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  • 1
    Publication Date: 2016-11-14
    Description: Assessments of climate sensitivity to projected greenhouse gas concentrations underpin environmental policy decisions, with such assessments often based on model simulations of climate during recent centuries and millennia1, 2, 3. These simulations depend critically on accurate records of past aerosol forcing from global-scale volcanic eruptions, reconstructed from measurements of sulphate deposition in ice cores4, 5, 6. Non-uniform transport and deposition of volcanic fallout mean that multiple records from a wide array of ice cores must be combined to create accurate reconstructions. Here we re-evaluated the record of volcanic sulphate deposition using a much more extensive array of Antarctic ice cores. In our new reconstruction, many additional records have been added and dating of previously published records corrected through precise synchronization to the annually dated West Antarctic Ice Sheet Divide ice core7, improving and extending the record throughout the Common Era. Whereas agreement with existing reconstructions is excellent after 1500, we found a substantially different history of volcanic aerosol deposition before 1500; for example, global aerosol forcing values from some of the largest eruptions (for example, 1257 and 1458) previously were overestimated by 20–30% and others underestimated by 20–50%.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 2
    ISSN: 1072-8368
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The ubiquitin conjugating enzyme complex Mms2–Ubc13 plays a key role in post-replicative DNA repair in yeast and the NF-κB signal transduction pathway in humans. This complex assembles novel polyubiquitin chains onto yet uncharacterized protein targets. Here we report the crystal ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1327
    Keywords: Key words Superoxide dismutase ; Manganese enzyme ; Crystal structure ; Metalloprotein ; DNA binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The three-dimensional structure of the manganese-dependent superoxide dismutase (MnSOD) from Escherichia coli has been determined by X-ray crystallography at 2.1 Å resolution. The protein crystallizes with two homodimers in the asymmetric unit, and a model comprising 6528 protein atoms (residues 1–205 of all four monomers), four manganese ions and 415 water molecules has been refined to an R factor of 0.188 (R free 0.218). The structure shows a high degree of similarity with other MnSOD and FeSOD enzymes. The Mn centres are 5-coordinate, trigonal bipyramidal, with His26 and a solvent molecule, probably a hydroxide ion, as apical ligands, and His81, Asp167 and His171 as equatorial ligands. The coordinated solvent molecule is linked to a network of hydrogen bonds involving the non-coordinated carboxylate oxygen of Asp167 and a conserved glutamine residue, Gln146. The MnSOD dimer is notable for the way in which the two active sites are interconnected and a "bridge" comprising His171 of one monomer and Glu170 of the other offers a route for inter-site communication. Comparison of E. coli MnSOD and FeSOD (a) reveals some differences in the dimer interface, (b) yields no obvious explanation for their metal specificities, and (c) provides a structural basis for differences in DNA binding, where for MnSOD the groove formed by dimerization is complementary in charge and surface contour to B-DNA.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cultured normal rat retinal pigment epithelium (PE) ingested six times more rod outer segments in the presence of 20% fetal bovine serum than in serumfree medium. PE cultured from Royal College of Surgeons (RCS) rats with hereditary retinal dystrophy, known to have a defect in vivo in the phagocytosis of shed outer segment tips, ingested amounts of outer segments comparable to normal PE in serum-free medium but did not show an increase in the presence of serum. In both strains of rat PE phagocytosis of latex spheres was similar in the absence of serum and was six-fold higher in the presence of serum, showing that the RCS phagocytic deficiency for outer segments in vitro is not due to a general defect in the phagocytic capacity of the cell. Increased phagocytosis of outer segments by normal PE was observed in the presence of the high molecular weight fraction of ultrafiltered serum but was not seen with serum that was heated at 93°C or precipitated with 5% trichloroacetic acid. Bovine serum albumin had no effect on phagocytosis. These results are consistent with the idea that the phagocytosis of outer segments by cultured normal rat PE, but not by cultured RCS rat PE, is increased in the presence of a specific protein or other macromolecular component of fetal bovine serum.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2019-07-17
    Description: Volcanism is a natural climate forcing causing short-term variations in temperatures. Histories of volcanic eruptions are needed to quantify their role in climate variability and assess human impacts. We present two new seasonally resolved, annually dated non-sea-salt sulfur records from polar ice cores - WAIS Divide (WDC06A) from West Antarctica spanning 408 B.C.E. to 2003 C.E. and NEEM (NEEM-2011-S1) from Greenland spanning 78 to 1997 C.E. - both analyzed using high-resolution continuous flow analysis coupled to two mass spectrometers. The high dating accuracy allowed placing the large bi-hemispheric deposition event ascribed to the eruption of Kuwae in Vanuatu (previously thought to be 1452/1453 C.E. and used as a tie-point in ice core dating) into the year 1458/1459 C.E. This new age is consistent with an independent ice core timescale from Law Dome and explains an apparent delayed response in tree rings to this volcanic event. A second volcanic event is detected in 1453 C.E. in both ice cores. We show for the first time ice core signals in Greenland and Antarctica from the strong eruption of Taupo in New Zealand in 232 C.E. In total, 133 volcanic events were extracted from WDC06A and 138 from NEEM-2011-S1, with 50 ice core signals - predominantly from tropical source volcanoes - identified simultaneously in both records. We assess the effect of large bipolar events on temperature-sensitive tree ring proxies. These two new volcanic records, synchronized with available ice core records to account for spatial variability in sulfate deposition, provide a basis for improving existing time series of volcanic forcing.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 6
    Publication Date: 2019-07-13
    Description: Ice core measurements in conjunction with climate model simulations are of tremendous value when examining anthropogenic and natural aerosol loads and their role in past and future climates. Refractory black carbon (BC) records from the Arctic, the Antarctic, and the Himalayas are analyzed using three transient climate simulations performed with the Goddard Institute for Space Studies ModelE. Simulations differ in aerosol schemes (bulk aerosols vs. aerosol microphysics) and ocean couplings (fully coupled vs. prescribed ocean). Regional analyses for past (1850-2005) and future (2005-2100) carbonaceous aerosol simulations focus on the Antarctic, Greenland, and the Himalayas. Measurements from locations in the Antarctic show clean conditions with no detectable trend over the past 150 years. Historical atmospheric deposition of BC and sulfur in Greenland shows strong trends and is primarily influenced by emissions from early twentieth century agricultural and domestic practices. Models fail to reproduce observations of a sharp eightfold BC increase in Greenland at the beginning of the twentieth century that could be due to the only threefold increase in the North American emission inventory. BC deposition in Greenland is about 10 times greater than in Antarctica and 10 times less than in Tibet. The Himalayas show the most complicated transport patterns, due to the complex terrain and dynamical regimes of this region. Projections of future climate based on the four CMIP5 Representative Concentration Pathways indicate further dramatic advances of pollution to the Tibetan Plateau along with decreasing BC deposition fluxes in Greenland and the Antarctic.
    Keywords: Geophysics
    Type: GSFC-E-DAA-TN10656 , Journal of Geophysical Research: Atmosphere (ISSN 2169-8996); 228; 14; 7948-7961
    Format: application/pdf
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  • 7
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    In:  Supplement to: Bertler, Nancy A; Conway, Howard; Dahl-Jensen, Dorthe; Emanuelsson, Urban; Winstrup, Mai; Vallelonga, Paul T; Lee, James E; Brook, Edward J; Severinghaus, Jeffrey P; Fudge, Tyler J; Keller, Elizabeth D; Baisden, W Troy; Hindmarsh, Richard C A; Neff, Peter D; Blunier, Thomas; Edwards, Ross L; Mayewski, Paul Andrew; Kipfstuhl, Sepp; Buizert, Christo; Canessa, Silvia; Dadic, Ruzica; Kjær, Helle Astrid; Kurbatov, Andrei; Zhang, Dongqi; Waddington, Edwin D; Baccolo, Giovanni; Beers, Thomas; Brightley, Hannah J; Carter, Lionel; Clemens-Sewall, David; Ciobanu, Viorela G; Delmonte, Barbara; Eling, Lukas; Ellis, Aja A; Ganesh, Shruthi; Golledge, Nicholas R; Haines, Skylar A; Handley, Michael; Hawley, Robert L; Hogan, Chad M; Johnson, Katelyn M; Korotkikh, Elena; Lowry, Daniel P; Mandeno, Darcy; McKay, Robert M; Menking, James A; Naish, Timothy R; Noerling, Caroline; Ollive, Agathe; Orsi, Anais J; Proemse, Bernadette C; Pyne, Alexander R; Pyne, Rebecca L; Renwick, James; Scherer, Reed P; Semper, Stefanie; Simonsen, Marius; Sneed, Sharon B; Steig, Eric J; Tuohy, Andrea; Ulayottil Venugopal, Abhijith; Valero-Delgado, Fernando; Venkatesh, Janani; Wang, Feitang; Wang, Shimeng; Winski, Dominic A; Winton, Victoria H L; Whiteford, Arran; Xiao, Cunde; Yang, Jiao; Zhang, Xin (2018): The Ross Sea dipole - temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years. Climate of the Past, 14, 193-214, https://doi.org/10.5194/cp-14-193-2018
    Publication Date: 2019-09-19
    Description: High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979-2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.
    Type: Dataset
    Format: text/tab-separated-values, 8136 data points
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  • 8
    Publication Date: 2019-09-23
    Description: Assessments of climate sensitivity to projected greenhouse gas concentrations underpin environmental policy decisions, with such assessments often based on model simulations of climate during recent centuries and millennia1, 2, 3. These simulations depend critically on accurate records of past aerosol forcing from global-scale volcanic eruptions, reconstructed from measurements of sulphate deposition in ice cores4, 5, 6. Non-uniform transport and deposition of volcanic fallout mean that multiple records from a wide array of ice cores must be combined to create accurate reconstructions. Here we re-evaluated the record of volcanic sulphate deposition using a much more extensive array of Antarctic ice cores. In our new reconstruction, many additional records have been added and dating of previously published records corrected through precise synchronization to the annually dated West Antarctic Ice Sheet Divide ice core7, improving and extending the record throughout the Common Era. Whereas agreement with existing reconstructions is excellent after 1500, we found a substantially different history of volcanic aerosol deposition before 1500; for example, global aerosol forcing values from some of the largest eruptions (for example, 1257 and 1458) previously were overestimated by 20–30% and others underestimated by 20–50%.
    Type: Article , PeerReviewed
    Format: text
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  • 9
  • 10
    Publication Date: 2019-10-26
    Type: Dataset
    Format: text/tab-separated-values, 272 data points
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