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  • Walter de Gruyter GmbH  (7)
  • 1
    Online Resource
    Online Resource
    Walter de Gruyter GmbH ; 2021
    In:  Current Directions in Biomedical Engineering Vol. 7, No. 2 ( 2021-10-01), p. 684-687
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 7, No. 2 ( 2021-10-01), p. 684-687
    Abstract: The selection of appropriate test conditions is of critical importance in mechanical testing of biomaterials. In particular the definition of dynamic test conditions is requiring high efforts. In this work, a thermoplastic semicrystalline polymer was characterized regarding mechanical properties by dynamic mechanical analysis (DMA). Timetemperature- superposition (TTS) of dynamic mechanical data provides an efficient method for the experimental design of follow-up studies. Our focus was to provide test conditions for cyclic tests, which correspond to viscoelastic materials. The results show, that the test temperature for dynamic mechanical fatigue tests, as an indicator of mechanical modification for viscoelastic materials, should necessarily remain below the onset temperatures of storage modulus and loss modulus. Moreover, changes in material characteristics due to varying frequencies should be considered when constructing a master curve for the evaluation of test frequencies. Therefore, TTS is particularly beneficial for the rapid determination of test parameters for accelerated material examination.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2835398-5
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  • 2
    Online Resource
    Online Resource
    Walter de Gruyter GmbH ; 2023
    In:  Current Directions in Biomedical Engineering Vol. 9, No. 1 ( 2023-09-01), p. 459-462
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 9, No. 1 ( 2023-09-01), p. 459-462
    Abstract: Dynamic mechanical properties of polymers for biomedical applications are crucial parameters for development and engineering of new medical devices. Here, the time-dependent material behavior is a key factor for durability. Varying the strain rate is a convenient implementation of time-dependency for uniaxial testing. This study investigates time-dependence of Poly(L-Lactide) (PLLA) through uniaxial testing with different strain rates and PLLA with different molecular weight. The results show strain dependence for elongation at break and yield stress, Young’s modulus however is not rate dependent. An increase in elongation at break is also seen with increasing molecular weight of PLLA. Plastic strain increases significantly only for PLLA with an intermediate inherent viscosity. Results show distinct time dependencies regarding strain rate for PLLA with slightly different inherent viscosities. For stent-related mechanical material characteristics, higher molecular weight PLLA seems to be advantageous. This study only considers base materials, although appropriate thermal, mechanical as well as chemical post processing approaches for further adjustment of different properties have already been shown. A combination of the best possible base material and a suitable post-processing should be targeted.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2835398-5
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  • 3
    Online Resource
    Online Resource
    Walter de Gruyter GmbH ; 2021
    In:  Current Directions in Biomedical Engineering Vol. 7, No. 2 ( 2021-10-01), p. 9-12
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 7, No. 2 ( 2021-10-01), p. 9-12
    Abstract: Dry electrodes enable a shorter preparation time for infant EEG. Since infant skin is more sensitive than adult skin, soft electrodes are required to reduce the mechanical stress for this sensitive skin. Thus, soft electrodes are crucial for eventual repetitive and long-term use like in neonatal intensive care units. A biocompatible polyurethane (PU) can be produced in low hardness resulting in a soft and flexible electrode substrate. Silver/silver chloride (Ag/AgCl) electroless plating provides a conductive, electrochemically stable coating but the process may alter the mechanical properties of the electrode substrate. In this study, we assess the hardness of PU material before and after Ag/AgCl plating. The test sample design for Shore hardness measurement is based on ISO 7619-1:2010. Sample production consists of a 3D print master model, silicone molding, PU casting, and finally electroless plating. UPX 8400-1 (Sika AG, Switzerland) is used for the sample substrates. Test samples are produced with 7 different Shore hardness (range A40-A95) and 14 samples (each hardness: 1 uncoated and 1 coated). The hardness measurements are carried out with a lever-operated test stand Shore hardness tester model with a digital hardness tester (TI-AC with HDA 100-1, KERN & SOHN GmbH, Germany).. It is shown that there is a hardness increase (Shore A) due to Ag/AgCl coating with a grand average of 1.1±0.7 (p 〈 0.05). The largest increase of 2.1±0.2 is seen on the initial lowest Shore hardness sample (Shore hardness: 43.4±0.1). The absolute increase of hardness due to the Ag/AgCl coating decreases with increasing substrate hardness. It is concluded that there is no strong hardness increase of PU substrates due to Ag/AgCl plating. Therefore, the material is suitable as a soft electrode for repetitive and long-term use in infant applications.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2835398-5
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  • 4
    Online Resource
    Online Resource
    Walter de Gruyter GmbH ; 2022
    In:  Current Directions in Biomedical Engineering Vol. 8, No. 2 ( 2022-09-02), p. 356-359
    In: Current Directions in Biomedical Engineering, Walter de Gruyter GmbH, Vol. 8, No. 2 ( 2022-09-02), p. 356-359
    Abstract: In this study, DSC experiments were used to elaborate an annealing protocol for injection molded very high molecular weight (VHMW) PLLA with two molecular masses, 320,000 g/mol and 700,000 g/mol. The initial material obtained from the injection molding process was found to be highly amorphous and not in thermodynamic equilibrium state, as distinct cold crystallization and enthalpy relaxation were observed in DSC data. Thermal annealing to 85 °C for 60 - 90 min under controlled conditions using a DSC device showed to be sufficient to stabilize the polymer and increase the crystallinity to up to 50 %. Annealing did not result in any signs of thermal decomposition. The elaborated thermal treatment has been transferred to manual annealing of large specimen geometries for subsequent DMA analysis.
    Type of Medium: Online Resource
    ISSN: 2364-5504
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2835398-5
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  • 5
    Online Resource
    Online Resource
    Walter de Gruyter GmbH ; 2015
    In:  Wirtschaftsdienst Vol. 95, No. 9 ( 2015-9), p. 609-613
    In: Wirtschaftsdienst, Walter de Gruyter GmbH, Vol. 95, No. 9 ( 2015-9), p. 609-613
    Type of Medium: Online Resource
    ISSN: 0043-6275 , 1613-978X
    RVK:
    Language: German
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2015
    detail.hit.zdb_id: 2079503-8
    detail.hit.zdb_id: 202814-1
    detail.hit.zdb_id: 2601588-2
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  • 6
    Online Resource
    Online Resource
    Walter de Gruyter GmbH ; 2021
    In:  Wirtschaftsdienst Vol. 101, No. 3 ( 2021-03), p. 235-236
    In: Wirtschaftsdienst, Walter de Gruyter GmbH, Vol. 101, No. 3 ( 2021-03), p. 235-236
    Type of Medium: Online Resource
    ISSN: 0043-6275 , 1613-978X
    RVK:
    Language: German
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2021
    detail.hit.zdb_id: 2079503-8
    detail.hit.zdb_id: 202814-1
    detail.hit.zdb_id: 2601588-2
    Library Location Call Number Volume/Issue/Year Availability
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  • 7
    Online Resource
    Online Resource
    Walter de Gruyter GmbH ; 2016
    In:  Review of Economics Vol. 67, No. 3 ( 2016-12-1), p. 231-253
    In: Review of Economics, Walter de Gruyter GmbH, Vol. 67, No. 3 ( 2016-12-1), p. 231-253
    Abstract: Globalization influences inflation and the transmission channels of monetary policy in various ways. The effects of globalization on the ability of monetary policy to control inflation have been discussed intensively. However, in the light of recent experiences following the global financial crisis with extended periods of disinflation in many advanced economies, the question whether the ability of monetary policy to control inflation has suffered significantly from increasing globalization has received new relevance. Based on a review of the literature, this paper discusses whether globalization is reducing the ability of central banks to control inflation and draws conclusion for the current situation in the euro area. We find that globalization has made it more complicated for central banks to ensure price stability and that it has tended to reduce the ability of monetary policy to control inflation in the short- to medium-run. However, in principle the ECB is still able to control inflation but may have to tolerate deviations from its inflation target for somewhat longer periods.
    Type of Medium: Online Resource
    ISSN: 0948-5139 , 2366-035X
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2178720-7
    detail.hit.zdb_id: 2670037-2
    detail.hit.zdb_id: 1240559-0
    SSG: 20,1
    SSG: 3,4
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