Search Results
Sperm Micromotors for Cargo Delivery through Flowing Blood
2020, Xu, Haifeng, Medina-Sánchez, Mariana, Maitz, Manfred F., Werner, Carsten, Schmidt, Oliver G.
Micromotors are recognized as promising candidates for untethered micromanipulation and targeted cargo delivery in complex biological environments. However, their feasibility in the circulatory system has been limited due to the low thrust force exhibited by many of the reported synthetic micromotors, which is not sufficient to overcome the high flow and complex composition of blood. Here we present a hybrid sperm micromotor that can actively swim against flowing blood (continuous and pulsatile) and perform the function of heparin cargo delivery. In this biohybrid system, the sperm flagellum provides a high propulsion force while the synthetic microstructure serves for magnetic guidance and cargo transport. Moreover, single sperm micromotors can assemble into a train-like carrier after magnetization, allowing the transport of multiple sperm or medical cargoes to the area of interest, serving as potential anticoagulant agents to treat blood clots or other diseases in the circulatory system.
Corona-Krise? - Welche Krise? Zum Umgang mit einer Pandemie
2022, Diebold, Steffen M.
The corona pandemic poses major challenges for society. Many people lack (basic) scientific knowledge. They are skeptical and distrust fundamental research principles and concepts. Esotericism and superstition replace them access to reality. Not only facts are recently considered "alternative". Pseudo-scientific healing methods and occult procedures have long been presented to the public as equivalent alternatives to modern medicine, despite the lack of evidence of their effectiveness. Just as if reason or nonsense were just a question of personal taste, a different world view. Seconded by talk of an "exaggeratedly scientific world view", empiricism and logic were systematically defamed. As a result of this distorted picture, all kinds of conspiracy theories are now rampant. Spiritual healers, seers, shamans, charlatans, quacks, sectarians, and zealots of all stripes and persuasions are in demand. Diffuse pandemic management and miserable communication do the rest and contribute to the fact that infection control measures are often flatly rejected and vaccination rates can hardly be increased significantly.
Surface modification of MWCNT and its influence on properties of paraffin/MWCNT nanocomposites as phase change material
2020, Avid, Arezoo, Jafari, Seyed Hassan, Khonakdar, Hossein Ali, Ghaffari, Mehdi, Krause, Beate, Pötschke, Petra
Multiwalled carbon nanotubes (MWCNTs) were modified by an organo-silane in order to improve their dispersion state and stability in paraffin wax. A family of paraffin-based phase change material (PCM) composites filled with MWCNTs was prepared with different loadings (0, 0.1, 0.5, and 1 wt%) of pristine MWCNTs and organo-silane modified MWCNTs (Si-MWCNT). Structural analyses were performed by means of Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and rheological studies using temperature sweeps. Moreover, phase change transition temperatures and heat of fusion as well as thermal and electrical conductivities of the developed PCM nanocomposites were determined. The SEM micrographs and FTIR absorption bands appearing at approximately 1038 and 1112 cm−1 confirmed the silane modification. Differential scanning calorimetery (DSC) results indicate that the presence of Si-MWCNTs leads to slightly favorable enhancement in the energy storage capacity at the maximum loading. It was also shown that the thermal conductivity of the PCM nanocomposites, in both solid and liquid phases, increased with increasing the MWCNT content independent of the kind of MWCNTs by up to about 30% at the maximum loading of MWCNTs. In addition, the modification of MWCNTs made the samples completely electrically nonconductive, and the electrical surface resistivity of the PCMs containing pristine MWCNTs decreased with increasing MWCNTs loading. Furthermore, the rheological assessment under consecutive cyclic phase change demonstrated that the samples containing modified MWCNTs are more stable compared to the PCM containing pristine MWCNTs. © 2019 Wiley
Comparative study of singlewalled, multiwalled, and branched carbon nanotubes melt mixed in different thermoplastic matrices
2018, Krause, Beate, Barbier, Carine, Kunz, Karina, Pötschke, Petra
In this contribution, three different types of CNTs, namely single-walled (SWCNT), multi-walled (MWCNT) and branched MWCNTs were melt mixed in amounts of 0.1–10 wt.-% in polypropylene (PP), polycarbonate (PC) and poly(vinylidene fluoride) (PVDF) using a small-scale microcompounder. The filler dispersion of compression-moulded samples was characterized using light and electron microscopy, and the electrical and thermal properties were measured. The lowest electrical percolation thresholds were found for composites of PP/SWCNT, PP/branched MWCNT and PC/branched MWCNT, which percolated already at <0.1 wt.-% CNT loading. Low values of electrical volume resistivity of about 3 Ohm·cm (PVDF), 7 Ohm·cm (PP) and 2 Ohm·cm (PC) could be reached when loading with 2 wt.-% branched MWCNT. A homogeneous dispersion in the macro- and microlevel was observed especially for composites containing branched MWCNTs. For all CNT types, a matrix nucleation effect was found in PP and PVDF using differential scanning calorimetry.
Medical Imaging of Microrobots: Toward In Vivo Applications
2020, Aziz, Azaam, Pane, Stefano, Iacovacci, Veronica, Koukourakis, Nektarios, Czarske, Jürgen, Menciassi, Arianna, Medina-Sánchez, Mariana, Schmidt, Oliver G
Medical microrobots (MRs) have been demonstrated for a variety of non-invasive biomedical applications, such as tissue engineering, drug delivery, and assisted fertilization, among others. However, most of these demonstrations have been carried out in in vitro settings and under optical microscopy, being significantly different from the clinical practice. Thus, medical imaging techniques are required for localizing and tracking such tiny therapeutic machines when used in medical-relevant applications. This review aims at analyzing the state of the art of microrobots imaging by critically discussing the potentialities and limitations of the techniques employed in this field. Moreover, the physics and the working principle behind each analyzed imaging strategy, the spatiotemporal resolution, and the penetration depth are thoroughly discussed. The paper deals with the suitability of each imaging technique for tracking single or swarms of MRs and discusses the scenarios where contrast or imaging agent's inclusion is required, either to absorb, emit, or reflect a determined physical signal detected by an external system. Finally, the review highlights the existing challenges and perspective solutions which could be promising for future in vivo applications.
Compacting frequent star patterns in RDF graphs
2020, Karim, Farah, Vidal, Maria-Esther, Auer, Sören
Knowledge graphs have become a popular formalism for representing entities and their properties using a graph data model, e.g., the Resource Description Framework (RDF). An RDF graph comprises entities of the same type connected to objects or other entities using labeled edges annotated with properties. RDF graphs usually contain entities that share the same objects in a certain group of properties, i.e., they match star patterns composed of these properties and objects. In case the number of these entities or properties in these star patterns is large, the size of the RDF graph and query processing are negatively impacted; we refer these star patterns as frequent star patterns. We address the problem of identifying frequent star patterns in RDF graphs and devise the concept of factorized RDF graphs, which denote compact representations of RDF graphs where the number of frequent star patterns is minimized. We also develop computational methods to identify frequent star patterns and generate a factorized RDF graph, where compact RDF molecules replace frequent star patterns. A compact RDF molecule of a frequent star pattern denotes an RDF subgraph that instantiates the corresponding star pattern. Instead of having all the entities matching the original frequent star pattern, a surrogate entity is added and related to the properties of the frequent star pattern; it is linked to the entities that originally match the frequent star pattern. Since the edges between the entities and the objects in the frequent star pattern are replaced by edges between these entities and the surrogate entity of the compact RDF molecule, the size of the RDF graph is reduced. We evaluate the performance of our factorization techniques on several RDF graph benchmarks and compare with a baseline built on top gSpan, a state-of-the-art algorithm to detect frequent patterns. The outcomes evidence the efficiency of proposed approach and show that our techniques are able to reduce execution time of the baseline approach in at least three orders of magnitude. Additionally, RDF graph size can be reduced by up to 66.56% while data represented in the original RDF graph is preserved.
Roadmap to FAIR Research Information in Open Infrastructures
2021, Hauschke, Christian, Nazarovets, Serhii, Altemeier, Franziska, Kaliuzhna, Nataliia
The FAIR Principles were designed to improve the findability, accessibility, interoperability and reusability of data holdings by humans and machines. The principles can be applied to research information too. We present the results of the discussions that took place during the series of online workshops with experts on Research Information and FAIR Guiding Principles. We provide high-level criteria on how to foster findable, accessible, interoperable and reusable, and we hope that our roadmap for FAIR research information in open infrastructures bring many benefits to a diverse group of stakeholders of the scientific ecosystem.
The force of MOFs: The potential of switchable metal-organic frameworks as solvent stimulated actuators
2020, Freund, Pascal, Senkovska, Irena, Zheng, Bin, Bon, Volodymyr, Krause, Beate, Maurin, Guillaume, Kaskel, Stefan
We evaluate experimentally the force exerted by flexible metal-organic frameworks through expansion for a representative model system, namely MIL-53(Al). The results obtained are compared with data collected from intrusion experiments while molecular simulations are performed to shed light on the re-opening of the guest-loaded structure. The critical impact of the transition stimulating medium on the magnitude of the expansion force is demonstrated.
Electrical and melt rheological characterization of PC and co-continuous PC/SAN blends filled with CNTs: Relationship between melt-mixing parameters, filler dispersion, and filler aspect ratio
2018, Liebscher, Marco, Domurath, Jan, Krause, Beate, Saphiannikova, Marina, Heinrich, Gert, Pötschke, Petra
Electrical and melt rheological properties of melt-mixed polycarbonate (PC) and co-continuous PC/poly(styrene–acrylonitrile) (SAN) blends with carbon nanotubes (CNTs) are investigated. Using two sets of mixing parameters, different states of filler dispersion are obtained. With increasing CNT dispersion, an increase in electrical resistivity near the percolation threshold of PC–CNT composites and (PC + CNT)/SAN blends is observed. This suggests that the higher mixing energies required for better dispersion also result in a more severe reduction of the CNT aspect ratio; this effect was proven by CNT length measurements. Melt rheological studies show higher reinforcing effects for composites with worse dispersion. The Eilers equation, describing the melt viscosity as function of filler content, was used to fit the data and to obtain information about an apparent aspect ratio change, which was in accordance with measured CNT length reduction. Such fitting could be also transferred to the blends and serves for a qualitatively based discussion. © 2017 Wiley Periodicals
Electrically conductive and piezoresistive polymer nanocomposites using multiwalled carbon nanotubes in a flexible copolyester: Spectroscopic, morphological, mechanical and electrical properties
2022, Dhakal, Kedar Nath, Khanal, Santosh, Krause, Beate, Lach, Ralf, Grellmann, Wolfgang, Le, Hai Hong, Das, Amit, Wießner, Sven, Heinrich, Gert, Pionteck, Jürgen, Adhikari, Rameshwar
Nanocomposites of multiwalled carbon nanotubes (MWCNTs) with poly(butylene adipate-co-terephthalate) (PBAT), a flexible aromatic–aliphatic copolyester, were prepared by melt mixing followed by compression moulding to investigate their spectroscopic, morphological, mechanical and electrical properties. A comparison of the Fourier transform infrared (FTIR) spectra of the neat polymer matrix and the composites showed no difference, implying a physical mixing of the matrix and the filler. A morphological investigation revealed the formation of a continuous and interconnected MWCNT network embedded in the polymer matrix with partial agglomeration. Increasing Martens hardness and indentation modulus and decreasing maximum indentation depth with increasing filler concentration demonstrated the reinforcement of the polymer by the MWCNTs. A volume resistivity of 4.6 × 105 Ω cm of the materials was achieved by the incorporation of only 1 wt.-% of the MWCNTs, which confirmed a quite low percolation threshold (below 1 wt.-%) of the nanocomposites. The electrical volume resistivity of the flexible nanocomposites was achieved up to 1.6 × 102 Ω cm, depending on the filler content. The elongation at the break of the nanocomposites at 374% and the maximum relative resistance changes (ΔR/R0) of 20 and 200 at 0.9 and 7.5% strains, respectively, were recorded in the nanocomposites (3 wt.-% MWCNTs) within the estimated volume resistivity range. A cyclic strain experiment shows the most stable and reproducible ΔR/R0 values in the 2%–5% strain range. The electrical conductivity and piezoresistivity of the investigated nanocomposites in correlation with the mechanical properties and observed morphology make them applicable for low-strain deformation-sensing.