Bremen University of Applied Sciences
Recent publications
This research aims to enhance fibre-matrix adhesion in bio-based fibre-reinforced polyolefins without using adhesion promoters. The primary focus is to establish a cross-linking mechanism between cellulose fibres and polyethylene by applying UV irradiation to a UV-transparent matrix and UV-absorbing fibres. The influence of UV treatment on the composite properties is evaluated by tensile, interfacial and interlaminar shear strength tests. The UV irradiation decreases the critical fragment length in single fibre fragmentation tests, indicating an improved fibre-matrix adhesion. The UV-irradiated composites’ tensile strength and Young’s modulus are found to be ~10% (for 3- and 8-minute irradiation) and ~50% (for 8-minute irradiation), respectively, higher than those of the untreated samples. Furthermore, the UV irradiation leads to an improvement in the interlaminar shear strength by 25%. The variation of the UV-irradiation time (3 min and 8 min) and the comparison of the properties of semi-finished composite sheets and composites also reveal chemical and physical changes in the regenerated cellulose fibres due to heat adsorption. The proposed mechanism of interfacial crosslinking is confirmed by FTIR spectroscopy. The results suggest an approach to overcome poor compatibility between hydrophobic polyolefin matrix and hydrophilic cellulose-based fibres, resulting in adhesive-free bio-based composites.
The need for claimant States and other stakeholders to cooperate in the South China Sea (SCS) in the conflict area has been a refrain oft reiterated. The SCS region is one of the most-exploited fishing areas in the world. The history of cooperation among and between SCS claimant States to address common ecological problems remain sparse. Many proposals for bilateral and regional cooperation did not materialize because of geopolitical obstacles. Inspired by the example of the Arctic States, this contribution suggests that SCS claimant States should manage their conflict by working towards achieving complex interdependence. One avenue where complex interdependence may flourish among SCS claimant States is cooperation on ocean science research within international organizations with mandate in ocean science research.
In ultrasonic fatigue tests, the VHCF properties can be determined in a reasonable time. Nevertheless, the high frequency can affect the fatigue behavior for some materials. This study investigated the fatigue capability of 34CrNiMo6 and 42CrMo4 steels, both of which find widespread applications in several mechanical components. These steels were carried out for conventional and ultrasonic fatigue tests under fully reversed testing conditions. A microplasticity strain amplitude was calculated, indicating an order of magnitude decreases around 10–100, when compared with the experimental results from low‐frequency tests. Cyclic strain rates were estimated for each steel and correlated with the number of cycles to failure. A conversion constant was obtained by fitting a curve to convert the high frequency results into theoretical results at low frequency. The experimental and predicted results were evaluated. The results proved the relevance of the strain rate in frequency effect. The converted results showed strong agreement with the experimental results in low‐frequency tests for the steels being studied.
Soziale Arbeit ist eine anspruchsvolle Profession komplexer Tätigkeiten und Wirkungsgefüge. In ihr vereinen sich die Erkenntnisse aus Bezugswissenschaften, der eigenen Expertise als Handlungswissenschaft und die Persönlichkeit ihrer Akteurinnen und Akteure als prägende Instanz des gelingenden Zusammenwirkens von Theorien, methodischem Können und dem Handeln in der Wirklichkeit. Daraufhin habe ich mich, mittlerweile seit über 20 Jahren in der Erwachsenenbildung (und über 16 Jahre in der Hochschullehre mit Berufstätigen) tätig, gefragt, wie (und ob) mir so eine Reflexion gelingen könnte, aus welchen Quellen sie sich speiste und auf wessen Schultern stehend der Blick auf das eigene Lehrwirken gerichtet ist.
Phycocyanin (C-PC) is a hydrophilic blue pigment found in cyanobacteria, rhodophytes, and cryptophytes. Its intense blue color and antioxidant capacity make phycocyanin an attractive substance for food and cosmetic industries. In this study, phycocyanin extracts from Arthrospira maxima , obtained by different extraction methods, were used to investigate the influence of preserving agents on thermostability of phycocyanin. C-PC remained stable at 60°C, but rapidly degraded at 70°C, and completely lost at 80°C within 5 minutes. Addition of sorbitol, sucrose, and glucose at 32% (w/v) to phycocyanin extracted through ultrasonication and flocculation with chitosan in organic acid provided the highest stabilizing effects, with C R values of 96.67 ± 0.01%, 83.41 ± 0.67%, and 76.21 ± 1.34%, respectively. The corresponding half-live values increased from 13.77 ± 0.21 min (control) to between 76.74 ± 5.12 and 614.83 ± 1.18 minutes, followed by xylitol, fructose, and maltose. Xylose, lactose, citric acid, and ascorbic acid showed no effects. The stabilizing effect of NaCl was dependent on pH of extracts, remaining stable at pH 6–7, but showing no significant effect at pH 3–4, and leading to precipitation. Incorporating 14–20% (w/v) NaCl in C-PC at pH 6.49 increased C R values from 88.61 ± 0.31 to 99.10 ± 0.01%, with half-life values ranging from 172.03 ± 4.92 to 2291.19 ± 14.51 minutes. Conversely, the stabilizing effect of sugars was most effective in C-PC at pH 3–4, and least effective in C-PC obtained by freeze/thawing at pH 6–7.
Mangroves provide habitat for a diverse array of marine species, especially snails. We used a MaxEnt model to predict potential global suitable habitat for Cerithidea rhizophorarum and Telescopium telescopium in the family Potamididae. A total of 667 occurrence data were obtained from the Global Biodiversity Information Facility (GBIF) with the following sub‐data set contribution, “iNaturalist Research Grade Observations” (85%), “International Barcode of Life project (iBOL)” (7%), “FBIP: SeaKeys_SANBI: Marine images iSpot_2013” (1%), “A dataset of marine macroinvertebrate diversity from Mozambique and São Tomé and Príncipe” (1%), occurrence data of some marine invertebrates and freshwater crabs housed in the natural history collection at the National Museums of Kenya (1%), and Natural History Museum Rotterdam‐Specimens (1%). Our results showed that temperature with a contribution of above 80% in the present and future model is the most important driver of the distribution of mangrove snails. In the present and future models, the most potentially suitable habitats for C. rhizophorarum and T. telescopium were observed along coastal areas with a temperature between 20°C–21°C and 30°C, respectively. Our model predicts that by 2100, high‐suitability areas will shrink as a result of global warming. The vulnerability of mangrove snails under future climate conditions is evident in our results. Our findings contribute significant insights into the intricate relationship between mangrove habitats and mangrove snails, offering a valuable foundation for conservation initiatives aimed at safeguarding the biodiversity and ecological functions of these crucial coastal ecosystems in the face of changing global environmental conditions.
Inspired by the starfish's unique ability to achieve flexibility and posture-holding with minimal energy expenditure, we present a novel bioinspired morphing structure. Our two-component design, consisting of a thermoplastic mesh and elastomeric jacket, effectively mimics the functions of the starfish's ossicles, mutable collagenous tissues, and derma. This structure exhibits a remarkable combination of self-healing, time-dependent shape memory, and self-posture-holding properties. Systematic variations in mesh geometry demonstrate precise control over structural stiffness and thermal response, enabling customization for specific applications. The structure's scalability and ease of fabrication further enhance its adaptability. We experimentally demonstrate the potential of our biomimetic morphing structure using several prototypes. This work lays the foundation for developing a new type of versatile morphing structures with applications in diverse fields, including robotics, biomedical devices, and adaptive structures.
The current state of marine mammal populations reflects increasing anthropogenic impacts on the global Ocean. Adopting a holistic approach towards marine mammal health, incorporating healthy individuals and healthy populations, these taxa present indicators of the health of the overall Ocean system. Their present deterioration at the animal, population and ecosystem level has implications for human health and the global system. In the Anthropocene, multiple planetary boundaries have already been exceeded, and quiet tipping points in the Ocean may present further uncertainties. Long and short-term monitoring of marine mammal health in the holistic sense is urgently required to assist in evaluating and reversing the impact on Ocean Health and aid in climate change mitigation.
Muslim organizations play important roles in shaping the publics’ reaction to terrorist attacks with Islamist background. The present study uses methods and models from the Situational Crisis Communication Theory to investigate whether and which response strategies affect attitudes toward Muslims and attention to positive and negative information about Muslims. Specifically, an eye tracking experiment was conducted with 202 residents of Germany. We found more positive attitudes after active vs. passive response styles. Effects on attention as measures with eye tracker were not observed. Across all experimental conditions, negative information about Muslims was inspected longer than positive information. The findings are discussed with regard to SCCT and possible ways to improve the media coverage in the aftermath of terrorist attacks.
Self-assembled fibrinogen nanofibers are promising candidates for skin tissue engineering due to their biocompatibility and ability to mimic the native blood clot architecture. Here, we studied the structure–property relationship and degradation of rehydrated fibrinogen nanofibers prepared by salt-induced self-assembly, focusing on the effect of scaffold layering, cross-linking time and freeze-drying. Optimal fiber stability was achieved with cross-linking by formaldehyde (FA) vapor, while treatment with liquid aldehydes, genipin, EDC, and transglutaminase failed to preserve the nanofibrous architecture upon rehydration. Scaffold layering did not significantly influence the mechanical properties but changed the scaffold architecture, with bulk fiber scaffolds being more compact than layered scaffolds. Freeze-drying maintained the mechanical properties and interconnected pore network with average pore diameters around 20 μm, which will enhance the storage stability of self-assembled fibrinogen scaffolds. Varying cross-linking times altered the scaffold mechanics without affecting the swelling behavior, indicating that scaffold hydration can be controlled independently of the mechanical characteristics. Cross-linking times of 240 min increased scaffold stiffness and decreased elongation, while 30 min resulted in mechanical properties similar to native skin. Cross-linking for 120 min was found to reduce scaffold degradation by various enzymes in comparison to 60 min. Overall, after 35 days of incubation, plasmin and a combination of urokinase and plasminogen exhibited the strongest degradative effect, with nanofibers being more susceptible to enzymatic degradation than planar fibrinogen due to their higher specific surface area. Based on these results, self-assembled fibrinogen fiber scaffolds show great potential for future applications in soft tissue engineering that require controlled structure–function relationships and degradation characteristics.
In mean-variance portfolio optimization, multi-index models often accelerate computation, reduce input requirements, facilitate understanding, and allow easy adjustment to changing conditions more effectively than full covariance matrix estimation in many situations. In this paper, we develop a multi-index model-based portfolio optimization approach that takes into account aspects of the environment, social responsibility and corporate governance (ESG). Investments in assets related to ESG have recently grown, attracting interest from both academic research and investment fund practice. Various literature strands in this area address the theoretical and empirical relation among return, risk and ESG. Our portfolio optimization approach is flexible enough to take these literature strands into account and does not require large-scale covariance matrix estimation. An extension of our approach even allows investors to empirically discriminate among the literature strands. A case study demonstrates the application of our portfolio optimization approach.
Introduction Advance care planning (ACP) ensures that patients receive medical care aligned with their values, goals, and preferences, especially regarding end-of-life decisions in serious chronic illnesses. Objective This project aimed to introduce and promote evidence-based ACP in oncology and palliative care at a midsized hospital near Berlin, Germany, during the COVID-19 pandemic. Methods This project was guided by the JBI Evidence Implementation Framework and used a mixed methods audit cycle. A baseline audit was conducted using qualitative interviews and workshops with representatives from all the health care disciplines involved in oncology and palliative care at the hospital. The findings were compared with eight best practice recommendations. Targeted strategies aimed at the key stakeholders involved in ACP practice were then implemented. Finally, a semi-quantitative questionnaire was used in a follow-up audit with the same participants as in the baseline audit. Results The baseline audit revealed a high level of familiarity with the concept of ACP. However, there was a lack of a uniformly accepted definition and understanding of ACP among the health care professionals, leading to a lack of coordination in task distribution. The follow-up audit revealed improvements with regard to education and training in ACP (Criterion 1: 50% to 100%) and organizational support to facilitate ACP conversations (Criterion 3: 87.5% to 100%). Other audit criteria compliance rates remained unchanged. Conclusion Clinical education and team-based process analysis can facilitate ACP implementation across disciplines in oncology and palliative care facilities. However, the project did not succeed in implementing lasting changes in clinical processes and best practice ACP due to the COVID-19 pandemic. Such an endeavor would demand considerable resources and time, both of which were constrained during the pandemic. Spanish abstract http://links.lww.com/IJEBH/A236
In economic applications, the behavior of objects (e.g., individuals, firms, or households) is often modeled as a function of microeconomic and/or macroeconomic conditions. While macroeconomic conditions are common to all objects and change only over time, microeconomic conditions are object-specific and thus vary both among objects and through time. The simultaneous modeling of microeconomic and macroeconomic conditions has proven to be extremely difficult for these applications due to the mismatch of dimensions, potential interactions, and the high number of parameters to estimate. By marrying recurrent neural networks with conditional factor models, we propose a new white-box machine learning method, the recurrent double-conditional factor model (RDCFM), which allows for the modeling of the simultaneous and combined influence of micro- and macroeconomic conditions while being parsimoniously parameterized. Due to the low degree of parameterization, the RDCFM generalizes well and estimation remains feasible even if the time-series and the cross-section are large. We demonstrate the suitability of our method using an application from the financial economics literature.
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2,804 members
Christian Spatscheck
  • Bremen Institute for Social Work and Development
Gerd Kloeck
  • Department of Biology
Annika Maschwitz
  • School of International Business (Faculty 1)
Volker Paelke
  • Faculty of Electrical Engineering and Computer Science (Faculty 4)
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Bremen, Germany
Head of institution
Prof. Dr. Karin Luckey