1,720,976 research outputs found
Multifunctional modalities of iron oxide magnetic nanoparticles: applications in diagnostics and magnetic fluid hyperthermia.
Full text linkThis PhD thesis, Multifunctional modalities of iron oxide magnetic nanoparticles: applications in diagnostics and magnetic fluid hyperthermia, has two major purposes. The first goal is to assess the anti-tumor efficacy and the potential of combining Hadron Therapy and Magnetic Fluid Hyperthermia (MFH) against pancreatic tumor cells; this is carried out with a perspective to establishing solid protocols for desirable future clinical applications. The second goal is to evaluate the Magnetic Resonance Imaging (MRI) image contrast efficiency of magnetic nanoparticles. This is accomplished by means of 1H Nuclear Magnetic Resonance relaxometry, magnetometry and morpho-dimensional characterization techniques, with a particular focus on the effect of size and coating. Data for this research were collected thanks to cross-collaborations between national and international research groups and hospital structures. For the MFH therapy, the properties of the magnetic nanoparticles that were employed have been optimized in order to maximize their heat release, and, at the same time, to give the patient an amount of magnetic material as low as possible, thus reducing any risk of detrimental side effects to his health. Cell culture conditions and hyperthermic treatment (partly of magnetic origin) were optimized to maximize the efficacy of the therapy, with the aim of decreasing the survival of cancer cells. Given the advantages of hadron therapy over conventional radiotherapy, it was decided to combine the hyperthermic treatment with the first one. This was possible thanks to the fact that Pavia, where most of the work behind this thesis was performed, hosts a state-of-the-art hadron therapy center, the CNAO foundation. This center is the only one in Italy where cancer patients can be treated with both protons and carbon ions. Two main results can be highlighted from the clonogenic survival data collected at 15 days after the combined therapeutic treatment. Firstly, at all hadrons/photon irradiation doses, an additional killing effect – i.e toxicity - of about 50-60% can be ascribed to the cellular uptake of the nanoparticles, with respect to simple irradiation of culture cells. Secondly, a significant killing effect of hyperthermia was observed for both irradiation protocols, consisting in an additional 15-30% of total survival decrease.
The enhanced efficacy of Hadron Therapy applied immediately after hyperthermia lays the foundations for future preclinical studies. Furthermore, these encouraging results point in the direction of further investigating this combination, with a view to finally translating it to clinical applications.
As to the second goal - i.e. the investigation of the properties of magnetic nanoparticles by means of nuclear magnetic resonance relaxometry and magnetometry - this thesis specifically concerned the influence of coating on the nuclear relaxation times. Two sets of samples, each consisting of four samples with different coatings, were obtained by means of the same synthesis procedure, while the nanoparticles coating has been realized with different polymers. A heuristic model for the field dependence of the NMR relaxivity curves allowed us to evaluate several parameters: among them, the saturation magnetization, the minimum approach distance, etc. Moreover, through the acquisition and analysis of experimental NMR dispersion curves, we observed that the relaxivities r1 and r2 of the four samples analyzed, for both sets, did not show significant differences in the whole range of frequencies investigated, at least within the experimental errors. Thus, we concluded that the four different coatings we analyzed on our spherical MNPs give essentially similar magnetic and relaxometric behavior.This PhD thesis, Multifunctional modalities of iron oxide magnetic nanoparticles: applications in diagnostics and magnetic fluid hyperthermia, has two major purposes. The first goal is to assess the anti-tumor efficacy and the potential of combining Hadron Therapy and Magnetic Fluid Hyperthermia (MFH) against pancreatic tumor cells; this is carried out with a perspective to establishing solid protocols for desirable future clinical applications. The second goal is to evaluate the Magnetic Resonance Imaging (MRI) image contrast efficiency of magnetic nanoparticles. This is accomplished by means of 1H Nuclear Magnetic Resonance relaxometry, magnetometry and morpho-dimensional characterization techniques, with a particular focus on the effect of size and coating. Data for this research were collected thanks to cross-collaborations between national and international research groups and hospital structures. For the MFH therapy, the properties of the magnetic nanoparticles that were employed have been optimized in order to maximize their heat release, and, at the same time, to give the patient an amount of magnetic material as low as possible, thus reducing any risk of detrimental side effects to his health. Cell culture conditions and hyperthermic treatment (partly of magnetic origin) were optimized to maximize the efficacy of the therapy, with the aim of decreasing the survival of cancer cells. Given the advantages of hadron therapy over conventional radiotherapy, it was decided to combine the hyperthermic treatment with the first one. This was possible thanks to the fact that Pavia, where most of the work behind this thesis was performed, hosts a state-of-the-art hadron therapy center, the CNAO foundation. This center is the only one in Italy where cancer patients can be treated with both protons and carbon ions. Two main results can be highlighted from the clonogenic survival data collected at 15 days after the combined therapeutic treatment. Firstly, at all hadrons/photon irradiation doses, an additional killing effect – i.e toxicity - of about 50-60% can be ascribed to the cellular uptake of the nanoparticles, with respect to simple irradiation of culture cells. Secondly, a significant killing effect of hyperthermia was observed for both irradiation protocols, consisting in an additional 15-30% of total survival decrease.
The enhanced efficacy of Hadron Therapy applied immediately after hyperthermia lays the foundations for future preclinical studies. Furthermore, these encouraging results point in the direction of further investigating this combination, with a view to finally translating it to clinical applications.
As to the second goal - i.e. the investigation of the properties of magnetic nanoparticles by means of nuclear magnetic resonance relaxometry and magnetometry - this thesis specifically concerned the influence of coating on the nuclear relaxation times. Two sets of samples, each consisting of four samples with different coatings, were obtained by means of the same synthesis procedure, while the nanoparticles coating has been realized with different polymers. A heuristic model for the field dependence of the NMR relaxivity curves allowed us to evaluate several parameters: among them, the saturation magnetization, the minimum approach distance, etc. Moreover, through the acquisition and analysis of experimental NMR dispersion curves, we observed that the relaxivities r1 and r2 of the four samples analyzed, for both sets, did not show significant differences in the whole range of frequencies investigated, at least within the experimental errors. Thus, we concluded that the four different coatings we analyzed on our spherical MNPs give essentially similar magnetic and relaxometric behavior
The effect of size, shape, coating and functionalization on nuclear relaxation properties in iron oxide core-shell nanoparticles: a brief review of the situation
No full textIn this perspective article, we present a short selection of some of the most significant case studies on magnetic nanoparticles for potential applications in nanomedicine, mainly magnetic resonance. For almost 10 years, our research activity focused on the comprehension of the physical mechanisms on the basis of the nuclear relaxation of magnetic nanoparticles in the presence of magnetic fields; taking advantage of the insights gathered over this time span, we report on the dependence of the relaxation behaviour on the chemico-physical properties of magnetic nanoparticles and discuss them in full detail. In particular, a critical review is carried out on the correlations between their efficiency as contrast agents in magnetic resonance imaging and the magnetic core of magnetic nanoparticles (mainly iron oxides), their size and shape, and the coating and solvent used for making them biocompatible and well dispersible in physiological media. Finally, the heuristic model proposed by Roch and coworkers is presented, as it was extensively adopted to describe most of the experimental data sets. The large amount of data analyzed allowed us to highlight both the advantages and limitations of the model
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Multi-input Deep Learning Model to Classify COVID-19 Pneumonia Severity from Imaging and Clinical Data
No full textThe study of multi-input models that can process heterogeneous data is a challenge at the frontier of machine learning. We implemented a multi-modal approach aiming at exploiting both imaging and clinical information of patients to predict the severity of their outcome. As a specific use case, we developed a fully automated algorithm to predict the outcome of COVID-19 patients based on chest X-Ray images and clinical data, provided by the AI4COVID Challenge (1589 subjects). The system can distinguish between severe cases, those who needed intensive care or died, and mild ones. The system is composed of three Convolutional Neural Networks (CNN) for pre-processing, lung segmentation (U-Net architecture), and outcome classification. The first CNN is devoted to recognize the gray-level encoding needed to standardize the images. The U-Net for lung segmentation has been trained using two datasets collected for Tuberculosis screening. We achieved a Dice Similarity Coefficient (DSC) equal to 0.96 ± 0.03. This was needed to focus the final classifier on evaluating features within the lung. Without the careful selection of the lung, in fact, the prediction strongly depended on features outside the lung district (e.g. ECG cables, respiratory masks). The outcome classifier is a multi-input CNN made of two branches joined at the bottom. The first branch is a ResNet that takes the segmented images as input, while the second branch is a Multi-Layer Perceptron (MLP) that takes in the preprocessed clinical parameters. We obtained an AUC equal to 0.84 and an accuracy equal to 76%. We also computed the saliency maps with the gradCAM and the feature importance to obtain a reasonable explanation of the classifier. This method based on data aggregation and on merging clinical and imaging information can be applied also to domains different from COVID-19 patients
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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