1,732 research outputs found

    Theoretical characterization of the lowest-energy absorption band of pyrrole

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    The lowest-energy band of the electronic spectrum of pyrrole has been studied with vibrational resolution by using multiconfigurational second-order perturbation theory (CASPT2) and its multistate extension (MS–CASPT2) in conjunction with large atomic natural orbital-type basis sets including Rydberg functions. The obtained results provide a consistent picture of the recorded spectrum in the energy region 5.5–6.5 eV and confirm that the bulk of the intensity of the band arises from a ππ∗ intravalence transition, in contradiction to recent theoretical claims. Computed band origins for the 3s,3p Rydberg electronic transitions are in agreement with the available experimental data, although new assignments are suggested. As illustrated in the paper, the proper treatment of the valence–Rydberg mixing is particularly challenging for ab initio methodologies and can be seen as the main source of deviation among the recent theoretical results as regards the position of the low-lying valence excited states of [email protected] ; [email protected]

    Mining gradual dependencies with variation strength

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    In this paper we propose a definition of gradual dependence as a fuzzy association rule. Gradual dependencies represent tendencies in the variation of the degree of fulfilment of properties in a set of objects. We define the degree of variation of a certain imprecise property for a pair of objects as the difference between their membership degrees to the fuzzy set defining the property. When considering a transaction for every pair of objects and considering items representing positive and negative variations foer each property of interest, fuzzy association rules become gradual dependencies and the accuray and support of the former can be employed to assess the corresponding dependencies. We study the new semantics and properties of the resulting fuzzy gradual dependence, and we propose a way to adapt existing fuzzy association rule mining algorithms for the new task of mining such dependenciesPeer Reviewe

    Evaluating anemometer drift: A statistical approach to correct biases in wind speed measurement

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    Recent studies on observed wind variability have revealed a decline (termed “stilling”) of near-surface wind speed during the last 30–50 years over many mid-latitude terrestrial regions, particularly in the Northern Hemisphere. The well-known impact of cup anemometer drift (i.e., wear on the bearings) on the observed weakening of wind speed has been mentioned as a potential contributor to the declining trend. However, to date, no research has quantified its contribution to stilling based on measurements, which is most likely due to lack of quantification of the ageing effect. In this study, a 3-year field experiment (2014–2016) with 10-minute paired wind speed measurements from one new and one malfunctioned (i.e., old bearings) SEAC SV5 cup anemometer which has been used by the Spanish Meteorological Agency in automatic weather stations since mid-1980s, was developed for assessing for the first time the role of anemometer drift on wind speed measurement. The results showed a statistical significant impact of anemometer drift on wind speed measurements, with the old anemometer measuring lower wind speeds than the new one. Biases show a marked temporal pattern and clear dependency on wind speed, with both weak and strong winds causing significant biases. This pioneering quantification of biases has allowed us to define two regression models that correct up to 37% of the artificial bias in wind speed due to measurement with an old anemometer

    Dye-conjugated complementary lipophilic nucleosides as useful probes to study association processes by fluorescence resonance energy transfer

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    Modern supramolecular chemistry relies on the combination of diverse analytical techniques that can provide complementary information on complex self-assembly landscapes. Among them, resonance energy transfer, monitored by fluorescence emission spectroscopy, arises as a sensitive and convenient phenomenon to report binding intermolecular interactions. The use of molecular probes labelled with suitable complementary energy-transfer pairs can provide valuable information about the thermodynamics, kinetics and self-sorting characteristics of a particular self-assembled system. The objective of this work is to generate a set of nucleoside FRET probes that can be reliably employed to prove and analyse quantitatively H-bonding interactions between complementary Watson-Crick pairs. We first describe the preparation of a set of lipophilic nucleosides that are linked to a π-conjugated functional fragment. The bases include guanosine and 2-aminoadenosine as purine heterocycles, and cytidine and uridine as complementary pyrimidine bases. The π-conjugated moiety comprises either a short phenylene-ethynylene oligomer, a bithiophene, or a BODIPY dye. We then demonstrate that the last two chromophores constitute an energy donor-acceptor couple and that donor emission quenching can be related to the ratio of molecules bound to the complementary acceptor pair. Hence, fluorescence spectroscopy in combination with resonance energy transfer, is shown here to be a useful tool to study and quantify the association and self-sorting events between complementary and non-complementary nucleosides in apolar aromatic solvents, where the binding strength is considerably high, and sensitive techniques that employ low concentrations are demandedFunding from the European Research Council (ERC-Starting Grant 279548 PROGRAM-NANO) and MINECO (CTQ2014-57729-P) is gratefully acknowledged. E. F. would like to thank the Sharif University of Technology of Iran for financial support. D. S.M. would like to acknowledge Comunidad de Madrid for financial support through contract PEJ16/IND/AI-084

    ¿Afectan los taninos condensados de la dieta a los resultados productivos, la composición de ácidos grasos y el color de la carne de cordero?

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    This meta-analysis evaluated the effect of condensed tannins (TC) (polyphenols formed from flavan-3-ol monomers) on the growth performance, fatty acid composition and lamb meat colour, based on the results of 41 publications (years 1998-2019) that allowed making up to 67 comparisons between batches of experimental lambs compared with a control lot within the same trial. These lots were divided into two groups, according to the dietary TC content difference between the control and experimental batch (medium level, 16 g/kg DM or high, 25 g/kg DM). The mean difference between each experimental group and its control lot was calculated for average daily gain, average feed intake, feed conversion rate, intramuscular fat, fatty acid profile and chromatic meat colour attributes. No significant differences were observed in the growth performance due to dietary TC inclusion, being much important the effect of other nutrients, such as crude protein and crude fat. A consistent reduction in the ratio of saturated fatty acids/polyunsaturated fatty acids and rumenic acid content in meat was observed. However, dietary inclusion of TC did not improve meat colour attributes compared to control groups

    Semiempirical in-cylinder pressure based model for NOx prediction oriented to control applications

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    This work describes the development of a fast NO X predictive model oriented to engine control in diesel engines. The in-cylinder pressure is the only instantaneous input signal required, along with several mean variables that are available in the ECU during normal engine operation. The proposed model is based on the instantaneous evolution of the heat release rate and the adiabatic flame temperature (both obtained among other parameters from the in-cylinder pressure evolution). Corrections for considering the NO X reduction due to the re-burning mechanism are also included. Finally, the model is used for providing a model-based correction of tabulated values for the NO X emission at the reference conditions. The model exhibits a good behaviour when varying exhaust gas recirculation rate, boost pressure and intake temperature, while changes in the engine speed and injection settings are considered in the tabulated values. Concerning the calculation time, the model is optimised by proposing simplified sub-models to calculate the heat release and the adiabatic flame temperature. The final result is suitable for real time applications since it takes less than a cycle to complete the NO X prediction.Guardiola García, C.; López Sánchez, JJ.; Martín Díaz, J.; García Sarmiento, D. (2011). Semiempirical in-cylinder pressure based model for NOx prediction oriented to control applications. Applied Thermal Engineering. 31(16):3275-3286. doi:10.1016/j.applthermaleng.2011.05.048S32753286311

    Assessment of vapor pressure deficit variability and trends in Spain and possible connections with soil moisture

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    The Vapor Pressure Deficit (VPD) is one of the most relevant surface meteorological variables; with important implications in ecology, hydrology, and atmosphere. By understanding the processes involved in the variability and trend of the VPD, it is possible to assess the possible impacts and implications related to both physical and human environments, like plant function, water use efficiency, net ecosystem production, atmospheric CO2 growth rate, etc. This study analysed recent temporal variability and trends in VPD in Spain between 1980 and 2020 using a recently developed high-quality dataset. Also, the connection between VPD and soil moisture and other key climate variables (e.g. air temperature, precipitation, and relative humidity) was assessed on different time scales varying from weekly to annual. The objective was to determine if changes in land-atmosphere feedbacks connected with soil moisture and evapotranspiration anomalies have been relevant to assess the interannual variability and trends in VPD. Results demonstrate that VPD exhibited a clear seasonality and dominant positive trends on both the seasonal (mainly spring and summer) and annual scales. Rather, trends were statistically non-significant (p > 0.05) during winter and autumn. Spatially, VPD positive trends were more pronounced in southern and eastern of Spain. Also, results suggest that recent trends of VPD shows low contribution of variables that drive land-atmosphere feedbacks (e.g. evapotranspiration, and soil moisture) in comparison to the role of global warming processes. Notably, the variability of VPD seems to be less coupled with soil moisture variability during summertime, while it is better interrelated during winter, indicating that VPD variability would be mostly related to climate variability mechanisms that control temperature and relative humidity than to land-atmosohere feedbacks. Overall, our findings highlight the importance of assessing driving forces and physical mechanisms that control VPD variability using high-quality climate datasets, especially, in semiarid and sub-humid regions of the world

    Low Latency Estimation of Motor Intentions to Assist Reaching Movements along Multiple Sessions in Chronic Stroke Patients: A Feasibility Study

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    A corrigendum on Low Latency Estimation of Motor Intentions to Assist Reaching Movements along Multiple Sessions in Chronic Stroke Patients: A Feasibility Study by Ibáñez, J., Monge-Pereira, E., Molina-Rueda, F., Serrano, J. I., del Castillo, M. D., Cuesta-Gómez, A., et al. (2017). Front. Neurosci. 11:126. doi: 10.3389/fnins.2017.00126. In the recently published article, there were incorrect and missing contents in the Acknowledgments section

    La subnutrición preparto y el hidroxitirosol en el equilibrio pro- y anti-oxidante de la sangre durante la etapa de lactación

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    La suplementación materna con HT mejoró la respuesta antioxidante de los terneros de vacas subnutridas. La capacidad antioxidante en vacas y el MDA en vacas y terneros incrementaron al avanzar la gestación.: Proyecto financiado por MCIN/AEI/ 10.13039/501100011033 (FETALNUT). Contrato predoctoral de la Universitat de Lleida N. Escalera-Moreno. Los autores agradecen a M. Joy y a J.R. Bertolín (CITA-IA2(UNIZAR)) la ayuda proporcionada en el análisis de las muestras

    Efecto de la subnutrición preparto y el hidroxitirosol en el equilibrio pro- y anti-oxidante de la sangre durante el último tercio de gestación

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    La subnutrición durante el último tercio de gestación en vacas disminuyó la capacidad total antioxidante y aumentó la peroxidación lipídica en el último tercio de la gestación. La suplementación con HT redujo el daño oxidativo en las vacas subnutridas.: Proyecto financiado por MCIN/AEI/ 10.13039/501100011033 (FETALNUT). Contrato predoctoral de la Universitat de Lleida N. Escalera-Moreno. Se agradece a M. Joy y a J.R. Bertolín (CI -TA-IA2-(Unizar)) la ayuda proporcionada en el análisis de las muestras
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