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  • 1
    Electronic Resource
    Electronic Resource
    Photopolymerization of N-substituted phenyl maleimide initiated with N,N-dimethyl-4-toluidine (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 643-650 
    Details
    ISSN: 0887-624X
    Keywords: photopolymerization of N-substituted phenyl maleimides ; N,N-dimethyl-4-Toluidine ; exciplex ; radical intermediate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several N-phenyl maleimides with different p-substituents have been synthesized from the maleic anhydride and relevant aromatic amine. In the presence of N,N-dimethyl-4-toluidine (DMT), the N-substituted phenyl maleimide (4-XPhMIs) could be polymerized under UV irradiation. It was observed that a new absorption appeared on the UV-Vis spectrum of the mixture solution of 4-XPhMI and DMT, which reveals the formation of charge-transfer complex in the ground state. It was found that the fluorescence of DMT was quenched by 4-XPhMI and the quenching constant of 4-XPhMI, obtained from the Stern-Volmer plot, increases with the electron-deficiency of ethylene double bond of 4-XPhMI. The dynamic quenching of the fluorescence of DMT by 4-XPhMI suggests the formation of exciplex in excited state between DMT and 4-XPhMI. The radicals formed in the systems have been detected by spin-trapping techniques and electron paramagnetic resonance (EPR) spectrometer. Based on all of these results, it has been proposed that the initiation process of the polymerization involves the formation of exciplex and the initial radicals were produced by proton-transfer in the exciplex from DMT to 4-XPhMI. © 1997 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    The electropolymerization of poly(styrene-co-4-carboxyphenyl maleimide) coatings onto steel (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 1303-1312 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Electropolymerization can be used to produce uniform and pin-hole free coatings on surfaces of complex shapes, due to the intrinsic characteristic of the process. In this article, the electrocopolymerization behavior of 4-carboxyphenyl maleimide (4CPMI) with styrene onto a steel surface is reported. The polymerization mechanism is by free radical, as might be expected for an aqueous reaction environment. Experimental results suggest that initially a charge transfer complex forms between styrene and 4CPMI, which is much more reactive than either of the two monomers. Alternating copolymers are always obtained at low conversion, even with significant changes in the monomer feed compositions. Because of the incorporation of rigid imide rings into the copolymer backbone, the coating formed has very good thermal properties and is thus a potential candidate for high-temperature applications. Furthermore, the copolymer dielectric constant is comparable to that of commercial polyimides, making it attractive for use in electrical and electronic insulation applications. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Some Synthetic Studies Related to Perylenequinones (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 35-41 
    Details
    ISSN: 0170-2041
    Keywords: Fungus pigments ; Perylenequinones, synthesis of ; Selenium dioxide oxidation ; Ullmann coupling ; Double coupling of 1,2-naphthalenediols ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two closely related routes to dimethyl 3,10-dihydro-2,11-dihydroxy-4,6,7,9-tetramethoxy-3,10-dioxo-1,12-perylenediacetate (10), one involving Ullmann phenol coupling and the other by double oxidative coupling are described. Regioselective demethylation of 10 followed by methylation or vice versa yields dimethyl 3,10-dihydro-4,9-dihydroxy-2,6,7,11-tetramethoxy-3,10-dioxo-1,12-perylenediacetate (22) which, except for its side chains, structurally resembles some of the natural perylenequinones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199319930107
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  • 4
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    The PMIP4 contribution to CMIP6 – Part 4: Scientific objectives and experimental design of the PMIP4-CMIP6 Last Glacial Maximum experiments and PMIP4 sensitivity experiments (2017)
    Copernicus Publications (EGU)
    In:  Geoscientific Model Development, 10 (11). pp. 4035-4055.
    Details
    Publication Date: 2020-02-06
    Description: The Last Glacial Maximum (LGM, 21 000 years ago) is one of the suite of paleoclimate simulations included in the current phase of the Coupled Model Intercomparison Project (CMIP6). It is an interval when insolation was similar to the present, but global ice volume was at a maximum, eustatic sea level was at or close to a minimum, greenhouse gas concentrations were lower, atmospheric aerosol loadings were higher than today, and vegetation and land-surface characteristics were different from today. The LGM has been a focus for the Paleoclimate Modelling Intercomparison Project (PMIP) since its inception, and thus many of the problems that might be associated with simulating such a radically different climate are well documented. The LGM state provides an ideal case study for evaluating climate model performance because the changes in forcing and temperature between the LGM and pre-industrial are of the same order of magnitude as those projected for the end of the 21st century. Thus, the CMIP6 LGM experiment could provide additional information that can be used to constrain estimates of climate sensitivity. The design of the Tier 1 LGM experiment (lgm) includes an assessment of uncertainties in boundary conditions, in particular through the use of different reconstructions of the ice sheets and of the change in dust forcing. Additional (Tier 2) sensitivity experiments have been designed to quantify feedbacks associated with land-surface changes and aerosol loadings, and to isolate the role of individual forcings. Model analysis and evaluation will capitalize on the relative abundance of paleoenvironmental observations and quantitative climate reconstructions already available for the LGM.
    Type: Article , PeerReviewed
    Format: text
    Format: archive
    DOI: 10.5194/gmd-10-4035-2017
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Abrupt North Atlantic circulation changes in response to gradual CO2 forcing in a glacial climate state (2017)
    Nature Research
    In:  Nature Geoscience, 10 (7). pp. 518-523.
    Details
    Publication Date: 2020-02-06
    Description: Glacial climate is marked by abrupt, millennial-scale climate changes known as Dansgaard–Oeschger cycles. The most pronounced stadial coolings, Heinrich events, are associated with massive iceberg discharges to the North Atlantic. These events have been linked to variations in the strength of the Atlantic meridional overturning circulation. However, the factors that lead to abrupt transitions between strong and weak circulation regimes remain unclear. Here we show that, in a fully coupled atmosphere–ocean model, gradual changes in atmospheric CO2 concentrations can trigger abrupt climate changes, associated with a regime of bi-stability of the Atlantic meridional overturning circulation under intermediate glacial conditions. We find that changes in atmospheric CO2 concentrations alter the transport of atmospheric moisture across Central America, which modulates the freshwater budget of the North Atlantic and hence deep-water formation. In our simulations, a change in atmospheric CO2 levels of about 15 ppmv—comparable to variations during Dansgaard–Oeschger cycles containing Heinrich events—is sufficient to cause transitions between a weak stadial and a strong interstadial circulation mode. Because changes in the Atlantic meridional overturning circulation are thought to alter atmospheric CO2 levels, we infer that atmospheric CO2 may serve as a negative feedback to transitions between strong and weak circulation modes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/NGEO2974
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  • 6
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    Tubulin cofactor a functions as a novel positive regulator of ccRCC progression, invasion and metastasis (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2013-06-08
    Description: Microtubules (Mts), which consist of α/β-tubulin heterodimers, are involved in cancer development and metastasis. Tubulin cofactor A (TBCA) plays crucial roles in modulating tubulin folding and α/β-tubulin heterodimer polymerization. Here, we identified the aberrant expression of TBCA in clear cell renal cell carcinoma (ccRCC) specimens as well as cell lines, and revealed the function of TBCA as a novel positive regulator in ccRCC progression, invasion, and metastasis. qRT-PCR, Western blot, and immunohistochemistry assays confirmed TBCA was significantly highly expressed in ccRCC specimens and cell lines compared to their corresponding normal kidney tissues and HKC. Accordingly, the influence of TBCA on cell proliferation, apoptosis, and invasion/migration was detected through overexpression and knockdown of endogenous TBCA protein level in ccRCC cells via plasmids. Silencing of TBCA expression inhibited the proliferation of 786-O cells and Caki-1 cells and promoted the apoptosis of 786-O cells. Down-regulation of TBCA expression also reduced the invasion and migration ability of 786-O cells. Interestingly, overexpression of TBCA did not induce bio-characteristics that directly contrasted to those of TBCA knockdown. Importantly, exploration of the mechanism showed that TBCA could function via modulating cytoskeleton integration and influencing cell cycle progress. Furthermore, down-regulation of TBCA expression in 786-O and Caki-1 cells affected cytoskeleton integration and cell size, induced S/G2 cell cycle arrest, and led to cyclineA/E and CDK2 aberrant expression. By investigating novel roles of TBCA in regulation of ccRCC cell progression, invasion, and metastasis, our study identified that TBCA may be a potential molecular target for ccRCC therapy. © 2013 Wiley Periodicals, Inc.
    Print ISSN: 0020-7136
    Electronic ISSN: 1097-0215
    Topics: Biology , Medicine
    Published by Wiley-Blackwell
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    PAPER CURRENT
  • 7
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    Centennial- to millennial-scale monsoon changes since the last deglaciation linked to solar activities and North Atlantic cooling (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: Rapid monsoon changes since the last deglaciation remain poorly constrained due to the scarcity of geological archives. Here we present a high-resolution scanning X-ray fluorescence (XRF) analysis of a 13.5 m terrace succession on the western Chinese Loess Plateau (CLP) to infer rapid monsoon changes since the last deglaciation. Our results indicate that Rb∕Sr and Zr∕Rb are sensitive indicators of chemical weathering and wind sorting, respectively, which are further linked to the strength of the East Asian summer monsoon (EASM) and the East Asian winter monsoon (EAWM). During the last deglaciation, two cold intervals of the Heinrich event 1 and Younger Dryas were characterized by intensified winter monsoon and weakened summer monsoon. The EAWM gradually weakened at the beginning of the Holocene, while the EASM remained steady till 9.9 ka and then grew stronger. Both the EASM and EAWM intensities were relatively weak during the Middle Holocene, indicating a mid-Holocene climatic optimum. Rb∕Sr and Zr∕Rb exhibit an antiphase relationship between the summer and winter monsoon changes on a centennial timescale during 16–1 ka. Comparison of these monsoon changes with solar activity and North Atlantic cooling events reveals that both factors can lead to abrupt changes on a centennial timescale in the Early Holocene. During the Late Holocene, North Atlantic cooling became the major forcing of centennial monsoon events.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    PISM-LakeCC: Implementing an adaptive proglacial lake boundary into an ice sheet model (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2022-03-10
    Description: Geological records show that vast proglacial lakes existed along the land terminating margins of palaeo ice sheets in Europe and North America. Proglacial lakes impact ice sheet dynamics by imposing marine-like boundary conditions at the ice margin. These lacustrine boundary conditions include changes in the ice sheet’s geometry, stress balance and frontal ablation and therefore affect the entire ice sheet’s mass balance. This interaction, however, has not been rigorously implemented in ice sheet models. In this study, the implementation of an adaptive lake boundary into the Parallel Ice Sheet Model (PISM) is described and applied to the glacial retreat of the Laurentide Ice Sheet (LIS). The results show that the presence of proglacial lakes locally enhances the ice flow. Along the continental ice margin, ice streams and ice lobes can be observed. Lacustrine terminating ice streams cause immense thinning of the ice sheet’s interior and thus play a significant role in the demise of the LIS. Due to the presence of lakes, a process similar to the marine ice sheet instability causes the collapse of the ice saddle over Hudson Bay, which blocked drainage via the Hudson Strait. In control experiments without a lake model, Hudson Bay is still glaciated at the end of the simulation. Future studies should target the development of parametrizations that better describe the glacial-lacustrine interactions.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Orbital- and millennial-scale Antarctic Circumpolar Current variability in Drake Passage over the past 140,000 years (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: The Antarctic Circumpolar Current (ACC) plays a crucial role in global ocean circulation by fostering deep-water upwelling and formation of new water masses. On geological time-scales, ACC variations are poorly constrained beyond the last glacial. Here, we reconstruct changes in ACC strength in the central Drake Passage in vicinity of the modern Polar Front over a complete glacial-interglacial cycle (i.e., the past 140,000 years), based on sediment grain-size and geochemical characteristics. We found significant glacial-interglacial changes of ACC flow speed, with weakened current strength during glacials and a stronger circulation in interglacials. Superimposed on these orbital-scale changes are high-amplitude millennial-scale fluctuations, with ACC strength maxima correlating with diatom-based Antarctic winter sea-ice minima, particularly during full glacial conditions. We infer that the ACC is closely linked to Southern Hemisphere millennial-scale climate oscillations, amplified through Antarctic sea ice extent changes. These strong ACC variations modulated Pacific-Atlantic water exchange via the “cold water route” and potentially affected the Atlantic Meridional Overturning Circulation and marine carbon storage.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    A new global ice sheet reconstruction for the past 80 000 years (2021)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: The evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26 000-19 000 years before present) – an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine δ18O proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80 000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and δ18O proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57 000-29 000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine δ18O and sea level may be more complex than assumed.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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