Search Results
Impact of energy dissipation on interface shapes and on rates for dewetting from liquid substrates
We revisit the fundamental problem of liquid-liquid dewetting and perform a detailed comparison of theoretical predictions based on thin-film models with experimental measurements obtained by atomic force microscopy. Specifically, we consider the dewetting of a liquid polystyrene layer from a liquid polymethyl methacrylate layer, where the thicknesses and the viscosities of both layers are similar. Using experimentally determined system parameters like viscosity and surface tension, an excellent agreement of experimentally and theoretically obtained rim profile shapes are obtained including the liquid-liquid interface and even dewetting rates. Our new energetic approach additionally allows to assess the physical importance of different contributions to the energy-dissipation mechanism, for which we analyze the local flow fields and the local dissipation rates. Using this approach, we explain why dewetting rates for liquid-liquid systems follow no universal power law, despite the fact that experimental velocities are almost constant. This is in contrast to dewetting scenarios on solid substrates and in contrast to previous results for liquid-liquid substrates using heuristic approaches.
Engineering biofunctional in vitro vessel models using a multilayer bioprinting technique
Recent advances in the field of bioprinting have led to the development of perfusable complex structures. However, most of the existing printed vascular channels lack the composition or key structural and physiological features of natural blood vessels or they make use of more easily printable but less biocompatible hydrogels. Here, we use a drop-on-demand bioprinting technique to generate in vitro blood vessel models, consisting of a continuous endothelium imitating the tunica intima, an elastic smooth muscle cell layer mimicking the tunica media, and a surrounding fibrous and collagenous matrix of fibroblasts mimicking the tunica adventitia. These vessel models with a wall thickness of up to 425 µm and a diameter of about 1 mm were dynamically cultivated in fluidic bioreactors for up to three weeks under physiological flow conditions. High cell viability (>83%) after printing and the expression of VE-Cadherin, smooth muscle actin, and collagen IV were observed throughout the cultivation period. It can be concluded that the proposed novel technique is suitable to achieve perfusable vessel models with a biofunctional multilayer wall composition. Such structures hold potential for the creation of more physiologically relevant in vitro disease models suitable especially as platforms for the pre-screening of drugs.
Yield trends, variability and stagnation analysis of major crops in France over more than a century
France is a major crop producer, with a production share of approx. 20% within the European Union. Yet, a discussion has recently started whether French yields are stagnating. While for wheat previous results are unanimously pointing to recent stagnation, there is contradictory evidence for maize and few to no results for other crops. Here we analyse a data set with more than 120,000 yield observations from 1900 to 2016 for ten crops (barley, durum and soft wheat, maize, oats, potatoes, rapeseed, sugar beet, sunflower and wine) in the 96 mainland French départements (NUTS3 administrative division). We dissect the evolution of yield trends over time and space, analyse yield variation and evaluate whether growth of yields has stalled in recent years. Yields have, on average across crops, multiplied four-fold over the course of the 20th century. While absolute yield variability has increased, the variation relative to the mean has halved – mean yields have increased faster than their variability. But growth of yields has stagnated since the 1990’s for winter wheat, barley, oats, durum wheat, sunflower and wine on at least 25% of their areas. Reaching yield potentials is unlikely as a cause for stagnation. Maize, in contrast, shows no evidence for stagnation.
Terminal restriction fragment length polymorphism is an “old school” reliable technique for swift microbial community screening in anaerobic digestion
The microbial community in anaerobic digestion has been analysed through microbial fingerprinting techniques, such as terminal restriction fragment length polymorphism (TRFLP), for decades. In the last decade, high-throughput 16S rRNA gene amplicon sequencing has replaced these techniques, but the time-consuming and complex nature of high-throughput techniques is a potential bottleneck for full-scale anaerobic digestion application, when monitoring community dynamics. Here, the bacterial and archaeal TRFLP profiles were compared with 16S rRNA gene amplicon profiles (Illumina platform) of 25 full-scale anaerobic digestion plants. The α-diversity analysis revealed a higher richness based on Illumina data, compared with the TRFLP data. This coincided with a clear difference in community organisation, Pareto distribution, and co-occurrence network statistics, i.e., betweenness centrality and normalised degree. The β-diversity analysis showed a similar clustering profile for the Illumina, bacterial TRFLP and archaeal TRFLP data, based on different distance measures and independent of phylogenetic identification, with pH and temperature as the two key operational parameters determining microbial community composition. The combined knowledge of temporal dynamics and projected clustering in the β-diversity profile, based on the TRFLP data, distinctly showed that TRFLP is a reliable technique for swift microbial community dynamics screening in full-scale anaerobic digestion plants. © 2018, The Author(s).
Quantification of the ozone and singlet delta oxygen produced in gas and liquid phases by a non-thermal atmospheric plasma with relevance for medical treatment
In the field of plasma medicine, the identification of relevant reactive species in the liquid phase is highly important. To design the plasma generated species composition for a targeted therapeutic application, the point of origin of those species needs to be known. The dominant reactive oxygen species generated by the plasma used in this study are atomic oxygen, ozone, and singlet delta oxygen. The species density changes with the distance to the active plasma zone, and, hence, the oxidizing potential of this species cocktail can be tuned by altering the treatment distance. In both phases (gas and liquid), independent techniques have been used to determine the species concentration as a function of the distance. The surrounding gas composition and ambient conditions were controlled between pure nitrogen and air-like by using a curtain gas device. In the gas phase, in contrast to the ozone density, the singlet delta oxygen density showed to be more sensitive to the distance. Additionally, by changing the surrounding gas, admixing or not molecular oxygen, the dynamics of ozone and singlet delta oxygen behave differently. Through an analysis of the reactive species development for the varied experimental parameters, the importance of several reaction pathways for the proceeding reactions was evaluated and some were eventually excluded.
Author Correction: Modulation of van der Waals and classical epitaxy induced by strain at the Si step edges in GeSbTe alloys
[no abstract available]
Cytochrome C oxidase Inhibition and Cold Plasma-derived Oxidants Synergize in Melanoma Cell Death Induction
Despite striking advances in the treatment of metastasized melanoma, the disease is often still fatal. Attention is therefore paid towards combinational regimens. Oxidants endogenously produced in mitochondria are currently targeted in pre-clinical and clinical studies. Cytotoxic synergism of mitochondrial cytochrome c oxidase (CcO) inhibition in conjunction with addition of exogenous oxidants in 2D and 3D melanoma cell culture models were examined. Murine (B16) and human SK-MEL-28 melanoma cells exposed to low-dose CcO inhibitors (potassium cyanide or sodium azide) or exogenous oxidants alone were non-toxic. However, we identified a potent cytotoxic synergism upon CcO inhibition and plasma-derived oxidants that led to rapid onset of caspase-independent melanoma cell death. This was mediated by mitochondrial dysfunction induced by superoxide elevation and ATP depletion. This observation was validated by siRNA-mediated knockdown of COX4I1 in SK-MEL-28 cells with cytotoxicity in the presence of exogenous oxidants. Similar effects were obtained with ADDA 5, a recently identified specific inhibitor of CcO activity showing low toxicity in vivo. Human keratinocytes were not affected by this combinational treatment, suggesting selective effects on melanoma cells. Hence, targeting mitochondrial CcO activity in conjunction with exogenous pro oxidant therapies may constitute a new and effective melanoma treatment modality.
Chemical fingerprints of cold physical plasmas – an experimental and computational study using cysteine as tracer compound
Reactive oxygen and nitrogen species released by cold physical plasma are being proposed as effectors in various clinical conditions connected to inflammatory processes. As these plasmas can be tailored in a wide range, models to compare and control their biochemical footprint are desired to infer on the molecular mechanisms underlying the observed effects and to enable the discrimination between different plasma sources. Here, an improved model to trace short-lived reactive species is presented. Using FTIR, high-resolution mass spectrometry, and molecular dynamics computational simulation, covalent modifications of cysteine treated with different plasmas were deciphered and the respective product pattern used to generate a fingerprint of each plasma source. Such, our experimental model allows a fast and reliable grading of the chemical potential of plasmas used for medical purposes. Major reaction products were identified to be cysteine sulfonic acid, cystine, and cysteine fragments. Less-abundant products, such as oxidized cystine derivatives or S-nitrosylated cysteines, were unique to different plasma sources or operating conditions. The data collected point at hydroxyl radicals, atomic O, and singlet oxygen as major contributing species that enable an impact on cellular thiol groups when applying cold plasma in vitro or in vivo.
Microfluidic cell sorting: Towards improved biocompatibility of extracorporeal lung assist devices
Extracorporeal lung assist technology is one of the last options in critical care medicine to treat patients suffering from severe oxygenation and decarboxylation disorders. Platelet activation along with the consequent thrombus formation is a potentially life-threatening complication of this technique. To avoid platelet-dependent clot formation, this study aims at developing a microfluidic cell sorting chip that can bypass platelets prior to the membrane oxygenator of the extracorporeal lung assist device. The cell sorting chips were produced by maskless dip-in laser lithography, followed by soft lithography replication using PDMS. Citrated porcine whole blood with a clinically relevant haematocrit of 17% was used for the cell sorting experiments involving three different blood flow rates. The joint effects of flow focusing and hydrodynamic lifting forces within the cell sorting chip resulted in a reduction of up to 57% of the baseline platelet count. This cell sorting strategy is suitable for the continuous and label-free separation of red blood cells and platelets and is potentially applicable for increasing the biocompatibility and lifetime of current extracorporeal lung assist devices.
Alberta wildfire 2016: Apt contribution from anomalous planetary wave dynamics
In May-June 2016 the Canadian Province of Alberta suffered one of the most devastating wildfires in its history. Here we show that in mid-April to early May 2016 the large-scale circulation in the mid- and high troposphere of the middle and sub-polar latitudes of the northern hemisphere featured a persistent high-amplitude planetary wave structure dominated by the non-dimensional zonal wave number 4. The strongest anticyclonic wing of this structure was located over western Canada. In combination with a very strong El Niño event in winter 2015/2016 this favored highly anomalous, tinder-dry and high-temperature conditions at the surface in that area, entailing an increased fire hazard there. This critically contributed to the ignition of the Alberta Wildfire in May 2016, appearing to be the costliest disaster in Canadian history thus far.