WISE morphological study of Wolf-Rayet nebulae

We present a morphological study of nebulae around Wolf-Rayet (WR) stars using archival narrow-band optical and Wide-field Infrared Survey Explorer (WISE) infrared images. The comparison among WISE images in different bands and optical images proves to be a very efficient procedure to identify the nebular emission from WR nebulae, and to disentangle it from that of the ISM material along the line of sight. In particular, WR nebulae are clearly detected in the WISE W4 band at 22 $\mu$m. Analysis of available mid-IR Spitzer spectra shows that the emission in this band is dominated by thermal emission from dust spatially coincident with the thin nebular shell or most likely with the leading edge of the nebula. The WR nebulae in our sample present different morphologies that we classified into well defined WR bubbles (bubble ${\cal B}$-type nebulae), clumpy and/or disrupted shells (clumpy/disrupted ${\cal C}$-type nebulae), and material mixed with the diffuse medium (mixed ${\cal M}$-type nebulae). The variety of morphologies presented by WR nebulae shows a loose correlation with the central star spectral type, implying that the nebular and stellar evolutions are not simple and may proceed according to different sequences and time-lapses. We report the discovery of an obscured shell around WR35 only detected in the infrared.Comment: 11 pages, 6 figures, plus 23 appendix figures; to appear in Astronomy and Astrophysic

JET Formation in Solar Atmosphere Due to Magnetic Reconnection

Using numerical simulations, we show that jets with features of type II spicules and cool coronal jets corresponding to temperatures of 104 K can be formed as a result of magnetic reconnection in a scenario with magnetic resistivity. For this, we model the low chromosphere–corona region using the C7 equilibrium solar atmosphere model, assuming that resistive MHD rules the dynamics of the plasma. The magnetic field configurations we analyze correspond to two neighboring loops with opposite polarity. The formation of a highspeed and sharp structure depends on the separation of the loops’ feet. We analyze the cases where the magnetic field strength of the two loops is equal and different. In the first case, with a symmetric configuration the jets rise vertically, whereas in an asymmetric configuration the structure shows an inclination. With a number of simulations carried out under a 2.5D approach, we explore various properties of the excited jets, namely, inclination, lifetime, and velocity. The parameter space involves a magnetic field strength between 20 and 40 G, and the resistivity is assumed to be uniform with a constant value of the order 10-2W · m

Customer orientation of service employees in family businesses in the hotel sector

The business interactions between front-line employees and customers are crucial to evaluating service quality and for business performance. A gap has been identified in the literature on both customer orientation of service employees (COSE) and family businesses (FBs). These two concepts have never been studied together before. This study presents a concept that develops a theoretical model based on Hennig-Thurau (2004). This model drives research about the COSE and FBs in the hotel sector. The two main contributions are: (1) electronic word-of-mouth (eWOM) is proposed as a consequence of COSE within FBs and (2) a questionnaire has been developed from relevant subscales to measure COSE and the two possible consequences derived from it (Customer Satisfaction and eWOM). A database from Iberic Balance Analysis System (SABI) has been selected to study these variables in the hotel sector, and it will be used in a future empirical study that is expected to provide support for the theory

Chemistry of the High-Mass Protostellar Molecular Clump IRAS 16562-3959

We present molecular line observations of the high-mass molecular clump IRAS 16562$-$3959 taken at 3 mm using the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.\!\!^{\prime\prime}7 angular resolution ($0.014$ pc spatial resolution). This clump hosts the actively accreting high-mass young stellar object (HMYSO) G345.4938+01.4677, associated with a hypercompact HII region. We identify and analyze emission lines from 22 molecular species (encompassing 34 isomers) and classify them into two groups, depending on their spatial distribution within the clump. One of these groups gathers shock tracers (e.g., SiO, SO, HNCO) and species formed in dust grains like methanol (CH$_3$OH), ethenone or ketene (H$_2$CCO), and acetaldehyde (CH$_3$CHO). The second group collects species resembling the dust continuum emission morphology and which are formed mainly in the gas-phase, like hydrocarbons (CCH, c-C$_3$H$_2$, CH$_3$CCH), cyanopolyynes (HC$_3$N and HC$_5$N) and cyanides (HCN and CH$_3$C$_3$N). Emission from complex organic molecules (COMs) like CH$_3$OH, propanenitrile (CH$_3$CH$_2$CN), and methoxymethane (CH$_3$OCH$_3$) arise from gas in the vicinity of a hot molecular core ($T\gtrsim100$ K) associated with the HMYSO. Other COMs such as propyne (CH$_3$CCH), acrylonitrile (CH$_2$CHCN), and acetaldehyde seem to better trace warm ($T\lesssim80$ K) dense gas. In addition, deuterated ammonia (NH$_2$D) is detected mostly in the outskirts of IRAS 16562$-$3959, associated with near-infrared dark globules, probably gaseous remnants of the clump's prestellar phase. The spatial distribution of molecules in IRAS 16562$-$3959 supports the view that in protostellar clumps, chemical tracers associated with different evolutionary stages --- starless to hot cores/HII regions --- exist coevally.Comment: 97 pages, Accepted in The Astrophysical Journal Supplement Series. Journal file version have better quality figure

The IRAM-30m line survey of the Horsehead PDR: III. High abundance of complex (iso-)nitrile molecules in UV-illuminated gas

Complex (iso-)nitrile molecules, such as CH3CN and HC3N, are relatively easily detected in our Galaxy and in other galaxies. We constrain their chemistry through observations of two positions in the Horsehead edge: the photo-dissociation region (PDR) and the dense, cold, and UV-shielded core just behind it. We systematically searched for lines of CH3CN, HC3N, C3N, and some of their isomers in our sensitive unbiased line survey at 3, 2, and 1mm. We derived column densities and abundances through Bayesian analysis using a large velocity gradient radiative transfer model. We report the first clear detection of CH3NC at millimeter wavelength. We detected 17 lines of CH3CN at the PDR and 6 at the dense core position, and we resolved its hyperfine structure for 3 lines. We detected 4 lines of HC3N, and C3N is clearly detected at the PDR position. We computed new electron collisional rate coefficients for CH3CN, and we found that including electron excitation reduces the derived column density by 40% at the PDR position. While CH3CN is 30 times more abundant in the PDR than in the dense core, HC3N has similar abundance at both positions. The isomeric ratio CH3NC/CH3CN is 0.15+-0.02. In the case of CH3CN, pure gas phase chemistry cannot reproduce the amount of CH3CN observed in the UV-illuminated gas. We propose that CH3CN gas phase abundance is enhanced when ice mantles of grains are destroyed through photo-desorption or thermal-evaporation in PDRs, and through sputtering in shocks. (abridged)Comment: Accepted for publication in Astronomy & Astrophysic

Agronomic, economic and ecological aspects of the papaya (Carica papaya) production in Tabasco, Mexico

The cultivation of papaya is important in the tropic because it provides source of income to the farmer within a short time. Statistical data were obtained from farmers located in the Chontalpa, Rios and Centro-Sierra regions; the size of the survey was 67 farmers. The study shows the results of the farmers’ problem in a drastic reduction of their productivity because of the virosis and low prices in commercialization. The farmers were classified into three levels of technology, “low”, “middle” and “high”. The first one covers 88% of the farmers in seasonal conditions in contrast with the high technology that concentrates 4.5% in irrigation conditions. According to the technology used, the fertilizer shows more yields. Economically, the high technology had an internal tax return of 0.43 in comparison with the low technology of 0.25, which means that the investment is recovered with different yields. However, the use of high technology makes the system more competitive. Key words

Neural controller for the trajectory tracking control of an inertia wheel pendulum

En este trabajo de investigación, se estudia el problema de control de seguimiento de trayectorias en un péndulo de rueda inercial. Los resultados son presentados de una forma constructiva. Primero, se obtiene un controlador basado en el modelo utilizando la técnica de linealización por retroalimentación de salida. Posteriormente, el controlador es rediseñado al incorporar una red neuronal con el propósito de evitar el conocimiento de los parámetros exactos del péndulo de rueda inercial, y se obtiene un diseño robusto. Se usa un perceptrón de dos capas, cuyos pesos de salida son actualizados en tiempo real utilizando una ley de adaptación derivada del análisis de convergencia de las soluciones del sistema de lazo cerrado. El lema de Barbalat se utiliza para concluir que las trayectorias del error de seguimiento del péndulo convergen a cero. Se presentan simulaciones numéricas y experimentos en tiempo real, que confirman los resultados teóricos.In this paper, the problem of trajectory tracking control in an inertia wheel pendulum is studied. Results are presented in a constructive form. First, a model-based controller is obtained by using the output feedback linearization technique. Then, the controller is redesigned by incorporating a neural network with the aim of avoiding the exact parameters knowledge of the inertia wheel pendulum, obtaining a robust control scheme. A two-layer perceptron is used, whose output weights are updated in real-time using an adaption law derived from the analysis of convergence of the closed-loop system solutions. Barbalats lemma is used to conclude that the pendulum tracking error trajectory converges to zero. Numerical simulations and real-time experiments are presented, which confirm the theoretical results.Peer Reviewe