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Sample records for 10be surface exposure

  1. 10Be surface exposure dating of rock glaciers in Larstigtal, Tyrol, Austria

    NASA Astrophysics Data System (ADS)

    Ivy-Ochs, S.; Kerschner, H.; Maisch, M.; Christl, M.; Kubik, P. W.; Schluchter, C.

    2009-04-01

    In the context of Lateglacial and Holocene climate change research, rock glaciers (creeping mountain permafrost) also play an important role. They are phenomena of discontinuous alpine permafrost and as such good indicators for the mean annual air temperature for the period they are active. We have 10Be surface exposure dated boulders from two relict rock glaciers in Larstigtal, Austria. This is the type area for a postulated mid-Holocene cold period called the Larstig oscillation. The period of activity was suggested to be of similar age as the mid-Holocene Frosnitz advance of glaciers in the Venediger Mountains farther to the east (Patzelt and Bortenschlager, 1973). For rock glaciers of this size to be active at 2200 m a.s.l. in Larstig valley would have required a significant drop in temperatures, thus a marked mid-Holocene cold pulse, for at least several centuries at around 7.0 ka. In contrast, our exposure dates show that the rock glaciers stabilized during the early Preboreal (Ivy-Ochs et al., submitted). We see no distinct pattern with respect to exposure age and boulder location on the rock glaciers. This implies that for our site the blocks did not acquire inherited 10Be during exposure in the free rock face, in the talus at the base of the slope, or during transport on the rock glaciers. Our data point to final stabilization of the Larstigtal rock glaciers in the earliest Holocene and not in the middle Holocene. Combined with data from other archives (Nicolussi et al., 2005), there appears to have been no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. Ivy-Ochs, S., Kerschner, H., Maisch, M., Christl, M., Kubik, P.W., Schlüchter, C., Latest Pleistocene and Holocene glacier variations in the European Alps. Quaternary Science Reviews (submitted). Nicolussi, K., Kaufmann, M., Patzelt, G., van der Plicht, J., Thurner, A., 2005. Holocene tree-line variability in the Kauner

  2. 10Be surface exposure dating reveals strong active deformation in the central Andean backarc interior

    NASA Astrophysics Data System (ADS)

    García Morabito, Ezequiel; Terrizzano, Carla; Zech, Roland; Willett, Sean; Yamin, Marcela; Haghipour, Negar; Wuethrich, Lorenz; Christl, Marcus; María Cortes, José; Ramos, Victor

    2016-04-01

    Understanding the deformation associated with active thrust wedges is essential to evaluate seismic hazard. How is active faulting distributed throughout the wedge, and how much deformation is taken up by individual structures? We address these questions for our study region, the central Andean backarc of Argentina. We combined a structural and geomorphological approach with surface exposure dating (10Be) of alluvial fans and strath terraces in two key localities at ~32° S: the Cerro Salinas, located in the active orogenic front of the Precordillera, and the Barreal block in the interior of the Andean mountain range. We analysed 22 surface samples and 6 depth profiles. At the thrust front, the oldest terrace (T1) yields an age of 100-130 ka, the intermediate terrace (T2) between 40-95 ka, and the youngest terrace (T3) an age of ~20 ka. In the Andean interior, T1´ dates to 117-146 ka, T2´ to ~70 ka, and T3´ to ~20 ka, all calculations assuming negligible erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. Vertical slip rates of fault offsets are 0.3-0.5 mm/yr and of 0.6-1.2 mm/yr at the thrust front and in the Andean interior, respectively. Our results highlight: i) fault activity related to the growth of the Andean orogenic wedge is not only limited to a narrow thrust front zone. Internal structures have been active during the last 150 ka, ii) deformation rates in the Andean interior are comparable or even higher that those estimated and reported along the emerging thrust front, iii) distribution of active faulting seems to account for unsteady state conditions, and iv) seismic hazards may be more relevant in the internal parts of the Andean orogen than assumed so far. References Lal, D., 1991: Cosmic ray labeling of erosion surfaces: In situ nuclide production rates and erosion models. Earth and Planetary Science Letters 104: 424-439. Stone, J.O., 2000: Air pressure and cosmogenic isotope production. Journal of Geophysical

  3. Advances in cosmogenic surface exposure dating: Using combined in situ 14C-10Be analysis for deglaciation scenarios

    NASA Astrophysics Data System (ADS)

    Hippe, Kristina; Ivy-Ochs, Susan; Kober, Florian; Christl, Marcus; Fogwill, Christopher; Turney, Chris; Rood, Dylan; Lupker, Maarten; Schlücher, Christian; Wieler, Rainer

    2016-04-01

    Cosmogenic nuclides are routinely used to investigate deglaciation histories by exposure dating of rock surfaces after glacier retreat. For bedrock surfaces that have been efficiently eroded by glacier ice, the most commonly applied cosmogenic 10Be isotope has proven to give reliable estimates of the integrated time of surface exposure since major ice decay. Due to its long half-life (~1.4 Ma), however, 10Be does not record short episodes of intermittent surface cover, e.g. during phases of glacier readvance, which might have interrupted the general deglaciation trend. To detect such cases of "complex exposure", 10Be-based dating can be combined with the analysis of the short-lived (5730 a) in situ cosmogenic 14C nuclide. We present two examples, in which combined in situ 14C-10Be analysis has been successfully applied to reconstruct in detail post-LGM surface exposures histories - in the Swiss Alps [1] and in Antarctica [2]. In a study on the Gotthard Pass, Central Swiss Alps, in situ 14C-10Be exposure dating was combined with extensive mapping of glacial erosional features. Data from both cosmogenic nuclides are in overall good agreement with each other confirming continuous exposure of the Gotthard Pass area throughout the Holocene. Some slightly younger in situ 14C ages compared to the corresponding 10Be ages are interpreted to result from partial surface shielding due to snow cover. Constraining the average Holocene snow depth from the in situ 14C data allowed to apply an appropriate snow shielding correction for the 10Be exposure ages. Integration of the snow-corrected exposure ages with field observations provided a detailed chronology of a progressive downwasting of ice from the maximum LGM ice volume with a gradual reorganization of the ice flow pattern and a southward migration of the ice divide. In a study on the evolution and reorganization of ice streams entering the Weddell Sea, Antarctica, during the last deglaciation, ice sheet modelling was

  4. Neotectonic deformation versus climate control in the Central Andes of Argentina, insights from 10Be Surface Exposure Dating

    NASA Astrophysics Data System (ADS)

    Terrizzano, Carla; Zech, Roland; Garcia Morabito, Ezequiel; Yamin, Marcela; Haghipour, Negar; Wüthrich, Lorenz; Christl, Marcus

    2015-04-01

    Mountainous regions and their forelands commonly supports a suite of landforms sensitive to climate change and tectonics, providing -if addressed with appropriate geomorphological and geochronological approaches- record for landscape, climate, and tectonic evolution. In particular, alluvial fans are valuable archives of Quaternary climate and tectonics. The southern Central Andes and their forelands provide a perfect setting to study such forcings, since first, the extreme aridity favors the geomorphological preservation of the fan surfaces, so that 10Be surface exposure dating can be applied to establish robust and precise chronologies. And second, the neotectonic activity in this region results in widespread deformation of Quaternary deposits and recent devastating earthquakes. However, rates of uplift and shortening on the reverse faults remain largely unknown and very little is known yet about the Pleistocene climate history in the southern Central Andes, which limits a robust evaluation of the role of climate for the alluvial fan formation and landscape evolution. We combined structural and geomorphic investigations with 10Be surface exposure dating in the western Precordillera of the Southern Central Andes of Argentina (31°30'-31°53' SL/69°20' WL) in order to establish a numeric chronology for four deformed alluvial fan surfaces, to estimate uplift rates and to evaluate the potential climate role in controlling the fan construction and evolution. Surface exposure ages were determined for a few large boulders, amalgamated pebbles, and via depth profiles on sand samples. Boulder ages range from 145 to 212 ka for the oldest well-preserved fan remnants (Q1a, n=3), from 63 to 108 ka (Q2, n=3) and 21-28 ka (Q3, n=2), amalgamated pebbles yield ages range from 106 to 127 ka for the oldest fan surface (Q1b, n=79), all calculations assuming no erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. Boulders from current channels have 10Be

  5. Examination of surface exposure age of Antarctic moraines using in situ produced [sup 10]Be and [sup 26]Al

    SciTech Connect

    Brown, E.T.; Edmond, J.M. ); Raisbeck, G.M.; Yiou, F. ); Kurz, M.D.; Brook, E.J. )

    1991-08-01

    Concentrations of [sup 10]Be (t[sub 1/2] = 1.5 [times] 10[sup 6]y) and [sup 26]Al (t[sub 1/2] = 0.72 [times] 10[sup 6]y) have been determined by accelerator mass spectrometry (AMS) in a suite of quartz samples taken from sandstone boulders in several moraines in Arena Valley, a dry valley adjacent to the Taylor Glacier in the Quatermain Mountains, Southern Victoria Land, East Antarctica. These isotopes are produced in surficial quartz by cosmic ray spallation of O and Si. The concentrations in these samples ranged from 6.1 [times] 10[sup 5] to 3.0 [times] 10[sup 7] at g[sup [minus]1] for [sup 10]Be and from 9.4 [times] 10[sup 6] to 1.2 [times] 10[sup 8] at g[sup [minus]1] for [sup 26]Al, depending upon the extent of exposure at the surface. Production rates of 17[sub [minus]4][sup +16] at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and 113[sub [minus]16][sup +54] at g[sup [minus]1]y[sup [minus]1] for [sup 26]Al at 1300 m and 87[degree]S and a [sup 26]Al:[sup 10]Be production ratio of 6.5[sub [minus]1.3][sup +1.3] were calculated from the data. These values correspond to sea-level production rates at high geomagnetic latitude of 6.4 at g[sup [minus]1]y[sup [minus]1] and 41.7 at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and [sup 26]Al, respectively, consistent with determinations based on [approximately]11 Ky glacially polished surfaces in the Sierra Nevada in California. These production rates imply exposure ages for the various moraines ranging from 50 Ky to 2.5 My, in accordance with other geological evidence. The [sup 10]Be and [sup 26]Al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of [sup 3]He.

  6. LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating

    NASA Astrophysics Data System (ADS)

    Zech, R.; Kull, Ch.; Kubik, P. W.; Veit, H.

    2007-06-01

    Surface exposure dating (SED) is an innovative tool being already widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22-25 ka and thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11-13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been substantially overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions further west and south.

  7. LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating

    NASA Astrophysics Data System (ADS)

    Zech, R.; Kull, Ch.; Kubik, P. W.; Veit, H.

    2007-10-01

    Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22-25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11-13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.

  8. Mid-late Pleistocene glacial evolution in the Grove Mountains, East Antarctica, constraints from cosmogenic 10Be surface exposure dating of glacial erratic cobbles

    NASA Astrophysics Data System (ADS)

    Dong, Guocheng; Huang, Feixin; Yi, Chaolu; Liu, Xiaohan; Zhou, Weijian; Caffee, Marc W.

    2016-08-01

    Glacial histories from the East Antarctic Ice Sheet (EAIS) provide keys to understanding correlations between the EAIS and global climate. They are especially helpful in the assessment of global sea level change, and as a means of quantifying the magnitude of past glacial activity and the rate at which ice responded to climate change. Given the significance of EAIS glacial histories, it is imperative that more glacial chronologic data for this region be obtained, especially for the mid-to-late Pleistocene. We report cosmogenic 10Be surface exposure dating results from glacially transported cobbles embedded in blue-ice moraine material at Mount Harding, the Grove Mountains, EAIS. Forty exotic cobbles sampled along two profiles (A and B) on this blue-ice moraine present apparent exposure-ages ranging from 7.2 to 542.2 ka. We explore this scattered dataset by using Principal Component Analysis (PCA) to identify statistically significant trends in the data. We identify a correlation between exposure-age and distance of the cobbles from Mount Harding. In profile A, cobbles further from Mount Harding yield older exposure-ages than those that are relatively close. In profile B, cobbles closer to Mount Harding are found to have relatively older exposure-ages. In term of glacial history we suggest that the direction of ice flow changed during the period from ∼60 to 200 ka, and that multiple glacial fluctuations occurred in the mid-late Pleistocene.

  9. Long-term slip rate of the southern San Andreas Fault, from 10Be-26Al surface exposure dating of an offset alluvial fan

    SciTech Connect

    der Woerd, J v; Klinger, Y; Sieh, K; Tapponnier, P; Ryerson, F; M?riaux, A

    2006-01-13

    We determine the long-term slip rate of the southern San Andreas Fault in the southeastern Indio Hills using {sup 10}Be and {sup 26}Al isotopes to date an offset alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images allow to precisely determine piercing points across the fault zone that are used to measure an offset of 565 {+-} 80 m. A total of twenty-six quartz-rich cobbles from three different fan surfaces were collected and dated. The tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history, negligible prior exposure and erosion, and yield an age of 35.5 {+-} 2.5 ka. The long-term slip rate of the San Andreas Fault south of Biskra Palms is thus 15.9 {+-} 3.4 mm/yr. This rate is about 10 mm/yr slower than geological (0-14 ka) and short-term geodetic estimates for this part of the San Andreas Fault implying changes in slip rate or in faulting behavior. This result puts new constraints on the slip rate of the San Jacinto and on the Eastern California Shear Zone for the last 35 ka. Our study shows that more sites along the major faults of southern California need to be targeted to better constrain the slip-rates over different time scales.

  10. The deglaciation history of the Simplon region (southern Swiss Alps) constrained by 10Be exposure dating of ice-molded bedrock surfaces

    NASA Astrophysics Data System (ADS)

    Dielforder, Armin; Hetzel, Ralf

    2014-01-01

    The deglaciation history of the Swiss Alps after the Last Glacial Maximum involved the decay of several ice domes and the subsequent disintegration of valley glaciers at high altitude. Here we use bedrock exposure dating to reconstruct the temporal and spatial pattern of ice retreat at the Simplon Pass (altitude: ˜2000 m) located 40 km southwest of the 'Rhône ice dome'. Eleven 10Be exposure ages from glacially polished quartz veins and ice-molded bedrock surfaces cluster tightly between 13.5 ± 0.6 ka and 15.4 ± 0.6 ka (internal errors) indicating that the Simplon Pass depression became ice-free at 14.1 ± 0.4 ka (external error of mean age). This age constraint is interpreted to record the melting of the high valley glaciers in the Simplon Pass region during the warm Bølling-Allerød interstadial shortly after the Oldest Dryas stadial. Two bedrock samples collected a few hundred meters above the pass depression yield older 10Be ages of 17.8 ± 0.6 ka and 18.0 ± 0.6 ka. These ages likely reflect the initial downwasting of the Rhône ice dome and the termination of the ice transfluence from the ice dome across the Simplon Pass toward the southern foreland. There, the retreat of the piedmont glacier in Val d'Ossola was roughly synchronous with the decay of the Rhône ice dome in the interior of the mountain belt, as shown by 10Be ages of 17.7 ± 0.9 ka and 16.1 ± 0.6 ka for a whaleback at ˜500 m elevation near Montecrestese in northern Italy. In combination with well-dated paleoclimate records derived from lake sediments, our new age data suggest that during the deglaciation of the European Alps the decay of ice domes was approximately synchronous with the retreat of piedmont glaciers in the foreland and was followed by the melting of high-altitude valley glaciers after the transition from the Oldest Dryas to the Bølling-Allerød, when mean annual temperatures rose rapidly by ˜3 °C.

  11. Surface exposure dating of Holocene basalt flows and cinder cones in the Kula volcanic field (western Turkey) using cosmogenic 3He and 10Be

    NASA Astrophysics Data System (ADS)

    Heineke, Caroline; Niedermann, Samuel; Hetzel, Ralf; Akal, Cüneyt

    2015-04-01

    The Kula volcanic field is the youngest volcanic province in western Anatolia and covers an area of about 600 km2 around the town Kula (Richardson-Bunbury, 1996). Its alkali basalts formed by melting of an isotopically depleted mantle in a region of long-lived continental extension and asthenospheric upwelling (Prelevic et al., 2012). Based on morphological criteria and 40Ar/39Ar dating, four phases of Quaternary activity have been distinguished in the Kula volcanic field (Richardson-Bunbury, 1996; Westaway et al., 2006). The youngest lava flows are thought to be Holocene in age, but so far only one sample from this group was dated by 40Ar/39Ar at 7±2 ka (Westaway et al., 2006). In this study, we analysed cosmogenic 3He in olivine phenocrysts from three basalt flows and one cinder cone to resolve the Holocene history of volcanic eruptions in more detail. In addition, we applied 10Be exposure dating to two quartz-bearing xenoliths found at the surface of one flow and at the top of one cinder cone. The exposure ages fall in the range between ~500 and ~3000 years, demonstrating that the youngest volcanic activity is Late Holocene in age and therefore distinctly younger than previously envisaged. Our results show that the Late Holocene lava flows are not coeval but formed over a period of a few thousand years. We conclude that surface exposure dating of very young volcanic rocks provides a powerful alternative to 40Ar/39Ar dating. References Prelevic, D., Akal, C. Foley, S.F., Romer, R.L., Stracke, A. and van den Bogaard, P. (2012). Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of southwestern Anatolia, Turkey. Journal of Petrology, 53, 1019-1055. Richardson-Bunbury, J.M. (1996). The Kula Volcanic Field, western Turkey: the development of a Holocene alkali basalt province and the adjacent normal-faulting graben. Geological Magazine, 133, 275-283. Westaway, R., Guillou, H., Yurtmen, S., Beck, A

  12. Pleistocene glaciations of Central Asia: results from 10Be surface exposure ages of erratic boulders from the Pamir (Tajikistan), and the Alay Turkestan range (Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Abramowski, U.; Bergau, A.; Seebach, D.; Zech, R.; Glaser, B.; Sosin, P.; Kubik, P. W.; Zech, W.

    2006-05-01

    We have determined the timing of glaciations in the Pamir (Tajikistan) and the Alay-Turkestan Range (Kyrgyzstan) using 10Be surface exposure dating. Glacial advances in the area have occurred >93-136, ˜60-80, (40-55), ˜27-25, ˜22-20, ˜19-17, ˜16-15, ˜15-13, and 11-9 cal ka BP. All Late Pleistocene glaciers in the Pamir, and the Alay-Turkestan Ranges have been valley glaciers except for the most extended glaciers on the Pamir plateau, which have formed local piedmont glaciations. In the eastern Pamir, these are characterized by ELA depressions of ˜370-380 m (THAR 0.5). In the Turkestan Range and Alay Range, ELA depressions at the same time were >750 and 600 m, respectively. Late Pleistocene glacier advances all over western High Asia were contemporaneous with climatic cold phases rather than monsoonal maxima. Their maximum extent and that of the western hemisphere ice sheets were asynchronous, due to increasing aridity in the region over the course of the Last Glacial. Late Pleistocene climate in Central Asia seems to have been influenced by the interplay of the westerly circulation and the Siberian anticyclone. Some indirect monsoonal influence in the eastern Pamir may be responsible for the existence of some of the Lateglacial moraine stages in this area. High altitude glaciers seem to have reached their maximum extent earlier (MIS 5-4) than low altitude glaciers (first half of MIS 3), possibly due to prolonged glacial aridity imparting with moisture advection onto high altitude sites, inducing glacial retreat, but prolonged cold during the same time imparting with glacier ablation at lower altitude sites, inducing glacial advance.

  13. Climatic and topographic controls on the style and timing of Late Quaternary glaciation throughout Tibet and the Himalaya defined by 10Be cosmogenic radionuclide surface exposure dating

    USGS Publications Warehouse

    Owen, L.A.; Finkel, R.C.; Barnard, P.L.; Haizhou, Ma; Asahi, K.; Caffee, M.W.; Derbyshire, E.

    2005-01-01

    Temporal and spatial changes in glacier cover throughout the Late Quaternary in Tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region, and the lack of numerical dating. To help reconstruct the timing and extent of glaciation throughout Tibet and the bordering mountains, we use geomorphic mapping and 10Be cosmogenic radionuclide (CRN) surface dating in study areas in southeastern (Gonga Shan), southern (Karola Pass) and central (Western Nyainqentanggulha Shan and Tanggula Shan) Tibet, and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands. Each of the study regions receives its precipitation mainly during the south Asian summer monsoon when it falls as snow at high altitudes. Gonga Shan receives the most precipitation (>2000 mm a-1) while, near the margins of monsoon influence, the Karola Pass receives moderate amounts of precipitation (500-600 mm a-1) and, in the interior of the plateau, little precipitation falls on the western Nyainqentanggulha Shan (???300 mm a -1) and the Tanggula Shan (400-700 mm a-1). The higher precipitation values for the Tanggula Shan are due to strong orographic effects. In each region, at least three sets of moraines and associated landforms are preserved, providing evidence for multiple glaciations. The 10Be CRN surface exposure dating shows that the formation of moraines in Gonga Shan occurred during the early-mid Holocene, Neoglacial and Little Ice Age, on the Karola Pass during the Lateglacial, Early Holocene and Neoglacial, in the Nyainqentanggulha Shan date during the early part of the last glacial cycle, global Last Glacial Maximum and Lateglacial, and on the Tanggula Shan during the penultimate glacial cycle and the early part of the last glacial cycle. The oldest moraine succession in each of these regions varies from the early Holocene (Gonga Shan), Lateglacial (Karola Pass), early Last Glacial (western

  14. Using 10Be cosmogenic surface exposure dating to determine the evolution of the Purgatorio active fault in the Andean forearc, southern Peru

    NASA Astrophysics Data System (ADS)

    Carlos, Benavente; Swann, Zerathe; Laurence, Audin; Fabrizio, Delgado; Marianne, Saillard; Sarah, Hall R.; Aster Team

    2015-04-01

    Active transpressive deformation has been occurring along the Andean hyperarid forearc for the last 3 Myrs but many of these faults are still not described even if able to produce large damaging earthquakes. Active faulting along the northern part of the Arica Bend can be recognized due to the presence of well-preserved and sharp fault scarps indicating recent surface slip. During the Mio-Pliocene, deposition within the forearc continental basins resulted in the formation of vast fan deposits and conglomerates of the Moquegua Formation, which can be considered as bedrock in this exposure study (~45-4 Ma; Tosdal et al., 1984; Sebrier et al., 1988a; Roperch et al., 2006). The typical vertical Purgatorio fault scarps offset both the Moquegua bedrock and several younger geomorphic features associated with <300kyrs climatic and 400 years old volcanic extreme events. This study focus on quantifying slip rate variations in time along a 5-meters high vertical fault scarp to understand how the fault is evolving. These results are achieved via surface exposure dating of the sampled seismically broken cobbolds of the Moquegua formation outcroping vertically along the fault scarp. These samples are well-suited to the application of in situ produced cosmogenic radionuclides for surface exposure dating, as the hyperarid region has extremely low erosion rates. We sampled the scarp away from any significant drainage so as to avoid possibly disturbed areas. The sampling did involve extracting quarzite conglomeratic material along the bedrock scarp and on the upper surrounding crests. The aim has been to measure Berylium-20 TCN (Terrestrial in situ Cosmogenic Nuclides) concentrations to determine exposure age as a function of height on the scarp. This has been successfully employed on one scarp in Italy based on Chlorine-36 TCN (Palumbo et al., 2004). However, slow faults behaviour remains unclear and more contributions are needed. Quaternary activity of the Purgatorio fault system

  15. Evaluating the reliability of Late Quaternary landform ages: Integrating 10Be cosmogenic surface exposure dating with U-series dating of pedogenic carbonate on alluvial and fluvial deposits, Sonoran desert, California

    NASA Astrophysics Data System (ADS)

    Blisniuk, K.; Sharp, W. D.

    2015-12-01

    To assess the reliability of Quaternary age determinations of alluvial and fluvial deposits across the Sonoran Desert (Coachella Valley and Anza Borrego) in southern California, we applied both 10Be exposure age dating of surface clasts and U-series dating of pedogenic carbonate from subsurface clast-coatings to the same deposits. We consider agreement between dates from the two techniques to indicate reliable age estimates because each technique is subject to distinct assumptions and therefore their systematic uncertainties are largely independent. 10Be exposure dates should yield maximum ages when no correction is made for inheritance and post-depositional erosion is negligible. U-series dating, in contrast, provides minimum dates because pedogenic carbonate forms after deposition. Our results show that: (1) For deposits ca. 70 ka or younger, 10Be and U-series dates were generally concordant. We note, however, that in most cases U-series soil dates exceed 10Be exposure dates that are corrected for inheritance when using 10Be in modern alluvium. This suggests that 10Be concentrations of modern alluvium may exceed the 10Be acquired by late Pleistocene deposits during fluvial transport and hillslope residence (i.e., Pleistocene inherited 10Be). (2) For deposits older than ~70 ka, U-series dates are significantly younger than the 10Be dates. This implies that U-series dates in this region may significantly underestimate the depositional age of older alluvium, probably because of delayed onset of deposition, slow accumulation, or poor preservation of secondary carbonate in response to climatic controls. Thus, whenever possible, multiple dating methods should be applied to obtain reliable ages for late Quaternary deposits.

  16. A global compilation of glacial 10Be and 26Al exposure ages

    NASA Astrophysics Data System (ADS)

    Heyman, Jakob

    2015-04-01

    Cosmogenic dating has enabled direct dating of glacial landforms and deposits, greatly improving our understanding of past glaciations in terms of timing as well as glacial erosion and preservation. Over the last 25 years a large (and growing) number of publications have reported cosmogenic exposure ages from glacial landforms around the world. Here a global compilation of glacial 10Be and 26Al exposure ages will be presented aiming at an analysis and quantification of cosmogenic dating uncertainties. The dataset consists of >9300 10Be exposure ages and >1400 26Al exposure ages with full input data (location, elevation, sample type, sample thickness, concentration, standardization etc.). All exposure ages have been recalculated with updated reference production rates and organized in discrete glacial landform groups enabling evaluation of exposure age scatter due to prior and incomplete exposure. Exposure age scatter is common and increase significantly for glacial landforms older than the global last glacial maximum, making precise cosmogenic dating of older glaciations difficult. The data will be used to evaluate exposure dating of different sample types (boulder vs bedrock surfaces) and sample selection based on boulder size. Exposure ages from the paleo-ice sheets will be compared with mountain glacier exposure ages, aiming at picking out the good (well-clustered) exposure ages. The full dataset will eventually be posted online and continuously updated with published exposure age data.

  17. East Antarctic deglaciation and the link to global cooling during the Quaternary: evidence from glacial geomorphology and 10Be surface exposure dating of the Sør Rondane Mountains, Dronning Maud Land

    NASA Astrophysics Data System (ADS)

    Suganuma, Yusuke; Miura, Hideki; Zondervan, Albert; Okuno, Jun'ichi

    2014-08-01

    Reconstructing past variability of the Antarctic ice sheets is essential to understand their stability and to anticipate their contribution to sea level change as a result of future climate change. Recent studies have reported a significant decrease in thickness of the East Antarctic Ice Sheet (EAIS) during the last several million years. However, the geographical extent of this decrease and subsequent isostatic rebound remain uncertain. In this study, we reconstruct the magnitude and timing of ice sheet retreat at the Sør Rondane Mountains in Dronning Maud Land, East Antarctica, based on detailed geomorphological survey, cosmogenic exposure dating, and glacial isostatic adjustment modeling. Three distinct deglaciation phases are identified for this sector during the Quaternary, based on rock weathering and 10Be surface exposure data. We estimate that the ice sheet thinned by at least 500 m during the Pleistocene. This thinning is attributed to the reorganization of Southern Ocean circulation associated with global cooling into the Pleistocene, which reduced the transport of moisture from the Southern Ocean to the interior of EAIS. The data also show that since the Last Glacial Maximum the ice surface has lowered less than ca 50 m and that this lowering probably started after ca 14 ka. This suggests that the EAIS in Dronning Maud Land is unlikely to have been a major contributor to postglacial sea-level rise and Meltwater pulse 1A.

  18. Extent of the last ice sheet in northern Scotland tested with cosmogenic 10Be exposure ages

    USGS Publications Warehouse

    Phillips, W.M.; Hall, A.M.; Ballantyne, C.K.; Binnie, S.; Kubik, P.W.; Freeman, S.

    2008-01-01

    The extent of the last British-Irish Ice Sheet (BIIS) in northern Scotland is disputed. A restricted ice sheet model holds that at the global Last Glacial Maximum (LGM; ca. 23-19 ka) the BIIS terminated on land in northern Scotland, leaving Buchan, Caithness and the Orkney Islands ice-free. An alternative model implies that these three areas were ice-covered at the LGM, with the BIIS extending offshore onto the adjacent shelves. We test the two models using cosmogenic 10Be surface exposure dating of erratic boulders and glacially eroded bedrock from the three areas. Our results indicate that the last BIIS covered all of northern Scotland during the LGM, but that widespread deglaciation of Caithness and Orkney occurred prior to rapid warming at ca. 14.5 ka. Copyright ?? 2008 John Wiley & Sons, Ltd.

  19. Late Pleistocene glacial chronology of the Retezat Mts, Southern Carpathians, using 10Be exposure ages

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Kern, Zoltán; Urdea, Petru; Braucher, Régis; Madarász, Balázs; Schimmelpfennig, Irene

    2015-04-01

    Our knowledge on the timing of glacial advances in the Southern Carpathians is limited. Recently, some attempts have been made to develop an improved temporal framework for the glaciations of the region using cosmogenic 10Be exposure dating. However, glacial chronology of the Romanian Carpathians remains contradictory. E.g. the timing of the maximum ice advance appears to be asynchronous within the area and also with other dated glacial events in Europe. Main objective of our study is to utilize cosmogenic in situ produced 10Be dating to disentangle the contradictions of the Southern Carpathian Late Pleistocene glacial chronology. Firstly, previously published 10Be data are recalculated in accordance with the new half-life, standardization and production rate of 10Be. The recalculated 10Be exposure ages of the second largest (M2) moraines in the Retezat Mts. appear to be ca. 19-24% older than exposure ages calculated by Reuther et al. (2007, Quat. Int. 164-165, 151-169). This contradicts the earlier conclusions suggesting post LGM age of M2 glacial advance and suggests that M2 moraines can be connected to the end of the LGM with final stabilization possibly at the beginning of the Late Glacial. We emphasize that it is ambiguous to correlate directly the exposure-dated glacier chronologies with millennial scale climate changes due to uncertainties in sample collection and in computation of exposure ages from measured nuclide concentrations. New 10Be samples were collected in order to determine the 10Be exposure age of moraines outside the most prominent generation (M2) including the largest and oldest moraine (M1) and the landforms connected to the smallest ice advances (M4), which remained undated so far. The new exposure ages of M2 moraines are well in harmony with the recalculated ages of Reuther at al. (2007). 10Be exposure age of boulders on the smallest moraine suggest that the last glaciers disappeared in the area during the Late Glacial, indicating no

  20. The CREp program, a fully parameterizable program to compute exposure ages (3He, 10Be)

    NASA Astrophysics Data System (ADS)

    Martin, L.; Blard, P. H.; Lave, J.; Delunel, R.; Balco, G.

    2015-12-01

    Over the last decades, cosmogenic exposure dating permitted major advances in Earth surface sciences, and particularly in paleoclimatology. Yet, exposure age calculation is a dense procedure. It requires numerous choices of parameterization and the use of an appropriate production rate. Nowadays, Earth surface scientists may either calculate exposure ages on their own or use the available programs. However, these programs do not offer the possibility to include all the most recent advances in Cosmic Ray Exposure (CRE) dating. Notably, they do not propose the most recent production rate datasets and they only offer few possibilities to test the impact of the atmosphere model and the geomagnetic model on the computed ages. We present the CREp program, a Matlab © code that computes CRE ages for 3He and 10Be over the last 2 million years. The CREp program includes the scaling models of Lal-Stone in the "Lal modified" version (Balco et al., 2008; Lal, 1991; Stone, 2000) and the LSD model (Lifton et al., 2014). For any of these models, CREP allows choosing between the ERA-40 atmosphere model (Uppala et al., 2005) and the standard atmosphere (National Oceanic and Atmospheric Administration, 1976). Regarding the geomagnetic database, users can opt for one of the three proposed datasets: Muscheler et al. 2005, GLOPIS-75 (Laj et al. 2004) and the geomagnetic framework proposed in the LSD model (Lifton et al., 2014). They may also import their own geomagnetic database. Importantly, the reference production rate can be chosen among a large variety of possibilities. We made an effort to propose a wide and homogenous calibration database in order to promote the use of local calibration rates: CREp includes all the calibration data published until July 2015 and will be able to access an updated online database including all the newly published production rates. This is crucial for improving the ages accuracy. Users may also choose a global production rate or use their own data

  1. Andean coastal uplift and active tectonics in southern Peru: 10Be surface exposure dating of differentially uplifted marine terrace sequences (San Juan de Marcona, ~ 15.4°S)

    NASA Astrophysics Data System (ADS)

    Saillard, M.; Hall, S. R.; Audin, L.; Farber, D. L.; Regard, V.; Hérail, G.

    2011-05-01

    Along the San Juan de Marcona Bay of southern Peru, two spectacular sequences of preserved marine terraces record net Quaternary uplift. Previous geomorphic analysis of these paleo-shorelines has revealed evidence of upper plate deformation and regional uplift. However, in the absence of a robust absolute dating method, these studies contain substantial uncertainties concerning the numerical dating of these marine markers and thus the corresponding calculated surface uplift rates. However, field mapping, surveying the neotectonic features and 10Be dating of abraded surfaces contained within two sequences of marine terraces along this margin should allow for the robust calculation of Pleistocene uplift rates. The San Juan de Marcona Bay lies on the southern flank of the subducting and south-migrating aseismic Nazca Ridge where the maximum rates of coastal uplift are expected. In this locality, we measure high uplift rates ranging from 0.4 m/ka to 0.9 m/ka during the Pleistocene. Margin-parallel normal faults displace several marine terraces and influence the development of bays, thereby contributing to the configuration of paleo- and present-day coastlines. The faults have relatively low slip rates, < 0.1 m/ka over 400 ka, and have been inactive for the last 80 ka. The presence and activity of these normal faults can be directly linked to subduction zone processes, with the release and accommodation of short-term coseismic compression during megathrust subduction-zone events. In contrast, the regional permanent uplift is probably controlled by post-seismic and/or interseismic strain accumulation over longer time-scales due to inelastic behavior of the upper plate. Since at least the latest Pliocene, the San Juan de Marcona area has experienced long-term regional tectonic uplift that has increased since about 800 ka due to the southward migration of the subducting Nazca Ridge. Based on migration velocity and geometry of the ridge, the influence of the Nazca Ridge on

  2. Cosmogenic 10Be Exposure Age Limits on the Angel Lake Glaciation, Ruby Mountains, Northeastern Nevada

    NASA Astrophysics Data System (ADS)

    Laabs, B. J.; Munroe, J. S.; Best, L. C.; Caffee, M. W.

    2011-12-01

    Evidence of Pleistocene glaciations in the northern Great Basin of the interior western U.S. has been known for decades. Nonetheless, this area has received considerably less attention than the eastern and western extremes of the Great Basin, despite being centrally located among numerous well-dated Pleistocene glacial chronologies and in a setting where such chronologies can provide clues to the influence of North American ice sheets, Great Basin paleolakes, and atmospheric circulation changes on climate change. Among the most extensively glaciated mountains in the Great Basin are the Ruby and East Humboldt Mountains in northeastern Nevada, where the type localities for the last two Pleistocene glaciations in the region, the Lamoille and Angel Lake Glaciations, are found. The glacial record in these two ranges includes sequences of moraines deposited during the Angel Lake Glaciation, displaying abundant material suitable for terrestrial cosmogenic 10Be surface-exposure dating. Exposure ages of boulders from atop a sequence of well-preserved moraines in Seitz Canyon in the western Ruby Mountains limit the end of the Angel Lake Glaciation to 19.3 ± 1.0 ka. This preliminary age limit verifies that the Angel Lake Glaciation coincided with marine oxygen-isotope stage 2 and the global Last Glacial Maximum, and suggests that mountain glaciers in northeastern Nevada began retreating in step with the Laurentide Ice Sheet. When compared to glacial chronologies from elsewhere in the region, this age limit indicates an early start of the last deglaciation relative to the Sierra Nevada and the Wasatch Mountains, at the western and eastern extremes of the Great Basin respectively. Furthermore, this age limit suggests that ice retreat began before the highstands of the largest Great Basin paleolakes, Lakes Bonneville and Lahontan. Further development of the glacial chronology of the northern Great Basin is needed to evaluate the significance of these apparent age differences

  3. 10Be exposure dating of Holocene moraines in the Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Hidy, Alan; Zimmerman, Susan; Finkel, Robert; Schaefer, Jeorg; Clark, Douglas

    2016-04-01

    Constraint on the extent and timing of Holocene glaciations is critical to addressing standing hypotheses that ascribe climatic fluctuations to changes in atmospheric and oceanic circulation patterns, or anthropogenic forcing. In the terrestrial record, such constraint typically relies on chronologies obtained from 10Be exposure dating of moraine deposits. However, the short exposure time of Holocene moraines, particularly those formed during the Little Ice Age (LIA), makes obtaining precise chronologies extremely challenging. To date, only a handful of LIA deposits in two locations (New Zealand and the Swiss Alps) have been successfully dated with 10Be. Here, we report new 10Be exposure ages from LIA and Neoglacial moraines from multiple sites in the Sierra Nevada (Lyell, Maclure, and Palisade glaciers). The Sierran LIA record will be compared to those from New Zealand and the Swiss Alps to test whether LIA deglaciation was globally synchronous. This result would support the contention that the LIA was terminated by anthropogenically-driven warming. Chronology from the neoglacial deposits will be used to test whether the timing of the return to glacial conditions in the Sierras correlates to a southward shift in the Intertropical Convergence Zone, which has been hypothesized to increase El Nino-like conditions in the Pacific Ocean. This record should be ideal for testing this hypothesis since precipitation in the Sierras is highly sensitive to El Nino conditions.

  4. Cosmogenic 10Be Exposure Age for the Cut Bank Creek terminal moraine, Glacier National Park, MT

    NASA Astrophysics Data System (ADS)

    Quirk, B.; Laabs, B. J.; Leonard, E. M.; Caffee, M. W.

    2012-12-01

    Mountain glaciers are highly sensitive to temperature and precipitation with geologic records that are superb proxies of climate change. In the Rocky Mountains of the western United States, abundant records of Late Pleistocene glaciation provide an opportunity for understanding paleoclimate throughout this region, especially in places where the chronology of glaciation is precisely known. Cosmogenic 10Be exposure dating has been widely applied to glacial deposits in the Rocky Mountains, providing precise numerical ages and improving the understanding of glacial chronologies in this region. Despite these improvements, the chronology of the last Pleistocene glaciation of the northernmost Rocky Mountains is not completely understood. Cosmogenic 10Be exposure dating was applied to the Cut Bank Creek valley in the Lewis Range of the Northern Rocky Mountains, where a discrete mountain glacier deposited a broad terminal moraine during the last Pleistocene glaciation. Exposure ages of eight quartzite and sandstone boulders at the crest of the ice-distal sector of the terminal moraine indicate that abandonment occurred at 15.6 ± 0.8 ka. This age is consistent with age limits of several terminal moraines elsewhere in the Northern Rocky Mountains, suggesting that the last Pleistocene glaciation culminated in this region after the global Last Glacial Maximum.

  5. Earth surface erosion and weathering from the 10Be (meteoric)/9Be ratio

    NASA Astrophysics Data System (ADS)

    von Blanckenburg, F.; Bouchez, J.; Wittmann, H.; Dannhaus, N.

    2012-12-01

    A perfect clock of the stability of the Earth surface is one that combines a first isotope the flux of which depends on the release rate during erosion, and a second isotope produced at constant rate. The ratio of the meteoric cosmogenic nuclide 10Be to stable 9Be is such a system. We provide a quantitative framework for its use. In a weathering zone some of the 9Be, present typically in 2.5ppm concentrations in silicate minerals, is released and partitioned between a reactive phase (adsorbed to clay and hydroxide surfaces, given the high partition coefficients at intermediate pH), and into the dissolved phase. The combined mass flux of both phases is defined by the soil formation rate and a mineral dissolution rate - and is hence proportional to the chemical weathering rate and the denudation rate. At the same time, the surface of the weathering zone is continuously exposed to fallout of meteoric 10Be. This 10Be percolates into the weathering zone where it mixes with dissolved 9Be. Both isotopes may exchange with the adsorbed Be, given that equilibration rate of Be is fast relative to soil residence times. Hence a 10Be/9Be(reactive) ratio results in soils from which the total denudation rate can be calculated. A prerequisite is that the flux of meteoric 10Be is known from field experiments or from global production models [1], that the 9Be concentration in bedrock (mostly 2.5ppm) is known [2], and that the reactive Be can be chemically extracted from soil or sediment [3]. In rivers, when reactive Be and dissolved Be equilibrate, a catchment-wide denudation rate can be determined from both sediment and a sample of filtered river water, where the sediment 10Be/9Be ratio is independent of grain size. We have tested this approach in sediment-bound Be and dissolved Be in water of the Amazon and Orinoco basin. The reactive Be was extracted from sediment by combined hydroxylamine and HCl leaches [2]. In the Amazon trunk stream, the Orinoco, Apure, and La Tigra river 10Be

  6. Timing of terminal Pleistocene deglaciation at high elevations in southern and central British Columbia constrained by 10Be exposure dating

    NASA Astrophysics Data System (ADS)

    Margold, Martin; Stroeven, Arjen P.; Clague, John J.; Heyman, Jakob

    2014-09-01

    The Cordilleran Ice Sheet (CIS) covered most of British Columbia and southern Yukon Territory at the local Last Glacial Maximum (lLGM) during Marine Oxygen Isotope Stage 2. However, its subsequent demise is not well understood, particularly at high elevations east of its ocean-terminating margin. We present 10Be exposure ages from two high-elevation sites in southern and central British Columbia that help constrain the time of initial deglaciation at these sites. We sampled granodiorite erratics at elevations of 2126-2230 m a.s.l. in the Marble Range and 1608-1785 m a.s.l. in the Telkwa Range at the western margin of the Interior Plateau. The erratics at both sites are near ice-marginal meltwater channels that delineate the local ice surface slope and thus the configuration of the ice sheet during deglaciation. The locations of the erratics and their relations to meltwater channels ensure that the resulting 10Be ages date CIS deglaciation and not the retreat of local montane glaciers. Our sample sites emerged above the surface of the CIS as its divide migrated westward from the Interior Plateau to the axis of the Coast Mountains. Two of the four samples from the summit area of the Marble Range yielded apparent exposure ages of 14.0 ± 0.7 and 15.2 ± 0.8 ka. These ages are 1.8-3.0 ka younger than the well-established lLGM age of ca 17 ka for the Puget lobe of the CIS in Washington State; they are 1.7 ka younger than the lLGM age for the Puget lobe if a snow-shielding correction to their uncertainty-weighted mean age is applied. The other two samples yielded much older apparent exposure ages (20.6 ± 1.4 and 33.0 ± 1.5 ka), indicating the presence of inherited isotopes. Four samples collected from the summit area of the Telkwa Range in the Hazelton Mountains yielded well clustered apparent exposure ages of 10.1 ± 0.6, 10.2 ± 0.7, 10.4 ± 0.5, and 11.5 ± 1.1 ka. Significant present-day snow cover introduces a large uncertainty in the apparent exposure ages from

  7. Understanding complex exposure history of Mount Hampton, West Antarctica using cosmogenic 3He, 21Ne and 10Be in olivine

    NASA Astrophysics Data System (ADS)

    Carracedo, Ana; Rodes, Angel; Stuart, Finlay; Smellie, John

    2016-04-01

    Combining stable and radioactive cosmogenic nuclides is an established tool for revealing the complexities of long-term landscape development. To date most studies have concentrated on 21Ne and 10Be in quartz. We have combined different chemical protocols for extraction of cosmogenic 10Be from olivine, and measured concentrations in olivine from lherzolite xenoliths from the peak of Mount Hampton (~3,200 m), an 11 Ma shield volcano on the West Antarctic rift flank. We combine this data with cosmogenic 3He (and 21Ne) in the olivines in order to unravel the long-term environmental history of the region. The mean 3He/21Ne ratio (1.98 ± 0.22) is consistent with the theoretical value and previous determinations. 10Be/3He ratios (0.012 to 0.018) are significantly lower than the instantaneous production ratio (~0.045). The data are consistent with 1-3 Ma of burial. The altitude of the volcano rules out over-topping of the peak by the West Antarctic Ice Sheet only possible burial could be generated by the growth of an ice cap although this contradicts the absence of evidence for ice cover. The 3He-10Be data can also be generated during episodic erosion of the volcanic ash over the last few million years. The data requires a minimum depth of 1 to 2.5 m for the samples during a minimum age of 5 Ma and maximum long-term erosion rate of ~0.5 m/Ma with at least one erosive episode reflecting short-term erosion rate of ~7 m/Ma that would have brought the samples into the surface during the last ~350 ka. Erosion in this type of landscape could be related to interglacial periods where cryostatic erosion can occur generating an increase in the erosion rate. This study shows that episodic erosion can produce stable-radioactive cosmogenic isotope systematics that are similar to those generated by exposure-burial cycles.

  8. Knickpoint retreat rates from cosmogenic 10Be; 30 exposure ages from western Scotland with implications for paraglacial bedrock incision

    NASA Astrophysics Data System (ADS)

    Jansen, J. D.; Fabel, D.; Codilean, A. T.; Bishop, P.; Hoey, Tb; Schnabel, C.; Xu, S.

    2009-04-01

    When a bedrock river is perturbed by accelerating rock uplift the perturbation is not transmitted instantaneously to the whole landscape; the new base level information must first spread through the channel network to hillslopes. Under detachment-limited conditions the new base level information is spread via knickpoint retreat, the rate of which ultimately governs response times to perturbation and therefore landscape evolution. Yet, owing to difficulties with measuring rates of erosional processes, knickpoint retreat rates are not widely documented. We examine bedrock river response to rapid, continuous rock uplift due to glacio-isostatic rebound following retreat of the Late Devensian icesheet from northern Britain. From four rivers in western Scotland, we infer knickpoint retreat rates from 30 measurements of cosmogenic 10Be concentrations on abandoned, fluvially-sculpted bedrock surfaces downstream of Holocene knickpoints. These data are among the first direct evidence that terrace exposure ages increase downstream consistent with the progressive abandonment of bedrock surfaces in the wake of a retreating knickpoint. We reflect upon our results in the context of paraglacial conditions that we infer to have involved initially high sediment flux declining over the Holocene. A simple unit stream power model is used to demonstrate how knickpoints affect erosional capacity along transient reaches. Bedrock channel width is insensitive to substrate erodibility, but we document here a sharp reduction in channel width at knickpoints, which is largely responsible for up to order-of-magnitude increases in stream power per unit area of the channel bed. The high rates of bedrock river incision that we document for postorogenic western Scotland are comparable to those reported for landside-dominated mountain belts. However, rather than stemming from towering relief or high-magnitude rock uplift, these rapid erosion rates seem to be the product of high sediment flux

  9. Cosmogenic 10Be and 26Al exposure ages of tors and erratics, Cairngorm Mountains, Scotland: Timescales for the development of a classic landscape of selective linear glacial erosion

    USGS Publications Warehouse

    Phillips, W.M.; Hall, A.M.; Mottram, R.; Fifield, L.K.; Sugden, D.E.

    2006-01-01

    The occurrence of tors within glaciated regions has been widely cited as evidence for the preservation of relic pre-Quaternary landscapes beneath protective covers of non-erosive dry-based ice. Here, we test for the preservation of pre-Quaternary landscapes with cosmogenic surface exposure dating of tors. Numerous granite tors are present on summit plateaus in the Cairngorm Mountains of Scotland where they were covered by local ice caps many times during the Pleistocene. Cosmogenic 10Be and 26Al data together with geomorphic relationships reveal that these landforms are more dynamic and younger than previously suspected. Many Cairngorm tors have been bulldozed and toppled along horizontal joints by ice motion, leaving event surfaces on tor remnants and erratics that can be dated with cosmogenic nuclides. As the surfaces have been subject to episodic burial by ice, an exposure model based upon ice and marine sediment core proxies for local glacial cover is necessary to interpret the cosmogenic nuclide data. Exposure ages and weathering characteristics of tors are closely correlated. Glacially modified tors and boulder erratics with slightly weathered surfaces have 10Be exposure ages of about 15 to 43 ka. Nuclide inheritance is present in many of these surfaces. Correction for inheritance indicates that the eastern Cairngorms were deglaciated at 15.6 ?? 0.9 ka. Glacially modified tors with moderate to advanced weathering features have 10Be exposure ages of 19 to 92 ka. These surfaces were only slightly modified during the last glacial cycle and gained much of their exposure during the interstadial of marine Oxygen Isotope Stage 5 or earlier. Tors lacking evidence of glacial modification and exhibiting advanced weathering have 10Be exposure ages between 52 and 297 ka. Nuclide concentrations in these surfaces are probably controlled by bedrock erosion rates instead of discrete glacial events. Maximum erosion rates estimated from 10Be range from 2.8 to 12.0 mm/ka, with

  10. 10Be exposure age chronology of the last glaciation in the Krkonoše Mountains, Central Europe

    NASA Astrophysics Data System (ADS)

    Engel, Zbyněk; Braucher, Régis; Traczyk, Andrzej; Laetitia, Léanni; AsterTeam

    2014-02-01

    A new chronology of the last glaciation is established for the Krkonoše (Giant) Mountains, Central Europe, based on in-situ produced 10Be in moraine boulders. Exposure ages and Schmidt Hammer rebound values obtained for terminal moraines on the northern and southern flank of the mountains suggest that the oldest preserved moraines represent early phases of the Last Glacial Maximum (LGM). Large moraines at the outlet of the Snowy Cirques (Śnieżne Kotły) and in the middle part of the Úpa (Obří důl) trough were deposited around 21 ka while a series of smaller moraines above the LGM deposits represent readvances that occurred no later than 18.1 ± 0.6 ka, 15.7 ± 0.5 ka, 13.5 ± 0.5 ka and 12.9 ± 0.7 ka. An exposure age of 13.8 ± 0.4 ka obtained for protalus ramparts at the foot of the Úpská jáma Cirque headwall indicates that glaciers advanced only in north- to east-facing cirques during the Lateglacial. The last glacier fluctuation was synchronous with the Younger Dryas cold event. The timing of local glacier advances during the last glacial episode correlates with the late Weichselian glacier phases in the Alps and in the Bavarian/Bohemian Forest.

  11. 10Be exposure dating of onset and timing of Neoglacial glacier advances in the Ecrins massif, French Alps

    NASA Astrophysics Data System (ADS)

    Le Roy, Melaine; Deline, Philip; Carcaillet, Julien

    2013-04-01

    Alpine glaciers are known to be highly sensitive to change in temperature and precipitation on decadal to centennial time scales. For two decades, numerous studies on Holocene climate revealed a period marked by abrupt cold reversals (e.g. 8.2 ka event) with increasing frequency and magnitude after the Holocene Climatic Optimum, during the so-called Neoglacial period (roughly the last 4 ka). State-of-the-art studies indicate that largest alpine glaciers failed to exceed their Little Ice Age (LIA) extent during these LIA Type-Events, unlike certain smaller glaciers. In the French Alps, very few investigations were conducted to date on Holocene glacier variability. Almost all studies focused on the most glacierized area: the Mont Blanc massif, where suitable organic remains to apply radiocarbon dating and dendrochronology are available. Other glacierized massifs are poorly studied, without any Holocene/Neoglacial glacier chronology up to now. Here, we present the results of a study focusing on six glacier forefields distributed in the Ecrins massif. Detailed geomorphological mapping and in-situ produced 10Be dating were carried on multi-crested so-called "LIA composite moraines". The targeted ridges are located in distal position with respect to late LIA drift in order to identify Holocene cold pulses that have led to (or slightly exceeded) LIA-like glacier extent. The 35 10Be ages obtained revealed that the onset of Neoglacial occurred at ~4.2 ka, and that at least two other advances were recorded at ~3.3 ka and ~0.85 ka. One site has yielded a nearly complete Neoglacial record as four discrete events have been dated. These results highlight the potential of lateral moraine ridge stratigraphy which could yield accurate record when sufficiently preserved, but also the different preservation of landforms along the glacier margin which could censor the record.

  12. 21Ne, 10Be and 26Al cosmogenic burial ages of near-surface eolian sand from the Packard Dune field, McMurdo Dry Valleys, Antarctica.

    NASA Astrophysics Data System (ADS)

    Fink, David; Augustinus, Paul; Rhodes, Ed; Bristow, Charles; Balco, Greg

    2015-04-01

    The McMurdo Dry Valleys, Antarctica, have been ice-free for at least 10 Ma. In Victoria Valley, the largest of the Dry Valleys, permafrosted yet still actively migrating dune-fields, occupy an area of ~8 km2 with dune thicknesses varying from ~5 to 70 meters. High-resolution ground penetrating radar (GPR) imaging of selected dunes reveal numerous unconformities and complex stratigraphy inferring cycles of sand accretion and deflation from westerly katabatic winter winds sourced from the East Antarctic Ice Sheet and anabatic summer winds sourced from the Ross Sea. Samples above permafrost depth were taken for OSL and cosmogenic 26Al/10Be burial ages. OSL ages from shallow (<1m) pits range from modern to ~1.3ka suggesting that deposition/reworking of the dunes is on-going and their present configuration is a late Holocene feature. The same 7 samples gave a mean 26Al/10Be = 4.53 +/- 5% with an average apparent continuous 10Be surface exposure age of 525 +/- 25 ka surprisingly indicating a common pre-history independent of depth. Correcting for minor post-burial production based on OSL ages, the minimum (integrated) burial period for these sand grains is 0.51+/- 0.12 Ma which represents the burial age at the time of arrival at the dune. A possible explanation is that this common burial signal reflects recycling episodes of exposure, deposition, burial and deflation, sufficiently frequent to move all grains towards a common pre-dune deposition history. However, it is unclear over what length of time this processes has been active and fraction of time the sand has been buried. Consequently we also analysed purified quartz aliquots of the same samples for a third and stable nuclide, 21Ne, to determine the total surface and burial exposure periods. Using the 21Ne/10Be system we obtain burial ages of 1.10 +/- 0.10 Ma. Further coring below permafrost is planned for austral summer 2015.

  13. El Niño forcing on 10Be-based surface denudation rates in the northwestern Peruvian Andes?

    NASA Astrophysics Data System (ADS)

    Abbühl, Luca M.; Norton, Kevin P.; Schlunegger, Fritz; Kracht, Oliver; Aldahan, Ala; Possnert, Göran

    2010-11-01

    therefore interpret that Holocene landscape evolution has largely been controlled by climate. The ky-timescale of the 10Be data together with the transience of the landscape implies that El Niño events in northwestern Peru have occurred since at least the Holocene, and that adjustment to channel incision is still taking place.

  14. Examples of sackungen in the French Western Alps and their geochronology based on the 10Be cosmic ray exposure dating method (Invited)

    NASA Astrophysics Data System (ADS)

    Hippolyte, J.; Bourles, D. L.; Braucher, R.; Léanni, L.; Chauvet, F.; Lebatard, A.; Arnold, M.; Aumaître, G.; Keddadouche, K.

    2013-12-01

    In the French Alps, sackung scarps were often interpreted as surface traces of active faults. A detailed mapping of the Arc and Rognier mountains shows that these scarps result from deep-seated gravitational slope deformation (DSGSD). They are short (less than 2.1 km long), numerous and organized in swarms (5.3 km long at the Arc; 9 km long at Rognier). There are mainly uphill facing scarps developed on steep slopes. Open tension cracks are present at ridge tops. These sackung fractures created ridge-top troughs, closed depressions and multiple-crests landforms. That the sackung scarps are parallel to the contour lines, and that they result from opening of fractures or from normal slips, indicates that they are controlled by topography and gravity. In the Western Alps, glacial erosion and subsequent debuttressing of oversteepened slopes seem to be the main factors for the occurrence of sackungen. However, gradual loss of rock strength, groundwater fluctuations, subsidence due to evaporite dissolution and earthquake shaking, may contribute to their formation. For a better understanding of the origin of sackungen, chronological data are crucial. We used the cosmic ray exposure (CRE) dating method for deciphering the activity of the Arc and Rognier sackungen. This method allows quantification of the exposure duration of a surface to cosmic rays, by measuring the amount of accumulated cosmogenic nuclides in surficial rocks. Because sackung scarps usually form in hard rocks containing quartz, we used the 10Be cosmogenic nuclide which is produced in situ by spallation reactions on Si and O (36Cl can be used for limestone). The measurements were performed at ASTER, the French accelerator mass spectrometry facility located at the CEREGE laboratory in Aix-en-Provence. The CRE dating method allows direct dating of most of the geomorphologic structures involved in sackungen: sackung fault scarps, rock slopes, debris slopes, screes, rock glaciers, glacier-polished rock surface

  15. Preliminary Vertical Slip Rate for the West Tahoe Fault from six new Cosmogenic 10Be Exposure Ages of Late Pleistocene Glacial Moraines at Cascade Lake, Lake Tahoe, California

    NASA Astrophysics Data System (ADS)

    Pierce, I. K. D.; Wesnousky, S. G.; Kent, G. M.; Owen, L. A.

    2015-12-01

    The West Tahoe Fault is the primary range bounding fault of the Sierra Nevada at the latitude of Lake Tahoe. It is a N-NW striking, east dipping normal fault that has a pronounced onshore quaternary scarp extending from highway 50 southwest of Meyers, CA to Emerald Bay. At Cascade Lake, the fault cuts and progressively offsets late Pleistocene right lateral moraines. The fault vertically offsets the previously mapped Tahoe moraine ~83 m and the Tioga moraine ~23 m, measured from lidar data. Seventeen samples were collected for 10Be cosmogenic age analysis from boulders on both the hanging and footwalls of the fault along the crests of these moraines.We report here the initial analysis of 6 of these boulders and currently await processing of the remainder. The 10Be exposure ages of 3 boulders each on the younger Tioga and older Tahoe moraines range from 12.7 +/- 1.6 to 20.7 +/- 3.3 ka and 13.3 +/- 2.1 to 72.5 +/- 8.8 ka, respectively. Using the oldest ages as minima, these preliminary results suggest that the slip rate has averaged ~1 mm/yr since the penultimate glaciation, in accord with estimates of previous workers, and place additional bounds on the age of glaciation in the Lake Tahoe basin. The Last Glacial Maxima and penultimate glaciation near Lake Tahoe thus appear to coincide with the Tioga and Tahoe II glaciations of the Eastern Sierra.

  16. Deglaciation of Antarctica since the Last Glacial Maximum - what can we learn from cosmogenic 10Be and 26Al exposure ages?

    NASA Astrophysics Data System (ADS)

    Fink, David

    2015-04-01

    Ice volume changes at the coastal margins of Antarctica during the global LGM are uncertain. The little evidence available suggests that behaviour of the East and West Antarctic Ice Sheets are markedly different and complex. It is hypothesised that during interglacials, thinning of the Ross Ice Shelf, a more open-water environment and increased precipitation, allowed outlet glaciers draining the Transantarctic Mnts and fed by interior Ice Sheets to advance during moist warmer periods, out of phase with colder arid periods. In contrast, glacier dynamics along the vast coastal perimeter of East Antarctica is strongly influenced by Southern Ocean conditions. Cosmogenic 10Be and 26Al chronologies, although restricted to ice-free oasis and mountains flanking drainage glaciers, has become an invaluable, if not unique, tool to quantify spatial and temporal Pleistocene ice sheet variability over the past 2 Ma. Despite an increasing number of well documented areas, extracting reliable ages from glacial deposits in polar regions is problematic. Recycling of previously exposed/ buried debris and continual post-depositional modification leads to age ambiguities for a coeval glacial landform. More importantly, passage of cold-based ice can leave a landform unmodified resulting in young erratics deposited on ancient bedrock. Advances in delivering in-situ radiocarbon to routine application offer some relief. Exposure ages from different localities throughout East Antarctica (Framnes Mnts, Lutzow-Holm Bay, Vestfold Hills) and West Antarctica (Denton Ranges, Hatherton Glacier, Shackleton Range) highlight some of the new findings. This talk presents results which quantify the magnitude and timing of paleo-ice sheet thickness changes, questions the validity of an Antarctic LGM and discusses the complexities encountered in the often excessive spread in exposure ages.

  17. Geomorphological evidence and 10Be exposure ages for the Last Glacial Maximum and deglaciation of the Velká and Malá Studená dolina valleys in the High Tatra Mountains, central Europe

    NASA Astrophysics Data System (ADS)

    Engel, Zbyněk; Mentlík, Pavel; Braucher, Régis; Minár, Jozef; Léanni, Laetitia

    2015-09-01

    10Be exposure age chronology of the last glaciation was established in a key area at the southern slopes of the High Tatra Mts., Western Carpathians. In-situ produced 10Be in moraine boulders, glacially transformed bedrock surfaces and rockfall accumulations constrains the timing of the Last Glacial Maximum (LGM) glacier expansion and provides chronological evidence for the post-LGM decay of one of the largest paleoglaciers in the range. The uncertainty-weighted mean age of 22.0 ± 0.8 ka obtained for the terminal moraine in the forefield of the Velká Studená dolina Valley indicates that the oldest moraine was deposited close to the global LGM. This finding confirms that well-preserved moraines in the range were formed during the last glacial cycle and that glaciation on the southern flank of the range was more extensive than earlier in the last glacial cycle. The maximum glacier extent correlates with late Würmian/Weichselian glacier phases in the Alps, the Bavarian/Bohemian Forest and the Krkonoše Mts., but probably postdates the period of maximum glaciation in the Southern Carpathians. Re-advance moraines at the mouth of the Velká Studená dolina Valley and in the middle part of the Malá Studená dolina Valley were deposited no later than around 20.5 ka and 15.5 ka, respectively. The timing of these advances is broadly synchronous within the High Tatra Mts. as well as with glacier advances in the Alps, Bavarian/Bohemian Forest and Krkonoše Mts. 10Be exposure ages obtained from glacially transformed bedrock surfaces range between 20.5 ± 1.7 ka and 10.7 ± 0.3 ka constraining the onset and the final phase of the deglaciation. Surface exposure dating of four rockfall accumulations produced uncertainty-weighted mean ages of 20.2 ± 1.2 ka, 17.0 ± 0.7 ka, 16.5 ± 0.4 ka and 15.6 ± 0.7 ka. These ages indicate that activation of rock-slope failures occurred under paraglacial conditions within a few centuries up to 1400 years after the formation of re

  18. Rapid Last Glacial Maximum deglaciation in the Indian Himalaya coeval with midlatitude glaciers: New insights from 10Be-dating of ice-polished bedrock surfaces in the Chandra Valley, NW Himalaya

    NASA Astrophysics Data System (ADS)

    Eugster, Patricia; Scherler, Dirk; Thiede, Rasmus C.; Codilean, Alexandru T.; Strecker, Manfred R.

    2016-02-01

    Despite a large number of dated glacial landforms in the Himalaya, the ice extent during the global Last Glacial Maximum (LGM) from 19 to 23 ka is only known to first order. New cosmogenic 10Be exposure ages from well-preserved glacially polished surfaces, combined with published data, and an improved production rate scaling model allow reconstruction of the LGM ice extent and subsequent deglaciation in the Chandra Valley of NW India. We show that a >1000 m thick valley glacier retreated >150 km within a few thousand years after the onset of LGM deglaciation. By comparing the recession of the Chandra Valley Glacier and other Himalayan glaciers with those of Northern and Southern Hemisphere glaciers, we demonstrate that post-LGM deglaciation was similar and nearly finished prior to the Bølling/Allerød interstadial. Our study supports the view that many Himalayan glaciers advanced during the LGM, likely in response to global variations in temperature.

  19. 10Be cosmic-ray exposure dating of moraines and rock avalanches in the Upper Romanche valley (French Alps): Evidence of two glacial advances during the Late Glacial/Holocene transition

    NASA Astrophysics Data System (ADS)

    Chenet, Marie; Brunstein, Daniel; Jomelli, Vincent; Roussel, Erwan; Rinterknecht, Vincent; Mokadem, Fatima; Biette, Melody; Robert, Vincent; Léanni, Laëtitia

    2016-09-01

    Cosmic-ray exposure (CRE) dating of moraines allow glacier fluctuations and past climate change reconstructions. In the French Alps, there is a lack of moraine dating for the Late Glacial/Holocene transition period. Here we present a chronology of glacier advances in the Upper Romanche valley (French Alps - Massif des Ecrins) based on 10Be CRE dating. CRE ages of moraines of 13.0 ± 1.1 ka and 12.4 ± 1.5 ka provide evidence for two stages of glacial advance or standstill at the end of the Late Glacial. The CRE dating of a rock avalanche deposit at 12.2 ± 1.5 ka is attributed to post-glacial debuttressing and reveals rapid deglaciation at the end of the Late Glacial. A CRE age of 7.1 ± 0.7 ka of a second mass-wasting, whose triggering factor is unidentified so far, indicates that up to an altitude of 2300 m a.s.l., the valley was ice-free as of ∼7 kyr at the latest. The re-evaluation of 21 moraine 10Be CRE ages from nine glacial valleys across the Alps shows multiple glacial advances occurring at the Late Glacial/Holocene transition. These results lead to a re-evaluation of the importance of cooling events during the Allerød and the Younger Dryas in the Alps.

  20. The Svalbard Barents Sea Ice Sheet deglaciation and its contribution to meltwater pulse 1a: Constraining ice sheet history with geomorphological mapping and 10Be exposure dating on Svalbard's southern cape

    NASA Astrophysics Data System (ADS)

    Nothaft, D. B.; Koffman, T.; Schaefer, J. M.; Young, N. E.; Hormes, A.; Briner, J. P.

    2014-12-01

    Pinpointing the sources of meltwater pulse (MWP) 1a—the most abrupt period of sea level rise during the last glacial termination—remains one of paleoclimatology's greatest challenges, with implications for the understanding of rapid climate change, isostatic rebound, and past ocean circulation. Here, we present an annotated geomorphological map of a southern region of Svalbard, Norway, that we will use in the interpretation of a soon-to-be published 10Be chronology of this study area where no cosmogenic nuclide exposure data has yet been produced. From this map, we infer historic ice sheet thickness, flow rate, and erosivity. Together, this data will enable us to constrain ice sheet volume change over time in southern Svalbard. The map identifies raised beaches at an altitude of 40 m, indicating an ice sheet thickness of 400-800 m during the Last Glacial Maximum (LGM) when compared to other shoreline data from the region and ice sheet models. We also observed an abundance of glacially smoothed features in valleys, despite an absence of such features at higher elevations. This could suggest a transition from warm-based, erosive ice to cold-based, non-destructive ice with increasing elevation. It is also possible that mountain peaks in this region were not glaciated at LGM. It is important to assess the historic erosivity of an ice sheet because cosmogenic nuclides may be inherited from prior interstadials when the bedrock was deglaciated, if not "reset" by erosion. This can result in erroneously old exposure dates. If this portion of the Svalbard Barents Sea Ice Sheet (SBSIS) did contribute largely to MWP-1a, then we would expect exposure dates from sites differing in elevation by 100 m or more to fall within a 500-year range, centered around 14 ka. Expeditions to collect samples for exposure dating at other field sites in southern Svalbard, scheduled for the coming field season, will help to further inform our understanding of the SBSIS deglaciation and the MWP

  1. Detailed chronology of a giant Pleistocene rock-avalanche sequence in the hyperarid southern Peru revealed by jointly applied 10Be and 3He cosmic ray exposure dating : The Study case of the Cerro Caquilluco landslide complex.

    NASA Astrophysics Data System (ADS)

    Swann, Zerathe; Laurence, Audin; Carlos, Benavente; Régis, Braucher; Pierre-Henri, Blard; Didier, Bourlès; Julien, Carcaillet; Fabrizio, Delgado; Pascal, Lacroix; Valderrama Patricio, Murillo; Aster Team

    2015-04-01

    suggesting sequential failures, this object appeared as a good target to bring additional knowledge on the previously exposed issues. Our goal was to use TCN and to sample a maximum of individual lobes to be able to discuss: (i) the time of recurrence of successive extreme events, (ii) the respective roles of past climate variations versus earthquake forcing on the landslide trigger, and (iii) the impact of these mass remobilizations on local erosion rates compared to fluvial erosion rates and tectonic uplift rates (both known in this region). On average, three samples were extracted from individual meter-scale boulders sampled on seven different lobes of debris (~20 samples). Due to the lack of quartz in that volcanic lithology, 10Be was extracted from feldspaths for all samples. Half were additionally processed for 3He measurements on pyroxene, allowing to reduce the uncertainty on the derived exposure ages and to solve the production equation for both time and erosion variables. The obtained ages show a perfect consistency with the pattern of erosion, geomorphic surfaces and relative position of each lobes (i.e. younger from the toe to the top). These results highlight sequential failures staggered at the Pleistocene timescale, with some surprising time of recurrence ranging from 30 to 100 ka that may correspond to the main last climate variations in that region. Crosta, G.B., Hermanns, R.L., Frattini, P., Valbuzzi, E., Valagussa, A., 2014a. Large slope instabilities in Northern Chile: Inventory, Characterisation and Possible Triggers. In: Proceedings of the 3rd world landslide Forum, 2-6 June 2014, Bejing, p 6. DOI: 10.1007/978/-3-319-04996-0_28. Crosta, G.B., Paolo, F., Elena, V., Hermanns, R.L., 2014b. The Cerro Caquilluco-Cerrillos Negros Giant Rock Avalanches (Tacna, Peru). IAEG - Torino 2014, N°159. McPhillips, D., Bierman, P.R., Rood, D.H., 2014. Millennial-scale record of landslides in the Andes consistent with earthquake trigger. Nature Geoscience, DOI: 10

  2. Detailed chronology of a giant Pleistocene rock-avalanche sequence in the hyperarid southern Peru revealed by jointly applied 10Be and 3He cosmic ray exposure dating : The Study case of the Cerro Caquilluco landslide complex.

    NASA Astrophysics Data System (ADS)

    Swann, Zerathe; Laurence, Audin; Carlos, Benavente; Régis, Braucher; Pierre-Henri, Blard; Didier, Bourlès; Julien, Carcaillet; Fabrizio, Delgado; Pascal, Lacroix; Valderrama Patricio, Murillo; Aster Team

    2015-04-01

    suggesting sequential failures, this object appeared as a good target to bring additional knowledge on the previously exposed issues. Our goal was to use TCN and to sample a maximum of individual lobes to be able to discuss: (i) the time of recurrence of successive extreme events, (ii) the respective roles of past climate variations versus earthquake forcing on the landslide trigger, and (iii) the impact of these mass remobilizations on local erosion rates compared to fluvial erosion rates and tectonic uplift rates (both known in this region). On average, three samples were extracted from individual meter-scale boulders sampled on seven different lobes of debris (~20 samples). Due to the lack of quartz in that volcanic lithology, 10Be was extracted from feldspaths for all samples. Half were additionally processed for 3He measurements on pyroxene, allowing to reduce the uncertainty on the derived exposure ages and to solve the production equation for both time and erosion variables. The obtained ages show a perfect consistency with the pattern of erosion, geomorphic surfaces and relative position of each lobes (i.e. younger from the toe to the top). These results highlight sequential failures staggered at the Pleistocene timescale, with some surprising time of recurrence ranging from 30 to 100 ka that may correspond to the main last climate variations in that region. Crosta, G.B., Hermanns, R.L., Frattini, P., Valbuzzi, E., Valagussa, A., 2014a. Large slope instabilities in Northern Chile: Inventory, Characterisation and Possible Triggers. In: Proceedings of the 3rd world landslide Forum, 2-6 June 2014, Bejing, p 6. DOI: 10.1007/978/-3-319-04996-0_28. Crosta, G.B., Paolo, F., Elena, V., Hermanns, R.L., 2014b. The Cerro Caquilluco-Cerrillos Negros Giant Rock Avalanches (Tacna, Peru). IAEG - Torino 2014, N°159. McPhillips, D., Bierman, P.R., Rood, D.H., 2014. Millennial-scale record of landslides in the Andes consistent with earthquake trigger. Nature Geoscience, DOI: 10

  3. Exposure testing of solar absorber surfaces

    SciTech Connect

    Moore, S.W.

    1986-01-01

    The Los Alamos National Laboratory has been involved in supporting, monitoring and conducting exposure testing of solar materials for approximately ten years. The Laboratory has provided technical monitoring of the IITRI, DSET, Lockheed, and Berry contracts and has operated the Los Alamos exposure Facility for over five years. This report will outline some of the past exposure testing, the testing still in progress, and describe some of the major findings. While this report will primarily emphasize solar absorber surfaces, some of the significant findings relative to advanced glazing will be discussed.

  4. 10Be accumulation in a soil chronosequence

    USGS Publications Warehouse

    Pavich, M.J.; Brown, L.; Klein, J.; Middleton, R.

    1984-01-01

    We have measured the concentration of the cosmogenic isotope 10Be in soil samples from various horizons at six sites, including three independently dated Rappahannock River terraces and a previously undated Piedmont soil to which we have assigned an age. All of the incident 10Be can be accounted for in one of these soils and a second is within a factor of two. In three soils, whose concentrations vary widely with depth, a significant fraction of the incident 10Be cannot be accounted for. Incomplete sampling, and enhanced Be mobility caused by organic components, are the probable reasons for the low inventory of Be from these three soils. Overall, the data from these six sites indicate that 10Be accumulation could be used to assign ages to soils if Be is not mobilized and lost from the soil profile. ?? 1984.

  5. 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.

  6. Exposure of phosphatidylserine on the cell surface.

    PubMed

    Nagata, S; Suzuki, J; Segawa, K; Fujii, T

    2016-06-01

    Phosphatidylserine (PtdSer) is a phospholipid that is abundant in eukaryotic plasma membranes. An ATP-dependent enzyme called flippase normally keeps PtdSer inside the cell, but PtdSer is exposed by the action of scramblase on the cell's surface in biological processes such as apoptosis and platelet activation. Once exposed to the cell surface, PtdSer acts as an 'eat me' signal on dead cells, and creates a scaffold for blood-clotting factors on activated platelets. The molecular identities of the flippase and scramblase that work at plasma membranes have long eluded researchers. Indeed, their identity as well as the mechanism of the PtdSer exposure to the cell surface has only recently been revealed. Here, we describe how PtdSer is exposed in apoptotic cells and in activated platelets, and discuss PtdSer exposure in other biological processes. PMID:26891692

  7. 10Be chronometry of bedrock-to-soil conversion rates

    NASA Astrophysics Data System (ADS)

    Monaghan, Marc C.; McKean, James; Dietrich, William; Klein, Jeffrey

    1992-07-01

    We report concentrations of cosmogenic 10Be ( t1/2 = 1.5 × 10 6 yrs) in soil excavated from a soil-mantled hillslope in Black Diamond Mines Regional Park, Contra Costa County, California. The most striking features of the data are: (1) the similarity in the downward decreasing trends of 10Be concentrations in two soil profiles collected 75 m apart, (2) the coincidence in each soil profile of the soil/bedrock interface (as defined by visual inspection of soil pits) and the level at which 10Be concentrations attain very low values ( ˜4 × 10 6 atoms/g), and (3) the extremely low 10Be concentrations in the underlying regolith (0.5 × 10 6 atoms/gram). The inventory of 10Be in these soils is low, equivalent to about 6000 yrs of 10Be accumulation in a soil initially containing no 10Be. On the basis of these measurements, and with the aid of simple models of soil ( 10Be) motions on the hillslope, we conclude that 10Be loss from the surface is dominated by its removal in soil by creep. We calculate local rates of bedrock-to-soil conversion of between 0.15 and 0.27 km/10 6 yrs. Comparing these with uplift rates determined for coastal regions of California indicates that soil creep alone is capable of removing soil from the local geomorphic system at a rate equivalent to the rate of uplift of much of the coast.

  8. Cosmogenic 10Be and Noble Gases in Diogenites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Lindner, L.; van der Borg, K.; Loeken, Th.; Scherer, P.; Schultz, L.

    1993-07-01

    Introduction: A recent reevaluation of the 3He, 21Ne, and 38Ar cosmic-ray exposure ages of eight non-Antarctic and three Antarctic diogenite falls led to a consistent set of exposure ages with a major cluster at 22 Ma and a possible second cluster around 40 Ma [1]. These clusters coincide with two major peaks in the exposure-age distributions of the genetically related eucrites and howardites [2], but the scarcity of young diogenites is remarkable [3]. An update of the exposure-age distribution for diogenites, including nine separate Antarctic falls, will be presented and possible differences in exposure history between Antarctic and non-Antarctic diogenites will be discussed. The exposure-age distributions of eucrites and howardites are still controversial [2,3], as conventional shielding corrections--on the basis of the 22Ne/21Ne ratio--cannot be applied. Therefore, the use of other shielding parameters, such as 10Be or 26Al, is considered. We examined the relation between 10Be contents and 22Ne/21Ne ratios in diogenites to obtain more insight into the shielding sensitivity of the 10Be production rate. Experimental: In addition to the existing database of more than 30 noble gas analyses [4] we carried out noble gas measurements on 5 non-Antarctic diogenites and on 12 Antarctic samples from 9 separate falls. On the same samples 10Be was measured by AMS. The experimental uncertainties in the 10Be values are 2-3%, those in the 22Ne/21Ne ratios are 0.5-1.0%. Results and Conclusions: The major exposure-age cluster at 22 Ma contains about 45% of the diogenite falls, indicating a major impact on its parent body. However, the presence of several younger diogenites suggests that this collisional event was not necessarily as destructive as previously suggested [3]. Four diogenites show exposure ages around 40 Ma, indicating a second major impact on the HED parent body. Although some Antarctic diogenites have unique mineralogical features [5,6], we didn't find any evidence

  9. 10Be and 26Al in Individual Cosmic Spherules

    NASA Astrophysics Data System (ADS)

    Nishiizumi, K.; Arnold, J. R.; Chaffee, M. W.; Finkel, R. C.; Southon, J.; Brownlee, D. E.; Harvey, R. P.

    1992-07-01

    Cosmic spherules and fragments in the size range 0.1-1 mm, originally extracted magnetically from deep-sea deposits, have now been isolated from ice in Greenland and Antarctica (Maurette et al., 1986; Koeberl and Hagen, 1989; Harvey and Maurette, 1990). Studies of cosmogenic radionuclides in individual spherules made possible by accelerator mass spectrometry (Raisbeck et al., 1985; Nishiizumi et al., 1991, 1992), have verified the model calculations that suggested that the spherules are mainly fused micrometeoroids, rather than spall droplets from larger objects (Dohnanyi, 1978; Grun et al., 1985; Olinger et al., 1990). However, the exposure lifetimes observed are much longer than those deduced from models (10^5- 10^7 years as against a few times 10^4) (Dohnanyi, 1978; Grun et al., 1985). As new sources of spherules become available, it is important to verify their extraterrestrial origin, and to see whether they confirm or modify earlier findings. It is also interesting to continue to search for spall droplets. In this paper we report on a group of large spherules collected from glacial till near Lewis Cliff, Antarctica (84.3 degrees S, 161.6 degrees E) (Harvey and Maurette, 1990). The concentrations of cosmogenic ^10Be and ^26Al were measured in 10 such spherules (LC-7 to LC-16). Typically these spherules have a lower Fe content, and are more weakly magnetic, than those studied earlier. In addition to these spherules, we analyzed 8 individual deep sea spherules (90-250 micrograms) (Murrell et al., 1980). All particles were individually mounted in acrylic resin and a small surface was polished flat with aluminum oxide. The quantitative elemental analysis of these polished surfaces was performed using an electron microprobe. After electron microprobe analysis, each particle was dissolved and Be and Al were separated for AMS. The ^10Be and ^26Al concentrations were determined at LLNL. In this and a preceding group of LC and deep-sea particles, three (LC-6, reported

  10. 10Be distribution in soils from Merced River terraces, California

    USGS Publications Warehouse

    Pavich, M.J.; Brown, L.; Harden, J.; Klein, J.; Middleton, R.

    1986-01-01

    The distribution and residence time of cosmogenic 10Be in clay-rich soil horizons is fundamental to understanding and modelling the migration of 10Be on terrestrial sediments and in groundwater solutions. We have analyzed seven profiles of clay-rich soils developed from terrace sediments of the Merced River, California. The terraces and soils of increasing age are used to compare the 10Be inventory with a simple model of accumulation, decay and erosion. The data show that the distribution of 10Be varies with soil horizon clay content, that the residence time of 10Be in these horizons exceeds 105 years, and that to a rough approximation the inventory of 10Be in a thoroughly sampled soil profile fits the equation: N = (q - Em)(1 - e-????)/?? where q is delivery rate, E is erosion rate, m is the concentration of 10Be in the eroding surface layer, ?? is the decay constant, and t is the age of the depositional unit from which the soil has developed. The general applicability of this model is uncertain and warrants further testing in well-calibrated terrace sequences. ?? 1986.

  11. 10Be in late deglacial climate simulated by ECHAM5-HAM - Part 1: Climatological influences on 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Phipps, S. J.; Smith, A. M.

    2013-11-01

    Reconstruction of solar irradiance has only been possible for the Holocene so far. During the last deglaciation, two solar proxies (10Be and 14C) deviate strongly, both of them being influenced by climatic changes in a different way. This work addresses the climate influence on 10Be deposition by means of ECHAM5-HAM atmospheric aerosol-climate model simulations, forced by sea surface temperatures and sea ice extent created by the CSIRO Mk3L coupled climate system model. Three time slice simulations were performed during the last deglaciation: 10 000 BP ("10k"), 11 000 BP ("11k") and 12 000 BP ("12k"), each 30 yr long. The same, theoretical, 10Be production rate was used in each simulation to isolate the impact of climate on 10Be deposition. The changes are found to follow roughly the reduction in the greenhouse gas concentrations within the simulations. The 10k and 11k simulations produce a surface cooling which is symmetrically amplified in the 12k simulation. The precipitation rate is only slightly reduced at high latitudes, but there is a northward shift in the polar jet in the Northern Hemisphere, and the stratospheric westerly winds are significantly weakened. These changes occur where the sea ice change is largest in the deglaciation simulations. This leads to a longer residence time of 10Be in the stratosphere by 30 (10k and 11k) to 80 (12k) days, increasing the atmospheric concentrations (25-30% in 10k and 11k and 100% in 12k). Furthermore the shift of westerlies in the troposphere leads to an increase of tropospheric 10Be concentrations, especially at high latitudes. The contribution of dry deposition generally increases, but decreases where sea ice changes are largest. In total, the 10Be deposition rate changes by no more than 20% at mid- to high latitudes, but by up to 50% in the tropics. We conclude that on "long" time scales (a year to a few years), climatic influences on 10Be deposition remain small (less than 50%) even though atmospheric

  12. Production Rate of Cosmogenic 10Be in Magnetite

    NASA Astrophysics Data System (ADS)

    Granger, D. E.; Rogers, H. E.; Riebe, C. S.; Lifton, N. A.

    2013-12-01

    Cosmogenic 10Be is widely used for determining exposure ages, soil production rates, and catchment-wide erosion rates. To date, measurements have been almost exclusively in the mineral quartz (SiO2), which is resistant to weathering and easily cleaned of meteoric 10Be contamination. However, this limits the method to quartz-bearing rocks and requires specialized laboratories due to the need for large quantities of hydrofluoric acid (HF). Here, we present initial results for 10Be production in the mineral magnetite (Fe3O4). Magnetite offers several advantages over quartz; it is (1) present in mafic rocks, (2) easily collected in the field, (3) quickly and easily separated in the lab, and (4) digested without HF. In addition, 10Be can be measured in both detrital quartz and magnetite from the same catchment to yield information about the intensity of chemical weathering (Rogers et al., this conference). The 10Be production rate in magnetite relative to quartz was determined for a granitic boulder from Mt. Evans, Colorado, USA. The boulder was crushed and homogenized to facilitate production rate comparisons among various minerals. We separated magnetite using a combination of hand magnets, froth flotation, and a variety of selective chemical dissolutions in dithionite-citrate-bicarbonate solution, 5% nitric acid (HNO3) and 1% HF/HNO3. Six aliquots of magnetite were analyzed for 10Be and compared to quartz. Three aliquots that were not exposed to 1% HF/HNO3 were contaminated with meteoric 10Be, probably associated with residual mica. Three aliquots that were exposed to 1% HF/HNO3 treatments agreed to within 2% measurement uncertainty. Our preliminary results indicate that the relative production rate by mass of 10Be in magnetite and quartz is 0.462 × 0.012. Our results are similar to theoretically predicted values. Recently updated excitation functions for neutron and proton spallation reactions allow us to partition 10Be production in quartz and magnetite among

  13. Resonances in 14C observed in the 4He(10Be ,α )10Be reaction

    NASA Astrophysics Data System (ADS)

    Freer, M.; Malcolm, J. D.; Achouri, N. L.; Ashwood, N. I.; Bardayan, D. W.; Brown, S. M.; Catford, W. N.; Chipps, K. A.; Cizewski, J.; Curtis, N.; Jones, K. L.; Munoz-Britton, T.; Pain, S. D.; Soić, N.; Wheldon, C.; Wilson, G. L.; Ziman, V. A.

    2014-11-01

    The α (10Be,α )10Be resonant scattering reaction has been measured at nine 10Be beam energies from 25 to 48 MeV, scanning out resonances in 14C from excitation energies of 13 to 24 MeV. Angular distribution measurements were used to assign the spin and parity of 5- to resonances at Ex=18.82 (2 ) and 19.67(2) MeV and 6+ at Ex=20.80 (2 ) MeV. The data also strongly indicate a 3- resonance at 17.32(2) MeV. The systematic uncertainty on the excitation energies is 175 keV. An R -matrix analysis has been performed for the excitation energy range 16.5 to 22 MeV. The data are discussed in terms of cluster bands in 14C.

  14. 26Al and 10Be Activities of Lodranites and Winona

    NASA Astrophysics Data System (ADS)

    Herzog, G. F.; Xue, S.; Klein, J.; Juenemann, D.; Middleton, R.

    1993-07-01

    Noble gas measurements by [1] indicate that four lodranites LEW 88280, Lodran (a fall), MAC 88177, and Yamato 791491 have the same cosmic ray exposure age of a few million years. The elevated ^22Ne/^21Ne ratios of these lodranites, from 1.22 to 1.28 [1], suggest that shielding was light and production rates appreciably lower than in average chondrites. Cosmic-ray irradiation in space for, say, 4 My would bring ^26Al and ^10Be to within 2% and 16% of their respective saturation values. Thus measurement of ^26Al may provide information about production rates and shielding and ^10Be about exposure age. We separated magnetically metal- and silicate-rich material from the four lodranites mentioned above and from Winona. The ^26Al and/or ^10Be activities (Table 1) were measured by accelerator mass spectrometry [2] with the statistical 1-sigma precision shown; the activities are thought to have an overall accuracy of 6-8%. Although the metal phases were etched with HF, they retained some silicate. To get a quantitative indication of the amounts of silicate present, the Mg concentrations in aliquots of the dissolved metal samples (Table 1) were measured by ICP/MS. The Mg, Al, Ca, Ti, Mn, and Fe contents of the silicate phases were determined by DCP emission spectrometry [3]. The measured activities in silicates from LEW 88280, Lodran, and Y 791491 resemble one another closely: The average ^26Al and ^10Be activities are 50.9 and 16.7 dpm/kg compared to estimated production rates of about 55 and 23 dpm/kg. These results lead to an exposure age of ~3.3 My, but do not indicate substantial lowering of production rates. The ^26Al and ^10Be contents of MAC 88177 are about half the values expected at saturation under normal shielding and are lower than those in the other three lodranites. These results are consistent with the very light shielding inferred from the exceptionally high ^22Ne/^21Ne ratio of 1.28, and perhaps with some lowering due to terrestrial age. Kirsten et al. [4

  15. 10Be in last deglacial climate simulated by ECHAM5-HAM - Part 1: Climatological influences on 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Phipps, S. J.; Smith, A. M.

    2013-07-01

    Reconstruction of solar irradiance has only been possible for the Holocene so far. During the last deglaciation two solar proxies (10Be and 14C) deviate strongly, both of them being influenced by climatic changes in a different way. This work addresses the climate influence on 10Be deposition by means of ECHAM5-HAM atmospheric aerosol-climate model simulations, forced by sea surface temperatures and sea ice extent created by the coupled climate system model CSIRO Mk3L. Three time slice simulations were performed during the last deglaciation: 10 000 BP ("10k"), 11 000 BP ("11k") and 12 000 BP ("12k"), each 30 yr long. The same 10Be production rate was used in each simulation to isolate the impact of climate on 10Be deposition. The changes are found to follow roughly the reduction in the greenhouse gas concentrations within the simulations. The 10k and 11k simulations produce a surface cooling which is symmetrically amplified in the 12k simulation. The precipitation rate is only slightly reduced at high latitudes, but there is a northward shift in the polar jet in the Northern Hemisphere and the stratospheric westerly winds are significantly weakened. These changes occur where the sea ice change is largest in the deglaciation simulations. This leads to a longer residence time of 10Be in the stratosphere by 30 (10k and 11k) to 80 (12k) days, heavily increasing the atmospheric concentrations. Furthermore the shift of westerlies in the troposphere leads to an increase of tropospheric 10Be concentrations, especially at high latitudes. The contribution of dry deposition generally increases, but decreases where sea ice changes are largest. In total, the 10Be deposition rate changes by no more than 20% at mid- to high latitudes, but by up to 50% in the tropics. We conclude that on "long" time scales (a year to a few years), climatic influences on 10Be deposition remain small even though atmospheric concentrations can vary significantly. Averaged over a longer period all 10

  16. Lateglacial surface exposure dating in the Monadhliath Mountains, Central Highlands, Scotland

    NASA Astrophysics Data System (ADS)

    Gheorghiu, D. M.; Fabel, D.; Hansom, J. D.; Xu, S.

    2012-05-01

    We constrain the deglaciation history of the Monadhliath Mountains since the Last Glacial Maximum using glacial geomorphology and surface exposure dating. Collectively these data clarify the glacial history of the Monadhliath Mountains at the close of the Devensian cold period. 10Be exposure ages indicate deglaciation of the Last Devensian ice sheet at 15.1 ± 1.4 ka at ca 640 m OD. The exposure ages are consistent with basal radiocarbon ages from nearby Loch Etteridge, 5 km to the south-east (15.3 ± 0.2 kcal BP

  17. Shielding Effects on 10Be and 26Al in Diogenites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Lindner, L.; van der Borg, K.; Loeken, Th.; Schultz, L.

    1995-09-01

    Due to the attenuation of primary particles and the variations in secondary part fluxes with depth, production rates of cosmogenic nuclides are affected by the s shape of the irradiated object. The effects of shielding conditions on the produduction rates of noble gases can be estimated on the basis of the cosmogenic 22Ne/21Ne r [1]. For the production of cosmogenic radionuclides, shielding studies mainly fo on large meteorites like St. Severin [2], Knyahinya [3], Chico [4] and Jilin [5] estimated preatmospheric radii between 25 and 85 cm. The 10Be and 26Al production were also measured in three smaller meteorites, but the cosmogenic 22Ne/21Ne rat were obscured by large amounts of trapped neon [6]. Therefore we carried out a systematic study on the 10Be and 26Al activities as a function of the 22Ne/21Ne in 7 non-Antarctic and 15 Antarctic diogenite samples. Diogenites show exposure long enough (>10 Ma) to have reached saturation levels for 10Be and 26Al and are similar to ordinary chondrites with respect to the target element composition fo production of 10Be, 26Al and Ne isotopes. The measured 10Be and 26Al activities were normalized to average diogenite compo on the basis of ICP and XRF measurements and the experimental production rate eq of [7] and [8]. For the Antarctic samples with known terrestrial ages [9] correc were made for radioactive decay. In figure 1, the resulting 10Be and 26Al production rates are plotted against the 22Ne/21Ne ratios, which were measured on the same The solid lines represent the results of an exponential fitting procedure, from two samples were excluded: EET83246 because of SCR-produced 26Al and LEW88008 be of an anomalously low 26Al/10Be ratio, which is not yet understood. Figure 1 illustrates that the 10Be and 26Al production rates are similarly affect shielding conditions: both 10Be and 26Al decrease about 30 - 40% when going from objects with low 22Ne/21Ne ratios (<1.10) to small objects with high 22Ne/21Ne r (>1.25). Recently

  18. Exposure age and erosional history of an upland planation surface in the US Atlantic Piedmont

    USGS Publications Warehouse

    Stanford, S.D.; Seidl, M.A.; Ashley, G.M.

    2000-01-01

    The upland planation surface in the Piedmont of central New Jersey consists of summit flats, as much as 130 km2 in area, that truncate bedding and structure in diabase, basalt, sandstone, mudstone and gneiss. These flats define a low-relief regional surface that corresponds in elevation to residual hills in the adjacent Coastal Plain capped by a fluvial gravel of late Miocene age. A Pliocene fluvial sand is inset 50 m below the upland features. These associations suggest a late Miocene or early Pliocene age for the surface. To assess exposure age and erosional history, a 4??4 m core of clayey diabase saprolite on a 3 km2 remnant of the surface was sampled at six depths for atmospherically produced cosmogenic 10Be. The measured inventory, assuming a deposition rate of 1??3 x 106 atoms cm-2 a-1, yields a minimum exposure age of 227 000 years, or, assuming continuous surface erosion, a constant erosion rate of 10 m Ma-1. Because the sample site lies about 60 m above the aggradation surface of the Pliocene fluvial deposit, and itself supports a pre-Pliocene fluvial gravel lag, this erosion rate is too high. Rather, episodic surface erosion and runoff bypassing probably have produced an inventory deficit. Reasonable estimates of surface erosion (up to 10 m) and bypassing (up to 50 per cent of total precipitation) yield exposure ages of as much as 6??4 Ma. These results indicate that (1) the surface is probably of pre-Pleistocene age and has been modified by Pleistocene erosion, and (2) exposure ages based on 10Be inventories are highly sensitive to surface erosion and runoff bypassing. Copyright (C) 2000 John Wiley and Sons, Ltd.

  19. Reprocessing of 10B-contaminated 10Be AMS targets

    NASA Astrophysics Data System (ADS)

    Simon, K. J.; Pedro, J. B.; Smith, A. M.; Child, D. P.; Fink, D.

    2013-01-01

    10Be accelerator mass spectrometry (AMS) is an increasingly important tool in studies ranging from exposure age dating and palaeo-geomagnetism to the impact of solar variability on the Earth’s climate. High levels of boron in BeO AMS targets can adversely impact the quality of 10Be measurements through interference from the isobar 10B. Numerous methods in chemical sample preparation and AMS measurement have been employed in order to reduce the impact of excessive boron rates. We present details of a method developed to chemically reprocess a set of forty boron-contaminated BeO targets derived from modern Antarctic ice. Previously, the excessive boron levels in these samples, as measured in an argon-filled absorber cell preceding the ionisation detector, had precluded routine AMS measurement. The procedure involved removing the BeO + Nb mixture from the target holders and dissolving the BeO in hot concentrated H2SO4. The solution was then heated with HF to remove the boron as volatile BF3 before re-precipitating as Be(OH)2 and calcining to BeO. This was again mixed with niobium and pressed into fresh target holders. Following reprocessing, the samples gave boron rates reduced by 10-100×, which were sufficiently low and similar to previous successful batches of ice core, snow and associated blank samples, thus allowing a successful 10Be measurement in the absence of any boron correction. Overall recovery of the BeO for this process averaged 40%. Extensive testing of relevant processing equipment and reagents failed to determine the source of the boron. As a precautionary measure, a similar H2SO4 + HF step has been subsequently added to the standard ice processing method.

  20. The drainage of the Baltic Ice Lake and a new Scandinavian reference 10Be production rate

    NASA Astrophysics Data System (ADS)

    Stroeven, Arjen P.; Heyman, Jakob; Fabel, Derek; Björck, Svante; Caffee, Marc W.; Fredin, Ola; Harbor, Jonathan M.

    2015-04-01

    An important constraint on the reliability of cosmogenic nuclide exposure dating is the derivation of tightly controlled production rates. We present a new dataset for 10Be production rate calibration from Mount Billingen, southern Sweden, the site of the final drainage of the Baltic Ice Lake, an event dated to 11,620 ± 100 cal yr BP. Nine samples of flood-scoured bedrock surfaces and depositional boulders and cobbles unambiguously connected to the drainage event yield a reference 10Be production rate of 4.09 ± 0.22 atoms g-1 yr-1 for the CRONUS Lm scaling and 3.93 ± 0.21 atoms g-1 yr-1 for the LSD general spallation scaling. We also recalibrate the reference 10Be production rates for four sites in Norway and combine these with the Billingen results to derive a tightly clustered Scandinavian reference 10Be production rate of 4.12 ± 0.10 (4.12 ± 0.25 for altitude scaling) atoms g-1 yr-1 for the Lm scaling scheme and 3.96 ± 0.10 (3.96 ± 0.24 for altitude scaling) atoms g-1 yr-1 for the LSD scaling scheme.

  1. Radiation exposure for manned Mars surface missions

    SciTech Connect

    Simonsen, L.C.; Nealy, J.E.; Townsend, L.W.; Wilson, J.W.

    1990-03-01

    The Langley cosmic ray transport code and the Langley nucleon transport code (BRYNTRN) are used to quantify the transport and attenuation of galactic cosmic rays (GCR) and solar proton flares through the Martian atmosphere. Surface doses are estimated using both a low density and a high density carbon dioxide model of the atmosphere which, in the vertical direction, provides a total of 16 g/sq cm and 22 g/sq cm of protection, respectively. At the Mars surface during the solar minimum cycle, a blood-forming organ (BFO) dose equivalent of 10.5 to 12 rem/yr due to galactic cosmic ray transport and attenuation is calculated. Estimates of the BFO dose equivalents which would have been incurred from the three large solar flare events of August 1972, November 1960, and February 1956 are also calculated at the surface. Results indicate surface BFO dose equivalents of approximately 2 to 5, 5 to 7, and 8 to 10 rem per event, respectively. Doses are also estimated at altitudes up to 12 km above the Martian surface where the atmosphere will provide less total protection.

  2. Radiation exposure for manned Mars surface missions

    NASA Technical Reports Server (NTRS)

    Simonsen, Lisa C.; Nealy, John E.; Townsend, Lawrence W.; Wilson, John W.

    1990-01-01

    The Langley cosmic ray transport code and the Langley nucleon transport code (BRYNTRN) are used to quantify the transport and attenuation of galactic cosmic rays (GCR) and solar proton flares through the Martian atmosphere. Surface doses are estimated using both a low density and a high density carbon dioxide model of the atmosphere which, in the vertical direction, provides a total of 16 g/sq cm and 22 g/sq cm of protection, respectively. At the Mars surface during the solar minimum cycle, a blood-forming organ (BFO) dose equivalent of 10.5 to 12 rem/yr due to galactic cosmic ray transport and attenuation is calculated. Estimates of the BFO dose equivalents which would have been incurred from the three large solar flare events of August 1972, November 1960, and February 1956 are also calculated at the surface. Results indicate surface BFO dose equivalents of approximately 2 to 5, 5 to 7, and 8 to 10 rem per event, respectively. Doses are also estimated at altitudes up to 12 km above the Martian surface where the atmosphere will provide less total protection.

  3. Photodocumentation of long-term lunar surface exposure experiment

    NASA Technical Reports Server (NTRS)

    Hoerz, F.

    1974-01-01

    Preflight photographs of selected Apollo 17 equipment taken for use in determining the effects on various surfaces of long-term exposure to the lunar environment are presented. Photographs of the articles deployed on the lunar surface also are included. The photographic procedure and the coding system used for the photodocumentation are explained. Other documentation measures planned to obtain items for use as controls in projected analyses are discussed.

  4. Smoothing Polymer Surfaces by Solvent-Vapor Exposure

    NASA Astrophysics Data System (ADS)

    Anthamatten, Mitchell

    2003-03-01

    Ultra-smooth polymer surfaces are of great importance in a large body of technical applications such as optical coatings, supermirrors, waveguides, paints, and fusion targets. We are investigating a simple approach to controlling surface roughness: by temporarily swelling the polymer with solvent molecules. As the solvent penetrates into the polymer, its viscosity is lowered, and surface tension forces drive surface flattening. To investigate sorption kinetics and surface-smoothing phenomena, a series of vapor-deposited poly(amic acid) films were exposed to dimethyl sulfoxide vapors. During solvent exposure, the surface topology was continuously monitored using light interference microscopy. The resulting power spectra indicate that high-frequency defects smooth faster than low-frequency defects. This frequency dependence was studied by depositing polymer films onto a series of 2D sinusoidal surfaces and performing smoothing experiments. Results show that the amplitudes of the sinusoidal surfaces decay exponentially with solvent exposure time, and the exponential decay constants are proportional to surface frequency. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  5. A note of caution on the use of boulders for exposure dating of depositional surfaces

    NASA Astrophysics Data System (ADS)

    Schmidt, S.; Hetzel, R.; Kuhlmann, J.; Ramos, V. A.

    2010-12-01

    Exposure dating of boulders has been widely applied to determine the age of depositional surfaces under the assumption that the pre-depositional nuclide component in most boulders is negligible (e.g. Bierman et al., 1995; van der Woerd et al., 2006). Here we present a case study on fluvial terraces at the active mountain front of the eastern Andes, where this assumption is clearly invalid, because sandstone boulders (n = 13) at two sites contain a highly variable inherited 10Be component and have apparent 10Be ages that exceed the age of the respective surface by up to 93 ka. Likewise, boulders from active stream channels (n = 5) contain a substantial inherited 10Be component, equivalent to 5-48 ka of exposure. The age of the fluvial terraces is well determined by 10Be depth profiles on sand samples, which allow to correct for the pre-depositional nuclide component. At site 1, three terraces have 10Be ages of 3.20 ± 0.42 ka (T2), 11.11 ± 0.87 ka (T3), and 16.0 ± 1.1 ka (T4). The age of T3 is furthermore confirmed by a calibrated 14C age of 12.61 ± 0.20 ka BP. At site 2, terrace T3 has an age of 13.5 ± 2.1 ka (derived on a 10Be depth profile), while boulders indicate apparent ages from 14 to 31 ka. The average inherited 10Be concentration of sand grains - determined from depth profiles and stream sediments - is small and equivalent to 1-3 ka of exposure, whereas the mean inheritance of the boulders is an order of magnitude higher. This causes great caution by determining erosion rates. The huge contrast is related to the different provenance and transport history of sand and boulders. While the sand is derived from rapidly eroding Miocene sediments exposed near the mountain front, the boulders originate from Triassic sandstones in the internal part of the fold-and-thrust belt. On their way to the mountain front the boulders were temporarily stored and irradiated in alluvial fans that are currently reworked. Sediment deposition in intramontane basins and

  6. Rapid thinning of the Welsh Ice Cap at 20-19 ka based on 10Be ages

    NASA Astrophysics Data System (ADS)

    Hughes, Philip D.; Glasser, Neil F.; Fink, David

    2016-01-01

    New 10Be ages from the summits of three mountain areas of North Wales reveal a very similar exposure timing as the Welsh Ice Cap thinned after the global Last Glacial Maximum. Eight bedrock and one boulder sample gave a combined arithmetic mean exposure age of 19.08 ± 0.80 ka (4.2%, 1σ). Similar exposure ages over a 320 m vertical range (824 to 581 m altitude) show that ice cap thinning was very rapid and spatially uniform. Using the same production rate and scaling scheme, we recalculated six published 10Be exposure ages from the nearby Arans, which also covered a similar elevation range from 608 to 901 m and obtained an arithmetic mean of 19.41 ± 1.45 ka (7.5%, 1σ). The average exposure age of all 15 accepted deglaciation ages is 19.21 ± 1.07 (5.6%, 1σ). The complete dataset from North Wales provides very strong evidence indicating that these summits became exposed as nunataks at 20-19 ka. This result provides important insight to the magnitude of ice surface lowering and behavior of the Welsh Ice Cap during the last deglaciation that can be compared to other ice masses that made up the British-Irish Ice Sheet.

  7. Recent progress of 10Be tracer studies in Chinese loess

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Xie, Xingjun; Beck, Warren; Kong, Xianghui; Xian, Feng; Du, Yajuan; Wu, Zhenkun

    2015-10-01

    Studies of cosmogenic 10Be in Chinese loess began about twenty-five years ago and since then a number of research groups worldwide have contributed to a firm understanding of the production, transport, deposition and storage of 10Be in loess. The essential characteristics that make 10Be a useful isotopic tracer in loess, include: (1) dominant atmospheric production directly linked to the intensity of the Earth's magnetic field; (2) climate-dependent deposition; and (3) subsequent immobility, so that as 10Be accumulates in a loess profile its stratigraphic integrity is preserved. This fact, combined with very high deposition rates in loess on the Chinese Loess Plateau, makes 10Be an especially valuable continental archive of paleoclimate and paleomagnetism, complementing marine and ice-core records. Here we provide in particular the most recent progress of 10Be tracer studies in Chinese loess, including the determination of the correct age of the Brunhes-Matuyama polarity reversal at 780 ± 3 ka B.P., in accord with marine and ice records, and quantitative reconstruction of 130-ka paleoprecipitation using 10Be from Chinese loess profiles.

  8. Meteoric 10Be in soil profiles - A global meta-analysis

    NASA Astrophysics Data System (ADS)

    Graly, Joseph A.; Bierman, Paul R.; Reusser, Lucas J.; Pavich, Milan J.

    2010-12-01

    In order to assess current understanding of meteoric 10Be dynamics and distribution in terrestrial soils, we assembled a database of all published meteoric 10Be soil depth profiles, including 104 profiles from 27 studies in globally diverse locations, collectively containing 679 individual measurements. This allows for the systematic comparison of meteoric 10Be concentration to other soil characteristics and the comparison of profile depth distributions between geologic settings. Percent clay, 9Be, and dithionite-citrate extracted Al positively correlate to meteoric 10Be in more than half of the soils where they were measured, but the lack of significant correlation in other soils suggests that no one soil factor controls meteoric 10Be distribution with depth. Dithionite-citrate extracted Fe and cation exchange capacity are only weakly correlated to meteoric 10Be. Percent organic carbon and pH are not significantly related to meteoric 10Be concentration when all data are complied. The compilation shows that meteoric 10Be concentration is seldom uniform with depth in a soil profile. In young or rapidly eroding soils, maximum meteoric 10Be concentrations are typically found in the uppermost 20 cm. In older, more slowly eroding soils, the highest meteoric 10Be concentrations are found at depth, usually between 50 and 200 cm. We find that the highest measured meteoric 10Be concentration in a soil profile is an important metric, as both the value and the depth of the maximum meteoric 10Be concentration correlate with the total measured meteoric 10Be inventory of the soil profile. In order to refine the use of meteoric 10Be as an estimator of soil erosion rate, we compare near-surface meteoric 10Be concentrations to total meteoric 10Be soil inventories. These trends are used to calibrate models of meteoric 10Be loss by soil erosion. Erosion rates calculated using this method vary based on the assumed depth and timing of erosional events and on the reference data selected.

  9. Testing a luminescence surface-exposure dating technique

    NASA Astrophysics Data System (ADS)

    Gliganic, Luke A.; Meyer, Michael; Gehring, Sebastian

    2016-04-01

    Recent work has shown that the relationship between the luminescence signal (optically stimulated [OSL] and infra-red stimulated [IRSL]) and depth into a rock surface can be used to estimate the length of time since that rock surface has been exposed to sunlight (Sohbati et al., 2012), thus serving as a means for surface-exposure dating. Despite the potential of this new dating tool, few published studies have tested or used this technique. Here, we present the results of two tests of the method. First, we perform laboratory bleaching experiments using two unexposed bedrock samples of different lithologies (granite and quartzite). Sub-samples were bleached for various durations (0 to 100,000 s) in a solar simulator, and IRSL/OSL-depth profiles were measured and fitted using the model of Sohbati et al. (2012). Results of fitting for each sub-sample were then compared. Second, we used a granite boulder from a known age moraine (1850 CE) to test the reproducibility of bleaching depth curves. Multiple cores were collected from the same ~5 cm2 surface area of the boulder, and IRSL-depth profiles were measured and modelled. While our systematic tests confirm the general physical basis of luminescence surface-exposure dating method, we found unexpected scatter in both adjacent bleaching depth curves and the fitting parameters of isochronous rock surfaces for some of our samples. Potential sources of error, including small-scale lithological variabilities and implications for accuracy and precision of the method are discussed. Sohbati, R., Murray, A.S., Chapot, M.S., Jain, M., Pederson, J. (2012) Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating. Journal of Geophysical Research 117 (B9), B09202. doi.org/10.1029/2012JB009383.

  10. Alpine Cliff Backwearing Rates Derived From Cosmogenic 10-Be in Active Medial Moraines

    NASA Astrophysics Data System (ADS)

    Ward, D. J.; Anderson, R. S.

    2008-12-01

    -order interpretation of these results yields minimum erosion rates of 0.2 to 0.5 mm/yr, consistent with erosion rates measured by various means in other glacial environments. This interpretation assumes a simple source area geometry and 10Be production rate scaling. To interpret these measurements in their full geological and topographic context, we present numerical models to describe how the expected distribution of 10Be concentrations should vary with erosion rate. This relationship is affected by source area hypsography and the distributions of size and recurrence interval of rockfall events. We randomly sample events based on a power-law size-recurrence relationship (constrained by field observations) from a numerical grid of production rates derived from a DEM of the source area. This yields the expected probability distribution of 10Be concentrations in the rockfall debris for a given mean erosion rate, weighted by event volume and source hypsography. The measured 10Be concentrations are low enough that accumulation during burial, exhumation, and transport in the medial moraine could account for up to ~1/4 of the signal, given our best estimates of glacier's surface speed (~30 m/yr). The slight downvalley increase in the concentrations supports a component of exposure in the moraine during transport. The amount of exposure depends on factors such as the entry and exit points of debris incorporated into the glacial ice, and the glacial mass balance pattern, and downvalley surface speed. We assess these effects with analytical and numerical models of debris transport in medial moraines, following Anderson (2000).

  11. Study of states in 14C via the 10Be(4He,4He)10Be reaction

    NASA Astrophysics Data System (ADS)

    Malcolm, J. D.; Freer, M.; Ashwood, N. I.; Curtis, N.; Munoz-Britton, T.; Wheldon, C.; Ziman, V. A.; Catford, W. N.; Brown, S.; Wilson, G.; Soic, N.; Bardayan, D.; Pain, S. D.; Achouri, N. L.; Chipps, K.; Crzywacz-Jones, K.

    2012-09-01

    A study of the 10Be(4He,4He)10Be reaction has been performed at 10Be beam energies of 25.0, 27.0, 29.0, 32.0, 34.0, 38.0, 40.0, 42.0, 44.0 and 46.0 MeV. The measurements were to explore possible molecular rotational bands in 14C. Three states at excitation energies of Ex = 18.8, 19.76 and 20.66 MeV have been measured and their spins have been determined to be 5-, 5- and 6+, respectively.

  12. Do Fungi Transport 10Be During Wood Degradation?

    NASA Astrophysics Data System (ADS)

    Conyers, G.; Granger, D. E.

    2010-12-01

    Meteoric cosmogenic 10Be is increasingly used to determine erosion and soil transport rates. To calculate these rates, it is assumed that 10Be is a conservative passive tracer of soil particles. However, there is experimental evidence that beryllium is mobilized in natural soils complexed with organic acids. For example, up to 50% of beryllium can be mobilized by humic acids in soils at pH 7 (Takahashi et al., 1999). Beryllium is also known to be taken up in plants such as tobacco and vegetables (World Health Organization, 1990) at ppm levels, primarily as organic acid chelates. It is not known to what extent biological beryllium transport in the environment affects the cosmogenic 10Be budget, or how it influences beryllium mobility. In this study, we address a problem recognized early in the development of meteoric 10Be methods. It has been observed that decayed organic matter in soils and sediments contains very high concentrations of 10Be of up to 109-1010 atoms/g (Lundberg, et al., 1983). On the other hand, living trees contain much lower concentrations of 106 atoms/g (Klein et al., 1982). The driving question for this study is how 10Be becomes bound to decayed organic matter. Direct fallout seems unlikely as the residence time of organic matter in soil is too short. One possibility is that 10Be is transported by fungi. Wood-degrading fungi are known to transport and bioaccumulate metals from large areas, facilitated by acids such as oxalic acid in the fungal hyphae. To test the hypothesis that fungi transport 10Be, we analyzed both intact and fungally degraded wood of oak, hickory, and hemlock. From these data, we reached two conclusions (observations?): 1) Oak has a 10Be concentration of about 2x106 at/g, similar to that observed by Klein et al. (1982). Hickory has a significantly higher concentration of about 3x107 atoms/g, confirming observations that hickory bioaccumulates beryllium. Using these data, the inventory of 10Be in a temperate forest is expected

  13. Preliminary AMS measurements of 10Be at the CENTA facility

    NASA Astrophysics Data System (ADS)

    Ješkovský, Miroslav; Steier, Peter; Priller, Alfred; Breier, Robert; Povinec, Pavel P.; Golser, Robin

    2015-10-01

    Very sensitive methods, presently mainly accelerator mass spectrometry (AMS) are necessary for analysis of cosmogenic 10Be in the environment. AMS is mainly limited by the stable isobar 10B, while the requirements for mass separation are the least stringent of all standard isotopes analyzed by AMS. We tested a possibility to measure 10Be using a small switching magnet as an analyzer of accelerated ions, and an ionization chamber with a silicon nitride foil stack used as a passive absorber. A detection limit of 10-12 for the 10Be/9Be isotopic ratio was obtained using this technique, which was mainly determined by scattering of 9Be+2 ions on residual gas inside the switching magnet.

  14. Dating chert using in-situ produced 10Be: Possible complications revealed on landslide scarps through a comparison with 36Cl applied to coexisting limestone.

    NASA Astrophysics Data System (ADS)

    Zerathe, Swann; Braucher, Régis; Lebourg, Thomas; Leani, Leatitia; Manetti, Michel; Bourles, Didier

    2013-04-01

    This abstract and presentation highlights potential complications that may arise while using in situ produced 10Be to date diagenetic silica (chert)exposure or burial event. The initiation and evolution of large gravitational collapses in sedimentary rocks were constrained using cosmic ray exposure dating. Because these collapses occurred in a stratigraphic level composed of chert (diagenetic silica) concretions interbedded in limestone layers, their development was studied by performing in situ-produced 36Cl and 10Be concentration measurements in both the limestone and coexisting diagenetic silica (chert), respectively. Following the routinely used decontamination and preparation protocols for 10Be produced in diagenetic silica, large discrepancies were observed with exposure ages determined by 36Cl within carbonate for samples originating from the same scarp. While 36Cl exposure ages were clustered as expected for a unique single gravitational event, 10Be exposure ages were scattered along the same studied scarps. To determine the origin of such a bias, petrological investigations were carried out for chert (diagenetic silica). Thin sections highlighted a complex mineralogical texture characterized by remnant silicified ooids showing calcitic cores, calcite inclusions and a dominant amorphous hydrated silica (grain > 20 μm). To decipher and characterize the potential origins of the excess measured 10Be within diagenetic silica, all samples were first reprocessed following the routine decontamination protocol (HCL-H2SiF6 leachings and three partial HF dissolutions) but starting from three different grain size fractions (GS1: 1000-500, GS2: 500-250 and GS3: 250-50 μm). The resulting concentrations clearly showed a decreasing 10Be content as a function of the grain size, but still yielded 10Be exposure ages significantly higher than 36Cl counterparts. Because potential adsorption of 10Be at the surface of amorphous silica grains was suspected, partial dissolution

  15. The quantitative reconstruction of paleoprecipitation from Chinese loess 10Be

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Xian, Feng; Du, Yajuan; Kong, Xianghui; Wu, Zhenkun

    2016-04-01

    Cosmogenic 10Be is a promising precipitation index, because its fallout flux in sediments is mainly controlled by wet precipitation after its production in the atmosphere. Here we report on a new study for reconstructing precipitation during the last 130 ka using 10Be measurements from Chinese loess, with multivariable linear regression to remove the geomagnetic field modulation and dust flux dilution effects from the loess 10Be record. The broad similarity between our result and speleothem δ18O indicates that the new precipitation record is robust. It also records an interesting increase in precipitation that occurred during Marine Isotope Stage 3 (MIS 3), exhibiting a similar rainfall amount with that of MIS 5, suggesting that MIS 3 is a special period with strengthened summer Monsoon intensity. By comparison with a stacked marine isotope record and a summer insolation record, our precipitation data clearly show a close correspondence with Northern Hemisphere summer (June, July, and August) solar insolation changes on orbital timescales. During MIS 3, our record follows the insolation differential between 30°N and 30°S, suggesting that rising rainfall changes during MIS 3 are a response to the interhemispheric summer insolation differential forcing.

  16. Atmospheric deposition of sup 7 Be and sup 10 Be

    SciTech Connect

    Brown, L. ); Stensland, G.J. ); Klein, J.; Middleton, R. )

    1989-01-01

    Measurements of {sup 10}Be in precipitation taken in Hawaii, Illinois and New Jersey over a period of five years are reported. The problem of contamination by the isotope being resuspended on wind blown soil that is also collected is addressed. Rain collected at Mauna Loa, Hawaii has such low values of dust contamination that it has been taken as clean, and the data from Illinois and New Jersey are evaluated on that assumption. The conclusion is that the deposition in a given amount of rain for the non-resuspended component is the same for all three stations, and the authors propose that the annual rate for mid-latitude locations have moderate rainfall is proportional to the local rainfall. {sup 7}Be, which is probably negligibly contributed to the measurements by soil contamination was measured for individual rains in Illinois and found to have a deposition of 1.4 {times} 10{sup 4} atom/cm{sup 3}. The authors have found that concentration variations between precipitation events greater than a factor of 20 exist for both isotopes and that relatively rare, high concentration events dominate deposition, thereby requiring long periods of observation to avoid significant error. Based on their own and other data they conclude that the best value for {sup 10}Be deposition is 1.5 {times} 10{sup 4} atom/cm{sup 3}, uncertain by 20%, and for {sup 7}Be is 1.2 {times} 10{sup 4} atom/cm{sup 3}, uncertain by 25%. A global average deposition rate cannot be inferred directly for either isotope from these kinds of data; however, the theoretical global deposition rate for {sup 10}Be is shown to be consistent with the deposition reported here, if the concentration in equatorial rain is about 3300 atom/g.

  17. A 10Be Chronology of Late Pleistocene and Holocene Glaciation in the Rwenzori Mountains, Uganda

    NASA Astrophysics Data System (ADS)

    Baber, M.; Kelly, M. A.; Russell, J. M.; Loomis, S. E.

    2012-12-01

    Although the retreat of glaciers in East Africa has been monitored over the last century, longer-term records of African glacier fluctuations are scarce. The Rwenzori Mountains, located on the border of Uganda and the Democratic Republic of Congo, host the largest glacial system in Africa and provide an opportunity for extensive investigation of past glaciations. We mapped and applied surface exposure (10Be) dating to glacial moraines deposited since the end of the last ice age in the Rwenzori Mountains to test the feasibility of 10Be dating at this site and to develop a chronology of glacial fluctuations. Our study is the first to use 10Be dating of glacial features in Africa and is possible because the Rwenzori host quartz-rich lithologies. By comparing the timing of Rwenzori glacial advances with other paleoclimate records from East Africa, we also will examine the climatic conditions which influenced tropical glacier fluctuations. Osmaston (1989) mapped moraines in the Rwenzori Mountains, documenting three stages of Pleistocene and Holocene glaciations, the Mahoma, Omurubaho and Lac Gris stages. The Mahoma stage moraines are estimated to be older than 17,980 ± 780 yr BP (D. M. Livingstone, 1962) by basal 14C dating of sediments from Lake Mahoma, situated in large lateral moraine at 2990 m asl. The age of the Omurubaho stage moraine is estimated from a basal 14C age (7,730 ± 150 yr BP) Lower Kitandara Lake (3990 m asl) and dammed by an Omurubaho stage moraine. The Lac Gris moraines are estimated at ~150-700 yr BP (de Heinzelin, 1953; Bergström, 1955) based on rates of lichen growth and plant colonization on moraines about 200 m below current glacial positions on Mt. Stanley. Though considerable uncertainty remains for the ages of these glacier deposits, these three stages most likely represent ages from the LGM to the LIA. We present two new 10Be ages of boulders from two moraines in the Nyamagusani Valley, ~4000 m asl. Sample KOP-2 (4033 m asl) is from the

  18. Incision of the Danube River (Hungary), inferred by cosmogenic in situ 10Be and luminescence dating of terrace sediments

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Novothny, Ágnes; Braucher, Régis; Csillag, Gábor; Fodor, László; Molnár, Gábor; Thamó-Bozsó, Edit

    2014-05-01

    Major part of the former chronological studies showed that Danube terraces, and connected uplift of the surrounding hills are significantly younger than it was suggested before. On the other hand, some studies provided older than expected ages. Accordingly, a novel terrace chronology is necessary, which we try to approach by using two different dating methods on the alluvial terraces: luminescence dating, which provides the burial ages and cosmogenic in situ 10Be dating, which yields the exposure ages of the sediments. Cosmogenic 10Be and luminescence samples were collected from several terrace horizons. Cosmogenic in situ 10Be sampling occurred along depth profiles, because this method allows determining both the exposure time and the denudation rate at each locality by using all particles involved in the cosmogenic nuclide production. Post-Infrared Infrared Stimulated Luminescence (post-IR IRSL) measurements were carried out on K-feldspar samples, comparing the post-IR IRSL 290 and post-IR IRSL 225 signals. Besides, quartz from younger samples was also measured using Optically Stimulated Luminescence (OSL). The lower horizons (tIIa,b) were datable by both luminescence and cosmogenic exposure age dating methods. However, the upper horizons (tIV, tV) were frequently above the datable time range for one or both methods. In these cases, instead of the 'exact' ages with errors, only minimum ages could be assessed. Most of the luminescence data show older ages than 10Be exposure ages for the terrace surfaces. This may be due to the fact that the dated processes are different. Luminescence ages reveal the time of deposition of the sediment, while 10Be ages show the time since the actual terrace surface has been exposed to cosmic irradiation. The effect of considerable surface erosion also has to be taken into account, as well as the possibility of incomplete bleaching of the luminescence signal. The possible effect of post-depositional sediment mixing could be excluded

  19. 10Be in late deglacial climate simulated by ECHAM5-HAM - Part 2: Isolating the solar signal from 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Shi, X.; Phipps, S. J.; Smith, A. M.

    2013-10-01

    This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 yr time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 BP and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol-climate model, driven with sea surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather or climate driven noise in the 10Be deposition flux during different stages of climate. The production signal varies on lower frequencies, dominated by the 11yr solar cycle within the 30 yr time scale of these experiments. The climatic noise is of higher frequencies. We first apply empirical orthogonal functions (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis on the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low frequency components and the long term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high frequency components represent climate driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that the 10Be atmospheric production signal is preserved

  20. 10Be in late deglacial climate simulated by ECHAM5-HAM - Part 2: Isolating the solar signal from 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Shi, X.; Phipps, S. J.; Smith, A. M.

    2014-04-01

    This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 year time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol-climate model, driven with sea-surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather- or climate-driven noise in the 10Be deposition flux during different stages of climate. The production signal varies at lower frequencies, dominated by the 11 year solar cycle within the 30 year timescale of these experiments. The climatic noise is of higher frequencies than 11 years during the 30 year period studied. We first apply empirical orthogonal function (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis to the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low-frequency components and the long-term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high-frequency components represent climate-driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that

  1. Distribution of 10Be and 9Be in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Kusakabe, M.; Ku, T. L.; Southon, J. R.; Vogel, J. S.; Nelson, D. E.; Measures, C. I.; Nozaki, Y.

    1987-04-01

    The vertical distributions of 10Be and 9Be at three locations in the Pacific (25°N, 170°E; 17°N, 118°W; 3°S, 117°W) are presented. The results show that both isotopes exhibit nutrient-like profiles. From the surface to the bottom, the increase for 10Be is two- to threefold and that for 9Be is about fivefold. While the inter-station variations in surface water concentrations may reach a factor of two, deep-water values tend to be much more uniform averaging about 2000 atoms/g for 10Be and 30 pM for 9Be. A similar situation applies to the 10Be/ 9Be ratio; it varies approximately from 1 to 3 × 10 -7 (atom/atom) at shallow depths but tends toward a value close to 1.1 × 10 -7 in the deep ocean. The variation of 10Be/ 9Be can be viewed as resulting from the fact that 10Be in a given parcel of water consists of two components: recycled and primary. The recycled component is that part of 10Be which has reached tracer equilibrium with 9Be, as opposed to the primary component which, upon entering the sea from the atmosphere, has yet to equilibrate with 9Be through particle cycling and mixing processes. It is estimated that 70% to nearly 100% of 10Be at the three stations are being recycled, and the recycled beryllium bears an atomic ratio of 10Be/ 9Be close to 1 × 10 -7. The oceanic residence time of Be is of the order of 1000-4000 years, comparable to or slightly longer than the ocean mixing time.

  2. Meteoric 10Be in Lake Cores as a Measure of Climatic and Erosional Change

    NASA Astrophysics Data System (ADS)

    Jensen, R. E.; Dixon, J. L.

    2015-12-01

    Utilization of meteoric 10Be as a paleoenvironmental proxy has the potential to offer new insights into paleoprecipitation records and paleoclimate models, as well as to long-term variations in erosion with climate. The delivery of meteoric 10Be to the surface varies with precipitation and its strong adsorption to sediment has already proven useful in studies of erosion. Thus, it is likely meteoric 10Be concentrations in lake sediments vary under both changing climate and changing sediment influx. Assessment of the relative importance of these changes requires the comparison of 10Be concentrations in well-dated lake cores with independent paleoenvironmental proxies, including oxygen isotope, pollen, and charcoal records, as well as variation in geochemical composition of the sediments. Blacktail Pond details 15,000 years of climatic change in the Yellowstone region. We develop a new model framework for predicting meteoric 10Be concentrations with depth in the core, based on sedimentation rates of both lake-derived and terrigenous sediments and changes in the flux of meteoric 10Be with precipitation. Titanium concentrations and previously determined 10Be concentrations in wind-derived loess provide proxies for changing delivery of 10Be to the lake by terrigenous sources. We use existing paleoenvironmental data obtained from this core and the surrounding region to develop models for changing rainfall across the region and predict meteoric 10Be delivery to the lake by precipitation. Based on a suite of ~10 models, sedimentation rate is the primary control of meteoric 10Be in the Blacktail Pond core unless terrestrial input is very high, as it was post-glacial in the early Holocene when the lake experienced a high influx of loess and terrigenous sediments. We used these models to inform sample selection for 10Be analysis along the Blacktail pond core. Core sediments are processed for meteoric 10Be analysis using sequential digestions and standard extraction procedures

  3. ISSUES IN UNDERSTANDING DERMAL EXPOSURES RESULTING FROM CONTACT WITH CONTAMINATED SURFACES, MEASURING SURFACE CONTAMINATION, AND CHARACTERIZING TRANSFERS

    EPA Science Inventory

    Although monitoring for surface contamination in work with radioactive materials and dermal monitoring of pesticide exposure to agricultural workers have been standard practice for 50 years, regular surface sampling and dermal monitoring methods have only been applied to indust...

  4. 10Be analysis of a Quaternary weathering profile in the Virginia Piedmont.

    USGS Publications Warehouse

    Pavich, M.J.; Brown, Louis; Valette-Silver, J. Nathalie; Klein, Jeffrey; Middleton, Roy

    1985-01-01

    Samples from a residual weathering profile in the Virginia Piedmont have been analyzed for cosmogenic 10Be. Concentrations are highest in clay-rich soil and decrease exponentially to a depth of about 15 m. Despite uncertainties about the processes by which 10Be may be intercepted before entering the solum and eroded after incorporation, a minimum age may be calculated for the regolith. This calculation is based on the delivery rate of 10Be and its decay rate and suggests that this residual profile developed during a period no shorter than 8 × 105 yr. The calculated minimum age may be within a factor of 2 of maximum-age estimates based on surface lowering by erosion and on the rate of rock weathering to saprolite. The vertical distribution of 10Be in the profile could result from a steady-state balance of deposition, weathering, radioactive decay, and erosion.

  5. A model-based evaluation of sedimentary reconstructions of 10Be production rates

    NASA Astrophysics Data System (ADS)

    Carney, Lewis; Plancherel, Yves; Khatiwala, Samar; Henderson, Gideon

    2016-04-01

    Atmospheric production of 10Be is small when solar activity and, therefore, solar magnetic field and total solar irradiance are strong. Variations in solar activity affect climate and the production of other climate-relevant isotopes, such as 14C. Solar activity is thus an important variable to constrain. Since 10Be production is clearly related to solar activity and the cycle of beryllium is simpler than that of carbon, 10Be records in ice cores have been used to reconstruct total solar irradiance variability. Unfortunately, 10Be records in ice cores are not only affected by variations in atmospheric production, but are also modulated by changes in wind patterns since spatiotemporal atmospheric 10Be gradients are quite large. In that context, sedimentary 10Be records from the abyssal ocean could be of great interest: since the residence time of 10Be in the ocean is thought to be comparable to the overturning time-scale of the ocean, spatial 10Be gradients may be relatively weaker than those in the atmosphere. Under these conditions, regional oceanic variability should only weakly affect the distribution of 10Be in the ocean and local sedimentary 10Be records are expected to represent the global average 10Be production better than 10Be measured in ice cores. We here show results from a global ocean model of 10Be that we use to investigate the spatial variability of simulated sedimentary 10Be records and test the sensitivity of the 10Be sedimentary flux to uncertainties in the circulation field and in the particle chemistry of beryllium. Our ocean model is based on the Transport Matrix method. The surface 10Be input fluxes are taken from atmospheric model simulations. Our model experiments, constrained by available dissolved 10Be data, show that there exist regions in the ocean where the sedimentary 10Be flux is relatively insensitive to changes in input patterns and magnitudes, assumed particle chemistry and flux patterns, and ocean circulation. We submit that

  6. 26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia

    NASA Astrophysics Data System (ADS)

    Fisher, Adrian; Fink, David; Chappell, John; Melville, Michael

    2014-08-01

    Aeolian dust mantle soils are an important element of many landscapes in south-eastern Australia, though the age of these aeolian deposits has not been radiometrically determined. At Fowlers Gap in western New South Wales, surface cobbles of silcrete and quartz overlie a stone-free, aeolian dust mantle soil, which has a thickness of about 1.6 m. The clay-rich aeolian dust deposit in turn lies upon a buried silcrete and quartz stone layer. Modelling in-situ cosmogenic 26Al and 10Be concentrations measured in both the surface quartz stones and in the buried quartz layer of rocks, reveals that each has experienced a complex exposure-burial history. Due to the absence of quartz stones or sand at intermediate depths, our cosmogenic 26Al and 10Be modelling was not able to determine a definitive mechanism of stone pavement formation and stone burial. Various scenarios of stone formation, transport, burial and exhumation were tested that constrain the age of the deposit to range from 0.9 ± 0.2 Ma to 1.8 ± 0.2 Ma, based largely on different assumptions taken for the time-dependency of the net sedimentation rate. This corresponds with the initiation of the Simpson Desert dune fields and the deflation of lakes in central Australia, which probably responded to the shift to longer-wavelength, larger-amplitude Quaternary glacial cycles at around 1 Ma. Sensitivity analyses were carried out to identify those parameters which better constrained model outputs. Within model errors, which largely are the result of analytical errors in measured 26Al and 10Be concentrations, all three competing theories of colluvial wash, upward displacement of stones, and cumulic pedogenesis are possible mechanisms for the formation of the surface stone pavement.

  7. 10Be depth profile dating in the Swiss Midlands: deposition ages versus erosion

    NASA Astrophysics Data System (ADS)

    Wüthrich, Lorenz; Zech, Roland; Haghipour, Negar; Terrizzano, Carla; Christl, Marcus; Gnägi, Christian; Veit, Heinz; Ivy-Ochs, Susan

    2015-04-01

    During the Pleistocene, glaciers advanced repeatedly from the Alps into the Swiss Midlands. The exact extents and timing are still under debate, even for the last glacial advances. Decalcification depths, for example, increase from west to east in the western Swiss Midlands and have been interpreted to indicate that the Rhone glacier may have been less extensive during the global Last Glacial Maximum (LGM) at 20 ka than assumed so far [1]. In an attempt to provide more quantitative age control, we applied 10Be depth profile dating [2] on till at five locations in the western part of Switzerland. Two of them lie outside the assumed LGM extent of the Rhone glacier (Niederbuchsiten, St.Urban), two inside the extent of the LGM Rhone glacier (Steinhof, Deisswil) and one profile was taken from the Berne stade (LGM) of the Aare glacier [3]. All surface concentrations are relatively low and indicate massive erosion. Without constrains for age and erosion, depth profile dating yields ages between roughly 15 ka up to more than 1 Ma for the profiles in St. Urban, Niederbuchsiten and Deisswil whereas the profiles in Steinhof and Bern yields only last glacial ages. The wide range of possible exposure ages illustrates, that independent estimates for erosion would be needed to precisely determine the deposition ages of the investigated tills. However, at this point, we interpret the best model fits to our depth profile concentrations as tentative verification of the assumed LGM extent [3]. The spatial patterns of decalcification depths and soil development in the Swiss Midlands deserves further evaluation. [1] Bitterli et al. (2011) Geologischer Atlas der Schweiz, Blatt 1108, Swisstopo [2] Hidy et al. (2010) Geochem. Geophys. Geosyst. 11, doi:10.1029/2010GC003084 . [3] Bini et al. (2009) Switzerland during the Last Glacial Maximum, Swisstopo

  8. Formation and geomorphologic history of the Lonar impact crater deduced from in situ cosmogenic 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Nakamura, Atsunori; Yokoyama, Yusuke; Sekine, Yasuhito; Goto, Kazuhisa; Komatsu, Goro; Kumar, P. Senthil; Matsuzaki, Hiroyuki; Kaneoka, Ichiro; Matsui, Takafumi

    2014-08-01

    Lonar impact crater is one of a few craters on Earth formed directly in basalt, providing a unique opportunity to study an analog for crater degradation processes on Mars. Here we present surface 10Be and 26Al exposure dates in order to determine the age and geomorphic evolution of Lonar crater. Together with a 14C age of preimpact soil, we obtain a crater age of 37.5 ± 5.0 ka, which contrasts with a recently reported and apparently older 40Ar/39Ar age (570 ± 47 ka). This suggests that the 40Ar/39Ar age may have been affected by inherited radiogenic 40Ar (40Ar*inherited) in the impact glass. The spatial distribution of surface exposure ages of Lonar crater differs from that for Barringer crater, indicating Lonar crater rim is actively eroding. Our new chronology provides a unique opportunity to compare the geomorphological history of the two craters, which have similar ages and diameters, but are located in different climate and geologic settings.

  9. Lichenometry and Cosmogenic Surface Exposure Dating of Possible Fossil Talus Deposits, Devil's Lake State Park, Wisconsin

    NASA Astrophysics Data System (ADS)

    Knochenhauer, K. J.; Weber, J. C.

    2011-12-01

    Lichenometry and cosmogenic surface exposure dating have been highly successful in deciphering landform evolution in tectonically active regions, but have not been widely applied in mid-continent settings. We propose to test the idea that many of the talus deposits in Devil's Lake State Park (DLSP) are ancient, fossil, periglacial deposits that have been frozen in space and time not moving since ~18,000 years ago. Our results may provide valuable information that could be applied to other settings and may also offer information on the effects of 2nd order climatic events such as the Little Ice Age of the 16th-19th centuries, and also help determine the relation between the last glacial maximum about 18ky ago and its related timing to major mass sediment movements. Our preliminary data was collected methodologically offering tight, unimodal peaks of lichen diameters/ages for Aspicilia cinerea and Dimelaena oreina most consistent with the idea that the deposits have not moved since the last ice age. A growth curve for Dimelaena oreina was established through the use of a neighboring cemetery giving a local growth rate of 67.13mm/100yr with R=68. Size-distribution results for DLSP peaked at only 65.2mm. This suggests that current talus block lichen cover is not a record of the first generation. We will pair our lichenometric results with the future use of 10Be cosmogenic surface exposure dating to determine the ages of the 3 major talus deposits themselves (as opposed to lichen initialization ages) which should allow us to test our initial hypothesis, enhance our lichenometry data set, and begin to develop a more robust sampling strategy for further work. Deciphering the landform evolution of this area would offer insight to past landslides and mass debris flows.

  10. Dry heat exposures of surface exposed and embedded Bacillus spores

    NASA Astrophysics Data System (ADS)

    Schubert, Wayne

    Dry heat microbial reduction (DHMR) is the primary technique used to reduce the microbial load of spacecraft and component parts. Often, manufacturing procedures require heating flight hardware to high temperatures for purposes other than planetary protection DHMR. The existing specifications, however, do not allow for additional planetary protection bioburden reduction credit if the hardware is exposed without controlled relative humidity. The intent of this study was to provide adequate data on the DHMR technique to support modification of four aspects of current requirements; expansion of acceptable time and temperature combinations used for spacecraft dry heat microbial reduction processes above 125° C, determining the effect that humidity has on spore lethality as a function of temperature, understanding the lethality for spores with exceptionally high thermal resistance and to investigate the extended exposure requirement for materials that might contain embedded microorganisms. Spores from two bacterial species were tested, B. atrophaeus ATCC 9372 and B. sp. ATCC 29669, under three conditions encompassing 5 temperature points. Embedded experiments utilized a silicone rubber polymer that is commonly used on robotic spacecraft, and surface exposed experiments were performed under both ambient and vacuum-controlled humidity conditions. The results obtained support the use of DHMR protocols that extend the maximum temperature range from 125° C to 170° C, with either controlled or ambient humidity. If implemented, this will give projects bioburden reduction credit for shorter treatments at extended temperatures, and allow spacecraft to be processed in more readily available and less expensive facilities that do not have humidity control, with significant cost and schedule benefits. The study also demonstrated that the required heating time for materials presumed to have embedded bioburden is conservative.

  11. Be2D: A model to understand the distribution of meteoric 10Be in soilscapes

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Govers, Gerard

    2016-04-01

    Cosmogenic nuclides have revolutionised our understanding of earth surface process rates. They have become one of the standard tools to quantify soil production by weathering, soil redistribution and erosion. Especially Beryllium-10 has gained much attention due to its long half-live and propensity to be relatively conservative in the landscape. The latter makes 10Be an excellent tool to assess denudation rates over the last 1000 to 100 × 103 years, bridging the anthropogenic and geological time scale. Nevertheless, the mobility of meteoric 10Be in soil systems makes translation of meteoric 10Be inventories into erosion and deposition rates difficult. Here we present a coupled soil hillslope model, Be2D, that is applied to synthetic and real topography to address the following three research questions. (i) What is the influence of vertical meteoric Be10 mobility, caused by chemical mobility, clay translocation and bioturbation, on its lateral redistribution over the soilscape, (ii) How does vertical mobility influence erosion rates and soil residence times inferred from meteoric 10Be inventories and (iii) To what extent can a tracer with a half-life of 1.36 Myr be used to distinguish between natural and human-disturbed soil redistribution rates? The model architecture of Be2D is designed to answer these research questions. Be2D is a dynamic model including physical processes such as soil formation, physical weathering, clay migration, bioturbation, creep, overland flow and tillage erosion. Pathways of meteoric 10Be mobility are simulated using a two step approach which is updated each timestep. First, advective and diffusive mobility of meteoric 10Be is simulated within the soil profile and second, lateral redistribution because of lateral soil fluxes is calculated. The performance and functionality of the model is demonstrated through a number of synthetic and real model runs using existing datasets of meteoric 10Be from case-studies in southeastern US. Brute

  12. Reactive and dissolved meteoric 10Be/9Be ratios in the Amazon basin

    NASA Astrophysics Data System (ADS)

    Wittmann, Hella; Dannhaus, Nadine; von Blanckenburg, Friedhelm; Bouchez, Julien; Suessenberger, Annette; Guyot, Jean-Loup; Maurice, Laurence; Filizola, Naziano; Gaillardet, Jerome; Christl, Marcus

    2014-05-01

    Recently, the ratio of the meteoric cosmogenic nuclide 10Be to stable 9Be has been established as a weathering and erosion proxy where meteoric 10Be/9Be ratios in reactive phases of secondary weathering products leached from detrital Amazonian river sediment were measured[1]. For this dataset, we derived a new 10Be-based mass balance, which compares the fluxes exported during erosion and weathering, Fout, calculated by the sum of [10Be]reac multiplied by gauging-derived sediment discharge and [10Be]dissmultiplied by water discharge, to the meteoric depositional flux Fin. This assessment allows evaluating the weathering state of the Amazon basin. Further, in order to assess equilibration of reactive phases in the water column, we measured (10Be/9Be)reac ratios leached from suspended sediments for two depth profiles of the Amazon (55m depth) and Madeira (12m depth) Rivers, their corresponding surface dissolved 10Be/9Be ratios, as well as dissolved ratios of smaller Amazon tributaries (Beni, Madre de Dios) to compare with published reactive ratios[1]. In these rivers, modest pH and salinity fluctuations help to constrain a 'simple' system that might however still be affected by seasonally changing isotopic compositions between water and suspended sediment[2] and seasonal fluctuations of TSS and TDS[3]. The 10Be-based mass balance shows that in Andean source areas Fout/Fin ≡1, indicating a balance between ingoing and exported flux, whereas in the Shield headwaters, Fout/Fin=0.3, indicating a combination of decay of 10Be during storage and little export of 10Be associated with particulate and dissolved loads. In central Amazonia, the export of 10Be decreases slightly relative to its atmospheric flux as evidenced by Fout/Fin=0.8 for the Amazon and Madeira Rivers. This value is interpreted as being close to steady state, but its modification could be due to additions of Shield-derived sediment to sediment carried in the main river[4]. Regarding the depth profiles, our

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  14. Particle trajectories on hillslopes: Implications for particle age and 10Be structure

    NASA Astrophysics Data System (ADS)

    Anderson, Robert S.

    2015-09-01

    Many geomorphic systems act as conveyor belts onto which material is loaded at a particular rate and is transported in one direction toward another system that serves as a sink. As the material travels, it ages, it changes in grain size, it accumulates cosmogenic radionuclides, it adsorbs or releases nutrients, and it weathers. Here I address the hillslope conveyor. As many geochemical processes are depth-dependent, the depth history of a particle becomes important to know. I calculate soil particle trajectories in the horizontal-depth plane and address three cases, one in which horizontal speeds decline exponentially with depth, a second in which they are uniform with depth, and a third in which horizontal speeds are also uniform but all profile values are vertically well-mixed. Vertical speeds are governed by continuity in an incompressible medium and by the boundary condition of zero vertical particle speed at the soil surface. Particle trajectories must therefore become surface parallel at the surface. Knowledge of soil particle trajectories allows calculation of residence times and concentration profiles of 10Be in the soil. The results inform strategies for interpretation of nuclide concentrations in soils and stream sediments and for inference of transport rate profiles. In all steady cases, the particle age and 10Be structure are uniform with distance from the divide. When significant vertical gradients in horizontal speed occur, the patterns of particle age and of 10Be concentration are dominated by the depth scale of the transport process. In unmixed cases, the particle age and 10Be concentration in near-surface samples can greatly exceed the vertically averaged values, reflecting the fact that the vertical speeds of particles slow dramatically as they near the surface. In cases in which horizontal speed varies significantly with depth, the vertically averaged concentration of 10Be within the soil can significantly underpredict the mean 10Be concentration

  15. Headwall erosion rates from cosmogenic (10) Be in supraglacial debris, Chhota Shigri Glacier, Indian Himalaya

    NASA Astrophysics Data System (ADS)

    Scherler, Dirk; Egholm, David

    2016-04-01

    Debris-covered glaciers are widespread within the Himalaya and other steep mountain ranges. They testify to active erosion of ice-free bedrock hillslopes that tower above valley glaciers, sometimes more than 1 km high. It is long known that debris cover significantly reduces surface ablation rates and thereby influences glacial mass balances; but its dynamic evolution along with climatic and topographic changes is poorly studied. Better understanding the coupling of ice-free bedrock hillslopes and glaciers in steep mountains requires means to assess headwall erosion rates. Here, we present headwall erosion rates derived from 10Be concentrations in the ablation-dominated medial moraine of the Chhota Shigri Glacier, Indian Himalaya. We combine our empirical, field-based approach with a numerical model of headwall erosion and glacial debris transport to assess permissible patterns of headwall erosion on the ice-free bedrock hillslopes surrounding the Chhota Shigri Glacier. Our five samples, each separated by approximately 500 m along the glacier, consist of an amalgamation of >1000 surface clasts with grain sizes between ˜1 and ˜30 mm that were taken from the medial moraine. Our results show that 10Be concentrations increase downglacier from ˜3×104 to ˜6×104 atoms g‑1, yielding headwall erosion rates of ˜1.3-0.6 mm yr‑1. The accumulation of 10Be during debris residence on the ice surface can only account for a small fraction (<20%) of the downglacier increase. Other potential explanations include (1) heterogeneous source areas with differences average productions rates, and (2) homogeneous source areas but temporally variable headwall erosion rates. We use the 10Be-derived headwall erosion rates to define debris supply rates from ice-free bedrock hillslopes in the numerical ice model iSOSIA. Headwall debris that is deposited in the ablation zone of the ice surface becomes englacial, is passively advected with the ice and emerges in the ablation zone where

  16. Formation age and geomorphologic history of the Lonar impact crater deduced from in- situ cosmogenic 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Nakamura, A.; Yokoyama, Y.; Sekine, Y.; Goto, K.; Komatsu, G.; Kumar, P.; Matsuzaki, H.; Matsui, T.

    2013-12-01

    Impact cratering is a dominant surface modification process on planetary surfaces. In the inner solar system, the large majority of impacts occur on bodies covered by primitive igneous rocks. However, most of the impacts remaining on Earth surface are on different rock types than that of the inner planet and hence geologic knowledge derived from Earth's surface cannot be translated readily. The Lonar crater is a 1.88-km-diameter crater located on the Deccan basaltic traps in India (ca. 65 Ma), and is one of a few craters on Earth bombarded directly on basaltic lava flows. Thus, the Lonar crater provides a rare opportunity to study impact structures on the basaltic surfaces of other terrestrial planets and the Moon. Since the ages of terrestrial impact structures is a key to understand geomorphological processes after the impact, various dating methods have been applied to the Lonar Crater such as fission track (Storzer and Koeberl, 2004), radiocarbon (Maloof, 2010), thermoluminescence (Sengupta et al., 1997), and 40Ar/39Ar (Jourdan et al., 2011). Yet, a large discrepancy between these methods ranging from ca. 1.79 to 570 ka has been resulted. Here we report surface exposure ages based on in-situ cosmogenic 10Be and 26Al in order to obtain a precise age of the Lonar crater formation as well as to study the geomorphologic evolution. The samples are collected from the topographic highs on the rim of the crater and from the ejecta blanket. Exposure ages together with newly obtained radiocarbon age of pre-impact soil indicate much younger ages than that of obtained from 40Ar/39Ar method. This suggests the potential bias because of inherited 40Ar in impact glass. Systematically young exposure age from the rim samples compared to the samples from the ejecta blanket indicate that the rim of the Lonar crater is being actively eroded. Spatial distributions of geomorphic ages observed from the Lonar creator is not the same as the pattern reported from the well

  17. Dating offset fans along the Mojave section of the San Andreas fault using cosmogenic 26Al and 10Be

    USGS Publications Warehouse

    Matmon, A.; Schwartz, D.P.; Finkel, R.; Clemmens, S.; Hanks, T.

    2005-01-01

    Analysis of cosmogenic 10Be and 26Al in samples collected from exposed boulders (n = 20) and from buried sediment (n = 3) from offset fans along the San Andreas fault near Little Rock, California, yielded ages, ranging from 16 to 413 ka, which increase with distance from their source at the mouth of Little Rock Creek. In order to determine the age of the relatively younger fans, the erosion rate of the boulders and the cosmogenic nuclide inheritance from exposure prior to deposition in the fan were established. Cosmogenic nuclide inheritance values that range between 8.5 ?? 103 and 196 ?? 103 atoms 10Be g-1 quartz were determined by measuring the concentrations and ratios of 10Be and 26Al in boulders (n = 10) and fine sediment (n = 7) at the outlet of the present active stream. Boulder erosion rate, ranging between 17 and 160 mm k.y.-1, was estimated by measuring 10Be and 26Al concentrations in nearby bedrock outcrops (n = 8). Since the boulders on the fans represent the most resistant rocks in this environment, we used the lowest rate for the age calculations. Monte Carlo simulations were used to determine ages of 16 ?? 5 and 29 ?? 7 ka for the two younger fan surfaces. Older fans (older than 100 ka) were dated by analyzing 10Be and 26Al concentrations in buried sand samples. The ages of the three oldest fans range between 227 ?? 242 and 413 ?? 185 ka. Although fan age determinations are accompanied by large uncertainties, the results of this study show a clear trend of increasing fan ages with increasing distance from the source near Little Rock Creek and provide a long-term slip rate along this section of the San Andreas fault. Slip rate along the Mojave section of the San Andreas fault for the past 413 k.y. can be determined in several ways. The average slip rate calculated from the individual fan ages is 4.2 ?? 0.9 cm yr-1. A linear regression through the data points implies a slip rate of 3.7 ?? 1.0 cm yr-1. A most probable slip rate of 3.0 ?? 1.0 cm yr-1 is

  18. Tectonic and climatic control on terrace formation: Coupling in situ produced 10Be depth profiles and luminescence approach, Danube River, Hungary, Central Europe

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Braucher, Régis; Novothny, Ágnes; Csillag, Gábor; Fodor, László; Molnár, Gábor; Madarász, Balázs

    2016-01-01

    The terrace sequence of the Hungarian part of the Danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages. To establish the chronology of formation of these terraces, two different dating methods were used on alluvial terraces: exposure age dating using in situ produced cosmogenic 10Be and luminescence dating. Using Monte Carlo approach to model the denudation rate-corrected exposure ages, in situ produced cosmogenic 10Be samples originated from vertical depth profiles enabled the determination of both the exposure time and the denudation rate. Post-IR IRSL measurements were carried out on K-feldspar samples to obtain the ages of sedimentation. The highest terrace horizon remnants of the study area provided a best estimate erosion-corrected minimum 10Be exposure age of >700 ka. We propose that the abandonment of the highest terrace of the Hungarian Danube valley was triggered by the combined effect of the beginning tectonic uplift and the onset of major continental glaciations of Quaternary age (around MIS 22). For the lower terraces it was possible to reveal close correlation with MIS stages using IRSL ages. The new chronology enabled the distinction of tIIb (∼90 ka; MIS 5b-c) and tIIIa (∼140 ka; MIS 6) in the study area. Surface denudation rates were well constrained by the cosmogenic 10Be depth profiles between 5.8 m/Ma and 10.0 m/Ma for all terraces. The calculated maximum incision rates of the Danube relevant for the above determined >700 ka time span were increasing from west (<0.06 mm/a) to east (<0.13 mm/a), toward the more elevated Transdanubian Range. Late Pleistocene incision rates derived from the age of the low terraces (∼0.13-0.15 mm/a) may suggest a slight acceleration of uplift towards present.

  19. Evidence of Early Holocene Glacial Advances in Southern South America from Cosmogenic Surface Exposure Dating

    NASA Astrophysics Data System (ADS)

    Douglass, D. C.; Singer, B. S.; Kaplan, M. R.; Ackert, R. P.; Mickelson, D. M.; Caffee, M. W.

    2004-12-01

    10Be and 36Cl cosmogenic nuclide surface exposure dating of erratic boulders reveal two glacier advances in southern South America (46°S) during the Early Holocene. Seven of ten boulders from the outer moraine yield a weighted mean of 8.5±0.7 ka and five of six boulders from the inner moraine yield a weighted mean age of 6.2±0.8 ka (2σ uncertainties). The four outliers are anomalously old (interpreted to contain inherited cosmogenic isotopes from prior exposure) and are identified on the basis of Chi-Squared statistics and bi-modal probability distribution curves. These glacial advances are likely the result of a northward migration of the southern westerlies causing an increase in precipitation and/or a decrease in temperature at this latitude. Reconstructions of equilibrium line altitudes (ELA) at the times of moraine deposition based on Accumulation Area Rations (AARs) are about 300 m lower than modern. This ELA depression is not particularly sensitive to the AAR used, and corresponds to conditions 2.4° C cooler (if no change in precipitation), or 1000 mm/a wetter (if no change in temperature) than the modern climate. The older advance precedes the currently accepted initiation of Holocene glacial activity in southern South America by about 3000 years, and appears to be temporally synchronous with the "8.2 ka event" recorded in Greenland and many other parts of the world. The younger advance is slightly older than, but indistinguishable from, documented neoglacial advances and climate changes in southern South America and four other continents. If there are causal links between these temporally synchronous, globally distributed events, then millennial scale climate changes appear to involve reorganization of global weather systems (such as migration of the southern westerlies), or may be externally forced (e.g. solar variability).

  20. Surface-exposure ages of Front Range moraines that may have formed during the Younger Dryas, 8.2 cal ka, and Little Ice Age events

    USGS Publications Warehouse

    Benson, L.; Madole, R.; Kubik, P.; McDonald, R.

    2007-01-01

    Surface-exposure (10Be) ages have been obtained on boulders from three post-Pinedale end-moraine complexes in the Front Range, Colorado. Boulder rounding appears related to the cirque-to-moraine transport distance at each site with subrounded boulders being typical of the 2-km-long Chicago Lakes Glacier, subangular boulders being typical of the 1-km-long Butler Gulch Glacier, and angular boulders being typical of the few-hundred-m-long Isabelle Glacier. Surface-exposure ages of angular boulders from the Isabelle Glacier moraine, which formed during the Little Ice Age (LIA) according to previous lichenometric dating, indicate cosmogenic inheritance values ranging from 0 to ???3.0 10Be ka.11Surface-exposure ages in this paper are labeled 10Be; radiocarbon ages are labeled 14C ka, calendar and calibrated radiocarbon ages are labeled cal ka, and layer-based ice-core ages are labeled ka. 14C ages, calibrated 14C ages, and ice core ages are given relative to AD 1950, whereas 10Be ages are given relative to the sampling date. Radiocarbon ages were calibrated using CALIB 5.01 and the INTCAL04 data base Stuiver et al. (2005). Ages estimated using CALIB 5.01 are shown in terms of their 1-sigma range. Subangular boulders from the Butler Gulch end moraine yielded surface-exposure ages ranging from 5 to 10.2 10Be ka. We suggest that this moraine was deposited during the 8.2 cal ka event, which has been associated with outburst floods from Lake Agassiz and Lake Ojibway, and that the large age range associated with the Butler Gulch end moraine is caused by cosmogenic shielding of and(or) spalling from boulders that have ages in the younger part of the range and by cosmogenic inheritance in boulders that have ages in the older part of the range. The surface-exposure ages of eight of nine subrounded boulders from the Chicago Lakes area fall within the 13.0-11.7 10Be ka age range, and appear to have been deposited during the Younger Dryas interval. The general lack of inheritance in

  1. Extremely eroded or incredibly young - 10Be depth profile dating of moraines in the Swiss Midlands

    NASA Astrophysics Data System (ADS)

    Wüthrich, Lorenz; Zech, Roland; Haghipour, Negar; Gnägi, Christian; Christl, Markus; Ivy-Ochs, Susan; Veit, Heinz

    2014-05-01

    During the Pleistocene, glaciers advanced repeatedly from the Alps into the Swiss Midlands. The exact extent and timing are still under debate, even for the last glacial advances. Decalcification depths, for example, increase from west to east in the western Swiss Midlands and have been interpreted to indicate that the Valais (Rhone) glacier may have been less extensive during the global Last Glacial Maximum (LGM) at 20 ka than assumed so far [1]. In an attempt to provide more quantitative age control, we applied 10Be depth profile dating [2] on moraines at two locations. Steinhof has previously been dated to the global LGM based on exposure ages from four boulders [3], and Niederbuchsiten presumably lies outside the last glacial ice extent [1]. The 10Be concentrations at both sites decrease consistently with depth, but are very similar. Assuming only a few decimeters of erosion since moraine deposition, we obtain apparent exposure ages of ~20 ka. Niederbuchsiten would thus be unexpectedly young, implying a much more extensive extent of the LGM glacier than assumed so far. Alternatively, if the till at Niederbuchsiten was deposited during or before the penultimate glaciation (>130 ka), the surprisingly low 10Be concentrations indicate several meters of erosion during the last glacial cycle and/or the Holocene, which seems to be at odds with the deep and intensive soil formation. References: [1] Bitterli et al. (2011) Geologischer Atlas der Schweiz, Blatt 1108. [2] Hidy et al. (2010) Geochem. Geophys. Geosyst. 11, doi:10.1029/2010GC003084. [3] Ivy- Ochs et al. (2004) Ecl. Geol. Helv. 97, 47-55.

  2. Constraints on the sedimentation history of San Francisco Bay from 14C and 10Be

    USGS Publications Warehouse

    VanGeen, A.; Valette-Silver, N. J.; Luoma, S.N.; Fuller, C.C.; Baskaran, M.; Tera, F.; Klein, J.

    1999-01-01

    Industrialization and urbanization around San Francisco Bay as well as mining and agriculture in the watersheds of the Sacramento and San Joaquin rivers have profoundly modified sedimentation patterns throughout the estuary. We provide some constraints on the onset of these erosional disturbances with 10Be data for three sediment cores: two from Richardson Bay, a small embayment near the mouth of San Francisco Bay, and one from San Pablo Bay, mid-way between the river delta and the mouth. Comparison of pre-disturbance sediment accumulation determined from three 14C-dated mollusk shells in one Richardson Bay core with more recent conditions determined from the distribution of 210Pb and 234Th [Fuller, C.C., van Geen, A., Baskaran, M, Anima, R.J., 1999. Sediment chronology in San Francisco Bay, California, defined by 210Pb, 234Th, 239,240Pu.] shows that the accumulation rate increased by an order of magnitude at this particular site. All three cores from San Francisco Bay show subsurface maxima in 10Be concentrations ranging in magnitude from 170 to 520 x 106 atoms/g. The transient nature of the increased 10Be input suggests that deforestation and agricultural develop- ment caused basin-wide erosion of surface soils enriched in 10Be. probably before the turn of the century.

  3. Constraints on the last deglaciation of the Ross Sea Sector of the West Antarctic Ice Sheet (WAIS) from 10Be dating

    NASA Astrophysics Data System (ADS)

    Bill, N. S.; Clark, P. U.; Kurz, M. D.; Marcott, S. A.; Caffee, M. W.

    2014-12-01

    We present new 10Be surface exposure ages from glacial erratic boulders from several locations in McMurdo Sound in order to constrain the deglacial history of the West Antarctic Ice Sheet. Previous model and field data indicate that the present day Ross Ice Shelf was a grounded ice sheet, with the grounding line extending to near the continental shelf edge during the Last Glacial Maximum (LGM). However, the timing and rate of the last deglaciation of the Ross Sea Sector of the West Antarctic Ice Sheet remain uncertain. We sampled granitic and basaltic erratic boulders for dating with the cosmogenic nuclides 10Be and 3He; in situ 14C dating will be used to assess complex burial histories. The 10Be ages on erratics near or at the upper limit of Ross Sea Drift that do not appear to have inheritance range from 17 to 26 ka. 10Be ages from erratics below the limit of the (LGM) Ross Sea Drift suggest final deglaciation by ~11 ka. New 10Be ages from more highly weathered glacial deposits above the Ross Sea drift near Blue Glacier suggest an age range of 141 to 171 ka.

  4. 10Be Content in Suevite Breccia from the Bosumtwi Impact Crater

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Wild, Eva Maria; Michlmayr, Leonard; Koeberl, Christian

    2013-04-01

    Introduction: According to the current understanding of meteorite impact processes, surface target material is transported from a crater in the form of ejecta or is vaporized/melted (e.g., [1]). The formation model of tektites from the surface of the target rocks has been established using the 10Be content of tektites (e.g., [2]), and chemical comparison with the possible target surface material (e.g., [3]); it was also reproduced by computer modeling (e.g., [4]). On the other hand, some observations ([5, 6]) suggest that part of the surface material may be incorporated into the crater-fill. The aim of this study is to check if surface-derived material is present in suevitic breccias to better understand formation mechanisms of fallback breccias. Also, 10Be can be used to trace contamination of rocks in the top layer of the suevitic layer by meteoric (lake) water. This abstract is an update (based on more data now available) of the previous report presented during the Metsoc75 conference. Samples: The Bosumtwi crater was chosen as study site because of its relatively large size (10.5 km in diameter), young age of 1.07 Ma [7], good state of preservation, and availability of core samples. Clasts from suevitic breccia selected for this study come from the LB-07A and LB-08A cores that are located within the crater and represent fallback breccia (e.g., [7]). Of 41 analyzed samples (22 single clasts and 21 matrix samples - 11 of those being monomictic breccia), 36 came from core LB-07A (in the zone outside the central uplift) and represent depths of 333.7 - 407.9 m and 5 are from core LB-08A (on the flank of the central uplift) from depths 239.5 - 264.9 m. Methods: For each sample, 0.8 g of finely grounded material from clasts containing in situ produced and meteoric 10Be was dissolved in a mixture of HF and HNO3 by microwave digestion. A 9Be carrier (1 mg or 0.6 mg, 10Be/9Be ratio: 2.82±0.31*10-15 [2? uncertainty]) was added to the sample, and then Be was chemically

  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. Eroding and Inflating the Atacama Desert, Chile: Insights Through Cosmogenic 10-Be, 26-Al and 21-Ne

    NASA Astrophysics Data System (ADS)

    Heimsath, A. M.; Jungers, M. C.; Amundson, R.; Balco, G.; Shuster, D. L.

    2010-12-01

    Enigmas of the Atacama Desert are as abundant as the hypotheses formulated to explain them. This fascinating and extreme landscape attracts scientists from disparate disciplines, spawning remarkable insights into the connections between climate, tectonics, biota and landscape evolution. Recent work explores such connections on timescales ranging from millions to thousands of years. Both the timing of the onset of hyperaridity in the Atacama and its relationship to the uplift of the Andes are especially well-debated topics. Similarly enigmatic, but less widely studied, are the connections between the timing of hyperaridity and the surface morphology of the region. Specifically, the extent, nature, and timing of formation for the extensive salars across the Atacama are undeniably linked to the climate history of the region. Adjacent to the extensive salars are landscapes that appear to be shaped by processes more typically associated with temperate landscapes: rilling and gullying, extensive terrace deposition, steep fault scarps, landslide deposits, and extensive fan and paleosurface deposits. Our primary goal in this project is to establish chronologies and rates for the surface processes driving landscape evolution for two field regions in the Atacama. To achieve this goal we are also testing and expanding upon the burial dating methodology (Balco and Shuster, 2009) that couples the stable cosmogenic nuclide, 21Ne, with the radiogenic nuclides, 10Be and 26Al. Here we present new results from remarkably different field settings from the north-central Atacama. The southern region, inland from Antofagasta, is relatively well studied to determine how the onset of hyperaridity impacted water-driven processes. The northern region, north of the Rio Loa and Calama, differs most notably by the enormous basin fills of salt (e.g. Salar de Llamara and Salar Grande) and evidence of more extensive recently active salars. Across both regions we use in 10Be, 26Al, and 21Ne to

  7. TRANSFER OF PESTICIDES FROM SURFACES TO FOODS FOR THE ESTIMATION OF DIETARY EXPOSURE OF CHILDREN

    EPA Science Inventory

    Since small children spend much of their time in contact with contaminated surfaces, residues of pesticides found on floors and other surfaces contribute to their aggregate exposures. Any dislodgeable pesticide residues on hands and surfaces may be transferred to foods while bei...

  8. Surface ozone exposures measured at clean locations around the world.

    PubMed

    Lefohn, A S; Krupa, S V; Winstanley, D

    1990-01-01

    For assessing the effects of air pollution on vegetation, some researchers have used control chambers as the basis of comparison between crops and trees grown in contemporary polluted rural locations and those grown in a clean environment. There has been some concern whether the arbitrary ozone level of 0.025 ppm and below, often used in charcoal-filtration chambers to simulate the natural background concentration of ozone, is appropriate. Because of the many complex and man-made factors that influence ozone levels, it is difficult to determine natural background. To identify a range of ozone exposures that occur at 'clean' sites, we have calculated ozone exposures observed at a number of 'clean' monitoring sites located in the United States and Canada. We do not claim that these sites are totally free from human influence, but rather than the ozone concentrations observed at these 'clean' sites may be appropriate for use by vegetation researchers in control chambers as pragmatic and defensible surrogates for natural background. For comparison, we have also calculated ozone exposures observed at four 'clean' remote sites in the Northern and Southern Hemispheres and at two remote sites (Whiteface Mountain, NY and Hohenpeissenberg, FRG) that are considered to be more polluted. Exposure indices relevant for describing the relationship between ozone and vegetation effects were applied. For studying the effects of ozone on vegetation, the higher concentrations are of interest. The sigmoidally-weighted index appeared to best separate those sites that experienced frequent high concentration exposures from those that experienced few high concentrations. Although there was a consistent seasonal pattern for the National Oceanic and Atmospheric Administration (NOAA) Geophysical Monitoring for Climate Change (GMCC) sites indicating a winter/spring maximum, this was not the case for the other remote sites. Some sites in the continental United States and southern Canada

  9. Atrazine and total triazines: Exposure patterns in midwestern surface waters

    SciTech Connect

    Richards, R.P.; Baker, D.B.

    1996-10-01

    Distributions of atrazine and total triazine exposures for aquatic organisms in the midwestern United States and Canada were characterized using the most complete datasets available, with attention to the sampling pattern used in obtaining the data. Distributions were established form stantaneous concentrations and for 96-hour and 21-day running averages. Time weighting and annualization were important to avoid distorted estimates of exposure concentrations; failure to use appropriate procedures can lead to order-of-magnitude errors in estimates of benchmarks such as the 90th percentile concentration. Atrazine and total triazine concentrations are characterized by strong seasonality, with elevated concentrations for a period of 6 to 10 weeks following application in May or June. Concentrations decline during July, August, and September, and for the rest of the year are near detection limit. Concentrations in running water are strongly influenced by storm runoff, with much higher concentrations during run off than during low-flow periods between run off events. Thus aquatic organisms in running waters experience pulsed exposures interspersed with recovery periods. 90th percentile concentrations were calculated for a number of rivers, streams, lakes, and reservoirs for comparison with ecological effects data. Total triazine concentrations are only slightly higher than atrazine concentrations in those waters for which comparisons were possible.

  10. Ethylene on silver: Development of surface enhanced Raman lines with exposure

    NASA Astrophysics Data System (ADS)

    Pockrand, I.

    1983-03-01

    Adsorption of ethylene on silver films ( Ts=120 K) as a function of exposure has been studied by following the surface enhanced Raman (SER) signal of the symmetric scissors mode. Exposures as low as 10 -3 L were easily detected demonstrating the very high sensitivity of SERS for this system.

  11. Long-Duration Orbit Exposure Experiment with Sub-Surface Microorganism from a Mars Terrestrial Analog

    NASA Astrophysics Data System (ADS)

    Davila, A. F.; Lim, D.; Fairen, A. G.; Uceda, E. R.; Zavaleta, J.; McKay, C.

    2007-07-01

    Orbit Exposure Experiments (OEE) allow us to test the possibility of life transfer between planets and moons. Deep sub-surface microorganisms may be the best candidates to survive long-term exposure to space conditions. A long duration OEE is proposed to test our hypothesis.

  12. Analysis of the relation between exposure parameters and critical dimension by response surface model

    NASA Astrophysics Data System (ADS)

    Sohn, Dong-Soo; Sohn, Young-Soo; Bak, Heungin; Oh, Hye-Keun

    2001-08-01

    It is important to know the relationship between the soft bake conditions and the Dill exposure parameters in order to control the lithographic process well. It has been reported that exposure parameter A can be significantly affected by the soft bake conditions, while the exposure parameters B and C show no dependency on the soft bake conditions. The exposure parameters have been considered less important in 193 nm chemically amplified resist (CAR) simulation. Since the critical dimension variation depends on the exposure parameters, if we know the relationship between them it would be helpful in developing resist and resist process. In this paper the profiles of a 193nm CAR were simulated with the various Dill exposure parameters and the results were analyzed by response surface model. The response surface methodology (RSM) approach was used to analyze the influence of independent factors on a dependent response, and to optimize each process. A method of steepest ascent was utilized to produce first-order models, which were verified by lack of fit testing. As optimum operation points were approached, a second-order model was fitted and analyzed. The Dill exposure parameter C affects critical dimension greatly whereas A and B have much less effect. Among parameters other than exposure parameters, PEB time and PEB temperature are great factors to affect critical dimension. Even small change of them can make great critical dimension changes. Process optimization for the target response value as well as process latitude was possible through the use of the response surface.

  13. 10Be ages of glacial and meltwater features northwest of Lake Superior: a chronology of Laurentide Ice sheet deglaciation and eastward flooding from Glacial Lake Agassiz

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Fisher, T. G.; Lowell, T.; Barnett, P.; Schaefer, J. M.; Schwartz, R.

    2009-12-01

    Significant controversy exists as to the role of Laurentide Ice Sheet meltwater in causing the Younger Dryas cold event. Recently, Lowell et al. (2009) presented a radiocarbon chronology of Laurentide Ice Sheet deglaciation along a north-south transect located northwest of Lake Superior. These authors concluded that the presence of the Laurentide Ice Sheet precluded an eastward drainage of glacial Lake Agassiz until mid-Younger Dryas time. Here, we use 10Be surface exposure dating to examine the timing of the eastward drainage of Lake Agassiz. We present 10Be ages of moraines and erratic boulders in meltwater pathways along the same transect as Lowell et al. (2009), northwest of Lake Superior. In general, 10Be ages of glacial features are similar to, or slightly older than, basal radiocarbon ages of nearby lakes. Based on the 10Be chronology, deglaciation of the Laurentide Ice Sheet in this region occurred between ~13,000 and 10,000 yr BP. We also present the first direct ages of flood deposits in bedrock channels presumably associated with the eastern drainage of Lake Agassiz. Evidence for flooding includes extensive channels incised into bedrock and enormous bedforms located north of Lake Superior. 10Be ages of two flood deposits near the Roaring River and Mundell Lake yield mean 10Be ages of ~11,700 and 11,000 yr BP, respectively. These ages indicate that occupation of the channels postdates initiation of the Younger Dryas by more than 1,000 years and are in general agreement with a basal radiocarbon age from nearby Lower Vail Lake (Teller et al., 2005). Preliminary paleohydrological estimates based on bedform clast sizes and channel geometries are velocities and discharges of 2.8-19.8 ms-1 and 4,200-30,000 m3s-1 at the Roaring River location and 2.5-17.5 ms-1 and 49,000-349,000 m3s-1 at the Mundell Lake location.

  14. Studies of Be migration in the JET tokamak using AMS with 10Be marker

    NASA Astrophysics Data System (ADS)

    Bykov, I.; Bergsåker, H.; Possnert, G.; Zhou, Y.; Heinola, K.; Pettersson, J.; Conroy, S.; Likonen, J.; Petersson, P.; Widdowson, A.

    2016-03-01

    The JET tokamak is operated with beryllium limiter tiles in the main chamber and tungsten coated carbon fiber composite tiles and solid W tiles in the divertor. One important issue is how wall materials are migrating during plasma operation. To study beryllium redistribution in the main chamber and in the divertor, a 10Be enriched limiter tile was installed prior to plasma operations in 2011-2012. Methods to take surface samples have been developed, an abrasive method for bulk Be tiles in the main chamber, which permits reuse of the tiles, and leaching with hot HCl to remove all Be deposited at W coated surfaces in the divertor. Quantitative analysis of the total amount of Be in cm2 sized samples was made with inductively coupled plasma atomic emission spectroscopy (ICP-AES). The 10Be/9Be ratio in the samples was measured with accelerator mass spectrometry (AMS). The experimental setup and methods are described in detail, including sample preparation, measures to eliminate contributions in AMS from the 10B isobar, possible activation due to plasma generated neutrons and effects of diffusive isotope mixing. For the first time marker concentrations are measured in the divertor deposits. They are in the range 0.4-1.2% of the source concentration, with moderate poloidal variation.

  15. 10Be and U-series dating of late Quaternary landforms along the southern San Jacinto fault: Implications for temporal slip rate variability

    NASA Astrophysics Data System (ADS)

    Blisniuk, K.; Oskin, M. E.; Fletcher, K.; Sharp, W. D.; Rockwell, T. K.

    2009-12-01

    Robust age control on faulted landforms with well-constrained offsets is essential to documenting the heterogeneous behavior of a fault zone over time. However, showing late Quaternary temporal slip rate variation is often challenging due to the difficultly of obtaining reliable ages for Quaternary deposits. Exposure ages from cosmogenic isotopes can be significantly affected by surface processes, and U-series dating of pedogenic carbonate provides only minimum ages because carbonate accumulation occurs after deposition. Fortunately, the controlling factors for the resulting age uncertainties of each method are relatively independent from each other, so a combination of cosmogenic isotope and U-series dating may significantly improve the reliability of landform dating and yield more robust slip rate estimates. We present preliminary results of this dual-dating approach at 4 sites along the southern San Jacinto fault zone in California: 2 sites along the Coyote Creek fault, and 2 sites along the Clark fault. These results show age agreement between the two dating methods. Along the southern Clark fault, a 10Be depth profile model age of 34.5 ±6.6 ka and a U-series age of 33.2 ±1.1 ka were obtained for an offset Q2b fan surface, and a Q3b surface yielded a weighted mean 10Be surface exposure age of 5.9 ±1.5 ka, similar to an U-series age of 6.3 ±0.4 ka. Along the northern Coyote Creek fault, preliminary data indicate a 10Be surface exposure age of 11.3 ±3.4 ka and a U-series age of 11.7 ±1.8 ka for an offset Q3a surface, and a 10Be surface exposure age of 6.9 ±1.0 ka and a U-series age of 7.8 ± 0.9 ka for an offset Q3b surface. The remarkable consistency among ages from the two dating methods suggest that: (1) U-series ages of pedogenic carbonate clast rinds closely approach depositional ages of the host alluvium; (2) erosion may be negligible at the sampled sites; and (3) inherited 10Be has been accurately quantified (via depth profile) for the late

  16. Surface exposure dating of moraines and alluvial fans in the Southern Central Andes

    NASA Astrophysics Data System (ADS)

    Terrizzano, Carla; Zech, Roland; García Morabito, Ezequiel; Haghipour, Negar; Christl, Marcus; Likermann, Jeremías; Tobal, Jonathan; Yamin, Marcela

    2016-04-01

    The role of tectonics versus climate in controlling the evolution of alluvial fans in discussed controversially. The southern Central Andes and their forelands provide a perfect setting to study climate versus tectonic control of alluvial fans. On the one hand, the region is tectonically active and alluvial fan surfaces are offset by faults. The higher summits, on the other hand, are glaciated today, and glacial deposits document past periods of lower temperatures and increased precipitation. We applied 10Be surface exposure dating on 5 fan terraces 4 moraines of the Ansilta range (31.6°S - 69.8°W) using boulders and amalgamated pebbles to explore their chronological relationship. From youngest to oldest, the alluvial fan terraces yield minimum ages of 15 ± 1 ka (T1), 97 ± 9 ka (T2), 141 ± 9 ka (T3), 286 ± 14 ka (T4) and 570 ± 57 ka (T5). Minimum ages derived from moraines are 14 ± 1 ka (M1), 22 ± 2 ka (M2), 157 ± 14 ka (M3) and 351 ± 33 ka (M4), all calculations assuming no erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. The moraines document glacial advances during cold periods at the marine isotope stages (MIS) 2, 6 and 10. The terraces T1, T3 seem to be geomorphologic counterparts during MIS 2 and 6. We suggest that T2, T4 and T5 document aggradation during the cold periods MIS 5d, 8 and 14 in response to glacial advances, although the respective moraines are not preserved. Our results highlight: i) the arid climate in the Southern Central Andes favors the preservation of glacial and alluvial deposits allowing landscape and climate reconstructions back to ~570 ka), ii) alluvial deposits correlate with moraines or fall into cold glacial times, so that climate, and in particular the existence of glaciers, seems to be the main forcing of alluvial fan formation at our study site. References Lal, D., 1991: Cosmic ray labeling of erosion surfaces: In situ nuclide production rates and erosion models. Earth and Planetary

  17. Radiogenic production of 10Be and 26Al in uranium and thorium ores: Implications for studying terrestrial samples containing low levels of 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Middleton, R.

    1989-03-01

    10Be and 26Al are produced by cosmic-ray-induced spallation of atmospheric constituents, and also as has recently been shown, by spallation in the rocks exposed to cosmic rays. We now present experimental data showing that these two isotopes can also be produced by radiation from uranium and thorium decay chain radionuclides contained within the host rocks. We have measured the 10Be and 26Al concentrations in a number of shielded uranium (spontaneous fission half-life ~10 26 years) and thorium (no spontaneous-fission-decay mode) ores using accelerator mass spectrometry. The concentrations of 10Be and 26Al range from 2.8·10 6 to 29.6·10 6 and 1.1 · 10 7 to 1.43· 10 atoms g -, respectively. The high concentrations of 10Be and 26Al imply unacceptably-high branching ratios (~ 10 -4 to 10 -1) for their production from spontaneous fission and coupled with the presence of 10Be and 26A1 in the Th ores, eliminate spontaneous fission as the major source of either isotope. The large 26A1 to 10Be ratio found in all the samples eliminates atmospheric production. The most likely sources are the alpha reactions, 7Li( α, p) 10Be and 23Na( α, n) 26Al, and neutron reactions, 9Be( n, γ) 10Be, 10B( n, p) 10Be and 13C( n, α) 10Be. Our work provides an upper limit on the contribution of in situ radioactivity to samples containing low levels of 10Be and 26Al. We have calculated the equilibrium concentrations of 10Be and 26Al in a wide variety of geologic materials including granites, ultramafic rocks, basalts, shales, pelagic sediments, ferromanganese nodules, tektites and Libyan Desert Glass. The calculated concentrations of 10Be and 26Al range from <1 to 4100 and 9 to 10.3 · 10 6 atoms g -1, respectively. Implications of these calculations are discussed. In general, the calculated amounts of radiogenically produced 10Be in geological materials are quite small and frequently negligible compared to cosmogenic production, while that of 26Al are significant and sometimes the

  18. Potentials and pitfalls of depth profile (10Be), burial isochron (26Al/10Be) and palaeomagnetic techniques for dating Early Pleistocene terrace deposits of the Moselle valley (Germany)

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Cordier, Stéphane; May, Simon Matthias; Kelterbaum, Daniel; Szemkus, Nina; Keulertz, Rebecca; Dunai, Tibor; Binnie, Steven; Hambach, Ulrich; Scheidt, Stephanie; Brueckner, Helmut

    2016-04-01

    Throughout the river network of the Rhenish Massif the so-called main terraces complex (MTC) forms the morphological transition between a wide upper palaeovalley and a deeply incised lower valley. The youngest level of this complex (YMT), directly located at the edge of the incised valley, represents a dominant geomorphic feature; it is often used as a reference level to identify the beginning of the main middle Pleistocene incision episode (Demoulin & Hallot, 2009). Although the main terraces are particularly well preserved in the lower Moselle valley, a questionable age of ca. 800 ka is assumed for the YMT, mainly based on the uncertain extrapolation of controversially interpreted palaeomagnetic data obtained in the Rhine valley. In this study, we applied terrestrial cosmogenic nuclide (TCN) dating (10Be/26Al) and palaeomagnetic dating to Moselle fluvial sediments of the MTC. To unravel the spatio-temporal characteristics of the Pleistocene evolution of the valley, several sites along the lower Moselle were sampled following two distinct TCN dating strategies: depth profiles where the original terrace (palaeo-) surface is well preserved and did not experience a major post-depositional burial (e.g., loess cover); and the isochron technique, where the sediment thickness exceeds 4.5-5 m. One terrace deposit was sampled for both approaches (reference site). In addition, palaeomagnetic sampling was systematically performed in each terrace sampled for TCN measurements. The TCN dating techniques show contrasting results for our reference site. Three main issues are observed for the depth profile method: (i) an inability of the modeled profile to constrain the 10Be concentration of the uppermost sample; (ii) an overestimated density value as model output; and (iii) a probable concentration steady state of the terrace deposits. By contrast, the isochron method yields a burial age estimate of 1.26 +0.29/-0.25 Ma, although one sample showed a depleted 26Al/10Be ratio

  19. Mass, surface area and number metrics in diesel occupational exposure assessment.

    PubMed

    Ramachandran, Gurumurthy; Paulsen, Dwane; Watts, Winthrop; Kittelson, David

    2005-07-01

    While diesel aerosol exposure assessment has traditionally been based on the mass concentration metric, recent studies have suggested that particle number and surface area concentrations may be more health-relevant. In this study, we evaluated the exposures of three occupational groups-bus drivers, parking garage attendants, and bus mechanics-using the mass concentration of elemental carbon (EC) as well as surface area and number concentrations. These occupational groups are exposed to mixtures of diesel and gasoline exhaust on a regular basis in various ratios. The three groups had significantly different exposures to workshift TWA EC with the highest levels observed in the bus garage mechanics and the lowest levels in the parking ramp booth attendants. In terms of surface area, parking ramp attendants had significantly greater exposures than bus garage mechanics, who in turn had significantly greater exposures than bus drivers. In terms of number concentrations, the exposures of garage mechanics exceeded those of ramp booth attendants by a factor of 5-6. Depending on the exposure metric chosen, the three occupational groups had quite different exposure rankings. This illustrates the importance of the choice of exposure metric in epidemiological studies. If these three occupational groups were part of an epidemiological study, depending on the metric used, they may or may not be part of the same similarly exposed group (SEG). The exposure rankings (e.g., low, medium, or high) of the three groups also changes with the metric used. If the incorrect metric is used, significant misclassification errors may occur. PMID:15986054

  20. Detrital 10Be Response to the 2008 Wenchuan Earthquake and Quantifying Evacuation of Coseismic Landslide Debris

    NASA Astrophysics Data System (ADS)

    Wang, W.; Godard, V.; Liu-Zeng, J.; Scherler, D.; Xu, C.; Xu, Q.; Xie, K.; Bellier, O.; Bourles, D. L.; Ansberque, C.

    2014-12-01

    In reverse fault-bounded high relief mountain ranges, large-magnitude earthquakes contribute to the topographic growth by co- and inter-seismic surface uplift on the hanging wall. Meanwhile, they also trigger widespread landslides along ridge lines or hillslopes. Coseismic landsliding lowers relief and causes a phase of high erosion in the period following the quake. The net effect of large-magnitude earthquakes in topographic evolution of active orogens partially depends on how fast the landslide debris are being evacuated out of the mountain range. The 2008 Mw7.9 Wenchuan earthquake, China activated the Longmen Shan reverse fault system in eastern Tibetan plateau, also induced enormous amount of landslides, volume comparable to the coseismic uplift, providing an excellent opportunity to address the question. We use cosmogenic 10Be concentration in river sand as a tracer to study the sediment routing process of coseismic landslide debris, because landslide debris contains low 10Be concentration. We sampling annually during 2008-2013, at 19 locations along the rivers that traverse the fault ruptures, with upstream catchment area varying between 4.4 km2 and 21775 km2, including 10 catchments sampled before Wenchuan earthquake in 2004 and 2005. A comparison with pre-earthquake measurements show reduced 10Be concentration at all sites. This dilution is more significant for small catchments on short range-front rivers: mostly half to one-fourth, and down to one-fifth in some cases. Multi-year time series of 10Be concentration at single sites show roughly constant level of dilution six years after the quake, with moderate temporal fluctuations, which may be related to the variation in precipitation and storm intensity. Under the assumption of constant dilution rate and a depth-mixing of 10Be concentration for landslide input, a simple calculation indicates it would take ~ 200 to 3000 years to completely evacuate the landslides debris within range-front transverse rivers

  1. Tropical glacier fluctuations in the Cordillera Blanca, Peru between 12.5 and 7.6 ka from cosmogenic 10Be dating

    NASA Astrophysics Data System (ADS)

    Glasser, Neil F.; Clemmens, Samuel; Schnabel, Christoph; Fenton, Cassandra R.; McHargue, Lanny

    2009-12-01

    We report cosmogenic surface exposure 10Be ages of 21 boulders on moraines in the Jeullesh and Tuco Valleys, Cordillera Blanca, Peru (˜10°S at altitudes above 4200 m). Ages are based on the sea-level at high-latitude reference production rate and scaling system of Lifton et al. (2005. Addressing solar modulation and long-term uncertainties in scaling secondary cosmic rays for in situ cosmogenic nuclide applications. Earth and Planetary Science Letters 239, 140-161) in the CRONUS-Earth online calculator of Balco et al. (2008. A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements. Quaternary Geochronology 3, 174-195). Using the Lifton system, large outer lateral moraines in the Jeullesh Valley have a 10Be exposure age of 12.4 ka, inside of which are smaller moraine systems dated to 10.8, 9.7 and 7.6 ka. Large outer lateral moraines in the Tuco Valley have a 10Be exposure age of 12.5 ka, with inner moraines dated to 11.3 and 10.7 ka. Collectively, these data indicate that glacier recession from the Last Glacial Maximum (LGM) in the Cordillera Blanca was punctuated by three to four stillstands or minor advances during the period 12.5-7.6 ka, spanning the Younger Dryas Chronozone (YDC; ˜12.9-11.6 ka) and the cold event identified in Greenland ice cores and many other parts of the world at 8.2 ka. The inferred fluctuations of tropical glaciers at these times, well after their withdrawal from the LGM, indicate an increase in precipitation or a decrease in temperature in this region. Although palaeoenvironmental records show regional and temporal variability, comparison with proxy records (lacustrine sediments and ice cores) indicate that regionally this was a cold, dry period so we ascribe these glacier advances to reduced atmospheric temperature rather than increased precipitation.

  2. Geltape method for measurement of work related surface contamination with cobalt containing dust: correlation between surface contamination and airborne exposure.

    PubMed Central

    Poulsen, O M; Olsen, E; Christensen, J M; Vinzent, P; Petersen, O H

    1995-01-01

    OBJECTIVES--The geltape method is a new method for optical measurement of total amount of dust on surfaces. The objectives were to study the potential applicability of this method to measurements of work related cobalt exposure during painting of plates with cobalt dye. METHODS--Consecutive series of work related geltape prints were taken from surfaces inside and outside the ventilation cabins of two plate painters during two full working days. The amount of dust picked up by the geltapes was measured optically with a field monitor. Also, personal air samples were collected on filters at the different work processes. In the laboratory the contents of cobalt on the geltape prints and the filters were measured with inductive coupled plasma atomic emission spectroscopy. RESULTS--The key results were: (a) when the geltape prints were taken from surfaces inside the cabins the optically measured area of the geltapes covered with total dust (area (%)) correlated well with the chemically measured amount of cobalt present on the geltapes. Linear correlation coefficient (R2) was 0.91 for geltape prints taken on the floor and 0.94 for prints taken on the ceiling; (b) the cumulative airborne cobalt exposure, calculated from data on work related exposure by personal sampling, correlated with the area (%) of geltape prints taken from the ceiling of the cabin (R2 = 0.98); (c) the geltape method could be used to distinguish both between work processes with different levels of cobalt exposure, and between plate painters subjected to significant differences in airborne cobalt exposure. CONCLUSION--The geltape method could produce measures of the work related exposures as well as whole day exposure for cobalt. The geltape results correlated with measurements of personal airborne cobalt exposure. In this industry the profile of exposure is well-defined in time, and it seems reasonable to apply this fast and low cost method in routine exposure surveillance to obtain a more detailed

  3. Evolution of surface stress during oxygen exposure of clean Si(111), Si(100), and amorphous Si surfaces

    SciTech Connect

    Flötotto, D. Wang, Z. M.; Jeurgens, L. P. H.; Mittemeijer, E. J.

    2014-01-14

    The evolutions of the surface stress of Si(111)-7 × 7, Si(100)-2 × 1, and a-Si surfaces upon oxygen exposure at pO{sub 2} = 1 × 10{sup −4} Pa and room temperature have been investigated in a comparative manner using a specimen-curvature based technique. To this end, a generally applicable, dedicated set of experiments has been devised and performed to deduce and correct for the surface stress change owing to oxygen reaction(s) at the (poorly-defined) back face of the specimen only. On this basis, it could be demonstrated that exposure of clean Si(111)-7 × 7, Si(100)-2 × 1 and a-Si surfaces to pure oxygen gas results in compressive surface stress changes for all three surfaces due to the incorporation of oxygen into Si backbonds. The measured surface stress change decreases with decreasing atomic packing density at the clean Si surfaces, which complies well with the less-densily packed Si surface regions containing more free volume for the accommodation of adsorbed O atoms.

  4. Climate-induced changes in sediment supply revealed by surface exposure dating of Sijiquan River terraces, northeastern Tibet

    NASA Astrophysics Data System (ADS)

    Shirahama, Yoshiki; Miyairi, Yosuke; He, Honglin; Fu, Bihong; Echigo, Tomoo; Kano, Ken'ichi; Yokoyama, Yusuke; Ikeda, Yasutaka

    2015-04-01

    In this paper, we report cosmogenic isotope evidence for dramatic changes in sediment supply during glacial-interglacial climatic cycles in the Late Quaternary. Previous work on fluvio-glacial processes in cold environments has qualitatively revealed that significant increases in debris production occurred in glacial periods, due typically to accelerated glacial and periglacial processes on high-relief slopes, resulting in river aggradation (accumulation) in the drainage. In interglacial periods, rivers behave in the opposite way, forming incised valleys. However, little has been studied on climatically controlled production-and-reworking processes with radiometric evidence. The evidence presented here is from the northeastern margin of the Tibetan Plateau, where lateral growth of the plateau is now ongoing. Reconstructions of fluvial response to Quaternary glacial fluctuations are crucial also to better understand the active tectonic process in the region using geomorphological information. The Sijiquan River drainage basin on the north of the East Kunlun Mountains was investigated. Detailed geomorphological mapping of fluvio-glacial landforms indicates two phases of aggradation, each of which was followed by valley incision. 10Be and 26Al concentrations in fluvial terrace deposits suggest that these two aggradational phases correspond most likely to the penultimate and last glacial periods, assuming a low rate of surface erosion on the terraces and zero inherited concentration. On the other hand, present-day river gravel has higher concentrations in amalgamated samples of 10Be and 26Al than the terrace deposits. Surface-exposure and burial analyses based on grain-by-grain measurements of both 10Be and 26Al indicate that the present-day river gravel consists mostly of reworked grains from terrace deposits and underlying fluvio-lacustrine rocks in the drainage basin. It is concluded that significant changes in clastic sediment supply occur in cold environments in

  5. Authigenic 10Be/9Be ratios and 10Be-fluxes (230Thxs-normalized) in central Baffin Bay sediments during the last glacial cycle: Paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Simon, Quentin; Thouveny, Nicolas; Bourlès, Didier L.; Nuttin, Laurence; Hillaire-Marcel, Claude; St-Onge, Guillaume

    2016-05-01

    Authigenic 10Be/9Be ratios and 10Be-fluxes reconstructed using the 230Thxs normalization, proxies of the cosmogenic radionuclide 10Be production rate in the atmosphere, have been measured in a sedimentary core from Baffin Bay (North Atlantic) spanning the last 136 ka BP. The normalization applied on the exchangeable (authigenic) 10Be concentrations using the authigenic 9Be isotope and 230Thxs methods yield equivalent results strongly correlated with sedimentological parameters (grain-size and mineralogy). Lower authigenic beryllium (Be) concentrations and 10Be/9Be ratios are associated with coarse-grained carbonate-rich layers, while higher authigenic Be values are related to fine-grained felspar-rich sediments. This variability is due to: i) sediment composition control over beryllium-scavenging efficiency and, ii) glacial history that contributed to modify the 10Be concentration in Baffin Bay by input and boundary scavenging condition changes. Most paleo-denudation rates inferred from the 10Be/9Be ratio vary weakly around 220 ± 76 tons.km-2.yr-1 (0.09 ± 0.03 mm.yr-1) corresponding to relatively steady weathering fluxes over the last glacial cycle except for six brief intervals characterized by sharp increases of the denudation rate. These intervals are related to ice-surging episodes coeval with Heinrich events and the last deglaciation period. An average freshwater flux of 180.6 km3.yr-1 (0.006 Sv), consistent with recent models, has been calculated in order to sustain glacially-derived 10Be inputs into Baffin Bay. It is concluded that in such environments, the authigenic 10Be measured mainly depends on climatic effects related to the glacial dynamics, which masks the 10Be production variation modulated by geomagnetic field changes. Altogether, these results challenge the simple interpretation of 10Be-concentration variation as a proxy of Interglacial/Glacial (interstadial/stadial) cycles in Arctic and sub-Arctic regions. They rather suggest the effect

  6. Constraints on 10Be and 41Ca distribution in the early solar system from 26Al and 10Be studies of Efremovka CAIs

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gopalan; Chaussidon, Marc

    2013-07-01

    Three refractory coarse grained CAIs from the Efremovka CV3 chondrite, one (E65) previously shown to have formed with live 41Ca, were studied by ion microprobe for their 26Al-26Mg and 10Be-10B systematic in order to better understand the origin of 10Be. The high precision Al-Mg data and the inferred 26Al/27Al values attest that the precursors of the three CAIs evolved in the solar nebula over a period of few hundred thousand years before last melting-crystallization events. The initial 10Be/9Be ratios and δ10B values defined by the 10Be isochrons for the three Efremovka CAIs are similar within errors. The CAI 10Be abundance in published data underscores the large range for initial 10Be/9Be ratios. This is contrary to the relatively small range of 26Al/27Al variations in CAIs around the canonical ratio. Two models that could explain the origin of this large 10Be/9Be range are assessed from the collateral variations predicted for the initial δ10B values: (i) closed system decay of 10Be from a "canonical" 10Be/9Be ratio and (ii) formation of CAIs from a mixture of solid precursors and nebula gas irradiated during up to a few hundred thousand years. The second scenario is shown to be the most consistent with the data. This shows that the major fraction of 10Be in CAIs was produced by irradiation of refractory grains, while contributions of galactic cosmic rays trapping and early solar wind irradiation are less dominant. The case for 10Be production by solar cosmic rays irradiation of solid refractory precursors poses a conundrum for 41Ca because the latter is easily produced by irradiation and should be more abundant than what is observed in CAIs. 10Be production by irradiation from solar energetic particles requires high 41Ca abundance in early solar system, however, this is not observed in CAIs.

  7. Erosion rates and landscape evolution of the lowlands of the Upper Paraguay river basin (Brazil) from cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Pupim, Fabiano do Nascimento; Bierman, Paul R.; Assine, Mario Luis; Rood, Dylan H.; Silva, Aguinaldo; Merino, Eder Renato

    2015-04-01

    The importance of Earth's low sloping areas in regard to global erosion and sediment fluxes has been widely and vigorously debated. It is a crucial area of research to elucidate geologically meaningful rates of land-surface change and thus the speed of element cycling on Earth. However, there are large portions of Earth where erosion rates have not been well or extensively measured, for example, the tropical lowlands. The Cuiabana lowlands are an extensive low-altitude and low-relief dissected metamorphic terrain situated in the Upper Paraguay river basin, central-west Brazil. Besides exposures of highly variable dissected metamorphic rocks, flat residual lateritic caps related to a Late Cenozoic planation surface dominate interfluves of the Cuiabana lowlands. The timescale over which the lowlands evolved and the planation surface developed, and the rate at which they have been modified by erosion, are poorly known. Here, we present measurements of in situ produced cosmogenic 10Be in outcropping metamorphic bedrock and clastic-lateritic caps to quantify rates of erosion of the surface and associated landforms in order to better understand the Quaternary landscape evolution of these lowlands. Overall, slow erosion rates (mean 10 m/Ma) suggest a stable tectonic environment in these lowlands. Erosion rates vary widely between different lithologies (range 0.57 to 28.3 m/Ma) consistent with differential erosion driving regional landform evolution. The lowest erosion rates are associated with the low-relief area (irregular plains), where clastic-laterite (mean 0.67 m/Ma) and quartzite (mean 2.6 m/Ma) crop out, whereas the highest erosion rates are associated with dissection of residual hills, dominated by metasandstone (mean 11.6 m/Ma) and phyllite (mean 27.6 m/Ma). These data imply that the Cuiabana lowland is comprised of two dominant landform sets with distinct and different dynamics. Because the planation surface (mostly lowlands) is lowering and losing mass more

  8. Modification of the Surface Properties of Polyimide Films using POSS Deposition and Oxygen Plasma Exposure

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Belcher, Marcus A.; Ghose, Sayata; Connell, John W.

    2008-01-01

    Topographically rich surfaces were generated by spray-coating organic solutions of a polyhedral oligomeric silsesquioxane, octakis (dimethylsilyloxy) silsesquioxane (POSS), on Kapton HN films and exposing them to radio frequency generated oxygen plasma. Changes in both surface chemistry and topography were observed. High-resolution scanning electron microscopy indicated substantial modification of the POSS-coated polyimide surface topographies as a result of oxygen plasma exposure. Water contact angles varied from 104 deg for unexposed POSS-coated surfaces to approximately 5 deg, for samples exposed for 5 h. Modulation of the dispersive and polar contributions to the surface energy was determined using van Oss Good Chaudhury theory.

  9. Millennial Rates of Sea Cliff Retreat Derived From Cosmogenic 10Be and Coastal Platform Morphology

    NASA Astrophysics Data System (ADS)

    Hurst, M. D.; Ellis, M. A.; Rood, D. H.

    2014-12-01

    Observation of cliff erosion are often limited to relatively short timescales (a few decades), which are within the timeframe of anthropogenic modification of the coast and may be shorter than the recurrence interval for erosion events. Here we present long-term (centennial-millennial) averaged rates of sea cliff retreat for chalk cliffs in SE England derived from cosmogenic isotopes and coastal morphology. We determine long-term rates of sea cliff erosion from 10Be measured from in situ flint samples collected from three transects across the coastal platform in East Sussex. A numerical model of 10Be accumulation on an evolving coastal profile allows estimation of cliff retreat rate averaged over several hundred years. The model accounts for variation in 10Be accumulation with tides and sea-level rise, and takes into account platform downwear and topographic shielding by adjacent cliffs. Additionally, we use high-resolution (1m) multibeam bathymetry to map the extent of the coastal platform based on the surface texture in order to infer the position of the coast at ~8 ka. The difference in position to the current coastline provides estimates of Holocene-averaged rates of cliff erosion for all chalk cliffed coastline in the region. Comparison to historic records of cliff retreat reveals key similarities and differences between long and short-term signals. In certain locations, there are significant discrepancies (either faster or slower) between historic records and long-term rates of retreat. Each type of discrepancy may be the result of human interaction with the coastal environment, whether that interaction is local or non-local, and it is worthwhile noting that sites of relatively low historic rates of erosion are likely subject to high-magnitude, low-frequency failure events that could have devastating effects on human lives and infrastructure in areas that are considered to be low risk.

  10. The efficacy of local exhaust ventilation for controlling dust exposures during concrete surface grinding.

    PubMed

    Croteau, Gerry A; Flanagan, Mary Ellen; Camp, Janice E; Seixas, Noah S

    2004-08-01

    This study assessed the effectiveness of a commercially available local exhaust ventilation (LEV) system for controlling respirable dust and crystalline silica exposures during concrete grinding activities. Surface grinding was conducted at six commercial building construction sites in Seattle, WA, by cement masons. Time-integrated filter samples and direct reading respirable dust concentrations were collected using a cyclone in line with a direct reading respirable dust monitor. Personal exposure levels were determined with and without LEV, one sample directly after the other. A total of 28 paired samples were collected in which three different dust collection shroud configurations were tested. Data obtained with a direct reading respirable dust monitor were adjusted to remove non-work task-associated dust exposures and was subsequently used to calculate the exposure reduction achieved. The application of LEV resulted in a reduction in the overall geometric mean respirable dust exposure from 4.5 to 0.14 mg/m(3), a mean exposure reduction of 92%. Despite the effective control of dust generated during surface grinding, 22 and 26% of the samples collected while LEV was being used were greater than the 8 h time-weighted average permissible exposure limit (Occupational Safety and Health Administration) and threshold limit value (American Congress of Governmental Industrial Hygienists) for respirable crystalline silica, respectively. PMID:15298850

  11. Full Mission Astronaut Radiation Exposure Assessments for Long Duration Lunar Surface Missions

    NASA Technical Reports Server (NTRS)

    Adamczyk, Anne; Clowdsley, Martha; Qualls, Garry; Blattnig, Steve; Lee, Kerry; Fry, Dan; Stoffle, Nicholas; Simonsen, Lisa; Slaba, Tony; Walker, Steven; Zapp, Edward

    2011-01-01

    Risk to astronauts due to ionizing radiation exposure is a primary concern for missions beyond Low Earth Orbit (LEO) and will drive mission architecture requirements, mission timelines, and operational practices. For short missions, radiation risk is dominated by the possibility of a large Solar Particle Event (SPE). Longer duration missions have both SPE and Galactic Cosmic Ray (GCR) risks. SPE exposure can contribute significantly toward cancer induction in combination with GCR. As mission duration increases, mitigation strategies must address the combined risks from SPE and GCR exposure. In this paper, full mission exposure assessments were performed for the proposed long duration lunar surface mission scenarios. In order to accomplish these assessments, previously developed radiation shielding models for a proposed lunar habitat and rover were utilized. End-to-End mission exposure assessments were performed by first calculating exposure rates for locations in the habitat, rover, and during Extra-Vehicular Activities (EVA). Subsequently, total mission exposures were evaluated for the proposed timelines. Mission exposure results, assessed in terms of effective dose, are presented for the proposed timelines and recommendations are made for improved astronaut shielding and safer operational practices.

  12. Surface modification of CaF 2 in atomic layer scale by electron beam exposure

    NASA Astrophysics Data System (ADS)

    Hwang, S. M.; Izumi, A.; Tsutsui, K.; Furukawa, S.

    1994-12-01

    Surface modification of CaF 2/Si(111) was studied for the purpose of 1 ML adsorption of group-V atoms on a fluoride surface which is applicable to heteroepitaxy of III—V compound semiconductors on CaF 2. By using Rutherford backscattering (RBS) and X-ray photoelectron spectroscopy (XPS), it was found that 1 ML of As and P were successfully adsorbed on a CaF 2 surface, and that a 1 ML self-limiting adsorption of As for the electron beam exposure was realized. Also, we propose a model for the adsorption conditions depending on the substrate temperature during surface modification.

  13. Platelet loss on exposure of citrated blood to various foreign surfaces.

    PubMed

    Perkins, H A; Rolfs, M R; Hymas, P G

    1975-01-01

    Citrated whole blood was rotated in tubes or closed loops of tubing and the percentage of platelets lost on exposure to the surface of the container was noted. Platelet loss in the presence of uncoated glass surfaces (mean loss 31%) was significantly less than in the presence of glass siliconed with two different reagents (82% and 86%). Platelets adhered to siliconed glass but not to uncoated glass. Other inert surfaces also resulted in a high degree of platelet loss: Teflon 90 per cent, silicone rubber 85 per cent, Parawax 84 per cent, polysytrene 82 per cent, polyethylene 79 per cent, polypropylene 60 per cent, and polycarbonate 58 per cent. One lot of polyvinyl chloride transfusion grade tubing resulted in only 2 per cent loss of platelets, but other lots varied between 35 and 84 per cent. Loss of platelets on exposure to the surface of plastic containers may have to be considered when evaluating new materials for preparation of blood components. PMID:804189

  14. 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. PMID:24324273

  15. 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.

  16. POTENTIAL INHALATION EXPOSURE TO VOLATILE CHEMICALS IN WATER-BASED HARD-SURFACE CLEANERS

    EPA Science Inventory

    Potential inhalation exposure of building occupants to volatile chemicals in water-based hard-surface cleaners was evaluated by analyzing 267 material safety data sheets (MSDSs). Among the 154 chemicals reported, 44 are volatile or semi-volatile. Hazardous air pollutants (HAPs) r...

  17. Minimum activation martensitic alloys for surface disposal after exposure to neutron flux

    DOEpatents

    Lechtenberg, Thomas

    1985-01-01

    Steel alloys for long-term exposure to neutron flux have a martensitic microstructure and contain chromium, carbon, tungsten, vanadium and preferably titanium. Activation of the steel is held to within acceptable limits for eventual surface disposal by stringently controlling the impurity levels of Ni, Mo, Cu, N, Co, Nb, Al and Mn.

  18. 10Be depth-profile dating of glaciofluvial sediments in the northern Alpine Foreland

    NASA Astrophysics Data System (ADS)

    Claude, Anne; Akçar, Naki; Ivy-Ochs, Susan; Schlunegger, Fritz; Kubik, Peter; Christl, Marcus; Vockenhuber, Christof; Dehnert, Andreas; Rahn, Meinert; Schlüchter, Christian

    2016-04-01

    10Be depth-profile dating is based on the fact that nuclide production is decreasing as an exponential function of depth. This method requires collecting at least four sediment samples in a vertical profile. The obtained nuclide concentrations are plotted against depth and fitted depth-profiles to the measured dataset. The age is then calculated based on the best-fit. The requirements for this method are the following: sampling geological units in artificial outcrops with minimum thickness of soil (less than around 80 cm), preferably with a flat-topped landform in order to guarantee that the uppermost surface of the deposit remains as unmodified as possible and is related to a defined geomorphologic process. Additionally at least one sample, preferably three, from the uppermost one meter of the profile as the exponential decrease mainly occurs around this depth. No sample is collected from the overlying soil. In this study, we aim to establish the chronology of the oldest Quaternary sediments in the northern Alpine Foreland using depth-profile dating with 10Be. These ages contribute to the understanding of the Quaternary landscape evolution of the Alpine Foreland. Here, we unravel the chronology of five sites at different morphostratigraphic positions: Mandach and Ängi (canton Aargau), Stadlerberg and Irchel (canton Zurich) and Rechberg (Germany, 4 km from the border to Switzerland). All sites are abandoned gravel pits and at each site we collected between four and seven sediment samples. First results yielded chronologies between 0.8 and 2 Ma for these glaciofluvial deposits. Our study shows that this relatively new method is successful when the geological setting matches the methodological requirements.

  19. A new method for estimating bedrock surface exposure ages and long-term erosion rates using a single in situ-produced cosmogenic radionuclide

    SciTech Connect

    Lifton, N.A.; Jull, A.J.T. . Dept. of Geosciences)

    1993-04-01

    Numerous ambiguities, limitations and uncertainties in geomorphic research have resulted from a historical inability to reliably and quantitatively estimate (1) the age of exposure of a geomorphic surface, and (2) spatial variability of long-term erosion rates. Radioactive and stable nuclides produced in situ by cosmic ray bombardment of rock materials exposed at the earth's surface may enable one to estimate surface exposure ages and long-term erosion rates directly. Recent development of techniques for measuring and interpreting concentrations of these nuclides may ultimately help to resolve many long-standing geomorphic debates. Cosmogenic radionuclide pairs such as [sup 10]Be and [sup 26]Al have been used most frequently to solve the governing equations for both erosion rates and surface exposure ages. However, the applicability of these techniques to geomorphic problems has been limited to some extent by the number of assumptions which had to be made to interpret the measured concentrations -- particularly those pertaining to steady-state or non-steady-state erosion conditions. The authors are developing a new method for interpreting the depth distribution of a single cosmogenic radionuclide in bedrock which avoids the need for many of these assumptions. Monte Carlo techniques are used to explore the range of erosion rate and exposure age conditions on a grid which would produce theoretical depth distributions of the radionuclide consistent with the measured depth profile. They plan to present new cosmogenic [sup 14]C data to corroborate the model results. Although unanswered questions and potential problems remain, this method appears to hold great promise for unraveling spatial variation in both erosion rates and exposure ages of a wide range of bedrock surfaces.

  20. Repeated exposure of acidic beverages on esthetic restorative materials: An in-vitro surface microhardness study

    PubMed Central

    Sunny, Steffy M.; Rai, Kavita; Hegde, Amitha M.

    2016-01-01

    Background A manifold increase in the consumption of aerated beverages has witnessed a twin increase in tooth wear and raised demand for esthetic restorative materials. This study aimed to evaluate the surface microhardness changes of esthetic restorative materials following treatment with aerated beverages in an in-vitro situation. Material and Methods The initial surface microhardness of the restorative materials GC Fuji II LC, GC Fuji IX, Nano Glass ionomer, Resin and Nano composite was recorded. These materials were studied under 3 groups that included those exposed to the acidic beverages daily, weekly once in a month and those that had no exposures at all. The final surface microhardness of the materials was recorded following experimentation and was subjected to statistical comparisons. Results The restorative materials were compared for their surface microhardness changes following respective treatments using the T-test and One-way ANOVA analysis. Inter-comparisons between the groups showed statistical significance (p<.05), when treated with both the beverages. The five restorative materials revealed surface microhardness loss; the maximum reduction noticed with the Nano glass ionomer cement tested (p<.0005). Conclusions The surface microhardness of restorative materials markedly reduced upon repeated exposures with acidic beverages; the product with phosphoric acid producing the maximum surface microhardness loss. Key words:Restorative materials, acidic beverages, surface microhardness, resin composites, glass ionomers. PMID:27398183

  1. Evaluation of entrance surface air kerma from exposure index in computed radiography

    NASA Astrophysics Data System (ADS)

    Costa, A. M.; Pelegrino, M. S.

    2014-11-01

    The aim of this study was to establish an indirect method to calculate the values of entrance surface air kerma in patients undergoing diagnostic examinations in X-ray systems with computed radiography based on the exposure index. The entrance surface air kerma values were compared with values obtained also indirectly based on measurements of X-ray tube output. The mean±standard deviation (1σ) and third quartile for entrance surface air kerma calculated from the exposure index were 2.1±1.0 mGy and 3.0 mGy, respectively. For entrance surface air kerma based on measurements of the X-ray tube output, the mean±standard deviation (1σ) and third quartile were respectively 3.1±1.9 mGy and 5.5 mGy. The observed values of entrance surface air kerma are smaller than the reference level adopted in Brazil (10 mGy). The results obtained with both methods were similar when taking into account the estimated uncertainties in the determination of air kerma values, although the reproducibility of the determinations based on the exposure index is better.

  2. Effect of exposure environment on surface decomposition of SiC-silver ion implantation diffusion couples

    DOE PAGESBeta

    Gerczak, Tyler J.; Zheng, Guiqui; Field, Kevin G.; Allen, Todd R.

    2014-10-05

    SiC is a promising material for nuclear applications and is a critical component in the construction of tristructural isotropic (TRISO) fuel. A primary issue with TRISO fuel operation is the observed release of 110m Ag from intact fuel particles. The release of Ag has prompted research efforts to directly measure the transport mechanism of Ag in bulk SiC. Recent research efforts have focused primarily on Ag ion implantation designs. The effect of the thermal exposure system on the ion implantation surface has been investigated. Results indicate the utilization of a mated sample geometry and the establishment of a static thermalmore » exposure environment is critical to maintaining an intact surface for diffusion analysis. In conclusion, the nature of the implantation surface and its potential role in Ag diffusion analysis are discussed.« less

  3. Effect of exposure environment on surface decomposition of SiC-silver ion implantation diffusion couples

    SciTech Connect

    Gerczak, Tyler J.; Zheng, Guiqui; Field, Kevin G.; Allen, Todd R.

    2014-10-05

    SiC is a promising material for nuclear applications and is a critical component in the construction of tristructural isotropic (TRISO) fuel. A primary issue with TRISO fuel operation is the observed release of 110m Ag from intact fuel particles. The release of Ag has prompted research efforts to directly measure the transport mechanism of Ag in bulk SiC. Recent research efforts have focused primarily on Ag ion implantation designs. The effect of the thermal exposure system on the ion implantation surface has been investigated. Results indicate the utilization of a mated sample geometry and the establishment of a static thermal exposure environment is critical to maintaining an intact surface for diffusion analysis. In conclusion, the nature of the implantation surface and its potential role in Ag diffusion analysis are discussed.

  4. Surface characterization of gallium nitride modified with peptides before and after exposure to ionizing radiation in solution.

    PubMed

    Berg, Nora G; Nolan, Michael W; Paskova, Tania; Ivanisevic, Albena

    2014-12-30

    An aqueous surface modification of gallium nitride was employed to attach biomolecules to the surface. The modification was a simple two-step process using a single linker molecule and mild temperatures. The presence of the peptide on the surface was confirmed with X-ray photoelectron spectroscopy. Subsequently, the samples were placed in water baths and exposed to ionizing radiation to examine the effects of the radiation on the material in an environment similar to the body. Surface analysis confirmed degradation of the surface of GaN after radiation exposure in water; however, the peptide molecules successfully remained on the surface following exposure to ionizing radiation. We hypothesize that during radiation exposure of the samples, the radiolysis of water produces peroxide and other reactive species on the sample surface. Peroxide exposure promotes the formation of a more stable layer of gallium oxyhydroxide which passivates the surface better than other oxide species. PMID:25479565

  5. Temporal variation of optimal UV exposure time over Korea: risks and benefits of surface UV radiation

    NASA Astrophysics Data System (ADS)

    Lee, Y. G.; Koo, J. H.

    2015-12-01

    Solar UV radiation in a wavelength range between 280 to 400 nm has both positive and negative influences on human body. Surface UV radiation is the main natural source of vitamin D, providing the promotion of bone and musculoskeletal health and reducing the risk of a number of cancers and other medical conditions. However, overexposure to surface UV radiation is significantly related with the majority of skin cancer, in addition other negative health effects such as sunburn, skin aging, and some forms of eye cataracts. Therefore, it is important to estimate the optimal UV exposure time, representing a balance between reducing negative health effects and maximizing sufficient vitamin D production. Previous studies calculated erythemal UV and vitamin-D UV from the measured and modelled spectral irradiances, respectively, by weighting CIE Erythema and Vitamin D3 generation functions (Kazantzidis et al., 2009; Fioletov et al., 2010). In particular, McKenzie et al. (2009) suggested the algorithm to estimate vitamin-D production UV from erythemal UV (or UV index) and determined the optimum conditions of UV exposure based on skin type Ⅱ according to the Fitzpatrick (1988). Recently, there are various demands for risks and benefits of surface UV radiation on public health over Korea, thus it is necessary to estimate optimal UV exposure time suitable to skin type of East Asians. This study examined the relationship between erythemally weighted UV (UVEry) and vitamin D weighted UV (UVVitD) over Korea during 2004-2012. The temporal variations of the ratio (UVVitD/UVEry) were also analyzed and the ratio as a function of UV index was applied in estimating the optimal UV exposure time. In summer with high surface UV radiation, short exposure time leaded to sufficient vitamin D and erythema and vice versa in winter. Thus, the balancing time in winter was enough to maximize UV benefits and minimize UV risks.

  6. 10Be concentrations and the long-term fate of particle-reactive nuclides in five soil profiles from California

    NASA Astrophysics Data System (ADS)

    Monaghan, M. C.; Krishnaswami, S.; Thomas, J. H.

    1983-10-01

    Concentration-depth profiles of cosmic-ray-produced 10Be ( t1/2 = 1.5m.y.) have been measured by accelerator-mass spectrometry in five soil profiles. These measurements were made in an effort (1) to understand the retentivity of soil surfaces for particle-reactive tracers depositing from the atmosphere on time scales of 10 4-10 6 years, and (2) to explore the application of 10Be as a chronometer of geomorphic surface age. The profiles sampled are from two wave-cut terraces located near Mendocino, California, a table mountain top and an alluvial fan, both located near Friant, California. The ages of the Mendocino terraces are inferred to be (1-5) × 10 5 years based on amino-stratigraphic correlations and models of terrace evolution; those of the table mountain top and alluvial fan are 9.5 × 10 6 years and 6.0 × 10 5 years, respectively, based on K-Ar analyses. All the surfaces sampled are nearly flat and exhibit few erosional features. In addition to 10Be we measured 210Pb, 239,240Pu and 7Be to ascertain the retentivity of the soils for particle-reactive nuclides and to assess the present-day delivery rate of nuclides from the atmosphere. The 7Be inventory is 4.0 dpm/cm 2 similar to those observed at nearby locations. The inventories of 210Pb and Pu isotopes conform to those predicted from model calculations and suggest that the soil surfaces sampled retain the entire burden of particle-reactive nuclides delivered to them over short time scales, ˜ 100 years. The 10Be concentrations in the sample range between (0.2 and 7) × 10 8 atoms/g soil and show strong correlations with leachable Fe and/or Al. The inventory of 10Be in the soil domain sampled is 1-2 orders of magnitude lower than that expected from the geological age of the surface and an average delivery rate of 10Be from the atmosphere, 5.2 × 10 5 atoms/cm 2 yr. The low inventory of 10Be is attributed to its loss from the soil domain sampled by solution transport. Based on a simple ☐-model type

  7. Influence of periglacial cover beds on in situ-produced cosmogenic 10Be in soil sections

    NASA Astrophysics Data System (ADS)

    Schaller, M.; von Blanckenburg, F.; Veit, H.; Kubik, P. W.

    2003-01-01

    Cover beds, widespread on hillslopes of temperate climate zones, represent layers of allochthonous material laterally transported by periglacial processes during the Late Pleistocene. Two soil sections comprised of cover beds from the Bavarian Forest, SE Germany, have been analysed for in situ-produced cosmogenic 10Be. Major changes in the nuclide concentration agree well with soil section boundaries defined by field observations and grain size analyses. Numeric modeling of these cosmogenic nuclide sections demonstrates that simple continuous erosion and regolith mixing models fail to explain the measured nuclide concentrations. Instead, the measured data can be best described by modeling an admixture of material such as loess or reworked allochthonous material, which have different nuclide concentrations. A comparison of cosmogenic nuclide concentrations from the two cover bed sections with concentrations from river bedload sediments of the Regen catchment reveals that cover bed formation might affect the result of basin-wide erosion rate determinations based on cosmogenic nuclides. Nuclide concentration of river bedload is potentially a binary mixture produced by (1) spatial erosion of the soil surfaces; and (2) spatially nonuniform incision into deep cover bed layers that contributes sediment low in nuclide concentration.

  8. The oldest ice on Earth in Beacon Valley, Antarctica: new evidence from surface exposure dating

    NASA Astrophysics Data System (ADS)

    Schäfer, Jörg M.; Baur, Heinrich; Denton, George H.; Ivy-Ochs, Susan; Marchant, Dave R.; Schlüchter, Christian; Wieler, Rainer

    2000-06-01

    Beacon Valley, Antarctica, contains unique remnants of glacier ice underneath a till layer covering the valley floor. To constrain the age and evolution of this important indicator of Antarctic paleoclimate, we analyzed two dolerite erratics from the till surface and one from within the ice for cosmogenic helium and neon. A conservative minimum exposure age of the older surface sample is 2.3 Ma, but taking into account erosion, the true exposure age of this boulder is likely to be considerably higher. The buried sample contains more than 20 times less cosmogenic noble gases than the old surface sample, although its current shielding would imply only a three times lower production rate. This indicates that the ice level has slowly been lowered by sublimation at the rate of a few m/Ma. The high exposure age of the surface sample as well as the very low sublimation rate of the relict ice both support the conclusion that the remnant ice in Beacon Valley was deposited many million years ago [Sugden et al., Nature 376 (1995) 412-414] and has never been thinner than at present. In addition, we found that cosmogenic helium and neon are released quantitatively from pyroxene at temperatures of <900°C and >1000°C, respectively.

  9. Timing of late Pleistocene glaciation in Mongolia: Surface exposure dating reveals a differentiated pattern of glacial forcing

    NASA Astrophysics Data System (ADS)

    Pötsch, Steffen; Rother, Henrik; Lorenz, Sebastian; Walther, Michael; Lehmkuhl, Frank

    2015-04-01

    The focus of this study is on the geochronological and paleoclimatic characterization of Pleistocene glaciation in central (Khangai Mountains) and western (Turgen Mountains, Mongolian Altai) Mongolia. These two mountain ranges form a 700 km long SE-NW transect through Mongolia and allow assumptions of the temporal and causal dynamics of regional glaciation and their correlation to other mountain glacier records from Central and High Asia. In order to evaluate the Pleistocene glaciations in Mongolia we undertook geomorphological mapping and cosmogenic radionuclide (CRN) surface exposure dating (10Be) in four valley systems located in the Khangai Mountains and Turgen Mountains. In total 46 glacial boulders and roche moutonnées were sampled, prepared and AMS measured to determine their 10Be surface exposure ages. Of these, 26 samples were obtained from the Khangai Mountains (three separate moraine sequences) and 20 samples were taken from the Turgen Mountains (one moraine sequence). Our results give evidence of major ice advances during early MIS-4 (74-71 ka) and MIS-2 (25-20 and 18- 17 ka) in both mountain ranges. However, in the Khangai Mountains of central Mongolia very significant ice advances also occurred during MIS-3 (37-32 ka), which exceeded the ice limits set during the MIS-2 glaciation. These results show that climatic conditions during phases of insolation minima characterized by extremely cold and dry conditions (MIS-4 and MIS-2) produced a favorable setting for major ice expansion in Mongolia. Yet, glacial accumulation in the Khangai Mountains also increased substantially in response to the cool-wet conditions of MIS-3, associated with a possibly greater-than-today input from winter precipitation. These records indicate that in addition to the thermally induced glaciations of MIS-4 and MIS-2, variations in atmospheric moisture supply are also capable of triggering large ice advances as observed during MIS-3. Taken together, this suggests that the role

  10. 10Be application to soil development on Marion Island, southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Haussmann, N.; Aldahan, A.; Boelhouwers, J.; Possnert, G.

    2010-04-01

    Marion Island, located in the southern Indian Ocean, constitutes the summit of an active shield volcano. It is a small terrestrial environment where glacially abraded bedrock became exposed c × 10 kyr ago. These conditions provide an interesting possibility for the assessment of 10Be accumulation rates and their application to soil erosion studies on the island. 10Be concentrations were measured in precipitation, soil profiles and an Azorella selago cushion plant. The data reveal a 10Be precipitation flux several times higher than model prediction. Estimation of the 10Be accumulation based on the soil inventory suggests a span between 2000 and 7000 yr. This time span is not in accordance with the accepted notion that the island was covered with ice about 10,000 yr ago and suggests either removal of 10Be from the soil profile, an overestimated Holocene 10Be-flux or a delayed soil development history. Our results provide new data on 10Be concentrations from the sub-Antarctic islands and contribute towards enlarging the southern-hemisphere 10Be database.

  11. 10Be in Lake Lisan sediments — A proxy for production or climate?

    NASA Astrophysics Data System (ADS)

    Belmaker, Reuven; Lazar, Boaz; Tepelyakov, Natalya; Stein, Mordechai; Beer, Jürg

    2008-05-01

    The geochemical behavior of 10Be in the modern Dead Sea hydrological-limnological system was studied in order to evaluate the feasibility of using Dead Sea and Lake Lisan (the late Pleistocene precursor of the Dead Sea) sediments as archives of the variations in the 10Be production rate. 10Be concentrations in detrital and aragonite material from Lake Lisan laminated sediments were compared to those measured in modern dust, terra rossa soil (aeolian in origin), loess from the Negev Desert, flood suspended load and waters along a rain-flood development pathway (the transition from rain to incipient runoff and fully developed floods). 10Be concentrations decreased throughout the flood development profile, from 8.2 × 10 3 atoms g - 1 in the runoff down to ~ 1 × 10 3 atoms g - 1 in Dead Sea brine due to fast removal of 10Be by the soil and dust particles. Thus, most of the 10Be in the lake is contained within the detrital sediments that collect the 10Be transported by particles from the surrounding terrain (e.g. desert dust with 1.6 ± 0.8 × 10 8 atoms g - 1 and terra rossa soil-material with up to 12.5 ± 0.5 × 10 8 atoms g - 1 ). The high-stand periods of Lake Lisan were characterized by annual deposition of silty-detritus sediments reflecting rapid transfer of desert dust to the lake by floods. Indeed, the bulk sediments of Lake Lisan (in which 10Be is associated mainly with silty-detritus) display 10Be concentrations similar to those of desert dust. This demonstrates that 10Be variations were modulated by climate (i.e., particle transport). Significant positive 10Be peaks (up to 1.6 × 10 8 atoms g - 1 ) appear during intervals of geomagnetic anomalies in Lake Lisan stratigraphy and in the global record (i.e. during the Laschamp geomagnetic event at ~ 41 ka BP). This indicates that 10Be atmospheric production signal is superimposed on the climatic 10Be variations. We conclude that after "de-trending" of the climatic signal, Lake Lisan sediments may be used as

  12. A 420 Year Annual 10Be Record from the WAIS Divide Ice Core

    NASA Astrophysics Data System (ADS)

    Woodruff, T. E.; Welten, K. C.; Caffee, M. W.; Nishiizumi, K.

    2011-12-01

    Annual ice layers archive the cosmogenic radionuclide 10Be, which is in turn an important proxy for solar activity, complementary to the 14C tree ring archive. Although production is primarily determined by the strength of the solar magnetic field 10Be deposition is also determined by local weather phenomena and snow accumulation rates, especially within shorter timescales. Accordingly, multiple ice core records of varying locations and accumulation rates are necessary to build a representative 10Be archive. We are presently engaged in a study to obtain continuous 10Be and 36Cl records in the West Antarctic Ice Sheet (WAIS) Divide ice core, a high snow accumulation site analogous to the GISP2 core from Greenland (Finkel and Nishiizumi1997). Here we present an annual resolution record of 10Be in the WAIS Divide core spanning the last 420 years including the Maunder (1645-1715 AD) and Dalton (1790-1830 AD) solar minima. Preliminary results for the periods of 1580-1740 and 1945-2006 AD show that the10Be flux during the Maunder Minimum was ~60% higher than in the last 60 years (4.8 vs. 3.0 x 105 atoms yr-1 cm-2). Although the low sunspot numbers during the Maunder Minimum suggest little change in solar activity, the 10Be data show that the heliomagnetic field strength continued to vary in a 11-year cycle, as observed in other annual 10Be records (e.g., Beer et al. 1990; Berggren et al. 2009). The 10Be record for the WAIS Divide core will be compared to 10Be records of Greenland ice cores as well as the 14C tree ring record. Acknowledgment. This work was supported by NSF grants ANT-0839042 and 0839137. Beer J. et al. 1990.Nature 347, 164. Finkel R. C. and Nishiizumi K. 1997.J. Geophys. Res. 102, 26,699. Berggren A.- M., et al. 2009. Geophys. Res. Lett. 36, L11801.

  13. Further improvement for 10Be measurement on an upgraded compact AMS radiocarbon facility

    NASA Astrophysics Data System (ADS)

    Fu, Dongpo; Ding, Xingfang; Liu, Kexin; Müller, Arnold Milenko; Suter, Martin; Christl, Marcus; Zhou, Liping; Synal, Hans-Arno

    2015-10-01

    The Peking University 500 kV NEC compact AMS radiocarbon facility (PKU-CAMS) has been modified in order to have additionally the possibility to measure 10Be. In the preliminary experiment a silicon nitride foil was mounted in front of the electrostatic deflector as passive boron degrader, and the original Si detector for radiocarbon detection was replaced by an ETHZ-designed high-resolution ΔE - Eres gas ionization chamber (GIC) for 10Be identification. This simple arrangement has yielded an overall 10Be transmission of 2.2% and a 10Be/9Be background level of 3.5 × 10-14. To further reduce the background and increase the transmission by re-focusing the 10Be ions, an additional 90° bending magnet with 350 mm radius was installed after the electrostatic deflector. The silicon detector was shifted slightly relative to its position of original NEC system setup in opposite direction of beam and can be lifted up manually without breaking vacuum when 10Be measurements are carried out. In this way the system can be easily and fast set up for 10Be without affecting any parameters for radiocarbon measurement. The gas detector for 10Be was mounted at the end of the beam line after the additional magnet. The lay-out of the upgraded spectrometer is very compact and does not require more space than the original instrument. Using this compact setup, the overall transmission for 10Be was doubled to 5-6% and the 10Be/9Be background level was reduced to radios as low as 2.4 × 10-15.

  14. Range fires: A significant factor in exposure-age determination and geomorphic surface evolution

    SciTech Connect

    Bierman, P.; Gillespie, A. )

    1991-06-01

    Physical weathering of rock (spalling), removal of adhered rock varnish, and diffusive loss of noble gases are accelerated by heating in range fires, a dramatic and widespread geomorphic process that must be considered when samples are collected for determining surface exposure ages or for measuring in situ production rates of cosmogenic isotopes. Exposure ages and production rates will be minima if the effects of spalling and/or the effects of accelerated diffusive loss of gaseous isotopes such as He and Ne are not considered. To minimize the effect of fire-induced diffusive loss, samples for noble-gas analysis should be collected 5-10 cm below the rock surface or form outcrops that are unlikely to have been heated by fire. In addition, by determining the concentration of in situ produced cosmogenic isotopes of different half-lives, the magnitude of spalling loss (site-specific erosion rate) can be constrained for each sample.

  15. Reconstruction of glacier fluctuations in the Western Alps since the LGM using OSL surface exposure dating

    NASA Astrophysics Data System (ADS)

    Lehmann, Benjamin; King, Georgina; Valla, Pierre; Herman, Frederic

    2016-04-01

    Providing tight spatial/temporal constraints on late-Pleistocene glacier fluctuations remains an important challenge for understanding glacier response to climate change. In most mountainous settings, paleo-glacier reconstructions are limited because they lack precise temporal constraint, which would enable their use as a paleoclimate proxy. OSL-surface exposure dating has been recently proposed [Sohbati et al., 2011] and offers the potential to improve paleo-glacier reconstruction. Because the OSL signal is sensitive to light, OSL-signal bleaching within a rock sample depends on its exposure time and environmental conditions, and can therefore be used to date the exposure time of glacially-polished bedrock or erratic boulders. However, successful application of this technique first requires calibration and validation. Here, we focus on the Mer de Glace glacier (Mont Blanc massif, France) where the post-LGM glacier dynamics remain poorly constrained with numerous short glacier re-advances occuring during the mid-Pleistocene and Holocene [LeRoy et al., 2015]. First, the different parameters involved in OSL surface exposure dating were calibrated. Vertical transect of polished bedrock surfaces with known exposure ages (from 10 to 165 years) from the Montenvers train station (1913 m a.sl.) to the present-day position of the Mer de Glace (1600 m a.s.l.) was sampled. Secondly, we sampled the Trelaporte transect where exposed bedrock surfaces are of uniform lithology. Here, we will apply similar approach on a much longer timescale, from the Last Glacial Maximum (LGM, ~24 ka, Coutterand et al., 2006) to the present day. OSL data from rock slices show increasing exposure age with elevation which is consitent with glacier thinning since the Little Ice Age. Moreover, our results confirmed the possibility to first calibrate the model parameters on known-age surface and use it to constrain the exposure time for nearby bedrock surfaces. In summary, OSL-surface exposure dating

  16. Surface morphology and morphometry of rat alveolar macrophages after ozone exposure

    SciTech Connect

    Dormans, J.A.; Rombout, P.J.; van Loveren, H. )

    1990-09-01

    As the ultrastructural data on the effects of ozone on pulmonary alveolar macrophages (PAM) are lacking, transmission (TEM) and scanning (SEM) electron microscopy were performed on rat PAM present in alveolar lavages following exposure to ozone. Rats were continuously exposed for 7 d to ozone concentrations ranging from 0.25 to 1.50 mg/m3 for 7 d followed by a 5-d recovery period. Additionally, morphometry on lung sections was performed to quantitate PAM. In a second experiment rats were continuously exposed to 1.50 mg O3/m3 for 1, 3, 5, or 7 d. To study the influence of concurrent ozone exposure and lung infection, due to Listeria monocytogenes, rats were exposed for 7 d to 1.50 mg O3/m3 after a Listeria infection. The surface area of lavaged control PAM was uniformly covered with ruffles as shown by SEM and TEM. Exposure to 0.5 mg ozone/m3 for 7 d resulted in cells partly covered with microvilli and blebs in addition to normal ruffles. The number of large size PAM increased with an increase in ozone concentration. After 1 d of exposure, normal-appearing as well as many small macrophages with ruffles and scattered lymphocytes were seen. Lavage samples taken after 5 or 7 d of exposure showed an identical cell composition to that taken after 3 d of exposure. After Listeria infection alone, lavage samples consisted of mainly lymphocytes and some macrophages. Small quantitative changes, such as an increase in the number of polymorphonuclear neutrophils and large-size PAM, occurred in lavages after ozone exposure and infection with L. monocytogenes. Morphometric examination of lung sections revealed a concentration-related increase in the number of PAM, even in animals exposed to 0.25 mg ozone/m3 for 7 d. Centriacinar regions were more severely affected than other regions of lung tissue.

  17. Aluminum 26, {sup 10}Be, and {sup 36}Cl depth profiles in the Canyon Diablo iron meteorite

    SciTech Connect

    Michlovich, E.S.; Elmore, D.; Vogt, S.; Lipschutz, M.E.; Masarik, J.; Reedy, R.C.

    1994-11-25

    The authors have measured activities of the long-lived cosmogenic radionuclides {sup 26}Al, {sup 10}Be, and {sup 36}Cl in 12 fragments of the iron meteorite Canyon Diablo and have constructed production rate-versus-depth profiles of those radionuclides. Profiles determined using differential particle fluxes calculated with the LAHET code system are in good agreement with {sup 26}Al, {sup 10}Be, and {sup 36}Cl experimental data, but the agreement for {sup 36}Cl was obtained only after neutron-induced cross sections were modified. Profiles calculated with lunar particle fluxes are much lower than experimental Canyon Diablo profiles. The cosmic ray exposure ages of most samples are near 540 m.y. 34 refs., 4 figs., 2 tabs.

  18. An episode of rapid bedrock channel incision during the last glacial cycle, measured with 10Be

    USGS Publications Warehouse

    Reusser, L.; Bierman, P.; Pavich, M.; Larsen, J.; Finkel, R.

    2006-01-01

    We use 10Be to infer when, how fast, and why the Susquehanna River incised through bedrock along the U.S. Atlantic seaboard, one of the world's most prominent and ancient passive margins. Although the rate at which large rivers incise rock is a fundamental control on the development of landscapes, relatively few studies have directly measured how quickly such incision occurs either in tectonically active environments or along passive margins. Exposure ages of fluvially carve d, bedrock strath terraces, preserved along the lower Susquehanna River, demonstrate that even along a passive margin, large rivers are capable of incising through rock for short periods of time at rates approaching those recorded in tectonically active regions, such as the Himalayas. Over eighty samples, collected along and between three prominent levels of strath terraces within Holtwood Gorge, indicate that the Susquehanna River incised more than 10 meters into the Appalachian Piedmont during the last glacial cycle. Beginning ???36 ka, incision rates increased dramatically, and remained elevated until ???14 ka. The northern half of the Susquehanna basin was glaciated during the late Wisconsinan; however, similar rates and timing of incision occurred in the unglaciated Potomac River basin immediately to the south. The concurrence of incision periods on both rivers suggests that glaciation and associated meltwater were not the primary drivers of incision. Instead, it appears that changing climatic conditions during the late Pleistocene promoted an increase in the frequency and magnitude of flood events capable of exceeding thresholds for rock detachment and bedrock erosion, thus enabling a short-lived episode of rapid incision into rock. Although this study has constraine d the timing and rate of bedrock incision along the largest river draining the Atlantic passive margin, the dates alone cannot explain fully why, or by what processes, this incision occurred. However, cosmogenic dating offers

  19. Last Glacial Maximum Dated by Means of 10Be in the Maritime Alps (Italy)

    NASA Astrophysics Data System (ADS)

    Granger, D. E.; Spagnolo, M.; Federici, P.; Pappalardo, M.; Ribolini, A.; Cyr, A. J.

    2006-12-01

    Relatively few exposure dates of LGM moraines boulders are available for the European Alps, and none on the southern flank. Ponte Murato (PM) is a frontal moraine at 860 m asl in the Gesso Basin (Maritime Alps, SW European Alps). The PM moraine dams the 157 km2 Gesso della Barra Valley and it represents the lowermost frontal moraine of the entire Gesso Valley, near the outlet of the valley in the Po Plain. Its ELA, determined from the paleo- shape of the supposed Gesso della Barra glacier, is 1746 m asl. Tetti Bandito (TB) is a small and badly preserved glacial deposit, tentatively attributed to a lateral-frontal moraine, that is positioned 5 km downvalley from the PM deposit at 800 m asl. There are no other glacial deposits downvalley from the TB moraine in the Gesso Basin or farther NE in the piedmont region of the upper Po Plain. Boulders sampled on the PM and on the TB moraine crests gave a 10Be cosmogenic age of respectively 16300 ± 880 ka (average value) and 18798 ± 973 ka. This result constrains the PM frontal moraine within the LGM interval but also suggests that the maximum expansion of the Gesso Basin glacier was more downvalley at some point during the last glaciation. If the TB is a lateral-frontal moraine as supposed, the two TB and PM moraines would represent the outer and inner moraine crests of the same LGM stadial, with the outer moraine much less pronounced than the inner moraine, similarly to the maximalstand and the hochstand described in the Eastern Alps (Van Husen, 1997). Within this perspective, the PM and TB dates are consistent with a European Alps LGM corresponding to MIS 2 (Ivy-Ochs et al., 2004). This study of the Maritime Alps moraines is also in agreement with the Upper Würm climatic theory (Florineth and Schlüchter, 2000) of a stronger influence of the W and SW incoming humid airflows in the European Alps, differently from the nearby Vosges and Pyrenees mountain chains where more dry conditions were probably responsible for a very

  20. Correlation of External Exposure and Dose Equivalent Rates with Uranium Surface Contamination

    SciTech Connect

    Ashley, J.C.; Bogard, J.S.; Brown, K.S.; England, C.A.; Hamm, R.N.; Turner, J.E.

    1999-06-01

    This report provides both calculated estimates and measured values of exposure in air and tissue dose from external penetrating radiation at a distance of 1 m from uranium contamination on surfaces at the Oak Ridge Y-12 Plant, in support of the Y-12 Site Radiological Characterization Study. Calculated values are based on the total energy from gamma rays and X rays emitted by uranium and its shordaughters at secular equilibrium. Results of a small number of measurements are provided for comparison. Dose rate values derived here are limited to those of external penetrating radiation from distributed sources with limited surface area and from point sources.

  1. Investigation of the possible association of 10Be and 26Al with biogenic matter in the marine environment

    NASA Astrophysics Data System (ADS)

    Bourles, D.; Raisbeck, G. M.; Yiou, F.; Loiseaux, J. M.; Lieuvin, M.; Klein, J.; Middleton, R.

    1984-11-01

    As part of a more general investigation of the mechanism by which 10Be and 26Al are transported in the ocean, and eventually incorporated in various marine reservoirs, and the extent to which they are homogenized with 9Be and 27Al, we are studying the possible association of these isotopes with biogenic matter in the marine environment. To this end we have made measurements of 10Be and 9Be in: (a) the carbonate fraction of several marine animals (clam, cockel, starfish, mussel) and the organic fraction of mussels; (b) 20 samples of a 460 m coral reef core extending from the present to ˜ 7 Ma ago; (c) 2 samples of marine plankton; (d) 1 sample of paniculate matter in ocean surface water. 26Al has been measured in two coral samples. 10Be measurements have been made on the Grenoble cyclotron, the University of Pennsylvania tandem and, most recently, on the French Tandetron. 26Al was measured at the Pennsylvania tandem. 9Be and 27Al were measured using flameless atomic absorption spectrometry. These investigations have taken on added significance with the discovery of 10Be in crude petroleum, and the possibility that 14Be concentration (or 10Be/ 9Be ratios) might be used to estimate the age of recent petroleum, or petroleum precursor, formation.

  2. Meteoric 10Be as a tool to investigate human induced soil fluxes: a conceptual model

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; De Vente, Joris; Boix-Fayos, Carolina; Minella, Jean; Baken, Stijn; Smolders, Erik

    2014-05-01

    The use of meteoric 10Be as a tool to understand long term landscape behavior is becoming increasingly popular. Due its high residence time, meteoric 10Be allows in principle to investigate in situ erosion rates over time scales exceeding the period studied with classical approaches such as 137Cs. The use of meteoric 10Be strongly contributes to the traditional interpretation of sedimentary archives which cannot be unequivocally coupled to sediment production and could provide biased information over longer time scales (Sadler, 1981). So far, meteoric 10Be has successfully been used in geochemical fingerprinting of sediments, to date soil profiles, to assess soil residence times and to quantify downslope soil fluxes using accumulated 10Be inventories along a hill slope. However, less attention is given to the potential use of the tracer to directly asses human induced changes in soil fluxes through deforestation, cultivation and reforestation. A good understanding of the processes governing the distribution of meteoric 10Be both within the soil profile and at landscape scale is essential before meteoric 10Be can be successfully applied to assess human impact. We developed a spatially explicit 2D-model (Be2D) in order to gain insight in meteoric 10Be movement along a hillslope that is subject to human disturbance. Be2D integrates both horizontal soil fluxes and vertical meteoric 10Be movement throughout the soil prolife. Horizontal soil fluxes are predicted using (i) well studied geomorphical laws for natural erosion and soil formation as well as (ii) human accelerated water and tillage erosion. Vertical movement of meteoric 10Be throughout the soil profile is implemented by inserting depth dependent retardation calculated using experimentally determined partition coefficients (Kd). The model was applied to different environments such as (i) the Belgian loess belt, characterized by aeolian deposits enriched in inherited meteoric 10Be, (ii) highly degraded and stony

  3. 10Be in ice - four decades, two ice sheets, 15 deep coring sites

    NASA Astrophysics Data System (ADS)

    Berggren, Ann-Marie; Aldahan, Ala; Possnert, Göran

    2010-05-01

    Over the last few decades, numerous studies of 10Be in ice cores from Antarctica and Greenland have comprised a significant source of information on climate, solar activity and geomagnetic field intensity over the past 800 000 years. There is, however, a large variability in the available 10Be records in terms of resolution and time coverage. We here present a comprehensive summary of results that have been put forward since the 1960s. Marine sediment was the first type of natural archive in which 10Be was detected (Arnold, 1956), and a decade later McCorkell et al. (1967) pioneered the ice archive field by counting 10Be beta activity in samples from Camp Century, Greenland. The method demands a large amount of material; in this case 1.2×106 litres of water were used. Using accelerator mass spectrometry, AMS, Raisbeck et al. (1978) undertook the second study of 10Be in polar ice, measuring 10Be concentrations in ice from Dome C, Antarctica. The AMS technique is exclusively used today for measurements of 10Be in small ice volumes (

  4. A preliminary study on the use of (10)Be in forensic radioecology of nuclear explosion sites.

    PubMed

    Whitehead, N E; Endo, S; Tanaka, K; Takatsuji, T; Hoshi, M; Fukutani, S; Ditchburn, R G; Zondervan, A

    2008-02-01

    Cosmogenic (10)Be, known for use in dating studies, unexpectedly is also produced in nuclear explosions with an atom yield almost comparable to (e.g.) (137)Cs. There are major production routes via (13)C(n, alpha)(10)Be, from carbon dioxide in the air and the organic explosives, possibly from other bomb components and to a minor extent from the direct fission reaction. Although the detailed bomb components are speculative, carbon was certainly present in the explosives and an order of magnitude calculation is possible. The (n, alpha) cross-section was determined by irradiating graphite in a nuclear reactor, and the resulting (10)Be estimated by Accelerator Mass Spectrometry (AMS) giving a cross-section of 34.5+/-0.7mb (6-9.3MeV), within error of previous work. (10)Be should have applications in forensic radioecology. Historical environmental samples from Hiroshima, and Semipalatinsk (Kazakhstan) showed two to threefold (10)Be excesses compared with the background cosmogenic levels. A sample from Lake Chagan (a Soviet nuclear cratering experiment) contained more (10)Be than previously reported soils. (10)Be may be useful for measuring the fast neutron dose near the Hiroshima bomb hypocenter at neutron energies double those previously available. PMID:17904707

  5. Cutaneous exposure scenarios for engineered nanoparticles used in semiconductor fabrication: a preliminary investigation of workplace surface contamination

    PubMed Central

    Shepard, Michele; Brenner, Sara

    2014-01-01

    Background: Numerous studies are ongoing in the fields of nanotoxicology and exposure science; however, gaps remain in identifying and evaluating potential exposures from skin contact with engineered nanoparticles in occupational settings. Objectives: The aim of this study was to identify potential cutaneous exposure scenarios at a workplace using engineered nanoparticles (alumina, ceria, amorphous silica) and evaluate the presence of these materials on workplace surfaces. Methods: Process review, workplace observations, and preliminary surface sampling were conducted using microvacuum and wipe sample collection methods and transmission electron microscopy with elemental analysis. Results: Exposure scenarios were identified with potential for incidental contact. Nanoparticles of silica or silica and/or alumina agglomerates (or aggregates) were identified in surface samples from work areas where engineered nanoparticles were used or handled. Conclusions: Additional data are needed to evaluate occupational exposures from skin contact with engineered nanoparticles; precautionary measures should be used to minimize potential cutaneous exposures in the workplace. PMID:25000112

  6. Short term variations of 7Be, 10Be concentrations in atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Yamagata, Takeyasu; Sugihara, Sinji; Morinaga, Ichiro; Matsuzaki, Hiroyuki; Nagai, Hisao

    2010-04-01

    To compare meteorological conditions, short term variations of atmospheric concentrations of 7Be ( T1/2 = 53.3 days) and 10Be ( T1/2 = 1.5 × 10 6 years) were investigated at Tokyo and Fukuoka, Japan, and Pacific Ocean nearby Japan. Atmospheric concentrations of 7Be and 10Be at anticyclone condition were higher than that at cyclone condition to a factor of 2-10. Because of being influenced by re-suspended components from soil ( 10Be/ 7Be > 1000), temporal variability of 10Be/ 7Be was high in daytime and low in nighttime. But when corrected for re-suspended component using Al concentration as an indicator of soil the 10Be/ 7Be ratio was constant. Comparing 7Be and 10Be concentrations with 212Pb concentration as soil-generated component, we make a conclusion that high 7Be and 10Be concentration air mass is brought into boundary layer by high convection at daytime. Those diurnal variations were not observed in marine boundary layer. When cyclone passed through Fukuoka to Tokyo, which is 12 h behind, 7Be and 10Be concentrations also decreased with 12 h lag between Fukuoka and Tokyo. The 10Be/ 7Be ratio was constant during anticyclone to cyclone condition, and between Tokyo and Fukuoka. We conclude that after stratospheric aerosols enter into the upper troposphere they reside there for a certain period and mix uniformly in horizontal strata; later they are transported down to lower troposphere by anticyclone and penetrate into ground level air at daytime by convective strong mixing of boundary layer.

  7. Testing the potential of 10Be in varved sediments from two lakes for solar activity reconstruction

    NASA Astrophysics Data System (ADS)

    Czymzik, Markus; Muscheler, Raimund; Brauer, Achim; Adolphi, Florian; Ott, Florian; Kienel, Ulrike; Dräger, Nadine; Slowinski, Michal; Aldahan, Ala; Possnert, Göran

    2015-04-01

    The potential of 10Be in annually laminated (varved) lake sediments for solar activity reconstruction is, to date, largely unexplored. It is hypothesized that 10Be contents in sediments from well-chosen lakes reflect the solar induced atmospheric production signal. The varved nature of these archives provides the chance to establish solar activity time-series with very high temporal precision. However, so far solar activity reconstruction from 10Be in varved lake sediments is hampered due to a lack of detailed knowledge of the process chain from production in the atmosphere to deposition on the lake floor. Calibrating 10Be time-series from varved lake sediments against complementary proxy records from the same sediment archive as well as instrumental meteorological and solar activity data will allow a process-based understanding of 10Be deposition in these lakes and a quantitative evaluation of their potential for solar activity reconstruction. 10Be concentration and flux time-series at annual resolution were constructed for the period 1983 to 2007 (approx. solar cycles 22 and 23) conducting accelerator mass spectrometry and varve chronology on varved sediments of Lakes Tiefer See and Czechowski, located on an east-west transect at a distance of about 450 km in the lowlands of northern-central Europe. 10Be concentrations vary between 0.9 and 1.8*108atoms/g, with a mean of 1.3*108atoms/g in Lake Tiefer See and between 0.6 and 1.6*108atoms/g, with a mean of 1*108atoms/g in Lake Czechowski. Calculated mean 10Be flux is 2.3*108atoms/cm2/year for Lake Tiefer See and 0.7*108atoms/cm2/year for Lake Czechowski. Calibrating the 10Be time-series against corresponding geochemical μ-XRF profiles, varve thickness and total organic carbon records as well as precipitation data from the nearby stations Schwerin for Lake Tiefer See and Koscierzyna for Lake Czechowski and a neutron monitor record of solar activity suggests (1) a complex interaction of varying processes influencing

  8. Full Mission Astronaut Radiation Exposure Assessments for Long Duration Lunar Surface Missions

    NASA Technical Reports Server (NTRS)

    Adamczyk, Anne M.; Clowdsley, Martha S.; Qualls, Garry D.; Blattnig, Steve B.; Lee, Kerry T.; Fry, Dan J.; Stoffle, Nicholas N.; Simonsen, Lisa C.; Slaba, Tony C.; Walker, Steven A.; Zapp, Edward N.

    2010-01-01

    Risk to astronauts due to ionizing radiation exposure is a primary concern for missions beyond Low Earth Orbit (LEO) and will drive mission architecture requirements, mission timelines, and operational practices. Both galactic cosmic ray (GCR) and solar particle event (SPE) environments pose a risk to astronauts for missions beyond LEO. The GCR environment, which is made up of protons and heavier ions covering a broad energy spectrum, is ever present but varies in intensity with the solar cycle, while SPEs are sporadic events, consisting primarily of protons moving outward through the solar system from the sun. The GCR environment is more penetrating and is more difficult to shield than SPE environments, but lacks the intensity to induce acute effects. Large SPEs are rare, but they could result in a lethal dose, if adequate shielding is not provided. For short missions, radiation risk is dominated by the possibility of a large SPE. Longer missions also require planning for large SPEs; adequate shielding must be provided and operational constraints must allow astronauts to move quickly to shielded locations. The dominant risk for longer missions, however, is GCR exposure, which accumulates over time and can lead to late effects such as cancer. SPE exposure, even low level SPE exposure received in heavily shielded locations, will increase this risk. In addition to GCR and SPE environments, the lunar neutron albedo resulting mainly from the interaction of GCRs with regolith will also contribute to astronaut risk. Full mission exposure assessments were performed for proposed long duration lunar surface mission scenarios. In order to accomplish these assessments, radiation shielding models were developed for a proposed lunar habitat and rover. End-to-End mission exposure assessments were performed by first calculating exposure rates for locations in the habitat, rover, and during extra-vehicular activities (EVA). Subsequently, total mission exposures were evaluated for

  9. 10Be dating of the Narsarsuaq moraine in southernmost Greenland: evidence for a late-Holocene ice advance exceeding the Little Ice Age maximum

    NASA Astrophysics Data System (ADS)

    Winsor, K.; Carlson, A. E.; Rood, D. H.

    2014-08-01

    In southernmost Greenland near Narsarsuaq, the terminal Narsarsuaq moraine was deposited well outside of a historical Little Ice Age (LIA) moraine adjacent to the modern ice margin. Using 10Be surface exposure dating, we determine Narsarsuaq moraine abandonment at 1.51 ± 0.11 ka. A second set of 10Be ages from a more ice-proximal position shows that ice has been within or at its historical (i.e., LIA) extent since 1.34 ± 0.15 ka. Notably, Narsarsuaq moraine abandonment was coincident with climate amelioration in southern Greenland. Southern Greenland warming at ˜1.5 ka was also concurrent with the end of the Roman Warm Period as climate along the northern North Atlantic sector of Europe cooled into the Dark Ages. The warming of southern Greenland and retreat of ice from the Narsarsuaq moraine is consistent with studies suggesting possible anti-phase centennial-scale climate variability between northwestern Europe and southern Greenland. Other southernmost Greenland ice-margin records do not preclude a pre-LIA ice-margin maximum, potentially concurrent with a Narsarsuaq advance prior to ˜1.51 ka, but also lack sufficient ice-margin control to confirm such a correlation. We conclude that there is a clear need to further determine whether a late-Holocene pre-LIA maximum was a local phenomenon or a regional southern Greenland ice maximum, and if this advance and retreat reflects a regional fluctuation in climate.

  10. Preliminary Cosmogenic Surface Exposure Ages on Laurentide Ice-sheet Retreat and Opening of the Eastern Lake Agassiz Outlets

    NASA Astrophysics Data System (ADS)

    Leydet, D.; Carlson, A. E.; Sinclair, G.; Teller, J. T.; Breckenridge, A. J.; Caffee, M. W.; Barth, A. M.

    2015-12-01

    The chronology for the eastern outlets of glacial Lake Agassiz holds important consequences for the cause of Younger Dryas cold event during the last deglaciation. Eastward routing of Lake Agassiz runoff was originally hypothesized to have triggered the Younger Dryas. However, currently the chronology of the eastern outlets is only constrained by minimum-limiting radiocarbon ages that could suggest the eastern outlets were still ice covered at the start of the Younger Dryas at ~12.9 ka BP, requiring a different forcing of this abrupt climate event. Nevertheless, the oldest radiocarbon ages are still consistent with an ice-free eastern outlet at the start of the Younger Dryas. Here we will present preliminary 10-Be cosmogenic surface exposure ages from the North Lake, Flat Rock Lake, glacial Lake Kaministiquia, and Lake Nipigon outlets located near Thunder Bay, Ontario. These ages will date the timing of the deglaciation of the Laurentide ice sheet in the eastern outlet region of glacial Lake Agassiz. This will provide an important constraint for the hypothesized freshwater forcing of the cause of Younger Dryas cold event.

  11. Investigation of 10Be and its cluster dynamics with the nonlocalized clustering approach

    NASA Astrophysics Data System (ADS)

    Lyu, Mengjiao; Ren, Zhongzhou; Zhou, Bo; Funaki, Yasuro; Horiuchi, Hisashi; Röpke, Gerd; Schuck, Peter; Tohsaki, Akihiro; Xu, Chang; Yamada, Taiichi

    2016-05-01

    We extend the concept of nonlocalized clustering to the nucleus 10Be with proton number Z =4 and neutron number N =6 (N =Z +2 ). The Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function is formulated for the description of different structures of 10Be. Physical properties such as energy spectrum and root-mean-square radii are calculated for the first two 0+ states and corresponding rotational bands. With only one single THSR wave function, the calculated results show good agreement with other models and experimental values. We apply, for the first time, the THSR wave function on the chain orbit (σ -orbit) structure in the 02+ state of 10Be. The ring-orbit (π -orbit) and σ -orbit structures are further illustrated by calculating the density distribution of the valence neutrons. We also investigate the nonlocalized dynamics of α clusters and the correlations of two valence neutrons in 10Be.

  12. Analysis of T = 1 {sup 10}B States Analogue to {sup 10}Be Cluster States

    SciTech Connect

    Uroic, M.; Miljanic, D.; Blagus, S.; Bogovac, M.; Prepolec, L.; Skukan, N.; Soic, N.; Majer, M.; Milin, M.; Lattuada, M.; Musumarra, A.; Acosta, L.

    2009-08-26

    Current status of the search for T = 1 cluster states in {sup 10}Be, {sup 10}B and {sup 10}C is presented. The best known of the three, {sup 10}Be, has an established rotational band (6.18, 7.54 and 10.15 MeV) with unusually large moment of inertia. Search of their isobaric analogue in {sup 10}B is presented, with emphasis on {sup 3}He+{sup 11}B reaction.

  13. /sup 10/Be in polar ice: Data reflect changes in cosmic ray flux or polar meteorology

    SciTech Connect

    Lal, D.

    1987-08-01

    We have theoretically estimated the expected changes in the global cosmic ray production of /sup 10/Be in the atmosphere with changes in solar activity, and the consequent variations in its fallout in the polar regions. The global /sup 10/Be production rate is found to be about 20% higher during periods of very low solar activity, compared to the average solar modulation level observed during the past 3 solar cycles. The stratospheric /sup 10/Be fallout pattern has been derived using the fallout data for /sup 90/Sr as an analog. This fallout shows an amplitude attenuation by a factor of about three at 70/sup 0/; the higher the latitude, the higher the attenuation. The results have been compared with the long time series available for /sup 10/Be in polar ice in Greenland and in Antarctica, 70/sup 0/--78/sup 0/ latitude. It is concluded that the observed variations in /sup 10/Be concentrations in ice cores are primarily due to climatic changes, for both short and long period variations. Thus /sup 10/Be data can be used as a proxy for climate induced meteorological changes in the polar region. copyright American Geophysical Union 1987

  14. Preparation of ASTER in-house 10Be/9Be standard solutions

    NASA Astrophysics Data System (ADS)

    Braucher, R.; Guillou, V.; Bourlès, D. L.; Arnold, M.; Aumaître, G.; Keddadouche, K.; Nottoli, E.

    2015-10-01

    Since its commissioning in 2006, the commercially available certificated National Institute of Standards and Technology standard reference material NIST SRM 4325 is used at the French national facility ASTER (CEREGE, Aix-en-Provence) to normalize 10Be measurements. This standard solution being no longer disposable, we thus decided to produce in-house standards. As a first attempt, a STD-12 standard (10Be/9Be = (4.939 ± 0.053) × 10-12) has been prepared from 2.5 kg of marine sediments with an adapted chemical protocol. Then, a 10Be enriched solution of known concentration being available, a STD-11 standard (10Be/9Be = (1.191 ± 0.013) × 10-11) that will be used at ASTER in the near future to calibrate 10Be measurements and its dilution to the 10-14 level (STD-14 (10Be/9Be = (5.468 ± 0.064) × 10-14)) have been prepared from it.

  15. Studies of Itokawa's Surface Exposure by Measurements of Cosmic-ray Produced Nuclides

    NASA Technical Reports Server (NTRS)

    Caffee, M. W.; Nishiizumi, K.; Tsuchiyama, A.; Uesugi, M.; Zolensky, M. E.

    2014-01-01

    We plan to investigate the evolutionary history of surface materials from 25143 Itokawa, the Hayabusa samples. Our studies are based on the measurement of nuclides produced in asteroidal surface materials by cosmic rays. Cosmogenic radionuclides are used to determine the duration and nature of the exposure of materials to energetic particles. Our goals are to understand both the fundamental processes on the asteroidal surface and the evolutionary history of its surface materials. They are also key to understanding the history of Itokawa's surface and asteroid-meteoroid evolutionary dynamics. To achieve our key goals, in particular reconstructing the evolutionary histories of the asteroidal surface, we proposed: (1) characterizing Itokawa particles using SXCT, SXRD, and FE-SEM without modification of the sample; (2) embedding each particle in acrylic resin, then slicing a small corner with an ultra-microtome and examining it using super-STEM and SIMS for characterizing surface morphology, space weathering, and oxygen three-isotope analysis; and finally (3) measuring small amounts of cosmogenic radionuclides (104-105 atoms) in Hayabusa samples by AMS. However, we have to modify our plan due to unexpected situation.

  16. Exterior surface dust lead, interior house dust lead and childhood lead exposure in an urban environment

    SciTech Connect

    Bornschein, R.L.; Succop, P.A.; Krafft, K.M.; Clark, C.S.; Peace, B.; Hammond, P.B.

    1986-01-01

    The impact of urban lead exposure is being examined in a prospective study of several hundred children followed from birth to five years of age. A wide range of social, behavioral, biological and environmental factors are being assessed at approximately one year intervals beginning at birth. Previous analyses on this cohort have indicated a strong relationship between hand lead and hand-to-mouth activity and suggests that this is an important mechanism of inadvertent ingestion of lead in infants and young children. The present analyses was undertaken to examine the joint influence of lead in exterior surface dust and interior lead-containing painted surfaces on lead levels in house dust. In addition the joint influence of exterior and interior surface dust lead on children's hand lead content and blood lead concentration was examined. At 18 months of age 38% of the observed variation in blood lead was accounted for by hand lead and dust lead. Interior paint lead and exterior surface dust lead accounted for 52% of the observed variation in interior surface dust lead concentration. Exterior surface dust lead, obtained from exterior surface scrapings, indirectly influenced blood lead through its impact on interior house dust lead and children's hand lead content, but had no observable direct impact on blood lead. 13 references, 4 figures, 3 tables.

  17. Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating

    NASA Astrophysics Data System (ADS)

    Sohbati, Reza; Murray, Andrew S.; Chapot, Melissa S.; Jain, Mayank; Pederson, Joel

    2012-09-01

    We pioneer a technique of surface-exposure dating based upon the characteristic form of an optically stimulated luminescence (OSL) bleaching profile beneath a rock surface; this evolves as a function of depth and time. As a field illustration of this new method, the maximum age of a premier example of Barrier Canyon Style (BCS) rock art in Canyonlands National Park, Utah, USA, is constrained. The natural OSL signal from quartz grains is measured from the surface to a depth of >10 mm in three different rock samples of the Jurassic Navajo Sandstone. Two samples are from talus with unknown daylight exposure histories; one of these samples was exposed at the time of sampling and one was buried and no longer light exposed. A third sample is known to have been first exposed 80 years ago and was still exposed at the time of sampling. First, the OSL-depth profile of the known-age sample is modeled to estimate material-dependent and environmental parameters. These parameters are then used to fit the model to the corresponding data for the samples of unknown exposure history. From these fits we calculate that the buried sample was light exposed for ˜700 years before burial and that the unburied sample has been exposed for ˜120 years. The shielded surface of the buried talus sample is decorated with rock art; this rock fell from the adjacent Great Gallery panel. Related research using conventional OSL dating suggests that this rockfall event occurred ˜900 years ago, and so we deduce that the rock art must have been created between ˜1600 and 900 years ago. Our results are the first credible estimates of exposure ages based on luminescence bleaching profiles. The strength of this novel OSL method is its ability to establish both ongoing and prior exposure times, at decadal to millennial timescales or perhaps longer (depending on the environmental dose rate) even for material subsequently buried. This has considerable potential in many archeological, geological and geo

  18. Dating Plio-Pleistocene glacial sediments using the cosmic-ray-produced radionuclides 10Be and 26Al

    USGS Publications Warehouse

    Balco, G.; Stone, J.O.H.; Jennings, C.

    2005-01-01

    We use the cosmic-ray-produced radionuclides 26Al and 10Be to date Plio-Pleistocene glacial sediment sequences. These two nuclides are produced in quartz at a fixed ratio, but have different decay constants. If a sample is exposed at the surface for a time and then buried by overburden and thus removed from the cosmic-ray flux, the 26Al/10Be ratio is related to the duration of burial. We first attempted to date pre-Wisconsinan tills by measuring 26Al and 10Be in fluvial sediments beneath them and applying the method of "burial dating," which previous authors have used to date river sediment carried into caves. This method, however, requires simplifying assumptions about the 26Al and 10Be concentrations in the sediment at the time of burial. We show that these assumptions are not valid for river sediment in glaciated regions. 26Al and 10Be analyses of such sediment do not provide accurate ages for these tills, although they do yield limiting ages in some cases. We overcome this difficulty by instead measuring 26Al and 10Be in quartz from paleosols that are buried by tills. We use a more general mathematical approach to determine the initial nuclide concentrations in the paleosol at the time it was buried, as well as the duration of burial. This technique provides a widely applicable improvement on other means of dating Plio-Pleistocene terrestrial glacial sediments, as well as a framework for applying cosmogenic-nuclide dating techniques in complicated stratigraphic settings. We apply it to pre-Wisconsinan glacial sediment sequences in southwest Minnesota and eastern South Dakota. Pre-Wisconsinan tills underlying the Minnesota River Valley were deposited 0.5 to 1.5 Ma, and tills beneath the Prairie Coteau in eastern South Dakota and adjacent Minnesota were deposited 1 to 2 Ma.

  19. [sup 14]C and [sup 10]Be evidence for no incursion of the Lake Michigan lobe in northern Illinois from ca. 170 to 25 ka

    SciTech Connect

    Curry, B.B. ); Pavich, M.J. )

    1994-04-01

    Uncorrected [sup 10]Be inventories of a 2.7 m-long section of core indicate surface exposure lasting 115 ka during development of the Sangamon Geosol and 30 ka for a soil complex developed in overlying loessial sediment (Robein Silt). The latter estimate is in agreement with [sup 14]C assays in the region. Taking into account the age of overlying late Wisconsin drift, the new data indicate an age of about 170 ka for the onset of Sangamon pedogenesis in northern Illinois. Previous to this study, there have been no numerical-age determinations for the start of the last interglacial in northern IL. The data confirm a previous hypothesis that the Lake Michigan Lobe did not invade IL contemporaneous with deposition of Roxana Silt, or during the other period of midcontinental loess deposition suggest by TL ages of ca. 70 to 85 ka. The core was collected immediately south of the IL-WI border (42[degree] 30 minutes N, 88[degree] 30 minutes W) near Hebron, IL. Buried by 14 m of late Wisconsin drift, and the interval assayed for [sup 10]Be included 2.0 m of pedogenically-altered Illinoian sand and gravel, and 0.7 m of Wisconsin silt. One AMS [sup 14]C assay of carbonized fragments from the A-horizon of the Sangamon Geosol yielded an age of 38,500 [+-] 5,000 yr B.P.; conventional [sup 14]C ages for the overlying silt are from wood fragments (24,780 [times] 360 yr B.P.) and a bulk soil sample (26,030 [+-] 450 yr B.P.). The range of ages is typical for this stratigraphic sequence in IL. The [sup 10]Be concentration in the lowest part of the silt is 600 atoms/gm. This value is three times greater than the concentration typical of calcareous Mississippi River valley loess and of the C-horizon of the Sangamon Geosol in the core. High concentration of [sup 10]Be in the Robein Silt likely was caused by redeposition of [sup 10]Be-rich B-horizon material eroded from soil profiles elsewhere in the paleobasin.

  20. Chronology of glaciations in the Cantabrian Mountains (NW Iberia) during the Last Glacial Cycle based on in situ-produced 10Be

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rodríguez, Laura; Jiménez-Sánchez, Montserrat; Domínguez-Cuesta, María José; Rinterknecht, Vincent; Pallàs, Raimon; Bourlès, Didier

    2016-04-01

    The mountain ranges of the Iberian Peninsula preserve a valuable record of past glaciations that may help reconstruct past atmospheric circulation patterns in response to cooling events in the North Atlantic Ocean. Available chronologies for the glacial record of the Cantabrian Mountains, which are mainly based on radiocarbon and luminescence dating of glacial-related sediments, suggest that glaciers recorded their Glacial Maximum (GM) during MIS 3 and experienced a later Last Glacial Maximum (LGM) advance. This LGM extent is not established yet, preventing a fair correlation with available Cosmic Ray Exposure (CRE) based chronologies for the glacial record of the Pyrenees and the Sistema Central. We present a glacial reconstruction and a 10Be CRE chronology for the Porma valley, in the southern slope of the central Cantabrian Mountains. Glacial evidence at the lowest altitudes correspond to erratic boulders and composite moraines whose minimum 10Be CRE age of 113.9 ± 7.1 ka suggests that glaciers were at their maximum extent during MIS 5d, most likely in response to the minima in summertime insolation of the Last Glacial Cycle. Recessional moraines preserved within the glacial maximum limits allow the assessment of subsequent glacier advances or stagnations. The most remarkable advance took place prior to 55.7 ± 4.0 ka (probably at the end of MIS 4), consistently with minimum radiocarbon ages previously reported for lacustrine glacial-related deposits in the Cantabrian Mountains. A limited number of 10Be CRE ages from a composite moraine suggest a possible advance of the Porma glacier coeval with the global LGM; the glacier front attributed to the LGM would be placed within the margins of the previous GM like in the western Pyrenees. Erratic boulders perched on an ice-moulded bedrock surface provided a mean 10Be CRE age of 17.7 ± 1.0 ka, suggesting that part of the recessional moraine sequence corresponds to minor advances or stagnations of the glacier fronts

  1. Giant Surface Conductivity Enhancement in a Carbon Nanotube Composite by Ultraviolet Light Exposure.

    PubMed

    Long, Christian J; Orloff, Nathan D; Twedt, Kevin A; Lam, Thomas; Vargas-Lara, Fernando; Zhao, Minhua; Natarajan, Bharath; Scott, Keana C; Marksz, Eric; Nguyen, Tinh; Douglas, Jack F; McClelland, Jabez; Garboczi, Edward; Obrzut, Jan; Liddle, J Alexander

    2016-09-01

    Carbon nanotube composites are lightweight, multifunctional materials with readily adjustable mechanical and electrical properties-relevant to the aerospace, automotive, and sporting goods industries as high-performance structural materials. Here, we combine well-established and newly developed characterization techniques to demonstrate that ultraviolet (UV) light exposure provides a controllable means to enhance the electrical conductivity of the surface of a commercial carbon nanotube-epoxy composite by over 5 orders of magnitude. Our observations, combined with theory and simulations, reveal that the increase in conductivity is due to the formation of a concentrated layer of nanotubes on the composite surface. Our model implies that contacts between nanotube-rich microdomains dominate the conductivity of this layer at low UV dose, while tube-tube transport dominates at high UV dose. Further, we use this model to predictably pattern conductive traces with a UV laser, providing a facile approach for direct integration of lightweight conductors on nanocomposite surfaces. PMID:27468781

  2. 10Be variation in surficial sediments of the Central Indian Basin

    NASA Astrophysics Data System (ADS)

    Nagender Nath, B.; Aldahan, A.; Possnert, G.; Selvaraj, K.; Mascarenhas-Pereira, M. B. L.; Chen, C. T. A.

    2007-06-01

    Distribution of 10Be in systematically collected (degree × degree interval at 10 to 16 °S; 73.5 to 76.5 °E) surficial siliceous ooze, siliceous clay and pelagic clay sediments (top 2 cm) from the abyssal Central Indian Basin and the Andaman Sea is used to evaluate sources and to decipher the transport pathways of sediment particles, demarcate sediment depocenters and erosional areas. While 10Be concentrations display a wide variation (0.12-5.56 × 109 atoms g-1) with an average of 3.58 × 109 atoms g-1 in the Central Indian Basin, the values in the Andaman Sea are uniform with an average of 1.49 × 109 atoms g-1. The 10Be/9Be values in the Central Indian Basin sediments range between 0.06 and 2.99 × 10-8 atoms atoms-1 and average to ∼1.56 × 10-8 atoms atoms-1. Correlation of 10Be data with some selected major (Al, Mn, Ti) and trace (Rb and Ba) elements suggest that large part of the isotope has been supplied through direct atmospheric fallout from the water column and minor part from lithogenic detrital flux. Significantly lower 10Be accumulation rates in the Central Indian Basin and an order of magnitude higher in the Andaman Sea sediments compared to the estimated global average production rates indicate removal of the isotopes at the continental margins. Bottom topography seems to exert control on local 10Be variation, where sediments deposited in valleys or topographic depressions contain higher 10Be concentrations in contrast to the probably erosion-dominated areas at the slopes and troughs.

  3. Using the 10-Be Grain Size Dependency in Alluvial Sediments to Investigate Hillslope and Channel Processes

    NASA Astrophysics Data System (ADS)

    Belmont, P.; Pazzaglia, F. J.; Gosse, J.

    2006-12-01

    The method for estimating basin-wide erosion rates from in situ produced 10-Be in alluvial sediments has matured over the past decade; nevertheless, several applications have not been fully explored. Foremost among these is identifying hillslope weathering and erosion processes through a study of the cosmogenic inventories of specific grain-size fractions of alluvial sediment. We applied a nested sampling strategy to two (6-12 km 2) basins on the Olympic Peninsula, western Washington State, to investigate how cosmogenic nuclides are sequestered across different alluvial grain sizes. Alluvium was sampled near the mouth and headwaters of each basin. The 10-Be concentration in river-borne quartz was measured for two grain-size fractions, medium-sized sand (0.25 - 0.50 mm) and an amalgamation of 80+ cobbles (22.6 - 90 mm). Extensive granulometry was conducted at each site and several different methods were used to qualify weathering intensity of channel boulders, which differs substantially for the two basins. We observed different concentrations of 10-Be in all eight grain size fractions. At both headwater sites the cobbles consistently exhibit 25% lower 10-Be concentrations, compared to sand. In contrast, the cobbles in the downstream sites differed with one basin exhibiting 22% higher 10-Be concentration compared to sand and the other site exhibiting 55% lower 10-Be concentration in the cobbles, compared to sand. A GIS was used to extract basin morphological metrics including basin hypsometry, hillslope gradient and channel gradient. Concentrations of 10-Be at the headwater sites are best explained by shielding of the coarser grain size fraction and its delivery to the channel by deep-seated landslide processes. The contrasting grain-size dependency at the two downstream sites requires a more complex interplay between hillslope and channel processes including cobble weathering and grain size reduction during fluvial transport. Although preliminary, these results

  4. Exploring ice core drilling chips from a cold Alpine glacier for cosmogenic radionuclide (10Be) analysis

    NASA Astrophysics Data System (ADS)

    Zipf, Lars; Merchel, Silke; Bohleber, Pascal; Rugel, Georg; Scharf, Andreas

    Ice cores offer unique multi-proxy paleoclimate records, but provide only very limited sample material, which has to be carefully distributed for various proxy analyses. Beryllium-10, for example, is analysed in polar ice cores to investigate past changes of the geomagnetic field, solar activity, and the aerosol cycle, as well as to more accurately date the material. This paper explores the suitability of a drilling by-product, the so-called drilling chips, for 10Be-analysis. An ice core recently drilled at a cold Alpine glacier is used to directly compare 10Be-data from ice core samples with corresponding drilling chips. Both sample types have been spiked with 9Be-carrier and identically treated to chemically isolate beryllium. The resulting BeO has been investigated by accelerator mass spectrometry (AMS) for 10Be/9Be-ratios to calculate 10Be-concentrations in the ice. As a promising first result, four out of five sample-combinations (ice core and drilling chips) agree within 2-sigma uncertainty range. However, further studies are needed in order to fully demonstrate the potential of drilling chips for 10Be-analysis in alpine and shallow polar ice cores.

  5. Artificial Targets to Refine Production Rate Scaling Factors for Surface Exposure Dating

    NASA Astrophysics Data System (ADS)

    Strasky, S.; Vermeesch, P.; Baur, H.; Kober, F.; Schlüchter, C.; Wieler, R.

    2005-12-01

    To determine surface exposure ages, an obviously crucial parameter is the production rate of a nuclide of interest at the site of exposure of a given sample. As the cosmic ray intensity depends on the exact location within the troposphere, also the cosmogenic nuclide production rates vary with the geographical position. Accurate scaling of cosmogenic nuclide production rates from a calibration site to another with different geomagnetic latitude and altitude is therefore required. The international community initiated the CRONUS (Cosmic-Ray-Originated NUclide Systematics) project to improve the knowledge on production systematics of cosmogenic nuclides on earth. In our project we approach the "scaling problem'' by measuring the variability of production rates of cosmogenic noble gases (3He and 21Ne) as a function of the geographical position in artificial targets. The idea is to expose artificial targets along altitude and latitude transects during 1-2 years and subsequently measure the cosmic-ray produced 3He and 21Ne concentrations. The vacuum containers built for the experiment are inconel stainless steel tubes. The main target material is quartz, as quartz is the most commonly used mineral for exposure dating and both, cosmogenic helium and neon are produced and retained in the target container. Each target contains 1 kg of artificial quartz sand, and is degassed in vacuum prior to exposure. Blank measurements are carried out after degassing. So far, four artificial targets have been exposed in Antarctica and Tibet. Further targets will be exposed along an altitude transect between sea level and about 4500 m altitude and a latitude transect between 20-50 degrees. Blank measurements for the first exposed targets revealed 21Ne- and 3He-concentrations of about 5·105 and 5·104 atoms per container, respectively. After 1-2 years of exposure we should be able to measure the cosmogenic excess over blank with sufficient accuracy.

  6. Surface structure of α-Cr2O3(0001) after activated oxygen exposure

    SciTech Connect

    Kaspar, Tiffany C.; Chamberlin, Sara E.; Chambers, Scott A.

    2013-09-13

    The surface structure of a-Cr2O3(0001) before and after exposure to activated oxygen from an ECR plasma source was investigated by x-ray photoelectron spectroscopy (XPS) and x-ray photoelectron diffraction (XPD). Epitaxial Cr2O3(0001) thin films were deposited on Al2O3(0001) substrates by oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE). When cooled or annealed in vacuum, strong evidence for a Cr-Cr-O3- termination was obtained by comparing the Cr3+ XPD azimuthal scan to single scattering simulations. However, after plasma exposure, a high binding energy feature was observed in the Cr 2p XPS spectrum that possesses an ordered structure distinct from the underlying Cr3+ of Cr2O3, which remains Cr-Cr-O3-like. Investigation of this new surface structure with simulations of various candidate structures tentatively rules out CrO2-like configurations. The high binding energy feature likely arises from a higher oxidation state of Cr. One possibility is the oxidation of the surface layer of Cr to Cr6- with a double chromyl structure (O=Cr=O).

  7. Surface structure of α-Cr2O3(0001) after activated oxygen exposure

    NASA Astrophysics Data System (ADS)

    Kaspar, Tiffany C.; Chamberlin, Sara E.; Chambers, Scott A.

    2013-12-01

    The surface structure of α-Cr2O3(0001) before and after exposure to activated oxygen from an ECR plasma source was investigated by x-ray photoelectron spectroscopy (XPS) and x-ray photoelectron diffraction (XPD). Epitaxial Cr2O3(0001) thin films were deposited on Al2O3(0001) substrates by oxygen-plasma-assisted molecular beam epitaxy (OPA-MBE). When cooled or annealed in vacuum, strong evidence for a Crsbnd Crsbnd O3sbnd termination was obtained by comparing the Cr3 + XPD azimuthal scan to single scattering simulations. However, after plasma exposure, a high binding energy feature was observed in the Cr 2p XPS spectrum that possesses an ordered structure distinct from the underlying Cr3 + of Cr2O3, which remains Cr-Cr-O3-like. Investigation of this new surface structure with simulations of various candidate structures tentatively rules out CrO2-like configurations. The high binding energy feature likely arises from a higher oxidation state of Cr. One possibility is the oxidation of the surface layer of Cr to Cr6 - δ with a double chromyl structure (Odbnd Crdbnd O).

  8. EVIDENCE FOR MULTIPLE SOURCES OF {sup 10}Be IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Wielandt, Daniel; Krot, Alexander N.; Bizzarro, Martin; Nagashima, Kazuhide; Huss, Gary R.; Ivanova, Marina A.

    2012-04-01

    Beryllium-10 is a short-lived radionuclide (t{sub 1/2} = 1.4 Myr) uniquely synthesized by spallation reactions and inferred to have been present when the solar system's oldest solids (calcium-aluminum-rich inclusions, CAIs) formed. Yet, the astrophysical site of {sup 10}Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical {sup 26}Al/{sup 27}Al ratio of {approx}5 Multiplication-Sign 10{sup -5} (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by {sup 26}Al/{sup 27}Al ratios much lower than the canonical value. Our measurements demonstrate the presence of four distinct fossil {sup 10}Be/{sup 9}Be isochrons, lower in the FUN-CAIs than in the canonical CAIs, and variable within these classes. Given that FUN-CAI precursors escaped evaporation-recondensation prior to evaporative melting, we suggest that the {sup 10}Be/{sup 9}Be ratio recorded by FUN-CAIs represents a baseline level present in presolar material inherited from the protosolar molecular cloud, generated via enhanced trapping of galactic cosmic rays. The higher and possibly variable apparent {sup 10}Be/{sup 9}Be ratios of canonical CAIs reflect additional spallogenesis, either in the gaseous CAI-forming reservoir, or in the inclusions themselves: this indicates at least two nucleosynthetic sources of {sup 10}Be in the early solar system. The most promising locale for {sup 10}Be synthesis is close to the proto-Sun during its early mass-accreting stages, as these are thought to coincide with periods of intense particle irradiation occurring on timescales significantly shorter than the formation interval of canonical CAIs.

  9. The cosmogenic radionuclides {sup 7}Be, {sup 10}Be, and {sup 36}Cl in precipitation

    SciTech Connect

    Knies, D.L.

    1994-12-31

    Two-thirds of atmospheric {sup 7}Be (t{sub 1/2}=53 d), {sup 10}Be(t{sub 1/2}= 1.5 My), and {sup 36}Cl(t{sub 1/2}=0.3 My) is produced in the stratosphere and one-third in the troposphere. The residence time of these radionuclides in the stratosphere is a few years and in the troposphere is a few weeks. Since {sup 7}Be`s half-life is short compared to its residence time in the stratosphere and similar to its residence time in the troposphere, the {sup 7}Be/{sup 10}Be and {sup 7}Be/{sup 36}Cl ratios should have distinct tropospheric and stratospheric values. Consequently, these isotopes can be used to study processes that involve mixing of air from the troposphere and stratosphere. Relationships between the radionuclide concentrations and air mass history, event type, season, and the major cation and anion concentrations will be presented. Evidence and mechanisms for the fractionation of the {sup 36}Cl and {sup 10}Be concentrations as a function of event type will be presented. Evidence and mechanisms for the fractionation of the {sup 36}Cl and {sup 10}Be concentrations as a function of event type will be presented. A departure from the theoretical {sup 10}Be/{sup 36}Cl production rate ratio of {approx}40 is seen only in one direction with an apparent limit right at the calculated ratio. For this reason, a new theoretical calculation of the {sup 10}Be/{sup 36}Cl production rate ratio was undertaken. The new calculated value is {approx}9.3. This value is in good agreement with the measured mean values in both the Greenland ice sheet and West Lafayette, IN wet precipitation of 8.1 and 9.1 respectively.

  10. Airborne benzene exposures from cleaning metal surfaces with small volumes of petroleum solvents.

    PubMed

    Hollins, Dana M; Kerger, Brent D; Unice, Kenneth M; Knutsen, Jeffrey S; Madl, Amy K; Sahmel, Jennifer E; Paustenbach, Dennis J

    2013-06-01

    Airborne benzene concentrations were measured in a room with controlled air exchange during surface cleaning with two petroleum-based solvents (a paint thinner and an engine degreaser). The solvents were spiked with benzene to obtain target concentrations of 0.001, 0.01, and 0.1% by volume in the liquid. Personal samples on the worker and area samples up to 1.8m away were collected over 12 events (n=84 samples) designed to examine variation in exposure with solvent type, cleaning method (rag wipe or spatula scrape), surface area cleaned, air exchange rate, solvent volume applied, and distance from the cleaned surface. Average task breathing zone concentrations of benzene represented by 18-32 min time-weighted averages were 0.01 ppm, 0.05 ppm, and 0.27 ppm, when the solvents contained approximately 0.003, 0.008, and 0.07% benzene. Solvent benzene concentration, volume applied, and distance from the handling activities had the greatest effect on airborne concentrations. The studied solvent products containing 0.07% benzene (spiked) did not exceed the current OSHA permissible exposure limit of 1 ppm (averaged over 8h) or the ACGIH Threshold Limit Value of 0.5 ppm, in any of the tested short-term exposure scenarios. These data suggest that, under these solvent use scenarios, petroleum-based solvent products produced in the United States after 1978 likely did not produce airborne benzene concentrations above those measured if the concentration was less than 0.1% benzene. PMID:23088855

  11. Cigarette smoke exposure induces CFTR internalization and insolubility, leading to airway surface liquid dehydration

    PubMed Central

    Clunes, Lucy A.; Davies, Catrin M.; Coakley, Raymond D.; Aleksandrov, Andrei A.; Henderson, Ashley G.; Zeman, Kirby L.; Worthington, Erin N.; Gentzsch, Martina; Kreda, Silvia M.; Cholon, Deborah; Bennett, William D.; Riordan, John R.; Boucher, Richard C.; Tarran, Robert

    2012-01-01

    Cigarette smoke (CS) exposure induces mucus obstruction and the development of chronic bronchitis (CB). While many of these responses are determined genetically, little is known about the effects CS can exert on pulmonary epithelia at the protein level. We, therefore, tested the hypothesis that CS exerts direct effects on the CFTR protein, which could impair airway hydration, leading to the mucus stasis characteristic of both cystic fibrosis and CB. In vivo and in vitro studies demonstrated that CS rapidly decreased CFTR activity, leading to airway surface liquid (ASL) volume depletion (i.e., dehydration). Further studies revealed that CS induced internalization of CFTR. Surprisingly, CS-internalized CFTR did not colocalize with lysosomal proteins. Instead, the bulk of CFTR shifted to a detergent-resistant fraction within the cell and colocalized with the intermediate filament vimentin, suggesting that CS induced CFTR movement into an aggresome-like, perinuclear compartment. To test whether airway dehydration could be reversed, we used hypertonic saline (HS) as an osmolyte to rehydrate ASL. HS restored ASL height in CS-exposed, dehydrated airway cultures. Similarly, inhaled HS restored mucus transport and increased clearance in patients with CB. Thus, we propose that CS exposure rapidly impairs CFTR function by internalizing CFTR, leading to ASL dehydration, which promotes mucus stasis and a failure of mucus clearance, leaving smokers at risk for developing CB. Furthermore, our data suggest that strategies to rehydrate airway surfaces may provide a novel form of therapy for patients with CB.—Clunes, L. A., Davies, C. M., Coakley, R. D., Aleksandrov, A. A., Henderson, A. G., Zeman, K. L., Worthington, E. N., Gentzsch, M., Kreda, S. M., Cholon, D., Bennett, W. D., Riordan, J. R., Boucher, R. C., Tarran, R. Cigarette smoke exposure induces CFTR internalization and insolubility, leading to airway surface liquid dehydration. PMID:21990373

  12. In situ produced 10Be depth profiles and luminescence data tracing climatic and tectonic control on terrace formation, Danube River, Central Europe, Hungary

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Braucher, Régis; Novothny, Ágnes; Csillag, Gábor; Fodor, László; Molnár, Gábor; Madarász, Balázs; Aster Team

    2015-04-01

    The terrace sequence of the Hungarian part of the Danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages. To establish the chronology of formation of these terraces, two different dating methods on alluvial terraces were used: 1) in situ produced cosmogenic 10Be, which yield the time of abandonment of the terrace and 2) luminescence dating, which provides burial ages of the sediment. In situ produced cosmogenic 10Be samples originated from vertical depth profiles to enable the determination of both the exposure time and the denudation rate at each locality. We used Monte Carlo approach to model the denudation rate-corrected exposure ages. Post-IR IRSL measurements were carried out on K-feldspar samples to obtain the ages of sedimentation. The highest and oldest terrace remnants (tIV-VI) yield a minimum 10Be exposure age of 800 ka close to MIS 22, the onset of major continental glaciations of Quaternary age, suggesting climatic signal of the abandonment of the uppermost terrace levels. For the lower terraces it was possible to reveal close correlation with MIS stages using IRSL ages. The new chronology enables the distinction of tIIb (60-110 ka; MIS 4-5d) and tIIIa (130-190 ka; MIS 6) in the study area. Surface denudation rates were well constrained by the cosmogenic 10Be depth profiles between 5.9 m/Ma and 10.0 m/Ma for all terraces. Maximum incision rates of the Danube were calculated for middle and late Pleistocene times. These rates were increasing from west to east, toward the more elevated Transdanubian Range from 0.05 mm/a to 0.12 mm/a. Incision rates derived from the age of the low terraces (0.13 mm/a) may suggest a slight acceleration of uplift towards present. Our research was supported by the OTKA PD83610, PD100315, NK60455, K062478, K83150 and F042799, the French-Hungarian Balaton-Tét Project (FR-32/2007; TÉT_11-2-2012-0005), the Bolyai János Scholarship of the Hungarian Academy

  13. Slip rate determination along the Southern Dead Sea fault: optically stimulated luminescence, 10Be cosmogenic radionuclide, and 14C ages brought face to face

    NASA Astrophysics Data System (ADS)

    Le Beon, Maryline; Jaiswal, Manoj; Kunz, Alexander; Al-Qaryouti, Mahmoud; Burr, George; Klinger, Yann; Moumani, Khaled; Chen, Yue-Gau; Abdelghafoor, Mohammed; Suppe, John

    2014-05-01

    Active tectonics studies are often limited by difficulties in accurately and precisely dating Late Quaternary alluvial deposits that commonly lack organic matter or date beyond the 14C dating limit. This is illustrated at a site called Fidan, in arid southern Jordan, where a series of alluvial fans are laterally offset by the southern Dead Sea fault. Geodetic, geomorphic and geologic studies converge to a fault slip rate of 5 ± 2 mm/a. Yet, Late Pleistocene slip rate at Fidan cover a wide range due to the dispersion of 10Be cosmogenic radionuclide (CRN) ages. The maximum slip rate since ~100 ka is up to a value of 11 mm/a, possibly suggesting significant variations in fault activity with time. In order to reduce the uncertainty on the Late Pleistocene slip rate and draw further conclusions regarding the fault seismic behavior, we implement complementary dating using optically stimulated luminescence (OSL) techniques on both quartz and K-feldspar minerals and using 14C when possible. OSL measurements include a newly developed technique called post-infra-red infra-red stimulated luminescence at 290°C (pIR290). We extensively sampled surface levels F2 and F4, digging ~50-cm deep pits into the geomorphic surfaces. Annual dose rates were determined in the laboratory from both geochemical analysis of the sediment and gamma-ray spectrometry. Due to sediment heterogeneity, we consider gamma-ray spectrometry as more reliable because it is based on a larger volume of sediment. Quartz OSL ages and preliminary pIR290 results on K-feldspars give consistent Early Holocene ages of 9-14 ka for F2, also in agreement with a 14C age of 13 ka from a landsnail shell. 10Be CRN exposure ages on F2 were significantly older, with 37 ± 4 ka, probably due to inheritance. On F4, 10Be CRN exposure ages showed a scattered distribution, from ~50 ka to ~120 ka, with most samples comprised in the mean interval of 87 ± 26 ka. Quartz OSL ages from 5 locations on F4 are comprised between 32 ± 3

  14. 10Be climate fingerprints during the Eemian in the NEEM ice core, Greenland

    PubMed Central

    Sturevik-Storm, Anna; Aldahan, Ala; Possnert, Göran; Berggren, Ann-Marie; Muscheler, Raimund; Dahl-Jensen, Dorthe; Vinther, Bo M.; Usoskin, Ilya

    2014-01-01

    Several deep Greenland ice cores have been retrieved, however, capturing the Eemian period has been problematic due to stratigraphic disturbances in the ice. The new Greenland deep ice core from the NEEM site (77.45°N, 51.06°W, 2450 m.a.s.l) recovered a relatively complete Eemian record. Here we discuss the cosmogenic 10Be isotope record from this core. The results show Eemian average 10Be concentrations about 0.7 times lower than in the Holocene which suggests a warmer climate and approximately 65–90% higher precipitation in Northern Greenland compared to today. Effects of shorter solar variations on 10Be concentration are smoothed out due to coarse time resolution, but occurrence of a solar maximum at 115.26–115.36 kyr BP is proposed. Relatively high 10Be concentrations are found in the basal ice sections of the core which may originate from the glacial-interglacial transition and relate to a geomagnetic excursion about 200 kyr BP. PMID:25266953

  15. A new 3D numerical model of cosmogenic nuclide 10Be production in the atmosphere

    NASA Astrophysics Data System (ADS)

    Kovaltsov, Gennady A.; Usoskin, Ilya G.

    2010-03-01

    A new quantitative model of production of the cosmogenic isotope 10Be by cosmic rays in the Earth's atmosphere is presented. The CRAC:10Be (Cosmic Ray induced Atmospheric Cascade for 10Be) model is based on a full numerical Monte-Carlo simulation of the nucleonic-electromagnetic-muon cascade induced by cosmic rays in the atmosphere and is able to compute the isotope's production rate at any given 3D location (geographical and altitude) and time, for all possible parameters including solar energetic particle events. The model was tested against the results of direct measurements of the 10Be production in a number of dedicated experiments to confirm its quantitative correctness. A set of tabulated values for the yield function is provided along with a detailed numerical recipe forming a "do-it-yourself" kit, which allows anyone interested to apply the model for any given conditions. This provides a useful tool for applying the cosmogenic isotope method in direct integration with other models, e.g., dynamical atmospheric transport.

  16. Dilute Nuclear States: {sup 12}C, {sup 10}Be and {sup 14}C

    SciTech Connect

    Freer, M.

    2008-11-11

    The experimental evidence for dilute {alpha}-particle states in {sup 12}C, {sup 10}Be and {sup 14}C is discussed. The question of the location of the 2{sup +} excitation of the 7.65 MeV {sup 12}C state remains unresolved, as does the existence of possible analogue states in {sup 14}C.

  17. Exposure to particle number, surface area and PM concentrations in pizzerias

    NASA Astrophysics Data System (ADS)

    Buonanno, G.; Morawska, L.; Stabile, L.; Viola, A.

    2010-10-01

    The aim of this work was to quantify exposure to particles emitted by wood-fired ovens in pizzerias. Overall, 15 microenvironments were chosen and analyzed in a 14-month experimental campaign. Particle number concentration and distribution were measured simultaneously using a Condensation Particle Counter (CPC), a Scanning Mobility Particle Sizer (SMPS), an Aerodynamic Particle Sizer (APS). The surface area and mass distributions and concentrations, as well as the estimation of lung deposition surface area and PM 1 were evaluated using the SMPS-APS system with dosimetric models, by taking into account the presence of aggregates on the basis of the Idealized Aggregate (IA) theory. The fraction of inhaled particles deposited in the respiratory system and different fractions of particulate matter were also measured by means of a Nanoparticle Surface Area Monitor (NSAM) and a photometer (DustTrak DRX), respectively. In this way, supplementary data were obtained during the monitoring of trends inside the pizzerias. We found that surface area and PM 1 particle concentrations in pizzerias can be very high, especially when compared to other critical microenvironments, such as the transport hubs. During pizza cooking under normal ventilation conditions, concentrations were found up to 74, 70 and 23 times higher than background levels for number, surface area and PM 1, respectively. A key parameter is the oven shape factor, defined as the ratio between the size of the face opening in respect to the diameter of the semicircular oven door, and particular attention must also be paid to hood efficiency.

  18. Dehydration-Driven Solvent Exposure of Hydrophobic Surfaces as a Driving Force in Peptide Folding

    SciTech Connect

    Daidone, Isabella; Ulmschneider, Martin; DiNola, Alfredo; Amadei, Andrea; Smith, Jeremy C

    2007-09-01

    Recent work has shown that the nature of hydration of pure hydrophobic surfaces changes with the length scale considered: water hydrogen-bonding networks adapt to small exposed hydrophobic species, hydrating or 'wetting' them at relatively high densities, whereas larger hydrophobic areas are 'dewetted' [Chandler D (2005), Nature 29:640-647]. Here we determine whether this effect is also present in peptides by examining the folding of a {beta}-hairpin (the 14-residue amyloidogenic prion protein H1 peptide), using microsecond time-scale molecular dynamics simulations. Two simulation models are compared, one explicitly including the water molecules, which may thus adapt locally to peptide configurations, and the other using a popular continuum approximation, the generalized Born/surface area implicit solvent model. The results obtained show that, in explicit solvent, peptide conformers with high solvent-accessible hydrophobic surface area indeed also have low hydration density around hydrophobic residues, whereas a concomitant higher hydration density around hydrophilic residues is observed. This dewetting effect stabilizes the fully folded {beta}-hairpin state found experimentally. In contrast, the implicit solvent model destabilizes the fully folded hairpin, tending to cluster hydrophobic residues regardless of the size of the exposed hydrophobic surface. Furthermore, the rate of the conformational transitions in the implicit solvent simulation is almost doubled with respect to that of the explicit solvent. The results suggest that dehydration-driven solvent exposure of hydrophobic surfaces may be a significant factor determining peptide conformational equilibria.

  19. Characterization of exposures among cemented tungsten carbide workers. Part II: Assessment of surface contamination and skin exposures to cobalt, chromium and nickel.

    PubMed

    Day, Gregory A; Virji, M Abbas; Stefaniak, Aleksandr B

    2009-05-01

    Cobalt, chromium and nickel are among the most commonly encountered contact allergens in the workplace, all used in the production of cemented tungsten carbides (CTC). Exposures to these metal-containing dusts are frequently associated with skin sensitization and/or development of occupational asthma. The objectives of this study were to assess the levels of cobalt, chromium and nickel on work surfaces and on workers' skin in three CTC production facilities. At least one worker in each of 26 work areas (among all facilities) provided hand and neck wipe samples. Wipe samples were also collected from work surfaces frequently contacted by the 41 participating workers. Results indicated that all surfaces in all work areas were contaminated with cobalt and nickel, with geometric means (GMs) ranging from 4.1 to 3057 microg/100 cm(2) and 1.1-185 microg/100 cm(2), respectively; most surfaces were contaminated with chromium (GM=0.36-67 microg/100 cm(2)). The highest GM levels of all metals were found on control panels, containers and hand tools, whereas lowest levels were on office and telecommunication equipment. The highest GM levels of cobalt and nickel on skin were observed among workers in the powder-handling facility (hands: 388 and 24 microg; necks: 55 and 6 microg, respectively). Levels of chromium on workers' skin were generally low among all facilities. Geometric standard deviations associated with surface and skin wipe measurements among work areas were highly variable. Exposure assessment indicated widespread contamination of multiple sensitizing metals in these three facilities, suggesting potential transfer of contaminants from surfaces to skin. Specific action, including improved housekeeping and training workers on appropriate use and care of personal protective equipment, should be implemented to reduce pathways of skin exposure. Epidemiologic studies of associated adverse health effects will likely require more biologically relevant exposure metrics to

  20. Cosmogenic production of 7Be and 10Be in water targets

    NASA Astrophysics Data System (ADS)

    Nishiizumi, K.; Finkel, R. C.; Klein, J.; Kohl, C. P.

    1996-10-01

    We have measured 10Be (t1/2=1.5×106 years) and 7Be (t1/2=53.28 days) concentrations in water targets exposed for 1 to 2 years at Echo Lake, Colorado (elevation=3246 m) and at La Jolla, California (140 m). Neutron monitor data were used to normalize the measured concentrations in order to calculate production rates equivalent to the cosmic ray flux averaged over four solar cycles (43 years). The 7Be production rates thus obtained correspond to 6.03+/-0.07×10-6 atomg-1.Os-1 at Echo Lake and 5.06+/-0.20×10-7 atomg-1.Os-1 at La Jolla. The 10Be production rates correspond to 3.14+/-0.18×10-6 atomg-1.Os-1 at Echo Lake and 2.68+/-0.47×10-7 atomg-1.Os-1 at La Jolla. When compared with 10Be production rates determined in 10Be-saturated rocks from the Antarctic and with theoretical calculations based on meteorite and lunar sample data, we find that the million-year average production rate is about 14-17% greater than the present production rate averaged over the last four solar cycles. Comparison with production rates determined by measuring glacially polished rocks from the Sierra Nevada in California indicates that average production (based on a revised 13,000-year deglaciation age and a geographic latitude correction) is about 11% greater than the average over the last four solar cycles. The measured 10Be/7Be production ratio in oxygen is 0.52+/-0.03 at Echo Lake and 0.55+/-0.07 at La Jolla.

  1. The Last Glacial Maximum at 44°S documented by a 10Be moraine chronology at Lake Ohau, Southern Alps of New Zealand

    NASA Astrophysics Data System (ADS)

    Putnam, Aaron E.; Schaefer, Joerg M.; Denton, George H.; Barrell, David J. A.; Birkel, Sean D.; Andersen, Bjørn G.; Kaplan, Michael R.; Finkel, Robert C.; Schwartz, Roseanne; Doughty, Alice M.

    2013-02-01

    Determining whether glaciers registered the classic Last Glacial Maximum (LGM; ˜26,500-˜19,000 yrs ago) coevally between the hemispheres can help to discriminate among hypothesized drivers of ice-age climate. Here, we present a record of glacier behavior from the Southern Alps of New Zealand during the 'local LGM' (LLGM). We used 10Be surface-exposure dating methods and detailed glacial geomorphologic mapping to produce a robust chronology of well-preserved terminal moraines deposited during the LLGM near Lake Ohau on central South Island. We then used a glaciological model to estimate a LLGM glacier snowline and atmospheric temperature from the Ohau glacier record. Seventy-three 10Be surface-exposure ages place culminations of terminal moraine construction, and hence completions of glacier advances to positions outboard of present-day Lake Ohau, at 138,600 ± 10,600 yrs, 32,520 ± 970 yrs ago, 27,400 ± 1300 yrs ago, 22,510 ± 660 yrs ago, and 18,220 ± 500 yrs ago. Recessional moraines document glacier recession into the Lake Ohau trough by 17,690 ± 350 yrs ago. Exposure of an ice-molded bedrock bench located inboard of the innermost LLGM moraines by 17,380 ± 510 yrs ago indicates that the ice tongue had receded about 40% of its overall length by that time. Comparing our chronology with distances of retreat suggests that the Ohau glacier terminus receded at a mean net rate of about 77 m yr-1 and its surface lowered by 200 m between 17,690 and 17,380 yrs ago. A long-term continuation of ice retreat in the Ohau glacier catchment is implied by moraine records at the head of Irishman Stream valley, a tributary of the Ohau glacier valley. The Irishman Stream cirque glacier advanced to produce a set of Lateglacial moraines at 13,000 ± 500 yrs ago, implying that the cirque glacier was less extensive prior to that advance. We employed a glaciological model, fit to these mapped and dated LLGM moraines, to derive snowline elevations and temperature parameters from the

  2. Effective denitrification at the groundwater surface-water interface: exposure rather than residence time

    NASA Astrophysics Data System (ADS)

    Peiffer, Stefan; Frei, Sven

    2014-05-01

    Effective processing of material in aquatic systems, e. g. removal of nitrate upon denitrification, requires sufficient reaction time. This statement sounds trivial albeit its implication for biogeochemistry seems to be not fully recognized. The time teff required for effective processing of nitrate is controlled by the underlying biogeochemical rate law. In the simplest case of a 1st order reaction, teff is often calculated as the time when 63% of the initial concentration is consumed setting teff as 1/kreaction. It may, however, be more appropriate to derive teff,90%or teff,99% from the respective rate law. Hence a minimum time t > teff is required that exposes a specific biogeochemical process to conditions favourable for this process, which is anoxia in case of denitrification. This exposure time τexp is not necessarily identical to the residence time τ of water in the particular system or flow path. Rather, the exposure time can be much shorter and may even fluctuate with time. As a consequence, Damköhler numbers (Da = τexp/teff) for denitrification < 1 may be the consequence even though the age of water may be comparatively high. We therefore argue that the key for understanding denitrification efficiency at the groundwater surface-water interface (or in groundwater systems in general) is the quantification of the exposure time. This contribution therefore aims i) to estimate exposure times required for effective denitrification based on an analysis of rate constants for denitrification, ii) to relate these time scales to typical residence time distributions found at the groundwater surface-water interface and iii) to discuss implications for denitrification efficiencies. References: Oldham, C; Farrow, DE; Peiffer, S (2013): A generalized Damköhler number for classifying material processing in hydrological systems, Hydrology and Earth System Sciences, 17, 1133-1148 Frei, S; Knorr, KH; Peiffer, S; Fleckenstein, J (2012): Surface micro-topography causes

  3. Identifying signals of Late Pleistocene climate change from cosmogenic 10Be chronologies of moraines in the western U.S.

    NASA Astrophysics Data System (ADS)

    Laabs, B. J. C.; Licciardi, J. M.; Leonard, E. M.; Munroe, J. S.

    2015-12-01

    Cosmogenic 10Be exposure dating has become the most widely applied method of developing ages of terminal moraines in the western U.S. Advances in the precision of analytical measurements along with a more accurate understanding of spatial and temporal variations in the production of in situ 10Be have improved the accuracy of cosmogenic exposure dating of moraines. Such improvements afford more accurate assessment of the impact of regional and global-scale climate changes of the Late Pleistocene on glaciation in the western U.S. A great number of new and recalculated cosmogenic 10Be exposure ages of moraines are considered here to identify the most probable drivers of changes in ice extent at the end of the last glacial period. The last Pleistocene glaciation culminated in the western U.S. during marine oxygen isotope stage 2, before or during the onset of the global Last Glacial Maximum at ca. 26.5 ka. Terminal moraine abandonment in several ranges corresponds to the end of the Last Glacial Maximum at ca. 19.0 ka. This observation indicates that most mountain glaciers started retreating in step with the decline of global ice volume, and possibly in response to rising insolation at northern middle latitudes. In some regions, such as the Northern Rocky Mountains and the Great Basin, mountain glaciers apparently advanced to or persisted near their maximum terminus positions well after the start of global deglaciation, during the interval of the Oldest Dryas/Heinrich Stadial 1 (ca. 19.0-14.6 ka). Although changes in atmospheric circulation and precipitation patterns during this time likely affected mountain glacier extent, rapid ice retreat commenced in nearly all settings by 17.0-16.0 ka. This indication of warming prior to the onset of the Bølling-Allerød interval at ca. 14.6 ka is consistent with records from elsewhere at northern middle latitudes, and supports the hypothesis that warming of the region was in phase with a global rise in atmospheric CO2. This

  4. Consideration of geomorphological uncertainties with terrestrial cosmogenic nuclide dating (TCND): combining Schmidt-hammer and 10Be dating, Southern Alps, New Zealand

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan

    2010-05-01

    As the importance of glaciers as key indicators of global change has increased during recent years, investigating Holocene glaciers chronologies has gained higher attention accordingly. One reason is the need for a better understanding of the climate - glacier relationship. Comparative studies play a major role in this field of research owing to the natural diversity of glacier behaviour. Detailed Holocene glacier chronologies are, furthermore, necessary to verify and eventually adjust glacier models indispensable for many attempts to predict future glacier changes. The Southern Alps of New Zealand are one of the few key study areas on the Southern Hemisphere where, in general, evidence is still sparse compared to its Northern counterpart. Improvement and reassessment of the Late Holocene glacier chronology in this region is, therefore, an important goal of current research. Recently, terrestrial (in situ) cosmogenic nuclide (10Be) surface exposure dating has been increasingly applied to Holocene moraines in New Zealand and elsewhere. In the context of numerical ("absolute") dating techniques, terrestrial cosmogenic nuclide dating (TCND) seems to have been established as an alternative to the previously dominating radiocarbon (14C) dating of organic material (plant remains, organic-rich soil layers etc.) buried beneath or within moraines. Precision and time resolution achieved by the newest laboratory standards and procedures (Schaefer et al. 2009) is truly a milestone and will promote future attempts of TCND in any comparable context. Maybe, TCND has the potential to at least partially replace radiocarbon (14C) dating in its dominating role for the "absolute" dating of Holocene glacial deposits. By contrast, field sampling for TCND often lacks appropriate consideration of geomorphological uncertainties. Whereas much effort is made with the high precision results achieved in the laboratory, the choice of boulders sampled on Holocene moraines is often purely made

  5. Space Weathering Effects in Lunar Soils: The Roles of Surface Exposure Time and Bulk Chemical Composition

    NASA Technical Reports Server (NTRS)

    Zhang, Shouliang; Keller, Lindsay P.

    2011-01-01

    Space weathering effects on lunar soil grains result from both radiation-damaged and deposited layers on grain surfaces. Typically, solar wind irradiation forms an amorphous layer on regolith silicate grains, and induces the formation of surficial metallic Fe in Fe-bearing minerals [1,2]. Impacts into the lunar regolith generate high temperature melts and vapor. The vapor component is largely deposited on the surfaces of lunar soil grains [3] as is a fraction of the melt [4, this work]. Both the vapor-deposits and the deposited melt typically contain nanophase Fe metal particles (npFe0) as abundant inclusions. The development of these rims and the abundance of the npFe0 in lunar regolith, and thus the optical properties, vary with the soil mineralogy and the length of time the soil grains have been exposed to space weathering effects [5]. In this study, we used the density of solar flare particle tracks in soil grains to estimate exposure times for individual grains and then perform nanometer-scale characterization of the rims using transmission electron microscopy (TEM). The work involved study of lunar soil samples with different mineralogy (mare vs. highland) and different exposure times (mature vs. immature).

  6. Cigarette smoke exposure induces CFTR internalization and insolubility, leading to airway surface liquid dehydration.

    PubMed

    Clunes, Lucy A; Davies, Catrin M; Coakley, Raymond D; Aleksandrov, Andrei A; Henderson, Ashley G; Zeman, Kirby L; Worthington, Erin N; Gentzsch, Martina; Kreda, Silvia M; Cholon, Deborah; Bennett, William D; Riordan, John R; Boucher, Richard C; Tarran, Robert

    2012-02-01

    Cigarette smoke (CS) exposure induces mucus obstruction and the development of chronic bronchitis (CB). While many of these responses are determined genetically, little is known about the effects CS can exert on pulmonary epithelia at the protein level. We, therefore, tested the hypothesis that CS exerts direct effects on the CFTR protein, which could impair airway hydration, leading to the mucus stasis characteristic of both cystic fibrosis and CB. In vivo and in vitro studies demonstrated that CS rapidly decreased CFTR activity, leading to airway surface liquid (ASL) volume depletion (i.e., dehydration). Further studies revealed that CS induced internalization of CFTR. Surprisingly, CS-internalized CFTR did not colocalize with lysosomal proteins. Instead, the bulk of CFTR shifted to a detergent-resistant fraction within the cell and colocalized with the intermediate filament vimentin, suggesting that CS induced CFTR movement into an aggresome-like, perinuclear compartment. To test whether airway dehydration could be reversed, we used hypertonic saline (HS) as an osmolyte to rehydrate ASL. HS restored ASL height in CS-exposed, dehydrated airway cultures. Similarly, inhaled HS restored mucus transport and increased clearance in patients with CB. Thus, we propose that CS exposure rapidly impairs CFTR function by internalizing CFTR, leading to ASL dehydration, which promotes mucus stasis and a failure of mucus clearance, leaving smokers at risk for developing CB. Furthermore, our data suggest that strategies to rehydrate airway surfaces may provide a novel form of therapy for patients with CB. PMID:21990373

  7. Pesticide residues on the external surfaces of field crop sprayers: occupational exposure.

    PubMed

    Ramwell, Carmel T; Johnson, Paul D; Boxall, Alistair B A; Rimmer, Duncan A

    2005-06-01

    There is a general perception, amongst farmers and researchers, that post-application residues on the external surfaces of sprayers are negligible compared with residues remaining on the internal surfaces, although there have been few attempts to verify this assumption. The aim of this study was to investigate, using cotton glove sampling, operator exposure resulting from three typical operations: entering and working in the cab, general handling of the sprayer and maintenance practices. Samples were analysed for azoxystrobin, carbendazim, chlorothalonil, cyanazine, cypermethrin, epoxiconazole, flusilazole, isoproturon, kresoxim-methyl, metazachlor, pendimethalin, pirimicarb and tebuconazole. Isoproturon, pendimethalin, chlorothalonil and carbendazim were detected >1 mg per glove pair on the cotton gloves, but on the whole there was variability in residue levels between and within compounds. Comparison of results with occupational exposure limits indicated that residues were such that they may not necessarily be considered insignificant. It may therefore be prudent to develop more efficient methods for the external decontamination of sprayers and/or raise awareness of the findings. PMID:15650013

  8. Radiative 10Be(n, γ)11Be capture at thermal and astrophysical energies

    NASA Astrophysics Data System (ADS)

    Dubovichenko, S. B.; Dzhazairov-Kakhramanov, A. V.

    2016-09-01

    The modified potential cluster model with the forbidden states and the classification of states according to the Young tableaux, which are irreducible representations of permutation symmetric group SU(4), was used in this paper. Within the framework of this model the possibility of describing the experimental data available for the total reaction cross sections and the reaction rate of neutron radiative capture on 10Be at thermal and astrophysical energies has been shown.

  9. 41Ca, 14C and 10Be concentrations in coral sand from the Bikini atoll.

    PubMed

    Lachner, Johannes; Christl, Marcus; Alfimov, Vasily; Hajdas, Irka; Kubik, Peter W; Schulze-König, Tim; Wacker, Lukas; Synal, Hans-Arno

    2014-03-01

    Activation measurements of materials exposed to nuclear bomb explosions are widely used to reconstruct the neutron flux for retrospective dosimetry. In this study the applicability of coral CaCO3 as a biogenic neutron fluence dosimeter is tested. The long-lived radioisotopes (41)Ca, (14)C and (10)Be, which had been produced in nuclear bomb explosions, are measured in several coral sand samples from the Bikini atoll at the 600 kV and 200 kV AMS facilities of ETH Zurich. Elevated concentrations of all studied isotopes are found in a sample from the crater that was initially formed by the high-yield nuclear explosion Castle Bravo in 1954 and that had been used as site for several tests afterward. The observed (14)C concentration is considered too large to originate from neutron irradiation of CaCO3 alone. The relatively low concentration of (10)Be found in the crater sample indicates that production of (10)Be during nuclear bomb testing is generally minor. A simple neutron fluence reconstruction is performed on basis of the (41)Ca/(40)Ca ratio. PMID:24378732

  10. Cobalt and chromium exposure affects osteoblast function and impairs the mineralization of prosthesis surfaces in vitro.

    PubMed

    Shah, Karan M; Wilkinson, Jeremy Mark; Gartland, Alison

    2015-11-01

    Cobalt (Co) and chromium (Cr) ions and nanoparticles equivalent to those released through tribo-corrosion of prosthetic metal-on-metal (MOM) bearings and taper junctions are detrimental to osteoblast activity and function in vitro when examined as individual species. Here we examined the effects of Co(2+):Cr(3+) and Co(2+):Cr(6+) combinations on osteoblast-like SaOS-2 cellular activity, alkaline phosphatase (ALP) activity and mineralization to better reflect clinical exposure conditions in vivo. We also assessed the effect of Co(2+):Cr(3+) combinations and Co:Cr nanoparticles on SaOS-2 cell osteogenic responses on grit-blasted, plasma-sprayed titanium-coated, and hydroxyapatite-coated prosthesis surfaces. Cellular activity and ALP activity were reduced to a greater extent with combination treatments compared to individual ions. Co(2+) and Cr(3+) interacted additively and synergistically to reduce cellular activity and ALP activity, respectively, while the Co(2+) with Cr(6+) combination was dominated by the effect of Cr(6+) alone. Mineralization by osteoblasts was greater on hydroxyapatite-coated surfaces compared to grit-blasted and plasma-sprayed titanium-coated surfaces. Treatments with Co(2+):Cr(3+) ions and Co:Cr nanoparticles reduced the percentage mineralization on all surfaces, with hydroxyapatite-coated surfaces having the least reduction. In conclusion, our data suggests that previous studies investigating individual metal ions underestimate their potential clinical effects on osteoblast activity. Furthermore, the data suggests that hydroxyapatite-coated surfaces may modulate osteoblast responses to metal debris. PMID:25929464

  11. Brunhes-Matuyama Magnetic Polarity Reversal Tracing using Chinese loess10Be

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Beck, W.; Kong, X.; An, Z.; Qiang, X.; Wu, Z.; Xian, F.; Ao, H.

    2014-12-01

    The geomagnetic polarity reversal is generally considered to occur synchronously around the world, and is commonly used as a time marker. However, in the case of the most recent reversal, the Brunhes-Matuyama (B-M) reversal (~780 ka), comparison of paleomagnetic studies in Chinese loess-paleosol sequences versus marine sediments revealed a marked discrepancy in timing of this event (Tauxe et al., 1996; Zhou and Shackleton, 1999), leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments (Wang et al., 2006; Liu et al., 2008; Jin and Liu, 2011). Based on this issue, here we propose to use the cosmogenic 10Be to address this conundrum. 10Be is a long-lived radionuclide produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols. Its atmospheric production rate is inversely proportional to the geomagnetic field intensity (Masarik and Beer, 1999). This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out the 10Be studies in Luochuan and Xifeng sections in Chinese Loess Plateau, both loess profiles show that 10Be production rate was at a maximum-an indication of the dipole field reversal-at ca. 780 ± 3 ka BP., in paleosol unit S7corresponding to MIS 19. These results have proven that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records (Tauxe et al., 1996) and reaffirmed the conventional paleoclimatic correlation of loess-paleosol sequences with marine isotope stages and the standard loess timescale as correct. However, it is ~25 ka younger than the age (depth) of the magnetic polarity reversal recorded in these same Chinese loess-paleosol sequences, demonstrating that loess magnetic overprinting has occurred. 1.Jin, C.S.,et al., 2011,PALAEOGEOGR PALAEOCL, 299, 309-3172.Liu, Q.S., et al., 2008, EARTH

  12. Loess 10Be evidence for an asynchronous Brunhes-Matuyama magnetic polarity reversal

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Beck, W.; Kong, X.; An, Z.; Qiang, X.; Wu, Z.; Xian, F.; Ao, H.

    2015-12-01

    In Chinese loess the Brunhes-Matuyama (B-M) geomagnetic reversal appears to occur about 25 ka prior to the established axial dipole reversal age found in many marine sediments, i.e., in Chinese loess this magnetic reversal boundary is found in glacial loess unit L8 which is thought to be correlated with Marine Isotope Stage 20 (MIS 20), in marine sediment records, however, this boundary is commonly found in interglacial period of MIS 19[1-2], leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments[3-5]. Based on this issue, here we propose to use the cosmogenic 10Be to address this conundrum. 10Be is a long-lived radionuclide produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols. Its atmospheric production rate is inversely proportional to the geomagnetic field intensity [6]. This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out both the 10Be studies and paleogeomagnetic measurements in Luochuan and Xifeng sections in Chinese Loess Plateau. Both loess profiles show that 10Be production rate was at a maximum-an indication of the dipole field reversal-at ca. 780 ± 3 ka BP., in paleosol unit S7 corresponding to MIS 19, proving that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records [1]. These results reaffirmed the conventional paleoclimatic correlation of loess-paleosol sequences with marine isotope stages and the standard loess timescale as correct. However, it is ~25 ka younger than the age (depth) of the paleogeomagnetic measurements, which show that the B-M boundary is in L8 in these two Chinese loess-paleosol sequences, demonstrating that loess magnetic overprinting has occurred. 1.Tauxe, L., et al., 1996, EARTH PLANET SC LETT, 140, 133-1462.Zhou, L.P., and Shackleton, 1999

  13. Solar Ion Processing of Itokawa Grains: Constraints on Surface Exposure Times

    NASA Technical Reports Server (NTRS)

    Christoffersen, R.; Keller, L. P.

    2015-01-01

    Analytical TEM observations obtained to date reveal that a significant sub-population of grains returned from the surface of asteroid Itokawa have had their outer 30-100 nm processed by space weathering effects. Although the effects include some surface deposition of condensed impact vapor and isolated impact melt splashes, much of the width of the space weathered outer margins or "rims" on grains is derived from solar wind processing of the original host grain. Similar to what has long been reported for some lunar grains, the ion-processed rims on Itokawa grains exhibit varing degrees and depths of penetration of atomic-displacement ion damage, resulting in complete amorphization for some rims (particularly in plagioclase), or formation of highly defective but still crystalline structures in others (particularly in pyroxene and olivine). Possibly different from lunar grains, however, is the presence of isolated internal cavities or voids in Itokawa grain rims, which may be implantation "bubbles" due to accumulating implanted solar wind H and/or He. For a given mineral exposed at a particular set of long term solar wind conditions, the level of ion damage in a given grain rim, the depth of damage penetration represented by the rim width, and the formation or lack of formation of implantation bubbles can all be linked to the time spent by the grain in an uncovered state on the topmost, space-exposed, regolith surface. For the lunar case, we have previously shown that with reasonable assumptions about solar wind characteristics over time, a model can be developed to estimate this exposure time based on the width of amorphous rims on lunar grains. Here we report on an expansion of the model to cover exposure time information contained in the array of solar ion-induced features in Itokawa grains.

  14. Infrared spectroscopy of sub-surface defects induced by remote hydrogen plasma exposure of silicon (100)

    SciTech Connect

    Lamb, H.H.; Bedge, S.G.; Wan, Z.

    1998-12-31

    Infrared multiple internal reflection (MIR) spectroscopy was used to investigate the local chemical bonding in sub-surface defects induced by remote hydrogen plasma exposure (RHPE) of Si(100) wafers. Exposure of very lightly doped n-type Si ([P] = 5 {times} 10{sup 13} cm{sup {minus}3}) to a remote hydrogen plasma for 2 min at 200 C results in the formation of Si monohydride species. An intense narrow band at 2078 cm{sup {minus}1} (FWHM = 7 cm{sup {minus}1}) and a small shoulder at 2065 cm{sup {minus}1} are observed. The data are consistent with monohydride termination of Si{l_brace}111{r_brace} platelet defects with a weak interaction between H atoms on opposing internal surfaces. In contrast, platelet nucleation at 200 C followed by growth at 300 C selectively generates Si dihydride species, as evidenced by a single broad infrared band at 2109 cm{sup {minus}1}. The P concentration was found to have a marked influence on the areal density and chemical bonding of sub-surface hydrogen. The MIR spectrum of lightly doped Si ([P] = 2 {times} 10{sup 14} cm{sup {minus}3}) after RHPE at 200 C contains broad peaks at 2078 and 2130 cm{sup {minus}1} consistent with Si monohydride and trihydride species. The authors infer that hydrogen saturates broken bonds along Si{l_brace}111{r_brace} Type 1 glide planes (one bond per Si atom) and along Si{l_brace}111{r_brace} Type II glide planes (three bonds per Si atom). The Si-H peak area indicates a H areal density {approximately}2 times higher than in very lightly doped Si.

  15. Impacts of hematite nanoparticle exposure on biomechanical, adhesive, and surface electrical properties of Escherichia coli cells.

    PubMed

    Zhang, Wen; Hughes, Joseph; Chen, Yongsheng

    2012-06-01

    Despite a wealth of studies examining the toxicity of engineered nanomaterials, current knowledge on their cytotoxic mechanisms (particularly from a physical perspective) remains limited. In this work, we imaged and quantitatively characterized the biomechanical (hardness and elasticity), adhesive, and surface electrical properties of Escherichia coli cells with and without exposure to hematite nanoparticles (NPs) in an effort to advance our understanding of the cytotoxic impacts of nanomaterials. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that E. coli cells had noticeable deformation with hematite treatment for 45 min with a statistical significance. The hematite-treated cells became significantly harder or stiffer than untreated ones, as evidenced by indentation and spring constant measurements. The average indentation of the hematite-treated E. coli cells was 120 nm, which is significantly lower (P < 0.01) than that of the untreated cells (approximately 400 nm). The spring constant of hematite-treated E. coli cells (0.28 ± 0.11 nN/nm) was about 20 times higher than that of untreated ones (0.01 ± 0.01 nN/nm). The zeta potential of E. coli cells, measured by dynamic light scattering (DLS), was shown to shift from -4 ± 2 mV to -27 ± 8 mV with progressive surface adsorption of hematite NPs, a finding which is consistent with the local surface potential measured by Kelvin probe force microscopy (KPFM). Overall, the reported findings quantitatively revealed the adverse impacts of nanomaterial exposure on physical properties of bacterial cells and should provide insight into the toxicity mechanisms of nanomaterials. PMID:22467500

  16. Impacts of Hematite Nanoparticle Exposure on Biomechanical, Adhesive, and Surface Electrical Properties of Escherichia coli Cells

    PubMed Central

    Zhang, Wen; Hughes, Joseph

    2012-01-01

    Despite a wealth of studies examining the toxicity of engineered nanomaterials, current knowledge on their cytotoxic mechanisms (particularly from a physical perspective) remains limited. In this work, we imaged and quantitatively characterized the biomechanical (hardness and elasticity), adhesive, and surface electrical properties of Escherichia coli cells with and without exposure to hematite nanoparticles (NPs) in an effort to advance our understanding of the cytotoxic impacts of nanomaterials. Both scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that E. coli cells had noticeable deformation with hematite treatment for 45 min with a statistical significance. The hematite-treated cells became significantly harder or stiffer than untreated ones, as evidenced by indentation and spring constant measurements. The average indentation of the hematite-treated E. coli cells was 120 nm, which is significantly lower (P < 0.01) than that of the untreated cells (approximately 400 nm). The spring constant of hematite-treated E. coli cells (0.28 ± 0.11 nN/nm) was about 20 times higher than that of untreated ones (0.01 ± 0.01 nN/nm). The zeta potential of E. coli cells, measured by dynamic light scattering (DLS), was shown to shift from −4 ± 2 mV to −27 ± 8 mV with progressive surface adsorption of hematite NPs, a finding which is consistent with the local surface potential measured by Kelvin probe force microscopy (KPFM). Overall, the reported findings quantitatively revealed the adverse impacts of nanomaterial exposure on physical properties of bacterial cells and should provide insight into the toxicity mechanisms of nanomaterials. PMID:22467500

  17. Effects of acid aerosol exposure on the surface properties of airway mucus

    SciTech Connect

    Lee, M.M.; Schuerch, S.; Roth, S.H.

    1995-12-31

    It was hypothesized that the mucous layer lining the tracheas of rats and guinea pigs contains surfactant material capable of lowering the air/mucus surface tension, {gamma}, and that exposure to an irritant aerosol would raise the {gamma}. The {gamma} of the surface film was measured directly by a spreading droplet technique and indirectly by displacement of polymethyl methacrylate particles into the aqueous layer. The morphology of the mucous film was examined by electron microscopy after nonaqueous fixation. {gamma} was 33.3 {plus_minus} 0.70 (SE) mN/m and 32.3 {plus_minus} 0.68 (SE) mN/m for the normal rat and guinea pig trachea, respectively. Exposure for 4 h to aerosols of sulfuric acid (94.1 {plus_minus} 18.68 (SD) and 43.3 {plus_minus} 4.57 (SD) mg/m{sup 3}) caused a several-fold increase in thickness of the mucous layer with exudation of protein-like material. The osmiophilic surfactant film at the air/mucus interface became irregularly thickened and multilayered. Despite these morphological changes {gamma} remained low, 33.2 {plus_minus} 0.43 (SE) mN/m and 32.6 {plus_minus} 0.60 (SE) mN/m for rats and guinea pigs, respectively, and displacement of particles into the subphase was not compromised. The results indicate that rodent tracheas are able to maintain a low surface tension in the presence of injury. 24 refs., 9 figs.

  18. A first 10Be cosmogenic glacial chronology from the High Atlas, Morocco, during the last glacial cycle.

    NASA Astrophysics Data System (ADS)

    Fink, David; Hughes, Philip; Fenton, Cassie

    2014-05-01

    Glacial geomorphological mapping, 10Be cosmogenic exposure ages of 21 erratics from cirque-valley systems and paleo-glacier climate modelling in the High Atlas Mountains, Morocco (31.1° N, 7.9° W), provides new and novel insights as to the history and evolution of the largest desert region on Earth. The Atlas Mountains display evidence of extensive and multiple Late Pleistocene glaciations whose extent is significantly larger than that recognised by previous workers. The largest glaciers formed in the Toubkal massif where we find 3 distinct phases of glacial advances within the last glacial cycle. The oldest moraines occurring at the lowest elevations have yielded eight 10Be ages ranging from 30 to 88 ka. Six of eight samples from moraines at intermediate elevations gave ages of 19 to 25 ka (2 outliers) which correlates well with the global Last Glacial Maximum (ca. 26-21 ka) and the last termination during marine isotope stage 2. Five erratics from the youngest and most elevated moraines yielded a suite of normally distributed exposure ages from 11 to 13 ka which supports a correlation with the northern hemisphere Younger Dryas (12.9-11.7 ka). The glacial record of the High Atlas effectively reflects moisture supply to the north-western Sahara Desert and can provide an indication of shifts between arid and pluvial conditions. The plaeo equilibrium line altitudes (ELA) of these three glacier phases was more than 1000 m lower than the predicted ELA based on today's temperatures. Glacier-climate modelling indicates that for each of these glacier phases climate was not only significantly cooler than today, but also much wetter. The new evidence on the extent, timing and palaeoclimatic significance of glaciations in this region has major implications for understanding moisture transfer between the North Atlantic Ocean and the Sahara Desert during Pleistocene cold stages.

  19. Suppression of blister formation and deuterium retention on tungsten surface due to mechanical polishing and helium pre-exposure

    NASA Astrophysics Data System (ADS)

    Nishijima, D.; Iwakiri, H.; Amano, K.; Ye, M. Y.; Ohno, N.; Tokunaga, K.; Yoshida, N.; Takamura, S.

    2005-07-01

    Low-energy deuterium (D) plasma exposure on tungsten (W), which is an important material for ITER, results in blister formation on the surface. Blister formation increases both micron-sized dust production and D retention. Blister formation depends greatly on surface pre-treatment. Deuterium plasma exposure on mirror-finished powder metallurgy W at 500 K for 3 h forms a blister with a diameter of a few hundred micrometres on the surface. Blister formations on the mechanically-polished and helium-pre-exposed surfaces are drastically suppressed. Deuterium retention is also reduced on both the mechanically-polished surface and the helium-pre-exposed surface compared with that on the mirror-finished surface. The suppressive effect of blister formation on the mechanically-polished surface is maintained for 50 h. The size of blisters and D retention on mirror-finished surface exposed for 50 h increases by some degrees (<~500 µm, 7 × 1020 m-2) compared with that on mirror-finished surface exposed for 3 h (<~200 µm, 5 × 1020 m-2), but is not proportional to the exposure time. The saturation level of D retention even on blister-rich surfaces seems to be lower than an order of 1021 D2 m-2.

  20. 10Be measured in a GRIP snow pit and modeled using the ECHAM5-HAM general circulation model

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Beer, J.; Jouzel, J.; Feichter, J.; Kubik, P.

    2008-03-01

    10Be measured in a Greenland Ice Core Project (GRIP) snow pit (1986-1990) with a seasonal resolution is compared with the ECHAM5-HAM GCM run. The mean modeled 10Be concentration in ice (1.0.104 atoms/g) agrees well with the measured value (1.2.104 atoms/g). The measured 10Be deposition flux (88 atoms/m2/s) also agrees well with the modeled flux (69 atoms/m2/s) and the measured precipitation rate (0.67 mm/day) agrees with the modeled rate (0.61 mm/day). The mean surface temperature of -31°C estimated from δ 18O is lower than the temperature measured at a near-by weather station (-29°C) and the modeled temperature (-26°C). During the 5-year period the concentrations and deposition fluxes, both measured and modeled, show a decreasing trend consistent with the increase in the solar activity. The variability of the measured and modeled concentrations and deposition fluxes is very similar suggesting that the variability is linked to a variability in production rather than the local meteorology.

  1. Reconciling tectonic shortening, sedimentation and spatial patterns of erosion from 10Be paleo-erosion rates in the Argentine Precordillera

    NASA Astrophysics Data System (ADS)

    Val, Pedro; Hoke, Gregory D.; Fosdick, Julie C.; Wittmann, Hella

    2016-09-01

    The temporal evolution of erosion over million-year timescales is key to understand the development of mountain ranges and adjacent fold-and-thrust belts. While models of orogenic wedge dynamics predict an instantaneous response of erosion to pulses of rock uplift, stream-power based models predict that catchment-wide erosion maxima significantly lag behind a pulse of rock uplift. Here, we explore the relationships between rock uplift, erosion, and sediment deposition in the Argentine Precordillera fold-and-thrust belt at 30°S. Using a combination of 10Be-derived paleo-erosion rates, constraints on re-exposure using 26Al/10Be ratios, geomorphic observations and detrital zircon provenance, we demonstrate that the attainment of maximum upland erosion rates lags the maximum rate of deformation over million-year timescales. The magnitudes and causes of the erosional delays shed new light on the catchment erosional response to tectonic deformation and rock uplift in orogenic wedges.

  2. COMMON ISSUES IN HUMAN AND ECOSYSTEM EXPOSURE ASSESSMENT: THE SIGNIFICANCE OF PARTITIONING, KINETICS, AND UPTAKE AT BIOLOGICAL EXCHANGE SURFACES

    EPA Science Inventory

    Exogenous chemicals enter organisms through critical surfaces in the lung, gills, gut, and skin. Transfer across these boundaries is the first step in characterizing the ratio of tissue dose to external exposure. Surface processes and fugacity are important elements of both human...

  3. The Treponema denticola Major Sheath Protein Is Predominantly Periplasmic and Has Only Limited Surface Exposure

    PubMed Central

    Caimano, Melissa J.; Bourell, Kenneth W.; Bannister, Teresa D.; Cox, David L.; Radolf, Justin D.

    1999-01-01

    The recent discovery that the Treponema pallidum genome encodes 12 orthologs of the Treponema denticola major sheath protein (Msp) prompted us to reexamine the cellular location and topology of the T. denticola polypeptide. Experiments initially were conducted to ascertain whether Msp forms an array on or within the T. denticola outer membrane. Transmission electron microscopy (EM) of negatively stained and ultrathin-sectioned organisms failed to identify a typical surface layer, whereas freeze-fracture EM revealed that the T. denticola outer membrane contains heterogeneous transmembrane proteins but no array. In contrast, a lattice-like structure was observed in vesicles released from mildly sonicated treponemes; combined EM and biochemical analyses demonstrated that this structure was the peptidoglycan sacculus. Immunoelectron microscopy (IEM) subsequently was performed to localize Msp in T. denticola. Examination of negatively stained whole mounts identified substantial amounts of Msp in sonicated organisms. IEM of ultrathin-sectioned, intact treponemes also demonstrated that the preponderance of antigen was unassociated with the outer membrane. Lastly, immunofluorescence analysis of treponemes embedded in agarose gel microdroplets revealed that only minor portions of Msp are surface exposed. Taken as a whole, our findings challenge the widely held belief that Msp forms an array within the T. denticola outer membrane and demonstrate, instead, that it is predominantly periplasmic with only limited surface exposure. These findings also have implications for our evolving understanding of the contribution(s) of Msp/Tpr orthologs to treponemal physiology and disease pathogenesis. PMID:10417176

  4. Long-Term Microturbine Exposure of an Advanced Alloy for Microturbine Primary Surface Recuperators

    SciTech Connect

    Matthews, Wendy; More, Karren Leslie; Walker, Larry R

    2009-01-01

    Haynes alloy HR-120 (Haynes and HR-120 are trademarks of Haynes International, Inc.) forms a protective oxide scale when exposed to the harsh operating environment of a microturbine primary surface recuperator. Primary surface recuperators manufactured from HR-120 are currently in use on the Capstone C65 MicroTurbine (MicroTurbine is a registered trademark of Capstone Turbine Corporation). Long-term microturbine tests of this alloy are currently being conducted at an elevated turbine exit temperature ({approx}100 F higher than that in a normal operation) at Capstone Turbine Corporation. Alloy samples that have been tested under steady-state microturbine operating conditions are removed after predetermined exposure intervals for characterization by Capstone Turbine Corporation in collaboration with Oak Ridge National Laboratory. Such evaluations include the characterization of surface oxide scales and the associated alloy compositional changes following a steady-state operation ranging from 1800 h to 14,500 h. Results from the microstructural and compositional analyses of these long-term steady-state engine-tested HR-120 samples are used to illustrate the progression of alloy oxidation in the microturbine operating environment.

  5. Monitoring of troponin release from cardiomyocytes during exposure to toxic substances using surface plasmon resonance biosensing.

    PubMed

    Andersson, Henrik; Kågedal, Bertil; Mandenius, Carl-Fredrik

    2010-10-01

    Troponin T (TnT) is a useful biomarker for studying drug-induced toxicity effects on cardiac cells. We describe how a surface plasmon resonance (SPR) biosensor was applied to monitor the release of TnT from active HL-1 cardiomyocytes in vitro when exposed to cardiotoxic substances. Two monoclonal human TnT antibodies were compared in the SPR immunosensor to analyse the TnT release. The detection limit of TnT was determined to be 30 ng/ml in a direct assay set-up and to be 10 ng/ml in a sandwich assay format. Exposure of the cardiomyocytes to doxorubicin, troglitazone, quinidine and cobalt chloride for periods of 6 and 24 h gave significant SPR responses, whereas substances with low toxicity showed insignificant effects (ascorbic acid, methotrexate). The SPR results were verified with a validated immunochemiluminescence method which showed a correlation of r (2) = 0.790. PMID:20694813

  6. Precise Electromagnetic Tests of Ab Initio Calculations of Light Nuclei: States in {sup 10}Be

    SciTech Connect

    McCutchan, E. A.; Lister, C. J.; Wiringa, R. B.; Pieper, Steven C.; Seweryniak, D.; Greene, J. P.; Carpenter, M. P.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Zhu, S.; Chiara, C. J.; Stefanescu, I.

    2009-11-06

    In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in {sup 10}Be using the Doppler shift attenuation method (DSAM) following the {sup 7}Li({sup 7}Li,alpha){sup 10}Be reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The J{sup p}i=2{sub 1}{sup +} state at 3.37 MeV has tau=205+-(5){sub stat}+-(7){sub sys} fs corresponding to a B(E2arrow down) of 9.2(3)e{sup 2} fm{sup 4} in broad agreement with many calculations. The J{sup p}i=2{sub 2}{sup +} state at 5.96 MeV was found to have a B(E2arrow down) of 0.11(2)e{sup 2} fm{sup 4} and provides a more discriminating test of nuclear models. New Green's function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.

  7. 26 Al - 10 Be burial ages of a Pleistocene Terrace in the Vienna Basin

    NASA Astrophysics Data System (ADS)

    Neuhuber, Stephanie; Braumann, Sandra; Lüthgens, Christopher; Schäfter, Jörg; Häuselmann, Philipp; Fiebig, Markus

    2015-04-01

    The Vienna Basin is a pull-apart basin located between the Eastern Alps and the Western Carpathians. Its main subsidence started in the Miocene and resulted in a maximum of 6 km sedimentary infill. Up to five Pleistocene terraces formed by the Danube river and its tributaries and are separated by their geometic cross cutting and topographic relationships. The ongoing tectonic displacement results in tilting of terrace levels and prevents the correlation of similar levels to one sedimentation event. For this reason absolute age dating is essential in this setting. This research applies 26Al/10Be isochrone dating of one selected Pleistocene Terrace, the Gänserndorf terrace at two different sampling sites. This terrace has already a numerical age determined by OSL age of 250 +/- 50 kyr. Isochrone age dating may be used for samples with different transport histories and exposition duration that share the same last burial event and is ideal for the sedimentary setting of the terrace gravels of the Gänserndorf terrace. The source area of the terrace consists mainly of metamorphic rocks that contain large quartz pebbles that are suitable for cosmogenic 26Al and 10Be extraction.

  8. Reactions with a 10Be beam to study the one-neutron halo nucleus 11Be

    NASA Astrophysics Data System (ADS)

    Jones, K. L.

    2016-07-01

    Halo nuclei are excellent examples of few-body systems consisting of a core and weakly-bound halo nucleons. Where there is only one nucleon in the halo, as in 11Be, the many-body problem can be reduced to a two-body problem. The contribution of the 1s1/2 orbital to the ground state configuration in 11Be, characterized by the spectroscopic factor, S, has been extracted from direct reaction data by many groups over the past five decades with discrepant results. An experiment was performed at the Holifield Radioactive Ion Beam Facility using a 10Be primary beam at four different energies with the goal of resolving the discrepancy through a consistent analysis of elastic, inelastic, and transfer channels. Faddeev-type calculations, released after the publication of the experimental results, show that dynamic core excitation in the transfer process can lead to reduced differential cross sections at higher beam energies. This reduction would lead to the extraction of decreasing values of S with increasing beam energy. A 10Be(d,p) measurement at Ed greater than 25 MeV is necessary to investigate the effects of core excitation in the reaction.

  9. Improved Timing of Deglaciation of the Southwestern Scandinavian Ice Sheet Using 10Be Dating

    NASA Astrophysics Data System (ADS)

    Gump, D.; Briner, J. P.; Svendsen, J. I.; Mangerud, J.

    2015-12-01

    We present 28 new 10Be ages from glacial erratic boulders to constrain Scandinavian Ice Sheet deglaciation along the major fjord system of Boknafjorden in southwest Norway. Results indicate ages in the range 20-14 ka and complement our previous findings that the Norwegian Channel Ice Stream (NCIS) had retreated some 400 km as early as ~20 ka (Svendsen et al., 2015) and further corroborate that this was followed by a second pulse of deglaciation at ~16 ka. After the immediate coast was rendered an ice-free corridor at ~20 ka, our new suite of ages identifies ~16 ka as a period of a possible culmination of re-advance, and almost certainly the onset of a subsequent period of retreat. These findings are promising for the possibility of long lake sediment archives from areas around the mouth of Boknafjorden. Additionally, by coupling our new 10Be ages of erratic boulders from sea level and from summits bordering Boknafjorden with topographic profiles and rudimentary ice-sheet profile calculations (Benn and Hulton, 2010), we are able to estimate spatial and temporal Scandinavian Ice Sheet history along both vertical and horizontal transects. Our results not only fill chronological gaps and add to a growing database of ages of deglaciation from the southwest Norway, but also provide new constraints for a three-dimensional reconstruction of the Scandinavian Ice Sheet during deglaciation.

  10. Calculated values of atomic oxygen fluences and solar exposure on selected surfaces of LDEF

    NASA Technical Reports Server (NTRS)

    Gillis, J. R.; Pippin, H. G.; Bourassa, R. J.; Gruenbaum, P. E.

    1995-01-01

    Atomic oxygen (AO) fluences and solar exposure have been modeled for selected hardware from the Long Duration Exposure Facility (LDEF). The atomic oxygen exposure was modeled using the microenvironment modeling code SHADOWV2. The solar exposure was modeled using the microenvironment modeling code SOLSHAD version 1.0.

  11. Loess 10Be evidence for an asynchronous Brunhes-Matuyama magnetic polarity reversal

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Beck, J. Warren; Kong, Xianghui; An, Zhisheng; Qiang, Xiaoke; Wu, Zhenkun; Xian, Feng; Ao, Hong

    2015-04-01

    In Chinese loess the Brunhes-Matuyama (B-M) geomagnetic reversal appears to occur about 25 ka prior to the established axial dipole reversal age found in many marine sediments, i.e., in Chinese loess this magnetic reversal boundary is found in glacial loess unit L8 which is thought to be correlated with Marine Isotope Stage 20 (MIS 20), in marine sediment records, however, this boundary is commonly found in interglacial period of MIS 19 (Tauxe et al., 1996; Zhou and Shackleton, 1999), leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments (Wang et al., 2006; Liu et al., 2008; Jin and Liu, 2011). Based on this issue, here we propose to use the cosmogenic 10Be to address this conundrum. 10Be is a long-lived radionuclide produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols. Its atmospheric production rate is inversely proportional to the geomagnetic field intensity (Masarik and Beer, 1999). This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out both the 10Be studies and paleogeomagnetic measurements in Luochuan and Xifeng sections in Chinese Loess Plateau. Both loess profiles show that 10Be production rate was at a maximum-an indication of the dipole field reversal-at ca. 780 ± 3 ka BP., in paleosol unit S7 corresponding to MIS 19, proving that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records (Tauxe et al., 1996). These results reaffirmed the conventional paleoclimatic correlation of loess-paleosol sequences with marine isotope stages and the standard loess timescale as correct. However, it is ~25 ka younger than the age (depth) of the paleogeomagnetic measurements which show that the B-M boundary is in L8 in these two Chinese loess-paleosol sequences, demonstrating that loess

  12. Quantifying denudation rates on inselbergs in the central Namib Desert using in situ-produced cosmogenic {sup 10}Be and {sup 26}Al

    SciTech Connect

    Cockburn, H.A.P.; Summerfield, M.A.; Seidl, M.A.

    1999-05-01

    In situ-produced cosmogenic isotope concentrations in bedrock surfaces provide valuable estimates of site-specific, long-term rates of denudation and provide constraints for numerical landscape-evolution models. Measurements of cosmogenic {sup 10}Be and {sup 26}Al from graphite inselbergs in the arid to hyperarid central Namib Desert, Namibia, indicate a mean rate of summit lowering of 5.07 {+-} 1.1 m/m.y. over the past {ge} 10{sup 5} yr. The persistence of an arid climate in the region suggests that a similar rate may have prevailed for the past {approximately} 10 m.y. and possibly throughout much of the Cenozoic. Some samples have complex exposure histories that can be explained by the mode of inselberg weathering and mass wasting. The denudation rates estimated here are an order of magnitude higher than those reported for inselbergs in a significantly more humid environment in South Australia. This difference may largely be due to active salt weathering in the central Namib as a result of high levels of coastal fog precipitation.

  13. Experimental Investigation of Weak Non-Mesonic Decay of 10Be(Lambda)Hypernuclei at CEBAF

    SciTech Connect

    S. Majewski; L. Majling; A. Margaryan; L. Tang

    2005-08-05

    Hypernuclei are convenient laboratory to study the baryon-baryon weak interaction and associated effective Hamiltonian. The strangeness changing process, in which a Lambda hyperon converts to a neutron with a release up to 176 MeV, provides a clear signal for a conversion of an s-quark to a d-quark. We propose to perform a non-mesonic weak decay study of 10Be(Lambda)hypernuclei using the (e,eK) reaction. These investigations will fully utilize the unique parameters of the CEBAF CW electron beam and RF system and are enabled by (1) the use of new detector for alpha particles based on the recently developed RF timing technique with picosecond resolution and (2) the small angle and large acceptance kaon spectrometer-HKS in Hall C.

  14. Tectonic control on 10Be-derived erosion rates in the Garhwal Himalaya, India

    NASA Astrophysics Data System (ADS)

    Scherler, Dirk; Bookhagen, Bodo; Strecker, Manfred R.

    2014-02-01

    Erosion in the Himalaya is responsible for one of the greatest mass redistributions on Earth and has fueled models of feedback loops between climate and tectonics. Although the general trends of erosion across the Himalaya are reasonably well known, the relative importance of factors controlling erosion is less well constrained. Here we present 25 10Be-derived catchment-averaged erosion rates from the Yamuna catchment in the Garhwal Himalaya, northern India. Tributary erosion rates range between ~0.1 and 0.5 mm yr-1 in the Lesser Himalaya and ~1 and 2 mm yr-1 in the High Himalaya, despite uniform hillslope angles. The erosion-rate data correlate with catchment-averaged values of 5 km radius relief, channel steepness indices, and specific stream power but to varying degrees of nonlinearity. Similar nonlinear relationships and coefficients of determination suggest that topographic steepness is the major control on the spatial variability of erosion and that twofold to threefold differences in annual runoff are of minor importance in this area. Instead, the spatial distribution of erosion in the study area is consistent with a tectonic model in which the rock uplift pattern is largely controlled by the shortening rate and the geometry of the Main Himalayan Thrust fault (MHT). Our data support a shallow dip of the MHT underneath the Lesser Himalaya, followed by a midcrustal ramp underneath the High Himalaya, as indicated by geophysical data. Finally, analysis of sample results from larger main stem rivers indicates significant variability of 10Be-derived erosion rates, possibly related to nonproportional sediment supply from different tributaries and incomplete mixing in main stem channels.

  15. OSL and Cosmogenic 10Be Dating of Fluvial Terraces on the Northeast Pamir Margin, Northwest China

    NASA Astrophysics Data System (ADS)

    Thompson, J. A.; Chen, J.; Yang, H.; Li, T.; Bookhagen, B.; Burbank, D. W.; Bufe, A.

    2015-12-01

    Along the northeast Pamir margin in northwest China, flights of late Pleistocene fluvial terraces span actively deforming structures. We present detailed results on three terraces that we dated using optically stimulated luminescence (OSL) and cosmogenic 10Be techniques. Quartz OSL dating of two different grain sizes (4-11 and 90-180 μm) revealed the fine-grain quartz fraction overestimates the terrace ages by up to an order of magnitude. Two-mm, small-aliquot, coarse-grain quartz OSL ages, calculated using the finite mixture model, yielded stratigraphically consistent ages within error and dated times of terrace deposition to ~15 ka, ~18.5 ka, and ~75 ka. We speculate the observed grain-size dependence of OSL ages is likely related to the mode of transport of the grains in the fluvial system, with coarser grains sizes spending more time on sand bars where they are more thoroughly bleached than grains in the turbid, commonly episodic flows that carry the silt fraction. Our study suggests that, in flashy, turbid fluvial systems, coarse-grain OSL samples are likely to yield more reliable depositional ages than will fine-grain samples. Cosmogenic 10Be depth profiles date the times of terrace abandonment to ~8 ka, ~15 ka, and ~75 ka, yielding ages in overall agreement with the coarse-grain OSL ages. These ages are generally consistent with other dated terraces in the region that place their deposition and subsequent abandonment during the last deglaciation (13-18 ka) and suggest the formation of these terraces on the margins of the Tarim Basin and along the flanks of the Tian Shan is climatically controlled.

  16. Isovector and isoscalar dipole excitations in 9Be and 10Be studied with antisymmetrized molecular dynamics

    NASA Astrophysics Data System (ADS)

    Kanada-En'yo, Yoshiko

    2016-02-01

    Isovector and isoscalar dipole excitations in 9Be and 10Be are investigated in the framework of antisymmetrized molecular dynamics, in which angular-momentum and parity projections are performed. In the present method, 1p-1h excitation modes built on the ground state and a large amplitude α -cluster mode are taken into account. The isovector giant dipole resonance (GDR) in E >20 MeV shows the two-peak structure, which is understood from the dipole excitation in the 2 α core part with the prolate deformation. Because of valence neutron modes against the 2 α core, low-energy E 1 resonances appear in E <20 MeV, exhausting about 20 % of the Thomas-Reiche-Kuhn sum rule and 10 % of the calculated energy-weighted sum. The dipole resonance at E ˜15 MeV in 10Be can be interpreted as the parity partner of the ground state having a 6He+α structure and has remarkable E 1 strength because of the coherent contribution of two valence neutrons. The isoscalar dipole strength for some low-energy resonances is significantly enhanced by the coupling with the α -cluster mode. For the E 1 strength of 9Be, the calculation overestimates the energy-weighted sum (EWS) in the low-energy (E <20 MeV) and GDR (20

  17. Influence of tropospheric ozone control on exposure to ultraviolet radiation at the surface.

    PubMed

    Madronich, Sasha; Wagner, Mark; Groth, Philip

    2011-08-15

    Improving air quality by reducing ambient ozone (O(3)) will likely lower O(3) concentrations throughout the troposphere and increase the transmission of solar ultraviolet (UV) radiation to the surface. The changes in surface UV radiation between two control scenarios (nominally 84 and 70 ppb O(3) for summer 2020) in the Eastern two-thirds of the contiguous U.S. are estimated, using tropospheric O(3) profiles calculated with a chemistry-transport model (Community Multi-Scale Air Quality, CMAQ) as inputs to a detailed model of the transfer of solar radiation through the atmosphere (tropospheric ultraviolet-visible, TUV) for clear skies, weighed for the wavelengths known to induce sunburn and skin cancer. Because the incremental emission controls differ according to region, strong spatial variability in O(3) reductions and in corresponding UV radiation increments is seen. The geographically averaged UV increase is 0.11 ± 0.03%, whereas the population-weighted increase is larger, 0.19 ± 0.06%, because O(3) reductions are greater in more densely populated regions. These relative increments in exposure are non-negligible given the already high incidence of UV-related health effects, but are lower by an order of magnitude or more than previous estimates. PMID:21755973

  18. Surface exposure to sunlight stimulates CO2 release from permafrost soil carbon in the Arctic

    PubMed Central

    Cory, Rose M.; Crump, Byron C.; Dobkowski, Jason A.; Kling, George W.

    2013-01-01

    Recent climate change has increased arctic soil temperatures and thawed large areas of permafrost, allowing for microbial respiration of previously frozen C. Furthermore, soil destabilization from melting ice has caused an increase in thermokarst failures that expose buried C and release dissolved organic C (DOC) to surface waters. Once exposed, the fate of this C is unknown but will depend on its reactivity to sunlight and microbial attack, and the light available at the surface. In this study we manipulated water released from areas of thermokarst activity to show that newly exposed DOC is >40% more susceptible to microbial conversion to CO2 when exposed to UV light than when kept dark. When integrated over the water column of receiving rivers, this susceptibility translates to the light-stimulated bacterial activity being on average from 11% to 40% of the total areal activity in turbid versus DOC-colored rivers, respectively. The range of DOC lability to microbes seems to depend on prior light exposure, implying that sunlight may act as an amplification factor in the conversion of frozen C stores to C gases in the atmosphere. PMID:23401500

  19. Cosmic rays 10Be biennal data and their relationship to aurorae and sunspots

    NASA Technical Reports Server (NTRS)

    Attolini, M. R.; Cecchini, S.; Castagnoli, G. C.; Galli, M.; Nanni, T.

    1985-01-01

    The galactic cosmic ray (C.R.) variations which should give information on three dimensional aspects of the heliospheric magnetic fields and on the solar wind, which modulate their influx into the Solar System were studied. In order to decode the information from the C.R. series it is necessary to know the mechanisms through which the modulation is produced. It it clear that a balance of effects with sources at different heliospheric latitudes results in the modulated C.R. intensity. It is found that the modulation of 10Be in polar ice may be due to at least two main contributions: (1) negative and in phase with the Solar flare activity modulating the cosmic ray flux in Forbush-type decreases, and (2) positive in phase with the appearance of large wind streams situated at both polar coronal holes. It is found that the high heliolatitude activity is related to a stable periodicity of 11.1y whereas the low heliolatitude activity contributes to the wondering of the solar cycles.

  20. 26Al/10Be burial dating of Xujiayao-Houjiayao site in Nihewan Basin, northern China.

    PubMed

    Tu, Hua; Shen, Guanjun; Li, Haixu; Xie, Fei; Granger, Darryl E

    2015-01-01

    The Xujiayao-Houjiayao site in Nihewan Basin is among the most important Paleolithic sites in China for having provided a rich collection of hominin and mammalian fossils and lithic artifacts. Based on biostratigraphical correlation and exploratory results from a variety of dating methods, the site has been widely accepted as early Upper Pleistocene in time. However, more recent paleomagnetic analyses assigned a much older age of ∼500 ka (thousand years). This paper reports the application of 26Al/10Be burial dating as an independent check. Two quartz samples from a lower cultural horizon give a weighted mean age of 0.24 ± 0.05 Ma (million years, 1σ). The site is thus younger than 340 ka at 95% confidence, which is at variance with the previous paleomagnetic results. On the other hand, our result suggests an age of older than 140 ka for the site's lower cultural deposits, which is consistent with recent post-infrared infrared stimulated luminescence (pIR-IRSL) dating at 160-220 ka. PMID:25706272

  1. 26Al/10Be Burial Dating of Xujiayao-Houjiayao Site in Nihewan Basin, Northern China

    PubMed Central

    Tu, Hua; Shen, Guanjun; Li, Haixu; Xie, Fei; Granger, Darryl E.

    2015-01-01

    The Xujiayao-Houjiayao site in Nihewan Basin is among the most important Paleolithic sites in China for having provided a rich collection of hominin and mammalian fossils and lithic artifacts. Based on biostratigraphical correlation and exploratory results from a variety of dating methods, the site has been widely accepted as early Upper Pleistocene in time. However, more recent paleomagnetic analyses assigned a much older age of ∼500 ka (thousand years). This paper reports the application of 26Al/10Be burial dating as an independent check. Two quartz samples from a lower cultural horizon give a weighted mean age of 0.24 ± 0.05 Ma (million years, 1σ). The site is thus younger than 340 ka at 95% confidence, which is at variance with the previous paleomagnetic results. On the other hand, our result suggests an age of older than 140 ka for the site’s lower cultural deposits, which is consistent with recent post-infrared infrared stimulated luminescence (pIR-IRSL) dating at 160–220 ka. PMID:25706272

  2. The impact of geomagnetic spikes on the production rates of cosmogenic 14C and 10Be in the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Fournier, Alexandre; Gallet, Yves; Usoskin, Ilya; Livermore, Philip W.; Kovaltsov, Gennady A.

    2015-04-01

    We seek corroborative evidence of the geomagnetic spikes detected in the Near East ca. 980 BC and 890 BC in the records of the past production rates of the cosmogenic nuclides 14C and 10Be. Our forward modeling strategy rests on global, time-dependent, geomagnetic spike field models feeding state-of-the-art models of cosmogenic nuclide production. We find that spike models with an energy budget in line with presently inferred large-scale flow at Earth's core surface fail to produce a visible imprint in the nuclide record. Spike models able to reproduce the intensity changes reported in the Near East require an unaccountably high-magnitude core flow, yet their computed impact on cosmogenic isotope production rates remains ambiguous. No simple and unequivocal agreement is obtained between the observed and modeled nuclide records at the epochs of interest. This indicates that cosmogenic nuclides cannot immediately be used to confirm the occurrence of these two geomagnetic spikes.

  3. Surface morphology changes to tungsten under exposure to He ions from an electron cyclotron resonance plasma source

    NASA Astrophysics Data System (ADS)

    Donovan, David; Maan, Anurag; Duran, Jonah; Buchenauer, Dean; Whaley, Josh

    2015-11-01

    Exposure of tungsten to low energy (<100 eV) helium plasmas at temperatures between 900-1900 K in both laboratory experiments and tokamaks has been shown to cause severe nanoscale modification of the near surface resulting the growth of tungsten tendrils. We used a relatively low flux (2.5x1019 ions m-2 s-1) compact ECR plasma source at Sandia-California to investigate the early stages of helium induced tungsten damage. Exposures of polished tungsten discs were performed and characterized using SEM, AFM, and FIB cross section imaging. Bubbles have been seen on the exposed tungsten surface and in sub-surface cross sections growing to up to 150 nm in diameter. Comparisons were made between exposures of warm rolled Plansee tungsten discs and ALMT ITER grade tungsten samples. A similar He plasma exposure stage has now been developed at the University of Tennessee-Knoxville with an improved compact ECR plasma source. Status of the new UTK exposure stage will be discussed as well as planned experiments and new material characterization techniques (EBSD, GIXRD). Work supported by US DOE Contract DE-AC04-94AL85000 and the PSI Science Center.

  4. Global scale analysis of the stream power law parameters based on worldwide 10Be denudation rates

    NASA Astrophysics Data System (ADS)

    Harel, Marie-Alice; Mudd, Simon; Attal, Mikael

    2015-04-01

    The stream power law, expressed as E = KAmSn where E is erosion rate [LT-1], K is erodibility [T-1L(1-2m)], A is drainage area [L2], S is channel gradient [L/L] and m and n are constants, is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for a large number of applications such as topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of uplift patterns and rates. However, the unknown parameters K, m and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably alters the use and interpretation of the model. In this study, we compile published 10Be basin-wide erosion rates (n = 1335) in order to assess the m/n ratio (or concavity index), the slope exponent n and erodibility coefficient K using the integral method of channel profile analysis. These three parameters are calculated for 66 areas and allow for a global scale analysis in terms of climatic, tectonic and environmental settings. Our results suggest that (i) many sites are too noisy or do not have enough data to predict n and K with a satisfying level of confidence; (ii) the slope exponent is predominantly greater than one, meaning that the relationship between erosion rate and the channel gradient is non-linear, supporting the idea that incision is a threshold controlled process. Furthermore, a multi-regression analysis and the calculation of n and K using a reference concavity index m/n = 0.45 demonstrate that (iii) many intuitive or previously demonstrated local-scale trends, such as the correlation between erosion rate and climate, do not appear at a global scale.

  5. Global Scale Analysis of the Stream Power Law Parameters based on Worldwide 10Be Denudation Rates

    NASA Astrophysics Data System (ADS)

    Harel, M. A.; Mudd, S. M.; Attal, M.

    2015-12-01

    The stream power law, expressed as E = KAmSn where E is erosion rate [LT-1], K is erodibility [T-1L(1-2m)], A is drainage area [L2], S is channel gradient [L/L] and m and n are constants, is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for a large number of applications such as topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of uplift patterns and rates. However, the unknown parameters K, m and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably alters the use and interpretation of the model. In this study, we compile published 10Be basin-wide erosion rates (N= 1423) in order to assess the m/n ratio (or concavity index), the slope exponent n and erodibility coefficient K using the integral method of channel profile analysis. These three parameters are calculated for 67 areas and allow for a global scale analysis in terms of climatic, tectonic and environmental settings. Our results suggest that (i) many sites are too noisy or do not have enough data to predict n and K with a satisfying level of confidence; (ii) the slope exponent is predominantly greater than one, meaning that the relationship between erosion rate and the channel gradient is non-linear, supporting the idea that incision is a threshold controlled process. Furthermore, a multi-regression analysis and the calculation of n and K using a reference concavity index m/n = 0.45 demonstrates that (iii) many intuitive or previously demonstrated local-scale trends, such as the correlation between erosion rate and climate, do not appear at a global scale.

  6. Conserved Regions of Gonococcal TbpB Are Critical for Surface Exposure and Transferrin Iron Utilization

    PubMed Central

    Ostberg, Karen L.; DeRocco, Amanda J.; Mistry, Shreni D.; Dickinson, Mary Kathryne

    2013-01-01

    The transferrin-binding proteins TbpA and TbpB enable Neisseria gonorrhoeae to obtain iron from human transferrin. The lipoprotein TbpB facilitates, but is not strictly required for, TbpA-mediated iron acquisition. The goal of the current study was to determine the contribution of two conserved regions within TbpB to the function of this protein. Using site-directed mutagenesis, the first mutation we constructed replaced the lipobox (LSAC) of TbpB with a signal I peptidase cleavage site (LAAA), while the second mutation deleted a conserved stretch of glycine residues immediately downstream of the lipobox. We then evaluated the resulting mutants for effects on TbpB expression, surface exposure, and transferrin iron utilization. Western blot analysis and palmitate labeling indicated that the lipobox, but not the glycine-rich motif, is required for lipidation of TbpB and tethering to the outer membrane. TbpB was released into the supernatant by the mutant that produces TbpB LSAC. Neither mutation disrupted the transport of TbpB across the bacterial cell envelope. When these mutant TbpB proteins were produced in a strain expressing a form of TbpA that requires TbpB for iron acquisition, growth on transferrin was either abrogated or dramatically diminished. We conclude that surface tethering of TbpB is required for optimal performance of the transferrin iron acquisition system, while the presence of the polyglycine stretch near the amino terminus of TbpB contributes significantly to transferrin iron transport function. Overall, these results provide important insights into the functional roles of two conserved motifs of TbpB, enhancing our understanding of this critical iron uptake system. PMID:23836816

  7. Origin of orbital debris impacts on Long Duration Exposure Facility's (LDEF) trailing surfaces

    NASA Technical Reports Server (NTRS)

    Kessler, Donald J.

    1992-01-01

    Orbital debris tracked by the US Space Command is mostly in near circular orbit around the Earth. If small debris were in the same types of orbits, there would be very few orbital debris impacts on the Long Duration Exposure Facility's (LDEF's) trailing surfaces. However, at least 15 percent of the impacts found on the trailing A03 gold surface was found to be orbital debris impacts. This measurement suggests that the orbital distribution of small debris is not the same as that of larger debris. Although this is not a total surprise, since modelling of satellite breakups has predicted different distributions, it does raise questions as to what types of orbits could be responsible for these impacts. A model was developed to explain these LDEF results. The model calculates the expected debris impact crater distribution around LDEF, as a function of debris orbital parameters. The results show that only low inclination and highly elliptical orbits could be responsible for these impacts. The most common object left in this type of orbit is an orbital transfer stage, used by the US and ESA to place objects into geosynchronous orbit, and inclinations near 28 and 7 degrees for the US and ESA, respectively. Even large fragments from satellites, which break up in these types of orbits, are difficult to observe from the ground; consequently, little is known about the number and characteristics of breakups in these orbits. The LDEF data suggest that these objects are breaking up. The LDEF data also suggest that the ratio of the contribution of small debris from this type of orbit to the contribution from circular orbits is about an order of magnitude larger than the same ratio for debris tracked by the US Space Command.

  8. Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite

    PubMed Central

    Moreau, David; Villain, Arthur; Ku, David N; Corté, Laurent

    2014-01-01

    Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments. PMID:25482413

  9. Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite.

    PubMed

    Moreau, David; Villain, Arthur; Ku, David N; Corté, Laurent

    2014-01-01

    Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments. PMID:25482413

  10. Selecting scenarios to assess exposure of surface waters to veterinary medicines in Europe.

    PubMed

    Schneider, Manuel K; Stamm, Christian; Fenner, Kathrin

    2007-07-01

    Registering a veterinary medicinal product (VMP) in the European Union requires assessing its potential to contaminate surface waters (SW) on a European scale. VMP are spread to land in manure or excreted during grazing and may enter SW through runoff, erosion, or leaching. Since the factors driving these processes vary largely across Europe, it is necessary to identify characteristic conditions, so-called scenarios, under which VMP enter SW. These scenarios may guide the parameterization of mechanistic fate models to predict environmental concentrations for environmental risk assessment. A number of such scenarios for pesticides and VMP have been developed rather pragmatically. Here, we describe how a geo-referenced European database of driving factors was used to divide the European environment into groups with similar conditions for SW contamination by VMP. Out of these groups, relevant exposure scenarios in Europe were selected by a simple scoring system. Comparing these to the existing scenarios showed that a number of situations are not well covered. The newly identified scenarios are primarily located in hilly areas of Central Europe and the Mediterranean, and in Eastern European plains with a continental climate. We recommend that they are included in the technical guidelines for higher-tier assessment of VMP. PMID:17695913

  11. Surface exposure dating of glacial lake shorelines: implications for constraining ice margin positions and meltwater outbursts during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Dube-Loubert, Hugo; Roy, Martin; Schaefer, Joerg

    2016-04-01

    The Laurentide ice sheet (LIS) played an important role in the climate variability of the last deglaciation, notably through large discharges of meltwater to the North Atlantic that disturbed the ocean's circulation and heat transport. Deglaciation of the northeastern sector of the LIS was complex and included the development of large ice-dammed lakes that were confined within the main river valleys draining northward into Ungava Bay. The history of these lakes is closely related to the temporal evolution of the Labrador ice dome, but large uncertainties regarding the position and dynamic of the ice margin through time currently limit our understanding of these glacial lakes. In the Ungava lowlands, glacial lake Naskaupi invaded the George River valley, leaving a series of well-developed shorelines and deltas. These spectacular raised shorelines are 10 to 20 meters wide and can be followed for several kilometers. Our field investigations and remote sensing analysis indicate that Lake Naskaupi experienced a complex history, as shown by the succession of shorelines that likely reflect the opening of new topographic outlets during ice retreat. Constraining the timing of the different phases of the lake and its drainage has traditionally been challenging, as organic material suitable for radiocarbon dating is scarce or lacking. Recent progress in Surface Exposure Dating (SED) by cosmogenic nuclides now inspires novel approaches to glacial and deglacial geomorphology. Here we apply 10Be SED to boulders that form part of these shorelines and mark the main (high-level) stage of Lake Naskaupi. We sampled 4-6 multi-meter size boulders at 4 different sites. Preliminary results show high internal consistency and, indicate that the main lake phase developed very late in the regional deglaciation, which extends from about 8500 to 6800 cal. yr BP (Dyke and Prest, 1987). We also present SED results from boulders deposited by a substantial outburst flood presumably associated with

  12. Global analysis of the stream power law parameters based on worldwide 10Be denudation rates

    NASA Astrophysics Data System (ADS)

    Harel, M.-A.; Mudd, S. M.; Attal, M.

    2016-09-01

    The stream power law, expressed as E = KAmSn - where E is erosion rate [LT - 1], K is an erodibility coefficient [T - 1L (1 - 2m)], A is drainage area [L 2], S is channel gradient [L/L], and m and n are constants - is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of rock uplift patterns and rates. However, the unknown parameters K, m, and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably limits the use and interpretation of the model. In this study, we compile a unique global data set of published basin-averaged erosion rates that use detrital cosmogenic 10Be. These data (N = 1457) enable values for fundamental river properties to be empirically constrained, often for the first time, such as the concavity of the river profile (m/n ratio or concavity index), the link between channel slope and erosion rate (slope exponent n), and substrate erodibility (K). These three parameters are calculated for 59 geographic areas using the integral method of channel profile analysis and allow for a global scale analysis in terms of climatic, tectonic, and environmental settings. In order to compare multiple sites, we also normalize n and K using a reference concavity index m/n = 0.5. A multiple regression analysis demonstrates that intuitive or previously demonstrated local-scale trends, such as the correlation between K and precipitation rates, do not appear at a global scale. Our results suggest that the slope exponent is generally > 1, meaning that the relationship between erosion rate and the channel gradient is nonlinear and thus support the hypothesis that incision is a threshold controlled process. This result questions the validity of many regional interpretations of climate and/or tectonics where

  13. Application of in situ-produced 10Be to the study of Australian stone line induced by termite activity

    NASA Astrophysics Data System (ADS)

    Colin, F.; Gurarie, E.; Bourles, D.; Braucher, R.; Brown, E.; Anan, R.; Gilkes, R.; Meunier, J. D.; Varajao, C.

    2001-12-01

    The aim of this study is to understand the genesis of a stoneline sequence located at the border of the Yilgarn Craton in southwest Austrtalia. The sequence was selected because a well-defined line of siliceous pebbles traces the limit between a typical tropical saprolite and a soil almost entirely composed of termite nests, providing an opportunity to study the role of biological processes in stoneline genesis. A roadcut along the Boyup Brook Road provided the opportunity to examine and sample a 100 m wide section of weathering mantle developed on a gently sloping hill. The sequence consists, from base to top, of three main weathering layers: a gneiss- and schist-inherited yellow saprolite that includes subvertical quartz veins ; a 10 to 20 cm thick stone line composed primarily of angular quartz pebble; and a 40 to 50 cm thick dark brown surficial soil rich in both active and dormant termite nests. The distribution of these layers does not vary significantly across the hill, but quartz rich veins are most abundant in the central part of the hill. Kaolinite and quartz are the major mineralogical components throughout the sequence. There is little variation in grain size distributions, other than a modest increase in the >63 micron fractions of surface samples due to termite activity (mixing of minerals with woody and grassy debris). Chemical and mineralogical analyses were used to characterise the weathering layers and to investigate the role of termite colonies. We determined the in situ produced 10Be contents of samples collected from a depth profile through the quartz-rich schist and of pebbles from the stoneline at distances up to 40 m from central quartz veins. The 10Be depth profile shows a simple exponential decrease with depth, consistent with attenuation of cosmic ray neutrons and erosion at a rate of 20 mMyr, consistent with rates of excavation by termites. The pebbles from the stoneline have nearly constant 10Be concentrations that are approximately

  14. Bedrock gorges incising glacial hanging valleys (Western Alps, France): results from morphometric analysis, numerical modeling and 10Be cosmogenic dating

    NASA Astrophysics Data System (ADS)

    Valla, Pierre G.; van der Beek, Peter A.; Lague, Dimitri; Carcaillet, Julien

    2010-05-01

    Bedrock gorges are frequent features in glacial or post-glacial landscapes and allow measurements of fluvial bedrock incision in mountainous relief. Using digital elevation models, aerial photographs, topographic maps and field reconnaissance in the Pelvoux-Ecrins Massif (French Western Alps), we have identified ~30 tributary hanging valleys incised by gorges toward their confluence with the trunk streams. Longitudinal profiles of these tributaries are all convex and have abrupt knickpoints at the upper limit of oversteepened gorge reaches. From morphometric analyses, we find that mean channel gradients and widths, as well as knickpoint retreat rates, display a drainage-area dependence modulated by bedrock lithology. However, there appears to be no relation between horizontal retreat and vertical downwearing of knickpoints. Numerical modeling has been performed to test the capacity of different fluvial incision models to predict the inferred evolution of the gorges. Results from simple end-member models suggest transport-limited behavior of the bedrock gorges. Using a more sophisticated model including dynamic width adjustment and sediment-dependent incision rates, we show that bedrock gorge evolution requires significant supply of sediment from the gorge sidewalls triggered by gorge deepening, combined with pronounced inhibition of bedrock incision by sediment transport and deposition. We then use in-situ produced 10Be cosmogenic nuclides to date and quantify bedrock gorge incision into a single glacial hanging valley (Gorge du Diable). We have sampled gorge sidewalls and the active channel bed to derive both long-term and present-day incision rates. 10Be ages of sidewall profiles reveal rapid incision through the late Holocene (ca 5 ka), implying either delayed initiation of gorge incision after final ice retreat from internal Alpine valleys at ca 12 ka, or post-glacial surface reburial of the gorge. Both modeling results and cosmogenic dating suggest that

  15. Depositional and surface exposure history of the Shorty Crater core 74001/2 - FMR and magnetic studies

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Gose, W. A.; Lauer, H. V., Jr.

    1978-01-01

    Surface exposure (maturity) indices and concentrations of FeO and metallic iron were determined at 0.5-cm intervals of the Apollo 17 core section, which sampled a pyroclastic deposit on the rim of Shorty Crater. The determinations showed that all of the soil in the core is extremely immature. An exposure history of the core is proposed: accumulation (about 3.6 billion years ago), shallow burial (during the first 20 million years), deep burial (till about 10-15 million years ago), followed by excavation (10-15 million years ago), and in situ reworking (till the present).

  16. U-Th and 10Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia

    NASA Astrophysics Data System (ADS)

    Cogez, Antoine; Herman, Frédéric; Pelt, Eric; Norton, Kevin; Darvill, Christopher; Christl, Marcus; Morvan, Gilles; Reuschlé, Thierry; Chabaux, François

    2016-04-01

    The sedimentary cycle includes the formation by erosion of rocks, transport and deposition. While erosion and deposition can be documented, the history of sediments between the time it is extracted from the rocks and ultimately deposited into basins remains a major challenge. However, the mechanism of transfer and alteration of the sediments during transport plays a key role in the evolution of basins, feedbacks between erosion and climate, and glacial-interglacial variability of sediment transport and weathering. This is particularly true in proglacial settings because large overdeepenings, in particular, are potential sediment traps for which the efficiency at evacuating those sediments is largely unknown. The Lago Buenos Aires moraines in Patagonia are particularly interesting because they are imbricated from the older in the outer part to the younger in the inner part of the system. We sampled fine grained sediments from these moraines and measured U-Th isotopes in the 4-50 μm silicate fraction. Deposition ages were refined using 10Be exposure ages. We show first that the comminution ages model can be improved by measuring also Th isotopes, from which weathering rates can be deduced. Moreover we show from our data that there is a time lag of 300 kyr on average between erosion and deposition in the moraine. This could be attributed to the long residence time of sediments in the lake overdeepening. This conclusion raises perspectives about the transport times and dynamic of the sediments during a whole sedimentary cycle, and the subsequent effect on weathering. This conclusion could also contradict some assumptions commonly made for our erosion rates/sediment fluxes reconstructions based on river sediments analysis, in recently deglaciated catchments.

  17. High-precision 10Be chronology of moraines in the Southern Alps indicates synchronous cooling in Antarctica and New Zealand 42,000 years ago

    NASA Astrophysics Data System (ADS)

    Kelley, Samuel E.; Kaplan, Michael R.; Schaefer, Joerg M.; Andersen, Bjørn G.; Barrell, David J. A.; Putnam, Aaron E.; Denton, George H.; Schwartz, Roseanne; Finkel, Robert C.; Doughty, Alice M.

    2014-11-01

    Millennial-scale temperature variations in Antarctica during the period 80,000 to 18,000 years ago are known to anti-correlate broadly with winter-centric cold-warm episodes revealed in Greenland ice cores. However, the extent to which climate fluctuations in the Southern Hemisphere beat in time with Antarctica, rather than with the Northern Hemisphere, has proved a controversial question. In this study we determine the ages of a prominent sequence of glacial moraines in New Zealand and use the results to assess the phasing of millennial climate change. Forty-four 10Be cosmogenic surface-exposure ages of boulders deposited by the Pukaki glacier in the Southern Alps document four moraine-building events from Marine Isotope Stage 3 (MIS 3) through to the end of the Last Glacial Maximum (∼18,000 years ago; LGM). The earliest moraine-building event is defined by the ages of nine boulders on a belt of moraine that documents the culmination of a glacier advance 42,000 years ago. At the Pukaki locality this advance was of comparable scale to subsequent advances that, from the remaining exposure ages, occurred between 28,000 and 25,000, at 21,000, and at 18,000 years ago. Collectively, all four moraine-building events represent the LGM. The glacier advance 42,000 years ago in the Southern Alps coincides in Antarctica with a cold episode, shown by the isotopic record from the EPICA Dome C ice core, between the prominent A1 and A2 warming events. Therefore, the implication of the Pukaki glacier record is that as early as 42,000 years ago an episode of glacial cold similar to that of the LGM extended in the atmosphere from high on the East Antarctic plateau to at least as far north as the Southern Alps (∼44°S). Such a cold episode is thought to reflect the translation through the atmosphere and/or the ocean of the anti-phased effects of Northern Hemisphere interstadial conditions to the southern half of the Southern Hemisphere. Regardless of the mechanism, any

  18. Effect of Air Exposure on Surface Properties, Electronic Structure, and Carrier Relaxation in PbSe Nanocrystals

    SciTech Connect

    Sykora, Milan; Koposov, Alexey Y.; McGuire, John A.; Schulze, Roland K.; Tretiak, Olexandr; Pietryga, Jeffrey M.; Klimov, Victor

    2010-04-27

    Effects of air exposure on surface properties, electronic structure, and carrier relaxation dynamics in colloidal PbSe nanocrystals (NCs) were studied using X-ray photoelectron spectroscopy, transmission electron microscopy, and steady-state and time-resolved photoluminescence (PL) spectroscopies. We show that exposure of NC hexane solutions to air under ambient conditions leads to rapid oxidation of NCs such that up to 50% of their volume is transformed into PbO, SeO{sub 2}, or PbSeO{sub 3} within 24 h. The oxidation is a thermally activated process, spontaneous at room temperature. The oxidation-induced reduction in the size of the PbSe “core” increases quantum confinement, causing shifts of the PL band and the absorption onset to higher energies. The exposure of NC solutions to air also causes rapid (within minutes) quenching of PL intensity followed by slow (within hours) recovery during which the PL quantum yield can reach values exceeding those observed prior to the air exposure. The short-term PL quenching is attributed to enhanced carrier trapping induced by adsorption of oxygen onto the NC surface, while the PL recovery at longer times is predominantly due to reduction in the efficiency of the “intrinsic” nonradiative interband recombination caused by the increase of the band gap in oxidized NCs. Although the analysis of subnanosecond relaxation dynamics in air-exposed NCs is complicated by a significant enhancement in fast carrier trapping, our picosecond PL measurements suggest that air exposure likely has only a weak effect on Auger recombination and also does not significantly affect the efficiency of carrier multiplication. We also show that the effects of air exposure are partially suppressed in PbSe/CdSe core/shell structures.

  19. Study of cluster structures in 10Be and 16C neutron-rich nuclei via break-up reactions

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.; Acosta, L.; Amorini, F.; Andolina, R.; Auditore, L.; Berceanu, I.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Grzeszczuk, A.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Minniti, T.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-05-01

    Projectile break-up reactions induced on polyethylene (CH2) target are used in order to study the spectroscopy of 10Be and 16C nuclei. For the present experiment we used 10Be and 16C beams delivered by the FRIBs facility at INFN-LNS, and the CHIMERA 4π multi-detector. 10Be and 16C structures are studied via a relative energy analysis of break-up fragments. The 4He+6He break-up channel allowed us to study the spectroscopy of 10Be; in particular we find evidence of a new state in 10Be at 13.5 MeV excitation energy. The 16C nucleus is studied via 6He-10Be correlation; we find the fingerprint of a possible state at about 20.6 MeV

  20. Alteration of the Carbon and Nitrogen Isotopic Composition in the Martian Surface Rocks Due to Cosmic Ray Exposure

    NASA Technical Reports Server (NTRS)

    Pavlov, A. A.; Pavlov, A. K.; Ostryakov, V. M.; Vasilyev, G. I.; Mahaffy, P.; Steele, A.

    2014-01-01

    C-13/C-12 and N-15/N-14 isotopic ratios are pivotal for our understanding of the Martian carbon cycle, history of the Martian atmospheric escape, and origin of the organic compounds on Mars. Here we demonstrate that the carbon and nitrogen isotopic composition of the surface rocks on Mars can be significantly altered by the continuous exposure of Martian surface to cosmic rays. Cosmic rays can effectively produce C-13 and N-15 isotopes via spallation nuclear reactions on oxygen atoms in various Martian rocks. We calculate that in the top meter of the Martian rocks, the rates of production of both C-13 and N-15 due to galactic cosmic rays (GCRs) exposure can vary within 1.5-6 atoms/cm3/s depending on rocks' depth and chemical composition. We also find that the average solar cosmic rays can produce carbon and nitrogen isotopes at a rate comparable to GCRs in the top 5-10 cm of the Martian rocks. We demonstrate that if the total carbon content in a surface Martian rock is <10 ppm, then the "light," potentially "biological" C-13/C-12 ratio would be effectively erased by cosmic rays over 3.5 billion years of exposure. We found that for the rocks with relatively short exposure ages (e.g., 100 million years), cosmogenic changes in N-15/N-14 ratio are still very significant. We also show that a short exposure to cosmic rays of Allan Hills 84001 while on Mars can explain its high-temperature heavy nitrogen isotopic composition (N-15/N-14). Applications to Martian meteorites and the current Mars Science Laboratory mission are discussed.

  1. Simulating the mobility of meteoric 10Be in the landscape through a coupled soil-hillslope model (Be2D)

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Baken, Stijn; Smolders, Erik; Govers, Gerard

    2016-04-01

    Meteoric 10Be allows for the quantification of vertical and lateral soil fluxes over long time scales (103-105 yr). However, the mobility of meteoric 10Be in the soil system makes a translation of meteoric 10Be inventories into erosion and deposition rates complex. Here, we present a spatially explicit 2D model simulating the behaviour of meteoric 10Be on a hillslope. The model consists of two parts. The first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile, and the second component describes lateral soil and meteoric 10Be fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering as well as downslope fluxes of soil due to creep, water and tillage erosion. Synthetic model simulations show that meteoric 10Be inventories can be related to erosion and deposition across a wide range of geomorphological and pedological settings. Our results also show that meteoric 10Be can be used as a tracer to detect human impact on soil fluxes for soils with a high affinity for meteoric 10Be. However, the quantification of vertical mobility is essential for a correct interpretation of the observed variations in meteoric 10Be profiles and inventories. Application of the Be2D model to natural conditions using data sets from the Southern Piedmont (Bacon et al., 2012) and Appalachian Mountains (Jungers et al., 2009; West et al., 2013) allows to reliably constrain parameter values. Good agreement between simulated and observed meteoric 10Be concentrations and inventories is obtained with realistic parameter values. Furthermore, our results provide detailed insights into the processes redistributing meteoric 10Be at the soil-hillslope scale.

  2. A continuous ice-core 10Be record from Mongolian mid-latitudes: Influences of solar variability and local climate

    NASA Astrophysics Data System (ADS)

    Inceoglu, F.; Knudsen, M. F.; Olsen, J.; Karoff, C.; Herren, P.-A.; Schwikowski, M.; Aldahan, A.; Possnert, G.

    2016-03-01

    High-resolution 10Be records used for studies of detailed changes in atmospheric 10Be production rates predominantly derive from polar ice cores. In this study, we present the first 10Be record from a mid-latitude ice core. The ice core derives from the Tsambagarav mountain range located in the Mongolian Altai region. The new 10Be concentration record spans the period from AD 1550 to 2009, while the flux record extends from AD 1816 to 2009. The 10Be concentration in the Tsambagarav ice core ranges between ˜ 1.5 ×104 and ˜ 10 ×104 atomsg-1, whereas the 10Be flux changes from ˜0.02 to ˜0.15 atoms cm-2 s-1. The average 10Be flux at Tsambagarav is four times higher than the average 10Be flux recorded in the NGRIP and Dome Fuji ice cores, which is in accordance with model predictions. In general, the long-term trends observed in the Tsambagarav 10Be concentration and flux records are reasonably similar to those observed in the NGRIP ice core. A comparison between the Tsambagarav 10Be record, group sunspot numbers (GSNs), and solar modulation potentials based on 14C in tree rings suggests that the Maunder Minimum was associated with a prolonged maximum in 10Be concentrations at Tsambagarav, whereas the Dalton Minimum was associated with a minor increase in the 10Be concentration and flux that was delayed relative to the primary minimum in GSNs. The sulphate record from Tsambagarav shows that large positive anomalies in the sulphate concentration are associated with negative anomalies in the 10Be concentration. A concurrent positive sulphate anomaly may explain why the main phase of the Dalton Minimum is subdued in the 10Be record from Tsambagarav. Spectral analysis indicates that the 11-yr solar-cycle signal may have influenced the new 10Be record, but the evidence supporting a direct link is ambiguous. Local and regional climatic changes, such as cyclonic versus anticyclonic conditions and related storm tracks, most likely played a significant role for the 10Be

  3. Proteins IA and IB exhibit different surface exposures and orientations in the outer membranes of Neisseria gonorrhoeae.

    PubMed Central

    Barrera, O; Swanson, J

    1984-01-01

    Exposure of whole gonococci to proteinase K resulted in cleavage of protein I (P.I) of the organism in situ. P.I subunits in the P.IB group were cleaved into two membrane-associated fragments, whereas P.IA subunits were cleaved by proteinase K to yield a single membrane-associated fragment slightly smaller in apparent size than the intact P.IA subunit. These data suggest that P.IA and P.IB subunits are quite different in their surface exposures and orientations in the gonococcal outer membrane; P.IB subunits likely have both termini buried in the membrane, whereas P.IA subunits have one of their termini exposed on the surface of the organism. Images PMID:6427111

  4. Formation of super'' As-rich GaAs(100) surfaces by high temperature exposure to arsine

    SciTech Connect

    Banse, B.A.; Creighton, J.R. )

    1992-02-17

    We report that arsine exposures between 100 and 350 {degree}C will produce super'' As-rich surfaces (arsenic coverages of up to {similar to}1.7 monolayers (ML, where 1 ML=6.26{times}10{sup 14} atoms cm{sup {minus}2})) of GaAs(100) that exhibit a {ital c}(4{times}4) low energy electron diffraction pattern. Temperature programmed desorption studies show that after AsD{sub 3} exposures of up to 2.6{times}10{sup 6} L (1 L=1{times}10{sup {minus}6} Torr s) to the Ga-stabilized surface, three excess As desorption speaks are observed with maxima at 440, 480, and 570 {degree}C. As{sub 4} desorption is detected from the lowest temperature state, while the other states desorb primarily as As{sub 2}. The significance of these results for the understanding of the atomic layer epitaxy process is addressed.

  5. Uniform metal patterning on micromachined 3D surfaces using multistep exposure of UV light

    NASA Astrophysics Data System (ADS)

    Suriadi, Arief; Berauer, Frank; Yasunaga, Akari; Pan, Alfred I.; Vander Plas, Hubert A.

    2002-07-01

    Focal depth limitations prevent use of normal lithography tools and processes on three-dimensional structures. A relatively little known form of uniform metal trace patterning over extreme 3-D structured wafers by a multi-step exposure method, called stitching technology, has recently been developed by Hewlett-Packard Company, with equipment support from the Ultratech Stepper Company, the result of which is being reported in this paper. The basic idea is to slice the metal lines to be patterned into topographic layers that can each be exposed in one step. Patches of patterned metal lines can thus be stitch-ed to one another (thus, the term stitching). Exposure of one photo-resist layer by stitching takes several individual exposures at different focus planes. A patent has been applied for this method on behalf of the Hewlett Packard Company. Results of the present investigation demonstrate the superior uniformity of metal trace pattern over 350-um deep trenches produced by multi-step exposure, as compared to the conventional single-step exposure method, typically used on planar semiconductor wafer. The integrated method offers an enabling technology for patterning of extensive topography typically required for a multitude of MEMS structures and designs, novel interconnect structures as well as advanced packaging applications. The method is simple, accurate and relatively low-cost in comparison with other 3-D exposure techniques available and capable of 3-D structure patterning.

  6. Multiple 10Be records revealing the history of cosmic-ray variations across the Iceland Basin excursion

    NASA Astrophysics Data System (ADS)

    Horiuchi, Kazuho; Kamata, Kanae; Maejima, Shun; Sasaki, Sho; Sasaki, Nobuyoshi; Yamazaki, Toshitsugu; Fujita, Shuji; Motoyama, Hideaki; Matsuzaki, Hiroyuki

    2016-04-01

    Cosmogenic 10Be is a proxy of cosmic-ray flux, and its natural records provide vital information about the past intensity variability of the geomagnetic field and solar activity. 10Be records also serve as powerful tools for global synchronization among a variety of paleoarchives and for elucidating sedimentary processes on natural remanent magnetization acquisition. However, high-resolution (multi-decadal to multi-centennial) records of 10Be are scarce, especially those older than several tens of thousands of years. Here we present multiple high-resolution 10Be records of the Iceland Basin geomagnetic excursion interval (ca. 170-200 kyr ago) obtained from sediment cores (authigenic 10Be/9Be ratio) and an ice core (atmospheric 10Be flux). Comparing sedimentary 10Be records with relative paleointensity from the same cores, we found differences in the magnetic lock-in depth, even between adjacent cores. The 10Be-proxy records from the sediment and ice cores exhibit common characteristics: an asymmetric large-scale variation, a ∼7-kyr quasi-plateau around the maximum with a characteristic mid-term depression, and multi-millennial fluctuations in cosmic-ray flux during this interval. Minimal-synchronized and stacked 10Be records show that maximum cosmic-ray flux occurred 188.5-190.0 kyr ago and was double the present flux. A wavelet analysis of the stacked curve reveals dominant 4-kyr and secondary 8-kyr periodicities, both of which can be interpreted as intrinsic geomagnetic cycles. The wavelet spectrum of the high-resolution ice-core record shows a periodicity of 1.7 kyr and somewhat intermingled multi-centennial cycles around the maxima of 10Be, which likely represent solar cycles in this period. High-resolution 10Be records from multiple paleoarchives provide both a robust proxy record of cosmic-ray flux and a valuable tool for detailed global synchronization based on cosmic-ray variations.

  7. Cosmogenic {sup 3}He surface-exposure dating of stone pavements. Implications for landscape evolution in deserts

    SciTech Connect

    Wells, S.G.; McFadden, L.D.; Poths, J.; Olinger, C.T.

    1995-07-01

    The formation of stone pavements, a ubiquitous gravel armor mantling landforms in arid regions of the world, has been previously attributed to erosion by wind and water or alternating shrinking and swelling of soil horizons, implying that gravel is concentrated at the land surface in a time-transgressive manner. A newly proposed model for pavement evolution differs from these models in that pavement clasts are continuously maintained at the land surface in response to deposition and pedogenic modification of windblown dust. In-situ cosmogenic {sup 3}He surface-exposure ages on volcanic and alluvial landforms in the Mojave Desert of California are used to understand pavement evolution over geologic time scales and to test this new model. These exposure ages are stratigraphically consistent, show internal consistency at each site, and, for stone pavements adjacent to pristine, continuously exposed volcanic bedrock, are indistinguishable at the 1{sigma} level. We conclude that stone pavements are born at the surface and that pavements may provide one of the longest-term records of geologic, hydrologic, and climatic processes operating on desert surfaces. 23 refs., 3 figs., 1 tab.

  8. Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes

    SciTech Connect

    Hierlemann, A.; Hill, M.; Ricco, A.J.; Staton, A.W.; Thomas, R.C.

    1999-01-11

    We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseous analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.

  9. Cosmogenic Surface-Exposure Age Limits for Latest-Pleistocene Glaciation and Paleoclimatic Inferences in the American Fork Canyon, Wasatch Mountains, Utah, U.S.A.

    NASA Astrophysics Data System (ADS)

    Laabs, B. J.; Bash, E. R.; Refsnider, K. A.; Becker, R. A.; Munroe, J. S.; Mickelson, D. M.; Singer, B. S.

    2007-12-01

    The Wasatch Mountains of north-central Utah bordered the eastern shore of Lake Bonneville and were occupied by numerous valley glaciers during the latest Pleistocene. Stratigraphic and morphostratigraphic observations near the mouths of Little Cottonwood and Bells Canyons reveal that glaciers in these two valleys began constructing terminal moraines before Lake Bonneville reached its maximum shoreline elevation at about 19-17 cal. ka. Although the chronology of the lake highstand is well constrained by numerous radiocarbon dates, the timing of deglaciation in the Wasatch Mountains is relatively unclear. Moreover, there is considerable disagreement over the climatic conditions (cold/dry vs. cool/wet) that led to the expansion of glaciers and the lake. To address these issues, we explore the glacial record in the American Fork canyon by combining field mapping with cosmogenic 10Be surface-exposure dating and numerical modeling of glacier mass balance and ice flow to limit the extent, timing and climate of the last glaciation in the Wasatch Mountains. Six of ten cosmogenic surface-exposure ages from a terminal moraine in the canyon are tightly clustered (ranging from 14.4 ± 1.3 to 15.2 ± 1.1 ka; 2σ analytical error) and yield an error-weighted mean age of 14.8 ± 0.4 ka (2σ, MSWD = 0.26; individual age calculations based on a high latitude/sea level production rate of 4.98 ± 0.34 atoms g SiO2-1 yr-1 scaled for elevation and latitude). This age is consistent with previously reported cosmogenic-exposure dates from elsewhere in the range, and suggests that ice retreat in the Wasatch Mountains began as much as 4 kyr later than in other Rocky Mountain ranges and was in phase with the hydrologic fall of Lake Bonneville from the Provo shoreline. Numerical glacier modeling experiments (based on methods of Plummer and Phillips, 2003) simulate maximum ice extent in the American Fork, Little Cottonwood and Dry Creek canyons under a broad range of potential temperature and

  10. Anterior cingulate cortex surface area relates to behavioral inhibition in adolescents with and without heavy prenatal alcohol exposure.

    PubMed

    Migliorini, Robyn; Moore, Eileen M; Glass, Leila; Infante, M Alejandra; Tapert, Susan F; Jones, Kenneth Lyons; Mattson, Sarah N; Riley, Edward P

    2015-10-01

    Prenatal alcohol exposure is associated with behavioral disinhibition, yet the brain structure correlates of this deficit have not been determined with sufficient detail. We examined the hypothesis that the structure of the anterior cingulate cortex (ACC) relates to inhibition performance in youth with histories of heavy prenatal alcohol exposure (AE, n = 32) and non-exposed controls (CON, n = 21). Adolescents (12-17 years) underwent structural magnetic resonance imaging yielding measures of gray matter volume, surface area, and thickness across four ACC subregions. A subset of subjects were administered the NEPSY-II Inhibition subtest. MANCOVA was utilized to test for group differences in ACC and inhibition performance and multiple linear regression was used to probe ACC-inhibition relationships. ACC surface area was significantly smaller in AE, though this effect was primarily driven by reduced right caudal ACC (rcACC). AE also performed significantly worse on inhibition speed but not on inhibition accuracy. Regression analyses with the rcACC revealed a significant group × ACC interaction. A smaller rcACC surface area was associated with slower inhibition completion time for AE but was not significantly associated with inhibition in CON. After accounting for processing speed, smaller rcACC surface area was associated with worse (i.e., slower) inhibition regardless of group. Examining processing speed independently, a decrease in rcACC surface area was associated with faster processing speed for CON but not significantly associated with processing speed in AE. Results support the theory that caudal ACC may monitor reaction time in addition to inhibition and highlight the possibility of delayed ACC neurodevelopment in prenatal alcohol exposure. PMID:26025509

  11. Changes of Ocular Surface and the Inflammatory Response in a Rabbit Model of Short-Term Exposure Keratopathy

    PubMed Central

    Lin, Szu-Yuan; Liu, Hsin-Yu; Chang, Huai-Wen; Hu, Fung-Rong; Chen, Wei-Li

    2015-01-01

    Purpose To evaluate the ocular surface change and the inflammatory response in a rabbit model of short-term exposure keratopathy. Methods Short term exposure keratopathy by continuous eyelid opening was induced in New Zealand white rabbits for up to 4 hours. Ultrasound pachymetry was used to detect central total corneal thickness. In vivo confocal microscopy and impression cytology were performed to evaluate the morphology of ocular surface epithelium and the infiltration of inflammatory cells. Immunohistochemistry for macrophage,neutrophil, CD4(+) T cells, and CD8(+) T cells were performed to classify the inflammatory cells. Scanning electron microscopy(SEM) was performed to detect ocular surface change.The concentrations of IL-8, IL-17, Line and TNF-αwere analyzed by multiplex immunobead assay. TUNEL staining was performed to detect cellular apoptosis. Results Significant decrease ofcentral total cornealthickness were found within the first 5 minutes and remained stable thereafter, while there were no changes of corneal epithelial thickness.No significant change of corneal, limbal and conjunctival epithelial morphology was found by in vivo confocal microscopy except the time dependent increase of superficial cellular defects in the central cornea. Impression cytology also demonstrated time dependent increase of sloughing superficial cells of the central cornea. Aggregations ofinflammatory cells were found at 1 hour in the limbal epithelium, 2 hours in the perilimbal conjunctival epithelium, and 3 hours in the peripheral corneal epithelium.In eyes receiving exposure for 4 hours, the infiltration of the inflammatory cells can still be detected at 8 hours after closing eyes.Immunohistochemical study demonstrated the cells to be macrophages, neutrophils, CD4-T cells and CD-8 T cells.SEM demonstrated time-depending increase of intercellular border and sloughing of superficial epithelial cells in corneal surface. Time dependent increase of IL-8, IL-17 and TNF-α in

  12. Modification of polymeric surface for improved adhesion via electron beam exposure

    DOEpatents

    Kelber, Jeffry A.

    1989-01-01

    Treating polymer surfaces, e.g., Teflon, particularly very thin surfaces, e.g., 50-10,000 .ANG. with low energy electron radiation, e.g., 100-1000 eV, in a high vacuum environment, e.g., less than 10.sup.-6 Torr, to enhance the ability of the surface to be adhered to a variety of substrates.

  13. Modeling cosmogenic radionuclides 10Be and 7Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Beer, J.; Feichter, J.

    2007-11-01

    All existing 10Be records from Greenland and Antarctica show increasing concentrations during the Maunder Minimum period (MM), 1645-1715, when solar activity was very low and the climate was colder (little ice age). In detail, however, the 10Be records deviate from each other. We investigate to what extent climatic changes influence the 10Be measured in ice by modeling this period using the ECHAM5-HAM general circulation model. Production calculations show that during the MM the mean global 10Be production was higher by 32% than at present due to lower solar activity. Our modeling shows that the zonally averaged modeled 10Be deposition flux deviates by only ~8% from the average increase of 32%, indicating that climatic effects are much smaller than the production change. Due to increased stratospheric production, the 10Be content in the downward fluxes is larger during MM, leading to larger 10Be deposition fluxes in the subtropics, where stratosphere-troposphere exchange (STE) is strongest. In polar regions the effect is small. In Greenland the deposition change depends on latitude and altitude. In Antarctica the change is larger in the east than in the west. We use the 10Be/7Be ratio to study changes in STE. We find larger change between 20° N-40° N during spring, pointing to a stronger STE in the Northern Hemisphere during MM. In the Southern Hemisphere the change is small. These findings indicate that climate changes do influence the 10Be deposition fluxes, but not enough to significantly disturb the production signal. Climate-induced changes remain small, especially in polar regions.

  14. Modeling cosmogenic radionuclides 10Be and 7Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Beer, J.; Feichter, J.

    2008-05-01

    All existing 10Be records from Greenland and Antarctica show increasing concentrations during the Maunder Minimum period (MM), 1645-1715, when solar activity was very low and the climate was colder (little ice age). In detail, however, the 10Be records deviate from each other. We investigate to what extent climatic changes influence the 10Be measured in ice by modeling this period using the ECHAM5-HAM general circulation model. Production calculations show that during the MM the mean global 10Be production was higher by 32% than at present due to lower solar activity. Our modeling shows that the zonally averaged modeled 10Be deposition flux deviates by only ~8% from the average increase of 32%, indicating that climatic effects are much smaller than the production change. Due to increased stratospheric production, the 10Be content in the downward fluxes is larger during MM, leading to larger 10Be deposition fluxes in the subtropics, where stratosphere-troposphere exchange (STE) is strongest. In polar regions the effect is small. In Greenland the deposition change depends on latitude and altitude. In Antarctica the change is larger in the east than in the west. We use the 10Be/7Be ratio to study changes in STE. We find larger change between 20° N-40° N during spring, pointing to a stronger STE in the Northern Hemisphere during MM. In the Southern Hemisphere the change is small. These findings indicate that climate changes do influence the 10Be deposition fluxes, but not enough to significantly disturb the production signal. Climate-induced changes remain small, especially in polar regions.

  15. Surface modifications of fusion reactor relevant materials on exposure to fusion grade plasma in plasma focus device

    NASA Astrophysics Data System (ADS)

    Niranjan, Ram; Rout, R. K.; Srivastava, R.; Chakravarthy, Y.; Mishra, P.; Kaushik, T. C.; Gupta, Satish C.

    2015-11-01

    An 11.5 kJ plasma focus (PF) device was used here to irradiate materials with fusion grade plasma. The surface modifications of different materials (W, Ni, stainless steel, Mo and Cu) were investigated using various available techniques. The prominent features observed through the scanning electron microscope on the sample surfaces were erosions, cracks, blisters and craters after irradiations. The surface roughness of the samples increased multifold after exposure as measured by the surface profilometer. The X-ray diffraction analysis indicated the changes in the microstructures and the structural phase transformation in surface layers of the samples. We observed change in volumes of austenite and ferrite phases in the stainless steel sample. The energy dispersive X-ray spectroscopic analysis suggested alloying of the surface layer of the samples with elements of the PF anode. We report here the comparative analysis of the surface damages of materials with different physical, thermal and mechanical properties. The investigations will be useful to understand the behavior of the perspective materials for future fusion reactors (either in pure form or in alloy) over the long operations.

  16. Results of the "Komplast" experiment on the long-term exposure of materials specimens on the ISS surface

    NASA Astrophysics Data System (ADS)

    Shumov, Andrey; Novikov, Lev

    The "Komplast" materials experiment was designed by the Khrunichev State Research and Production Space Center together with Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University and other Russian scientific institutes, and has been carried out since 1998. The aim of the experiment is to study the complex effects of space factors on specimens of various materials. Eight “Komplast” panels fitted with material specimens equipped UV-sensors and temperature sensors were located on the International Space Station (ISS) Functional Cargo Block (FGB) module exterior surface. The panels were sent into orbit with the FGB when it launched on November 20, 1998. Two of these panels were subsequently returned to Earth by Space Shuttle Discovery after 12 years of LEO exposure. The uniqueness of the "Komplast" experiment determined by long duration of open space exposure, which is much longer than in other similar experiments. For example LDEF: 1984-1990, МЕЕР (Space Station «Mir»): 1996-1997, MISSE-1, -2 (ISS): 1,5-2 years. In this work reveals laboratory research results of some materials specimens, which had been exposed on “Komplast” panels. A distinctive feature of this research was additional irradiation of specimens by atomic oxygen and electrons with energies of ~ 1-8 MeV in laboratory. In the interpretation of the experiment results was taken into account the specimens exposure temperature conditions on the ISS exterior surface and the conditions of their sunlit, defined by the above-mentioned sensors readings. Lot of attention was paid to the investigation of rubber materials specimens. The deformation, mechanical and relaxation characteristics were defined for the specimens. Also were investigations the seals-ability of model rubber seals after the long-term outer exposure. It was determined conservation volumetric deformation and relaxation characteristics of the exposed specimens and the localization of structural changes in the thin

  17. Low level ozone exposure induces airways inflammation and modifies cell surface phenotypes in healthy humans

    EPA Science Inventory

    Background: The effects of low level ozone exposure (0.08 ppm) on pulmonary function in healthy young adults are well known, however much less is known about the inflammatory and immuno-modulatory effects oflow level ozone in the airways. Techniques such as induced sputum and flo...

  18. Occupational and environmental exposure to tribromophenol used for wood surface protection in sawmills.

    PubMed

    Gutiérrez, Manuel; Becerra, José; Godoy, Juan; Barra, Ricardo

    2005-06-01

    This study analyses the occupational and environmental conditions of sawmills where the lumber is protected from microorganism action by dipping it in 2,4,6 tribromophenol (TBP). Three processes were evaluated: hydraulic immersion, chain conveyor system and manual immersion. The biggest occupational exposure to TBP was registered in manual and chain conveyor systems. The average values in the workers' urine for TBP were 6.9 and 5.7 mg/g creatinine, respectively. For environmental exposure, the highest value in well waters was 25.1 microg/L and in soil was 4,602 mg/kg. It could be established that the hydraulic immersion system presents less occupational TBP exposure. Nevertheless, the hydraulic system, as well as the other two anti-stain alternatives, requires the introduction of pollution prevention efforts. To reduce the environmental exposure to TBP, the lumber-dipping tank area, the forklift traffic areas, and the storage areas need to be waterproofed. It is also necessary to implement a TBP solution recovery system to eliminate dripping from the lumber once it is removed from the fungicide dipping tanks. PMID:16134480

  19. Measurement of proton production cross sections of (sup 10)Be and (sup 26)Al from elements found in lunar rocks

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.; Kim, K.; Englert, P. A. J.; Caffee, M.; Jull, A. J. T.; Donahue, D. J.; McHargue, L.; Castaneda, C.; Vincent, J.; Reedy, R. C.

    1996-01-01

    Cosmic rays penetrate the lunar surface and interact with the lunar rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in lunar rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in lunar rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and (similar to)87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of lunar rocks. We have reported already C-14 production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x)(sup 10)Be from 58 160 MeV[6]. Here we present new measurements for the cross sections O(p,x)Be-10,O(p,x)Be-7, Si(p,x)Be-7,Si(p,x)Al-26, and Si(p,x)Na-22 from approximately 30 - 500 MeV.

  20. Beryllium geochemistry in soils: Evaluation of 10Be/9Be ratios in authigenic minerals as a basis for age models

    USGS Publications Warehouse

    Barg, E.; Lal, D.; Pavich, M.J.; Caffee, M.W.; Southon, J.R.

    1997-01-01

    Soils contain a diverse and complex set of chemicals and minerals. Being an 'open system', both in the chemical and nuclear sense, soils have defied quantitative nuclear dating. However, based on the published studies of the cosmogenic atmospheric 10Be in soils, its relatively long half-life (1.5 Ma), and the fact that 10Be gets quickly incorporated in most soil minerals, this radionuclide appears to be potentially the most useful for soil dating. We therefore studied the natural variations in the specific activities of 10Be with respect to the isotope 9Be in mineral phases in eight profiles of diverse soils from temperate to tropical climatic regimes and evaluated the implications of the data for determining the time of formation of soil minerals, following an earlier suggestion [Lal et al., 1991. Development of cosmogenic nuclear methods for the study of soil erosion and formation rates. Current Sci. 61, 636-639.]. We find that the 10Be/9Be ratios in both bulk soils and in the authigenic mineral phases are confined within a narrower range than in 10Be concentrations. Also, the highest 10Be/9Be ratios in authigenic minerals are observed at the soil-rock interface as predicted by the model. We present model 10Be/9Be ages of the B-horizon and the corresponding soil formation rates for several soil profiles. The present study demonstrates that the 10Be/9Be ratios in the authigenic phases, e.g. clay and Fe-hydroxides, can indeed be used for obtaining useful model ages for soils younger than 10-15 Ma. However, the present work has to be pushed considerably further, to take into account more realistic age models in which, for instance, downward transport of 10Be and clays, and in-situ dissolution of clay minerals at depths, altering the 10Be/9Be ratios of the acidic solutions, are included. We show that in the case of younger soils (< 1 Ma) studied here, their 10Be inventories and 10Be/9Be ratios have been significantly disturbed possibly by mixing with transported

  1. Pesticide exposure assessment for surface waters in the EU. Part 1: Some comments on the current procedure.

    PubMed

    Bach, Martin; Diesner, Mirjam; Großmann, Dietlinde; Guerniche, Djamal; Hommen, Udo; Klein, Michael; Kubiak, Roland; Müller, Alexandra; Priegnitz, Jan; Reichenberger, Stefan; Thomas, Kai; Trapp, Matthias

    2016-07-01

    In 2001, the European Commission introduced a risk assessment project known as FOCUS (FOrum for the Coordination of pesticide fate models and their USe) for the surface water risk assessment of active substances in the European Union. Even for the national authorisation of plant protection products (PPPs), the vast majority of EU member states still refer to the four runoff and six drainage scenarios selected by the FOCUS Surface Water Workgroup. However, our study, as well as the European Food Safety Authority (EFSA), has stated the need for various improvements. Current developments in pesticide exposure assessment mainly relate to two processes. Firstly, predicted environmental concentrations (PECs) of pesticides are calculated by introducing model input variables such as weather conditions, soil properties and substance fate parameters that have a probabilistic nature. Secondly, spatially distributed PECs for soil-climate scenarios are derived on the basis of an analysis of geodata. Such approaches facilitate the calculation of a spatiotemporal cumulative distribution function (CDF) of PECs for a given area of interest and are subsequently used to determine an exposure concentration endpoint as a given percentile of the CDF. For national PPP authorisation, we propose that, in the future, exposure endpoints should be determined from the overall known statistical PEC population for an area of interest, and derived for soil and climate conditions specific to the particular member state. © 2016 Society of Chemical Industry. PMID:27059427

  2. New ways of using an old isotopic system - meteoric 10-Be is back and ready to do geomorphology

    NASA Astrophysics Data System (ADS)

    Bierman, P.; Reusser, L.; Pavich, M.

    2009-04-01

    Meteoric 10-Be, produced in the atmosphere and delivered in precipitation, is an important tracer of sediment and geomorphic processes. This talk will review several decades of work measuring 10-Be adhered to soil and sediment collected from varied terrains around the world. We will then present new data and modeling approaches demonstrating the rich potential but complex, dynamic nature of this isotope system. Considering all of these data, we will examine the utility of meteoric10-Be, produced in the atmosphere and delivered in precipitation, as a tracer of watershed and hillslope sediment transport processes at a variety of spatial scales. We will finish the talk by examining uncertainties that require additional research to resolve. After a brief hay-day in the 1980s, tracing sediment down rivers, dating a few terraces, and following sediment through subduction zones, meteoric or garden variety 10-Be was largely forgotten. It's been lurking somewhere in the dark corners of isotope geoscience while its more famous but difficult-to-measure twin, the 10-Be produced in quartz, got all the attention. Recently, several research groups have again begun to build upon the excellent foundation constructed by those working in the 1980s and early 1990s. New data from a series of soil pits on hillslopes from around the world suggest that meteoric 10-Be is mobile in the soil column moving from the more acidic, organic-rich A-horizon to the B-horizon. Meteoric 10-Be concentrations are well correlated with both soil pH and extractable Al suggesting that Be is retained in Al-rich grain coatings that we know, from numerous attempts to purify riverine quartz, survive fluvial transport all too well. The important take-away message is that meteoric 10-Be is mobile in soil fluids while in situ 10-Be only moves with the quartz grains in which it resides. Depth profiles of in situ and meteoric 10-Be can be quite different, helping us to learn about rates of soil stirring and 10-Be

  3. Combination of in situ cosmogenic nuclide (10Be) and Schmidt-hammer dating for the investigation of Late-Holocene lateral moraines in the Southern Alps of New Zealand

    NASA Astrophysics Data System (ADS)

    Winkler, S.

    2009-04-01

    absolute' age of the boulder surfaces was needed to allow the construction of a dating curve by reliable fixed points to, radiocarbon (14C) dating could not provide those information because of the lack of organic material indisputable be related to the glacier advance forming the moraine ridges. On base on these considerations, this study comprises the first attempt to combine in situ (terrestrial) cosmogenic nuclide (10Be) surface exposure dating with Schmidt-hammer measurements for the dating of Holocene moraines and the reconstruction of a regional glacier chronology. Cosmogenic 10Be dating has the important advantage of delivering an ‘absolute' age for the exposure of boulder or bedrock surfaces, i.e. the same surface tested with the Schmidt-hammer. One disadvantage of cosmogenic nuclide exposure dating is, however, the limited number of boulders sampled due to high costs. From this background, a combination with the Schmidt-hammer technique seems ideal as the latter could provide measurement of a large number of boulders. The Schmidt-hammer measurements can, on the other hand, help with the selection of representative boulders for cosmogenic nuclide (10Be) surface exposure dating avoiding boulders that have been exposed to post-depositional movement (e.g. rotation). Results from the application of this combined ‘multi-proxy-approach' at Strauchon Glacier in Westland/Tai Poutini National Park and Hooker Glacier in Mt Cook/Aoraki National Park on large lateral moraine complex with several individual moraine ridges proof its potential. Three pre-‘Little Ice Age' moraine sequences each related to an individual Late-Holocene Little Ice Age-type event unambiguously distinguished by Schmidt-hammer measurements provides cosmogenic (10Be) ages of 2,400/2,500 a BP, c. 1,700 a BP, and c. 1,000/1,100 a BP. The preliminary construction of a dating curve based on both Schmidt-hammer and cosmogenic (10Be) dating results shows high significance and confirms the successful

  4. Interaction of gases with lunar materials. [surface properties of lunar fines, especially on exposure to water vapor

    NASA Technical Reports Server (NTRS)

    Holmes, H. F.; Gammage, R. B.

    1975-01-01

    The surface properties of lunar fines were investigated. Results indicate that, for the most part, these properties are independent of the chemical composition and location of the samples on the lunar surface. The leaching of channels and pores by adsorbed water vapor is a distinguishing feature of their surface chemistry. The elements of air, if adsorbed in conjunction with water vapor or liquid water, severely impedes the leaching process. In the absence of air, liquid water is more effective than water vapor in attacking the grains. The characteristics of Apollo 17 orange fines were evaluated and compared with those of other samples. The interconnecting channels produced by water vapor adsorption were found to be wider than usual for other types of fines. Damage tracks caused by heavy cosmic ray nuclei and an unusually high halogen content might provide for stronger etching conditions upon exposure to water vapor.

  5. Using meteoric 10Be to constrain the age and structure of the frontal wedge at the Japan Trench

    NASA Astrophysics Data System (ADS)

    Regalla, C.; Bierman, P. R.; Rood, D.; Motoyama, I.; Fisher, D. M.

    2013-12-01

    We present new meteoric 10Be concentration data from marine sediments recovered during International Ocean Drilling Program (IODP) Exp. 343 that help constrain the age and internal structure of the frontal prism at the Japan trench in the vicinity of the 2011 Tohoku-oki M9 earthquake rupture. Exp. 343 recovered sediments from an ~200 m interval of the frontal wedge at site C0019. Core and log observations identify the plate boundary décollement at ~820 mbsf, which separates a deformed sedimentary wedge from relatively undeformed underthrust sediments. However, reconstructions of the structural evolution of the wedge are difficult because of similarity in lithology between sediments from the incoming and overriding plate, and the chaotic character of seismic reflectors in the frontal wedge. We utilize the radiogenic decay of 10Be (t1/2 =1.36 Ma) in marine sediments to constrain variations in sediment age with depth in core C0019. Meteoric 10Be was isolated from marine sediments at the University of Vermont using total fusion and 10Be/9Be ratios were measured at the Scottish Universities Environmental Research Centre. Concentrations of meteoric 10Be in core C0019 range from 1.7x107 to 2.1x109 atm/g and are consistent with 10Be concentrations at nearby DSDP sites 436 and 434. We calculate 10Be sediment ages for analyzed samples assuming a range of initial 10Be concentrations from 1.6 to 2.1x109 atm/g. These concentrations are constrained by a 10Be sample co-located with a radiolarian micropaleontology sample at 780 mbsf that yields a Quaternary age, and from previously reported 10Be concentrations for Quaternary sediments in nearby DSDP cores. 10Be and radiolarian micropaleontology samples from similar depths yield consistent ages for late Miocene to Quaternary sediments (R2 = 0.89). Calculated 10Be ages range from 0-10 Ma, with ~50% of analyzed samples yielding ages <2 Ma. Repetition and inversion of high (109 atm/g) and low (107 atm/g) concentration sediments with

  6. Use of land surface remotely sensed satellite and airborne data for environmental exposure assessment in cancer research

    USGS Publications Warehouse

    Maxwell, S.K.; Meliker, J.R.; Goovaerts, P.

    2010-01-01

    In recent years, geographic information systems (GIS) have increasingly been used for reconstructing individual-level exposures to environmental contaminants in epidemiological research. Remotely sensed data can be useful in creating space-time models of environmental measures. The primary advantage of using remotely sensed data is that it allows for study at the local scale (e.g., residential level) without requiring expensive, time-consuming monitoring campaigns. The purpose of our study was to identify how land surface remotely sensed data are currently being used to study the relationship between cancer and environmental contaminants, focusing primarily on agricultural chemical exposure assessment applications. We present the results of a comprehensive literature review of epidemiological research where remotely sensed imagery or land cover maps derived from remotely sensed imagery were applied. We also discuss the strengths and limitations of the most commonly used imagery data (aerial photographs and Landsat satellite imagery) and land cover maps. ?? 2010 Nature Publishing Group All rights reserved.

  7. Surface Evaluation by X-Ray Photoelectron Spectroscopy of High Performance Polyimide Foams After Exposure to Oxygen Plasma

    NASA Technical Reports Server (NTRS)

    Melendez, Orlando; Hampton, Michael D.; Williams, Martha K.; Brown, Sylvia F.; Nelson, Gordon L.; Weiser, Erik S.

    2002-01-01

    Aromatic polyimides have been attractive in the aerospace and electronics industries for applications such as cryogenic insulation, flame retardant panels and structural subcomponents. Newer to the arena of polyimides is the synthesis of polyimide foams and their applications. In the present work, three different, closely related, polyimide foams developed by NASA Langley Research Center (LaRC) are studied by X-ray Photoelectron Spectroscopy (XPS) after exposure to radio frequency generated Oxygen Plasma. Although polyimide films exposure to atomic oxygen and plasma have been studied previously and reported, the data relate to films and not foams. Foams have much more surface area and thus present new information to be explored. Understanding degradation mechanisms and properties versus structure, foam versus solid is of interest and fundamental to the application and protection of foams exposed to atomic oxygen in Low Earth Orbit (LEO).

  8. XCAMS: The compact 14C accelerator mass spectrometer extended for 10Be and 26Al at GNS Science, New Zealand

    NASA Astrophysics Data System (ADS)

    Zondervan, A.; Hauser, T. M.; Kaiser, J.; Kitchen, R. L.; Turnbull, J. C.; West, J. G.

    2015-10-01

    A detailed description is given of the 0.5 MV tandem accelerator mass spectrometry (AMS) system for 10Be, 14C, 26Al, installed in early 2010 at GNS Science, New Zealand. Its design follows that of previously commissioned Compact 14C-only AMS (CAMS) systems based on the Pelletron tandem accelerator. The only basic departure from that design is an extension of the rare-isotope achromat with a 45° magnet and a two-anode gas-ionisation detector, to provide additional filtering for 10Be. Realised performance of the three AMS modes is discussed in terms of acceptance-test scores, 14C Poisson and non-Poisson errors, and 10Be detection limit and sensitivity. Operational details and hardware improvements, such as 10Be beam transport and particle detector setup, are highlighted. Statistics of repeat measurements of all graphitised 14C calibration cathodes since start-up show that 91% of their total uncertainty values are less than 0.3%, indicating that the rare-isotope beamline extension has not affected precision of 14C measurement. For 10Be, the limit of detection in terms of the isotopic abundance ratio 10Be/9Be is 6 × 10-15 at at-1 and the total efficiency of counting atoms in the sample cathode is 1/8500 (0.012%).

  9. Controlled free edge effects in surface wrinkling via combination of external straining and selective O2 plasma exposure.

    PubMed

    Yang, Yang; Han, Xue; Ding, Weilian; Jiang, Shichun; Cao, Yanping; Lu, Conghua

    2013-06-11

    Herein the edge effect from the traction-free boundary condition is utilized to direct the spontaneous surface wrinkling. This boundary condition is attained by a simple combination of mechanical straining and selective exposure of polydimethylsiloxane (PDMS) substrate to O2 plasma (OP) through a copper grid. When the strained PDMS sheet is subjected to selective OP treatment, a patterned heterogeneous surface composed of the OP-exposed "hard" oxidized SiOx region (denoted as D1) and the OP-unexposed "soft" region (denoted as D2) is produced. The subsequent full release of the prestrain (ε(pre)) leads to the selective wrinkling in D1, rather than in D2. It is seen that even in D1, no wrinkling occurs in the vicinity of the D1 edge that is perpendicular to the wavevector. Furthermore, the average wrinkle wavelength in D1 (λ(D1)) is smaller than that of the exposed copper grid-free blank area (λ(blank)). This wavelength decrement between λ(D1) and λ(blank), which can be used to roughly estimate the edge-effect extent, increases with the applied mesh number of copper grids and exposure duration, while decreases with the increase of ε(pre). Meanwhile, there exists a decrease in the amplitude of the patterned wrinkles, when compared with that of the blank region. Additionally, hierarchical wrinkling is induced when the strain-free PDMS substrate is selectively exposed to OP, followed by uniaxial stretching and the subsequent blanket exposure. Consequently, oriented wrinkles perpendicular to the stretching direction are generated in D2. With respect to D1, no wrinkling happens or orthogonal wrinkles occur in this region depending on the applied mesh number, exposure duration, and ε(pre). In the above wrinkling process, the combinative edge effects in two perpendicular directions that are involved sequentially have been discussed. PMID:23705830

  10. Estimating dermal transfer of copper particles from the surfaces of pressure-treated lumber and implications for exposure.

    PubMed

    Platten, William E; Sylvest, Nicholas; Warren, Casey; Arambewela, Mahendranath; Harmon, Steve; Bradham, Karen; Rogers, Kim; Thomas, Treye; Luxton, Todd Peter

    2016-04-01

    Lumber pressure-treated with micronized copper was examined for the release of copper and copper micro/nanoparticles using a surface wipe method to simulate dermal transfer. In 2003, the wood industry began replacing CCA treated lumber products for residential use with copper based formulations. Micronized copper (nano to micron sized particles) has become the preferred treatment formulation. There is a lack of information on the release of copper, the fate of the particles during dermal contact, and the copper exposure level to children from hand-to-mouth transfer. For the current study, three treated lumber products, two micronized copper and one ionic copper, were purchased from commercial retailers. The boards were left to weather outdoors for approximately 1year. Over the year time period, hand wipe samples were collected periodically to determine copper transfer from the wood surfaces. The two micronized formulations and the ionic formulation released similar levels of total copper. The amount of copper released was high initially, but decreased to a constant level (~1.5mgm(-2)) after the first month of outdoor exposure. Copper particles were identified on the sampling cloths during the first two months of the experiment, after which the levels of copper were insufficient to collect interpretable data. After 1month, the particles exhibited minimal changes in shape and size. At the end of 2-months, significant deterioration of the particles was evident. Based on the wipe sample data, a playground visit may result in a potential exposure to 2.58mg of copper, which is near or exceeds the daily tolerable upper intake limits for children under the age of 8, if completely ingested through hand-to-mouth transfer. While nanoparticles were found, there is not enough information to estimate the exposure from the released particles due to a lack of published literature on copper carbonate. PMID:26826852

  11. Experimental studies of first mirror exposure and surface recovery on EAST

    NASA Astrophysics Data System (ADS)

    Yan, R.; Ding, R.; Chen, J. L.; Chen, L. W.

    2015-08-01

    Systematic studies of first mirrors (FMs) contamination, deposition mitigation and cleaning have been performed in EAST and laboratory. It turned out that the auxiliary systems such as gas puffing, wall conditioning and limiters could lead to a serious deposition on FMs and result in at least 60% degradation of the reflectivity. Besides, the exposure environment and depth-diameter ratios (DDRs) of the protective ducts will influence the degree of deposition mitigation and homogeneity of deposition. The reflectivity of the FM protected with duct at the wavelength of 240-400 nm could sharply decrease at the beginning of the exposure, which differs from that in the wavelength range more than 400 nm. In addition, the total and specular reflectivity of FM cleaned by radio frequency magnetron sputtering plasma (RFMSP) could be recovered by up to 90% and 80 % respectively in the wavelength range of 300-800 nm.

  12. Acute exposure to silica nanoparticles aggravate airway inflammation: different effects according to surface characteristics

    PubMed Central

    Park, Hye Jung; Sohn, Jung-Ho; Kim, Yoon-Ju; Park, Yoon Hee; Han, Heejae; Park, Kyung Hee; Lee, Kangtaek; Choi, Hoon; Um, Kiju; Choi, In-Hong; Park, Jung-Won; Lee, Jae-Hyun

    2015-01-01

    Silica nanoparticles (SNPs) are widely used in many scientific and industrial fields despite the lack of proper evaluation of their potential toxicity. This study examined the effects of acute exposure to SNPs, either alone or in conjunction with ovalbumin (OVA), by studying the respiratory systems in exposed mouse models. Three types of SNPs were used: spherical SNPs (S-SNPs), mesoporous SNPs (M-SNPs), and PEGylated SNPs (P-SNPs). In the acute SNP exposure model performed, 6-week-old BALB/c female mice were intranasally inoculated with SNPs for 3 consecutive days. In the OVA/SNPs asthma model, the mice were sensitized two times via the peritoneal route with OVA. Additionally, the mice endured OVA with or without SNP challenges intranasally. Acute SNP exposure induced significant airway inflammation and airway hyper-responsiveness, particularly in the S-SNP group. In OVA/SNPs asthma models, OVA with SNP-treated group showed significant airway inflammation, more than those treated with only OVA and without SNPs. In these models, the P-SNP group induced lower levels of inflammation on airways than both the S-SNP or M-SNP groups. Interleukin (IL)-5, IL-13, IL-1β and interferon-γ levels correlated with airway inflammation in the tested models, without statistical significance. In the mouse models studied, increased airway inflammation was associated with acute SNPs exposure, whether exposed solely to SNPs or SNPs in conjunction with OVA. P-SNPs appear to be relatively safer for clinical use than S-SNPs and M-SNPs, as determined by lower observed toxicity and airway system inflammation. PMID:26183169

  13. Surface Exposure Ages of Space-Weathered Grains from Asteroid 25143 Itokawa

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Berger, E. L.; Christoffersen, R.

    2015-01-01

    We use the observed effects of solar wind ion irradiation and the accumulation of solar flare particle tracks recorded in Itokawa grains to constrain the rates of space weathering and yield information about regolith dynamics. The track densities are consistent with exposure at mm depths for 104-105 years. The solar wind damaged rims form on a much faster timescale, <10(exp 3) years.

  14. New experimental investigation of the structure of 10Be and 16C by means of intermediate-energy sequential breakup

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.; Lombardo, I.; Acosta, L.; Andolina, R.; Auditore, L.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Lanzalone, G.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-02-01

    10Be and 16C spectroscopy has been investigated by analyzing their breakup events on CH2 and CD2 targets. Breakup fragments have been detected by means of the CHIMERA detector. In particular, we investigated cluster decays of 10Be in 4He+6He and of 16C in 6He+10Be and 4He+6He+6He . From the relative energy analysis of breakup fragments, we investigate the spectroscopy of excited states of projectile nuclei. In the 10Be case we observe known states at 9.51, 10.16, 10.6, and 11.8 MeV. Further, we suggest the existence of a new state at 13.5 MeV, possibly 6+ as indicated from angular correlation analysis. The relative energy (Erel+Eth) spectrum of 16C, reconstructed starting from 6He+10Be correlations, shows a peak at about 20.6 MeV, probably related to the existence of an high-lying excited state. Non-vanishing yields are also seen in the triple coincidences 4He+6He+6He .

  15. Studying 10Be and 11Be Halo States through the (p,d) Single-Neutron Transfer Reaction

    NASA Astrophysics Data System (ADS)

    Kuhn, Keri; Sarazin, Fred; (Pcb)2 Collaboration; Tigress Collaboration

    2015-10-01

    One-neutron transfer reactions are being used to study single-particle neutron states in nuclei. For one-neutron halo nuclei, such as 11Be, the (p,d) reaction enables the removal of the halo neutron or of one of the core neutrons. This way, it is possible to simultaneously study the halo wavefunction of the 11Be ground-state but also a possible excited halo state in 10Be. The 11Be(p, d)10Be transfer reaction at 10 MeV/nucleon is being investigated at the TRIUMF-ISAC II facility with the Printed Circuit Board Based Charged Particle ((PCB)2) array inside the TRIUMF ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS). The ground state and first excited state of 10Be can be directly identified using deuteron identification and kinematics from the charged particle array, while the four excited states in10Be around 6 MeV, including the suspected halo state (2- state), are identified using coincident gamma rays from TIGRESS with the identified deuterons. Angular distributions for the 10Be populated states will be shown along with their FRESCO fits. This work is partially supported by the US Department of Energy through Grant/Contract No. DE-FG03-93ER40789 (Colorado School of Mines).

  16. Mars surface radiation exposure for solar maximum conditions and 1989 solar proton events.

    NASA Astrophysics Data System (ADS)

    Simonsen, L. C.; Nealy, J. E.

    1993-02-01

    The Langley heavy-ion/nucleon and the high-energy nucleon transport codes are used to predict the propagation of galactic cosmic rays (GCR's) and solar flare protons through the carbon dioxide atmosphere of Mars. Particle fluences and the resulting doses are estimated on the surface of Mars for GCR's during solar maximum conditions and the August, September, and October 1989 solar proton events. Surface doses are estimated with both a low-density and a high-density carbon dioxide model of the atmosphere for altitudes of 0, 4, 8, and 12 km above the surface. A solar modulation function is incorporated to estimate the GCR dose variation between solar minimum and maximum conditions over the 11-year solar cycle. By using current Mars mission scenarios, doses to the skin, eye, and blood-forming organs are predicted for short- and long-duration stay times on the Martian surface throughout the solar cycle.

  17. Surface modifications of W divertor components for EAST during exposure to high heat loads with He

    NASA Astrophysics Data System (ADS)

    Li, C.; Greuner, H.; Yuan, Y.; Zhao, S. X.; Luo, G. N.; Böswirth, B.; Fu, B. Q.; Jia, Y. Z.; Liu, X.; Liu, W.

    2015-08-01

    Flat-type W/Cu plasma-facing components have been developed for the new generation divertor of the Chinese Experimental Advanced Superconducting Tokamak. Surface modifications of such actively water-cooled W components following short and long pulse high heat loading coupled with He particle loads with fluence of 3 × 1022 m-2 have been investigated. An adiabatically loaded W block was investigated as a comparison and exposed to short pulse loads. Blistering was observed on all sample surfaces, but was less pronounced on the components than on the W block, due to the significant lower surface temperature caused by active cooling. For components, longer pulse loads gave rise to a rougher surface. Furthermore, most blisters on components are found to be less than 1 μm in diameter, with just a very few blisters larger than 1 μm, observed only in some near <1 1 1> grains.

  18. Cell-based metabolomics for assessing chemical exposure and toxicity of environmental surface waters (presentation)

    EPA Science Inventory

    Introduction: Waste water treatment plants (WWTPs), concentrated animal feeding operations (CAFOs), mining activities, and agricultural operations release contaminants that negatively affect surface water quality. Traditional methods using live animals (e.g. fish) to monitor/as...

  19. Cell-based Metabolomics for Assessing Chemical Exposure and Toxicity of Environmental Surface Waters

    EPA Science Inventory

    Waste water treatment plants (WWTPs), concentrated animal feeding operations (CAFOs), mining activities, and agricultural operations release contaminants that negatively affect surface water quality. Traditional methods using live animals/fish to monitor/assess contaminant exposu...

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

    NASA Astrophysics Data System (ADS)

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

    1992-07-01

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

  1. Denudation rates determined from the accumulation of in situ-produced 10Be in the luquillo experimental forest, Puerto Rico

    USGS Publications Warehouse

    Brown, Erik Thorson; Stallard, Robert F.; Larsen, Matthew C.; Raisbeck, Grant M.; Yiou, Francoise

    1995-01-01

    We present a simple method for estimation of long-term mean denudation rates using in situ-produced cosmogenic 10Be in fluvial sediments. Procedures are discussed to account for the effects of soil bioturbation, mass wasting and attenuation of cosmic rays by biomass and by local topography. Our analyses of 10Be in quartz from bedrock outcrops, soils, mass-wasting sites and riverine sediment from the Icacos River basin in the Luquillo Experimental Forest, Puerto Rico, are used to characterize denudation for major landform elements in that basin. The 10Be concentration of a discharge-weighted average of size classes of river sediment corresponds to a long-term average denudation of ≈ 43 m Ma −1, consistent with mass balance results. 

  2. Constraining Regolith Production on a Hillslope Over Long Timescales: Interpreting In Situ 10Be Concentrations on an Evolving Landscape

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Duehnforth, M.; Kelly, P. J.

    2011-12-01

    In situ produced 10Be cosmogenic radionuclide (CRN) concentrations provide geomorphologists with a quantitative tool to calculate regolith production rates in a variety of landscapes. However, the power of CRN dating is limited by the care with which these hard-earned numbers are interpreted. As rock is exhumed through the weathered zone, it accumulates in situ produced CRNs. Most studies assume a steady-state condition to calculate regolith production rates from 10Be concentrations obtained from rock at the base of mobile regolith; ignoring decay, the regolith production rate becomes simply Poe-H/z*/[10Be]. Although the balance of regolith production and the spatial pattern of divergence required to maintain steady regolith thickness is valid in some landscapes, steady-state is unlikely on hillslopes where time scales for generating soils are longer than climatic cycles. We report in situ 10Be concentrations to calculate production rates for mobile regolith in 8 soil pits along north- and south-facing slopes in Gordon Gulch, an intensively studied catchment in the Boulder Creek CZO. Gordon Gulch hillslopes exhibit variable regolith and saprolite thicknesses over gneissic and granitic parent rock; mean regolith thickness is 0.65 m. Local denudation rates in nearby catchments are 25 ± 8 m/Ma (Dethier and Lazarus, 2006). The mean residence time of mobile regolith in Gordon Gulch catchment is therefore 20-45 ka; less than half of this time is spent in Holocene climatic conditions. Although Gordon Gulch presently has mean annual temperature (MAT) ~4°C, it was likely at least 6°C cooler during the Last Glacial Maximum, meaning that periglacial conditions likely dominated. We therefore anticipate that parent rock could be more rapidly damaged by increased frost-cracking, and regolith transport be enhanced by increased frost-heave; thus steady-state conditions cannot be assumed over this timescale. To develop strategies for interpretation of 10Be, we employ a 1D

  3. 13C(n,α0)10Be cross section measurement with sCVD diamond detector

    NASA Astrophysics Data System (ADS)

    Kavrigin, P.; Griesmayer, E.; Belloni, F.; Plompen, A. J. M.; Schillebeeckx, P.; Weiss, C.

    2016-06-01

    This paper presents 13C(n, α0)10Be cross section measurements performed at the Van de Graaff facility of the Joint Research Centre Geel. The 13C(n, α0)10Be cross section was measured relative to the 12C(n, α0)9Be cross section at 14.3 MeV and 17.0 MeV neutron energies. The measurements were performed with an sCVD (single-crystal chemical vapor deposition) diamond detector which acted as sample and as sensor simultaneously. A novel analysis technique was applied, which is based on the pulse-shape analysis of the detector's ionization current. This technique resulted in an efficient separation of background events and consequently in a well-determined selection of the nuclear reaction channels 12C(n, α0)9Be and 13C(n, α0)10Be.

  4. High-resolution authigenic 10Be/9Be records : A proxy indicator of the past geomagnetic field variability

    NASA Astrophysics Data System (ADS)

    Carcaillet, J.; Thouveny, N.; Bourlès, D. L.

    2003-04-01

    At global scale, the synchronicity of abnormal directions of the paleomagnetic field and minimum intensities supports the hypothesis of a relationship between the occurrence of excursions and/or polarity changes and the collapse of the dipolar component. We present quantitative evaluations of relationships between 10Be production rate variations and geomagnetic events using high resolution authigenic 10Be/9Be ratios and continuous paleointensity records measured in three marine sediment sequences located on the Portuguese margin, (MD95-2042 and MD95-2040), and in the Western Pacific, (MD97-2140). Since 10Be concentrations measured in marine sediments not only depend on 10Be production rates but also on oceanic and sedimentary effects, authigenic (i.e. adsorbed onto particles from the water column) 10Be concentrations were normalized to their related authigenic 9Be concentrations in order to account for these disturbing effects on the sedimentation rate as well as on the chemical and granulometric composition of the sediments. Due to their different sources, only the soluble form of both beryllium isotopes may indeed have been homogenized in the water column before deposition in the sediment. The measured 10Be/9Be ratios increase significantly at all identified excursions and reversals, associated with decreased paleointensities, consistently with the expected relationship between magnetic moment and cosmic ray flux (Q/Qo=(M/Mo)-1/2). Our results confirm the global occurrence of well-recognized and well-dated phases of low geomagnetic moments associated to well known geomagnetic excursions, short events or polarity reversals that occurred between 0 and 300 ka BP and between 0.6 and 1.3 Ma BP: the Laschamp excursion, the Blake event, the Jamaica/Pringle falls excursion, the Brunhes-Matuyama Reversal, the upper and lower Jaramillo transitions and the Cobb Mountain event. They strengthen the validity of recently reported excursions: Icelandic basin, Calabrian Ridge 0

  5. A new 10Be record recovered from an Antarctic ice core: validity and limitations to record the solar activity

    NASA Astrophysics Data System (ADS)

    Baroni, Mélanie; Bard, Edouard; Aster Team

    2015-04-01

    Cosmogenic nuclides provide the only possibility to document solar activity over millennia. Carbon-14 (14C) and beryllium-10 (10Be) records are retrieved from tree rings and ice cores, respectively. Recently, 14C records have also proven to be reliable to detect two large Solar Proton Events (SPE) (Miyake et al., Nature, 2012, Miyake et al., Nat. Commun., 2013) that occurred in 774-775 A.D. and in 993-994 A.D.. The origin of these events is still under debate but it opens new perspectives for the interpretation of 10Be ice core records. We present a new 10Be record from an ice core from Dome C (Antarctica) covering the last millennium. The chronology of this new ice core has been established by matching volcanic events on the WAIS Divide ice core (WDC06A) that is the best dated record in Antarctica over the Holocene (Sigl et al., JGR, 2013, Sigl et al., Nat. Clim. Change, 2014). The five minima of solar activity (Oort, Wolf, Spörer, Maunder and Dalton) are detected and characterized by a 10Be concentration increase of ca. 20% above average in agreement with previous studies of ice cores drilled at South Pole and Dome Fuji in Antarctica (Bard et al., EPSL, 1997; Horiuchi et al., Quat. Geochrono., 2008) and at NGRIP and Dye3 in Greenland (Berggren et al., GRL, 2009). The high resolution, on the order of a year, allows the detection of the 11-year solar cycle. Sulfate concentration, a proxy for volcanic eruptions, has also been measured in the very same samples, allowing a precise comparison of both 10Be and sulfate profiles. We confirm the systematic relationship between stratospheric eruptions and 10Be concentration increases, first evidenced by observations of the stratospheric volcanic eruptions of Agung in 1963 and Pinatubo in 1991 (Baroni et al., GCA, 2011). This relationship is due to an increase in 10Be deposition linked to the role played by the sedimentation of volcanic aerosols. In the light of these new elements, we will discuss the limitations and

  6. Combination of in situ cosmogenic nuclide (10Be) and Schmidt-hammer dating for the investigation of Late-Holocene lateral moraines in the Southern Alps of New Zealand

    NASA Astrophysics Data System (ADS)

    Winkler, S.

    2009-04-01

    absolute' age of the boulder surfaces was needed to allow the construction of a dating curve by reliable fixed points to, radiocarbon (14C) dating could not provide those information because of the lack of organic material indisputable be related to the glacier advance forming the moraine ridges. On base on these considerations, this study comprises the first attempt to combine in situ (terrestrial) cosmogenic nuclide (10Be) surface exposure dating with Schmidt-hammer measurements for the dating of Holocene moraines and the reconstruction of a regional glacier chronology. Cosmogenic 10Be dating has the important advantage of delivering an ‘absolute' age for the exposure of boulder or bedrock surfaces, i.e. the same surface tested with the Schmidt-hammer. One disadvantage of cosmogenic nuclide exposure dating is, however, the limited number of boulders sampled due to high costs. From this background, a combination with the Schmidt-hammer technique seems ideal as the latter could provide measurement of a large number of boulders. The Schmidt-hammer measurements can, on the other hand, help with the selection of representative boulders for cosmogenic nuclide (10Be) surface exposure dating avoiding boulders that have been exposed to post-depositional movement (e.g. rotation). Results from the application of this combined ‘multi-proxy-approach' at Strauchon Glacier in Westland/Tai Poutini National Park and Hooker Glacier in Mt Cook/Aoraki National Park on large lateral moraine complex with several individual moraine ridges proof its potential. Three pre-‘Little Ice Age' moraine sequences each related to an individual Late-Holocene Little Ice Age-type event unambiguously distinguished by Schmidt-hammer measurements provides cosmogenic (10Be) ages of 2,400/2,500 a BP, c. 1,700 a BP, and c. 1,000/1,100 a BP. The preliminary construction of a dating curve based on both Schmidt-hammer and cosmogenic (10Be) dating results shows high significance and confirms the successful

  7. Mars surface radiation exposure for solar maximum conditions and 1989 solar proton events

    NASA Astrophysics Data System (ADS)

    Simonsen, Lisa C.; Nealy, John E.

    1992-02-01

    The Langley heavy-ion/nucleon transport code, HZETRN, and the high-energy nucleon transport code, BRYNTRN, are used to predict the propagation of galactic cosmic rays (GCR's) and solar flare protons through the carbon dioxide atmosphere of Mars. Particle fluences and the resulting doses are estimated on the surface of Mars for GCR's during solar maximum conditions and the Aug., Sep., and Oct. 1989 solar proton events. These results extend previously calculated surface estimates for GCR's at solar minimum conditions and the Feb. 1956, Nov. 1960, and Aug. 1972 solar proton events. Surface doses are estimated with both a low-density and a high-density carbon dioxide model of the atmosphere for altitudes of 0, 4, 8, and 12 km above the surface. A solar modulation function is incorporated to estimate the GCR dose variation between solar minimum and maximum conditions over the 11-year solar cycle. By using current Mars mission scenarios, doses to the skin, eye, and blood-forming organs are predicted for short- and long-duration stay times on the Martian surface throughout the solar cycle.

  8. Mars surface radiation exposure for solar maximum conditions and 1989 solar proton events

    NASA Technical Reports Server (NTRS)

    Simonsen, Lisa C.; Nealy, John E.

    1992-01-01

    The Langley heavy-ion/nucleon transport code, HZETRN, and the high-energy nucleon transport code, BRYNTRN, are used to predict the propagation of galactic cosmic rays (GCR's) and solar flare protons through the carbon dioxide atmosphere of Mars. Particle fluences and the resulting doses are estimated on the surface of Mars for GCR's during solar maximum conditions and the Aug., Sep., and Oct. 1989 solar proton events. These results extend previously calculated surface estimates for GCR's at solar minimum conditions and the Feb. 1956, Nov. 1960, and Aug. 1972 solar proton events. Surface doses are estimated with both a low-density and a high-density carbon dioxide model of the atmosphere for altitudes of 0, 4, 8, and 12 km above the surface. A solar modulation function is incorporated to estimate the GCR dose variation between solar minimum and maximum conditions over the 11-year solar cycle. By using current Mars mission scenarios, doses to the skin, eye, and blood-forming organs are predicted for short- and long-duration stay times on the Martian surface throughout the solar cycle.

  9. Exposure of the hydrophobic components of porcine lung surfactant to oxidant stress alters surface tension properties.

    PubMed Central

    Gilliard, N; Heldt, G P; Loredo, J; Gasser, H; Redl, H; Merritt, T A; Spragg, R G

    1994-01-01

    We have tested the hypothesis that oxidation of lung surfactant results in loss of surface tension lowering function. Porcine lung surfactant was exposed to conditions known to cause lipid peroxidation (0.2 mM FeCl2 + 0.1 mM H2O2 or 5 microM CuCl2). Lipid peroxidation was verified by detection of conjugated dienes, thiobarbituric acid reactive substances, fluorescent products, hydroxy alkenals, and loss of unsaturated fatty acids. Exposed samples had significantly diminished surface tension lowering ability in vitro as measured in a bubble surfactometer. Samples exposed to FeCl2 + H2O2 had significantly diminished surface tension lowering ability in vivo as indicated by their reduced ability to improve lung compliance of surfactant-deficient fetal rabbits. Oxidation of phospholipid mixtures with surface tension lowering activity and containing unsaturated acyl groups resulted in partial loss of activity as determined in vitro. These results suggest that the effect of oxidants on lung surfactant function is due, in part, to effects on the phospholipid components and that acute pulmonary inflammation accompanied by oxygen radical production may result in surfactant lipid peroxidation and loss of surface tension lowering function. PMID:8200999

  10. In-Plane Shielding for CT: Effect of Off-Centering, Automatic Exposure Control and Shield-to-Surface Distance

    PubMed Central

    Dang, Pragya; Singh, Sarabjeet; Saini, Sanjay; Shepard, Jo-Anne O.

    2009-01-01

    Objective To assess effects of off-centering, automatic exposure control, and padding on attenuation values, noise, and radiation dose when using in-plane bismuth-based shields for CT scanning. Materials and Methods A 30 cm anthropomorphic chest phantom was scanned on a 64-multidetector CT, with the center of the phantom aligned to the gantry isocenter. Scanning was repeated after placing a bismuth breast shield on the anterior surface with no gap and with 1, 2, and 6 cm of padding between the shield and the phantom surface. The "shielded" phantom was also scanned with combined modulation and off-centering of the phantom at 2 cm, 4 cm and 6 cm below the gantry isocenter. CT numbers, noise, and surface radiation dose were measured. The data were analyzed using an analysis of variance. Results The in-plane shield was not associated with any significant increment for the surface dose or CT dose index volume, which was achieved by comparing the radiation dose measured by combined modulation technique to the fixed mAs (p > 0.05). Irrespective of the gap or the surface CT numbers, surface noise increased to a larger extent compared to Hounsfield unit (HU) (0-6 cm, 26-55%) and noise (0-6 cm, 30-40%) in the center. With off-centering, in-plane shielding devices are associated with less dose savings, although dose reduction was still higher than in the absence of shielding (0 cm off-center, 90% dose reduction; 2 cm, 61%) (p < 0.0001). Streak artifacts were noted at 0 cm and 1 cm gaps but not at 2 cm and 6 cm gaps of shielding to the surface distances. Conclusion In-plane shields are associated with greater image noise, artifactually increased attenuation values, and streak artifacts. However, shields reduce radiation dose regardless of the extent of off-centering. Automatic exposure control did not increase radiation dose when using a shield. PMID:19270862

  11. Colloidal stability of gold nanorod solution upon exposure to excised human skin: Effect of surface chemistry and protein adsorption.

    PubMed

    Mahmoud, Nouf N; Al-Qaoud, Khaled M; Al-Bakri, Amal G; Alkilany, Alaaldin M; Khalil, Enam A

    2016-06-01

    In this study, we evaluated the colloidal stability of gold nanorods (with positive, negative and neutral surface charge) in solution upon contact with excised human skin. UV-vis absorption, plasmon peak broadening index (PPBI%) and transmission electron microscope analysis were used to follow nanoparticles aggregation in solution. Our results show that positively charged gold nanorods aggregate extensively upon exposure to excised human skin compared to negatively and neutrally charged gold nanorods. Skin-induced aggregation of cationic gold nanorods was linked to the adsorption of proteins released from the dermis layer to the surface of gold nanorods. Protein adsorption significantly screen nanorod's effective surface charge and induce their aggregation. Moreover, we demonstrate that the presence of polyethylene glycol polymer on the surface of cationic gold nanorods minimize this aggregation significantly by providing steric repulsion (non-electrostatic stabilization mechanism). This work highlights the importance of evaluating the colloidal stability of nanoparticles in solution upon contact with skin, which is a "usually overlooked" parameter when studying the nanoparticle-skin interaction. PMID:26923289

  12. Species specificity, surface exposure, protein expression, immunogenicity, and participation in biofilm formation of Porphyromonas gingivalis HmuY

    PubMed Central

    2010-01-01

    Background Porphyromonas gingivalis is a major etiological agent of chronic periodontitis. The aim of this study was to examine the species specificity, surface exposure, protein expression, immunogenicity, and participation in biofilm formation of the P. gingivalis heme-binding protein HmuY. Results HmuY is a unique protein of P. gingivalis since only low amino-acid sequence homology has been found to proteins encoded in other species. It is exposed on the cell surface and highly abundant in the outer membrane of the cell, in outer-membrane vesicles, and is released into culture medium in a soluble form. The protein is produced constitutively at low levels in bacteria grown under high-iron/heme conditions and at higher levels in bacteria growing under the low-iron/heme conditions typical of dental plaque. HmuY is immunogenic and elicits high IgG antibody titers in rabbits. It is also engaged in homotypic biofilm formation by P. gingivalis. Anti-HmuY antibodies exhibit inhibitory activity against P. gingivalis growth and biofilm formation. Conclusions Here it is demonstrated that HmuY may play a significant role not only in heme acquisition, but also in biofilm accumulation on abiotic surfaces. The data also suggest that HmuY, as a surface-exposed protein, would be available for recognition by the immune response during chronic periodontitis and the production of anti-HmuY antibodies may inhibit biofilm formation. PMID:20438645

  13. Cosmogenic 10Be Depth Profile in top 560 m of West Antarctic Ice Sheet Divide Ice Core

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Woodruff, T. E.; Caffee, M. W.; Edwards, R.; McConnell, J. R.; Bisiaux, M. M.; Nishiizumi, K.

    2009-12-01

    Concentrations of cosmogenic 10Be in polar ice samples are a function of variations in solar activity, geomagnetic field strength, atmospheric mixing and annual snow accumulation rates. The 10Be depth profile in ice cores also provides independent chronological markers to tie Antarctic to Greenland ice cores and to tie Holocene ice cores to the 14C dendrochronology record. We measured 10Be concentrations in 187 samples from depths of 0-560 m of the main WAIS Divide core, WDC06A. The ice samples are typically 1-2 kg and represent 2-4 m of ice, equivalent to an average temporal resolution of ~12 years, based on the preliminary age-depth scale proposed for the WDC core, (McConnell et al., in prep). Be, Al and Cl were separated using ion exchange chromatography techniques and the 10Be concentrations were measured by accelerator mass spectrometry (AMS) at PRIME lab. The 10Be concentrations range from 8.1 to 19.1 x 10^3 at/g, yielding an average of (13.1±2.1) x 10^3 at/g. Adopting an average snow accumulation rate of 20.9 cm weq/yr, as derived from the age-depth scale, this value corresponds to an average 10Be flux of (2.7±0.5) x 10^5 atoms/yr/cm2. This flux is similar to that of the Holocene part of the Siple Dome (Nishiizumi and Finkel, 2007) and Dome Fuji (Horiuchi et al. 2008) ice cores, but ~30% lower than the value of 4.0 x 10^5 atoms/yr/cm2 for GISP2 (Finkel and Nishiizumi, 1997). The periods of low solar activity, known as Oort, Wolf, Spörer, Maunder and Dalton minima, show ~20% higher 10Be concentrations/fluxes than the periods of average solar activity in the last millennium. The maximum 10Be fluxes during some of these periods of low solar activity are up to ~50% higher than average 10Be fluxes, as seen in other polar ice cores, which makes these peaks suitable as chronologic markers. We will compare the 10Be record in the WAIS Divide ice core with that in other Antarctic as well as Greenland ice cores and with the 14C treering record. Acknowledgment. This

  14. Towards sediment residence time in a Himalayan catchment? Insights from paired in-situ 14C and 10Be measurements in river sands

    NASA Astrophysics Data System (ADS)

    Lupker, M.; Hippe, K.; Wacker, L.; Wieler, R.

    2014-12-01

    Cosmogenic nuclides in detrital river sediments have been widely applied to derive denudation rates and sediment fluxes across entire catchments. Nuclides, such as 10Be, allow the derivation of denudation rates integrated over several hundreds to thousands of years, but single isotopic systems often provide little information on the intricate dynamics that control the export of sediments from catchments. The quantification of sediment storage and recycling within catchments is nevertheless crucial for a better understanding of the variability of sediments fluxes and their implication for landscape evolution. The paired measurement of 10Be along with cosmogenic, in-situ 14C in river sediments may provide new insides into sediment dynamics over kyr time scales for which other nuclides are not suitable [1,2]. In an effort to better understand the sediment dynamics in active orogens we combine in-situ 14C and 10Be measurements from the Kosi basin in eastern Nepal (~53 000 km2). Our preliminary 14C/10Be data shows apparent burial/storage ages of 14 to 21 kyr in the sediments currently exported by the river. These elevated burial ages suggest a larger storage component than previously thought in these catchments, even though possible biases associated to the use of 14C/10Be in sediments as burial chronometer have to be considered: First, the short half-life of 14C cannot be neglected and hence basin wide denudation cannot be considered as a simple mixing of sediments from individually eroding surfaces, introducing bias towards higher apparent burial ages in most settings. Second, in steep environments, sediments supplied by deep-seated landslides carry a buried signature that should not be confounded with sediment storage in the catchment. The importance of both biases needs to be quantified carefully, before basin-wide storage can be quantified. [1] Lauer & Willenbring, 2010 - JGR-Earth, vol. 115, F04018. [2] Hippe et al., 2012 - Geomorphology, vol. 179, pp. 58-70.

  15. Surface exposure dates of cirque basin deglaciation along a western Ireland transect

    NASA Astrophysics Data System (ADS)

    Barth, A. M.; Clark, J.; Clark, P. U.; McCabe, A.

    2013-12-01

    During the last deglaciation (20ka -11ka), variations in the Atlantic Meridional Overturning Circulation (AMOC), accompanied by changes in North Atlantic Deep Water production, caused centennial-to-millennial abrupt climate change. Because of Ireland's proximity to North Atlantic deep-water convection sites, changes in climate associated with variations in the AMOC would be particularly pronounced there, and are recorded by fluctuations of the Irish Ice Sheet. Many of Ireland's mountains also hosted cirque glaciers during the last glaciation, which would have been particularly sensitive to abrupt climate changes of the last deglaciation. Dating of cirque glacier moraines with cosmogenic nuclides can provide a millennial-scale reconstruction of variability in these highly sensitive cirque glaciers. We report 11 new 10Be ages from two cirques basins in County Mayo, western Ireland. A moraine adjacent to Lougaharry Lough near Killary Harbour suggests deglaciation at 13.81 × 0.14 ka during the Bølling-Allerød interval. Two moraines, one inner and one outer, at Lough Accorymore on Achill Island returned ages of 17.04 × 0.31 ka and 18.43 × 0.79 ka, respectively. Both Accorymore dates are Oldest Dryas in age and suggest variability during the millennial-scale Clogher Head Stadial in Ireland. To develop a more regional reconstruction of glacier-climate variability during the last deglaciation, we have also sampled moraines from cirque basins spanning western Ireland from County Kerry in the south to County Donegal in the north. Boulders were sampled from a total of 23 moraines from seven additional cirques to provide this more expansive coverage.

  16. The study of the geomagnetic excursions and the relative intensities from Chinese loess 10Be over the past 130 ka

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Xian, F.; Beck, J.; An, Z.; Wu, Z.; Liu, M.; Chen, M.; Priller, A.; Kutschera, W.; Jull, A. T.; Yu, H.; Song, S.; Cheng, P.; Kong, X.

    2009-12-01

    Chinese loess is well-known archive for the paleogeomagnetic and paleoclimatic studies [Zhou et al., 1990; An et al., 1990; Zhu et al., 2007]. However, earlier efforts to extract weak geomagnetic excursion signals from Chinese loess 10Be were always unsuccessful due to the complexities of loess 10Be, which results in the fact that loess 10Be was only used as a climatic proxy [Shen et al., 1992; Beer et al.,1993; Gu et al.,1996]. Meanwhile, knowledge on the precise stratigraphic horizons of geomagnetic excursions with a reliable dating [Channell, 2006], on whether the short-lived excursions such as Blake can not be recorded in paleosol unit are still controversial. Here, we present the reconstructed past 130ka geomagnetic excursions and relative paleointensities for the first time from 10Be records in two Chinese loess sections. Results are comparative with those of independent geomagnetic research on Atlantic and Pacific sediments. The derived Laschamp and Blake events lie in the loess-paleosol (L1SS1 and S1SS3) corresponding to mid MIS 3 and 5e respectively. Our studies prove the potential application of the complex loess 10Be for long-term geomagnetic tracing and provide new evidence to answer the long-existing debates on the precise stratigraphic horizon of geomagnetic excursions. Our study suggests the potential application of loess-paleosol 10Be for reconstructing geomagnetic intensity variations spanning the whole Quaternary. References 1. Zhou, L. P., F. Oldfield, A. G. Wintle, S. G. Robinson, and J. T. Wang (1990), Partly pedogenic origin of magnetic variations in Chinese loess, Nature, 346, 737-739. 2. An, Z. S., T. S. Liu, Y. C. Lu, S. C. Porter, G. Kukla, X. H. Wu, and Y. M. Hua (1990), The long-term paleomonsoon variation recorded by the loess-paleosol sequence in Central China, Quat. Int., 7-8, 91-95. 3. Zhu, R. X., R. Zhang, C. L. Deng, Y. X. Pan, Q. S. Liu, and Y. B. Sun (2007), Are Chinese loess deposits essentially continuous?, Geophys. Res. Lett

  17. Cosmogenic 10Be Chronologies of Moraines and Glacially Scoured Bedrock in the Teton Range, with Implications for Paleoclimatic Events and Tectonic Activity

    NASA Astrophysics Data System (ADS)

    Licciardi, J. M.; Pierce, K. L.; Thackray, G. D.; Finkel, R. C.; Zimmerman, S. R. H.

    2015-12-01

    At its Pleistocene maximum, the greater Yellowstone glacial system consisted of an ice cap on the Yellowstone Plateau joined by glaciers from adjacent high mountains, including the Teton Range. In prior research, we obtained 112 exposure ages from moraines and bedrock in this region. These chronologies identified asynchronous outlet glacier culminations around the periphery of the Yellowstone glacier complex, supporting a model of spatial and temporal progressions in buildup and decay of the various ice source regions. Here we build on this previous work and present >30 recently developed 10Be exposure ages on glacial features in the Teton Range. Although the Tetons harbored a relatively small portion of the greater Yellowstone ice complex, glaciers in this range left behind some of the region's best-preserved moraine sequences and scoured bedrock. Ongoing investigations are focused on developing moraine chronologies in several drainages on the eastern and western Teton Range fronts, and obtaining exposure ages along scoured bedrock transects in glacial troughs upvalley from the dated moraines to define rates of ice recession. Notably, our dating campaign includes lateral moraines that are offset by the Teton fault, providing a rare opportunity to establish direct constraints on integrated long-term slip rates. All new and previously obtained 10Be ages are calculated using recently published calibrations and scaling of 10Be production rates. Initial results show that massive lateral moraines in selected drainages are several thousands of years older than adjacent distal end moraines, implying that the laterals were constructed during an earlier phase of the last glaciation and then acted to topographically confine subsequent ice advances. Mean ages of ca. 17-16 ka from terminal moraine loops along with limiting ages from scoured bedrock upvalley of the moraines indicate glacier culminations followed by the onset of rapid ice retreat long after the end of the global

  18. Surface Exposure Ages of Space-Weathered Grains from Asteroid 25143 Itokawa

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Berger, E. L.; Christoffersen, R.

    2015-01-01

    Space weathering processes such as solar wind ion irradiation and micrometeorite impacts are widely known to alter the properties of regolith materials exposed on airless bodies. The rates of space weathering processes however, are poorly constrained for asteroid regoliths, with recent estimates ranging over many orders of magnitude. The return of surface samples by JAXA's Hayabusa mission to asteroid 25143 Itokawa, and their laboratory analysis provides "ground truth" to anchor the timescales for space weathering processes on airless bodies.

  19. Exposure of fibrinogen receptors in human platelets by surface proteolysis with elastase.

    PubMed Central

    Kornecki, E; Ehrlich, Y H; De Mars, D D; Lenox, R H

    1986-01-01

    Human platelets that were preincubated with porcine elastase aggregated spontaneously upon the addition of fibrinogen. Maximal aggregation to fibrinogen was observed with platelets pretreated with an elastase concentration of 111 micrograms/ml, and half-maximal aggregation occurred after treatment with 11 micrograms/ml elastase. Binding of radiolabeled fibrinogen to elastase-treated platelets was specific, saturable, and showed a single class of 48,400 +/- 9,697 fibrinogen-binding sites per platelet with a dissociation constant of 6.30 +/- 1.48 X 10(-7) M. ATP, apyrase, and the stimulators of platelet adenylate cyclase forskolin, prostaglandin E1, prostacyclin, and N6, 2'-O-dibutyryl cyclic AMP did not inhibit the fibrinogen-induced aggregation of elastase-treated platelets. EDTA completely blocked the initiation of aggregation and reversed the fibrinogen-induced aggregation of elastase-treated platelets. Monoclonal and polyclonal antibodies directed against glycoproteins (GP) IIb and IIIa completely blocked the fibrinogen-induced aggregation of elastase-treated platelets. Immunoprecipitates with these antibodies obtained from detergent extracts of surface-radiolabeled, intact, and elastase-treated platelets contained the glycoproteins IIb and IIIa. We conclude that surface proteolysis by low concentrations of elastase can expose fibrinogen-binding sites associated with GPIIb and GPIIIa on the platelet surface, resulting in spontaneous aggregation upon the addition of fibrinogen. These findings may be relevant to hemostatic changes observed in patients with increased levels of circulating elastase. Images PMID:3005363

  20. Intra-catchment variability and significance of catchment-averaged denudation rates from 10Be concentrations in stream sediments: a 10Be-budget of the Etages catchment, French Western Alps

    NASA Astrophysics Data System (ADS)

    Delunel, Romain; van der Beek, Peter; Carcaillet, Julien; Bourlès, Didier

    2010-05-01

    As most of the European Alps, The Ecrins-Pelvoux massif (French Western Alps) was extensively glaciated during Quaternary glaciations, leading to strong rejuvenation of its morphology. The massif therefore provides a suitable area to study the efficiency of erosion processes in relief evolution on postglacial timescales. Denudation rates inferred from in-situ produced 10Be concentrations in stream sediments, obtained from 12 catchments throughout the Ecrins-Pelvoux massif, have been recently shown to correlate with mean catchment elevation in the absence of significant relationships with other morphometric parameters (Delunel et al., in press). We have proposed that the present-day denudation of Ecrins-Pelvoux massif climatically driven trough increasing frost-controlled processes with elevation, providing a mechanistic link for the inferred feedback between uplift, elevation and denudation rates observed in the European Alps (Wittmann et al., 2007; Champagnac et al., 2009). However, cosmogenic isotope measurements of stream sediments do not allow distinguishing the intrinsic spatial variability of denudation within a catchment. Therefore, we have sought to verify our previous conclusions on a smaller scale within a single catchment, from exhaustive measurements of 10Be concentrations carried by quartz fraction of different sources feeding the high-altitude stream sediment routing system. We focus our current study on the Etages catchment, a high-elevation hanging tributary of the Vénéon valley (western part of the Ecrins-Pelvoux massif) underlain by homogenous granitic bedrock. This 14 km2 catchment presents elevations ranging from 1600 m to ~3600 m (mean catchment elevation ~2700 m), within the altitudinal range where frost-controlled processes are most efficient in the Western Alps (Delunel et al., in press). This catchment also hosts a small cirque-glacier, remaining from the Little Ice Age glacial advance. We have collected 19 samples on the most

  1. 10Be-derived denudation rates from the Burdekin catchment: The largest contributor of sediment to the Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Croke, Jacky; Bartley, Rebecca; Chappell, John; Austin, Jenet M.; Fifield, Keith; Tims, Stephen G.; Thompson, Chris J.; Furuichi, Takahisa

    2015-07-01

    Terrestrial cosmogenic nuclides (TCNs) such as Beryllium-10 (10Be) are now routinely used to reconstruct erosional rates over tens of thousands of years at increasingly large basin scales (> 100,000 km2). In Australia, however, the approach and its assumptions have not been systematically tested within a single, large drainage basin. This study measures 10Be concentrations in river sediments from the Burdekin catchment, one of Australia's largest coastal catchments, to determine long-term (> 10,000 years), time-integrated rates of sediment generation and denudation. A nested-sampling design was used to test for effects of increasing catchment scale on nuclide concentrations with upstream catchment areas ranging from 4 to 130,000 km2. Beryllium-10 concentrations in sediment samples collected from the upstream headwater tributaries and mid-stream locations range from 1.8 to 2.89 × 105 atoms g- 1 and data confirm that nuclide concentrations are well and rapidly mixed downstream. Sediment from the same tributaries consistently yielded 10Be concentrations in the range of their upstream samples. Overall, no decrease in 10Be concentrations can be observed at the range of catchment scales measured here. The mean denudation rate for all river sediment samples throughout the Fanning subcatchment (1100 km2) is 18.47 m Ma- 1, which compares with the estimate at the end of the Burdekin catchment (130,000 km2) of 16.22 m Ma- 1. Nuclide concentrations in the lower gradient western and southern catchments show a higher degree of variability, and several complications emerged as a result of the contrasting geomorphic processes and settings. This study confirms the ability of TCNs to determine long-term denudation rates in Australia and highlights some important considerations in the model assumptions that may affect the accuracy of limited sampling in large, low-gradient catchments with long storage times.

  2. Observations of historical sea cliff retreat rates exceed long-term estimates derived from cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Hurst, Martin D.; Rood, Dylan H.; Ellis, Michael A.; Anderson, Robert S.

    2015-04-01

    Historical observation of coastal retreat are limited to relatively short timescales (< 150 years), during which time humans may have modified the coastal environment. There is growing concern that rates of coastal change may be accelerated in the face of anticipated stormier climates and rising sea level, yet there is little knowledge of rates of coastal change prior to the relatively brief historical records. In order to make predictions about potential future coastal change it is important to establish baseline conditions averaged over longer time periods. Here we present analysis of sea cliff retreat throughout the Holocene averaged for chalk cliffs in south-east England using cosmogenic isotopes. We determine long-term rates of sea cliff erosion from 10Be measured from in-situ flint samples collected from three transects across coastal platforms in East Sussex. A numerical model of 10Be accumulation on an evolving coastal profile allows estimation of cliff retreat rate during the Holocene. The model accounts for variation in 10Be accumulation with tides and sea-level rise, and takes into account platform downwear and topographic shielding by adjacent cliffs. We find that cliff retreat rates during the Holocene were significantly slower (2-6 cm yr-1) than those derived from recent historical observations (15-25 cm yr-1). Modelled accumulation of 10Be requires retreat rates that increase rapidly in recent times, potentially reflecting human modification of the coastal sediment budget through construction of sea defences, flood defenses and aggregate extraction. Therefore knowledge of past human activity at the coastline may be important in anticipating future rates of coastal retreat.

  3. Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be

    SciTech Connect

    Itagaki, N.; Ito, M.; Milin, M.; Hashimoto, T.; Ishiyama, H.; Miyatake, H.

    2008-06-15

    The coexistence of the {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in the excited states of {sup 10}Be has been discussed. In the previous analysis, all the low-lying states of {sup 10}Be were found to be well described by the motion of the two valence neutrons around two {alpha} clusters. However, the {alpha}+t+t cluster structure was found to coexist with the {alpha}+{alpha}+n+n structure around E{sub x}=15 MeV, close to the corresponding threshold. We have introduced a microscopic model to solve the coupling effect between these two configurations. The K=0 and K=1 states are generated from the {alpha}+t+t configurations due to the spin coupling of two triton clusters. The present case of {sup 10}Be is one of the few examples in which completely different configurations of triton-type ({alpha}+t+t three-center) and {alpha}-type ({alpha}+{alpha}+n+n two-center) clusters coexist in a single nucleus in the same energy region.

  4. Dental ceramics coated with bioactive glass: Surface changes after exposure in a simulated body fluid under static and dynamic conditions

    NASA Astrophysics Data System (ADS)

    Papadopoulou, L.; Kontonasaki, E.; Zorba, T.; Chatzistavrou, X.; Pavlidou, E.; Paraskevopoulos, K.; Sklavounos, S.; Koidis, P.

    2003-07-01

    Bioactive materials develop a strong bond with living tissues through a carbonate-containing hydroxyapatite layer, similar to that of bone. The fabrication of a thin bioactive glass coating on dental ceramics used in metal-ceramic restorations, could provide a bioactive surface, which in combination with a tissue regenerative technique could lead to periodontal tissues attachment. The aim of this study was the in vitro investigation of the surface structure changes of dental ceramics used in metal-ceramic restorations, coated with a bioactive glass heat-treated at 950 °C, after exposure in a simulated body fluid (SBF) under two different soaking conditions. Coating of dental ceramics with a bioactive glass resulted in the formation of a stable and well bonded with the ceramic substrate thin layer. The growth of a well-attached carbonate apatite layer on their surface after immersion in a simulated body fluid is well evidenced under both experimental conditions, although in static environment the rate of apatite growth is constant and the grown layers seem to be more dense and compact compared with the respective layers observed on specimens under dynamic conditions.

  5. Influence of virtual height exposure on postural reactions to support surface translations.

    PubMed

    Cleworth, Taylor W; Chua, Romeo; Inglis, J Timothy; Carpenter, Mark G

    2016-06-01

    As fear of falling is related to the increased likelihood of falls, it is important to understand the effects of threat-related factors (fear, anxiety and confidence) on dynamic postural reactions. Previous studies designed to examine threat effects on dynamic postural reactions have methodological limitations and lack a comprehensive analysis of simultaneous kinetic, kinematic and electromyographical recordings. The current study addressed these limitations by examining postural reactions of 26 healthy young adults to unpredictable anterior-posterior support-surface translations (acceleration=0.6m/s(2), constant velocity=0.25m/s, total displacement=0.75m) while standing on a narrow virtual surface at Low (0.4cm) and High (3.2m) virtual heights. Standing at virtual height increased fear and anxiety, and decreased confidence. Prior to perturbations, threat led to increased tonic muscle activity in tibialis anterior, resulting in a higher co-contraction index between lower leg muscles. For backward perturbations, muscle activity in the lower leg and arm, and center of pressure peak displacements, were earlier and larger when standing at virtual height. In addition, arm flexion significantly increased while leg, trunk and center of mass displacements remained unchanged across heights. When controlling for leaning, threat-related factors can influence the neuro-mechanical responses to an unpredictable perturbation, causing specific characteristics of postural reactions to be facilitated in young adults when their balance is threatened. PMID:27264411

  6. Effects of artificial tears on rabbit ocular surface healing after exposure to benzalkonium chloride.

    PubMed

    Zhang, Yuqiu; Cao, Hong; Lin, Tong; Gong, Lan

    2016-10-01

    The aim of the study was to observe the effect of different artificial tears on healing the drug-induced keratopathy. To this aim, 64 rabbits received topical administration of 0.01% benzalkonium chloride to establish models and were divided into four groups. The control group received ocular saline solution (Saline), while the others were treated with Refresh Plus® (RF), Hycosan® (H) and Systane® Ultra (SU). Surface abnormalities were examined daily using slit-lamp. Fluorescein staining, histopathological and transmission electron microscopic (TEM) examination were performed at day 0, 2 weeks, and 1 and 2 months. A significant difference was observed between RF and SU, but not between H and SU at 2 weeks. TEM examination revealed new microvilli close to the cavity surface, and the number of microvilli in SU was greater than in H at 2 weeks and 1 month. Based on the results, the effect in the SU group was the most significant. Eye drops with nontoxic preservative such as SU are an alternative to treat drug-induced keratopathy. PMID:26890221

  7. Spatial patterns of mobile regolith thickness and meteoric 10Be in the Boulder Creek Critical Zone Observatory, Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Shea, N.; Ouimet, W. B.; Dethier, D. P.; Bierman, P. R.; Rood, D. H.

    2012-12-01

    The Boulder Creek Critical Zone Observatory (BcCZO) aims to understand the history, architecture and evolution of hillslopes found within the diverse topography and climate regimes of the Colorado Front Range. This information is crucial for testing and developing models of hillslope evolution, giving especial consideration to the production and downslope transport of mobile regolith on the hillslopes. Here, we present the results of a systematic study aiming to document spatial patterns of mobile regolith thickness and meteoric Beryllium-10 (10Be) concentrations in the Gordon Gulch basin of the BcCZO. Gordon Gulch lies within the unglaciated portion of the Colorado Front Range and is thought to be an artifact of long-term steady state evolution. The basin is characterized by mixed bedrock-soil mantled hillslopes, with intermittent bedrock outcrops (tors) on ~10% of slopes. It is currently unclear how the hillslopes of Gordon Gulch have evolved given the variable rock type and strength (i.e., fracture spacing), gradients (steep slopes in lower basin compared to gradual in the upper), and hillslope aspects (north versus south facing hillslopes, with varying tree types and soil moisture for frost cracking and heaving) that exist within the basin. Furthermore, climate data suggest that the current climate regime (relatively warm) is representative of only 20% of the last 65 ka. Mobile regolith thickness measurements provide a snapshot of hillslope evolution in the basin given these controls, and meteoric 10Be can used to constrain residence times and trace mobile regolith transport. We measure mobile regolith thickness as the depth to immobile weathered bedrock and/or saprolite. Preliminary analysis of over 200 soil pits reveals a high degree of variability in mobile regolith thickness. In general, the mobile regolith cover is thinner on the south facing slopes than the north facing and a general thickening of mobile regolith occurs on steeper slopes, especially along

  8. Applications of Surface-Enhanced Raman Spectroscopy for the Study of Indicators of Exposure to Selected Genotoxins

    NASA Astrophysics Data System (ADS)

    Helmenstine, Anne Marie

    Surface-enhanced Raman scattering spectroscopy (SERS) was used to detect and analyze certain genotoxic chemicals, their metabolites, and selected deoxyribonucleic acid/ribonucleic acid (DNA/RNA) adducts that may be produced from exposure to specific toxins. Substances examined included nucleic acid (purine/pyrimidine) etheno adducts of adenine and cytosine and carcinogens benzo (a) pyrene and aflatoxins. SERS was shown to be an effective tool for sensitive, selective detection and analysis of these genotoxins and related substances. Detection was accomplished even at such low concentrations as might be present in biological systems, and in minute volumes of approximately one microliter per sample. Most substances were found to possess unique spectral signatures and could be distinguished from other chemicals in this study. The sample molecules were also analyzed in body fluids (e.g. plasma, serum, and urine) and adducted to DNA. In this study SERS was demonstrated to open a new dimension in chemical analysis not previously available by utilizing other spectroscopies or methods of chemical detection. Special attention was given to the various factors affecting the quality and reproducibility of a SERS spectrum, emphasizing the importance of optimization of Raman cross-scattering enhancement. Methods for adapting SERS to deal with specific research problems and for expanding the capabilities of SERS to address the health effects from human exposure to toxic pollutants were addressed in the concluding remarks section of this manuscript.

  9. An Innovative Approach for the Calculation of Exposure Point Concentrations for Large Areas of Surface Radionuclide Contamination

    SciTech Connect

    Winchester Chromec, F.; Myers, Jeffrey C.

    2008-01-15

    The Department of Energy Rocky Flats site was designated as a wildlife refuge by the Rocky Flats National Wildlife Refuge Act of 2001. Rocky Flats was considered to be one of the most highly contaminated radiological sites in the country. Some portions of the site have low-level radionuclide contamination in surface soils. A site-wide risk and dose assessment to evaluate threats to human health and the environment were performed, so that the site could be released for this land use. The aggressive accelerated action program combined with defensible and innovative risk assessment methods resulted in there being no radionuclides of concern in the final comprehensive risk assessment (DOE 2006). An innovative approach for delineating functional exposure areas and area-weighted exposure point concentration-activities (EPCs) was negotiated with the regulatory agencies in Colorado. This procedure leads to realistic estimates of risk and dose to workers and visitors. This innovative approach to the calculation of EPCs was negotiated with both State and Federal regulators. The value of developing and maintaining good working relationships with regulators responsible for a site can not be overestimated. The building of trust and confidence among responsible parties and regulators is essential for the development and implementation of innovative methods and technologies.

  10. Decreased blood hepatitis B surface antibody levels linked to e-waste lead exposure in preschool children.

    PubMed

    Xu, Xijin; Chen, Xiaojuan; Zhang, Jian; Guo, Pi; Fu, Tingzao; Dai, Yifeng; Lin, Stanley L; Huo, Xia

    2015-11-15

    Lead (Pb) is a widespread environmental contaminant that can profoundly affect the immune system in vaccinated children. To explore the association between blood Pb and HBsAb levels in children chronically exposed to Pb, we measured hepatitis B surface antibody (HBsAb) titers, to reflect the immune response in the children of Guiyu, an electronic and electrical waste (e-waste) recycling area well known for environmental Pb contamination. We performed secondary exploratory analyses of blood Pb levels and plasma HBsAb titers in samples, taken in two phases between 2011 and 2012, from 590 children from Guiyu (exposed group) and Haojiang (reference group). Children living in the exposed area had higher blood Pb levels and lower HBsAb titers compared with children from the reference area. At each phase, generalized linear mixed models (GLMMs) showed that HBsAb titers were significantly negatively associated with child blood Pb levels. This work shows that a decreased immune response to hepatitis B vaccine and immune system might have potential harm to children with chronic Pb exposure. Importantly, nearly 50% of chronically exposed children failed to develop sufficient immunity to hepatitis in response to vaccination. Thus different vaccination strategies are needed for children living under conditions of chronic Pb exposure. PMID:26022852

  11. Terrestrial cosmogenic nuclide surface exposure dating of the oldest glacial successions in the Himalayan orogen: Ladakh Range, northern India

    USGS Publications Warehouse

    Owen, L.A.; Caffee, M.W.; Bovard, K.R.; Finkel, R.C.; Sharma, M.C.

    2006-01-01

    Terrestrial cosmogenic nuclide surface exposure dating of moraine boulders and alluvial fan sediments define the timing of five glacial advances over at least the last five glacial cycles in the Ladakh Range of the Transhimalaya. The glacial stages that have been identified are: the Indus Valley glacial stage, dated at older than 430 ka; the Leh glacial stage occurring in the penultimate glacial cycle or older; the Karglacial stage, occurring during the early part of the last glacial cycle; the Bazgo glacial stage, at its maximum during the middle of the last glacial cycle; and the early Holocene Khalling glacial stage. The exposure ages of the Indus Valley moraines are the oldest observed to date throughout the Himalayan orogen. We observe a pattern of progressively more restricted glaciation during the last five glacial cycles, likely indicating a progressive reduction in the moisture supply necessary to sustain glaciation. A possible explanation is that uplift of Himalayan ranges to the south and/or of the Karakoram Mountains to the west of the region may have effectively blocked moisture supply by the south Asian summer monsoon and mid-latitude westerlies, respectively. Alternatively, this pattern of glaciation may reflect a trend of progressively less extensive glaciation in mountain regions that has been observed globally throughout the Pleistocene. ?? 2006 Geological Society of America.

  12. Single-exposure two-dimensional superresolution in digital holography using a vertical cavity surface-emitting laser source array.

    PubMed

    Granero, Luis; Zalevsky, Zeev; Micó, Vicente

    2011-04-01

    We present a new implementation capable of producing two-dimensional (2D) superresolution (SR) imaging in a single exposure by aperture synthesis in digital lensless Fourier holography when using angular multiplexing provided by a vertical cavity surface-emitting laser source array. The system performs the recording in a single CCD snapshot of a multiplexed hologram coming from the incoherent addition of multiple subholograms, where each contains information about a different 2D spatial frequency band of the object's spectrum. Thus, a set of nonoverlapping bandpass images of the input object can be recovered by Fourier transformation (FT) of the multiplexed hologram. The SR is obtained by coherent addition of the information contained in each bandpass image while generating an enlarged synthetic aperture. Experimental results demonstrate improvement in resolution and image quality. PMID:21479012

  13. Linking morphology across the glaciofluvial interface: A 10Be supported chronology of glacier advances and terrace formation in the Garonne River, northern Pyrenees, France

    NASA Astrophysics Data System (ADS)

    Stange, K. M.; van Balen, R. T.; Kasse, C.; Vandenberghe, J.; Carcaillet, J.

    2014-02-01

    The Garonne River drains an important part of the northern Pyrenees and its northern foreland. We investigated the middle reaches of the Garonne River establishing a detailed morphogenetic profile of its foreland terrace staircase and the preserved palaeoglacier margins. We particularly focussed on the glaciofluvial interface, linking (also genetically) the fluvial sediment archives in the foreland with the terminal glacial basin upstream of the Pyrenees mountain front. Using cosmogenic nuclide 10Be analyses, two terrace exposures have been dated, including a prominent fluvioglacial outwash fan at the foreland transition. We identified three terminal margins of late Pleistocene glacier advances. The prominent Garonne staircase consists of three major terrace complexes, comprising eight individual terrace levels. Results indicate a young age of the lower terrace complex of the Garonne staircase (MIS 4-2). The morphogenetic relationships and the new 10Be exposure age constraints suggest that during the last glaciation (Würmian) the Garonne glacier reached its maximum extent at the north Pyrenean mountain front, apparently already during MIS 4. Two different ice margins were associated with MIS 2, indicating close to maximum ice-extent during early MIS 2 (LGM) and relatively stationary ice-recession in the late MIS 2. The extensive Garonne terrace complexes formed under cold-climate conditions and were abandoned by incision during major glacial-interglacial transitions. During warm-cold climate transitions lateral erosion caused the reworking of previously abandoned palaeofloodplains. The long-term (Quaternary) incision of the Garonne and other north Pyrenean rivers indicates that the proximal Aquitaine foreland basin experienced uplift. However, non-uniform lateral course migrations and valley asymmetries of the north Pyrenean piedmont rivers indicate that uplift magnitude is variable, with maximum amounts in the centre of the molasse-fan of Lannemezan: Rivers on

  14. Microscopic analysis of Be,1110 elastic scattering on protons and nuclei, and breakup processes of 11Be within the 10Be +n cluster model

    NASA Astrophysics Data System (ADS)

    Lukyanov, V. K.; Kadrev, D. N.; Zemlyanaya, E. V.; Spasova, K.; Lukyanov, K. V.; Antonov, A. N.; Gaidarov, M. K.

    2015-03-01

    The density distributions of 10Be and 11Be nuclei obtained within the quantum Monte Carlo model and the generator coordinate method are used to calculate the microscopic optical potentials (OPs) and cross sections of elastic scattering of these nuclei on protons and 12C at energies E <100 MeV/nucleon. The real part of the OP is calculated using the folding model with the exchange terms included, while the imaginary part of the OP that reproduces the phase of scattering is obtained in the high-energy approximation. In this hybrid model of OP the free parameters are the depths of the real and imaginary parts obtained by fitting the experimental data. The well-known energy dependence of the volume integrals is used as a physical constraint to resolve the ambiguities of the parameter values. The role of the spin-orbit potential and the surface contribution to the OP is studied for an adequate description of available experimental elastic scattering cross-section data. Also, the cluster model, in which 11Be consists of a n -halo and the 10Be core, is adopted. Within the latter, the breakup cross sections of 11Be nucleus on 9Be,93Nb,181Ta , and 238U targets and momentum distributions of 10Be fragments are calculated and compared with the existing experimental data.

  15. Northern San Andreas Fault slip rates on the Santa Cruz Mountain section: 10Be dating of an offset alluvial fan complex, Sanborn County Park, Saratoga, CA

    NASA Astrophysics Data System (ADS)

    Guns, K. A.; Prentice, C. S.; DeLong, S. B.; Kiefer, K.; Blisniuk, K.; Burgmann, R.

    2015-12-01

    To better assess seismic hazard and fault behavior along the southern peninsula in the San Francisco Bay Area on the Santa Cruz Mountain section of the San Andreas Fault, we combine field observations and high-resolution lidar topography data with 10Be exposure dating on offset landforms to estimate geologic fault slip rates. Our mapping at Sanborn County Park near Saratoga reveals a progression of alluvial fans and debris flows offset from their upstream sources by dextral slip on the San Andreas Fault. These upstream sources are 3 drainages, Todd Creek, Service Road Creek and Aubry Creek. Coarse alluvial deposits from each of these creeks contain large Tertiary sandstone boulders of varying size and abundance, derived from the Vaqueros Formation, that allow us to constrain the provenance of offset alluvial deposits to their upstream sources. Initial reconstruction, based on clast-count data on lithology and size from Todd Creek (n=68), Service Road Creek (N=32) and the offset deposits (n=68), suggest ≥140 m of dextral fault movement. Initial 10Be cosmogenic dating of sandstone boulders on an offset deposit from Service Road Creek yields a maximum date of 8 ka, a date uncorrected for hillslope residence and fluvial transport of inherited 10Be concentrations. These data suggest a minimum slip rate of at least 17 mm/yr on the Santa Cruz Mountain section of the San Andreas Fault in the peninsula. Ongoing analysis will refine this fault slip rate. Our preliminary data underscore the potential of this site to provide geologic slip rate estimates, and therefore answer a question critical to seismic hazard assessment, in a region where steep terrain, mass wasting, vegetation and urban development have generally made slip rate estimates challenging to obtain.

  16. 10Be in Quartz Gravel from the Gobi Desert and Evolutionary History of Alluvial Sedimentation in the Ejina Basin, Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Lyu, Y.

    2014-12-01

    Reconstructing the evolutionary history of the Gobi deserts developed from alluvial sediments in arid regions has great significance in unraveling changes in both tectonic activity and climate. However, such work is limited by a lack of suitable dating material preserved in the Gobi Desert, but cosmogenic 10Be has great potential to date the Gobi deserts. In the present study, 10Be in quartz gravel from the Gobi deserts of the Ejina Basin in Inner Mongolia of China has been measured to assess exposure ages. Results show that the Gobi Desert in the northern margin of the basin developed 420 ka ago, whereas the Gobi Desert that developed from alluvial plains in the Heihe River drainage basin came about during the last 190 ka. The latter developed gradually northward and eastward to modern terminal lakes of the river. These temporal and spatial variations in the Gobi deserts are a consequence of alluvial processes influenced by Tibetan Plateau uplift and tectonic activities within the Ejina Basin. Possible episodes of Gobi Desert development within the last 420 ka indicate that the advance/retreat of alpine glaciers during glacial/interglacial cycles might have been the dominant factor to influencing the alluvial intensity and water volume in the basin. Intense floods and large water volumes would mainly occur during the short deglacial periods.

  17. Comparing past accumulation rate reconstructions in East Antarctic ice cores using 10Be, water isotopes and CMIP5-PMIP3 models

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Landais, A.; Raisbeck, G. M.; Jouzel, J.; Bazin, L.; Kageyama, M.; Peterschmitt, J.-Y.; Werner, M.; Bard, E.; Aster Team

    2015-03-01

    Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 kyr in Antarctica. Inferring the variations in past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic Plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such an assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high-resolution beryllium-10 (10Be) as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high-resolution 10Be record covering a full climatic cycle over the period 269 to 355 ka from Marine Isotope Stage (MIS) 9 to 10, including a period warmer than pre-industrial (MIS 9.3 optimum). After correcting 10Be for the estimated effect of the palaeomagnetic field, we deduce that the 10Be reconstruction is in reasonably good agreement with EDC3 values for the full cycle except for the period warmer than present. For the latter, the accumulation is up to 13% larger (4.46 cm ie yr-1 instead of 3.95). This result is in agreement with the studies suggesting an underestimation of the deuterium-based accumulation for the optimum of the Holocene (Parrenin et al. 2007a). Using the relationship between accumulation rate and surface temperature from the saturation vapour relationship, the 10Be-based accumulation rate reconstruction suggests that the temperature increase between the MIS 9.3 optimum and present day may be 2.4 K warmer than estimated by the water isotopes reconstruction. We compare these reconstructions to the available model results from CMIP5-PMIP3 for a glacial and an interglacial state, i

  18. Search for the isovector monopole resonance via the 28Si(10Be,10B+ γ)28Al reaction

    NASA Astrophysics Data System (ADS)

    Scott, Michael; e11021 Collaboration Team

    2013-10-01

    The isovector giant monopole resonance (IVGMR) is a fundamental mode of collective oscillation in which the neutron and proton fluids in a nucleus radially expand and contract in an out-of-phase manner. Observation of the IVGMR has been difficult due to the lack of a probe that will excite only its non-spin-flip (ΔS = 0) transitions. The IVGMR's spin-transfer (ΔS = 1) counterpart, the isovector spin giant monopole resonance, is much more strongly excited at bombarding energies higher than 60 MeV/ u. By way of the (10Be,10B+ γ) charge-exchange reaction, the selectivity for the excitation of the IVGMR can be gained. In this probe, the superallowed Fermi transition 10Be(0+,g.s.) -->10B(01+,1.74 MeV, T = 1) allows a nearly pure isolation of the ΔS = 0 component by detecting the 1022 keV gamma rays from the deexcitation of the 10B. We measured the double differential cross sections for the 28Si(10Be,10B+ γ) reaction at 100 MeV/ u using the large acceptance S800 Spectrometer at the National Superconducting Cyclotron Laboratory with the GRETINA array detecting the gamma rays emitted from the 10B ejectile. In this presentation, we will report preliminary reults of the IVGMR in 28Al. GRETINA was funded by the US DOE - Office of Science. Operation of the array at NSCL is supported by NSF under Cooperative Agreement PHY-1102511(NSCL) and DOE under grant DE-AC02-05CH11231(LBNL).

  19. Grand solar minima and maxima deduced from 10Be and 14C: magnetic dynamo configuration and polarity reversal

    NASA Astrophysics Data System (ADS)

    Inceoglu, F.; Simoniello, R.; Knudsen, M. F.; Karoff, C.; Olsen, J.; Turck-Chiéze, S.; Jacobsen, B. H.

    2015-05-01

    Aims: This study aims to improve our understanding of the occurrence and origin of grand solar maxima and minima. Methods: We first investigate the statistics of peaks and dips simultaneously occurring in the solar modulation potentials reconstructed using the Greenland Ice Core Project (GRIP) 10Be and IntCal13 14C records for the overlapping time period spanning between ~1650 AD to 6600 BC. Based on the distribution of these events, we propose a method to identify grand minima and maxima periods. By using waiting time distribution analysis, we investigate the nature of grand minima and maxima periods identified based on the criteria as well as the variance and significance of the Hale cycle during these kinds of events throughout the Holocene epoch. Results: Analysis of grand minima and maxima events occurring simultaneously in the solar modulation potentials, reconstructed based on the 14C and the 10Be records, shows that the majority of events characterized by periods of moderate activity levels tend to last less than 50 years: grand maxima periods do not last longer than 100 years, while grand minima can persist slightly longer. The power and the variance of the 22-year Hale cycle increases during grand maxima and decreases during grand minima, compared to periods characterized by moderate activity levels. Conclusions: We present the first reconstruction of the occurrence of grand solar maxima and minima during the Holocene based on simultaneous changes in records of past solar variability derived from tree-ring 14C and ice-core 10Be, respectively. This robust determination of the occurrence of grand solar minima and maxima periods will enable systematic investigations of the influence of grand solar minima and maxima episodes on Earth's climate.

  20. Solar Particle Event Exposures and Local Tissue Environments in Free Space and on Martian Surface

    NASA Technical Reports Server (NTRS)

    Kim, M. Y.; Shinn, J. L.; Singleterry, R. C.; Atwell, W.; Wilson, J. W.

    1999-01-01

    Solar particle events (SPEs) are a concern to space missions outside Earth s geomagnetic field. The September 29, 1989 SPE is the largest ground-level event since February 23, 1956. It is an iron-rich event for which the spectra are well measured. Because ten times this event matches the ground level data of the February 1956 SPE, it is suggested that an event with ten-times the scaled spectra of the September 29, 1989 SPE be used as a worst case SPE for spacecraft design. For the worst case SPE, the input spectra were reconstructed using Nymmik's (1995) model for protons, the O and Fe ion spectra of Tylka et al. (1997) to evaluate the iron enhancement ratio, and the Solar Energetic Particle Baseline (SEPB) composition of McGuire et al. (1986) for the heavy ions. The necessary transport properties of the shielding materials and the astronaut s body tissues are evaluated using the HZETRN code. Three shield configurations (assumed to be aluminum) are considered: space suit taken as 0.3 g/sq cm, helmet/pressure vessel as 1 g/sq cm, and equipment room of 5 g/sq cm. A shelter is taken as 10 g/sq cm on the Martian surface. The effect of shielding due to the Martian atmosphere is included. The astronaut geometry is taken from the computerized anatomical man (CAM) model.

  1. Assessment of cell-surface exposure and vaccinogenic potentials of Treponema pallidum candidate outer membrane proteins

    PubMed Central

    Tomson, Farol L.; Conley, Patrick G.; Norgard, Michael V.; Hagman, Kayla E.

    2007-01-01

    Syphilis, a sexually transmitted infection caused by the spirochetal bacterium Treponema pallidum, remains a global public health problem. T. pallidum is believed to be an extracellular pathogen and, as such, the identification of T. pallidum outer membrane proteins that could serve as targets for opsonic or bactericidal antibodies has remained a high research priority for vaccine development. However, the identification of T. pallidum outer membrane proteins has remained highly elusive. Recent studies and bioinformatics have implicated four treponemal proteins as potential outer membrane proteins (TP0155, TP0326, TP0483 and TP0956). Indirect immunofluorescence assays performed on treponemes encapsulated within agarose gel microdroplets failed to provide evidence that any of these four molecules were surface-exposed in T. pallidum. Second, recombinant fusion proteins corresponding to all four candidate outer membrane proteins were used separately, or in combination, to vaccinate New Zealand White rabbits. Despite achieving high titers (>1:50,000) of serum antibodies, none of the rabbits displayed chancre immunity after intradermal challenge with viable T. pallidum. PMID:17890130

  2. Cholesterol Exposure at the Membrane Surface Is Necessary and Sufficient to Trigger Perfringolysin O Binding†

    PubMed Central

    Flanagan, John J.; Tweten, Rodney K.; Johnson, Arthur E.; Heuck, Alejandro P.

    2010-01-01

    Perfringolysin O (PFO) is the prototype for the cholesterol-dependent cytolysins, a family of bacterial pore-forming toxins that act on eukaryotic membranes. The pore-forming mechanism of PFO exhibits an absolute requirement for membrane cholesterol, but the complex interplay between the structural arrangement of the PFO C-terminal domain and the distribution of cholesterol in the target membrane is poorly understood. Herein we show that PFO binding to the bilayer and the initiation of the sequence of events that culminate in the formation of a transmembrane pore depend on the availability of free cholesterol at the membrane surface, while changes in the acyl chain packing of the phospholipids and cholesterol in the membrane core, or the presence or absence of detergent-resistant domains do not correlate with PFO binding. Moreover, PFO association with the membrane was inhibited by the addition of sphingomyelin, a typical component of membrane rafts in cell membranes. Finally, addition of molecules that do not interact with PFO, but intercalate into the membrane and displace cholesterol from its association with phospholipids (e.g., epicholesterol), reduced the amount of cholesterol required to trigger PFO binding. Taken together, our studies reveal that PFO binding to membranes is triggered when the concentration of cholesterol exceeds the association capacity of the phospholipids, and this cholesterol excess is then free to associate with the toxin. PMID:19292457

  3. Assessment of DNA damages caused by exposure of bacterial cells and spores to the Mars surface environment

    NASA Astrophysics Data System (ADS)

    Fajardo-Cavazos, Patricia; Schuerger, Andrew; Robles-Martinez, Jose; Douki, Thierry; Nicholson, Wayne

    Joint NASA and ESA missions are planned for the next decade to investigate the possibility of present or past life on Mars [1]. Evidence of extraterrestrial life will likely rely on the de-tection of biomarkers, highlighting the importance of preventing forward contamination not only with viable microorganisms, but also with biomolecules that could compromise the valid-ity of life-detection experiments [2-4]. The designation of DNA as a high-priority biomarker makes it necessary to evaluate its persistence in extraterrestrial environments, and the effects of exposure on its biological activity. To accomplish this, we deposited naked DNA, cells and spores of Bacillus subtilis 168 or B. pumilus SAFR-032, or cells of Acinetobacter radioresistens 50v1 onto spacecraft-qualified aluminum coupons. Samples were exposed to a simulated Mars surface environment as described in detail previously [4, 5] for various periods of time, and DNA damage was assessed by a number of measurements. Double-and single-strand breaks were measured by neutral and alkaline agarose gel electrophoresis, and DNA bipyrimidine pho-toproducts were measured by HPLC-mass spectrometry, as described previously [6, 7]. Loss of functionality of DNA to serve as a template for replication by DNA polymerase was measured using a quantitative polymerase chain reaction (qPCR) assay [8]. In all cases, DNA damage was directly correlated with time of exposure to simulated martian solar radiation (UV, visible, and infrared wavelengths). Exposure of samples to Mars surface conditions, but shielded from solar radiation, did not result in appreciable damage over the time periods tested, relative to controls. DNA contained within cells or spores was much less susceptible to damage than was naked DNA. Using the qPCR assay, we found that inactivation of naked DNA or DNA extracted from exposed spores of B. subtilis followed a multiphasic dose-response, and that a fraction of DNA molecules retained functionality after

  4. Surface exposure chronology of the Waimakariri glacial sequence in the Southern Alps of New Zealand: Implications for MIS-2 ice extent and LGM glacial mass balance

    NASA Astrophysics Data System (ADS)

    Rother, Henrik; Shulmeister, James; Fink, David; Alexander, David; Bell, David

    2015-11-01

    During the late Quaternary, the Southern Alps of New Zealand experienced multiple episodes of glaciation with large piedmont glaciers reaching the coastal plains in the west and expanding into the eastern alpine forelands. Here, we present a new 10Be exposure age chronology for a moraine sequence in the Waimakariri Valley (N-Canterbury), which has long been used as a reference record for correlating glacial events across New Zealand and the wider Southern Hemisphere. Our data indicate that the Waimakariri glacier reached its maximum last glaciation extent prior to ∼26 ka well before the global last glaciation maximum (LGM). This was followed by a gradual reduction in ice volume and the abandonment of the innermost LGM moraines at about 17.5 ka. Significantly, we find that during its maximum extent, the Waimakariri glacier overflowed the Avoca Plateau, previously believed to represent a mid-Pleistocene glacial surface (i.e. MIS 8). At the same time, the glacier extended to a position downstream of the Waimakariri Gorge, some 15 km beyond the previously mapped LGM ice limit. We use a simple steady-state mass balance model to test the sensitivity of past glacial accumulation to various climatic parameters, and to evaluate possible climate scenarios capable of generating the ice volume required to reach the full local-LGM extent. Model outcomes indicate that under New Zealand's oceanic setting, a cooling of 5 °C, assuming modern precipitation levels, or a cooling of 6.5 °C, assuming a one third reduction in precipitation, would suffice to drive the Waimakariri glacier to the eastern alpine forelands (Canterbury Plains). Our findings demonstrate that the scale of LGM glaciation in the Waimakariri Valley and adjacent major catchments, both in terms of ice volume and downvalley ice extent, has been significantly underestimated. Our observation that high-lying glacial surfaces, so far believed to represent much older glacial episodes, were glaciated during the LGM

  5. Nano-scale topography of bearing surface in advanced alumina/zirconia hip joint before and after severe exposure in water vapor environment.

    PubMed

    Pezzotti, Giuseppe; Saito, Takuma; Padeletti, Giuseppina; Cossari, Pierluigi; Yamamoto, Kengo

    2010-06-01

    The aim of this study was to perform a surface morphology assessment with nanometer scale resolution on femoral heads made of an advanced zirconia toughened alumina (ZTA) composite. Femoral heads were characterized to a degree of statistical accuracy in the as-received state and after exposures up to 100 h in severe vapor-moist environment. Surface screening was made using an atomic force microscope (AFM). Scanning was systematically repeated on portions of surface as large as several tens of micrometers, randomly selected on the head surface, to achieve sufficient statistical reliability without lowering the nanometer-scale spatial resolution of the roughness measurement. No significant difference was found in the recorded values of surface roughness after environmental exposure (at 134 degrees C, under 2 bar), which was always comparable to that of the as-received head. Surface roughness safely lay <10 nm after environmental exposures up to 100 h, which corresponded to an exposure time in vivo of several human lifetimes (i.e., according to an experimentally derived thermal activation energy). In addition, the roughness results were significantly (about one order of magnitude) lower as compared to those recorded on femoral heads made of monolithic zirconia tested under the same conditions. PMID:20058275

  6. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 3. Estimating Surface Area Exposure by Deuterium Uptake.

    PubMed

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Donohoe, Gregory C; Valentine, Stephen J

    2016-03-01

    Gas-phase hydrogen deuterium exchange (HDX), collision cross section (CCS) measurement, and molecular dynamics simulation (MDS) techniques were utilized to develop and compare three methods for estimating the relative surface area exposure of separate peptide chains within bovine insulin ions. Electrosprayed [M - 3H](3-) and [M - 5H](5-) insulin ions produced a single conformer type with respective collision cross sections of 528 ± 5 Å(2) and 808 ± 2 Å(2). [M - 4H](4-) ions were comprised of more compact (Ω = 676 ± 3 Å(2)) and diffuse (i.e., more elongated, Ω = 779 ± 3 Å(2)) ion conformer types. Ions were subjected to HDX in the drift tube using D2O as the reagent gas. Collision-induced dissociation was used to fragment mobility-selected, isotopically labeled [M - 4H](4-) and [M - 5H](5-) ions into the protein subchains. Deuterium uptake levels of each chain can be explained by limited inter-chain isotopic scrambling upon collisional activation. Using nominal ion structures from MDS and a hydrogen accessibility model, the deuterium uptake for each chain was correlated to its exposed surface area. In separate experiments, the per-residue deuterium content for the protonated and deprotonated ions of the synthetic peptide KKDDDDDIIKIIK were compared. The differences in deuterium content indicated the regional HDX accessibility for cations versus anions. Using ions of similar conformational type, this comparison highlights the complementary nature of HDX data obtained from positive- and negative-ion analysis. PMID:26620531

  7. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 3. Estimating Surface Area Exposure by Deuterium Uptake

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

    2016-03-01

    Gas-phase hydrogen deuterium exchange (HDX), collision cross section (CCS) measurement, and molecular dynamics simulation (MDS) techniques were utilized to develop and compare three methods for estimating the relative surface area exposure of separate peptide chains within bovine insulin ions. Electrosprayed [M - 3H]3- and [M - 5H]5- insulin ions produced a single conformer type with respective collision cross sections of 528 ± 5 Å2 and 808 ± 2 Å2. [M - 4H]4- ions were comprised of more compact (Ω = 676 ± 3 Å2) and diffuse (i.e., more elongated, Ω = 779 ± 3 Å2) ion conformer types. Ions were subjected to HDX in the drift tube using D2O as the reagent gas. Collision-induced dissociation was used to fragment mobility-selected, isotopically labeled [M - 4H]4- and [M - 5H]5- ions into the protein subchains. Deuterium uptake levels of each chain can be explained by limited inter-chain isotopic scrambling upon collisional activation. Using nominal ion structures from MDS and a hydrogen accessibility model, the deuterium uptake for each chain was correlated to its exposed surface area. In separate experiments, the per-residue deuterium content for the protonated and deprotonated ions of the synthetic peptide KKDDDDDIIKIIK were compared. The differences in deuterium content indicated the regional HDX accessibility for cations versus anions. Using ions of similar conformational type, this comparison highlights the complementary nature of HDX data obtained from positive- and negative-ion analysis.

  8. CERAMIDE AND SPHINGOSINE-1-PHOSPHATE ACT AS PHOTODYNAMIC THERAPY-ELICITED DAMAGE-ASSOCIATED MOLECULAR PATTERNS: CELL SURFACE EXPOSURE

    PubMed Central

    Korbelik, Mladen; Banáth, Judit; Sun, Jinghai; Canals, Daniel; Hannun, Yusuf A.; Separovic, Duska

    2014-01-01

    Molecules that appear on the surface of tumor cells after their therapy treatment may have important roles either as damage-associated molecular patterns (DAMPs) or signals for phagocytes influencing the disposal of these cells. Treatment of SCCVII and CAL27 cells, models of mouse and human squamous cell carcinoma respectively, by photodynamic therapy (PDT) resulted in the presentation of ceramide and sphingosine-1-phposphate (S1P) on the cell surface. This was documented by anti-ceramide and anti-S1P antibody staining followed by flow cytometry. The exposure of these key sphingolipid molecules on PDT-treated tumor cells was PDT dose-dependent and it varied in intensity with different photosensitizers used for PDT. The above results, together with the finding that both ceramide and S1P can activate NFκB signaling in macrophages co-incubated with PDT-treated tumor cells, establish that these two sphingolipids can act as DAMPs stimulating inflammatory/immune reactions critical for tumor therapy response. PMID:24713544

  9. Pseudomonas aeruginosa biofilm formation and UV/irradiation exposure change surface and chemical structures of Pre-Production Resin Pellets

    NASA Astrophysics Data System (ADS)

    Stam, C. N.; Neal, A.; Park, S.; Mielke, R.; Tsapin, A. I.; Bhartia, R.; Salas, E.; Hug, W.; Behar, A. E.; Nadeau, J. L.

    2011-12-01

    Microbial interactions with synthetic polymers in open ocean is poorly understood. Plastics are a major and persistent contaminant of ocean waters. Many of these plastics are contaminated with toxic and synthetic chemicals that persist in the environment with minimal degradation. The purpose of this study is to look at the effects that microbial biofilm communities have on both surface and chemical structures of pre-production resin pellets (PRPs). Pseudomonas aeruignosa was grown with PRPs under multiple growth and nutrient conditions. These conditions were combined with varying lengths of UV exposures common to ocean environments. Material degradation of the PRPs and the changing surface and chemical structures of these synthetic polymers was evaluated using a combination of Fourier transform infrared spectroscopy, environmental scanning electron microscopy, scanning transmission electron microscopy, X-ray microtomography, and ArcGIS mapping. This study correlates with previous studies conducted on environmental PRP's , collected on the 2009 Project Kaisei expedition in the Subtropical Convergence Zone of the North Pacific Gyre. Further studies are needed to develop a full understanding of degradation rates of synthetic polymers in oceanic environments.

  10. Precise electromagnetic tests of ab-initio calculations of light nucle i: states in {sup10}Be.

    SciTech Connect

    McCutchan, E. A.; Lister, C. J.; Wiringa, R. B.; Pieper, S. C.; Seweryniak, D.; Greene, J. P.; Carpenter, M. P.; Chiara, C. J.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Stefanescu, I.; Zhu, S.; Physics; Univ. of Maryland

    2009-01-01

    In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in {sup 10}Be using the Doppler shift attenuation method (DSAM) following the {sup 7}Li({sup 7}Li,{alpha}){sup 10}Be reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The J{sup TT} = 2{sub 1}{sup +} state at 3.37 MeV has T = 205 {+-} (5){sub stat}{+-}(7){sub sys} fs corresponding to a B(E2{down_arrow}) of 9.2(3)e{sup 2}fm{sup 4} in broad agreement with many calculations. The J{sup TT} = 2{sub 2}{sup +} state at 5.96 MeV was found to have a B(E2{down_arrow}) of 0.11(2)e{sup 2}fm{sup 4} and provides a more discriminating test of nuclear models. New Green's function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.

  11. Structures in 9,10Be and 10B studied with the tensor-optimized shell model

    NASA Astrophysics Data System (ADS)

    Myo, Takayuki; Umeya, Atsushi; Toki, Hiroshi; Ikeda, Kiyomi

    2015-06-01

    We study the structures of ^{9,10}Be and ^{10}B with the tensor-optimized shell model (TOSM) using an effective interaction based on the bare nucleon-nucleon interaction AV8^'. The tensor correlation is treated in TOSM using the full space of 2p2h configurations including high-momentum components. The short-range correlation is treated with the unitary correlation operator method. It is found that the level orders of the low-lying states of ^{9,10}Be and ^{10}B are entirely reproduced. For ^9Be, ground band states are located at relatively higher energies than the experiments, which indicates missing α clustering correlation in these states as seen in the case of ^8Be. In addition, the tensor force gives a larger attraction for T=1/2 states than for T=3/2 ones for ^9Be. The level order of the three nuclei is found to be sensitive to the presence of the tensor force in comparison with the results using the Minnesota effective interaction without the tensor force.

  12. Placing Absolute Timing on Basin Incision Adjacent to the Colorado Front Range: Results from Meteoric and in Situ 10BE Dating

    NASA Astrophysics Data System (ADS)

    Duehnforth, M.; Anderson, R. S.; Ward, D.

    2010-12-01

    A sequence of six levels of gravel-capped surfaces, mapped as Pliocene to Holocene in age, are cut into Cretaceous shale in the northwestern part of the Denver Basin immediately adjacent to the Colorado Front Range (CFR). The existing relative age constraints and terrace correlations suggest that the incision of the Denver Basin occurred at a steady and uniform rate of 0.1 mm yr-1 since the Pliocene. As absolute ages in this landscape are rare, they have the potential to test the reliability of the existing chronology, and to illuminate the detailed history of incision. We explore the timing of basin incision and the variability of geomorphic process rates through time by dating the three highest surfaces at the northwestern edge of the Denver Basin using both in situ and meteoric 10Be concentrations. As the tectonic conditions have not changed since the Pliocene, much of the variability of generation and abandonment of alluvial surfaces likely reflects the influence of glacial-interglacial climate variations. We selected Gunbarrel Hill (mapped as pre-Rocky Flats (Pliocene)), Table Mountain (mapped as Rocky Flats (early Pleistocene)), and the Pioneer surface (mapped as Verdos (Pleistocene, ~640 ka)) as sample locations. We took two amalgamated clast samples on the Gunbarrel Hill surface, and dated depth profiles using meteoric and in situ 10Be on the Table Mountain and Pioneer surfaces. In addition, we measured the in situ 10Be concentrations of 6 boulder samples from the Table Mountain surface. We find that all three surfaces are significantly younger than expected and that in situ and meteoric age measurements largely agree with each other. The samples from the pre-Rocky Flats site (Gunbarrel Hill) show ages of 250 and 310 ka, ignoring post-depositional surface erosion. The ages of the Table Mountain and Pioneer sites fall within the 120 to 150 ka window. These absolute ages overlap with the timing of the penultimate glaciation during marine isotope stage (MIS) 6

  13. Transfer of contaminants from surface to hands: experimental assessment of linearity of the exposure process, adherence to the skin, and area exposed during fixed pressure and repeated contact with surfaces contaminated with a powder.

    PubMed

    Brouwer, D H; Kroese, R; Van Hemmen, J J

    1999-04-01

    Estimation of dermal exposure in the workplace resulting from contact with contaminated surfaces is important in risk assessment. Models have been developed to describe the process of exposure due to transfer, but for major input parameters--that is, contact area surface and adherence--defaults are used. This study examines the effect of one single-hand press contact and repeated contacts with a contaminated glass plate on both skin area exposed and loading of the skin for three volunteers. A fluorescent whitening agent was used to study the process of exposure and to determine the increase of the area exposed as well as the adherence of the compound to the skin surface after 1 to 12 consecutive contacts by a video imaging technique. In addition, loading of the skin after 12 contacts was compared to loading of a cotton glove monitor with similar hand pressures. The results show that after one single-hand contact only 4 to 16 percent of the total surface of the palm of the hand was exposed, whereas after 12 contacts this was increased to about 40 percent. The efficiency of transfer was < or = 2 percent of the contamination of the surface. The adherence to the skin was 1.07 micrograms/cm2 after 12 contacts and tended to increase non-linearly with increase in contacts. Because defaults of adherence for use in exposure models are generally a factor 500 to 5,000 higher, and the area exposed is assumed to be the total surface of the hand, overestimation of dermal exposure due to a single hand-surface contact in workplaces may occur. Therefore, additional studies on multi-contact exposure scenarios are indicated to adjust defaults for hand-surface transfer processes. PMID:10457645

  14. Long-term background denudation rates of southern and southeastern Brazilian watersheds estimated with cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Sosa Gonzalez, Veronica; Bierman, Paul R.; Fernandes, Nelson F.; Rood, Dylan H.

    2016-09-01

    In comparison to humid temperate regions of the Northern Hemisphere, less is known about the long-term (millennial scale) background rates of erosion in Southern Hemisphere tropical watersheds. In order to better understand the rate at which watersheds in southern and southeastern Brazil erode, and the relationship of that erosion to climate and landscape characteristics, we made new measurements of in situ produced 10Be in river sediments and we compiled all extant measurements from this part of the country. New data from 14 watersheds in the states of Santa Catarina (n = 7) and Rio de Janeiro (n = 7) show that erosion rates vary there from 13 to 90 m/My (mean = 32 m/My; median = 23 m/My) and that the difference between erosion rates of basins we sampled in the two states is not significant. Sampled basin area ranges between 3 and 14,987 km2, mean basin elevation between 235 and 1606 m, and mean basin slope between 11 and 29°. Basins sampled in Rio de Janeiro, including three that drain the Serra do Mar escarpment, have an average basin slope of 19°, whereas the average slope for the Santa Catarina basins is 14°. Mean basin slope (R2 = 0.73) and annual precipitation (R2 = 0.57) are most strongly correlated with erosion in the basins we studied. At three sites where we sampled river sand and cobbles, the 10Be concentration in river sand was greater than in the cobbles, suggesting that these grain sizes are sourced from different parts of the landscape. Compiling all cosmogenic 10Be-derived erosion rates previously published for southern and southeastern Brazil watersheds to date (n = 76) with our 14 sampled basins, we find that regional erosion rates (though low) are higher than those of watersheds also located on other passive margins including Namibia and the southeastern North America. Brazilian basins erode at a pace similar to escarpments in southeastern North America. Erosion rates in southern and southeastern Brazil are directly and positively related to

  15. Effects of Ambient High Temperature Exposure on Alumina-Titania High Emittance Surfaces for Solar Dynamic Systems

    NASA Technical Reports Server (NTRS)

    deGroh, Kim K.; Smith, Daniela C.; Wheeler, Donald R.; MacLachlam, Brian J.

    1998-01-01

    Solar dynamic (SD) space power systems require durable, high emittance surfaces on a number of critical components, such as heat receiver interior surfaces and parasitic load radiator (PLR) elements. To enhance surface characteristics, an alumina-titania coating has been applied to 500 heat receiver thermal energy containment canisters and the PLR of NASA Lewis Research Center's (LeRC) 2 kW SD ground test demonstrator (GTD). The alumina-titania coating was chosen because it had been found to maintain its high emittance under vacuum (less than or equal to 10(exp -6) torr) at high temperatures (1457 F (827 C)) for an extended period (approximately 2,700 hours). However, preflight verification of SD systems components, such as the PLR require operation at ambient pressure and high temperatures. Therefore, the purpose of this research was to evaluate the durability of the alumina-titania coating at high temperature in air. Fifteen of sixteen alumina-titania coated Incoloy samples were exposed to high temperatures (600 F (316 C) to l500 F (816 C)) for various durations (2 to 32 hours). Samples, were characterized prior to and after heat treatment for reflectance, solar absorptance, room temperature emittance and emittance at 1,200 F (649 C). Samples were also examined to detect physical defects and to determine surface chemistry using optical microscopy, scanning electron microscopy operated with an energy dispersive spectroscopy (EDS) system, and x ray photoelectron spectroscopy (XPS). Visual examination of the heat-treated samples showed a whitening of samples exposed to temperatures of 1,000 F (538 C) and above. Correspondingly, the optical properties of these samples had degraded. A sample exposed to 1,500 F (816 C) for 24 hours had whitened and the thermal emittance at 1,200 F (649 C) had decreased from the non-heat treated value of 0.94 to 0.62. The coating on this sample had become embrittled with spalling off the substrate noticeable at several locations. Based

  16. A cosmogenic 10Be chronology for the local last glacial maximum and termination in the Cordillera Oriental, southern Peruvian Andes: Implications for the tropical role in global climate

    NASA Astrophysics Data System (ADS)

    Bromley, Gordon R. M.; Schaefer, Joerg M.; Hall, Brenda L.; Rademaker, Kurt M.; Putnam, Aaron E.; Todd, Claire E.; Hegland, Matthew; Winckler, Gisela; Jackson, Margaret S.; Strand, Peter D.

    2016-09-01

    Resolving patterns of tropical climate variability during and since the last glacial maximum (LGM) is fundamental to assessing the role of the tropics in global change, both on ice-age and sub-millennial timescales. Here, we present a10Be moraine chronology from the Cordillera Carabaya (14.3°S), a sub-range of the Cordillera Oriental in southern Peru, covering the LGM and the first half of the last glacial termination. Additionally, we recalculate existing 10Be ages using a new tropical high-altitude production rate in order to put our record into broader spatial context. Our results indicate that glaciers deposited a series of moraines during marine isotope stage 2, broadly synchronous with global glacier maxima, but that maximum glacier extent may have occurred prior to stage 2. Thereafter, atmospheric warming drove widespread deglaciation of the Cordillera Carabaya. A subsequent glacier resurgence culminated at ∼16,100 yrs, followed by a second period of glacier recession. Together, the observed deglaciation corresponds to Heinrich Stadial 1 (HS1: ∼18,000-14,600 yrs), during which pluvial lakes on the adjacent Peruvian-Bolivian altiplano rose to their highest levels of the late Pleistocene as a consequence of southward displacement of the inter-tropical convergence zone and intensification of the South American summer monsoon. Deglaciation in the Cordillera Carabaya also coincided with the retreat of higher-latitude mountain glaciers in the Southern Hemisphere. Our findings suggest that HS1 was characterised by atmospheric warming and indicate that deglaciation of the southern Peruvian Andes was driven by rising temperatures, despite increased precipitation. Recalculated 10Be data from other tropical Andean sites support this model. Finally, we suggest that the broadly uniform response during the LGM and termination of the glaciers examined here involved equatorial Pacific sea-surface temperature anomalies and propose a framework for testing the viability

  17. Morphogenetic evolution of the Têt river valley (eastern Pyrenees) using 10Be/21Ne cosmogenic burial dating

    NASA Astrophysics Data System (ADS)

    Sartégou, Amandine; Blard, Pierre-Henri; Braucher, Régis; Bourlès, Didier L.; Calvet, Marc; Zimmermann, Laurent; Tibari, Bouchaïb; Hez, Gabriel; Gunnell, Yanni; Aumaitre, Georges; Keddadouche, Karim

    2016-04-01

    The rates and chronologies of valley incision are closely modulated by the tectonic uplift of active mountain ranges and were controlled by repeated climate changes during the Quaternary. The continental collision between the Iberian and Eurasian plates induced a double vergence orogen, the Pyrenees, which has been considered as a mature mountain range in spite of significant seismicity (e.g. Chevrot et al., 2011) and evidence of neotectonics (e.g. Goula et al., 1999). Nevertheless, recent studies indicate that the range may have never reached a steady state (Ford et al., in press). One option for resolving this controversy is to quantify the incision rates since the Miocene by reconstructing the vertical movement of geometric markers such as fluvial terraces. However, the few available ages from the Pyrenean terrace systems do not exceed the middle Pleistocene. Thus, to enlarge the time span of this dataset, we studied alluvium-filled horizontal epiphreatic passages in limestone karstic networks. Such landforms are used as substitutes of fluvial terraces because they represent former valley floors (e.g. Palmer, 2007; Audra et al., 2013). They record the transient position of former local base levels during the process of valley deepening. The Têt river valley (southern Pyrenees) was studied near the Villefranche-de-Conflent limestone gorge where 8 cave levels have been recognized over a vertical height of 600 meters. Given that 26Al/10Be cosmogenic burial dating in this setting was limited to the last ~5 Ma (Calvet et al., 2015), here we used the cosmogenic 10Be/21Ne method in order to restore a more complete chronology of valley incision (e.g. Balco & Shuster, 2009; McPhilipps et al., 2016). Burial age results for alluvial deposits from 12 caves document incision rates since the Langhian (~14 Ma). Preliminary results indicate a history of valley deepening in successive stages. The data show a regular incision rate of 70-80 mm/a from the Langhian to the Messinian

  18. Analysis of the French insurance market exposure to floods: a stochastic model combining river overflow and surface runoff

    NASA Astrophysics Data System (ADS)

    Moncoulon, D.; Labat, D.; Ardon, J.; Leblois, E.; Onfroy, T.; Poulard, C.; Aji, S.; Rémy, A.; Quantin, A.

    2014-09-01

    The analysis of flood exposure at a national scale for the French insurance market must combine the generation of a probabilistic event set of all possible (but which have not yet occurred) flood situations with hazard and damage modeling. In this study, hazard and damage models are calibrated on a 1995-2010 historical event set, both for hazard results (river flow, flooded areas) and loss estimations. Thus, uncertainties in the deterministic estimation of a single event loss are known before simulating a probabilistic event set. To take into account at least 90 % of the insured flood losses, the probabilistic event set must combine the river overflow (small and large catchments) with the surface runoff, due to heavy rainfall, on the slopes of the watershed. Indeed, internal studies of the CCR (Caisse Centrale de Reassurance) claim database have shown that approximately 45 % of the insured flood losses are located inside the floodplains and 45 % outside. Another 10 % is due to sea surge floods and groundwater rise. In this approach, two independent probabilistic methods are combined to create a single flood loss distribution: a generation of fictive river flows based on the historical records of the river gauge network and a generation of fictive rain fields on small catchments, calibrated on the 1958-2010 Météo-France rain database SAFRAN. All the events in the probabilistic event sets are simulated with the deterministic model. This hazard and damage distribution is used to simulate the flood losses at the national scale for an insurance company (Macif) and to generate flood areas associated with hazard return periods. The flood maps concern river overflow and surface water runoff. Validation of these maps is conducted by comparison with the address located claim data on a small catchment (downstream Argens).

  19. Analysis of the French insurance market exposure to floods: a stochastic model combining river overflow and surface runoff

    NASA Astrophysics Data System (ADS)

    Moncoulon, D.; Labat, D.; Ardon, J.; Onfroy, T.; Leblois, E.; Poulard, C.; Aji, S.; Rémy, A.; Quantin, A.

    2013-07-01

    The analysis of flood exposure at a national scale for the French insurance market must combine the generation of a probabilistic event set of all possible but not yet occurred flood situations with hazard and damage modeling. In this study, hazard and damage models are calibrated on a 1995-2012 historical event set, both for hazard results (river flow, flooded areas) and loss estimations. Thus, uncertainties in the deterministic estimation of a single event loss are known before simulating a probabilistic event set. To take into account at least 90% of the insured flood losses, the probabilistic event set must combine the river overflow (small and large catchments) with the surface runoff due to heavy rainfall, on the slopes of the watershed. Indeed, internal studies of CCR claim database has shown that approximately 45% of the insured flood losses are located inside the floodplains and 45% outside. 10% other percent are due to seasurge floods and groundwater rise. In this approach, two independent probabilistic methods are combined to create a single flood loss distribution: generation of fictive river flows based on the historical records of the river gauge network and generation of fictive rain fields on small catchments, calibrated on the 1958-2010 Météo-France rain database SAFRAN. All the events in the probabilistic event sets are simulated with the deterministic model. This hazard and damage distribution is used to simulate the flood losses at the national scale for an insurance company (MACIF) and to generate flood areas associated with hazard return periods. The flood maps concern river overflow and surface water runoff. Validation of these maps is conducted by comparison with the address located claim data on a small catchment (downstream Argens).

  20. Deuterium retention and morphological modifications of the surface in five grades of tungsten after deuterium plasma exposure

    NASA Astrophysics Data System (ADS)

    Balden, M.; Manhard, A.; Elgeti, S.

    2014-09-01

    Five tungsten (W) grades were simultaneously exposed to deuterium (D) plasma with 1020 D/(m2 s) of 38 eV/D up to 1026 D/m2 at 500 K specimen temperature. The D inventories and their depth profiles within the topmost 12 μm were determined by nuclear reaction analysis (D(3He, p)α). Morphological modifications at and below the surface were analysed by confocal laser scanning microscopy and scanning electron microscopy assisted by focused ion beam cross-sectioning. The observed variation of the D inventory by more than one order of magnitude (0.5-15 × 1020 D/m2) is attributed only to the different properties of each W grade. Spherical blisters and stepped flat-topped extrusions are observed depending on the W grade. These modifications are interpreted as an indication for hydrogen loading-induced damaging. The exposure conditions and W grades were chosen to allow a comparison between published data sets.

  1. Results of the Komplast experiment on the long-term exposure of materials specimens on the ISS surface

    NASA Astrophysics Data System (ADS)

    Shumov, A. E.; Novikov, L. S.; Shaevich, S. K.; Aleksandrov, N. G.; Smirnova, T. N.; Nikishin, E. F.; Chernik, V. N.; Petukhov, V. P.; Voronina, E. N.; Sedov, V. V.; Salnikova, I. A.; Babaevskiy, P. G.; Kozlov, N. A.; Deev, I. S.; Startsev, O. V.; Shindo, D. J.; Golden, J. L.; Kravchenko, M.

    2015-11-01

    The Komplast materials experiment was designed by Khrunichev State Research and Production Space Center together with Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University and other Russian scientific institutes, and has been carried out by Mission Control Moscow since 1998. The purpose of this experiment is to study the complex effect of the low Earth orbit environment on samples of various spacecraft materials. On November 20, 1998 the Komplast experiment began with the launch of the first International Space Station module Zarya, or Functional Cargo Block (FGB). Eight Komplast panels with samples of materials and sensors were installed on the outer surface of FGB module. Two of eight experiment panels were retrieved during Russian extravehicular activity in February 2011 after 12 years of space exposure and were subsequently returned to Earth by Space Shuttle "Discovery" on the STS-133/ULF-5 mission in March 2011. The article presents the results obtained from this unique long-duration experiment on board of the International Space Station.

  2. 10Be evidence for the Matuyama-Brunhes geomagnetic reversal in the EPICA Dome C ice core.

    PubMed

    Raisbeck, G M; Yiou, F; Cattani, O; Jouzel, J

    2006-11-01

    An ice core drilled at Dome C, Antarctica, is the oldest ice core so far retrieved. On the basis of ice flow modelling and a comparison between the deuterium signal in the ice with climate records from marine sediment cores, the ice at a depth of 3,190 m in the Dome C core is believed to have been deposited around 800,000 years ago, offering a rare opportunity to study climatic and environmental conditions over this time period. However, an independent determination of this age is important because the deuterium profile below a depth of 3,190 m depth does not show the expected correlation with the marine record. Here we present evidence for enhanced 10Be deposition in the ice at 3,160-3,170 m, which we interpret as a result of the low dipole field strength during the Matuyama-Brunhes geomagnetic reversal, which occurred about 780,000 years ago. If correct, this provides a crucial tie point between ice cores, marine cores and a radiometric timescale. PMID:17080088

  3. Rates of sediment supply to arroyos from upland erosion determined using in situ produced cosmogenic 10Be and 26Al

    USGS Publications Warehouse

    Clapp, Erik M.; Bierman, Paul R.; Nichols, Kyle K.; Pavich, Milan; Caffee, Marc A.

    2001-01-01

    Using 10Be and 26Al measured in sediment and bedrock, we quantify rates of upland erosion and sediment supply to a small basin in northwestern New Mexico. This and many other similar basins in the southwestern United States have been affected by cycles of arroyo incision and backfilling several times in the past few millennia. The sediment generation (275 ± 65 g m−2 yr−1) and bedrock equivalent lowering rates (102 ± 24 m myr−1) we determine are sufficient to support at least three arroyo cycles in the past 3,000 years, consistent with rates calculated from a physical sediment budget within the basin and regional rates determined using other techniques. Nuclide concentrations measured in different sediment sources and reservoirs suggest that the arroyo is a good spatial and temporal integrator of sediment and associated nuclide concentrations from throughout the basin, that the basin is in steady-state, and that nuclide concentration is independent of sediment grain size. Differences between nuclide concentrations measured in sediment sources and reservoirs reflect sediment residence times and indicate that subcolluvial bedrock weathering on hillslopes supplies more sediment to the basin than erosion of exposed bedrock.

  4. Weathering histories of Chinese loess deposits based on uranium and thorium series nuclides and cosmogenic {sup 10}Be

    SciTech Connect

    Gu, Z.Y. |; Lal, D.; Liu, T.S.

    1997-12-01

    The long, continuous deposition of dust in the Chinese loess plateau offers an unique opportunity to study the nature of soil weathering in a wide range of climatic conditions. In this paper we report on measurements of concentrations of U- and Th-series nuclides and of major cations in 150 loess and paleosol samples from five sites, going back 2.5 Ma. Using the results for {sup 10}Be concentrations in these soils, we determined the absolute amounts of water added to several soil units and obtained: (1) first-order leaching constants for U and several cations and (2) the compositions of the soils contributing to the dust-source regions and of the dust at deposition. Further, based on analyses of {sup 230}Th in soils deposited in the past ca. 140 ka, we determined when the soils weathered in the source regions. We conclude that most of the weathering in the dust-source regions may have occurred during the interglacials. 34 refs., 8 figs., 2 tabs.

  5. Detailed diesel exhaust characteristics including particle surface area and lung deposited dose for better understanding of health effects in human chamber exposure studies

    NASA Astrophysics Data System (ADS)

    Wierzbicka, Aneta; Nilsson, Patrik T.; Rissler, Jenny; Sallsten, Gerd; Xu, Yiyi; Pagels, Joakim H.; Albin, Maria; Österberg, Kai; Strandberg, Bo; Eriksson, Axel; Bohgard, Mats; Bergemalm-Rynell, Kerstin; Gudmundsson, Anders

    2014-04-01

    Several diesel exhaust (DE) characteristics, comprising both particle and gas phase, recognized as important when linking with health effects, are not reported in human chamber exposure studies. In order to understand effects of DE on humans there is a need for better characterization of DE when performing exposure studies. The aim of this study was to determine and quantify detailed DE characteristics during human chamber exposure. Additionally to compare to reported DE properties in conducted human exposures. A wide battery of particle and gas phase measurement techniques have been used to provide detailed DE characteristics including the DE particles (DEP) surface area, fraction and dose deposited in the lungs, chemical composition of both particle and gas phase such as NO, NO2, CO, CO2, volatile organic compounds (including aldehydes, benzene, toluene) and polycyclic aromatic hydrocarbons (PAHs). Eyes, nose and throat irritation effects were determined. Exposure conditions with PM1 (<1 μm) mass concentration 280 μg m-3, number concentration 4 × 105 cm-3 and elemental to total carbon fraction of 82% were generated from a diesel vehicle at idling. When estimating the lung deposited dose it was found that using the size dependent effective density (in contrast to assuming unity density) reduced the estimated respiratory dose by 132% by mass. Accounting for agglomerated structure of DEP prevented underestimation of lung deposited dose by surface area by 37% in comparison to assuming spherical particles. Comparison of DE characteristics reported in conducted chamber exposures showed that DE properties vary to a great extent under the same DEP mass concentration and engine load. This highlights the need for detailed and standardized approach for measuring and reporting of DE properties. Eyes irritation effects, most probably caused by aldehydes in the gas phase, as well as nose irritation were observed at exposure levels below current occupational exposure limit

  6. 26Al - 10Be cosmogenic nuclide isochron burial dating in combination with luminescence dating of two Danube terraces

    NASA Astrophysics Data System (ADS)

    Neuhuber, Stephanie; Braumann, Sandra; Lüthgens, Christopher; Fiebig, Markus; Häuselmann, Philipp; Schäfer, Jörg

    2016-04-01

    The Quaternary sediment record in the Vienna Basin is influenced by two main factors: (1) the tectonic development of a pull apart basin along a sinistral strike slip fault system between the Eastern Alps and the West Carpathians and by (2) strongly varying sediment supply during the Plio- and Pleistocene. From the Late Pannonian (8.8 Ma) onward a large-scale regional uplift (Decker et al., 2005) controls terrace formation in the Vienna Basin. The main sediment supply into the Vienna Basin originates from the Danube, and subordinately from tributaries to the south such as Piesting, Fischa, Leitha and from the north by the river March. Today the Danube forms a large floodplain that is bordered to the north by one large Pleistocene terrace, the Gänserndorf Terrace that is situated 17 m above todays water level. Farther to the east a smaller terrace, the Schlosshof Terrace, reaches 25 m above todays water level. These terrace levels are tilted by movement of underlying blocks (Peresson, 2006). Both, the Schlosshof and Gänserndorf terraces consist of successions of up to 2 m thick gravel beds with intercalated sand layers or -lenses that may locally reach thicknesses up to 0.8 m. At each terrace one gavel pit was selected to calculate the time of terrace deposition by luminescence dating in combination with 26Al/10Be cosmogenic nuclide isochrone dating (Balco and Rovery, 2008). Five quartz stones from the base of each terrace were physically and chemically processed to obtain Al and Be oxides for Acceleration Mass Spectrometry. Sand samples for luminescence dating were taken above the cosmogenic nuclide samples from the closest suitable sand body. Decker et al., 2005. QSR 24, 307-322 Peresson, 2006 Geologie der österreichischen Bundesländer Niederösterreich 255-258 Balco and Rovey, 2008. AJS 908, 1083-1114 Thanks to FWF P 23138-N19, OMAA 90öu17

  7. Effectiveness of dust control methods for crystalline silica and respirable suspended particulate matter exposure during manual concrete surface grinding.

    PubMed

    Akbar-Khanzadeh, Farhang; Milz, Sheryl A; Wagner, Cynthia D; Bisesi, Michael S; Ames, April L; Khuder, Sadik; Susi, Pam; Akbar-Khanzadeh, Mahboubeh

    2010-12-01

    Concrete grinding exposes workers to unacceptable levels of crystalline silica dust, known to cause diseases such as silicosis and possibly lung cancer. This study examined the influence of major factors of exposure and effectiveness of existing dust control methods by simulating field concrete grinding in an enclosed workplace laboratory. Air was monitored during 201 concrete grinding sessions while using a variety of grinders, accessories, and existing dust control methods, including general ventilation (GV), local exhaust ventilation (LEV), and wet grinding. Task-specific geometric mean (GM) of respirable crystalline silica dust concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled-grinding, while GV was off/on, were 0.17/0.09, 0.57/0.13, 1.11/0.44, and 23.1/6.80, respectively. Silica dust concentrations (mg/m³ using 100-125 mm (4-5 inch) and 180 mm (7 inch) grinding cups were 0.53/0.22 and 2.43/0.56, respectively. GM concentrations of silica dust were significantly lower for (1) GV on (66.0%) vs. off, and (2) LEV:HEPA- (99.0%), LEV:Shop-vac- (98.1%) or wet- (94.4%) vs. uncontrolled-grinding. Task-specific GM of respirable suspended particulate matter (RSP) concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled grinding, while GV was off/on, were 1.58/0.63, 7.20/1.15, 9.52/4.13, and 152/47.8, respectively. GM concentrations of RSP using 100-125 mm and 180 mm grinding cups were 4.78/1.62 and 22.2/5.06, respectively. GM concentrations of RSP were significantly lower for (1) GV on (70.2%) vs. off, and (2) LEV:HEPA- (98.9%), LEV:Shop-vac- (96.9%) or wet- (92.6%) vs. uncontrolled grinding. Silica dust and RSP were not significantly affected by (1) orientation of grinding surfaces (vertical vs. inclined); (2) water flow rates for wet grinding; (3) length of task-specific sampling time; or, (4) among cup sizes of 100, 115 or 125 mm. No combination of factors or control methods reduced an 8-hr exposure level to below the

  8. Production Rates of Noble Gases in the Near-Surface Layers of Europa by Energetic Charged Particles and the Potential for Determining Exposure Ages

    NASA Technical Reports Server (NTRS)

    Swindle, T. D.; Reedy, R. C.; Masarik, J.

    2003-01-01

    The surface of Europa is expected to be extremely active, undergoing tectonic and/or tidal geological activity and sputtering/ deposition, as well as impact cratering. Determination of the actual age of the surface at one or more places would greatly simplify trying to sort out what processes are occurring, and at what rate. If there is K present, as the spectral and compositional modeling discussed predict, it should be possible, in principle, to determine K-Ar crystallization ages. Whether or not there is K present, a consideration of the environment suggests we can determine an energetic particle exposure age if we can make in situ measurements of the abundances of major elements and of noble gas isotopes. This requires instrumentation that is within reach of current technology. In this paper, we calculate production rates for noble-gas isotopes in a simplified Europan surface, to quantify the amount of light noble gases produced by exposure to energetic particles.

  9. Radon 222 permeation through different polymers (PVC, EVA, PE and PP) after exposure to gamma radiation or surface treatment by cold plasma

    NASA Astrophysics Data System (ADS)

    Klein, D.; Tomasella, E.; Labed, V.; Meunier, C.; Cetier, Ph.; Robé, M. C.; Chambaudet, A.

    1997-08-01

    In order to limit radon emission during the storage of radioactive wastes and to comply with the different regulations in the storage facility, the packaging used for these types of wastes should include intermediate enclosures, such as polymer membranes used as radon barriers. However, the membrane would be subjected to different types of radiation during long periods of storage, it would have to be regularly monitored for damage. The first aim of this study is to check the efficiency and the continuity of such polymer membranes subjected to different accelerated ageing processes by exposure to gamma radiation. PolyVinyl Chloride (PVC) and Ethylene Vinyl Acetate (EVA) membranes were studied after gamma exposures. Thus, we evaluated the effects of the gamma radiations on the radon permeation coefficient, and the degradation of these polymers due to this exposure. The second objective of this study is to evaluate the modifications of the polymer surface by cold plasma. PolyEthylene (PE) and PolyPropylene (PP) membranes were studied. Exposure of a polymer to a plasma creates reactive sites on the polymer's surface. Different modifications in the surface composition (chemical composition, molecular weight, etc.) can be obtained. The advantage of the plasma process is that it acts within seconds and does not produce any noticeable effects on the bulk properties. The obtained results show that this treatment increases the polymer's efficiency as a radon barrier.

  10. Patterns of landscape evolution on the central and northern Tibetan Plateau investigated using in-situ produced 10Be concentrations from river sediments

    NASA Astrophysics Data System (ADS)

    Li, Yingkui; Li, Dewen; Liu, Gengnian; Harbor, Jon; Caffee, Marc; Stroeven, Arjen P.

    2014-07-01

    Quantifying long-term erosion rates across the Tibetan Plateau and its bordering mountains is of critical importance to an understanding of the interaction between climate, tectonic movement, and landscape evolution. We present a new dataset of basin-wide erosion rates from the central and northern Tibetan Plateau derived using in-situ produced 10Be concentrations of river sediments. Basin-wide erosion rates from the central plateau range from 10.1±0.9 to 36.8±3.2 mm/kyr, slightly higher than published local erosion rates measured from bedrock surfaces. These values indicate that long-term downwearing of plateau surfaces proceeds at low rates and that the landscape is demonstrably stable in the central plateau. In contrast, basin-wide erosion rates from the Kunlun Shan on the northern Tibetan Plateau range from 19.9±1.7 to 163.2±15.9 mm/kyr. Although the erosion rates of many of these basins are much higher than the rates from the central plateau, they are lower than published basin-wide erosion rates from other mountains fringing the Tibetan Plateau, probably because the basins in the Kunlun Shan include both areas of low-relief plateau surface and high-relief mountain catchments and may also result from retarded fluvial sediment transport in an arid climate. Significantly higher basin-wide erosion rates derived from the Tibetan Plateau margin, compared to the central plateau, reflect a relatively stable plateau surface that is being dissected at its margins by active fluvial erosion.

  11. Late Pleistocene to Holocene slip rates for the Gurvan Bulag thrust fault (Gobi-Altay, Mongolia) estimated with 10Be dates

    NASA Astrophysics Data System (ADS)

    Ritz, J.-F.; BourlèS, D.; Brown, E. T.; Carretier, S.; ChéRy, J.; Enhtuvshin, B.; Galsan, P.; Finkel, R. C.; Hanks, T. C.; Kendrick, K. J.; Philip, H.; Raisbeck, G.; Schlupp, A.; Schwartz, D. P.; Yiou, F.

    2003-03-01

    We surveyed morphotectonic markers along the central part of the Gurvan Bulag thrust, a fault that ruptured with the Bogd fault during the Gobi-Altay earthquake (1957, M 8.3), to document climatic and tectonic processes along the fault for the late Pleistocene-Holocene period. The markers were dated using 10Be produced in situ. Two major periods of alluviation ended at 131 ± 20 and 16 ± 4.8 ka. These appear to be contemporaneous with global climatic changes at the terminations of marine isotope stages (MIS) 6 and 2. The vertical slip rates, determined from offset measurements and surfaces ages, are 0.14 ± 0.03 mm/yr over the late Pleistocene-Holocene and between 0.44 ± 0.11 and 1.05 ± 0.25 mm/yr since the end of the late Pleistocene. The higher of these slip rates for the last ˜16 kyr is consistent with paleoseismic investigations along the fault [, 2002], and suggests that, at the end of late Pleistocene, the fault evolved from quiescence to having recurrence intervals of 4.0 ± 1.2 kyr for surface ruptures with ˜4 m vertical offset (similar to that of 1957). The inferred recurrence interval is comparable to that of the Bogd fault (3.7 ± 1.3 kyr) suggesting that the two faults may have ruptured together also earlier during the last ˜16 kyr.

  12. Estimating source-attributable health impacts of ambient fine particulate matter exposure: global premature mortality from surface transportation emissions in 2005

    NASA Astrophysics Data System (ADS)

    Chambliss, S. E.; Silva, R.; West, J. J.; Zeinali, M.; Minjares, R.

    2014-10-01

    Exposure to ambient fine particular matter (PM2.5) was responsible for 3.2 million premature deaths in 2010 and is among the top ten leading risk factors for early death. Surface transportation is a significant global source of PM2.5 emissions and a target for new actions. The objective of this study is to estimate the global and national health burden of ambient PM2.5 exposure attributable to surface transportation emissions. This share of health burden is called the transportation attributable fraction (TAF), and is assumed equal to the proportional decrease in modeled ambient particulate matter concentrations when surface transportation emissions are removed. National population-weighted TAFs for 190 countries are modeled for 2005 using the MOZART-4 global chemical transport model. Changes in annual average concentration of PM2.5 at 0.5 × 0.67 degree horizontal resolution are based on a global emissions inventory and removal of all surface transportation emissions. Global population-weighted average TAF was 8.5 percent or 1.75 μg m-3 in 2005. Approximately 242 000 annual premature deaths were attributable to surface transportation emissions, dominated by China, the United States, the European Union and India. This application of TAF allows future Global Burden of Disease studies to estimate the sector-specific burden of ambient PM2.5 exposure. Additional research is needed to capture intraurban variations in emissions and exposure, and to broaden the range of health effects considered, including the effects of other pollutants.

  13. Fate of Extended-Spectrum β-Lactamase-Producing Escherichia coli from Faecal Sources in Surface Water and Probability of Human Exposure through Swimming.

    PubMed

    Schijven, Jack F; Blaak, Hetty; Schets, Franciska M; de Roda Husman, Ana Maria

    2015-10-01

    The goal of this study was to determine the fate of ESBL-producing Escherichia coli (ESBL-EC) emitted from faecal sources in surface water, and the probability of human exposure through swimming. Concentrations of ESBL-EC were measured in recreational waters and in source waters, being water in ditches surrounding poultry farms and municipal wastewater. Additionally, the potential of ESBL-EC in source waters to reach recreational waters located downstream of these sources was modeled. Modeled ESBL-EC concentrations in recreational waters appeared to be mostly determined by the concentrations in the source waters and by subsequent dilution in surface water, and less by inactivation. The mean (95%) risk of human exposure to ESBL-EC per person per swimming event, as assessed from measured ESBL-EC concentrations in recreational waters, was 0.16 (0.89) for men, 0.13 (0.72) for women and 0.20 (0.95) for children. Similar exposure risks were estimated for hypothetical recreational waters containing 100- or 1000-times diluted source water, located 10 days water travel time downstream of the sources. Human exposure to ESBL-EC through swimming is likely, if recreational waters are located downstream of poultry farms and municipal wastewater discharge points. PMID:26338143

  14. DEVELOPMENT AND EVALUATION OF AN AGGREGATE SURFACE SAMPLING METHOD FOR USE IN ASSESSING DERMAL EXPOSURES OF YOUNG CHILDREN

    EPA Science Inventory

    In the macroactivity approach, dermal exposure is estimated using empirically-derived transfer coefficients to aggregate the mass transfer associated with a series of contacts with a contaminated medium. The macroactivity approach affords the possibility of developing screenin...

  15. Dectin-1 and IL-17A suppress murine asthma induced by Aspergillus versicolor but not Cladosporium cladosporioides due to differences in β-glucan surface exposure.

    PubMed

    Mintz-Cole, Rachael A; Gibson, Aaron M; Bass, Stacey A; Budelsky, Alison L; Reponen, Tiina; Hershey, Gurjit K Khurana

    2012-10-01

    There is considerable evidence supporting a role for mold exposure in the pathogenesis and expression of childhood asthma. Aspergillus versicolor and Cladosporium cladosporioides are common molds that have been implicated in asthma. In a model of mold-induced asthma, mice were repeatedly exposed to either A. versicolor or C. cladosporioides spores. The two molds induced distinct phenotypes, and this effect was observed in both BALB/c and C57BL/6 strains. C. cladosporioides induced robust airway hyperresponsiveness (AHR), eosinophilia, and a predominately Th2 response, whereas A. versicolor induced a strong Th17 response and neutrophilic inflammation, but very mild AHR. Neutralization of IL-17A resulted in strong AHR and eosinophilic inflammation following A. versicolor exposure. In Dectin-1-deficient mice, A. versicolor exposure resulted in markedly attenuated IL-17A and robust AHR compared with wild-type mice. In contrast, C. cladosporioides induced AHR and eosinophilic inflammation independent of IL-17A and Dectin-1. A. versicolor, but not C. cladosporioides, spores had increased exposure of β-glucans on their surface and were able to bind Dectin-1. Thus, the host response to C. cladosporioides was IL-17A- and Dectin-1-independent, whereas Dectin-1- and IL-17A-dependent pathways were protective against the development of asthma after exposure to A. versicolor. PMID:22962686

  16. Occupational Exposure to Cobalt and Tungsten in the Swedish Hard Metal Industry: Air Concentrations of Particle Mass, Number, and Surface Area.

    PubMed

    Klasson, Maria; Bryngelsson, Ing-Liss; Pettersson, Carin; Husby, Bente; Arvidsson, Helena; Westberg, Håkan

    2016-07-01

    Exposure to cobalt in the hard metal industry entails severe adverse health effects, including lung cancer and hard metal fibrosis. The main aim of this study was to determine exposure air concentration levels of cobalt and tungsten for risk assessment and dose-response analysis in our medical investigations in a Swedish hard metal plant. We also present mass-based, particle surface area, and particle number air concentrations from stationary sampling and investigate the possibility of using these data as proxies for exposure measures in our study. Personal exposure full-shift measurements were performed for inhalable and total dust, cobalt, and tungsten, including personal real-time continuous monitoring of dust. Stationary measurements of inhalable and total dust, PM2.5, and PM10 was also performed and cobalt and tungsten levels were determined, as were air concentration of particle number and particle surface area of fine particles. The personal exposure levels of inhalable dust were consistently low (AM 0.15mg m(-3), range <0.023-3.0mg m(-3)) and below the present Swedish occupational exposure limit (OEL) of 10mg m(-3) The cobalt levels were low as well (AM 0.0030mg m(-3), range 0.000028-0.056mg m(-3)) and only 6% of the samples exceeded the Swedish OEL of 0.02mg m(-3) For continuous personal monitoring of dust exposure, the peaks ranged from 0.001 to 83mg m(-3) by work task. Stationary measurements showed lower average levels both for inhalable and total dust and cobalt. The particle number concentration of fine particles (AM 3000 p·cm(-3)) showed the highest levels at the departments of powder production, pressing and storage, and for the particle surface area concentrations (AM 7.6 µm(2)·cm(-3)) similar results were found. Correlating cobalt mass-based exposure measurements to cobalt stationary mass-based, particle area, and particle number concentrations by rank and department showed significant correlations for all measures except for particle number

  17. Occupational Exposure to Cobalt and Tungsten in the Swedish Hard Metal Industry: Air Concentrations of Particle Mass, Number, and Surface Area

    PubMed Central

    Bryngelsson, Ing-Liss; Pettersson, Carin; Husby, Bente; Arvidsson, Helena; Westberg, Håkan

    2016-01-01

    Exposure to cobalt in the hard metal industry entails severe adverse health effects, including lung cancer and hard metal fibrosis. The main aim of this study was to determine exposure air concentration levels of cobalt and tungsten for risk assessment and dose–response analysis in our medical investigations in a Swedish hard metal plant. We also present mass-based, particle surface area, and particle number air concentrations from stationary sampling and investigate the possibility of using these data as proxies for exposure measures in our study. Personal exposure full-shift measurements were performed for inhalable and total dust, cobalt, and tungsten, including personal real-time continuous monitoring of dust. Stationary measurements of inhalable and total dust, PM2.5, and PM10 was also performed and cobalt and tungsten levels were determined, as were air concentration of particle number and particle surface area of fine particles. The personal exposure levels of inhalable dust were consistently low (AM 0.15mg m−3, range <0.023–3.0mg m−3) and below the present Swedish occupational exposure limit (OEL) of 10mg m−3. The cobalt levels were low as well (AM 0.0030mg m−3, range 0.000028–0.056mg m−3) and only 6% of the samples exceeded the Swedish OEL of 0.02mg m−3. For continuous personal monitoring of dust exposure, the peaks ranged from 0.001 to 83mg m−3 by work task. Stationary measurements showed lower average levels both for inhalable and total dust and cobalt. The particle number concentration of fine particles (AM 3000 p·cm−3) showed the highest levels at the departments of powder production, pressing and storage, and for the particle surface area concentrations (AM 7.6 µm2·cm−3) similar results were found. Correlating cobalt mass-based exposure measurements to cobalt stationary mass-based, particle area, and particle number concentrations by rank and department showed significant correlations for all measures except for particle

  18. Distribution of 2,4-D in air and on surfaces inside residences after lawn applications: comparing exposure estimates from various media for young children.

    PubMed Central

    Nishioka, M G; Lewis, R G; Brinkman, M C; Burkholder, H M; Hines, C E; Menkedick, J R

    2001-01-01

    We collected indoor air, surface wipes (floors, table tops, and window sills), and floor dust samples at multiple locations within 11 occupied and two unoccupied homes both before and after lawn application of the herbicide 2,4-D. We measured residues 1 week before and after application. We used collected samples to determine transport routes of 2,4-D from the lawn into the homes, its subsequent distribution between the indoor surfaces, and air concentration as a function of airborne particle size. We used residue measurements to estimate potential exposures within these homes. After lawn application, 2,4-D was detected in indoor air and on all surfaces throughout all homes. Track-in by an active dog and by the homeowner applicator were the most significant factors for intrusion. Resuspension of floor dust was the major source of 2,4-D in indoor air, with highest levels of 2,4-D found in the particle size range of 2.5-10 microm. Resuspended floor dust was also a major source of 2,4-D on tables and window sills. Estimated postapplication indoor exposure levels for young children from nondietary ingestion may be 1-10 microg/day from contact with floors, and 0.2-30 microg/day from contact with table tops. These are estimated to be about 10 times higher than the preapplication exposures. By comparison, dietary ingestion of 2,4-D is approximately 1.3 microg/day. PMID:11713005

  19. Paleo-ocean chemistry records in marine opal: Implications for fluxes of trace elements, cosmogenic nuclides ( 10Be and 26Al), and biological productivity

    NASA Astrophysics Data System (ADS)

    Lal, D.; Charles, C.; Vacher, L.; Goswami, J. N.; Jull, A. J. T.; McHargue, L.; Finkel, R. C.

    2006-07-01

    Here, we provide evidence suggesting that marine (diatom) opal contains not only a high fidelity record of dissolved oceanic concentrations of cosmic ray-produced radionuclides, 10Be and 26Al, but also a record of temporal variations in a large number of trace elements such as Ti, Fe, Zn and Mn. This finding is derived from measurements in purified biogenic opal that can be separated from detrital materials using a newly developed technique based on surface charge characteristics. Initial results from a sediment core taken near the present-day position of the Antarctic Polar Front (ODP Site 1093) show dramatic changes in the intrinsic concentrations of, Be, Al, Ti, Fe, Mn and Zn in the opal assemblages during the past ˜140 kyr BP. The results imply appreciable climatically controlled fluctuations in the level of bioreactive trace elements. The time series of total Be, Al, Ti, Fe and 10Be in the sediment core are all well correlated with each other and with dust records in the polar ice cores. The observations suggest that a significant flux of these trace metals to oceans is contributed by the aeolian dust, in this case, presumably from the Patagonia. This observation also allows determination of fluxes of dust-contributed 10Be to the Antarctica ice sheets. However, our data show that the relationships among the various metals are not perfectly linear. During periods of higher dissolved concentrations of trace elements (indicated by Fe and Ti) the relative concentrations of bioreactive elements, Be, Al, Mn and Zn are decreased. By contrast, the Fe/Zn and Fe/Mn ratios decrease significantly during each transition from cold to warm periods. The relative behavior could be consistent with any of the following processes: (i) enhanced biological productivity due to greater supply of the bioreactive elements (e.g. Zn) during cold periods (ii) increased biological and inorganic scavenging of particle active elements (e.g. Be and Al) during early interglacial periods (iii

  20. Coupling data from U-series and 10Be CRN to evaluate soil steady-state in the Betic Cordillera

    NASA Astrophysics Data System (ADS)

    Schoonejans, Jerome; Vanacker, Veerle; Opfergelt, Sophie; Granet, Mathieu; Chabaux, François

    2015-04-01

    The regolith mantel is produced by weathering of bedrock through physical and biochemical processes. At the same time, the upper part of the regolith is eroded by gravity mass movements, water and wind erosion. Feedback's between production and erosion of soil material are important for soil development, and are essential to reach long-term steady-state in soil chemical and physical properties. Nowadays, long-term denudation rates of regolith can be quantified by using in-situ cosmogenic nuclides (CRN). If the soil thickness remains constant over sufficiently long time, soil production rates can be determined. However, the a priori assumption of long-term steady-state can be questionable in highly dynamic environments. In this study, we present analytical data from two independent isotopic techniques, in-situ cosmogenic nuclides and Uranium series disequilibrium. The disequilibrium of Uranium isotopes (238U, 234U, 230Th, 226Ra) is an alternative method that allows assessing soil formation rates through isotopic analysis of weathering products. Nine soil profiles were sampled in three different mountain ranges of the Betic Cordillera (SE Spain): Sierra Estancias, Filabres, Cabrera. All soils overly fractured mica schist and are very thin (< 60cm). In each soil profile, we sampled 4 to 6 depth slices in the soil profile, the soil-bedrock interface and (weathered) bedrock. Three of the nine soil profiles were sampled for U-series isotope measurements at EOST (University of Strasbourg). The surface denudation rates (CRN) are about the same in the Sierra Estancias and Filabres (26 ± 10 mm/ky) and increase up to 103 ± 47 mm/ky in the Sierra Cabrera. The spatial variation in soil denudation rates is in agreement with the variation in catchment-wide denudation rates presented by Bellin et al. (2014) which present the highest rates in the Sierra Cabrera (104-246mm/kyr). Moreover it roughly coincides with the pattern of long-term exhumation of the Betic Cordillera. Results

  1. A preliminary study of direct 10Be2+ counting in AMS using the super-halogen anion BeF3-

    NASA Astrophysics Data System (ADS)

    Fu, Yun-Chong; Zhang, Li; Zhou, Wei-Jian; Zhao, Xiao-Lei; Wu, Zhen-Kun; Zhao, Guo-Qing; Liu, Qi; Lu, Xue-Feng; Zhao, Wen-Nian; Huang, Chun-Hai

    2015-10-01

    The key to effective 10Be measurements by AMS is to efficiently suppress the interference of the isobar 10B and at the same time optimize 10Be transmission. In this work, a new approach of measuring 10Be by AMS has been studied. It uses the super-halogen anion of beryllium, BeF3-, which inherently suppresses 10B interference by nearly 5 orders of magnitude because the accompanying BF3- anion is rarely formed. The resulting 10B suppression factor is not as high as that achieved with energy degrader foils, but the 10B and 10Be separation in the final ionization detector was found to result in sufficient total 10B suppression for 10Be2+ to be counted directly at ∼6 MeV energies. Although the stripping yield from 10BeF3- to 10Be2+ is not as large as that from 10BeO-, this inefficiency is compensated by avoiding the reduction in transmission due to charge fraction splitting and optical transmission losses after the degrader foil. This paper summarizes our first observation of the direct 10Be2+ counting approach using the 3 MV multi-element system at the Xi'an AMS.

  2. Uplift and denudation rates of an actively growing mountain range inferred from in-situ produced cosmogenic 10Be: the Yumu Shan (NE Tibetan Plateau)

    NASA Astrophysics Data System (ADS)

    Palumbo, L.; Hetzel, R.; Minxing, T.; Li, X.; Guo, J.

    2009-04-01

    Located in the foreland of the Quilian Shan (NE Tibet), the Yumu Shan is an isolated mountain range bounded by an active NW-SE striking thrust fault. Geomorphic and structural features such as fault scarps and wind gaps suggest that the ~70 km long range is actively growing (Hetzel et al., 2004; Tapponnier et al., 1990), hence the tectonic uplift should exceed the rate of denudation. Here we quantify the rate of these two competing processes using in-situ produced cosmogenic 10Be. Catchment-wide denudation rates are derived from 10Be concentrations in stream sediments, whereas rock uplift rates are obtained by combining scarp topographic profiles with dating of geomorphic surfaces deformed by active thrust faults at the Yumu Shan mountain front. Both denudation and rock uplift rates integrate over a similar temporal scale (~10-100 ka) and thus over many earthquake cycles. Our data document that catchment wide-denudation rates vary from ~100 to ~400 mm ka-1 as a function of morphology and lithology, while rock uplift takes place at the rate of ~0.7 mm ka-1. The difference between these values confirms that the Yumu Shan is in a topographic pre-steady state and in accordance with geomorphic and structural features. Tectonic features indicate that over few millions of years the Yumu Shan may rise to a similar height as the main ranges of the Qilian Shan farther south, which have peaks with elevations between ~5 and ~5.5 km. References: Hetzel R., Tao M., Niedermann S., Strecker M.R., Ivy-Ochs S., Kubik P.W., Gao B. (2004). Implications of the fault scaling law for the growth of topography: Mountain ranges in the broken foreland of NE Tibet, Terra Nova, 16, 157-162. Tapponnier P., Meyer B., Avouac J.P., Peltzer G., Gaudemer Y., Guo S., Xiang H., Yin K., Chen Z., Cai S., Dai H. (1990). Active thrusting and folding in the Quilian Shan, and decoupling between upper crust and mantle in northeastern Tibet, Earth Planet. Sci. Lett., 97, 382-403.

  3. Using 10Be erosion rates and fluvial channel morphology to constrain fault throw rates in the southwestern Sacramento River Valley, California, USA

    NASA Astrophysics Data System (ADS)

    Cyr, A. J.

    2013-12-01

    The Sacramento - San Joaquin River Delta, California, USA, is a critical region for California water resources, agriculture, and threatened or endangered species. This landscape is affected by an extensive set of levees that enclose artificial islands created for agricultural use. In addition to their importance for sustaining agriculture, this levee system also supports extensive transport and power transmission infrastructure and urban/suburban development. These levees are susceptible to damage from even moderate ground shaking by either a large earthquake on one of the high-activity faults in the nearby San Francisco Bay region, or even a moderate earthquake on one of the low-activity faults in the Delta region itself. However, despite this danger the earthquake hazards in this region are poorly constrained due to our lack of understanding of faults in and near the Delta region. As part of an effort to better constrain the seismic hazard associated with known, but poorly constrained, faults in the region, a geomorphic analysis of the Dunnigan Hills, northwest of Woodland, CA, is being combined with cosmogenic 10Be catchment-averaged erosion rates. The Dunnigan Hills are a low-relief (maximum elevation 87 m) landscape generated by fault-bend folding above the west-vergent Sweitzer reverse fault that soles into a blind east-vergent reverse fault. These faults have been imaged by seismic reflection data, and local microseismicity indicates that this system is actively propagating to the east. However, the throw rates on the faults in this system remain unconstrained, despite the potential for significant shaking such as that experienced in the nearby April, 1892 earthquake sequence between Winters and Vacaville, Ca, ~25 km to the south, which has been estimated at magnitude 6.0 or greater. Geomorphic and cosmogenic 10Be analyses from 12 catchments draining the eastern flank of the Dunnigan Hills will be used to infer vertical rock uplift rates to better constrain

  4. MODELED RESIDENTIAL CHLORPYRIFOS EXPOSURE AND DOSE TO CHILDREN VIA DERMAL SURFACE RESIDUE CONTACT AND NON-DIETARY INGESTION

    EPA Science Inventory

    A physically-based stochastic model has been applied to estimate residential chlorpyrifos exposure and dace to children via the non-dietary ingestion and dermal residue contact pathways. Time-location-activity data for 2825 children were sampled from national surveys to generat...

  5. Exposure to Phthalate Emitted from Vinyl Flooring and Sorbed to Interior Surfaces, Dust, Airborne Particles and Human Skin

    EPA Science Inventory

    There is an urgent need to characterize potential risk to human health and the environment that arises from the manufacture and use of tens of thousands of chemicals. Computational tools and approaches for characterizing and prioritizing exposure are required: to provide input f...

  6. Chronic TiO₂ nanoparticle exposure to a benthic organism, Hyalella azteca: impact of solar UV radiation and material surface coatings on toxicity.

    PubMed

    Wallis, Lindsay K; Diamond, Stephen A; Ma, Hongbo; Hoff, Dale J; Al-Abed, Souhail R; Li, Shibin

    2014-11-15

    There is limited information on the chronic effects of nanomaterials to benthic organisms, as well as environmental mitigating factors that might influence this toxicity. The present study aimed to fill these data gaps by examining various growth endpoints (weight gain, instantaneous growth rate, and total protein content) for up to a 21 d sediment exposure of TiO2 nanoparticles (nano-TiO2) to a representative benthic species, Hyalella azteca. An uncoated standard, P25, and an Al(OH)3 coated nano-TiO2 used in commercial products were added to sediment at 20 mg/L or 100 mg/L Under test conditions, UV exposure alone was shown to be a greater cause of toxicity than even these high levels of nano-TiO2 exposure, indicating that different hazards need to be addressed in toxicity testing scenarios. In addition, this study showed the effectiveness of a surface coating on the decreased photoactivity of the material, as the addition of an Al(OH)3 coating showed a dramatic decrease in reactive oxygen species (ROS) production. However, this reduced photoactivity was found to be partially restored when the coating had been degraded, leading to the need for future toxicity tests which examine the implications of weathering events on particle surface coatings. PMID:25203828

  7. Assessing exposure to transformation products of soil-applied organic contaminants in surface water: comparison of model predictions and field data.

    PubMed

    Kern, Susanne; Singer, Heinz; Hollender, Juliane; Schwarzenbach, René P; Fenner, Kathrin

    2011-04-01

    Transformation products (TPs) of chemicals released to soil, for example, pesticides, are regularly detected in surface and groundwater with some TPs even dominating observed pesticide levels. Given the large number of TPs potentially formed in the environment, straightforward prioritization methods based on available data and simple, evaluative models are required to identify TPs with a high aquatic exposure potential. While different such methods exist, none of them has so far been systematically evaluated against field data. Using a dynamic multimedia, multispecies model for TP prioritization, we compared the predicted relative surface water exposure potential of pesticides and their TPs with experimental data for 16 pesticides and 46 TPs measured in a small river draining a Swiss agricultural catchment. Twenty TPs were determined quantitatively using solid-phase extraction liquid chromatography mass spectrometry (SPE-LC-MS/MS), whereas the remaining 26 TPs could only be detected qualitatively because of the lack of analytical reference standards. Accordingly, the two sets of TPs were used for quantitative and qualitative model evaluation, respectively. Quantitative comparison of predicted with measured surface water exposure ratios for 20 pairs of TPs and parent pesticides indicated agreement within a factor of 10, except for chloridazon-desphenyl and chloridazon-methyl-desphenyl. The latter two TPs were found to be present in elevated concentrations during baseflow conditions and in groundwater samples across Switzerland, pointing toward high concentrations in exfiltrating groundwater. A simple leaching relationship was shown to qualitatively agree with the observed baseflow concentrations and to thus be useful in identifying TPs for which the simple prioritization model might underestimate actual surface water concentrations. Application of the model to the 26 qualitatively analyzed TPs showed that most of those TPs categorized as exhibiting a high aquatic

  8. Effects of prenatal exposure to surface-coated nanosized titanium dioxide (UV-Titan). A study in mice

    PubMed Central

    2010-01-01

    Background Engineered nanoparticles are smaller than 100 nm and designed to improve or achieve new physico-chemical properties. Consequently, also toxicological properties may change compared to the parent compound. We examined developmental and neurobehavioral effects following maternal exposure to a nanoparticulate UV-filter (UV-titan L181). Methods Time-mated mice (C57BL/6BomTac) were exposed by inhalation 1h/day to 42 mg/m3 aerosolized powder (1.7·106 n/cm3; peak-size: 97 nm) on gestation days 8-18. Endpoints included: maternal lung inflammation; gestational and litter parameters; offspring neurofunction and fertility. Physicochemical particle properties were determined to provide information on specific exposure and deposition. Results Particles consisted of mainly elongated rutile titanium dioxide (TiO2) with an average crystallite size of 21 nm, modified with Al, Si and Zr, and coated with polyalcohols. In exposed adult mice, 38 mg Ti/kg was detected in the lungs on day 5 and differential cell counts of bronchoalveolar lavage fluid revealed lung inflammation 5 and 26-27 days following exposure termination, relative to control mice. As young adults, prenatally exposed offspring tended to avoid the central zone of the open field and exposed female offspring displayed enhanced prepulse inhibition. Cognitive function was unaffected (Morris water maze test). Conclusion Inhalation exposure to nano-sized UV Titan dusts induced long term lung inflammation in time-mated adult female mice. Gestationally exposed offspring displayed moderate neurobehavioral alterations. The results are discussed in the light of the observed particle size distribution in the exposure atmosphere and the potential pathways by which nanoparticles may impart changes in fetal development. PMID:20546558

  9. 10Be dating of the end of low-altitude rock glacier activity in the Alps - evidence for cold conditions during the early Preboreal.

    NASA Astrophysics Data System (ADS)

    Kerschner, Hanns; Ivy-Ochs, Susan

    2010-05-01

    Large relict rock glacier complexes are conspicious features in the Alps. Their occurence can roughly be subdivided into a "lower rock glacier belt", which reaches down to about 1900 m a.s.l., an "intermediate rock glacier belt" with rock glacier snouts at around present-day timberline (approx. 2200 m a.s.l) in the central Alps and an "upper rock glacier belt" at similar altitudes as presently active rock glaciers. All these rock glaciers indicate the former presence of discontinuous permafrost at their respective altitudes and are good indicators for the mean annual air temperature during their active period. The end of rock glacier activity at a given altitude marks also the end of the existence of permafrost conditions. Experience from the Alps shows that it may take about a century until the surface of a rock glacier is stabilized, Hence, if it is possible to date the surface of a relict rock glacier with 10Be, we get a close date for the end of permafrost activity at the altitude of the rock glacier. From the difference between the altitude of the relict rock glacier and presently active rock glaciers, the rise of mean annual air temperature can be calculated. Relict rock glaciers at present-day timberline at Julierpass (Swiss Alps) and at Larstigtal (Austrian Alps) gave ages in the order of 10.5 ka BP for surface stabilization. Both rock glaciers, which belong to the "intermediate rock glacier belt", developed from lateral moraines and scree slopes. They started to move into former glacier beds after ice recession from the Younger Dryas "Egesen" advance. Their age indicates that climatic conditions favouring permafrost existence about 300 - 400 m below 20th century permafrost occurence prevailed during most of the Preboreal. Taken together with the Kartell glacier advance (10.8 ka) they show that rapid climatic warming at the Younger Dryas / Holocene boundary was followed by more unstable climatic conditions and and somewhat slower warming until full Holocene

  10. Late Holocene denudation rates and sediment fluxes in the Po basin from source to sink based on in situ cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Wittmann, Hella; Malusà, Marco; Resentini, Alberto; Garzanti, Eduardo; Niedermann, Samuel

    2016-04-01

    We constrain the long-term sediment delivery within the Po basin from source to lowland sink using sediment fluxes from in situ 10Be-derived denudation rates and compare these to published short-term estimates from gauging. We measured in situ 10Be concentrations in nearly all Alpine and Apennine upstream catchments draining to the Po River and in the Po lowlands down to the Po delta, respectively. In the upstream reaches of the Po basin, short-term sediment interception in dams and reservoirs and long-term sediment trapping in periglacial lakes may modify 10Be concentrations, whereas in lowland reaches, sediment burial and storage may affect nuclide concentrations. From the comparison of 10Be nuclide data measured upstream of dam influence to those measured downstream of major dams, we find that the average 10Be signal is not significantly modified. In the lowland reaches, we find that the average 10Be concentration is only marginally modified by floodplain processes, as 26Al/10Be ratios do not show differential decay due to burial and 21Ne concentrations change only slightly along the floodplain reach. Thus we interpret the average 10Be concentration of lowland samples to reflect the average 10Be concentration of all upstream catchments in terms of a preservation of the source area erosion signal. The close similarity in 10Be concentrations from the sources to the Po lowland sink suggests that LGM denudation rates prior to sediment trapping in periglacial lakes were similar to today's, as the sediment now contained in the Po lowlands must have been eroded from the orogen and deposited in the lowlands prior to lake formation. This source-sink assessment shows the robustness of cosmogenic 10Be as erosion rate tracer. From these in situ 10Be-derived denudation rates integrating over the last few thousand years, we constrain the sediment contributions of the Alpine and Apennine source areas arriving at the Po delta. In total, ca. 60 Mt/yr of sediment are exported to

  11. Roughening, recession, and chemical alteration of marble and limestone sample surfaces during atmospheric exposure in the eastern United States

    SciTech Connect

    Youngdahl, C.A.; Doe, B.R.

    1986-02-01

    Marble and limestone surfaces were exposed to atmospheric conditions at four eastern US sites and were monitored for changes in surface chemistry, surface roughness/recession, and weight. The effect of acid deposition, to which calcareous materials are especially sensitive, was of particular interest. Results are described for the first year of testing, and aspects of a preliminary equation to relate damage to environmental factors are discussed. Thus far, findings support that acid deposition substantially damages marble and limestone surfaces. Improvements in methods to reduce uncertainties in the quantitative contributions of important chemical species are outlined for the ongoing effort.

  12. Surface potential due to charge accumulation during vacuum ultraviolet exposure for high-k and low-k dielectrics

    SciTech Connect

    Ren, H.; Sinha, H.; Sehgal, A.; Nichols, M. T.; Shohet, J. L.; Antonelli, G. A.; Nishi, Y.

    2010-08-16

    The surface potential due to charge accumulation during vacuum ultraviolet irradiation of high-k and low-k thin dielectric films is measured. Measurement of the substrate current, which is the sum of the charge-accumulation and photoinjection currents, allows an in situ monitoring of the charge accumulation during irradiation. The relationship between the substrate current and the calculated in situ surface potential is also found, eliminating the need for a separate surface-potential measurement. With a high photon dose, the surface potential and substrate current reach a steady-state value with no further net charge accumulation.

  13. Lunar surface dynamics: Some general conclusions and new results from Apollo 16 and 17. [exposure age determination of lunar rocks, boulders, and craters

    NASA Technical Reports Server (NTRS)

    Crozaz, G.; Drozd, R.; Hohenberg, C.; Morgan, C.; Ralston, C.; Walker, R.; Yuhas, D.

    1974-01-01

    Exposure ages of Apollo 17 rocks as measured by tracks and the Kr-Kr rare gas method are reported. Concordant ages of 22 - or + 1 million year (my) are obtained for the station 6 boulder sample 76315. This value is interpreted as the time when the station 6 boulder was emplaced in its present position. Reasonable agreement is also obtained by the two methods for another station 6 boulder, sample 76015. Discordant ages (respectively 5 and 28 my by the track and rare gas methods) are obtained for the station 7 boulder sample, 77135, indicating that the boulder was emplaced at least 5 my ago. The 72 my exposure age of 75035, in general agreement with previous measurements of approximately 85 my for another Camelot boulder, may well date the formation of Camelot. Rock 76015 was split and one surface exposed to the sky through a very small solid angle.

  14. Spatial variations in 10Be-derived catchment wide denudation rates and the timing of glaciation in the NW Pamir SW Tien Shan Mountains, Tajikistan

    NASA Astrophysics Data System (ADS)

    Grin, E.; Ehlers, T. A.; Schaller, M.

    2014-12-01

    Mountain topography evolves in response to interactions between climate and tectonic processes. This study investigates the role of glaciation and catchment wide denudation rates in forming the 40.000 km2 large Vakhsh catchment in Tajikistan. The Vakhsh river is located in the Pamir - Tian Shan transition zone. The river drains the North Pamir as well as parts of the Alay Range, which is the western extension of the Tian Shan Mountains. The southward Vakhsh -Trans -Alay thrusting is the expression of ongoing tectonic activity in this area. Today the rate of convergence between the two mountain ranges adds up to at least 15 mm/yr. We analyzed the upstream part of the Vakhsh catchment with in situ-produced cosmogenic 10Be and 26Al in quartz. Modern river samples, terrace depth profiles, and moraine boulder samples were used for quantifying modern and paleo-denudation rates, and timing of the most recent glaciation. A recessional moraine was dated with a total number of 18 boulders and a sequence of five lateral moraines with 41 samples. Results from well-preserved moraines indicate in the North Pamir a maximal glacial extent at around 17 ka (+/- 1.9 ka). The analysis of modern river samples derived from several locations along the main channel of the Vakhsh river reveal denudation rates between 1.8 - 2.6 mm/yr. Spatial variations in denudation were also evaluated using cosmogenic nuclide-derived denudation rates from rivers ranging between Strahler order 4 and 7. Preliminary results for these rates vary between 0.7 and 2.9 mm/yr within the catchments. A correlation between Strahler order and the denudation rate has not been observed. Exposure ages for the lowest, middle, and highest of the 10 terraces are all ~3.2 ka (+/- 0.29 ka) indicating synchronous and rapid terrace formation in the late Holocene. Taken together, these results indicate: a) the most recent maximum extent of glaciation is in this valley is ~17 ka, b) terrace formation significantly post

  15. Cosmic ray event of A.D. 774-775 shown in quasi-annual 10Be data from the Antarctic Dome Fuji ice core

    NASA Astrophysics Data System (ADS)

    Miyake, Fusa; Suzuki, Asami; Masuda, Kimiaki; Horiuchi, Kazuho; Motoyama, Hideaki; Matsuzaki, Hiroyuki; Motizuki, Yuko; Takahashi, Kazuya; Nakai, Yoichi

    2015-01-01

    content in tree rings and 10Be concentration records in polar ice core provide information about past cosmic ray intensities. The A.D. 774-775 cosmic ray event has been identified by 14C measurement in several tree rings from all over the world. Although the quasi-decadal 10Be Dome Fuji data in the Antarctic ice core also shows a sharp peak around A.D. 775, annual 10Be variations in the Dome Fuji core or in other cores have not been revealed. We have measured quasi-annual 10Be concentrations from approximately A.D. 763-794 in the Dome Fuji ice core, and detected a clear increase (~80% above the baseline) in 10Be concentration around A.D. 775. However, an accurate height of this increase is not straightforwardly estimated due to the background variation in 10Be concentration. The 10Be increase can be due to the same cosmic ray event as shown in the 14C content in A.D. 774-775.

  16. Hillslope lowering rates and mobile-regolith residence times from in situ and meteoric 10Be analysis: Boulder Creek Critical Zone Observatory, Colorado

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Wyshnytzky, C.; Ouimet, W. B.; Dethier, D. P.

    2014-12-01

    Mobile regolith is produced as weathered saprolite is entrained into the mobile layer. The rate of mobile-regolith production and its residence time on hillslopes shapes the topography and evolution of hillslopes. We calculate the production rate of mobile regolith and the mobile-regolith residence times on active hillslopes in Gordon Gulch, within the Boulder Creek Critical Zone Observatory (CZO), Colorado. We find mobile-regolith production rates (average 3.1 cm/ka) and residence times (average 10-20 ka) derived from both in situand meteoric methods agree. Lowering-rates derived from our study are also comparable to basin-averaged denudation rates for small basins in the Colorado Front Range (Dethier and Lazarus, 2006). In this study, we have measured both in situ and meteoric 10Be in saprolite and mobile regolith separately. We find that, on average, two-thirds of in situ 10Be is produced within saprolite, and that at least one-tenth of the meteoric 10Be inventories are stored in saprolite. In the case of in situ 10Be, this simply reflects the exponential fall-off in production rates through a thin mobile-regolith cover. In the case of meteoric 10Be, our calculations suggest that >40% of the meteoric 10Be deposition occurs within the saprolite. Most studies that utilize 10Be report residence times and soil-production rates based on concentrations in either the mobile regolith or saprolite; therefore, our 10Be data highlight the importance of clearly identifying mobile and immobile portions of the regolith, constraining its 10Be inventory, and use of consistent terminology for the mobile-layer.

  17. Use of a variable exposure photographic pyrometer to measure surface temperatures on a hemispherical-face model

    NASA Technical Reports Server (NTRS)

    Kantsios, A. G.; Henley, W. C., Jr.; Snow, W. L.

    1982-01-01

    The use of a photographic pyrometer for nonintrusive measurement of high temperature surfaces in a wind tunnel test is described. The advantages of the pyrometer for measuring surfaces whose unique shape makes use of thermocouples difficult are pointed out. The use of computer operated densitometers or optical processors for the data reduction is recommended.

  18. Late Quaternary slip rate gradient defined using high-resolution topography and 10Be dating of offset landforms on the southern San Jacinto Fault zone, California

    NASA Astrophysics Data System (ADS)

    Blisniuk, Kimberly; Rockwell, Thomas; Owen, Lewis A.; Oskin, Michael; Lippincott, Caitlin; Caffee, Marc W.; Dortch, Jason

    2010-08-01

    Recent studies suggest the San Jacinto fault zone may be the dominant structure accommodating PA-NA relative plate motion. However, because the late Quaternary slip history of the southern San Andreas fault system is insufficiently understood, it is difficult to evaluate the partitioning of deformation across the plate boundary and its evolution. Landforms displaced by the Clark fault of the southern San Jacinto fault zone were mapped using high-resolution airborne laser-swath topography and selected offset landforms were dated using cosmogenic 10Be. Beheaded channels at Rockhouse Canyon, displaced by 500 ± 70 m and 220 ± 70 m, have been dated to 47 ± 8 ka and 28 ± 9 ka, respectively. Farther south, near the southern Santa Rosa Mountains, an alluvial deposit displaced by 51 ± 9 m has been dated to 35 ± 7 ka. From these sites, the slip rate of the Clark fault is determined to diminish southward from 8.9 ± 2.0 to 1.5 ± 0.4 mm/yr. This implies a slip-rate decrease along the Clark fault from Anza southeastward to its surface termination near the Salton Trough, where slip is transferred to the Coyote Creek fault, and additional deformation is compensated by folding and thrusting in the basin. These data suggest that since ˜30 to 50 ka, the slip rate along the southern San Jacinto fault zone has been lower than, or equivalent to, the rate along the southernmost San Andreas fault. Accordingly, either the slip rate of the San Jacinto fault has substantially decreased since fault initiation, or fault slip began earlier than previously suggested.

  19. Production rate and climate influences on the variability of 10Be deposition simulated by ECHAM5-HAM: Globally, in Greenland, and in Antarctica

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Smith, A. M.

    2013-03-01

    Ice core concentrations of 10Be are used as a proxy for solar activity, but they might be affected by atmospheric transport and deposition and their changes. During the Holocene, the influence is likely to be small, but during glacials it has to be accounted for. First, the climate influence has to be understood during the present climate. This study uses an ECHAM5-HAM 30-year climatological simulation of 10Be to investigate the production and climate-related influences on 10Be deposition with focus on Greenland and Antarctica. We examine the climate modes driving snow accumulation and hence potentially 10Be deposition over a climatologically relevant period. The North Atlantic Oscillation (NAO) is found to be the main driver of changes in precipitation and 10Be deposition in Greenland, in agreement with previous studies. In Antarctica, the picture is more complex as precipitation and 10Be deposition are only weakly correlated with the Southern Annular Mode (SAM), El Niño-Southern Oscillation (ENSO), or Zonal Wave 3 pattern (ZW3). The results suggest that on seasonal scale, 10Be deposition is linked with both precipitation rate and tropopause height, mainly due to the similar seasonal cycle. However, the correlation with tropopause height persists on the annual time scale. All in all, 10Be variability in Antarctica is an interplay of several processes whose contribution varies in time and space. When interpreting 10Be ice core records for solar activity, the time scale is essentially important. On seasonal scale, the 10Be signal is dominated by weather influences, but on multiannual scales, the production rate is the main driver. On multidecadal scale, large long-term trends in climatic factors have the potential to distort the signal again as is seen in 10Be records during glacials. This study shows how climate modes connect to 10Be variability and how this connection could be used to correct for the climate impact. The established connections during present

  20. Atmospheric constituents and surface-level UVB: Implications for a paleoaltimetry proxy and attempts to reconstruct UV exposure during volcanic episodes

    NASA Astrophysics Data System (ADS)

    Thomas, Brian C.; Goracke, Byron D.; Dalton, Sean M.

    2016-11-01

    Chemical and morphological features of spores and pollens have been linked to changes in solar ultraviolet radiation (specifically UVB, 280-315 nm) at Earth's surface. Variation in UVB exposure as inferred from these features has been suggested as a proxy for paleoaltitude; such proxies are important in understanding the uplift history of high altitude plateaus, which in turn is important for testing models of the tectonic processes responsible for such uplift. While UVB irradiance does increase with altitude above sea level, a number of other factors affect the irradiance at any given place and time. In this modeling study we use the TUV atmospheric radiative transfer model to investigate dependence of surface-level UVB irradiance and relative biological impact on a number of constituents in Earth's atmosphere that are variable over long and short time periods. We consider changes in O3 column density, and SO2 and sulfate aerosols due to periods of volcanic activity, including that associated with the formation of the Siberian Traps. We find that UVB irradiance may be highly variable under volcanic conditions and variations in several of these atmospheric constituents can easily mimic or overwhelm changes in UVB irradiance due to changes in altitude. On the other hand, we find that relative change with altitude is not very sensitive to different sets of atmospheric conditions. Any paleoaltitude proxy based on UVB exposure requires confidence that the samples under comparison were located at roughly the same latitude, under very similar O3 and SO2 columns, with similar atmospheric aerosol conditions. In general, accurate estimates of the surface-level UVB exposure at any time and location require detailed radiative transfer modeling taking into account a number of atmospheric factors; this result is important for paleoaltitude proxies as well as attempts to reconstruct the UV environment through geologic time and to tie extinctions, such as the end-Permian mass

  1. Characterization of the formyl peptide chemotactic receptor appearing at the phagocytic cell surface after exposure to phorbol myristate acetate

    SciTech Connect

    Gardner, J.P.; Melnick, D.A.; Malech, H.L.

    1986-02-15

    The biochemistry and subcellular source of new formyl peptide chemotactic receptor appearing at the human neutrophil and differentiated HL-60 (d-HL-60) cell surface after stimulation with phorbol myristate acetate (PMA) were examined. Formyl peptide receptor was analyzed by affinity labeling with formyl-norleu-leu-phe-norleu- (/sup 125/I)iodotyr-lys and ethylene glycol bis(succinimidyl succinate) followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and densitometric analysis of autoradiographs. PMA, a specific granule secretagogue, increases affinity labeling of formyl peptide receptors on the neutrophil surface by 100%, and on d-HL-60, which lack specific granule markers, by 20%. Papain treatment markedly reduces surface labeling of formyl peptide receptor in both neutrophils and d-HL-60, and results in the appearance of a lower m.w. membrane-bound receptor fragment. PMA stimulation of papain-treated cells increases uncleaved surface receptor on neutrophils by 400%, and on D-HL-60 by only 45%. This newly appearing receptor is the same apparent m.w. (55,000 to 75,000 for neutrophils; 62,000 to 80,000 for d-HL-60) and yields the same papain cleavage product as receptor on the surface of unstimulated cells. These observations suggest that specific granule membranes contain large amounts of formyl peptide receptor, which is biochemically identical to that found on the cell surface and can be mobilized to the cell surface with appropriate stimulation.

  2. {alpha}-decaying states in {sup 10,12}Be populated in the {sup 10}Be({sup 14}C,{sup 10,12}Be) reaction

    SciTech Connect

    Curtis, N.; Ashwood, N.I.; Bloxham, T.R.; Freer, M.; McEwan, P.; Price, D.L.; Baby, L.T.; Caussyn, D.D.; Spingler, D.; Wiedenhover, I.; Baldwin, T.D.; Catford, W.N.; Harlin, C.W.

    2006-05-15

    A search has been made for the {sup 6}He+{sup 6}He and {alpha} + {sup 8}He decay of the molecular rotational band in {sup 12}Be using the {sup 10}Be({sup 14}C,{sup 12}Be*){sup 12}C reaction at 88.5 MeV. Although the {alpha} + {sup 6}He decay of {sup 10}Be was observed in the data set there is no evidence for the breakup of {sup 12}Be. The cross-section upper limits for the {sup 10}Be({sup 14}C,{sup 6}He {sup 6}He){sup 12}C and {sup 10}Be({sup 14}C,{alpha} {sup 8}He){sup 12}C reactions are 50 and 300 nb respectively.

  3. Linking the10Be continental record of Lake Baikal to marine and ice archives of the last 50 ka: Implication for the global dust-aerosol input

    USGS Publications Warehouse

    Aldahan, A.; Possnert, G.; Peck, J.; King, J.; Colman, S.

    1999-01-01

    We present here a 10Be profile from the continental sediments of Lake Baikal (the world's largest fresh water lake), which, for the first time, shows the ??? 40 ka 10Be enhancement and a pattern that strongly matches those from the marine and ice records for the last 50 ka. This finding provides a new horizon for global and regional correlation of continental archives. Additionally, our VADM-predicted 10Be production confirms and further strengthens a common global cause (geomagnetic field intensity) for the change in atmospheric 10Be over the last 50 ka. We also show that most of the 10Be inventory to the lake has been provided by riverine input, but with a significant addition from direct precipitation and dust-aerosol fallout. We estimate a higher dust-aerosol contribution of 10Be during the Holocene and interstadial stage 3 (22-50 ka) as compared with the glacial period (12-22 ka). Copyright 1999 by the American Geophysical Union.

  4. OSIRIS observations of meter-sized exposures of H2O ice at the surface of 67P/Churyumov-Gerasimenko and interpretation using laboratory experiments

    NASA Astrophysics Data System (ADS)

    Pommerol, A.; Thomas, N.; El-Maarry, M. R.; Pajola, M.; Groussin, O.; Auger, A.-T.; Oklay, N.; Fornasier, S.; Feller, C.; Davidsson, B.; Gracia-Berná, A.; Jost, B.; Marschall, R.; Poch, O.; Barucci, M. A.; Bertaux, J.-L.; La Forgia, F.; Keller, H. U.; Kührt, E.; Lowry, S. C.; Mottola, S.; Naletto, G.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; De Cecco, M.; Debei, S.; Güttler, C.; Fulle, M.; Gutierrez, P. J.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Küppers, E.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. L.; Marzari, F.; Michalik, H.; Preusker, F.; Scholten, F.; Tubiana, C.; Vincent, J.-B.

    2015-11-01

    Since OSIRIS started acquiring high-resolution observations of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, over one hundred meter-sized bright spots have been identified in numerous types of geomorphologic regions, but mostly located in areas receiving low insolation. The bright spots are either clustered, in debris fields close to decameter-high cliffs, or isolated without structural relation to the surrounding terrain. They can be up to ten times brighter than the average surface of the comet at visible wavelengths and display a significantly bluer spectrum. They do not exhibit significant changes over a period of a few weeks. All these observations are consistent with exposure of water ice at the surface of boulders produced by dislocation of the weakly consolidated layers that cover large areas of the nucleus. Laboratory experiments show that under simulated comet surface conditions, analog samples acquire a vertical stratification with an uppermost porous mantle of refractory dust overlaying a layer of hard ice formed by recondensation or sintering under the insulating dust mantle. The evolution of the visible spectrophotometric properties of samples during sublimation is consistent with the contrasts of brightness and color seen at the surface of the nucleus. Clustered bright spots are formed by the collapse of overhangs that is triggered by mass wasting of deeper layers. Isolated spots might be the result of the emission of boulders at low velocity that are redepositioned in other regions.

  5. Carbon monoxide concentration and exposure time effects on the depth of CO penetration and surface color of raw and cooked beef longissimus lumborum steaks.

    PubMed

    Sakowska, A; Guzek, D; Głąbska, D; Wierzbicka, A

    2016-11-01

    This study investigated the influence of carbon monoxide (CO) exposure time (0, 7, 14, and 21days) and concentration in gas mixture on depth of penetration and the surface color of raw and cooked striploin steaks. Seven packaging treatments were evaluated: vacuum, vacuum after 48h of exposure to 0.1%, 0.3% or 0.5% CO (mixed with 30% CO2 and 69.5-69.9% N2), and modified atmosphere packaging (MAP) containing the same gas mixtures. CO penetration depth increased as exposure times and CO concentration in gas mixtures increased (p<0.05). However, the carboxymyoglobin that formed did not always turn brown during thermal treatment. In cooked samples treated with 0.3% and 0.5% CO-MAP, a red carboxymyoglobin border was visible at the cross section, whereas other CO packaging treatments had its partial or total browning. To create a red color in raw and avoid a red boarder in cooked beef, up to 0.5% CO in vacuum packages and only 0.1% for MAP can be recommended. PMID:27337678

  6. Conditions for the formation of various surface-plasma states upon quasi-steady-state exposure to CO2 laser radiation

    NASA Astrophysics Data System (ADS)

    Danshchikov, E. V.; Dymshakov, V. A.; Lebedev, F. V.; Riazanov, A. V.

    1985-09-01

    Experiments were carried out to study the conditions for the formation of an erosion flame in a target vapor on the surface of various metals during quasi-steady-state exposure to CO2 laser radiation. The duration of the CO2 laser pulses was 1 ms. The composition of the metal target specimens and the locations of the focusing spots are given in a table, together with the ambient gas pressures. The formation of an optical discharge in the ambient gas near the surface of the metal target specimens is described in detail. Some fundamental relationships between the laser parameters and the plasma characteristics of the different metal specimens are discussed on the basis of the experimental data.

  7. Unraveling the Quaternary river incision in the Moselle valley (Rhenish Massif, Germany): new insights from cosmogenic nuclide dating (10Be/26Al) of the Main Terrace complex

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Cordier, Stéphane; Harmand, Dominique; May, Simon Matthias; Kelterbaum, Daniel; Dunai, Tibor; Binnie, Steven; Brückner, Helmut

    2014-05-01

    Throughout the whole river network of the Rhenish Massif, the terrace complex of the so-called Main Terrace forms the morphological transition between a wide upper palaeovalley (plateau valley) and a deeply incised lower valley. The youngest level of this Main Terrace complex (YMT), directly located at the edge of the incised valley, represents a dominant geomorphic feature in the terrace flight; it is often used as a reference level to identify the start of the main middle Pleistocene incision episode (Demoulin & Hallot, 2009). The latter probably reflects the major tectonic pulse that affected the whole Massif and was related to an acceleration of the uplift rates (Demoulin & Hallot, 2009). The Main terraces are particularly well preserved in the lower Moselle valley and are characterized by a constant absolute elevation of their base along a 150 km-long reach. Despite that various hypotheses have been proposed to explain this horizontality (updoming, faulting...), all studies assumed an age of ca. 800 ka for the YMT, mainly based on the questionable extrapolation of palaeomagnetic data obtained in the Rhine valley. Therefore, a reliable chronological framework is still required to unravel the spatio-temporal characteristics of the Pleistocene evolution of the Moselle valley. In this study, we apply cosmogenic nuclide dating (10Be/26Al) to fluvial sediments pertaining to the Main Terrace complex or to the upper Middle Terraces. Several sites along the lower Moselle were sampled following two distinct sampling strategies: (i) depth profiles where the original terrace (palaeo-)surface is well preserved and did not experience much postdepositional burial (e.g., loess cover); and (ii) the isochron technique where the sediment thickness exceeds 3 m. Cosmogenic nuclide ages recently obtained for three rivers in the Meuse catchment in the western Rhenish Massif demonstrated that the Main Terraces were younger than expected and their abandonment was diachronic along the

  8. Authigenic 10Be/9Be Ratio Signatures of the Cosmogenic Nuclide Production Linked to Geomagnetic Dipole Moment Variation During and Since the Brunhes/Matuyama Boundary

    NASA Astrophysics Data System (ADS)

    Simon, Q.; Thouveny, N.; Bourles, D. L.; Ménabréaz, L.; Valet, J. P.; Valery, G.; Choy, S.

    2015-12-01

    The atmospheric production rate of cosmogenic nuclides is linked to the geomagnetic dipole moment (GDM) by a non-linear inverse relationship. Large amplitude GDM variations associated with reversals and excursions can potentially be reconstructed using time variation of the cosmogenic beryllium-10 (10Be) production recorded in ocean sediments. Downcore profiles of authigenic 10Be/9Be ratios (proxy of atmospheric 10Be production) in oceanic cores provide independent and additional records of the evolution of the geomagnetic intensity and complete previous information derived from relative paleointensity (RPI). Here are presented new authigenic 10Be/9Be results obtained from cores MD05-2920 and from the top of core MD05-2930 collected in the West Equatorial Pacific Ocean. Completing data of Ménabréaz et al. (2012, 2014), these results provide the first continuous 10Be production rate sedimentary record covering the last 800 ka. Along these cores, authigenic 10Be/9Be ratio peaks are recorded - within methodological errors - at the stratigraphic level of RPI lows. High-resolution chronologies (δ18O-derived) lead to interpret these peaks as successive global 10Be overproduction events triggered by geomagnetic dipole lows present in the PISO-1500 and Sint-2000 stacks. The largest amplitude 10Be production enhancement is synchronous to the very large decrease of the dipole field associated with the last polarity reversal (772 ka). It is consistent in shape and duration with the peak recorded in core MD90-0961 from the Maldive area (Indian Ocean) (Valet et al. 2014). Two significant 10Be production enhancements are coeval with the Laschamp (41 ka) and Icelandic basin (190 ka) excursions, while 10Be production peaks of lower amplitude correlate to other recognized excursions such as the Blake (120 ka), Pringle-Falls (215 ka), Portuguese Margin (290 ka), Big Lost (540 ka) among others. This study provides new data on the amplitude and timing of dipole field variations

  9. Geometries and electronic structures of the hydrogenated diamond (100) surface upon exposure to active ions: A first principles study

    NASA Astrophysics Data System (ADS)

    Liu, Feng-Bin; Li, Jing-Lin; Chen, Wen-Bin; Cui, Yan; Jiao, Zhi-Wei; Yan, Hong-Juan; Qu, Min; Di, Jie-Jian

    2016-02-01

    To elucidate the effects of physisorbed active ions on the geometries and electronic structures of hydrogenated diamond films, models of HCO 3 - , H3O+, and OH- ions physisorbed on hydrogenated diamond (100) surfaces were constructed. Density functional theory was used to calculate the geometries, adsorption energies, and partial density of states. The results showed that the geometries of the hydrogenated diamond (100) surfaces all changed to different degrees after ion adsorption. Among them, the H3O+ ion affected the geometry of the hydrogenated diamond (100) surfaces the most. This is well consistent with the results of the calculated adsorption energies, which indicated that a strong electrostatic attraction occurs between the hydrogenated diamond (100) surface and H3O+ ions. In addition, electrons transfer significantly from the hydrogenated diamond (100) surface to the adsorbed H3O+ ion, which induces a downward shift in the HOMO and LUMO energy levels of the H3O+ ion. However, for active ions like OH- and HCO 3 - , no dramatic change appears for the electronic structures of the adsorbed ions.

  10. Coincident exposure/drowning surfaces within Middle Cambrian Grand Cycles, East Tennessee: A model for abrupt limestone/shale transitions/sequence boundaries

    SciTech Connect

    Rankey, E.C.; Srinivasan, K.; Walker, K.R. . Dept. of Geological Science)

    1992-01-01

    Vertical transition from limestones to shales mark the boundaries of Cambrian Grand Cycles in Passive Margin Sequences over a wide geographic area. Field, petrographic, and geochemical evidence from near platform-edge mudstones and boundstones and platform-edge boundstones at the tops of the Craig Limestone and Maryville Limestone of the Conasauga Group in the southern Appalachians indicate platform death by subaerial exposure, followed by platform drowning and subsequent onlap of siliciclastic deposits. Physical evidence, in the form of scalloped truncation surfaces, as well as petrographic evidence consisting of wholesale and fabric-selective dissolution, internal brecciation, and vadose silt deposition indicate meteoric diagenesis following exposure. Depleted stable oxygen isotope compositions of inter- and intragranular blocky clear calcite spar of the Maryville Limestone have a mean delta O-18 composition of [minus]9.3[per thousand] (PDB) and a mean delta C-13 composition of +0.01[per thousand](PDB). Preliminary data from the Craig Limestone indicate similar delta C-13 values, but more depleted. Thus, the authors propose a common origin for the limestone-shale transitions at the top of these two units. Subaerial exposure during a sea-level fall at the top of these carbonate units terminated carbonate deposition. During exposure, a meteoric-water lens developed in the platform sediments leading to early diagenetic alteration. A rapid relative sea-level rise then drowned the platform, followed by subsidence and deepening during the lag-time before the onset of carbonate deposition. The deepening suppressed carbonate production and allowed fine siliciclastics characteristic of the adjacent basin to onlap the drowned platform.

  11. The effects of nitric acid and silane surface treatments on carbon fibers and carbon/vinyl ester composites before and after seawater exposure

    NASA Astrophysics Data System (ADS)

    Langston, Tye A.

    This research focuses on carbon fiber treatment by nitric acid and 3-(trimethoxysilyl)propyl methacrylate silane, and how this affects carbon/vinyl ester composites. These composites offer great benefits, but it is difficult to bond the fiber and matrix together, and without a strong interfacial bond, composites fall short of their potential. Silanes work well with glass fiber, but do not bond directly to carbon fiber because its surface is not reactive to liquid silanes. Oxidizing surface treatments are often prescribed for improved wetting and bonding to carbon, but good results are not always achieved. Furthermore, there is the unanswered question of environmental durability. This research aimed to form a better understanding of oxidizing carbon fiber treatments, determine if silanes can be bonded to oxidized surfaces, and how these treatments affect composite strength and durability before and after seawater exposure. Nitric acid treatments on carbon fibers were found to improve their tensile strength to a constant level by smoothing surface defects and chemically modifying their surfaces by increasing carbonyl and carboxylic acid concentrations. Increasing these surface group concentrations raises fiber polar energy and causes them to cohere. This impedes wetting, resulting in poor quality, high void content composites, even though there appeared to be improved adhesion between the fibers and matrix. Silane was found to bond to the oxidized carbon fiber surfaces, as evidenced by changes in both fiber and composite properties. The fibers exhibited low polarity and cohesion, while the composites displayed excellent resin wetting, low void content, and low seawater weight gain and swelling. On the contrary, the oxidized fibers that were not treated with silane exhibited high polarity and fiber cohesion. Their composites displayed poor wetting, high void content, high seawater weight gain, and low swelling. Both fiber treatment types resulted in great improvements

  12. Estimating Dermal Transfer of Copper Particles from the Surfaces of Pressure-Treated Lumber and Implications for Exposure

    EPA Science Inventory

    Lumber pressure-treated with micronized copper was examined for the release of copper and copper micro/nanoparticles using a surface wipe method to simulate dermal transfer. In 2003, the wood industry began replacing CCA treated lumber products for residential use with copper ba...

  13. Detection of erosion events using 10Be profiles: example of the impact of agriculture on soil erosion in the Chesapeake Bay area (U.S.A.)

    USGS Publications Warehouse

    Valette-Silver, J. N.; Brown, L.; Pavich, M.; Klein, J.; Middleton, R.

    1986-01-01

    10Be concentration, total carbon and grain-size were measured in cores collected in undisturbed estuarine sediments of three tributaries of the Chesapeake Bay. These cores were previously studied by Davis [1] and Brush [2,3] for pollen content, age and sedimentation rate. In this work, we compare the results obtained for these various analyses. In the cores, we observed two increases in 10Be concentration concomitant with two major changes in the pollen composition of the sediments. These two pollen changes each correspond to well-dated agricultural horizons reflecting different stages in the introduction of European farming techniques [2]. In the Chesapeake Bay area, the agricultural development, associated with forest clearing, appears to have triggered the erosion, transport, and sedimentation into the river mouths of large quantities of 10Be-rich soils. This phenomenon explains the observed rise in the sedimentation rate associated with increases in agricultural land-use. ?? 1986.

  14. Characterization of Missouri surface waters near point sources of pollution reveals potential novel atmospheric route of exposure for bisphenol A and wastewater hormonal activity pattern

    USGS Publications Warehouse

    Kassotis, Christopher D.; Alvarez, David A.; Taylor, Julia A.; vom Saal, Frederick S.; Nagel, Susan C.; Tillitt, Donald E.

    2015-01-01

    Surface water contamination by chemical pollutants increasingly threatens water quality around the world. Among the many contaminants found in surface water, there is growing concern regarding endocrine disrupting chemicals, based on their ability to interfere with some aspect of hormone action in exposed organisms, including humans. This study assessed water quality at several sites across Missouri (near wastewater treatment plants and airborne release sites of bisphenol A) based on hormone receptor activation potencies and chemical concentrationspresent in the surface water. We hypothesized that bisphenol A and ethinylestradiol would be greater in water near permitted airborne release sites and wastewater treatment plant inputs, respectively, and that these two compounds would be responsible for the majority of activities in receptor-based assays conducted with water collected near these sites. Concentrations of bisphenol A and ethinylestradiol were compared to observed receptor activities using authentic standards to assess contribution to total activities, and quantitation of a comprehensive set of wastewater compounds was performed to better characterize each site. Bisphenol A concentrations were found to be elevated in surface water near permitted airborne release sites, raising questions that airborne releases of BPA may influence nearby surface water contamination and may represent a previously underestimated source to the environment and potential for human exposure. Estrogen and androgen receptor activities of surface water samples were predictive of wastewater input, although the lower sensitivity of the ethinylestradiol ELISA relative to the very high sensitivity of the bioassay approaches did not allow a direct comparison. Wastewater-influenced sites also had elevated anti-estrogenic and anti-androgenic equivalence, while sites without wastewater discharges exhibited no antagonist activities.

  15. Quaternary downcutting rate of the new river, Virginia, measured from differential decay of cosmogenic {sup 26}Al and {sup 10}Be in cave-deposited alluvium

    SciTech Connect

    Granger, D.E.; Kirchner, J.W.; Finkel, R.C.

    1997-02-01

    The concentrations of the cosmogenic radionuclides {sup 26}Al and {sup 10}Be in quartz can be used to date sediment burial. Here we use {sup 26} Al and {sup 10}Be in cave-deposited river sediment to infer the time of sediment emplacement. Sediment burial dates from a vertical sequence of caves along the New River constrain its Quaternary downcutting rate to 27.3{+-}4.5 m/m.y. and may provide evidence of regional tectonic tilt. 32 refs., 3 figs., 1 tab.

  16. BiVO4 {010} and {110} Relative Exposure Extent: Governing Factor of Surface Charge Population and Photocatalytic Activity.

    PubMed

    Tan, Hui Ling; Wen, Xiaoming; Amal, Rose; Ng, Yun Hau

    2016-04-01

    The {010} and {110} crystal facets of monoclinic bismuth vanadate (m-BiVO4) has been demonstrated to be the active reduction and oxidation sites, respectively. Here, we show using dual-faceted m-BiVO4 with distinctly different dominant exposed facets, one which is {010}-dominant and the other {110}-dominant, contrary to prediction, the former m-BiVO4 exhibits superior photooxidation activities. The population of photogenerated electrons and holes on the surface are revealed to be proportional to the respective surface areas of {010} and {110} exposed on m-BiVO4, as evidenced by steady-state photoluminescence (PL) measurements in the presence of charge scavengers. The better photoactivity of {010}-dominant m-BiVO4 is attributed to prompt electron transfer facilitated by the presence of more photogenerated electrons on the larger {010} surface. Additionally, the greater extent of electron trapping in {110}-dominant m-BiVO4 also deteriorates its photoactivity by inducing electron-hole pair recombination. PMID:27007807

  17. Rate and style of ice stream retreat constrained by new surface-exposure ages: The Minch, NW Scotland

    NASA Astrophysics Data System (ADS)

    Bradwell, Tom; Small, David; Fabel, Derek; Dove, Dayton; Cofaigh, Colm O.; Clark, Chris; Consortium, Britice-Chrono

    2016-04-01

    Chronologically constrained studies of former ice-sheet extents and dynamics are important for understanding past cryospheric responses and modelling future ice-sheet and sea-level change. As part of the BRITICE-CHRONO project, we present new geomorphological and chronological data from a marine-terminating ice stream system in NW Europe that operated during the Late Weichselian Glaciation. A suite of 51 cosmogenic-nuclide exposure ages from ice sheet moraines and glacially transported boulders constrain the maximum extent of the ice sheet on the continental shelf (~28 ka BP) and its subsequent retreat, between ~27 and 16 ka BP, into a large marine embayment (ca. 7000 km2; the Minch, NW Scotland). Recently acquired swath bathymetry and acoustic sub-bottom profiler data reveal several large transverse grounding-zone wedges up to 40 m thick and 5 km wide with diagnostic acoustic-facies architecture. These seabed sediment wedges mark former quasi-stable positions of grounded marine-terminating ice-stream fronts; their size and thickness suggest long-lived stillstands of the order of centuries. Statistically significant clusters of exposure ages from glacial deposits on islands and intervening headlands shed important new light on the age of these marine grounding-zone wedges and, by inference, the rate and timing of Minch palaeo-ice stream retreat. We find strong evidence for episodic ice stream retreat on the continental shelf between ~28-24 ka BP, in the outer Minch between ~24-22 ka BP, and in the central Minch between 22-18.5 ka BP. In contrast, final ice stream deglaciation (<18 ka) across the deepest parts of the inner Minch embayment, was probably rapid and uninterrupted - with the ice sheet margin at or close to the present-day coastline in NW Scotland by 16.1 ka BP. It is hoped that these results will form the empirical basis for future ice-sheet modelling of this dynamically sensitive sector of the British-Irish Ice Sheet.

  18. Nanomechanical and surface properties of rMSCs post-exposure to CAP treated UHMWPE wear particles

    PubMed Central

    Preedy, Emily Callard; Perni, Stefano; Prokopovich, Polina

    2016-01-01

    Wear debris generated by ultra-high molecular weight polyethylene (UHMWPE) used in joint replacement devices has been of concern due to reductions of the implant longevity. Cold atmospheric plasma (CAP) has been used to improve the wear performance of UHMWPE. Our aim was to investigate the elastic and adhesive properties of rat mesenchymal stem cells (rMSCs), through AFM, after exposure to UHMWPE wear debris pre- and post-CAP treatment. The results indicated that the main changes in cell elasticity and spring constant of MSC exposed to wear particles occurred in the first 24 h of contact and the particle concentration from 0.5 to 50 mg/l did not play a significant role. For UHMWPE treated for 7.5 min, with progression of the wear simulation the results of the CAP treated samples were getting closer to the result of untreated samples; while with longer CAP treatment this was not observed. From the Clinical Editor Joint replacements are now common clinical practice. However, the use of ultra-high molecular weight polyethylene (UHMWPE) still poses a concern, due to the presence of wear debris. The authors here investigated the effects of wear debris after cold atmospheric plasma treatment on rat mesenchymal stem cells. The positive results provided new strategies in future design of joint replacement materials. PMID:26554392

  19. Endocrine disrupting chemicals-Linking internal exposure to vitellogenin levels and ovotestis in Abramis brama from Dutch surface waters.

    PubMed

    Reinen, Jelle; Suter, Marc J-F; Vögeli, A Christiane; Fernandez, Mariana F; Kiviranta, Hannu; Eggen, Rik I L; Vermeulen, Nico P E

    2010-11-01

    The exposure of male bream from three Dutch freshwater locations to endocrine disrupting compounds (EDCs) and corresponding effects are described in this study. Fish specimen displaying reproductive disorders associated with high levels of plasma vitellogenin (VTG) concentrations and occurrence of ovotestis (OT) were investigated. To provide information on the full spectrum of EDCs in fish tissue, adipose tissue samples of individual fish were analyzed for nearly 130 chemicals targeting different compound classes (bisphenols, alkylphenols, pesticides, polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), hydroxylated polychlorinated biphenyls (OH-PCBs), polybrominated diphenyl ethers (PBDEs) and biphenyls (PBBs)) and steroid hormones. To establish whether tissue from specimen with reproductive disorders shows a spectrum of EDCs that is qualitatively and quantitatively different from that of controls free of symptoms, bioassay-directed fractionation was performed using the recombinant yeast estrogen screen (YES), the E-Screen bioassay, the human sulfotransferase 1E1 (SULT1E1) inhibition assay, and the coumestrol-based estrogen receptor α (ERα) high resolution screening (HRS) assay. No differences in estrogenicity could be observed between the cases and controls and steroidal estrogens accounted for the majority of estrogenicity found in the complex mixtures. In this study, the combination of the different assays employed to measure total estrogenicity and the SULT1E1 inhibition does not predict the outcome of unwanted physiological effects, however, it can be used to determine the presence of EDCs in fish samples and their estrogenic effects. PMID:21787654

  20. The new AMS system at CEDAD for the analysis of 10Be, 26Al, 129I and actinides: Set-up and performances

    NASA Astrophysics Data System (ADS)

    Calcagnile, Lucio; Quarta, Gianluca; Maruccio, Lucio; Synal, Hans-Arno; Müller, Arnold Milenko

    2015-10-01

    The Centre for Dating and Diagnostics (CEDAD) at the University of Salento was established in 2001 and became fully operational for routine 14C radiocarbon dating in 2003. The facility has been continuously upgraded over the years with the installation of different beam lines for high energy ion implantation, IBA analyses both in vacuum and in air and nuclear microprobe. In 2011 a second AMS beamline was installed consisting of a dedicated high energy mass spectrometer for the AMS analysis of rare nuclides such as 10Be, 26Al, 129I and actinides. First tests on 10Be allowed to optimize the operating parameters resulting in the proper separation of 10Be from the interfering isobar 10B. In this paper we present the further tests and optimizations which resulted in an enhancement of the overall transmission efficiency, the reduction of the background (in the 10-15 range) and in the possibility to obtain precision levels in routine 10Be/9Be measurements of the order of 0.5%. Furthermore the first results obtained for the analysis of 26Al and 129I are also presented.

  1. Evaluating the steady-state assumption for mobile-regolith on hillslopes using in situ-produced 10Be, Boulder Creek CZO, Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Spitzmiller, B. L.

    2012-12-01

    Release of mobile regolith from underlying weathered rock (saprolite) is a crucial process in the evolution of landscapes. To calculate the lowering rate of the saprolite interface with cosmogenic radionuclides (CRN), it is often assumed that the mobile-regolith cover was steady over a timescale characterized by the saprolite-exhumation rate (w) and decay length scale of CRN production. We collected in situ 10Be data along north- and south-facing transects in Gordon Gulch, within the Boulder Creek CZO, to test the steady-state condition on a complex hillslope. At steady state, the mean concentration of 10Be within a mobile-regolith column of thickness H may be calculated if the saprolite-exhumation rate is known independently. In situ 10Be data from saprolite samples may be used to document the saprolite-exhumation rate. We report data from 9 saprolite samples, 24 mobile-regolith samples, and 3 samples from outcrops adjacent to soil pits. In Gordon Gulch study-pits, saprolite-lowering rates (w) vary significantly between 15 and 55 μm/a, with mean values of 36 and 32 μm/a for north- and south-facing slopes, respectively. Calculated mobile-regolith residence times (t=H/w) also vary widely from ~10-115 ka. Local lowering rates (w) exceed the basin-averaged denudation rate of ~22 μm/a calculated from 10Be concentrations in modern Gordon Gulch stream sediment [D. Dethier, unpublished data]. Preliminary results from 10Be concentrations in mobile regolith suggest that vertical mixing is minimal. Mean 10Be concentrations in the mobile-regolith column are close to those expected for the steady-state case. Thus our data appear to support the steady-state assumption. However, these steady state-predictions are only as sound as the local lowering rates calculated from 10Be in saprolite samples. We suspect that the mismatch between local lowering rates and basin-wide denudation may arise from temporal variations in mobile-regolith cover (H). Changes in hillslope transport

  2. Photon-exposure-dependent photon-stimulated desorption for obtaining photolysis cross section of molecules adsorbed on surface by monochromatic soft x-ray photons.

    PubMed

    Chou, L-C; Jang, C-Y; Wu, Y-H; Tsai, W-C; Wang, S-K; Chen, J; Chang, S-C; Liu, C-C; Shai, Y; Wen, C-R

    2008-12-01

    Photon-exposure-dependent positive- and negative-ion photon-stimulated desorption (PSD) was proposed to study the photoreactions and obtain the photolysis cross sections of molecules adsorbed on a single-crystal surface by monochromatic soft x-ray photons with energy near the core level of adsorbate. The changes in the F(+) and F(-) PSD ion yields were measured from CF(3)Cl molecules adsorbed on Si(111)-7x7 at 30 K (CF(3)Cl dose=0.3x10(15) molecules/cm(2), approximately 0.75 monolayer) during irradiation of monochromatic soft x-ray photons near the F(1s) edge. The PSD ion yield data show the following characteristics: (a) The dissociation of adsorbed CF(3)Cl molecules is due to a combination of direct photodissociation via excitation of F(1s) core level and substrate-mediated dissociation [dissociative attachment and dipolar dissociation induced by the photoelectrons emitting from the silicon substrate]. (b) the F(+) ion desorption is associated with the bond breaking of the surface CF(3)Cl, CF(2)Cl, CFCl, and SiF species. (c) the F(-) yield is mainly due to DA and DD of the adsorbed CF(3)Cl molecules. (d) The surface SiF is formed by reaction of the surface Si atom with the neutral fluorine atom, F(+), or F(-) ion produced by scission of C-F bond of CF(3)Cl, CF(2)Cl, or CF