22 research outputs found

    Design an Iterative Learning Observer to Reconstruct the Interaction Force in AM-AFM

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    Trabajo presentado en la conferencia Fuerzas y Túnel (FyT2014), celebrada en San Sebastián del 27 al 29 de agosto de 2014.Extracting the time varying tip-sample interaction force in dynamic atomic force microscopy has been an important goal to improve the imaging capabilities of AFM with simultaneous measurements of material properties. Here, we design an Iterative Learning Observer to reconstruct the interaction force from the wave profile of the cantilever. In this method, the interaction force is considered as an unknown time varying parameter and estimated by the designed observer. Simulations and experiments prove the accuracy of this method in liquid and air for different materials. From the reconstructed force signals, we are able to obtain the average peak force, and consequently, using Hu and Raman equation, the Young modulus of the materials.N

    Molecular and Nanoscale Compositional Contrast of Soft Matter in Liquid: Interplay Between Elastic and Dissipative Interactions

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    We demonstrate that the phase contrast observed with an amplitude modulation atomic force microscope depends on two factors, the generation of higher harmonics components and the energy dissipated on the sample surface. Those factors are ultimately related to the chemical composition and structure of the surface. Our findings are general, but they specifically describe the results obtained while imaging soft materials in liquid. Molecular resolution experiments performed on a protein membrane surface in liquid confirm the theory.This work was supported by the Spanish Ministry of Science (MICINN) through Grants CSD2010-00024 and MAT2009-08650. J.R.R. has a JAE-Predoc fellowship from the European Social fund.Peer reviewe

    General Force Reconstruction Method for Amplitude Modulation Force Microscopy Experiment

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    Trabajo presentado en la conferencia Fuerzas y Túnel (FyT2014), celebrada en San Sebastián del 27 al 29 de agosto de 2014.Amplitude Modulation Atomic Force Microscopy (AM-AFM) is the most widely used technique for nanoscale characterization of materials and surfaces in the air and liquid environments. High detection or sensitivities and smaller lateral forces with respect to contact AFM are the advantages of the dynamic modes of AFM. However, in AM-AFM experiments the interaction force is not direct observable.N

    Optimization of Basic Magnetic Field Homogeneity in MR Tomography

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    This thesis is concerned with problems of measuring and mapping of magnetic field in MR tomograph, for purpose of magnetic flux density homogeneity optimization. Attention is paid to mapping techniques on rotary symmetric volume and to ways of magnetic fields optimization with utilization of passive and active correction systems. Theoretical analysis of magnetic field decomposition with utilization of spherical harmonics and numerical decomposition is made. Mapping and approximation techniques of basic magnetic field are verified by experiments in the laboratory at the Institute of Scientific Instruments AS CR in Brno

    Biopolymer-based composites for tissue engineering applications:a basis for future opportunities

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    Abstract Biomimetic scaffolds supporting tissue regeneration are complex materials with multifunctional characteristics. The unique biocompatibility and biodegradability of biopolymers make them excellent candidates for tissue engineering and regenerative medicine. Biopolymers, which have a wide range of properties, can be obtained from different natural sources. Depending on the target tissue, biopolymers can be engineered to meet a series of specific functions. We review different types of biopolymers and their composites, besides their interactions with specific cells and tissues. Specific cellular mechanisms in tissue regeneration are also considered to elucidate the effects of biopolymers on controlling cellular mechanisms given their advantages and challenging aspects. Furthermore, the modifications required to mimic the properties of neural, cardiac, bone, and skin tissues are discussed. Utilization of biopolymer-based composites in tissue engineering requires additional improvements, where several challenges should be overcome. This work is mainly focused on biopolymers used in tissue engineering, providing support for engineering of future biocomposites for the same purpose. Some examples of biocomposites are also provided, a general guide for selection of biopolymers and the secondary component (biopolymers as complements, additives, or nano-scale biomaterials) to develop biocomposites

    Safety and outcomes of intravenous thrombolytic therapy in ischemic stroke patients with COVID-19: CASCADE initiative

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    BACKGROUND: There is little information regarding the safety of intravenous tissue plasminogen activator (IV-tPA) in patients with stroke and COVID-19. METHODS: This multicenter study included consecutive stroke patients with and without COVID-19 treated with IV-tPA between February 18, 2019, to December 31, 2020, at 9 centers participating in the CASCADE initiative. Clinical outcomes included modified Rankin Scale (mRS) at hospital discharge, in-hospital mortality, the rate of hemorrhagic transformation. Using Bayesian multiple regression and after adjusting for variables with significant value in univariable analysis, we reported the posterior adjusted odds ratio (OR, with 95% Credible Intervals [CrI]) of the main outcomes. RESULTS: A total of 545 stroke patients, including 101 patients with COVID-19 were evaluated. Patients with COVID-19 had a more severe stroke at admission. In the study cohort, 85 (15.9%) patients had a hemorrhagic transformation, and 72 (13.1%) died in the hospital. After adjustment for confounding variables, discharge mRS score ≥2 (OR: 0.73, 95% CrI: 0.16, 3.05), in-hospital mortality (OR: 2.06, 95% CrI: 0.76, 5.53), and hemorrhagic transformation (OR: 1.514, 95% CrI: 0.66, 3.31) were similar in COVID-19 and non COVID-19 patients. High-sensitivity C reactive protein level was a predictor of hemorrhagic transformation in all cases (OR:1.01, 95%CI: 1.0026, 1.018), including those with COVID-19 (OR:1.024, 95%CI:1.002, 1.054). CONCLUSION: IV-tPA treatment in patients with acute ischemic stroke and COVID-19 was not associated with an increased risk of disability, mortality, and hemorrhagic transformation compared to those without COVID-19. IV-tPA should continue to be considered as the standard of care in patients with hyper acute stroke and COVID-19
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