359 research outputs found
New epoxy thermosets derived from clove oil prepared by epoxy-amine curing
New thermosets from a triglycidyl eugenol derivative (3EPOEU) as a renewable epoxy monomer were obtained by an epoxy-amine curing process. A commercially-available Jeffamine® and isophorone diamine, both obtained from renewable resources, were used as crosslinking agents, and the materials obtained were compared with those obtained from a standard diglycidylether of bisphenol A (DGEBA). The evolution of the curing process was studied by differential scanning calorimetry and the materials obtained were characterized by means of calorimetry, thermogravimetry, thermodynamomechanical analysis, stress–strain tests and microindentation. 3EPOEU formulations were slightly less reactive, and the thermosets obtained showed higher Tgs than those prepared from DGEBA, since they had higher crosslinking density than formulations with DGEBA because of the more compact structure and higher functionality of the eugenol derivative. 3EPOEU thermosets showed good thermal stability and mechanical properties. The results obtained in this study allow us to conclude that the triglycidyl derivative of eugenol, 3EPOEU, is a safe and environmentally friendly alternative to DGEBA.Postprint (published version
Hard epoxy thermosets obtained via two sequential epoxy-amine condensations
A new family of dual-curable poly(ß-hydroxyamine ether) thermosets based on amine-epoxy formulations has been prepared and characterized. Both curing stages consist in an epoxy-amine polycondensation, each having different reactivity. Whereas the first one is carried out at relatively low temperature using an aliphatic flexible amine, the second is carried out at high temperature with a rigid aromatic amine. The sequentiality of the curing and the stability of the intermediate materials can be established in the basis of the different nucleophilicity of the amines used. The aromatic amine, with a weakly nucleophilic character, is not able to react with epoxides during the first stage at low temperature. The intermediate and final materials exhibit a wide range of properties, thanks to the different glass transition of both epoxy-amine networks, and can be tuned by changing the relative proportion of both diamines in the formulation. The participation of the epoxy resin in both curing stages ensures the homogeneity of the prepared materials, rendering them excellent candidates for applications such as adhesives or smart materials.Postprint (author's final draft
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
Estrategias de afrontamiento en familias con hijos adolescentes
Los objetivos de este estudio son: a) Describir
las estrategias de afrontamiento que usan los padres con
hijos adolescentes y las que les son más útiles, y b) Verificar
las posibles diferencias en función del nivel académico en
cuanto a las estrategias de afrontamiento que usan y que les
son útiles. A tal fin, una muestra de 386 padres (193 matrimonios)
de hijos adolescentes fueron evaluados a partir
del F-COPES (McCubbin et al., 1981). Los resultados obtenidos
demuestran que a) las estrategias de afrontamiento
usadas y consideradas útiles en mayor medida son las de
Reestructuración y la de Obtención de Apoyo Social; b)
tanto mujeres como varones puntúan en el mismo sentido;
c) se producen diferencias significativas entre la frecuencia
de uso y la de utilidad en todos los factores de F-COPES,
pero únicamente la estrategias de Reestructuración es considerada
como más útil aunque se use en menor medida; d)
son los varones y mujeres con estudios universitarios quienes
consideran la estrategia de Reestructuración como más
útil frente al resto de categorías de la variable nivel de estudios
Virtual mobility: A Higher Education Challenge in Europe 2020
Education and Training 2020, the new strategic framework for the European cooperation in the education and training field, highlights the need to boost transnational mobility with educational purposes, after having been proved to have a positive influence on university education and on the European youth access to the labour market. In this context, virtual mobility is key, complementing physical mobility and based on the growing chances of the ICT, and therefore it will be one of the upcoming challenges in the virtual educational possibilities at the Spanish universities. In this paper, we focus on the advantages of using the electronic version of the European Portfolio-e-PEL-as a methodological tool which enables the development of general competences-such as lifelong learning, self-evaluation or ICT application-encouraging motivation and international mobility. At the same time, we present an example of an activity in which the learning of both ICT and second language competences is integrated, and which confirms e-PEL as a necessary tool in university education.Educación y Formación 2020, el nuevo marco estratégico para la cooperación europea en el ámbito de la educación y formación, pone de manifiesto la necesidad de intensificar la movilidad transnacional con fines educativos, al haberse constatado su positiva repercusión en la formación universitaria y en el acceso al mercado laboral de los jóvenes europeos. En este contexto ha de destacarse la "movilidad virtual" que, de forma complementaria a la movilidad física y apoyándose en las crecientes posibilidades que nos ofrecen las TIC, será uno de los próximos retos de la oferta educativa virtual realizada por las universidades españolas. En este trabajo centramos nuestra atención en las ventajas que supone la utilización del Portfolio Europeo de las Lenguas en su versión electrónica (e-PEL) como herramienta metodológica que posibilita el desarrollo de competencias genéricas -como el aprendizaje a lo largo de la vida, la autoevaluación o la aplicación de las TIC- facilitando así la motivación y la movilidad internacional. Así mismo, presentamos también un ejemplo de actividad en la que se integran el aprendizaje de ambas competencias (TIC y lengua extranjera) y que confirma al e-PEL como una herramienta necesaria en la formación universitaria europea
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