1,720,957 research outputs found
Synthesis and characterisation of Y2O3 co-doped with Co (III) or Eu (III) and Ba (II) or Ca (II)
No full textTreball Final de Grau en Química. Codi: QU0943. Curs: 2014/2015Two years ago, the solid state chemistry research group at Jaume I University studied the possibility of developing new lanthanide-based inorganic pigments. The synthesis of M (II) (Ca or Ba) and Tb (III) co-doped Y2O3 ceramics by a modified Pechini method was reported to obtain new environmental friendly yellow pigments as an alternative to the toxic existing ones Different solid solutions were prepared to accomplish the best composition. The general structure was Y1.86−xMxTb0.14O3−x/2 where M represents calcium or barium ions and x ranges from 0.06 to 0.64.
Spectroscopic measurements and thermal treatments showed that all samples incorporated terbium (IV) and terbium (III) ions into the Y2O3 structure. However, samples with calcium showed more intense yellow colouration due to the higher amount of terbium (IV) ions, whereas samples with barium were pale beige. It was concluded that the presence of calcium
(rCa (II) (IC=6) = 114 pm) or barium (rBa (II) (IC=6)= 149 pm) alters the structure of the Y2O3 lattice varying the distance terbium-oxygen. A possible explanation to those results was that calcium, with a similar radius to yttrium (rY(III) (IC=6)= 104 pm) allows the charge transfer between terbium and oxygen ions and thus the oxidation of terbium ions, but barium is bigger than
yttrium and the charge transfer transitions are hindered.
Additional studies on the same structure were performed substituting terbium (IV) ions for other chromophores such as chromium (III) or iron (III). Results also showed a major deviation in colour for the samples containing calcium in the matrix. The present project deepens into the reasons behind the change in colour between samples doped with barium and calcium
Synthesis of novel carbohydrate delivery agents for Boron Neutron Capture Therapy
No full textBoron neutron capture therapy is an emerging cancer treatment due to its unique capability to selectively remove tumor cells and spare healthy ones. The bottleneck of the technique are the current boron delivery agents which do not display enough selectivity towards cancer cells. To overcome this challenge our aim was to synthesize novel delivery agents entailing a glucose molecule functionalized with a polyhedral boron cluster in the form of dicarba-closo-ortho-dodecaborane which target glucose transporters overexpressed on the surface of cancer cells.
Some carbohydrate conjugates have previously been prepared with positive biological response but none of them incorporate the boron cage at the sixth position. In this study, three end products were prepared: 6-O-o-carboranylmethyl-D-glucopyranose, methyl 6-O-o-carboranylmethyl-α-D-glucopyrano-side and methyl 6-O-o-carboranylmethyl-β-D-glucopyranoside starting from commercially available compounds. Multistep synthetic routes were investigated and the characterization of the intermediates and the target molecules by means of NMR spectroscopy and mass spectrometry is described in detail. The three final products have been summited for cytotoxicity studies and cellular accumulation studies in tumor cell lines
SYNTHESIS OF SMART GLYCOSIDES TO ENHANCE GLYCO-NANOMATERIALS CIRCULATION HALF-TIME
No full textNanoparticle (NP)-based therapies have proven to offer potential solutions for conventional medicine while minimizing its side effects. In particular, glycosylated gold NPs (AuGNPs) represent attractive imaging and/or delivery platforms combining the biological activity of carbohydrates with the biocompatibility and physicochemical versatility of the metallic core. However and despite their rapid growth, the full clinical potential of these glyconanosystems will only be reached when their underlying safety concerns are understood and accurately addressed. When placed in biological fluids, AuGNPs, interact with a high number of biomolecules forming a so-called protein corona (PC), a coating that covers them and has severe consequences for their fate, efficacy and toxicity. As a consequence, AuGNPs are often recognized by the immune system and cleared from the blood stream before they have had enough circulation time to reach their therapeutic target.
In order to address the first issue, the initial chapter of the present thesis deals with the preparation of a library of six different AuGNPs functionalized with three monosaccharides (α-mannose, α-galactose and α-fucose) and two polyethylene glycol alternatives (PEG5000 and alkyl-PEG600) as an anchor to the Au nanomaterials (NMs). In collaboration with CICBiomaGUNE (Spain), the interaction of these AuGNPs with different lectins is investigated using Fluorescence Correlation Spectroscopy (FCS) to evaluate the effect of the PEG length on the interaction with proteins and the carbohydrates binding specificity. The second part of the chapter is dedicated to the preparation of an additional set of AuGNPs functionalized with negatively charged monosaccharides such as mannose-6-phosphate, mannose-6-sulfate or N-acetyl neuraminic acid. The final goal is to compare the results with neutral mannosylated AuGNPs in terms of colloidal stability and protein binding. These measurements will be performed at RCSI (Ireland) by means of Differential Centrifugal Sedimentation (DCS) and Dynamic Light Scattering (DLS). The final aim of the work described in Chapter I is to provide a better understanding of the PC formation and a correlation to the main NMs’ surface characteristics influencing it. The immunosuppressive properties of AuGNPs functionalized with N-acetyl neuraminic acid will also be tested in vivo in collaboration with Mario Negri Institute (Italy).
The second chapter focuses on the synthesis of ABO blood sugar epitopes, terminal di- (Fucα1-2Galβ1-O-R) and tri-saccharides (GalNAcα1-3(Fucα1-2)Galβ1-O-R and Galα1-3(Fucα1-2)Galβ1-O-R) covering the surface of human red blood cells and other body tissues. Our synthetic derivatives have been prepared adapting previously reported procedures and include a linear aglycone with a free amino group for NM conjugation. Functionalization of NMs with these self-antigens may improve their immunotolerance and biocompatibility in comparison to PEGylated counterparts, prolonging their blood circulation time, improving their delivery efficiency and granting them new therapeutic possibilities. These assumptions are to be tested in the near future in collaboration with RCSI (Ireland).
Chapter III describes the functionalization of mannose (Manα1), dimannose (Manα1-2Manα1) and trimannose (Manα1-3(Manα1-6)Manα1) derivatives with an amine-ending linker at their reducing-end for Au nanorods functionalization at VITO (Belgium). The end goal of the project is to develop a simple and label-free biosensor to detect mannose binding lectin (MBL) from human plasma samples based on optical measurements. The near IR shift due to the effective lectin binding can be correlated to potential cardiovascular disease for prevention and early onset stroke diagnosis.
In summary, this thesis aims to provide a better understanding of AuGNPs’ behavior in biological fluids, to face the main concerns impairing nanomedicine translation into clinics and to pave the way towards novel glyco-nanosystems with enhanced therapeutic performance for healthcare applications
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Variations on the Author
No full text“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
No full textWe 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
No full textWe 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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