328 research outputs found
Adhesion and non-linear rheology of adhesives with supramolecular crosslinking points
Soft supramolecular materials are promising for the design of innovative and
highly tunable adhesives. These materials are composed of polymer chains
functionalized by strongly interacting moieties, sometimes called "stickers".
In order to systematically investigate the effect of the presence of
associative groups on the debonding properties of a supramolecular adhesive, a
series of supramolecular model systems has been characterized by probe-tack
tests. These model materials, composed of linear and low dispersity
poly(butylacrylate) chains functionalized in the middle by a single tri-urea
sticker, are able to self-associate by six hydrogen bonds and range in
molecular weight (M n) between 5 and 85 kg/mol. The linear rheology and the
nanostructure of the same materials (called "PnBA3U") was the object of a
previous study 1,2. At room temperature, the association of polymers via
hydrogen bonds induces the formation of rod-like aggregates structured into
bundles for M n \textless{} 40kg/mol and the behavior of a soft elastic
material was observed (G'\textgreater{}\textgreater{}G "and G'~ 0). For
higher M n , the filaments were randomly oriented and polymers displayed a
crossover towards viscous behavior although terminal relaxation was not reached
in the experimental frequency window. All these materials show however similar
adhesive properties characterized by a cohesive mode of failure and low
debonding energies (W adh \textless{}40J/m 2 for a debonding speed of
100m/s). The debonding mechanisms observed during the adhesion tests have
been investigated in detail with an Image tools analysis developed by our group
3. The measure of the projected area covered by cavities growing in the
adhesive layer during debonding can be used to estimate the true stress in the
walls of the cavities and thus, to characterize the in-situ large strain
deformation of the thin layer during the adhesion test itself. This analysis
revealed in particular that the PnBA3U materials with M n \textless{} 40 kg/mol
soften very markedly at large deformation like yield stress fluids, explaining
the low adhesion energies measured for these viscoelastic gels.
Observing the Earth as an exoplanet with LOUPE, the Lunar Observatory for Unresolved Polarimetry of Earth
The detections of small, rocky exoplanets have surged in recent years and
will likely continue to do so. To know whether a rocky exoplanet is habitable,
we have to characterise its atmosphere and surface. A promising
characterisation method for rocky exoplanets is direct detection using
spectropolarimetry. This method will be based on single pixel signals, because
spatially resolving exoplanets is impossible with current and near-future
instruments. Well-tested retrieval algorithms are essential to interpret these
single pixel signals in terms of atmospheric composition, cloud and surface
coverage. Observations of Earth itself provide the obvious benchmark data for
testing such algorithms. The observations should provide signals that are
integrated over the Earth's disk, that capture day and night variations, and
all phase angles. The Moon is a unique platform from where the Earth can be
observed as an exoplanet, undisturbed, all of the time. Here, we present LOUPE,
the Lunar Observatory for Unresolved Polarimetry of Earth, a small and robust
spectropolarimeter to observe our Earth as an exoplanet.Comment: 14 pages, 3 figures, submitted in special Issue of Planetary and
Space Science on Scientific Preparations for Lunar Exploratio
Acute perioperative-stress-induced increase of atherosclerotic plaque volume and vulnerability to rupture in apolipoprotein-E-deficient mice is amenable to statin treatment and IL-6 inhibition
Myocardial infarction and stroke are frequent after surgical procedures and consume a considerable amount of benefit of surgical therapy. Perioperative stress, induced by surgery, is composed of hemodynamic and inflammatory reactions. The effects of perioperative stress on atherosclerotic plaques are ill-defined. Murine models to investigate the influence of perioperative stress on plaque stability and rupture are not available. We developed a model to investigate the influence of perioperative stress on plaque growth and stability by exposing apolipoprotein-E-deficient mice, fed a high cholesterol diet for 7â
weeks, to a double hit consisting of 30â
min of laparotomy combined with a substantial blood loss (approximately 20% of total blood volume; 400â
”l). The innominate artery was harvested 72â
h after the intervention. Control groups were sham and baseline controls. Interleukin-6 (IL-6) and serum amyloid A (SAA) plasma levels were determined. Plaque load, vascular smooth muscle cell (VSMC) and macrophage content were quantified. Plaque stability was assessed using the Stary score and frequency of signs of plaque rupture were assessed. High-dose atorvastatin (80â
mg/kg body weight/day) was administered for 6â
days starting 3â
days prior to the double hit. A single dose of an IL-6-neutralizing antibody or the fusion protein gp130-Fc selectively targeting IL-6 trans-signaling was subcutaneously injected. IL-6 plasma levels increased, peaking at 6â
h after the intervention. SAA levels peaked at 24â
h (n=4, P<0.01). Plaque volume increased significantly with the double hit compared to sham (n=8, P<0.01). More plaques were scored as complex or bearing signs of rupture after the double hit compared to sham (n=5-8, P<0.05). Relative VSMC and macrophage content remained unchanged. IL-6-inhibition or atorvastatin, but not blocking of IL-6 trans-signaling, significantly decreased plaque volume and complexity (n=8, P<0.01). Using this model, researchers will be able to further investigate the pathophysiology of perioperative plaque stability, which can result in myocardial infarction, and, additionally, to test potential protective strategies
Communication of pharmacogenetic research results to HIV-infected treated patients: standpoints of professionals and patients.
International audienceThe aim of pharmacogenetic studies is to adapt therapeutic strategies to individual genetic profiles, thus maximising their efficacy and minimising the likelihood of adverse side effects. Since the advent of personalised medicine, the issue of communicating research results to participants has become increasingly important. We addressed this question in the context of HIV infection, as patients and associations are particularly concerned by research and therapeutic advances. We explored the standpoints of both research professionals and participants involved in a pharmacogenetic study conducted in a cohort of HIV-infected patients. The setting of the research protocol was followed over a 2-year period. Participants' standpoints were collected through a questionnaire and interviews were conducted with research professionals. Of 125 participants, 76% wished to receive individual results and 71% wished to receive collective results; 39% did not know when results might be expected. Communication of global research results is a principle that is generally accepted by professionals. Concerning individual feedback, the professionals felt that it was necessary if it could be of direct benefit to the participant, but they expressed doubts for situations with no recognised benefit. Our results highlight the necessity to consider this issue in greater detail. We suggest the need to anticipate the debates concerning individual feedback, to differentiate between situations and the importance of further investigations on the opportunities and modalities of communication. Finally, our work emphasised the opposite pressures between the pursuit of scientific knowledge and the therapeutic orientation of clinical trials
Wissenschaftliche Monitoringkonzepte fĂŒr die Deutsche Bucht (WIMO) - Abschlussbericht
The state and development of coastal marine systems and an understanding of the interaction of
organisms, sea floor, water column, and biochemical and physical processes can only be obtained by
a combination of long-term monitoring and modelling approaches of different complexity. A need for the development and evaluation of monitoring strategies is driven by a framework of different
European and German regulations. The research project WIMO (Scientific Monitoring Concepts for the German Bight) has developed concepts and methods that aim at a fundamental scientific understanding of marine systems and also meet monitoring requirements of European legislation and regulations like the EU Marine Strategy Framework Directive. In this final report examples of common descriptors of ecosystem state like seabed integrity, eutrophication, and biodiversity are discussed. It has been assessed to what extent established measuring procedures used to survey the characteristics of the sea floor, and newly developed technologies are eligible for governmental monitoring. The significance of integrative modelling for linking and visualising results of measurements and
models is illustrated. It is shown how new concepts have been implemented into governmental monitoring in the form of web based data sheets. These insights enable continuous analyses and developments in the future
Biophysical Assessment of Single Cell Cytotoxicity: Diesel Exhaust Particle-Treated Human Aortic Endothelial Cells
Exposure to diesel exhaust particles (DEPs), a major source of traffic-related air pollution, has become a serious health concern due to its adverse influences on human health including cardiovascular and respiratory disorders. To elucidate the relationship between biophysical properties (cell topography, cytoskeleton organizations, and cell mechanics) and functions of endothelial cells exposed to DEPs, atomic force microscope (AFM) was applied to analyze the toxic effects of DEPs on a model cell line from human aortic endothelial cells (HAECs). Fluorescence microscopy and flow cytometry were also applied to further explore DEP-induced cytotoxicity in HAECs. Results revealed that DEPs could negatively impair cell viability and alter membrane nanostructures and cytoskeleton components in a dosage- and a time-dependent manner; and analyses suggested that DEPs-induced hyperpolarization in HAECs appeared in a time-dependent manner, implying DEP treatment would lead to vasodilation, which could be supported by down-regulation of cell biophysical properties (e.g., cell elasticity). These findings are consistent with the conclusion that DEP exposure triggers important biochemical and biophysical changes that would negatively impact the pathological development of cardiovascular diseases. For example, DEP intervention would be one cause of vasodilation, which will expand understanding of biophysical aspects associated with DEP cytotoxicity in HAECs
Biomimetic transferable surface for a real time control over wettability and photoerasable writing with water drop lens
We demonstrate a transferable device that can turn wettability of surfaces to sticky or slippy, as per requirement. It is composed of polymeric yarn with a fibrous structure, which can be lifted and placed on any surface to render it the unique wettability properties. We introduce Polyvinylidenefluoride (PVDF) random fiber as biomimetic rose petal surface. When it is decorated with PVDF nanofibers yarns, the random mesh transform from rose petal sticky state into grass leaf slippy state. When it is placed on sticky, hydrophilic metal coin, it converts the surface of the coin to super hydrophobic. Adjustments in the yarn system, like interyarn spacing, can be done in real time to influence its wettability, which is a unique feature. Next, we load the polymer with a photochromic compound for chemical restructuring. It affects the sliding angle of water drop and makes the fibers optically active. We also demonstrate a âwater droplets lensâ concept that enables erasable writing on photochromic rose petal sticky fibrous surface. The droplet on a highly hydrophobic surface acts as a ball lens to concentrate light onto a hot spot; thereby we demonstrate UV light writing with water lenses and visible light erasing
1H nuclear magnetic resonance spectroscopy characterisation of metabolic phenotypes in the medulloblastoma of the SMO transgenic mice
BACKGROUND: Human medulloblastomas exhibit diverse molecular pathology. Aberrant hedgehog signalling is found in 20-30% of human medulloblastomas with largely unknown metabolic consequences. METHODS: Transgenic mice over-expressing smoothened (SMO) receptor in granule cell precursors with high incidence of exophytic medulloblastomas were sequentially followed up by magnetic resonance imaging (MRI) and characterised for metabolite phenotypes by ÂčH MR spectroscopy (MRS) in vivo and ex vivo using high-resolution magic angle spinning (HR-MAS) ÂčH MRS. RESULTS: Medulloblastomas in the SMO mice presented as Tâ hyperintense tumours in MRI. These tumours showed low concentrations of N-acetyl aspartate and high concentrations of choline-containing metabolites (CCMs), glycine, and taurine relative to the cerebellar parenchyma in the wild-type (WT) C57BL/6 mice. In contrast, ÂčH MRS metabolite concentrations in normal appearing cerebellum of the SMO mice were not different from those in the WT mice. Macromolecule and lipid ÂčH MRS signals in SMO medulloblastomas were not different from those detected in the cerebellum of WT mice. The HR-MAS analysis of SMO medulloblastomas confirmed the in vivo ÂčH MRS metabolite profiles, and additionally revealed that phosphocholine was strongly elevated in medulloblastomas accounting for the high in vivo CCM. CONCLUSIONS: These metabolite profiles closely mirror those reported from human medulloblastomas confirming that SMO mice provide a realistic model for investigating metabolic aspects of this disease. Taurine, glycine, and CCM are potential metabolite biomarkers for the SMO medulloblastomas. The MRS data from the medulloblastomas with defined molecular pathology is discussed in the light of metabolite profiles reported from human tumours
Complex terrain experiments in the New European Wind Atlas
The New European Wind Atlas project will create a freely accessible wind atlas covering Europe and Turkey, develop the model chain to create the atlas and perform a series of experiments on flow in many different kinds of complex terrain to validate the models. This paper describes the experiments of which some are nearly completed while others are in the planning stage. All experiments focus on the flow properties that are relevant for wind turbines, so the main focus is the mean flow and the turbulence at heights between 40 and 300âm. Also extreme winds, wind shear and veer, and diurnal and seasonal variations of the wind are of interest. Common to all the experiments is the use of Doppler lidar systems to supplement and in some cases replace completely meteorological towers. Many of the lidars will be equipped with scan heads that will allow for arbitrary scan patterns by several synchronized systems. Two pilot experiments, one in Portugal and one in Germany, show the value of using multiple synchronized, scanning lidar, both in terms of the accuracy of the measurements and the atmospheric physical processes that can be studied. The experimental data will be used for validation of atmospheric flow models and will by the end of the project be freely available. This article is part of the themed issue âWind energy in complex terrainsâ
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