215 research outputs found
The Effect of Patterned Micro-Structure on the Apparent Contact Angle and Three-Dimensional Contact Line
The measurement of the apparent contact angle on structured surfaces is much more difficult to obtain than on smooth surfaces because the pinning of liquid to the roughness has a tremendous influence on the three phase contact line. The results presented here clearly show an apparent contact angle variation along the three phase contact line. Accordingly, not only one value for the apparent contact angle can be provided, but a contact angle distribution or an interval has to be given to characterize the wetting behavior. For measuring the apparent contact angle distribution on regularly structured surfaces, namely micrometric pillars and grooves, an experimental approach is presented and the results are provided. A short introduction into the manufacturing process of such structured surfaces, which is a combination of Direct LASER Writing (DLW) lithography, electroforming and hot embossing shows the high quality standard of the used surfaces
Mathematics students' characteristics of basic mental models of the derivative
The concept of derivative is characterised with reference to four basic mental models. These are described as theoretical constructs based on theoretical considerations. The four basic mental modelsâlocal rate of change, tangent slope, local linearity and amplification factorâare not only quantified empirically but are also validated. To this end, a test instrument for measuring studentsâ characteristics of basic mental models is presented and analysed regarding quality criteria.
Mathematics students (nâŻ=â266) were tested with this instrument. The test results show that the four basic mental models of the derivative can be reconstructed among the students with different characteristics. The tangent slope has the highest agreement values across all tasks. The agreement on explanations based on the basic mental model of rate of change is not as strongly established among students as one would expect due to framework settings in the school system by means of curricula and educational standards. The basic mental model of local linearity plays a rather subordinate role. The amplification factor achieves the lowest agreement values. In addition, cluster analysis was conducted to identify different subgroups of the student population. Moreover, the test results can be attributed to characteristics of the task types as well as to the studentsâ previous experiences from mathematics classes by means of qualitative interpretation. These and other results of studentsâ basic mental models of the derivative are presented and discussed in detail.Der Begriff der Ableitung wird anhand von vier Grundvorstellungen charakterisiert. Diese werden als theoretische Konstrukte beschrieben, die auf theoretischen Ăberlegungen beruhen. Die vier Grundvorstellungen â lokale Ănderungsrate, Tangentensteigung, lokale Linearität und Verstärkungsfaktor â werden empirisch quantifiziert und validiert. Zu diesem Zweck wird ein Testinstrument zur Messung der Charakteristika dieser Grundvorstellungen von Lernenden erstellt, bzgl. GĂźtekriterien ausgewertet und an Mathematikstudierenden (nâŻ=â266) getestet. Die Ergebnisse zeigen, dass die vier Grundvorstellungen der Ableitung bei den Lernenden mit unterschiedlichen Merkmalen rekonstruiert werden kĂśnnen. Die Tangentensteigung weist Ăźber alle Aufgaben hinweg die hĂśchsten Ăbereinstimmungswerte auf. Die Ăbereinstimmung bei Erklärungen, die auf der Grundvorstellung der lokalen Ănderungsrate beruhen, ist bei den Studierenden nicht so stark ausgeprägt, wie man es aufgrund der Rahmenbedingungen im Schulsystem durch Lehrpläne und Bildungsstandards erwarten wĂźrde. Die Grundvorstellung der lokalen Linearität spielt eine eher untergeordnete Rolle. Der Verstärkungsfaktor erzielt die geringsten Ăbereinstimmungswerte. DarĂźber hinaus wurde eine Clusteranalyse durchgefĂźhrt, um verschiedene Untergruppen der SchĂźlerpopulation zu identifizieren. Die Testergebnisse kĂśnnen mittels qualitativer Interpretation auf Merkmale der Aufgabentypen sowie auf die Vorerfahrungen der Studierenden aus dem Mathematikunterricht zurĂźckgefĂźhrt werden. Diese und weitere Ergebnisse zu den grundlegenden mentalen Modellen der Studierenden zur Ableitung werden ausfĂźhrlich dargestellt und diskutiert
Cytidine-5-diphosphocholine reduces microvascular permeability during experimental endotoxemia
Background: Microvascular permeability and leukocyte adhesion are pivotal mechanisms in sepsis pathophysiology contributing to the development of shock and mortality. No effective pharmacological therapy is currently available to restore microvascular barrier function in sepsis. Cholinergic mediators have been demonstrated to exert anti-inflammatory effects during inflammation. Cytidine-5-diphosphocholine (CDP-choline) is an extensively studied cholinergic drug due to its brain protective characteristics in cerebrovascular diseases. This study evaluated the effect of CDP-choline on microvascular permeability and leukocyte adhesion during endotoxemia. Methods: Macromolecular leakage, leukocyte adhesion, and venular wall shear rate were examined in mesenteric postcapillary venules of rats by using intravital microscopy (IVM). Lipopolysaccharide (LPS) (4Â mg/kg/h) or equivalent volumes of saline were continuously infused following baseline IVM at 0Â min. IVM was repeated after 60 and 120Â min in endotoxemic and nonendotoxemic animals. CDP-choline (100Â mg/kg) was applied as an i.v. bolus. Animals received either saline alone, CDP-choline alone, CDP-choline 10Â min before or 30Â min after LPS administration, or LPS alone. Due to nonparametric data distribution, Wilcoxon test and Dunn's multiple comparisons test were used for data analysis. Data were considered statistically significant at pâ<â0.05. Results: Treatment with LPS alone significantly increased microvascular permeability and leukocyte adhesion and decreased venular wall shear rate. CDP-choline significantly reduced microvascular permeability in animals treated with LPS. Leukocyte adhesion and venular wall shear rate were not affected by CDP-choline during endotoxemia. Conclusion: CDP-choline has a protective effect on microvascular barrier function during endotoxemia. Considering the excellent pharmacologic safety profile of CDP-choline, its use could be an approach for the treatment of capillary leakage in sepsis
Experimental and Numerical Investigation of Phase Separation due to Multi-Component Mixing at High-Pressure Conditions
[EN] Experiments and numerical simulations were carried out in order to contribute to a better understanding and prediction
of high-pressure injection into a gaseous environment. Specifically, the focus was put on the phase separation
processes of an initially supercritical fluid due to the interaction with its surrounding. N-hexane was injected into a
chamber filled with pure nitrogen at 5 MPa and 293 K and three different test cases were selected such that they
cover regimes in which the thermodynamic non-idealities, in particular the effects that stem from the potential phase
separation, are significant. Simultaneous shadowgraphy and elastic light scattering experiments were conducted to
capture both the flow structure as well as the phase separation. In addition, large-eddy simulations with a vaporliquid
equilibrium model were performed. Both experimental and numerical results show phase formation for the
cases, where the a-priori calculation predicts two-phase flow. Moreover, qualitative characteristics of the formation
process agree well between experiments and numerical simulations and the transition behaviour from a dense-gas
to a spray-like jet was captured by bothThe authors gratefully acknowledge the German Research Foundation (Deutsche Forschungsgemeinschaft) for providing
financial support in the framework of SFB/TRR 40. Financial support was also provided by Munich Aerospace
(www.munich-aerospace.de). Furthermore, the authors thank the Gauss Centre for Supercomputing e.V. (GCS)
(www.gauss-centre.eu) for supporting this project by providing computing time on the GCS Supercomputer SuperMUC
at Leibniz Supercomputing Centre (www.lrz.de).Traxinger, C.; Mßller, H.; Pfitzner, M.; Baab, S.; Lamanna, G.; Weigand, B.; Matheis, J.... (2018). Experimental and Numerical Investigation of Phase Separation due to Multi-Component Mixing at High-Pressure Conditions. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 130-137. https://doi.org/10.4995/ILASS2017.2017.4756OCS13013
Muscarinic M1 receptors modulate endotoxemia-induced loss of synaptic plasticity
Septic encephalopathy is associated with rapid deterioration of cortical functions. Using magnetic resonance imaging (MRI) we detected functional abnormalities in the hippocampal formation of patients with septic delirium. Hippocampal dysfunction was further investigated in an animal model for sepsis using lipopolysaccharide (LPS) injections to induce endotoxemia in rats, followed by electrophysiological recordings in brain slices. Endotoxemia induced a deficit in long term potentiation which was completely reversed by apamin, a blocker of small conductance calcium-activated potassium (SK) channels, and partly restored by treatment with physostigmine (eserine), an acetylcholinesterase inhibitor, or TBPB, a selective M1 muscarinic acetylcholine receptor agonist. These results suggest a novel role for SK channels in the etiology of endotoxemia and explain why boosting cholinergic function restores deficits in synaptic plasticity. Drugs which enhance cholinergic or M1 activity in the brain may prove beneficial in treatment of septic delirium in the intensive care unit
Redox Responses in Patients with Sepsis: High Correlation of Thioredoxin-1 and Macrophage Migration Inhibitory Factor Plasma Levels
Background. Redox active substances (e.g., Thioredoxin-1, Macrophage Migration Inhibitory Factor) seem to be central hubs in the septic inflammatory process.
Materials and Methods. Blood samples from patients with severe sepsis or septic shock (n = 15) were collected at the time of sepsis diagnosis (t0), and 24 (t24) and 48 (t48) hours later; samples from healthy volunteers (n = 18) were collected once; samples from postoperative patients (n = 28) were taken one time immediately after surgery. In all patients, we measured plasma levels of IL-6, TRX1 and MIF.
Results. The plasma levels of MIF and TRX1 were significantly elevated in patients with severe sepsis or septic shock. Furthermore, TRX1 and MIF plasma levels showed a strong correlation (t0: rsp = 0.720, Ď = 0.698/t24: rsp = 0.771, Ď = 0.949).
Conclusions. Proinflammatory/~oxidative and anti-inflammatory/~oxidative agents show a high correlation in order to maintain a redox homeostasis and to avoid the harmful effects of an excessive inflammatory/oxidative response
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