Copolimerización aniónica de acroleina

Tesis inédita de la Universidad de Madrid, Facultad de Ciencias , leída el 23 de junio de 1970.Universidad de MadridTRUEProQuestpu

Laser performance of Coumarin 540A dye molecules in polymeric host media with different viscosities: From liquid solution to solid polymer matrix

11 pages, 12 figures, 3 tables.-- PACS: 42.70.Hj; 42.55.Rz; 42.55.Mv; 66.20.+d; 78.55.Bq; 78.55.KzPhotophysical parameters and lasing properties of Coumarin 540A dye molecules are studied in solutions of increasing viscosity, from liquid solutions in 1,4-dioxane to solid solutions in poly(methyl methacrylate). The fluorescence quantum yield and lasing efficiencies decrease as the viscosity of the solution increases, reflecting the strong influence of the rigidity of the medium on the radiative processes. The photodegradation mechanisms acting on the fluorophores are analyzed by following the dependence of laser induced fluorescence and laser output on the number of pump laser pulses. The fluorescence redistribution after pattern photobleaching technique is used, and Fick's second law is applied to study the diffusion of dye molecules in the highly viscous polymer solutions. The diffusion coefficients of the dye molecules as a function of the increased viscosity of the medium are determined.This work was supported by the Spanish CICYT Project MAT94-0757.Peer reviewe

Highly photostable solid-state dye lasers based on silicon-modified organic matrices

11 pages, 13 figures, 4 tables.-- PACS: 42.55.Rz; 42.60.FcWe report on the synthesis, characterization, and physical properties of modified polymeric matrices incorporating silicon atoms in their structure and doped with laser dyes. When the silicon-modified organic matrices incorporated pyrromethene 567 (PM567) and pyrromethene 597 (PM597) dyes as actual solid solutions, highly photostable laser operation with reasonable, nonoptimized efficiencies was obtained under transversal pumping at 532 nm. At a pump repetition rate of 10 Hz, the intensity of the laser emission remained at the level or above the initial lasing intensity after 100 000 pump pulses in the same position of the sample, corresponding to an estimated accumulated pump energy absorbed by the system of 518 and 1295 GJ/mol for PM567 and PM597, respectively. When the pump repetition rate was increased to 30 Hz, the laser emission of dye PM567 decreased steadily and the output energy fell to one-half its initial value after an accumulated pump energy of 989 GJ/mol. Dye PM597 demonstrated a remarkable photostability, and under 30 Hz pumping the laser emission from some samples remained stable after 700 000 pump pulses in the same position of the sample, corresponding to an accumulated pump energy of 17 300 GJ/mol. Narrow linewidth operation with tuning ranges of up to 31 nm was obtained with both pyrromethene dyes when some of the samples were incorporated into a grazing-incidence grating oscillator.This work was supported by Project Nos. 7N/0100/02 of the Comunidad Autónoma de Madrid ( CAM) and MAT2004- 04643-C03-01 of the Spanish CICYT. One of the authors (O.G.) thanks the MEC for awarding her a Ramón y Cajal scientific contract. Another author (D.A.) thanks CAM for a predoctoral scholarship.Peer reviewe

Composites de hidroxiapatita con matrices biodegradables

Mucho se ha publicado sobre el empleo de la hídroxíapatita (HAP) como un sustituto del hueso en diferentes áreas de la medicina Desde hace algunos años, se viene criticando el uso de este sistema debido a la capacidad de migración de las partí­culas de HAP del sitio del implante. Su posible estabilización se viene investigando y se han desarrollado métodos para lograrlo. Se prepararon composites de hídroxíapatita con quitosana (CHI) y ácido acrílico (AA) con el objetivo de obtener sistemas biodegradables con características osteoconductoras. Se estudió la influencia de dife­rentes factores: método de preparación, contenido de HAP y la concentración de CID sobre la cinética de fotopolimerización de estos composites bajo irradación con luz visible. Como sistema de iniciación se empleó el par canforquinona-alcohol N,N­dirnetilaminobencílico, ambos al 1 % en peso con respecto al AA. Se encontró que el método de preparación influye sobre las propiedades fisico-quínúcas y cinéticas de los composites. Por ejemplo, para los sistemas preparados sobre la base de geles de AA y CHl previamente hinchada con agua, se observan menores velocidades de polimeriza­ción (R,) que para los composites obtenidos a partir de los llamados geles inversos, donde el AA se pone previamente en contacto con la CHI (antes de la formación de su gel con agua)

Bichromatic laser emission from dipyrromethene dyes incorporated into solid polymeric media

9 pages, 9 figures.Bichromatic laser emission from dipyrromethene-based solid-state dye lasers is reported. The dependence of this dual emission on different factors and its origin and causes are discussed in the light of different models proposed in the literature. Our experimental results indicate that the long-wavelength emission can be explained in terms of reabsorption/reemission effects and inhomogeneous broadening of the S0-S1 transition. The short-wavelength emission corresponds to the usual S0-S1 transition and dominates at low dye concentration.This work was supported by Project Nos. MAT2004-04643-C03-01 and MAT2004-04643-C03-02 of the Spanish CICYT. One of the authors (M.Á.) thanks Ministerio de Ciencia y Tecnología (MCT) for a predoctoral grant. Another author (M.L.) thanks Comunidad Autónoma de Madrid for a postdoctoral grant and MCT for a Juan de la Cierva contract.Peer reviewe

Multi-parametric MR Imaging Biomarkers Associated to Clinical Outcomes in Gliomas: A Systematic Review

[EN] Purpose: To systematically review evidence regarding the association of multi-parametric biomarkers with clinical outcomes and their capacity to explain relevant subcompartments of gliomas. Materials and Methods: Scopus database was searched for original journal papers from January 1st, 2007 to February 20th , 2017 according to PRISMA. Four hundred forty-nine abstracts of papers were reviewed and scored independently by two out of six authors. Based on those papers we analyzed associations between biomarkers, subcompartments within the tumor lesion, and clinical outcomes. From all the articles analyzed, the twenty-seven papers with the highest scores were highlighted to represent the evidence about MR imaging biomarkers associated with clinical outcomes. Similarly, eighteen studies defining subcompartments within the tumor region were also highlighted to represent the evidence of MR imaging biomarkers. Their reports were critically appraised according to the QUADAS-2 criteria. Results: It has been demonstrated that multi-parametric biomarkers are prepared for surrogating diagnosis, grading, segmentation, overall survival, progression-free survival, recurrence, molecular profiling and response to treatment in gliomas. Quantifications and radiomics features obtained from morphological exams (T1, T2, FLAIR, T1c), PWI (including DSC and DCE), diffusion (DWI, DTI) and chemical shift imaging (CSI) are the preferred MR biomarkers associated to clinical outcomes. Subcompartments relative to the peritumoral region, invasion, infiltration, proliferation, mass effect and pseudo flush, relapse compartments, gross tumor volumes, and high-risk regions have been defined to characterize the heterogeneity. For the majority of pairwise cooccurrences, we found no evidence to assert that observed co-occurrences were significantly different from their expected co-occurrences (Binomial test with False Discovery Rate correction, alpha=0.05). The co-occurrence among terms in the studied papers was found to be driven by their individual prevalence and trends in the literature. Conclusion: Combinations of MR imaging biomarkers from morphological, PWI, DWI and CSI exams have demonstrated their capability to predict clinical outcomes in different management moments of gliomas. Whereas morphologic-derived compartments have been mostly studied during the last ten years, new multi-parametric MRI approaches have also been proposed to discover specific subcompartments of the tumors. MR biomarkers from those subcompartments show the local behavior within the heterogeneous tumor and may quantify the prognosis and response to treatment of gliomas.This work was supported by the Spanish Ministry for Investigation, Development and Innovation project with identification number DPI2016-80054-R.Oltra-Sastre, M.; Fuster García, E.; Juan -Albarracín, J.; Sáez Silvestre, C.; Perez-Girbes, A.; Sanz-Requena, R.; Revert-Ventura, A.... (2019). 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New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Laser performance of Coumarin 540A dye molecules in polymeric host media with different viscosities: From liquid solution to solid polymer matrix

11 pages, 12 figures, 3 tables.-- PACS: 42.70.Hj; 42.55.Rz; 42.55.Mv; 66.20.+d; 78.55.Bq; 78.55.KzPhotophysical parameters and lasing properties of Coumarin 540A dye molecules are studied in solutions of increasing viscosity, from liquid solutions in 1,4-dioxane to solid solutions in poly(methyl methacrylate). The fluorescence quantum yield and lasing efficiencies decrease as the viscosity of the solution increases, reflecting the strong influence of the rigidity of the medium on the radiative processes. The photodegradation mechanisms acting on the fluorophores are analyzed by following the dependence of laser induced fluorescence and laser output on the number of pump laser pulses. The fluorescence redistribution after pattern photobleaching technique is used, and Fick's second law is applied to study the diffusion of dye molecules in the highly viscous polymer solutions. The diffusion coefficients of the dye molecules as a function of the increased viscosity of the medium are determined.This work was supported by the Spanish CICYT Project MAT94-0757.Peer reviewe

Laser performance of pyrromethene 567 dye in solid polymeric matrices with different cross-linking degrees

8 pages, 5 figures, 2 tables.We report on the laser action of pyrromethene 567 (PM567) incorporated into copolymers of methyl methacrylate (MMA) with different methacrylic and acrylic cross-linking monomers: ethyleneglycol dimethacrylate, trimethylolpropane trimethacrylate, tetraethyleneglycol diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate (PETRA). The vol/vol proportion of the different co-monomers in each copolymer formulation was systematically varied, and the effect of each composition on the lasing properties of PM567 was evaluated. The laser samples were transversely pumped at 534 nm with 5.5 mJ/pulse from a frequency doubled Q-switched Nd:KGW laser. Lasing efficiencies of up 26% and good stability with a drop of the initial laser output of 30% after 100 000 pump pulses at 5 Hz in P(MMA:PETRA 95:5) were demonstrated.This work was supported by Project No. MAT2000- 1361-C04-01 of the Spanish CICYT.Peer reviewe