TY - JOUR A1 - Tötzke, Christian A1 - Manke, Ingo A1 - Gaiselmann, Gerd A1 - Bohner, John A1 - Müller, Bernd R. A1 - Kupsch, Andreas A1 - Hentschel, Manfred P. A1 - Schmidt, Volker A1 - Banhart, Jens A1 - Lehnert, Werner T1 - A dedicated compression device for high resolution X-ray tomography of compressed gas diffusion layers JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - We present an experimental approach to study the three-dimensional microstructure of gas diffusion layer (GDL) materials under realistic compression conditions. A dedicated compression device was designed that allows for synchrotron-tomographic investigation of circular samples under well-defined compression conditions. The tomographic data provide the experimental basis for stochastic modeling of nonwoven GDL materials. A plain compression tool is used to study the fiber courses in the material at different compression stages. Transport relevant geometrical parameters, such as porosity, pore size, and tortuosity distributions, are exemplarily evaluated for a GDL sample in the uncompressed state and for a compression of 30 vol.%. To mimic the geometry of the flow-field, we employed a compression punch with an integrated channel-rib-profile. It turned out that the GDL material is homogeneously compressed under the ribs, however, much less compressed underneath the channel. GDL fibers extend far into the channel volume where they might interfere with the convective gas transport and the removal of liquid water from the cell. (C) 2015 AIP Publishing LLC. Y1 - 2015 U6 - https://doi.org/10.1063/1.4918291 SN - 0034-6748 SN - 1089-7623 VL - 86 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - THES A1 - Hentschel, Jens T1 - Synthese und kontrollierte Mikrostrukturbildung funktionaler Peptid-Polymerkonjugate in organischen Lösungsmitteln T1 - Synthesis and controlled microstructure formation of functional peptide-polymer conjugates in organic media N2 - In der vorliegenden Arbeit wurde ein Ansatz verfolgt, die besonderen Eigenschaften der Strukturbildung sequenzdefinierter Peptide mit den vielseitigen Materialeigenschaften synthetischer Blockcopolymere zu kombinieren. Dazu wurde ein synthetisches Polymer kovalent mit einer definierten Peptidsequenz verknüpft. Der Peptidblock (die Organisationseinheit) wurde speziell designt, um später die Strukturbildung des Peptid-Polymerkonjugates induzieren und leiten zu können. Als Organisationsmotiv diente hierbei das aus der Natur bekannte β-Faltblatt Strukturmotiv. Das Peptidsegment wurde in einer festphasengebundenen Synthese aufgebaut. Dabei wurden temporäre Stör-Segmente (Switch-Segmente) in die Peptidsequenz integriert. Diese Segmente unterdrücken die Aggregationstendenz während der Synthese und können durch einen pH-abhängigen Schaltvorgang in das natürliche Peptidrückgrat überführt werden. Zusätzlich zu der verbesserten Ausbeute und Reinheit der entsprechenden Peptide war auf diese Weise eine kontrollierte Aktivierung der Mikrostrukturbildung möglich. Mit Hilfe zwei verschiedener Synthesestrategien (Kupplungs- bzw. Polymerisationsstrategie) wurde ein Satz von definierten Peptid-Polymerkonjugaten mit unterschiedlich großen Polymersegmenten synthetisiert. Diese wurden anschließend im Hinblick auf ihre Strukturbildungseigenschaften in organischen Lösungsmitteln untersucht. Durch mikroskopische Verfahren (AFM, TEM), konnte für alle Konjugate, die Bildung faserartiger Aggregate mit Dimensionen im Nano- bis Mikrometerbereich beobachtet werden. Genauere Untersuchungen zeigten, dass die Peptidsegmente in diesen Faserstrukturen ein β-Faltblatt ausbilden. Dies ist ein deutlicher Hinweis darauf, dass die Strukturbildung der Konjugate tatsächlich durch den Peptidblock gesteuert und kontrolliert wurde. N2 - The aim of this work was to combine the particular structuring properties of sequence-defined peptides with the versatile material properties of synthetic block-copolymers. Therefor, synthetic polymers were linked covalently to a defined oligopeptide-sequence using varying synthetic approaches. The oligopeptide was designed to guide and control the microstructure formation of the peptide-polymer conjugate. For this reason a peptide sequence with a high propensity to adopt the β-sheet motif was chosen. Thus, highly attractive, anisometric tape, fibrillar or fibre-like nanostructures can be accessed. However, such peptide-sequences are very difficult to synthesize and handle, as a result of their strong aggregation tendency. Therefore, temporary structure breaking units, so called switch-segments, were integrated into the peptide sequence, disturbing the peptide backbone and thus, temporarily suppressing the peptide properties. The controlled rearrangement of these defects reestablishes the native peptide backbone, switching the aggregation tendency of the peptide segment on, and triggers the assembly process. A set of defined peptide-polymer conjugates with different polymer block-lengths was synthesized either by an coupling approach or by RAFT polymerization using a switch-peptide macro chain transfer agent. Afterwards, the structure formation properties of these conjugates were investigated. By the use of microscopic techniques (AFM, TEM), the formation of densely twisted tape-like microstructures was observed for all conjugates. The formation of extended β-sheets was confirmed by different techniques (FT-IR, TEM-SAED), indicating a peptide guided microstructure formation process. Thus, it could be demonstrated that the peptide guided organization of synthetic polymers can be successfully transferred into organic solvents. KW - Peptid KW - Polymer KW - Strukturbildung KW - RAFT KW - peptide KW - polymer KW - switch KW - RAFT KW - nanostructure Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-19840 ER - TY - JOUR A1 - Nellesen, Jens A1 - Laquai, R. A1 - Müller, B. R. A1 - Kupsch, Andreas A1 - Hentschel, M. P. A1 - Anar, N. B. A1 - Soppa, E. A1 - Tillmann, W. A1 - Bruno, Giovanni T1 - In situ analysis of damage evolution in an Al/ Al2O3 MMC under tensile load by synchrotron X-ray refraction imaging JF - Journal of materials science N2 - The in situ analysis of the damage evolution in a metal matrix composite (MMC) using synchrotron X-ray refraction radiography (SXRR) is presented. The investigated material is an Al alloy (6061)/10 vol MMC after T6 heat treatment. In an interrupted tensile test the gauge section of dog bone-shaped specimens is imaged in different states of tensile loading. On the basis of the SXRR images, the relative change of the specific surface (proportional to the amount of damage) in the course of tensile loading was analyzed. It could be shown that the damage can be detected by SXRR already at a stage of tensile loading, in which no observation of damage is possible with radiographic absorption-based imaging methods. Moreover, the quantitative analysis of the SXRR images reveals that the amount of damage increases homogeneously by an average of 25% with respect to the initial state. To corroborate the experimental findings, the damage distribution was imaged in 3D after the final tensile loading by synchrotron X-ray refraction computed tomography (SXRCT) and absorption-based synchrotron X-ray computed tomography (SXCT). It could be evidenced that defects and damages cause pronounced indications in the SXRCT images. Y1 - 2018 U6 - https://doi.org/10.1007/s10853-017-1957-x SN - 0022-2461 SN - 1573-4803 VL - 53 IS - 8 SP - 6021 EP - 6032 PB - Springer CY - New York ER - TY - JOUR A1 - Deeken, Friederike A1 - Reichert, Markus A1 - Zech, Hilmar A1 - Wenzel, Julia A1 - Wedemeyer, Friederike A1 - Aguilera, Alvaro A1 - Aslan, Acelya A1 - Bach, Patrick A1 - Bahr, Nadja Samia A1 - Ebrahimi, Claudia A1 - Fischbach, Pascale Christine A1 - Ganz, Marvin A1 - Garbusow, Maria A1 - Großkopf, Charlotte M. A1 - Heigert, Marie A1 - Hentschel, Angela A1 - Karl, Damian A1 - Pelz, Patricia A1 - Pinger, Mathieu A1 - Riemerschmid, Carlotta A1 - Rosenthal, Annika A1 - Steffen, Johannes A1 - Strehle, Jens A1 - Weiss,, Franziska A1 - Wieder, Gesine A1 - Wieland, Alfred A1 - Zaiser, Judith A1 - Zimmermann, Sina A1 - Walter, Henrik A1 - Lenz, Bernd A1 - Deserno, Lorenz A1 - Smolka, Michael N. A1 - Liu, Shuyan A1 - Ebner-Priemer, Ulrich Walter A1 - Heinz, Andreas A1 - Rapp, Michael A. T1 - Patterns of Alcohol Consumption Among Individuals With Alcohol Use Disorder During the COVID-19 Pandemic and Lockdowns in Germany JF - JAMA Network Open N2 - Importance Alcohol consumption (AC) leads to death and disability worldwide. Ongoing discussions on potential negative effects of the COVID-19 pandemic on AC need to be informed by real-world evidence. Objective To examine whether lockdown measures are associated with AC and consumption-related temporal and psychological within-person mechanisms. Design, Setting, and Participants This quantitative, intensive, longitudinal cohort study recruited 1743 participants from 3 sites from February 20, 2020, to February 28, 2021. Data were provided before and within the second lockdown of the COVID-19 pandemic in Germany: before lockdown (October 2 to November 1, 2020); light lockdown (November 2 to December 15, 2020); and hard lockdown (December 16, 2020, to February 28, 2021). Main Outcomes and Measures Daily ratings of AC (main outcome) captured during 3 lockdown phases (main variable) and temporal (weekends and holidays) and psychological (social isolation and drinking intention) correlates. Results Of the 1743 screened participants, 189 (119 [63.0%] male; median [IQR] age, 37 [27.5-52.0] years) with at least 2 alcohol use disorder (AUD) criteria according to the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) yet without the need for medically supervised alcohol withdrawal were included. These individuals provided 14 694 smartphone ratings from October 2020 through February 2021. Multilevel modeling revealed significantly higher AC (grams of alcohol per day) on weekend days vs weekdays (β = 11.39; 95% CI, 10.00-12.77; P < .001). Alcohol consumption was above the overall average on Christmas (β = 26.82; 95% CI, 21.87-31.77; P < .001) and New Year’s Eve (β = 66.88; 95% CI, 59.22-74.54; P < .001). During the hard lockdown, perceived social isolation was significantly higher (β = 0.12; 95% CI, 0.06-0.15; P < .001), but AC was significantly lower (β = −5.45; 95% CI, −8.00 to −2.90; P = .001). Independent of lockdown, intention to drink less alcohol was associated with lower AC (β = −11.10; 95% CI, −13.63 to −8.58; P < .001). Notably, differences in AC between weekend and weekdays decreased both during the hard lockdown (β = −6.14; 95% CI, −9.96 to −2.31; P = .002) and in participants with severe AUD (β = −6.26; 95% CI, −10.18 to −2.34; P = .002). Conclusions and Relevance This 5-month cohort study found no immediate negative associations of lockdown measures with overall AC. Rather, weekend-weekday and holiday AC patterns exceeded lockdown effects. Differences in AC between weekend days and weekdays evinced that weekend drinking cycles decreased as a function of AUD severity and lockdown measures, indicating a potential mechanism of losing and regaining control. This finding suggests that temporal patterns and drinking intention constitute promising targets for prevention and intervention, even in high-risk individuals. Y1 - 2022 U6 - https://doi.org/10.1001/jamanetworkopen.2022.24641 SN - 2574-3805 VL - 5 SP - 1 EP - 11 PB - JAMA Network / American Medical Association CY - Chicago, Illinois, USA ET - 8 ER - TY - GEN A1 - Deeken, Friederike A1 - Reichert, Markus A1 - Zech, Hilmar A1 - Wenzel, Julia A1 - Wedemeyer, Friederike A1 - Aguilera, Alvaro A1 - Aslan, Acelya A1 - Bach, Patrick A1 - Bahr, Nadja Samia A1 - Ebrahimi, Claudia A1 - Fischbach, Pascale Christine A1 - Ganz, Marvin A1 - Garbusow, Maria A1 - Großkopf, Charlotte M. A1 - Heigert, Marie A1 - Hentschel, Angela A1 - Karl, Damian A1 - Pelz, Patricia A1 - Pinger, Mathieu A1 - Riemerschmid, Carlotta A1 - Rosenthal, Annika A1 - Steffen, Johannes A1 - Strehle, Jens A1 - Weiss, Franziska A1 - Wieder, Gesine A1 - Wieland, Alfred A1 - Zaiser, Judith A1 - Zimmermann, Sina A1 - Walter, Henrik A1 - Lenz, Bernd A1 - Deserno, Lorenz A1 - Smolka, Michael N. A1 - Liu, Shuyan A1 - Ebner-Priemer, Ulrich Walter A1 - Heinz, Andreas A1 - Rapp, Michael A. T1 - Patterns of Alcohol Consumption Among Individuals With Alcohol Use Disorder During the COVID-19 Pandemic and Lockdowns in Germany T2 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe N2 - Importance Alcohol consumption (AC) leads to death and disability worldwide. Ongoing discussions on potential negative effects of the COVID-19 pandemic on AC need to be informed by real-world evidence. Objective To examine whether lockdown measures are associated with AC and consumption-related temporal and psychological within-person mechanisms. Design, Setting, and Participants This quantitative, intensive, longitudinal cohort study recruited 1743 participants from 3 sites from February 20, 2020, to February 28, 2021. Data were provided before and within the second lockdown of the COVID-19 pandemic in Germany: before lockdown (October 2 to November 1, 2020); light lockdown (November 2 to December 15, 2020); and hard lockdown (December 16, 2020, to February 28, 2021). Main Outcomes and Measures Daily ratings of AC (main outcome) captured during 3 lockdown phases (main variable) and temporal (weekends and holidays) and psychological (social isolation and drinking intention) correlates. Results Of the 1743 screened participants, 189 (119 [63.0%] male; median [IQR] age, 37 [27.5-52.0] years) with at least 2 alcohol use disorder (AUD) criteria according to the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) yet without the need for medically supervised alcohol withdrawal were included. These individuals provided 14 694 smartphone ratings from October 2020 through February 2021. Multilevel modeling revealed significantly higher AC (grams of alcohol per day) on weekend days vs weekdays (β = 11.39; 95% CI, 10.00-12.77; P < .001). Alcohol consumption was above the overall average on Christmas (β = 26.82; 95% CI, 21.87-31.77; P < .001) and New Year’s Eve (β = 66.88; 95% CI, 59.22-74.54; P < .001). During the hard lockdown, perceived social isolation was significantly higher (β = 0.12; 95% CI, 0.06-0.15; P < .001), but AC was significantly lower (β = −5.45; 95% CI, −8.00 to −2.90; P = .001). Independent of lockdown, intention to drink less alcohol was associated with lower AC (β = −11.10; 95% CI, −13.63 to −8.58; P < .001). Notably, differences in AC between weekend and weekdays decreased both during the hard lockdown (β = −6.14; 95% CI, −9.96 to −2.31; P = .002) and in participants with severe AUD (β = −6.26; 95% CI, −10.18 to −2.34; P = .002). Conclusions and Relevance This 5-month cohort study found no immediate negative associations of lockdown measures with overall AC. Rather, weekend-weekday and holiday AC patterns exceeded lockdown effects. Differences in AC between weekend days and weekdays evinced that weekend drinking cycles decreased as a function of AUD severity and lockdown measures, indicating a potential mechanism of losing and regaining control. This finding suggests that temporal patterns and drinking intention constitute promising targets for prevention and intervention, even in high-risk individuals. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 805 Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-571460 SN - 1866-8364 IS - 805 ER -