Belle-Roche palaeocave (eastern Belgium) pertain to the Early (˜1 Ma) or Middle (˜0.5 Ma) Pleistocene. Here, in situ-produced cosmogenic 10Be concentrations from a depth profile in nearby sediments of the Belle-Roche terrace (Amblève Main Terrace level) are used as an indirect solution of this chronological issue. The distribution of 10Be concentrations in the upper 3 m of this profile displays the theoretically expected exponential decrease with depth. Assuming a single exposure episode, we obtain a best fit age of 222.5±31 ka for the time of terrace abandonment. However, below 3 m, the 10Be concentrations show a marked progressive increase with depth. This distinctive cosmogenic signal is interpreted as the result of slow aggradation of the fluvial deposits over a lengthy interval. Modelling of the whole profile thus suggests that the onset of the terrace formation occurred at around 550 ka, with a sediment accumulation rate of ˜20 mm/ka. Based on two slightly different reconstructions of the geomorphic evolution of the area and a discussion of the temporal link between the cave and Main Terrace levels, we conclude that the fossil-bearing layers in the palaeokarst pertain most probably to MIS 14-13 (or possibly MIS 12-11) and the artifact-bearing layer to MIS 13 (or possibly MIS 11). This age estimate for the large mammal association identified in the Belle-Roche palaeokarst and the attribution to MIS 14-13 of a similar fauna found in the lowermost fossiliferous layers of the Caune de l'Arago (Tautavel) are in mutual support. Our results therefore confirm the status of the Belle-Roche site as a reference site for the Cromerian mammal association and the Early Palaeolithic industry in NW Europe.

  12. Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters from their RR Lyrae and Non-variable Horizontal-branch Stars. I. M3, M15, and M92

    NASA Astrophysics Data System (ADS)

    VandenBerg, Don A.; Denissenkov, P. A.; Catelan, Márcio

    2016-08-01

    Up-to-date isochrones, zero-age horizontal-branch (ZAHB) loci, and evolutionary tracks for core He-burning stars are applied to the color–magnitude diagrams of M3, M15, and M92, focusing in particular on their RR Lyrae populations. Periods for the ab- and c-type variables are calculated using the latest theoretical calibrations of {log} {P}{ab} and {log} {P}c as a function of luminosity, mass, effective temperature ({T}{{eff}}), and metallicity. Our models are generally able to reproduce the measured periods to well within the uncertainties implied by the stellar properties on which pulsation periods depend, as well as the mean periods and cluster-to-cluster differences in < {P}{ab}> and < {P}c> , on the assumption of well-supported values of E(B-V), {(m-M)}V, and [Fe/H]. While many of RR Lyrae in M3 lie close to the same ZAHB that fits the faintest horizontal-branch (HB) stars at bluer or redder colors, the M92 variables are all significantly evolved stars from ZAHB locations on the blue side of the instability strip. M15 appears to contain a similar population of HB stars as M92, along with additional helium-enhanced populations not present in the latter which comprise most of its RR Lyrae stars. The large number of variables in M15 and the similarity of the observed values of < {P}{ab}> and < {P}c> in M15 and M92 can be explained by HB models that allow for variations in Y. Similar ages (∼12.5 Gyr) are found for all three clusters, making them significantly younger than the field halo subgiant HD 140283. Our analysis suggests a preference for stellar models that take diffusive processes into account.

  13. Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters from their RR Lyrae and Non-variable Horizontal-branch Stars. I. M3, M15, and M92

    NASA Astrophysics Data System (ADS)

    VandenBerg, Don A.; Denissenkov, P. A.; Catelan, Márcio

    2016-08-01

    Up-to-date isochrones, zero-age horizontal-branch (ZAHB) loci, and evolutionary tracks for core He-burning stars are applied to the color–magnitude diagrams of M3, M15, and M92, focusing in particular on their RR Lyrae populations. Periods for the ab- and c-type variables are calculated using the latest theoretical calibrations of {log} {P}{ab} and {log} {P}c as a function of luminosity, mass, effective temperature ({T}{{eff}}), and metallicity. Our models are generally able to reproduce the measured periods to well within the uncertainties implied by the stellar properties on which pulsation periods depend, as well as the mean periods and cluster-to-cluster differences in < {P}{ab}> and < {P}c> , on the assumption of well-supported values of E(B-V), {(m-M)}V, and [Fe/H]. While many of RR Lyrae in M3 lie close to the same ZAHB that fits the faintest horizontal-branch (HB) stars at bluer or redder colors, the M92 variables are all significantly evolved stars from ZAHB locations on the blue side of the instability strip. M15 appears to contain a similar population of HB stars as M92, along with additional helium-enhanced populations not present in the latter which comprise most of its RR Lyrae stars. The large number of variables in M15 and the similarity of the observed values of < {P}{ab}> and < {P}c> in M15 and M92 can be explained by HB models that allow for variations in Y. Similar ages (˜12.5 Gyr) are found for all three clusters, making them significantly younger than the field halo subgiant HD 140283. Our analysis suggests a preference for stellar models that take diffusive processes into account.

  14. Mini-implants and miniplates generate sub-absolute and absolute anchorage

    PubMed Central

    Consolaro, Alberto

    2014-01-01

    The functional demand imposed on bone promotes changes in the spatial properties of osteocytes as well as in their extensions uniformly distributed throughout the mineralized surface. Once spatial deformation is established, osteocytes create the need for structural adaptations that result in bone formation and resorption that happen to meet the functional demands. The endosteum and the periosteum are the effectors responsible for stimulating adaptive osteocytes in the inner and outer surfaces.Changes in shape, volume and position of the jaws as a result of skeletal correction of the maxilla and mandible require anchorage to allow bone remodeling to redefine morphology, esthetics and function as a result of spatial deformation conducted by orthodontic appliances. Examining the degree of changes in shape, volume and structural relationship of areas where mini-implants and miniplates are placed allows us to classify mini-implants as devices of subabsolute anchorage and miniplates as devices of absolute anchorage. PMID:25162561

  15. Absolute brightness temperature measurements at 2.1-mm wavelength

    NASA Technical Reports Server (NTRS)

    Ulich, B. L.

    1974-01-01

    Absolute measurements of the brightness temperatures of the Sun, new Moon, Venus, Mars, Jupiter, Saturn, and Uranus, and of the flux density of DR21 at 2.1-mm wavelength are reported. Relative measurements at 3.5-mm wavelength are also preented which resolve the absolute calibration discrepancy between The University of Texas 16-ft radio telescope and the Aerospace Corporation 15-ft antenna. The use of the bright planets and DR21 as absolute calibration sources at millimeter wavelengths is discussed in the light of recent observations.

  16. Absolute Antenna Calibration at the US National Geodetic Survey

    NASA Astrophysics Data System (ADS)

    Mader, G. L.; Bilich, A. L.

    2012-12-01

    Geodetic GNSS applications routinely demand millimeter precision and extremely high levels of accuracy. To achieve these accuracies, measurement and instrument biases at the centimeter to millimeter level must be understood. One of these biases is the antenna phase center, the apparent point of signal reception for a GNSS antenna. It has been well established that phase center patterns differ between antenna models and manufacturers; additional research suggests that the addition of a radome or the choice of antenna mount can significantly alter those a priori phase center patterns. For the more demanding GNSS positioning applications and especially in cases of mixed-antenna networks, it is all the more important to know antenna phase center variations as a function of both elevation and azimuth in the antenna reference frame and incorporate these models into analysis software. Determination of antenna phase center behavior is known as "antenna calibration". Since 1994, NGS has computed relative antenna calibrations for more than 350 antennas. In recent years, the geodetic community has moved to absolute calibrations - the IGS adopted absolute antenna phase center calibrations in 2006 for use in their orbit and clock products, and NGS's CORS group began using absolute antenna calibration upon the release of the new CORS coordinates in IGS08 epoch 2005.00 and NAD 83(2011,MA11,PA11) epoch 2010.00. Although NGS relative calibrations can be and have been converted to absolute, it is considered best practice to independently measure phase center characteristics in an absolute sense. Consequently, NGS has developed and operates an absolute calibration system. These absolute antenna calibrations accommodate the demand for greater accuracy and for 2-dimensional (elevation and azimuth) parameterization. NGS will continue to provide calibration values via the NGS web site www.ngs.noaa.gov/ANTCAL, and will publish calibrations in the ANTEX format as well as the legacy ANTINFO

  17. The absolute chronology and thermal processing of solids in the solar protoplanetary disk.

    PubMed

    Connelly, James N; Bizzarro, Martin; Krot, Alexander N; Nordlund, Åke; Wielandt, Daniel; Ivanova, Marina A

    2012-11-01

    Transient heating events that formed calcium-aluminum-rich inclusions (CAIs) and chondrules are fundamental processes in the evolution of the solar protoplanetary disk, but their chronology is not understood. Using U-corrected Pb-Pb dating, we determined absolute ages of individual CAIs and chondrules from primitive meteorites. CAIs define a brief formation interval corresponding to an age of 4567.30 ± 0.16 million years (My), whereas chondrule ages range from 4567.32 ± 0.42 to 4564.71 ± 0.30 My. These data refute the long-held view of an age gap between CAIs and chondrules and, instead, indicate that chondrule formation started contemporaneously with CAIs and lasted ~3 My. This time scale is similar to disk lifetimes inferred from astronomical observations, suggesting that the formation of CAIs and chondrules reflects a process intrinsically linked to the secular evolution of accretionary disks. PMID:23118187

  18. Seismological Constraints on Geodynamics

    NASA Astrophysics Data System (ADS)

    Lomnitz, C.

    2004-12-01

    Earth is an open thermodynamic system radiating heat energy into space. A transition from geostatic earth models such as PREM to geodynamical models is needed. We discuss possible thermodynamic constraints on the variables that govern the distribution of forces and flows in the deep Earth. In this paper we assume that the temperature distribution is time-invariant, so that all flows vanish at steady state except for the heat flow Jq per unit area (Kuiken, 1994). Superscript 0 will refer to the steady state while x denotes the excited state of the system. We may write σ 0=(J{q}0ṡX{q}0)/T where Xq is the conjugate force corresponding to Jq, and σ is the rate of entropy production per unit volume. Consider now what happens after the occurrence of an earthquake at time t=0 and location (0,0,0). The earthquake introduces a stress drop Δ P(x,y,z) at all points of the system. Response flows are directed along the gradients toward the epicentral area, and the entropy production will increase with time as (Prigogine, 1947) σ x(t)=σ 0+α {1}/(t+β )+α {2}/(t+β )2+etc A seismological constraint on the parameters may be obtained from Omori's empirical relation N(t)=p/(t+q) where N(t) is the number of aftershocks at time t following the main shock. It may be assumed that p/q\\sim\\alpha_{1}/\\beta times a constant. Another useful constraint is the Mexican-hat geometry of the seismic transient as obtained e.g. from InSAR radar interferometry. For strike-slip events such as Landers the distribution of \\DeltaP is quadrantal, and an oval-shaped seismicity gap develops about the epicenter. A weak outer triggering maxiμm is found at a distance of about 17 fault lengths. Such patterns may be extracted from earthquake catalogs by statistical analysis (Lomnitz, 1996). Finally, the energy of the perturbation must be at least equal to the recovery energy. The total energy expended in an aftershock sequence can be found approximately by integrating the local contribution over

  19. Constraints on ice volume changes of the WAIS and Ross Ice Shelf since the LGM based on cosmogenic exposure ages in the Darwin-Hatherton glacial system of the Transantarctic Mountains

    NASA Astrophysics Data System (ADS)

    Fink, David; Storey, Bryan; Hood, David; Joy, Kurt; Shulmeister, James

    2010-05-01

    glacially transported debris. Our glacial geomorphic survey from ice sheet contact edge (~850 masl) to mountain peak at 1600 masl together with a suite of 10Be and 26Al exposure ages, documents a pre-LGM ice volume at least 800 meters thicker than current ice levels which was established at least 2 million years ago. However a complex history of exposure and re-exposure of the ice free regions in this area is seen in accordance with advance and retreat of the ice sheets that feeds into the Darwin -Hatherton system. A cluster of mid-altitude boulders, located below a prominent moraine feature mapped previously as demarcating the LGM ice advance limits, have exposure ages ranging from 30 to 40 ka. Exposure ages for boulders just above the ice contact range from 1to 19 ka and allow an estimate of inheritance. Hence, we conclude that LGM ice volume was not as large as previously estimated and actually little different from what is observed today. These results raise rather serious questions about the implications of a reduced WAIS at the LGM, its effect on the development of the Ross Ice Shelf, and how the Antarctic ice sheets respond to global warming. J. O. Stone et al., Science v299, 99 (2003). A. Mackintosh, D. White, D. Fink, D. Gore et al, Geology, v 35; 551-554 (2007).

  20. U-Pb zircon, geochemical and Sr-Nd-Hf-O isotopic constraints on age and origin of the ore-bearing intrusions from the Nurkazgan porphyry Cu-Au deposit in Kazakhstan

    NASA Astrophysics Data System (ADS)

    Shen, Ping; Pan, Hongdi; Seitmuratova, Eleonora; Jakupova, Sholpan

    2016-02-01

    Nurkazgan, located in northeastern Kazakhstan, is a super-large porphyry Cu-Au deposit with 3.9 Mt metal copper and 229 tonnage gold. We report in situ zircon U-Pb age and Hf-O isotope data, whole rock geochemical and Sr-Nd isotopic data for the ore-bearing intrusions from the Nurkazgan deposit. The ore-bearing intrusions include the granodiorite porphyry, quartz diorite porphyry, quartz diorite, and diorite. Secondary ion mass spectrometry (SIMS) zircon U-Pb dating indicates that the granodiorite porphyry and quartz diorite porphyry emplaced at 440 ± 3 Ma and 437 ± 3 Ma, respectively. All host rocks have low initial 87Sr/86Sr ratios (0.70338-0.70439), high whole-rock εNd(t) values (+5.9 to +6.3) and very high zircon εHf(t) values (+13.4 to +16.5), young whole-rock Nd and zircon Hf model ages, and consistent and slightly high zircon O values (+5.7 to +6.7), indicating that the ore-bearing magmas derived from the mantle without old continental crust involvement and without marked sediment contamination during magma emplacement. The granodiorite porphyry and quartz diorite porphyry are enriched in large ion lithophile elements (LILE) and light rare earth elements (LREE) and depleted in high-field strength elements (HFSE), Eu, Ba, Nb, Sr, P and Ti. The diorite and quartz diorite have also LILE and LREE enrichment and HFSE, Nb and Ti depletion, but have not negative Eu, Ba, Sr, and P anomalies. These features suggest that the parental magma of the granodiorite porphyry and quartz diorite porphyry originated from melting of a lithospheric mantle and experienced fractional crystallization, whereas the diorite and quartz diorite has a relatively deeper lithospheric mantle source region and has not experienced strong fractional crystallization. Based on these, together with the coeval ophiolites in the area, we propose that a subduction of the Balkhash-Junggar oceanic plate took place during the Early Silurian and the ore-bearing intrusions and associated Nurkazgan

  1. Absolute parameters for AI Phoenicis using WASP photometry

    NASA Astrophysics Data System (ADS)

    Kirkby-Kent, J. A.; Maxted, P. F. L.; Serenelli, A. M.; Turner, O. D.; Evans, D. F.; Anderson, D. R.; Hellier, C.; West, R. G.

    2016-06-01

    Context. AI Phe is a double-lined, detached eclipsing binary, in which a K-type sub-giant star totally eclipses its main-sequence companion every 24.6 days. This configuration makes AI Phe ideal for testing stellar evolutionary models. Difficulties in obtaining a complete lightcurve mean the precision of existing radii measurements could be improved. Aims: Our aim is to improve the precision of the radius measurements for the stars in AI Phe using high-precision photometry from the Wide Angle Search for Planets (WASP), and use these improved radius measurements together with estimates of the masses, temperatures and composition of the stars to place constraints on the mixing length, helium abundance and age of the system. Methods: A best-fit ebop model is used to obtain lightcurve parameters, with their standard errors calculated using a prayer-bead algorithm. These were combined with previously published spectroscopic orbit results, to obtain masses and radii. A Bayesian method is used to estimate the age of the system for model grids with different mixing lengths and helium abundances. Results: The radii are found to be R1 = 1.835 ± 0.014 R⊙, R2 = 2.912 ± 0.014 R⊙ and the masses M1 = 1.1973 ± 0.0037 M⊙, M2 = 1.2473 ± 0.0039 M⊙. From the best-fit stellar models we infer a mixing length of 1.78, a helium abundance of YAI = 0.26 +0.02-0.01 and an age of 4.39 ± 0.32 Gyr. Times of primary minimum show the period of AI Phe is not constant. Currently, there are insufficient data to determine the cause of this variation. Conclusions: Improved precision in the masses and radii have improved the age estimate, and allowed the mixing length and helium abundance to be constrained. The eccentricity is now the largest source of uncertainty in calculating the masses. Further work is needed to characterise the orbit of AI Phe. Obtaining more binaries with parameters measured to a similar level of precision would allow us to test for relationships between helium

  2. Radial velocity studies and absolute parameters of contact binaries. I - AB Andromedae

    NASA Technical Reports Server (NTRS)

    Hrivnak, Bruce J.

    1988-01-01

    New radial velocity curves have been obtained for the contact binary AB And, using the cross-correlation technique. A mass ratio of 0.479 is determined, which is revised to 0.491 when the velocities are corrected for proximity effects using a light curve model. These values differ by less than ten percent from the photometric mass ratio. An analysis of the symmetric B and V light curves reported by Rigterink in 1973 using the spectroscopic mass ratio yields a consistent set of light and velocity curve elements. These also produce a reasonably good fit to the infrared J and K light curves reported by Jameson and Akinci in 1979. Absolute elements are determined, and these indicate that both components have a main-sequence internal structure. These absolute parameters, together with the Galactic kinematics, suggest an age for the system similar to or greater than that of the Sun.

  3. Credit Constraints for Higher Education

    ERIC Educational Resources Information Center

    Solis, Alex

    2012-01-01

    This paper exploits a natural experiment that produces exogenous variation on credit access to determine the effect on college enrollment. The paper assess how important are credit constraints to explain the gap in college enrollment by family income, and what would be the gap if credit constraints are eliminated. Progress in college and dropout…

  4. On Constraints in Assembly Planning

    SciTech Connect

    Calton, T.L.; Jones, R.E.; Wilson, R.H.

    1998-12-17

    Constraints on assembly plans vary depending on product, assembly facility, assembly volume, and many other factors. Assembly costs and other measures to optimize vary just as widely. To be effective, computer-aided assembly planning systems must allow users to express the plan selection criteria that appIy to their products and production environments. We begin this article by surveying the types of user criteria, both constraints and quality measures, that have been accepted by assembly planning systems to date. The survey is organized along several dimensions, including strategic vs. tactical criteria; manufacturing requirements VS. requirements of the automated planning process itself and the information needed to assess compliance with each criterion. The latter strongly influences the efficiency of planning. We then focus on constraints. We describe a framework to support a wide variety of user constraints for intuitive and efficient assembly planning. Our framework expresses all constraints on a sequencing level, specifying orders and conditions on part mating operations in a number of ways. Constraints are implemented as simple procedures that either accept or reject assembly operations proposed by the planner. For efficiency, some constraints are supplemented with special-purpose modifications to the planner's algorithms. Fast replanning enables an interactive plan-view-constrain-replan cycle that aids in constraint discovery and documentation. We describe an implementation of the framework in a computer-aided assembly planning system and experiments applying the system to a number of complex assemblies, including one with 472 parts.

  5. Fixed Costs and Hours Constraints

    ERIC Educational Resources Information Center

    Johnson, William R.

    2011-01-01

    Hours constraints are typically identified by worker responses to questions asking whether they would prefer a job with more hours and more pay or fewer hours and less pay. Because jobs with different hours but the same rate of pay may be infeasible when there are fixed costs of employment or mandatory overtime premia, the constraint in those…

  6. Placing Absolute Timing on Basin Incision Adjacent to the Colorado Front Range: Results from Meteoric and in Situ 10BE Dating

    NASA Astrophysics Data System (ADS)

    Duehnforth, M.; Anderson, R. S.; Ward, D.

    2010-12-01

    A sequence of six levels of gravel-capped surfaces, mapped as Pliocene to Holocene in age, are cut into Cretaceous shale in the northwestern part of the Denver Basin immediately adjacent to the Colorado Front Range (CFR). The existing relative age constraints and terrace correlations suggest that the incision of the Denver Basin occurred at a steady and uniform rate of 0.1 mm yr-1 since the Pliocene. As absolute ages in this landscape are rare, they have the potential to test the reliability of the existing chronology, and to illuminate the detailed history of incision. We explore the timing of basin incision and the variability of geomorphic process rates through time by dating the three highest surfaces at the northwestern edge of the Denver Basin using both in situ and meteoric 10Be concentrations. As the tectonic conditions have not changed since the Pliocene, much of the variability of generation and abandonment of alluvial surfaces likely reflects the influence of glacial-interglacial climate variations. We selected Gunbarrel Hill (mapped as pre-Rocky Flats (Pliocene)), Table Mountain (mapped as Rocky Flats (early Pleistocene)), and the Pioneer surface (mapped as Verdos (Pleistocene, ~640 ka)) as sample locations. We took two amalgamated clast samples on the Gunbarrel Hill surface, and dated depth profiles using meteoric and in situ 10Be on the Table Mountain and Pioneer surfaces. In addition, we measured the in situ 10Be concentrations of 6 boulder samples from the Table Mountain surface. We find that all three surfaces are significantly younger than expected and that in situ and meteoric age measurements largely agree with each other. The samples from the pre-Rocky Flats site (Gunbarrel Hill) show ages of 250 and 310 ka, ignoring post-depositional surface erosion. The ages of the Table Mountain and Pioneer sites fall within the 120 to 150 ka window. These absolute ages overlap with the timing of the penultimate glaciation during marine isotope stage (MIS) 6

  7. Cosmological Constraints from the SDSS maxBCG Cluster Catalog

    SciTech Connect

    Rozo, Eduardo; Wechsler, Risa H.; Rykoff, Eli S.; Annis, James T.; Becker, Matthew R.; Evrard, August E.; Frieman, Joshua A.; Hansen, Sarah M.; Hao, Jia; Johnston, David E.; Koester, Benjamin P.; McKay, Timothy A.; Sheldon, Erin S.; Weinberg, David H.; /CCAPP /Ohio State U.

    2009-08-03

    We use the abundance and weak lensing mass measurements of the SDSS maxBCG cluster catalog to simultaneously constrain cosmology and the richness-mass relation of the clusters. Assuming a flat {Lambda}CDM cosmology, we find {sigma}{sub 8}({Omega}{sub m}/0.25){sup 0.41} = 0.832 {+-} 0.033 after marginalization over all systematics. In common with previous studies, our error budget is dominated by systematic uncertainties, the primary two being the absolute mass scale of the weak lensing masses of the maxBCG clusters, and uncertainty in the scatter of the richness-mass relation. Our constraints are fully consistent with the WMAP five-year data, and in a joint analysis we find {sigma}{sub 8} = 0.807 {+-} 0.020 and {Omega}{sub m} = 0.265 {+-} 0.016, an improvement of nearly a factor of two relative to WMAP5 alone. Our results are also in excellent agreement with and comparable in precision to the latest cosmological constraints from X-ray cluster abundances. The remarkable consistency among these results demonstrates that cluster abundance constraints are not only tight but also robust, and highlight the power of optically-selected cluster samples to produce precision constraints on cosmological parameters.

  8. Absolute calibration of sniffer probes on Wendelstein 7-X.

    PubMed

    Moseev, D; Laqua, H P; Marsen, S; Stange, T; Braune, H; Erckmann, V; Gellert, F; Oosterbeek, J W

    2016-08-01

    Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m(2) per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m(2) per MW injected beam power is measured. PMID:27587121

  9. Absolute Value Boundedness, Operator Decomposition, and Stochastic Media and Equations

    NASA Technical Reports Server (NTRS)

    Adomian, G.; Miao, C. C.

    1973-01-01

    The research accomplished during this period is reported. Published abstracts and technical reports are listed. Articles presented include: boundedness of absolute values of generalized Fourier coefficients, propagation in stochastic media, and stationary conditions for stochastic differential equations.

  10. The conditions of absolute summability of multiple trigonometric series

    NASA Astrophysics Data System (ADS)

    Bitimkhan, Samat; Akishev, Gabdolla

    2015-09-01

    In this work necessary and sufficient conditions of absolute summability of multiple trigonometric Fourier series of functions from anisotropic spaces of Lebesque are found in terms of its best approximation, the module of smoothness and the mixed smoothness module.

  11. Absolute calibration of sniffer probes on Wendelstein 7-X

    NASA Astrophysics Data System (ADS)

    Moseev, D.; Laqua, H. P.; Marsen, S.; Stange, T.; Braune, H.; Erckmann, V.; Gellert, F.; Oosterbeek, J. W.

    2016-08-01

    Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m2 per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m2 per MW injected beam power is measured.

  12. Zircon U-Pb ages, geochemistry, and Sr-Nd-Pb-Hf isotopes of the Nuri intrusive rocks in the Gangdese area, southern Tibet: Constraints on timing, petrogenesis, and tectonic transformation

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Qin, Ke-Zhang; Li, Guang-Ming; Li, Jin-Xiang; Xiao, Bo; Zhao, Jun-Xing; Fan, Xin

    2015-01-01

    Abundant magmatic rocks of various ages are exposed in Gangdese, southern Tibet. These rocks play an important role in understanding the tectonic transformation from the subduction of Neo-Tethyan oceanic crust to the collision of the Indian and Asian continents. Based on zircon U-Pb ages, geochemistry, and Sr-Nd-Pb-Hf isotopic data of the Late Cretaceous to early Oligocene (~ 96-30 Ma) intrusive rocks in the Nuri Cu-W-Mo deposit, we discuss the Late Cretaceous to early Oligocene tectonic transformation of the region and the origin of Oligocene Cu-W-Mo mineralization in southern Gangdese. The Nuri intrusive rocks represent three magmatic episodes: 96-91, 56-52, and 33-30 Ma. The 96-91 and 56-52 Ma rocks have relatively low (87Sr/86Sr)i (0.7041 to 0.7060), and high εNd(t) (+ 3.1 to + 3.5) and εHf(t) values (+ 3.7 to + 15); the 33-30 Ma rocks have relatively high (87Sr/86Sr)i (0.7061 to 0.7063) and Pb isotopes, and low εNd(t) (- 3.8 to - 1.8) and εHf(t) values (+ 0.6 to + 10.1). The three stages of intrusive rocks have geochemical characteristics that are similar to those of coeval rocks in Gangdese. The 96-91 and 33-30 Ma rocks are adakitic, whereas the 56-52 Ma rocks have characteristics of arc calc-alkaline magmatic rocks. The 96-91 Ma rocks were produced by the partial melting of Neo-Tethyan basaltic oceanic crust and minor sediments, whereas the 56-52 Ma rocks were generated by the partial melting of juvenile crust and the 33-30 Ma rocks were formed by the melting of Indian plate lower crust contaminated with overlying mantle materials. On the basis of the regional tectonic and magmatic characteristics, we suggest that Neo-Tethyan oceanic slab subduction and slab roll-back occurred from ~ 100 to 65 Ma, collision between the Indian and Asian continents occurred at 65 to 40 Ma, Neo-Tethyan oceanic slab break-off took place at ~ 50 Ma, and the Indian continent subducted northwards beneath the Asian continent at ~ 30 Ma. From the Late Cretaceous (96-91 Ma) to

  13. Zircon U-Pb ages, Hf-O isotopes and trace elements of Mesozoic high Sr/Y porphyries from Ningzhen, eastern China: Constraints on their petrogenesis, tectonic implications and Cu mineralization

    NASA Astrophysics Data System (ADS)

    Wang, Fangyue; Liu, Sheng-Ao; Li, Shuguang; Akhtar, Shamim; He, Yongsheng

    2014-07-01

    The relationship between high Sr/Y (adakitic) rocks and Cu mineralization has been long recognized but the mechanism remains unclear. The Cretaceous high Sr/Y porphyries in the Ningzhen area host major Cu polymetallic deposits in the Lower Yangtze River Belt (LYRB) of eastern China. These rocks exhibit some geochemical characteristics (e.g., non-radiogenic Pb isotope ratios) that differ from adakitic rocks from adjacent locations in the LYRB. In this study, we present a study of the zircon U-Pb-Hf-O isotope and trace element compositions for five porphyries from Ningzhen to reveal their petrogenesis and how that correlates with Cu-Fe-Mo mineralization. Zircon U-Pb ages of Anjishan (Cu deposit), Tongshan (Cu-Mo deposit) and Xiangshan (Fe deposit) plutons in the Ningzhen area are 108.8 ± 1.5 Ma, 105-107 Ma and 100-105 Ma, respectively, which are significantly younger than the ore-bearing adakites (140 ± 5 Ma) in the western part of the LYRB. Zircon εHf(t) and δ18O values range from - 23.4 to - 10.6 and from 5.7 to 7.0‰, respectively, falling between subduction-related adakites from the other regions in the LYRB and delamination-related adakitic rocks from the adjacent South Tan-Lu Fault Zone. The similarities of Ce4 +/Ce3 + and Eu/Eu* ratios in zircons from Ningzhen and those from the western LYRB indicate higher oxygen fugacity in their magma sources. Ti-in-zircon thermometer yields magma temperatures of 550 to 700 °C (with an average of ~ 650 °C) for the Ningzhen porphyries, which are significantly lower than those of the South Tan-Lu Fault adakites (> 750 °C), but similar to those for the LYRB adakites (< 700 °C). In summary, the Ningzhen high Sr/Y porphyries have high Mg# (> 50), non-radiogenic Pb, enriched Sr-Nd isotopic compositions, negative zircon εHf(t), mantle-like δ18O values, high oxygen fugacities and low magma temperatures. Mafic rocks that co-exist with ore-bearing porphyries or occur as xenoliths in porphyries are widespread. We proposed

  14. Bushveld-aged fluid flow, peak metamorphism, and gold mobilization in the Witwatersrand basin, South Africa: Constraints from in situ SHRIMP U-Pb dating of monazite and xenotime

    NASA Astrophysics Data System (ADS)

    Rasmussen, Birger; Fletcher, Ian R.; Muhling, Janet R.; Mueller, Andreas G.; Hall, Greg C.

    2007-10-01

    In situ U-Pb dating of monazite and xenotime in gold reefs and unmineralized greenschist facies sedimentary rocks from the Witwatersrand basin, South Africa, reveals two episodes of tectonothermal activity. A major event between 2.06 and 2.03 Ga is recorded in the Wit-watersrand and Transvaal Supergroups in the northwestern and central basin, and broadly coincides with the ca. 2.06 Ga Bushveld event. In the central and southern basin, a previously unrecognized event has been dated between 2.14 and 2.12 Ga. The widespread geographic and stratigraphic occurrence of Bushveld-aged monazite and xenotime, including both auriferous reefs and unmineralized strata, indicates that metamorphism and fluid flow associated with magmatism was pervasive, affecting most of the succession (>10 km thick) in the central and northern parts of the basin. The metamorphic phosphate dates, which are younger away from the complex, indicate a lag of 20-30 m.y. between emplacement and phosphate growth in the central basin (˜100 km south), suggesting that heat related to magmatism was transferred southward at an average rate of 3-5 mm yr-1. The absence of 2.06-2.03 Ga phosphates in the Welkom goldfield at the southern end of the basin implies that Bushveld-related heating and fluid flow did not affect this part of the basin. The intergrowth of ca. 2.045 Ga monazite with gold in quartz-pebble conglomerate from the West Rand goldfield indicates that fluid flow related to the Bushveld event caused mobilization of gold in the Witwatersrand basin.

  15. Absolute and Convective Instability of a Liquid Jet in Microgravity

    NASA Technical Reports Server (NTRS)

    Lin, Sung P.; Vihinen, I.; Honohan, A.; Hudman, Michael D.

    1996-01-01

    The transition from convective to absolute instability is observed in the 2.2 second drop tower of the NASA Lewis Research Center. In convective instability the disturbance grows spatially as it is convected downstream. In absolute instability the disturbance propagates both downstream and upstream, and manifests itself as an expanding sphere. The transition Reynolds numbers are determined for two different Weber numbers by use of Glycerin and a Silicone oil. Preliminary comparisons with theory are made.

  16. Absolute biphoton meter of the quantum efficiency of photomultipliers

    NASA Astrophysics Data System (ADS)

    Ginzburg, V. M.; Keratishvili, N. G.; Korzhenevich, E. L.; Lunev, G. V.; Sapritskii, V. I.

    1992-07-01

    An biphoton absolute meter of photomultiplier quantum efficiency is presented which is based on spontaneous parametric down-conversion. Calculation and experiment results were obtained which made it possible to choose the parameters of the setup that guarantee a linear dependence of wavelength on the Z coordinate (along the axicon axis). Results of a series of absolute measurements of the quantum efficiency of a specific photomultiplier (FEU-136) are presented.

  17. Absolute/convective instability of planar viscoelastic jets

    NASA Astrophysics Data System (ADS)

    Ray, Prasun K.; Zaki, Tamer A.

    2015-01-01

    Spatiotemporal linear stability analysis is used to investigate the onset of local absolute instability in planar viscoelastic jets. The influence of viscoelasticity in dilute polymer solutions is modeled with the FENE-P constitutive equation which requires the specification of a non-dimensional polymer relaxation time (the Weissenberg number, We), the maximum polymer extensibility, L, and the ratio of solvent and solution viscosities, β. A two-parameter family of velocity profiles is used as the base state with the parameter, S, controlling the amount of co- or counter-flow while N-1 sets the thickness of the jet shear layer. We examine how the variation of these fluid and flow parameters affects the minimum value of S at which the flow becomes locally absolutely unstable. Initially setting the Reynolds number to Re = 500, we find that the first varicose jet-column mode dictates the presence of absolute instability, and increasing the Weissenberg number produces important changes in the nature of the instability. The region of absolute instability shifts towards thin shear layers, and the amount of back-flow needed for absolute instability decreases (i.e., the influence of viscoelasticity is destabilizing). Additionally, when We is sufficiently large and N-1 is sufficiently small, single-stream jets become absolutely unstable. Numerical experiments with approximate equations show that both the polymer and solvent contributions to the stress become destabilizing when the scaled shear rate, η = /W e dU¯1/dx 2L ( /d U ¯ 1 d x 2 is the base-state velocity gradient), is sufficiently large. These qualitative trends are largely unchanged when the Reynolds number is reduced; however, the relative importance of the destabilizing stresses increases tangibly. Consequently, absolute instability is substantially enhanced, and single-stream jets become absolutely unstable over a sizable portion of the parameter space.

  18. Heat capacity and absolute entropy of iron phosphides

    SciTech Connect

    Dobrokhotova, Z.V.; Zaitsev, A.I.; Litvina, A.D.

    1994-09-01

    There is little or no data on the thermodynamic properties of iron phosphides despite their importance for several areas of science and technology. The information available is of a qualitative character and is based on assessments of the heat capacity and absolute entropy. In the present work, we measured the heat capacity over the temperature range of 113-873 K using a differential scanning calorimeter (DSC) and calculated the absolute entropy.

  19. Global absolut gravity reference system as replacement of IGSN 71

    NASA Astrophysics Data System (ADS)

    Wilmes, Herbert; Wziontek, Hartmut; Falk, Reinhard

    2015-04-01

    The determination of precise gravity field parameters is of great importance in a period in which earth sciences are achieving the necessary accuracy to monitor and document global change processes. This is the reason why experts from geodesy and metrology joined in a successful cooperation to make absolute gravity observations traceable to SI quantities, to improve the metrological kilogram definition and to monitor mass movements and smallest height changes for geodetic and geophysical applications. The international gravity datum is still defined by the International Gravity Standardization Net adopted in 1971 (IGSN 71). The network is based upon pendulum and spring gravimeter observations taken in the 1950s and 60s supported by the early free fall absolute gravimeters. Its gravity values agreed in every case to better than 0.1 mGal. Today, more than 100 absolute gravimeters are in use worldwide. The series of repeated international comparisons confirms the traceability of absolute gravity measurements to SI quantities and confirm the degree of equivalence of the gravimeters in the order of a few µGal. For applications in geosciences where e.g. gravity changes over time need to be analyzed, the temporal stability of an absolute gravimeter is most important. Therefore, the proposition is made to replace the IGSN 71 by an up-to-date gravity reference system which is based upon repeated absolute gravimeter comparisons and a global network of well controlled gravity reference stations.

  20. Revisiting absolute and relative judgments in the WITNESS model.

    PubMed

    Fife, Dustin; Perry, Colton; Gronlund, Scott D

    2014-04-01

    The WITNESS model (Clark in Applied Cognitive Psychology 17:629-654, 2003) provides a theoretical framework with which to investigate the factors that contribute to eyewitness identification decisions. One key factor involves the contributions of absolute versus relative judgments. An absolute contribution is determined by the degree of match between an individual lineup member and memory for the perpetrator; a relative contribution involves the degree to which the best-matching lineup member is a better match to memory than the remaining lineup members. In WITNESS, the proportional contributions of relative versus absolute judgments are governed by the values of the decision weight parameters. We conducted an exploration of the WITNESS model's parameter space to determine the identifiability of these relative/absolute decision weight parameters, and compared the results to a restricted version of the model that does not vary the decision weight parameters. This exploration revealed that the decision weights in WITNESS are difficult to identify: Data often can be fit equally well by setting the decision weights to nearly any value and compensating with a criterion adjustment. Clark, Erickson, and Breneman (Law and Human Behavior 35:364-380, 2011) claimed to demonstrate a theoretical basis for the superiority of lineup decisions that are based on absolute contributions, but the relationship between the decision weights and the criterion weakens this claim. These findings necessitate reconsidering the role of the relative/absolute judgment distinction in eyewitness decision making. PMID:23943556

  1. Temporal-spatial distribution and tectonic implications of the batholiths in the Gaoligong-Tengliang-Yingjiang area, western Yunnan: Constraints from zircon U-Pb ages and Hf isotopes

    NASA Astrophysics Data System (ADS)

    Xu, Yi-Gang; Yang, Qi-Jun; Lan, Jiang-Bo; Luo, Zhen-Yu; Huang, Xiao-Long; Shi, Yu-Ruo; Xie, Lie-Wen

    2012-07-01

    lithospheric strength and compressive plate-convergence forces and to a less degree to the collision between Burma and Sundaland blocks. The Gaoligong early Cretaceous granites, which bear strong similarities in lithology, geochemistry and emplacement age to those in the northern magmatic belt in the Lhasa Terrane, are also the magmatic expression of crustal thickening. This crustal thickening may have stemmed from the collision between the Lhasa Block and the Qiangtang Block in late Jurassic and Early Cretaceous. The magmatism in western Yunnan thus recorded a long-term subduction of the Neo-Tethyan plate, enhanced by continental collisions at different time.

  2. Sulfide mineralization associated with arc magmatism in the Qilian Block, western China: zircon U-Pb age and Sr-Nd-Os-S isotope constraints from the Yulonggou and Yaqu gabbroic intrusions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao-Wei; Li, Wen-Yuan; Gao, Yong-Bao; Li, Chusi; Ripley, Edward M.; Kamo, Sandra

    2014-02-01

    The sulfide-bearing Yulonggou and Yaqu mafic intrusions are located in the southern margin of the Qilian Block, Qinghai Province, western China. They are small dike-like bodies mainly composed of gabbros and diorites. Disseminated sulfides (pyrrhotite, pentlandite, and chalcopyrite) are present as concordant lenses within the intrusions. Precise CA-ID-TIMS zircon U-Pb dating yields the crystallization ages of 443.39 ± 0.42 and 440.74 ± 0.33 Ma for the Yulonggou and Yaqu intrusions, respectively. Whole rock samples from both intrusions show light rare earth element (REE) enrichments relative to heavy REE and pronounced negative Nb-Ta anomalies relative to Th and La, which are consistent with the products of arc basaltic magmatism. The Yulonggou intrusion has negative ɛ Nd values from -5.7 to -7.7 and elevated (87Sr/86Sr) i ratios from 0.711 to 0.714. In contrast, the Yaqu intrusion has higher ɛ Nd values from -4.1 to +8.4 and lower (87Sr/86Sr) i ratios from 0.705 to 0.710. The δ34S values of sulfide separates from the Yulonggou and Yaqu deposits vary from 0.8 to 2.4 ‰ and from 2 to 4.3 ‰, respectively. The γ Os values of sulfide separates from the Yulonggou and Yaqu deposits vary between 80 and 123 and between 963 and 1,191, respectively. Higher γ Os values coupled with higher δ34S values for the Yaqu deposit relative to the Yulonggou deposit indicate that external sulfur played a bigger role in sulfide mineralization in the Yaqu intrusion than in the Yulonggou intrusion. Mixing calculations using Sr-Nd isotope data show that contamination with siliceous crustal materials is more pronounced in the Yulonggou intrusion (up to 20 wt%) than in the Yaqu intrusion (<15 wt%). The distribution of sulfides in both intrusions is consistent with multiple emplacements of sulfide-saturated magmas from depth. The Yulonggou and Yaqu sulfide deposits are not economically valuable under current market condition due to small sizes and low Ni grades, which can be explained

  3. Absolute bioavailability and disposition of lanthanum in healthy human subjects administered lanthanum carbonate.

    PubMed

    Pennick, Michael; Dennis, Kerry; Damment, Stephen J P

    2006-07-01

    Lanthanum carbonate [La2(CO3)3] is a noncalcium, non-aluminum phosphate binder indicated for hyperphosphatemia treatment in end-stage renal disease. A randomized, open-label, parallel-group, phase I study was conducted to determine absolute bioavailability and investigate excretory routes for systemic lanthanum in healthy subjects. Twenty-four male subjects were randomized to a single lanthanum chloride (LaCl3) intravenous infusion (120 microg elemental lanthanum over a 4-hour period), a single 1-g oral dose [chewable La2(CO3)3 tablets; 4 x 250 mg elemental lanthanum], or no treatment (control). Serial blood, urine, and fecal samples were collected for 7 days postdosing. The absolute bioavailability of lanthanum [administered as La2(CO3)3] was extremely low (0.00127% +/- 0.00080%), with individual values in the range of 0.00015% to 0.00224%. Renal clearance was negligible following oral administration (1.36 +/- 1.43 mL/min). Intravenous administration confirmed low renal clearance (0.95 +/- 0.60 mL/min), just 1.7% of total plasma clearance. Fecal lanthanum excretion was not quantifiable after intravenous administration owing to high and variable background fecal lanthanum and constraints on the size of the intravenous dose. These findings demonstrate that lanthanum absorption from the intestinal tract into the systemic circulation is extremely low and that absorbed drug is cleared predominantly by nonrenal mechanisms. PMID:16809799

  4. Absolute and convective instabilities and their roles in the forecasting of large frontal meanderings

    NASA Astrophysics Data System (ADS)

    Liang, X. San; Robinson, Allan R.

    2013-10-01

    Frontal meanderings are generally difficult to predict. In this study, we demonstrate through an exercise with the Iceland-Faeroe Front (IFF) that satisfactory predictions may be achieved with the aid of hydrodynamic instability analysis. As discovered earlier on, underlying the IFF meandering is a convective instability in the western boundary region followed by an absolute instability in the interior; correspondingly the disturbance growth reveals a switch of pattern from spatial amplification to temporal amplification. To successfully forecast the meandering, the two instability processes must be faithfully reproduced. This sets stringent constraints for the tunable model parameters, e.g., boundary relaxation, temporal relaxation, eddy diffusivity, etc. By analyzing the instability dispersion properties, these parameters can be rather accurately set and their respective ranges of sensitivity estimated. It is shown that too much relaxation inhibits the front from varying; on the other hand, too little relaxation may have the model completely skip the spatial growth phase, leading to a meandering way more upstream along the front. Generally speaking, dissipation/diffusion tends to stabilize the simulation, but unrealistically large dissipation/diffusion could trigger a spurious absolute instability, and hence a premature meandering intrusion. The belief that taking in more data will improve the forecast does not need to be true; it depends on whether the model setup admits the two instabilities. This study may help relieve modelers from the laborious and tedious work of parameter tuning; it also provides us criteria to distinguish a physically relevant forecast from numerical artifacts.

  5. Evolutionary constraints or opportunities?

    PubMed Central

    Sharov, Alexei A.

    2014-01-01

    Natural selection is traditionally viewed as a leading factor of evolution, whereas variation is assumed to be random and non-directional. Any order in variation is attributed to epigenetic or developmental constraints that can hinder the action of natural selection. In contrast I consider the positive role of epigenetic mechanisms in evolution because they provide organisms with opportunities for rapid adaptive change. Because the term “constraint” has negative connotations, I use the term “regulated variation” to emphasize the adaptive nature of phenotypic variation, which helps populations and species to survive and evolve in changing environments. The capacity to produce regulated variation is a phenotypic property, which is not described in the genome. Instead, the genome acts as a switchboard, where mostly random mutations switch “on” or “off” preexisting functional capacities of organism components. Thus, there are two channels of heredity: informational (genomic) and structure-functional (phenotypic). Functional capacities of organisms most likely emerged in a chain of modifications and combinations of more simple ancestral functions. The role of DNA has been to keep records of these changes (without describing the result) so that they can be reproduced in the following generations. Evolutionary opportunities include adjustments of individual functions, multitasking, connection between various components of an organism, and interaction between organisms. The adaptive nature of regulated variation can be explained by the differential success of lineages in macro-evolution. Lineages with more advantageous patterns of regulated variation are likely to produce more species and secure more resources (i.e., long-term lineage selection). PMID:24769155

  6. Infrared Kuiper Belt Constraints

    SciTech Connect

    Teplitz, V.L.; Stern, S.A.; Anderson, J.D.; Rosenbaum, D.; Scalise, R.J.; Wentzler, P.

    1999-05-01

    We compute the temperature and IR signal of particles of radius {ital a} and albedo {alpha} at heliocentric distance {ital R}, taking into account the emissivity effect, and give an interpolating formula for the result. We compare with analyses of {ital COBE} DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance {ital R}, particle radius {ital a}, and particle albedo {alpha}. We then apply these results to a recently developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40{lt}R{lt}50{endash}90 AU) and a more distant sector with a higher density. We consider the case in which passage through a molecular cloud essentially cleans the solar system of dust. We apply a simple model of dust production by comet collisions and removal by the Poynting-Robertson effect to find limits on total and dust masses in the near and far sectors as a function of time since such a passage. Finally, we compare Kuiper belt IR spectra for various parameter values. Results of this work include: (1) numerical limits on Kuiper belt dust as a function of ({ital R}, {ital a}, {alpha}) on the basis of four alternative sets of constraints, including those following from recent discovery of the cosmic IR background by Hauser et al.; (2) application to the two-sector Kuiper belt model, finding mass limits and spectrum shape for different values of relevant parameters including dependence on time elapsed since last passage through a molecular cloud cleared the outer solar system of dust; and (3) potential use of spectral information to determine time since last passage of the Sun through a giant molecular cloud. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

  7. A Hybrid Constraint Representation and Reasoning Framework

    NASA Technical Reports Server (NTRS)

    Golden, Keith; Pang, Wan-Lin

    2003-01-01

    This paper introduces JNET, a novel constraint representation and reasoning framework that supports procedural constraints and constraint attachments, providing a flexible way of integrating the constraint reasoner with a run- time software environment. Attachments in JNET are constraints over arbitrary Java objects, which are defined using Java code, at runtime, with no changes to the JNET source code.

  8. Orion Absolute Navigation System Progress and Challenges

    NASA Technical Reports Server (NTRS)

    Holt, Greg N.; D'Souza, Christopher

    2011-01-01

    The Orion spacecraft is being designed as NASA's next-generation exploration vehicle for crewed missions beyond Low-Earth Orbit. The navigation system for the Orion spacecraft is being designed in a Multi-Organizational Design Environment (MODE) team including contractor and NASA personnel. The system uses an Extended Kalman Filter to process measurements and determine the state. The design of the navigation system has undergone several iterations and modifications since its inception, and continues as a work-in-progress. This paper seeks to benchmark the current state of the design and some of the rationale and analysis behind it. There are specific challenges to address when preparing a timely and effective design for the Exploration Flight Test (EFT-1), while still looking ahead and providing software extensibility for future exploration missions. The primary measurements in a Near-Earth or Mid-Earth environment consist of GPS pseudorange and deltarange, but for future explorations missions the use of star-tracker and optical navigation sources need to be considered. Discussions are presented for state size and composition, processing techniques, and consider states. A presentation is given for the processing technique using the computationally stable and robust UDU formulation with an Agee-Turner Rank-One update. This allows for computational savings when dealing with many parameters which are modeled as slowly varying Gauss-Markov processes. Preliminary analysis shows up to a 50% reduction in computation versus a more traditional formulation. Several state elements are discussed and evaluated, including position, velocity, attitude, clock bias/drift, and GPS measurement biases in addition to bias, scale factor, misalignment, and non-orthogonalities of the accelerometers and gyroscopes. Another consideration is the initialization of the EKF in various scenarios. Scenarios such as single-event upset, ground command, pad alignment, cold start are discussed as are

  9. Ages of plains volcanism on Mars

    NASA Astrophysics Data System (ADS)

    Hauber, Ernst; Jagert, Felix; Broz, Petr

    2010-05-01

    Plain-style volcanism [1] is widespread in the Tharsis and Elysium volcanic provinces on Mars, [2,3]. Detailed images and topographic data reveal the morphology and topography of clusters of low shields and associated lava flows. The landforms of plains volcanism on Mars have all well-known terrestrial analogues in basaltic volcanic regions, such as Hawaii, Iceland, and in particular the Snake River Plains [4]. The very gentle flank slopes (<1°) indicate low-viscosity lavas [4-6], and topographic investigations hint at emplacement times for the low shields in the order of a few hundred to a few thousand years [7]. Emplacement itself was characterized by complex interactions between ascending magma bodies and tectonic structures of various ages [8]. Despite these recent studies, the chronology of plains volcanism was only poorly constrained, with a few exceptions of regionally limited studies [e.g., 6]. Here we report on our absolute age determinations of plains volcanism on Mars, as derived from cratering models [9,10] and crater counts that were performed with the software tools CraterTools (crater counting; see [11]) and Craterstats (analysis of crater statistics; see [12]), both developed at FU Berlin. We used images of the Context Camera Investigation (CTX) on Mars Reconnaissance Orbiter [13], which are ideally suited for this purpose due to their good contrast, high resolution (5-6 m/pixel), and wide coverage (swath width ~30 km). Representative surface areas for age determination were mapped on image maps, and several low shields in each shield cluster were dated by crater counts. The goal was to derive absolute ages for a given shield, but also to determine whether the shields within one shield cluster formed at roughly the same time or over a prolonged period. The second question was whether or not the clusters have comparable ages. The results are essential to determine the history of late-stage volcanism in Tharsis and, therefore, help to put constraints

  10. Synchronizing the Absolute and Relative Clocks: Pb-Pb and Al-Mg Systematics in CAIs from the Allende and NWA 2364 CV3 Chondrites

    NASA Astrophysics Data System (ADS)

    Bouvier, A.; Wadhwa, M.

    2009-03-01

    A Pb-Pb internal isochron of a type-B CAI from the NWA 2364 CV3 chondrite gives an absolute age of 4568.6 ± 0.2 Ma which contrasts with previous internal Pb-Pb ages of CAIs from Allende and Efremovka. Al-Mg systematics are also reported for CV3 CAIs.

  11. Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85 ± 6 years) and 19 young adults (mean age, 28 ± 4 years). Non-invasive measurements were obtained on the forehead using a commercially a...

  12. Integrated Science--Reasons & Constraints.

    ERIC Educational Resources Information Center

    Fox, M.; Oliver, P. M.

    1978-01-01

    Describes the philosophy and development of an integrated science program in a British secondary school. Discusses constraints to the program including laboratory facilities, money, and fewer laboratory technicians. (MA)

  13. Constraint-based stereo matching

    NASA Technical Reports Server (NTRS)

    Kuan, D. T.

    1987-01-01

    The major difficulty in stereo vision is the correspondence problem that requires matching features in two stereo images. Researchers describe a constraint-based stereo matching technique using local geometric constraints among edge segments to limit the search space and to resolve matching ambiguity. Edge segments are used as image features for stereo matching. Epipolar constraint and individual edge properties are used to determine possible initial matches between edge segments in a stereo image pair. Local edge geometric attributes such as continuity, junction structure, and edge neighborhood relations are used as constraints to guide the stereo matching process. The result is a locally consistent set of edge segment correspondences between stereo images. These locally consistent matches are used to generate higher-level hypotheses on extended edge segments and junctions to form more global contexts to achieve global consistency.

  14. Fluid convection, constraint and causation

    PubMed Central

    Bishop, Robert C.

    2012-01-01

    Complexity—nonlinear dynamics for my purposes in this essay—is rich with metaphysical and epistemological implications but is receiving sustained philosophical analysis only recently. I will explore some of the subtleties of causation and constraint in Rayleigh–Bénard convection as an example of a complex phenomenon, and extract some lessons for further philosophical reflection on top-down constraint and causation particularly with respect to causal foundationalism. PMID:23386955

  15. Photogeological constraints on lunar and planetary vulcanism, part 1

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Central volcanic constructs were studied as constraints on the thermal evolution and regional tectonics of the Moon and terrestrial planets. The origins of sub-kilometer lunar craters were examined with regards to implications for mare basalt petrogenesis. The morphology, distribution, age, and tectonic setting of the volcanic constructs were studied using Viking Orbiter data.

  16. Absolute irradiance of the Moon for on-orbit calibration

    USGS Publications Warehouse

    Stone, T.C.; Kieffer, H.H.

    2002-01-01

    The recognized need for on-orbit calibration of remote sensing imaging instruments drives the ROLO project effort to characterize the Moon for use as an absolute radiance source. For over 5 years the ground-based ROLO telescopes have acquired spatially-resolved lunar images in 23 VNIR (Moon diameter ???500 pixels) and 9 SWIR (???250 pixels) passbands at phase angles within ??90 degrees. A numerical model for lunar irradiance has been developed which fits hundreds of ROLO images in each band, corrected for atmospheric extinction and calibrated to absolute radiance, then integrated to irradiance. The band-coupled extinction algorithm uses absorption spectra of several gases and aerosols derived from MODTRAN to fit time-dependent component abundances to nightly observations of standard stars. The absolute radiance scale is based upon independent telescopic measurements of the star Vega. The fitting process yields uncertainties in lunar relative irradiance over small ranges of phase angle and the full range of lunar libration well under 0.5%. A larger source of uncertainty enters in the absolute solar spectral irradiance, especially in the SWIR, where solar models disagree by up to 6%. Results of ROLO model direct comparisons to spacecraft observations demonstrate the ability of the technique to track sensor responsivity drifts to sub-percent precision. Intercomparisons among instruments provide key insights into both calibration issues and the absolute scale for lunar irradiance.

  17. Absolute luminosity measurements with the LHCb detector at the LHC

    NASA Astrophysics Data System (ADS)

    LHCb Collaboration

    2012-01-01

    Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. Using data taken in 2010, LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic ``van der Meer scan'' method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overal precision of 3.5% in the absolute luminosity determination is reached. The techniques used to transport the absolute luminosity calibration to the full 2010 data-taking period are presented.

  18. Foundations of support constraint machines.

    PubMed

    Gnecco, Giorgio; Gori, Marco; Melacci, Stefano; Sanguineti, Marcello

    2015-02-01

    The mathematical foundations of a new theory for the design of intelligent agents are presented. The proposed learning paradigm is centered around the concept of constraint, representing the interactions with the environment, and the parsimony principle. The classical regularization framework of kernel machines is naturally extended to the case in which the agents interact with a richer environment, where abstract granules of knowledge, compactly described by different linguistic formalisms, can be translated into the unified notion of constraint for defining the hypothesis set. Constrained variational calculus is exploited to derive general representation theorems that provide a description of the optimal body of the agent (i.e., the functional structure of the optimal solution to the learning problem), which is the basis for devising new learning algorithms. We show that regardless of the kind of constraints, the optimal body of the agent is a support constraint machine (SCM) based on representer theorems that extend classical results for kernel machines and provide new representations. In a sense, the expressiveness of constraints yields a semantic-based regularization theory, which strongly restricts the hypothesis set of classical regularization. Some guidelines to unify continuous and discrete computational mechanisms are given so as to accommodate in the same framework various kinds of stimuli, for example, supervised examples and logic predicates. The proposed view of learning from constraints incorporates classical learning from examples and extends naturally to the case in which the examples are subsets of the input space, which is related to learning propositional logic clauses. PMID:25380338

  19. Observables sensitive to absolute neutrino masses: A reappraisal after WMAP 3-year and first MINOS results

    SciTech Connect

    Fogli, G. L.; Lisi, E.; Marrone, A.; Melchiorri, A.; Serra, P.; Palazzo, A.; Silk, J.; Slosar, A.

    2007-03-01

    In the light of recent neutrino oscillation and nonoscillation data, we revisit the phenomenological constraints applicable to three observables sensitive to absolute neutrino masses: The effective neutrino mass in single beta decay (m{sub {beta}}); the effective Majorana neutrino mass in neutrinoless double beta decay (m{sub {beta}}{sub {beta}}); and the sum of neutrino masses in cosmology ({sigma}). In particular, we include the constraints coming from the first Main Injector Neutrino Oscillation Search (MINOS) data and from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year (3y) data, as well as other relevant cosmological data and priors. We find that the largest neutrino squared mass difference is determined with a 15% accuracy (at 2{sigma}) after adding MINOS to world data. We also find upper bounds on the sum of neutrino masses {sigma} ranging from {approx}2 eV (WMAP-3y data only) to {approx}0.2 eV (all cosmological data) at 2{sigma}, in agreement with previous studies. In addition, we discuss the connection of such bounds with those placed on the matter power spectrum normalization parameter {sigma}{sub 8}. We show how the partial degeneracy between {sigma} and {sigma}{sub 8} in WMAP-3y data is broken by adding further cosmological data, and how the overall preference of such data for relatively high values of {sigma}{sub 8} pushes the upper bound of {sigma} in the sub-eV range. Finally, for various combination of data sets, we revisit the (in)compatibility between current {sigma} and m{sub {beta}}{sub {beta}} constraints (and claims), and derive quantitative predictions for future single and double beta decay experiments.

  20. System and method for calibrating a rotary absolute position sensor

    NASA Technical Reports Server (NTRS)

    Davis, Donald R. (Inventor); Permenter, Frank Noble (Inventor); Radford, Nicolaus A (Inventor)

    2012-01-01

    A system includes a rotary device, a rotary absolute position (RAP) sensor generating encoded pairs of voltage signals describing positional data of the rotary device, a host machine, and an algorithm. The algorithm calculates calibration parameters usable to determine an absolute position of the rotary device using the encoded pairs, and is adapted for linearly-mapping an ellipse defined by the encoded pairs to thereby calculate the calibration parameters. A method of calibrating the RAP sensor includes measuring the rotary position as encoded pairs of voltage signals, linearly-mapping an ellipse defined by the encoded pairs to thereby calculate the calibration parameters, and calculating an absolute position of the rotary device using the calibration parameters. The calibration parameters include a positive definite matrix (A) and a center point (q) of the ellipse. The voltage signals may include an encoded sine and cosine of a rotary angle of the rotary device.

  1. Method and apparatus for two-dimensional absolute optical encoding

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    2004-01-01

    This invention presents a two-dimensional absolute optical encoder and a method for determining position of an object in accordance with information from the encoder. The encoder of the present invention comprises a scale having a pattern being predetermined to indicate an absolute location on the scale, means for illuminating the scale, means for forming an image of the pattern; and detector means for outputting signals derived from the portion of the image of the pattern which lies within a field of view of the detector means, the field of view defining an image reference coordinate system, and analyzing means, receiving the signals from the detector means, for determining the absolute location of the object. There are two types of scale patterns presented in this invention: grid type and starfield type.

  2. Absolute and Convective Instability in Fluid-Conveying Flexible Pipes

    NASA Astrophysics Data System (ADS)

    de Langre, E.; Ouvrard, A. E.

    1998-11-01

    The effect of internal plug flow on the lateral stability of fluid conveying flexible pipes is investigated by determining the absolute/convective nature of the instability from the analytically derived linear dispersion relation. The fluid-structure interaction is modeled following the work of Gregory and Paidoussis (1966). The different domains of stability, convective instability, and absolute instability are explicitly derived in parameter space. The effect of flow velocity, mass ratio between the fluid and the structure, stiffness of the elastic foundation and axial tension is considered. Absolute instability prevails over a wide range of parameters. Convective instability only takes place at very high mass ratio, small stiffness and small axial tension. Relation is made with previous work of Brazier-Smith & Scott (1984) and Crighton (1991), considered here as a short wave approximation.

  3. Absolute surface metrology by rotational averaging in oblique incidence interferometry.

    PubMed

    Lin, Weihao; He, Yumei; Song, Li; Luo, Hongxin; Wang, Jie

    2014-06-01

    A modified method for measuring the absolute figure of a large optical flat surface in synchrotron radiation by a small aperture interferometer is presented. The method consists of two procedures: the first step is oblique incidence measurement; the second is multiple rotating measurements. This simple method is described in terms of functions that are symmetric or antisymmetric with respect to reflections at the vertical axis. Absolute deviations of a large flat surface could be obtained when mirror antisymmetric errors are removed by N-position rotational averaging. Formulas are derived for measuring the absolute surface errors of a rectangle flat, and experiments on high-accuracy rectangle flats are performed to verify the method. Finally, uncertainty analysis is carried out in detail. PMID:24922410

  4. Non-Invasive Method of Determining Absolute Intracranial Pressure

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Cantrell, John H., Jr. (Inventor); Hargens, Alan E. (Inventor)

    2004-01-01

    A method is presented for determining absolute intracranial pressure (ICP) in a patient. Skull expansion is monitored while changes in ICP are induced. The patient's blood pressure is measured when skull expansion is approximately zero. The measured blood pressure is indicative of a reference ICP value. Subsequently, the method causes a known change in ICP and measured the change in skull expansion associated therewith. The absolute ICP is a function of the reference ICP value, the known change in ICP and its associated change in skull expansion; and a measured change in skull expansion.

  5. Measurements of the reactor neutron power in absolute units

    NASA Astrophysics Data System (ADS)

    Lebedev, G. V.

    2015-12-01

    The neutron power of the reactor of the Yenisei space nuclear power plant is measured in absolute units using the modernized method of correlation analysis during the ground-based tests of the Yenisei prototypes. Results of the experiments are given. The desired result is obtained in a series of experiments carried out at the stage of the plant preparation for tests. The acceptability of experimental data is confirmed by the results of measuring the reactor neutron power in absolute units at the nominal level by the thermal balance during the life cycle tests of the ground prototypes.

  6. In-flight absolute radiometric calibration of the thematic mapper

    NASA Technical Reports Server (NTRS)

    Castle, K. R.; Holm, R. G.; Kastner, C. J.; Palmer, J. M.; Slater, P. N.; Dinguirard, M.; Ezra, C. E.; Jackson, R. D.; Savage, R. K.

    1983-01-01

    The TM multispectral scanner system was calibrated in an absolute manner before launch. To determine the temporal changes of the absolute radiometric calibration of the entire system, spectroradiometric measurements of the ground and the atmosphere were made simultaneously with TM collections over White Sands, New Mexico. By entering the measured values in an atmospheric radiative transfer program, the radiance levels of the in four of the spectral bands of the TM were determined. Tables show values for the reflectance of snow at White Sands measured by a modular 8 channel radiometer, and values for exoatmospheric irradiance within the TM passbands, calculated for the Earth-Sun distance using a solar radiometer.

  7. Absolute photon-flux measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Haddad, G. N.

    1974-01-01

    Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

  8. Notes on Van der Meer scan for absolute luminosity measurement

    NASA Astrophysics Data System (ADS)

    Balagura, Vladislav

    2011-10-01

    The absolute luminosity can be measured in an accelerator by sweeping beams transversely across each other in the so-called van der Meer scan. We prove that the method can be applied in the general case of arbitrary beam directions and a separation scan plane. A simple method to develop an image of the beam in its transverse plane from spatial distributions of interaction vertexes is also proposed. From the beam images one can determine their overlap and the absolute luminosity. This provides an alternative way of the luminosity measurement during van der Meer scan.

  9. Measurements of the reactor neutron power in absolute units

    SciTech Connect

    Lebedev, G. V.

    2015-12-15

    The neutron power of the reactor of the Yenisei space nuclear power plant is measured in absolute units using the modernized method of correlation analysis during the ground-based tests of the Yenisei prototypes. Results of the experiments are given. The desired result is obtained in a series of experiments carried out at the stage of the plant preparation for tests. The acceptability of experimental data is confirmed by the results of measuring the reactor neutron power in absolute units at the nominal level by the thermal balance during the life cycle tests of the ground prototypes.

  10. A general relativistic model for free-fall absolute gravimeters

    NASA Astrophysics Data System (ADS)

    Tan, Yu-Jie; Shao, Cheng-Gang; Li, Jia; Hu, Zhong-Kun

    2016-04-01

    Although the relativistic manifestations of gravitational fields in gravimetry were first studied 40 years ago, the relativistic effects combined with free-fall absolute gravimeters have rarely been considered. In light of this, we present a general relativistic model for free-fall absolute gravimeters in a local-Fermi coordinates system, where we focus on effects related to the measuring devices: relativistic transverse Doppler effects, gravitational redshift effects and Earth’s rotation effects. Based on this model, a general relativistic expression of the measured gravity acceleration is obtained.

  11. The Impact of Spatio-Temporal Constraints on Cursive Letter Handwriting in Children

    ERIC Educational Resources Information Center

    Chartrel, Estelle; Vinter, Annie

    2008-01-01

    The study assessed the impact of spatial and temporal constraints on handwriting movements in young children. One hundred children of 5-7 years of age of both genders were given the task of copying isolated cursive letters under four conditions: normal, with temporal, spatial, or spatio-temporal constraints. The results showed that imposing…

  12. Tungsten isotopic constraints on the age and origin of chondrules

    PubMed Central

    Kleine, Thorsten; Kruijer, Thomas S.; Burkhardt, Christoph; Metzler, Knut

    2016-01-01

    Chondrules may have played a critical role in the earliest stages of planet formation by mediating the accumulation of dust into planetesimals. However, the origin of chondrules and their significance for planetesimal accretion remain enigmatic. Here, we show that chondrules and matrix in the carbonaceous chondrite Allende have complementary 183W anomalies resulting from the uneven distribution of presolar, stellar-derived dust. These data refute an origin of chondrules in protoplanetary collisions and, instead, indicate that chondrules and matrix formed together from a common reservoir of solar nebula dust. Because bulk Allende exhibits no 183W anomaly, chondrules and matrix must have accreted rapidly to their parent body, implying that the majority of chondrules from a given chondrite group formed in a narrow time interval. Based on Hf-W chronometry on Allende chondrules and matrix, this event occurred ∼2 million years after formation of the first solids, about coeval to chondrule formation in ordinary chondrites. PMID:26929340

  13. Tungsten isotopic constraints on the age and origin of chondrules

    NASA Astrophysics Data System (ADS)

    Budde, Gerrit; Kleine, Thorsten; Kruijer, Thomas S.; Burkhardt, Christoph; Metzler, Knut

    2016-03-01

    Chondrules may have played a critical role in the earliest stages of planet formation by mediating the accumulation of dust into planetesimals. However, the origin of chondrules and their significance for planetesimal accretion remain enigmatic. Here, we show that chondrules and matrix in the carbonaceous chondrite Allende have complementary 183W anomalies resulting from the uneven distribution of presolar, stellar-derived dust. These data refute an origin of chondrules in protoplanetary collisions and, instead, indicate that chondrules and matrix formed together from a common reservoir of solar nebula dust. Because bulk Allende exhibits no 183W anomaly, chondrules and matrix must have accreted rapidly to their parent body, implying that the majority of chondrules from a given chondrite group formed in a narrow time interval. Based on Hf-W chronometry on Allende chondrules and matrix, this event occurred ˜2 million years after formation of the first solids, about coeval to chondrule formation in ordinary chondrites.

  14. GEM: Performance and aging tests

    SciTech Connect

    Cho, H.S.; Kadyk, J.; Han, S.H.; Hong, W.S.; Perez-Mendez, V.; Wenzel, W.; Pitts, K.; Martin, M.D.; Hutchins, J.B.

    1999-06-01

    Performance and aging tests have been done to characterize Gas Electron Multipliers (GEMs), including further design improvements such as a thicker GEM and a closed GEM. Since the effective GEM gain is typically smaller than the absolute GEM gain, due to trapping of avalanche electrons at the bottom GEM electrode, the authors performed field simulations and measurements for better understanding, and discuss methods to eliminate this effect. Other performance parameters of the GEMs are also presented, including absolute GEM gain, short-term and long-term gain stabilities.

  15. Relationship between LIBS Ablation and Pit Volume for Geologic Samples: Applications for in situ Absolute Geochronology

    NASA Technical Reports Server (NTRS)

    Devismes, D.; Cohen, Barbara A.

    2014-01-01

    In planetary sciences, in situ absolute geochronology is a scientific and engineering challenge. Currently, the age of the Martian surface can only be determined by crater density counting. However this method has significant uncertainties and needs to be calibrated with absolute ages. We are developing an instrument to acquire in situ absolute geochronology based on the K-Ar method. The protocol is based on the laser ablation of a rock by hundreds of laser pulses. Laser Induced Breakdown Spectroscopy (LIBS) gives the potassium content of the ablated material and a mass spectrometer (quadrupole or ion trap) measures the quantity of 40Ar released. In order to accurately measure the quantity of released 40Ar in cases where Ar is an atmospheric constituent (e.g., Mars), the sample is first put into a chamber under high vacuum. The 40Arquantity, the concentration of K and the estimation of the ablated mass are the parameters needed to give the age of the rocks. The main uncertainties with this method are directly linked to the measures of the mass (typically some µg) and of the concentration of K by LIBS (up to 10%). Because the ablated mass is small compared to the mass of the sample, and because material is redeposited onto the sample after ablation, it is not possible to directly measure the ablated mass. Our current protocol measures the ablated volume and estimates the sample density to calculate ablated mass. The precision and accuracy of this method may be improved by using knowledge of the sample's geologic properties to predict its response to laser ablation, i.e., understanding whether natural samples have a predictable relationship between laser energy deposited and resultant ablation volume. In contrast to most previous studies of laser ablation, theoretical equations are not highly applicable. The reasons are numerous, but the most important are: a) geologic rocks are complex, polymineralic materials; b) the conditions of ablation are unusual (for example

  16. Developmental constraints on behavioural flexibility

    PubMed Central

    Holekamp, Kay E.; Swanson, Eli M.; Van Meter, Page E.

    2013-01-01

    We suggest that variation in mammalian behavioural flexibility not accounted for by current socioecological models may be explained in part by developmental constraints. From our own work, we provide examples of constraints affecting variation in behavioural flexibility, not only among individuals, but also among species and higher taxonomic units. We first implicate organizational maternal effects of androgens in shaping individual differences in aggressive behaviour emitted by female spotted hyaenas throughout the lifespan. We then compare carnivores and primates with respect to their locomotor and craniofacial adaptations. We inquire whether antagonistic selection pressures on the skull might impose differential functional constraints on evolvability of skulls and brains in these two orders, thus ultimately affecting behavioural flexibility in each group. We suggest that, even when carnivores and primates would theoretically benefit from the same adaptations with respect to behavioural flexibility, carnivores may nevertheless exhibit less behavioural flexibility than primates because of constraints imposed by past adaptations in the morphology of the limbs and skull. Phylogenetic analysis consistent with this idea suggests greater evolutionary lability in relative brain size within families of primates than carnivores. Thus, consideration of developmental constraints may help elucidate variation in mammalian behavioural flexibility. PMID:23569298

  17. Data assimilation with inequality constraints

    NASA Astrophysics Data System (ADS)

    Thacker, W. C.

    If values of variables in a numerical model are limited to specified ranges, these restrictions should be enforced when data are assimilated. The simplest option is to assimilate without regard for constraints and then to correct any violations without worrying about additional corrections implied by correlated errors. This paper addresses the incorporation of inequality constraints into the standard variational framework of optimal interpolation with emphasis on our limited knowledge of the underlying probability distributions. Simple examples involving only two or three variables are used to illustrate graphically how active constraints can be treated as error-free data when background errors obey a truncated multi-normal distribution. Using Lagrange multipliers, the formalism is expanded to encompass the active constraints. Two algorithms are presented, both relying on a solution ignoring the inequality constraints to discover violations to be enforced. While explicitly enforcing a subset can, via correlations, correct the others, pragmatism based on our poor knowledge of the underlying probability distributions suggests the expedient of enforcing them all explicitly to avoid the computationally expensive task of determining the minimum active set. If additional violations are encountered with these solutions, the process can be repeated. Simple examples are used to illustrate the algorithms and to examine the nature of the corrections implied by correlated errors.

  18. Developmental constraints on behavioural flexibility.

    PubMed

    Holekamp, Kay E; Swanson, Eli M; Van Meter, Page E

    2013-05-19

    We suggest that variation in mammalian behavioural flexibility not accounted for by current socioecological models may be explained in part by developmental constraints. From our own work, we provide examples of constraints affecting variation in behavioural flexibility, not only among individuals, but also among species and higher taxonomic units. We first implicate organizational maternal effects of androgens in shaping individual differences in aggressive behaviour emitted by female spotted hyaenas throughout the lifespan. We then compare carnivores and primates with respect to their locomotor and craniofacial adaptations. We inquire whether antagonistic selection pressures on the skull might impose differential functional constraints on evolvability of skulls and brains in these two orders, thus ultimately affecting behavioural flexibility in each group. We suggest that, even when carnivores and primates would theoretically benefit from the same adaptations with respect to behavioural flexibility, carnivores may nevertheless exhibit less behavioural flexibility than primates because of constraints imposed by past adaptations in the morphology of the limbs and skull. Phylogenetic analysis consistent with this idea suggests greater evolutionary lability in relative brain size within families of primates than carnivores. Thus, consideration of developmental constraints may help elucidate variation in mammalian behavioural flexibility. PMID:23569298

  19. Dynamics of intraoceanic subduction initiation: 2. Suprasubduction zone ophiolite formation and metamorphic sole exhumation in context of absolute plate motions

    NASA Astrophysics Data System (ADS)

    van Hinsbergen, Douwe J. J.; Peters, Kalijn; Maffione, Marco; Spakman, Wim; Guilmette, Carl; Thieulot, Cedric; Plümper, Oliver; Gürer, Derya; Brouwer, Fraukje M.; Aldanmaz, Ercan; Kaymakcı, Nuretdin

    2015-06-01

    Analyzing subduction initiation is key for understanding the coupling between plate tectonics and the underlying mantle. Here we focus on suprasubduction zone (SSZ) ophiolites and how their formation links to intraoceanic subduction initiation in an absolute plate motion frame. SSZ ophiolites form the majority of exposed oceanic lithosphere fragments and are widely recognized to have formed during intraoceanic subduction initiation. Structural, petrological, geochemical, and plate kinematic constraints on their kinematic evolution show that SSZ crust forms at fore-arc spreading centers at the expense of a mantle wedge, thereby flattening the nascent slab. This leads to the typical inverted pressure gradients found in metamorphic soles that form at the subduction plate contact below and during SSZ crust crystallization. Former spreading centers are preserved in forearcs when subduction initiates along transform faults or off-ridge oceanic detachments. We show how these are reactivated when subduction initiates in the absolute plate motion direction of the inverting weakness zone. Upon inception of slab pull due to, e.g., eclogitization, the sole is separated from the slab, remains welded to the thinned overriding plate lithosphere, and can become intruded by mafic dikes upon asthenospheric influx into the mantle wedge. We propound that most ophiolites thus formed under special geodynamic circumstances and may not be representative of normal oceanic crust. Our study highlights how far-field geodynamic processes and absolute plate motions may force intraoceanic subduction initiation as key toward advancing our understanding of the entire plate tectonic cycle.

  20. Absolute determination of inelastic mean-free paths and surface excitation parameters by absolute reflection electron energy loss spectrum analysis

    NASA Astrophysics Data System (ADS)

    Nagatomi, T.; Goto, K.

    2005-11-01

    An analytical approach was proposed for simultaneously determining an inelastic mean-free path (IMFP) and a surface excitation parameter (SEP) with absolute units by the analysis of an absolute experimental reflection electron energy loss spectrum. The IMFPs and SEPs in Ni were deduced for electrons of 300 to 3000 eV. The obtained IMFPs were in good agreement with those calculated using the TPP-2M equation. The Chen-type empirical formula was proposed for determining the SEP. The results confirmed the applicability of the present approach for determining the IMFP and SEP for medium-energy electrons.

  1. Series that Converge Absolutely but Don't Converge

    ERIC Educational Resources Information Center

    Kantrowitz, Robert; Schramm, Michael

    2012-01-01

    If a series of real numbers converges absolutely, then it converges. The usual proof requires completeness in the form of the Cauchy criterion. Failing completeness, the result is false. We provide examples of rational series that illustrate this point. The Cantor set appears in connection with one of the examples.

  2. Population-based absolute risk estimation with survey data.

    PubMed

    Kovalchik, Stephanie A; Pfeiffer, Ruth M

    2014-04-01

    Absolute risk is the probability that a cause-specific event occurs in a given time interval in the presence of competing events. We present methods to estimate population-based absolute risk from a complex survey cohort that can accommodate multiple exposure-specific competing risks. The hazard function for each event type consists of an individualized relative risk multiplied by a baseline hazard function, which is modeled nonparametrically or parametrically with a piecewise exponential model. An influence method is used to derive a Taylor-linearized variance estimate for the absolute risk estimates. We introduce novel measures of the cause-specific influences that can guide modeling choices for the competing event components of the model. To illustrate our methodology, we build and validate cause-specific absolute risk models for cardiovascular and cancer deaths using data from the National Health and Nutrition Examination Survey. Our applications demonstrate the usefulness of survey-based risk prediction models for predicting health outcomes and quantifying the potential impact of disease prevention programs at the population level. PMID:23686614

  3. Invalid phase values removal method for absolute phase recovery.

    PubMed

    Lu, Jin; Mo, Rong; Sun, Huibin; Chang, Zhiyong; Zhao, Xiaxia

    2016-01-10

    A novel approach is presented for more effectively removing invalid phase values in absolute phase recovery. The approach is based on a detailed study involving the types and cases of invalid phase values. Meanwhile, some commonalities of the existing removal algorithms also are thoroughly analyzed. It is well known that rough absolute phase and fringe order maps can very easily be obtained by temporal phase unwrapping techniques. After carefully analyzing the components and fringe order distribution of the rough fringe order map, the proposed method chiefly adopts an entirely new strategy to refine a pure fringe order map. The strategy consists of three parts: (1) the square of an image gradient, (2) subregion areas of the binary image, and (3) image decomposition and composition. In combination with the pure fringe order map and a removal criterion, the invalid phase values can be identified and filtered out from the rough absolute phase map. This new strategy not only gets rid of the limitations of traditional removal methods but also has a two-fold function. The paper also offers different metrics from the experiment to evaluate the quality of the final absolute phase. In contrast with other removal methods, experimental results have verified the feasibility, effectiveness, and superiority of the proposed method. PMID:26835776

  4. Absolute Value Inequalities: High School Students' Solutions and Misconceptions

    ERIC Educational Resources Information Center

    Almog, Nava; Ilany, Bat-Sheva

    2012-01-01

    Inequalities are one of the foundational subjects in high school math curricula, but there is a lack of academic research into how students learn certain types of inequalities. This article fills part of the research gap by presenting the findings of a study that examined high school students' methods of approaching absolute value inequalities,…

  5. Lyman alpha SMM/UVSP absolute calibration and geocoronal correction

    NASA Technical Reports Server (NTRS)

    Fontenla, Juan M.; Reichmann, Edwin J.

    1987-01-01

    Lyman alpha observations from the Ultraviolet Spectrometer Polarimeter (UVSP) instrument of the Solar Maximum Mission (SMM) spacecraft were analyzed and provide instrumental calibration details. Specific values of the instrument quantum efficiency, Lyman alpha absolute intensity, and correction for geocoronal absorption are presented.

  6. An improved generalized Newton method for absolute value equations.

    PubMed

    Feng, Jingmei; Liu, Sanyang

    2016-01-01

    In this paper, we suggest and analyze an improved generalized Newton method for solving the NP-hard absolute value equations [Formula: see text] when the singular values of A exceed 1. We show that the global and local quadratic convergence of the proposed method. Numerical experiments show the efficiency of the method and the high accuracy of calculation. PMID:27462490

  7. Relative versus Absolute Stimulus Control in the Temporal Bisection Task

    ERIC Educational Resources Information Center

    de Carvalho, Marilia Pinhiero; Machado, Armando

    2012-01-01

    When subjects learn to associate two sample durations with two comparison keys, do they learn to associate the keys with the short and long samples (relational hypothesis), or with the specific sample durations (absolute hypothesis)? We exposed 16 pigeons to an ABA design in which phases A and B corresponded to tasks using samples of 1 s and 4 s,…

  8. Absolute calibration of Landsat instruments using the moon.

    USGS Publications Warehouse

    Kieffer, H.H.; Wildey, R.L.

    1985-01-01

    A lunar observation by Landsat could provide improved radiometric and geometric calibration of both the Thematic Mapper and the Multispectral Scanner in terms of absolute radiometry, determination of the modulation transfer function, and sensitivity to scattered light. A pitch of the spacecraft would be required. -Authors

  9. Absence of absolutely continuous spectrum for random scattering zippers

    NASA Astrophysics Data System (ADS)

    Boumaza, Hakim; Marin, Laurent

    2015-02-01

    A scattering zipper is a system obtained by concatenation of scattering events with equal even number of incoming and outgoing channels. The associated scattering zipper operator is the unitary analog of Jacobi matrices with matrix entries. For infinite identical events and independent and identically distributed random phases, Lyapunov exponents positivity is proved and yields absence of absolutely continuous spectrum by Kotani's theory.

  10. Individual Differences in Absolute and Relative Metacomprehension Accuracy

    ERIC Educational Resources Information Center

    Maki, Ruth H.; Shields, Micheal; Wheeler, Amanda Easton; Zacchilli, Tammy Lowery

    2005-01-01

    The authors investigated absolute and relative metacomprehension accuracy as a function of verbal ability in college students. Students read hard texts, revised texts, or a mixed set of texts. They then predicted their performance, took a multiple-choice test on the texts, and made posttest judgments about their performance. With hard texts,…

  11. Mathematical Model for Absolute Magnetic Measuring Systems in Industrial Applications

    NASA Astrophysics Data System (ADS)

    Fügenschuh, Armin; Fügenschuh, Marzena; Ludszuweit, Marina; Mojsic, Aleksandar; Sokół, Joanna

    2015-09-01

    Scales for measuring systems are either based on incremental or absolute measuring methods. Incremental scales need to initialize a measurement cycle at a reference point. From there, the position is computed by counting increments of a periodic graduation. Absolute methods do not need reference points, since the position can be read directly from the scale. The positions on the complete scales are encoded using two incremental tracks with different graduation. We present a new method for absolute measuring using only one track for position encoding up to micrometre range. Instead of the common perpendicular magnetic areas, we use a pattern of trapezoidal magnetic areas, to store more complex information. For positioning, we use the magnetic field where every position is characterized by a set of values measured by a hall sensor array. We implement a method for reconstruction of absolute positions from the set of unique measured values. We compare two patterns with respect to uniqueness, accuracy, stability and robustness of positioning. We discuss how stability and robustness are influenced by different errors during the measurement in real applications and how those errors can be compensated.

  12. Absolute Radiometer for Reproducing the Solar Irradiance Unit

    NASA Astrophysics Data System (ADS)

    Sapritskii, V. I.; Pavlovich, M. N.

    1989-01-01

    A high-precision absolute radiometer with a thermally stabilized cavity as receiving element has been designed for use in solar irradiance measurements. The State Special Standard of the Solar Irradiance Unit has been built on the basis of the developed absolute radiometer. The Standard also includes the sun tracking system and the system for automatic thermal stabilization and information processing, comprising a built-in microcalculator which calculates the irradiance according to the input program. During metrological certification of the Standard, main error sources have been analysed and the non-excluded systematic and accidental errors of the irradiance-unit realization have been determined. The total error of the Standard does not exceed 0.3%. Beginning in 1984 the Standard has been taking part in a comparison with the Å 212 pyrheliometer and other Soviet and foreign standards. In 1986 it took part in the international comparison of absolute radiometers and standard pyrheliometers of socialist countries. The results of the comparisons proved the high metrological quality of this Standard based on an absolute radiometer.

  13. Multifrequency continuous wave terahertz spectroscopy for absolute thickness determination

    SciTech Connect

    Scheller, Maik; Baaske, Kai; Koch, Martin

    2010-04-12

    We present a tunable multifrequency continuous wave terahertz spectrometer based on two laser diodes, photoconductive antennas, and a coherent detection scheme. The system is employed to determine the absolute thickness of samples utilizing a proposed synthetic difference frequency method to circumvent the 2pi uncertainty known from conventional photomixing systems while preserving a high spatial resolution.

  14. Ion chambers simplify absolute intensity measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Sampson, J. A. R.

    1966-01-01

    Single or double ion chamber technique measures absolute radiation intensities in the extreme vacuum ultraviolet region of the spectrum. The ion chambers use rare gases as the ion carrier. Photon absorbed by the gas creates one ion pair so a measure of these is a measure of the number of incident photons.

  15. Is There a Rule of Absolute Neutralization in Nupe?

    ERIC Educational Resources Information Center

    Krohn, Robert

    1975-01-01

    A previously prosed rule of absolute neutralization (merging underlying low vowels) is eliminated in an alternative analysis including instead a rule that "breaks" the feature matrix of certain low vowels and redistributes the features of each vowel as a sequence of vowel-like transition plus (a). (Author/RM)

  16. Assignment of absolute stereochemistry by computation of optical rotation angles

    NASA Astrophysics Data System (ADS)

    Kondru, Rama Krishna

    We have developed simple wire and molecular orbital models to qualitatively and quantitatively understand optical rotation angles of molecules. We reported the first ab initio theoretical approach to determine the absolute stereochemistry of a complex natural product by calculating molar rotation angles, [M]D. We applied this method for an unambiguous assignment of the absolute stereochemistry of the hennoxazole A. A protocol analogous to population analysis was devised to analyze atomic contributions to the rotation angles for oxiranes, orthoesters, and other organic compounds. The molar rotations for an indoline, an indonone, menthol and menthone were calculated using ab inito methods and compared with experimental values. We reported the first prediction of the absolute configuration of a natural product, i.e. an a priori assignment of the relative and absolute stereochemistry of pitiamide A. Furthermore, we described a strategy that may help to establish structure-function relations for rotation angles by visualizing the electric and magnetic-field perturbations to a molecule's molecular orbitals.

  17. Hitting the target: relatively easy, yet absolutely difficult.

    PubMed

    Mapp, Alistair P; Ono, Hiroshi; Khokhotva, Mykola

    2007-01-01

    It is generally agreed that absolute-direction judgments require information about eye position, whereas relative-direction judgments do not. The source of this eye-position information, particularly during monocular viewing, is a matter of debate. It may be either binocular eye position, or the position of the viewing-eye only, that is crucial. Using more ecologically valid stimulus situations than the traditional LED in the dark, we performed two experiments. In experiment 1, observers threw darts at targets that were fixated either monocularly or binocularly. In experiment 2, observers aimed a laser gun at targets while fixating either the rear or the front gunsight monocularly, or the target either monocularly or binocularly. We measured the accuracy and precision of the observers' absolute- and relative-direction judgments. We found that (a) relative-direction judgments were precise and independent of phoria, and (b) monocular absolute-direction judgments were inaccurate, and the magnitude of the inaccuracy was predictable from the magnitude of phoria. These results confirm that relative-direction judgments do not require information about eye position. Moreover, they show that binocular eye-position information is crucial when judging the absolute direction of both monocular and binocular targets. PMID:17972479

  18. Absolute Risk Aversion and the Returns to Education.

    ERIC Educational Resources Information Center

    Brunello, Giorgio

    2002-01-01

    Uses 1995 Italian household income and wealth survey to measure individual absolute risk aversion of 1,583 married Italian male household heads. Uses this measure as an instrument for attained education in a standard-log earnings equation. Finds that the IV estimate of the marginal return to schooling is much higher than the ordinary least squares…

  19. Improved cavity-type absolute total-radiation radiometer

    NASA Technical Reports Server (NTRS)

    Kendall, J. M., Sr.; Plamondon, J. A., Jr.

    1967-01-01

    Conical cavity-type absolute radiometer measures the intensity of radiant energy to an accuracy of one to two percent in a vacuum of ten to the minus fifth torr or lower. There is a uniform response over the ultraviolet, visible, and infrared range, and it requires no calibration or comparison with a radiation standard.

  20. Absolute Interrogative Intonation Patterns in Buenos Aires Spanish

    ERIC Educational Resources Information Center

    Lee, Su Ar

    2010-01-01

    In Spanish, each uttered phrase, depending on its use, has one of a variety of intonation patterns. For example, a phrase such as "Maria viene manana" "Mary is coming tomorrow" can be used as a declarative or as an absolute interrogative (a yes/no question) depending on the intonation pattern that a speaker produces. Patterns of usage also…