3,022 research outputs found
Functionalization of p-activated alcohols by trapping carbocations in pure water under smooth conditions
Acetic acid as catalyst in pure water was found to be an excellent reaction medium for the direct dehydrative functionalization of p-activated alcohols using a wide variety of interesting C-, P-, and S-centered nucleophiles, such as indoles, pyrrole, anilines, 1, 3-dicarbonyl compounds, diphenyl phosphite and pyridine-2-thiol. The smooth reaction conditions, along with high yields, short reaction times, clean reaction crudes, an easy product isolation procedure, plus the reusability of the catalyst and the use of no excess of nucleophiles, make this approach an atom economical, green and appealing method to efficiently trap carbocations in pure water, leading to new Csp3 X bonds (X = Csp2, Csp3, P and S)
SpectroscopicTechniques and DFT Calculations to Understand Charge Transport Mechinisms in OFETs
The organic electronics research field has advanced tremendously in the last decades, but there is still an incomplete understanding of the main mechanisms governing charge injection and transport in such devices. The performance of organic semiconductors is governed not only by their molecular structures but also by their intermolecular assembly in the solid state. Here we use a combination of Raman spectroscopy and charge modulation spectroscopy (CMS) to gather information on molecular and supramolecular levels, of organic semiconductors [1,2] (Figure 1) [3]. This last one is an optical-spectroscopy technique conducted on a real OFETs, that allows us to study in situ the charge carriers present at the semiconductor-dielectric interface, where the largest contribution to charge transport occurs. [3] In this communication we will present the study of the bithiophene imide (BTIn) molecules which exhibit encouraging electron mobilities in OFETs [1,2], by using the spectroscopic techniques presented above, supported by DFT quantum chemical calculations in order to shed light on the mechanism of charge transport in OFETs.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Revisiting the Problem of Searching on a Line
We revisit the problem of searching for a target at an unknown location on a
line when given upper and lower bounds on the distance D that separates the
initial position of the searcher from the target. Prior to this work, only
asymptotic bounds were known for the optimal competitive ratio achievable by
any search strategy in the worst case. We present the first tight bounds on the
exact optimal competitive ratio achievable, parameterized in terms of the given
bounds on D, along with an optimal search strategy that achieves this
competitive ratio. We prove that this optimal strategy is unique. We
characterize the conditions under which an optimal strategy can be computed
exactly and, when it cannot, we explain how numerical methods can be used
efficiently. In addition, we answer several related open questions, including
the maximal reach problem, and we discuss how to generalize these results to m
rays, for any m >= 2
Dynamics of Executive Functions, Basic Psychological Needs, Impulsivity, and Depressive Symptoms in American Football Players
Executive functions play an important role in sports since the ability to plan, organize,and regulate behavior to reach an objective or goal depends on these functions. Someof the components of executive functions, such as inhibition of impulsive behavior andcognitive flexibility, are necessary for contact sports (e.g., American football) to carryout successful plays on the sports field. Executive functions have been studied in thesporting environment, but their relationship with the athletes’ basic psychological needs(BPN), such as autonomy, competence, and relatedness, remains unexplored. Due tothe importance of motivational processes over cognitive functions and in the generatedadaptive results in athletes, this relationship should be taken into account. Therefore, theaim of this study was to analyze and compare executive functioning and psychologicalneed thwarting overimpulsivity and psychological distress, before and after the season(4 months) in 28 undergraduate football players. Neuropsychological and psychologicaltests were applied. The results showed that there was an improvement in inhibitionand planning at the end of the season. There was also an increase in attention andmotor impulsiveness, and a decrease in need thwarting at the end of the season.A positive association between executive function, impulsiveness, psychological needs,and affective symptoms were also found. Our findings reveal the dynamics of sport-related psychological variables throughout the sport season in American football players,the association of these for the achievement of sport success, and the importance ofencouraging proper management of emotions
Turbiditas carbonatadas del Cretácico inferior en el Arroyo Bercho, Prebético de Jaén: Interpretación genética e implicaciones paleogeográficas
[ES] El análisis de las características sedimentarias de las turbiditas
carbonatadas permite precisar la interpretación paleogeográfica del
Prebético de Jaén, durante el Cretácico. Se pueden distinguir dos
asociaciones de facies: a) Turbiditas de estatificación fina, intercaladas
en abundante sedimento pelágico, e interpretadas como facies
de borde de lóbulo. b) Cuerpos turbidíticos lenticulares interpretados
como lóbulos de depósito formados por agradación. Aparecen
asociadas a una serie depositada en una cuenca que progresivamente
se fue haciendo más somera y que terminó con la implantación de
una plataforma carbonatada en el Cenomanense. Se calcula que el
depósito de las turbidítas debió realizarse a unos pocos centenares
de metros de profundidad.[EN] The analysis of the sedimentary characteristics of the carbonate
turbidites allows to accurate the paleogeographic interpretation of
the Prebetie of laen. Two types of facies associations can be distinguished: a) Thin bedded turbidites> as intercalations into mainly hemipelapic
sediments, interpreted as lobe fringe facies, b) Lents like
turbiditie bodies corresponding to agradational depositional lobes.
They occur associated to an shallowing upward sequence ending
with Cenomanian carbonated platform facies. The turbiditic deposit
supodselly took place in a few hundreds meters deep sedimentary
basin.Trabajo patrocinado por la C.A.I.C.Y.T.,
dentro del proyecto «El Mesozoico de las Cordilleras Béticas» realizado
en este centro del C.S.I.C.Peer reviewe
Pressure-Induced Phase-Transition Sequence In Cof 2 : An Experimental And First-Principles Study On The Crystal, Vibrational, And Electronic Properties
We report a complete structural study of CoF2 under pressure. Its crystal structure and vibrational and electronic properties have been studied both theoretically and experimentally using first-principles density functional theory (DFT) methods, x-ray diffraction, x-ray absorption at Co K-edge experiments, Raman spectroscopy, and optical absorption in the 0–80 GPa range. We have determined the structural phase-transition sequence in CoF2 and corresponding transition pressures. The results are similar to other transition-metal difluorides such as FeF2 but different to ZnF2 and MgF2, despite that the Co2+ size (ionic radius) is similar to Zn2+ and Mg2+. We found that the complete phase-transition sequence is tetragonal rutile (P42/mnm) → CaCl2 type (orthorhombic Pnnm) → distorted PdF2 (orthorhombic Pbca)+PdF2 (cubic Pa3¯) in coexistence → fluorite (cubic Fm3¯m) → cotunnite (orthorhombic Pnma). It was observed that the structural phase transition to the fluorite at 15 GPa involves a drastic change of coordination from sixfold octahedral to eightfold cubic with important modifications in the vibrational and electronic properties. We show that the stabilization of this high-pressure cubic phase is possible under nonhydrostatic conditions since ideal hydrostaticity would stabilize the distorted-fluorite structure (tetragonal I4/mmm) instead. Although the first rutile → CaCl2-type second-order phase transition is subtle by Raman spectroscopy, it was possible to define it through the broadening of the Eg Raman mode which is split in the CaCl2-type phase. First-principles DFT calculations are in fair agreement with the experimental Raman mode frequencies, thus providing an accurate description for all vibrational modes and elastic properties of CoF2 as a function of pressure
Umbral Dynamics in the Near Infrared Continuum
We detected peaks of oscillatory power at 3 and ~6.5 minutes in the umbra of
the central sunspot of the active region NOAA AR 10707 in data obtained in the
near infrared (NIR) continuum at 1565.7 nm. The NIR dataset captured umbral
dynamics around 50 km below the photospheric level. The umbra does not
oscillate as a whole, but rather in distinct parts that are distributed over
the umbral surface. The most powerful oscillations, close to a period of ~ 6.5,
do not propagate upward. We noted a plethora of large umbral dots that
persisted for more than 30 minutes and stayed in the same locations. The peaks
of oscillatory power above the detected umbral dots are located at 3 and 5
minutes oscillations, but are very weak in comparison with the oscillations of
~ 6.5 minutes.Comment: 16 pages, 8 figures, accepted in Ap
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