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  • 1
    Publication Date: 2012-03-16
    Description: The transpolar drift is strongly enriched in 228Ra accumulated on the wide Arctic shelves with subsequent rapid offshore transport. We present new data of Polarstern expeditions to the central Arctic and to the Kara and Laptev seas. Because 226Ra activities in Pacific waters are 30% higher than in Atlantic waters, we correct 226Ra for the Pacific admixture when normalizing 228Ra with 226Ra. The use of 228Ra decay as age marker critically depends on the constancy in space and time of the source activity, a condition that has not yet adequately been tested. While 228Ra decays during transit over the central basin, ingrowth of 228Th could provide an alternative age marker. The high 228Th/228Ra activity ratio (AR = 0.8–1.0) in the central basins is incompatible with a mixing model based on horizontal eddy diffusion. An advective model predicts that 228Th grows to an equilibrium AR, the value of which depends on the scavenging regime. The low AR over the Lomonosov Ridge (AR = 0.5) can be due to either rapid transport (minimum age without scavenging 1.1 year) or enhanced scavenging. Suspended particulate matter load (derived from beam transmission and particulate 234Th) and total 234Th depletion data show that scavenging, although extremely low in the central Arctic, is enhanced over the Lomonosov Ridge, making an age of 3 years more likely. The combined data of 228Ra decay and 228Th ingrowth confirm the existence of a recirculating gyre in the surface water of the eastern Eurasian Basin with a river water residence time of at least 3 years.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
    Publication Date: 2012-07-10
    Description: Aims Nighttime sap flow of trees may indicate transpiration and/or recharge of stem water storage at night. This paper deals with the water use of Acacia mangium at night in the hilly lands of subtropical South China. Our primary goal was to reveal and understand the nature of nighttime sap flow and its functional significance. Methods Granier’s thermal dissipation method was used to determine the nighttime sap flux of A. mangium . Gas exchange system was used to estimate nighttime leaf transpiration and stomatal conductance of studied trees. Important Findings Nighttime sap flow was substantial and showed seasonal variation similar to the patterns of daytime sap flow in A. mangium . Mean nighttime sap flow was higher in the less precipitation year of 2004 (1122.4 mm) than in the more precipitation year of 2005 (1342.5 mm) since more daytime transpiration and low soil water availability in the relatively dry 2004 can be the cause of more nighttime sap flow. Although vapor pressure deficit and air temperature were significantly correlated with nighttime sap flow, they could only explain a small fraction of the variance in nighttime sap flow. The total accumulated water loss ( E L ) by transpiration of canopy leaves was only ~2.6–8.5% of the total nighttime sap flow ( E t ) during the nights of July 17–18 and 18–19, 2006. Therefore, it is likely that the nighttime sap flow was mainly used for refilling water in the trunk. The stem diameter at breast height, basal area and sapwood area explained much more variance of nighttime water recharge than environmental factors and other tree form features, such as tree height, stem length below the branch, and canopy size. The contribution of nighttime water recharge to the total transpiration ranged from 14.7 to 30.3% depending on different DBH class and was considerably higher in the dry season compared to the wet season.
    Print ISSN: 1752-993X
    Electronic ISSN: 1752-9921
    Topics: Biology
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  • 3
    Publication Date: 2014-09-17
    Description: Endogenous metabolism, environmental exposure, and treatment with some chemotherapeutic agents can all give rise to DNA alkylation, which can occur on the phosphate backbone as well as the ring nitrogen or exocyclic nitrogen and oxygen atoms of nucleobases. Previous studies showed that the minor-groove O 2 -alkylated thymidine ( O 2 -alkyldT) lesions are poorly repaired and persist in mammalian tissues. In the present study, we synthesized oligodeoxyribonucleotides harboring seven O 2 -alkyldT lesions, with the alkyl group being a Me, Et, n Pr, i Pr, n Bu, i Bu or s Bu, at a defined site and examined the impact of these lesions on DNA replication in Escherichia coli cells. Our results demonstrated that the replication bypass efficiencies of the O 2 -alkyldT lesions decreased with the chain length of the alkyl group, and these lesions directed promiscuous nucleotide misincorporation in E. coli cells. We also found that deficiency in Pol V, but not Pol II or Pol IV, led to a marked drop in bypass efficiencies for most O 2 -alkyldT lesions. We further showed that both Pol IV and Pol V were essential for the misincorporation of dCMP opposite these minor-groove DNA lesions, whereas only Pol V was indispensable for the T-〉A transversion introduced by these lesions. Depletion of Pol II, however, did not lead to any detectable alterations in mutation frequencies for any of the O 2 -alkyldT lesions. Thus, our study provided important new knowledge about the cytotoxic and mutagenic properties of the O 2 -alkyldT lesions and revealed the roles of the SOS-induced DNA polymerases in bypassing these lesions in E. coli cells.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 4
    Publication Date: 2014-08-15
    Description: Energy & Fuels DOI: 10.1021/ef5008825
    Print ISSN: 0887-0624
    Electronic ISSN: 1520-5029
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Process Engineering, Biotechnology, Nutrition Technology
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  • 5
    Publication Date: 2014-12-06
    Description: In the Kondo insulator samarium hexaboride (SmB6), strong correlation and band hybridization lead to an insulating gap and a diverging resistance at low temperature. The resistance divergence ends at about 3 kelvin, a behavior that may arise from surface conductance. We used torque magnetometry to resolve the Fermi surface topology in this material. The observed oscillation patterns reveal two Fermi surfaces on the (100) surface plane and one Fermi surface on the (101) surface plane. The measured Fermi surface cross sections scale as the inverse cosine function of the magnetic field tilt angles, which demonstrates the two-dimensional nature of the conducting electronic states of SmB6.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, G -- Xiang, Z -- Yu, F -- Asaba, T -- Lawson, B -- Cai, P -- Tinsman, C -- Berkley, A -- Wolgast, S -- Eo, Y S -- Kim, Dae-Jeong -- Kurdak, C -- Allen, J W -- Sun, K -- Chen, X H -- Wang, Y Y -- Fisk, Z -- Li, Lu -- New York, N.Y. -- Science. 2014 Dec 5;346(6214):1208-12. doi: 10.1126/science.1250366.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA. ; Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA. Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei Anhui 230026, China. ; Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA. Department of Physics, Tsinghua University, Beijing, China. ; Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697, USA. ; Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei Anhui 230026, China. ; Department of Physics, Tsinghua University, Beijing, China. ; Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA. luli@umich.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25477456" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2014-07-29
    Description: Author(s): L.-L. Jia, Z.-H. Liu, Y.-P. Cai, T. Qian, X.-P. Wang, H. Miao, P. Richard, Y.-G. Zhao, Y. Li, D.-M. Wang, J.-B. He, M. Shi, G.-F. Chen, H. Ding, and S.-C. Wang We report an observation of a highly anisotropic Dirac-cone structure, and its unconventional electronic behaviors, in high quality SrMnBi2 crystal by angle-resolved photoemission spectroscopy measurement. We observed a well-defined sharp quasiparticle peak in a wide energy range, linearly dispersiv... [Phys. Rev. B 90, 035133] Published Fri Jul 25, 2014
    Keywords: Electronic structure and strongly correlated systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 7
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    In:  Supplement to: Middag, Rob; de Baar, Hein J W; Laan, Patrick; Cai, P H; van Ooijen, Jan C (2011): Dissolved manganese in the Atlantic sector of the Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 58(25-26), 2661-2677, https://doi.org/10.1016/j.dsr2.2010.10.043
    Publication Date: 2023-12-13
    Description: The first comprehensive dataset (492 samples) of dissolved Mn in the Southern Ocean shows extremely low values of 0.04 up to 0.64 nM in the surface waters and a subsurface maximum with an average concentration of 0.31 nM (n=20; S.D.=0.08 nM). The low Mn in surface waters correlates well with the nutrients PO4 and NO3 and moderately well with Si(OH)4 and fluorescence. Furthermore, elevated concentrations of Mn in the surface layer coincide with elevated Fe and light transmission and decreased export (234Th/238U deficiency) and fluorescence. It appears that Mn is a factor of importance in partly explaining the HNLC conditions in the Southern Ocean, in conjunction with significant controls by the combination of Fe limitation and light limitation. No input of Mn from the continental margins was observed. This is ascribed to the protruding continental ice sheet that covers the shelf and shuts down the usual biological production, microbial breakdown and sedimentary geochemical cycling. The low concentrations of Mn in the deep ocean basins (0.07-0.23 nM) were quite uniform, but some elevations were observed. The highest deep concentrations of Mn were observed at the Bouvet Triple Junction region and coincided with high concentrations of Fe and are deemed to be from hydrothermal input. The deep basins on both sides of the ridge were affected by this input. In the deep Weddell Basin the input of Weddell Sea Bottom Water appears to be the source of the slightly elevated concentrations of Mn in this water layer.
    Keywords: ANT-XXIV/3; AWI; Bottle number; CTD/Rosette, ultra clean; CTD-UC; DATE/TIME; DEPTH, water; Elevation of event; Event label; GEOTRACES; Global marine biogeochemical cycles of trace elements and their isotopes; International Polar Year (2007-2008); IPY; Latitude of event; Longitude of event; Manganese, dissolved; Manganese, standard deviation; Polarstern; PS71; PS71/101-2; PS71/103-1; PS71/104-2; PS71/107-3; PS71/110-1; PS71/113-3; PS71/116-1; PS71/119-1; PS71/122-1; PS71/128-1; PS71/131-5; PS71/135-1; PS71/138-1; PS71/141-1; PS71/144-1; PS71/147-3; PS71/150-2; PS71/161-6; PS71/163-1; PS71/167-1; PS71/175-3; PS71/178-4; Quality flag; South Atlantic Ocean; Weddell Sea
    Type: Dataset
    Format: text/tab-separated-values, 1980 data points
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  • 8
    Publication Date: 2011-07-30
    Description: Record low austral winter rainfall totals over southwest Western Australia (SWWA) in 2010 saw a continuation of the multidecade-long winter drought plaguing the region. During this season, the highest recorded positive Southern Annular Mode (SAM) value was measured, adding weight to an association of a positive SAM with anomalously low SWWA winter rainfall (SWR), and vice-versa. However, such a SAM-SWR teleconnection has been recently questioned. Using observational data in the post-1979 satellite era, it is shown that such a SAM influence does exist. This coherence is confirmed with 1150 years of modelled 20th century SWR anomalies and SAM values from 23 climate models, showing that a nonlinear impact operates: the influence from a negative SAM is greater than that from a positive SAM. This explains why a small positive shift in the SAM can cause a large SWR reduction, as has been observed. A further test shows that models with a greater positive SAM trend systematically produce a greater future SWR reduction. As all climate models project an increase in the SAM these results suggest that as global warming continues unabated, SWWA winter droughts will be more persistent as atmospheric conditions become more unfavourable for drought-breaking rains.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
    Publication Date: 2013-12-22
    Description: Axial pumps play an important role in water supply and flood control projects. Along with growing requirements for high reliability and large capacity, the dynamic stress of axial pumps has become a key problem. Unsteady flow is a significant reason which results structural dynamic stress of a pump. This paper reports on a flow-induced dynamic stress simulation in an axial pump impeller at three flow conditions by using FEM code. The pressure pulsation obtained from flow simulation using CFD code was set as the force boundary condition. The results show that the maximum stress of impeller appeared at joint between blade and root flange near trailing edge or joint between blade and root flange near leading edge. The dynamic stress of the two zones was investigated under three flow conditions (0.8 Q d , 1.0 Q d , 1.1 Q d ) in time domain and frequency domain. The frequencies of stress at zones of maximum stress are 22.9Hz and 37.5Hz as ...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
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