254 research outputs found
Noether-Wald energy in Critical Gravity
Criticality represents a specific point in the parameter space of a
higher-derivative gravity theory, where the linearized field equations become
degenerate. In 4D Critical Gravity, the Lagrangian contains a Weyl-squared
term, which does not modify the asymptotic form of the curvature. The
Weyl coupling is chosen such that it eliminates the massive scalar mode
and it renders the massive spin-2 mode massless. In doing so, the theory turns
consistent around the critical point.
Here, we employ the Noether-Wald method to derive the conserved quantities
for the action of Critical Gravity. It is manifest from this energy definition
that, at the critical point, the mass is identically zero for Einstein
spacetimes, what is a defining property of the theory. As the entropy is
obtained from the Noether-Wald charges at the horizon, it is evident that it
also vanishes for any Einstein black hole.Comment: 7 pages, no figures, Final version for PL
A new IRT-based standard setting method: application to eCat-Listening
Criterion-referenced interpretations of tests are highly necessary, which usually involves the diffi cult task of establishing cut scores. Contrasting with other Item Response Theory (IRT)-based standard setting methods, a non-judgmental approach is proposed in this study, in which Item Characteristic Curve (ICC) transformations lead to the final cut scores. Method: eCat-Listening, a computerized adaptive test for the
evaluation of English Listening, was administered to 1,576 participants, and the proposed standard setting method was applied to classify them into the performance standards of the Common European Framework of Reference for Languages (CEFR). Results: The results showed a classifi cation closely related to relevant external measures of the English language domain, according to the CEFR. Conclusions: It is concluded that the proposed method is a practical and valid standard setting alternative for IRT-based tests interpretationsUn nuevo método de standard setting basado en la TRI: aplicación a eCat-Listening. Antecedentes: las interpretaciones de los tests referidas a criterio son muy necesarias, lo cual normalmente implica la difícil tarea de establecer puntos de corte. En contraste con otros métodos de standard setting basados en la Teoría de la Respuesta al Ítem (TRI), en
este estudio se propone una aproximación no basada en juicios, en que transformaciones de las Curvas Características de los Ítems (CCIs) dan lugar a los puntos de corte finales. Método: se administró eCat-Listening, un test adaptativo informatizado de evaluación de la comprensión oral del inglés, a 1.576 participantes y se aplicó el método de standard setting propuesto para clasificarles en los estándares de ejecución del Marco Común Europeo de Referencia para las lenguas (MCER). Resultados: los resultados mostraron una clasificación estrechamente relacionada con
variables externas relevantes sobre dominio del inglés, de acuerdo con el MCER. Conclusiones: se concluye que el método de standard setting propuesto es una alternativa práctica y válida para las interpretaciones de tests basados en TRIThis research was partly supported by two grants from the Spanish Ministerio de Educación y Ciencia (projects PSI2008-01685 and PSI2009-10341
Solubilization of phenols by multimolecular aggregates formed by low molecular weight hyperbranched polyglycidol
Hyperbranched polymers have been proposed as potential carriers or host compartments for controlled drug delivery. In this work the solubilization of alkylphenols into aggregates formed by hyperbranched polyglycidol HPG and its ester derivative has been studied. HPG17 was synthesized by ring-opening polymerization of glycidol, and then the ester HPG4-RBr13 has been obtained by reaction of hPG17 with 2-bromo isobutyryl bromide. The critical aggregate concentration CAC and micropolarity of aggregates were determined by using pyrene as fluorescence probe. CAC values obtained are 2.5mM and 0.25mM, for HPG17 and HPG4-RBr13, respectively. Our results indicate that the hydrophobic effect is larger for HPG4-RBr13, and that their aggregates are more hydrophobic, than for HPG17. In addition, their sizes and sizes distribution were determined by DLS.The partition of phenols between the micellar and aqueous phase was studied by using the pseudo-phase model, and the results show that the partition coefficients increases with increasing length of the side alkyl chain, and are larger for HPG4-RBr13 micelles than for HPG17 micelles
eCat-Listening: diseño y propiedades psicométricas de un test adaptativo informatizado de comprensión auditiva de la lengua inglesa
In this study, eCAT-Listening, a new computerized adaptive test for the evaluation of English Listening, is described. Item bank development, anchor design for data collection, and the study of the psychometric properties of the item bank and the adaptive test are described. The calibration sample comprised 1.576 participants. Good psychometric guarantees: the bank is unidimensional, the items are satisfactorily fi tted to the 3-parameter logistic model, and an accurate estimation of the trait level is obtained. As validity evidence, a high correlation was obtained between the estimated trait level and a latent factor made up of the diverse criteria selected. The analysis of the trait level estimation by means of a simulation led us to fi x the test length at 20 items, with a maximum exposure rate of .40En este trabajo se describe eCAT-Listening, un nuevo test adaptativo informatizado para la medición del nivel de comprensión auditiva del inglés. Se describe la elaboración del banco de ítems, el diseño de anclaje para la recogida de datos y el estudio de las
propiedades psicométricas del banco de ítems y del test adaptativo. La muestra de calibración fue de 1.576 personas. Se obtienen unas buenas garantías psicométricas: el banco es unidimensional, los ítems se ajustan satisfactoriamente al modelo logístico de 3 parámetros y se consigue una estimación precisa de los diferentes niveles de rasgo. Como prueba de validez, se obtuvo una alta correlación entre el rasgo estimado y un factor latente de nivel de inglés compuesto por las diferentes puntuaciones criterio utilizadas en el estudio. El análisis de la estimación del nivel de rasgo mediante simulación nos lleva a fijar la longitud del test adaptivo en 20 ítems, con una tasa máxima de exposición de 0,40This research was supported by two grants from the Spanish Ministry of Science and Innovation (project numbers PSI2009-10341 and PSI2008-01685) and by the UAM-IIC Chair
«Psychometric Models and Applications
Item parameter drift in computerized adaptive testing: study with eCAT
En el presente trabajo se muestra el análisis realizado sobre un Test Adaptativo Informatizado (TAI) diseñado para la evaluación del nivel de inglés, denominado eCAT, con el objetivo de estudiar el deterioro de parámetros (parameter drift) producido desde la calibración inicial del banco de ítems. Se ha comparado la calibración original desarrollada para la puesta en servicio del TAI (N= 3224) y la calibración actual obtenida con las aplicaciones reales del TAI (N= 7254). Se ha analizado el Funcionamiento Diferencial de los Ítems (FDI) en función de los parámetros utilizados y se ha simulado el impacto que sobre el nivel de rasgo estimado tiene la variación en los parámetros. Los
resultados muestran que se produce especialmente un deterioro de los parámetros a y c, que hay un importante número de ítems del banco para los que existe FDI y que la variación de los parámetros produce un impacto moderado en la estimación de θ de los evaluados con nivel de inglés alto. Se concluye que los parámetros de los ítems se han deteriorado y deben ser actualizadosThis study describes the parameter drift analysis conducted on eCAT (a Computerized Adaptive Test to assess the written English level of Spanish speakers). The original calibration of the item bank (N = 3224) was compared to a new calibration obtained from the data provided by most eCAT operative administrations (N = 7254). A Differential Item Functioning (DIF) study was conducted between the original and the new calibrations. The impact that the new parameters have on the trait level estimates was obtained by
simulation. Results show that parameter drift is found especially for a and c parameters, an important number of bank items show DIF, and the parameter change has a moderate impact on high-level-English θ estimates. It is then recommended to replace the original estimates by the new se
A global database of plant services for humankind
Humanity faces the challenge of conserving the attributes of biodiversity that may be essential to secure human wellbeing. Among all the organisms that are beneficial to humans,
plants stand out as the most important providers of natural resources. Therefore, identifying
plant uses is critical to preserve the beneficial potential of biodiversity and to promote basic
and applied research on the relationship between plants and humans. However, much of
this information is often uncritical, contradictory, of dubious value or simply not readily
accessible to the great majority of scientists and policy makers. Here, we compiled a genuslevel dataset of plant-use records for all accepted vascular plant taxa (13489 genera) using
the information gathered in the 4th Edition of Mabberley’s plant-book, the most comprehensive global review of plant classification and their uses published to date. From 1974 to 2017
all the information was systematically gathered, evaluated, and synthesized by David Mabberley, who reviewed over 1000 botanical sources including modern Floras, monographs,
periodicals, handbooks, and authoritative websites. Plant uses were arranged across 28
standard categories of use following the Economic Botany Data Collection Standard guidelines, which resulted in a binary classification of 9478 plant-use records pertaining human
and animal nutrition, materials, fuels, medicine, poisons, social and environmental uses. Of
all the taxa included in the dataset, 33% were assigned to at least one category of use, the
most common being “ornamental” (26%), “medicine” (16%), “human food” (13%) and “timber” (8%). In addition to a readily available binary matrix for quantitative analyses, we provide a control text matrix that links the former to the description of the uses in Mabberley’s
plant-book. We hope this dataset will serve to establish synergies between scientists and
policy makers interested in plant-human interactions and to move towards the complete
compilation and classification of the nature’s contributions to people upon which the wellbeing of future generations may depen
Investigating the Role of Micromammals in the Ecology of Coxiella burnetii in Spain
Coxiella burnetii, the causal agent of human Q fever and animal Coxiellosis, is a zoonotic infectious bacterium with a complex ecology that results from its ability to replicate in multiple (in)vertebrate host species. Spain notifies the highest number of Q fever cases to the ECDC annually and wildlife plays a relevant role in C. burnetii ecology in the country. However, the whole picture of C. burnetii hosts is incomplete, so this study seeks to better understand the role of micromammals in C. burnetii ecology in the country. Spleen samples from 816 micromammals of 10 species and 130 vaginal swabs from Microtus arvalis were analysed by qPCR to detect C. burnetii infection and shedding, respectively. The 9.7% of the spleen samples were qPCR positive. The highest infection prevalence (10.8%) was found in Microtus arvalis, in which C. burnetii DNA was also detected in 1 of the 130 vaginal swabs (0.8%) analysed. Positive samples were also found in Apodemus sylvaticus (8.7%), Crocidura russula (7.7%) and Rattus rattus (6.4%). Positive samples were genotyped by coupling PCR with reverse line blotting and a genotype II+ strain was identified for the first time in one of the positive samples from M. arvalis, whereas only partial results could be obtained for the rest of the samples. Acute Q fever was diagnosed in one of the researchers that participated in the study, and it was presumably linked to M. arvalis handling. The results of the study are consistent with previous findings suggesting that micromammals can be infected by C. burnetii. Our findings additionally suggest that micromammals may be potential sources to trace back the origin of human Q fever and animal Coxiellosis cases in Europe.This work was supported by grants CGL2011-30274 and CGL2015-71255-P of the Spanish Ministry for the Science and Innovation (MCI), and by the ‘Fundación BBVA’ Research Project TOPIGEPLA (2014 call). This is also a contribution to MCI-funded projects CGL2017-89866-R and E-RTA-2015-0002-C02-02. D.G.-B. was funded by MCI through Juan de la Cierva (FJCI-2016-27875) and ‘Sara Borrell’ (CD19CIII/00011) postdoctoral fellowships. GREFA provided partial financial support and invaluable logistic and workforce support for samplings in NW Spain, along with many students and staff from UAM.S
Enhancing safety in hyperbaric environments through analysis of autonomic nervous system responses: a comparison of dry and humid conditions
Diving can have significant cardiovascular effects on the human body and increase the risk of developing cardiac health issues. This study aimed to investigate the autonomic nervous system (ANS) responses of healthy individuals during simulated dives in hyperbaric chambers and explore the effects of the humid environment on these responses. Electrocardiographic- and heart-rate-variability (HRV)-derived indices were analyzed, and their statistical ranges were compared at different depths during simulated immersions under dry and humid conditions. The results showed that humidity significantly affected the ANS responses of the subjects, leading to reduced parasympathetic activity and increased sympathetic dominance. The power of the high-frequency band of the HRV after removing the influence of respiration, PHF⊥¯, and the number of pairs of successive normal-to-normal intervals that differ by more than 50 ms divided by the total number of normal-to-normal intervals, pNN50¯, indices were found to be the most informative in distinguishing the ANS responses of subjects between the two datasets. Additionally, the statistical ranges of the HRV indices were calculated, and the classification of subjects as “normal” or “abnormal” was determined based on these ranges. The results showed that the ranges were effective at identifying abnormal ANS responses, indicating the potential use of these ranges as a reference for monitoring the activity of divers and avoiding future immersions if many indices are out of the normal ranges. The bagging method was also used to include some variability in the datasets’ ranges, and the classification results showed that the ranges computed without proper bagging represent reality and its associated variability. Overall, this study provides valuable insights into the ANS responses of healthy individuals during simulated dives in hyperbaric chambers and the effects of humidity on these responses
Reconstitution of respiratory complex I on a biomimetic membrane supported on gold electrodes
For the first time, respiratory complex I has been reconstituted on an electrode preserving its structure and activity. Respiratory complex I is a membrane-bound enzyme that has an essential function in cellular energy production. It couples NADH:quinone oxidoreduction to translocation of ions across the cellular (in prokaryotes) or mitochondrial membranes. Therefore, complex I contributes to the establishment and maintenance of the transmembrane difference of electrochemical potential required for adenosine triphosphate synthesis, transport, and motility. Our new strategy has been applied for reconstituting the bacterial complex I from Rhodothermus marinus onto a biomimetic membrane supported on gold electrodes modified with a thiol self-assembled monolayer (SAM). Atomic force microscopy and faradaic impedance measurements give evidence of the biomimetic construction, whereas electrochemical measurements show its functionality. Both electron transfer and proton translocation by respiratory complex I were monitored, simulating in vivo conditions. © 2014 American Chemical Society.This work was funded by the Spanish MINECO (project CTQ2012-32448) and by Fundação para a Ciência e a Tecnologia (PTDC/BBB-BQB/2294/2012 to M.M.P.). The work was also supported by Fundação para a Ciência e a Tecnologia through grant # PEst-OE/EQB/LA0004/2011. M.P. and O.G.-S. acknowledge the Ramon y Cajal and the FPI programs respectively from the Spanish MINECO. A.P.B. is recipient of a grant from Fundação para a Ciência e a Tecnologia (SFRH/BPD/80741/2011).Peer Reviewe
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