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)

Blades design for a small wind turbine to supply a rural house. Case study

[EN] Nowadays the global warming has caused a growing increase of sensitivity of the population to reduce the consumption of non-renewable resources. Therefore, the use of renewable energies is currently increasing and the development of studies to install small renewable generators to supply domestic uses also does. In this line, the present research develops a methodology to design the blades of a small wind turbine with horizontal axis, applying it to a real case study. To improve the design of the wind turbine, a meteorological station was installed in the study point as well as historic registered data were used. Finally, the estimated energy produced by this generator was 1453 kWh/year and the energy could be used to supply in the rural house to complement the electrical consumption, reducing the consumption of the other non-renewable resources.Ortiz-Juan, R.; Pérez-Sánchez, M.; López Jiménez, PA. (2018). Blades design for a small wind turbine to supply a rural house. Case study. International Journal of Energy and Environment (IJEE). 9(1):27-36. http://hdl.handle.net/10251/114608S27369

Effects of cannabis on visual function and self-perceived visual quality

Cannabis is one of the most used drugs of abuse in the world. The objective of this study was to analyze the effects of smoking cannabis on vision and to relate these to those perceived by the user. Thirty-one cannabis users participated in this study. Visual function assessment was carried out in a baseline session as well as after smoking cannabis. We evaluated static visual acuity, contrast sensitivity, stereoacuity, accommodative response, straylight, night-vision disturbances (halos) and pupil size. The participants were also divided into two groups depending on whether they perceived their vision to have worsened after smoking cannabis. A logistic regression analysis was employed to identify which visual test could best predict self-perceived visual effects. The study found that smoking cannabis has significant adverse effects on all the visual parameters analyzed (p < 0.05). Self-perceived visual quality results revealed that about two thirds of the sample think that smoking cannabis impairs their vision. Contrast sensitivity, specifically for the spatial frequency 18 cpd, was identified as the only visual parameter significantly associated with self-perceived visual quality (Odds Ratio: 1.135; p = 0.040). Smoking cannabis is associated with negative effects on visual function. Self-perceived visual quality after smoking cannabis could be related to impaired contrast sensitivity

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

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

El penitente: una profesión trágica de la minería del carbón

Hubo una época en que la forma más habitual para evitar las explosiones de grisú y asfixias provocadas por este fluido gaseoso en las explotaciones de carbón era mediante el trabajo del penitente. En aquellos tiempos los tajos no eran muy grandes, se laboreaba en ellos de forma manual, y el gas generado no aparecía, por lo general, en gran cantidad. El penitente era una persona de experiencia que entraba en las minas antes de que los mineros llegasen a su trabajo, para explosionar los gases que allí existieran. Estaba cubierto con una especie de pasamontañas, guantes y capa, prendas realizados con tejidos gruesos o cuero, que eran humedecidas para protegerse del fuego. Iba arrastrándose sobre su vientre, mientras que con una larga pértiga, que portaba delante de él, llevaba una candela encendida en el extremo de la misma, para favorecer la explosión del grisú acumulado en el techo de las labores. Este personaje desaparecerá paulatinamente tras el invento de la lámpara de seguridad de Davy (1815). Aunque hay bastantes datos dispersos sobre esta profesión, en nuestro trabajo pretendemos abordar los siguientes aspectos: 1.-Cuándo y cómo aparece este personaje y hasta que época permanece en la minería. 2.- En que ámbitos geográficos se presenta y cuáles son sus diferentes denominaciones. 3.-Cuánto duraba su trabajo y cuál era su salario, en el caso de que lo tuviese. 4.-Cuál era su modus operandi. 5.-Cuáles y cómo son sus representaciones, indicando si es posible el nombre de los artistas que las hicieron. 6.-Cuál ha sido su presencia en la literatura. In a certain time, the most common way to avoid explosions and suffocation due to the presence of methane (fire damp) in coal mines was the labour of the fireman, also called penitent. As the coal beds were no so large, manual extraction were employed, and fire damp did not appeared in high amounts, but it was dangerous. The fireman was an experienced man who entered the mines before miners, in order to ascertain if gas exists and provoke the explosion of firedamp. He was covered by a mask, gloves and a cap, all of them made by thick textiles or leather, which were humidified to protect from fire. The fireman creep over his belly, and with the aid of a pole with a candle at its edge, to produce the explosion of fire damp. The work of fireman progressively disappeared after the discovery of the Davy´s lamp. Although there are some data about the existence of firemans, this paper deals with the following topics: 1.-When and how the fireman appeared and for how long was employed in coal mines. 2.- In which regions the fireman was employed, and which were the different names. 3.-Which was his workday and which was his salary. 4.- Which was his modus operandi. 5.-Which and how were the artistic representations, indicating, if possible, the name of the artists. 6.-Which was his presence in literatur

Primeval very low-mass stars and brown dwarfs - IV. New L subdwarfs, Gaia astrometry, population properties, and a blue brown dwarf binary

30 pages, 23 figuresWe present 27 new L subdwarfs and classify five of them as esdL and 22 as sdL. Our L subdwarf candidates were selected with the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Spectroscopic follow-up was carried out primarily with the OSIRIS spectrograph on the Gran Telescopio Canarias. Some of these new objects were followed up with the X-shooter instrument on the Very Large Telescope. We studied the photometric properties of the population of known L subdwarfs using colour-spectral type diagrams and colour-colour diagrams, by comparison with L dwarfs and main-sequence stars, and identified new colour spaces for L subdwarf selection/study in current and future surveys. We further discussed the brown dwarf transition-zone and the observational stellar/substellar boundary. We found that about one-third of 66 known L subdwarfs are substellar objects, with two-thirds being very low-mass stars. We also present the Hertzsprung-Russell diagrams, spectral type-absolute magnitude corrections, and tangential velocities of 20 known L subdwarfs observed by the Gaia astrometry satellite. One of our L subdwarf candidates, ULAS J233227.03+123452.0, is a mildly metal-poor spectroscopic binary brown dwarf: a ~L6p dwarf and a ~T4p dwarf. This binary is likely a thick disc member according to its kinematics.Peer reviewedFinal Accepted Versio

A three-dimensional Galactic extinction model

A large-scale three-dimensional model of Galactic extinction is presented based on the Galactic dust distribution model of Drimmel and Spergel (2001). The extinction A_V to any point within the Galactic disk can be quickly deduced using a set of three-dimensional cartesian grids. Extinctions from the model are compared to empirical extinction measures, including lines-of-sight in and near the Galactic plane using optical and NIR extinction measures; in particular we show how extinction can be derived from NIR color-magnitude diagrams in the Galactic plane to a distance of 8 kiloparsec.Comment: 12 pages, to be published in A&

Confinement Effects in Antiferromagnets

Phase equilibrium in confined Ising antiferromagnets was studied as a function of the coupling (v) and a magnetic field (h) at the surfaces, in the presence of an external field H. The ground state properties were calculated exactly for symmetric boundary conditions and nearest-neighbor interactions, and a full zero-temperature phase diagram in the plane v-h was obtained for films with symmetry-preserving surface orientations. The ground-state analysis was extended to the H-T plane using a cluster-variation free energy. The study of the finite-T properties (as a function of v and h) reveals the close interdependence between the surface and finite-size effects and, together with the ground-state phase diagram, provides an integral picture of the confinement in anisotropic antiferromagnets with surfaces that preserve the symmetry of the order parameter.Comment: 10 pages, 8 figures, Accepted in Phys. Rev.