Science.gov

Sample records for absolute age dating

  1. 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.

  2. Towards an Absolute Chronology for the Aegean Iron Age: New Radiocarbon Dates from Lefkandi, Kalapodi and Corinth

    PubMed Central

    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 8th 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 11th century BCE according to the Conventional Aegean Chronology and in the late 12th century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11th century BCE. PMID:24386150

  3. Plutonium age dating reloaded

    NASA Astrophysics Data System (ADS)

    Sturm, Monika; Richter, Stephan; Aregbe, Yetunde; Wellum, Roger; Mayer, Klaus; Prohaska, Thomas

    2014-05-01

    Although the age determination of plutonium is and has been a pillar of nuclear forensic investigations for many years, additional research in the field of plutonium age dating is still needed and leads to new insights as the present work shows: Plutonium is commonly dated with the help of the 241Pu/241Am chronometer using gamma spectrometry; in fewer cases the 240Pu/236U chronometer has been used. The age dating results of the 239Pu/235U chronometer and the 238Pu/234U chronometer are scarcely applied in addition to the 240Pu/236U chronometer, although their results can be obtained simultaneously from the same mass spectrometric experiments as the age dating result of latter. The reliability of the result can be tested when the results of different chronometers are compared. The 242Pu/238U chronometer is normally not evaluated at all due to its sensitivity to contamination with natural uranium. This apparent 'weakness' that renders the age dating results of the 242Pu/238U chronometer almost useless for nuclear forensic investigations, however turns out to be an advantage looked at from another perspective: the 242Pu/238U chronometer can be utilized as an indicator for uranium contamination of plutonium samples and even help to identify the nature of this contamination. To illustrate this the age dating results of all four Pu/U clocks mentioned above are discussed for one plutonium sample (NBS 946) that shows no signs of uranium contamination and for three additional plutonium samples. In case the 242Pu/238U chronometer results in an older 'age' than the other Pu/U chronometers, contamination with either a small amount of enriched or with natural or depleted uranium is for example possible. If the age dating result of the 239Pu/235U chronometer is also influenced the nature of the contamination can be identified; enriched uranium is in this latter case a likely cause for the missmatch of the age dating results of the Pu/U chronometers.

  4. 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.

  5. Toward The Absolute Age of M92 With MIST

    NASA Astrophysics Data System (ADS)

    Choi, Jieun; Conroy, Charlie; Dotter, Aaron; Weisz, Daniel; Rosenfield, Philip; Dolphin, Andrew

    2016-08-01

    Globular clusters provide a fundamental link between stars and galaxies. For example, it has been suggested that ultra faint dwarf galaxies formed all of their stars prior to the epoch of reionization, but this conclusion hinges entirely on the striking similarity of their stellar populations to the ancient, metal-poor globular cluster M92. The accurate measurement of absolute ages of ancient globular clusters therefore has direct implications for the formation histories of the smallest galaxies in the Universe. However, a reliable determination of the absolute ages of globular clusters has proven to be a challenge due to uncertainties in stellar physics and complications in how the models are compared to observations. I will present preliminary results from a comprehensive study to measure the absolute age of M92 using high-quality HST archival imaging data. We pair our new MESA Isochrones and Stellar Tracks (MIST) models with a full CMD fitting framework to jointly fit multi-color CMDs, taking into account the uncertainties in abundances, distance, and stellar physics. The goal of this project is two-fold. First, we aim to provide the most secure absolute age of M92 to date with robustly estimated uncertainties. Second, we explore and quantify the degeneracies between uncertain physical quantities and model variables, such as the distance, mixing-length-alpha parameter, and helium abundance, with the ultimate goal of better constraining these unknowns with data from ongoing and future surveys such as K2, Gaia, TESS, JWST, and WFIRST.

  6. Geomorphological Dating Using an Improved Scarp Degradation Model: Is This a Reliable Approach Compared With Common Absolute Dating Methods?

    NASA Astrophysics Data System (ADS)

    Oemisch, M.; Hergarten, S.; Neugebauer, H. J.

    2002-12-01

    Geomorphological dating of a certain landform or geomorphological structure is based on the evolution of the landscape itself. In this context it is difficult to use common absolute dating techniques such as luminescence and radiocarbon dating because they require datable material which is often not available. Additionally these methods do not always date the time since the formation of these structures. For these reasons the application of geomorphological dating seems one reliable possibility to date certain geomorphological features. The aim of our work is to relate present-day shapes of fault scarps and terrace risers to their ages. The time span since scarp formation ceased is reflected by the stage of degradation as well as the rounding of the profile edges due to erosive processes. It is assumed that the average rate of downslope soil movement depends on the local slope angle and can be described in terms of a diffusion equation. On the basis of these assumptions we present a model to simulate the temporal development of scarp degradation by erosion. A diffusivity reflecting the effects of soil erosion, surface runoff and detachability of particles as well as present-day shapes of scarps are included in the model. As observations of present-day scarps suggest a higher diffusivity at the toe than at the head of a slope, we suggest a linear approach with increasing diffusivities in downslope direction. First results show a better match between simulated and observed profiles of the Upper Rhine Graben in comparison to models using a constant diffusivity. To date the scarps the model has to be calibrated. For this purpose we estimate diffusivities by fitting modelled profiles to observed ones of known age. Field data have been collected in the area around Bonn, Germany and in the Alps, Switzerland. It is a matter of current research to assess the quality of this dating technique and to compare the results and the applicability with some of the absolute dating

  7. Absolute dating and palaeoenvironmental evolution in Palaeolithic Mani, SW Peloponnesus

    NASA Astrophysics Data System (ADS)

    Christodoulakis, John; Bassiakos, Yannis; Athanassas, Constantin

    2013-04-01

    Data derived from palaeoenvironmental indicators are considered the most reliable in back casting former environmental contexts and also, where possible, in forecasting future trends in the environment. The peninsula of Mani, southern Peloponnesus, southwestern Greece, is a challenging area for studying past environmental changes of the Upper Quaternary, because of its nodal position between three continents, its long and multifarious coastal zone, as well as its active local tectonic regime. A great deal of sea level oscillations and palaeoclimatic and palaeoanthropological evidence have been well-documented in the terrestrial and coastal sedimentery deposits of the peninsula, particularly for the later part of the Quaternary (Kelletat und Gassert, 1975, Imperatori, 1966). That evidence mostly comes from paleoenvironmental indicators such as raised marine notches and marine terraces, as well as from other,indicators, and is frequently associated with sites of paleoanthropological significance An important parameter of those sedimentary deposits is their chronology. To date, the chronological framework of those processes is only loosely constrained. A first effort to produce chronological data for this area was made about twenty years ago by applying electron spin resonance (ESR) dating to speleothems from the local subsurface caverns system and other karst formations. Here, by engaging luminescence dating, we aimed to further control former ESR chronology as well as to extend numeric dating on sedimentary formations previously non-datable through ESR alone (i.e. fluvial/deltaic sediments occurring in the area as well as anthropogenic composite deposits usually including burnt bones and fragments of stone tools). Specifically, optically stimulated luminescence (OSL) dating, combined with the single-aliquot regenerative dose (SAR) protocol, produced a number of ages that are in fair agreement with the previous ESR chronology. Current data allowed us to comprehend

  8. Passive absolute age and temperature history sensor

    DOEpatents

    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.

  9. The quest for an absolute chronology in human prehistory: anthropologists, chemists and the fluorine dating method in palaeoanthropology.

    PubMed

    Goodrum, Matthew R; Olson, Cora

    2009-03-01

    By the early twentieth century there was a growing need within palaeoanthropology and prehistoric archaeology to find a way of dating fossils and artefacts in order to know the age of specific specimens, but more importantly to establish an absolute chronology for human prehistory. The radiocarbon and potassium-argon dating methods revolutionized palaeoanthropology during the last half of the twentieth century. However, prior to the invention of these methods there were attempts to devise chemical means of dating fossil bone. Collaborations between Emile Rivière and Adolphe Carnot in the 1890s led to the development of the fluorine dating method, but it was not until the 1940s that this method was improved and widely implemented by Kenneth Oakley to resolve a number of problems in palaeoanthropology, including the Piltdown Man controversy. The invention of the fluorine dating method marked a significant advance in the quest for absolute dating in palaeoanthropology, but it also highlights interesting problems and issues relating to the ability of palaeoanthropologists and chemists to bring together different skills and bodies of knowledge in order successfully to develop and apply the fluorine dating method.

  10. Computational Age Dating of Special Nuclear Materials

    SciTech Connect

    None, None

    2012-06-30

    This slide-show presented an overview of the Constrained Progressive Reversal (CPR) method for computing decays, age dating, and spoof detecting. The CPR method is: Capable of temporal profiling a SNM sample; Precise (compared with known decay code, such a ORIGEN); Easy (for computer implementation and analysis). We have illustrated with real SNM data using CPR for age dating and spoof detection. If SNM is pure, may use CPR to derive its age. If SNM is mixed, CPR will indicate that it is mixed or spoofed.

  11. Absolute dating of Caribbean cores p6304-8 and p6304-9.

    PubMed

    Rona, E; Emiliani, C

    1969-01-03

    Two deep-sea cores from the central Caribbean have been dated by the thorium-230/ protactinium-231 method. The ages obtained are in agreement with the ages previously obtained from other deep-sea cores from the same area. Because of their greater precision, the new dates provide a more accurate time scale for the past 170,000 years.

  12. An absolute chronology for early Egypt using radiocarbon dating and Bayesian statistical modelling.

    PubMed

    Dee, Michael; Wengrow, David; Shortland, Andrew; Stevenson, Alice; Brock, Fiona; Girdland Flink, Linus; Bronk Ramsey, Christopher

    2013-11-08

    The Egyptian state was formed prior to the existence of verifiable historical records. Conventional dates for its formation are based on the relative ordering of artefacts. This approach is no longer considered sufficient for cogent historical analysis. Here, we produce an absolute chronology for Early Egypt by combining radiocarbon and archaeological evidence within a Bayesian paradigm. Our data cover the full trajectory of Egyptian state formation and indicate that the process occurred more rapidly than previously thought. We provide a timeline for the First Dynasty of Egypt of generational-scale resolution that concurs with prevailing archaeological analysis and produce a chronometric date for the foundation of Egypt that distinguishes between historical estimates.

  13. 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.

  14. Age and forgetfulness: absolute versus comparison decisions about capability.

    PubMed

    Erber, J T; Prager, I G

    1997-01-01

    Perceivers were assigned to one of two decision conditions. In an absolute decision condition, perceivers rated how likely they would be to allow a young or old highly forgetful, slightly forgetful, or nonforgetful target to perform a challenging task. In a comparison decision condition, perceivers rated two targets, one young and one old, who had a similar level of forgetfulness. Separate Decision Type x Target Forgetfulness analyses of variance were conducted on ratings of the two target age groups. Young targets received higher ratings in the comparison than in the absolute condition, whereas old targets were rated the same in the two conditions. There was some preference for young targets in a comparison situation, but it was concluded that forgetfulness was a more important factor than age in perceivers' ratings.

  15. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  16. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  17. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  18. 27 CFR 19.410 - Age and fill date.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Age and fill date. 19.410... Spirits from Customs Custody § 19.410 Age and fill date. For purposes of this part, the age and fill date for spirits imported or brought into the United States will be: (a) The claimed age, as shown on...

  19. 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

  20. Absolute Dating of Strath Terraces along the Western High Plains Reveals Complicated History of Occupation and Incision

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Gray, H. J.; Mahan, S.

    2015-12-01

    Gravel-capped strath terraces are preserved along the western High Plains, adjacent to the Colorado Front Range. Terrace elevations appear to connect across the landscape, representing previous levels of the Denver Basin during fluvial exhumation. In this tectonically quiescent region, climatically-driven fluctuations in sediment supply are often interpreted to drive terrace occupation and basin exhumation. We dated a series of strath terraces near Boulder, CO using 10Be/26Al cosmogenic radionuclides (CRNs) and optically stimulated luminescence. Results reveal: (1) a long history of fluvial occupation (0.5-1.0 Myr duration), with recent (<120 ka) fluvial abandonment of the highest surface; (2) a brief occupation of a narrow spillway, abandoned at 97.0 ± 4.2 ka, preserved because the stream was subsequently pirated; and (3) a long period of fluvial occupation of a lower terrace, recorded by the deposition of distinct gravel packages at 50-75 ka and 40.5 ± 5.0 ka. In conjunction with absolute dating on nearby terraces, our study indicates the system is more complex than originally thought. Ages are not consistent among terraces of similar elevations deposited by different stream systems. The link between terrace age and climate is not straightforward, as terraces can be occupied through several glacial-interglacial cycles. When a surface is abandoned, incision to the next level appears to occur quite rapidly through the soft Cretaceous shales. Long-term incision rates may be derived from elevations and ages of high preserved surfaces, but such incision rates reflect long periods of no vertical erosion punctuated with short periods of rapid incision. Such interpretations would not be possible without paired CRNs or combination with other geochronologic techniques. This study therefore represents a cautionary tale for the interpretation of tectonic or climatic processes and process rates from single-method dating of fluvial terraces.

  1. 27 CFR 19.482 - Age and fill date.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Age and fill date. 19.482... OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Spirits from Customs Custody § 19.482 Age and fill date. For the purpose of this part, the age and fill date for spirits that are imported or brought...

  2. Age-specific absolute and relative organ weight distributions for Fischer 344 rats.

    PubMed

    Marino, Dale J

    2012-01-01

    The Fischer 344 (F344) rat has been the standard rat strain used in toxicology studies conducted by the National Cancer Institute (NCI) and the National Toxicology Program (NTP). However, the numerous reports published to date on growth, survival, and tumor incidence have not included an overall compilation of organ weight data. Notably, dose-related organ weight effects are endpoints used by regulatory agencies to develop toxicity reference values (TRVs) for use in human health risk assessments. In addition, physiologically-based pharmacokinetic (PBPK) models, which utilize relative organ weights, are increasingly being used to develop TRVs. Because a compilation of organ weights for F344 rats could prove beneficial for TRV development and PBPK modeling, all available absolute and relative organ weight data for untreated control F344 rats were collected from NCI/NTP feed, drinking-water, and inhalation studies in order to develop age-specific distributions. Results showed that organ weights were collected more frequently at 2-wk (59 studies), 3-mo (148 studies), and 15-mo (38 studies) intervals than at other intervals and more frequently from feeding and inhalation than from drinking-water studies. Liver, right kidney, lung, heart, thymus, and brain weights were most frequently collected. From the collected data, the mean and standard deviation for absolute and relative organ weights were calculated. Findings showed age-related increases in absolute weights and decreases in relative weights for brain, liver, right kidney, lung, heart, thyroid, and right testis. The results suggest a general variability trend in absolute organ weights of brain < right testis < heart < right kidney < liver < lung < thymus < thyroid.

  3. Combined use of relative and absolute dating techniques for detecting signals of Alpine landscape evolution during the late Pleistocene and early Holocene

    NASA Astrophysics Data System (ADS)

    Favilli, Filippo; Egli, Markus; Brandova, Dagmar; Ivy-Ochs, Susan; Kubik, Peter; Cherubini, Paolo; Mirabella, Aldo; Sartori, Giacomo; Giaccai, Daniele; Haeberli, Wilfried

    2009-11-01

    A combination of three relative and two absolute (numerical) dating techniques, applied on nine soil profiles in an Alpine environment located in Val di Rabbi (Trentino, Northern Italy), was used to improve the investigation methodology of Alpine sites in response to climate change and to reconstruct the chronology of late Pleistocene and early Holocene landscape evolution. The degree of podzolisation, clay mineral evolution and the element mass balances of each site were investigated. Furthermore, the stable fraction of the soil organic matter (SOM) was extracted with 10% H 2O 2 and 14C-dated. The age of the organic residues was compared with the age of charcoal fragments found in one of the studied soils and with the age of rock boulders obtained by surface exposure dating (SED) with cosmogenic 10Be. Numerical dating and weathering characteristics of the soils showed a fairly good agreement and enabled a relative and absolute differentiation of landscape elements. The combination of 14C-dating of SOM and SED indicated that deglaciation processes in Val di Rabbi were already far advanced by around 14 000 cal BP and that glacier oscillations affected the highest part of the region until about 9000 cal BP. The development of clay minerals is time-dependent and reflects weathering intensity. We found a close link between secondary clay minerals like smectite or vermiculite and soil age as obtained by the dating of the organic residues after the H 2O 2 treatment. Calculated element mass balances strongly correlated with the ages derived from 14C measurements. Old soils have lost a major part of base cations (up to 75% compared to the parent material), Fe and Al, which indicates a continuous high weathering intensity. Results of the chemical and mineralogical analyses were in good agreement with numerical dating techniques, showing the dynamics of an Alpine landscape within a relatively small area. The combination of relative and absolute dating techniques is a

  4. Age-dating of rockslides: Methods and limitations

    NASA Astrophysics Data System (ADS)

    Ostermann, M.; Sanders, D.; Prager, C.

    2009-04-01

    Age-dating of deposits of catastrophic rockslides is prerequisite to unravel the potential relation between the frequency of mass-wasting events with climatic change or earthquakes. In the Alps, about 250 rockslides exceeding 106 m3 in volume are known, but the age as yet is determined only for a comparatively small number of events. For age determination of rockslide events, different methods are available (e. g. Lang et al., 1999). Radiocarbon Dating In the past few decades, rockslide deposits commonly were proxy-dated by 14C age determination of organic remnants preserved (a) in glacial, fluvio-glacial sediments overridden by the rockslide, (b) within the rockslide mass, or (c) in rockslide-dammed backwater deposits or lakes situated atop the rockslide mass. In each case, the 14C age provides a different constraint on the age of the rockslide event: in case (a), the 14C age represents a maximum age of the event; in case (b), which is quite rare, the 14C age is generally considered as a good proxy of the event age; in case (c) the 14C age represents a minimum age for the rockslide event. Unfortunately, radiocarbon dating often cannot be applied because of absence of suited deposits or exposures thereof, lack of organic remnants or of remnants suited for age-dating, and/or because determined 14C ages are substantially biased. Optically Stimulated Luminescence (OSL) Proxy-dating of rockslide events by OSL can be applied to silt- to sand-sized quartzose sediments present (a) directly below, (b) within, or (c) above/laterally aside a rockslide mass. For each case (a) to (c), the determined ages are subject to the same constraints as outlined for radiocarbon dating. Unfortunately, situations allowing for application of OSL to rockslide event dating are comparatively rare, and the resulting ages tend to have a wide error range. Surface Exposure Dating with cosmogenic radionuclides Surface exposure ages can be determined for rock samples taken from the sliding planes at

  5. Tectonic structures on Mercury: kinematics and age dating

    NASA Astrophysics Data System (ADS)

    Giacomini, Lorenza; Massironi, Matteo; Rothery, David; Di Achille, Gaetano; Marchi, Simone; Galluzzi, Valentina; Ferrari, Sabrina; Fassett, Caleb; Cremonese, Gabriele

    2015-04-01

    At a global scale, Mercury is dominated by contractional features manifested as lobate scarps, wrinkle ridges and high-relief ridges. Here, we show that some of these features are associated with strike-slip kinematic indicators, which we identified using flyby and orbital Mercury Dual Imaging System (MDIS) data and digital terrain models. We recognize oblique-shear kinematics along lobate scarps and high-relief ridges by means of (1) map geometries of fault patterns (frontal thrusts bordered by lateral ramps, strike-slip duplexes, restraining bends); (2) structural morphologies indicating lateral shearing (en echelon folding, pop-ups, pull-aparts); and (3) estimates of offsets based on displaced crater rims and differences in elevation between pop-up structures and pull-apart basins and their surroundings. Transpressional faults, documented across a wide range of latitudes, are found associated with reactivated rims of ancient buried basins and, in most cases, linked to frontal thrusts as lateral ramps hundreds of kilometres long. This latter observation suggests stable directions of tectonic transport over wide regions of Mercury's surface. In contrast, global cooling would imply an overall isotropic contraction with limited processes of lateral shearing induced by pre-existent lithospheric heterogeneities. Mantle convection therefore may have played an important role during the early tectonic evolution of Mercury. Estimating absolute model ages for compressional features and comparing it from what it is envisaged with thermal modeling based on cooling alone can be useful in determining if other processes could have been responsible for lobate scarps nucleation. In particular, ages more ancient that the one predicted by the models would imply other kind of tectonic processes ongoing during the early evolution of Mercury . For this reason, we date an extended thrust system, which we term the Blossom Thrust System, located between 80°E and 100°E, and 30°N and 15

  6. 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

  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. Absolute age Determinations on Diamond by Radioisotopic Methods: NOT the way to Accurately Identify Diamond Provenance

    NASA Astrophysics Data System (ADS)

    Shirey, S. B.

    2002-05-01

    Gem-quality diamond contains such low abundances of parent-daughter radionuclides that dating the diamond lattice directly by isotopic measurements has been and will be impossible. Absolute ages on diamonds typically are obtained through measurements of their syngenetic mineral inclusions: Rb-Sr in garnet; Sm-Nd in garnet and pyroxene; Re-Os and U-Th-Pb in sulfide; K-Ar in pyroxene; and U-Pb in zircon. The application of the first two isotope schemes in the list requires putting together many inclusions from many diamonds whereas the latter isotope schemes permit ages on single diamonds. The key limitations on the application of these decay pairs are the availability and size of the inclusions, the abundance levels of the radionuclides, and instrumental sensitivity. Practical complications of radioisotope dating of inclusions are fatal to the application of the technique for diamond provenance. In all mines, the ratio of gem-quality diamonds to stones with datable inclusions is very high. Thus there is no way to date the valuable, marketable stones that are part of the conflict diamond problem, just their rare, flawed cousins. Each analysis destroys the diamond host plus the inclusion and can only be carried out in research labs by highly trained scientists. Thus, these methods can not be automated or applied to the bulk of diamond production. The geological problems with age dating are equally fatal to its application to diamond provenance. From the geological perspective, for age determination to work as a tool for diamond provenance studies, diamond ages would have to be specific to particular kimberlites or kimberlite fields and different between fields. The southern African Kaapvaal-Zimbabwe Craton and Limpopo Mobile Belt is the only cratonic region where age determinations have been applied on a large enough scale to a number of kimberlites to illustrate the geological problems in age measurements for diamond provenance. However, this southern African example

  9. Luminescence dating of Middle Stone Age deposits at Die Kelders.

    PubMed

    Feathers, J K; Bush, D A

    2000-01-01

    Luminescence dating of sediments has not been used extensively for dating Middle Stone Age deposits in South Africa, despite its potential for contributing to a poorly dated record. Such deposits at Die Kelders cave, on the southern South African coast, consist of narrow bands of occupation debris separated by thicker layers of aeolian sands containing much less evidence of occupation. Homogeneous, aeolian sediments are usually considered ideal for luminescence dating. Here we report luminescence analyses of five samples from these sands that demonstrate sufficient bleaching prior to burial to validate dating and that yield ages of about 60-70 ka, in agreement with other evidence from sedimentology, archaeology and electron spin resonance. Lack of significant differences in the ages suggests the deposits accumulated fairly rapidly during the early part of the Last Glaciation.

  10. Archaeomagnetic Dating of Bronze Age Pottery in Syria: New Intensity Data for 2300 to 1000 BCE

    NASA Astrophysics Data System (ADS)

    Stillinger, M. D.; Feinberg, J. M.; Frahm, E.

    2013-12-01

    In order to construct meaningful site chronologies, Near Eastern archaeologists have traditionally relied on relative dating techniques, such as ceramic seriation and textual/glyptic evidence. The introduction of radiocarbon dating provided archaeologists with an absolute dating tool to address age discrepancies. However, many sites do not contain sufficient or suitable materials for radiocarbon analysis, requiring the need for an alternative absolute dating tool. Archaeomagnetic dating provides such an alternative. Excavations at Tell Mozan (Bronze-Age Urkesh) in northeastern Syria have revealed evidence for nearly 5000 years of occupation in strata containing a variety of diagnostic ceramic artifacts, which form the basis for a well-established relative site chronology. In order to test the agreement between seriation ages and paleomagnetic-derived ages, archaeointensity experiments were conducted on pottery specimens from six well-stratified occupational layers spanning more than a thousand years of the site's primary occupation. Archaeointensity was determined using the IZZI paleointensity protocol of Tauxe and Staudigel (2004), and all estimates were corrected for remanence anisotropy and cooling rate effects, resulting in an 88% success rate (n = 51). The magnetic mineral assemblage of each sample was also characterized using a comprehensive suite of rock magnetic techniques. Final results were compared with previous archaeointensity studies in the region, and 70% of the magnetically-derived ages agree with the archaeologically-derived dates within a 1σ confidence interval, while 76% agreed within 2σ. Artifacts showing disagreement with the seriation chronology are most likely objects in use long after their original firing or the result of contamination of strata from the re-use of previous occupational materials in construction. One specimen appears to confirm the presence of a geomagnetic spike around 1000 BCE previously identified in Syria, Israel

  11. Age Dating of Mixed SNM--Preliminary Investigations

    SciTech Connect

    Yuan, D., Guss, P. P., Yfantis, E., Klingensmith, A., Emer, D.

    2011-12-01

    Recently we investigated the nuclear forensics problem of age determination for mixed special nuclear material (SNM). Through limited computational mixing experiments and interactive age analysis, it was observed that age dating results are generally affected by the mixing of samples with different assays or even by small radioactive material contamination. The mixing and contamination can be detected through interactive age analysis, a function provided by the Decay Interaction, Visualization and Analysis (DIVA) software developed by NSTec. It is observed that for mixed SNM with two components, the age estimators typically fall into two distinct clusters on the time axis. This suggests that averaging or other simple statistical methods may not always be suitable for age dating SNM mixtures. Instead, an interactive age analysis would be more suitable for age determination of material components of such SNM mixtures. This work was supported by the National Center for Nuclear Security (NCNS).

  12. On the Absolute Age of the Globular Cluster M92

    NASA Astrophysics Data System (ADS)

    Di Cecco, A.; Becucci, R.; Bono, G.; Monelli, M.; Stetson, P. B.; Degl’Innocenti, S.; Prada Moroni, P. G.; Nonino, M.; Weiss, A.; Buonanno, R.; Calamida, A.; Caputo, F.; Corsi, C. E.; Ferraro, I.; Iannicola, G.; Pulone, L.; Romaniello, M.; Walker, A. R.

    2010-09-01

    We present precise and deep optical photometry of the globular M92. Data were collected in three different photometric systems: Sloan Digital Sky Survey (g‧, r‧, i‧, and z‧ MegaCam at CFHT), Johnson-Kron-Cousins (B, V, and I; various ground-based telescopes), and Advanced Camera for Surveys (ACS) Vegamag (F475W, F555W, and F814W; Hubble Space Telescope). Special attention was given to the photometric calibration, and the precision of the ground-based data is generally better than 0.01 mag. We computed a new set of α-enhanced evolutionary models accounting for the gravitational settling of heavy elements at fixed chemical composition ([α/Fe] = +0.3, [Fe/H] = -2.32 dex, and Y = 0.248). The isochrones—assuming the same true distance modulus (μ = 14.74 mag), the same reddening [E(B - V) = 0.025 ± 0.010 mag], and the same reddening law—account for the stellar distribution along the main sequence and the red giant branch in different color-magnitude diagrams (i‧, g‧ - i‧ i‧, and g‧ - r‧ i‧, g‧ - z‧ I, and B - I and F814W and F475W–F814W). The same outcome applies to the comparison between the predicted zero-age horizontal-branch (ZAHB) and the HB stars. We also found a cluster age of 11 ± 1.5 Gyr, in good agreement with previous estimates. The error budget accounts for uncertainties in the input physics and the photometry. To test the possible occurrence of CNO-enhanced stars, we also computed two sets of α- and CNO-enhanced (by a factor of 3) models, both at fixed total metallicity ([M/H] = -2.10 dex) and at fixed iron abundance. We found that the isochrones based on the former set give the same cluster age (11 ± 1.5 Gyr) as the canonical α-enhanced isochrones. The isochrones based on the latter set also give a similar cluster age (10 ± 1.5 Gyr). These findings support previous results concerning the weak sensitivity of cluster isochrones to CNO-enhanced chemical mixtures. This paper makes use of data obtained from the Isaac

  13. Radiocarbon dating of marine material: mollusc versus foraminifera ages

    NASA Astrophysics Data System (ADS)

    Callard, L.; Long, A. J.; Plets, R. M.; Cooper, A.; Belknap, D. F.; Edwards, R.; Jackson, D.; Kelley, J. T.; Long, D.; Milne, G. A.; Monteys, X.; Quinn, R.

    2013-12-01

    A key challenge in reconstructing Quaternary environmental change from marine archives is developing a robust chronology. During the last ~50k a-1, radiocarbon dating is the mainstay for many studies. Often investigators are restricted in the material that is available for dating, with studies relying on AMS dating of either mono-specific or mixed assemblages of foraminifera. In some instances, marine molluscs (broken or whole, articulated or disarticulated) may also be present and can provide an alternative or complementary dating target. Previous radiocarbon dating of paired foraminiferal and marine molluscan samples from the Kattegat (Denmark) revealed significant age offsets between these materials, inferred to reflect greater reworking of foraminifera compared to the marine molluscs (Heier-Nielsen et al., 1995). Here we present the results of a comparable study from the Irish Sea Basin, which forms part of a wider investigation into the evidence for the Late Glacial sea-level minima at offshore sites from around Britain and Ireland. We have collected and AMS 14C-dated twelve paired samples of foraminifera and marine shells. The results shows a systematic age offset with the monospecific foraminifera samples consistently giving older ages than their shell counterparts. This offset increases with sample age, reaching a maximum offset of 3000 years in the oldest sample (~ 13 ka cal a BP). These results are consistent with the observations of Heier-Nielsen et al. (1995), and we hypothesize that foraminifera may be more susceptible to reworking from older deposits because of their lower effective density than the shell samples. However, foraminifera size and shape may also be contributing factors. These findings are potentially significant for studies that develop chronologies based on radiocarbon dating of foraminifera alone, since the resulting dates may over-estimate sample age by several thousand years. We conclude by outlining an experimental design that seeks

  14. Older Adults' Online Dating Profiles and Successful Aging.

    PubMed

    Wada, Mineko; Mortenson, William Bennett; Hurd Clarke, Laura

    2016-12-01

    This study examined how relevant Rowe and Kahn's three criteria of successful aging were to older adults' self-portrayals in online dating profiles: low probability of disease and disability, high functioning, and active life engagement. In this cross-sectional study, 320 online dating profiles of older adults were randomly selected and coded based on the criteria. Logistic regression analyses determined whether age, gender, and race/ethnicity predicted self-presentation. Few profiles were indicative of successful aging due to the low prevalence of the first two criteria; the third criterion, however, was identified in many profiles. Native Americans were significantly less likely than other ethnic groups to highlight the first two criteria. Younger age predicted presenting the first criterion. Women's presentation of the third criterion remained significantly high with age. The findings suggest that the criteria may be unimportant to older adults when seeking partners, or they may reflect the exclusivity of this construct.

  15. Surface dating of dynamic landforms: young boulders on aging moraines.

    PubMed

    Hallet, B; Putkonen, J

    1994-08-12

    The dating of landforms is crucial to understanding the evolution, history, and stability of landscapes. Cosmogenic isotope analysis has recently been used to determine quantitative exposure ages for previously undatable landform surfaces. A pioneering application of this technique to date moraines illustrated its considerable potential but suggested a chronology partially inconsistent with existing geological data. Consideration of the dynamic nature of landforms and of the ever-present processes of erosion, deposition, and weathering leads to a resolution of this inconsistency and, more generally, offers guidance for realistic interpretation of exposure ages.

  16. Cation-ratio dating: A new rock varnish age-determination technique

    NASA Astrophysics Data System (ADS)

    Dorn, Ronald I.

    1983-07-01

    Rock varnish coats many surfaces of geomorphic and archaeologic interest in arid lands. All varnish dating techniques are limited by the time lag between the exposure of a surface to subaerial processes and the onset of varnishing. They are valid only where manganese is not remobilized after deposition, for example, in most arid environments. The premise of a new age-determination method, cation-ratio dating, is that the ratio of the more mobile cations (e.g., K and Ca) to titanium in varnish decreases with time. Although there are many inherent assumptions and potential limitations, cation-ratio dating has been verified on relative age-sequences from a Death Valley debris cone, Negev Desert talus flatirons, and prehistoric lake levels at Searles Lake in California. Varnish cation ratios have been calibrated to independently dated surfaces in the Coso volcanic field and vicinity in California. Tentative absolute dates have been assigned to geomorphic surfaces in the Coso area. Cation ratios have been used to distinguish relative ages of archaeologic artifacts in southwestern North America and to demonstrate that varnish at the South Stoddard locality, Mojave Desert, did not form in 25 yr.

  17. Rewriting the Central European Early Bronze Age Chronology: Evidence from Large-Scale Radiocarbon Dating

    PubMed Central

    Knipper, Corina; Friedrich, Ronny; Kromer, Bernd; Lindauer, Susanne; Radosavljević, Jelena; Wittenborn, Fabian; Krause, Johannes

    2015-01-01

    The transition from the Neolithic to the Early Bronze Age in Central Europe has often been considered as a supra-regional uniform process, which led to the growing mastery of the new bronze technology. Since the 1920s, archaeologists have divided the Early Bronze Age into two chronological phases (Bronze A1 and A2), which were also seen as stages of technical progress. On the basis of the early radiocarbon dates from the cemetery of Singen, southern Germany, the beginning of the Early Bronze Age in Central Europe was originally dated around 2300/2200 BC and the transition to more complex casting techniques (i.e., Bronze A2) around 2000 BC. On the basis of 140 newly radiocarbon dated human remains from Final Neolithic, Early and Middle Bronze Age cemeteries south of Augsburg (Bavaria) and a re-dating of ten graves from the cemetery of Singen, we propose a significantly different dating range, which forces us to re-think the traditional relative and absolute chronologies as well as the narrative of technical development. We are now able to date the beginning of the Early Bronze Age to around 2150 BC and its end to around 1700 BC. Moreover, there is no transition between Bronze (Bz) A1 and Bronze (Bz) A2, but a complete overlap between the type objects of the two phases from 1900–1700 BC. We thus present a revised chronology of the assumed diagnostic type objects of the Early Bronze Age and recommend a radiocarbon-based view on the development of the material culture. Finally, we propose that the traditional phases Bz A1 and Bz A2 do not represent a chronological sequence, but regionally different social phenomena connected to the willingness of local actors to appropriate the new bronze technology. PMID:26488413

  18. Rewriting the Central European Early Bronze Age Chronology: Evidence from Large-Scale Radiocarbon Dating.

    PubMed

    Stockhammer, Philipp W; Massy, Ken; Knipper, Corina; Friedrich, Ronny; Kromer, Bernd; Lindauer, Susanne; Radosavljević, Jelena; Wittenborn, Fabian; Krause, Johannes

    2015-01-01

    The transition from the Neolithic to the Early Bronze Age in Central Europe has often been considered as a supra-regional uniform process, which led to the growing mastery of the new bronze technology. Since the 1920s, archaeologists have divided the Early Bronze Age into two chronological phases (Bronze A1 and A2), which were also seen as stages of technical progress. On the basis of the early radiocarbon dates from the cemetery of Singen, southern Germany, the beginning of the Early Bronze Age in Central Europe was originally dated around 2300/2200 BC and the transition to more complex casting techniques (i.e., Bronze A2) around 2000 BC. On the basis of 140 newly radiocarbon dated human remains from Final Neolithic, Early and Middle Bronze Age cemeteries south of Augsburg (Bavaria) and a re-dating of ten graves from the cemetery of Singen, we propose a significantly different dating range, which forces us to re-think the traditional relative and absolute chronologies as well as the narrative of technical development. We are now able to date the beginning of the Early Bronze Age to around 2150 BC and its end to around 1700 BC. Moreover, there is no transition between Bronze (Bz) A1 and Bronze (Bz) A2, but a complete overlap between the type objects of the two phases from 1900-1700 BC. We thus present a revised chronology of the assumed diagnostic type objects of the Early Bronze Age and recommend a radiocarbon-based view on the development of the material culture. Finally, we propose that the traditional phases Bz A1 and Bz A2 do not represent a chronological sequence, but regionally different social phenomena connected to the willingness of local actors to appropriate the new bronze technology.

  19. Reliability of current CFC data for age dating of water

    NASA Astrophysics Data System (ADS)

    Davila, Pablo; Kuells, Christoph

    2010-05-01

    Age dating of water based on dissolved CFCs and Krypton-85 has been applied extensively for many years. CFCs were adopted as an approach for water dating due to the availability of global input functions and because of a straightforward methodology. In the last decade, due to international treaties, CFCs production and atmospheric concentrations of some trace gases (e.g. Krypton-85) are decreasing. The impact of reduced atmospheric trace gas concentrations on precision and uncertainty of age dating are investigated. Methods for the quantification of uncertainties and approaches for data analysis are presented. The uncertainty analysis is based on the application of different residence time distributions (piston-flow, exponential, advection-dispersion models and combined thereof) for trace gas concentrations and trace gas ratios. Different ways forward are presented to solve the problem of age ambiguity and increased uncertainty: the use of trace gas ratios is demonstrated and their potential of separating pre- and post-peak samples; the combined use of CFCs with additional tracers such as SF6 and 3H are discussed. While both SF6 and tritium have technical limitations themselves, such as multi-finality and observed deviations from the input function, benefit can be gained by combining them with other tracers or combined data analysis approaches. The quantification of uncertainties and of the adaptation of stringent data analysis provides a basis for the use and critical evaluation of CFCs as water age dating methods in the future.

  20. Ar/Ar Dating Independent of Monitor Standard Ages

    NASA Astrophysics Data System (ADS)

    Boswell, S.; Hemming, S. R.

    2015-12-01

    Because the reported age of an analyzed sample is dependent on the age of the co-irradiated monitor standard(s), Ar/Ar dating is a relative dating technique. There is disagreement at the 1% scale in the age of commonly used monitor standards, and there is a great need to improve the inter-laboratory calibrations. Additionally, new approaches and insights are needed to meet the challenge of bringing the Ar/Ar chronometer to the highest possible precision and accuracy. In this spirit, we present a conceptual framework for Ar/Ar dating that does not depend on the age of monitor standards, but only on the K content of a solid standard. The concept is demonstrated by introducing a re-expressed irradiation parameter (JK) that depends on the ratio of 39ArK to 40Ar* rather than the 40Ar*/39ArK ratio. JK is equivalent to the traditional irradiation parameter J and is defined as JK = (39Ar/40K) • (λ/λe). The ultimate precision and accuracy of the method will depend on how precisely and accurately the 39Ar and 40K can be estimated, and will require isotope dilution measurements of both from the same aliquot. We are testing the workability of our technique at the 1% level by measuring weighed and irradiated hornblende and biotite monitor standards using GLO-1 glauconite to define a calibration curve for argon signals versus abundance.

  1. Young asteroidal fluid activity revealed by absolute age from apatite in carbonaceous chondrite.

    PubMed

    Zhang, Ai-Cheng; Li, Qiu-Li; Yurimoto, Hisayoshi; Sakamoto, Naoya; Li, Xian-Hua; Hu, Sen; Lin, Yang-Ting; Wang, Ru-Cheng

    2016-09-29

    Chondritic meteorites, consisting of the materials that have formed in the early solar system (ESS), have been affected by late thermal events and fluid activity to various degrees. Determining the timing of fluid activity in ESS is of fundamental importance for understanding the nature, formation, evolution and significance of fluid activity in ESS. Previous investigations have determined the relative ages of fluid activity with short-lived isotope systematics. Here we report an absolute (207)Pb/(206)Pb isochron age (4,450±50 Ma) of apatite from Dar al Gani (DaG) 978, a type ∼3.5, ungrouped carbonaceous chondrite. The petrographic, mineralogical and geochemical features suggest that the apatite in DaG 978 should have formed during metamorphism in the presence of a fluid. Therefore, the apatite age represents an absolute age for fluid activity in an asteroidal setting. An impact event could have provided the heat to activate this young fluid activity in ESS.

  2. Young asteroidal fluid activity revealed by absolute age from apatite in carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Zhang, Ai-Cheng; Li, Qiu-Li; Yurimoto, Hisayoshi; Sakamoto, Naoya; Li, Xian-Hua; Hu, Sen; Lin, Yang-Ting; Wang, Ru-Cheng

    2016-09-01

    Chondritic meteorites, consisting of the materials that have formed in the early solar system (ESS), have been affected by late thermal events and fluid activity to various degrees. Determining the timing of fluid activity in ESS is of fundamental importance for understanding the nature, formation, evolution and significance of fluid activity in ESS. Previous investigations have determined the relative ages of fluid activity with short-lived isotope systematics. Here we report an absolute 207Pb/206Pb isochron age (4,450+/-50 Ma) of apatite from Dar al Gani (DaG) 978, a type ~3.5, ungrouped carbonaceous chondrite. The petrographic, mineralogical and geochemical features suggest that the apatite in DaG 978 should have formed during metamorphism in the presence of a fluid. Therefore, the apatite age represents an absolute age for fluid activity in an asteroidal setting. An impact event could have provided the heat to activate this young fluid activity in ESS.

  3. Molecular dating, evolutionary rates, and the age of the grasses.

    PubMed

    Christin, Pascal-Antoine; Spriggs, Elizabeth; Osborne, Colin P; Strömberg, Caroline A E; Salamin, Nicolas; Edwards, Erika J

    2014-03-01

    Many questions in evolutionary biology require an estimate of divergence times but, for groups with a sparse fossil record, such estimates rely heavily on molecular dating methods. The accuracy of these methods depends on both an adequate underlying model and the appropriate implementation of fossil evidence as calibration points. We explore the effect of these in Poaceae (grasses), a diverse plant lineage with a very limited fossil record, focusing particularly on dating the early divergences in the group. We show that molecular dating based on a data set of plastid markers is strongly dependent on the model assumptions. In particular, an acceleration of evolutionary rates at the base of Poaceae followed by a deceleration in the descendants strongly biases methods that assume an autocorrelation of rates. This problem can be circumvented by using markers that have lower rate variation, and we show that phylogenetic markers extracted from complete nuclear genomes can be a useful complement to the more commonly used plastid markers. However, estimates of divergence times remain strongly affected by different implementations of fossil calibration points. Analyses calibrated with only macrofossils lead to estimates for the age of core Poaceae ∼51-55 Ma, but the inclusion of microfossil evidence pushes this age to 74-82 Ma and leads to lower estimated evolutionary rates in grasses. These results emphasize the importance of considering markers from multiple genomes and alternative fossil placements when addressing evolutionary issues that depend on ages estimated for important groups.

  4. A revised burial dose estimation procedure for optical dating of youngand modern-age sediments

    USGS Publications Warehouse

    Arnold, L.J.; Roberts, R.G.; Galbraith, R.F.; DeLong, S.B.

    2009-01-01

    The presence of genuinely zero-age or near-zero-age grains in modern-age and very young samples poses a problem for many existing burial dose estimation procedures used in optical (optically stimulated luminescence, OSL) dating. This difficulty currently necessitates consideration of relatively simplistic and statistically inferior age models. In this study, we investigate the potential for using modified versions of the statistical age models of Galbraith et??al. [Galbraith, R.F., Roberts, R.G., Laslett, G.M., Yoshida, H., Olley, J.M., 1999. Optical dating of single and multiple grains of quartz from Jinmium rock shelter, northern Australia: Part I, experimental design and statistical models. Archaeometry 41, 339-364.] to provide reliable equivalent dose (De) estimates for young and modern-age samples that display negative, zero or near-zero De estimates. For this purpose, we have revised the original versions of the central and minimum age models, which are based on log-transformed De values, so that they can be applied to un-logged De estimates and their associated absolute standard errors. The suitability of these 'un-logged' age models is tested using a series of known-age fluvial samples deposited within two arroyo systems from the American Southwest. The un-logged age models provide accurate burial doses and final OSL ages for roughly three-quarters of the total number of samples considered in this study. Sensitivity tests reveal that the un-logged versions of the central and minimum age models are capable of producing accurate burial dose estimates for modern-age and very young (<350??yr) fluvial samples that contain (i) more than 20% of well-bleached grains in their De distributions, or (ii) smaller sub-populations of well-bleached grains for which the De values are known with high precision. Our results indicate that the original (log-transformed) versions of the central and minimum age models are still preferable for most routine dating applications

  5. 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

  6. 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.

  7. 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/.

  8. Young asteroidal fluid activity revealed by absolute age from apatite in carbonaceous chondrite

    PubMed Central

    Zhang, Ai-Cheng; Li, Qiu-Li; Yurimoto, Hisayoshi; Sakamoto, Naoya; Li, Xian-Hua; Hu, Sen; Lin, Yang-Ting; Wang, Ru-Cheng

    2016-01-01

    Chondritic meteorites, consisting of the materials that have formed in the early solar system (ESS), have been affected by late thermal events and fluid activity to various degrees. Determining the timing of fluid activity in ESS is of fundamental importance for understanding the nature, formation, evolution and significance of fluid activity in ESS. Previous investigations have determined the relative ages of fluid activity with short-lived isotope systematics. Here we report an absolute 207Pb/206Pb isochron age (4,450±50 Ma) of apatite from Dar al Gani (DaG) 978, a type ∼3.5, ungrouped carbonaceous chondrite. The petrographic, mineralogical and geochemical features suggest that the apatite in DaG 978 should have formed during metamorphism in the presence of a fluid. Therefore, the apatite age represents an absolute age for fluid activity in an asteroidal setting. An impact event could have provided the heat to activate this young fluid activity in ESS. PMID:27682449

  9. Geophysical Age Dating of Seamounts using Dense Core Flexure Model

    NASA Astrophysics Data System (ADS)

    Hwang, Gyuha; Kim, Seung-Sep

    2016-04-01

    Lithospheric flexure of oceanic plate is thermo-mechanical response of an elastic plate to the given volcanic construct (e.g., seamounts and ocean islands). If the shape and mass of such volcanic loads are known, the flexural response is governed by the thickness of elastic plate, Te. As the age of oceanic plate increases, the elastic thickness of oceanic lithosphere becomes thicker. Thus, we can relate Te with the age of plate at the time of loading. To estimate the amount of the driving force due to seamounts on elastic plate, one needs to approximate their density structure. The most common choice is uniform density model, which utilizes constant density value for a seamount. This approach simplifies computational processes for gravity prediction and error estimates. However, the uniform density model tends to overestimate the total mass of the seamount and hence produces more positive gravitational contributions from the load. Minimization of gravity misfits using uniform density, therefore, favors thinner Te in order to increase negative contributions from the lithospheric flexure, which can compensate for the excessive positives from the seamount. An alternative approach is dense core model, which approximate the heterogeneity nature of seamount density as three bodies of infill sediment, edifice, and dense core. In this study, we apply the dense core model to the Louisville Seamount Chain for constraining flexural deformation. We compare Te estimates with the loading time of the examined seamounts to redefine empirical geophysical age dating of seamounts.

  10. Premises and physical mechanisms to explain plateau boundaries in marine planktic 14C records as absolute age markers

    NASA Astrophysics Data System (ADS)

    Sarnthein, Michael; Grootes, Pieter M.

    2010-05-01

    Changes in marine planktic reservoir age variations hamper severely our ability to age calibrate and use marine records as atmospheric 14C records. Genuine atmospheric 14C changes may overlap with changes induced by massive changes in surface ocean hydrography. However, the deglacial Cariaco Basin record (tuned to U/Th ages of the Hulu record) forms a rare case, where the near-surface ocean and its planktic foraminifera may be in reasonably good exchange with the atmosphere, undisturbed by upwelled old deepwater masses. Accordingly, this core was used to connect IntCal09 with the marine record. High-density dating of this core resolved a suite of ~8 sediment sections over glacial-to-interglacial intervals of 400-1500 yr, where planktic 14C ages stay largely constant ("plateaus"), interspersed with sections, where 14C ages rapidly increase with depth ("jumps"). In harmony with IntCal09 we don't discard this pattern and its potentially important information as mere noise but accept it as real, per analogy to 14C plateaus and jumps established for the tree ring calibrated Holocene. This plateau suite was used for plateau tuning in 8 other high-sedimentation rate and high sampling rate (75-200 yr) deep-sea cores. Here, the plateaus with their characteristic internal structure can hardly be ascribed to irregular pulses of extremely high hemipelagic sedimentation rates leading to 5-50 cm long but otherwise undisturbed sediment sections with constant 14C age. The favored explanation is varying atmospheric 14C concentrations reflected in the near-surface ocean. The age difference between locally measured and atmospheric plateau ages in the reference record serves for deducing local planktic reservoir ages. However, occasional but rare millennial-scale events of changing admixture of old deep-ocean waters may disrupt the atmospheric plateaus in deep-sea cores. The latter influence is distinguished by evaluating the complete deglacial plateau suite in each core, keeping

  11. 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.

  12. The absolute age of events in Earth and human history on the basis of radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Pazdur, Anna

    2011-01-01

    Radiocarbon chronometry holds a special place among the many discoveries made in the field of applied nuclear research. Few discoveries in fact, even among those being honored with the Nobel Prize, have had such a powerful and lasting impact on the further development of science. This method, as well as many other complex research methods, which appear to constitute an independent scientific discipline, arose as a result of many years of work by a team of several scientists. However, the actual founder of radiocarbon chronometry was one man, Willard Frank Libby, honored for his contribution with the Nobel Prize in Chemistry in 1960. In Poland, the creative activity in this area was begun in the late 1940s by Włodzimierz Mościcki, who continued it in the last 10 years of his life in the Silesian University of Technology in Gliwice, where he founded the Gliwice Radiocarbon Laboratory.

  13. Dating the end of the Greek Bronze Age: a robust radiocarbon-based chronology from Assiros Toumba.

    PubMed

    Wardle, Kenneth; Higham, Thomas; Kromer, Bernd

    2014-01-01

    Over 60 recent analyses of animal bones, plant remains, and building timbers from Assiros in northern Greece form an unique series from the 14th to the 10th century BC. With the exception of Thera, the number of 14C determinations from other Late Bronze Age sites in Greece has been small and their contribution to chronologies minimal. The absolute dates determined for Assiros through Bayesian modelling are both consistent and unexpected, since they are systematically earlier than the conventional chronologies of southern Greece by between 70 and 100 years. They have not been skewed by reference to assumed historical dates used as priors. They support high rather than low Iron Age chronologies from Spain to Israel where the merits of each are fiercely debated but remain unresolved.

  14. Dating the End of the Greek Bronze Age: A Robust Radiocarbon-Based Chronology from Assiros Toumba

    PubMed Central

    Wardle, Kenneth; Higham, Thomas; Kromer, Bernd

    2014-01-01

    Over 60 recent analyses of animal bones, plant remains, and building timbers from Assiros in northern Greece form an unique series from the 14th to the 10th century BC. With the exception of Thera, the number of 14C determinations from other Late Bronze Age sites in Greece has been small and their contribution to chronologies minimal. The absolute dates determined for Assiros through Bayesian modelling are both consistent and unexpected, since they are systematically earlier than the conventional chronologies of southern Greece by between 70 and 100 years. They have not been skewed by reference to assumed historical dates used as priors. They support high rather than low Iron Age chronologies from Spain to Israel where the merits of each are fiercely debated but remain unresolved. PMID:25222862

  15. Absolute Ages and Distances of 22 GCs Using Monte Carlo Main-sequence Fitting

    NASA Astrophysics Data System (ADS)

    O'Malley, Erin M.; Gilligan, Christina; Chaboyer, Brian

    2017-04-01

    The recent Gaia Data Release 1 of stellar parallaxes provides ample opportunity to find metal-poor main-sequence stars with precise parallaxes. We select 21 such stars with parallax uncertainties better than σ π /π ≤ 0.10 and accurate abundance determinations suitable for testing metal-poor stellar evolution models and determining the distance to Galactic globular clusters (GCs). A Monte Carlo analysis was used, taking into account uncertainties in the model construction parameters, to generate stellar models and isochrones to fit to the calibration stars. The isochrones that fit the calibration stars best were then used to determine the distances and ages of 22 GCs with metallicities ranging from ‑2.4 dex to ‑0.7 dex. We find distances with an average uncertainty of 0.15 mag and absolute ages ranging from 10.8 to 13.6 Gyr with an average uncertainty of 1.6 Gyr. Using literature proper motion data, we calculate orbits for the clusters, finding six that reside within the Galactic disk/bulge, while the rest are considered halo clusters. We find no strong evidence for a relationship between age and Galactocentric distance, but we do find a decreasing age–[Fe/H] relation.

  16. Summary of potassium/argon age dating, 1980

    SciTech Connect

    Evans, S.H. Jr.; Brown, F.H.

    1980-11-01

    A significant improvement in efficiency of the K-Ar laboratory was brought about by completion of a second extraction line. Two extractions can now be done routinely each day and the /sup 38/Ar spike ratios of the new table will permit dating of much younger samples than previously. Extensive K-Ar dating of samples from the Mineral Mountains shows intervals of silicic volcanism at 0.5, 0.8 and 7.5 m.y. K-Ar dating of plutonic units does not present a consistent picture, however. Plutonic events 35 to 40 m.y., 29 m.y. and 19 to 21 m.y. ago are suggested but interpretation must be considered preliminary. Joint programs with the US Geological Survey now underway to study the Rb-Sr and U-Pb systematics of the Mineral Mountains pluton should aid in unravelling its history. Dating of basalts from the Cove Creek Domes/Twin Peaks area, Utah, has aided in delineating the timing of basaltic volcanism. This adds to the already extensive data on the chronology of volcanic activity in the area. Dating of samples from the Beowawe Known Geothermal Resources Area, Nevada have confirmed earlier dates indicating major volcanism took place 38 m.y. ago and 17 to 16 m.y. ago.

  17. Age-Sensitive Effect of Adolescent Dating Experience on Delinquency and Substance Use

    ERIC Educational Resources Information Center

    Kim, Ryang Hui

    2013-01-01

    This study uses a developmental perspective and focuses on examining whether the impact of adolescent dating is age-sensitive. Dating at earlier ages is hypothesized to have a stronger effect on adolescent criminal behavior or substance use, but the effect would be weaker as one ages. The data obtained from the National Longitudinal Survey of…

  18. Fine structure of the age-chromospheric activity relation in solar-type stars. I. The Ca II infrared triplet: Absolute flux calibration

    NASA Astrophysics Data System (ADS)

    Lorenzo-Oliveira, D.; Porto de Mello, G. F.; Dutra-Ferreira, L.; Ribas, I.

    2016-10-01

    Context. Strong spectral lines are useful indicators of stellar chromospheric activity. They are physically linked to the convection efficiency, differential rotation, and angular momentum evolution and are a potential indicator of age. However, for ages > 2 Gyr, the age-activity relationship remains poorly constrained thus hampering its full application. Aims: The Ca II infrared triplet (IRT lines, λλ 8498, 8542, and 8662) has been poorly studied compared to classical chromospheric indicators. We report in this paper absolute chromospheric fluxes in the three Ca II IRT lines, based on a new calibration tied to up-to-date model atmospheres. Methods: We obtain the Ca II IRT absolute fluxes for 113 FGK stars from high signal-to-noise ratio (S/N) and high-resolution spectra covering an extensive domain of chromospheric activity levels. We perform an absolute continuum flux calibration for the Ca II IRT lines anchored in atmospheric models calculated as an explicit function of effective temperatures (Teff), metallicity ([Fe/H]), and gravities (log g) avoiding the degeneracy usually present in photometric continuum calibrations based solely on color indices. Results: The internal uncertainties achieved for continuum absolute flux calculations are ≈2% of the solar chromospheric flux, one order of magnitude lower than for photometric calibrations. Using Monte Carlo simulations, we gauge the impact of observational errors on the final chromospheric fluxes due to the absolute continuum flux calibration and find that Teffuncertainties are properly mitigated by the photospheric correction leaving [Fe/H] as the dominating factor in the chromospheric flux uncertainty. Conclusions: Across the FGK spectral types, the Ca II IRT lines are sensitive to chromospheric activity. The reduced internal uncertainties reported here enable us to build a new chromospheric absolute flux scale and explore the age-activity relation from the active regime down to very low activity levels and

  19. 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.

  20. Terrestrial Ages of Antarctic Meteorites: Up Date 1999

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.; Caffee, M. W.; Welten, K. C.

    2000-01-01

    We are continuing our ongoing study of cosmogenic nuclides in Antarctic meteorites. In addition to the studies of exposure histories of meteorites, we study terrestrial ages and pairing of Antarctic meteorites and desert meteorites. Terrestrial ages of Antarctic meteorites provide information on meteorite accumulation mechanisms, mean weathering lifetimes, and influx rates. The determination of Cl-36 (half-life=3.01 x 10(exp 5) y) terrestrial ages is one of our long-term on-going projects, however, in many instances neither Cl-36 or C-14 (5,730 y) yields an accurate terrestrial age. Using Ca-41 (1.04 x 10(exp 5) y) for terrestrial age determinations solves this problem by filling the gap in half-life between C-14 and Cl-36 ages. We are now applying the new Ca-41 - Cl-36 terrestrial age method as well as the Cl-36 - Be-10 method to Antarctic meteorites. Our measurements and C-14 terrestrial age determinations by the University of Arizona group are always complementary.

  1. 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.

  2. A high-resolution, absolute-dated deglacial speleothem record of Indian Ocean climate from Socotra Island, Yemen

    NASA Astrophysics Data System (ADS)

    Shakun, Jeremy D.; Burns, Stephen J.; Fleitmann, Dominik; Kramers, Jan; Matter, Albert; Al-Subary, Abdulkarim

    2007-07-01

    Stalagmite M1-5 from Socotra Island, Yemen in the northwest Indian Ocean provides a robust, high-resolution paleoclimate record from ˜ 27.4-11.1 ka based on 717 stable isotope and 28 230Th measurements. Variations in M1-5 oxygen isotope ratios ( δ18O) are interpreted to be primarily driven by an amount effect related to changes in the mean position and/or intensity of convection of the intertropical convergence zone, the island's only source of precipitation. The M1-5 δ18O time series is strongly correlated to the Greenland ice cores, similar to an older Socotra speleothem deposited from 53-40 ka [S.J. Burns, D. Fleitmann, A. Matter, J. Kramers, A. Al-Subbary, Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13, Science 301 (2003) 1365-1367], indicating that a North Atlantic-Indian Ocean cold-dry/warm-wet teleconnection persisted through the end of the last glacial period. Peak aridification occurred at ˜ 23 ka and a gradual increase in moisture thereafter was interrupted by an abrupt drying event at ˜ 16.4 ka, perhaps related to Heinrich event 1. Indian Ocean rainfall increased dramatically during the Bølling period and then decreased continuously and gradually through the Allerød and Younger Dryas. The Holocene began abruptly with increased precipitation at 11.4 ka and was followed by a major but short-lived drying during the Preboreal Oscillation at ˜ 11.2 ka. M1-5 is highly correlated to the Dongge Cave record from 15.5-11 ka, suggesting much of the Indian Ocean monsoon region responded similarly to the major climate changes of the last deglaciation. The transitions into the Younger Dryas and to a lesser extent the Bølling are remarkably gradual in M1-5, as they are in all other Asian speleothem records, occurring over several centuries. These gradual transitions are in striking contrast to high-resolution records from around the North Atlantic basin where the transitions are extremely abrupt and generally occur in

  3. On the Absolute Age of the Metal-rich Globular M71 (NGC 6838). I. Optical Photometry

    NASA Astrophysics Data System (ADS)

    Di Cecco, A.; Bono, G.; Prada Moroni, P. G.; Tognelli, E.; Allard, F.; Stetson, P. B.; Buonanno, R.; Ferraro, I.; Iannicola, G.; Monelli, M.; Nonino, M.; Pulone, L.

    2015-08-01

    We investigated the absolute age of the Galactic globular cluster M71 (NGC 6838) using optical ground-based images (u\\prime ,g\\prime ,r\\prime ,i\\prime ,z\\prime ) collected with the MegaCam camera at the Canada-France-Hawaii Telescope (CFHT). We performed a robust selection of field and cluster stars by applying a new method based on the 3D (r\\prime ,u\\prime -g\\prime ,g\\prime -r\\prime ) color-color-magnitude diagram. A comparison between the color-magnitude diagram (CMD) of the candidate cluster stars and a new set of isochrones at the locus of the main sequence turn-off (MSTO) suggests an absolute age of 12 ± 2 Gyr. The absolute age was also estimated using the difference in magnitude between the MSTO and the so-called main sequence knee, a well-defined bending occurring in the lower main sequence. This feature was originally detected in the near-infrared bands and explained as a consequence of an opacity mechanism (collisionally induced absorption of molecular hydrogen) in the atmosphere of cool low-mass stars. The same feature was also detected in the r‧, u\\prime -g\\prime , and in the r\\prime ,g\\prime -r\\prime CMD, thus supporting previous theoretical predictions by Borysow et al. The key advantage in using the {{{Δ }}}{TO}{Knee} as an age diagnostic is that it is independent of uncertainties affecting the distance, the reddening, and the photometric zero point. We found an absolute age of 12 ± 1 Gyr that agrees, within the errors, with similar age estimates, but the uncertainty is on average a factor of two smaller. We also found that the {{{Δ }}}{TO}{Knee} is more sensitive to the metallicity than the MSTO, but the dependence vanishes when using the difference in color between the MSK and the MSTO.

  4. Age-specific absolute and relative organ weight distributions for B6C3F1 mice.

    PubMed

    Marino, Dale J

    2012-01-01

    The B6C3F1 mouse is the standard mouse strain used in toxicology studies conducted by the National Cancer Institute (NCI) and the National Toxicology Program (NTP). While numerous reports have been published on growth, survival, and tumor incidence, no overall compilation of organ weight data is available. Importantly, organ weight change is an endpoint used by regulatory agencies to develop toxicity reference values (TRVs) for use in human health risk assessments. Furthermore, physiologically based pharmacokinetic (PBPK) models, which utilize relative organ weights, are increasingly being used to develop TRVs. Therefore, all available absolute and relative organ weight data for untreated control B6C3F1 mice were collected from NCI/NTP studies in order to develop age-specific distributions. Results show that organ weights were collected more frequently in NCI/NTP studies at 2-wk (60 studies), 3-mo (147 studies), and 15-mo (40 studies) intervals than at other intervals, and more frequently from feeding and inhalation than drinking water studies. Liver, right kidney, lung, heart, thymus, and brain weights were most frequently collected. From the collected data, the mean and standard deviation for absolute and relative organ weights were calculated. Results show age-related increases in absolute liver, right kidney, lung, and heart weights and relatively stable brain and right testis weights. The results suggest a general variability trend in absolute organ weights of brain < right testis < right kidney < heart < liver < lung < spleen < thymus. This report describes the results of this effort.

  5. Dating, Sex, and Substance Use as Correlates of Adolescents' Subjective Experience of Age

    ERIC Educational Resources Information Center

    Arbeau, Kelly J.; Galambos, Nancy L.; Jansson, S. Mikael

    2007-01-01

    This study examined in a random community-based sample of 664 12-19-year-olds, the relation of subjective experience of age (SEA) with chronological age, dating experience, sexual activity, and substance use. The results revealed a positive linear relation between SEA and chronological age: individuals who were chronologically older felt…

  6. 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

  7. In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Sinha, Mahadeva P.; Hecht, Michael H.; Hurowitz, Joel A.

    2012-01-01

    A miniaturized instrument for performing chemical and isotopic analysis of rocks has been developed. The rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented miniature mass spectrometer. The direct sampling of neutral ablated material and the simultaneous measurement of all the elemental and isotopic species are the novelties of this method. In this laser ablation-miniature mass spectrometer (LA-MMS) method, the ablated neutral atoms are led into the electron impact ionization source of the MMS, where they are ionized by a 70-eV electron beam. This results in a secondary ion pulse typically 10-100 microsecond wide, compared to the original 5-10-nanosecond laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer and measured in parallel by a modified CCD (charge-coupled device) array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LAMMS offers a more quantitative assessment of elemental composition than techniques that detect laser-ionized species produced directly in the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the laser beam, and the ionization energies of the elements. The measurement of high-precision isotopic ratios and elemental composition of different rock minerals by LAMMS method has been demonstrated. The LA-MMS can be applied for the absolute age determination of rocks. There is no such instrument available presently in a miniaturized version that can be used for NASA space missions. Work is in progress in the laboratory for geochronology of rocks using LA-MMS that is based on K-Ar radiogenic dating technique.

  8. Age calibration of weathering fractures in desert clasts: A new approach to dating geomorphic surfaces in arid landscapes

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Roda Boluda, Duna; Whittaker, Alex

    2014-05-01

    Advances in geomorphological and sedimentological research depend on the availability of reliable exposure age constraints. Establishing robust age models at a high spatial and temporal resolution is crucial for measuring rates of geomorphological change and decoding complex landscapes shaped by time-dependent forces, e.g. climate fluctuations. A number of isotopic and luminescence techniques are now available for dating geomorphic surfaces, however they remain expensive and time-consuming to deploy with detailed coverage over space and time in many study areas. For this reason, quick and accessible methods for correlating and extrapolating these chronologies are needed. In arid landscapes, among others, a variety of weathering-induced changes occur to geomorphic and sedimentary surfaces, and many of these processes occur at predictable rates and can be quantified using objective, field based measurements. One example is the gradual widening of fractures that exist within boulders on desert surfaces, by a combination of processes including salt weathering and freeze-thaw cycles. The recent emergence of very detailed exposure age models in a number of locations means it is now possible to measure the rates of desert weathering processes, and use them as fully calibrated age indicators themselves. With the potential to significantly extend the coverage of existing age constraints, this kind of quantitative age correlation would enable a broad range of geomorphological and sedimentological research that depends on detailed absolute age models. We have measured the mean widths of hundreds of vertical fractures that dissect granitic boulders, on a variety of alluvial surfaces in Owens Valley, California, which have themselves been independently dated in detail using cosmogenic nuclides. Our data demonstrates for the first time that these fractures widen at a predictable, steady rate of approximately 1 mm ka-1 for at least the last 150 ka, in this arid study area in the

  9. Cross-checking groundwater age by 4He and 14C dating in a granite, Tono area, central Japan

    NASA Astrophysics Data System (ADS)

    Hasegawa, Takuma; Nakata, Kotaro; Tomioka, Yuichi; Goto, Kazuyuki; Kashiwaya, Koki; Hama, Katsuhiro; Iwatsuki, Teruki; Kunimaru, Takanori; Takeda, Masaki

    2016-11-01

    Groundwater dating was performed simultaneously by the 4He and 14C methods in granite of the Tono area in central Japan. Groundwater was sampled at 30 packed-off sections of six 1000-m boreholes. 4He concentrations increased and 14C concentrations decreased along a groundwater flow path on a topographic gradient. 4He ages were calculated by using the in situ 4He production rate derived from the porosity, density, and U and Th content of the rock, neglecting external flux. 14C ages were calculated with a noncorrected model in which the initial 14C content was 100 percent of the modern radiocarbon level (Co = 100 pmC), a statistical model using the average 14C content of tritium-bearing samples (Co = 46.4 pmC), and a δ13C model based on the isotopic mass balance. Although the absolute 14C ages calculated by the models were different, the relative 14C ages were almost identical. The relative 14C ages were considered reliable because dissolved inorganic carbon has no significant geochemical reactions in granite. The relation between the 4He ages and the noncorrected 14C ages was [4He age] = 1.15 [14C age] + 7200 (R2 = 0.81), except in the discharge area. The slope of this relation was equivalent to unity, which indicates that the 4He accumulation rate is confirmed by the relative 14C ages. Moreover, the accumulated 3He/4He ratio was equivalent to that derived from the 6Li(α,n)3H reaction in granite. These results show that the accumulated He is of crustal origin, produced in situ without external flux, except in the discharge area. The intercept value of 7200 a implies that the 14C concentrations were diluted due to geochemical reactions. Tritium-bearing samples supported this result. Simultaneous measurements make it feasible to estimate the accumulation rate of 4He and initial dilution of 14C, which cannot be done with a single method. Cross-checking groundwater dating has the potential to provide more reliable groundwater ages. The circulation time of the

  10. Age of Sexual Debut and Physical Dating Violence Victimization: Sex Differences among US High School Students

    ERIC Educational Resources Information Center

    Ihongbe, Timothy O.; Cha, Susan; Masho, Saba W.

    2017-01-01

    Background: Research has shown that early age of sexual debut is associated with physical dating violence (PDV), but sex-specific associations are sparse. We estimated the prevalence of PDV victimization in high school students who have initiated sexual intercourse and examined sex-specific association between age of sexual debut and PDV…

  11. The Impact of Enhanced He and CNONa Abundances on Globular Cluster Relative Age-Dating Methods

    NASA Astrophysics Data System (ADS)

    Marín-Franch, Antonio; Cassisi, Santi; Aparicio, Antonio; Pietrinferni, Adriano

    2010-05-01

    The impact that unrecognized differences in the chemical patterns of Galactic globular clusters (GGCs) have on their relative age determinations is studied. The two most widely used relative age-dating methods, horizontal and vertical, together with the more recent relative MS-fitting method, were carefully analyzed on a purely theoretical basis. The BaSTI library was adopted to perform the present analysis. We find that relative ages derived using the horizontal and vertical methods are largely dependent on the initial He content and heavy element distribution. Unrecognized cluster-to-cluster chemical abundance differences can lead to an error in the derived relative ages as large as ~0.5 (or ~6 Gyr if an age of 12.8 Gyr is adopted for normalization) and even larger for some extreme cases. It is shown that the relative MS-fitting method is by far the age-dating technique for which undetected cluster-to-cluster differences in the He abundance have less impact. Present results are used in order to pose constraints on the maximum possible spread in the He and CNONa elements abundances on the basis of the estimates—taken from the literature—of the GGCs relative age dispersion obtained with the various relative age-dating techniques. Finally, it is shown that the age-metallicity relation found for young GGCs by the GC Treasury program is a real age sequence and cannot be produced by variations in the He and/or heavy element distribution.

  12. Round-robin 230Th–234U age dating of bulk uranium for nuclear forensics

    DOE PAGES

    Gaffney, Amy M.; Hubert, Amélie; Kinman, William S.; ...

    2015-07-30

    In an inter-laboratory measurement comparison study, four laboratories determined 230Th–234U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. As a result, these model ages are concordant with to slightly older than the known production age of NBL U050.

  13. 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

  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. Thermoluminescence dating of sediments: a re-extension of age range for loess

    SciTech Connect

    Johnson, R.J.; Stipp, J.J.; Wintle, A.G.; Tamers, M.A.

    1985-01-01

    Thermoluminescence (TL) dating of wind blown minerals provides a technique whereby non-carbonaceous sediments could be dated to several hundred thousand years. Two recent reports, however, indicate age underestimates on feldspar in some European loesses older than 50 ka, the effect increasing in severity with age. Suggested causes include decay of luminescence centers, or does dependent sensitivity changes. Data presented in this paper do not support these limitations or explanations. TL provides 3 separate techniques of dating sediments, which, when used together, prove to be efficient internal cross checks for mineralogical anomalies or inconsistencies created by any of the individual methods. In the authors studies each sample was dated by all 3 methods whereas the Europeans analyses employed only the Regeneration technique. This work presents results from loess sections in Mississippi, Illinois and Alaska. These show excellent internal consistency, and consistency with both independent dating methods and stratigraphy, with 2 exceptions. Both exceptions were by the Regen technique giving age underestimates up to 30%. The underestimates were found to be caused by a change in mineral sensitivity resulting from the Regen requirements of strong laboratory light-bleaching followed by irradiations. A simple method to test and correct for this condition is presented. TL thus appears to remain a powerful and increasingly flexible method of sediment dating.

  16. Dating earthquakes with high-precision thorium-230 ages of very young corals

    NASA Technical Reports Server (NTRS)

    Edwards, R. Lawrence; Wasserburg, G. J.; Taylor, F. W.

    1988-01-01

    Three corals from Vanuatu Islands, whose ages were known from counting annual growth bands, were analyzed by Th-230 age analysis to asses the accuracy of the Th-230 method. The comparison of Th-230 ages with the growth-band ages showed that the Th-230 ages were accurate within an error of + or - 3-5 y. Th-230 dates were then determined for two adjacent emerged heads from Santo Island; the dates were the same, indicating that the heads died at the same time, and consistent with the theory that they were killed by coseismic emergence around 1865 AD. The difference between this data and the data of the only major historically documented earthquake that caused an uplift (1973) suggests a seismic recurrence interval of 108 + or - 4 y for Santo. It is suggested that this approach may be extended back in time and to other localities.

  17. 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…

  18. Age Dating Fluvial Sediment Storage Reservoirs to Construct Sediment Waiting Time Distributions

    NASA Astrophysics Data System (ADS)

    Skalak, K.; Pizzuto, J. E.; Benthem, A.; Karwan, D. L.; Mahan, S.

    2015-12-01

    Suspended sediment transport is an important geomorphic process that can often control the transport of nutrients and contaminants. The time a particle spends in storage remains a critical knowledge gap in understanding particle trajectories through landscapes. We dated floodplain deposits in South River, VA, using fallout radionuclides (Pb-210, Cs-137), optically stimulated luminescence (OSL), and radiocarbon dating to determine sediment ages and construct sediment waiting time distributions. We have a total of 14 age dates in two eroding banks. We combine these age dates with a well-constrained history of mercury concentrations on suspended sediment in the river from an industrial release. Ages from fallout radionuclides document sedimentation from the early 1900s to the present, and agree with the history of mercury contamination. OSL dates span approximately 200 to 17,000 years old. We performed a standard Weibull analysis of nonexceedance to construct a waiting time distribution of floodplain sediment for the South River. The mean waiting time for floodplain sediment is 2930 years, while the median is approximately 710 years. When the floodplain waiting time distribution is combined with the waiting time distribution for in-channel sediment storage (available from previous studies), the mean waiting time shifts to approximately 680 years, suggesting that quantifying sediment waiting times for both channel and floodplain storage is critical in advancing knowledge of particle trajectories through watersheds.

  19. Age of Zhoukoudian Homo erectus determined with (26)Al/(10)Be burial dating.

    PubMed

    Shen, Guanjun; Gao, Xing; Gao, Bin; Granger, Darryl E

    2009-03-12

    The age of Zhoukoudian Homo erectus, commonly known as 'Peking Man', has long been pursued, but has remained problematic owing to the lack of suitable dating methods. Here we report cosmogenic (26)Al/(10)Be burial dating of quartz sediments and artefacts from the lower strata of Locality 1 in the southwestern suburb of Beijing, China, where early representatives of Zhoukoudian Homo erectus were discovered. This study marks the first radioisotopic dating of any early hominin site in China beyond the range of mass spectrometric U-series dating. The weighted mean of six meaningful age measurements, 0.77 +/- 0.08 million years (Myr, mean +/- s.e.m.), provides the best age estimate for lower cultural layers 7-10. Together with previously reported U-series dating of speleothem calcite and palaeomagnetic stratigraphy, as well as sedimentological considerations, these layers may be further correlated to S6-S7 in Chinese loess stratigraphy or marine isotope stages (MIS) 17-19, in the range of approximately 0.68 to 0.78 Myr ago. These ages are substantially older than previously supposed and may imply early hominin's presence at the site in northern China through a relatively mild glacial period corresponding to MIS 18.

  20. Improving age constraints on Patagonian glaciations using a new luminescence dating method for feldspars

    NASA Astrophysics Data System (ADS)

    Smedley, R. K.; Glasser, N. F.; Duller, G. A.

    2013-12-01

    Multiple moraine ridges are preserved in the Lago Buenos Aires and Lago Pueyrrédon valleys, east of the Northern Patagonian Icefield and offer a unique perspective on understanding past environmental change in the mid-latitudes of the Southern Hemisphere. Previous age constraints provided for the moraine ridges relies on cosmogenic isotope dating and constraining radiocarbon and 40Ar/36Ar ages. Providing age constraints using luminescence dating of the glaciofluvial landforms associated with the moraine ridges offers great potential to contribute towards improving the accuracy and precision of age constraints in such challenging glacial settings. This is the first study to use a new luminescence dating method recently developed for feldspars (Thomsen et al. 2008) to constrain the ages of moraine deposition. A range of sediments were sampled from the outwash plains and glaciofluvial channels that are associated with moraine deposition in the Lago Buenos Aires and Lago Pueyrrédon valleys. Elevation measurements and the geomorphological context of the outwash plains and glaciofluvial channels are used to relate the sampled material to the associated moraine ridges, and therefore constrain the ages of moraine deposition in the valleys. Moraine ridges dated using cosmogenic isotope dating to the Last Glacial Maximum are the main focus of this study, but the overall aim is to provide a new dating technique that can be used to understand the temporal and spatial extent of terrestrial environmental change during past glaciations of the mid-latitudes in the Southern Hemisphere. Thomsen, K.J., Murray, A.S., Jain, M. and Bøtter-Jensen, L. 2008. Laboratory fading rates of various luminescence signals from feldspar-rich sediment extracts. Radiation Measurements 43, 1474 - 1486.

  1. Thermoluminescence dating of archaeological artefacts from the Middle Neolithic, Bronze Age and the Roman Empire period.

    PubMed

    Berger, T; Hajek, M; Primerano, W; Vana, N

    2002-01-01

    Thermoluminescence (TL) dating was applied for artefacts found near the small village of Michelstetten, Lower Austria. Settlements in this region can be traced hack a long time and, according to archaeologists, the discovered artefacts may be as old as 6000 years. A modified sample preparation technique based on the fine-grain method was developed. This technique results in a higher reproducibility and reduces the overall preparation time. For some artefacts the new information of the TL dating leads to an unforeseen re-interpretation of the archaeological age. Furthermore, an iron furnace from the period of the Roman Empire could be dated. For the first time, it was possible to estimate correctly the point of time of the burn-down of an ancient wooden house via an analysis of the house's clay plaster. The fire took place in the sixth century; this was confirmed by dating ceramic artefacts.

  2. 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}⊙ ) 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.

  3. ENHANCED RECOVERY METHODS FOR 85KR AGE-DATING GROUNDWATER: ROYAL WATERSHED, MAINE

    EPA Science Inventory

    Potential widespread use of 85Kr, having a constant input function in the northern hemisphere, for groundwater age-dating would advance watershed investigations. The current input function of tritium is not sufficient to estimate young modern recharge waters. While tri...

  4. Deep-ocean basalts: inert gas content and uncertainties in age dating.

    PubMed

    Noble, C S; Naughton, J J

    1968-10-11

    The radiogenic argon and helium contents of three basalts erupted into the deep ocean from an active volcano (Kilauea) have been measured. Ages calculated from these measurements increase with sample depth up to 22 million years for lavas deduced to be recent. Caution is urged in applying dates from deep-ocean basalts in studies on ocean-floor spreading.

  5. THE IMPACT OF ENHANCED He AND CNONa ABUNDANCES ON GLOBULAR CLUSTER RELATIVE AGE-DATING METHODS

    SciTech Connect

    MarIn-Franch, Antonio; Aparicio, Antonio; Cassisi, Santi; Pietrinferni, Adriano E-mail: antapaj@iac.e E-mail: pietrinferni@oa-teramo.inaf.i

    2010-05-10

    The impact that unrecognized differences in the chemical patterns of Galactic globular clusters (GGCs) have on their relative age determinations is studied. The two most widely used relative age-dating methods, horizontal and vertical, together with the more recent relative MS-fitting method, were carefully analyzed on a purely theoretical basis. The BaSTI library was adopted to perform the present analysis. We find that relative ages derived using the horizontal and vertical methods are largely dependent on the initial He content and heavy element distribution. Unrecognized cluster-to-cluster chemical abundance differences can lead to an error in the derived relative ages as large as {approx}0.5 (or {approx}6 Gyr if an age of 12.8 Gyr is adopted for normalization) and even larger for some extreme cases. It is shown that the relative MS-fitting method is by far the age-dating technique for which undetected cluster-to-cluster differences in the He abundance have less impact. Present results are used in order to pose constraints on the maximum possible spread in the He and CNONa elements abundances on the basis of the estimates-taken from the literature-of the GGCs relative age dispersion obtained with the various relative age-dating techniques. Finally, it is shown that the age-metallicity relation found for young GGCs by the GC Treasury program is a real age sequence and cannot be produced by variations in the He and/or heavy element distribution.

  6. Deciphering relative timing of fabric development in granitoids with similar absolute ages based on AMS study (Dharwar Craton, South India)

    NASA Astrophysics Data System (ADS)

    Bhatt, Sandeep; Rana, Virendra; Mamtani, Manish A.

    2017-01-01

    Anisotropy of Magnetic Susceptibility (AMS) data are presented from the Koppal Granitoid (Dharwar Craton, South India) that has U-Pb zircon age of 2528 ± 9 Ma. The magnetic fabric is oriented in NNE-SSW direction. This is parallel to the planar structures that developed during regional D3 deformation, but oblique to the NNW-SSE oriented magnetic foliation as well as field foliation (D1/D2 deformation) recorded in the country rock Peninsular Gneiss. Variation in the intensity of fabric within the granitoid is mapped. It is inferred that the emplacement of Koppal Granitoid took place by ballooning and fabric development within the pluton was syntectonic with regional D3. These results are compared with the time-relationship between emplacement/fabric development and regional deformation reported from the Mulgund Granite (2555 ± 6 Ma; U-Pb zircon), which is also located in the Dharwar Craton and is equivalent to the Koppal Granitoid in age. This granite is known to have emplaced syntectonically with regional D1/D2 deformation, and is thus not related to the same deformation event as the Koppal Granitoid, despite their similar absolute ages. It is argued that in the study area, D3 is ≤2537 Ma, while D1/D2 is ≥2549 Ma in age. Thus, this study highlights the use of AMS in (a) deciphering the relative timing of regional deformation and emplacement of granitoids of equivalent age and (b) constraining the timing of regional superposed deformation events.

  7. Estimation of submarine mass failure probability from a sequence of deposits with age dates

    USGS Publications Warehouse

    Geist, Eric L.; Chaytor, Jason D.; Parsons, Thomas E.; ten Brink, Uri S.

    2013-01-01

    The empirical probability of submarine mass failure is quantified from a sequence of dated mass-transport deposits. Several different techniques are described to estimate the parameters for a suite of candidate probability models. The techniques, previously developed for analyzing paleoseismic data, include maximum likelihood and Type II (Bayesian) maximum likelihood methods derived from renewal process theory and Monte Carlo methods. The estimated mean return time from these methods, unlike estimates from a simple arithmetic mean of the center age dates and standard likelihood methods, includes the effects of age-dating uncertainty and of open time intervals before the first and after the last event. The likelihood techniques are evaluated using Akaike’s Information Criterion (AIC) and Akaike’s Bayesian Information Criterion (ABIC) to select the optimal model. The techniques are applied to mass transport deposits recorded in two Integrated Ocean Drilling Program (IODP) drill sites located in the Ursa Basin, northern Gulf of Mexico. Dates of the deposits were constrained by regional bio- and magnetostratigraphy from a previous study. Results of the analysis indicate that submarine mass failures in this location occur primarily according to a Poisson process in which failures are independent and return times follow an exponential distribution. However, some of the model results suggest that submarine mass failures may occur quasiperiodically at one of the sites (U1324). The suite of techniques described in this study provides quantitative probability estimates of submarine mass failure occurrence, for any number of deposits and age uncertainty distributions.

  8. A multi-centennial time series of well-constrained ΔR values for the Irish Sea derived using absolutely-dated shell samples from the mollusc Arctica islandica

    NASA Astrophysics Data System (ADS)

    Butler, P. G.; Scourse, J. D.; Richardson, C. A.; Wanamaker, A. D., Jr.

    2009-04-01

    Determinations of the local correction (ΔR) to the globally averaged marine radiocarbon reservoir age are often isolated in space and time, derived from heterogeneous sources and constrained by significant uncertainties. Although time series of ΔR at single sites can be obtained from sediment cores, these are subject to multiple uncertainties related to sedimentation rates, bioturbation and interspecific variations in the source of radiocarbon in the analysed samples. Coral records provide better resolution, but these are available only for tropical locations. It is shown here that it is possible to use the shell of the long-lived bivalve mollusc Arctica islandica as a source of high resolution time series of absolutely-dated marine radiocarbon determinations for the shelf seas surrounding the North Atlantic ocean. Annual growth increments in the shell can be crossdated and chronologies can be constructed in a precise analogue with the use of tree-rings. Because the calendar dates of the samples are known, ΔR can be determined with high precision and accuracy and because all the samples are from the same species, the time series of ΔR values possesses a high degree of internal consistency. Presented here is a multi-centennial (AD 1593 - AD 1933) time series of 31 ΔR values for a site in the Irish Sea close to the Isle of Man. The mean value of ΔR (-62 14C yrs) does not change significantly during this period but increased variability is apparent before AD 1750.

  9. Surface exposure dating of Little Ice Age ice cap advances on Disko Island, West Greenland

    NASA Astrophysics Data System (ADS)

    Lane, Timothy; Jomelli, Vincent; Rinterknecht, Vincent; Brunstein, Daniel; Schimmelpfennig, Irene; Swingedouw, Didier; Favier, Vincent; Masson-Delmotte, Valerie

    2015-04-01

    Little Ice Age (LIA: 1200-1920 AD) glacier advances in Greenland often form the most extensive positions of Greenland Ice Sheet (GrIS) ice cap and margins since the Early Holocene. Across Greenland these advances are commonly represented by un-vegetated moraines, usually within 1-5 km of the present ice margin. However, chronological constraints on glacier advances during this period are sparse, meaning that GrIS and ice cap behavior and advance/retreat chronology remains poorly understood during this period. At present the majority of ages are based on historical accounts, ice core data, and radiocarbon ages from proglacial threshold lakes. However, developments in the accuracy and precision of surface exposure methods allow dating of LIA moraine boulders, permitting an opportunity to better understand of ice dynamics during this period. Geomorphological mapping and surface exposure dating (36Cl) were used to interpret moraine deposits from the Lyngmarksbræen on Disko Island, West Greenland. A Positive Degree Day (PDD) model was used to estimate Equilibrium Line Altitude (ELA) and mass balance changes for two distinct paleo-glacial extents. Three moraines (M1, M2, and M3) were mapped in the field, and sampled for 36Cl surface exposure dating. The outermost moraine (M1) was of clearly different morphology to the inner moraines, and present only in small fragments. M2 and M3 were distinct arcuate termino-lateral moraines within 50 m of one another, 1.5 km from the present ice margin. The weighted average of four 36Cl ages from M1 returned an early Holocene age of 8.4 ± 0.6 ka. M2 (four samples) returned an age of 0.57 ± 0.04 ka (1441 AD) and M3 (four samples) returned an age of 0.28 ± 0.02 ka (1732 AD). These surface exposure ages represent the first robustly dated Greenlandic ice cap moraine sequence from the LIA. The two periods of ice cap advance and marginal stabilisation are similar to recorded periods of LIA GrIS advance in west Greenland, constrained

  10. What is the true age uncertainty of radiocarbon dated Holocene records?

    NASA Astrophysics Data System (ADS)

    Ho, Sze Ling; Groeneveld, Jeroen; Refeld, Kira; Mollenhauer, Gesine; De Pol-Holz, Ricardo; Nürnberg, Dirk; Laepple, Thomas

    2016-04-01

    Radiocarbon-based age-depth models are the backbone of the chronology of Holocene sediment records. The uncertainty of such age-depth models is often estimated from the uncertainty of the calibrated radiocarbon samples. A necessary assumption hereby is that the age of the samples is representative for the proxies in the same sediment layer they originate from. Here we generate radiocarbon and multiple temperature proxy data in three Holocene sediment cores from the same multi-corer employed in the Southwest Pacific. Surprisingly, whilst radiocarbon ages at the same sediment depth strongly differ between the tubes, multiple independent proxy time-series measured in each of the sediment cores suggest stratified sediments at the site. This is based on the finding that proxy time-series correlate significantly better between sediment cores when analyzed over depth, rather than against core-specific age-depth models based on the radiocarbon dates. If our site is not a pathological special case - an argument which we have no evidence for - our finding has important implications for age-depth modeling and the interpretations of paleoclimate time-series. It suggests that the true age uncertainty of a sediment layer can be much higher than the uncertainty obtained from the radiocarbon dates. An alternative but less likely hypothesis is that the proxy values are modified post-deposition in the sediments, resulting in more consistent stratification than the original climate signal time-series. Our study demonstrates the usefulness of replication of the proxy time series and radiocarbon dates in the quest for chronologic precision and proxy reliability, which are crucial for a more quantitative understanding of Holocene climate evolution.

  11. Geoarchaeological dating of Holocene-age, earthquake-induced paleoliquefaction features in southwestern Indiana

    SciTech Connect

    Munson, C.A. ); Munson, P.J.; Garniewicz, R.C. . Dept. of Anthropology)

    1992-01-01

    Although archaeological geology generally involves the application of geological methods to archaeological research questions, recent research on earthquake-induced paleoliquefaction in Indiana provides an example off archeological methods applied to geological questions. Surveys in 1990-1992 have documented numerous paleoliquefaction features in Holocene-age alluvial sediments in the Wabash Valley region of southwestern Indiana that resulted from strong-earthquake shaking. A combination of archaeological and geological dating is critical to the study of prehistoric earthquakes in this region, where evidence of surface faulting is absent. Both direct dating and cross-dating are being used to develop a chronology for stratigraphic sequences within the alluvial facies of the Martinsville Formation. Temporally diagnostic artifacts and archaeological features such as hearths add significantly to the traditional array of datable samples from strata that underlie, overlie, or are penecontemporary with the sand- or gravel-filled dikes and buried sand blows that resulted from liquefaction. Dating of stratigraphic sequences and paleoliquefaction features is essential for estimating the recurrence intervals of prehistoric earthquakes and the geographic extents, epicentral locations, and magnitudes of specific events. Dating of stratigraphic sequences is also relevant to reconstructions of the prehistoric landscapes that were used for human settlement throughout the last 11,000 years.

  12. Age of Zinjanthropus: The potassium-argon dates recently obtained from Olduvai Gorge, Tanganyika, raise several questions.

    PubMed

    Straus, W L; Hunt, C B

    1962-04-27

    Because some of the Olduvai Gorge dates are inconsistent, some must be inaccurate; they may all be. Until further tests determine which materials give dependable dates, we do not know which dates are accurate. Until this is learned, the indicated ages must be taken cum grano salis.

  13. 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

  14. 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.

  15. A practical method of estimating standard error of age in the fission track dating method

    USGS Publications Warehouse

    Johnson, N.M.; McGee, V.E.; Naeser, C.W.

    1979-01-01

    A first-order approximation formula for the propagation of error in the fission track age equation is given by PA = C[P2s+P2i+P2??-2rPsPi] 1 2, where PA, Ps, Pi and P?? are the percentage error of age, of spontaneous track density, of induced track density, and of neutron dose, respectively, and C is a constant. The correlation, r, between spontaneous are induced track densities is a crucial element in the error analysis, acting generally to improve the standard error of age. In addition, the correlation parameter r is instrumental is specifying the level of neutron dose, a controlled variable, which will minimize the standard error of age. The results from the approximation equation agree closely with the results from an independent statistical model for the propagation of errors in the fission-track dating method. ?? 1979.

  16. Suggested terminology for Quaternary dating methods

    USGS Publications Warehouse

    Colman, Steven M.; Pierce, K.L.; Birkeland, P.W.

    1987-01-01

    Classification of Quaternary dating methods should be based on the level of quantitative information and the degree of confidence contained in the age estimates produced by the dating methods. We recommend the use of the terms numerical-age, calibrated-age, relative-age, and correlated-age to describe these levels. We also classify dating methods by type into sideral, isotopic, radiogenic, chemical and biological, geomorphic, and correlation methods. The use of "absolute" is inappropriate for most dating methods, and should be replaced by "numerical." The use of "date" should be minimized in favor of "age" or "age estimate." We recommend use of the abbreviations ka and Ma for most ages; calender dates can be used where appropriate and yr B.P. can be used for radiocarbon ages. ?? 1987.

  17. Relation of Chlorofluorocarbon Ground-Water Age Dates to Water Quality in Aquifers of West Virginia

    USGS Publications Warehouse

    ,; Kurt, J.; Kozar, Mark D.

    2007-01-01

    The average apparent age of ground water in fractured-bedrock aquifers in West Virginia was determined using chlorofluorocarbon (CFC) dating methods. Since the introduction of CFC gases as refrigerants in the late 1930s, atmospheric concentrations have increased until production ceased in the mid-1990s. CFC dating methods are based on production records that date to the early 1940s, and the preservation of atmospheric CFC concentrations in ground water at the time of recharge. As part of the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) and Ambient Ground-Water Monitoring Network (AGN) programs in West Virginia from 1997 to 2005, 80 samples from the Appalachian Plateaus Physiographic Province, 27 samples from the Valley and Ridge Physiographic Province, and 5 samples from the Ohio River alluvial aquifers were collected to estimate ground-water ages in aquifers of West Virginia. Apparent CFC ages of water samples from West Virginia aquifers ranged from 5.8 to 56 years. In the Appalachian Plateaus, topographically driven ground-water flow is evident from apparent ages of water samples from hilltop, hillside, and valley settings (median apparent ages of 12, 14, and 25 years, respectively). Topographic setting was the only factor that was found to be related to apparent ground-water age in the Plateaus at the scale of this study. Similar relations were not found in Valley and Ridge aquifers, indicating that other factors such as bedding or geologic structure may serve larger roles in controlling ground-water flow in that physiographic province. Degradation of CFCs was common in samples collected from methanogenic/anoxic aquifers in the Appalachian Plateaus and suboxic to anoxic aquifers in the Valley and Ridge. CFC contamination was most common in Ohio River alluvial aquifers and carbonate units of the Valley and Ridge, indicating that these highly transmissive surficial aquifers are the most vulnerable to water-quality degradation and may

  18. The evolutionary relationships and age of Homo naledi: An assessment using dated Bayesian phylogenetic methods.

    PubMed

    Dembo, Mana; Radovčić, Davorka; Garvin, Heather M; Laird, Myra F; Schroeder, Lauren; Scott, Jill E; Brophy, Juliet; Ackermann, Rebecca R; Musiba, Chares M; de Ruiter, Darryl J; Mooers, Arne Ø; Collard, Mark

    2016-08-01

    Homo naledi is a recently discovered species of fossil hominin from South Africa. A considerable amount is already known about H. naledi but some important questions remain unanswered. Here we report a study that addressed two of them: "Where does H. naledi fit in the hominin evolutionary tree?" and "How old is it?" We used a large supermatrix of craniodental characters for both early and late hominin species and Bayesian phylogenetic techniques to carry out three analyses. First, we performed a dated Bayesian analysis to generate estimates of the evolutionary relationships of fossil hominins including H. naledi. Then we employed Bayes factor tests to compare the strength of support for hypotheses about the relationships of H. naledi suggested by the best-estimate trees. Lastly, we carried out a resampling analysis to assess the accuracy of the age estimate for H. naledi yielded by the dated Bayesian analysis. The analyses strongly supported the hypothesis that H. naledi forms a clade with the other Homo species and Australopithecus sediba. The analyses were more ambiguous regarding the position of H. naledi within the (Homo, Au. sediba) clade. A number of hypotheses were rejected, but several others were not. Based on the available craniodental data, Homo antecessor, Asian Homo erectus, Homo habilis, Homo floresiensis, Homo sapiens, and Au. sediba could all be the sister taxon of H. naledi. According to the dated Bayesian analysis, the most likely age for H. naledi is 912 ka. This age estimate was supported by the resampling analysis. Our findings have a number of implications. Most notably, they support the assignment of the new specimens to Homo, cast doubt on the claim that H. naledi is simply a variant of H. erectus, and suggest H. naledi is younger than has been previously proposed.

  19. Allanite age-dating: Non-matrix-matched standardization in quadrupole LA-ICP-MS

    NASA Astrophysics Data System (ADS)

    Burn, M.; Lanari, P.; Pettke, T.; Engi, M.

    2014-12-01

    Allanite Th-U-Pb age-dating has recently been found to be powerful in unraveling the timing of geological processes such as the metamorphic dynamics in subduction zones and crystallization velocity of magmas. However, inconsistencies among analytical techniques have raised doubts about the accuracy of allanite age data. Spot analysis techniques such as LA-ICP-MS are claimed to be crucially dependent on matrix-matched standards, the quality of which is variable. We present a new approach in LA-ICP-MS data reduction that allows non-matrix-matched standardization via well constrained zircon reference materials as primary standards. Our data were obtained using a GeoLas Pro 193 nm ArF excimer laser ablation system coupled to an ELAN DRC-e quadrupole ICP-MS. We use 32 μm and 24 μm spot sizes; laser operating conditions of 9 Hz repetition rate and 2.5 J/cm2 fluence have proven advantageous. Matrix dependent downhole fractionation evolution is empirically determined by analyzing 208Pb/232Th and 206Pb/238U and applied prior to standardization. The new data reduction technique was tested on three magmatic allanite reference materials (SISSb, CAPb, TARA); within error these show the same downhole fractionation evolution for all allanite types and in different analytical sessions, provided measurement conditions remain the same. Although the downhole evolution of allanite and zircon differs significantly, a link between zircon and allanite matrix is established by assuming CAPb and TARA to be fixed at the corresponding reference ages. Our weighted mean 208Pb/232Th ages are 30.06 ± 0.22 (2σ) for SISSb, 275.4 ± 1.3 (2σ) for CAPb, and 409.9 ± 1.8 (2σ) for TARA. Precision of single spot age data varies between 1.5 and 8 % (2σ), dependent on spot size and common lead concentrations. Quadrupole LA-ICP-MS allanite age-dating has thus similar uncertainties as do other spot analysis techniques. The new data reduction technique is much less dependent on quality and homogeneity

  20. I-Pu-Xe dating and the relative ages of the earth and moon

    NASA Technical Reports Server (NTRS)

    Swindle, T. D.; Caffee, M. W.; Hohenberg, C. M.; Taylor, S. R.

    1986-01-01

    The ages of the earth and moon as determined by various chronometric systems are discussed with primary emphasis placed on the development of an I-Pu-Xe chronometer. Data on excess fission xenon are reviewed with attention given to the strengths and weaknesses of the assumptions required for lunar I-Pu-Xe chronometry. Using I-Pu-Xe dating, it is estimated that the retention of excess fission xenon in lunar samples began no more than 63 + or - 42 m.y. after the time of primitive meteorite formation.

  1. Ages of Sevier thrusting from dating of metamorphic garnet using the Lu-Hf method

    NASA Astrophysics Data System (ADS)

    Cruz-Uribe, A. M.; Hoisch, T. D.; Wells, M. L.; Vervoort, J. D.

    2008-12-01

    Combined thermodynamic modeling of garnet growth zoning and Lu-Hf dating of garnet yield well-constrained pressure-temperature-time (PTt) paths. Here we present PTt paths from amphibolite-facies pelitic garnet from the Raft River-Albion-Grouse Creek metamorphic core complex that constrain the timing of thrusting in the hinterland of the Sevier thrust belt. Three general times of thrust burial are indicated: 150, 138, and 85 Ma. Lu-Hf garnet dating of burial-related garnet growth in the Raft River Mountains yielded a Late Jurassic age of 149.9 ± 1.2 Ma (2σ, MSWD = 1.1) based on three garnet fractions and a whole rock. A PT path from the schist of Mahogany Peaks in the Albion Range, Idaho, records an isothermal pressure increase indicating growth during thrusting. Lu-Hf dating of garnet from the same rock yielded an Early Cretaceous age of 138.7 ± 0.7 Ma (2σ, MSWD = 1.6) based on seven garnet fractions. An additional PT path from a nearby outcrop also records an isothermal pressure increase and a similar Lu-Hf garnet age of 132.1 ± 5.1 Ma (2σ, MSWD = 9.5) based on three garnet fractions and a whole rock. PT paths of multiple garnet grains from the schist of Stevens Spring in the Grouse Creek Mountains, Utah, exhibit isothermal pressure increases and yielded a Lu-Hf garnet age of 85.5 ± 1.9 Ma (2σ, MSWD = 3.9) based on five garnet fractions and a whole rock. The Late Jurassic burial event recorded in the Raft River Mountains is older than the ages of inception of thrusting of the western thrusts of the Sevier fold-thrust belt including the Canyon Range and Paris - Willard thrusts, but consistent with an eastward progression in initial shortening in the orogenic wedge and development of an inferred thrust load responsible for the retroarc Morrison Formation basin. Early Cretaceous hinterland burial recorded in the Albion Range is permissively coeval with activity on the Willard and Canyon Range thrusts. Finally, renewed hinterland thrust burial during the Late

  2. Resolving the age of Wilson Creek Formation tephras and the Mono Lake excursion using high-resolution SIMS dating of allanite and zircon rims

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Lidzbarski, M. I.

    2012-12-01

    Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and interbedded rhyolitic tephras yield discordant 14C and 40Ar/39Ar results due to open-system effects, carbon reservoir uncertainties, as well as abundant xenocrysts entrained during eruption. Ion microprobe (SIMS) 238U-230Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yields ages that effectively date eruption of key tephra beds and resolve age uncertainties about the Wilson Creek stratigraphy. To date the final several micrometers of crystal growth, individual allanite and zircon crystals were embedded in soft indium to allow sampling of unpolished rims. Isochron ages derived from rims on coexisting allanite and zircon (± glass) from hand-selected pumiceous pyroclasts delimit the timing of Wilson Creek sedimentation between Ashes 7 and 19 (numbering of Lajoie, 1968) to the interval between ca. 27 to ca. 62 ka. The interiors of individual allanite and zircon crystals sectioned in standard SIMS mounts yield model 238U-230Th ages that are mostly <10 k.y. older than their corresponding rim age, suggesting a relatively brief interval of allanite + zircon crystallization before eruption. A minority of allanite and zircon crystals yield rim and interior model ages of ca. 90-100 ka, and are likely to be antecrysts recycled from relatively early Mono Craters volcanism and/or intrusions. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields a rim isochron age of ca. 41 ka indicating that

  3. Impacts of age-dependent tree sensitivity and dating approaches on dendrogeomorphic time series of landslides

    NASA Astrophysics Data System (ADS)

    Šilhán, Karel; Stoffel, Markus

    2015-05-01

    Different approaches and thresholds have been utilized in the past to date landslides with growth ring series of disturbed trees. Past work was mostly based on conifer species because of their well-defined ring boundaries and the easy identification of compression wood after stem tilting. More recently, work has been expanded to include broad-leaved trees, which are thought to produce less and less evident reactions after landsliding. This contribution reviews recent progress made in dendrogeomorphic landslide analysis and introduces a new approach in which landslides are dated via ring eccentricity formed after tilting. We compare results of this new and the more conventional approaches. In addition, the paper also addresses tree sensitivity to landslide disturbance as a function of tree age and trunk diameter using 119 common beech (Fagus sylvatica L.) and 39 Crimean pine (Pinus nigra ssp. pallasiana) trees growing on two landslide bodies. The landslide events reconstructed with the classical approach (reaction wood) also appear as events in the eccentricity analysis, but the inclusion of eccentricity clearly allowed for more (162%) landslides to be detected in the tree-ring series. With respect to tree sensitivity, conifers and broad-leaved trees show the strongest reactions to landslides at ages comprised between 40 and 60 years, with a second phase of increased sensitivity in P. nigra at ages of ca. 120-130 years. These phases of highest sensitivities correspond with trunk diameters at breast height of 6-8 and 18-22 cm, respectively (P. nigra). This study thus calls for the inclusion of eccentricity analyses in future landslide reconstructions as well as for the selection of trees belonging to different age and diameter classes to allow for a well-balanced and more complete reconstruction of past events.

  4. First direct dating of a presumed Pleistocene hominid from China: AMS radiocarbon age of a femur from the Ordos Plateau.

    PubMed

    Keates, Susan G; Hodgins, Gregory W L; Kuzmin, Yaroslav V; Orlova, Lyobov A

    2007-07-01

    Human remains from the Xarusgol Valley, Ordos Plateau, northwestern China, have been considered to date to the Late Pleistocene. In order to ascertain their true age, direct AMS (14)C dating of a femur collected in the early 1920s was conducted. The results demonstrate that the femur is very young, with one sample of 'post-bomb' age and the other sample c. 200 years old. This first direct dating of a Chinese fossil hominid underscores the need to apply the same methodology to other Chinese modern human fossils currently believed to be of Pleistocene age.

  5. 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, Joseph 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.

  6. Age Dating from Electron Microprobe Analyses of U, Th, and Pb: Geological Advantages and Analytical Difficulties.

    PubMed

    Bowles, John F W

    2015-10-01

    Electron microprobe analysis of U, Th, and Pb in naturally occurring minerals can indicate their age. Where the Pb is entirely due to the radioactive decay of U and Th, the time since mineral formation or equilibration can be calculated. Uraninite (UO2), monazite (REE PO4), zircon (ZrSiO4), and xenotime (YPO4) have been used, the latter containing U and/or Th in minor proportions. Any stable U- or Th-bearing phase can be considered. Careful analysis is required with attention to interferences, background measurement, detection limits, and Pb-free sample preparation. Extended counting times (600 s) at a probe current >200 nA are recommended. Ages can be determined from uraninite older than 2 Ma for a Pb detection limit of 0.02% and up to 700-1,000 Ma, after which Pb can be lost from the structure. The youngest monazite ages permitted by the Pb detection limit are 50-100 Ma and ages greater than 3,000 Ma have been determined. The method does not provide the detail of isotopic methods, but results can be obtained more readily. Examples show dating of cheralite ((Ca,Ce)(Th,Ce)(PO4)2), a rock containing primary and secondary UO2, and a suite of detrital uraninite grains that formed a part of a mineral exploration program.

  7. Between a rock and a soft place: Using optical ages to date ancient clam gardens on the Pacific Northwest.

    PubMed

    Neudorf, Christina M; Smith, Nicole; Lepofsky, Dana; Toniello, Ginevra; Lian, Olav B

    2017-01-01

    Rock-walled archaeological features are notoriously hard to date, largely because of the absence of suitable organic material for radiocarbon dating. This study demonstrates the efficacy of dating clam garden wall construction using optical dating, and uses optical ages to determine how sedimentation rates in the intertidal zone are affected by clam garden construction. Clam gardens are rock-walled, intertidal terraces that were constructed and maintained by coastal First Nation peoples to increase bivalve habitat and productivity. These features are evidence of ancient shellfish mariculture on the Pacific Northwest and, based on radiocarbon dating, date to at least the late Holocene. Optical dating exploits the luminescence signals of quartz or feldspar minerals to determine the last time the minerals were exposed to sunlight (i.e., their burial age), and thus does not require the presence of organic material. Optical ages were obtained from three clam garden sites on northern Quadra Island, British Columbia, and their reliability was assessed by comparing them to radiocarbon ages derived from shells underneath the clam garden walls, as well as below the terrace sediments. Our optical and radiocarbon ages suggest that construction of these clam garden walls commenced between ~1000 and ~1700 years ago, and our optical ages suggest that construction of the walls was likely incremental and increased sedimentation rates in the intertidal zone by up to fourfold. Results of this study show that when site characteristics are not amenable to radiocarbon dating, optical dating may be the only viable geochronometer. Furthermore, dating rock-walled marine management features and their geomorphic impact can lead to significant advances in our understanding of the intimate relationships that Indigenous peoples worldwide developed with their seascapes.

  8. Between a rock and a soft place: Using optical ages to date ancient clam gardens on the Pacific Northwest

    PubMed Central

    Neudorf, Christina M.; Smith, Nicole; Lepofsky, Dana; Toniello, Ginevra; Lian, Olav B.

    2017-01-01

    Rock-walled archaeological features are notoriously hard to date, largely because of the absence of suitable organic material for radiocarbon dating. This study demonstrates the efficacy of dating clam garden wall construction using optical dating, and uses optical ages to determine how sedimentation rates in the intertidal zone are affected by clam garden construction. Clam gardens are rock-walled, intertidal terraces that were constructed and maintained by coastal First Nation peoples to increase bivalve habitat and productivity. These features are evidence of ancient shellfish mariculture on the Pacific Northwest and, based on radiocarbon dating, date to at least the late Holocene. Optical dating exploits the luminescence signals of quartz or feldspar minerals to determine the last time the minerals were exposed to sunlight (i.e., their burial age), and thus does not require the presence of organic material. Optical ages were obtained from three clam garden sites on northern Quadra Island, British Columbia, and their reliability was assessed by comparing them to radiocarbon ages derived from shells underneath the clam garden walls, as well as below the terrace sediments. Our optical and radiocarbon ages suggest that construction of these clam garden walls commenced between ~1000 and ~1700 years ago, and our optical ages suggest that construction of the walls was likely incremental and increased sedimentation rates in the intertidal zone by up to fourfold. Results of this study show that when site characteristics are not amenable to radiocarbon dating, optical dating may be the only viable geochronometer. Furthermore, dating rock-walled marine management features and their geomorphic impact can lead to significant advances in our understanding of the intimate relationships that Indigenous peoples worldwide developed with their seascapes. PMID:28182645

  9. Pesticide and transformation product detections and age-dating relations from till and sand deposits

    USGS Publications Warehouse

    Warner, K.L.; Morrow, W.S.

    2007-01-01

    Pesticide and transformation product concentrations and frequencies in ground water from areas of similar crop and pesticide applications may vary substantially with differing lithologies. Pesticide analysis data for atrazine, metolachlor, alachlor, acetochlor, and cyanazine and their pesticide transformation products were collected at 69 monitoring wells in Illinois and northern Indiana to document occurrence of pesticides and their transformation products in two agricultural areas of differing lithologies, till, and sand. The till is primarily tile drained and has preferential fractured flow, whereas the sand primarily has surface water drainage and primary porosity flow. Transformation products represent most of the agricultural pesticides in ground water regardless of aquifer material - till or sand. Transformation products were detected more frequently than parent pesticides in both the till and sand, with metolachlor ethane sulfonic acid being most frequently detected. Estimated ground-water recharge dates for the sand were based on chlorofluorocarbon analyses. These age-dating data indicate that ground water recharged prior to 1990 is more likely to have a detection of a pesticide or pesticide transformation product. Detections were twice as frequent in ground water recharged prior to 1990 (82%) than in ground water recharged on or after 1990 (33%). The highest concentrations of atrazine, alachlor, metolachlor, and their transformation products, also were detected in samples from ground water recharged prior to 1990. These age/pesticide detection relations are opposite of what would normally be expected, and may be the result of preferential flow and/or ground-water mixing between aquifers and aquitards as evident by the detection of acetochlor transformation products in samples with estimated ground-water ages predating initial pesticide application. ?? 2007 American Water Resources Association.

  10. Radiocarbon Dating and age Inversions in Lake Chapala Late Holocene Sediments, Western Mexico.

    NASA Astrophysics Data System (ADS)

    Zarate-Del Valle, P.; Israde-Alcantara, I.; Ramírez-Sánchez, H.; Gómez-Salazar, S.; Ríos-Donato, N.

    2006-12-01

    Neotectonic Lake Chapala, the major Mexican freshwater reservoir lies at the north and northeast of the Citala Rift and is linked to history of the active Plio-Quaternary Transmexican Volcanic Belt geological province. Eight radiocarbon 14C dates were obtained on shallow sediment samples from a gravity corer (T46) of 5 cm in diameter and 1.7 m long. The core was collected from the western sector of Lake Chapala (103° 15.43' W, 20° 14.45' N) at water depth of 3.7 m (june 2000). In general, shallow sediments (<2m deep) in Lake Chapala are dark and silty with granulometric median ranging from 10 to 50 μm. Major oxides in sediments are: SiO2 (54.05%), Al2O3 (18.94%), Fe2O3 (6.75%) and CaO (2.57%). The major mineralogical composition of sediments is as follows: plagioclases (25.86%), quartz (20.92%), clays (38.5%), carbonates (2.99%) and TiO2 (1.05%). Radiocarbon ages were measured by accelerator mass spectrometry (AMS) and were obtained through the organic carbon fraction extracted from the bulk sediment samples sliced every 20 cm taken from the whole core. Stratigraphically ordered from highest to lowest, the eight ages reported are: 1) 2,000 ±40 yr on sediments at 30 cm deep; 2) 1,920 ±35 yr on sediments at 50 cm deep; 3) 1,900 ±35 yr on sediments at 70 cm deep; 4) 2,080 ±35 yr on sediments at 90 cm deep; 5) 2,090 ±50 yr on sediments at 110 cm deep; 6) 2,190 ±35 yr on sediments at 130 cm deep; 7) 2,050 ±35 yr on sediments at 150 cm deep and, 8) 1,500 ±35 yr on sediments at 170 cm deep. From the top until 70 cm and from 130 to bottom we observe two age inversions; the interval apparently with no age inversions is from 70cm to 130cm. As it is known the age inversions observed may be due to a) ancient carbon being incorporated into the sediment during deposition; b) unrecognized bioturbation, c) Postdepositional alteration and, d) variations in the apparent geological ages of the different chemical phases comprising the total sediment. Basically, the factors

  11. 187Re - 187Os nuclear geochronometry: age dating with permil precision

    NASA Astrophysics Data System (ADS)

    Roller, Goetz

    2016-04-01

    Recently, 187Re - 187Os nuclear geochronometry, a new dating method combining ideas of nuclear astrophysics with geochronology, has successfully been used to calculate two-point-isochron (TPI) ages for Devonian black gas shales using the isotopic signature of an r-process geochronometer as one data point in a TPI diagram [1]. Based upon a nuclear production ratio 187Re/188Os = 5.873, TPI ages were calculated for 12 SDO-1 (Devonian Ohio Shale, Appalachian Basin) aliquants, for which repeated Re-Os measurements are reported in the literature [2]. TPI ages range from 384.5 ± 2.7 Ma (187Os/188Osi = 0.29413 ± 0.00023) to 387.7 ± 2.1 Ma (187Os/188Osi = 0.29407 ± 0.00019) with a mean of 386.67 ± 1.79 Ma). The result is consistent with the isochronous age from the 12 aliquants alone (386 ± 16 Ma, 187Os/188Osi = 0.31±0.31), which is bracketed by U-Pb ages for the Belpre Ash (381.1 ± 3.3 Ma) and the Tioga Ash bed (390.0 ± 2.5 Ma) [3] from the Appalachian Basin. Hence, SDO-1 can be assigned to the Givetian stage (varcus-zone) of the Middle Devonian, close to the Eifelian/Givetian boundary (using the time-scale of [3] or [4]). If an age is calculated from an isochron diagram for the 12 aliquants including the nuclear geochronometer, a permil precision can be achieved, an interesting feature with respect to any effort towards calibrating the Geologic Timescale. Additionally, a Th/U evolution (or: Th/U-time) diagram can be plotted using U-Pb zircon age data and Th/U ratios from volcanic rocks and ashes reported in the literature [3] for specific Devonian samples from the Appalachian Basin. Since the Re-Os age obtained for SDO-1 can also be connected to its Th/U ratio, it turns out, that Th/U ratios might be helpful age indicators, as demonstrated for the Devonian using the U-Pb and Re-Os datasets. [1] Roller (2015), GSA Abstr. with Programs 47, #248-14. [2] Du Vivier et al. (2014), Earth Planet. Sci. Lett. 389, 23 - 33. [3] Tucker et al. (1998), Earth Planet. Sci. Lett

  12. Dating of Holocene lateral moraines in the western Southern Alps, New Zealand, applying Schmidt-hammer exposure-age dating (SHD)

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan

    2014-05-01

    Research on Holocene mountain glacier chronologies has recently intensified due to the importance of mountain glaciers as key indicators for past and present climate change. This progress is closely connected with major improvements in modern dating techniques and the application of multi-proxy approaches adapted to specific local/regional conditions. Despite recent progress there is, however, still a need for better spatial differentiation and a lack of generally accepted concepts for global and inter-hemispheric correlation of Holocene glacier chronologies. Furthermore, the "geomorphological uncertainty" inevitably connected with numerical dating of moraines in neotectonic active mountain ranges characterised by highly dynamic geomorphological process systems requires careful consideration of any subsequent palaeoclimatic interpretation. During the past few years Schmidt-hammer exposure-age dating (SHD) has revealed its potential to successfully challenge those specific circumstances. The Southern Alps of New Zealand have provided one of only a few suitable study sites for investigating Holocene glacier chronologies in the mid-latitudinal Southern Hemisphere. Recent years have seen a significant increase in terrestrial cosmogenic nuclide dating (TCND)-ages published for the Southern Alps, mainly for the last Glaciation, but also for the Holocene. The availability of a regional 10Be-production curve has improved the calibration of TCND-ages. These studies applying TCND alongside previous chronological studies using a variety of different dating techniques focus, however, primarily on a few selected glacier forelands east of the Main Divide in Aoraki/Mt Cook National Park. Bad accessibility and methodological problems account for comparatively few investigations on glacier forelands west of the Main Divide. Chronological studies applying Schmidt-hammer exposure-age dating (SHD) were performed on six glacier forelands in the western part of the Southern Alps

  13. I-Xe Dating: Comparison of I-Xe and Pb-Pb Ages of Richardton Chondrules and Separated Mineral Phases

    NASA Technical Reports Server (NTRS)

    Pravdivtseva, O. V.; Amelin, Y.; Hohenberg, C. M.; Meshik, A. P.

    2002-01-01

    I-Xe and Pb-Pb ages of individual Richardton chondrules and different mineral phases were compared in order to test the absolute I-Xe age normalization. Additional information is contained in the original extended abstract.

  14. Ground-Water Age Dating in Community Wells in Oswego County, New York

    USGS Publications Warehouse

    Komor, Stephen C.

    2001-01-01

    Officials in Oswego County, in north-central New York, have been concerned about potential contamination of community wells. Many of these wells are completed in unconfined glacial sand-and-gravel aquifers, although some are finished in till or in the underlying fractured and jointed bedrock of Late Ordovician and Early Silurian ages. Local shallow ground-water flow is affected by the orientation and hydraulic characteristics of the local topography and surficial sediments, whereas deeper regional flow is toward Lake Ontario. Concentrations of chlorofluorocarbons and tritium in water samples from 28 wells in the county were measured in 1999 for ground-water-age dating; results yield recharge dates ranging from about 1955 to 1994. The presence of water older than about 15 years in the sand-and-gravel aquifers differs from previous concepts of recharge sources and ground-water movement that were based on numerical modeling of ground-water flow. Young ground water (1 to 5 years old) probably represents recharge from recent precipitation and seepage from streams, whereas the oldest ground water (more than 40 years old) probably is derived from the fractured bedrock that underlies the glacial sediments or has moved along long flow paths in unconsolidated deposits, or through poorly permeable material. Some sand-and-gravel aquifers in Oswego County contain mixtures of old and young water. Wellhead-protection efforts need to focus on protection of the quality of young water in the sand-and-gravel aquifers because young water is more likely to be contaminated than old water.

  15. Using Dissolved Organic Carbon Isotopes for Groundwater Age Dating in Southern Nevada, USA

    NASA Astrophysics Data System (ADS)

    Thomas, James; Hershey, Ronald; Fereday, Wyatt

    2016-04-01

    Dissolved organic carbon (DOC) 14C offers a method to calculate groundwater ages that is more straightforward than dissolved inorganic carbon (DIC) 14C. To obtain corrected DIC 14C groundwater ages requires models that account for chemical and physical processes that affect both 13C and 14C. This is especially true in carbonate-rock aquifers where a fair amount of dissolution and precipitation of carbonate minerals can occur. A first important step in calculating 14C DOC groundwater ages is to determine the initial 14C DOC (A0) values of the groundwater recharge. For this study, recharge area groundwater samples of DOC 14C, collected from 14 different sites, were used to determine the recharge DOC 14C values. These values ranged from 96 to 120 percent modern carbon (pmc), with an average value of 106.2 pmc. These 14C A0 values support the use of a 100 pmc 14C A0 pre-bomb value to calculate DOC 14C groundwater ages for southern Nevada. Several conditions to successfully use DOC 14C to date groundwater need to be met. First, soluble organic carbon content of aquifers needs to be low, so that little DOC is added to the groundwater as it flows from recharge areas down gradient in an aquifer. For this study, volcanic and carbonate aquifer outcrop rocks showed that these rocks contained low soluble organic carbon. Second, it is important that the DOC does not change character down a flow path, which could indicate transformation of DOC along a flow path and/or addition of DOC to the groundwater. Although specific DOC compounds could not be identified for samples collected at four sites, all four groundwater sample spectra show the same general shape over the duration of the HPLC run indicating that the DOC compound composition of groundwater does not significantly change from up-gradient to down-gradient. Third, another factor that could greatly affect DOC 14C groundwater age calculations is matrix diffusion/adsorption of DOC 14C. Laboratory experiments showed that

  16. Dating violence victimization across the teen years: Abuse frequency, number of abusive partners, and age at first occurrence

    PubMed Central

    2012-01-01

    Background Prior longitudinal studies have shown high cumulative dating violence exposure rates among U.S adolescents, with 36 percent of males and 44 percent to 88 percent of females experiencing victimization across adolescence/young adulthood. Despite promising information characterizing adolescents’ dating violence experiences longitudinally, prior studies tended to concentrate on physical and sexual types of violence only, and did not report information on the number of times dating violence was experienced across multiple abusive partners. We used a method similar to the timeline follow-back interview to query adolescents about dating violence victimization from age 13 to 19—including dating violence types (physical, sexual, and psychological), frequency, age at first occurrence, and number of abusive partners. Methods A total of 730 subjects were randomly sampled from university registrar records and invited to complete an online survey, which utilized methods similar to the timeline follow-back interview, to retrospectively assess relationship histories and dating violence victimization from age 13 to 19 (eight questions adapted from widely-used surveys covering physical, sexual, and psychological abuse). Then, for each dating violence type, we asked about the number of occurrences, number of abusive partners, and age at first occurrence. Of 341 subjects who completed the survey, we included 297 (64 percent females; 36 percent males) who had a dating partner from age 13 to 19. Results Fully 64.7 percent of females and 61.7 percent of males reported dating violence victimization between age 13 and 19, with most experiencing multiple occurrences. More than one-third of abused females had two or more abusive partners: controlling behavior (35.6 percent); put downs/name calling (37.0); pressured sex (42.9); insults (44.3); slapped/hit (50.0); and threats (62.5). Males also had two or more abusive partners, as follows: controlling behavior (42.1 percent

  17. Statistical methods to adjust for date and age misreporting to improve estimates of vital rates in Pakistan.

    PubMed

    Pullum, T W

    1991-02-01

    Misreporting of dates and ages poses serious difficulties for the estimation of the age distribution and birth and death rates in many developing countries. The pervasiveness of these problems is illustrated with data from a well-designed on-going survey in Pakistan, the Pakistan Demographic Survey. Methods for reconciling discrepancies, based on the assumptions of constant misreporting and survivorship patterns, are presented. The reasoning behind these methods could be applied much more generally. Research into the cultural interpretations of age and dates, and the nature of possible biases, is called for.

  18. Methods for using argon-39 to age-date groundwater using ultra-low-background proportional counting

    DOE PAGES

    Mace, Emily; Aalseth, Craig; Brandenberger, Jill; ...

    2016-12-21

    Argon-39 can be used as a tracer for age-dating glaciers, oceans, and more recently, groundwater. With a half-life of 269 years, 39Ar fills an intermediate age range gap (50–1,000 years) not currently covered by other common groundwater tracers. Therefore, adding this tracer to the data suite for groundwater studies provides an important tool for improving our understanding of groundwater systems. Lastly, we present the methods employed for arriving at an age-date for a given sample of argon degassed from groundwater.

  19. Methods for using argon-39 to age-date groundwater using ultra-low-background proportional counting

    SciTech Connect

    Mace, Emily; Aalseth, Craig; Brandenberger, Jill; Day, Anthony; Hoppe, Eric; Humble, Paul; Keillor, Martin; Kulongoski, Justin; Overman, Cory; Panisko, Mark; Seifert, Allen; White, Signe; Freeburg, Eric Wilcox; Williams, Richard

    2016-12-21

    Argon-39 can be used as a tracer for age-dating glaciers, oceans, and more recently, groundwater. With a half-life of 269 years, 39Ar fills an intermediate age range gap (50–1,000 years) not currently covered by other common groundwater tracers. Therefore, adding this tracer to the data suite for groundwater studies provides an important tool for improving our understanding of groundwater systems. Lastly, we present the methods employed for arriving at an age-date for a given sample of argon degassed from groundwater.

  20. Methods for using argon-39 to age-date groundwater using ultra-low-background proportional counting.

    PubMed

    Mace, Emily; Aalseth, Craig; Brandenberger, Jill; Day, Anthony; Hoppe, Eric; Humble, Paul; Keillor, Martin; Kulongoski, Justin; Overman, Cory; Panisko, Mark; Seifert, Allen; White, Signe; Wilcox Freeburg, Eric; Williams, Richard

    2016-12-21

    Argon-39 can be used as a tracer for age-dating glaciers, oceans, and more recently, groundwater. With a half-life of 269 years, (39)Ar fills an intermediate age range gap (50-1,000 years) not currently covered by other common groundwater tracers. Therefore, adding this tracer to the data suite for groundwater studies provides an important tool for improving our understanding of groundwater systems. We present the methods employed for arriving at an age-date for a given sample of argon degassed from groundwater.

  1. Radiocarbon Dating

    SciTech Connect

    Buchholz, B A

    2007-12-20

    Radiocarbon dating can be used to determine the age of objects that contain components that were once alive. In the case of human remains, a radiocarbon date can distinguish between a crime scene and an archeological site. Documents, museum artifacts and art objects can be dated to determine if their age is correct for the historical context. A radiocarbon date does not confirm authenticity, but it can help identify a forgery.

  2. Psychiatric Disorders Prior to Dating Initiation and Physical Dating Violence Before Age 21: Findings from the National Comorbidity Survey Replication (NCS-R)

    PubMed Central

    McCauley, Heather L.; Breslau, Joshua A.; Saito, Naomi; Miller, Elizabeth

    2015-01-01

    Purpose Poor mental health is associated with teen dating violence (TDV), but whether there are specific types of psychiatric disorders that could be targeted with intervention to reduce TDV remains unknown. Methods Multivariable logistic regression models were used to assess the associations of psychiatric disorders that emerged prior to dating initiation with subsequent physical dating violence in a nationally representative sample from the National Comorbidity Survey Replication, adjusting statistically for adverse childhood experiences. Results In adjusted models, internalizing disorders (AOR 1.14, 95% CI 1.04, 1.25; no sex differences noted) and externalizing disorders (males: AOR 1.28, 95% CI 1.10, 1.49; females: AOR 1.85, 95% CI 1.55, 2.21) were associated with subsequent involvement in any physical dating violence victimization or perpetration before the age of 21. Those at greatest risk included girls with ADHD and substance use, in particular. Conclusions The range of psychiatric disorders associated with of TDV is broader than has generally been recognized for both boys and girls. Clinical and public health prevention programs should incorporate strategies for addressing multiple pathways through which poor mental health may put adolescents at risk for TDV. PMID:25773524

  3. Neighbourhood socioeconomic inequalities in incidence of acute myocardial infarction: a cohort study quantifying age- and gender-specific differences in relative and absolute terms

    PubMed Central

    2012-01-01

    Background Socioeconomic status has a profound effect on the risk of having a first acute myocardial infarction (AMI). Information on socioeconomic inequalities in AMI incidence across age- gender-groups is lacking. Our objective was to examine socioeconomic inequalities in the incidence of AMI considering both relative and absolute measures of risk differences, with a particular focus on age and gender. Methods We identified all patients with a first AMI from 1997 to 2007 through linked hospital discharge and death records covering the Dutch population. Relative risks (RR) of AMI incidence were estimated by mean equivalent household income at neighbourhood-level for strata of age and gender using Poisson regression models. Socioeconomic inequalities were also shown within the stratified age-gender groups by calculating the total number of events attributable to socioeconomic disadvantage. Results Between 1997 and 2007, 317,564 people had a first AMI. When comparing the most deprived socioeconomic quintile with the most affluent quintile, the overall RR for AMI was 1.34 (95 % confidence interval (CI): 1.32 – 1.36) in men and 1.44 (95 % CI: 1.42 – 1.47) in women. The socioeconomic gradient decreased with age. Relative socioeconomic inequalities were most apparent in men under 35 years and in women under 65 years. The largest number of events attributable to socioeconomic inequalities was found in men aged 45–74 years and in women aged 65–84 years. The total proportion of AMIs that was attributable to socioeconomic inequalities in the Dutch population of 1997 to 2007 was 14 % in men and 18 % in women. Conclusions Neighbourhood socioeconomic inequalities were observed in AMI incidence in the Netherlands, but the magnitude across age-gender groups depended on whether inequality was expressed in relative or absolute terms. Relative socioeconomic inequalities were high in young persons and women, where the absolute burden of AMI was low. Absolute

  4. Advancing knowledge gained from sediment budgets through sediment age dating and fingerprinting in small watersheds

    NASA Astrophysics Data System (ADS)

    Skalak, K.; Benthem, A.; Gellis, A.; Harvey, J. W.; Hupp, C. R.; Larsen, L.; Noe, G. B.; Pizzuto, J. E.; Schenk, E.

    2013-12-01

    Dynamics and long-term trajectories of fine sediment generally remain poorly quantified in rivers, which have implications for nutrient and contaminant transport and remediation strategies. Here we focus on two streams within the Chesapeake Bay watershed, Difficult Run and Accotink Creek. These streams have varying degrees of urbanization and diverse best management practices, making possible a comparison of sediment sources, sinks, and residence times to illuminate how land management impacts fine sediment transport. Bank erosion and floodplain accumulation in Difficult Run has been previously determined and is ongoing in Accotink Creek. Current work advances sediment budgets by quantifying the role of in-channel fine sediment storage in the bed and margins. To understand the relative storage timescales for various geomorphic features (floodplain, in-channel, etc.) and develop age distributions, sediment is dated using radionuclides of varying half-lives such as Pb-210, Cs-137, Be-7, bomb radiocarbon, and optically stimulated luminescence (OSL). To determine the source of sediment that is transported in suspension, sediment fingerprinting has been completed in Difficult Run and initiated in Accotink Creek. Furthermore, the present study furthers our understanding of fine sediment dynamics by fingerprinting sources of stored sediment and evaluating how they evolve over storm events and stream size. For this, we sampled sediment in storage zones before and after storm events of a specified magnitude to determine their chemical signatures with respect to various source-tracking elements and isotopes. This study represents the first such work to integrate sediment dating, sediment fingerprinting and an analysis of storage zones to understand fine sediment dynamics and long-term trajectories.

  5. 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 Central

    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

  6. 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.

  7. Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques: lead-radium and bomb radiocarbon dating.

    SciTech Connect

    Andrews, A H; Kerr, L A; Cailliet, G M; Brown, T A; Lundstrom, C C; Stanley, R D

    2007-11-04

    Canary rockfish (Sebastes pinniger) have long been an important part of recreational and commercial rockfish fishing from southeast Alaska to southern California, but localized stock abundances have declined considerably. Based on age estimates from otoliths and other structures, lifespan estimates vary from about 20 years to over 80 years. For the purpose of monitoring stocks, age composition is routinely estimated by counting growth zones in otoliths; however, age estimation procedures and lifespan estimates remain largely unvalidated. Typical age validation techniques have limited application for canary rockfish because they are deep dwelling and may be long lived. In this study, the unaged otolith of the pair from fish aged at the Department of Fisheries and Oceans Canada was used in one of two age validation techniques: (1) lead-radium dating and (2) bomb radiocarbon ({sup 14}C) dating. Age estimate accuracy and the validity of age estimation procedures were validated based on the results from each technique. Lead-radium dating proved successful in determining a minimum estimate of lifespan was 53 years and provided support for age estimation procedures up to about 50-60 years. These findings were further supported by {Delta}{sup 14}C data, which indicated a minimum estimate of lifespan was 44 {+-} 3 years. Both techniques validate, to differing degrees, age estimation procedures and provide support for inferring that canary rockfish can live more than 80 years.

  8. Pliocene Cosmogenic Nuclide Burial Ages of the Nenana Gravel: Progress in Dating and Implications for Alaska Range Evolution

    NASA Astrophysics Data System (ADS)

    Goehring, B. M.; Bemis, S. P.; Ward, D.; Caffee, M. W.; Sortor, R. N.

    2015-12-01

    The Nenana Gravel is an up to 1.2 km thick foreland basin deposit that spans the north flank of the Alaska Range. It is uplifted relative to the active foreland basin to the north. It is also deformed to various degree dependent on its location within the northern Alaska Range thrust system. Because this foreland basin sequence records the unroofing and northward propagation of the Alaska Range, direct dating of the Nenana Gravel, especially over wide spatial distribution along the Alaska Range, will substantially advance our understanding of the style and timing of deformation of the Alaska Range. At present though, age estimates for the Nenana Gravel are limited to a single maximum limiting age and uncertain minimum limiting age with no little or no insight as to the spatial variation in Nenana Gravel deposition timing. We present the first direct dates of deposition ages of the Nenana Gravel using cosmogenic nuclide burial dating. Results indicate that deposition of the Nenana Gravel began ca. 6.5 Ma, in stratigraphic agreement with a maximum limiting tephra age from the underlying Usibelli Group. Additional samples from the Nenana Gravel basal contact and higher in the section are presently underway. The resultant burial ages are amongst the oldest 26Al-10Be burial ages ever produced and highlight the potential of the method to directly date sediments in the Pliocene, particularly given recent advancements in the accelerator mass spectrometry measurement of 26Al/27Al isotope ratios.

  9. 230Th-234U Age-Dating Uranium by Mass Spectrometry

    SciTech Connect

    Williams, R W; Gaffney, A M

    2012-04-18

    This is the standard operating procedure used by the Isotope Ratio Mass Spectrometry Group of the Chemical Sciences Division at LLNL for the preparation of a sample of uranium oxide or uranium metal for {sup 230}Th-{sup 234}U age-dating. The method described here includes the dissolution of a sample of uranium oxide or uranium metal, preparation of a secondary dilution, spiking of separate aliquots for uranium and thorium isotope dilution measurements, and purification of uranium and thorium aliquots for mass spectrometry. This SOP may be applied to uranium samples of unknown purity as in a nuclear forensic investigation, and also to well-characterized samples such as, for example, U{sub 3}O{sub 8} and U-metal certified reference materials. The sample of uranium is transferred to a quartz or PFA vial, concentrated nitric acid is added and the sample is heated on a hotplate at approximately 100 C for several hours until it dissolves. The sample solution is diluted with water to make the solution approximately 4 M HNO{sub 3} and hydrofluoric acid is added to make it 0.05 M HF. A secondary dilution of the primary uranium solution is prepared. Separate aliquots for uranium and thorium isotope dilution measurements are taken and spiked with {sup 233}U and {sup 229}Th, respectively. The spiked aliquot for uranium isotope dilution analysis is purified using EiChrom UTEVA resin. The spiked aliquot for thorium isotope dilution analysis is purified by, first, a 1.8 mL AG1x8 resin bed in 9 M HCl on which U adsorbs and Th passes through; second, adsorbing Th on a 1 mL AG1x8 resin bed in 8 M HNO{sub 3} and then eluting it with 9 M HCl followed by 0.1 M HCl + 0.005 M HF; and third, by passing the Th through a final 1.0 mL AG1x8 resin bed in 9 M HCl. The mass spectrometry is performed using the procedure 'Th and U Mass Spectrometry for {sup 230}Th-{sup 234}U Age Dating'.

  10. Radiocarbon Dating, Memories, and Hopes

    DOE R&D Accomplishments Database

    Libby, W. F.

    1972-10-01

    The history of radiocarbon dating from 1939 to the present is reviewed. The basic principles of radiocarbon dating are that cosmic rays make living things radioactive with {sup 14}C to a certain level fixed by the environment and that at death the intake of food stops so no replenishment of the {sup 14}C steadily lost by the immutable decay occurs. Therefore measurement of the degree of decay gives the time lapse since death, i.e., the radiocarbon age. The equipment developed and experiments performed to measure the specific activity of specimens to be dated are described. The results obtained by world-wide experimenters are discussed. These showed that on simultaneity radiocarbon dating is apparently reliable but that absolute dates may be incorrect by as much as 600 to 700 y. The value of radiocarbon dating to archaeologists, geologists, climatologists, and historians is stressed. (LCL)

  11. Reconstruction of settlement phases at Intermediate Bronze Age structures in the Negev Highlands (Israel) using luminescence dating

    NASA Astrophysics Data System (ADS)

    Junge, Andrea; Lomax, Johanna; Shahack-Gross, Ruth; Dunseth, Zachary C.; Finkelstein, Israel; Fuchs, Markus

    2016-04-01

    OSL dating is usually applied to sediments in paleoenvironmental sciences. However, there is only limited experience with determining the age of archaeological stone structures by OSL using dust deposits associated with these structures. The age of trapped dust deposits may be used to date the onset of settlement (sediment below structures), settlement activity (occupation layer), or the time after settlement (sediment between collapsed walls and roofs). In this study, OSL dating is applied for establishing a chronology of settlement structures situated in the Negev Highlands, Israel. Two archaeological sites are investigated to identify the occupation history, by dating the aeolian dust trapped within the remains of ancient buildings. OSL dating techniques are applied using coarse grain quartz and a standard SAR protocol. First results indicate that the luminescence properties of the trapped sediments are suitable for OSL dating. Therefore, it was possible to date the onset of sedimentation in a later phase of the human occupation or shortly after the settlement was abandoned, which is supported by archaeological evidence gained from pottery finds and the architecture of the buildings.

  12. Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques.

    PubMed

    Pederson, Joel L; Chapot, Melissa S; Simms, Steven R; Sohbati, Reza; Rittenour, Tammy M; Murray, Andrew S; Cox, Gary

    2014-09-09

    Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock's exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼ 1-1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region.

  13. Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques

    NASA Astrophysics Data System (ADS)

    Pederson, Joel L.; Chapot, Melissa S.; Simms, Steven R.; Sohbati, Reza; Rittenour, Tammy M.; Murray, Andrew S.; Cox, Gary

    2014-09-01

    Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock's exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼1-1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region.

  14. Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques

    PubMed Central

    Pederson, Joel L.; Chapot, Melissa S.; Simms, Steven R.; Sohbati, Reza; Rittenour, Tammy M.; Murray, Andrew S.; Cox, Gary

    2014-01-01

    Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock’s exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼1–1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region. PMID:25157162

  15. 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

  16. Common-Lead Corrected U-Pb Age Dating of Perovskite by LA-SF-ICP-MS

    NASA Astrophysics Data System (ADS)

    Frei, D.

    2014-12-01

    Perovskite is a very useful mineral for dating the age of emplacement of kimberlites and associated rocks. Conventionally, U-Pb dating of perovskite is achieved using isotope dilution (ID-TIMS) or ion-probe (SHRIMP) techniques, which are time- and cost-intensive. The potential of the rapid and inexpensive laser ablation ICP-MS technique for U-Pb dating of perovskite has been demonstrated recently. We investigated the benefits of single collector magnetic sectorfield ICP-MS (SF-ICP-MS) instruments for U-Pb dating of perovskite by laser ablation. To this end perovskites from two kimberlites from Garnet Lake, W Greenland, and Pyramidefjeld, SW Greenland, have been separated. Multigrain aliquots of both perovskite separates were U-Pb dated by ID-TIMS, yielding emplacement ages of 568 ±11 Ma for the Garnet Lake kimberlite and 151 ±2 Ma for the Pyramidefjeld kimberlite. Subsequently both samples have been dated in-situ by laser ablation employing a ThermoFinnigan Element2 SF-ICP-MS coupled to a NewWave UP 213 laser system. A common lead correction was applied based on the measured 204Pb intensity (after correction for the measured 204(Pb+Hg) gas blank). Perovskite from the Ice River Complex, British Columbia, was used as a secondary standard for quality control purposes. Multiple in-situ measurements of the Ice River perovskite in two different analytical sessions yielded concordia ages of 359 ±3 Ma and 357 ±3 Ma, in excellent agreement with the age of 356 Ma determined by ID-TIMS (Heaman, pers. comm.). Nineteen in-situ analyses of perovskite grains extracted from the Garnet Lake kimberlite yielded a concordia age of 566 ±5 Ma, also in excellent agreement with the age obtained by ID-TIMS. Because of the very low Pb contents in perovskites from the Pyramidefjeld (around 1 ppm) and the associated large uncertainties of the common lead correction, no concordia age could be obtained. However, the in-situ laser ablation analysis yielded a common lead corrected weighted

  17. Ascertaining year of birth/age at death in forensic cases: A review of conventional methods and methods allowing for absolute chronology.

    PubMed

    Lynnerup, Niels; Kjeldsen, Henrik; Zweihoff, Ralf; Heegaard, Steffen; Jacobsen, Christina; Heinemeier, Jan

    2010-09-10

    Based on an actual case, where we were able to ascertain the year of birth of three dead babies found in a deep-freezer to within 1-2 years (1986, 1988 and 2004, respectively), we review the current state of forensic age determination/year of birth determination. The age of an individual (year of birth) is often a fundamental piece of data in connection with forensic identification of unidentified bodies. The methods most often used are based on determining various morphological, age-related, changes on the skeleton (or teeth, although odontological methods are not reviewed in this paper). As such, these methods are all relative, i.e. they do not furnish calendar ages or years, but an estimate of the age at death, with a rather large range, i.e. the methods rely on biological aging following the chronological aging. More recently, methods have been proposed using more direct ascertainment of age at death, e.g. protein racemisation, or, as in our case, radiocarbon methods. Especially the latter method may in fact yield absolute ages (years of birth), because (14)C activity, as measured in specific proteins in specific cells or tissues in the body, were in equilibrium with the so-called bomb-pulse, when these proteins were formed (at birth). The bomb pulse reflects a dramatic change in atmospheric (14)C content due to nuclear bomb testing, and these dramatic changes can be rather tightly related to single calendar years.

  18. An evaluation of fossil tip-dating versus node-age calibrations in tetraodontiform fishes (Teleostei: Percomorphaceae).

    PubMed

    Arcila, Dahiana; Alexander Pyron, R; Tyler, James C; Ortí, Guillermo; Betancur-R, Ricardo

    2015-01-01

    Time-calibrated phylogenies based on molecular data provide a framework for comparative studies. Calibration methods to combine fossil information with molecular phylogenies are, however, under active development, often generating disagreement about the best way to incorporate paleontological data into these analyses. This study provides an empirical comparison of the most widely used approach based on node-dating priors for relaxed clocks implemented in the programs BEAST and MrBayes, with two recently proposed improvements: one using a new fossilized birth-death process model for node dating (implemented in the program DPPDiv), and the other using a total-evidence or tip-dating method (implemented in MrBayes and BEAST). These methods are applied herein to tetraodontiform fishes, a diverse group of living and extinct taxa that features one of the most extensive fossil records among teleosts. Previous estimates of time-calibrated phylogenies of tetraodontiforms using node-dating methods reported disparate estimates for their age of origin, ranging from the late Jurassic to the early Paleocene (ca. 150-59Ma). We analyzed a comprehensive dataset with 16 loci and 210 morphological characters, including 131 taxa (95 extant and 36 fossil species) representing all families of fossil and extant tetraodontiforms, under different molecular clock calibration approaches. Results from node-dating methods produced consistently younger ages than the tip-dating approaches. The older ages inferred by tip dating imply an unlikely early-late Jurassic (ca. 185-119Ma) origin for this order and the existence of extended ghost lineages in their fossil record. Node-based methods, by contrast, produce time estimates that are more consistent with the stratigraphic record, suggesting a late Cretaceous (ca. 86-96Ma) origin. We show that the precision of clade age estimates using tip dating increases with the number of fossils analyzed and with the proximity of fossil taxa to the node under

  19. Characterization of depositional age and structure of sedimentary successions by U-Pb TIMS and LA-ICP-MS dating of volcanic horizons and detrital zircons: an example from the western Trondheim Nappe Complex, Scandinavian Caledonides

    NASA Astrophysics Data System (ADS)

    Gasser, Deta; Grenne, Tor; Corfu, Fernando; Eivind Augland, Lars

    2016-04-01

    Revealing the absolute depositional age of non-fossiliferous sedimentary successions represents a long-lasting challenge in Earth Sciences. Lacking age control hampers the correct interpretation of the temporal evolution of depositional systems, and, if deformed, of the architecture of fold-and-thrust belts. Dating of detrital zircons within clastic sedimentary successions has over the past decades become a popular method to approximate the absolute depositional age and to characterize the source areas of such rocks. If combined with other geochronological information, such as dating of contemporaneous volcanic horizons, a much better resolution of the stratigraphy and structure of non-fossiliferous sedimentary successions can be achieved. The western Trondheim nappe complex in the central Scandinavian Caledonides is a classical area in this respect. On top of Late Cambrian to Early Ordovician ophiolitic fragments, various volcanic, volcano-clastic and clastic successions tell a complex story of island-arc formation, ocean closure and continent collision. Several famous fossil horizons indicate deposition during the Middle to Upper Ordovician (ca. 470-445 Ma), but large areas lack an absolute age control and several contrasting stratigraphic schemes and structural interpretations have been presented in the past. In this contribution we present the results of LA-ICP-MS detrital U-Pb zircon dating of clastic horizons as well as U-Pb TIMS zircon dating of volcanic horizons and magmatic clasts in conglomerates in order to characterize the depositional age and structure of the western Trondheim nappe complex in more detail. Together with field observations, including way up criteria, the zircon data enable significant revisions of existing stratigraphic and structural models. At least four (volcano-)sedimentary successions can be distinguished above the ca. 480-485 Ma greenstones: (1) ca. 470-463 Ma shales, limestones and andesitic porphyrites (Hølonda and Fanabekken

  20. Dating a Small Impact Crater: An Age of Kaali Crater (Estonia) Based on Charcoal Emplaced Within Proximal Ejecta

    NASA Astrophysics Data System (ADS)

    Losiak, A.; Wild, E. M.; Geppert, W. D.; Huber, M. S.; Jõeleht, A.; Kriiska, A.; Kulkov, A.; Paavel, K.; Pirkovic, I.; Plado, J.; Steier, P.; Välja, R.; Wilk, J.; Wisniowski, T.; Zanetti, M.

    2015-09-01

    The Kaali crater was formed shortly after (tpq) 1530-1455 BC (3237 ± 10 14C yr BP). This age is based on dating charcoal within the ejecta blanket that makes it directly related to the impact, and not susceptible to potential reservoir effects.

  1. 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.

  2. Combined 238U/235U and Pb Isotopics of Planetary Core Material: The Absolute Age of the IVA Iron Muonionalusta

    NASA Astrophysics Data System (ADS)

    Brennecka, G. A.; Amelin, Y.; Kleine, T.

    2016-08-01

    We report a measured 238U/235U for the IVA iron Muonionalusta. This measured value requires an age correction of ~7 Myr to the previously published Pb-Pb age. This has major implications for our understanding of planetary core formation and cooling.

  3. Radiometric dating of the Earlier Stone Age sequence in excavation I at Wonderwerk Cave, South Africa: preliminary results.

    PubMed

    Chazan, Michael; Ron, Hagai; Matmon, Ari; Porat, Naomi; Goldberg, Paul; Yates, Royden; Avery, Margaret; Sumner, Alexandra; Horwitz, Liora Kolska

    2008-07-01

    We present here the results of 44 paleomagnetic measurements, and single cosmogenic burial and optically stimulated luminescence ages for the Earlier Stone Age deposits from Wonderwerk Cave, Northern Cape, South Africa. The resulting paleomagnetic sequence: N>R>N>R>N constrains the Earlier Stone Age strata in this part of the site to between approximately 0.78-1.96 Ma. A single cosmogenic date of approximately 2.0 Ma from the base of the section offers some corroboration for the paleomagnetic sequence. Preliminary results indicate that the small lithic assemblage from the basal stratum may contain an Oldowan facies. This is overlain by several strata containing Acheulean industries. The preliminary radiometric dates reported here place the onset of the Acheulean at this site to approximately 1.6 Ma, which is roughly contemporaneous with that of East Africa.

  4. New uppermost Cambrian U-Pb date from Avalonian Wales and age of the Cambrian-Ordovician boundary

    USGS Publications Warehouse

    Davidek, K.; Landing, E.; Bowring, S.A.; Westrop, S.R.; Rushton, A.W.A.; Fortey, R.A.; Adrain, J.M.

    1998-01-01

    A crystal-rich volcaniclastic sandatone in the lower Peltura scarabaeoides Zone at Ogof-odi near Criccieth, North Wales, yields a U-Pb zircon age of 491 ?? 1 Ma. This late Late Cambrian date indicates a remarkably young age for the Cambrian-Ordovician boundary whose age must be less than 491 Ma. Hence the revised duration of the post-Placentian (trilobite-bearing) Cambrian indicates that local trilobite zonations allow a biostratigraphic resolution comparble to that provided by Ordovician graptolites and Mesozoic ammonites.

  5. Uranium-series dating of mollusks and corals, and age of Pleistocene deposits, Chesapeake Bay area, Virginia and Maryland

    USGS Publications Warehouse

    Mixon, Robert B.; Szabo, B. J.; Owens, James Patrick

    1982-01-01

    Geologic mapping in conjunction with uranium-series dating of fossil mollusks and corals suggests that the low-lying ( < 17 m in altitude) terrace deposits in the central and southern Chesapeake Bay area include two main depositional sequences, each of which represents a high stand of the sea in late Pleistocene time. The older depositional sequence includes the Accomack and Omar beds of the Delmarva area, the fossiliferous deposits along the lower Rappahannock River, and the Norfolk Formation deposits west of the Suffolk scarp. These beds have yielded a single reliable coral age estimate of 184,000?20,000 years B.P., suggesting an early late Pleistocene age. The younger sequence, including the type beds of the Norfolk Formation and equivalent strata east of the Suffolk scarp, has yielded several coral ages ranging from about 62,000 to 86,000 years B.P. (including ages from our samples and previously reported age estimates); thus, it is clearly late Pleistocene in age. Groupings of ages obtained from our quahog analyses also suggest two transgressive sequences; however, the estimated quahog ages are consistently younger than ages based on coral samples from the same and equivalent stratigraphic units. Stratigraphic, paleoclimatic, and geomorphic data suggest that the estimated uranium-series age of 71,000?7,000 years B.P. for the type beds of the Norfolk, obtained by averaging our coral dates, may be too young by as much as several tens of thousands of years. A postulated equivalency of the type Norfolk beds, upper Pleistocene deposits near Charleston, S.C. (apparent uranium-series age = 95,000?5,000 years), and deposits in the Caribbean area thought to represent the highest sea stand during the last interglacial period (apparent age, 125,000?10,000 years) implies diagenetic modification of coralline material possibly in part because of regional differences in depositional and postdepositional environments.

  6. Confirmation of a late middle Pleistocene age for the Omo Kibish 1 cranium by direct uranium-series dating.

    PubMed

    Aubert, Maxime; Pike, Alistair W G; Stringer, Chris; Bartsiokas, Antonis; Kinsley, Les; Eggins, Stephen; Day, Michael; Grün, Rainer

    2012-11-01

    While it is generally accepted that modern humans evolved in Africa, the specific physical evidence for that origin remains disputed. The modern-looking Omo 1 skeleton, discovered in the Kibish region of Ethiopia in 1967, was controversially dated at ~130 ka (thousands of years ago) by U-series dating on associated Mollusca, and it was not until 2005 that Ar-Ar dating on associated feldspar crystals in pumice clasts provided evidence for an even older age of ~195 ka. However, questions continue to be raised about the age and stratigraphic position of this crucial fossil specimen. Here we present direct U-series determinations on the Omo 1 cranium. In spite of significant methodological complications, which are discussed in detail, the results indicate that the human remains do not belong to a later intrusive burial and are the earliest representative of anatomically modern humans. Given the more archaic morphology shown by the apparently contemporaneous Omo 2 calvaria, we suggest that direct U-series dating is applied to this fossil as well, to confirm its age in relation to Omo 1.

  7. 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

  8. 235U–231Pa age dating of uranium materials for nuclear forensic investigations

    SciTech Connect

    Eppich, Gary R.; Williams, Ross W.; Gaffney, Amy M.; Schorzman, Kerri C.

    2013-04-03

    Here, age dating of nuclear material can provide insight into source and suspected use in nuclear forensic investigations. We report here a method for the determination of the date of most recent chemical purification for uranium materials using the 235U-231Pa chronometer. Protactinium is separated from uranium and neptunium matrices using anion exchange resin, followed by sorption of Pa to an SiO2 medium. The concentration of 231Pa is measured by isotope dilution mass spectrometry using 233Pa spikes prepared from an aliquot of 237Np and calibrated in-house using the rock standard Table Mountain Latite and the uranium isotopic standard U100. Combined uncertainties of age dates using this method are 1.5 to 3.5 %, an improvement over alpha spectrometry measurement methods. Model ages of five uranium standard reference materials are presented; all standards have concordant 235U-231Pa and 234U-230Th model ages.

  9. 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. .

  10. Using age of colonizing douglas-fir for the dating of young geomorphic surfaces: a case study

    USGS Publications Warehouse

    Pierson, Thomas C.

    2013-01-01

    Dating of many types of young (<500 year), dynamic, geomorphic landforms (e.g. mass-movement erosional tracks and deposits, alluvial terraces, flood plains, etc.) for purposes of hazard assessment and mitigation commonly requires greater dating precision than is available through radiocarbon dating or other methods. Ages of trees growing on landform surfaces have been used in a number of studies to estimate the time of landform creation or surface clearing, but the time lag between surface formation or disturbance and the reestablishment of trees can vary from 1 to more than 200 years (Desloges and Ryder 1990; Frenzen et al. 1988, 2005; Larsen and Bliss 1998; McCarthy and Luckman 1993; Sigafoos and Hendricks 1969; Winter et al. 2002). Appropriate lag times for selected tree species and for particular climatic and altitudinal ranges must be determined for the method to be useful.

  11. Age dating of shallow groundwater with chlorofluorocarbons, tritium/helium 3, and flow path analysis, southern New Jersey coastal plain

    USGS Publications Warehouse

    Szabo, Z.; Rice, D.E.; Plummer, L.N.; Busenberg, E.; Drenkard, S.; Schlosser, P.

    1996-01-01

    Groundwater age dating through the combination of transient tracer methods (chlorofluorocarbons (CFCs) and tritium/helium 3 (3H/3He)) and groundwater flow path analysis is useful for investigating groundwater travel times, flow patterns, and recharge rates, as demonstrated by this study of the homogeneous shallow, unconfined Kirkwood-Cohansey aquifer system in the southern New Jersey coastal plain. Water samples for age dating were collected from three sets of nested observation wells (10 wells) with 1.5-m-long screens located near groundwater divides. Three steady state finite difference groundwater flow models were calibrated by adjusting horizontal and vertical hydraulic conductivities to match measured heads and head differences (range, 0.002-0.23 m) among the nested wells, with a uniform recharge rate of 0.46 m per year and porosities of 0.35 (sand) and 0.45 (silt) that were assumed constant for all model simulations and travel time calculations. The simulated groundwater travel times increase with depth in the aquifer, ranging from about 1.5 to 6.5 years for the shallow wells (screen bottoms 3-4 m below the water table), from about 10 to 25 years for the medium-depth wells (screen bottoms 8-19 m below the water table), and from about 30 to more than 40 years for the deep wells (screen bottoms 24-26 m below the water table). Apparent groundwater ages based on CFC- and 3H/3He-dating techniques and model-based travel times could not be statistically differentiated, and all were strongly correlated with depth. Confinement of 3He was high because of the rapid vertical flow velocity (of the order of 1 m/yr), resulting in clear delineation of groundwater travel times based on the 3H/3He-dating technique. The correspondence between the 3H/3He and CFC ages indicates that dispersion has had a minimal effect on the tracer-based ages of water in this aquifer. Differences between the tracer-based apparent ages for seven of the 10 samples were smaller than the error values

  12. Dating young geomorphic surfaces using age of colonizing Douglas fir in southwestern Washington and northwestern Oregon, USA

    USGS Publications Warehouse

    Pierson, T.C.

    2007-01-01

    Dating of dynamic, young (<500 years) geomorphic landforms, particularly volcanofluvial features, requires higher precision than is possible with radiocarbon dating. Minimum ages of recently created landforms have long been obtained from tree-ring ages of the oldest trees growing on new surfaces. But to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores: (1) the time interval between stabilization of the new landform surface and germination of the sampled trees (germination lag time or GLT); and (2) the interval between seedling germination and growth to sampling height, if the trees are not cored at ground level. The sum of these two time intervals is the colonization time gap (CTG). Such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the Cascade Range, where significant eruption-induced lateral shifting and vertical aggradation of channels can occur over years to decades, and where timing of such geomorphic changes can be critical to emergency planning. Earliest colonizing Douglas fir (Pseudotsuga menziesii) were sampled for tree-ring dating at eight sites on lowland (<750 m a.s.l.), recently formed surfaces of known age near three Cascade volcanoes - Mount Rainier, Mount St. Helens and Mount Hood - in southwestern Washington and northwestern Oregon. Increment cores or stem sections were taken at breast height and, where possible, at ground level from the largest, oldest-looking trees at each study site. At least ten trees were sampled at each site unless the total of early colonizers was less. Results indicate that a correction of four years should be used for GLT and 10 years for CTG if the single largest (and presumed oldest) Douglas fir growing on a surface of unknown age is sampled. This approach would have a potential error of up to 20 years. Error can be reduced by sampling the five largest Douglas fir instead of the

  13. Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Hartig, George

    1990-12-01

    The absolute sensitivity of the FOS will be determined in SV by observing 2 stars at 3 epochs, first in 3 apertures (1.0", 0.5", and 0.3" circular) and then in 1 aperture (1.0" circular). In cycle 1, one star, BD+28D4211 will be observed in the 1.0" aperture to establish the stability of the sensitivity and flat field characteristics and improve the accuracy obtained in SV. This star will also be observed through the paired apertures since these are not calibrated in SV. The stars will be observed in most detector/grating combinations. The data will be averaged to form the inverse sensitivity functions required by RSDP.

  14. AgeFinder”: A Mac OS X computer program to evaluate electron microprobe data of monazite for chemical age dating

    NASA Astrophysics Data System (ADS)

    Appel, Peter

    2010-04-01

    A computer program is presented that can be used to obtain ages of geological significance from compositional data of monazite. The program calculates dates and their errors from U, Th and Pb concentration data obtained with the electron microprobe. The results can be displayed in isochron and gauss curve diagrams. Subsets of the data can be selected and interactively evaluated with a user friendly graphical interface. For each selected data set a cumulative date, an isochron date, their errors and the mean squared weighted deviates (MSWD) are calculated and a chi-square test is performed. The diagrams can be saved to pdf and all calculated data can be exported to a text file or saved in native format. The software runs on any Apple Macintosh with Mac OS X Tiger or later versions.

  15. Mississippi Valley-type lead-zinc deposits through geological time: Implications from recent age-dating research

    USGS Publications Warehouse

    Leach, D.L.; Bradley, D.; Lewchuk, Michael T.; Symons, David T. A.; De Marsily, G.; Brannon, J.

    2001-01-01

    Remarkable advances in age dating Mississippi Valley-type (MVT) lead-zinc deposits provide a new opportunity to understand how and where these deposits form in the Earth's crust. These dates are summarized and examined in a framework of global tectonics, paleogeography, fluid migration, and paleoclimate. Nineteen districts have been dated by paleomagnetic and/or radiometric methods. Of the districts that have both paleomagnetic and radiometric dates, only the Pine Point and East Tennessee districts have significant disagreements. This broad agreement between paleomagnetic and radiometric dates provides added confidence in the dating techniques used. The new dates confirm the direct connection between the genesis of MVT lead-zinc ores with global-scale tectonic events. The dates show that MVT deposits formed mainly during large contractional tectonic events at restricted times in the history of the Earth. Only the deposits in the Lennard Shelf of Australia and Nanisivik in Canada have dates that correspond to extensional tectonic events. The most important period for MVT genesis was the Devonian to Permian time, which corresponds to a series of intense tectonic events during the assimilation of Pangea. The second most important period for MVT genesis was Cretaceous to Tertiary time when microplate assimilation affected the western margin of North America and Africa-Eurasia. There is a notable paucity of MVT lead-zinc ore formation following the breakup of Rodinia and Pangea. Of the five MVT deposits hosted in Proterozoic rocks, only the Nanisivik deposit has been dated as Proterozoic. The contrast in abundance between SEDEX and MVT lead-zinc deposits in the Proterozoic questions the frequently suggested notion that the two types of ores share similar genetic paths. The ages of MVT deposits, when viewed with respect to the orogenic cycle in the adjacent orogen suggest that no single hydrologic model can be universally applied to the migration of the ore fluids

  16. A new Application of Ar-40/Ar-39 Dating: A Provenance Study of Middle Stone Age Obsidian Tools from Ethiopia

    NASA Astrophysics Data System (ADS)

    Nomade, S.; Vogel, N.; Renne, P. R.; Negash, A.

    2004-12-01

    The identification and geographic origin of potential sources for obsidian tools manufactured by MSA (Middle Stone Age) hominid groups is important to reconstruct source utilization and trade routes. Obsidian sourcing is done by geochemical investigation of obsidian artifacts and potential source materials and the identification of possible matches between them [e.g., 1]. Due to uncertainties arising, e.g., from intrasource inhomogeneities [2] additional methods are desirable. As a part of a pilot study, we dated by Ar-40/Ar-39 stepwise heating numerous debitage pieces of obsidian artifacts from an MSA excavation site and several potential source rock samples from a nearby obsidian outcrop in the Gademotta-Kulkuletti area near Ziway lake, Ethiopia. The ages were used, along with chemical data, to trace possible source rocks used to manufacture the artifacts. Most of the debitage samples show ages around 1.29 Ma and exhibit flat, well behaved spectra. Less well behaved spectra are obtained for two debitage samples with ages of about 1.26 Ma, and two with ages of about 0.62 Ma. We point out that despite this significant spread in the ages found, all debitage samples as well as the potential source rocks show homogeneous major and trace elemental compositions generally indicating a positive match in archeological sourcing. The ages of two potential source rocks are about 1.26 and 0.87 Ma. Thus, while there is a match with the two debitage pieces dated at 1.26 Ma, the exact outcrop of the major source for the 1.29 Ma old artifacts has not been identified yet. A second set of samples with further possible source materials for the Kulkuletti artifacts as well as another potential debitage-source material pair from a second excavation site in the Ziway lake area, Porc Epic, are currently being dated and will be presented at the conference. Already this first set of data shows not only the general applicability of Ar-40/Ar-39 dating to archeological obsidian sourcing, but

  17. Episodes of brittle deformation within the Dien Bien Phu Fault zone, Vietnam: Evidence from K-Ar age dating of authigenic illite

    NASA Astrophysics Data System (ADS)

    Bui, Hoang Bac; Ngo, Xuan Thanh; Khuong, The Hung; Golonka, Jan; Nguyen, Tien Dung; Song, Yungoo; Itaya, Tetsumaru; Yagi, Koshi

    2017-01-01

    Constraining the timing of fault zone origin and movement history is of fundamental geotectonic importance to understand the evolution and processes of the brittle fault structures. The authors present in this paper authigenic illite K-Ar age data from the fault gouge samples, collected from the Dien Bien Phu Fault (DBPF) in the Dien Bien province, Vietnam as well as in a major strike-slip fault zone in South-East Asia; all of which played important roles in the structural formation and geotectonic development of northwestern Vietnam. The gouge fault samples were separated into four grain-size fractions (< 0.1 μm, 0.1-0.4 μm, 0.4-1.0 μm and 1.0-2.0 μm). The K-Ar ages of the fractions were divided into two age groups, from 26 to 29 Ma and 130 Ma. The timing of the fault movements is defined at 26 ± 0.24 Ma, 29 ± 0.61 Ma, 130.1 ± 1.27 Ma and 130.7 ± 1.29 Ma. This indicates that the Dien Bien Phu Fault underwent two movements, first in the Early Cretaceous, with an age of about 130 Ma and second in the Oligocene (Paleogene), with an age of about 26-29 Ma. The ductile deformation of the DBPF terminated during the Early Cretaceous. These studies also indicate slow exhumation of the Dien Bien granitoid complex during the Cretaceous times. The Oligocene ages indicate that the DBPF had been reactivated by the SE extrusion and clock-wise rotation of the Indochina block, caused by the collision of the Indian and Eurasian plates. This tectonic event led to the DBPF brittle-sinistral movement, causing the exhumation phase along the fault. This movement period (ca. 26-29 Ma) is coexistent with 600-700 km sinistral shearing along the Red River-Ailao Shan fault. This is the first report determining the absolute age constraints of multi-activated tectonic events, affecting the Dien Bien Phu Fault using the K-Ar dating method for the gouge samples.

  18. Age assessment and implications of late Quaternary periglacial and paraglacial landforms on Muckish Mountain, northwest Ireland, based on Schmidt-hammer exposure-age dating (SHD)

    NASA Astrophysics Data System (ADS)

    Wilson, Peter; Matthews, John A.

    2016-10-01

    Schmidt-hammer exposure-age dating (SHD) was applied to a variety of late Quaternary periglacial and paraglacial landforms composed of coarse rock debris on Muckish Mountain, northwest Ireland. Landform ages were determined using a linear high-precision age-calibration curve, derived from young and old control surfaces of known age on the same rock type. The SHD ages represent maximum estimates of the time elapsed since the boulders stabilised and the landforms became inactive. Most ages are also minimum estimates for the start of landform development because older boulders are buried beneath the sampled surface boulders. Ages and 95% confidence intervals obtained for blockfield, boulder lobes and talus indicate these features were likely active during several of the early Holocene cold events evidenced in Greenland ice cores and North Atlantic sediment records. Activity ceased at different times ~ 9-7 ka BP. These landforms are the first indication of a geomorphological response to early Holocene cooling in the oceanic mountains of Ireland. Late Holocene ages, obtained for rock-slope failure run-out debris and debris cone boulders, overlap with shifts to cooler and/or wetter conditions, including the Little Ice Age. Geomorphological impacts associated with these changes in climate have not previously been recorded in the Irish uplands. The SHD results indicate that previously implied timings for the stabilisation of some accumulations of coarse rock debris on mountain slopes are in need of revision.

  19. Spatial gradients in Clovis-age radiocarbon dates across North America suggest rapid colonization from the north.

    PubMed

    Hamilton, Marcus J; Buchanan, Briggs

    2007-10-02

    A key issue in the debate over the initial colonization of North America is whether there are spatial gradients in the distribution of the Clovis-age occupations across the continent. Such gradients would help indicate the timing, speed, and direction of the colonization process. In their recent reanalysis of Clovis-age radiocarbon dates, Waters and Stafford [Waters MR, Stafford TW, Jr (2007) Science 315:1122-1126] report that they find no spatial patterning. Furthermore, they suggest that the brevity of the Clovis time period indicates that the Clovis culture represents the diffusion of a technology across a preexisting pre-Clovis population rather than a population expansion. In this article, we focus on two questions. First, we ask whether there is spatial patterning to the timing of Clovis-age occupations and, second, whether the observed speed of colonization is consistent with demic processes. With time-delayed wave-of-advance models, we use the radiocarbon record to test several alternative colonization hypotheses. We find clear spatial gradients in the distribution of these dates across North America, which indicate a rapid wave of advance originating from the north. We show that the high velocity of this wave can be accounted for by a combination of demographic processes, habitat preferences, and mobility biases across complex landscapes. Our results suggest that the Clovis-age archaeological record represents a rapid demic colonization event originating from the north.

  20. Spatial gradients in Clovis-age radiocarbon dates across North America suggest rapid colonization from the north

    PubMed Central

    Hamilton, Marcus J.; Buchanan, Briggs

    2007-01-01

    A key issue in the debate over the initial colonization of North America is whether there are spatial gradients in the distribution of the Clovis-age occupations across the continent. Such gradients would help indicate the timing, speed, and direction of the colonization process. In their recent reanalysis of Clovis-age radiocarbon dates, Waters and Stafford [Waters MR, Stafford TW, Jr (2007) Science 315:1122–1126] report that they find no spatial patterning. Furthermore, they suggest that the brevity of the Clovis time period indicates that the Clovis culture represents the diffusion of a technology across a preexisting pre-Clovis population rather than a population expansion. In this article, we focus on two questions. First, we ask whether there is spatial patterning to the timing of Clovis-age occupations and, second, whether the observed speed of colonization is consistent with demic processes. With time-delayed wave-of-advance models, we use the radiocarbon record to test several alternative colonization hypotheses. We find clear spatial gradients in the distribution of these dates across North America, which indicate a rapid wave of advance originating from the north. We show that the high velocity of this wave can be accounted for by a combination of demographic processes, habitat preferences, and mobility biases across complex landscapes. Our results suggest that the Clovis-age archaeological record represents a rapid demic colonization event originating from the north. PMID:17898176

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

  2. The Couple Who Facebooks Together, Stays Together: Facebook Self-Presentation and Relationship Longevity Among College-Aged Dating Couples.

    PubMed

    Toma, Catalina L; Choi, Mina

    2015-07-01

    Drawing on public commitment theory, this research examined the association between Facebook self-presentations of coupledom and relationship longevity among college-aged dating partners. Using a longitudinal design and a path model analytic approach, this study shows that Facebook self-presentational cues (i.e., being listed as "in a relationship," posting dyadic photographs, writing on the partner's wall) were associated with an increase in relationship commitment for dating couples, which, in turn, increased their likelihood of remaining together after 6 months. Contrary to predictions, the number of mutual Friends and the number of posts written by partners on participants' walls were negatively related to relationship commitment. This study is the first to apply public commitment theory to an online romantic relationship context, and one of the few to examine the effects of Facebook on the state and fate of romantic relationships.

  3. Initial excavation and dating of Ngalue Cave: a Middle Stone Age site along the Niassa Rift, Mozambique.

    PubMed

    Mercader, Julio; Asmerom, Yemane; Bennett, Tim; Raja, Mussa; Skinner, Anne

    2009-07-01

    Direct evidence for a systematic occupation of the African tropics during the early late Pleistocene is lacking. Here, we report a record of human occupation between 105-42ka, based on results from a radiometrically-dated cave section from the Mozambican segment of the Niassa (Malawi/Nyasa) Rift called Ngalue. The sedimentary sequence from bottom to top has five units. We concentrate on the so-called "Middle Beds," which contain a Middle Stone Age industry characterized by the use of the discoidal reduction technique. A significant typological feature is the presence of formal types such as points, scrapers, awls, and microliths. Special objects consist of grinders/core-axes covered by ochre. Ngalue is one of the few directly-dated Pleistocene sites located along the biogeographical corridor for modern human dispersals that links east, central, and southern Africa, and, with further study, may shed new light on hominin cave habitats during the late Pleistocene.

  4. 40Ar/39Ar dating of Pleistocene tuffs: an accurate age for the Matuyama-Brunhes geomagnetic reversal (MBGR)

    NASA Astrophysics Data System (ADS)

    Mark, D. F.; Renne, P. R.; Morgan, L. E.; Deino, A.; Smith, V. C.; Ellis, B. S.; Pearce, N. J.

    2012-12-01

    Recent recalibrations of the 40Ar/39Ar system [1,2] reveal inconsistencies with some previous ages inferred for the MBGR. An Ar/Ar age [3] for the Bishop Tuff (BT) (which post-dates the MBGR by at least 15.3 ± 2.2 ka [3]) recalculated [2] yields an age of 778.0 ± 3.8 ka (1σ, full systematic uncertainty). The age is c. 10 ka older than the BT zircon ID-TIMS U-Pb age [4] and places the MBGR at c. 793 ka, c. 13 and 20 ka older than astronomical ages for the MBGR of 780 ka [5] and 773 ka [6], respectively. To determine an accurate age for the MBGR, we have made a series of 40Ar/39Ar age determinations for Pleistocene tuffs from both Indonesia and North America that have direct relationships to the MBGR. Blind analyses were conducted at SUERC and BGC. We observed excellent inter-laboratory agreement and no systematic offset in data. Ar/Ar ages are reported relative to [2] (1σ, full systematic uncertainty). Drill cores from ODP Site 758 show the precise location of the MBGR. Below the MBGR are two distal tephra horizons that we have identified as products of two temporally distinct Old Toba Tuff (OTT) eruptions (layer d OTT1 and layer D OTT2). Continuous sedimentation between OTT1 (802.8 ± 0.7 ka, n = 100, MSWD 1.2) and OTT2 (796.2 ± 0.8 ka, n = 62, MSWD 1.3) allows for calculation of an accurate sedimentation rate and for extrapolation of an age from OTT2 to the MBGR. Data define an age for the MBGR of 795.2 ± 0.9 ka. Using tephra above the MBGR boundary, the Middle Toba Tuff (layer C) and Young Toba Tuff (layer A), extrapolation down core supports a MBGR age of c. 795 ka. Recent age data for BT sanidine reported relative to FCs at 28.172 Ma (767.4 ± 1.1 Ma) [7] oddly yielded an Ar/Ar age that was indistinguishable from the BT zircon U-Pb age [4], which is consistent with previous 40Ar/39Ar age measurements made relative to FCs at 28.02 Ma [3]. Thus we made a series of 40Ar/39Ar measurements on the exact same sample as used by Rivera et al. [7] and observed

  5. Precise Surface Exposure Dating of Early Holocene and Little Ice Age Moraines in the Cordillera Vilcabamba of Southern Peru

    NASA Astrophysics Data System (ADS)

    Licciardi, J. M.; Schaefer, J. M.; Lund, D. C.; Taggart, J. R.

    2008-12-01

    We have established precise ages of two glacial events in the tropical Andean highlands of southern Peru. The field site is located on the flanks of Nevado Salcantay (6271 m asl; 13°20'S latitude), the highest peak in the Cordillera Vilcabamba. A two-fold sequence of nested lateral and end moraines was mapped in a glacial trough emanating from the south face of Salcantay. Well-defined outer and inner moraines were deposited by valley glaciers that terminated 5 km and 3 km, respectively, from their head on the Salcantay massif. Cosmogenic 10Be surface exposure dating of boulders on the outer (n = 7) and inner (n = 7) moraine crests expands upon initial age control for these deposits and improves substantially on the precision of earlier 10Be measurements. The new results yield mean ages of 9.0 ± 0.3 ka for the outer moraine and 195 ± 24 years for the inner moraine, corresponding to glacial events during the early and latest Holocene. These ages are derived using the CRONUS-Earth 10Be exposure age calculator with Lal-Stone production rate scaling and the default height-pressure relationship. The inner moraine age correlates with the timing of the Little Ice Age as defined from northern mid- and high latitude records, and indicates considerable expansion of glaciers heading on Nevado Salcantay during this climatic minimum. Recent geomorphic mapping has identified similar sequences of moraines in adjacent drainages on and near Salcantay, suggesting a broader regional signal of two prominent Holocene glacial events in this segment of the southern Peruvian Andes; 10Be dating of these additional moraines is underway. Our new glacier chronologies complement ice core and lacustrine paleoclimate records in the vicinity, thereby increasing spatial and temporal coverage for identifying patterns of climate change in the tropical Andes during the Holocene. Apart from their paleoclimatic significance, the results also demonstrate a newly- developed capability of 10Be exposure

  6. 17 CFR 210.3-12 - Age of financial statements at effective date of registration statement or at mailing date of...

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... balance sheet as of an interim date within the number of days specified in paragraph (g) of this section... fiscal year and the date of the interim balance sheet provided and for the corresponding period of the... interim financial statements shall be at least as current as the most recent financial statements...

  7. Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil.

    PubMed

    Hartmann, Léo A; Liu, Dunyi; Wang, Yenbin; Massonne, Hans-Joachim; Santos, João O S

    2008-09-01

    U-Pb dating of zircon was undertaken with the Beijing SHRIMP II (sensitive high resolution ion microprobe) on anamphibolite facies granodiorite and an almandine-albite granulite from the Santa Maria Chico Granulitic Complex, southern Brazilian Shield. This work was also done to unravel protolith ages which are often hidden in the array of partly reset data. The obtained metamorphic ages of the granodiorite gneiss and the granulite are 2035 +/- 9 Ma and 2006 +/- 3 Ma, respectively. These data are within the range of metamorphic ages determined in previous studies (2022 +/- 18 Ma and 2031 +/- 40 Ma). However, protolith ages for the granodiorite (2366 +/- 8 Ma) and the granulite (2489 +/- 6 Ma) were obtained which are outside the previously recognized range (> 2510-2555 Ma). The magmatic protolith age of the granodiorite refers to a previously little known magmatic event in the shield. Further investigations may demonstrate that amphibolite facies zircon crystals are useful as a window into geological events in associated granulites, because zircon ages are blurred in the studied granulites.

  8. New ages for Middle and Later Stone Age deposits at Mumba rockshelter, Tanzania: optically stimulated luminescence dating of quartz and feldspar grains.

    PubMed

    Gliganic, Luke A; Jacobs, Zenobia; Roberts, Richard G; Domínguez-Rodrigo, Manuel; Mabulla, Audax Z P

    2012-04-01

    The archaeological deposits at Mumba rockshelter, northern Tanzania, have been excavated for more than 70 years, starting with Margit and Ludwig Köhl-Larsen in the 1930s. The assemblages of Middle Stone Age (MSA) and Later Stone Age (LSA) artefacts collected from this site constitute the type sequences for these cultural phases in East Africa. Despite its archaeological importance, however, the chronology of the site is poorly constrained, despite the application since the 1980s of several dating methods (radiocarbon, uranium-series and amino acid racemisation) to a variety of materials recovered from the deposits. Here, we review these previous chronologies for Mumba and report new ages obtained from optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) measurements on single grains of quartz and multi-grain aliquots of potassium (K) feldspar from the MSA and LSA deposits. Measurements of single grains of quartz allowed the rejection of unrepresentative grains and the application of appropriate statistical models to obtain the most reliable age estimates, while measurements of K-feldspars allowed the chronology to be extended to older deposits. The seven quartz ages and four K-feldspar ages provide improved temporal constraints on the archaeological sequence at Mumba. The deposits associated with the latest Kisele Industry (Bed VI-A) and the earliest Mumba Industry (Bed V) are dated to 63.4 ± 5.7 and 56.9 ± 4.8 ka (thousands of years ago), respectively, thus constraining the time of transition between these two archaeological phases to ~60 ka. An age of 49.1 ± 4.3 ka has been obtained for the latest deposits associated with the Mumba Industry, which show no evidence for post-depositional mixing and contain ostrich eggshell (OES) beads and abundant microlithics. The Nasera Industry deposits (Bed III) contain large quantities of OES beads and date to 36.8 ± 3.4 ka. We compare the luminescence ages with the previous chronologies for

  9. Isotopic composition analysis and age dating of uranium samples by high resolution gamma ray spectrometry

    NASA Astrophysics Data System (ADS)

    Apostol, A. I.; Pantelica, A.; Sima, O.; Fugaru, V.

    2016-09-01

    Non-destructive methods were applied to determine the isotopic composition and the time elapsed since last chemical purification of nine uranium samples. The applied methods are based on measuring gamma and X radiations of uranium samples by high resolution low energy gamma spectrometric system with planar high purity germanium detector and low background gamma spectrometric system with coaxial high purity germanium detector. The ;Multigroup γ-ray Analysis Method for Uranium; (MGAU) code was used for the precise determination of samples' isotopic composition. The age of the samples was determined from the isotopic ratio 214Bi/234U. This ratio was calculated from the analyzed spectra of each uranium sample, using relative detection efficiency. Special attention is paid to the coincidence summing corrections that have to be taken into account when performing this type of analysis. In addition, an alternative approach for the age determination using full energy peak efficiencies obtained by Monte Carlo simulations with the GESPECOR code is described.

  10. In Situ Radiometric and Exposure Age Dating of the Martian Surface

    NASA Technical Reports Server (NTRS)

    Farley, K. A.; Malespin, C.; Mahaffy, P.; Grotzinger, J. P.; Vasconcelos, P. M.; Milliken, R. E.; Malin, M.; Edgett, K. S.; Pavlov, A. A.; Hurowitz, J. A.; Grant, J. A.; Miller, H. B.; Arvidson, R.; Beegle, L.; Calef, F.; Conrad, P. G.; Dietrich, W. E.; Eigenbrode, J.; Gellert, R.; Gupta, S.; Hamilton, V.; Hassler, D. M.; Lewis, K. W.; McLennan, S. M.; Ming, D. M.; Navarro-Gonzalez, R.; Schwenzer, S. P.; Steele, A.; Stolper, E. M.; Sumner, D. Y.; Vaniman, D.; Vasavada, A.; Williford, K.; Wimmer-Schweingruber, R. F.

    2014-01-01

    We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 +/- 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced 3He, 21Ne, and 36Ar yield concordant surface exposure ages of 78 T 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.

  11. In situ radiometric and exposure age dating of the martian surface.

    PubMed

    Farley, K A; Malespin, C; Mahaffy, P; Grotzinger, J P; Vasconcelos, P M; Milliken, R E; Malin, M; Edgett, K S; Pavlov, A A; Hurowitz, J A; Grant, J A; Miller, H B; Arvidson, R; Beegle, L; Calef, F; Conrad, P G; Dietrich, W E; Eigenbrode, J; Gellert, R; Gupta, S; Hamilton, V; Hassler, D M; Lewis, K W; McLennan, S M; Ming, D; Navarro-González, R; Schwenzer, S P; Steele, A; Stolper, E M; Sumner, D Y; Vaniman, D; Vasavada, A; Williford, K; Wimmer-Schweingruber, R F

    2014-01-24

    We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced (3)He, (21)Ne, and (36)Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.

  12. Age-Dating Star Clusters in the Luminous Infrared Galaxy VV340

    NASA Astrophysics Data System (ADS)

    Yarber, Aara'L.; Evans, A. S.

    2014-01-01

    The luminous infrared galaxy (LIRG: i.e., L_IR [8-1000 microns] > 10^11 L_sun) VV 340 is observed to be a pair of z = 0.03 interacting spiral galaxies, with one being observed face-on (VV340North) and one edge-on (VV 340South). The interaction has triggered a burst of star formation in both galaxies, and we make use of Hubble Space Telescope ultraviolet (ACS/SBC) and optical (ACS/WFC) imaging data to constrain the age of luminous optical clusters in the face-on galaxy VV 340South. We find that, for an instantaneous starburst, a Salpeter IMF and no reddening, the cluster ages are in the range of 10-300 million years old. However, the clusters can be a young as a few million years with significant amounts of reddening. The upper limit cluster age range is consistent with detailed modeling of a subset of LIRGs which show that pericentric passage in many LIRGs occurred 200-500 million years prior to when these systems are being observed. This study is part of the Great Observatories All-sky LIRG Survey (GOALS), which is a multi-wavelength campaign designed, in part, to study the evolution of star formation in LIRGs.

  13. Estimating limiting age for Pleistocene erosional surfaces in central Montana by uranium-series dating of associated travertines.

    USGS Publications Warehouse

    Szabo, B. J.; Lindsey, D.A.

    1986-01-01

    Analysis of three travertine samples from the southeast side of The Park (central Montana) yield an average uranium-thorium age of 73 000 yr. Another sample from the west side of The Park is 320 000 yr old. These results indicate that travertine deposits may have formed at several intervals. The surface beneath The Park travertine is older than about 320 000 yr. Number 2 pediment gravels that contain travertine downslope from the oldest dated sample may be younger than about 320 000 yr. -Authors

  14. The AMS 14C dating of Iron Age rice chaff ceramic temper from Ban Non Wat, Thailand: First results and its interpretation

    NASA Astrophysics Data System (ADS)

    Higham, Charles F. W.; Kuzmin, Yaroslav V.; Burr, G. S.

    2010-04-01

    Pottery tempered with rice chaff from the early Iron Age cemetery of Ban Non Wat site, northeast Thailand, has been subjected to direct AMS 14C dating, using low temperature combustion with oxygen as originally developed by authors. The carbon yield (0.2-0.5%) testifies the suitability of this pottery for dating. However, not all the results are in agreement with expected archaeological ages and other 14C dates from the studied site and neighboring site of Noen U-Loke. This calls for a thorough analysis and interpretation of pottery temper dates from the region.

  15. Phylogenomic Dating-A Method of Constraining the Age of Microbial Taxa That Lack a Conventional Fossil Record

    NASA Astrophysics Data System (ADS)

    Blank, Carrine E.

    2009-03-01

    A phylogenomic dating approach was used to identify potential age constraints for multiple archaeal groups, many of which have no fossil, isotopic, or biomarker record. First, well-resolved phylogenetic trees were inferred with the use of multiple gene sequences obtained from whole genome sequences. Next, the ability to use oxygen as a terminal electron acceptor was coded into characters, and ancestral state reconstruction was used to identify clades with taxa that metabolize oxygen and likely had an aerobic ancestor. Next, the habitat of the ancestor was inferred. If the local presence of Cyanobacteria could be excluded from the putative ancestral habitat, then these clades would have originated after the rise in atmospheric oxygen 2.32 Ga. With this method, an upper age of 2.32 Ga (an "oxygen age constraint") is proposed for four major archaeal clades: the Sulfolobales, Thermoplasmatales, Thermoproteus neutrophilus/Pyrobaculum spp., and the Thermoproteales. It was also shown that the halophilic archaea likely had an aerobic common ancestor, yet the possibility of local oxygen oases before oxygenation of the atmosphere could not be formally rejected. Thus, an oxygen age constraint was not assessed for this group. This work suggests that many archaeal groups are not as ancient as many in the research community have previously assumed, and it provides a new method for establishing upper age constraints for major microbial groups that lack a conventional fossil record.

  16. Age and Date for Early Arrival of the Acheulian in Europe (Barranc de la Boella, la Canonja, Spain)

    PubMed Central

    Vallverdú, Josep; Saladié, Palmira; Rosas, Antonio; Huguet, Rosa; Cáceres, Isabel; Mosquera, Marina; Garcia-Tabernero, Antonio; Estalrrich, Almudena; Lozano-Fernández, Iván; Pineda-Alcalá, Antonio; Carrancho, Ángel; Villalaín, Juan José; Bourlès, Didier; Braucher, Régis; Lebatard, Anne; Vilalta, Jaume; Esteban-Nadal, Montserrat; Bennàsar, Maria Lluc; Bastir, Marcus; López-Polín, Lucía; Ollé, Andreu; Vergés, Josep Maria; Ros-Montoya, Sergio; Martínez-Navarro, Bienvenido; García, Ana; Martinell, Jordi; Expósito, Isabel; Burjachs, Francesc; Agustí, Jordi; Carbonell, Eudald

    2014-01-01

    The first arrivals of hominin populations into Eurasia during the Early Pleistocene are currently considered to have occurred as short and poorly dated biological dispersions. Questions as to the tempo and mode of these early prehistoric settlements have given rise to debates concerning the taxonomic significance of the lithic assemblages, as trace fossils, and the geographical distribution of the technological traditions found in the Lower Palaeolithic record. Here, we report on the Barranc de la Boella site which has yielded a lithic assemblage dating to ∼1 million years ago that includes large cutting tools (LCT). We argue that distinct technological traditions coexisted in the Iberian archaeological repertoires of the late Early Pleistocene age in a similar way to the earliest sub-Saharan African artefact assemblages. These differences between stone tool assemblages may be attributed to the different chronologies of hominin dispersal events. The archaeological record of Barranc de la Boella completes the geographical distribution of LCT assemblages across southern Eurasia during the EMPT (Early-Middle Pleistocene Transition, circa 942 to 641 kyr). Up to now, chronology of the earliest European LCT assemblages is based on the abundant Palaeolithic record found in terrace river sequences which have been dated to the end of the EMPT and later. However, the findings at Barranc de la Boella suggest that early LCT lithic assemblages appeared in the SW of Europe during earlier hominin dispersal episodes before the definitive colonization of temperate Eurasia took place. PMID:25076416

  17. Age and date for early arrival of the Acheulian in Europe (Barranc de la Boella, la Canonja, Spain).

    PubMed

    Vallverdú, Josep; Saladié, Palmira; Rosas, Antonio; Huguet, Rosa; Cáceres, Isabel; Mosquera, Marina; Garcia-Tabernero, Antonio; Estalrrich, Almudena; Lozano-Fernández, Iván; Pineda-Alcalá, Antonio; Carrancho, Ángel; Villalaín, Juan José; Bourlès, Didier; Braucher, Régis; Lebatard, Anne; Vilalta, Jaume; Esteban-Nadal, Montserrat; Bennàsar, Maria Lluc; Bastir, Marcus; López-Polín, Lucía; Ollé, Andreu; Vergés, Josep Maria; Ros-Montoya, Sergio; Martínez-Navarro, Bienvenido; García, Ana; Martinell, Jordi; Expósito, Isabel; Burjachs, Francesc; Agustí, Jordi; Carbonell, Eudald

    2014-01-01

    The first arrivals of hominin populations into Eurasia during the Early Pleistocene are currently considered to have occurred as short and poorly dated biological dispersions. Questions as to the tempo and mode of these early prehistoric settlements have given rise to debates concerning the taxonomic significance of the lithic assemblages, as trace fossils, and the geographical distribution of the technological traditions found in the Lower Palaeolithic record. Here, we report on the Barranc de la Boella site which has yielded a lithic assemblage dating to ∼1 million years ago that includes large cutting tools (LCT). We argue that distinct technological traditions coexisted in the Iberian archaeological repertoires of the late Early Pleistocene age in a similar way to the earliest sub-Saharan African artefact assemblages. These differences between stone tool assemblages may be attributed to the different chronologies of hominin dispersal events. The archaeological record of Barranc de la Boella completes the geographical distribution of LCT assemblages across southern Eurasia during the EMPT (Early-Middle Pleistocene Transition, circa 942 to 641 kyr). Up to now, chronology of the earliest European LCT assemblages is based on the abundant Palaeolithic record found in terrace river sequences which have been dated to the end of the EMPT and later. However, the findings at Barranc de la Boella suggest that early LCT lithic assemblages appeared in the SW of Europe during earlier hominin dispersal episodes before the definitive colonization of temperate Eurasia took place.

  18. Dating a small impact crater: An age of Kaali crater (Estonia) based on charcoal emplaced within proximal ejecta

    NASA Astrophysics Data System (ADS)

    Losiak, A.; Wild, E. M.; Geppert, W. D.; Huber, M. S.; Jõeleht, A.; Kriiska, A.; Kulkov, A.; Paavel, K.; Pirkovic, I.; Plado, J.; Steier, P.; VäLja, R.; Wilk, J.; Wisniowski, T.; Zanetti, M.

    2016-04-01

    The estimates of the age of the Kaali impact structure (Saaremaa Island, Estonia) provided by different authors vary by as much as 6000 years, ranging from ~6400 to ~400 before current era (BCE). In this study, a new age is obtained based on 14C dating charred plant material within the proximal ejecta blanket, which makes it directly related to the impact structure, and not susceptible to potential reservoir effects. Our results show that the Kaali crater was most probably formed shortly after 1530-1450 BCE (3237 ± 10 14C yr BP). Saaremaa was already inhabited when the bolide hit the Earth, thus, the crater-forming event was probably witnessed by humans. There is, however, no evidence that this event caused significant change in the material culture (e.g., known archeological artifacts) or patterns of human habitation on Saaremaa.

  19. Age-dating the Tully-Fisher relation at moderate redshift

    NASA Astrophysics Data System (ADS)

    Ferreras, Ignacio; Böhm, Asmus; Ziegler, Bodo; Silk, Joseph

    2014-01-01

    We analyse the Tully-Fisher relation at moderate redshift from the point of view of the underlying stellar populations, by comparing optical and NIR photometry with a phenomenological model that combines population synthesis with a simple prescription for chemical enrichment. The sample comprises 108 late-type galaxies extracted from the FORS Deep Field and William Herschel Deep Field surveys at z ≲ 1 (median redshift z = 0.45). A correlation is found between stellar mass and the parameters that describe the star formation history, with massive galaxies forming their populations early (zFOR ˜ 3), with star formation time-scales, τ1 ˜ 4 Gyr, although with very efficient chemical enrichment time-scales (τ2 ˜ 1 Gyr). In contrast, the stellar-to-dynamical mass ratio - which, in principle, would track the efficiency of feedback in the baryonic processes driving galaxy formation - does not appear to correlate with the model parameters. On the Tully-Fisher plane, no significant age segregation is found at fixed circular speed, whereas at fixed stellar-to-dynamical mass fraction, age splits the sample, with older galaxies having faster circular speeds at fixed Ms/Mdyn. Although our model does not introduce any prior constraint on dust reddening, we obtain a strong correlation between colour excess and stellar mass.

  20. Conception rates in farm mink (Neovison vison) in relation to first mating date, age and color variety.

    PubMed

    Felska-Błaszczyk, Lidia; Lasota, Bogdan; Seremak, Beata

    2016-07-01

    The aim of the study was to analyze the effects of the first mating date, age and color variety on the conception rates in farm mink. We analyzed female mink reproductive performance in 492 Sapphire and 463 Standard Black females over 3 or 4 years. The analysis included the number of inefficient matings, the interval between the first inefficient mating and the efficient mating (copulation) and the conception rates. The results show a significant effect of female's age and color variety on the conception rates. The youngest, yearling females of either color needed a higher number of matings per conception, as compared to older, 2- and 3-year-old females. Black females demonstrated a higher number of inefficient matings (1.066), as compared with Sapphires (0.730). Yearling females were most often mated from 1 to 10 March, and older females from 11 to 20 March. Older females achieved better conception rates than the yearlings. Dates between 11 and 25 March proved to be the optimum for the first mating, since the highest conception rates were observed if the females had mated during this period.

  1. Using 40Ar/39Ar ages of intercalated silicic tuffs to date flood basalts: Precise ages for Steens Basalt Member of the Columbia River Basalt Group

    NASA Astrophysics Data System (ADS)

    Mahood, Gail A.; Benson, Thomas R.

    2017-02-01

    To establish causality between flood basalt eruptions and extinction events and global environmental effects recorded by isotopic excursions in marine sediments, highly accurate and precise ages for the flood basalts are required. But flood basalts are intrinsically difficult to date. We illustrate how 40Ar/39Ar feldspar ages for silicic tuffs intercalated with and overlying sections of Steens Basalt, the earliest lavas of the Middle Miocene Columbia River Basalt Group in the northwestern United States, provide high-precision ages that, for the first time, make it possible to resolve age differences with stratigraphic position within a section of these flood lavas. The stratigraphically lowest rhyolitic tuff, a fall deposit, yielded an age of 16.592 ± ± 0.028 Ma (FCs = 28.02 Ma), and the uppermost, the alkali rhyolite ignimbrite Tuff of Oregon Canyon, is 16.468 ± ± 0.014 Ma. The argon and stratigraphic data indicate that Steens Basalt eruptions occurred from ∼16.64 to 16.43 Ma in the southern end of its distribution. We estimate that the Steens Mountain geomagnetic reversal occurred at 16.496 ± ± 0.028 Ma (±0.18 Ma total error). Our estimates of the timing for initiation of volcanism and volumetric eruptive rates do not seem to support volcanic forcing by the initial stages of Columbia River Basalt Group eruptions as an explanation for the abrupt warming and carbonate dissolution at the beginning of the Miocene Climatic Optimum.

  2. Summary of Age-Dating Analysis in the Fenner Basin, Eastern Mojave Desert, California

    SciTech Connect

    Davisson, M.L.

    2000-06-01

    Stable isotopes of oxygen (oxygen-18) and hydrogen (deuterium) in water were measured to determine recharge sources for Fenner Basin groundwater. The deuterium and oxygen-18 signatures (reported as {delta}D and {delta}{sup 18}O values) ranged from -11.9 to -9.3 per mil. The more negative values originate from high elevation recharge in the New York Mountains and were also observed in the northern and eastern parts of the groundwater basin. less negative values were observed in the Providence Mountains along the western part of the basin. Groundwater collected in the Fenner Gap (i.e. Project Area) had signatures between -10.6 and -10.9 per mil, suggesting a mixture of recharge from both northern, western, and probably local recharge areas in the basin. The annual contribution of groundwater recharge to Fenner Gap from the Clipper, Marble, and Old Woman mountains is still inconclusive due to lack of isotopic data. Isotopic signatures of mean annual precipitation collected by Friendman and others (1992) at Mitchell Caverns, as well as recently recharged groundwater in the Providence and New York mountains, are similar to the isotopic values in Fenner Gap groundwater. This indicates that this groundwater has a Holocene age (less than 10,000 years old), since groundwater recharged during the Pleistocene had isotopic signatures significantly more negative than today due to past global cooling.

  3. Age Dating Merger Events in Early Type Galaxies via the Detection of AGB Light

    NASA Technical Reports Server (NTRS)

    Bothun, G.

    2005-01-01

    A thorough statistical analysis of the J-H vs. H-K color plane of all detected early type galaxies in the 2MASS catalog with velocities less than 5000 km/s has been performed. This all sky survey is not sensitive to one particular galactic environment and therefore a representative range of early type galaxy environments have been sampled. Virtually all N-body simulation so major mergers produces a central starburst due to rapid collection of gas. This central starburst is of sufficient amplitude to change the stellar population in the central regions of the galaxy. Intermediate age populations are given away by the presence of AGB stars which will drive the central colors redder in H-K relative to the J- H baseline. This color anomaly has a lifetime of 2-5 billion years depending on the amplitude of the initial starburst Employing this technique on the entire 2MASS sample (several hundred galaxies) reveals that the AGB signature occurs less than 1% of the time. This is a straightforward indication that virtually all nearby early type galaxies have not had a major merger occur within the last few billion years.

  4. Inter-comparison exercises on dissolved gases for groundwater dating (GDAT 2012) : analytical uncertainties, apparent ages and other derived parameters.

    NASA Astrophysics Data System (ADS)

    Labasque, Thierry; Aquilina, Luc; Visser, Ate; Vergnaud, Virginie

    2014-05-01

    An inter-laboratory comparison exercise dedicated to environmental tracers used for groundwater dating was organized in 2012 in France. The goal was to compare sampling and analytical protocols through results obtained by the community of groundwater dating laboratories. Sampling and analytical protocols were compared through three different exercises on various supports : (1) on groundwater from a homogeneous aquifer, (2) on groundwater from a fractured heterogeneous aquifer and (3) on an air standard. The two tests allowed 31 Laboratories from 14 countries to compare their protocols for both sampling and analyses. It allows discussing the uncertainties related to sampling protocols issuing from each laboratory methods. The results show a good agreement between laboratories on the aquifers and the air standard. The dispersion of SF6 results in air standard is low (rsd 2%) compared to CFCs (rsd 3 to 7%), even if its concentration is two orders of magnitude lower. Results obtained in recent groundwater (recharge after 1980) show that the uncertainty on groundwater dating with SF6 is between 3 and 4 years. This large uncertainty is mainly due to sampling and/or analytical problems. For CFCs, uncertainties obtained over all the laboratories are less than 2 years for groundwater with recharge between 1965 and 1996. The goal of the inter-laboratory comparison exercise was also to quantify the analytical uncertainty of the 3H and noble gas measurements and to assess whether they meet the requirements for 3H/3He dating and noble gas paleotemperature reconstruction. The reproducibility of the tritium measurements was 13.5%. The reproducibility of the 3He/4He ratio and 4He, Ne, Ar, Kr and Xe concentrations was 1.4%, 1.8%, 1.5%, 2.2%, 2.9%, and 2.4%. The propagated uncertainty of the tritium and noble gas measurements meets the desired precision for typical 3H/3He dating applications. However, the measurement uncertainties for the noble gas concentrations are insufficient to

  5. Comparison of chlorofluorocarbon-age dating with particle-tracking results of a regional ground-water flow model of the Portland Basin, Oregon and Washington

    USGS Publications Warehouse

    Hinkle, Stephen R.; Snyder, Daniel T.

    1997-01-01

    This report describes the results of a study in which chlorofluorocarbon-age dating was used to evaluate the results of a ground-water particle tracker for the Portland Basin in Oregon and Washington.

  6. A simple-rapid method to separate uranium, thorium, and protactinium for U-series age-dating of materials.

    PubMed

    Knight, Andrew W; Eitrheim, Eric S; Nelson, Andrew W; Nelson, Steven; Schultz, Michael K

    2014-08-01

    Uranium-series dating techniques require the isolation of radionuclides in high yields and in fractions free of impurities. Within this context, we describe a novel-rapid method for the separation and purification of U, Th, and Pa. The method takes advantage of differences in the chemistry of U, Th, and Pa, utilizing a commercially-available extraction chromatographic resin (TEVA) and standard reagents. The elution behavior of U, Th, and Pa were optimized using liquid scintillation counting techniques and fractional purity was evaluated by alpha-spectrometry. The overall method was further assessed by isotope dilution alpha-spectrometry for the preliminary age determination of an ancient carbonate sample obtained from the Lake Bonneville site in western Utah (United States). Preliminary evaluations of the method produced elemental purity of greater than 99.99% and radiochemical recoveries exceeding 90% for U and Th and 85% for Pa. Excellent purity and yields (76% for U, 96% for Th and 55% for Pa) were also obtained for the analysis of the carbonate samples and the preliminary Pa and Th ages of about 39,000 years before present are consistent with (14)C-derived age of the material.

  7. Mechanism of inflammation in age-related macular degeneration: an up-to-date on genetic landmarks.

    PubMed

    Parmeggiani, Francesco; Sorrentino, Francesco S; Romano, Mario R; Costagliola, Ciro; Semeraro, Francesco; Incorvaia, Carlo; D'Angelo, Sergio; Perri, Paolo; De Nadai, Katia; Bonomo Roversi, Elia; Franceschelli, Paola; Sebastiani, Adolfo; Rubini, Michele

    2013-01-01

    Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment among people over 50 years of age, accounting for up to 50% of all cases of legal blindness in Western countries. Although the aging represents the main determinant of AMD, it must be considered a multifaceted disease caused by interactions among environmental risk factors and genetic backgrounds. Mounting evidence and/or arguments document the crucial role of inflammation and immune-mediated processes in the pathogenesis of AMD. Proinflammatory effects secondary to chronic inflammation (e.g., alternative complement activation) and heterogeneous types of oxidative stress (e.g., impaired cholesterol homeostasis) can result in degenerative damages at the level of crucial macular structures, that is photoreceptors, retinal pigment epithelium, and Bruch's membrane. In the most recent years, the association of AMD with genes, directly or indirectly, involved in immunoinflammatory pathways is increasingly becoming an essential core for AMD knowledge. Starting from the key basic-research notions detectable at the root of AMD pathogenesis, the present up-to-date paper reviews the best-known and/or the most attractive genetic findings linked to the mechanisms of inflammation of this complex disease.

  8. Paleointensity record in zero-age submarine basalt glasses: testing a new dating technique for recent MORBs

    NASA Astrophysics Data System (ADS)

    Carlut, J.; Kent, D. V.

    2000-12-01

    Thellier-Thellier paleointensity experiments were conducted on a collection of glasses from three very recent submarine axial flows. Two were erupted along the Juan de Fuca ridge at around 46°N and one along the East Pacific Rise South at around 18°S. The within-sample dispersion of paleointensity results from the 'Animal Farm' flow (EPR south) is very low and leads to a well-defined mean value of 35.6±1 μT (95% error on the mean) based on 11 glass chips from four independent samples. Today's geomagnetic field intensity in the area is 31.2 μT. Comparing Animal Farm results with published field model reference curves developed for the past 400 yr suggests an eruptive date estimated between 1880 A.D. and 1950 A.D. (taking into account different sources of errors). This is consistent with qualitative evidence for the age of this flow and constitutes the first precise demonstration of using paleointensity as a dating tool for very recent mid-ocean ridge basalts (MORBs). However in the Juan de Fuca area results show a more erratic pattern with samples varying by up to 30% higher and lower from the expected value of about 55 μT. The dispersion is attributed to the large local crustal magnetic anomalies in this area that can lead to inconsistent intensity values over the same unit. Local magnetic anomalies should thus always be checked when doing paleointensity on MORB samples which should also be distributed as widely as possible in a flow unit. When no significant magnetic anomalies are detected the paleointensity dating tool is anticipated to be especially efficient to investigate the volcanic cyclicity along the EPR axis during the last several hundred years.

  9. Age and evolution of the Grand Canyon revealed by U-Pb dating of water table-type speleothems.

    PubMed

    Polyak, Victor; Hill, Carol; Asmerom, Yemane

    2008-03-07

    The age and evolution of the Grand Canyon have been subjects of great interest and debate since its discovery. We found that cave mammillaries (water table indicator speleothems) from nine sites in the Grand Canyon showed uranium-lead dating evidence for an old western Grand Canyon on the assumption that groundwater table decline rates are equivalent to incision rates. Samples in the western Grand Canyon yielded apparent water table decline rates of 55 to 123 meters per million years over the past 17 million years, in contrast to eastern Grand Canyon samples that yielded much faster rates (166 to 411 meters per million years). Chronology and inferred incision data indicate that the Grand Canyon evolved via headward erosion from west to east, together with late-stage ( approximately 3.7 million years ago) accelerated incision in the eastern block.

  10. Detecting, sourcing, and age-dating dredged sediments on the open shelf, southern California, using dead mollusk shells.

    PubMed

    Bizjack, Matthew T; Kidwell, Susan M; Velarde, Ronald G; Leonard-Pingel, Jill; Tomašových, Adam

    2017-01-15

    Molluscan shell debris is an under-exploited means of detecting, sourcing, and age-dating dredged sediments in open-shelf settings. Backscatter features on the Southern California shelf are suggestive of dredged sediment hauled from San Diego Bay but deposited significantly inshore of the EPA-designated ocean disposal site. We find that 36% of all identifiable bivalve shells >2mm (44% of shells >4mm) in sediment samples from this 'short dump' area are from species known to live exclusively in the Bay; such shells are absent at reference sites of comparable water depth, indicating that their presence in the short-dump area signals non-compliant disposal rather than natural offshore transport or sea level rise. These sediments lack the shells of species that invaded California bays in the 1970s, suggesting that disposal preceded federal regulations. This inexpensive, low-tech method, with its protocol for rejecting alternative hypotheses, will be easy to adapt in other settings.

  11. Meteoric diagenesis of catastrophic rockslide deposits of the Alps: diagenetic systems and implications for radiometric age-dating.

    NASA Astrophysics Data System (ADS)

    Sanders, D.; Ostermann, M.; Kramers, J.; Brandner, R.

    2009-04-01

    Deposits of catastrophic subaerial rockslides (=rapid mass-wasting events involving more than a million cubic meters of rock) composed of lithologies rich in carbonate minerals may undergo precipitation of cements that, in many cases, can be used to U/Th proxy-date the rockslide event and/or subsequent changes of the rockslide mass. In the Alps, lithification of rockslide masses into breccias is observed in rockslides composed of limestones, dolostones, calcitic-dolomitic marbles, and calcphyllites. Cementation may be localized to meteoric 'runoff-shadows' below larger boulders, or may comprise a continous surface veneer of breccia or, more rarely, may affect the entire rockslide mass. In addition, precipitation of flowstone cements and stalactites may take place in megapores along the underside of boulders. Cements comprise skalenohedral calcite, prismatic calcite, blocky calcite, calcimicrite, micropeloidal calcitic cement and, rarely, isopachous to botryoidal aragonite. Cement formation probably is driven by meteoric dissolution-reprecipitation of fine-grained, abrasive rock powder generated during the rockslide event. U/Th ages of cements indicate that most, but not all, precipitation starts closely after a rockslide event. In rockslides composed of calcphyllites with an accessory content of pyrite, aside of 'normal' meteoric dissolution-reprecipitation of abrasive carbonate gauge, oxidation of pyrite drives widespread carbonate dissolution followed by reprecipitation, as a cement, of part of the dissolved calcium carbonate. Drill coring indicates that rockslide deposits composed of pyritiferous calcphyllites can be lithified from top to bottom. Limestone-precipitating springs emerging from rockslide deposits, and well-cemented 'secondary' deposits (e. g. talus slopes or fluvial conglomerates onlapping rockslide deposits) percolated by groundwaters emerging from rockslide masses, indicate that rockslide deposits remain diagenetically active for thousands of

  12. Use of chlorofluorocarbons (CCl3F and CCl2F2) as hydrologic tracers and age-dating tools: The alluvium and terrace system of central Oklahoma

    USGS Publications Warehouse

    Busenberg, Eurybiades; Plummer, L. Niel

    1992-01-01

    The use of Chlorofluorocarbons (CFCs) as an age-dating tool and tracer in shallow groundwaters has been investigated. New methodology for field sampling and preserving groundwaters containing parts per trillion concentrations of the CFCs, F-1l and F-12, is presented. Samples are analyzed by purge-and-trap gas chromatography with an electron capture detector. Physical and chemical processes that can alter natural concentrations (air-water equilibrium) of CFCs were investigated to assess dating uncertainties. CFC model recharge ages appear to be defined within 2 years under optimum conditions. The method was applied to central Oklahoma to demonstrate the usefulness of CFCs as (1) an age-dating tool of shallow groundwaters, (2) a tracer of sewage effluent in surface and shallow groundwaters, and (3) a tracer of shallow groundwater. Results of dating indicate two primary recharge periods in central Oklahoma over the past 45 years that correspond to the wet periods 1945–1960 and 1967–1975.

  13. Isotopic age of the Black Forest Bed, Petrified Forest Member, Chinle Formation, Arizona: An example of dating a continental sandstone

    USGS Publications Warehouse

    Riggs, N.R.; Ash, S.R.; Barth, A.P.; Gehrels, G.E.; Wooden, J.L.

    2003-01-01

    Zircons from the Black Forest Bed, Petrified Forest Member, Chinle Formation, in Petrified Forest National Park, yield ages that range from Late Triassic to Late Archean. Grains were analyzed by multigrain TIMS (thermal-ionization mass spectrometry), single-crystal TIMS, and SHRIMP (sensitive, high-resolution ion-microprobe). Multiple-grain analysis yielded a discordia trajectory with a lower intercept of 207 ?? 2 Ma, which because of the nature of multiple-grain sampling of a detrital bed, is not considered conclusive. Analysis of 29 detrital-zircon grains by TIMS yielded U-PB ages of 2706 ?? 6 Ma to 206 ?? 6 Ma. Eleven of these ages lie between 211 and 216 ?? 6.8 Ma. Our statistical analysis of these grains indicates that the mean of the ages, 213 ?? 1.7 Ma, reflects more analytical error than geologic variability in sources of the grains. Grains with ages of ca. 1400 Ma were derived from the widespread plutons of that age exposed throughout the southwestern Cordillera and central United States. Twelve grains analyzed by SHRIMP provide 206Pb*/238U ages from 214 ?? 2 Ma to 200 ?? 4 Ma. We use these data to infer that cores of inherited material were present in many zircons and that single-crystal analysis provides an accurate estimation of the age of the bed. We further propose that, even if some degree of reworking has occurred, the very strong concentration of ages at ca. 213 Ma provides a maximum age for the Black Forest Bed of 213 ?? 1.7 Ma. The actual age of the bed may be closer to 209 Ma. Dating continental successions is very difficult when distinct ash beds are not clearly identified, as is the case in the Chinle Formation. Detrital zircons in the Black Forest Bed, however, are dominated by an acicular morphology with preserved delicate terminations. The shape of these crystals and their inferred environment of deposition in slow-water settings suggest that the crystals were not far removed from their site of deposition in space and likely not far in time

  14. Age of the North Anatolian Fault Segments in the Yalova with U/Th Dating Method by Travertine Data

    NASA Astrophysics Data System (ADS)

    Selim, Haluk; Ömer Taş, K.

    2016-04-01

    Travertine occurrences developed along the segments of the North Anatolian Fault (NAF) in the south of Yalova. Travertines outcrop approximately 1 km2 area. These are middle-thick bedded approximately 20-40 m and back-tilted southward or horizontally. Lithology of travertines deposited such as physolite, stalactites-stalagmites, cave pearls, sharp pebble carbonate nodules, spherical-roller-intricate shapes or laminated banded travertine. Geochemical analyses were performed on the six samples of the travertines. X-ray analysis indicates that all samples are entirely composed of low-Mg calcite. Banded travertines with some tubular structures formed by precipitation from rising hot water are best developed near the toes of the large, hanging-wall-derived alluvial fans, whereas phreatic cement preferentially exists in footwall-derived, alluvial-fan conglomerates. The unit developed clarity which is controlled by normal fault as the structural and morphological, relationship with active tectonics. The travertines are a range-front type. U/Th series age dating results indicate that the travertine deposition extends back to 155 ka and yields ages of 60.000 (± 3, 091) to 153.149 (±13,466) from the range-front type travertines.

  15. Noble Gas Analysis for Mars Robotic Missions: Evaluating K-Ar Age Dating for Mars Rock Analogs and Martian Shergottites

    NASA Technical Reports Server (NTRS)

    Park, J.; Ming, D. W.; Garrison, D. H.; Jones, J. H.; Bogard, D. D.; Nagao, K.

    2009-01-01

    The purpose of this noble gas investigation was to evaluate the possibility of measuring noble gases in martian rocks and air by future robotic missions such as the Mars Science Laboratory (MSL). The MSL mission has, as part of its payload, the Sample Analysis at Mars (SAM) instrument, which consists of a pyrolysis oven integrated with a GCMS. The MSL SAM instrument has the capability to measure noble gas compositions of martian rocks and atmosphere. Here we suggest the possibility of K-Ar age dating based on noble gas release of martian rocks by conducting laboratory simulation experiments on terrestrial basalts and martian meteorites. We provide requirements for the SAM instrument to obtain adequate noble gas abundances and compositions within the current SAM instrumental operating conditions, especially, a power limit that prevents heating the furnace above approx.1100 C. In addition, Martian meteorite analyses from NASA-JSC will be used as ground truth to evaluate the feasibility of robotic experiments to constrain the ages of martian surface rocks.

  16. Practicability of In Situ K-Ar Age Dating by Martian Landers; A Study of Mars Analogs and Meteorites

    NASA Astrophysics Data System (ADS)

    Park, Jisun; Ming, D. W.; Garrison, D. H.; Jones, J. H.; Bogard, D. D.

    2009-12-01

    Purpose of this noble gas investigation was to evaluate the feasibility of in situ K-Ar radiometric age dating of Martian surface rocks by future robotic missions, such as the Mars Science Laboratory(MSL), under constraints inherent to the Martian surface and lander design. The MSL Sample Analysis at Mars(SAM) instrument has the capability to measure noble gas compositions of Martain rocks and atmosphere. We evaluate requirements for SAM to obtain adequate noble gas abundances and compositions within the current instrumental operating conditions. In particular, maximum furnace temperature is limited to 1100ºC or lower due to power supply constraints. As a simulation experiment, we analyzed three Martian shergottites and terrestrial MORB, under the same conditions afforded SAM on the Martian surface. Our results suggest that SAM noble gas recoveries might be sufficient for K-Ar age determinations. Comparing these results with previous experiments performed on Martian meteorites at NASA-JSC, we can asses the capability of Mars lander designs with a variety of Martian rock types. The noble gas composition of Martian meteorites can be difficult to interpret due to the combined signals of in situ 40K decay, shock implanted 40Ar from Martian atmosphere[2,3], and 40Ar inherited from parent magma[4,5]. These components should also be considered in interpreting lander data. A possible advantage for landers is that K concentrations reported from the Martian surface are variable and possibly quite high, a desirable trait for K-Ar age dating. Spirit APXS reports 3000-7000ppm K for most locations but in some areas, concentrations as high as 25000ppm have been observed[6,7]. [1] Bogard (2009) MaPS44, 3-14; [2] Bogard and Johnson (1983) Science221,651-654 [3] Marti et al. (1995) Science267, 1981-1984; [4] Bogard and Park (2008) MAPS43, 1113-1126. [5] Bogard et al. (2009) MAPS44, 905-923. [6] Ming et al. (2006) JGR111, E02S12. [7] Ming D.W. et al. (2008) JGR113, E12S39.

  17. Dating Wood-Benthic Foram-Planktic Foram Trios from the Panama Basin to Better Constrain Antarctic Intermediate Water Ventilation Age during the Last Deglaciation

    NASA Astrophysics Data System (ADS)

    Zhao, N.; Keigwin, L. D.

    2014-12-01

    Surface reservoir age complicates the age models of marine sediment records. Age model uncertainty may cause different interpretations of the same process. For example, in order to circumvent dealing with surface reservoir age, Marchitto et al. (2007) built their age model on a linkage to Greenland oxygen isotope record. But the proxy they used for the linkage was a minor factor of the sediment diffuse spectral reflectance, and they assumed the sedimentation rate was constant between the tie points which could be several thousand years apart. Based on that age model they showed the Antarctic Intermediate Water (AAIW) was significantly older during deglaciation than LGM and Holocene. However, de Pol-Holz et al. (2010) argued that the change of deglacial AAIW radiocarbon age was not clearly different from the atmospheric change. Their age model was based on planktic foram (PF) 14C dates and an assumption that the surface reservoir age was constantly 400 years for a site near an upwelling region. These records are only as good as their age models. Here, we present a new way to build the age model of marine records, which is to date wood in marine sediments. We found a core in Panama Basin with constantly-present twigs at the same water depth with the core used by Marchitto et al. (705m), and the radiocarbon dates of the wood samples give a very good age-depth relationship without any age reversal. With benthic foram (BF) dated in the same layer where the twigs appear, we will be able to compare the AAIW radiocarbon concentration directly with the atmosphere. In this way, we can get the AAIW ventilation age without worrying about the surface reservoir age and elucidate whether there indeed was old water transported northward by AAIW during the last deglaciation. This would be very important to testify the hypothesis of LGM carbon sequestration in the deep ocean. On the other hand, we can evaluate how the surface reservoir age and/or upwelling strength changed in

  18. 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…

  19. Asteroseismology for "à la carte" stellar age-dating and weighing. Age and mass of the CoRoT exoplanet host HD 52265

    NASA Astrophysics Data System (ADS)

    Lebreton, Y.; Goupil, M. J.

    2014-09-01

    Context. In the context of the space missions CoRoT, Kepler, Gaia, TESS, and PLATO, precise and accurate stellar ages, masses, and radii are of paramount importance. For instance, they are crucial for constraining scenarii of planetary formation and evolution. Aims: We aim at quantifying how detailed stellar modelling can improve the accuracy and precision on age and mass of individual stars. To that end, we adopt a multifaceted approach where we carefully examine how the number of observational constraints as well as the uncertainties on observations and on model input physics affect the results of age-dating and weighing. Methods: We modelled in detail the exoplanet host-star HD 52265, a main-sequence, solar-like oscillator that CoRoT observed for four months. We considered different sets of observational constraints (Hertzsprung-Russell data, metallicity, various sets of seismic constraints). For each case, we determined the age, mass, and properties of HD 52265 inferred from stellar models, and we quantified the impact of the model input physics and free parameters. We also compared model ages with ages derived by empirical methods or Hertzsprung-Russell diagram inversion. Results: For our case study HD 52265, our seismic analysis provides an age A = 2.10-2.54 Gyr, a mass M = 1.14-1.32 M⊙, and a radius R = 1.30-1.34 R⊙, which corresponds to age, mass, and radius uncertainties of ~10, ~7, and ~1.5 per cent, respectively. These uncertainties account for observational errors and current state-of-the-art stellar model uncertainties. Our seismic study also provides constraints on surface convection properties through the mixing-length, which we find to be 12-15 per cent lower than the solar value. On the other hand, because of helium-mass degeneracy, the initial helium abundance is determined modulo the mass value. Finally, we evaluate the seismic mass of the exoplanet to be Mpsini = 1.17-1.26 MJupiter, much more precise than what can be derived by Hertzsprung

  20. Collection, analysis, and age-dating of sediment cores from 56 U.S. lakes and reservoirs sampled by the U.S. Geological Survey, 1992-2001

    USGS Publications Warehouse

    Van Metre, Peter; Wilson, Jennifer T.; Fuller, Christopher C.; Callender, Edward; Mahler, Barbara J.

    2004-01-01

    The U.S. Geological Survey Reconstructed Trends National Synthesis study collected sediment cores from 56 lakes and reservoirs between 1992 and 2001 across the United States. Most of the sampling was conducted as part of the National Water-Quality Assessment (NAWQA) Program. The primary objective of the study was to determine trends in particle-associated contaminants in response to urbanization; 47 of the 56 lakes are in or near one of 20 U.S. cities. Sampling was done with gravity, piston, and box corers from boats and push cores from boats or by wading, depending on the depth of water and thickness of sediment being sampled. Chemical analyses included major and trace elements, organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, cesium-137, and lead-210. Age-dating of the cores was done on the basis of radionuclide analyses and the position of the pre-reservoir land surface in the reservoir and, in a few cases, other chemical or lithologic depth-date markers. Dates were assigned in many cores on the basis of assumed constant mass accumulation between known depth-date markers. Dates assigned were supported using a variety of other date markers including first occurrence and peak concentrations of DDT and polychlorinated biphenyls and peak concentration of lead. A qualitative rating was assigned to each core on the basis of professional judgment to indicate the reliability of age assignments. A total of 122 cores were collected from the 56 lakes and age dates were assigned to 113 of them, representing 54 of the 56 lakes. Seventy-four of the 122 cores (61 percent) received a good rating for the assigned age dates, 28 cores (23 percent) a fair rating, and 11 cores (9 percent) a poor rating; nine cores (7 percent) had no dates assigned. An analysis of the influence of environmental factors on the apparent quality of age-dating of the cores concluded that the most important factor was the mass accumulation rate (MAR) of sediment: the

  1. Round-robin 230Th–234U age dating of bulk uranium for nuclear forensics

    SciTech Connect

    Gaffney, Amy M.; Hubert, Amélie; Kinman, William S.; Magara, Masaaki; Okubo, Ayako; Pointurier, Fabien; Schorzman, Kerri C.; Steiner, Robert E.; Williams, Ross W.

    2015-07-30

    In an inter-laboratory measurement comparison study, four laboratories determined 230Th–234U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. As a result, these model ages are concordant with to slightly older than the known production age of NBL U050.

  2. 40K- 40Ar dating of the Main Deccan large igneous province: Further evidence of KTB age and short duration

    NASA Astrophysics Data System (ADS)

    Chenet, Anne-Lise; Quidelleur, Xavier; Fluteau, Frédéric; Courtillot, Vincent; Bajpai, Sunil

    2007-11-01

    Most mass extinctions coincide in time with outpourings of continental flood basalts (CFB). Some 20 years ago, it was shown [Courtillot, V., Besse, J., Vandamme, D., Montigny, R., Jaeger, J.-J., Cappetta, H., 1986. Deccan flood basalts at the Cretaceous/Tertiary boundary? Earth Planet. Sci. Lett. 80, 361-374; Courtillot, V., Feraud, G., Maluski, H., Vandamme, D., Moreau, M.G., Besse, J., 1988. Deccan flood basalts and the Cretaceous/Tertiary boundary. Nature 333, 843-846; Duncan, R.A., Pyle, D.G., 1988. Rapid eruption of the Deccan flood basalts at the Cretaceous/Tertiary boundary. Nature 333 841-843] that the age of the Deccan traps was close to the Cretaceous-Tertiary (KT) boundary and its duration under 1 Myr. We have undertaken a new geochronological study, using the (unconventional) 40K- 40Ar Cassignol-Gillot technique which is particularly well suited to the potassium-poor Deccan lavas. The mean of 4 determinations from the topmost (Ambenali and Mahabaleshwar) Formations is 64.5 ± 0.6 Ma. They straddle the C29r/C29n reversal boundary for which they provide a new constraint. The mean age of 3 determinations from the oldest (Jawhar) Formation is 64.8 ± 0.6 Ma. The difference in age between top and bottom of a 3500 m composite section, probably comprising 80% of the total Deccan volume, is statistically insignificant, with the overall mean age being 64.7 ± 0.6 Ma ( N = 7). Our results are consistent with the most recent 40Ar/ 39Ar determinations [Knight, K.B., Renne, P.R., Halkett, A., White, N., 2003. 40Ar/ 39Ar dating of the Rajahmundry Traps, eastern India and their relationship to the Deccan traps. Earth Planet. Sci. Lett. 208, 85-99; Knight, K.B., Renne, P.R., Baker, J., Waight, T., White, N., 2005. Reply to '40Ar/39Ar dating of the Rajahmundry Traps, Eastern India and their relationship to the Deccan Traps: Discussion' by A.K. Baksi. Earth Planet. Sci. Lett. 239, 374-382], confirming that there should be no systematic difference between the two methods

  3. 10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland

    NASA Astrophysics Data System (ADS)

    Cronauer, Sandra L.; Briner, Jason P.; Kelley, Samuel E.; Zimmerman, Susan R. H.; Morlighem, Mathieu

    2016-09-01

    We reconstruct the history of the Greenland Ice Sheet margin on the Nuussuaq Peninsula in central West Greenland through the Holocene using lake sediment analysis and cosmogenic 10Be exposure dating of the prominent Drygalski Moraines. Erratics perched on bedrock outboard of the Drygalski Moraines constrain local deglaciation to ∼9.9 ± 0.6 ka (n = 2). Three Drygalski Moraine crests yield mean 10Be ages of 8.6 ± 0.4 ka (n = 2), 8.5 ± 0.2 ka (n = 3), and 7.6 ± 0.1 ka (n = 2) from outer to inner. Perched erratics between the inner two moraines average 7.8 ± 0.1 ka (n = 2) and are consistent with the moraine ages. Sediments from a proglacial lake with a catchment area extending an estimated 2 km beneath (inland of) the present ice sheet terminus constrain an ice sheet minimum extent from 5.4 ka to 0.6 ka. The moraine chronology paired with the lake sediment stratigraphy reveals that the ice margin likely remained within ∼2 km of its present position from ∼9.9 to 5.4 ka. This unexpected early Holocene stability, preceded by rapid ice retreat and followed by minimum ice extent between ∼5.4 and 0.6 ka, contrasts with many records of early Holocene warmth and the Northern Hemisphere summer insolation maximum. We suggest ice margin stability may instead be tied to adjacent ocean temperatures, which reached an optimum in the middle Holocene.

  4. Age of the Druksiai-Polotsk deformation zone, Lithuania: a U-Pb dating of metamorphic titanite

    NASA Astrophysics Data System (ADS)

    Vejelyte, Irma; Bogdanova, Svetlana; Salnikova, Ekaterina

    2010-05-01

    The studied Druksiai-Polotsk deformation zone (DPDZ) transects the East Lithuanian Domain (ELD), representing the southern margin of the major Polotsk-Kurzeme zone of faulting in the Baltic-Belarus region. The DPDZ is of 35-40 km wide, E-W trending, and marked well by linear gravity and magnetic anomalies. The crystalline rocks within the DPDZ are granulites, biotite granites, and migmatites, the latter consisting of amphibole-plagioclase paleo- and mesosomes, and plagioclase-quartz-biotite±microcline±amphibole neosomes. Because of ductile shearing gneisses, augen mylonites, mylonites and ultramylonites were produced while tectonic breccias and pseudotachyllite were formed by later brittle deformation. According to geophysical data and the surface morphology of the crystalline basement, a horst-graben structure have recognized along the DPDZ. The graben is filled with Vendian, Cambrian, Ordovician, Silurian and Devonian deposits. A U-Pb dating of titanite from an augen granitoid mylonite in the DPDZ has yielded a concordant age of 1534±9 Ma. This light brown titanite follows the folation in the host rock and was obviously formed during retrogression from amphibolite- to epidote-amphibolite facies and coeval mylonitization. Shear zones of the same age are known in southern and central Sweden and in NE Poland. These E-W trending deformation zones accommodate both mafic and granitoid intrusions and are probably related to an extensional period in the Mesoproterozoic evolution in the western part of the East European Craton. This is a contribution to the project "The Precambrian structure of Baltica as a control of its recent environment and evolution" of the Visby Programme supported by the Swedish Institute and the Lithuanian State Science and Studies Foundation.

  5. Geochemical analyses, age dates, and flow-volume estimates for quaternary volcanic rocks, Southern Cascade Mountains, Washington

    SciTech Connect

    Hammond, P.E.; Korosec, M.A.

    1983-12-01

    Data collected over the last three years as part of a continuing study of the Quaternary volcanic rocks of the southern Cascade Mountains are presented. Whole-rock chemical analyses, selected trace element geochemistry, volume approximations, specific gravity determinations, and locations are provided for most of the 103 samples collected, and 21 radiometric age dates are included. In addition, partial information, including names and flow-volumes, are presented for 98 additional samples, collected for related studies. The study extends from the Columbia River north to the Cowlitz River and Goat Rocks Wilderness area, and from the Klickitat River west to the Puget-Willamette Trough. The volcanic rocks are all younger than 3 million years and consist primarily of tholeiitic and high-alumina basalts and basaltic-andesites erupted from numerous shield volcanoes and cinder cones. A few analyses of more silicic rocks, including hornblende and/or pyroxene andesites and dacites characteristic of the stratovolcanoes of the region, are also presented. However, systematic sampling of the stratovolcanoes in the study area, Mount Adams and Mount St. Helens, was not conducted. A map of the areal extent of Quaternary volcanic units and sample locations is included. It has been based on the 1:125,000 reconnaissance geologic map of the southern Cascade Range by Hammond (1980).

  6. Geochemical analyses, age dates, and flow-volume estimates for quaternary volcanic rocks, Southern Cascade Mountains, Washington

    NASA Astrophysics Data System (ADS)

    Hammond, P. E.; Korosec, M. A.

    1983-12-01

    Data collected over the last three years as part of a continuing study of the Quaternary volcanic rocks of the southern Cascade Mountains are presented. Whole-rock chemical analyses, selected trace element geochemistry, volume approximations, specific gravity determinations, and locations are provided for most of the 103 samples collected, and 21 radiometric age dates are included. In addition, partial information, including names and flow-volumes, are presented for 98 additional samples, collected for related studies. The study extends from the Columbia River north to the Cowlitz River and Goat Rocks Wilderness area, and from the Klickitat River west to the Puget-Williamette Trough. The volcanic rocks are all younger than 3 million years and consist primarily of tholeitic and high-alumina basalts and basaltic-andesites erupted from numerous shield volcanoes and cinder cones. A few analyses of more silicic rocks, including hornblende and/or pyroxene andesites and dacites characteristic of the stratovolcanoes of the region, are also presented.

  7. Thermochronology of economic mineral deposits: dating the stages of mineralization at Panasqueira, Portugal, by high-precision 40Ar/ 39Ar age spectrum techniques on muscovite

    USGS Publications Warehouse

    Snee, L.W.; Sutter, J.F.; Kelly, W.C.

    1988-01-01

    This study is an example of a new and powerful application of 40Ar/39Ar age spectrum dating of muscovite. It is now possible to establish time constraints necessary for solving some of the long-standing problems in economic geology. Beyond this, the unique geologic situation of Panasqueira has allowed us to quantify the thermal characteristics of muscovite. Published fluid inclusion data have been used to estimate a muscovite argon closure temperature of ~325??C during rapid cooling or short reheating and a temperature of ~270??C during slow cooling or extended reheating. Argon-loss patterns displayed by all dated muscovites resulted from reheating after original closure; the mechanism for this argon loss appears to have been argon transport by volume diffusion. Thus, 40Ar/39Ar age spectrum dating of muscovite can be used to evaluate thermal conditions controlling argon diffusion as well as age, duration, and number of episodes of mineralization. -from Authors

  8. I-Xe systematics of the impact plume produced chondrules from the CB carbonaceous chondrites: Implications for the half-life value of 129I and absolute age normalization of 129I-129Xe chronometer

    NASA Astrophysics Data System (ADS)

    Pravdivtseva, O.; Meshik, A.; Hohenberg, C. M.; Krot, A. N.

    2017-03-01

    It is inferred that magnesian non-porphyritic chondrules in the CB (Bencubbin-type) carbonaceous chondrites formed in an impact generated plume of gas and melt at 4562.49 ± 0.21 Ma (Bollard et al., 2015) and could be suitable for the absolute age normalization of relative chronometers. Here xenon isotopic compositions of neutron irradiated chondrules from the CB chondrites Gujba and Hammadah al Hamra (HH) 237 have been analyzed in an attempt to determine closure time of their I-Xe isotope systematics. One of the HH 237 chondrules, #1, yielded a well-defined I-Xe isochron that corresponds to a closure time of 0.29 ± 0.16 Ma after the Shallowater aubrite standard. Release profiles and diffusion properties of radiogenic 129*Xe and 128*Xe, extracted from this chondrule by step-wise pyrolysis, indicate presence of two iodine host phases with distinct activation energies of 73 and 120 kcal/mol. In spite of the activation energy differences, the I-Xe isotope systematics of these two phases closed simultaneously, suggesting rapid heating and cooling (possibly quenching) of the CB chondrules. The release profiles of U-fission Xe and I-derived Xe correlate in the high temperature host phase supporting simultaneous closure of 129I-129Xe and 207Pb-206Pb systematics. The absolute I-Xe age of Shallowater standard is derived from the observed correlation between I-Xe and Pb-Pb ages in a number of samples. It is re-evaluated here using Pb-Pb ages adjusted for an updated 238U/235U ratio of 137.794 and meteorite specific U-isotope ratios. With the addition of the new data for HH 237 chondrule #1, the re-evaluated absolute I-Xe age of Shallowater is 4562.4 ± 0.2 Ma. The absolute I-Xe age of the HH 237 chondrule #1 is 4562.1 ± 0.3 Ma, in good agreement with U-corrected Pb-Pb ages of the Gujba chondrules (Bollard et al., 2015) and HH 237 silicates (Krot et al., 2005). All I-Xe data used here, and in previous estimates of the absolute age of Shallowater, are calculated using 15.7

  9. Bayesian methods applied to the interpretation of multiple OSL dates: high precision sediment ages from Old Scatness Broch excavations, Shetland Isles

    NASA Astrophysics Data System (ADS)

    Rhodes, E. J.; Bronk Ramsey, C.; Outram, Z.; Batt, C.; Willis, L.; Dockrill, S.; Bond, J.

    2003-05-01

    In this paper, we illustrate the ways in which Bayesian statistical techniques may be used to enhance chronological resolution when applied to a series of OSL sediment dates. Such application can achieve an optimal chronological model by incorporating stratigraphic and age information. The application to luminescence data is not straightforward owing to the sources of uncertainty in each date, and here we present one solution to overcoming these difficulties, and introduce the concept of "unshared systematic" errors. Using OSL sediment dates from the site of Old Scatness Broch, Shetland Isles, UK, many measured with a high degree of precision, we illustrate some of the ways in which Bayesian techniques may be applied, as a tool for assessing systematic errors when combined with independent chronological information, and to determine the optimum chronological information for specific events and contexts. We provide a detailed procedure for the application of Bayesian methods to OSL dates using the widely available radiocarbon calibration programme OxCal.

  10. An extended magnetic viscous relaxation dating for calibrating an older age: an example of tsunamigenic coral boulders in Ishigaki Island, Japan

    NASA Astrophysics Data System (ADS)

    Sato, T.; Nakamura, N.; Goto, K.; Kumagai, Y.; Minoura, K.; Nagahama, H.

    2015-12-01

    A key to the understanding of past tsunami events is the ability to accurately date them. Analysis of past tsunami sediments is one of the most important tools for past tsunami reconstruction. A typical example of such tsunami sediment is tsunamigenic boulders. In Ishigaki Island, Japan, coral boulders that had been transported by tsunamis were distributed on the beach and land areas. Although the historical occurrences of several huge tsunamis were estimated based on large numbers of radiocarbon dating for coral boulders, radiocarbon dating can not determine a multiple rotational history by multiple tsunamis. A viscous remanet magnetization (VRM) dating method can be used to date any geological event that results in significant movements of a rock. Sato et al. (2014) applied VRM dating for comparing the radiocarbon age of these boulders. If a magnetic-mineral bearing rock is moved or re-oriented, the magnetism of the smaller magnetic grains re-aligns to the direction of the ambient magnetic field with time. This phenomenon is well known as Néel's (1949, 1955) single-domain (SD) relaxation theory. Pullaiah et al. (1975) derived a time-temperature (t-T relation) relation by assuming Néel's (1949, 1955) theory of magnetite. In principle, an experimental combination of short relaxation time and high temperature for removing VRM can determine the unknown relaxation time (tsunami age) at room temperature. We have been applied t-T relation to the coral boulders on Ishigaki Island, but their estimated ages showed older than radiocarbon dating. The longer relaxation time means that the observed magnetic relaxation is slower than the original Néel's theory. Such slow relaxation has been described by a stretched exponential function. The stretched exponential law provided a reasonable fit to the published experimental data. Thus, in this study, we revisit Néel's theory to provide a new t-T relation based on stretched exponential function.

  11. Absolutely classical spin states

    NASA Astrophysics Data System (ADS)

    Bohnet-Waldraff, F.; Giraud, O.; Braun, D.

    2017-01-01

    We introduce the concept of "absolutely classical" spin states, in analogy to absolutely separable states of bipartite quantum systems. Absolutely classical states are states that remain classical (i.e., a convex sum of projectors on coherent states of a spin j ) under any unitary transformation applied to them. We investigate the maximal size of the ball of absolutely classical states centered on the maximally mixed state and derive a lower bound for its radius as a function of the total spin quantum number. We also obtain a numerical estimate of this maximal radius and compare it to the case of absolutely separable states.

  12. Aging of target lipid parameters in fingermark residue using GC/MS: Effects of influence factors and perspectives for dating purposes.

    PubMed

    Girod, Aline; Spyratou, Alexandra; Holmes, David; Weyermann, Céline

    2016-05-01

    Despite the recurrence of fingermark dating issues and the research conducted on fingermark composition and aging, no dating methodology has yet been developed and validated. In order to further evaluate the possibility of developing dating methodologies based on the fingermark composition, this research proposed an in-depth study of the aging of target lipid parameters found in fingermark residue and exposed to different influence factors. The selected analytical technique was gas chromatography coupled with mass spectrometry (GC/MS). The effects of donor, substrate and enhancement techniques on the selected parameters were firstly evaluated. These factors were called known factors, as their value could be obtained in real caseworks. Using principal component analysis (PCA) and univariate exponential regression, this study highlighted the fact that the effects of these factors were larger than the aging effects, thus preventing the observation of relevant aging patterns. From a fingermark dating perspective, the specific value of these known factors should thus be included in aging models newly built for each case. Then, the effects of deposition moment, pressure, temperature and lighting were also evaluated. These factors were called unknown factors, as their specific value would never be precisely obtained in caseworks. Aging models should thus be particularly robust to their effects and for this reason, different chemometric tools were tested: PCA, univariate exponential regression and partial least square regression (PLSR). While the first two models allowed observing interesting aging patterns regardless of the value of the applied influence factors, PLSR gave poorer results, as large deviations were obtained. Finally, in order to evaluate the potential of such modelling in realistic situations, blind analyses were carried out on eight test fingermarks. The age of five of them was correctly estimated using soft independent modelling of class analogy analysis

  13. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    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.

  14. 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.

  15. An absolutely dated high-resolution stalagmite record from Lianhua Cave in central China: Climate forcing and comparison with Wanxiang Cave and Dongge Cave records over the past 2000 years

    NASA Astrophysics Data System (ADS)

    Li, Hong-Chun; Yin, Jian-Jun; Shen, Chuan-Chou; Mii, Horng-Sheng; Li, Ting-Yong

    2015-04-01

    A 33-cm long aragonite stalagmite (LHD-1) from Lianhua Cave has been dated by MC-ICPMS 230Th/U method on 41 horizons. Very high U contents (1~6ppm) and low Th contents yield excellent 230Th/U dates which provide reliable chronology of the stalagmite on sub-decadal time scale over the past 3350 years. A total of 1716 samples have been measured for δ18O and δ13C, spanning annual resolution over the past 1820 years. The stalagmite δ18O is not only influenced by the 'amount effect', but also affected by the moisture source. Enhanced the tropical monsoon trough under strong EASM brings higher spring quarter rainfall with isotopically light monsoonal moisture in the cave site, resulting in lighter stalagmite δ18O. On decadal or longer time scales, increased solar activity produces warmer condition and stronger summer monsoon which lead to wet climates. On interannual-to-decadal scales, the Walker Circulation under El Niño conditions during cold periods will shift toward the central Pacific and result in weakening of EASM. Under such a circumstance, dry climates will be prevailed in the study area. Based on the δ18O and δ13C records, we have deciphered climatic and vegetation changes of the study area in decadal scales. The highly precise dated LHD-1 record has been compared with previous published Wanxiang Cave and Dongge Cave records. Although some similarities can be found, there are major discrepancies among the three well-dated records, especially during AD 500-700 and AD 1300-1600. In additional, the major weak monsoon periods defined in the Wanxiang Cave record during late Tang Dynasty, late Yuan Dynasty and late Ming Dynasty are not supported by the LHD-1 record. The heaviest δ18O peaks (more than five continuous heavy values) over the past 2000 years appeared around AD 1990-2003, 1657-1662, 1220-1228, 663-669, 363-370, and 1082-1090 (in the order of heavy to light). None of these periods occurred Chinese dynasty collapse.

  16. Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40Ar/39Ar and U-Pb dating of sanidine and zircon crystals

    USGS Publications Warehouse

    Matthews, Naomi E.; Vazquez, Jorge A.; Calvert, Andrew T.

    2015-01-01

    The last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff. Tephra from the Lava Creek eruption is a key Quaternary chronostratigraphic marker, in particular for dating the deposition of mid Pleistocene glacial and pluvial deposits in western North America. To resolve the timing of eruption and crystallization history for the Lava Creek magma, we performed (1) 40Ar/39Ar dating of single sanidine crystals to delimit eruption age and (2) ion microprobe U-Pb and trace-element analyses of the crystal faces and interiors of single zircons to date the interval of zircon crystallization and characterize magmatic evolution. Sanidines from the two informal members composing Lava Creek Tuff yield a preferred 40Ar/39Ar isochron date of 631.3 ± 4.3 ka. Crystal faces on zircons from both members yield a weighted mean 206Pb/238U date of 626.5 ± 5.8 ka, and have trace element concentrations that vary with the eruptive stratigraphy. Zircon interiors yield a mean 206Pb/238U date of 659.8 ± 5.5 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high U concentration cores that likely grew from highly evolved melt. The occurrence of distal Lava Creek tephra in stratigraphic sequences marking the Marine Isotope Stage 16–15 transition supports the apparent eruption age of ∼631 ka. The combined results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up-temperature evolution for Yellowstone's subvolcanic reservoir in the 103−104 year interval before eruption.

  17. Dating of Modern Human Evolution

    NASA Astrophysics Data System (ADS)

    Grun, R.

    Dating studies on palaoeanthropological sites is usually carried out on material associ- ated with the human remains, such as the sediment, charcoal or other fauna rather than the human specimen itself. The reason lies in the fact that most dating techniques are destructive and because the hominid remains are too rare to be sacrificed for dating. This indirect dating approach is in many cases not satisfactory, because: (i) the human remains are often buried into the sediments and the association with other materials is uncertain (e.g. Skhul, Qafzeh, etc.); (ii) faunal remains or minerals from the sediment are re-worked from older deposits (see e.g. present discussion of the age of the Homo erectus remains in Indonesia; (iii) the hominid fossils were discovered at a time when no careful excavations were carried out and it is impossible to correlate the specimen with other datable material (which applies tonearly 90% of all palaeoanthropological specimens). For example, the hominid burial site of Qafzeh in Israel has been dated by several independent dating laboratories with a multitude of methods. However, the data are still not accepted by some because the dating has not been carried out on the hominid specimen. Until recently, hominid fossils could only be dated by radiocarbon. This method reaches back to about 40,000 years. As a consequence, all the older fossils could not be analysed and many important questions in our understanding of human evolution could not be addressed. Human remains are scarce and extremely valuable, therefore any sort of destruction has to be kept to an absolute minimum. This is of particular importance in Australia where any human fossils are sacred. Thus, for the analysis of hominid material it was necessary to develop a more or less non-destructive techniques. This has been ac- complished in recent years by the application of ESR dating of tooth enamel and a combination of gamma spectrometric and TIMS U-series dating of bones. The exam

  18. Radiometric Dating Does Work!

    ERIC Educational Resources Information Center

    Dalrymple, G. Brent

    2000-01-01

    Discusses the accuracy of dating methods and creationist arguments that radiometric dating does not work. Explains the Manson meteorite impact and the Pierre shale, the ages of meteorites, the K-T tektites, and dating the Mount Vesuvius eruption. (Author/YDS)

  19. Potential for timing high-energy marine inundation events in the recent geological past through age-dating of reef boulders in Fiji

    NASA Astrophysics Data System (ADS)

    Terry, James P.; Etienne, Samuel

    2014-12-01

    Transported coastal boulders have increasingly come to represent a valuable element of investigations within the broader framework of multi-proxy approaches applied to coastal hazard studies. Through a case study on Taveuni Island in Fiji, this paper outlines some approaches and hindrances to effective timing of prehistorical high-energy marine inundation events (storms and tsunamis) on tropical coastlines from the evidence of reef-platform carbonate boulders. Various sources of errors are outlined that investigators must consider when attempting to use carbonate boulder ages as a surrogate for timing past events. On Taveuni, uranium : thorium dates with a high level of precision (1-7 years) suggest that major inundation events have a return period of approximately 40-45 years since 1650 AD. Of particular importance, considerably different age dates are provided by coral samples sourced from the top and bottom (i.e. opposite faces) of individual boulders, so highlighting interpretation biases that must be avoided.

  20. 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

  1. Ultra-high precision 40Ar/39Ar ages for Fish Canyon Tuff and Alder Creek Rhyolite sanidine: New dating standards required?

    NASA Astrophysics Data System (ADS)

    Phillips, D.; Matchan, E. L.

    2013-11-01

    The 40Ar/39Ar dating technique is a high precision (<0.1%) method with wide application to geological samples. However, the method is predicated on the availability of natural mineral standards of known age. Widely used 40Ar/39Ar standards include sanidine from the (ca. 28 Ma) Fish Canyon Tuff (FCT) and the (ca. 1.2 Ma) Alder Creek Rhyolite (ACR). Despite common usage, the ages of FCT and ACR sanidine have proven contentious, with reported values varying by >2%; well outside the ±0.1% aspiration of EARTHTIME (http://www.earth-time.org).

  2. Age determination of nephrite by in-situ SIMS U-Pb dating syngenetic titanite: A case study of the nephrite deposit from Luanchuan, Henan, China

    NASA Astrophysics Data System (ADS)

    Ling, Xiao-Xiao; Schmädicke, Esther; Li, Qiu-Li; Gose, Jürgen; Wu, Rui-Hua; Wang, Shi-Qi; Liu, Yu; Tang, Guo-Qiang; Li, Xian-Hua

    2015-04-01

    Nephrite is a kind of valuable jade which forms during metamorphism under greenschist facies conditions. Most investigations focus on the genesis of nephrite, however, the formation age of nephrite remains poorly constrained due to the lack of suitable dating methods. In this paper, the petrological, chemical characteristics, and mineral inclusions of nephrite collected from Luanchuan, Henan, China have been studied by optical and electron microscopy and wavelength-dispersive electron microprobe (EMP). The petrological observations show that nephrite consists mainly of tremolite, minor calcite and titanite, occasionally with rutile, quartz, serpentine, chlorite, pyrite, and apatite. The titanite and tremolite which are intergrown with each other share low-energy grain boundaries. It indicates that the two phases are equilibrated and can be considered as cogenetic. The chemical composition of tremolite is high in Si, Mg, Ca, but low in Fe, Cr, and Ni, which indicates that the nephrite from Luanchuan belongs to the dolomite type rather than the serpentinite type. The petrography of different nephrite structures suggests that the grain size of tremolite was determined by the stress intensity undergone during the nephrite formation progress. In-situ Secondary Ion Mass Spectrometer (SIMS) U-Pb dating of titanite from nephrite yielded an age of 361 ± 4 Ma, which is the first estimate for the time of formation of the Luanchuan nephrite deposit. This investigation provides a powerful in-situ dating method to unravel the age of nephrite, which could be served as a tool for future research on other nephrite deposits.

  3. In situ SIMS U-Pb dating of hydrothermal rutile: reliable age for the Zhesang Carlin-type gold deposit in the golden triangle region, SW China

    NASA Astrophysics Data System (ADS)

    Pi, Qiaohui; Hu, Ruizhong; Xiong, Bin; Li, Qiuli; Zhong, Richen

    2017-02-01

    The contiguous region between Guangxi, Guizhou, and Yunnan, commonly referred to as the Golden Triangle region in SW China, hosts many Carlin-type gold deposits. Previously, the ages of the gold mineralization in this region have not been well constrained due to the lack of suitable minerals for radiometric dating. This paper reports the first SIMS U-Pb age of hydrothermal rutile crystals for the Zhesang Carlin-type gold deposit in the region. The hydrothermal U-bearing rutile associated with gold-bearing sulfides in the deposit yields an U-Pb age of 213.6 ± 5.4 Ma, which is within the range of the previously reported arsenopyrite Re-Os isochron ages (204 ± 19 to 235 ± 33 Ma) for three other Carlin-type gold deposits in the region. Our new and more precise rutile U-Pb age confirms that the gold mineralization was contemporaneous with the Triassic W-Sn mineralization and associated granitic magmatism in the surrounding regions. Based on the temporal correlation, we postulate that coeval granitic plutons may be present at greater depths in the Golden Triangle region and that the formation of the Carlin-type gold deposits is probably linked to the coeval granitic magmatism in the region. This study clearly demonstrates that in situ rutile U-Pb dating is a robust tool for the geochronogical study of hydrothermal deposits that contain hydrothermal rutile.

  4. No Relative Age Effect in the Birth Dates of Award-Winning Athletes in Male Professional Team Sports

    ERIC Educational Resources Information Center

    Ford, Paul R.; Williams, A. Mark

    2011-01-01

    Athletes born early within an annual youth age-group selection year are probably more likely to be selected for sports teams and talent development programs than those born later in that year. Overrepresentation of these relatively older athletes in youth and adult sport is known as the relative age effect (RAE). RAEs were found in these popular…

  5. Using an independent geochronology based on palaeomagnetic secular variation (PSV) and atmospheric Pb deposition to date Baltic Sea sediments and infer 14C reservoir age

    NASA Astrophysics Data System (ADS)

    Lougheed, Bryan C.; Snowball, Ian; Moros, Matthias; Kabel, Karoline; Muscheler, Raimund; Virtasalo, Joonas J.; Wacker, Lukas

    2012-05-01

    Dating of sediment cores from the Baltic Sea has proven to be difficult due to uncertainties surrounding the 14C reservoir age and a scarcity of macrofossils suitable for dating. Here we present the results of multiple dating methods carried out on cores in the Gotland Deep area of the Baltic Sea. Particular emphasis is placed on the Littorina stage (8 ka ago to the present) of the Baltic Sea and possible changes in the 14C reservoir age of our dated samples. Three geochronological methods are used. Firstly, palaeomagnetic secular variations (PSV) are reconstructed, whereby ages are transferred to PSV features through comparison with varved lake sediment based PSV records. Secondly, lead (Pb) content and stable isotope analysis are used to identify past peaks in anthropogenic atmospheric Pb pollution. Lastly, 14C determinations were carried out on benthic foraminifera (Elphidium spec.) samples from the brackish Littorina stage of the Baltic Sea. Determinations carried out on smaller samples (as low as 4 μg C) employed an experimental, state-of-the-art method involving the direct measurement of CO2 from samples by a gas ion source without the need for a graphitisation step - the first time this method has been performed on foraminifera in an applied study. The PSV chronology, based on the uppermost Littorina stage sediments, produced ten age constraints between 6.29 and 1.29 cal ka BP, and the Pb depositional analysis produced two age constraints associated with the Medieval pollution peak. Analysis of PSV data shows that adequate directional data can be derived from both the present Littorina saline phase muds and Baltic Ice Lake stage varved glacial sediments. Ferrimagnetic iron sulphides, most likely authigenic greigite (Fe3S4), present in the intermediate Ancylus Lake freshwater stage sediments acquire a gyroremanent magnetisation during static alternating field (AF) demagnetisation, preventing the identification of a primary natural remanent magnetisation for

  6. Age and timing of the Permian mass extinctions: U/Pb dating of closed-system zircons.

    PubMed

    Mundil, Roland; Ludwig, Kenneth R; Metcalfe, Ian; Renne, Paul R

    2004-09-17

    The age and timing of the Permian-Triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts. Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss. The U/Pb age of the main pulse of the extinction is 252.6 +/- 0.2 million years, synchronous with the Siberian flood volcanism, and it occurred within the quoted uncertainty.

  7. Interactions between hatch dates, growth rates, and mortality of Age-0 native Rainbow Smelt and nonnative Alewife in Lake Champlain

    USGS Publications Warehouse

    Parrish, Donna; Simonin, Paul W.; Rudstam, Lars G.; Pientka, Bernard; Sullivan, Patrick J.

    2016-01-01

    Timing of hatch in fish populations can be critical for first-year survival and, therefore, year-class strength and subsequent species interactions. We compared hatch timing, growth rates, and subsequent mortality of age-0 Rainbow Smelt Osmerus mordax and Alewife Alosa pseudoharengus, two common open-water fish species of northern North America. In our study site, Lake Champlain, Rainbow Smelt hatched (beginning May 26) almost a month earlier than Alewives (June 20). Abundance in the sampling area was highest in July for age-0 Rainbow Smelt and August for age-0 Alewives. Late-hatching individuals of both species grew faster than those hatching earlier (0.6 mm/d versus 0.4 for Rainbow Smelt; 0.7 mm/d versus 0.6 for Alewives). Mean mortality rate during the first 45 d of life was 3.4%/d for age-0 Rainbow Smelt and was 5.5%/d for age-0 Alewives. Alewife mortality rates did not differ with hatch timing but daily mortality rates of Rainbow Smelt were highest for early-hatching fish. Cannibalism is probably the primary mortality source for age-0 Rainbow Smelt in this lake. Therefore, hatching earlier may not be advantageous because the overlap of adult and age-0 Rainbow Smelt is highest earlier in the season. However, Alewives, first documented in Lake Champlain in 2003, may increase the mortality of age-0 Rainbow Smelt in the summer, which should favor selection for earlier hatching.

  8. An expansion of age constraints for microbial clades that lack a conventional fossil record using phylogenomic dating.

    PubMed

    Blank, Carrine E

    2011-10-01

    Most microbial taxa lack a conventional microfossil or biomarker record, and so we currently have little information regarding how old most microbial clades and their associated traits are. Building on the previously published oxygen age constraint, two new age constraints are proposed based on the ability of microbial clades to metabolize chitin and aromatic compounds derived from lignin. Using the archaeal domain of life as a test case, phylogenetic analyses, along with published metabolic and genetic data, showed that members of the Halobacteriales and Thermococcales are able to metabolize chitin. Ancestral state reconstruction combined with phylogenetic analysis of the genes underlying chitin degradation predicted that the ancestors of these two groups were also likely able to metabolize chitin or chitin-related compounds. These two clades were therefore assigned a maximum age of 1.0 Ga (when chitin likely first appeared). Similar analyses also predicted that the ancestor to the Sulfolobus solfataricus-Sulfolobus islandicus clade was able to metabolize phenol using catechol dioxygenase, so this clade was assigned a maximum age of 475 Ma. Inferred ages of archaeal clades using relaxed molecular clocks with the new age constraints were consistent with those inferred with the oxygen age constraints. This work expands our current toolkit to include Paleoproterozoic, Neoproterozoic, and Paleozoic age constraints, and should aid in our ability to phylogenetically reconstruct the antiquity of a wide array of microbial clades and their associated morphological and biogeochemical traits, spanning deep geologic time. Such hypotheses-although built upon evolutionary inferences-are fundamentally testable.

  9. Age of the Lava Creek supereruption and magma chamber assembly at Yellowstone based on 40Ar/39Ar and U-Pb dating of sanidine and zircon crystals

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Matthews, N. E.; Calvert, A. T.

    2015-12-01

    The last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the >1000 km3 of rhyolite that composes the Lava Creek Tuff (LCT). Tephra from the eruption blanketed much of the western United States, and is a key Quaternary chronostratigraphic marker, in particular for dating deposition of mid-Pleistocene glacial and pluvial deposits in western North America. We performed 40Ar/39Ar dating of single sanidines to delimit eruption age, and ion microprobe U-Pb and trace-element analyses of crystal faces on single zircons to characterize magmatic evolution and date near-eruption crystallization, as well as analyses of crystal interiors to date the interval of zircon crystallization. Sanidines from the two LCT members A and B yield an 40Ar/39Ar isochron date of 631 ± 4 ka (2σ). Crystal faces on zircons from both members yield a weighted mean 206Pb/238U date of 627 ± 6 ka (2σ) and have trace element concentrations that vary with eruptive stratigraphy. Zircon interiors yield a weighted mean 206Pb/238U date of 660 ± 6 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high-U concentrations and dark cathodoluminescence (CL) cores. These crystals with high-U cores are possibly sourced from 'defrosting' of melt-impregnated margins of the growing subvolcanic reservoir. LCT sanidines mirror the variation of zircon composition within the eruptive stratigraphy, with crystals from upper LCT-A and basal LCT-B having bright-CL rims with high Ba concentrations, suggesting late crystallization after addition of less evolved silicic magma. The occurrence of distal LCT in stratigraphic sequences marking the Marine Isotope Stage 16-15 transition supports the apparent eruption age of ca. 631 ka. These results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up-temperature evolution for Yellowstone's subvolcanic reservoir in the 103-104 year interval

  10. Ultrasonic measurements of second and third trimester fetuses to predict gestational age and date of parturition in captive and wild spotted hyenas Crocuta crocuta.

    PubMed

    Place, Ned J; Weldele, Mary L; Wahaj, Sofia A

    2002-09-01

    Parturition in spotted hyenas (Crocuta crocuta) is a fascinating event to witness, as females of this species are highly masculinized and give birth through a penis-like clitoris. Furthermore, shortly after birth, a high rate of aggression occurs between littermates that can sometimes end in siblicide. To study these events thoroughly, an accurate estimate of the date of parturition is necessary. To this end, we performed transabdominal ultrasounds every 20-30 days in five captive spotted hyenas of known gestational age, beginning approximately 30 days after mating. We measured the femur length (FL), abdominal circumference (AC), and biparietal diameter (BPD) of eight fetuses from Days 42 to 100 of their 110 days of gestation. FL proved to be the most effective measurement, as it correlated well with gestational age and was easy to obtain consistently. The relationship between estimated gestational age (EGA) and FL is described by the equation: [EGA = 37.3 + (14.0 x FL)]. AC also correlated well with EGA, but was more difficult to measure than FL. Measuring BPD became increasingly difficult as pregnancies advanced beyond 70 days of gestation. Because gestational age is often not known in captive and free-ranging spotted hyenas, measuring fetal FL ultrasonographically is a rapid and reliable way to determine an approximate date of parturition. This technique proved invaluable when used to track and monitor a free-ranging spotted hyena during the days just before and after parturition.

  11. Eruption and magma crystallization ages of Las Tres Vírgenes (Baja California) constrained by combined 230Th/ 238U and (U-Th)/He dating of zircon

    NASA Astrophysics Data System (ADS)

    Schmitt, Axel K.; Stockli, Daniel F.; Hausback, Brian P.

    2006-11-01

    Las Tres Vírgenes volcano is a calc-alkaline composite cone located near the main Gulf of California escarpment on the E coast of the Baja California peninsula. High-sensitivity ion microprobe U-series ( 230Th/ 238U) ages for zircon from La Vírgen tephra average 121 - 10 + 12 ka (1σ; MSWD = 2.7), with discrete age peaks at ˜ 100 and 160 ka. The noble gas mass spectrometric (U-Th)/He zircon age, corrected for disequilibrium and pre-eruptive storage, is 36 ± 3 ka. This result for the eruption age of La Vírgen tephra is significantly older than previously postulated historic or Holocene ages that were based on an 18th century map reference and 14C dating of accidental charcoal, respectively. The new (U-Th)/He zircon age is consistent with a > 26 ± 4 ka age derived from cosmogenic He exposure dating of an overlying basaltic lava flow [Hausback, B.P. and Abrams, M.J., 1996. Plinian eruption of La Virgen Tephra, Volcán Las Tres Virgenes, Baja California Sur, Mexico. Eos, Transactions, American Geophysical Union, 77(46, Suppl.): 813-814.]. U-Pb zircon analysis of ignimbrites erupted from the adjacent Early Pleistocene La Reforma and El Aguajito calderas yielded ages of 1.38 ± 0.03 Ma ( n = 12; MSWD = 1.0) and 1.17 ± 0.07 Ma ( n = 23; MSWD = 1.3), respectively. No evidence for these ages is found among La Vírgen zircons, whereas pre-Quaternary zircon xenocrysts are common. The La Vírgen magma, therefore, evolved unrelated to Early Pleistocene magmatism in adjacent calderas, but assimilated local basement rocks. A gap between average Th-U and (U-Th)/He zircon ages suggests that zircon crystallization was discontinuous in the La Vírgen magma chamber. In addition, partial resorption of zircon suggests episodic thermal rejuvenation, most likely by basaltic recharge. Based on the zircon record, the > 100 ka lifetime of the thermal anomaly that sustained repeated intrusive pulses significantly exceeds the age of the last eruption. This strengthens the view that Tres

  12. Heritability of white matter microstructure in late middle age: A twin study of tract-based fractional anisotropy and absolute diffusivity indices.

    PubMed

    Vuoksimaa, Eero; Panizzon, Matthew S; Hagler, Donald J; Hatton, Sean N; Fennema-Notestine, Christine; Rinker, Daniel; Eyler, Lisa T; Franz, Carol E; Lyons, Michael J; Neale, Michael C; Tsuang, Ming T; Dale, Anders M; Kremen, William S

    2017-04-01

    There is evidence that differences among individuals in white matter microstructure, as measured with diffusion tensor imaging (DTI), are under genetic control. However, little is known about the relative contribution of genetic and environmental effects on different diffusivity indices among late middle-aged adults. Here, we examined the magnitude of genetic influences for fractional anisotropy (FA), and mean (MD), axial (AD), and radial (RD) diffusivities in male twins aged 56-66 years old. Using an atlas-based registration approach to delineate individual white matter tracts, we investigated mean DTI-based indices within the corpus callosum, 12 bilateral tracts and all these regions of interest combined. All four diffusivity indices had high heritability at the global level (72%-80%). The magnitude of genetic effects in individual tracts varied from 0% to 82% for FA, 0% to 81% for MD, 8% to 77% for AD, and 0% to 80% for RD with most of the tracts showing significant heritability estimates. Despite the narrow age range of this community-based sample, age was correlated with all four diffusivity indices at the global level. In sum, all diffusion indices proved to have substantial heritability for most of the tracts and the heritability estimates were similar in magnitude for different diffusivity measures. Future studies could aim to discover the particular set of genes that underlie the significant heritability of white matter microstructure. Hum Brain Mapp 38:2026-2036, 2017. © 2017 Wiley Periodicals, Inc.

  13. High precision dating of mass extinction events: a combined zircon geochronology, apatite tephrochronology, and Bayesian age modelling approach of the Permian-Triassic boundary extinction

    NASA Astrophysics Data System (ADS)

    Baresel, Björn; Bucher, Hugo; Brosse, Morgane; Bagherpour, Borhan; Schaltegger, Urs

    2016-04-01

    Chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb dating of single-zircon crystals is preferably applied to tephra beds intercalated in sedimentary sequences. By assuming that the zircon crystallization age closely approximate that of the volcanic eruption and ash deposition, U-Pb zircon geochronology is the preferred approach for dating mass extinction events (such as the Permian-Triassic boundary mass extinction) in the sedimentary record. As tephra from large volcanic eruptions is often transported over long distances, it additionally provide an invaluable tool for stratigraphic correlation across distant geologic sections. Therefore, the combination of high-precision zircon geochronology with apatite chemistry of the same tephra bed (so called apatite tephrochronology) provides a robust fingerprint of one particular volcanic eruption. In addition we provide coherent Bayesian model ages for the Permian-Triassic boundary (PTB) mass extinction, then compare it with PTB model ages at Meishan after Burgess et al. (2014). We will present new high-precision U-Pb zircon dates for a series of volcanic ash beds in deep- and shallow-marine Permian-Triassic sections in the Nanpanjiang Basin, South China. In addition, apatite crystals out of the same ash beds were analysed focusing on their halogen (F, Cl) and trace-element (e.g. Fe, Mg, REE) chemistry. We also show that Bayesian age models produce reproducible results from different geologic sections. On the basis of these data, including litho- and biostratigraphic correlations, we can precisely and accurately constrain the Permian-Triassic boundary in an equatorial marine setting, and correlate tephra beds over different sections and facies in the Nanpanjiang Basin independently from litho-, bio- or chemostratigraphic criteria. The results evidence that data produced in laboratories associated to the global EARTHTIME consortium can provide age information at the 0.05% level of 206

  14. Luminescence- and Infrared-Radiofluorescence dating of the Acheulean- to Middle Stone Age sedimentary sequence at Montagu Cave, Western Cape Provence, South Africa

    NASA Astrophysics Data System (ADS)

    Lauer, Tobias; Archer, Will; Sumner, Alexandra

    2016-04-01

    Montagu Cave is an archaeological site located on the edge of the Langeberg mountain range, about 160 km NE of Cape Town, in South Africa. The archaeological and sedimentary units at Montagu Cave comprise two Acheulean sequences which are separated from one another by a substantial archaeological hiatus. There is an additional Middle Stone Age sequence which overlies the Acheulean horizons, and contains layers attributed to the Howiesons Poort, as well as multiple other Middle Stone Age sub-stages. Hence, Montagu Cave provides a unique opportunity to investigate quite complex population level questions concerning the behavioral differences between modern and pre-modern populations in southern Africa. However, thus far, the chronological context of the sediment-layers at the site remains unclear. It is therefore critical to provide a resilient chronological framework for the timing of human activity at the site. This study concerns the potential of luminescence dating for the sedimentary sequence preserved at Montagu cave. The collected samples are tested on their quartz- and feldspar luminescence signal properties. Various optical dating techniques (quartz OSL; pIRIR290) will be applied, and the results of each compared in order to obtain information on the suitability of the material for luminescence dating, and to establish a chronological framework for this important archaeological site. Furthermore, the infrared-radiofluorescence (IR-RF) signal behavior will be tested on potassium feldspars, as IR-RF is a method being able to date back up to > 600 ka. IR-RF therefore has the potential to cover the expected time-frame of the sediments at Montagu-cave.

  15. The effect of body condition, live weight, breed, age, calf performance, and calving date on reproductive performance of spring-calving beef cows.

    PubMed

    Osoro, K; Wright, I A

    1992-06-01

    Data from 321 spring-calving cows (mean calving date March 27) were used to assess the effects of body condition, live weight, cow age (from 4 to 13 yr), and breed (237 Hereford x Friesians and 84 Blue-Greys) and time of calving on the proportion of cows that became pregnant, the number of days from the start of mating to pregnancy, and calving interval. Mating started at turn-out to pasture in mid-May and lasted 9 to 10 wk. Body condition at calving and breed were the most significant animal factors affecting reproductive performance. Cows calving in higher body condition had shorter (P less than .001) calving intervals (11.2 d per unit of body condition at calving). Blue-Grey cows became pregnant in a higher proportion (90%) and calving interval was shorter (364 d) than in Hereford x Friesians (83%; 374 d). Body condition at the start of mating was less important and body condition at the end of mating had no effect. Live weight at calving and changes in live weight from calving to the start of mating and during the mating period had no significant effect. The proportion of cows becoming pregnant decreased significantly with age in Hereford x Friesian cows older than 7 yr. The variance in calving interval accounted for by calving date, body condition at calving, breed, and age was 42%.

  16. 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.

  17. Recent documents dating: an approach using radiocarbon techniques.

    PubMed

    Zavattaro, D; Quarta, G; D'Elia, M; Calcagnile, L

    2007-04-11

    The possibility to develop an absolute technique, independent from the paper conservation conditions, to date recent paper documents (i.e. less than 50 years old) for forensics purposes is discussed. We suggest the possibility to use the curve representing the strong increase in the atmospheric radiocarbon concentration induced in the last 50 years by nuclear weapons tests as reference to date paper documents, with a resolution down to a few months. The results obtained in the analysis of two known age documents are presented together with a first order mathematical model developed in order to take into account the contributions of the different tree rings employed in the paper production.

  18. On the age of the Onverwacht Group, Swaziland sequence, South Africa. [radioactive dating of stratified igneous rocks

    NASA Technical Reports Server (NTRS)

    Jahn, B.-M.; Shih, C.-Y.

    1974-01-01

    Some rocks of the Onverwacht Group, South Africa, have been analyzed for Rb and Sr concentrations and Sr isotopic composition. These rocks include volcanic rocks, layered ultramafic differentiates and cherty sediments. Whole rock data indicate that the Rb-Sr isotopic systems in many samples were open and yield no reasonable isochron relationships. However, the data of mineral separates from a basaltic komatiite define a good isochron of 3.50 (plus or minus .2) b.y. with an initial Sr-87/Sr-86 ratio of 0.70048 plus or minus 5. The orthodox interpretation of this age is the time of the low grade metamorphism. It is reasonable to assume that the age of 3.50 b.y. might also represent the time of initial Onverwacht volcanism and deposition. The initial Sr-87/Sr-86 ratio obtained above is important to an understanding of the Sr isotopic composition of the Archean upper mantle.

  19. Dating Melt Rock 63545 By Rb-Sr and Sm-Nd: Age of Imbrium; Spa Dress Rehearsal

    NASA Technical Reports Server (NTRS)

    Nyquist, L. E.; Shih, C. Y.; Reese, Y. D.

    2011-01-01

    Apollo 16 sample 63545 was initially described as one of a group of 19 generally rounded, fine-grained, crystalline rocks that were collected as rake samples [1]. This 16 g "rocklet" was collected at Station 13 on the ejecta blanket of North Ray Crater at the foot of Smoky Mountain [2]. Originally classified as a Very High Alumina (VHA) basalt on geochemical grounds [3], it was later argued to be an impact melt rock [4]. Here we report a Rb-Sr and Sm-Nd isotopic study that shows that some portions of the rock failed to reach isotopic equilibrium on last melting in agreement with the impact melt rock interpretation. Nevertheless, by omitting mineral fractions that are discordant with the majority of the data, we arrive at the time of last melting as 3.88 plus or minus 0.05 Ga ago. This age is in agreement with the Ar-39/Ar-40 plateau age of 3839 plus or minus 23 Ma [5], if the latter is adjusted for the 1.4-1.8% revision in the age of the hornblende monitor [6]. This investigation was undertaken in part as proof-of-concept for SPA-basin sample return.

  20. Absolute and relative blindsight.

    PubMed

    Balsdon, Tarryn; Azzopardi, Paul

    2015-03-01

    The concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham's experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight.

  1. Criminal history and assault of dating partners: the role of type of prior crime, age of onset, and gender.

    PubMed

    Straus, Murray A; Ramirez, I Luis

    2004-08-01

    Some studies of assaults on intimate partners have found that most of the perpetrators are not violent outside the family, which suggests a specialized type of crime. However, other studies found domestic violence offenders tend to have extensive criminal histories. To further investigate the extent to which partner assaults are part of a more general pattern of criminal behavior or a specialized type of crime, we studied the dating relationships of 653 university students. Thirty-one percent reported assaulting a partner in the previous 12 months. The rate of assault on partners by females did not differ significantly for males (29%) and females (32%). We also found high rates of other self-reported crime, and much higher rates by males. For example, over one half of the male students and almost one third of the female students reported having stolen money. The male students reported an average of 3.4 crimes committed, and the female students an average of 1.4 crimes. These high crime rates and gender differences are consistent with many previous studies. Logistic regression analysis revealed that a history of prior criminal acts is associated with an increased probability of assaulting a partner. The relationship was greater when there was prior violent crime compared to property crime, when there was early onset of criminal behavior, and when the offender was female. The implications of the findings for understanding partner assaults, criminal careers, and gender differences in the etiology of violence against intimate partners are discussed.

  2. Investigation of Small-Scale Age Inversions in Stalagmites Using in Situ 230Th/U-Dating By Laser Ablation-MC-ICP-MS

    NASA Astrophysics Data System (ADS)

    Jochum, K. P.; Lin, Y.; Scholz, D.; Weis, U.; Stoll, B.; Andreae, M. O.

    2014-12-01

    Post-depositional U loss or addition in stalagmites lead to increasing/decreasing (230Th/238U) activity ratios and thus to older/younger 230Th/U-ages, respectively. In order to determine potential small-scale age inversions, we determined 230Th, 234U, and 238U isotope abundances in a stalagmite from the Hüttenbläserschachthöhle, western Germany, applying a high-spatial-resolution in-situ LA-MC-ICP-MS technique. This sample has the advantage that - because of its aragonitic composition - the U content is high (several µg g-1) and that large-scale age inversions have been previously detected by solution MC-ICP-MS. Due to the low intensity of 230Th (20 - 80 cps), we carefully optimized the operating parameters of the 213 nm Nd:YAG laser, such as scan speed (4 µm s-1), ablation time (1000 s), spot size (110 µm), and pulse repetition rate (20 Hz). We obtained a repeatability (RSE) of about 0.6 % - 0.9 % for 230Th/238U. The isotope ratios were corrected for instrumental biases using an external carbonate reference material (i.e., a flowstone in secular equilibrium). Including all sources of analytical uncertainty, we obtain a total age error (2 SE) of ca. 8 ka for a 215 ka old sample. Repeated dating of the same layers of the stalagmite yields a reproducibility of ca. 4 %. The LA-MC-ICPMS ages agree with the solution MC-ICP-MS ages within the analytical uncertainty. The high spatial resolution enables to detect small, but significant age inversions, which could not be detected by solution MC-ICP-MS. These inversions can be explained by diagenesis of speleothem CaCO3, which may play an important role for the alteration of speleothem ages.

  3. New 40Ar/ 39Ar dating results from the Shanwang Basin, eastern China: Constraints on the age of the Shanwang Formation and associated biota

    NASA Astrophysics Data System (ADS)

    He, Huaiyu; Deng, Chenglong; Pan, Yongxin; Deng, Tao; Luo, Zhaohua; Sun, Jimin; Zhu, Rixiang

    2011-07-01

    The fluvio-lacustrine sequence of the Shanwang Basin, eastern China, preserves a rich and important terrestrial fossil fauna and flora; the exceptional preservation of these fossils reveals the dynamics of ancient mammalian ecosystems and plant biology. However, the timing of this sedimentary sequence has been the subject of debate for decades. Here we contribute to this debate by presenting the detailed results of 40Ar/ 39Ar analysis of the basalts above, below, and within the Shanwang Formation. These dates place stringent constraints on the age of Shanwang Formation and associated biota. 40Ar/ 39Ar ages obtained from basalts of the Niushan and Yaoshan Formations, which underlie and overlie the Shanwang Formation, are 21.0 ± 2.5 Ma (2σ, full external error) and 17.3 ± 1.5 Ma (2σ, full external error), respectively. The 40Ar/ 39Ar age of the basalt in the Shanwang Formation is 17-18 Ma. Given the age constraints of the basalts of the Yaoshan and Shanwang Formations, the age of the Shanwang biota is estimated to be ca. 17 Ma, late Burdigalian of the Early Miocene, indicating that the deposition of this fauna coincided with the onset of the mid-Miocene Climatic Optimum. The results provide new age constraints on the Shanwang mammal fauna, and independently support interpretations that this fauna can be assigned to chronozone MN4, and correlated with middle Orleanian of the European Land Mammal Age, and to late Hemingfordian of the North American Land Mammal Age. Biological diversity of the Shanwang Formation could reflect the global-scale mid-Miocene Climatic Optimum.

  4. Refined depositional history and dating of the Tongaporutuan reference section, north Taranaki, New Zealand: new volcanic ash U-Pb zircon ages, biostratigraphy and sedimentation rates

    USGS Publications Warehouse

    Maier, K.L.; Crundwell, Martin P.; Coble, Matthew A.; Kingsley-Smith, Peter R.; Graham, Stephan A.

    2016-01-01

    This study presents new radiometric ages from volcanic ash beds within a c. 1900 m thick, progradational, deep-water clastic slope succession of late Miocene age exposed along the north Taranaki coast of the North Island, New Zealand. The ash beds yield U–Pb zircon ages ranging from 10.63 ± 0.65 Ma to 8.97 ± 0.22 Ma. The new ages are compatible with and provide corroboration of New Zealand Tongaporutuan Stage planktic foraminiferal and bolboformid biostratigraphic events identified in the same section. The close accord between these two age datasets provides a stratigraphically consistent and coherent basis for examining margin evolution. The arrival of a prograding clastic wedge and ensuing upward shoaling is recorded by sedimentation rates c. 2000 m/Ma–1 that are an order of magnitude higher than sedimentation rates on the precursor deep basin floor. This outcrop study provides new constraints for interpreting analogous subsurface deposits in Taranaki Basin and complements the regional late Miocene biostratigraphic dating framework.

  5. Absolute neutrino mass scale

    NASA Astrophysics Data System (ADS)

    Capelli, Silvia; Di Bari, Pasquale

    2013-04-01

    Neutrino oscillation experiments firmly established non-vanishing neutrino masses, a result that can be regarded as a strong motivation to extend the Standard Model. In spite of being the lightest massive particles, neutrinos likely represent an important bridge to new physics at very high energies and offer new opportunities to address some of the current cosmological puzzles, such as the matter-antimatter asymmetry of the Universe and Dark Matter. In this context, the determination of the absolute neutrino mass scale is a key issue within modern High Energy Physics. The talks in this parallel session well describe the current exciting experimental activity aiming to determining the absolute neutrino mass scale and offer an overview of a few models beyond the Standard Model that have been proposed in order to explain the neutrino masses giving a prediction for the absolute neutrino mass scale and solving the cosmological puzzles.

  6. Origins of the Iberomaurusian in NW Africa: new AMS radiocarbon dating of the Middle and Later Stone Age deposits at Taforalt Cave, Morocco.

    PubMed

    Barton, R N E; Bouzouggar, A; Hogue, J T; Lee, S; Collcutt, S N; Ditchfield, P

    2013-09-01

    Recent genetic studies based on the distribution of mtDNA of haplogroup U6 have led to subtly different theories regarding the arrival of modern human populations in North Africa. One proposes that groups of the proto-U6 lineage spread from the Near East to North Africa around 40-45 ka (thousands of years ago), followed by some degree of regional continuity. Another envisages a westward human migration from the Near East, followed by further demographic expansion at ∼22 ka centred on the Maghreb and associated with a microlithic bladelet culture known as the Iberomaurusian. In evaluating these theories, we report on the results of new work on the Middle (MSA) and Later Stone (LSA) Age deposits at Taforalt Cave in Morocco. We present 54 AMS radiocarbon dates on bone and charcoals from a sequence of late MSA and LSA occupation levels of the cave. Using Bayesian modelling we show that an MSA non-Levallois flake industry was present until ∼24.5 ka Cal BP (calibrated years before present), followed by a gap in occupation and the subsequent appearance of an LSA Iberomaurusian industry from at least 21,160 Cal BP. The new dating offers fresh light on theories of continuity versus replacement of populations as presented by the genetic evidence. We examine the implications of these data for interpreting the first appearance of the LSA in the Maghreb and providing comparisons with other dated early blade and bladelet industries in North Africa.

  7. Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

    DOE PAGES

    Kayzar, Theresa M.; Williams, Ross W.

    2015-09-26

    The model age or ‘date of purification’ of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226 Ra and 227Ac: grand-daughter nuclides in the 238U and 235U decay chains respectively. The 230Th-234U, 226Ra-238U, 231Pa-235U, and 227Ac-235U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. In conclusion, the results demonstrate the accuracy of the 226Ra-238U and 227Ac-235U chronometers and provide information about nuclide migration during uranium processing.

  8. The effects of acid leaching on 40Ar/39Ar age dating results using samples from the Walvis Ridge hotspot trail

    NASA Astrophysics Data System (ADS)

    Klath, J. F.; Koppers, A. A.; Heaton, D. E.; Schnur, S.

    2013-12-01

    In this study we systematically explore how acid leaching can be used to reduce the negative effects of seawater alteration on the 40Ar/39Ar age dating of submarine basalts. Koppers et al (2000) showed that acid leaching of groundmass samples generated more consistent ages as well as ages more concordant with phenocrystic mineral phases, compared to samples that were left untreated. By studying the effects of progressively increasing the strength and length of acid treatment, we will show how acid leaching of groundmass separates reduces alteration while leaving the initial eruption signature intact. Samples were chosen from the Walvis ridge hotspot trail in the southeast Atlantic. Three samples were selected based on degree and style of alteration. Two samples (basalt and basaltic andesite) appear highly altered in thin section. The basalt contains diffuse iddingsite alteration that is pervasive throughout the groundmass. The basaltic andesite displays focused secondary mineral phases within and around abundant vesicles. The third sample, a trachyte, shows relatively minor degrees of alteration in thin section. These groundmass separates were divided into four splits and treated with a progressively stronger acid and for longer duration. One split from each rock was left untreated to act as a baseline. Of the other three splits from each sample, one was treated with a mild leach (1N HCl and 1N HNO3), one a strong leach (1N HCl, 1N HNO3, 6N HCl, and 3N HNO3), and lastly the strong leach performed twice. The samples were then handpicked to remove any remaining visible alteration. The untreated samples were picked as well, removing the most distinctly altered grains. All splits were analyzed by electron microprobe, x-ray fluorescence (XRF) and the incremental heating 40Ar/39Ar dating method. We will report on the results of an image analysis of microprobe backscatter images and elemental maps taken of individual groundmass grains. This analysis will show the location

  9. 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.

  10. Dating Violence

    ERIC Educational Resources Information Center

    Stader, David L.

    2011-01-01

    Dating violence is a form of student-on-student victimization and is a serious school safety issue. Research indicates that at a minimum, 10 percent of high school students are victims of dating violence in one form or another. Among female high school students that date, some data indicate that as many as 30 percent may be victims of dating…

  11. Age and correlation of a paleomagnetic episode in the western United States by Ar-40/Ar-39 dating and tephrochronology: The Jamaica, Blake, or a new polarity episode?

    NASA Astrophysics Data System (ADS)

    Herrero-Bervera, Emilio; Helsley, C. E.; Sarna-Wojcicki, A. M.; Lajoie, K. R.; Meyer, C. E.; McWilliams, M. O.; Negrini, R. M.; Turrin, B. D.; Donnelly-Nolan, J. M.; Liddicoat, J. C.

    1994-12-01

    High-resolution paleomagnetic records from two sites near Pringle Falls, Oregon, are compared with similar records from Summer Lake, Oregon, approximately 170 km to the southeast: Paoha Island, in Mono Lake, approximately 660 km to the southeast and Benton Crossing, in Long Valley, approximately 700 km to the southeast, in east-central California. The sequences at Pringle Falls contain a distinctive coarse pumice-lapilli tephra layer which we have dated as 218 +/- 10 ka by Ar-40/Ar-39 step-heating of plagioclase feldspar. Stratigraphically, this tephra is closely associated with a suite of several other tephra layers that bracket the interval studied paleomagnetically. Each tephra layer is distinguished by the unique chemical composition of its volcanic glass shards. The pumice layer dated at Pringle Falls is correlated with layers at three of the other localities. Using all the tephra layers, we can correlate the lake stratigraphic sequences and associated paleomagnetic records among the four distant localities. Additional age control is obtained from a fifth locality at Tulelake in northern California, where the stratigraphic interval of interest is bracketed between approximately 171 +/- 43 and approximately 140 ka. Characteristics of the paleomagnetic records indicate virtually identical paleofield variation, particularly the geometry of a normal to normal (N-N) geomagnetic polarity episode. The observed paleofield behavior resembles the Blake geomagnetic polarity episode, but is significantly older than the generally accepted age of the Blake episode. Either the age of the Blake episode is significantly underestimated, or the polarity episode documented here is older, perhaps the Jamaica episode, or is an as yet unreported episode. A corollary of the latter option is that paleomagnetic polarity episodes of different ages may have similar transition polar paths, a conclusion implying that a common mechanism is involved.

  12. The SEEDS High-Contrast Imaging Survey: Exoplanet and Brown Dwarf Survey for Nearby Young Stars Dated with Gyrochronology and Activity Age Indicators

    NASA Astrophysics Data System (ADS)

    Kuzuhara, Masayuki; Tamura, Motohide; Helminiak, Kris; Mede, Kyle; Brandt, Timothy; Janson, Markus; Kandori, Ryo; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun

    2015-12-01

    The SEEDS campaign has successfully discovered and characterized exoplanets, brown dwarfs, and circumstellar disks since it began in 2009, via the direct imaging technique. The survey has targeted nearby young stars, as well as stars associated to star-forming regions, the Pleiades open cluster, moving groups, and debris disks. We selected the nearby young stars that have been dated with age indicators based on stellar rotation periods (i.e., gyrochronology) and chromoshperic/coronal activities. Of these, nearly 40 were observed, with ages mainly between 100 and 1000 Myr and distances less than 40 pc. Our observations typically attain the contrast of ~6 x 10-6 at 1'' and better than ~1 x 10-6 beyond 2'', enabling us to detect a planetary-mass companion even around such old stars. Indeed, the SEEDS team reported the discovery that the nearby Sun-like star GJ 504 hosts a Jovian companion GJ 504b, which has a mass of 3-8.5 Jupiter masses that is inferred according to the hot-start cooling models and our estimated system age of 100-510 Myr. The remaining observations out of the selected ~40 stars have resulted in no detection of additional planets or brown dwarf companions. Meanwhile, we have newly imaged a low-mass stellar companion orbiting the G-type star HIP 10321, for which the presence of companion was previously announced via radial velocity technique. The astrometry and radial velocity measurements are simultaneously analyzed to determine the orbit, providing constraints on the dynamical mass of both objects and stellar evolution models. Here we summarize our direct imaging observations for the nearby young stars dated with gyrochrolorogy and activity age indicators. Furthermore, we report the analysis for the HIP 10321 system with the imaged low-mass companion.

  13. Dating stratified settlement sites at Kom K and Kom W: Fifth millennium BCE radiocarbon ages for the Fayum Neolithic

    NASA Astrophysics Data System (ADS)

    Wendrich, W.; Taylor, R. E.; Southon, J.

    2010-04-01

    The earliest evidence of the use of domesticated plants, a traditional hallmark of Neolithic societies in the ancient Near East, first appears in Egypt in archaeological sites in the Fayum depression. Due to wind erosion often resulting in deflation of sediments in this region, stratified sites containing organic materials are rare and the depositional contexts of some earlier 14C measurements on Fayum Neolithic materials are not precisely documented. We report the results of 29 AMS-based 14C determinations on charcoal recovered from stratified contexts in two Fayum Neolithic village sites, Kom K and Kom W. These data assign a mid-5th millennium BCE age to these sites and permit an estimate of the length of their occupation to be approximately three centuries.

  14. Dating the Vinland Map

    ScienceCinema

    None

    2016-07-12

    Scientists from Brookhaven National Laboratory, the University of Arizona, and the Smithsonian Institution used carbon-dating technology to determine the age of a controversial parchment that might be the first-ever map of North America.

  15. Dating the Vinland Map

    SciTech Connect

    2013-01-04

    Scientists from Brookhaven National Laboratory, the University of Arizona, and the Smithsonian Institution used carbon-dating technology to determine the age of a controversial parchment that might be the first-ever map of North America.

  16. Radiocarbon dating of glacier ice: overview, optimisation, validation and potential

    NASA Astrophysics Data System (ADS)

    Uglietti, Chiara; Zapf, Alexander; Jenk, Theo Manuel; Sigl, Michael; Szidat, Sönke; Salazar, Gary; Schwikowski, Margit

    2016-12-01

    High-altitude glaciers and ice caps from midlatitudes and tropical regions contain valuable signals of past climatic and environmental conditions as well as human activities, but for a meaningful interpretation this information needs to be placed in a precise chronological context. For dating the upper part of ice cores from such sites, several relatively precise methods exist, but they fail in the older and deeper parts, where plastic deformation of the ice results in strong annual layer thinning and a non-linear age-depth relationship. If sufficient organic matter such as plant, wood or insect fragments were found, radiocarbon (14C) analysis would have thus been the only option for a direct and absolute dating of deeper ice core sections. However such fragments are rarely found and, even then, they would not be very likely to occur at the desired depth and resolution. About 10 years ago, a new, complementary dating tool was therefore introduced by our group. It is based on extracting the µg-amounts of the water-insoluble organic carbon (WIOC) fraction of carbonaceous aerosols embedded in the ice matrix for subsequent 14C dating. Since then this new approach has been improved considerably by reducing the measurement time and improving the overall precision. Samples with ˜ 10 µg WIOC mass can now be dated with reasonable uncertainty of around 10-20 % (variable depending on sample age). This requires about 300 to 800 g of ice for WIOC concentrations typically found in midlatitude and low-latitude glacier ice. Dating polar ice with satisfactory age precision is still not possible since WIOC concentrations are around 1 order of magnitude lower. The accuracy of the WIOC 14C method was validated by applying it to independently dated ice. With this method, the deepest parts of the ice cores from Colle Gnifetti and the Mt Ortles glacier in the European Alps, Illimani glacier in the Bolivian Andes, Tsambagarav ice cap in the Mongolian Altai, and Belukha glacier

  17. Using chemical, hydrologic, and age dating analysis to delineate redox processes and flow paths in the riparian zone of a glacial outwash aquifer-stream system

    USGS Publications Warehouse

    Puckett, L.J.; Cowdery, T.K.; McMahon, P.B.; Tornes, L.H.; Stoner, J.D.

    2002-01-01

    A combination of chemical and dissolved gas analyses, chlorofluorocarbon age dating, and hydrologic measurements were used to determine the degree to which biogeochemical processes in a riparian wetland were responsible for removing NO3- from groundwaters discharging to the Otter Tail River in west central Minnesota. An analysis of river chemistry and flow data revealed that NO3- concentrations in the river increased in the lower half of the 8.3 km study reach as the result of groundwater discharge to the river. Groundwater head measurements along a study transect through the riparian wetland revealed a zone of groundwater discharge extending out under the river. On the basis of combined chemical, dissolved gas, age date, and hydrologic results, it was determined that water chemistry under the riparian wetland was controlled largely by upgradient groundwaters that followed flow paths up to 16 m deep and discharged under the wetland, creating a pattern of progressively older, more chemically reduced, low NO3- water the farther one progressed from the edge of the wetland toward the river. These findings pose challenges for researchers investigating biogeochemical processes in riparian buffer zones because the progressively older groundwaters entered the aquifer in earlier years when less NO3- fertilizer was being used. NO3- concentrations originally present in the groundwater had also decreased in the upgradient aquifer as a result of denitrification and progressively stronger reducing conditions there. The resulting pattern of decreasing NO3- concentrations across the riparian zone may be incorrectly interpreted as evidence of denitrification losses there instead of in the upgradient aquifer. Consequently, it is important to understand the hydrogeologic setting and age structure of the groundwaters being sampled in order to avgid misinterpreting biogeochemical processes in riparian zones.

  18. Radiocarbon Dating.

    PubMed

    Van Strydonck, Mark

    2016-04-01

    Although most historians and art historians consider the radiocarbon dating technique not to be very precise by their criteria, the method has gained much importance over the last decades. Radiocarbon dating is increasingly used in the field of textile research and old polychrome statues, but also objects made of ivory, stucco, paper, and parchment are dated with the technique. Especially after the introduction of the AMS technique, a boom of this type of research has been noticed.

  19. Fine-tuning of age integrating magnetostratigraphy, radiocarbon dating, and carbonate cyclicity: Example of lacustrine sediments from Heqing basin (Yunnan, China) covering the past 1 Myr

    NASA Astrophysics Data System (ADS)

    Hu, Shouyun; Goddu, Srinivasa Rao; Appel, Erwin; Verosub, Ken

    2007-05-01

    High-resolution magnetostratigraphy, wavelength spectra of carbonate cyclicities, and AMS radiocarbon dating are integrated to establish an optimum age model for a 168 m long drill core of lacustrine sediments from Heqing basin, Yunnan Province, southwestern China. A 14C age of 51.62 +2.42/-1.85 kyr BP is obtained at a depth of 7.3 m. Remanent magnetization is carried by maghemite and partly in addition by magnetite, both showing the same direction. The polarity sequence clearly reveals the Brunhes/Matuyama (B/M) boundary at 141.5 m. Blake Event is found between 16.3 and 17.5 m, and the upper boundary of Jaramillo is indicated at 167.0 m. Carbonate content and magnetic susceptibility were used for spectral analysis. Fourier analysis was done on the depth section for sliding windows with different window lengths. The spectra within the range of window centers (30-140 m) show a dominant long wavelength, which changes from about 18.5 m in the lower part (>65 m depth) to about 14.5 m in the upper part (<65 m depth) of the core. It is assumed that the long wavelength peak represents the 95-kyr Milankovitch eccentricity cycle. The B/M boundary and Blake Event match very well with this model, but the age of Jaramillo is strongly underestimated. Fourier spectra of sliding windows slightly indicate a drop of the sedimentation rate at the lowermost part of the core. An optimum age model is calculated by cubic spline interpolation using tie points from 14C dating, magnetostratigraphy ('true' ages of Blake Event, B/M boundary, and Jaramillo), and wavelengths of carbonate (change in sedimentation rate at 65 m). Alternative depth-to-age transfer functions were tested, i.e. a wavelength age model (using sedimentation rates with 14C as a tie point), a cyclostratigraphic model (using bandpass-filtered carbonate data corresponding to 95 kyr eccentricity cycles) and correlation of carbonate variations to the marine oxygen isotope curve. However, none of the approaches lead to a

  20. Radiocarbon dating accuracy improved

    NASA Astrophysics Data System (ADS)

    Scientists have extended the accuracy of carbon-14 (14C) dating by correlating dates older than 8,000 years with uranium-thorium dates that span from 8,000 to 30,000 years before present (ybp, present = 1950). Edouard Bard, Bruno Hamelin, Richard Fairbanks and Alan Zindler, working at Columbia University's Lamont-Doherty Geological Observatory, dated corals from reefs off Barbados using both 14C and uranium-234/thorium-230 by thermal ionization mass spectrometry techniques. They found that the two age data sets deviated in a regular way, allowing the scientists to correlate the two sets of ages. The 14C dates were consistently younger than those determined by uranium-thorium, and the discrepancy increased to about 3,500 years at 20,000 ybp.

  1. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    USGS Publications Warehouse

    Vazquez, Jorge A.; Woolford, Jeff M

    2015-01-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  2. Strategies for potential age dating of fingerprints through the diffusion of sebum molecules on a nonporous surface analyzed using time-of-flight secondary ion mass spectrometry.

    PubMed

    Muramoto, Shin; Sisco, Edward

    2015-08-18

    Age dating of fingerprints could have a significant impact in forensic science, as it has the potential to facilitate the judicial process by assessing the relevance of a fingerprint found at a crime scene. However, no method currently exists that can reliably predict the age of a latent fingerprint. In this manuscript, time-of-flight secondary ion imaging mass spectrometry (TOF-SIMS) was used to measure the diffusivity of saturated fatty acid molecules from a fingerprint on a silicon wafer. It was found that their diffusion from relatively fresh fingerprints (t ≤ 96 h) could be modeled using an error function, with diffusivities (mm(2)/h) that followed a power function when plotted against molecular weight. The equation x = 0.02t(0.5) was obtained for palmitic acid that could be used to find its position in millimeters (where the concentration is 50% of its initial value or c0/2) as a function of time in hours. The results show that on a clean silicon substrate, the age of a fingerprint (t ≤ 96 h) could reliably be obtained through the extent of diffusion of palmitic acid.

  3. ALPHA SPECTROMETRIC EVALUATION OF SRM-995 AS A POTENTIAL URANIUM/THORIUM DOUBLE TRACER SYSTEM FOR AGE-DATING URANIUM MATERIALS

    SciTech Connect

    Beals, D.

    2011-12-06

    Uranium-233 (t{sub 1/2} {approx} 1.59E5 years) is an artificial, fissile isotope of uranium that has significant importance in nuclear forensics. The isotope provides a unique signature in determining the origin and provenance of uranium-bearing materials and is valuable as a mass spectrometric tracer. Alpha spectrometry was employed in the critical evaluation of a {sup 233}U standard reference material (SRM-995) as a dual tracer system based on the in-growth of {sup 229}Th (t{sub 1/2} {approx} 7.34E3 years) for {approx}35 years following radiochemical purification. Preliminary investigations focused on the isotopic analysis of standards and unmodified fractions of SRM-995; all samples were separated and purified using a multi-column anion-exchange scheme. The {sup 229}Th/{sup 233}U atom ratio for SRM-995 was found to be 1.598E-4 ({+-} 4.50%) using recovery-corrected radiochemical methods. Using the Bateman equations and relevant half-lives, this ratio reflects a material that was purified {approx} 36.8 years prior to this analysis. The calculated age is discussed in contrast with both the date of certification and the recorded date of last purification.

  4. Schmidt-hammer exposure-age dating (SHD) of Lateglacial rock glacier systems near the eastern margin of the European Alps

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas

    2016-04-01

    Rock glaciers are widespread permafrost landforms in Austria. Various rock glacier inventories list more than 4500 rock glaciers in the country; some 30-40% of them are intact. Relict (permafrost free) and pseudo-relict rock glaciers (sporadic and isolated permafrost particularly near the root zone) prevail in number. Rock glaciers are commonly formed over a period of several ka. Dating such landforms helps to understand palaeoclimatic conditions. In this study three rock glaciers consisting of gneiss were dated applying the Schmidt-hammer exposure-age dating (SHD) method. The rock glaciers are located at three neighbouring cirques in the Seckauer Tauern Range named Reichart Rock Glacier (RRG, area 1.26 km², length 1800 m, elevation range 1520-1940 m a.s.l.), Schöneben Rock Glacier (SRG, 0.11 km², 750 m, 1715-1905 m a.s.l.), and Dürrtal Rock Glacier (DRG, 0.08 km², 850 m, 1750-1980 m a.s.l.). RRG is one of the largest rock glaciers in Austria. All three landforms are influenced by lenses of permafrost at present (as indicated by ERT). During the LGM the Seckauer Tauern were covered by valley glaciers and deglaciation occurred presumably already early in the Alpine Lateglacial period. An analogue N-type Schmidt-hammer (proceq) was used for measuring the surface strength of stable blocks at the rock glacier surface by recording a rebound value (R-value) of a spring-loaded bolt. The R-value gives a relative measure of the surface hardness and hence time since exposure to weathering. Eight (RRG) or six (SRG, DRG) Schmidt-hammer measurement sites (with 50-100 individual readings) aligned along longitudinal transects (=former central flow line) between a talus slope (with relatively fresh boulders) in the root zone and the frontal ridge were measured. Mean R-value differences of 30.5 at RRG, 25.1 at SRG, and 20.7 at DRG were revealed along the three transects. The differences between the lowest and the highest R-value at the rock glaciers itself were 19.0 at RRG, 15

  5. Precise Crystallization Age of the Bushveld Complex, South Africa: Direct Dating of the Platiniferous Merensky Reef Using the Zircon U-Pb Chemical Abrasion ID-TIMS Technique

    NASA Astrophysics Data System (ADS)

    Scoates, J. S.; Friedman, R. M.

    2006-12-01

    Determining the age of the Bushveld Complex, the world's largest layered intrusion and host to the majority of the known resources of platinum group elements, chromium and vanadium, has been difficult given the very low abundance of U-bearing minerals in the ultramafic-mafic cumulate rocks that comprise the body. This study provides a precise crystallization age for this giant layered intrusion and associated PGE mineralization, and allows for a re-evaluation of the duration and areal extent of Bushveld-related magmatic activity. Abundant, clear and colorless, anhedral zircon grains were separated from a sample of pegmatoidal feldspathic orthopyroxenite collected from the Merensky Reef in the West Mine (Townlands Shaft), Rustenburg Section. Low-U (21-105 ppm) zircon occurs with interstitial biotite and is locally directly in contact with sulfide. The zircon grains were subjected to different pre-treatment methods (no pre-treatment, air abrasion, and chemical abrasion [CA]) and isotope ratios for individual grains were analyzed by ID-TIMS. U-Pb data for the unabraded and air-abraded grains, and leachates from the CA procedure, are slightly discordant (0.1-1.6%) and yield overlapping 207Pb/206Pb dates ranging from 2052.5 to 2058.9 Ma. For the CA zircon grains (n=6), all data are concordant and give a Concordia age of 2054.3 ± 2.5 Ma (2sd, decay-constant errors included), which is interpreted as the age of crystallization of the Merensky Reef. This age is within error of published ages for the overlying, and locally cross-cutting, Bushveld or Lebowa granite suite, which implies that the entire Bushveld Complex was emplaced within a 2-3 myr interval. Comparison with ages from satellite intrusions (e.g. Moshaneng, Botswana; Uitkomst, South Africa) indicates that the Bushveld magmatic event at ca. 2054 Ma was regionally extensive across the northern Kaapvaal Craton and is consistent with relatively rapid emplacement of mantle-derived magmas along the Thabazimbi

  6. Prediction of the impact of nonpoint sources on a drinking production well field using 85Kr, 39Ar and 3H/3He age dating

    NASA Astrophysics Data System (ADS)

    Broers, H.; Visser, A.; Heerdink, R.; Marsman, A.

    2011-12-01

    Nonpoint agricultural source pollution threatens drinking water supply in the Netherlands. The water quality of a drinking water production well field is determined by the land use in the capture area, geochemistry of the aquifer and the travel time distributions of the production wells. The aim of our study was to project the water quality of the production well field Holten (The Netherlands) based solely on the travel time distributions of the production wells and water quality data from the monitoring network in the vicinity of the well field. The Holten production wells are located in the east of the Netherlands, in sandy ice-pushed ridges. The travel time distributions of 4 shallow production wells (15-45 m below surface) and 3 deep production wells (45-70 m below surface) have been determined by a combination of 85Kr, 3H/3He and 39Ar dating. Sampled groundwater from 9 monitoring wells (27 screens) has been dated with 3H/3He to relate the water quality data to the time of recharge. Water quality data from the monitoring network provided the regional aggregated trend in water quality parameters, related to the time of recharge. These trends generally show an increase in agricultural contamination up to the 1980s, but decreasing concentrations in younger water. The regional aggregated trend of nitrate shows complete denitrification in groundwater older than 15 years. Excess N2 coincides with elevated sulfate concentrations, demonstrating denitrification by pyrite oxidation. The regional aggregated trends from the monitoring wells provided the source input for the water quality prognosis based on the travel time distributions of the production wells. Shallow production wells with a large young component are projected to show water quality improvements in the near future, while production wells with intermediate age distributions respond slower. The three deep wells produce a mixture of groundwater containing both young and very old water. These are projected to

  7. Quantifying Cancer Absolute Risk and Cancer Mortality in the Presence of Competing Events after a Myotonic Dystrophy Diagnosis

    PubMed Central

    Gadalla, Shahinaz M.; Pfeiffer, Ruth M.; Kristinsson, Sigurdur Y.; Björkholm, Magnus; Hilbert, James E.; Moxley, Richard T.; Landgren, Ola; Greene, Mark H.

    2013-01-01

    Recent studies show that patients with myotonic dystrophy (DM) have an increased risk of specific malignancies, but estimates of absolute cancer risk accounting for competing events are lacking. Using the Swedish Patient Registry, we identified 1,081 patients with an inpatient and/or outpatient diagnosis of DM between 1987 and 2007. Date and cause of death and date of cancer diagnosis were extracted from the Swedish Cause of Death and Cancer Registries. We calculated non-parametric estimates of absolute cancer risk and cancer mortality accounting for the high non-cancer competing mortality associated with DM. Absolute cancer risk after DM diagnosis was 1.6% (95% CI=0.4-4%), 5% (95% CI=3-9%) and 9% (95% CI=6-13%) at ages 40, 50 and 60 years, respectively. Females had a higher absolute risk of all cancers combined than males: 9% (95% CI=4-14), and 13% (95% CI=9-20) vs. 2% (95%CI= 0.7-6) and 4% (95%CI=2-8) by ages 50 and 60 years, respectively) and developed cancer at younger ages (median age =51 years, range=22-74 vs. 57, range=43-84, respectively, p=0.02). Cancer deaths accounted for 10% of all deaths, with an absolute cancer mortality risk of 2% (95%CI=1-4.5%), 4% (95%CI=2-6%), and 6% (95%CI=4-9%) by ages 50, 60, and 70 years, respectively. No gender difference in cancer-specific mortality was observed (p=0.6). In conclusion, cancer significantly contributes to morbidity and mortality in DM patients, even after accounting for high competing DM mortality from non-neoplastic causes. It is important to apply population-appropriate, validated cancer screening strategies in DM patients. PMID:24236163

  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. Absolute airborne gravimetry

    NASA Astrophysics Data System (ADS)

    Baumann, Henri

    This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation. The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber. The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data. In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airborne absolute gravimetry is feasible and

  10. Paleo-Environment and C-14 Dating: The Key to the Depositional Age of the Tha Chang and Related Sand Pits, Northeastern Thailand

    NASA Technical Reports Server (NTRS)

    Putthapiban, P.; Zolensky, M.; Jull, T.; Demartino, M.; Salyapongse, S.

    2012-01-01

    Tha Chang sand pits, Nakhon Ratchasima Province and many other sand pits in the area adjacent to the Mun River are characterized by their fluviatile environment in association with mass wasting deposits, along the paleo-river channel and the flood plain of the Mun River. Sediments of these deposits are characterized by clasts of various rock types especially the resistant ones with frequent big tree trunks, logs and wood fragments in different sizes and various stages of transformation from moldering stage to lignification and petrification. Widespread pyritization of the lower horizon suggests strongly reducing environment during burial. The Tha Chang deposits have been received much attention from geoscientists especially paleontologist communities, as they contain fragments of some distinct vertebrate species such as Stegadon sp., hominoid primate, rhinoceros Aceratherium and others. Based on the associated mammal fauna and hominoid fossils, the late Miocene ( 9 - 6 Ma) was given for the time of deposition of this sand and gravel unit. Some other reports believed that sediments and materials of these sand and gravel quarries (pits) were deposited by high-energy flood pulses contemporaneous with the tektites forming event during mid-Pleistocene at c. 0.8 Ma. Interpretation from Palynostratigraphical study suggested that the lower horizon of Tha Chang sand pit was deposited during Pliocene/Pleistocene period and the upper horizons are Pleistoncene/Holocene. It is crystal clear that all the fluviatile sediments including tektites and almost all fossil fragments being deposited in these sand pits were, likely a multiple times reworked materials. Only some old bamboo trees, some old crowling trees and fossils grasses observed on the old river bank are considered in situ. C-14 dating of 5 old wood specimens from Tha Chang Sand Pits, 15 old wood specimens from Chumpuang Sand Pits and one sample of old pottery from a Chumpuang Sand Pit were carried out in the NSF

  11. Absolute-structure reports.

    PubMed

    Flack, Howard D

    2013-08-01

    All the 139 noncentrosymmetric crystal structures published in Acta Crystallographica Section C between January 2011 and November 2012 inclusive have been used as the basis of a detailed study of the reporting of absolute structure. These structure determinations cover a wide range of space groups, chemical composition and resonant-scattering contribution. Defining A and D as the average and difference of the intensities of Friedel opposites, their level of fit has been examined using 2AD and selected-D plots. It was found, regardless of the expected resonant-scattering contribution to Friedel opposites, that the Friedel-difference intensities are often dominated by random uncertainty and systematic error. An analysis of data collection strategy is provided. It is found that crystal-structure determinations resulting in a Flack parameter close to 0.5 may not necessarily be from crystals twinned by inversion. Friedifstat is shown to be a robust estimator of the resonant-scattering contribution to Friedel opposites, very little affected by the particular space group of a structure nor by the occupation of special positions. There is considerable confusion in the text of papers presenting achiral noncentrosymmetric crystal structures. Recommendations are provided for the optimal way of treating noncentrosymmetric crystal structures for which the experimenter has no interest in determining the absolute structure.

  12. Age of most Recent Motion on the Western Denali Fault from Lichenometric Dating of a Large Rockfall Avalanche and Offset Moraines

    NASA Astrophysics Data System (ADS)

    Keskinen, M.; Beget, J.

    2005-12-01

    No major historic earthquakes are known to have occurred on the portion of the Denali Fault lying west of the 7.9 M 2002 rupture zone. The 2002 earthquake produced large rockfall avalanches at several locations within a few kilometers of the 2002 fault trace. Panorama Mountain lies 60 km west of the limit of the 2002 fault zone, and just 4 km off the trend of the western Denali Fault. The west face of Panorama Mountain was the source of a large prehistoric rockfall avalanche that traveled 2 km across the Nenana River, covering an area of ca. 8 km2. The rockfall avalanche deposit consists of fractured blocks as much as 7 m high in a finer, comminuted matrix. Lichenometric dating of the rockfall avalanche based on the central Alaska Range lichen curve of Beget (1991) indicates this rockfall occurred about 300-500 years ago. This is similar to a lichenometric date on an ice-cored moraine offset >5m by the Denali Fault 40 km to the west near Mt. McKinley. The "Bains Creek fault" lies only 1 km south of Panorama Peak, and although Pleistocene glacial deposits are offset by this fault in an exposure along the Parks Highway, we found no evidence this fault was active in the Holocene. In contrast, there is good agreement between the age of offset moraines on the main, active strand of the Denali Fault near Mt. McKinley and the rockfall avalanche deposit near Panorama Mountain. This suggests the most recent large earthquake on the western Denali Fault occurred ca. 300-500 years ago. If the long-term slip rate on the western Denali Fault is ca. 1 cm/yr, i.e. similar to the slip rate inferred for the portion that broke in the 2002 event, then at least several meters of strain have accumulated since the last seismic event.

  13. 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.

  14. Sex Role and Dating Orientation.

    ERIC Educational Resources Information Center

    McCabe, M. P.; Collins, J. K.

    1979-01-01

    Male and female subjects from three age groups completed questionnaires on sex roles and dating orientations. Males approached dating from both a psychoaffectional and psychobiological orientation, while females approached it from a psychoaffectional orientation. Significant differences were found in dating attitudes between male and female…

  15. Absolute multilateration between spheres

    NASA Astrophysics Data System (ADS)

    Muelaner, Jody; Wadsworth, William; Azini, Maria; Mullineux, Glen; Hughes, Ben; Reichold, Armin

    2017-04-01

    Environmental effects typically limit the accuracy of large scale coordinate measurements in applications such as aircraft production and particle accelerator alignment. This paper presents an initial design for a novel measurement technique with analysis and simulation showing that that it could overcome the environmental limitations to provide a step change in large scale coordinate measurement accuracy. Referred to as absolute multilateration between spheres (AMS), it involves using absolute distance interferometry to directly measure the distances between pairs of plain steel spheres. A large portion of each sphere remains accessible as a reference datum, while the laser path can be shielded from environmental disturbances. As a single scale bar this can provide accurate scale information to be used for instrument verification or network measurement scaling. Since spheres can be simultaneously measured from multiple directions, it also allows highly accurate multilateration-based coordinate measurements to act as a large scale datum structure for localized measurements, or to be integrated within assembly tooling, coordinate measurement machines or robotic machinery. Analysis and simulation show that AMS can be self-aligned to achieve a theoretical combined standard uncertainty for the independent uncertainties of an individual 1 m scale bar of approximately 0.49 µm. It is also shown that combined with a 1 µm m‑1 standard uncertainty in the central reference system this could result in coordinate standard uncertainty magnitudes of 42 µm over a slender 1 m by 20 m network. This would be a sufficient step change in accuracy to enable next generation aerospace structures with natural laminar flow and part-to-part interchangeability.

  16. Timing of European fluvial terrace formation and incision rates constrained by cosmogenic nuclide dating

    NASA Astrophysics Data System (ADS)

    Schaller, Mirjam; Ehlers, Todd A.; Stor, Tomas; Torrent, Jose; Lobato, Leonardo; Christl, Marcus; Vockenhuber, Christof

    2016-10-01

    Age constraints of late Cenozoic fluvial terraces are important for addressing surface process questions related to the incision rates of rivers, or tectonic and climate controls on denudation and sedimentation. Unfortunately, absolute age constraints of fluvial terraces are not always possible, and many previous studies have often dated terraces with relative age constraints that do not allow for robust interpretations of incision rates and timing of terrace formation. However, in situ-produced cosmogenic nuclides allow absolute age determination, and hence incision rates, of fluvial deposits back to 5 Ma. Here we present, cosmogenic depth profile dating and isochron burial dating of four different river systems in Europe spanning 12° of latitude. We do this to determine river incision rates and spatial variations in the timing of terrace formation. Isochron burial age constraints of four selected terraces from the Vltava river (Czech Republic) range between 1.00 ± 0.21 to 1.99 ± 0.45Ma. An isochron burial age derived for the Allier river (Central France) is 2.00 ± 0.17Ma. Five terrace levels from the Esla river (NW Spain) were dated between 0.08 + 0.04 / - 0.01Ma and 0.59 + 0.13 / - 0.20Ma with depth profile dating. The latter age agrees with an isochron burial age of 0.52 ± 0.20Ma. Two terrace levels from the Guadalquivir river (SW Spain) were dated by depth profile dating to 0.09 + 0.03 / - 0.02Ma and 0.09 + 0.04 / - 0.03Ma. The one terrace level from the Guadalquivir river dated by isochron burial dating resulted in an age of 1.79 ± 0.18Ma. Results indicate that the cosmogenic nuclide-based ages are generally older than ages derived from previous relative age constraints leading to a factor 2-3 lower incision rates than previous work. Furthermore, the timing of terrace formation over this latitudinal range is somewhat obscured by uncertainties associated with dating older terraces and not clearly synchronous with global climate variations.

  17. Accurate dating of fluvial deposits in the Lateglacial Niers Valley system (Germany) using a multiple dating strategy

    NASA Astrophysics Data System (ADS)

    Hoek, W. Z.; Kasse, C.; Peeters, J.; Wallinga, J.

    2009-04-01

    The River Rhine occupied the Niers Valley (Germany) from the Saalian Glaciation (MIS 6) until the Early Holocene (Kasse et al., Journal of Quaternary Science 2005). The fluvial landscape of the time of abandonment has been exceptionally well preserved, leaving a series of cut-off meanders and residual channels. This unique preservation provides the possibility to investigate Late Weichselian fluvial dynamics of the River Rhine. We combined several dating techniques to accurately determine the age of the deposits. We developed a sampling strategy based on detailed field survey and cross sectioning. 1) The geomorphological relationships of the cut-off meanders gave a relative age for the successive stages of meandering. 2) The occurrence of Laacher See Pumice in the point bar deposits gave a maximum age for these deposits. 3) Optically Stimulated Luminescence (OSL)-dating on sandy point bar and channel-fill deposits yielded absolute ages for active meandering and channel abandonment. 4) AMS-14C dates on terrestrial macrofossils from the basal fills of the residual channels yielded minimum ages for abandonment. 5) Biostratigraphy of the organic channel fills using palynology gave a relative chronology, which could be linked to the well-dated regional biostratigraphy of the nearby Netherlands and is cross-checked by additional AMS-14C dates. By combining these dating techniques we obtained a firm chronological framework that allows linkage to climate records and above the cross-validation of the different dating techniques. All techniques gave consistent ages that confirm the Lateglacial age and Early Holocene abandonment of the Niers Valley by the River Rhine. Palynology and 14C-dating on the channels fills supported the relative chronology indicated by the cross-cut relationships. The presence of the Laacher See Pumice in the point bar deposits, which has an unambiguous age of 12.9 ka cal. BP concurs with the organic channel fill ages. Because OSL signals in some

  18. A developmental study of latent absolute pitch memory.

    PubMed

    Jakubowski, Kelly; Müllensiefen, Daniel; Stewart, Lauren

    2017-03-01

    The ability to recall the absolute pitch level of familiar music (latent absolute pitch memory) is widespread in adults, in contrast to the rare ability to label single pitches without a reference tone (overt absolute pitch memory). The present research investigated the developmental profile of latent absolute pitch (AP) memory and explored individual differences related to this ability. In two experiments, 288 children from 4 to12 years of age performed significantly above chance at recognizing the absolute pitch level of familiar melodies. No age-related improvement or decline, nor effects of musical training, gender, or familiarity with the stimuli were found in regard to latent AP task performance. These findings suggest that latent AP memory is a stable ability that is developed from as early as age 4 and persists into adulthood.

  19. Ground water/surface water interactions in Lake Naivasha, Kenya, using delta 18O, delta D, and 3H/3He age-dating.

    PubMed

    Ojiambo, B S; Poreda, R J; Lyons, W B

    2001-01-01

    We have analyzed a series of ground water samples from the Lake Naivasha region, Kenya, for their helium isotopic composition. Lake Naivasha is unique among the East Africa Rift Valley lakes in that it is fresh. It has long been thought that the low salinity of this lake is due, in part, to rapid water loss from the lake into the local ground water system. Our results show that the Olkaria geothermal waters, south of the lake, are devoid of tritium and, thus, are more than 50 years old. An important implication of these results is that even if Olkaria geothermal reservoir water originated from Lake Naivasha, it has been underground for a long time, (> 50 years) and is not derived from present-day Lake Naivasha water. This flow time is of the same order of magnitude as conservative major solutes, such as chloride, as determined through residence time calculations. On the north side of Lake Naivasha, deep wells (91 m) have water approximately 20 years old. Water from these wells has stable isotopic values resembling those of nearby rivers, and high-elevation eastern Rift water. This indicates that this water recharges from rains from high eastern Rift Valley escarpments. Many of the shallow wells on the south side of the lake have 3H/3He ages between four and 17 years. The young ages and the delta 18 O-enriched signature of the water from these wells indicate that they are recharged by a mixture of water from the lake, Rift flanks, and water from deep pumping wells that is recharged during irrigation. Water mixing ratio calculations using delta 18O and delta D isotopes show that about 50% to 70% of the southern ground water system is derived from the lake, while the Olkaria geothermal reservoir water shows that 40% to 50% of this water is originally lake water. Calculated mean recharge rates range from 0.10 to 1.59 m/yr with a mean of 0.52 +/- 0.40 m/yr. Estimated horizontal velocity from 3H/3He age dating between Lake Naivasha and a well about 3 km to the south is

  20. Coupling 3D groundwater modeling with CFC-based age dating to classify local groundwater circulation in an unconfined crystalline aquifer

    NASA Astrophysics Data System (ADS)

    Kolbe, Tamara; Marçais, Jean; Thomas, Zahra; Abbott, Benjamin W.; de Dreuzy, Jean-Raynald; Rousseau-Gueutin, Pauline; Aquilina, Luc; Labasque, Thierry; Pinay, Gilles

    2016-12-01

    Nitrogen pollution of freshwater and estuarine environments is one of the most urgent environmental crises. Shallow aquifers with predominantly local flow circulation are particularly vulnerable to agricultural contaminants. Water transit time and flow path are key controls on catchment nitrogen retention and removal capacity, but the relative importance of hydrogeological and topographical factors in determining these parameters is still uncertain. We used groundwater dating and numerical modeling techniques to assess transit time and flow path in an unconfined aquifer in Brittany, France. The 35.5 km2 study catchment has a crystalline basement underneath a ∼60 m thick weathered and fractured layer, and is separated into a distinct upland and lowland area by an 80 m-high butte. We used groundwater discharge and groundwater ages derived from chlorofluorocarbon (CFC) concentration to calibrate a free-surface flow model simulating groundwater flow circulation. We found that groundwater flow was highly local (mean travel distance = 350 m), substantially smaller than the typical distance between neighboring streams (∼1 km), while CFC-based ages were quite old (mean = 40 years). Sensitivity analysis revealed that groundwater travel distances were not sensitive to geological parameters (i.e. arrangement of geological layers and permeability profile) within the constraints of the CFC age data. However, circulation was sensitive to topography in the lowland area where the water table was near the land surface, and to recharge rate in the upland area where water input modulated the free surface of the aquifer. We quantified these differences with a local groundwater ratio (rGW-LOCAL), defined as the mean groundwater travel distance divided by the mean of the reference surface distances (the distance water would have to travel across the surface of the digital elevation model). Lowland, rGW-LOCAL was near 1, indicating primarily topographical controls. Upland, r

  1. Estimating divergence dates and evaluating dating methods using phylogenomic and mitochondrial data in squamate reptiles.

    PubMed

    Mulcahy, Daniel G; Noonan, Brice P; Moss, Travis; Townsend, Ted M; Reeder, Tod W; Sites, Jack W; Wiens, John J

    2012-12-01

    Recently, phylogenetics has expanded to routinely include estimation of clade ages in addition to their relationships. Various dating methods have been used, but their relative performance remains understudied. Here, we generate and assemble an extensive phylogenomic data set for squamate reptiles (lizards and snakes) and evaluate two widely used dating methods, penalized likelihood in r8s (r8s-PL) and Bayesian estimation with uncorrelated relaxed rates among lineages (BEAST). We obtained sequence data from 25 nuclear loci (∼500-1,000 bp per gene; 19,020bp total) for 64 squamate species and nine outgroup taxa, estimated the phylogeny, and estimated divergence dates using 14 fossil calibrations. We then evaluated how well each method approximated these dates using random subsets of the nuclear loci (2, 5, 10, 15, and 20; replicated 10 times each), and using ∼1 kb of the mitochondrial ND2 gene. We find that estimates from r8s-PL based on 2, 5, or 10 loci can differ considerably from those based on 25 loci (mean absolute value of differences between 2-locus and 25-locus estimates were 9.0 Myr). Estimates from BEAST are somewhat more consistent given limited sampling of loci (mean absolute value of differences between 2 and 25-locus estimates were 5.0 Myr). Most strikingly, age estimates using r8s-PL for ND2 were ∼68-82 Myr older (mean=73.1) than those using 25 nuclear loci with r8s-PL. These results show that dates from r8s-PL with a limited number of loci (and especially mitochondrial data) can differ considerably from estimates derived from a large number of nuclear loci, whereas estimates from BEAST derived from fewer nuclear loci or mitochondrial data alone can be surprisingly similar to those from many nuclear loci. However, estimates from BEAST using relatively few loci and mitochondrial data could still show substantial deviations from the full data set (>50 Myr), suggesting the benefits of sampling many nuclear loci. Finally, we found that confidence

  2. Estimating Absolute Site Effects

    SciTech Connect

    Malagnini, L; Mayeda, K M; Akinci, A; Bragato, P L

    2004-07-15

    The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from

  3. Topics in Chemical Instrumentation: Cl. Thermoluminescence. Part III. Application to Archeological Dating.

    ERIC Educational Resources Information Center

    Manche, Emanuel P.; Ewing, Galen W., Ed.

    1979-01-01

    Thermoluminescence and its application to archeological dating are considered in this article. Descriptions are given of the method, the required doses, absolute and relative dating, complications, and the relation of this type of dating to other methods. (SA)

  4. 36Chlorine exposure dating of a terminal moraine in the Galicica Mountains, Macedonia

    NASA Astrophysics Data System (ADS)

    Gromig, R.; Mechernich, S.; Ribolini, A.; Dunai, T. J.; Wagner, B.

    2015-12-01

    The glaciation history of the Balkan Peninsula is subject of research since the late 19th century. To date, only a few moraines on the Balkan Peninsula are dated, mainly using 10Be exposure dating applied on quartz bearing rocks. Since large parts of the Balkan Peninsula mountains are composed of carbonatic rocks, absolute age dating is restricted to 36Cl exposure dating, which, to date, was not conducted in this region yet. So far, an absolute chronological control in limestone-dominated areas is limited to U-series minimum ages of calcitic cements. In order to obtain more information about the timing of the glaciation history on the Balkan Peninsula, we investigated a terminal moraine in a NNE-facing cirque in the Galicica Mountains (40°56´N, 20°49´E) in the Former Yugoslav Republic of Macedonia. The cirque comprises a series of nested moraine ridges at the base of the cirque wall, with the largest one being sampled. Samples from five limestone boulders in crest position (≈ 2050 m a.s.l.) were taken and pre-treated for AMS measurement at the University of Cologne. Three preliminary ages point to a moraine formation in the course of a late Pleistocene glaciation, either Last Glacial Maximum or Younger Dryas. The data were discussed concerning corrections for topographic shielding, snow cover, inheritance, and erosion. However, five AMS re-measurements are currently in progress in order to refine the correlation of the moraine formation to a specific glacial period. The resulting ages will be compared to sediments of the adjacent Lakes Ohrid and Prespa, which represent valuable climatic and environmental archives. Several studies on these sediments were carried out in order to reconstruct relative changes in temperature and moisture availability. Moreover, the inferred moraine formation ages will be compared to glaciation reconstructions of other mountainous regions on the Balkan Peninsula to improve the knowledge on past climatic conditions.

  5. An Astronomically Dated Standard in 40Ar/39Ar Geochronology?

    NASA Astrophysics Data System (ADS)

    Kuiper, K.; Hilgen, F.; Krijgsman, W.; Wijbrans, J.

    2003-12-01

    The standard geological time scale of Berggren et al. (1995) and Cande and Kent (1995) is calibrated with different absolute dating techniques, i.e. the Plio - Pleistocene relies on astronomical tuning, and older parts of the time scale are based on radio-isotopic (40Ar/39Ar and U/Pb) calibration methods. In the new edition of the standard geological timescale (Lourens et al., to be published in 2004) the entire Neogene will rely on astronomical dating. Therefore, it is of crucial importance that all dating methods produce equivalent absolute ages when the same geological event is dated. The Mediterranean Neogene provides an excellent opportunity to compare different dating methods by isotopic dating (40Ar/39Ar, U/Pb) of volcanic ash layers intercalated in astronomically dated sediments. Here we will show that in spite of potential errors in all methods, we succeeded to intercalibrate the 40Ar/39Ar and astronomical methods, arriving at astronomically calibrated age of 28.24 +/- 0.01 Ma for the in 40Ar/39Ar geochronology commonly used standard FCT sanidine. The advantage of an astronomically calibrated FCT above a K/Ar calibrated standard is a smaller error in the absolute age due to the lack of uncertainties related to 40K and radiogenic 40Ar contents in the primary standard and a decreasing influence of errors in the decay constant (branching ratio is not required). In addition to an astronomically calibrated FCT age we propose to introduce an astronomically dated standard. A direct astronomically dated standard can be regarded as a "primary" standard and does not require intercalibration with other standards, thus reducing analytical (and geological) uncertainties. Ash layers intercalated in sedimentary sequences in the Melilla Basin, Morocco appear to be the most suitable for this purpose. A reliable astronomical time control is available and intercalated ash layers contain sanidine phenocrysts up to 2 mm. Four ash layers are not or barely affected by

  6. Early Acheulean technology in the Rietputs Formation, South Africa, dated with cosmogenic nuclides.

    PubMed

    Gibbon, Ryan J; Granger, Darryl E; Kuman, Kathleen; Partridge, Timothy C

    2009-02-01

    An absolute dating technique based on the build-up and decay of (26)Al and (10)Be in the mineral quartz provides crucial evidence regarding early Acheulean hominid distribution in South Africa. Cosmogenic nuclide burial dating of an ancient alluvial deposit of the Vaal River (Rietputs Formation) in the western interior of South Africa shows that coarse gravel and sand aggradation there occurred ca 1.57+/-0.22Ma, with individual ages of samples ranging from 1.89+/-0.19 to 1.34+/-0.22Ma. This was followed by aggradation of laminated and cross-bedded fine alluvium at ca 1.26+/-0.10Ma. The Rietputs Formation provides an ideal situation for the use of the cosmogenic nuclide burial dating method, as samples could be obtained from deep mining pits at depths ranging from 7 to 16 meters. Individual dates provide only a minimum age for the stone tool technology preserved within the deposits. Each assemblage represents a time averaged collection. Bifacial tools distributed throughout the coarse gravel and sand unit can be assigned to an early phase of the Acheulean. This is the first absolute radiometric dated evidence for early Acheulean artefacts in South Africa that have been found outside of the early hominid sites of the Gauteng Province. These absolute dates also indicate that handaxe-using hominids inhabited southern Africa as early as their counterparts in East Africa. The simultaneous appearance of the Acheulean in different parts of the continent implies relatively rapid technology development and the widespread use of large cutting tools in the African continent by ca 1.6Ma.

  7. Cryogenic, Absolute, High Pressure Sensor

    NASA Technical Reports Server (NTRS)

    Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

    2001-01-01

    A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

  8. Estimating Divergence Dates and Substitution Rates in the Drosophila Phylogeny

    PubMed Central

    Obbard, Darren J.; Maclennan, John; Kim, Kang-Wook; Rambaut, Andrew; O’Grady, Patrick M.; Jiggins, Francis M.

    2012-01-01

    An absolute timescale for evolution is essential if we are to associate evolutionary phenomena, such as adaptation or speciation, with potential causes, such as geological activity or climatic change. Timescales in most phylogenetic studies use geologically dated fossils or phylogeographic events as calibration points, but more recently, it has also become possible to use experimentally derived estimates of the mutation rate as a proxy for substitution rates. The large radiation of drosophilid taxa endemic to the Hawaiian islands has provided multiple calibration points for the Drosophila phylogeny, thanks to the "conveyor belt" process by which this archipelago forms and is colonized by species. However, published date estimates for key nodes in the Drosophila phylogeny vary widely, and many are based on simplistic models of colonization and coalescence or on estimates of island age that are not current. In this study, we use new sequence data from seven species of Hawaiian Drosophila to examine a range of explicit coalescent models and estimate substitution rates. We use these rates, along with a published experimentally determined mutation rate, to date key events in drosophilid evolution. Surprisingly, our estimate for the date for the most recent common ancestor of the genus Drosophila based on mutation rate (25–40 Ma) is closer to being compatible with independent fossil-derived dates (20–50 Ma) than are most of the Hawaiian-calibration models and also has smaller uncertainty. We find that Hawaiian-calibrated dates are extremely sensitive to model choice and give rise to point estimates that range between 26 and 192 Ma, depending on the details of the model. Potential problems with the Hawaiian calibration may arise from systematic variation in the molecular clock due to the long generation time of Hawaiian Drosophila compared with other Drosophila and/or uncertainty in linking island formation dates with colonization dates. As either source of error will

  9. Accelerator mass spectrometry 14C dating of lime mortars: Methodological aspects and field study applications at CIRCE (Italy)

    NASA Astrophysics Data System (ADS)

    Marzaioli, Fabio; Nonni, Sara; Passariello, Isabella; Capano, Manuela; Ricci, Paola; Lubritto, Carmine; De Cesare, Nicola; Eramo, Giacomo; Quirós Castillo, Juan Antonio; Terrasi, Filippo

    2013-01-01

    Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) has, recently, obtained some promising results in testing the feasibility of mortar radiocarbon dating by means of an ad hoc developed purification procedure (CryoSoniC: Cryobraking, Sonication, Centrifugation) applied to a series of laboratory mortars. Observed results encouraged CryoSoniC accuracy evaluation on genuine mortars sampled from archeological sites of known or independently constrained age (i.e., other 14C dates on different materials). In this study, some 14C measurements performed on genuine mortars will be discussed and compared with independently estimated (i.e., radiocarbon/archaeometrical dating) absolute chronologies of two Spanish sites. Observed results confirm the agreement of the CryoSoniC mortar dates with the archaeological expectations for both examined cases. Several authors reported the possibility of obtaining accurate radiocarbon dates of mortar matrices by analyzing lime lumps: binder-related particles of different sizes exclusively composed of calcium carbonate. In this paper, preliminary data for the absolute chronology reconstruction of the Basilica of the cemetery complex of Ponte della Lama (Canosa di Puglia, Italy) based on lime lumps will also be discussed. Dating accuracy will be quantified by comparing 14C data on mortar lime lumps from a funerary inscription of known age found near the Basilica, in the same study site. For this site, a comparison between absolute chronologies performed by bulk and CryoSoniC purified lime lumps, and charcoal incased in mortars (when found) will also be discussed. Observed results for this site provide evidence of how bulk lime lump dating may introduce systematic overestimations of the analyzed sample while CryoSoniC purification allows accurate dating.

  10. Dating slate belts using 40Ar/39Ar geochronology and zircon ages from crosscutting plutons: A case study from east-central Maine, USA

    NASA Astrophysics Data System (ADS)

    Ghanem, Hind; Kunk, Michael; Ludman, Allan; Bish, David; Wintsch, Robert

    2016-04-01

    Determining the tectonic significance of slate belts is a persistent problem in many orogenic belts because of the lack of time constraints on the age of deposition and the age(s) of cleavages. We have solved this problem in east-central Maine where the ages of the regional Acadian cleavage (S1) and local ductile fault zone cleavage (S2) were both constrained using 40Ar/39Ar geochronology and the ages of crosscutting plutons. Applying 40Ar/39Ar geochronology to rocks with multiple generations of muscovite was possible because each cleavage-forming muscovite records a crystallization age rather than a cooling age due to the low grade of regional metamorphism. Evidence for metamorphic crystallization in rocks dominated by regional Acadian cleavage (S1) comes from the truncations of detrital and authigenic muscovite and chlorite grains by new muscovite and chlorite grains that define the S1 foliation. In rocks that display two foliations, the evidence comes from the truncations of chlorite and muscovite grains defining all earlier fabrics by new muscovite grains in the younger folia (S2). Step-heating experiments using the 40Ar/39Ar technique on twelve samples all yielded sigmoidal age spectra. The low-temperature steps produced a hump in the age spectra, indicating 39Ar recoil into adjacent interlayered chlorite grains, the latter interlayering confirmed by back-scattered electron imaging. Continuing steps climbed steadily from those with minimum apparent ages as young as ~381 Ma to steps with maximum ages as old as 466 Ma. The samples with the lowest minimum apparent age steps are those in which the S2 cleavage-forming mica population dominates. In contrast, the oldest apparent age steps are from samples that have the highest modal abundance of detrital micas. The Middle Ordovician age of the maximum age steps is interpreted to be the minimum cooling age of the detrital micas. The minimum 40Ar/39Ar age steps of muscovite in the samples that display only S1 cleavage

  11. Dating human bone: is racemization dating species-specific?

    PubMed

    Moini, Mehdi; Rollman, Christopher M; France, Christine A M

    2013-12-03

    Our recently developed dating technique based on the racemization rate of aspartic acid was applied to dating human bone, as well as that of other mammals, utilizing capillary electrophoresis mass spectrometry. First, several well-dated (mostly (14)C-dated and with strong archeological evidence) human bones ranging in age from 150 to ~10,000 years were used to develop a calibration curve for human bone. The D/L ratio of aspartic acid for these specimens ranged from 2.4% to ~10%, with a correlation coefficient of better than 0.99, indicating a strong linear relationship between the d/l ratio of aspartic acid and the age of the specimens. This calibration curve can now be used to date human archeological specimens of unknown age, up to ~10,000 years. However, when the technique was applied to well-dated mixed species of larger mammal bones such as bison, whale, llama, etc., the calibration curve showed a slower rate of racemization with a lower correlation (0.88). As additional large mammal bones with less certain age (i.e., using archeological evidence alone with no (14)C-dating) were dated the correlation coefficient decreased to 0.70. The correlation coefficient decreased further to 0.58 when the racemization data from all mammals (including human) were added to the calibration curve, indicating the importance of using well-dated, species-specific specimens for forming a calibration curve. This conclusion is consistent with our previously published calibration curve for a single species of silk (Bombyx mori), which followed the expected reversible first-order kinetics. These results support species specificity of amino acid racemization dating.

  12. AMS 14C and OSL/IRSL dating of the Dunaszekcső loess sequence (Hungary): chronology for 20 to 150 ka and implications for establishing reliable age-depth models for the last 40 ka

    NASA Astrophysics Data System (ADS)

    Újvári, Gábor; Molnár, Mihály; Novothny, Ágnes; Páll-Gergely, Barna; Kovács, János; Várhegyi, András

    2014-12-01

    As revealed by 18 AMS radiocarbon and 24 OSL/IRSL ages the Dunaszekcső loess-paleosol sequence is an excellent terrestrial record of paleoenvironmental change in the Carpathian Basin for the last 130 ka, with significant soil forming episodes during the Eemian interglacial (130-115 ka, MIS 5e) and in some subsequent MIS 5 stages, and distinct periods of loess accumulations during the MIS 4 and MIS 2. Charcoals from the sequence made it possible to test the accuracy of 14C ages from mollusc shells. This approach revealed that 14C ages from some gastropods having small shells (<10 mm) (Succinella oblonga, Vitrea crystallina) are statistically indistinguishable from the ages of charcoals, while others (Clausiliidae sp., Chondrula tridens) show age anomalies up to 600-800 years. OSL and pIRIR@290 ages are found to be consistently older, while post-IR OSL ages are younger than the 14C ages from charcoals and molluscs by some thousands of years, except for pIRIR@225 ages that match the radiocarbon ages quite well. OSL and IRSL ages have scatters up to 7-10 thousand years within 40 ka, while charcoals and small molluscs yield consistent ages with relatively low variability. Beyond the observation that some small molluscs seem to yield reliable 14C ages, calibrated 2σ age ranges of the radiocarbon data (ca 500-800 years for 20 to 30 ka) are an order of magnitude narrower than those of the OSL/IRSL methods (1800-4000 years for 25 to 35 ka). Thus, for establishing chronologies within 40 ka, which are both accurate and precise enough to address issues like synchroneity of millennial-scale paleoenvironmental events across regions (e.g. North Atlantic and Europe), AMS radiocarbon dating of shells of specific loess molluscs and charcoals may probably be a powerful chronological tool. However, additional work is definitely required involving 14C and OSL/IRSL dates from other loess sequences to further test the performance of these two supposedly robust chronometers.

  13. Dating slate belts using 40Ar/39Ar geochronology and zircon ages from crosscutting plutons: A case study from east-central Maine, USA

    NASA Astrophysics Data System (ADS)

    Ghanem, Hind; Kunk, Michael J.; Ludman, Allan; Bish, David L.; Wintsch, Robert P.

    2016-12-01

    We report the ages of cleavage development in a normally intractable lower greenschist facies slate belt, the Central Maine-Aroostook-Matapedia belt in east-central Maine. We have attacked this problem by identifying the minimum ages of muscovite in a regional Acadian cleavage (S1) and in a local ductile fault zone cleavage (S2) using 40Ar/39Ar geochronology and the ages of crosscutting plutons. Our success stems from the regional low-grade metamorphism of the rocks in which each crystallization event preserves a40Ar/39Ar crystallization age and not a cooling age. Evidence for recrystallization via a pressure solution mechanism comes from truncations of detrital, authigenic, and in some rocks S1 muscovite and chlorite grains by new cleavage-forming muscovite and chlorite grains. Low-blank furnace age spectra from meta-arkosic and slaty rocks climb from moderate temperature Devonian age-steps dominated by cleavage-forming muscovite to Ordovician age-steps dominated by a detrital muscovite component. S1- and S2-cleaved rocks were hornfelsed by granitoids of ∼407 and 377 Ma, respectively. The combination of these minimum ages with the maximum metamorphic crystallization ages establishes narrow constraints on the timing of these two cleavage-forming events, ∼410 Ma (S1) and ∼380 Ma (S2). These two events coincide in time with a change in the plate convergence kinematics from the arrival of the Avalon terrane (Acadian orogeny), to a right-lateral transpression arrival of the Meguma terrane in the Neoacadian orogeny.

  14. Database applicaton for absolute spectrophotometry

    NASA Astrophysics Data System (ADS)

    Bochkov, Valery V.; Shumko, Sergiy

    2002-12-01

    32-bit database application with multidocument interface for Windows has been developed to calculate absolute energy distributions of observed spectra. The original database contains wavelength calibrated observed spectra which had been already passed through apparatus reductions such as flatfielding, background and apparatus noise subtracting. Absolute energy distributions of observed spectra are defined in unique scale by means of registering them simultaneously with artificial intensity standard. Observations of sequence of spectrophotometric standards are used to define absolute energy of the artificial standard. Observations of spectrophotometric standards are used to define optical extinction in selected moments. FFT algorithm implemented in the application allows performing convolution (deconvolution) spectra with user-defined PSF. The object-oriented interface has been created using facilities of C++ libraries. Client/server model with Windows Socket functionality based on TCP/IP protocol is used to develop the application. It supports Dynamic Data Exchange conversation in server mode and uses Microsoft Exchange communication facilities.

  15. 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.

  16. Absolute classification with unsupervised clustering

    NASA Technical Reports Server (NTRS)

    Jeon, Byeungwoo; Landgrebe, D. A.

    1992-01-01

    An absolute classification algorithm is proposed in which the class definition through training samples or otherwise is required only for a particular class of interest. The absolute classification is considered as a problem of unsupervised clustering when one cluster is known initially. The definitions and statistics of the other classes are automatically developed through the weighted unsupervised clustering procedure, which is developed to keep the cluster corresponding to the class of interest from losing its identity as the class of interest. Once all the classes are developed, a conventional relative classifier such as the maximum-likelihood classifier is used in the classification.

  17. Age dating and flow path evaluation of groundwater by SF6 and microbe in the foot of Mt. Fuji, central Japan

    NASA Astrophysics Data System (ADS)

    Yamamoto, Chisato; Tsujimura, Maki; Kato, Kenji; Nagaosa, Kazuyo; Sakakibara, Koichi; Umei, Yohei; Ohara, Kazuma

    2016-04-01

    A variety of industries are developed at the foot of volcanic mountains in Japan and the groundwater is major source for industrial activity in those regions. The age of groundwater has been estimated to be from 10 to 30 years in Mt. Fuji regions by using 36Cl and 3H. However, the age has not been evaluated using SF6 with higher time resolution in these regions. Also, the total number of prokaryotes shows a specific value in each spring water, suggesting different path and age of the groundwater. Therefore, we aim to estimate residence time and the groundwater flow in three dimensions using the multi-tracers approach; CFCs, SF6, the total number of prokaryotes, the stable isotopes of oxygen-18, deuterium. We collected totally 25 spring water samples in Mt. Fuji and analyzed concentration of inorganic ions, the stable isotopes of oxygen-18, deuterium, CFCs, SF6. The apparent age of the spring water was estimated to be ranging from 4 to 19 years at the foot of Mt. Fuji. These results are reasonable as considering the existed age data by36Cl (Tosaki, 2008) in this region. The spring water with younger age tends to show higher total number of prokaryotes, suggesting that the groundwater flows dominantly through the shallow and young lava with the higher total number of prokaryotes, leads to younger age. Focusing on a specific spring water, the seasonal change of SF6 and total number of prokaryotes were monitored. The spring water showed a younger age and higher total number of prokaryotes during the high water flow season, whereas it showed an older age and lower total number of prokaryotes. Therefore, the total number of prokaryotes shows a good negative correlation with the residence time of the spring/ groundwater in space and time. This shows a possibility that the total number of prokaryotes could be a useful tracer of groundwater for time and space in the three dimensions information.

  18. Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica.

    PubMed

    Buizert, Christo; Baggenstos, Daniel; Jiang, Wei; Purtschert, Roland; Petrenko, Vasilii V; Lu, Zheng-Tian; Müller, Peter; Kuhl, Tanner; Lee, James; Severinghaus, Jeffrey P; Brook, Edward J

    2014-05-13

    We present successful (81)Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ∼350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The (81)Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 ± 2.5 ka. Our experimental methods and sampling strategy are validated by (i) (85)Kr and (39)Ar analyses that show the samples to be free of modern air contamination and (ii) air content measurements that show the ice did not experience gas loss. We estimate the error in the (81)Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130-115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA (81)Kr analysis requires a 40-80-kg ice sample; as sample requirements continue to decrease, (81)Kr dating of ice cores is a future possibility.

  19. Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica

    PubMed Central

    Buizert, Christo; Baggenstos, Daniel; Jiang, Wei; Purtschert, Roland; Petrenko, Vasilii V.; Lu, Zheng-Tian; Müller, Peter; Kuhl, Tanner; Lee, James; Severinghaus, Jeffrey P.; Brook, Edward J.

    2014-01-01

    We present successful 81Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ∼350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The 81Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 ± 2.5 ka. Our experimental methods and sampling strategy are validated by (i) 85Kr and 39Ar analyses that show the samples to be free of modern air contamination and (ii) air content measurements that show the ice did not experience gas loss. We estimate the error in the 81Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130–115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA 81Kr analysis requires a 40–80-kg ice sample; as sample requirements continue to decrease, 81Kr dating of ice cores is a future possibility. PMID:24753606

  20. 40Ar/39Ar dating of ignimbrite from Inner Mongolia, northeastern China, indicates a post-Middle Jurassic age for the overlying Daohugou Bed

    NASA Astrophysics Data System (ADS)

    He, H. Y.; Wang, X. L.; Zhou, Z. H.; Zhu, R. X.; Jin, F.; Wang, F.; Ding, X.; Boven, A.

    2004-10-01

    The 40Ar/39Ar step heating analyses of K-feldspar derived from the ignimbrite in Inner Mongolia, China indicates that they were formed at 159.8 +/- 0.8 Ma, which provides a maximum age for the overlying fossil-bearing lacustrine deposits (Daohugou Bed). This result favors a post-Middle Jurassic (Late Jurassic or younger), rather than the Middle Jurassic age for the Daohugou Bed. Such a result is generally consistent with vertebrate biostratigraphic evidence, providing a maximum known age for the first appearance of several major animal groups such as Cryptobranchidae of Urodela (salamanders) and Maniraptora (birds and their closest dinosaurian relatives).

  1. Optical and thermoluminescence dating of Middle Stone Age and Kintampo bearing sediments at Birimi, a multi-component archaeological site in Ghana

    NASA Astrophysics Data System (ADS)

    Quickert, Nicole A.; Godfrey-Smith, Dorothy I.; Casey, Joanna L.

    2003-05-01

    We report the first luminescence ages for the archeological and geological sediments forming the substrate of the Birimi archaeological site in the Northern Region of Ghana. The site's significance rests on the fact that it contains a rich collection of artifact assemblages representative of three distinct cultures, and that, on the basis of artifact typology, the earliest assemblage is diagnostic of the Middle Stone Age (MSA) . In situ occurrences of MSA artifacts are found at over 1 m below today's surface. They are overlain by a ceramic-rich complex of a sedentary or semi-sendentary Later Stone Age culture known as the Kintampo. The western half of the site is dominated by the industrial remains of Iron Age smelting activity. Elemental, mineralogical, and sedimentological analysis of the cultural and sub-cultural sedimentary horizons at the site revealed at least three distinct lithostratigraphic units. The quartz sediments are derived from the sandstone of the Gambaga escarpment, mass wasted and accreted fluvially at a rate of 3.2 cm/ka, forming a wide terrace at Birimi. Silts and finer fractions derive from windblown dust, likely from White Volta River and granitic sources to the north. Soil forming processes and wide fluctuations in moisture have progressively reduced the sediments at depth to the resistant quartz and kaolinite, with rich iron oxide coatings, and created two ironstone horizons composed of goethite-cemented quartz nodules. Multiple aliquot green-light stimulated optical ages for 125-150 μm quartz grains yielded ages of 23.6±2.9 and 40.8±11.8 ka for the MSA-bearing sediments, and 58.4±15.3 ka for the base of the terrace. Radiocarbon ages on charcoal from Kintampo-bearing units are 3.36-3.83 ka cal BP, and are supported by thermoluminescence (TL) ages on pottery sherds and burnt house daub fragments of this cultural complex. A 0.4 ka age on sediment from the site's surface confirms that the quartz zeroes well when exposed to natural light

  2. The age of the Keystone thrust: laser-fusion 40Ar/39Ar dating of foreland basin deposits, southern Spring Mountains, Nevada

    USGS Publications Warehouse

    Fleck, R.J.; Carr, M.D.

    1990-01-01

    Nonmarine sedimentary and volcaniclastic foreland-basin deposits in the Spring Mountains are cut by the Contact and Keystone thrusts. These synorogenic deposits, informally designated the Lavinia Wash sequence by Carr (1980), previously were assigned a Late Jurassic to Early Cretaceous(?) age. New 40Ar.39Ar laser-fusion and incremental-heating studies of a tuff bed in the Lavinia Wash sequence support a best estimate age of 99.0 ?? 0.4 Ma, indicating that the Lavinia Wash sequence is actually late Early Cretaceous in age and establishing a maximum age for final emplacement of the Contact and Keystone thrust plates consistent with the remainder of the Mesozoic foreland thrust belt. -from Authors

  3. Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating

    NASA Astrophysics Data System (ADS)

    Mollenhauer, Gesine; Inthorn, Maik; Vogt, Thomas; Zabel, Matthias; Sinninghe Damsté, Jaap S.; Eglinton, Timothy I.

    2007-09-01

    Organic matter accumulation and burial on the Namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers. Much of the material deposited in depo-centers on the slope ultimately derives from the shelf. Supply of organic matter from the shelf involves selective transport of organic matter. We studied these selective transport processes by analyzing the radiocarbon content of co-occurring sediment fractions. Here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity (phytoplankton-derived alkenones, membrane lipids of pelagic crenarchaeota (crenarchaeol), and calcareous microfossils of planktic foraminifera) in core-top and near-surface sediment samples. The samples were collected on the Namibian margin along a shelf-slope transect (85 to 1040 m) at 24°S and from the upper slope depo-center at 25.5°S. In core-top sediments, alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth. Crenarchaeol, while younger than alkenones, also increased in age with distance offshore. It was concluded that the observed ages were a consequence of cross-shelf transport and associated aging of organic matter. Radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied, pre-aged material present in a sample, highlighting the importance of nepheloid transport for the sedimentation of organic matter over the Namibian margin.

  4. 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.-

  5. Relativistic Absolutism in Moral Education.

    ERIC Educational Resources Information Center

    Vogt, W. Paul

    1982-01-01

    Discusses Emile Durkheim's "Moral Education: A Study in the Theory and Application of the Sociology of Education," which holds that morally healthy societies may vary in culture and organization but must possess absolute rules of moral behavior. Compares this moral theory with current theory and practice of American educators. (MJL)

  6. Absolute Standards for Climate Measurements

    NASA Astrophysics Data System (ADS)

    Leckey, J.

    2016-10-01

    In a world of changing climate, political uncertainty, and ever-changing budgets, the benefit of measurements traceable to SI standards increases by the day. To truly resolve climate change trends on a decadal time scale, on-orbit measurements need to be referenced to something that is both absolute and unchanging. One such mission is the Climate Absolute Radiance and Refractivity Observatory (CLARREO) that will measure a variety of climate variables with an unprecedented accuracy to definitively quantify climate change. In the CLARREO mission, we will utilize phase change cells in which a material is melted to calibrate the temperature of a blackbody that can then be observed by a spectrometer. A material's melting point is an unchanging physical constant that, through a series of transfers, can ultimately calibrate a spectrometer on an absolute scale. CLARREO consists of two primary instruments: an infrared (IR) spectrometer and a reflected solar (RS) spectrometer. The mission will contain orbiting radiometers with sufficient accuracy to calibrate other space-based instrumentation and thus transferring the absolute traceability. The status of various mission options will be presented.

  7. New Sakmarian ages for the Rio Bonito formation (Paraná Basin, southern Brazil) based on LA-ICP-MS U-Pb radiometric dating of zircons crystals

    NASA Astrophysics Data System (ADS)

    Cagliari, Joice; Lavina, Ernesto Luiz Correa; Philipp, Ruy Paulo; Tognoli, Francisco Manoel Wohnrath; Basei, Miguel Angelo Stipp; Faccini, Ubiratan Ferrucio

    2014-12-01

    Two ash fall beds (tonstein) sampled from the post-glacial Permian deposits of the Paraná Basin have provided new U-Pb radiometric age constraints for this stratigraphic interval. The zircon grains were recovered from tonstein layers interbedded with fine-grained and carbonaceous lithologies in the middle portion of the Rio Bonito Formation. In both samples, the dominant population is interpreted as generated by explosive volcanism, as having formed immediately before the eruption. Based on 238U/206Pb, the selected zircon grains from the dominant population have weighted mean ages of 290.6 ± 2.8 Ma and 281.7 ± 3.2 Ma, corresponding to the Sakmarian and Kungurian ages in the Cisuralian epoch, respectively. These ages constrain the time of the deposition of the tonstein horizons and have important stratigraphic implications for the Late Paleozoic evolution of both the Paraná Basin and the southwestern region of Gondwana. The results presented here and the radiometric data already published suggest that deposition of the post-glacial coal-bearing deposits of the Rio Bonito Formation was probably initiated before the Early Permian. Thus, we infer that the climate had already ameliorated by this period in order to allow for the formation and accumulation of peat in this region of Gondwana.

  8. Integrated J- and H-band spectra of globular clusters in the LMC: implications for stellar population models and galaxy age dating

    NASA Astrophysics Data System (ADS)

    Lyubenova, M.; Kuntschner, H.; Rejkuba, M.; Silva, D. R.; Kissler-Patig, M.; Tacconi-Garman, L. E.

    2012-07-01

    Context. The rest-frame near-IR spectra of intermediate age (1-2 Gyr) stellar populations are dominated by carbon based absorption features offering a wealth of information. Yet, spectral libraries that include the near-IR wavelength range do not sample a sufficiently broad range of ages and metallicities to allow for accurate calibration of stellar population models and thus the interpretation of the observations. Aims: In this paper we investigate the integrated J- and H-band spectra of six intermediate age and old globular clusters in the Large Magellanic Cloud (LMC). Methods: The observations for six clusters were obtained with the SINFONI integral field spectrograph at the ESO VLT Yepun telescope, covering the J (1.09-1.41 μm) and H-band (1.43-1.86 μm) spectral range. The spectral resolution is 6.7 Å in J and 6.6 Å in H-band (FWHM). The observations were made in natural seeing, covering the central 24″ × 24″ of each cluster and in addition sampling the brightest eight red giant branch and asymptotic giant branch (AGB) star candidates within the clusters' tidal radii. Targeted clusters cover the ages of ~1.3 Gyr (NGC 1806, NGC 2162), 2 Gyr (NGC 2173) and ~13 Gyr (NGC 1754, NGC 2005, NGC 2019). Results.H-band C2 and K-band 12CO (2-0) feature strengths for the LMC globular clusters are compared to the models of Maraston (2005). C2 is reasonably well reproduced by the models at all ages, while 12CO (2-0) shows good agreement for older (age ≥ 2 Gyr) populations, but the younger (1.3 Gyr) globular clusters do not follow the models. We argue that this is due to the fact that the empirical calibration of the models relies on only a few Milky Way carbon star spectra, which show different 12CO (2-0) index strengths than the LMC stars. The C2 absorption feature strength correlates strongly with age. It is present essentially only in populations that have 1-2 Gyr old stars, while its value is consistent with zero for older populations. The distinct spectral

  9. Radiocarbon dating of terrestrial carbonates

    USGS Publications Warehouse

    Pigati, Jeffrey S.; Rink, W. Jack; Thompson, Jeroen

    2014-01-01

    Terrestrial carbonates encompass a wide range of materials that potentially could be used for radiocarbon (14C) dating. Biogenic carbonates, including shells and tests of terrestrial and aquatic gastropods, bivalves, ostracodes, and foraminifera, are preserved in a variety of late Quaternary deposits and may be suitable for 14C dating. Primary calcareous deposits (marls, tufa, speleothems) and secondary carbonates (rhizoliths, fracture fill, soil carbonate) may also be targeted for dating when conditions are favorable. This chapter discusses issues that are commonly encountered in 14C dating of terrestrial carbonates, including isotopic disequilibrium and open-system behavior, as well as methods used to determine the reliability of ages derived from these materials. Recent methodological advancements that may improve the accuracy and precision of 14C ages of terrestrial carbonates are also highlighted.

  10. Dating sediments using luminescence signals

    SciTech Connect

    Wintle, A. )

    1993-05-01

    Before siting a nuclear power station or a nuclear waste repository, it is necessary to establish that the area has been free of earthquake activity for a sufficient period of time. Evidence of past earthquake activity is often provided by faults in surface sediments. Age limits for fault formation can be set by obtaining the depositional ages of the sediment unit in which the fault was formed and the overlying sediment. A useful technique would be one that dating could be applied to the mineral grains that make up the sediments and that would give the time that has passed since the grains were blown or washed into position. Luminescence dating techniques, of which the most well known is thermo-luminescence (TL), provide such information. This approach has been successful in dating movement on the Wasatch Fault in Utah. A combination of TL and radiocarbon dates indicated that three faulting events had occurred within the past 5000 years. 2 refs., 1 fig.

  11. 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.

  12. 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.

  13. Physics of negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Abraham, Eitan; Penrose, Oliver

    2017-01-01

    Negative absolute temperatures were introduced into experimental physics by Purcell and Pound, who successfully applied this concept to nuclear spins; nevertheless, the concept has proved controversial: a recent article aroused considerable interest by its claim, based on a classical entropy formula (the "volume entropy") due to Gibbs, that negative temperatures violated basic principles of statistical thermodynamics. Here we give a thermodynamic analysis that confirms the negative-temperature interpretation of the Purcell-Pound experiments. We also examine the principal arguments that have been advanced against the negative temperature concept; we find that these arguments are not logically compelling, and moreover that the underlying "volume" entropy formula leads to predictions inconsistent with existing experimental results on nuclear spins. We conclude that, despite the counterarguments, negative absolute temperatures make good theoretical sense and did occur in the experiments designed to produce them.

  14. 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.

  15. Radioactive dating of the elements

    NASA Technical Reports Server (NTRS)

    Cowan, John J.; Thielemann, Friedrich-Karl; Truran, James W.

    1991-01-01

    The extent to which an accurate determination of the age of the Galaxy, and thus a lower bound on the age of the universe, can be obtained from radioactive dating is discussed. Emphasis is given to the use of the long-lived radioactive nuclei Re-187, Th-232, U-238, and U-235. The nature of the production sites of these and other potential Galactic chronometers is examined along with their production ratios. Age determinations from models of nucleocosmochronology are reviewed and compared with age determination from stellar sources and age constraints form cosmological considerations.

  16. The impact of minimum legal drinking age laws on alcohol consumption, smoking, and marijuana use: evidence from a regression discontinuity design using exact date of birth.

    PubMed

    Yörük, Barış K; Yörük, Ceren Ertan

    2011-07-01

    This paper uses a regression discontinuity design to estimate the impact of the minimum legal drinking age laws on alcohol consumption, smoking, and marijuana use among young adults. Using data from the National Longitudinal Survey of Youth (1997 Cohort), we find that granting legal access to alcohol at age 21 leads to an increase in several measures of alcohol consumption, including an up to a 13 percentage point increase in the probability of drinking. Furthermore, this effect is robust under several different parametric and non-parametric models. We also find some evidence that the discrete jump in alcohol consumption at age 21 has negative spillover effects on marijuana use but does not affect the smoking habits of young adults. Our results indicate that although the change in alcohol consumption habits of young adults following their 21st birthday is less severe than previously known, policies that are designed to reduce drinking among young adults may have desirable impacts and can create public health benefits.

  17. In situ radiometric dating on Mars: Investigation of the feasibility of K-Ar dating using flight-type mass and X-ray spectrometers

    NASA Astrophysics Data System (ADS)

    Talboys, D. L.; Barber, S.; Bridges, J. C.; Kelley, S. P.; Pullan, D.; Verchovsky, A. B.; Butcher, G.; Fazel, A.; Fraser, G. W.; Pillinger, C. T.; Sims, M. R.; Wright, I. P.

    2009-09-01

    The absolute chronology of Mars is poorly known and, as a consequence, a key science aim is to perform accurate radiometric dating of martian geological materials. The scientific benefits of in situ radiometric dating are significant and arguably of most importance is the calibration of the martian cratering rate, similar to what has been achieved for the Moon, to reduce the large uncertainties on absolute boundary ages of martian epochs. The Beagle 2 Mars lander was capable of performing radiometric date measurements of rocks using the analyses from two instruments in its payload: (i) the X-ray Spectrometer (XRS) and (ii) the Gas Analysis Package (GAP). We have investigated the feasibility of in situ radiometric dating using the K-Ar technique employing flight-like versions of Beagle 2 instrumentation. The K-Ar ages of six terrestrial basalts were measured and compared to the 'control' Ar-Ar radiometric ages in the range 171-1141 Ma. The K content of each basalt was measured by the flight spare XRS and the 40Ar content using a laboratory analogue of the GAP. The K-Ar ages of five basalts broadly agreed with their corresponding Ar-Ar ages. For one final basalt, the 40Ar content was below the detection limit and so an age could not be derived. The precision of the K-Ar ages was ˜30% on average. The conclusions from this study are that careful attention must be paid to improving the analytical performance of the instruments, in particular the accuracy and detection limits. The accuracy of the K and Ar measurements are the biggest source of uncertainty in the derived K-Ar age. Having investigated the technique using flight-type planetary instrumentation, we conclude that come of the principle challenges of conducting accurate in situ radiometric dating on Mars using instruments of these types include determining the sample mass, ensuring all the argon is liberated from the sample given the maximum achievable temperature of the mass spectrometer ovens, and argon loss

  18. 210Pb dating

    USGS Publications Warehouse

    Swarzenski, Peter W.

    2014-01-01

    Roughly fifty years ago, a small group of scientists from Belgium and the United States, trying to better constrain ice sheet accumulation rates, attempted to apply what was then know about environmental lead as a potential geochronometer. Thus Goldberg (1963) developed the first principles of the 210Pb dating method, which was soon followed by a paper by Crozaz et al. (1964), who examined accumulation history of Antarctic snow using 210Pb. Shortly thereafter, Koide et al. (1972, 1973) adapted this technique to unravel sediment deposition and accumulation records in deep-sea environments. Serendipitously, they chose to work in a deep basin off California, where an independent and robust age model had already been developed. Krishanswami et al. (1971) extended the use of this technique to lacustrine deposits to reconstruct depositional histories of lake sediment, and maybe more importantly, contaminant inputs and burial. Thus, the powerful tool for dating recent (up to about one century old) sediment deposits was established and soon widely adopted. Today almost all oceanographic or limnologic studies that address recent depositional reconstructions employ 210Pb as one of several possible geochronometers (Andrews et al., 2009; Gale, 2009; Baskaran, 2011; Persson and Helms, 2011). This paper presents a short overview of the principles of 210Pb dating and provides a few examples that illustrate the utility of this tracer in contrasting depositional systems. Potential caveats and uncertainties (Appleby et al., 1986; Binford, 1990; Binford et al., 1993; Smith, 2001; Hancock et al., 2002) inherent to the use and interpretation of 210Pb-derived age-models are also introduced. Recommendations as to best practices for most reliable uses and reporting are presented in the summary.

  19. Antiquity of man in America indicated by radiometric dates on the Yuha burial site

    USGS Publications Warehouse

    Bischoff, J.L.; Merriam, R.; Childers, W.M.; Protsch, R.

    1976-01-01

    MUCH evidence suggests that man was present in the Western Hemisphere before 12,000 yr ago, but the case has remained less than conclusive 1. In some situations, the geological age of the site is reasonably well established but the association or nature of the artefacts is questionable2,3. In other cases, museum specimens of human bones dated by radiocarbon analysis of collagen lack desirable information concerning site location, geology, and stratigraphy even though the accuracy of their absolute ages seems valid4-6. We report here the results of radiometric dates of the Yuha burial site from Imperial County, California, for which the geology and stratigraphy have been documented and reported in detail7. ?? 1976 Nature Publishing Group.

  20. Suitability of biogenic carbonate of Lithospermum fruits for 14C dating

    NASA Astrophysics Data System (ADS)

    Pustovoytov, Konstantin; Riehl, Simone

    2006-05-01

    Lithospermum (Boraginaceae) belongs to a small group of plant taxa that accumulate biogenic carbonate in their fruits. In this genus, carbonate incrustations form in the cells of the epidermis and sclerenchyma of the pericarp. Fossil Lithospermum fruits (nutlets) with well-preserved calcified tissues commonly occur in Quaternary sediments and cultural layers. We tested the suitability of biogenic carbonate of Lithospermum fruits for radiocarbon dating using a total of 15 AMS measurement results from four modern and 11 fossil samples. The 14C data from modern samples suggest that Lithospermum utilises only atmospheric carbon to synthesise calcite in the nutlets. In general, the ages determined through 14C dating of fossil fruitscorresponded well with the absolute-age intervals for archaeological sites over the last 5000 yr. Biogenic carbonate of Lithospermum fruits, like that of Celtis, represents a new source of chronological information for late Quaternary studies.

  1. [Estimation of absolute risk for fracture].

    PubMed

    Fujiwara, Saeko

    2009-03-01

    Osteoporosis treatment aims to prevent fractures and maintain the QOL of the elderly. However, persons at high risk of future fracture cannot be effectively identified on the basis of bone density (BMD) alone, although BMD is used as an diagnostic criterion. Therefore, the WHO recommended that absolute risk for fracture (10-year probability of fracture) for each individual be evaluated and used as an index for intervention threshold. The 10-year probability of fracture is calculated based on age, sex, BMD at the femoral neck (body mass index if BMD is not available), history of previous fractures, parental hip fracture history, smoking, steroid use, rheumatoid arthritis, secondary osteoporosis and alcohol consumption. The WHO has just announced the development of a calculation tool (FRAX: WHO Fracture Risk Assessment Tool) in February this year. Fractures could be prevented more effectively if, based on each country's medical circumstances, an absolute risk value for fracture to determine when to start medical treatment is established and persons at high risk of fracture are identified and treated accordingly.

  2. Using postnatal age to determine test dates leads to misinterpretations when treatments alter gestation length: results from a collaborative behavioral teratology study in Japan.

    PubMed

    Tachibana, T; Narita, H; Ogawa, T; Tanimura, T

    1998-01-01

    A collaborative study was conducted by researchers from 18 laboratories that participated in the Behavioral Teratology Meeting in Japan. Pregnant Sprague-Dawley rats from four breeders received subcutaneous injections of nicotine (6 mg/kg body weight) from day 7 to day 20 of gestation. Results of preweaning tests were closely related to length of gestation, and prolonged gestation was seen in the nicotine group. The effects of nicotine were compared with and without the adjustment of the mean difference in gestational lengths. Without the adjustment (i.e., by employing assessment in terms of postnatal day) several perplexing results were obtained, indicating that the nicotine group developed more quickly than the control group on several preweaning tests. By employing the adjustment, these perplexing results disappeared, indicating that the nicotine group developed more slowly than the control group. The merit of employing gestational day (or postcoital age) as an alternative index is emphasized.

  3. Identifying sources of dissolved organic carbon in agriculturally dominated rivers using radiocarbon age dating: Sacramento-San Joaquin River Basin, California

    USGS Publications Warehouse

    Sickman, James O.; DiGiorgio, Carol L.; Davisson, M. Lee; Lucero, Delores M.; Bergamaschi, Brian A.

    2010-01-01

    We used radiocarbon measurements of dissolved organic carbon (DOC) to resolve sources of riverine carbon within agriculturally dominated landscapes in California. During 2003 and 2004, average Δ14C for DOC was −254‰ in agricultural drains in the Sacramento–San Joaquin Delta, −218‰ in the San Joaquin River, −175‰ in the California State Water Project and −152‰ in the Sacramento River. The age of bulk DOC transiting the rivers of California’s Central Valley is the oldest reported for large rivers and suggests wide-spread loss of soil organic matter caused by agriculture and urbanization. Using DAX 8 adsorbent, we isolated and measured 14C concentrations in hydrophobic acid fractions (HPOA); river samples showed evidence of bomb-pulse carbon with average Δ14C of 91 and 76‰ for the San Joaquin and Sacramento Rivers, respectively, with older HPOA, −204‰, observed in agricultural drains. An operationally defined non-HPOA fraction of DOC was observed in the San Joaquin River with seasonally computed Δ14C values of between −275 and −687‰; the source of this aged material was hypothesized to be physically protected organic-matter in high clay-content soils and agrochemicals (i.e., radiocarbon-dead material) applied to farmlands. Mixing models suggest that the Sacramento River contributes about 50% of the DOC load in the California State Water Project, and agricultural drains contribute approximately one-third of the load. In contrast to studies showing stabilization of soil carbon pools within one or two decades following land conversion, sustained loss of soil organic matter, occurring many decades after the initial agricultural-land conversion, was observed in California’s Central Valley.

  4. A New Absolute Plate Motion Model for Africa

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    The India-Eurasia collision, a change in relative plate motion between Australia and Antarctica, and the coeval ages of the Hawaiian Emperor Bend (HEB) and Louisville Bend of ~Chron 22-21 all provide convincing evidence of a global tectonic plate reorganization at ~50 Ma. Yet if it were a truly global event, then there should be a contemporaneous change in Africa absolute plate motion (APM) reflected by physical evidence somewhere on the Africa plate. This evidence might be visible in the Reunion-Mascarene bend, which exhibits many HEB-like features such as a large angular change close to ~50 Ma. Recently, the Reunion hotpot trail has been interpreted as a continental feature with incidental hotspot volcanism. Here we propose the alternative hypothesis that the northern portion of the chain between Saya de Malha and the Seychelles (Mascarene Plateau) formed as the Reunion hotspot was situated on the Carlsberg Ridge, contemporaneously forming the Chagos-Laccadive Ridge on the India plate. We have created a 4-stage model that explores how a simple APM model fitting the Mascarene Plateau can also satisfy the age progressions and geometry of other hotspot trails on the Africa plate. This type of model could explain the apparent bifurcation of the Tristan hotspot chain, the age reversals seen along the Walvis Ridge and the diffuse nature of the St. Helena chain. To test this hypothesis we have made a new African APM model that goes 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 its motion through time. The positions of the hotspots can be moved to get the best fit for the model and to explore the possibility that the ~50 Ma bend in the Reunion-Mascarene chain reflects Africa plate motion. We will examine how well this model can predict the key features reflecting Africa plate motion and

  5. Dating volcanic ash by use of thermoluminescence

    SciTech Connect

    Berger, G.W. )

    1992-01-01

    The fine-silt-sized (4-11 {mu}m) grains of glass separated from four samples of independently dated, 8 to 400 ka, tephra beds provide accurate thermoluminescence (TL) ages. This demonstration of reliable TL dating of volcanic glass provides a new tephrochronometer for deposits spanning the Holocene to middle Pleistocene age range.

  6. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N.

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  7. New zircon ages on the Cambrian-Ordovician volcanism of the Southern Gemericum basement (Western Carpathians, Slovakia): SHRIMP dating, geochemistry and provenance

    NASA Astrophysics Data System (ADS)

    Vozárová, Anna; Rodionov, Nickolay; Šarinová, Katarína; Presnyakov, Sergey

    2016-11-01

    The Southern Gemericum basement in the Inner Western Carpathians, composed of low-grade volcano-sedimentary rock complexes, constitutes a record of the polyphase Cambrian-Ordovician continental volcanic arc volcanism. These metavolcanic rocks are characterized by the enrichment in K, Rb, Ba, Th and Ce and Sm relative to Ta, Nb, Hf, Zr, Y and Yb that are the characteristic features for volcanic arc magmatites. The new SHRIMP U-Pb zircon data and compilation of previously published and re-evaluated zircon ages, contribute to a new constrain of the timing of the Cambrian-Ordovician volcanism that occurred between 496 and 447 Ma. The following peaks of the volcanic activity of the Southern Gemericum basement have been recognized: (a) mid-late Furongian at 492 Ma; (b) Tremadocian at 481 Ma; (c) Darriwilian at 464 Ma prolonged to 453 Ma within the early Upper Ordovician. The metavolcanic rocks are characterized by a high zircon inheritance, composed of Ediacaran (650-550 Ma), Tonian-Stenian (1.1-0.9 Ma), and, to a lesser extent, Mesoproterozoic (1.3 Ga), Paleoproterozoic (1.9 Ga) and Archaean assemblages (2.6 Ga). Based on the acquired zircon populations, it could be deduced that Cambrian-Ordovician arc crust was generated by a partial melting of Ediacaran basement in the subduction-related setting, into which old crustal fragments were incorporated. The ascertained zircon inheritances with Meso-, Paleoproterozoic and Archaean cores indicate the similarities with the Saharan Metacraton provenance.

  8. 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.

  9. Dating for Older Women: Experiences and Meanings of Dating in Later Life

    PubMed Central

    Watson, Wendy K.; Stelle, Charlie

    2013-01-01

    Research over the last 20 years has provided an increased understanding of intimate relationships in later life; however, dating in later life remains largely unexplored. The purpose of this study was to examine the meanings of dating for women in later life. In this study, dating was examined through semistructured, in-depth interviews with 14 women ages 64 to 77 who had all dated in later life. Themes that emerged from an interpretative phenomenological analysis included multiple meanings of dating in later life, how dating in later life compared to earlier points in life, and dating in the future. PMID:21767089

  10. Radiocarbon dates of late quaternary mammals in the Archangelsk Region and their contribution to reconstructions of the last glaciation in Eastern Europe

    NASA Astrophysics Data System (ADS)

    Ponomarev, D. V.; Markova, A. K.; van Kolfschoten, T.; van der Plicht, J.

    2012-06-01

    Twelve new AMS (Accelerator Mass Spectrometry) dates of large Quaternary mammal remains were reported: mammoth ( Mammuthus primigenius, bison ( Bison priscus), and musk ox ( Ovibos pallantis) found in the Archangelsk Region. The absolute age of the identified samples varies from 46 000 to 22 000 calibrated years ago. These data suggest that a substantial part of the Archangelsk Region was not covered by ice during the indicated time interval.

  11. First krypton-81 dating of glacial ice at Taylor Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Severinghaus, J. P.

    2015-12-01

    A long-held dream of glaciologists has been the direct radiometric dating of ancient glacial ice. Carbon-14 is unfortunately complicated by in-situ cosmogenic production of this isotope from cosmic ray spallation on oxygen nuclei in the ice. Krypton-81 is an ideal tracer in several ways: it has no anthropogenic sources, is made in the atmosphere by cosmic ray spallation on stable krypton nuclei, and it has a half-life of 229 kyr, which is a useful age range for ancient glacial ice samples. However, the abundance of krypton-81 is dauntingly low. Recent analytical advances by a team of physicists at Argonne National Labs has now made it possible to measure practical quantities of ice (50 kg) by Atom Trap Trace Analysis (ATTA), a technique using lasers to cool krypton-81 atoms to absolute zero and trap them, enabling accurate counting of single atoms. The precision attained by this technique approaches 0.5%, implying an age accuracy of about 1000 yr for samples from the last interglacial period. Here we show that krypton-81 dating has been successfully applied for the first time, to an outcrop of ancient ice dating from the last interglacial period (125 kyr BP) at Taylor Glacier, Antarctica, which is independently dated using methane and d18O of atmospheric oxygen for stratigraphic matching to well-dated Chinese speleothem records.

  12. Laboratory for Radiokrypton Dating

    NASA Astrophysics Data System (ADS)

    Zappala, J. C.; Jiang, W.; Bailey, K. G.; Lu, Z. T.; Mueller, P.; O'Connor, T. P.

    2015-12-01

    Due to its simple production and transport in the terrestrial environment, 81Kr (half-life = 230,000 yr) is the ideal tracer for old water and ice with mean residence times in the range of 105-106 years, a range beyond the reach of 14C. 81Kr-dating is now available to the earth science community at large thanks to the development of an efficient and selective atom counter based on the Atom Trap Trace Analysis (ATTA) method. ATTA is a laser-based atom counting method where individual neutral atoms of the desired isotope are selectively captured by laser beams, and their fluorescence detected via a CCD camera. ATTA is unique among trace analysis techniques in that it is free of interferences from any other isotopes, isobars, atomic or molecular species. The ATTA instrument at Argonne's Laboratory for Radiokrypton Dating is capable of measuring both 81Kr/Kr and 85Kr/Kr ratios of environmental samples in the range of 10-14-10-10. For 81Kr-dating in the age range of 150 kyr - 1500 kyr, the required sample size is 5 micro-L STP of krypton gas, which can be extracted from approximately 100 kg of water or 40 kg of ice. For 85Kr/Kr analysis, the sample size can be smaller by an order of magnitude. We are continually developing the method towards higher counting efficiency, smaller sample sizes requirements, and higher sample throughput rates. In the past four years, we have performed radiokrypton analysis of over 150 groundwater and ice samples extracted by collaborators from all seven continents. Sample collection and purification was performed by groups including the University of Chicago, the University of Illinois at Chicago, the University of Bern, and the International Atomic Energy Agency. This work is supported by the U.S. DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

  13. Planets Around Low-mass Stars (PALMS). V. Age-dating Low-mass Companions to Members and Interlopers of Young Moving Groups

    NASA Astrophysics Data System (ADS)

    Bowler, Brendan P.; Shkolnik, Evgenya L.; Liu, Michael C.; Schlieder, Joshua E.; Mann, Andrew W.; Dupuy, Trent J.; Hinkley, Sasha; Crepp, Justin R.; Johnson, John Asher; Howard, Andrew W.; Flagg, Laura; Weinberger, Alycia J.; Aller, Kimberly M.; Allers, Katelyn N.; Best, William M. J.; Kotson, Michael C.; Montet, Benjamin T.; Herczeg, Gregory J.; Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Nielsen, Eric L.; Wahhaj, Zahed; Biller, Beth A.; Hayward, Thomas L.

    2015-06-01

    We present optical and near-infrared adaptive optics (AO) imaging and spectroscopy of 13 ultracool (>M6) companions to late-type stars (K7-M4.5), most of which have recently been identified as candidate members of nearby young moving groups (YMGs; 8-120 Myr) in the literature. Three of these are new companions identified in our AO imaging survey, and two others are confirmed to be comoving with their host stars for the first time. The inferred masses of the companions (˜10-100 MJup) are highly sensitive to the ages of the primary stars; therefore we critically examine the kinematic and spectroscopic properties of each system to distinguish bona fide YMG members from old field interlopers. The new M7 substellar companion 2MASS J02155892-0929121 C (40-60 MJup) shows clear spectroscopic signs of low gravity and, hence, youth. The primary, possibly a member of the ˜40 Myr Tuc-Hor moving group, is visually resolved into three components, making it a young low-mass quadruple system in a compact (≲100 AU) configuration. In addition, Li i λ6708 absorption in the intermediate-gravity M7.5 companion 2MASS J15594729+4403595 B provides unambiguous evidence that it is young (≲200 Myr) and resides below the hydrogen-burning limit. Three new close-separation (<1″) companions (2MASS J06475229-2523304 B, PYC J11519+0731 B, and GJ 4378 Ab) orbit stars previously reported as candidate YMG members, but instead are likely old (≳1 Gyr) tidally locked spectroscopic binaries without convincing kinematic associations with any known moving group. The high rate of false positives in the form of old active stars with YMG-like kinematics underscores the importance of radial velocity and parallax measurements to validate candidate young stars identified via proper motion and activity selection alone. Finally, we spectroscopically confirm the cool temperature and substellar nature of HD 23514 B, a recently discovered M8 benchmark brown dwarf orbiting the dustiest-known member of the

  14. PLANETS AROUND LOW-MASS STARS (PALMS). V. AGE-DATING LOW-MASS COMPANIONS TO MEMBERS AND INTERLOPERS OF YOUNG MOVING GROUPS

    SciTech Connect

    Bowler, Brendan P.; Montet, Benjamin T.; Riddle, Reed; Shkolnik, Evgenya L.; Flagg, Laura; Liu, Michael C.; Howard, Andrew W.; Aller, Kimberly M.; Best, William M. J.; Kotson, Michael C.; Baranec, Christoph; Schlieder, Joshua E.; Mann, Andrew W.; Dupuy, Trent J.; Hinkley, Sasha; Crepp, Justin R.; Johnson, John Asher; Weinberger, Alycia J.; Allers, Katelyn N.; Herczeg, Gregory J.; and others

    2015-06-10

    We present optical and near-infrared adaptive optics (AO) imaging and spectroscopy of 13 ultracool (>M6) companions to late-type stars (K7–M4.5), most of which have recently been identified as candidate members of nearby young moving groups (YMGs; 8–120 Myr) in the literature. Three of these are new companions identified in our AO imaging survey, and two others are confirmed to be comoving with their host stars for the first time. The inferred masses of the companions (∼10–100 M{sub Jup}) are highly sensitive to the ages of the primary stars; therefore we critically examine the kinematic and spectroscopic properties of each system to distinguish bona fide YMG members from old field interlopers. The new M7 substellar companion 2MASS J02155892–0929121 C (40–60 M{sub Jup}) shows clear spectroscopic signs of low gravity and, hence, youth. The primary, possibly a member of the ∼40 Myr Tuc-Hor moving group, is visually resolved into three components, making it a young low-mass quadruple system in a compact (≲100 AU) configuration. In addition, Li i λ6708 absorption in the intermediate-gravity M7.5 companion 2MASS J15594729+4403595 B provides unambiguous evidence that it is young (≲200 Myr) and resides below the hydrogen-burning limit. Three new close-separation (<1″) companions (2MASS J06475229–2523304 B, PYC J11519+0731 B, and GJ 4378 Ab) orbit stars previously reported as candidate YMG members, but instead are likely old (≳1 Gyr) tidally locked spectroscopic binaries without convincing kinematic associations with any known moving group. The high rate of false positives in the form of old active stars with YMG-like kinematics underscores the importance of radial velocity and parallax measurements to validate candidate young stars identified via proper motion and activity selection alone. Finally, we spectroscopically confirm the cool temperature and substellar nature of HD 23514 B, a recently discovered M8 benchmark brown dwarf orbiting the

  15. Absolute measurements of the uranium concentration in thick samples using fission-track detectors

    NASA Astrophysics Data System (ADS)

    Enkelmann, Eva; Jonckheere, Raymond; Ratschbacher, Lothar

    2005-04-01

    We propose an improved equation for calculating the uranium concentration in thick samples based on induced fission-track counts in an external detector that takes into consideration (1) the fission-fragment ranges in the sample and external detector, (2) the etchable track length and (3) the track counting efficiency in the external detector. The values of these parameters have been determined by calculation and experiment and are shown to have a significant effect on the calculated uranium concentrations. The new equation was tested by calculating the uranium concentrations in standard uranium glasses (CN-5; IRMM-540R) and apatite samples (Durango; horse tooth) in which the uranium content was also determined with independent methods (INAA; ENAA; TIMS). The results show that: (1) accurate measurements with the fission-track method are feasible within a broad range of uranium concentrations and (2) uranium determinations based on standards are only accurate if the standard and sample are made of the same material. Because the absolute fission-tack dating method is also based on accurate thermal neutron fluence measurements and similar correction factors for the track registration and counting efficiencies, this study provides a strong endorsement for the fact that absolute fission-track ages are accurate.

  16. Formation ages and thermal histories of fracture-filling hematite and Mn-oxide in Precambrian basement from (U-Th)/He dating and 4He/3He diffusion experiments

    NASA Astrophysics Data System (ADS)

    Reiners, P. W.; Shuster, D. L.; Evenson, N.

    2015-12-01

    Secondary Fe- and Mn-oxides in bedrock form from fluid flow associated with events that may not be preserved in stratigraphic records. (U-Th)/He chronometry is well suited for dating these phases but potential diffusive loss of 4He can complicate interpretations. Here we show that measuring He diffusion kinetics of dated samples can resolve whether ages record formation or cooling. Proterozoic (1.6 Ga) volcanics in Aravaipa Canyon, southern Arizona, contain 1.4-1.6-Ga quartz-vein-hosted hematite, as well as 1.0-1.1-Ga hematite precipitated on fractures and overlain by 20-30-Ma Mn-oxide. Hematite 4He/3He age spectra and multi-domain (MD) diffusion models are consistent with a small proportion (4-10%) of domains between 1-500 nm, larger proportions (5-15%) of 1-10 μm domains, and a majority (60-75%) of domains of 80-150 μm. Although the smallest domains would have extremely low He retentivity, models predict bulk "closure temperatures" of 180-200 °C. The 1.4-1.6-Ga quartz-vein hematite likely formed soon after eruption of its host rock, and has not been hotter than ~250 °C for Ma durations. The 1.0-1.1 Ga age of the fracture-fill hematite likely also records the timing of precipitation, but from fluids associated with nearby diabase of the same age. In contrast, the 4He/3He MD model of the 20-30-Ma Mn-oxide requires ~80% of 1-100 nm domains and 20% between 1-10 μm. Although the Mn-oxide likely formed at the same time as the hematite it coats, its age records transient heating from overlying 28-Ma volcanics. In all cases, approximate crystal sizes observed in SEM images are consistent with the predictions of MD modeling, and support the assumed kinetics of He diffusion (~147-157 kJ/mol and ~2.2×10-4 cm2/s for hematite, and ~134 kJ/mol and ~4×10-3 cm2/s for Mn-oxide).These results suggest that specular hematite can have bulk He closure temperatures at least as high as 200 °C and in some cases record precipitation; this is supported by our results on specularite

  17. Post-glacial landforms dating by lichenometry in Iceland - the accuracy of relative results and conversely

    NASA Astrophysics Data System (ADS)

    Decaulne, Armelle

    2014-05-01

    Lichenometry studies are carried out in Iceland since 1970 all over the country, using various techniques to solve a range of geomorphologic issues, from moraine dating and glacial advances, outwash timing, proglacial river incision, soil erosion, rock-glacier development, climate variations, to debris-flow occurrence and extreme snow-avalanche frequency. Most users have sought to date proglacial landforms in two main areas, around the southern ice-caps of Vatnajökull and Myrdalsjökull; and in Tröllaskagi in northern Iceland. Based on the results of over thirty five published studies, lichenometry is deemed to be successful dating tool in Iceland, and seems to approach an absolute dating technique at least over the last hundred years, under well constrained environmental conditions at local scale. With an increasing awareness of the methodological limitations of the technique, together with more sophisticated data treatments, predicted lichenometric 'ages' are supposedly gaining in robustness and in precision. However, comparisons between regions, and even between studies in the same area, are hindered by the use of different measurement techniques and data processing. These issues are exacerbated in Iceland by rapid environmental changes across short distances and, more generally, by the common problems surrounding lichen species mis-identification in the field; not mentioning the age discrepancy offered by other dating tools, such as tephrochronology. Some authors claim lichenometry can help to a precise reconstruction of landforms and geomorphic processes in Iceland, proposing yearly dating, others includes margin errors in their reconstructions, while some limit its use to generation identifications, refusing to overpass the nature of the gathered data and further interpretation. Finally, can lichenometry be a relatively accurate dating technique or rather an accurate relative dating tool in Iceland?

  18. 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.

  19. 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.

  20. New developments with Schmidt-hammer exposure-age dating (SHD): Comparison of mechanical and electronic Schmidt-hammers - towards a conversion factor for Q- and R-values

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan; Matthews, John; Corbett, David

    2014-05-01

    Developed as an instrument for in situ destruction-free testing of concrete hardness in construction works, the Schmidt-hammer has subsequently been introduced and applied in various fields of geomorphology and geology. In the context of investigating Late Glacial and Holocene glacier chronologies, the Schmidt-hammer has been widely used as a relative-age dating technique. Such applications have for example successfully separated moraines formed during different glacier advance periods ('Little Ice Age'-type events). Pilot studies combined Schmidt-hammer measurements with available radiocarbon ages in order to achieve age constraints. Schmidt-hammer exposure-age dating (SHD) combining Schmidt-hammer and terrestrial cosmogenic nuclide dating (TCND) has recently been successfully applied in Norway and New Zealand. Schmidt-hammer tests have also been used to ensure the representativeness of boulders selected for TCND sampling. Especially in mountain regions with a high "geomorphological uncertainty" with the dating of Holocene moraines the inherited multi-proxy approach of SHD owns a considerable potential for reliable investigations of Late Glacial/Holocene glacier chronologies and their palaeoclimatic interpretation. An electronic Schmidt-hammer (named SilverSchmidt) was introduced by the manufacturer of the original mechanical Schmidt-hammer (Proceq SA) a few years ago. It offers especially facilities for much easier data processing and constitutes, therefore, a major improvement and potential replacement for the mechanical Schmidt-hammer. However, its different approach to the measurement of surface hardness - based on Q-(velocity) values instead of R-(rebound) values - means that measurements from the two instruments are not easily interconvertible. Prior to any considerations of using the instruments interchangeably or replacing the mechanical Schmidt-hammer in future studies with the SilverSchmidt, comparative tests under field conditions need to be undertaken

  1. The influence of year, laying date, egg fertility and incubation, individual hen, hen age and mass and clutch size on maternal immunoglobulin Y concentration in captive Steller's and spectacled eider egg yolk.

    PubMed

    Counihan, Katrina L; Maniscalco, John M; Bozza, Maryann; Hendon, Jill M; Hollmén, Tuula E

    2015-09-01

    Steller's eiders and spectacled eiders are sea duck species whose populations have declined significantly and infectious diseases could influence offspring survival. Therefore, the maternal transfer of immunoglobulin Y (IgY) into yolk was investigated in captive Steller's and spectacled eiders during the 2007-2013 breeding seasons. This project had two objectives: establish baseline IgY levels in Steller's and spectacled eider yolk under controlled captive conditions and evaluate the effect of year, laying date, egg fertility, egg incubation duration, individual hen, hen age and mass, and laying order to determine which variables influenced IgY levels. Average IgY concentrations were 0.03-0.48 mg ml(-1) in Steller's eider yolk and 0.10-0.51 mg ml(-1) in spectacled eider yolk. The year and individual hen influenced IgY concentration in Steller's and spectacled eider yolk. The laying date was negatively correlated with egg IgY levels for most Steller's eider hens, but laying order was positively correlated with egg IgY concentration for spectacled eiders.

  2. Peer involvement in adolescent dating violence.

    PubMed

    Stephenson, Pam S; Martsolf, Donna; Draucker, Claire Burke

    2013-06-01

    This study investigated the ways in which peers are involved in adolescent dating violence. Eighty-eight young adults aged 18-21 were interviewed and asked to reflect on aggressive dating relationships they experienced as teens. The researchers used grounded theory to analyze the data. Findings showed that male and female peers were involved in adolescent dating violence in unique ways. Male peers were involved in dating violence by participating in the aggression, agitating the aggression, being the competition, trivializing the aggression, and keeping tabs on the recipient. Female peers were involved in dating violence by deserting the recipient, cheating with the boyfriend, being the audience, needling the male dating partner, and helping the recipient. Male and female peers were involved similarly in adolescent dating violence by confronting the partner. School nurses working with adolescents are uniquely positioned to approach adolescents about dating violence. Interventions aimed at promoting discussions with adolescents are discussed.

  3. Hydrogeology, Ground-Water-Age Dating, Water Quality, and Vulnerability of Ground Water to Contamination in a Part of the Whitewater Valley Aquifer System near Richmond, Indiana, 2002-2003

    USGS Publications Warehouse

    Buszka, Paul M.; Watson, Lee R.; Greeman, Theodore K.

    2007-01-01

    Results of detailed water-quality analyses, ground-waterage dating, and dissolved-gas analyses indicated the vulnerability of ground water to specific types of contamination, the sequence of contaminant introduction to the aquifer relative to greenfield development, and processes that may mitigate the contamination. Concentrations of chloride and sodium and chloride/bromide weight ratios in sampled water from five wells indicated the vulnerability of the upper aquifer to roaddeicer contamination. Ground-water-age estimates from these wells indicated the onset of upgradient road-deicer use within the previous 25 years. Nitrate in the upper aquifer predates the post-1972 development, based on a ground-water-age date (30 years) and the nitrate concentration (5.12 milligrams per liter as nitrogen) in water from a deep well. Vulnerability of the aquifer to nitrate contamination is limited partially by denitrification. Detection of one to four atrazine transformation products in water samples from the upper aquifer indicated biological and hydrochemical processes that may limit the vulnerability of the ground water to atrazine contamination. Microbial processes also may limit the aquifer vulnerability to small inputs of halogenated aliphatic compounds, as indicated by microbial transformations of trichlorofluoromethane and trichlorotrifluoroethane relative to dichlorodifluoromethane. The vulnerability of ground water to contamination in other parts of the aquifer system also may be mitigated by hydrodynamic dispersion and biologically mediated transformations of nitrate, pesticides, and some organic compounds. Identification of the sequence of contamination and processes affecting the vulnerability of ground water to contamination would have been unlikely with conventional assessment methods.

  4. Absolute and relative family affluence and psychosomatic symptoms in adolescents.

    PubMed

    Elgar, Frank J; De Clercq, Bart; Schnohr, Christina W; Bird, Phillippa; Pickett, Kate E; Torsheim, Torbjørn; Hofmann, Felix; Currie, Candace

    2013-08-01

    Previous research on the links between income inequality and health and socioeconomic differences in health suggests that relative differences in affluence impact health and well-being more than absolute affluence. This study explored whether self-reported psychosomatic symptoms in adolescents relate more closely to relative affluence (i.e., relative deprivation or rank affluence within regions or schools) than to absolute affluence. Data on family material assets and psychosomatic symptoms were collected from 48,523 adolescents in eight countries (Austria, Belgium, Canada, Norway, Scotland, Poland, Turkey, and Ukraine) as part of the 2009/10 Health Behaviour in School-aged Children study. Multilevel regression analyses of the data showed that relative deprivation (Yitzhaki Index, calculated in regions and in schools) and rank affluence (in regions) (1) related more closely to symptoms than absolute affluence, and (2) related to symptoms after differences in absolute affluence were held constant. However, differences in family material assets, whether they are measured in absolute or relative terms, account for a significant variation in adolescent psychosomatic symptoms. Conceptual and empirical issues relating to the use of material affluence indices to estimate socioeconomic position are discussed.

  5. Potential improvement of Schmidt-hammer exposure-age dating (SHD) of moraines in the Southern Alps, New Zealand, by application of the new electronic Schmidt-hammer (SilverSchmidt)

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan; Corbett, David

    2014-05-01

    The Southern Alps of New Zealand are among the few key study sites for investigating Holocene glacier chronologies in the mid-latitudinal Southern Hemisphere. Their characteristic highly dynamic geomorphological process systems prove, however, to be a considerable challenge for all attempts to date and palaeoclimatologically interpret the existing Holocene moraines record. As a multi-proxy approach combining 10Be terrestrial cosmogenic nuclide dating (TCND) with Schmidt-hammer testing, the recently developed Schmidt-hammer exposure-age dating (SHD) has already shown its potential in this study area (cf. Winkler 2005, 2009, 2013). An electronic Schmidt-hammer (named SilverSchmidt) was introduced by the manufacturer of the original mechanical Schmidt-hammer (Proceq SA) a few years ago. It offers, in particular, facilities for much easier data processing and constitutes a major improvement and potential replacement for the mechanical Schmidt-hammer. However, its different approach to the measurement of surface hardness - based on Q-(velocity) values instead of R-(rebound) values - is a potential drawback. This difference effectively means that measurements from the two instruments are not easily interconvertible and, hence, that the instruments cannot be used interchangeably without previous comparative tests of both instruments under field conditions. Both instruments used in this comparative study were N-type models with identical impact energy of 2.207 Nm for the plunger. To compare both instruments and explore interconvertibility, parallel measurements were performed on a selected number of boulders (10 boulders per site with 5 impacts each, at least 2 sites per moraine) on moraines of homogeneous lithology but different established ages covering the entire Holocene and the Late Glacial. All moraines are located east of the Main Divide of the Southern Alps at Mueller Glacier, Tasman Glacier, and in the outer Tasman River Valley. All paired samples (n = 50) were

  6. Establishing ion ratio thresholds based on absolute peak area for absolute protein quantification using protein cleavage isotope dilution mass spectrometry.

    PubMed

    Loziuk, Philip L; Sederoff, Ronald R; Chiang, Vincent L; Muddiman, David C

    2014-11-07

    Quantitative mass spectrometry has become central to the field of proteomics and metabolomics. Selected reaction monitoring is a widely used method for the absolute quantification of proteins and metabolites. This method renders high specificity using several product ions measured simultaneously. With growing interest in quantification of molecular species in complex biological samples, confident identification and quantitation has been of particular concern. A method to confirm purity or contamination of product ion spectra has become necessary for achieving accurate and precise quantification. Ion abundance ratio assessments were introduced to alleviate some of these issues. Ion abundance ratios are based on the consistent relative abundance (RA) of specific product ions with respect to the total abundance of all product ions. To date, no standardized method of implementing ion abundance ratios has been established. Thresholds by which product ion contamination is confirmed vary widely and are often arbitrary. This study sought to establish criteria by which the relative abundance of product ions can be evaluated in an absolute quantification experiment. These findings suggest that evaluation of the absolute ion abundance for any given transition is necessary in order to effectively implement RA thresholds. Overall, the variation of the RA value was observed to be relatively constant beyond an absolute threshold ion abundance. Finally, these RA values were observed to fluctuate significantly over a 3 year period, suggesting that these values should be assessed as close as possible to the time at which data is collected for quantification.

  7. Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad.

    PubMed

    Lebatard, Anne-Elisabeth; Bourlès, Didier L; Duringer, Philippe; Jolivet, Marc; Braucher, Régis; Carcaillet, Julien; Schuster, Mathieu; Arnaud, Nicolas; Monié, Patrick; Lihoreau, Fabrice; Likius, Andossa; Mackaye, Hassan Taisso; Vignaud, Patrick; Brunet, Michel

    2008-03-04

    Ages were determined at two hominid localities from the Chad Basin in the Djurab Desert (Northern Chad). In the Koro Toro fossiliferous area, KT 12 locality (16 degrees 00'N, 18 degrees 53'E) was the site of discovery of Australopithecus bahrelghazali (Abel) and in the Toros-Menalla fossiliferous area, TM 266 locality (16 degrees 15'N, 17 degrees 29'E) was the site of discovery of Sahelanthropus tchadensis (Toumaï). At both localities, the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains: early Pliocene (3-3.5 Ma) at KT 12 and late Miocene ( approximately 7 Ma) at TM 266. Atmospheric (10)Be, a cosmogenic nuclide, was used to quasicontinuously date these sedimentary units. The authigenic (10)Be/(9)Be dating of a pelite relic within the sedimentary level containing Abel yields an age of 3.58 +/- 0.27 Ma that points to the contemporaneity of Australopithecus bahrelghazali (Abel) with Australopithecus afarensis (Lucy). The 28 (10)Be/(9)Be ages obtained within the anthracotheriid unit containing Toumaï bracket, by absolute dating, the age of Sahelanthropus tchadensis to lie between 6.8 and 7.2 Ma. This chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock.

  8. Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad

    PubMed Central

    Lebatard, Anne-Elisabeth; Bourlès, Didier L.; Duringer, Philippe; Jolivet, Marc; Braucher, Régis; Carcaillet, Julien; Schuster, Mathieu; Arnaud, Nicolas; Monié, Patrick; Lihoreau, Fabrice; Likius, Andossa; Mackaye, Hassan Taisso; Vignaud, Patrick; Brunet, Michel

    2008-01-01

    Ages were determined at two hominid localities from the Chad Basin in the Djurab Desert (Northern Chad). In the Koro Toro fossiliferous area, KT 12 locality (16°00′N, 18°53′E) was the site of discovery of Australopithecus bahrelghazali (Abel) and in the Toros-Menalla fossiliferous area, TM 266 locality (16°15′N, 17°29′E) was the site of discovery of Sahelanthropus tchadensis (Toumaï). At both localities, the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains: early Pliocene (3–3.5 Ma) at KT 12 and late Miocene (≈7 Ma) at TM 266. Atmospheric 10Be, a cosmogenic nuclide, was used to quasicontinuously date these sedimentary units. The authigenic 10Be/9Be dating of a pelite relic within the sedimentary level containing Abel yields an age of 3.58 ± 0.27 Ma that points to the contemporaneity of Australopithecus bahrelghazali (Abel) with Australopithecus afarensis (Lucy). The 28 10Be/9Be ages obtained within the anthracotheriid unit containing Toumaï bracket, by absolute dating, the age of Sahelanthropus tchadensis to lie between 6.8 and 7.2 Ma. This chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock. PMID:18305174

  9. Laboratory for Radiokrypton Dating

    NASA Astrophysics Data System (ADS)

    Lu, Z.; Bailey, K.; Jiang, W.; Müller, P.; O'Connor, T. P.; Zappala, J. C.

    2013-12-01

    Due to its simple production and transport processes in the terrestrial environment, the long-lived noble-gas isotope 81Kr (half-life = 230 kyr) is the ideal tracer for studying old water and ice in the age range of 10^5-10^6 years, a range beyond the reach of 14C. 81Kr dating, a concept pursued in the past four decades by numerous laboratories employing a variety of techniques, is now available for the first time to the earth science community at large. This is made possible by the development of ATTA-3 (Jiang et al., GCA 91, 1-6; 2012), an efficient and selective atom counter based on the Atom Trap Trace Analysis method (Chen et al., Science 286, 1139-1141; 1999). The instrument is capable of measuring both 81Kr/Kr and 85Kr/Kr ratios of environmental samples in the range of 10^-14-10^-10. For 81Kr-dating in the age range of 150 - 1,500 kyr, the required sample size is 5 - 10 micro-L STP of krypton gas, which can be extracted from approximately 100 - 200 kg of water or 40 - 80 kg of ice. For 85Kr/Kr analysis, the required sample size is generally smaller by an order of magnitude because of the isotope's higher initial abundance in the atmosphere. The Laboratory for Radiokrypton Dating is currently equipped to analyze up to 120 samples per year. With future equipment upgrades, this limit can be increased as demand grows. In the period since November 2011, the Laboratory has measured both 81Kr/Kr and 85Kr/Kr ratios in over 50 samples that had been extracted by collaborators from six different continents. The samples were from groundwater wells in the Great Artesian Basin (Australia), Guarani Aquifer (Brazil), and Locust Grove (Maryland); from brine wells of the Waste Isolation Pilot Plant (New Mexico); from geothermal steam vents in Yellowstone National Park; from near-surface ice at Taylor Glacier, Antarctica; and from deep mines in South Africa. Sample collection and purification was performed by groups including the University of Illinois at Chicago, University

  10. Developing 226Ra and 227Ac age-dating techniques for nuclear forensics to gain insight from concordant and non-concordant radiochronometers

    SciTech Connect

    Kayzar, Theresa M.; Williams, Ross W.

    2015-09-26

    The model age or ‘date of purification’ of a nuclear material is an important nuclear forensic signature. In this study, chemical separation and MC-ICP-MS measurement techniques were developed for 226 Ra and 227Ac: grand-daughter nuclides in the 238U and 235U decay chains respectively. The 230Th-234U, 226Ra-238U, 231Pa-235U, and 227Ac-235U radiochronometers were used to calculate model ages for CRM-U100 standard reference material and two highly-enriched pieces of uranium metal from the International Technical Working Group Round Robin 3 Exercise. In conclusion, the results demonstrate the accuracy of the 226Ra-238U and 227Ac-235U chronometers and provide information about nuclide migration during uranium processing.

  11. Food Product Dating

    MedlinePlus

    ... of date you might find on a meat, poultry, or egg product label. Are dates required on ... is not required by Federal regulations. For meat, poultry, and egg products under the jurisdiction of the ...

  12. Combined use of relative and numerical dating techniques for detecting signals of Alpine landscape evolution during the late Pleistocene and early Holocene in Val di Rabbi (Trentino, northern Italy)

    NASA Astrophysics Data System (ADS)

    Favilli, F.; Egli, M.; Brandova, D.; Ivy-Ochs, S.; Kubik, P.; Cherubini, P.; Mirabella, A.; Sartori, G.; Giaccai, D.; Haeberli, W.

    2009-04-01

    A combined use of relative and absolute dating techniques was applied on nine soil profiles in order to reconstruct late Pleistocene and early Holocene landscape evolution in an Alpine environment located in Val di Rabbi (Trentino, northern Italy). The degree of podzolisation, clay mineral evolution and element mass balances of each site were investigated. Furthermore, the stable fraction of the soil organic matter (SOM) was extracted from selected horizons with 10% H2O2 and 14C-dated. The ages of the organic residues were compared with the ages of charcoal fragments found in one of the studied soils and with the ages of rock boulders obtained by the surface exposure dating (SED) method with cosmogenic 10Be. The combination of 14C dating of SOM and SED indicated that deglaciation processes in Val di Rabbi were very much advanced around 14000 cal BP and that glacier oscillations have affected the highest part of the region until about 9000 cal BP. The development of clay mineral reflects weathering intensity. We found a close link between secondary clay minerals like smectite and vermiculite and soil age as obtained by H2O2. The degree of podzolisation is time dependent and was used as an evidence of surface stability. The amount of Fe and Al forms that migrated and accumulated in the illuvial horizon correlated well with the time of soil development. Element mass balance calculations strongly correlated with the ages derived from 14C measurements. Old soils have lost a major part of base cations (up to 75%), Fe and Al. Chemical and mineralogical analyses were in good agreement with numerical dating techniques, showing the dynamics of an Alpine landscape within a relatively small area and enabling a relative and absolute differentiation of landscape elements. The combination of relative and numerical dating techniques is a promising tool to understand landscape evolution and to provide absolute chronologies of the Late glacial in high-elevation Alpine areas with

  13. Electron-microprobe Th-U-Pb monazite dating in Early-Palaeozoic high-grade gneisses as a completion of U-Pb isotopic ages (Wilson Terrane, Antarctica)

    NASA Astrophysics Data System (ADS)

    Schulz, B.; Schüssler, U.

    2013-08-01

    The electron microprobe (EMP) Th-U-Pb monazite bulk chemical dating method was applied to granulite-facies rocks of the Wilson Terrane in Antarctica. A combination of this method to isotopic U-Pb-SHRIMP ages for the evaluation of metamorphic processes required the analysis of reference monazites. These can be subdivided into three groups: a) Monazite with variable total Pb at constant Th (e.g. VK-1) is unsuitable for EMP data evaluation; b) Monazite with highly variable total Pb and Th, but with at least some Th/Pb approximating an apparent isochrone (e.g. MPN) is partly useful; and c) Monazite with constant Th/Pb at high Th (e.g. Madmon monazite) is best suitable for the combined approach and can be additionally used to improve the Th calibration for EMP. Study of monazite in grain mounts and in thin sections led to partly different but complementary results: Older monazites with EMP ages up to 680 Ma occur mainly in a grain mount from diatexite and metatexite and are interpreted as detrital relics. Some of these monazites show structures and mineral-chemical zonation trends resembling metasomatism by alkali-bearing fluids. A marked mobility of Th, P, Ce, Si and U is observed. The age of the metasomatic event can be bracketed between 510 and 450 Ma. Furthermore, in the grain mount and in numerous petrographic thin sections of migmatites and gneisses, the EMP Th-U-Pb and SHRIMP U-Pb monazite data uniformly signal a major metamorphic event with a medium-pressure granulite facies peak between 512 and 496 Ma. Subsequent isothermal uplift and then amphibolite-facies conditions between 488 and 466 Ma led to crystallisation of pristine monazite. The high-grade metamorphic event, related to the Ross Orogeny, can be uniformly traced more than 600 km along strike in the Wilson Terrane.

  14. High-Resolution Inductively Coupled Plasma Optical Emission Spectrometry for (234)U/(238)Pu Age Dating of Plutonium Materials and Comparison to Sector Field Inductively Coupled Plasma Mass Spectrometry.

    PubMed

    Krachler, Michael; Alvarez-Sarandes, Rafael; Rasmussen, Gert

    2016-09-06

    spectrometric approach and thus effectively adds to the quality assurance of (234)U/(238)Pu age dates.

  15. Optically stimulated luminescence dating of late Holocene raised strandplain sequences adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan, USA

    USGS Publications Warehouse

    Argyilan, Erin P.; Forman, Steven L.; Johnston, John W.; Wilcox, Douglas A.

    2005-01-01

    This study evaluates the accuracy of optically stimulated luminescence to date well-preserved strandline sequences at Manistique/Thompson bay (Lake Michigan), and Tahquamenon and Grand Traverse Bays (Lake Superior) that span the past ∼4500 yr. The single aliquot regeneration (SAR) method is applied to produce absolute ages for littoral and eolian sediments. SAR ages are compared against AMS and conventional 14C ages on swale organics. Modern littoral and eolian sediments yield SAR ages 14C ages on swale organics. Significant variability in 14C ages >2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 ± 390 yr (UIC913) on ridge77 at Tahquamenon Bay is consistent with regional regression from the high lake level of the Nipissing II phase ca. 4500 cal yr B.P. SAR ages indicate a decrease in ridge formation rate after ∼1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to 14C methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where 14C methods prove problematic.

  16. Peer Involvement in Adolescent Dating Violence

    ERIC Educational Resources Information Center

    Stephenson, Pam S.; Martsolf, Donna; Draucker, Claire Burke

    2013-01-01

    This study investigated the ways in which peers are involved in adolescent dating violence. Eighty-eight young adults aged 18-21 were interviewed and asked to reflect on aggressive dating relationships they experienced as teens. The researchers used grounded theory to analyze the data. Findings showed that male and female peers were involved in…

  17. Radiocarbon dating of the Shroud of Turin

    NASA Astrophysics Data System (ADS)

    Damon, P. E.; Donahue, D. J.; Gore, B. H.; Hatheway, A. L.; Jull, A. J. T.; Linick, T. W.; Sercel, P. J.; Toolin, L. J.; Bronk, C. R.; Hall, E. T.; Hedges, R. E. M.; Housley, R.; Law, I. A.; Perry, C.; Bonani, G.; Trumbore, S.; Woelfli, W.; Ambers, J. C.; Bowman, S. G. E.; Leese, M. N.; Tite, M. S.

    1989-02-01

    Very small samples from the Shroud of Turin have been dated by accelerator mass spectrometry in laboratories at Arizona, Oxford and Zurich. As controls, three samples whose ages had been determined independently were also dated. The results provide conclusive evidence that the linen of the Shroud of Turin is mediaeval.

  18. Dating of ballpoint pen ink.

    PubMed

    Hofer, R

    2004-11-01

    In this paper we describe a case in which a cash book, dated of the year 2000, was sent to the Forensic Science Division, Document Laboratory, Zurich Canton Police in March 2003. The questioned document was a list of 29 pages containing a consecutive handwritten numbering and dated entries (payments) made of blue ballpoint pen ink. By definition, a cash book has to be written by hand and the entries have to be made daily. The questioned document was suspected to have been written within a short period (e.g., a few hours) and backdated. The document lab was asked to determine the date of the entries of the questioned list. On one hand, we were asked, if the cash book had been kept on account consecutively during the period of one year, and on the other hand, the judges were interested in knowing, if the document could have been written in 2003 and back dated to 2000. To answer these questions, the document was examined for latent elements by electrostatic detection device (ESDA). The relative dating of the entries was performed by the quantification of the ballpoint pen ink dyes and their degradation products using HPLC. Results show that it is possible to determine the relative age of entries written by ballpoint pen within a relatively short time scale, if storage and supporting material of the different samples are the same or at least similar.

  19. 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.

  20. ON A SUFFICIENT CONDITION FOR ABSOLUTE CONTINUITY.

    DTIC Science & Technology

    The formulation of a condition which yields absolute continuity when combined with continuity and bounded variation is the problem considered in the...Briefly, the formulation is achieved through a discussion which develops a proof by contradiction of a sufficiently theorem for absolute continuity which uses in its hypothesis the condition of continuity and bounded variation .

  1. 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…

  2. Monolithically integrated absolute frequency comb laser system

    SciTech Connect

    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.

  3. 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.

  4. Bullying Predicts Reported Dating Violence and Observed Qualities in Adolescent Dating Relationships.

    PubMed

    Ellis, Wendy E; Wolfe, David A

    2015-10-01

    The relationship between reported bullying, reported dating violence, and dating relationship quality measured through couple observations was examined. Given past research demonstrating similarity between peer and dating contexts, we expected that bullying would predict negative dating experiences. Participants with dating experience (n = 585; 238 males, M(age) = 15.06) completed self-report assessments of bullying and dating violence perpetration and victimization. One month later, 44 opposite-sex dyads (M(age) = 15.19) participated in behavioral observations. In 10-min sessions, couples were asked to rank and discuss areas of relationship conflict while being video-recorded. Qualities of the relationship were later coded by trained observers. Regression analysis revealed that bullying positively predicted dating violence perpetration and victimization. Self-reported bullying also predicted observations of lower relationship support and higher withdrawal. Age and gender interactions further qualified these findings. The bullying of boys, but not girls, was significantly related to dating violence perpetration. Age interactions showed that bullying was positively predictive of dating violence perpetration and victimization for older, but not younger adolescents. Positive affect was also negatively predicted by bullying, but only for girls. These findings add to the growing body of evidence that adolescents carry forward strategies learned in the peer context to their dating relationships.

  5. The Hamburg/ESO R-process enhanced star survey (HERES). IV. Detailed abundance analysis and age dating of the strongly r-process enhanced stars CS 29491-069 and HE 1219-0312

    NASA Astrophysics Data System (ADS)

    Hayek, W.; Wiesendahl, U.; Christlieb, N.; Eriksson, K.; Korn, A. J.; Barklem, P. S.; Hill, V.; Beers, T. C.; Farouqi, K.; Pfeiffer, B.; Kratz, K.-L.

    2009-09-01

    We report on a detailed abundance analysis of two strongly r-process enhanced, very metal-poor stars newly discovered in the HERES project, CS 29491-069 ([Fe/H]=-2.51, [r/Fe]=+1.1) and HE 1219-0312 ([Fe/H]=-2.96, [r/Fe]=+1.5). The analysis is based on high-quality VLT/UVES spectra and MARCS model atmospheres. We detect lines of 15 heavy elements in the spectrum of CS 29491-069, and 18 in HE 1219-0312; in both cases including the Th II 4019 Å line. The heavy-element abundance patterns of these two stars are mostly well-matched to scaled solar residual abundances not formed by the s-process. We also compare the observed pattern with recent high-entropy wind (HEW) calculations, which assume core-collapse supernovae of massive stars as the astrophysical environment for the r-process, and find good agreement for most lanthanides. The abundance ratios of the lighter elements strontium, yttrium, and zirconium, which are presumably not formed by the main r-process, are reproduced well by the model. Radioactive dating for CS 29491-069 with the observed thorium and rare-earth element abundance pairs results in an average age of 9.5 Gyr, when based on solar r-process residuals, and 17.6 Gyr, when using HEW model predictions. Chronometry seems to fail in the case of HE 1219-0312, resulting in a negative age due to its high thorium abundance. HE 1219-0312 could therefore exhibit an overabundance of the heaviest elements, which is sometimes called an “actinide boost”. Based on observations collected at the European Southern Observatory, Paranal, Chile (Proposal Number 170.D-0010). Table 8 is only available in electronic form at http://www.aanda.org

  6. The Antarctica component of postglacial rebound model ICE-6G_C (VM5a) based on GPS positioning, exposure age dating of ice thicknesses, and relative sea level histories

    NASA Astrophysics Data System (ADS)

    Argus, Donald F.; Peltier, W. R.; Drummond, R.; Moore, Angelyn W.

    2014-07-01

    A new model of the deglaciation history of Antarctica over the past 25 kyr has been developed, which we refer to herein as ICE-6G_C (VM5a). This revision of its predecessor ICE-5G (VM2) has been constrained to fit all available geological and geodetic observations, consisting of: (1) the present day uplift rates at 42 sites estimated from GPS measurements, (2) ice thickness change at 62 locations estimated from exposure-age dating, (3) Holocene relative sea level histories from 12 locations estimated on the basis of radiocarbon dating and (4) age of the onset of marine sedimentation at nine locations along the Antarctic shelf also estimated on the basis of 14C dating. Our new model fits the totality of these data well. An additional nine GPS-determined site velocities are also estimated for locations known to be influenced by modern ice loss from the Pine Island Bay and Northern Antarctic Peninsula regions. At the 42 locations not influenced by modern ice loss, the quality of the fit of postglacial rebound model ICE-6G_C (VM5A) is characterized by a weighted root mean square residual of 0.9 mm yr-1. The Southern Antarctic Peninsula is inferred to be rising at 2 mm yr-1, requiring there to be less Holocene ice loss there than in the prior model ICE-5G (VM2). The East Antarctica coast is rising at approximately 1 mm yr-1, requiring ice loss from this region to have been small since Last Glacial Maximum. The Ellsworth Mountains, at the base of the Antarctic Peninsula, are inferred to be rising at 5-8 mm yr-1, indicating large ice loss from this area during deglaciation that is poorly sampled by geological data. Horizontal deformation of the Antarctic Plate is minor with two exceptions. First, O'Higgins, at the tip of the Antarctic Peninsula, is moving southeast at a significant 2 mm yr-1 relative to the Antarctic Plate. Secondly, the margins of the Ronne and Ross Ice Shelves are moving horizontally away from the shelf centres at an approximate rate of 0.8 mm yr-1, in

  7. Age Estimation in Forensic Sciences

    PubMed Central

    Alkass, Kanar; Buchholz, Bruce A.; Ohtani, Susumu; Yamamoto, Toshiharu; Druid, Henrik; Spalding, Kirsty L.

    2010-01-01

    Age determination of unknown human bodies is important in the setting of a crime investigation or a mass disaster because the age at death, birth date, and year of death as well as gender can guide investigators to the correct identity among a large number of possible matches. Traditional morphological methods used by anthropologists to determine age are often imprecise, whereas chemical analysis of tooth dentin, such as aspartic acid racemization, has shown reproducible and more precise results. In this study, we analyzed teeth from Swedish individuals using both aspartic acid racemization and radiocarbon methodologies. The rationale behind using radiocarbon analysis is that aboveground testing of nuclear weapons during the cold war (1955–1963) caused an extreme increase in global levels of carbon-14 (14C), which has been carefully recorded over time. Forty-four teeth from 41 individuals were analyzed using aspartic acid racemization analysis of tooth crown dentin or radiocarbon analysis of enamel, and 10 of these were split and subjected to both radiocarbon and racemization analysis. Combined analysis showed that the two methods correlated well (R2 = 0.66, p < 0.05). Radiocarbon analysis showed an excellent precision with an overall absolute error of 1.0 ± 0.6 years. Aspartic acid racemization also showed a good precision with an overall absolute error of 5.4 ± 4.2 years. Whereas radiocarbon analysis gives an estimated year of birth, racemization analysis indicates the chronological age of the individual at the time of death. We show how these methods in combination can also assist in the estimation of date of death of an unidentified victim. This strategy can be of significant assistance in forensic casework involving dead victim identification. PMID:19965905

  8. Absolute quantitation of protein posttranslational modification isoform.

    PubMed

    Yang, Zhu; Li, Ning

    2015-01-01

    Mass spectrometry has been widely applied in characterization and quantification of proteins from complex biological samples. Because the numbers of absolute amounts of proteins are needed in construction of mathematical models for molecular systems of various biological phenotypes and phenomena, a number of quantitative proteomic methods have been adopted to measure absolute quantities of proteins using mass spectrometry. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with internal peptide standards, i.e., the stable isotope-coded peptide dilution series, which was originated from the field of analytical chemistry, becomes a widely applied method in absolute quantitative proteomics research. This approach provides more and more absolute protein quantitation results of high confidence. As quantitative study of posttranslational modification (PTM) that modulates the biological activity of proteins is crucial for biological science and each isoform may contribute a unique biological function, degradation, and/or subcellular location, the absolute quantitation of protein PTM isoforms has become more relevant to its biological significance. In order to obtain the absolute cellular amount of a PTM isoform of a protein accurately, impacts of protein fractionation, protein enrichment, and proteolytic digestion yield should be taken into consideration and those effects before differentially stable isotope-coded PTM peptide standards are spiked into sample peptides have to be corrected. Assisted with stable isotope-labeled peptide standards, the absolute quantitation of isoforms of posttranslationally modified protein (AQUIP) method takes all these factors into account and determines the absolute amount of a protein PTM isoform from the absolute amount of the protein of interest and the PTM occupancy at the site of the protein. The absolute amount of the protein of interest is inferred by quantifying both the absolute amounts of a few PTM

  9. Dating the Crucifixion

    NASA Astrophysics Data System (ADS)

    Humphreys, Colin J.; Waddington, W. G.

    1983-12-01

    The date of the Crucifixion has been debated for many years, but there has been no agreement on the year nor the day. Astronomical calculations have now been used to reconstruct the Jewish calendar in the first century AD and to date a lunar eclipse that biblical and other references suggest followed the Crucifixion. The evidence points to Friday 3 April AD 33 as the date when Jesus Christ died.

  10. Thermoluminescence dating of Australian palaeo-earthquakes

    USGS Publications Warehouse

    Hutton, J.T.; Prescott, J.R.; Bowman, J.R.; Dunham, M.N.E.; Crone, A.J.; Machette, M.N.; Twidale, C.R.

    1994-01-01

    Thermoluminescence (TL) dating is a useful tool for determining the age of prehistoric earthquakes by dating deposits that are stratigraphically related to fault scarps that formed during the earthquakes. TL dating of aeolian sand in the area of the 1988 Tennant Creek, Northern Territory, earthquakes provides evidence that similar earthquakes have not ruptured the causative faults for at least 50 ka. Pilot TL measurements of deposits associated with the Roopena and Ash Ridge fault scarps near Whyalla on Eyre Peninsula, South Australia, suggest an age of 140 ka for the Quaternary deposits associated with the formation of the scarps. ?? 1994.

  11. Absolute realization of low BRDF value

    NASA Astrophysics Data System (ADS)

    Liu, Zilong; Liao, Ningfang; Li, Ping; Wang, Yu

    2010-10-01

    Low BRDF value is widespread used in many critical domains such as space and military fairs. These values below 0.1 Sr-1 . So the Absolute realization of these value is the most critical issue in the absolute measurement of BRDF. To develop the Absolute value realization theory of BRDF , defining an arithmetic operators of BRDF , achieving an absolute measurement Eq. of BRDF based on radiance. This is a new theory method to solve the realization problem of low BRDF value. This theory method is realized on a self-designed common double orientation structure in space. By designing an adding structure to extend the range of the measurement system and a control and processing software, Absolute realization of low BRDF value is achieved. A material of low BRDF value is measured in this measurement system and the spectral BRDF value are showed within different angles allover the space. All these values are below 0.4 Sr-1 . This process is a representative procedure about the measurement of low BRDF value. A corresponding uncertainty analysis of this measurement data is given depend on the new theory of absolute realization and the performance of the measurement system. The relative expand uncertainty of the measurement data is 0.078. This uncertainty analysis is suitable for all measurements using the new theory of absolute realization and the corresponding measurement system.

  12. Isotope age of the rare metal pegmatite formation in the Kolmozero-Voron'ya greenstone belt (Kola region of the Fennoscandian shield): U-Pb (TIMS) microlite and tourmaline dating

    NASA Astrophysics Data System (ADS)

    Kudryashov, Nikolay; Lyalina, Ludmila; Mokrushin, Artem; Zozulya, Dmitry; Groshev, Nikolay; Steshenko, Ekaterina; Kunakkuzin, Evgeniy

    2016-04-01

    surface contamination being placed the ultrasonic bath with the 7N HNO3 solution. The discordia constructed for seven measured microlite weights is characterized by upper intercepts with concordia at 2454±8 Ma, which probably reflects the time of rare metal pegmatite crystallization, coeval with the age of tourmaline granites. Taking into consideration the obtained U--Pb age of microlite, it may be assumed that the tourmaline granites dated back to 2520±70 Ma served as the most probable parental rocks for rare metal pegmatites of the Vasin-Myl'k deposit. The work is supported by RFBR No 16-05-00367, No 16-05-00427 and project No 0231-2015-0005

  13. Chemical Principles Revisited: Archaeological Dating.

    ERIC Educational Resources Information Center

    Rowe, M. W.

    1986-01-01

    Discusses methods used to date archaeological artifacts and other remains. They include: (1) nuclear dating techniques (radiocarbon dating, accelerator radiocarbon dating, thermoluminescence, and others); (2) chemical dating techniques (amino acid racemization, obsidian hydration dating, elemental content changes, and thermal analysis dating); and…

  14. U-series Dating of Stalagmites from Borneo

    NASA Astrophysics Data System (ADS)

    Adkins, J. F.; Partin, J.; Cobb, K.; Clark, B.

    2006-12-01

    In a series of field campaigns dating back to the fall of 2003 we have collected over 60 stalagmites from the Gunung Buda cave system in Sarawak, Malaysia (4°N, 115°E). At least twenty of these samples have excellent calcite preservation and span an age range from modern to over 500,000 years old. The bulk of the collection is of early glacial to Holocene age and can provide multiple overlapping records of climate variability from the Western Pacific Warm Pool. However, generating absolute U-series ages from this collection is challenging. The host rock is a Miocene aged limestone that is covered by rainforest with virtually no topsoil development. This setting leaves the typical stalagmite sample with a low uranium concentration (100s of ppb), a low initial δ234U (-650‰ to -100‰), and a relatively high detrital Th concentration (10s to 100s of pmol/g). We have generated age models in these difficult circumstances by making over 150 MC-ICP-MS measurements of the 238U-234U-230Th-232Th disequilibrium system. Ages are limited by our correction for initial 230Th. This is a common problem in U-series dating of stalagmites that we have addressed by generating a "histogram" of initial 230/232 values. With 14 isochrons from four separate stalagmites spanning the glacial maximum through the Holocene we can conservatively constrain the initial 230/232 atom ratio to be 60±10x10-6. There are small differences in the weighted mean of this value between stalagmites, but no systematic differences with time within a stalagmite. The very low δ234U values are intriguing and must represent the effects of recent weathering of the host limestone. These low and variable δ234U ratios also make it imperative to calculate the initial 230/232 ratios with full three-dimensional isochrons, extrapolating to zero U-238 on a "Rosholt Diagram" does not produce a consistent answer between the samples. Overall we can produce 2 sigma age errors that are better than 1% for the combined

  15. Choosing a calving date

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calving date affects cost and timing of production events. Due to the polyestrous nature of beef females, producers can choose a calving date that fits their production system and geographic region. Any time an entire production system is considered, decision making becomes complex. Any calving syst...

  16. Pests of stored dates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dates are a major food crop across a large band of Africa and Eurasia, and to a lesser extent elsewhere. In most of its growing range, dates are threatened with infestation in the field by a complex of pests including nitidulid beetles and pyralid moths of the Subfamily Phycitinae. They are further ...

  17. Date Palm Germplasm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This book chapter reviews date palm genetic resources and their conservation. Date palm (Phoenix dactylifera) is an important food crop in the Middle East and North Africa. Its center of origin and diversity most probably is the area near Iraq/Iran. From there, it spread throughout its present range...

  18. Dating Violence in Russia

    ERIC Educational Resources Information Center

    Lysova, A. V.

    2007-01-01

    The phenomenon of violence in interpersonal relationships has been little studied in Russia, and the phenomenon of violence between dating partners has not been the object of scientific interest at all. The study on which the present article is based was designed to obtain information about the violence in dating among students enrolled in…

  19. Radiometric Dating in Geology.

    ERIC Educational Resources Information Center

    Pankhurst, R. J.

    1980-01-01

    Described are several aspects and methods of quantitatively measuring geologic time using a constant-rate natural process of radioactive decay. Topics include half lives and decay constants, radiogenic growth, potassium-argon dating, rubidium-strontium dating, and the role of geochronology in support of geological exploration. (DS)

  20. The Sea Peoples, from Cuneiform Tablets to Carbon Dating

    PubMed Central

    Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

    2011-01-01

    The 13th century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ∼3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192–1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations. PMID:21687714

  1. The Sea Peoples, from cuneiform tablets to carbon dating.

    PubMed

    Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

    2011-01-01

    The 13(th) century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ∼3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192-1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations.

  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. Magnifying absolute instruments for optically homogeneous regions

    SciTech Connect

    Tyc, Tomas

    2011-09-15

    We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

  4. The Simplicity Argument and Absolute Morality

    ERIC Educational Resources Information Center

    Mijuskovic, Ben

    1975-01-01

    In this paper the author has maintained that there is a similarity of thought to be found in the writings of Cudworth, Emerson, and Husserl in his investigation of an absolute system of morality. (Author/RK)

  5. 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.

  6. Absolute cross sections of compound nucleus reactions

    NASA Astrophysics Data System (ADS)

    Capurro, O. A.

    1993-11-01

    The program SEEF is a Fortran IV computer code for the extraction of absolute cross sections of compound nucleus reactions. When the evaporation residue is fed by its parents, only cumulative cross sections will be obtained from off-line gamma ray measurements. But, if one has the parent excitation function (experimental or calculated), this code will make it possible to determine absolute cross sections of any exit channel.

  7. Kelvin and the absolute temperature scale

    NASA Astrophysics Data System (ADS)

    Erlichson, Herman

    2001-07-01

    This paper describes the absolute temperature scale of Kelvin (William Thomson). Kelvin found that Carnot's axiom about heat being a conserved quantity had to be abandoned. Nevertheless, he found that Carnot's fundamental work on heat engines was correct. Using the concept of a Carnot engine Kelvin found that Q1/Q2 = T1/T2. Thermometers are not used to obtain absolute temperatures since they are calculated temperatures.

  8. A Multi-isotope (B, Sr, O, H) and Age-Dating (3H-3He, 14C) Study of Saline- Water Intrusion and Cross-Formational Flow in the Southern High Plains Aquifer

    NASA Astrophysics Data System (ADS)

    Langman, J. B.; Ellis, A. S.

    2007-12-01

    Identification of aquifer source waters can be difficult with traditional geochemical tracers such as solute concentrations because of the variability of rock-water interactions and complex recharge pathways. The growing use of traditional and non-traditional stable isotopes for identification of hydrologic processes allows the coupling of multiple stable isotopes and ion concentrations for cross-validation and better constraint of influences within an aquifer. A multi-isotope and age-dating study of ground water along the Western Caprock Escarpment of the Southern High Plains was implemented to identify saline-water intrusion and cross-formational flow in the Southern High Plains aquifer. This study coupled major ion and trace element concentrations with the stable isotopes of boron, strontium, hydrogen, and oxygen along with tritium-helium and carbon-14 age dating to identify potential source waters through differences in rock-water interactions and recharge pathways. Ground-water samples were collected from 16 wells, 13 of which were completed in the Ogallala Formation (primary formation of the Southern High Plains aquifer) and three that were completed in a minor aquifer of the underlying Dockum Group. Within the study area, a separate, local flow system originates at a topographic high and flows into a regional flow system defined by a large paleochannel. At a recharge area atop the topographic high and within the regional flow system, ground water is composed of a mixed cation-bicarbonate water, but a sodium-chloride type is present in parts of the local flow system and in ground water from the underlying aquifer in the Dockum Group. Major ion and trace element concentrations and the stable isotope composition of water (δ2H of -43.29 to -71.74 ‰ and δ18O of -5.85 to -9.95 ‰) do not indicate a simple two member mixing scenario but likely multiple sources and cross-formational flow between three formation deposits-- Permian salts, Dockum shales, and

  9. Paleontological evidence to date the tree of life.

    PubMed

    Benton, Michael J; Donoghue, Philip C J

    2007-01-01

    The role of fossils in dating the tree of life has been misunderstood. Fossils can provide good "minimum" age estimates for branches in the tree, but "maximum" constraints on those ages are poorer. Current debates about which are the "best" fossil dates for calibration move to consideration of the most appropriate constraints on the ages of tree nodes. Because fossil-based dates are constraints, and because molecular evolution is not perfectly clock-like, analysts should use more rather than fewer dates, but there has to be a balance between many genes and few dates versus many dates and few genes. We provide "hard" minimum and "soft" maximum age constraints for 30 divergences among key genome model organisms; these should contribute to better understanding of the dating of the animal tree of life.

  10. Date Rape Drugs

    MedlinePlus

    ... also are used to help people commit other crimes, like robbery and physical assault. They are used ... be misleading because the person who commits the crime might not be dating the victim. Rather, it ...

  11. Date Rape (For Teens)

    MedlinePlus

    ... ve been drinking. continue Protect Yourself The best defense against date rape is to try to prevent ... for help if you feel threatened. Take self-defense courses. These can build confidence and teach valuable ...

  12. Teen Dating Violence

    MedlinePlus

    ... Violence Featured Topic: Opportunities for Action Featured Topic: Bullying Research Featured Topic: Prevent Gang Membership Featured Topic: ... and alcohol Involvement in antisocial behaviors Thoughts about suicide Additionally, youth who are victims of dating violence ...

  13. Ice Core Dating Software for Interactive Dating of Ice Cores

    NASA Astrophysics Data System (ADS)

    Kurbatov, A. V.; Mayewski, P. A.; Abdul Jawad, B. S.

    2005-12-01

    Scientists involved in ice core dating are well familiar with the problem of identification and recording the depth of annual signals using stable isotopes, glaciochemistry, ECM (electrical conductivity), DEP (dielectric properties) and particle counter data. Traditionally all parameters used for ice core dating were plotted as a function of depth, printed and after years were marked on the paper, converted to depth vs. age time scale. To expedite this tedious and manual process we developed interactive computer software, Ice core Dating (ICD) program. ICD is written in Java programming language, and uses GPL and GPL site licensed graphic libraries. The same 3.5 Mb in size pre-compiled single jar file, that includes all libraries and application code, was successfully tested on WinOS, Mac OSX, Linux, and Solaris operating systems running Java VM version 1.4. We have followed the modular design philosophy in our source code so potential integration with other software modules, data bases and server side distributed computer environments can be easily implemented. We expect to continue development of new suites of tools for easy integration of ice core data with other available time proxies. ICD is thoroughly documented and comes with a technical reference and cookbook that explains the purpose of the software and its many features, and provides examples to help new users quickly become familiar with the operation and philosophy of the software. ICD is available as a free download from the Climate Change Institute web site ( under the terms of GNU GPL public license.

  14. 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.

  15. Meteorite bombardment and dating of planetary surfaces. Thesis - Feb. 1983

    NASA Technical Reports Server (NTRS)

    Neukum, G.

    1984-01-01

    Dating by measurement of impact crater frequencies developed in the past years primarily on the basis of the data from the missions to the Moon and Mars. The method allows a good relative dating to be obtained and the moons of Jupiter and Saturn through photographic analyses. A cratering chronology was obtained for the period between the oldest Moon crust (4.3 to 4.4 billion years) to the present time which gives a good absolute dating of any areas of the Moon's surface.

  16. DATINK pilot study: an effective methodology for ballpoint pen ink dating in questioned documents.

    PubMed

    San Román, I; Bartolomé, L; Alonso, M L; Alonso, R M; Ezcurra, M

    2015-09-10

    Establishing the approximate age of an ink entry from a questioned document is often a complicated task and a controversial issue in forensic sciences. Among the existing approaches, the analysis of solvents in ballpoint inks may be a useful parameter for determining the age of ink on paper. In recent years, several ink dating methods have been proposed. These methods have been based on the analysis of common ink solvents using gas chromatography/mass spectrometry (GC/MS) as the analytical platform. Despite these recent methods, several questions remain. The aim of this work was to develop an ink dating methodology (DATINK) for documents written by ballpoint pens based on the disappearance of volatile solvents from the ink entry. Multiple solid-phase microextraction (MHS-SPME) coupled to GC/MS was used to measure the solvents from ink entries made with four BIC(®) ballpoint pens. The β parameter, the remaining fraction of the analyte in the system after one equilibration, corresponding to the successive extractions was considered for modelling a mathematical equation for later ink age dating. Preliminary tests of DATINK method showed that it was possible to detect the presence of ink solvents on documents up to the studied five years. The analyses of different real samples of known age were analyzed in terms of β values, which provided a mean relative error of 21%. The proposed use of β parameter for estimating the absolute age of ballpoint ink entries has shown promising results with a standard deviation of β ranging from 0.002 to 0.004.

  17. 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.

  18. Comparison of amino acid racemization geochronometry with lithostratigraphy, biostratigraphy, uranium-series coral dating, and magnetostratigraphy in the Atlantic Coastal Plain of the southeastern United States

    USGS Publications Warehouse

    McCartan, L.; Owens, J.P.; Blackwelder, B. W.; Szabo, B. J.; Belknap, D.F.; Kriausakul, N.; Mitterer, R.M.; Wehmiller, J. F.

    1982-01-01

    The results of an integrated study comprising litho- and biostratigraphic investigations, uranium-series coral dating, amino acid racemization in molluscs, and paleomagnetic measurements are compared to ascertain relative and absolute ages of Pleistocene deposits of the Atlantic Coastal Plain in North and South Carolina. Four depositional events are inferred for South Carolina and two for North Carolina by all methods. The data suggest that there are four Pleistocene units containing corals that have been dated at about 100,000 yr, 200,000 yr, 450,000 yr, and over 1,000,000 yr. Some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between Charleston and Myrtle Beach. Lack of good uranium-series dates for the younger material at Myrtle Beach makes the correlation with the deposits at Charleston more difficult. ?? 1982.

  19. Comparison of amino acid racemization geochronometry with lithostratigraphy, biostratigraphy, uranium-series coral dating, and magnetostratigraphy in the Atlantic Coastal Plain of the southeastern United States

    NASA Astrophysics Data System (ADS)

    McCartan, L.; Owens, J. P.; Blackwelder, B. W.; Szabo, B. J.; Belknap, D. F.; Kriausakul, N.; Mitterer, R. M.; Wehmiller, J. F.

    1982-11-01

    The results of an integrated study comprising litho- and biostratigraphic investigations, uranium-series coral dating, amino acid racemization in molluscs, and paleomagnetic measurements are compared to ascertain relative and absolute ages of Pleistocene deposits of the Atlantic Coastal Plain in North and South Carolina. Four depositional events are inferred for South Carolina and two for North Carolina by all methods. The data suggest that there are four Pleistocene units containing corals that have been dated at about 100,000 yr, 200,000 yr, 450,000 yr, and over 1,000,000 yr. Some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between Charleston and Myrtle Beach. Lack of good uranium-series dates for the younger material at Myrtle Beach makes the correlation with the deposits at Charleston more difficult.

  20. Petroleum fingerprinting: Dating a gasoline release

    SciTech Connect

    Johnson, M.D.; Morrison, R.D.

    1996-09-01

    Dating a gasoline releases is particularly important in situations involving a contaminated gasoline service station. Often the station begins under the control of a major oil company, and as it ages and deteriorates it may be operated by a series of smaller operators. When facing a claim for contamination, often operators blame former operators. Fingerprinting is one of several successful methods used to date petroleum releases on contaminated sites. The topics covered in this article are inventory reconciliation; reverse groundwater modeling; hydrocarbon fingerprinting.

  1. Helium-uranium dating of corals.

    NASA Technical Reports Server (NTRS)

    Bender, M. L.

    1973-01-01

    Fanale and Schaeffer (1965) determined He/U ages of corals and other aragonitic fossils, and found that the results generally agreed with independent age estimates. As a more extensive and rigorous test of the reliability of He/U ages of fossil corals, I have determined He/U ages of forty-five independently dated Cenozoic corals. Uranium and thorium isotope compositions and Rn-222 retentivities were also determined as consistency checks. The results indicate that reliable ages are obtained when certain consistency tests are met and specified corrections are made.

  2. Quantitative standards for absolute linguistic universals.

    PubMed

    Piantadosi, Steven T; Gibson, Edward

    2014-01-01

    Absolute linguistic universals are often justified by cross-linguistic analysis: If all observed languages exhibit a property, the property is taken to be a likely universal, perhaps specified in the cognitive or linguistic systems of language learners and users. In many cases, these patterns are then taken to motivate linguistic theory. Here, we show that cross-linguistic analysis will very rarely be able to statistically justify absolute, inviolable patterns in language. We formalize two statistical methods--frequentist and Bayesian--and show that in both it is possible to find strict linguistic universals, but that the numbers of independent languages necessary to do so is generally unachievable. This suggests that methods other than typological statistics are necessary to establish absolute properties of human language, and thus that many of the purported universals in linguistics have not received sufficient empirical justification.

  3. 238U-230Th dating of chevkinite in high-silica rhyolites from La Primavera and Yellowstone calderas

    USGS Publications Warehouse

    Vazquez, Jorge A.; Velasco, Noel O.; Schmitt, Axel K.; Bleick, Heather A.; Stelten, Mark E.

    2014-01-01

    Application of 238U-230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolites, may be particularly useful as a chronometer of crystallization and differentiation because its composition may reflect the chemical changes of its host melt. Ion microprobe 128U-230Th dating of single chevkinite microphenocrysts from pre- and post-caldera La Primavera, Mexico, rhyolites yields model crystallization ages that are within 10's of k.y. of their corresponding K-Ar ages of ca. 125 ka to 85 ka, while chevkinite microphenocrysts from a post-caldera Yellowstone, USA, rhyolite yield a range of ages from ca. 110 ka to 250 ka, which is indistinguishable from the age distribution of coexisting zircon. Internal chevkinite-zircon isochrons from La Primavera yield Pleistocene ages with ~5% precision due to the nearly two order difference in Th/U between both minerals. Coupling chevkinite 238U-230Th ages and compositional analyses reveals a secular trend of Th/U and rare earth elements recorded in Yellowstone rhyolite, likely reflecting progressive compositional evolution of host magma. The relatively short timescale between chevkinite-zircon crystallization and eruption suggests that crystal-poor rhyolites at La Primavera were erupted shortly after differentiation and/or reheating. These results indicate that 238U-230Th dating of chevkinite via ion microprobe analysis may be used to date crystallization and chemical evolution of silicic magmas.

  4. Landsat-5 TM reflective-band absolute radiometric calibration

    USGS Publications Warehouse

    Chander, G.; Helder, D.L.; Markham, B.L.; Dewald, J.D.; Kaita, E.; Thome, K.J.; Micijevic, E.; Ruggles, T.A.

    2004-01-01

    The Landsat-5 Thematic Mapper (TM) sensor provides the longest running continuous dataset of moderate spatial resolution remote sensing imagery, dating back to its launch in March 1984. Historically, the radiometric calibration procedure for this imagery used the instrument's response to the Internal Calibrator (IC) on a scene-by-scene basis to determine the gain and offset of each detector. Due to observed degradations in the IC, a new procedure was implemented for U.S.-processed data in May 2003. This new calibration procedure is based on a lifetime radiometric calibration model for the instrument's reflective bands (1-5 and 7) and is derived, in part, from the IC response without the related degradation effects and is tied to the cross calibration with the Landsat-7 Enhanced Thematic Mapper Plus. Reflective-band absolute radiometric accuracy of the instrument tends to be on the order of 7% to 10%, based on a variety of calibration methods.

  5. U-Pb Dating of Carbonates: A Complement to Clumped Isotope Analyses

    NASA Astrophysics Data System (ADS)

    Rasbury, T.; Suarez, M. B.

    2014-12-01

    Carbonates are ubiquitous in nature, forming in a variety of settings at the surface and through burial. The field and petrographic relationships of carbonate phases can often be linked to the depositional setting and burial path(s) that the sedimentary pile has experienced. Clumped isotopes are taking on an important role of testing the temperature of formation of the carbonates, and combined with other approaches such as fluid inclusion analyses offers tremendous potential for testing basin evolution models. However, while the relative ages of carbonates are often fairly easily elucidated, the absolute ages of the events recorded in carbonates are not. U-Pb dating of carbonates offers the best potential for constraining the ages. However, not all fluids have favorable U/Ca ratios. U-Pb dated groundwater carbonates from the Late Triassic New Haven Arkose give an age of 211 +/- 2 Ma, consistent with the known age of deposition. Late bright luminescent calcite from the same formation gives an age of 81+/-11 Ma, constraining the age (both primary and secondary) of carbonate formation. Clumped isotope analyses of primary carbonate phases show somewhat elevated temperatures between 50-60o C, some 30 degrees hotter than other estimates for this Triassic equatorial setting, and are more likely the result of re-ordering of 13C-18O bonds at depth. Apparently the primary calcite, appears to have preserved its depositional U-Pb systematics, however bond re-ordering or recrystallization of these carbonates appear to reflect values closer to thermal equilibrium with the last phase of carbonate formation (bright luminescent calcite, 81 ± 11 Ma). Further work on these samples will target these younger calcites to determine if this later calcite phase records similar temperatures.

  6. Absolute Distance Measurement with the MSTAR Sensor

    NASA Technical Reports Server (NTRS)

    Lay, Oliver P.; Dubovitsky, Serge; Peters, Robert; Burger, Johan; Ahn, Seh-Won; Steier, William H.; Fetterman, Harrold R.; Chang, Yian

    2003-01-01

    The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. The sensor uses a single laser in conjunction with fast phase modulators and low frequency detectors. We describe the design of the system - the principle of operation, the metrology source, beamlaunching optics, and signal processing - and show results for target distances up to 1 meter. We then demonstrate how the system can be scaled to kilometer-scale distances.

  7. 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.

  8. Radiocarbon Dating the Anthropocene

    NASA Astrophysics Data System (ADS)

    Chaput, M. A.; Gajewski, K. J.

    2015-12-01

    The Anthropocene has no agreed start date since current suggestions for its beginning range from Pre-Industrial times to the Industrial Revolution, and from the mid-twentieth century to the future. To set the boundary of the Anthropocene in geological time, we must first understand when, how and to what extent humans began altering the Earth system. One aspect of this involves reconstructing the effects of prehistoric human activity on the physical landscape. However, for global reconstructions of land use and land cover change to be more accurately interpreted in the context of human interaction with the landscape, large-scale spatio-temporal demographic changes in prehistoric populations must be known. Estimates of the relative number of prehistoric humans in different regions of the world and at different moments in time are needed. To this end, we analyze a dataset of radiocarbon dates from the Canadian Archaeological Radiocarbon Database (CARD), the Palaeolithic Database of Europe and the AustArch Database of Australia, as well as published dates from South America. This is the first time such a large quantity of dates (approximately 60,000) has been mapped and studied at a global scale. Initial results from the analysis of temporal frequency distributions of calibrated radiocarbon dates, assumed to be proportional to population density, will be discussed. The utility of radiocarbon dates in studies of the Anthropocene will be evaluated and potential links between population density and changes in atmospheric greenhouse gas concentrations, climate, migration patterning and fire frequency coincidence will be considered.

  9. Radioactive fallouts as temporal makers for glacier ice cores dating

    NASA Astrophysics Data System (ADS)

    Clemenza, M.; Cucciati, G.; Maggi, V.; Pattavina, L.; Previtali, E.

    2012-06-01

    In this paper, we intend to show how analytical methods used in nuclear physics, as gamma spectroscopy, are powerful tools for the dating of environmental archives. Specifically, we will show how events related to the release in the environment of great amount of radioactive isotopes ( e.g., atmospheric nuclear test explosions) can be used as temporal markers in alpine glaciers. The radio-isotope selected for the dating of ice carrots is 137Cs , because of its chemical and nuclear properties. The radioactive measurements have been conducted using a low-background high-purity germanium detector. The sensitivity for the prepared samples is 10mBq/kg. We will illustrate how dating curves (date versus depth of the sample) can be considered as an absolute calibrator for all the other chemical dating methods used on glacier samples analyses.

  10. The Realities of Date Rape.

    ERIC Educational Resources Information Center

    Presley, Cara; Watson, Jennifer; Williams, Audrey R.

    This poster presentation addresses the issue of date rape, specifically in the college environment. Highlighted are date rape statistics, demographics, and date rape drugs. Also discussed are date rape warnings and prevention strategies. It is concluded that college and university administrators must place the issue of date rape and acquaintance…

  11. Comparative vs. Absolute Judgments of Trait Desirability

    ERIC Educational Resources Information Center

    Hofstee, Willem K. B.

    1970-01-01

    Reversals of trait desirability are studied. Terms indicating conservativw behavior appeared to be judged relatively desirable in comparative judgement, while traits indicating dynamic and expansive behavior benefited from absolute judgement. The reversal effect was shown to be a general one, i.e. reversals were not dependent upon the specific…

  12. New Techniques for Absolute Gravity Measurements.

    DTIC Science & Technology

    1983-01-07

    Hammond, J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J. A., and Iliff, R. L. (1979) The AFGL absolute gravity system...International Gravimetric Bureau, No. L:I-43. 7. Hammond. J.A. (1978) Bollettino Di Geofisica Teorica ed Applicata Vol. XX. 8. Hammond, J.A., and

  13. An Absolute Electrometer for the Physics Laboratory

    ERIC Educational Resources Information Center

    Straulino, S.; Cartacci, A.

    2009-01-01

    A low-cost, easy-to-use absolute electrometer is presented: two thin metallic plates and an electronic balance, usually available in a laboratory, are used. We report on the very good performance of the device that allows precise measurements of the force acting between two charged plates. (Contains 5 footnotes, 2 tables, and 6 figures.)

  14. 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…

  15. Absolute Positioning Using the Global Positioning System

    DTIC Science & Technology

    1994-04-01

    Global Positioning System ( GPS ) has becom a useful tool In providing relativ survey...Includes the development of a low cost navigator for wheeled vehicles. ABSTRACT The Global Positioning System ( GPS ) has become a useful tool In providing...technique of absolute or point positioning involves the use of a single Global Positioning System ( GPS ) receiver to determine the three-dimenslonal

  16. Dating the Homo erectus bearing travertine from Kocabaş (Denizli, Turkey) at at least 1.1 Ma

    NASA Astrophysics Data System (ADS)

    Lebatard, Anne-Elisabeth; Alçiçek, M. Cihat; Rochette, Pierre; Khatib, Samir; Vialet, Amélie; Boulbes, Nicolas; Bourlès, Didier L.; Demory, François; Guipert, Gaspard; Mayda, Serdar; Titov, Vadim V.; Vidal, Laurence; de Lumley, Henry

    2014-03-01

    Since its discovery within a travertine quarry, the fragmentary cranium of the only known Turkish Homo erectus, the Kocabaş hominid, has led to conflicting biochronological estimations. First estimated to be ˜500 ka old, the partial skull presents a combination of archaic and evolved features that puts it as an intermediate specimen between the Dmanisi fossils (Homo georgicus) and the Chinese Zhoukoudian skulls (Homo erectus) respectively dated to 1.8 to ˜0.8 Ma. Here we present a multidisciplinary study combining sedimentological, paleontological and paleoanthropological observations together with cosmogenic nuclide concentration and paleomagnetic measurements to provide an absolute chronological framework for the Upper fossiliferous Travertine unit where the Kocabaş hominid and fauna were discovered. The 26Al/10Be burial ages determined on pebbles from conglomeratic levels framing the Upper fossiliferous Travertine unit, which exhibits an inverse polarity, constrains its deposition to before the Cobb Mountain sub-chron, that is between 1.22 and ˜1.5 Ma. The alternative match of the normal polarity recorded above the travertine with the Jaramillo subchron (lower limit 1.07 Ma) may also be marginally compatible with cosmogenic nuclides interpretation, thus the proposed minimum age of 1.1 Ma for the end of massive travertine deposition. The actual age of the fossils is likely to be in the 1.1-1.3 Ma range. This absolute date is in close agreement with the paleoanthropological conclusions based on morphometric comparisons implying that Kocabaş hominid belongs to the Homo erectus s.l. group that includes Chinese and African fossils, and is different from Middle and Upper Pleistocene specimens. Furthermore, this date is confirmed by the large mammal assemblage, typical of the late Villafranchian. Because it attests to the antiquity of human occupation of the Anatolian Peninsula and one of the waves of settlements out of Africa, this work challenges the current

  17. Biodiversity of date palm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The date palm (Phoenix dactylifera) is the dominant component upon which the sustainable biophysical and socio-economic structures of the oasis ecosystem are based; a fruit tree with unique nutritional, biochemical and biophysical characteristics, a rich source of aesthetic and cultural values, and ...

  18. The Dating Game.

    ERIC Educational Resources Information Center

    Zerger, Monte J.

    1998-01-01

    Presents activities to cultivate the tendency to see special qualities in numbers that can be played on certain calendar days. Includes games on the constant of the day, Fibonacci and golden ratio dates, primes, powers, December 25, and the day of the year. (ASK)

  19. Thermoluminescence dating of Hawaiian basalt

    USGS Publications Warehouse

    May, Rodd James

    1979-01-01

    The thermoluminescence (TL) properties of plagioclase separates from 11 independently dated alkalic basalts 4,500 years to 3.3 million years old and 17 tholeiitic basalts 16 years to 450,000 years old from the Hawaiian Islands were investigated for the purpose of developing a TL dating method for young volcanic rocks. Ratios of natural to artificial TL intensity, when normalized for natural radiation dose rates, were used to quantify the thermoluminescence response of individual samples for age-determination purposes. The TL ratios for the alkalic basalt plagioclase were found to increase with age at a predictable exponential rate that permits the use of the equation for the best-fit line through a plot of the TL ratios relative to known age as a TL age equation. The equation is applicable to rocks ranging in composition from basaltic andesite to trachyte over the age range from about 2,000 to at least 250,000 years before present (B.P.). The TL ages for samples older than 50,000 years have a calculated precision of less than :t 10 percent and a potential estimated accuracy relative to potassium-argon ages of approximately :t 10 percent. An attempt to develop a similar dating curve for the tholeiitic basalts was not as successful, primarily because the dose rates are on the average lower than those for the alkalic basalts by a factor of 6, resulting in lower TL intensities in the tholeiitic basalts for samples of equivalent age, and also because the age distribution of dated material is inadequate. The basic TL properties of the plagioclase from the two rock types are similar, however, and TL dating of tholeiitic basalts should eventually be feasible over the age range 10,000 to at least 200,000 years B.P. The average composition of the plagioclase separates from the alkalic basalts ranges from oligoclase to andesine; compositional variations within this range have no apparent effect on the TL ratios. The average composition of the plagioclase from the tholeiitic

  20. Absolute Radiation Thermometry in the NIR

    NASA Astrophysics Data System (ADS)

    Bünger, L.; Taubert, R. D.; Gutschwager, B.; Anhalt, K.; Briaudeau, S.; Sadli, M.

    2017-04-01

    A near infrared (NIR) radiation thermometer (RT) for temperature measurements in the range from 773 K up to 1235 K was characterized and calibrated in terms of the "Mise en Pratique for the definition of the Kelvin" (MeP-K) by measuring its absolute spectral radiance responsivity. Using Planck's law of thermal radiation allows the direct measurement of the thermodynamic temperature independently of any ITS-90 fixed-point. To determine the absolute spectral radiance responsivity of the radiation thermometer in the NIR spectral region, an existing PTB monochromator-based calibration setup was upgraded with a supercontinuum laser system (0.45 μm to 2.4 μm) resulting in a significantly improved signal-to-noise ratio. The RT was characterized with respect to its nonlinearity, size-of-source effect, distance effect, and the consistency of its individual temperature measuring ranges. To further improve the calibration setup, a new tool for the aperture alignment and distance measurement was developed. Furthermore, the diffraction correction as well as the impedance correction of the current-to-voltage converter is considered. The calibration scheme and the corresponding uncertainty budget of the absolute spectral responsivity are presented. A relative standard uncertainty of 0.1 % (k=1) for the absolute spectral radiance responsivity was achieved. The absolute radiometric calibration was validated at four temperature values with respect to the ITS-90 via a variable temperature heatpipe blackbody (773 K ...1235 K) and at a gold fixed-point blackbody radiator (1337.33 K).

  1. Dating, Sexual Activity, and Well-Being in Italian Adolescents

    ERIC Educational Resources Information Center

    Ciairano, Silvia; Bonino, Silvia; Kliewer, Wendy; Miceli, Renato; Jackson, Sandy

    2006-01-01

    Associations among dating, sexual activity, gender, and adjustment were investigated in 2,273 Italian adolescents (54% female, ages 14 to 19 years) attending public high schools. After controlling for age and type of school attended, both being in a dating relationship and being male were associated with less alienation, more positive views of the…

  2. A method to estimate the absolute ultrasonic nonlinearity parameter from relative measurements.

    PubMed

    Kim, Jongbeom; Song, Dong-Gi; Jhang, Kyung-Young

    2017-02-17

    The ultrasonic nonlinearity parameter, β, is determined from the displacement amplitude of the second-order harmonic frequency component generated during the propagation of ultrasonic waves through a material. This parameter is generally referred to as the absolute parameter. Meanwhile, it is difficult to measure the small displacement amplitude of the second-order harmonic component; therefore, most studies measure the relative parameter determined from the detected signal amplitude. However, for quantitative assessment of material degradation, the absolute parameter is still required. This study proposes a method to estimate the absolute parameter for damaged material by measuring the relative parameter. This method is based on the fact that the fractional ratio of the relative parameters between different materials is identical to that of the absolute parameters after compensation for material dependent differences such as the wavenumber and detection-sensitivity. In order to experimentally verify the method, the relative parameters of heat-treated Al6061-T6 alloy specimens with different aging times were measured to compare with absolute parameters directly measured by piezo-electric detection. The results show that the fluctuations of both parameters with respect to aging time were very similar to each other, and that the absolute parameters estimated by the proposed method were in good agreement with those measured directly.

  3. Radiometric dating of the Siloam Tunnel, Jerusalem.

    PubMed

    Frumkin, Amos; Shimron, Aryeh; Rosenbaum, Jeff

    2003-09-11

    The historical credibility of texts from the Bible is often debated when compared with Iron Age archaeological finds (refs. 1, 2 and references therein). Modern scientific methods may, in principle, be used to independently date structures that seem to be mentioned in the biblical text, to evaluate its historical authenticity. In reality, however, this approach is extremely difficult because of poor archaeological preservation, uncertainty in identification, scarcity of datable materials, and restricted scientific access into well-identified worship sites. Because of these problems, no well-identified Biblical structure has been radiometrically dated until now. Here we report radiocarbon and U-Th dating of the Siloam Tunnel, proving its Iron Age II date; we conclude that the Biblical text presents an accurate historic record of the Siloam Tunnel's construction. Being one of the longest ancient water tunnels lacking intermediate shafts, dating the Siloam Tunnel is a key to determining where and when this technological breakthrough took place. Siloam Tunnel dating also refutes a claim that the tunnel was constructed in the second century bc.

  4. Neighborhood Factors and Dating Violence Among Youth

    PubMed Central

    Johnson, Renee M.; Parker, Elizabeth M.; Rinehart, Jenny; Nail, Jennifer; Rothman, Emily F.

    2015-01-01

    Context The purpose of this review is to summarize the empirical research on neighborhood-level factors and dating violence among adolescents and emerging adults to guide future research and practice. Evidence acquisition In 2015, 20 articles were identified through a search of the literature using PubMed. Eligible articles included those that: (1) had been published in a peer-reviewed journal since 2005; (2) reported a measure of association between at least one neighborhood-level factor and dating violence; and (3) had a study population of youth aged <26 years. We abstracted information about the studies, including measurement of dating violence and neighborhood factors, and measures of effect. Evidence synthesis Results were summarized into three categories based on the aspect of neighborhood which was the focus of the work: demographic and structural characteristics (n=11), neighborhood disorder (n=12), and social disorganization (n=8). There was some evidence to suggest that neighborhood disadvantage is associated with dating violence, but very little evidence to suggest that residence characteristics (e.g., racial heterogeneity) are associated with dating violence. Results do suggest that perceived neighborhood disorder is associated with physical dating violence perpetration, but do not suggest that it is associated with physical dating violence victimization. Social control and community connectedness are both associated with dating violence, but findings on collective efficacy are mixed. Conclusions Existing research suggests that neighborhood factors may be associated with dating violence. However, there is a limited body of research on the neighborhood context of dating violence and more rigorous research is needed. PMID:26296444

  5. Development of a luminescence planetary surface dating instrument

    NASA Astrophysics Data System (ADS)

    Jain, M.; Lapp, T.; Andersen, M. T.; Hannemann, S.; Murray, A. S.; Duller, G. A. T.; Merrrisen, J.

    2012-04-01

    Luminescence dating (LD) is uniquely positioned for absolute, in-situ, dating of recent (< 1Ma) events on Mars such as the formation of sedimentary landforms, volcanic rocks and salt precipitates. These data can in turn help understand and predict the impact of climate-driven changes on Mars, for example, atmosphere-land interactions, global sand and dust movements and redistribution of volatiles (H2O and CO2). This understanding is critical for any manned mission to Mars and for our understanding of the planetary surface evolution. Despite this potential, the technology transfer from terrestrial to in-situ Martian dating is not trivial. Here we first provide a brief overview of the scientific issues involved in luminescence dating on Mars (e.g. dosimetric characteristics of Martian materials and modelling of cosmic-ray dose rate) and then the technical constraints on an instrument design appropriate for remotely-programmable mobile use on the Martian surface. The challenge is to develop a miniaturised portable luminescence reader that is as sensitive as a laboratory-based instrument and at the same time has sufficient flexibility for fully automated performance. Such an instrument could provide stratigraphic ages if deployed on a rover with a sub-surface drilling capability, or provide a survey of surface chronologies over extensive areas. To this end we have designed and manufactured an 'elegant breadboard' Planetary Surface Dating Instrument (PSDI) in a project supported by ESA. The PSDI is light weight and compact (~1 kg, ~1.4 litres) and has 3 different reloadable sample positions which can be rotated to sit under 3 different optical subunits or an x-ray irradiator. The optical subunits consists of three different detection channels (one red and two UV/blue) each based on a miniature photomultiplier tube, and three types of laser light stimulation sources (two 915 nm, one 530 nm and one 405 nm) that can be operated in continuous-wave or pulsed mode. The

  6. 76 FR 77831 - 2012 Presidential Candidate Matching Fund Submission Dates and Post Date of Ineligibility Dates...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-14

    ... Submit Statements of Net Outstanding Campaign Obligations AGENCY: Federal Election Commission. ACTION: Notice of matching fund submission dates and submission dates for statements of net outstanding campaign... statements of net outstanding campaign obligations (``NOCO statement'') after their dates of...

  7. 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.

  8. Consistent thermostatistics forbids negative absolute temperatures

    NASA Astrophysics Data System (ADS)

    Dunkel, Jörn; Hilbert, Stefan

    2014-01-01

    Over the past 60 years, a considerable number of theories and experiments have claimed the existence of negative absolute temperature in spin systems and ultracold quantum gases. This has led to speculation that ultracold gases may be dark-energy analogues and also suggests the feasibility of heat engines with efficiencies larger than one. Here, we prove that all previous negative temperature claims and their implications are invalid as they arise from the use of an entropy definition that is inconsistent both mathematically and thermodynamically. We show that the underlying conceptual deficiencies can be overcome if one adopts a microcanonical entropy functional originally derived by Gibbs. The resulting thermodynamic framework is self-consistent and implies that absolute temperature remains positive even for systems with a bounded spectrum. In addition, we propose a minimal quantum thermometer that can be implemented with available experimental techniques.

  9. Absolute measurement of length with nanometric resolution

    NASA Astrophysics Data System (ADS)

    Apostol, D.; Garoi, F.; Timcu, A.; Damian, V.; Logofatu, P. C.; Nascov, V.

    2005-08-01

    Laser interferometer displacement measuring transducers have a well-defined traceability route to the definition of the meter. The laser interferometer is de-facto length scale for applications in micro and nano technologies. However their physical unit -half lambda is too large for nanometric resolution. Fringe interpolation-usual technique to improve the resolution-lack of reproducibility could be avoided using the principles of absolute distance measurement. Absolute distance refers to the use of interferometric techniques for determining the position of an object without the necessity of measuring continuous displacements between points. The interference pattern as produced by the interference of two point-like coherent sources is fitted to a geometric model so as to determine the longitudinal location of the target by minimizing least square errors. The longitudinal coordinate of the target was measured with accuracy better than 1 nm, for a target position range of 0.4μm.

  10. 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.

  11. Computer processing of spectrograms for absolute intensities.

    PubMed

    Guttman, A; Golden, J; Galbraith, H J

    1967-09-01

    A computer program was developed to process photographically recorded spectra for absolute intensity. Test and calibration films are subjected to densitometric scans that provide digitally recorded densities on magnetic tapes. The nonlinear calibration data are fitted by least-squares cubic polynomials to yield a good approximation to the monochromatic H&D curves for commonly used emulsions (2475 recording film, Royal-X, Tri-X, 4-X). Several test cases were made. Results of these cases show that the machine processed absolute intensities are accurate to within 15%o. Arbitrarily raising the sensitivity threshold by 0.1 density units above gross fog yields cubic polynomial fits to the H&D curves that are radiometrically accurate within 10%. In addition, curves of gamma vs wavelength for 2475, Tri-X, and 4-X emulsions were made. These data show slight evidence of the photographic Purkinje effect in the 2475 emulsion.

  12. 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.

  13. 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.

  14. Absolute and relative dosimetry for ELIMED

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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. 10Be dating of Neogene halite

    NASA Astrophysics Data System (ADS)

    Belmaker, Reuven; Lazar, Boaz; Beer, Jürg; Christl, Marcus; Tepelyakov, Natalya; Stein, Mordechai

    2013-12-01

    Direct radioactive dating of ancient halite formations is difficult because this mineral typically lacks conventionally datable material. We describe an attempt to date Neogene halite using the cosmogenic isotope 10Be (T1/2 = 1.39 Ma). We dated marine-derived salt deposits from the Sedom and Amora (The Hebrew forms of Sodom and Gomorrah) Formations, Dead Sea basin, Israel. To verify whether Be is incorporated into marine halite we measured the stable isotope 9Be, 7Be (the short lived “cosmogenic brother” of 10Be having T1/2 = 53.3 d), and 10Be in evaporation pans of sea-salt production plants. The data suggest that seawater beryllium is incorporated into the halite with a halite-brine distribution coefficient, (KD) of about unity. A 10Be/9Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of ∼2-6 Ma. The 10Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of 3-5 Ma. This age is consistent with previous estimates of the Sedom Formation age. Furthermore, this age lies in the same range of 10Be in situ ages obtained on the lacustrine Erq El Ahmer Formation located in the northern Jordan Valley. This may imply that during the Mid Pliocene the Sedom Lagoon, the water-body that deposited the Sedom Formation, might have been already disconnected from the open sea.

  16. Developing a Relationship Between LIBS Ablation and Pit Volume for In Situ Dating of Geologic Samples

    NASA Technical Reports Server (NTRS)

    Devismes, D.; Cohen, B. A.; Gillot, P.-Y.

    2015-01-01

    In planetary exploration, in situ absolute geochronology is an important measurement. Thus far, on Mars, the age of the surface has largely been determined by crater density counting, which gives relative ages. These ages can have significant uncertainty as they depend on many poorly constrained parameters. More than that, the curves must be tied to absolute ages to relate geologic timescales on Mars to the rest of the solar system. Thus far, only the lost lander Beagle 2 was designed to conduct absolute geochronology measurements, though some recent attempts using MSL Curiosity show that this investigation is feasible (Reference Farley here) and should be strongly encouraged for future flight.

  17. Physical Dating Aggression Growth during Adolescence

    ERIC Educational Resources Information Center

    Nocentini, Annalaura; Menesini, Ersilia; Pastorelli, Concetta

    2010-01-01

    The development of Physical Dating Aggression from the age of 16 to 18 years was investigated in relation to time-invariant predictors (gender, parental education, family composition, number of partners) and to time-varying effects of delinquent behavior and perception of victimization by the partner. The sample consisted of 181 adolescents with a…

  18. Historical Analysis of College Campus Interracial Dating

    ERIC Educational Resources Information Center

    Firmin, Michael W.; Firebaugh, Stephanie

    2008-01-01

    Interracial dating on American campuses has had a relatively stormy past. Until the past three decades or so, it was outlawed in some states. Southern institutions, in particular, such as the infamous Bob Jones University have made this issue divisive even among their own constituencies. Age and generation seem to be cogent factors with younger…

  19. 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.

  20. Première datation des lydiennes paléozoïques dans les Hellénides internes (mont Parnis, Grèce); implications géologiquesFirst age dating of the Lydian stones in the Inner Hellenides (Mount Parnis, Greece); geological significances.

    NASA Astrophysics Data System (ADS)

    Caridroit, Martial; Ferrière, Jacky; Dégardin, Jean-Marie; Vachard, Daniel; Clément, Bernard

    2000-09-01

    Using radiolarian and conodont remains, a Tournaisian age has been obtained from the Lydian rocks (or lydites) of the Parnis Mount (Greece); this result is the first direct age dating of the Lydian rocks of continental Greece. In the same area, some limestone strata, interbedded in sandstones, yield Carboniferous and Permian foraminifers; the established stratigraphy is not consistent and so, the Lydian rocks have to be considered as blocks in an olistostrome unconformably overlain or thrusted by Triassic limestones. Otherwise, the Lydian rocks are interpreted as biogenic siliceous deposits due to the absence of carbonate sedimentation (not as a high siliceous production).

  1. Negative absolute temperature for mobile particles

    NASA Astrophysics Data System (ADS)

    Braun, Simon; Ronzheimer, Philipp; Schreiber, Michael; Hodgman, Sean; Bloch, Immanuel; Schneider, Ulrich

    2013-05-01

    Absolute temperature is usually bound to be strictly positive. However, negative absolute temperature states, where the occupation probability of states increases with their energy, are possible in systems with an upper energy bound. So far, such states have only been demonstrated in localized spin systems with finite, discrete spectra. We realized a negative absolute temperature state for motional degrees of freedom with ultracold bosonic 39K atoms in an optical lattice, by implementing the attractive Bose-Hubbard Hamiltonian. This new state strikingly revealed itself by a quasimomentum distribution that is peaked at maximum kinetic energy. The measured kinetic energy distribution and the extracted negative temperature indicate that the ensemble is close to degeneracy, with coherence over several lattice sites. The state is as stable as a corresponding positive temperature state: The negative temperature stabilizes the system against mean-field collapse driven by negative pressure. Negative temperatures open up new parameter regimes for cold atoms, enabling fundamentally new many-body states. Additionally, they give rise to several counterintuitive effects such as heat engines with above unity efficiency.

  2. Measurement of absolute gravity acceleration in Firenze

    NASA Astrophysics Data System (ADS)

    de Angelis, M.; Greco, F.; Pistorio, A.; Poli, N.; Prevedelli, M.; Saccorotti, G.; Sorrentino, F.; Tino, G. M.

    2011-01-01

    This paper reports the results from the accurate measurement of the acceleration of gravity g taken at two separate premises in the Polo Scientifico of the University of Firenze (Italy). In these laboratories, two separate experiments aiming at measuring the Newtonian constant and testing the Newtonian law at short distances are in progress. Both experiments require an independent knowledge on the local value of g. The only available datum, pertaining to the italian zero-order gravity network, was taken more than 20 years ago at a distance of more than 60 km from the study site. Gravity measurements were conducted using an FG5 absolute gravimeter, and accompanied by seismic recordings for evaluating the noise condition at the site. The absolute accelerations of gravity at the two laboratories are (980 492 160.6 ± 4.0) μGal and (980 492 048.3 ± 3.0) μGal for the European Laboratory for Non-Linear Spectroscopy (LENS) and Dipartimento di Fisica e Astronomia, respectively. Other than for the two referenced experiments, the data here presented will serve as a benchmark for any future study requiring an accurate knowledge of the absolute value of the acceleration of gravity in the study region.

  3. System for absolute measurements by interferometric sensors

    NASA Astrophysics Data System (ADS)

    Norton, Douglas A.

    1993-03-01

    The most common problem of interferometric sensors is their inability to measure absolute path imbalance. Presented in this paper is a signal processing system that gives absolute, unambiguous reading of optical path difference for almost any style of interferometric sensor. Key components are a wide band (incoherent) optical source, a polychromator, and FFT electronics. Advantages include no moving parts in the signal processor, no active components at the sensor location, and the use of standard single mode fiber for sensor illumination and signal transmission. Actual absolute path imbalance of the interferometer is determined without using fringe counting or other inferential techniques. The polychromator extracts the interference information that occurs at each discrete wavelength within the spectral band of the optical source. The signal processing consists of analog and digital filtering, Fast Fourier analysis, and a peak detection and interpolation algorithm. This system was originally designed for use in a remote pressure sensing application that employed a totally passive fiber optic interferometer. A performance qualification was made using a Fabry-Perot interferometer and a commercially available laser interferometer to measure the reference displacement.

  4. Chemical composition of French mimosa absolute oil.

    PubMed

    Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas

    2010-02-10

    Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound.

  5. Constrained Least Absolute Deviation Neural Networks

    PubMed Central

    Wang, Zhishun; Peterson, Bradley S.

    2008-01-01

    It is well known that least absolute deviation (LAD) criterion or L1-norm used for estimation of parameters is characterized by robustness, i.e., the estimated parameters are totally resistant (insensitive) to large changes in the sampled data. This is an extremely useful feature, especially, when the sampled data are known to be contaminated by occasionally occurring outliers or by spiky noise. In our previous works, we have proposed the least absolute deviation neural network (LADNN) to solve unconstrained LAD problems. The theoretical proofs and numerical simulations have shown that the LADNN is Lyapunov-stable and it can globally converge to the exact solution to a given unconstrained LAD problem. We have also demonstrated its excellent application value in time-delay estimation. More generally, a practical LAD application problem may contain some linear constraints, such as a set of equalities and/or inequalities, which is called constrained LAD problem, whereas the unconstrained LAD can be considered as a special form of the constrained LAD. In this paper, we present a new neural network called constrained least absolute deviation neural network (CLADNN) to solve general constrained LAD problems. Theoretical proofs and numerical simulations demonstrate that the proposed CLADNN is Lyapunov stable and globally converges to the exact solution to a given constrained LAD problem, independent of initial values. The numerical simulations have also illustrated that the proposed CLADNN can be used to robustly estimate parameters for nonlinear curve fitting, which is extensively used in signal and image processing. PMID:18269958

  6. Retrospective Birth Dating of Cells

    SciTech Connect

    L.Spalding, K; Bhardwaj, R D; Buchholz, B A; Druid, H; Frisen, J

    2005-04-19

    The generation of cells in the human body has been difficult to study and our understanding of cell turnover is limited. Extensive testing of nuclear weapons resulted in a dramatic global increase in the levels of the isotope {sup 14}C in the atmosphere, followed by an exponential decrease after the test ban treaty in 1963. We show that the level of {sup 14}C in genomic DNA closely parallels atmospheric levels, and can be used to establish the time point when the DNA was synthesized and cells were born. We use this strategy to determine the age of cells in the cortex of the adult human brain, and show that whereas non-neuronal cells are exchanged, occipital neurons are as old as the individual, supporting the view that postnatal neurogenesis does not take place in this region. Retrospective birth dating is a generally applicable strategy that can be used to measure cell turnover in man under physiological and pathological conditions.

  7. Dating Violence among College Students

    ERIC Educational Resources Information Center

    Iconis, Rosemary

    2013-01-01

    Dating violence is a significant problem on college campuses. More than one-fifth of the undergraduate dating population are physically abused by their dating partners and an even greater percentage are psychologically abused. Researchers have identified risk factors for college student dating violence. Preventive interventions are strongly…

  8. Uranium-series dating and growth characteristics of the deep-sea scleractinian coral: Enallopsammia rostrata from the Equatorial Pacific

    NASA Astrophysics Data System (ADS)

    Houlbrèque, Fanny; McCulloch, Malcolm; Roark, Brendan; Guilderson, Tom; Meibom, Anders; Kimball, Justine; Mortimer, Graham; Cuif, Jean-Pierre; Dunbar, Robert

    2010-04-01

    The deep-sea coral, Enallopsammia rostrata, a member of the Dendrophylliidae family, is a major structure-forming species that creates massive dendroid colonies, up to 1 m wide and 0.5 m tall. Living colonies of E. rostrata have been collected using the PISCES submersibles from three locations from 480 to 788 m water depth in the Line Islands (˜160°W) in the Equatorial Pacific. We have applied to these colonies a high sensitivity, low blank technique to determine U-series ages in small quantities (70 ± 15 mg) of modern and near modern calcareous skeletons using MC-ICP-MS (Multi-collector Inductively Coupled Plasma Mass Spectrometer). The application of this method to living slow-growing colonies from a range of sites as well as the observations of axial growth patterns in thin sections of their skeletons offer the first expanded and well constrained data on longevity, growth pattern and mean growth rates in E. rostrata. Absolute dated specimens indicate life spans of colonies ranging from 209 ± 8 yrs to 605 ± 7 yrs with radial growth rates from 0.012 to 0.072 mm yr -1 and vertical extension rates from 0.6 to 1.9 mm yr -1. The linear growth rates reported here are lower than those reported for other deep-sea scleractinian corals ( Lophelia pertusa and Madrepora oculata). The U-series dating indicates that the growth ring patterns of E. rostrata are not consistent with annual periodicity emphasizing the importance of absolute radiometric dating methods to constrain growth rates. Slow accretion and extreme longevity make this species and its habitat especially vulnerable to disturbances and impacts from human activities. This dating method combined with observation of growth patterns opens up new perspectives in the field of deep-sea corals since it can provide quantitative estimates of growth rates and longevity of deep-sea corals in general.

  9. Combined K-Ar and 40Ar/39Ar dating of the upper Jaramillo reversal

    NASA Astrophysics Data System (ADS)

    Guillou, Herve; Carracedo, Juan Carlos; Kissel, Catherine; Laj, Carlo; Nomade, Sebastien; Perez Torrado, Francisco Jose; Rodriguez Gonzalez, Alejandro; Wandres, Camille

    2013-04-01

    The Jaramillo subchron was first evidenced in 1966 (Doell and Dalrymple) through the Rhyolotic domes of the Valles Caldera, New Mexico (USA). 40Ar/39Ar studies achieved by Spell et McDougall (1992), Spell et Harrison (1993), Izett and Obradovich (1994) and Singer et al. (1994) defined the base of this subchron at 1053±6 ka, and the ceiling at 986±5 ka. Channell et al. (2009) delimited the age of the Jaramillo subchron by astronomic calibration (base 1071 ka, top 990 ka). To provide additional absolute ages on this geomagnetic period, which is critical to improve our knowledge of the earth magnetic field behaviour, we have carried out a study combining paleomagnetism and isotopic dating of a lava sequence from Tenerife island. This sequence of basaltic lava flows is some 500 m thick. The first 400 m present, based on field magnetometer measurements, normal polarity lavas, with dykes of normal and reverse polarity, passing at the top to reverse polarity lavas. Preliminary K-Ar ages bracketed this sequence between 1018 ± 18 ka and 978 ± 17 ka. Therefore, the upper Jaramillo reversal at least appeared to be potentially recorded in this sequence. A more detailed paleomagnetic study was then carried out to more precisely delimit the reversal itself (see Laj et al., session EMRP3.4). We have undertaken 40Ar/39Ar incremental heating and unspiked K-Ar experiments on groundmass from four transitionally magnetized flows. The first transitional flow is K-Ar dated at 993 ± 18 ka and 40Ar/39Ar dated at 991 ± 13 ka, the second at 981 ± 17 ka (K-Ar) and 1000 ± 13 ka (40Ar/39Ar), the third at 950 ± 17 ka (K-Ar) and 1000 ± 8 ka (40Ar/39Ar) and the fourth at 984 ± 17 ka (K-Ar) and 977 ± 12 (40Ar/39Ar). 40Ar/39Ar ages and K-Ar ages (relative to FCT 28.02 Ma) are indistinguishable at 2σ. The age of the upper boundary of the Jaramillo event calculated combining 40Ar/39Ar ages and K-Ar ages is 992 ± 6 ka, in agreement with previous estimates.

  10. Vulcanism and Radiocarbon Dates

    DOE R&D Accomplishments Database

    Libby, L. M.; Libby, W. F.

    1972-10-01

    We consider whether the long term perturbation of radiocarbon dates, which is known to be approximately a sin function of period about 8000 years and amplitude of about 8% peak-to-peak, could have been caused in any major part by vulcanism. We conclude that this is not the case. On the contrary, present day volcanoes are a far less important source of inert CO{sub 2} (about 100 fold less) than is man's burning of fossil fuels which has caused the Suess dilution of about 2%. (auth)

  11. Hunting for eruption ages in accessory minerals

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.

    2012-12-01

    A primary goal in geochronology is to provide precise and accurate ages for tephras that serve as chronostratigraphic markers for constraining the timing and rates of volcanism, sedimentation, climate change, and catastrophic events in Earth history. Zircon remains the most versatile accessory mineral for dating silicic tephras due to its common preservation in distal pyroclastic deposits, as well as the robustness of its U-Pb and U-series systems even after host materials have been hydrothermally altered or weathered. Countless studies document that zircon may be complexly zoned in age due to inheritance, contamination, recycling of antecrysts, protracted crystallization in long-lived magma reservoirs, or any combination of these. Other accessory minerals such as allanite or chevkinite can retain similar records of protracted crystallization. If the goal is to date the durations of magmatic crystallization, differentiation, and/or magma residence, then these protracted chronologies within and between accessory minerals are a blessing. However, if the goal is to date the timing of eruption with high precision, i.e., absolute ages with millennial-scale uncertainties, then this age zoning is a curse. Observations from ion microprobe 238U-230Th dating of Pleistocene zircon and allanite provide insight into the record of near-eruption crystallization in accessory minerals and serve as a guide for high-precision whole-crystal dating. Although imprecise relative to conventional techniques, ion probe analysis allows high-spatial resolution 238U-230Th dating that can document multi-millennial age distributions at the crystal scale. Analysis of unpolished rims and continuous depth profiling of zircon from small and large volume eruptions (e.g., Coso, Mono Craters, Yellowstone) reveals that the final several micrometers of crystallization often yield ages that are indistinguishable from associated eruption ages from the 40Ar/39Ar or (U-Th)/He methods. Using this approach, we

  12. Ages and Stages: Teen

    MedlinePlus

    ... Pediatrician Ages & Stages Prenatal Baby Toddler Preschool Gradeschool Teen Dating & Sex Fitness Nutrition Driving Safety School Substance Abuse Young Adult Healthy Children > Ages & Stages > Teen Teen Article Body Adolescence can be a rough ...

  13. Optical dating of tufa via in situ aeolian sand grains: A case example from the Southern High Plains, USA

    USGS Publications Warehouse

    Rich, J.; Stokes, S.; Wood, W.; Bailey, R.

    2003-01-01

    Precipitated carbonates (commonly termed tufas or travertines) maybe of considerable utility for palaeoenvironmental reconstruction. Their potential, however, for such reconstruction is commonly limited by difficulties associated with their absolute age control. Attempts to date such deposits via uranium series techniques have been complicated by their chemically open behaviour. Here we describe an alternative approach to date tufa deposits associated with ephemeral saline lake basins from the Southern High Plains, USA. We have optically dated sand grains of a mixed aeolian/fluvial (spring fed) origin as the integrating dosimeter. We assume that the grains are fully resetting prior to their incorporation into the tufa deposits and employ a time-dependent disequilibrium dosimetric model to account for the build-up of uranium series daughter products. The approach was applied to a set of four samples with known stratigraphic association. We obtained stratigraphically sensible optical ages ranging from 78??8 to 56??4ka. These data are consistent with existing palaeoenvironmental models of regional recharge. ?? 2003 Elsevier Science Ltd. All rights reserved.

  14. Positives and negatives of online dating according to women 50.

    PubMed

    Vandeweerd, Carla; Myers, Jaime; Coulter, Martha; Yalcin, Ali; Corvin, Jaime

    2016-01-01

    To understand the positives and negatives of online dating according to the lived experience of older women, telephone interviews were conducted with 45 women ages 50+ who date online. Interviews were audio recorded, transcribed verbatim, and thematically team coded. The opportunity to expand one's social network for both friendships and romantic partners, the ability to control dating risks and pace of relationship formation, and knowing more about one's partner were significant reported benefits of online dating. Dating online also includes unique risks, such as pervasive lying, attempted financial exploitation in the form of scammers, and unwanted electronic sexual aggression.

  15. Luminescence dating of ancient Darhad basin, Mongolia

    NASA Astrophysics Data System (ADS)

    Cheul Kim, Jin; Yi, Sangheon; Lim, Jaesoo; Kim, Ju-Yong

    2016-04-01

    Darhad basin is located in the northern Mongolia, in the western end of the Baikal Rift Zone. In contrast to the neighboring Lake Hovsgol, Mongolia's largest and deepest lake, the Darhad is a drained lake basin. It is ~100 km long (north-south), 20-40 km wide and covered by sediments which locally exceed 500 m thickness (Zorin et al., 1989). Darhad basin is characterized by alternating episodes of expansion and desiccation that are closely related with the Pleistocene damming events. Previous studies of the Darhad Basin suggest that the last paleolake was dammed by a large glacier or the sediments (Selivanov, 1967, 1968; Krivonogov et al., 2005; Gillespie et al., 2008). Especially, recent expansion of the paleolake might be caused by the two glacial maxima during MIS 4 and 2. However, glacier-dammed lakes might be short-lived, dried up and permafrost occurred in the drained basin during the Holocene period. The uppermost paleolake sediments (13.2 m depth) are exposed following the curvature of the meandering river (called "Hodon outcrop"). It is considered the most likely site for the youngest paleolake sediments because it is distributed in the northern middle part of the paleolake. Krivonogov et al. 2012 described the Hodon outcrop with the sedimentological and chronological data. Age dating of 16 samples (11 mollusk shells, 5 wood fragments) indicated that Hodon outcrop sediments were deposited between 10.1±7 and 4.9±5 ka. However, the ages obtained on shells much older dates than the matched wood samples because of ingestion of old carbon by mollusks. The age difference between shells and wood fragments is a minimum of 1.73 ka and a maximum of 3.41 ka (average 2.5 ka). In this case, 14C ages from shells should be corrected with appropriate correction factor. However, the old carbon effects could vary temperally and spatially in the Darhad paleolake. The limited number of the 14C ages from wood fragments result in a simple linear trend in the depth-age curve

  16. Landsat-7 ETM+ radiometric stability and absolute calibration

    USGS Publications Warehouse

    Markham, B.L.; Barker, J.L.; Barsi, J.A.; Kaita, E.; Thome, K.J.; Helder, D.L.; Palluconi, Frank Don; Schott, J.R.; Scaramuzza, P.; ,

    2002-01-01

    Launched in April 1999, the Landsat-7 ETM+ instrument is in its fourth year of operation. The quality of the acquired calibrated imagery continues to be high, especially with respect to its three most important radiometric performance parameters: reflective band instrument stability to better than ??1%, reflective band absolute calibration to better than ??5%, and thermal band absolute calibration to better than ??0.6 K. The ETM+ instrument has been the most stable of any of the Landsat instruments, in both the reflective and thermal channels. To date, the best on-board calibration source for the reflective bands has been the Full Aperture Solar Calibrator, which has indicated changes of at most -1.8% to -2.0% (95% C.I.) change per year in the ETM+ gain (band 4). However, this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on ground observations, which bound the changes in gain in band 4 at -0.7% to +1.5%. Also, ETM+ stability is indicated by the monitoring of desert targets. These image-based results for four Saharan and Arabian sites, for a collection of 35 scenes over the three years since launch, bound the gain change at -0.7% to +0.5% in band 4. Thermal calibration from ground observations revealed an offset error of +0.31 W/m 2 sr um soon after launch. This offset was corrected within the U. S. ground processing system at EROS Data Center on 21-Dec-00, and since then, the band 6 on-board calibration has indicated changes of at most +0.02% to +0.04% (95% C.I.) per year. The latest ground observations have detected no remaining offset error with an RMS error of ??0.6 K. The stability and absolute calibration of the Landsat-7 ETM+ sensor make it an ideal candidate to be used as a reference source for radiometric cross-calibrating to other land remote sensing satellite systems.

  17. 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.

  18. Absolute Radiometric Calibration of EUNIS-06

    NASA Technical Reports Server (NTRS)

    Thomas, R. J.; Rabin, D. M.; Kent, B. J.; Paustian, W.

    2007-01-01

    The Extreme-Ultraviolet Normal-Incidence Spectrometer (EUNIS) is a soundingrocket payload that obtains imaged high-resolution spectra of individual solar features, providing information about the Sun's corona and upper transition region. Shortly after its successful initial flight last year, a complete end-to-end calibration was carried out to determine the instrument's absolute radiometric response over its Longwave bandpass of 300 - 370A. The measurements were done at the Rutherford-Appleton Laboratory (RAL) in England, using the same vacuum facility and EUV radiation source used in the pre-flight calibrations of both SOHO/CDS and Hinode/EIS, as well as in three post-flight calibrations of our SERTS sounding rocket payload, the precursor to EUNIS. The unique radiation source provided by the Physikalisch-Technische Bundesanstalt (PTB) had been calibrated to an absolute accuracy of 7% (l-sigma) at 12 wavelengths covering our bandpass directly against the Berlin electron storage ring BESSY, which is itself a primary radiometric source standard. Scans of the EUNIS aperture were made to determine the instrument's absolute spectral sensitivity to +- 25%, considering all sources of error, and demonstrate that EUNIS-06 was the most sensitive solar E W spectrometer yet flown. The results will be matched against prior calibrations which relied on combining measurements of individual optical components, and on comparisons with theoretically predicted 'insensitive' line ratios. Coordinated observations were made during the EUNIS-06 flight by SOHO/CDS and EIT that will allow re-calibrations of those instruments as well. In addition, future EUNIS flights will provide similar calibration updates for TRACE, Hinode/EIS, and STEREO/SECCHI/EUVI.

  19. 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.

  20. 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

  1. Absolute Power Spectral Density Changes in the Magnetoencephalographic Activity During the Transition from Childhood to Adulthood.

    PubMed

    Gómez, Carlos M; Rodríguez-Martínez, Elena I; Fernández, Alberto; Maestú, Fernando; Poza, Jesús; Gómez, Carlos

    2017-01-01

    The aim of this study was to define the pattern of reduction in absolute power spectral density (PSD) of magnetoencephalography (MEG) signals throughout development. Specifically, we wanted to explore whether the human skull's high permeability for electromagnetic fields would allow us to question whether the pattern of absolute PSD reduction observed in the human electroencephalogram is due to an increase in the skull's resistive properties with age. Furthermore, the topography of the MEG signals during maturation was explored, providing additional insights about the areas and brain rhythms related to late maturation in the human brain. To attain these goals, spontaneous MEG activity was recorded from 148 sensors in a sample of 59 subjects divided into three age groups: children/adolescents (7-14 years), young adults (17-20 years) and adults (21-26 years). Statistical testing was carried out by means of an analysis of variance (ANOVA), with "age group" as between-subject factor and "sensor group" as within-subject factor. Additionally, correlations of absolute PSD with age were computed to assess the influence of age on the spectral content of MEG signals. Results showed a broadband PSD decrease in frontal areas, which suggests the late maturation of this region, but also a mild increase in high frequency PSD with age in posterior areas. These findings suggest that the intensity of the neural sources during spontaneous brain activity decreases with age, which may be related to synaptic pruning.

  2. Brownian motion: Absolute negative particle mobility

    NASA Astrophysics Data System (ADS)

    Ros, Alexandra; Eichhorn, Ralf; Regtmeier, Jan; Duong, Thanh Tu; Reimann, Peter; Anselmetti, Dario

    2005-08-01

    Noise effects in technological applications, far from being a nuisance, can be exploited with advantage - for example, unavoidable thermal fluctuations have found application in the transport and sorting of colloidal particles and biomolecules. Here we use a microfluidic system to demonstrate a paradoxical migration mechanism in which particles always move in a direction opposite to the net acting force (`absolute negative mobility') as a result of an interplay between thermal noise, a periodic and symmetric microstructure, and a biased alternating-current electric field. This counterintuitive phenomenon could be used for bioanalytical purposes, for example in the separation and fractionation of colloids, biological molecules and cells.

  3. Arbitrary segments of absolute negative mobility

    NASA Astrophysics Data System (ADS)

    Chen, Ruyin; Nie, Linru; Chen, Chongyang; Wang, Chaojie

    2017-01-01

    In previous research work, investigators have reported only one or two segments of absolute negative mobility (ANM) in a periodic potential. In fact, many segments of ANM also occur in the system considered here. We investigate transport of an inertial particle in a gating ratchet periodic potential subjected to a constant bias force. Our numerical results show that its mean velocity can decrease with the bias force increasing, i.e. ANM phenomenon. Furthermore, the ANM can take place arbitrary segments, even up to more than thirty. Intrinsic physical mechanism and conditions for arbitrary segments of ANM to occur are discussed in detail.

  4. Absolute quantification of myocardial blood flow.

    PubMed

    Yoshinaga, Keiichiro; Manabe, Osamu; Tamaki, Nagara

    2016-07-21

    With the increasing availability of positron emission tomography (PET) myocardial perfusion imaging, the absolute quantification of myocardial blood flow (MBF) has become popular in clinical settings. Quantitative MBF provides an important additional diagnostic or prognostic information over conventional visual assessment. The success of MBF quantification using PET/computed tomography (CT) has increased the demand for this quantitative diagnostic approach to be more accessible. In this regard, MBF quantification approaches have been developed using several other diagnostic imaging modalities including single-photon emission computed tomography, CT, and cardiac magnetic resonance. This review will address the clinical aspects of PET MBF quantification and the new approaches to MBF quantification.

  5. 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.

  6. Absolute Rate Theories of Epigenetic Stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, Jose N.; Wolynes, Peter G.

    2006-03-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape, and the transmission factor, depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic and strictly adiabatic regimes, characterized by the relative values of those input rates.

  7. Absolute rate theories of epigenetic stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, José N.; Wolynes, Peter G.

    2005-12-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape and the transmission factor depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic, and strictly adiabatic regimes, characterized by the relative values of those input rates. rate theory | stochastic gene expression | gene switches

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. The importance of calculating absolute rather than relative fracture risk.

    PubMed

    Tucker, Graeme; Metcalfe, Andrew; Pearce, Charles; Need, Allan G; Dick, Ian M; Prince, Richard L; Nordin, B E Christopher

    2007-12-01

    The relation between fracture risk and bone mineral density (BMD) is commonly expressed as a multiplicative factor which is said to represent the increase in risk for each standard deviation fall in BMD. This practice assumes that risk increases multiplicatively with each unit fall in bone density, which is not correct. Although odds increase multiplicatively, absolute risk, which lies between 0 and 1, cannot do so though it can be derived from odds by the term Odds/(1+Odds). This concept is illustrated in a prospective study of 1098 women over age 69 followed for 6 years in a calcium trial in which hip BMD was measured in the second year. 304 Women (27.6%) had prevalent fractures and 198 (18.1%) incident fractures with a significant association between them (P 0.005). Age-adjusted hip BMD and T-score were significantly lower in those with prevalent fractures than in those without (P 0.003) and significantly lower in those with incident fractures than in those without (P 0.001). When the data were analysed by univariate logistic regression, the fracture odds at zero T-score were 0.130 and the rise in odds for each unit fall in hip T-score was 1.55. When these odds were converted to risks, there was a progressive divergence between odds and risk at T-scores below zero. Multiple logistic regression yielded significant odds ratios of 1.47 for each 5-year increase in age, 1.47 for prevalent fracture and 1.49 for each unit fall in hip T-score. Calcium therapy was not significant. Poisson regression, logistic regression and Cox's proportional hazards yielded very similar outcomes when converted into absolute risks. A nomogram was constructed to enable clinicians to estimate the approximate 6-year fracture risk from hip T-score, age and prevalent fracture which can probably be applied (with appropriate correction) to men as well as to women. We conclude that multiplicative factors can be applied to odds but not to risk and that multipliers of risk tend to overstate the

  14. Radioisotope Dating with Accelerators.

    ERIC Educational Resources Information Center

    Muller, Richard A.

    1979-01-01

    Explains a