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  • 1
    Electronic Resource
    Electronic Resource
    pH-Dependent Protein Profiles of Helicobacter pylori Analyzed by Two-Dimensional Gels (2000)
    Boston, MA, USA : Blackwell Science Ltd
    Helicobacter 5 (2000), S. 0 
    Details
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background. Helicobacter pylori survives transient exposure to extreme acid prior to adherence and growth on the gastric epithelium at neutral pH.Materials and Methods. The effect of pH stress on protein profiles of H. pylori was observed using two-dimensional gel electrophoresis (2-D gels). H. pylori 26695 was grown microaerobically in tryptone-yeast extract broth, 3% fetal bovine serum. Growth in acid alkalinized the medium, whereas growth in base caused acidification. For 2-D gel analysis of protein profiles, cultures were grown in media buffered at pH 5.7 and at pH 7.5.Results. Under all pH conditions, the most abundant proteins observed were the urease structural subunit UreB and the chaperonin GroEL. Growth in acid significantly increased the abundance of UreB. Thus, urease expression is not completely constitutive, as reported previously, but shows regulation by pH. Another protein observed only at low pH was identified as mammalian apolipoprotein A-I, possibly taken up by H. pylori from bovine serum in the growth medium. This finding, if confirmed, suggests that uptake of high-density lipoprotein from the human host may facilitate acquisition of cholesterol, required for formation of the unique cholesteryl glucosides in the membrane of H. pylori. In growth above pH 7, three stress proteins were induced: GroES (HspA), GroEL (HspB), and the antioxidant AhpC homolog TsaA. In addition, N-terminal sequence analysis identified five additional proteins that had not previously been reported on 2-D gels of H. pylori (FMN, SodB, TrxB, TsaA, and Tsr).Conclusions. In summary, our 2-D gel study reveals expression of several proteins dependent on growth pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1523-5378.2000.00037.x
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Making Up Mind: The Early Sociology of Invention (1995)
    Detroit, Mich. : Periodicals Archive Online (PAO)
    Technology and Culture. 36:4 (1995:Oct.) 773 
    Details
    ISSN: 0040-165X
    Topics: Technology
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5129-1995-036-04-000003
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Use of the bioluminescent bacterium Photobacterium phosphoreum to detect potentially biohazardous materials in water (1993)
    Springer
    Bulletin of environmental contamination and toxicology 51 (1993), S. 538-544 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192169
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    Paper (German National Licenses)
    Fulltext
  • 4
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    Past abrupt changes, tipping points and cascading impacts in the Earth system (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: The geological record shows that abrupt changes in the Earth system can occur on timescales short enough to challenge the capacity of human societies to adapt to environmental pressures. In many cases, abrupt changes arise from slow changes in one component of the Earth system that eventually pass a critical threshold, or tipping point, after which impacts cascade through coupled climate–ecological–social systems. The chance of detecting abrupt changes and tipping points increases with the length of observations. The geological record provides the only long-term information we have on the conditions and processes that can drive physical, ecological and social systems into new states or organizational structures that may be irreversible within human time frames. Here, we use well-documented abrupt changes of the past 30 kyr to illustrate how their impacts cascade through the Earth system. We review useful indicators of upcoming abrupt changes, or early warning signals, and provide a perspective on the contributions of palaeoclimate science to the understanding of abrupt changes in the Earth system.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    230 Th normalization: New insights on an essential tool for quantifying sedimentary fluxes in the modern and Quaternary ocean (2020)
    In:  EPIC3Paleoceanography and Paleoclimatology, ISSN: 2572-4517
    Details
    Publication Date: 2020-02-26
    Description: 230Th‐normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of 230Th systematics, with regards to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of 230Th from across the global ocean at two time slices, the Late Holocene (0‐5000 years ago, or 0‐5 ka) and the Last Glacial Maximum (18.5‐23.5 ka), and investigated the spatial structure of 230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79‐2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48‐1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size dependent sediment fractionation, and carbonate dissolution on the efficacy of 230Th as a constant flux proxy. Anomalous 230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that 230Th‐normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (〉 1000 m water depth).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Eolian dust input to the Subarctic North Pacific (2014)
    ELSEVIER SCIENCE BV
    In:  EPIC3Earth and Planetary Science Letters, ELSEVIER SCIENCE BV, 387, pp. 252-263, ISSN: 0012-821X
    Details
    Publication Date: 2019-07-17
    Description: Eolian dust is a significant source of iron and other nutrients that are essential for the health of marine ecosystems and potentially a controlling factor of the high nutrient-low chlorophyll status of the Subarctic North Pacific. We map the spatial distribution of dust input using three different geochemical tracers of eolian dust, 4He, 232Th and rare earth elements, in combination with grain size distribution data, from a set of core-top sediments covering the entire Subarctic North Pacific. Using the suite of geochemical proxies to fingerprint different lithogenic components, we deconvolve eolian dust input from other lithogenic inputs such as volcanic ash, ice-rafted debris, riverine and hemipelagic input. While the open ocean sites far away from the volcanic arcs are dominantly composed of pure eolian dust, lithogenic components other than eolian dust play a more crucial role along the arcs. In sites dominated by dust, eolian dust input appears to be characterized by a nearly uniform grain size mode at ∼4 μm. Applying the 230Th-normalization technique, our proxies yield a consistent pattern of uniform dust fluxes of 1–2 g/m2/yr across the Subarctic North Pacific. Elevated eolian dust fluxes of 2–4 g/m2/yr characterize the westernmost region off Japan and the southern Kurile Islands south of 45° N and west of 165° E along the main pathway of the westerly winds. The core-top based dust flux reconstruction is consistent with recent estimates based on dissolved thorium isotope concentrations in seawater from the Subarctic North Pacific. The dust flux pattern compares well with state-of-the-art dust model predictions in the western and central Subarctic North Pacific, but we find that dust fluxes are higher than modeled fluxes by 0.5–1 g/m2/yr in the northwest, northeast and eastern Subarctic North Pacific. Our results provide an important benchmark for biogeochemical models and a robust approach for downcore studies testing dust-induced iron fertilization of past changes in biological productivity in the Subarctic North Pacific.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Climatically driven changes in the supply of terrigenous sediment to the East China Sea (2018)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 19 (2018): 2463-2477, doi:10.1029/2017GC007339.
    Description: We examine the paleoceanographic record over the last ∼400 kyr derived from major, trace, and rare earth elements in bulk sediment from two sites in the East China Sea drilled during Integrated Ocean Drilling Program Expedition 346. We use multivariate statistical partitioning techniques (Q‐mode factor analysis, multiple linear regression) to identify and quantify five crustal source components (Upper Continental Crust (UCC), Luochuan Loess, Xiashu Loess, Southern Japanese Islands, Kyushu Volcanics), and model their mass accumulation rates (MARs). UCC (35–79% of terrigenous contribution) and Luochuan Loess (16–55% contribution) are the most abundant end‐members through time, while Xiashu Loess, Southern Japanese Islands, and Kyushu Volcanics (1–22% contribution) are the lowest in abundance when present. Cycles in UCC and Luochuan Loess MARs may indicate continental and loess‐like material transported by major rivers into the Okinawa Trough. Increases in sea level and grain size proxy (e.g., SiO2/Al2O3) are coincident with increased flux of Southern Japanese Islands, indicating localized sediment supply from Japan. Increases in total terrigenous MAR precede minimum relative sea levels by several thousand years and may indicate remobilization of continental shelf material. Changes in the relative contribution of these end‐members are decoupled from total MAR, indicating compositional changes in the sediment are distinct from accumulation rate changes but may be linked to variations in sea level, riverine and eolian fluxes, and shelf‐bypass processes over glacial‐interglacials, complicating accurate monsoon reconstructions from fluvial dominated sediment.
    Description: U.S. National Science Foundation Grant Numbers: NSF‐EAR1434175, NSF‐EAR1433665, NSF‐EAR1434138
    Keywords: East China Sea ; Bulk sediment ; Provenance ; Multivariate statistics ; East Asian Monsoon ; Loess
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Thorium isotopes tracing the iron cycle at the Hawaii Ocean Time-series Station ALOHA (2015)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 169 (2015): 1-16, doi:10.1016/j.gca.2015.07.019.
    Description: The role of iron as a limiting micronutrient motivates an effort to understand the supply and removal of lithogenic trace metals in the ocean. The long-lived thorium isotopes (232 Th and 230 Th) in seawater can be used to quantify the input of lithogenic metals attributable to the partial dissolution of aerosol dust. Thus, Th can help in disentangling the Fe cycle by providing an estimate of its ultimate supply and turnover rate. Here we present time-series (1994-2014) data on thorium isotopes and iron concentrations in seawater from the Hawaii Ocean Time-series Station ALOHA. By comparing Th-based dissolved Fe fluxes with measured dissolved Fe inventories, we derive Fe residence times of 6-12 months for the surface ocean. Therefore, Fe inventories in the surface ocean are sensitive to seasonal changes in dust input. Ultrafiltration results further reveal that Th has a much lower colloidal content than Fe does, despite a common source. On this basis, we suggest Fe colloids may be predominantly organic in composition, at least at Station ALOHA. In the deep ocean (〉2 km), Fe approaches a solubility limit while Th, surprisingly, is continually leached from lithogenic particles. This distinction has implications for the relevance of Fe ligand availability in the deep ocean, but also suggests Th is not a good tracer for Fe in deep waters. While uncovering divergent behavior of these elements in the water column, this study finds that dissolved Th flux is a suitable proxy for the supply of Fe from dust in the remote surface ocean.
    Description: We acknowledge funding from the W.O. Crosby Postdoctoral Fellowship to CTH and the National Science Foundation through C-MORE, NSF-OIA EF-0424599 to EAB, and NSF-DMR Author Posting.
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
    Format: application/vnd.ms-excel
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  • 9
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    Orbital- and millennial-scale variability in northwest African dust emissions over the past 67,000 years (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-10-19
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology 37(1), (2022): e020PA004137, https://doi.org/10.1029/2020PA004137.
    Description: Reconstructions of aeolian dust flux to West African margin sediments can be used to explore changing atmospheric circulation and hydroclimate over North Africa on millennial to orbital timescales. Here, we extend West African margin dust flux records back to 37 ka in a transect of sites from 19° to 27°N, and back to 67 ka at Ocean Drilling Program (ODP) Hole 658C, in order to explore the interplay of orbital and high-latitude forcings on North African climate and make quantitative estimates of dust flux during the core of the Last Glacial Maximum (LGM). The ODP 658C record shows a Green Sahara interval from 60 to 50 ka during a time of high Northern Hemisphere summer insolation, with dust fluxes similar to levels during the early Holocene African Humid Period, and an abrupt peak in flux during Heinrich event 5a (H5a). Dust fluxes increase from 50 to 35 ka while the high-latitude Northern Hemisphere cools, with peaks in dust flux associated with North Atlantic cool events. From 35 ka through the LGM dust deposition decreases in all cores, and little response is observed to low-latitude insolation changes. Dust fluxes at sites from 21° to 27°N were near late Holocene levels during the LGM time slice, suggesting a more muted LGM response than observed from mid-latitude dust sources. Records along the northwest African margin suggest important differences in wind responses during different stadials, with maximum dust flux anomalies centered south of 20°N during H1 and north of 20°N during the Younger Dryas.
    Description: This research was supported by NSF #OCE-1103262 to L. Bradtmiller, NSF #OCE-1030784 to D. McGee, P. deMenocal, and G. Winckler, and by internal grants from Macalester College and MIT.
    Description: 2022-06-07
    Keywords: North Africa ; Dust flux ; Aeolian dust ; Green Sahara ; Stadials
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
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    Evidence for decreased precipitation variability in the Yucatán Peninsula during the mid-Holocene (2021)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography and Paleoclimatology 36(5), (2021): e2021PA004219, https://doi.org/10.1029/2021PA004219.
    Description: The Yucatán Peninsula (YP) has a complex hydroclimate with many proposed drivers of interannual and longer-term variability, ranging from coupled ocean–atmosphere processes to frequency of tropical cyclones. The mid-Holocene, a time of higher Northern Hemisphere summer insolation, provides an opportunity to test the relationship between YP precipitation and ocean temperature. Here, we present a new, ∼annually resolved speleothem record of stable isotope (δ18O and δ13C) and trace element (Mg/Ca and Sr/Ca) ratios for a section of the mid-Holocene (5.2–5.7 kyr BP), before extensive agriculture began in the region. A meter-long stalagmite from Río Secreto, a cave system in Playa del Carmen, Mexico, was dated using U–Th geochronology and layer counting, yielding multidecadal age uncertainty (median 2SD of ±70 years). New proxy data were compared to an existing late Holocene stalagmite record from the same cave system, allowing us to examine changes in hydrology over time and to paleoclimate records from the southern YP. The δ18O, δ13C, and Mg/Ca data consistently indicate higher mean precipitation and lower precipitation variability during the mid-Holocene compared to the late Holocene. Despite this reduced variability, multidecadal precipitation variations were persistent in regional hydroclimate during the mid-Holocene. We therefore conclude that higher summer insolation led to increased mean precipitation and decreased precipitation variability in the northern YP but that the region is susceptible to dry periods across climate mean states. Given projected decreases in wet season precipitation in the YP’s near future, we suggest that climate mitigation strategies emphasize drought preparation.
    Description: This work was funded by US National Science Foundation grants AGS-1702848 (M. Medina-Elizalde) and AGS-1502877 (S. Burns). This material is based on work supported by the National Science Foundation Graduate Research Fellowship under grant 1122374 (G. Serrato Marks). Additional support was provided by the MIT EAPS Student Research Fund and the WHOI Ocean Ventures Fund.
    Description: 2021-11-06
    Keywords: Carbon isotopes ; Drought ; Hydroclimate ; Oxygen isotopes ; Speleothems ; Trace elements ; Yucatán Peninsula
    Repository Name: Woods Hole Open Access Server
    Type: Article
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