Encontrado(s) 2197590 resultado(s)
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Photoinduced charge separation in the carbon nano-onion C60@C240

  • Voityuk, Alexander A.
  • Solà i Puig, Miquel
The double-shell fullerene C60@C240 formed by inclusion of C60 into C240 is the smallest stable carbon nano-onion. In the paper, we analyze in detail the character of excited states of C60@C240 in terms of exciton localization and charge transfer between the inner and outer shells. The unique structure of the buckyonion leads to a large electrostatic stabilization of charge-separated (CS) states in the C60@C240. As a result, the CS states C60+@C240 lie in the same region of the electronic spectrum (2.4-2.6 eV) as strongly absorbing locally excited states, and therefore, can be effectively populated. The CS states C60 @C240+ are found to be by 0.5 eV higher in energy than the states C60+@C240 . Unlike the situation observed in donor-acceptor systems, the energy of the CS states in C60@C240 does not practically depend on the environment polarity. This leads to exceptionally small reorganization energies for electron transfer between the shells. Electronic couplings for photoinduced charge separation and charge recombination processes are calculated. The absolute rate of the formation of the CS states C60+@C240 is estimated at ~ 4 ps-1. The electronic features found in C60@C240 are likely to be shared by other carbon nano-onions, We are grateful for financial support from the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects CTQ2014-54306-P and CTQ2015-69363-P), the Catalan DIUE (Project 2014SGR931, ICREA Academia 2014 Award to MS, and Xarxa de Referència en Química Teòrica i Computacional), and the FEDER fund (UNGI10-4E-801)

Exploring the validity of the Glidewell-Lloyd extension of Clar's π-sextet rule: assessment from polycyclic conjugated hydrocarbons

  • El Bakouri, Ouissam
  • Poater i Teixidor, Jordi
  • Feixas Geronès, Ferran
  • Solà i Puig, Miquel
The Clar pi-sextet rule was formulated as a tool to qualitatively assign the local aromatic character of six-membered rings in benzenoid species. This simple rule has been widely validated both experimentally and theoretically. In 1984, Glidewell and Lloyd reported an extension of this rule to polycyclic conjugated hydrocarbons having rings with any even number of carbon atoms in their structure. In this work, we assess the validity of the Glidewell-Lloyd extension in 69 polycyclic conjugated hydrocarbons composed of different combinations of four-, six-, and eight-membered rings. Our results support the validity of this extension with some exceptions that are discussed. Finally, a minor modification to the rule is proposed, This work has been supported by the Ministerio de Economía y Competitividad (MINECO) of Spain (Project CTQ2014-54306-P) and the Generalitat de Catalunya (project 2014SGR931, Xarxa de Referència en Química Teòrica i Computacional, ICREA Academia 2014 prize for M.S., and grant No. 2014FI_B 00429 to O.E.B.). The EU under the FEDER grant UNGI10-4E-801 (European Fund for Regional Development) has also funded this research

Combining Symbolic Tools with Interval Analysis: An Application to Solve Robust Control Problems

  • Ferrer Mallorquí, Inès
  • Vehí, Josep
Complex systems are often subjected to uncertainties that make its model difficult, if not impossible to obtain. A quantitative model may be inadequate to represent the behavior of systems which require an explicit representation of imprecision and uncertainty. Assuming that the uncertainties are structured, these models can be handled with interval models in which the values of the parameters are allowed to vary within numeric intervals. Robust control uses such mathematical models to explicitly have uncertainty into account. Solving robust control problems, like finding the robust stability or designing a robust controller, involves hard symbolic and numeric computation. When interval models are used, it also involves interval computation. The main advantage using interval analysis is that it provides guaranteed solutions, but as drawback its use requires the interaction with multiple kinds of data. We present a methodology and a framework that combines symbolic and numeric computation with interval analysis to solve robust control problems

Variació intralingüística en la categorització i l'etiquetatge de les parts del cos en català: una reflexió metodològica

  • Ferrerós Pagès, Carla
Starting from the evidence that there exists linguistic variation (individual or collective) in the classification and labelling of the parts of the body in Catalan (Ferrerós, 2012), we analyse the kind of relationship that holds between the observed variation and the methodology applied to collect the data (including both the sample and the procedure). The results of the study show, first, that different information is obtained according to whether the system used to elicit the data triggers spontaneous discourse or discourse deriving from metalinguistic reflection. Furthermore, it has been found that some variables in the sample (age, education and gender of the informants) are important to explain the variation between different speakers. Therefore, we conclude that the data that the researcher handles and, consequently, the validity of the conclusions reached will depend largely on the decisions taken regarding methodology, Partint de l'evidència que hi ha variació intralingüística (individual o entre parlants) en la categorització i l'etiquetatge de parts del cos en català (Ferrerós, 2012), analitzem quin tipus de relació hi ha entre la variació observada i la metodologia utilitzada per obtenir les dades (tant la mostra com els procediments). Els resultats de l'estudi mostren, d'una banda, que s'obté informació diferent segons si el sistema que s'ha fet servir per elicitar les dades origina un discurs espontani o un discurs fruit d'una reflexió metalingüística. I d'altra banda, s'ha constatat que algunes variables de la mostra (edat, nivell d'estudis i sexe dels informants) són rellevants per explicar la variació entre els diferents parlants. Per tant, concloem que les dades amb què treballa l'investigador i, per tant, la validesa de les conclusions que n'obté, dependran en gran part de les decisions metodològiques que prengui

Glycomic Approaches for the Discovery of Targets in Gastrointestinal Cancer

  • Mereiter, Stefan
  • Balmaña, Meritxell
  • Gomes, Joana
  • Magalhães, Ana
  • Reis, Celso A.
Gastrointestinal (GI) cancer is the most common group of malignancies and many of its types are among the most deadly. Various glycoconjugates have been used in clinical practice as serum biomarker for several GI tumors, however, with limited diagnose application. Despite the good accessibility by endoscopy of many GI organs, the lack of reliable serum biomarkers often leads to late diagnosis of malignancy and consequently low 5-year survival rates. Recent advances in analytical techniques have provided novel glycoproteomic and glycomic data and generated functional information and putative biomarker targets in oncology. Glycosylation alterations have been demonstrated in a series of glycoconjugates (glycoproteins, proteoglycans, and glycosphingolipids) that are involved in cancer cell adhesion, signaling, invasion, and metastasis formation. In this review, we present an overview on the major glycosylation alterations in GI cancer and the current serological biomarkers used in the clinical oncology setting. We further describe recent glycomic studies in GI cancer, namely gastric, colorectal, and pancreatic cancer. Moreover, we discuss the role of glycosylation as a modulator of the function of several key players in cancer cell biology. Finally, we address several state-of-the-art techniques currently applied in this field, such as glycomic and glycoproteomic analyses, the application of glycoengineered cell line models, microarray and proximity ligation assay, and imaging mass spectrometry, and provide an outlook to future perspectives and clinical applications

La consideración de la heterogeneidad del mosaico paisajístico en la cartografía de unidades de paisaje aplicación al caso de la isla central de Puerto Rico

  • Soto-Bayó, Sandra
  • Pintó i Fusalba, Josep
65: Número especial dedicat al Segon Congrés Català de Geografia : el mapa com a llenguatge geogràfic, En este trabajo se ha seguido una metodología de tipo analítico para delimitar las grandes unidades de paisaje de la isla principal de Puerto Rico, a partir de la utilización de las capas de información sobre la geología, la altitud, las cubiertas de suelo, la “rugosidad del terreno” y la heterogeneidad o entropía del paisaje. Se pretende distinguir unidades con un alto grado de homogeneidad y que se diferencien netamente de las unidades vecinas, en el supuesto que la homogeneidad del paisaje es relativa, es una cuestión de escala, ya que precisamente una propiedad del paisaje es su diversidad interna, la cual se manifiesta nítidamente a medida que aumenta el detalle de la escala de observación

Diversitat cultural, convivència i drets: una anàlisi en el marc de la Constitució Espanyola

  • Aparicio Wilhelmi, Marco
In the context of the rapid transformation of Spain from a country of emigration to one of immigration, both the social and political debate and academic analysis have taken place fundamentally within the area of foreign status. There has been little debate, on the other hand, about the model of society and framework for living together that are being sought. This text proposes to offer some thoughts on the legal and constitutional parameters for the construction of an egalitarian system of inclusion that would be compatible with differences. To do this, it has twomajor sections. A first section is devoted to how the foreign status system affects the debate being proposed here, as a necessary first step, or series of preconditions, for living together. In this area, the paper analyzes the general characteristics of the regulation of foreign status and questions the grounds the Constitutional Court cited to admit the restrictions on the rights of immigrants now in effect. The second section tries to offer some guidelines for constitutional reflection to cope with the disputes that can arise in societies that are culturally diverse. More specifically, it champions the insertion of the recognition of minority rights in the constitution, proposes cultural comprehension of the mandate of material equalization contained inArticle 9.2 of the Constitution, and lastly, insists on the need to ensure spaces for dialogue and true participation of the various actors in potential cultural conflicts, En el contexto de la acelerada transformación del Estado español de país de emigrantes a país de inmigración, tanto el debate social y político como el análisis académico se han desarrollado fundamentalmente dentro del terreno de la extranjería.Poco, en cambio, se ha debatido en torno almodelo de sociedad, del marco de convivencia,que se quiere construir. El presente texto pretende ofrecer una reflexión sobre los parámetros jurídico-constitucionales de la construcción de un sistema de inclusión igualitaria compatible con las diferencias. Con este objetivo, incorpora dos grandes apartados. Un primer apartado está dedicado a la incidencia en el debate propuesto del régimen de extranjería, en tanto que paso previo o conjunto de precondiciones de la convivencia. En este ámbito, se analizan los caracteres generales de la regulación de extranjería y se cuestionan los fundamentos que han servido al Tribunal Constitucional para dar cabida al conjunto de restricciones a los derechos de las personas inmigradas vigentes hoy en día. El segundo apartado trata de ofrecer algunas pautas de reflexión constitucional para hacer frente a las disputas que pueden originarse en sociedades culturalmente diversas. Concretamente, se reivindica el encaje constitucional del reconocimiento de derechos diferenciados, se propone una comprensión cultural del mandato de igualaciónmaterial contenido al artículo 9.2 constitucional y, finalmente, se insiste en la necesidad de asegurar espacios de diálogo y participación efectiva de los diferentes protagonistas en los posibles conflictos de tipo cultural, En el context de l'accelerada transformació de l'Estat espanyol d'un país d'emigrants a un país d'immigració, tant el debat social i polític com l'anàlisi acadèmica s'han dut a terme fonamentalment dins el terreny de l'estrangeria. En canvi, poc s'ha debatut al voltant del model de societat, del marc de convivència, que es vol construir. Aquest text pretén oferir una reflexió sobre els paràmetres jurídico-constitucionals de la construcció d'un sistema d'inclusió igualitària compatible amb les diferències. Amb aquest objectiu, incorpora dos grans apartats. Un primer apartat es dedica a la incidència del règim d'estrangeria en el debat proposat, com a pas previ o conjunt de precondicions de la convivència.En aquest àmbit, s'analitzen els caràcters generals de la regulació d'estrangeria i es qüestionen els fonaments que han servit al Tribunal Constitucional per donar cabuda al conjunt de restriccions als drets de les persones immigrades vigents avui en dia. El segon apartat tracta d'oferir algunes pautes de reflexió constitucional per fer front a les disputes que es poden originar en societats culturalment diverses.Concretament, es reivindica l'encaix constitucional del reconeixement de drets diferenciats, es proposa una comprensió cultural del mandat d'igualació material contingut a l'article 9.2 constitucional i, finalment, s'insisteix en la necessitat d'asse

Approaching a Low-Cost Production of Cellulose Nanofibers for Papermaking Applications

  • Delgado Aguilar, Marc
  • González Tovar, Israel
  • Tarrés Farrés, Quim
  • Alcalà Vilavella, Manel
  • Pèlach Serra, Maria Àngels
  • Mutjé Pujol, Pere
The use of cellulose nanofibers (CNF) as an additive in papermaking is an attractive alternative to improve paper’s strength. However, the costs of CNF production need to be competitive compared to other approaches aimed at reducing mechanical beating. Five different types of CNFs were prepared following different pretreatments: TEMPO-mediated oxidation at basic and neutral conditions, soft acid hydrolysis, enzymatic treatment, and mechanical beating. All of the pretreated fibers were later passed through a high-pressure homogenizer. The resulting CNFs were each applied to a papermaking pulp to investigate their reinforcing ability. Results indicated that the TEMPO-oxidized CNFs offered the highest increase at the same nanofiber content compared to the other types of CNFs. However, an analysis of the cost of increasing paper’s breaking length by 75% indicated that TEMPO-oxidized CNFs were more expensive than the other CNF grades, whereas CNFs from mechanical and acid pre-treatment offered similar increases at lower prices. The results indicated that CNFs of high fibrillation degree were not necessary to induce dramatic increases in paper strength. This finding offers a new possibility for the escalation of CNF production to industrial levels with competitive prices, The authors whis to aknowledge the finalcial support of the Spanish Economy and Competitiveness Ministry to the project CTM2011-28506-C02-01

Case-Crossover Analysis of Air Pollution Health Effects: A Systematic Review of Methodology and Application

  • Carracedo Martínez, Eduardo
  • Taracido, Margarida
  • Tobías, Aurelio
  • Sáez Zafra, Marc
  • Figueiras, Adolfo
Case-crossover is one of the most used designs for analyzing the health-related effects of air pollution. Nevertheless, no one has reviewed its application and methodology in this context. Objective: We conducted a systematic review of case-crossover (CCO) designs used to study the relationship between air pollution and morbidity and mortality, from the standpoint of methodology and application.Data sources and extraction: A search was made of the MEDLINE and EMBASE databases.Reports were classified as methodologic or applied. From the latter, the following information was extracted: author, study location, year, type of population (general or patients), dependent variable(s), independent variable(s), type of CCO design, and whether effect modification was analyzed for variables at the individual level. Data synthesis: The review covered 105 reports that fulfilled the inclusion criteria. Of these, 24 addressed methodological aspects, and the remainder involved the design’s application. In the methodological reports, the designs that yielded the best results in simulation were symmetric bidirectional CCO and time-stratified CCO. Furthermore, we observed an increase across time in the use of certain CCO designs, mainly symmetric bidirectional and time-stratified CCO. The dependent variables most frequently analyzed were those relating to hospital morbidity; the pollutants most often studied were those linked to particulate matter. Among the CCO-application reports, 13.6% studied effect modification for variables at the individual level.Conclusions: The use of CCO designs has undergone considerable growth; the most widely used designs were those that yielded better results in simulation studies: symmetric bidirectional and time-stratified CCO. However, the advantages of CCO as a method of analysis of variables at the individual level are put to little use

Tensile Strength Assessment of Injection-Molded High Yield Sugarcane Bagasse-Reinforced Polypropylene

  • Jiménez, Ana M.
  • Espinach Orús, Xavier
  • Granda Garcia, Luis Angel
  • Delgado Aguilar, Marc
  • Quintana, Germán
  • Fullana i Palmer, Pere
  • Mutjé Pujol, Pere
Sugarcane bagasse was treated to obtain sawdust, in addition to mechanical, thermomechanical, and chemical-thermomechanical pulps. The obtained fibers were used to obtain reinforced polypropylene composites prepared by injection molding. Coupling agent contents ranging from 2 to 10% w/w were added to the composite to obtain the highest tensile strength. All the composites included 30% w/w of reinforcing fibers. The tensile strength of the different sugarcane bagasse fiber composites were tested and discussed. The results were compared with that of other natural fiber- or glass fiber-reinforced polypropylene composites. Pulp-based composites showed higher tensile strength than sawdust-based composites. A micromechanical analysis showed the relationship of some micromechanical properties to the orientation angle, critical length, the intrinsic tensile strength, and the interfacial shear strength. The pulps showed similar intrinsic tensile strengths and were higher than that of sawdust. The properties of the sugarcane bagasse composites compared well with other natural fiber-reinforced composites

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