3,610 research outputs found
Synthesis, characterization, bioactivity and biocompatibility of nanostructured materials based on the wollastonite-poly(ethylmethacrylate-co-vinylpyrrolidone) system
Composite materials are very promising biomaterials
for hard tissue augmentation. The approach assayed
in this work involves the manufacturing of a composite
made of a bioactive ceramic, natural wollastonite (W) and a
nanostructured copolymer of ethylmethacrylate (EMA) and
vinylpyrrolidone (VP) to yield a bioresorbable and biocompatible
VP–EMA copolymer. A bulk polymerization was
induced thermally at 508C, using 1 wt % azobis(isobutyronitrile)
(AIBN) as free-radical initiator. Structural characterization,
compressive strength, flexural strength (FS), degradation,
bioactivity, and biocompatibility were evaluated in
specimens with a 60/40 VP/EMA ratio and ceramic content
in the range 0–60%. A good integration between phases
was achieved. Greater compression and FS, in comparison
with the pure copolymer specimens was obtained only
when the ceramic load got up to 60% of the total weight.
The soaking in NaCl solution resulted in the initial swelling
of the specimens tested. The maximum swelling was
reached after 2–3 h of immersion and it was significantly
greater for lower ceramic loads. This result makes the polymer
component the main responsible for the interactions
with the media. After soaking in SBF, microdomains segregation
can be observed in the polymer component that can
be related with a dramatic difference in the reactivity of
both monomers in free radical polymerization, whereas the
formation of an apatite-like layer on the W surfaces can be
observed. Biocompatibility in vitro studies showed the absence
of cytotoxicity of all formulations. The cells were able
to adhere on the polystyrene negative control and on specimens
containing 60 wt % wollastonite forming a monolayer
and showing a normal morphology. However, a low cellular
growth was observed. 2008 Wiley Periodicals, Inc.
J Biomed Mater Res 88A: 53–64, 2009Peer reviewe
Bayesian inference and data cloning in population projection matrices
Discrete time models are used in Ecology for describing the evolution of an agestructured
population. Usually, they are considered from a deterministic viewpoint but,
in practice, this is not very realistic.
The statistical model we propose in this article is a reasonable model for the case in
which the evolution of the population is described by means of a projection matrix.
In this statistical model, fertility rates and survival rates are unknown parameters and
they are estimated by using a Bayesian approach. Usual Bayesian and data cloning methods (based on Bayesian methodology) are applied
to real data from the population of the Steller sea lions located in the Alaska coast since
1978 to 2004. The estimates obtained from these methods show a good behavior when
they are compared to the actual value
Analysis and visualization of the dynamics of research groups in terms of projects and co-authored publications : A case study of library and information science in Argentina
Objective: The present study offers a novel methodological contribution to the study of the configuration and dynamics of research groups, through a comparative perspective of the projects funded (inputs) and publication co-authorships (output).
Method: A combination of bibliometric techniques and social network analysis was applied to a case study: the Departmento de Bibliotecología (DHUBI), Universidad Nacional de La Plata, Argentina, for the period 2000-2009. The results were interpreted statistically and staff members of the department, were interviewed.
Results: The method makes it possible to distinguish groups, identify their members and reflect group make-up through an analytical strategy that involves the categorization of actors and the interdisciplinary and national or international projection of the networks that they configure. The integration of these two aspects (input and output) at different points in time over the analyzed period leads to inferences about group profiles and the roles of actors.
Conclusions: The methodology presented is conducive to micro-level interpretations in a given area of study, regarding individual researchers or research groups. Because the comparative input-output analysis broadens the base of information and makes it possible to follow up, over time, individual and group trends, it may prove very useful for the management, promotion and evaluation of scienceFacultad de Humanidades y Ciencias de la Educació
Validación de un nuevo método de preconcentración y medición de mercurio en sedimentos utilizando materiales sol-gel dopados con extractantes sulfurados
El mercurio es un metal pesado altamente tóxico presente en el ambiente por causas naturales o
antropogénicas. El mercurio contenido en los cuerpos receptores de agua tiende a precipitarse y acumularse
en los sedimentos. Por lo tanto, las mediciones de mercurio en sedimentos representan un buen indicativo de
la calidad del ecosistema.
En este trabajo se presentan las diferentes etapas involucradas en el desarrollo de un nuevo método de
separación, preconcentración y medición de mercurio en sedimentos con contenidos naturales de este
elemento. La separación y preconcentración se realizó mediante el uso de nuevos materiales sorbentes
preparados a través del proceso sol-gel utilizando CYANEX 471X (sulfuro de triisobutilfosfina) y CYANEX 301
(ácido bis (2,4,4-trimetilpentil) ditiofosfínico) como extractantes de mercurio. Se describe la optimización de la
etapa de acoplamiento de los materiales empacados en columna, utilizando un sistema automatizado de
inyección de flujo, para conectarla en línea con un espectrómetro de absorción atómica donde se realizó la
medición de mercurio por generación de vapor frío. Como parte importante en el desarrollo de un nuevo
método analítico, se encuentra su validación, la cual es materia de este trabajo. Por lo tanto, una vez
optimizado, el método fue validado evaluando los siguientes parámetros: robustez, intervalo lineal y de
trabajo, límite de detección y de cuantificación, selectividad, exactitud (repetibilidad y veracidad) e
incertidumbre. El método fue aplicado para la medición de mercurio en un sedimento de presa con
contenidos naturales de este analito. Los resultados se compararon con los obtenidos mediante
espectrometría de masas con plasma inductivamente acoplado (ICP-MS) y espectrometría de fluorescencia
atómica con generación de vapor frío (CV-AFS
Analysis and visualization of the dynamics of research groups in terms of projects and co-authored publications : A case study of library and information science in Argentina
Objective: The present study offers a novel methodological contribution to the study of the configuration and dynamics of research groups, through a comparative perspective of the projects funded (inputs) and publication co-authorships (output).
Method: A combination of bibliometric techniques and social network analysis was applied to a case study: the Departmento de Bibliotecología (DHUBI), Universidad Nacional de La Plata, Argentina, for the period 2000-2009. The results were interpreted statistically and staff members of the department, were interviewed.
Results: The method makes it possible to distinguish groups, identify their members and reflect group make-up through an analytical strategy that involves the categorization of actors and the interdisciplinary and national or international projection of the networks that they configure. The integration of these two aspects (input and output) at different points in time over the analyzed period leads to inferences about group profiles and the roles of actors.
Conclusions: The methodology presented is conducive to micro-level interpretations in a given area of study, regarding individual researchers or research groups. Because the comparative input-output analysis broadens the base of information and makes it possible to follow up, over time, individual and group trends, it may prove very useful for the management, promotion and evaluation of scienceFacultad de Humanidades y Ciencias de la Educació
Revealing patterns of local species richness along environmental gradients with a novel network tool
How species richness relates to environmental gradients at large extents is commonly investigatedaggregating local site data to coarser grains. However, such relationships often change with the grainof analysis, potentially hiding the local signal. Here we show that a novel network technique, the"method of reflections", could unveil the relationships between species richness and climate withoutsuch drawbacks. We introduced a new index related to potential species richness, which revealedlarge scale patterns by including at the local community level information about species distributionthroughout the dataset (i.e., the network). The method effectively removed noise, identifying howfar site richness was from potential. When applying it to study woody species richness patterns inSpain, we observed that annual precipitation and mean annual temperature explained large parts ofthe variance of the newly defined species richness, highlighting that, at the local scale, communitiesin drier and warmer areas were potentially the species richest. Our method went far beyond whatgeographical upscaling of the data could unfold, and the insights obtained strongly suggested that itis a powerful instrument to detect key factors underlying species richness patterns, and that it couldhave numerous applications in ecology and other fields.Comunidad de MadridMinisterio de Economía y Competitivida
Synthesis, Photochemical, and Redox Properties of Gold(I) and Gold(III) Pincer Complexes Incorporating a 2,2′:6′,2″-Terpyridine Ligand Framework
Reaction of [Au(C6F5)(tht)] (tht = tetrahydrothiophene) with 2,2′:6′,2″-terpyridine (terpy) leads to complex [Au(C6F5)(η1-terpy)] (1). The chemical oxidation of complex (1) with 2 equiv of [N(C6H4Br-4)3](PF6) or using electrosynthetic techniques affords the Au(III) complex [Au(C6F5)(η3-terpy)](PF6)2 (2). The X-ray diffraction study of complex 2 reveals that the terpyridine acts as tridentate chelate ligand, which leads to a slightly distorted square-planar geometry. Complex 1 displays fluorescence in the solid state at 77 K due to a metal (gold) to ligand (terpy) charge transfer transition, whereas complex 2 displays fluorescence in acetonitrile due to excimer or exciplex formation. Time-dependent density functional theory calculations match the experimental absorption spectra of the synthesized complexes. In order to further probe the frontier orbitals of both complexes and study their redox behavior, each compound was separately characterized using cyclic voltammetry. The bulk electrolysis of a solution of complex 1 was analyzed by spectroscopic methods confirming the electrochemical synthesis of complex 2
Cr3+ substituted Zn-Al layered double hydroxides as UV–Vis light photocatalysts for NO gas removal from the urban environment
The ZnAl-CO3, ZnAlCr-CO3 and ZnCr-CO3 LDH samples were studied as De-NOx photocatalysts in this work. Samples without Cr and increasing the presence of Cr3+ in the LDH framework in the 0.06, 0.15 and 0.3 Cr/Zn ratio were prepared by co-precipitation method, all of them constituted by pure LDH phase. The increase of chromium content in the LDH framework leads to lower crystallinity and higher specific surface area in the samples. Moreover, the CrO6 octahedron centres expand the photo-activity from UV to Visible light and assist to decrease the recombination rate of the electrons and holes. The favourable textural, optical and electronic properties of Cr-containing LDH samples explain the good NO removal efficiency (55%) and outstanding selectivity (90%) found for the analysed De-NOx process
Towards a greener endoscopy: considerations on the strategies to improve sustainability
Climate crisis is dramatically changing life on earth. Environmental sustainability and waste management
are rapidly gaining centrality in quality improvement strategies of healthcare, especially in procedure-
dominant fields such as gastroenterology and digestive endoscopy. Therefore, healthcare interventions
and endoscopic procedures must be evaluated through the ‘triple bottom line’ of financial, social, and
environmental impact. The purpose of the paper is to provide information on the carbon footprint of gas-
troenterology and digestive endoscopy and outline a set of measures that the sector can take to reduce
the emission of greenhouse gases while improving patient outcomes. Scientific societies, hospital execu-
tives, single endoscopic units can structure health policies and investment to build a “green endoscopy”.
The AIGO study group reinforces the role of gastrointestinal endoscopy professionals as advocates of sus-
tainability in digestive endoscopy. The “green endoscopy” can shape a more sustainable health service
and lead to an equitable, climate-smart, and healthier future.info:eu-repo/semantics/publishedVersio
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