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  1. AU="Völker, Christoph"
  2. AU="El Aoud, S"
  3. AU="Yi, Tongpei"
  4. AU="Anil K. Mantha"
  5. AU="Artzner, Christoph"
  6. AU=Diana Giovanni
  7. AU="Kinloch, Sabine"
  8. AU="Nuertey, David"
  9. AU="Ojubolamo, Olakunle"

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  1. Book ; Thesis: Pulsoximetrie während intra-aortaler Ballonpumpen-Gegenpulsation (IABP)

    Thiel, Volker Christoph Günther

    2011  

    Author's details vorgelegt von Volker Christoph Günther Thiel
    Language German
    Size 67 S. : Ill., graph. Darst.
    Publishing country Germany
    Document type Book ; Thesis
    Thesis / German Habilitation thesis Aachen, Techn. Hochsch., Diss., 2011
    HBZ-ID HT017098888
    Database Catalogue ZB MED Medicine, Health

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    In stock of ZB MED Cologne/Königswinter

    Shelf markLoan statusLocation
    2012 D 683 order for loan Magazin

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  2. Article ; Online: Concreting a sustainable future: A dataset of alkali-activated concrete and its properties.

    Torres, Benjamin Moreno / Völker, Christoph / Firdous, Rafia

    Data in brief

    2023  Volume 50, Page(s) 109525

    Abstract: This data article introduces a dataset comprising 1630 alkali-activated concrete (AAC) mixes, compiled from 106 literature sources. The dataset underwent extensive curation to address feature redundancy, transcription errors, and duplicate data, yielding ...

    Abstract This data article introduces a dataset comprising 1630 alkali-activated concrete (AAC) mixes, compiled from 106 literature sources. The dataset underwent extensive curation to address feature redundancy, transcription errors, and duplicate data, yielding refined data ready for further data-driven science in the field of AAC, where this effort constitutes a novelty. The carbon footprint associated with each material used in the AAC mixes, as well as the corresponding CO
    Language English
    Publishing date 2023-08-28
    Publishing country Netherlands
    Document type Journal Article
    ZDB-ID 2786545-9
    ISSN 2352-3409 ; 2352-3409
    ISSN (online) 2352-3409
    ISSN 2352-3409
    DOI 10.1016/j.dib.2023.109525
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Book ; Online: Alkalinity biases in CMIP6 Earth System Models and implications for simulated CO2 drawdown via artificial alkalinity enhancement

    Hinrichs, Claudia / Köhler, Peter / Völker, Christoph / Hauck, Judith

    eISSN: 1726-4189

    2023  

    Abstract: The partitioning of CO 2 between atmosphere and ocean depends to a large degree not only on the amount of dissolved inorganic carbon (DIC) but also of alkalinity in the surface ocean. That is also why, in the context of negative emission approaches ocean ...

    Abstract The partitioning of CO 2 between atmosphere and ocean depends to a large degree not only on the amount of dissolved inorganic carbon (DIC) but also of alkalinity in the surface ocean. That is also why, in the context of negative emission approaches ocean alkalinity enhancement is discussed as one potential approach. Although alkalinity is thus an important variable of the marine carbonate system little knowledge exists how its representation in models compares with measurements. We evaluated the large-scale alkalinity distribution in 14 CMIP6 models against the observational data set GLODAPv2 and showed that most models as well as the multi-model-mean underestimate alkalinity at the surface and in the upper ocean, while overestimating alkalinity in the deeper ocean. The decomposition of the global mean alkalinity biases into contributions from physical processes (preformed alkalinity), remineralization, and carbonate formation and dissolution showed that the bias stemming from the physical redistribution of alkalinity is dominant. However, below the upper few hundred meters the bias from carbonate dissolution can become similarly important as physical biases, while the contribution from remineralization processes is negligible. This highlights the critical need for better understanding and quantification of processes driving calcium carbonate dissolution in microenvironments above the saturation horizons, and implementation of these processes into biogeochemical models. For the application of the models to assess the potential of ocean alkalinity enhancement to increase ocean carbon uptake and counteract ocean acidification, a back-of-the-envelope calculation was conducted with each model’s global mean surface alkalinity and DIC as input parameters. We find that the degree of compensation of DIC and alkalinity biases at the surface is more important for the marine CO 2 uptake capacity than the alkalinity biases themselves. The global mean surface alkalinity bias relative to GLODAPv2 in the different models ...
    Subject code 551
    Language English
    Publishing date 2023-02-09
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Book ; Online: New / improved model parametrizations for responses in phytoplankton growth and calcification to changes in alkalinity implemented

    Seifert, Miriam / Hinrichs, Claudia / Hauck, Judith / Völker, Christoph

    2023  

    Abstract: Global biogeochemical ocean models that are currently in place to investigate alkalinity enhancement at a global scale do usually not consider the effects of a changing carbonate system on phytoplankton. We introduce new and modified parameterizations of ...

    Abstract Global biogeochemical ocean models that are currently in place to investigate alkalinity enhancement at a global scale do usually not consider the effects of a changing carbonate system on phytoplankton. We introduce new and modified parameterizations of phytoplankton carbonate systems sensitivities into the biogeochemistry model REcoM. We then compare phytoplankton biomass and net primary production at different atmospheric CO2 concentrations to results from other deliverables (D5.3, 5.6, 5.7) based on experiments and models. The resilience of phytoplankton biomass towards low CO2 concentrations in our model compares well with the results of mesocosm experiments. Or model results differ in the phytoplankton responses compared to the results of a 1D biogeochemical model that employs similar parameterizations regarding the effects on calcifying phytoplankton and total net primary production, which we explain primarily with differences in the spatial scales and phytoplankton communities investigated.
    Subject code 551
    Language English
    Publishing date 2023-03-20
    Publisher OceanNETs
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Interaction matters: Bottom‐up driver interdependencies alter the projected response of phytoplankton communities to climate change

    Seifert, Miriam / Nissen, Cara / Rost, Björn / Vogt, Meike / Völker, Christoph / Hauck, Judith

    Global Change Biology. 2023 Aug., v. 29, no. 15 p.4234-4258

    2023  

    Abstract: Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large‐scale ocean biogeochemistry models mostly account for ... ...

    Abstract Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large‐scale ocean biogeochemistry models mostly account for growth responses to each driver separately and leave the results of these experimental multiple‐driver studies largely unused. Here, we amend phytoplankton growth functions in a biogeochemical model by dual‐driver interactions (CO₂ and temperature, CO₂ and light), based on data of a published meta‐analysis on multiple‐driver laboratory experiments. The effect of this parametrization on phytoplankton biomass and community composition is tested using present‐day and future high‐emission (SSP5‐8.5) climate forcing. While the projected decrease in future total global phytoplankton biomass in simulations with driver interactions is similar to that in control simulations without driver interactions (5%–6%), interactive driver effects are group‐specific. Globally, diatom biomass decreases more with interactive effects compared with the control simulation (−8.1% with interactions vs. no change without interactions). Small‐phytoplankton biomass, by contrast, decreases less with on‐going climate change when the model accounts for driver interactions (−5.0% vs. −9.0%). The response of global coccolithophore biomass to future climate conditions is even reversed when interactions are considered (+33.2% instead of −10.8%). Regionally, the largest difference in the future phytoplankton community composition between the simulations with and without driver interactions is detected in the Southern Ocean, where diatom biomass decreases (−7.5%) instead of increases (+14.5%), raising the share of small phytoplankton and coccolithophores of total phytoplankton biomass. Hence, interactive effects impact the phytoplankton community structure and related biogeochemical fluxes in a future ocean. Our approach is a first step to integrate the mechanistic understanding of interacting driver effects on phytoplankton growth gained by numerous laboratory experiments into a global ocean biogeochemistry model, aiming toward more realistic future projections of phytoplankton biomass and community composition.
    Keywords Bacillariophyceae ; biogeochemistry ; biomass ; carbon dioxide ; climate ; climate change ; community structure ; meta-analysis ; models ; oceans ; phytoplankton ; temperature
    Language English
    Dates of publication 2023-08
    Size p. 4234-4258.
    Publishing place John Wiley & Sons, Ltd
    Document type Article ; Online
    Note JOURNAL ARTICLE
    ZDB-ID 1281439-8
    ISSN 1365-2486 ; 1354-1013
    ISSN (online) 1365-2486
    ISSN 1354-1013
    DOI 10.1111/gcb.16799
    Database NAL-Catalogue (AGRICOLA)

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    In stock of ZB MED Bonn / Germany

    Z 6338: Show issues

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    Inter-library loan at ZB MED

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  6. Book ; Thesis: Bewegungsverhalten und Neurosestruktur

    Völker, Christoph

    eine Bewegungsstudie

    1987  

    Author's details Christoph Völker
    Keywords Neurotic Disorders ; Motor Activity
    Size 146 S. : graph. Darst.
    Document type Book ; Thesis
    Thesis / German Habilitation thesis München, Techn. Univ., Diss., 1988
    HBZ-ID HT003581690
    Database Catalogue ZB MED Medicine, Health

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    In stock of ZB MED Cologne/Königswinter

    Shelf markLoan statusLocation
    90 D 1473 order for loan Magazin

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  7. Article: Sequential learning to accelerate discovery of alkali-activated binders

    Völker, Christoph / Firdous, Rafia / Stephan, Dietmar / Kruschwitz, Sabine

    Journal of materials science. 2021 Oct., v. 56, no. 28

    2021  

    Abstract: Alkali-activated binders (AAB) can provide a clean alternative to conventional cement in terms of CO₂ emissions. However, as yet there are no sufficiently accurate material models to effectively predict the AAB properties, thus making optimal mix design ... ...

    Abstract Alkali-activated binders (AAB) can provide a clean alternative to conventional cement in terms of CO₂ emissions. However, as yet there are no sufficiently accurate material models to effectively predict the AAB properties, thus making optimal mix design highly costly and reducing the attractiveness of such binders. This work adopts sequential learning (SL) in high-dimensional material spaces (consisting of composition and processing data) to find AABs that exhibit desired properties. The SL approach combines machine learning models and feedback from real experiments. For this purpose, 131 data points were collected from different publications. The data sources are described in detail, and the differences between the binders are discussed. The sought-after target property is the compressive strength of the binders after 28 days. The success is benchmarked in terms of the number of experiments required to find materials with the desired strength. The influence of some constraints was systematically analyzed, e.g., the possibility to parallelize the experiments, the influence of the chosen algorithm and the size of the training data set. The results show the advantage of SL, i.e., the amount of data required can potentially be reduced by at least one order of magnitude compared to traditional machine learning models, while at the same time exploiting highly complex information. This brings applications in laboratory practice within reach.
    Keywords algorithms ; carbon dioxide ; cement ; compression strength ; data collection
    Language English
    Dates of publication 2021-10
    Size p. 15859-15881.
    Publishing place Springer US
    Document type Article
    ZDB-ID 2015305-3
    ISSN 1573-4803 ; 0022-2461
    ISSN (online) 1573-4803
    ISSN 0022-2461
    DOI 10.1007/s10853-021-06324-z
    Database NAL-Catalogue (AGRICOLA)

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  8. Article ; Online: Interaction matters: Bottom-up driver interdependencies alter the projected response of phytoplankton communities to climate change.

    Seifert, Miriam / Nissen, Cara / Rost, Björn / Vogt, Meike / Völker, Christoph / Hauck, Judith

    Global change biology

    2023  Volume 29, Issue 15, Page(s) 4234–4258

    Abstract: Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large-scale ocean biogeochemistry models mostly account for ... ...

    Abstract Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large-scale ocean biogeochemistry models mostly account for growth responses to each driver separately and leave the results of these experimental multiple-driver studies largely unused. Here, we amend phytoplankton growth functions in a biogeochemical model by dual-driver interactions (CO
    MeSH term(s) Phytoplankton/physiology ; Climate Change ; Carbon Dioxide ; Diatoms/physiology ; Biomass ; Oceans and Seas
    Chemical Substances Carbon Dioxide (142M471B3J)
    Language English
    Publishing date 2023-06-02
    Publishing country England
    Document type Meta-Analysis ; Journal Article
    ZDB-ID 1281439-8
    ISSN 1365-2486 ; 1354-1013
    ISSN (online) 1365-2486
    ISSN 1354-1013
    DOI 10.1111/gcb.16799
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Bonn / Germany

    Z 6338: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

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  9. Book ; Thesis: Arterielle Verschlußkrankheit der Beckenetage im Stadium II nach Fontaine

    Schupp, Volker Christoph

    (Indikation, Operation, Beobachtungszeit 10 Jahre)

    1990  

    Author's details vorgelegt von Volker Christoph Schupp
    Size [2], 65, [4] S. : Ill., graph. Darst.
    Document type Book ; Thesis
    Thesis / German Habilitation thesis Ulm, Univ., Diss., 1991
    HBZ-ID HT003985316
    Database Catalogue ZB MED Medicine, Health

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    In stock of ZB MED Cologne/Königswinter

    Shelf markLoan statusLocation
    92 D 709 order for loan Magazin

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  10. Book ; Online: Carbon isotopes in the marine biogeochemistry model FESOM2.1-REcoM3

    Butzin, Martin / Ye, Ying / Völker, Christoph / Gürses, Özgür / Hauck, Judith / Köhler, Peter

    eISSN:

    2024  

    Abstract: In this paper we describe the implementation of the carbon isotopes 13 C and 14 C (radiocarbon) into the marine biogeochemistry model REcoM3. The implementation is tested in long-term equilibrium simulations where REcoM3 is coupled with the ocean general ...

    Abstract In this paper we describe the implementation of the carbon isotopes 13 C and 14 C (radiocarbon) into the marine biogeochemistry model REcoM3. The implementation is tested in long-term equilibrium simulations where REcoM3 is coupled with the ocean general circulation model FESOM2.1, applying a low-resolution configuration and idealized climate forcing. Focusing on the carbon-isotopic composition of dissolved inorganic carbon ( δ 13 C DIC and Δ 14 C DIC ), our model results are largely consistent with reconstructions for the pre-anthropogenic period. Our simulations also exhibit discrepancies, e.g. in upwelling regions and the interior of the North Pacific. Some of these differences are due to the limitations of our ocean circulation model setup, which results in a rather shallow meridional overturning circulation. We additionally study the accuracy of two simplified modelling approaches for dissolved inorganic 14 C, which are faster (15 % and about a factor of five, respectively) than the complete consideration of the marine radiocarbon cycle. The accuracy of both simplified approaches is better than 5 %, which should be sufficient for most studies of Δ 14 C DIC .
    Subject code 333
    Language English
    Publishing date 2024-02-26
    Publishing country de
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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