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  • 2015-2019  (21)
  • 1970-1974  (7)
  • 1
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    Chironomid-based temperature reconstruction for the Eemian Interglacial (MIS 5e) at Sokli, northeast Finland (2019)
    SPRINGER
    In:  EPIC3Journal of Paleolimnology, SPRINGER, 61(3), pp. 355-371, ISSN: 0921-2728
    Details
    Publication Date: 2019-12-23
    Description: The Last Interglacial (Eemian, MIS 5e) can be considered a test-bed for climate dynamics under a warmer-than-present climate. In this study we present a chironomid record from the high latitude Sokli site (N Finland), where a long continuous sediment sequence from the last interglacial has been preserved from glacial erosion. The chironomidanalysis shows a diverse fauna, with dominance of warm-water indicators and shifts in assemblage composition that can be attributed to temperature, lake depth, productivity and habitat availability. Quantitative mean July paleotemperature estimates based on the chironomid data indicate overall mean July air temperatures up to 1 �C warmer than present. Two cooling events can be discerned, the Tunturi event, dated to about 127.5 ka BP, in the lower part of the sequence, and the Va ¨rrio ¨ event, dated to about 119 ka BP, associated with the beginning of a cooling trend in the upper part of the record. Warm conditions already at the onset of the interglacial contrast with a recent chironomid-based last interglacial temperature reconstruction from Denmark, which suggests a late onset of Eemian warming. The relatively small increase in inferred temperatures compared to present day temperatures at Sokli differs from other high latitude Eemian sites, and likely reflects the influence of the Atlantic Meridional Overturning Circulation in maintaining already elevated temperatures in Fennoscandia during interglacials
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
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    Climate change as a driver of biodiversity: subfossil chironomids as an indicator of long-term trends in insect diversity (2019)
    In:  EPIC3Global Change Biology
    Details
    Publication Date: 2020-01-13
    Description: Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial- or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a meta-data analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric datasets overall consisting of 837 lakes. Our results indicate that in most of our datasets summer temperature (Tjul) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing Tjul in regions with present day Tjul between 2.5-14 °C. In some areas with Tjul 〉14 °C chironomid diversity stabilises or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (~15,000-11,000 years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
    Electronic Resource
    Electronic Resource
    Feststoffreaktionen in Katalysatoren und Katalysatorkomponenten. I. Feststoffreaktionen in Katalysatoren zur autothermen Methankonvertierung (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 405 (1974), S. 211-224 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Solid Reactions in Catalysts and Catalyst Components. I. Solid Reactions in Catalysts for Autothermic Conversion of MethaneSolid reactions in the systems kaolin-NiO, kaolin-α-Al2O3NiO, and kaolin-MgO-NiO are described and investigated by means of X-ray measurements. Data on the reducibility of NiAl2O4 and on the dispersity of nickel on the supports are given. For further characterization of the samples electron-microscopic investigations have also been applied.
    Notes: Es werden die in den Systemen Kaolin-NiO,Kaolin-α-Al2O3-NiO und Kaolin-MgO-NiO ablaufenden Feststoffreaktionen beschrieben. Die Analyse der Reaktionsprodukte erfolgte mittels Röntgenuntersuchungen. Zur Reduzierbarkeit von NiAl2O4 sowie zum Dispersitätsverhalten von Nickel auf Katalysatorträgern werden Angaben gemacht. Elektronenoptische Untersuchungen dienten zur weiteren Charakterisierung der Proben.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744050212
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  • 4
    Electronic Resource
    Electronic Resource
    Untersuchungen an Metallkatalysatoren. IVorbericht: Z. anorg. allg. Chem. 403, 353 (1974). Strukturelle und katalytische Untersuchungen an pulverförmigen Palladium-Silber-LegierungenProfessor Günther Rienäcker zum 70. Geburtstage am 13. Mai 1974 gewidmet (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 405 (1974), S. 239-249 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations on Metal Catalysts. I. Structural and Catalytical Investigations on Palladium-Silver PowdersSeveral conditions for preparation of palladium-silver powders are described. By choice of suitable preparation metal crystallites were obtained, in which exists a gradient of concentration with respect to the metals. This gradient determines the behaviour of sorption and catalytical activity, respectively.Characterization of catalysts with regard to their structure takes place by means of X-ray measurements and investigations of sorption (adsorption of N2, chemisorption of CO, sorption of H2), respectively. The catalytical activity of alloys has been measured by means of hydrogenation of benzene.
    Notes: Es werden verschiedene Präparationsbedingungen pulverförmiger Pd-Ag-Katalysatoren beschrieben. Durch Wahl geeigneter Herstellungsverfahren läßt sich in den Metallkristalliten ein Konzentrationsgradient erzeugen, der das Sorptionsverhalten der Legierungen sowie ihre katalytische Aktivität bestimmt.Die Charakterisierung der Proben erfolgte durch Röntgenuntersuchungen sowie Sorptionsmessungen (N2-Adsorption, CO-Chemisorption, Wasserstoffsorption); das katalytische Verhalten der Legierungen wurde mittels der Benzolhydrierung ermittelt.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744050304
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  • 5
    Electronic Resource
    Electronic Resource
    Untersuchungen an Metallkatalysatoren. IIVorbericht: Z. anorg. allg. Chem. 403, 353 (1974).. Sorptionsverhalten und Hydrieraktivität pulverförmiger Palladium-Rhodium-Legierungen (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 406 (1974), S. 45-51 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations on Metal Catalysts. II. Behaviour in Sorption and Activity of Hydrogenation of Powders of Palladium-Rhodium AlloysExperiments for preparing Pd—Rh alloys by reduction in aqueous solutions and characterization of catalysts by X-ray measurements are described. Behaviour in sorption (adsorption of nitrogen, chemisorption of carbon monoxide, sorption of hydrogen) and catalytical activity of the alloys in hydrogenation of benzene are determined by existence of the two phase region and X-ray amorphous rhodium, respectively.
    Notes: Es wird über die Herstellung von Palladium-Rhodium-Legierungen durch Reduktion aus wäßrigen Lösungen sowie ihre röntgenorgraphische Charakterisierung berichtet. Das Sorptionsverhalten (N2-Adsorption, CO-Chemisorption, Wasserstoffsorption) sowie die katalytische Aktivität der Legierungen bei der Benzolhydrierung werden durch das Auftreten eines Zweiphasengebietes sowie das Vorliegen röntgenamorphen Rhodiums bestimmt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744060107
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  • 6
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    Sialylated antigens impose T-cell tolerance [Immunology and Inflammation] (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-03-24
    Description: Sialic acids are negatively charged nine-carbon carboxylated monosaccharides that often cap glycans on glycosylated proteins and lipids. Because of their strategic location at the cell surface, sialic acids contribute to interactions that are critical for immune homeostasis via interactions with sialic acid-binding Ig-type lectins (siglecs). In particular, these interactions may...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 7
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    Centennial-scale lake-level lowstand at Lake Uddelermeer (The Netherlands) indicates changes in moisture source region prior to the 2.8-kyr event (2016)
    Sage
    In: Holocene
    Details
    Publication Date: 2016-06-28
    Description: The Uddelermeer is a unique lake for The Netherlands, containing a sediment record that continuously registered environmental and climatic change from the late Pleistocene on to the present. A 15.6-m-long sediment record was retrieved from the deepest part of the sedimentary basin and an age–depth model was developed using radiocarbon dating, 210 Pb dating, and Bayesian modeling. Lake-level change was reconstructed using a novel combination of high-resolution palaeoecological proxies (e.g. pollen, non-pollen palynomorphs, chironomids), quantitative determinations of lake-level change (ground-penetrating radar), and estimates of changes in precipitation (lipid biomarker stable isotopes). We conclude that lake levels were at least as high as present-day water levels from the late glacial to 3150 cal. yr BP, with the exception of at least one lake-level lowstand during the Preboreal period. Lake levels were ca. 2.5 m lower than at present between 3150 and 2800 cal. yr BP, which might have been the result of a change in moisture source region prior to the so-called 2.8-kyr event. Increasing precipitation amounts around 2800 cal. yr BP resulted in a lake-level rise of about 3.5–4 m to levels that were 1–1.5 m higher than at present, in line with increased precipitation levels as inferred for the 2.8-kyr event from nearby raised bog areas as well as with reconstructions of higher lake levels in the French Alps, all of which have been previously attributed to a phase of decreased solar activity. Lake levels decreased to their present level only during recent times, although the exact timing of the drop in lake levels is unclear.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 8
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    Calibrating aquatic microfossil proxies with regression-tree ensembles: Cross-validation with modern chironomid and diatom data (2016)
    Sage
    In: Holocene
    Details
    Publication Date: 2016-06-28
    Description: We examine the ability of four different regression-tree ensemble techniques (bagging, random forest, rotation forest and boosted tree) in calibration of aquatic microfossil proxies. The methods are tested with six chironomid and diatom datasets, using a variety of cross-validation schemes. We find random forest, rotation forest and the boosted tree to have a similar performance, while bagging performs less well and in several cases has trouble producing continuous predictions. In comparison with commonly used parametric transfer-function approaches (PLS, WA, WA-PLS), we find that in some cases tree-ensemble methods outperform the best-performing transfer-function technique, especially with large datasets characterized by complex taxon responses and abundant noise. However, parametric transfer functions remain competitive with datasets characterized by low number of samples or linear taxon responses. We present an implementation of the rotation forest algorithm in R.
    Print ISSN: 0959-6836
    Electronic ISSN: 1477-0911
    Topics: Geography , Geosciences
    Published by Sage
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  • 9
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    Late Holocene changes in vegetation and atmospheric circulation at Lake Uddelermeer (The Netherlands) reconstructed using lipid biomarkers and compound-specific δD analysis (2018)
    Wiley
    Details
    Publication Date: 2018-01-06
    Description: ABSTRACT We reconstructed middle to late Holocene changes in atmospheric circulation patterns and vegetation in north-west Europe by applying novel geochemical techniques to the sediment record of Lake Uddelermeer (The Netherlands). A comparison of higher plant-derived leaf wax n -alkane distributions archived in the lake sediments with those in living plant material, combined with palynological analysis, indicates that the vegetation immediately surrounding the lake became more open at 3150 cal a  BP , while the regional vegetation responded more gradually and ∼650 years later. Our record of the hydrogen isotopic composition of plant leaf waxes (δD wax ) shows a deuterium enrichment starting from 3500 cal a  BP , which we interpret as a change in atmospheric circulation. A similar δD wax record from nearby Meerfelder Maar (Germany) shows an opposite trend around this time, which could be explained by a change in sea-level pressure resembling a negative North Atlantic Oscillation phase. This could account for depleted δD values of precipitation at Meerfelder Maar, while confounding factors related to the more maritime position of Uddelermeer cause the opposite shift there.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
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  • 10
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    Ultrahigh-mobility graphene devices from chemical vapor deposition on reusable copper (2015)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2015-08-01
    Description: Graphene research has prospered impressively in the past few years, and promising applications such as high-frequency transistors, magnetic field sensors, and flexible optoelectronics are just waiting for a scalable and cost-efficient fabrication technology to produce high-mobility graphene. Although significant progress has been made in chemical vapor deposition (CVD) and epitaxial growth of graphene, the carrier mobility obtained with these techniques is still significantly lower than what is achieved using exfoliated graphene. We show that the quality of CVD-grown graphene depends critically on the used transfer process, and we report on an advanced transfer technique that allows both reusing the copper substrate of the CVD growth and making devices with mobilities as high as 350,000 cm 2 V –1 s –1 , thus rivaling exfoliated graphene.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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