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The reinforcing effect of boehmite nanoparticles (BNP) in epoxy resins for fiber composite lightweight construction is related to the formation of a soft but bound interphase between filler and polymer. The interphase is able to dissipate crack propagation energy and consequently increases the fracture toughness of the epoxy resin. Usually, the nanoparticles are dispersed in the resin and then mixed with the hardener to form an applicable mixture to impregnate the fibers. If one wishes to locally increase the fracture toughness at particularly stressed positions of the fiber-reinforced polymer composites (FRPC), this could be done by spraying nanoparticles from a suspension. However, this would entail high costs for removing the nanoparticles from the ambient air. We propose that a fiber fleece containing bound nanoparticles be inserted at exposed locations. For the present proof-of-concept study, an electrospun polycarbonate nonwoven and taurine modified BNP are proposed. After fabrication of suitable PC/EP/BNP composites, the thermomechanical properties were tested by dynamic mechanical analysis (DMA). Comparatively, the local nanomechanical properties such as stiffness and elastic modulus were determined by atomic force microscopy (AFM). An additional investigation of the distribution of the nanoparticles in the epoxy matrix, which is a prerequisite for an effective nanocomposite, is carried out by scanning electron microscopy in transmission mode (TSEM). From the results it can be concluded that the concept of carrier fibers for nanoparticles is viable.
Natalia Cano Murillo; Media Ghasem Zadeh Khorasani; Dorothee Silbernagl; Farnaz Emamverdi; Karen Cacua; Vasile-Dan Hodoroaba; Heinz Sturm. Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin. Nanomaterials 2021, 11, 1591 .
AMA StyleNatalia Cano Murillo, Media Ghasem Zadeh Khorasani, Dorothee Silbernagl, Farnaz Emamverdi, Karen Cacua, Vasile-Dan Hodoroaba, Heinz Sturm. Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin. Nanomaterials. 2021; 11 (6):1591.
Chicago/Turabian StyleNatalia Cano Murillo; Media Ghasem Zadeh Khorasani; Dorothee Silbernagl; Farnaz Emamverdi; Karen Cacua; Vasile-Dan Hodoroaba; Heinz Sturm. 2021. "Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin." Nanomaterials 11, no. 6: 1591.
The reinforcing effect of boehmite nanoparticles (BNP) in epoxy resins for fiber composite lightweight construction is related to the formation of a soft but bound interphase between filler and polymer. The interphase is able to dissipate crack propagation energy and consequently increases the fracture toughness of the epoxy resin. Usually, the nanoparticles are dispersed in the resin and then mixed with the hardener to form an applicable mixture to impregnate the fibers. If one wishes to locally increase the fracture toughness at particularly stressed positions of the fiber-reinforced polymer composites (FRPC), this could be done by spraying nanoparticles from a suspension. However, this would entail high costs for removing the nanoparticles from the ambient air. We propose that a fiber fleece containing bound nanoparticles be inserted at exposed locations. For the present proof-of-concept study, an electrospun polycarbonate nonwoven and taurine modified BNP are proposed. After fabrication of suitable PC/EP/BNP composites, the thermomechanical properties were tested by dynamic mechanical analysis (DMTA). Comparatively, the local nano-mechanical properties such as stiffness and elastic modulus were determined by atomic force microscopy (AFM). An additional investigation of the distribution of the nanoparticles in the epoxy matrix, which is a prerequisite for an effective nanocomposite, is carried out by scanning electron microscopy in transmission mode (TSEM). From the results it can be concluded that the concept of carrier fibers for nanoparticles is viable.
Natalia Cano Murillo; Media Ghasem Zadeh Khorasani; Dorothee Silbernagl; Farnaz Emamverdi; Karen Cacua; Vasile-Dan Hodoroaba; Heinz Sturm. Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin. 2021, 1 .
AMA StyleNatalia Cano Murillo, Media Ghasem Zadeh Khorasani, Dorothee Silbernagl, Farnaz Emamverdi, Karen Cacua, Vasile-Dan Hodoroaba, Heinz Sturm. Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin. . 2021; ():1.
Chicago/Turabian StyleNatalia Cano Murillo; Media Ghasem Zadeh Khorasani; Dorothee Silbernagl; Farnaz Emamverdi; Karen Cacua; Vasile-Dan Hodoroaba; Heinz Sturm. 2021. "Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin." , no. : 1.
The enhancing effect on mechanical properties of boehmite (γ-AlOOH) nanoparticles (BNP) in epoxy-based nanocomposites on the macroscopic scale encouraged recent research to investigate the micro- and nanoscopic properties. Several studies presented different aspects relatable to an alteration of the epoxy polymer network formation by the BNP with need for further experiments to identify the mode of action. With FTIR-spectroscopic methods this study identifies interactions of the BNP with the epoxy polymer matrix during the curing process as well as in the cured nanocomposite. The data reveals that not the BNP themselves, but the water released from them strongly influences the curing process by hydrolysis of the anhydride hardener or protonation of the amine accelerator. The changes of the curing processes are discussed in detail. The changes of the curing processes enable new explanation for the changed material properties by BNP discussed in recent research like a lowered glass transition temperature region (Tg) and an interphase formation.
Tassilo Waniek; Ulrike Braun; Dorothee Silbernagl; Heinz Sturm. The impact of water released from boehmite nanoparticles during curing in epoxy‐based nanocomposites. Journal of Applied Polymer Science 2021, 138, 51006 .
AMA StyleTassilo Waniek, Ulrike Braun, Dorothee Silbernagl, Heinz Sturm. The impact of water released from boehmite nanoparticles during curing in epoxy‐based nanocomposites. Journal of Applied Polymer Science. 2021; 138 (39):51006.
Chicago/Turabian StyleTassilo Waniek; Ulrike Braun; Dorothee Silbernagl; Heinz Sturm. 2021. "The impact of water released from boehmite nanoparticles during curing in epoxy‐based nanocomposites." Journal of Applied Polymer Science 138, no. 39: 51006.
In this work the flexural rigidity of individual large diameter multi-walled carbon nanotubes (MWCNTs) was investigated. The bending modulus were obtained by detecting the resonance frequencies of mechanically excited cantilevered carbon nanotubes using the so-called dynamic scanning electron microscopy technique, and applying the Euler–Bernoulli beam theory. For the nanotubes studied, we determined a modulus of up to 160 GPa. This agrees with values reported by other authors for MWCNTs produced by catalytic chemical vapor deposition, however, it is 6-8 times smaller than values reported for single and multi-walled carbon nanotubes produced by arc-discharge synthesis. Toxicological studies with carbon nanotubes have been showing that inhaled airborne nanofibers that reach the deep airways of the respiratory system may lead to serious, asbestos-like lung diseases. These studies suggested that their toxicity critically depends on the fiber flexural rigidity, with high rigidity causing cell lesions. To complement the correlation between observed toxicological effects and fiber rigidities, reliable and routinely applicable measurement techniques for the flexural rigidity of nanofibers are required.
Renata Fortini; Asmus Meyer-Plath; Dominic Kehren; Ulrich Gernert; Leonardo Agudo Jácome; Heinz Sturm. Measurement of Flexural Rigidity of Multi-Walled Carbon Nanotubes by Dynamic Scanning Electron Microscopy. Fibers 2020, 8, 31 .
AMA StyleRenata Fortini, Asmus Meyer-Plath, Dominic Kehren, Ulrich Gernert, Leonardo Agudo Jácome, Heinz Sturm. Measurement of Flexural Rigidity of Multi-Walled Carbon Nanotubes by Dynamic Scanning Electron Microscopy. Fibers. 2020; 8 (5):31.
Chicago/Turabian StyleRenata Fortini; Asmus Meyer-Plath; Dominic Kehren; Ulrich Gernert; Leonardo Agudo Jácome; Heinz Sturm. 2020. "Measurement of Flexural Rigidity of Multi-Walled Carbon Nanotubes by Dynamic Scanning Electron Microscopy." Fibers 8, no. 5: 31.
Ectoine is a small zwitterionic osmolyte and compatible solute, which interacts with DNA and modifies ultraviolet radiation damage to DNA.
Marc Benjamin Hahn; Glen Smales; Harald Seitz; Tihomir Solomun; Heinz Sturm. Ectoine interaction with DNA: influence on ultraviolet radiation damage. Physical Chemistry Chemical Physics 2020, 22, 6984 -6992.
AMA StyleMarc Benjamin Hahn, Glen Smales, Harald Seitz, Tihomir Solomun, Heinz Sturm. Ectoine interaction with DNA: influence on ultraviolet radiation damage. Physical Chemistry Chemical Physics. 2020; 22 (13):6984-6992.
Chicago/Turabian StyleMarc Benjamin Hahn; Glen Smales; Harald Seitz; Tihomir Solomun; Heinz Sturm. 2020. "Ectoine interaction with DNA: influence on ultraviolet radiation damage." Physical Chemistry Chemical Physics 22, no. 13: 6984-6992.
Mechanical flexibility in single crystals of covalently bound materials is a fascinating and poorly understood phenomenon. We present here the first example of a plastically flexible one‐dimensional (1D) coordination polymer. The compound [Zn(μ‐Cl)2(3,5‐dichloropyridine)2]n is flexible over two crystallographic faces. Remarkably, the single crystal remains intact when bent to 180°. A combination of microscopy, diffraction, and spectroscopic studies have been used to probe the structural response of the crystal lattice to mechanical bending. Deformation of the covalent polymer chains does not appear to be responsible for the observed macroscopic bending. Instead, our results suggest that mechanical bending occurs by displacement of the coordination polymer chains. Based on experimental and theoretical evidence, we propose a new model for mechanical flexibility in 1D coordination polymers. Moreover, our calculations propose a cause of the different mechanical properties of this compound and a structurally similar elastic material.
Biswajit Bhattacharya; Adam A. L. Michalchuk; Dorothee Silbernagl; Max Rautenberg; Thomas Schmid; Torvid Feiler; Dr. Klaus Reimann; Ahmed Ghalgaoui; Dr. Heinz Sturm; Dr. Beate Paulus; Priv.‐Doz. Dr. Franziska Emmerling. A Mechanistic Perspective on Plastically Flexible Coordination Polymers. Angewandte Chemie International Edition 2019, 59, 5557 -5561.
AMA StyleBiswajit Bhattacharya, Adam A. L. Michalchuk, Dorothee Silbernagl, Max Rautenberg, Thomas Schmid, Torvid Feiler, Dr. Klaus Reimann, Ahmed Ghalgaoui, Dr. Heinz Sturm, Dr. Beate Paulus, Priv.‐Doz. Dr. Franziska Emmerling. A Mechanistic Perspective on Plastically Flexible Coordination Polymers. Angewandte Chemie International Edition. 2019; 59 (14):5557-5561.
Chicago/Turabian StyleBiswajit Bhattacharya; Adam A. L. Michalchuk; Dorothee Silbernagl; Max Rautenberg; Thomas Schmid; Torvid Feiler; Dr. Klaus Reimann; Ahmed Ghalgaoui; Dr. Heinz Sturm; Dr. Beate Paulus; Priv.‐Doz. Dr. Franziska Emmerling. 2019. "A Mechanistic Perspective on Plastically Flexible Coordination Polymers." Angewandte Chemie International Edition 59, no. 14: 5557-5561.
Die mechanische Flexibilität von kovalenten Einkristallen ist ein faszinierendes und wenig verstandenes Phänomen. Wir stellen hier das erste Beispiel eines plastisch flexiblen 1D‐Koordinationspolymers vor. Die Verbindung [Zn(μ‐Cl)2(3,5‐Cl2Py)2]n ist über zwei kristallographische Flächen flexibel und bleibt bemerkenswerterweise auch bei 180° Biegung als Einkristall intakt. Mittels einer Kombination von Mikroskopie‐, Beugungs‐ und spektroskopischen Methoden untersuchen wir die strukturelle Reaktion des Kristallgitters auf mechanische Verformung. Laut den Ergebnissen scheint nicht die Deformation der kovalenten Polymerketten für die beobachtete makroskopische Biegung verantwortlich, sondern eine Verschiebung der Koordinationspolymerketten. Basierend auf experimentellen und theoretischen Erkenntnissen schlagen wir ein neues Modell für die mechanische Flexibilität von 1D‐Koordinationspolymeren vor. Darüber hinaus liefern unsere Berechnungen eine Ursache für die unterschiedlichen mechanischen Eigenschaften dieser Verbindung und eines strukturell ähnlichen elastisches Materials.
Biswajit Bhattacharya; Adam A. L. Michalchuk; Dorothee Silbernagl; Max Rautenberg; Thomas Schmid; Torvid Feiler; Klaus Reimann; Ahmed Ghalgaoui; Dr. Heinz Sturm; Dr. Beate Paulus; Priv.‐Doz. Dr. Franziska Emmerling. Ein mechanistischer Blick auf plastisch flexible Koordinationspolymere. Angewandte Chemie 2019, 132, 5602 -5607.
AMA StyleBiswajit Bhattacharya, Adam A. L. Michalchuk, Dorothee Silbernagl, Max Rautenberg, Thomas Schmid, Torvid Feiler, Klaus Reimann, Ahmed Ghalgaoui, Dr. Heinz Sturm, Dr. Beate Paulus, Priv.‐Doz. Dr. Franziska Emmerling. Ein mechanistischer Blick auf plastisch flexible Koordinationspolymere. Angewandte Chemie. 2019; 132 (14):5602-5607.
Chicago/Turabian StyleBiswajit Bhattacharya; Adam A. L. Michalchuk; Dorothee Silbernagl; Max Rautenberg; Thomas Schmid; Torvid Feiler; Klaus Reimann; Ahmed Ghalgaoui; Dr. Heinz Sturm; Dr. Beate Paulus; Priv.‐Doz. Dr. Franziska Emmerling. 2019. "Ein mechanistischer Blick auf plastisch flexible Koordinationspolymere." Angewandte Chemie 132, no. 14: 5602-5607.
Understanding the interaction between boehmite and epoxy and the formation of their interphases with different mechanical and chemical structures is crucial to predict and optimize the properties of epoxy-boehmite nanocomposites. Probing the interfacial properties with atomic force microscopy (AFM)-based methods, especially particle-matrix long-range interactions, is challenging. This is due to size limitations of various analytical methods in resolving nanoparticles and their interphases, the overlap of interphases, and the effect of buried particles that prevent the accurate interphase property measurement. Here, we develop a layered model system in which the epoxy is cured in contact with a thin layer of hydrothermally synthesized boehmite. Different microscopy methods are employed to evaluate the interfacial properties. With intermodulation atomic force microscopy (ImAFM) and amplitude dependence force spectroscopy (ADFS), which contain information about stiffness, electrostatic, and van der Waals forces, a soft interphase was detected between the epoxy and boehmite. Surface potential maps obtained by scanning Kelvin probe microscopy (SKPM) revealed another interphase about one order of magnitude larger than the mechanical interphase. The AFM-infrared spectroscopy (AFM-IR) technique reveals that the soft interphase consists of unreacted curing agent. The long-range electrical interphase is attributed to the chemical alteration of the bulk epoxy and the formation of new absorption bands.
Media Ghasem Zadeh Khorasani; Anna-Maria Elert; Vasile-Dan Hodoroaba; Leonardo Agudo Jácome; Korinna Altmann; Dorothee Silbernagl; Heinz Sturm. Short- and Long-Range Mechanical and Chemical Interphases Caused by Interaction of Boehmite (γ-AlOOH) with Anhydride-Cured Epoxy Resins. Nanomaterials 2019, 9, 853 .
AMA StyleMedia Ghasem Zadeh Khorasani, Anna-Maria Elert, Vasile-Dan Hodoroaba, Leonardo Agudo Jácome, Korinna Altmann, Dorothee Silbernagl, Heinz Sturm. Short- and Long-Range Mechanical and Chemical Interphases Caused by Interaction of Boehmite (γ-AlOOH) with Anhydride-Cured Epoxy Resins. Nanomaterials. 2019; 9 (6):853.
Chicago/Turabian StyleMedia Ghasem Zadeh Khorasani; Anna-Maria Elert; Vasile-Dan Hodoroaba; Leonardo Agudo Jácome; Korinna Altmann; Dorothee Silbernagl; Heinz Sturm. 2019. "Short- and Long-Range Mechanical and Chemical Interphases Caused by Interaction of Boehmite (γ-AlOOH) with Anhydride-Cured Epoxy Resins." Nanomaterials 9, no. 6: 853.
In this work, a novel boehmite (BA)-embedded organic/inorganic nanocomposite coating based on cycloaliphatic epoxy oligosiloxane (CEOS) resin was fabricated applying UV-induced cationic polymerization. The main changes of the material behavior caused by the nanofiller were investigated with regard to its photocuring kinetics, thermal stability, and glass transition. The role of the particle surface was of particular interest, thus, unmodified nanoparticles (HP14) and particles modified with p-toluenesulfonic acid (OS1) were incorporated into a CEOS matrix in the concentration range of 1–10 wt.%. Resulting nanocomposites exhibited improved thermal properties, with the glass transition temperature (Tg) being shifted from 30 °C for unfilled CEOS to 54 °C (2 wt.% HP14) and 73 °C (2 wt.% OS1) for filled CEOS. Additionally, TGA analysis showed increased thermal stability of samples filled with nanoparticles. An attractive interaction between boehmite and CEOS matrix influenced the curing. Real-time infrared spectroscopy (RT-IR) experiments demonstrated that the epoxide conversion rate of nanocomposites was slightly increased compared to neat resin. The beneficial role of the BA can be explained by the participation of hydroxyl groups at the particle surface in photopolymerization processes and by the complementary contribution of p-toluenesulfonic acid surface modifier and water molecules introduced into the system with nanoparticles.
Ievgeniia Topolniak; Vasile-Dan Hodoroaba; Dietmar Pfeifer; Ulrike Braun; Heinz Sturm. Boehmite Nanofillers in Epoxy Oligosiloxane Resins: Influencing the Curing Process by Complex Physical and Chemical Interactions. Materials 2019, 12, 1513 .
AMA StyleIevgeniia Topolniak, Vasile-Dan Hodoroaba, Dietmar Pfeifer, Ulrike Braun, Heinz Sturm. Boehmite Nanofillers in Epoxy Oligosiloxane Resins: Influencing the Curing Process by Complex Physical and Chemical Interactions. Materials. 2019; 12 (9):1513.
Chicago/Turabian StyleIevgeniia Topolniak; Vasile-Dan Hodoroaba; Dietmar Pfeifer; Ulrike Braun; Heinz Sturm. 2019. "Boehmite Nanofillers in Epoxy Oligosiloxane Resins: Influencing the Curing Process by Complex Physical and Chemical Interactions." Materials 12, no. 9: 1513.
Understanding the interaction between nanoparticles and the matrix and the properties of interphase is crucial to predict the macroscopic properties of a nanocomposite system. Here, we investigate the interaction between boehmite nanoparticles (BNPs) and epoxy using different atomic force microscopy (AFM) approaches. We demonstrate benefits of using multifrequency intermodulation AFM (ImAFM) to obtain information about conservative, dissipative and van der Waals tip-surface forces and probing local properties of nanoparticles, matrix and the interphase. We utilize scanning kelvin probe microscopy (SKPM) to probe surface potential as a tool to visualize material contrast with a physical parameter, which is independent from the mechanics of the surface. Combining the information from ImAFM stiffness and SKPM surface potential results in a precise characterization of interfacial region, demonstrating that the interphase is softer than epoxy and boehmite nanoparticles. Further, we investigated the effect of boehmite nanoparticles on the bulk properties of epoxy matrix. ImAFM stiffness maps revealed the significant stiffening effect of boehmite nanoparticles on anhydride-cured epoxy matrix. The energy dissipation of epoxy matrix locally measured by ImAFM shows a considerable increase compared to that of neat epoxy. These measurements suggest a substantial alteration of epoxy structure induced by the presence of boehmite.
Media Ghasem Zadeh Khorasani; Dorothee Silbernagl; Daniel Platz; Heinz Sturm. Insights into Nano-Scale Physical and Mechanical Properties of Epoxy/Boehmite Nanocomposite Using Different AFM Modes. Polymers 2019, 11, 235 .
AMA StyleMedia Ghasem Zadeh Khorasani, Dorothee Silbernagl, Daniel Platz, Heinz Sturm. Insights into Nano-Scale Physical and Mechanical Properties of Epoxy/Boehmite Nanocomposite Using Different AFM Modes. Polymers. 2019; 11 (2):235.
Chicago/Turabian StyleMedia Ghasem Zadeh Khorasani; Dorothee Silbernagl; Daniel Platz; Heinz Sturm. 2019. "Insights into Nano-Scale Physical and Mechanical Properties of Epoxy/Boehmite Nanocomposite Using Different AFM Modes." Polymers 11, no. 2: 235.
In recent years, an increasing trend towards investigating and monitoring the contamination of the environment by microplastics (MP) (plastic pieces < 5 mm) has been observed worldwide. Nonetheless, a reliable methodology that would facilitate and automate the monitoring of MP is still lacking. With the goal of selecting practical and standardized methods, and considering the challenges in microplastics detection, we present here a critical evaluation of two vibrational spectroscopies, Raman and Fourier transform infrared (FTIR) spectroscopy, and two extraction methods: thermal extraction desorption gas chromatography mass spectrometry (TED-GC-MS) and liquid extraction with subsequent size exclusion chromatography (SEC) using a soil with known contents of PE, PP, PS and PET as reference material. The obtained results were compared in terms of measurement time, technique handling, detection limits and requirements for sample preparation. The results showed that in designing and selecting the right methodology, the scientific question that determines what needs to be understood is significant, and should be considered carefully prior to analysis. Depending on whether the object of interest is quantification of the MP particles in the sample, or merely a quick estimate of sample contamination with plastics, the appropriate method must be selected. To obtain overall information about MP in environmental samples, the combination of several parallel approaches should be considered.
Anna M. Elert; Roland Becker; Erik Duemichen; Paul Eisentraut; Jana Falkenhagen; Heinz Sturm; Ulrike Braun. Comparison of different methods for MP detection: What can we learn from them, and why asking the right question before measurements matters? Environmental Pollution 2017, 231, 1256 -1264.
AMA StyleAnna M. Elert, Roland Becker, Erik Duemichen, Paul Eisentraut, Jana Falkenhagen, Heinz Sturm, Ulrike Braun. Comparison of different methods for MP detection: What can we learn from them, and why asking the right question before measurements matters? Environmental Pollution. 2017; 231 ():1256-1264.
Chicago/Turabian StyleAnna M. Elert; Roland Becker; Erik Duemichen; Paul Eisentraut; Jana Falkenhagen; Heinz Sturm; Ulrike Braun. 2017. "Comparison of different methods for MP detection: What can we learn from them, and why asking the right question before measurements matters?" Environmental Pollution 231, no. : 1256-1264.
Ectoine plays an important role in protecting biomolecules and entire cells against environmental stressors such as salinity, freezing, drying and high temperatures. Recent studies revealed that ectoine also provides effective protection for human skin cells from damage caused by UV-A radiation. These protective properties make ectoine a valuable compound and it is applied as an active ingredient in numerous pharmaceutical devices and cosmetics. Interestingly, the underlying mechanism resulting in protecting cells from radiation is not yet fully understood. Here we present a study on ectoine and its protective influence on DNA during electron irradiation. Applying gel electrophoresis and atomic force microscopy, we demonstrate for the first time that ectoine prevents DNA strand breaks caused by ionizing electron radiation. The results presented here point to future applications of ectoine for instance in cancer radiation therapy.
M.- A. Schröter; S. Meyer; M. B. Hahn; T. Solomun; H. Sturm; H. J. Kunte. Ectoine protects DNA from damage by ionizing radiation. Scientific Reports 2017, 7, 1 -7.
AMA StyleM.- A. Schröter, S. Meyer, M. B. Hahn, T. Solomun, H. Sturm, H. J. Kunte. Ectoine protects DNA from damage by ionizing radiation. Scientific Reports. 2017; 7 (1):1-7.
Chicago/Turabian StyleM.- A. Schröter; S. Meyer; M. B. Hahn; T. Solomun; H. Sturm; H. J. Kunte. 2017. "Ectoine protects DNA from damage by ionizing radiation." Scientific Reports 7, no. 1: 1-7.
The chemical characteristics of two different types of laser-induced periodic surface structures (LIPSS), so-called high and low spatial frequency LIPSS (HSFL and LSFL), formed upon irradiation of titanium surfaces by multiple femtosecond laser pulses in air (30 fs, 790 nm, 1 kHz), are analyzed by various optical and electron beam based surface analytical techniques, including micro-Raman spectroscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The latter method was employed in a high-resolution mode being capable of spatially resolving even the smallest HSFL structures featuring spatial periods below 100 nm. In combination with an ion sputtering technique, depths-resolved chemical information of superficial oxidation processes was obtained, revealing characteristic differences between the two different types of LIPSS. Our results indicate that a few tens of nanometer shallow HSFL are formed on top of a ∼150 nm thick graded superficial oxide layer without sharp interfaces, consisting of amorphous TiO2 and partially crystallized Ti2O3. The larger LSFL structures with periods close to the irradiation wavelength originate from the laser-interaction with metallic titanium. They are covered by a ∼200 nm thick amorphous oxide layer, which consists mainly of TiO2 (at the surface) and other titanium oxide species of lower oxidation states underneath.
Sabrina V. Kirner; Thomas Wirth; Heinz Sturm; Jörg Krüger; Jörn Bonse. Nanometer-resolved chemical analyses of femtosecond laser-induced periodic surface structures on titanium. Journal of Applied Physics 2017, 122, 104901 .
AMA StyleSabrina V. Kirner, Thomas Wirth, Heinz Sturm, Jörg Krüger, Jörn Bonse. Nanometer-resolved chemical analyses of femtosecond laser-induced periodic surface structures on titanium. Journal of Applied Physics. 2017; 122 (10):104901.
Chicago/Turabian StyleSabrina V. Kirner; Thomas Wirth; Heinz Sturm; Jörg Krüger; Jörn Bonse. 2017. "Nanometer-resolved chemical analyses of femtosecond laser-induced periodic surface structures on titanium." Journal of Applied Physics 122, no. 10: 104901.
Ectoine, a compatible solute and osmolyte, is known to be an effective protectant of biomolecules and whole cells against heating, freezing and extreme salinity.
Marc Benjamin Hahn; Susann Meyer; Maria-Astrid Schröter; Hans Jörg Kunte; Tihomir Solomun; Heinz Sturm. DNA protection by ectoine from ionizing radiation: molecular mechanisms. Physical Chemistry Chemical Physics 2017, 19, 25717 -25722.
AMA StyleMarc Benjamin Hahn, Susann Meyer, Maria-Astrid Schröter, Hans Jörg Kunte, Tihomir Solomun, Heinz Sturm. DNA protection by ectoine from ionizing radiation: molecular mechanisms. Physical Chemistry Chemical Physics. 2017; 19 (37):25717-25722.
Chicago/Turabian StyleMarc Benjamin Hahn; Susann Meyer; Maria-Astrid Schröter; Hans Jörg Kunte; Tihomir Solomun; Heinz Sturm. 2017. "DNA protection by ectoine from ionizing radiation: molecular mechanisms." Physical Chemistry Chemical Physics 19, no. 37: 25717-25722.
Strand breaks and conformational changes of DNA have consequences for the physiological role of DNA. The natural protecting molecule ectoine is beneficial to entire bacterial cells and biomolecules such as proteins by mitigating detrimental effects of environmental stresses. It was postulated that ectoine-like molecules bind to negatively charged spheres that mimic DNA surfaces. We investigated the effect of ectoine on DNA and whether ectoine is able to protect DNA from damages caused by ultraviolet radiation (UV-A). In order to determine different isoforms of DNA, agarose gel electrophoresis and atomic force microscopy experiments were carried out with plasmid pUC19 DNA. Our quantitative results revealed that a prolonged incubation of DNA with ectoine leads to an increase in transitions from supercoiled (undamaged) to open circular (single-strand break) conformation at pH 6.6. The effect is pH dependent and no significant changes were observed at physiological pH of 7.5. After UV-A irradiation in ectoine solution, changes in DNA conformation were even more pronounced and this effect was pH dependent. We hypothesize that ectoine is attracted to the negatively charge surface of DNA at lower pH and therefore fails to act as a stabilizing agent for DNA in our in vitro experiments.
S. Meyer; M.-A. Schröter; Marc Benjamin Hahn; T. Solomun; H. Sturm; H. J. Kunte. Ectoine can enhance structural changes in DNA in vitro. Scientific Reports 2017, 7, 1 -10.
AMA StyleS. Meyer, M.-A. Schröter, Marc Benjamin Hahn, T. Solomun, H. Sturm, H. J. Kunte. Ectoine can enhance structural changes in DNA in vitro. Scientific Reports. 2017; 7 (1):1-10.
Chicago/Turabian StyleS. Meyer; M.-A. Schröter; Marc Benjamin Hahn; T. Solomun; H. Sturm; H. J. Kunte. 2017. "Ectoine can enhance structural changes in DNA in vitro." Scientific Reports 7, no. 1: 1-10.
The determination of the microscopic dose-damage relationship for DNA in an aqueous environment is of a fundamental interest for dosimetry and applications in radiation therapy and protection. We combine geant4 particle-scattering simulations in water with calculations concerning the movement of biomolecules to obtain the energy deposit in the biologically relevant nanoscopic volume. We juxtaposition these results to the experimentally determined damage to obtain the dose-damage relationship at a molecular level. This approach is tested for an experimentally challenging system concerning the direct irradiation of plasmid DNA (pUC19) in water with electrons as primary particles. Here a microscopic target model for the plasmid DNA based on the relation of lineal energy and radiation quality is used to calculate the effective target volume. It was found that on average fewer than two ionizations within a 7.5-nm radius around the sugar-phosphate backbone are sufficient to cause a single strand break, with a corresponding median lethal energy deposit being E1/2=6±4 eV. The presented method is applicable for ionizing radiation (e.g., γ rays, x rays, and electrons) and a variety of targets, such as DNA, proteins, or cells.
Marc Benjamin Hahn; Susann Meyer; Hans-Jörg Kunte; Tihomir Solomun; Heinz Sturm. Measurements and simulations of microscopic damage to DNA in water by 30 keV electrons: A general approach applicable to other radiation sources and biological targets. Physical Review E 2017, 95, 052419 -052419.
AMA StyleMarc Benjamin Hahn, Susann Meyer, Hans-Jörg Kunte, Tihomir Solomun, Heinz Sturm. Measurements and simulations of microscopic damage to DNA in water by 30 keV electrons: A general approach applicable to other radiation sources and biological targets. Physical Review E. 2017; 95 (5):052419-052419.
Chicago/Turabian StyleMarc Benjamin Hahn; Susann Meyer; Hans-Jörg Kunte; Tihomir Solomun; Heinz Sturm. 2017. "Measurements and simulations of microscopic damage to DNA in water by 30 keV electrons: A general approach applicable to other radiation sources and biological targets." Physical Review E 95, no. 5: 052419-052419.
Intumescent coatings have been used for fire protection of steel for decades, but there is still a need for improvement and adaptation. The key parameters of such coatings in a fire scenario are thermal insulation, foaming dynamics, and cohesion. The fire resistance tests, large furnaces applying the standard time temperature (STT) curve, demand coated full-scale components or intermediate-scale specimen. The STT Mufu+ (standard time temperature muffle furnace+) approach is presented. It is a recently developed bench-scale testing method to analyze the performance of intumescent coatings. The STT Mufu+ provides vertical testing of specimens with reduced specimen size according to the STT curve. During the experiment, the foaming process is observed with a high-temperature endoscope. Characteristics of this technique like reproducibility and resolution are presented and discussed. The STT Mufu+ test is highly efficient in comparison to common tests because of the reduced sample size. Its potential is extended to a superior research tool by combining it with advanced residue analysis (μ-computed tomography and scanning electron microscopy) and mechanical testing. The benefits of this combination are demonstrated by a case study on 4 intumescent coatings. The evaluation of all collected data is used to create performance-based rankings of the tested coatings.
Michael Morys; Bernhard Illerhaus; Heinz Sturm; Bernhard Schartel. Revealing the inner secrets of intumescence: Advanced standard time temperature oven (STT Mufu+ )-μ-computed tomography approach. Fire and Materials 2017, 41, 927 -939.
AMA StyleMichael Morys, Bernhard Illerhaus, Heinz Sturm, Bernhard Schartel. Revealing the inner secrets of intumescence: Advanced standard time temperature oven (STT Mufu+ )-μ-computed tomography approach. Fire and Materials. 2017; 41 (8):927-939.
Chicago/Turabian StyleMichael Morys; Bernhard Illerhaus; Heinz Sturm; Bernhard Schartel. 2017. "Revealing the inner secrets of intumescence: Advanced standard time temperature oven (STT Mufu+ )-μ-computed tomography approach." Fire and Materials 41, no. 8: 927-939.
In addition to the acid source, charring agent, and blowing agent, the binder is a crucial part of an intumescent coating. Its primary task is to bind all compounds, but it also acts as a carbon source and influences the foaming process. A series of intumescent coatings based on five different binders was investigated in terms of insulation, foaming, mechanical impact resistance, and residue morphology. The Standard Time-Temperature modified Muffle Furnace (STT MuFu+) was used for the bench-scale fire resistance tests and provided data on temperature and residue thickness as well as well-defined residues. The residue morphology was analyzed by nondestructive µ-computed tomography and scanning electron microscopy. A moderate influence of the binder on insulation performance was detected in the set of coatings investigated, whereas the foaming dynamics and thickness achieved were affected strongly. In addition, the inner structure of the residues showed a rich variety. High expansion alone did not guarantee good insulation. Furthermore, attention was paid to the relation between the microstructure transition induced by carbon loss due to thermo-oxidation of the char and the development of the thermal conductivity and thickness of the coatings during the fire test.
Michael Morys; Bernhard Illerhaus; Heinz Sturm; Bernhard Schartel. Size is not all that matters: Residue thickness and protection performance of intumescent coatings made from different binders. Journal of Fire Sciences 2017, 35, 284 -302.
AMA StyleMichael Morys, Bernhard Illerhaus, Heinz Sturm, Bernhard Schartel. Size is not all that matters: Residue thickness and protection performance of intumescent coatings made from different binders. Journal of Fire Sciences. 2017; 35 (4):284-302.
Chicago/Turabian StyleMichael Morys; Bernhard Illerhaus; Heinz Sturm; Bernhard Schartel. 2017. "Size is not all that matters: Residue thickness and protection performance of intumescent coatings made from different binders." Journal of Fire Sciences 35, no. 4: 284-302.
Maren Erdmann; Volker Trappe; Heinz Sturm; Ulrike Braun; Erik Duemichen. Cure conversion of structural epoxies by cure state analysis and in situ cure kinetics using nondestructive NIR spectroscopy. Thermochimica Acta 2017, 650, 8 -17.
AMA StyleMaren Erdmann, Volker Trappe, Heinz Sturm, Ulrike Braun, Erik Duemichen. Cure conversion of structural epoxies by cure state analysis and in situ cure kinetics using nondestructive NIR spectroscopy. Thermochimica Acta. 2017; 650 ():8-17.
Chicago/Turabian StyleMaren Erdmann; Volker Trappe; Heinz Sturm; Ulrike Braun; Erik Duemichen. 2017. "Cure conversion of structural epoxies by cure state analysis and in situ cure kinetics using nondestructive NIR spectroscopy." Thermochimica Acta 650, no. : 8-17.
Thermal insulation and mechanical resistance play a crucial role for the performance of an intumescent coating. Both properties depend strongly on the morphology and morphological development of the foamed residue. Small amounts (4 wt%) of fiberglass, clay and a copper salt, respectively, are incorporated into an intumescent coating to study their influence on the morphology and performance of the residues. The bench scale fire tests were performed on 75 × 75 × 2 mm coated steel plates according to the standard time–temperature curve in the Standard Time Temperature Muffle Furnace (STT Mufu). It provided information about foaming dynamics (expansion rates) and thermal insulation. Adding the copper salt halved the expansion height, whereas the clay and fiberglass change the height of the residue only moderately. The time to reach 500°C was improved by 31% for clay and 15% for the other two fillers. Nondestructive micro computed tomography is used to assess the inner structure of the residues. A transition of the residue from a black, carbonaceous foam with closed cells into an inorganic, residual open cell sponge occurs at high temperatures. This transition is due to a loss of carbon; the change in microstructure is analyzed by scanning electron microscopy. Additional mechanical tests are performed and interpreted with respect to the results of the morphology analysis. Adding clay or copper salt improved the mechanical resistance tested by a factor 4. The additives significantly influence the thickness and foaming dynamics as well as the inner structure of the residues, whereas their influence on insulation performance is moderate. In conclusion, different modes of action are observed to achieve similar insulation performance during the fire test.
Michael Morys; Bernhard Illerhaus; Heinz Sturm; Bernhard Schartel. Variation of Intumescent Coatings Revealing Different Modes of Action for Good Protection Performance. Fire Technology 2017, 53, 1569 -1587.
AMA StyleMichael Morys, Bernhard Illerhaus, Heinz Sturm, Bernhard Schartel. Variation of Intumescent Coatings Revealing Different Modes of Action for Good Protection Performance. Fire Technology. 2017; 53 (4):1569-1587.
Chicago/Turabian StyleMichael Morys; Bernhard Illerhaus; Heinz Sturm; Bernhard Schartel. 2017. "Variation of Intumescent Coatings Revealing Different Modes of Action for Good Protection Performance." Fire Technology 53, no. 4: 1569-1587.